| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Peter Zijlstra | 14375 | 37.26% | 309 | 24.45% |
| Patrick Bellasi | 2929 | 7.59% | 18 | 1.42% |
| Dario Faggioli | 2249 | 5.83% | 5 | 0.40% |
| Mark Rutland | 1520 | 3.94% | 7 | 0.55% |
| Mathieu Desnoyers | 1502 | 3.89% | 9 | 0.71% |
| Frédéric Weisbecker | 1108 | 2.87% | 39 | 3.09% |
| Tejun Heo | 1076 | 2.79% | 27 | 2.14% |
| Thomas Gleixner | 1025 | 2.66% | 52 | 4.11% |
| Ingo Molnar | 953 | 2.47% | 84 | 6.65% |
| Paul Turner | 760 | 1.97% | 12 | 0.95% |
| Waiman Long | 641 | 1.66% | 10 | 0.79% |
| Qais Yousef | 558 | 1.45% | 18 | 1.42% |
| Will Deacon | 470 | 1.22% | 8 | 0.63% |
| Srivatsa Vaddagiri | 455 | 1.18% | 7 | 0.55% |
| Josh Don | 404 | 1.05% | 3 | 0.24% |
| Paul E. McKenney | 293 | 0.76% | 14 | 1.11% |
| Huaixin Chang | 283 | 0.73% | 3 | 0.24% |
| Mel Gorman | 280 | 0.73% | 14 | 1.11% |
| Juri Lelli | 275 | 0.71% | 18 | 1.42% |
| Valentin Schneider | 265 | 0.69% | 18 | 1.42% |
| Vincent Guittot | 253 | 0.66% | 18 | 1.42% |
| Andi Kleen | 246 | 0.64% | 7 | 0.55% |
| Christian Göttsche | 236 | 0.61% | 1 | 0.08% |
| Steven Rostedt | 232 | 0.60% | 12 | 0.95% |
| Dietmar Eggemann | 213 | 0.55% | 7 | 0.55% |
| Josh Poimboeuf | 191 | 0.50% | 6 | 0.47% |
| Nico Pitre | 190 | 0.49% | 6 | 0.47% |
| Andrew Morton | 187 | 0.48% | 22 | 1.74% |
| Linus Torvalds | 150 | 0.39% | 16 | 1.27% |
| Quentin Perret | 145 | 0.38% | 6 | 0.47% |
| Chengming Zhou | 142 | 0.37% | 6 | 0.47% |
| Kirill V Tkhai | 141 | 0.37% | 12 | 0.95% |
| Linus Torvalds (pre-git) | 138 | 0.36% | 23 | 1.82% |
| Mike Galbraith | 137 | 0.36% | 14 | 1.11% |
| Zhen Ni | 135 | 0.35% | 3 | 0.24% |
| Hao Jia | 133 | 0.34% | 6 | 0.47% |
| Venkatesh Pallipadi | 129 | 0.33% | 7 | 0.55% |
| Huang Ying | 126 | 0.33% | 3 | 0.24% |
| Wanpeng Li | 123 | 0.32% | 6 | 0.47% |
| Phil Auld | 112 | 0.29% | 3 | 0.24% |
| Gregory Haskins | 111 | 0.29% | 5 | 0.40% |
| Joel A Fernandes | 110 | 0.29% | 3 | 0.24% |
| rodrigosiqueira | 106 | 0.27% | 1 | 0.08% |
| Nikhil P Rao | 105 | 0.27% | 4 | 0.32% |
| Konstantin Khlebnikov | 103 | 0.27% | 5 | 0.40% |
| Alexey Dobriyan | 99 | 0.26% | 5 | 0.40% |
| Zhang Qiao | 92 | 0.24% | 1 | 0.08% |
| Al Viro | 83 | 0.22% | 3 | 0.24% |
| Kees Cook | 80 | 0.21% | 3 | 0.24% |
| Nicholas Piggin | 77 | 0.20% | 12 | 0.95% |
| Giovanni Gherdovich | 77 | 0.20% | 2 | 0.16% |
| Davidlohr Bueso A | 70 | 0.18% | 4 | 0.32% |
| Daniel Vetter | 69 | 0.18% | 1 | 0.08% |
| Viresh Kumar | 63 | 0.16% | 4 | 0.32% |
| Oleg Nesterov | 63 | 0.16% | 11 | 0.87% |
| Johannes Weiner | 60 | 0.16% | 2 | 0.16% |
| Mathias Krause | 58 | 0.15% | 1 | 0.08% |
| Zhen Lei | 58 | 0.15% | 3 | 0.24% |
| Jens Axboe | 57 | 0.15% | 4 | 0.32% |
| Ben Gardon | 53 | 0.14% | 1 | 0.08% |
| Yue haibing | 53 | 0.14% | 2 | 0.16% |
| Matt Fleming | 52 | 0.13% | 3 | 0.24% |
| Yun Wang | 49 | 0.13% | 1 | 0.08% |
| Mathieu J. Poirier | 49 | 0.13% | 1 | 0.08% |
| Chi Wu | 47 | 0.12% | 1 | 0.08% |
| Sebastian Andrzej Siewior | 46 | 0.12% | 8 | 0.63% |
| Dhaval Giani | 45 | 0.12% | 6 | 0.47% |
| Eric W. Biedermann | 42 | 0.11% | 12 | 0.95% |
| Chen Yu | 42 | 0.11% | 1 | 0.08% |
| Cruz Zhao | 41 | 0.11% | 1 | 0.08% |
| Vegard Nossum | 40 | 0.10% | 2 | 0.16% |
| Paul Menage | 38 | 0.10% | 6 | 0.47% |
| Chuansheng Liu | 38 | 0.10% | 1 | 0.08% |
| Rohit Jain | 38 | 0.10% | 2 | 0.16% |
| Rusty Russell | 36 | 0.09% | 11 | 0.87% |
| Byungchul Park | 34 | 0.09% | 3 | 0.24% |
| Joonwoo Park | 33 | 0.09% | 1 | 0.08% |
| Barry Song | 33 | 0.09% | 1 | 0.08% |
| Glauber de Oliveira Costa | 32 | 0.08% | 3 | 0.24% |
| Li Zefan | 31 | 0.08% | 1 | 0.08% |
| Andrew Lutomirski | 31 | 0.08% | 7 | 0.55% |
| Art Haas | 30 | 0.08% | 1 | 0.08% |
| Roland McGrath | 29 | 0.08% | 3 | 0.24% |
| Anton Blanchard | 28 | 0.07% | 2 | 0.16% |
| Yafang Shao | 27 | 0.07% | 1 | 0.08% |
| Daniel Lezcano | 26 | 0.07% | 2 | 0.16% |
| Srikar Dronamraju | 24 | 0.06% | 3 | 0.24% |
| Tianchen Ding | 23 | 0.06% | 3 | 0.24% |
| Heiko Carstens | 23 | 0.06% | 3 | 0.24% |
| Rik Van Riel | 23 | 0.06% | 3 | 0.24% |
| Vineeth Pillai | 23 | 0.06% | 1 | 0.08% |
| Kefeng Wang | 23 | 0.06% | 1 | 0.08% |
| Dean Nelson | 22 | 0.06% | 1 | 0.08% |
| Thara Gopinath | 22 | 0.06% | 2 | 0.16% |
| Chris Zankel | 21 | 0.05% | 1 | 0.08% |
| Suresh B. Siddha | 21 | 0.05% | 6 | 0.47% |
| KeMeng Shi | 20 | 0.05% | 1 | 0.08% |
| Scott Wood | 20 | 0.05% | 2 | 0.16% |
| Eric Dumazet | 19 | 0.05% | 2 | 0.16% |
| Peter Williams | 18 | 0.05% | 1 | 0.08% |
| Ben Segall | 18 | 0.05% | 1 | 0.08% |
| Tetsuo Handa | 18 | 0.05% | 2 | 0.16% |
| Hiroshi Shimamoto | 18 | 0.05% | 2 | 0.16% |
| xiaofeng.yan | 17 | 0.04% | 1 | 0.08% |
| Greg Kroah-Hartman | 17 | 0.04% | 2 | 0.16% |
| Chris Wilson | 16 | 0.04% | 1 | 0.08% |
| Vincent Donnefort | 16 | 0.04% | 3 | 0.24% |
| Mike Travis | 15 | 0.04% | 3 | 0.24% |
| Christoph Hellwig | 15 | 0.04% | 3 | 0.24% |
| Adrian Bunk | 15 | 0.04% | 1 | 0.08% |
| Hideaki Yoshifuji / 吉藤英明 | 14 | 0.04% | 2 | 0.16% |
| Wei Yang | 14 | 0.04% | 1 | 0.08% |
| Seth Jennings | 13 | 0.03% | 1 | 0.08% |
| Aleksa Sarai | 13 | 0.03% | 1 | 0.08% |
| Yuan ZhaoXiong | 13 | 0.03% | 1 | 0.08% |
| Avi Kivity | 13 | 0.03% | 1 | 0.08% |
| Rafael J. Wysocki | 13 | 0.03% | 3 | 0.24% |
| Chris Metcalf | 12 | 0.03% | 1 | 0.08% |
| Uros Bizjak | 12 | 0.03% | 2 | 0.16% |
| Paul Jackson | 12 | 0.03% | 2 | 0.16% |
| Henrik Austad | 12 | 0.03% | 1 | 0.08% |
| Srivatsa S. Bhat | 12 | 0.03% | 3 | 0.24% |
| Sami Tolvanen | 12 | 0.03% | 2 | 0.16% |
| Jason Baron | 12 | 0.03% | 2 | 0.16% |
| Tal Zussman | 11 | 0.03% | 1 | 0.08% |
| Tang Chen | 10 | 0.03% | 2 | 0.16% |
| Luca Abeni | 10 | 0.03% | 4 | 0.32% |
| Dominik Brodowski | 10 | 0.03% | 1 | 0.08% |
| Hidetoshi Seto | 10 | 0.03% | 2 | 0.16% |
| Martin Schwidefsky | 10 | 0.03% | 3 | 0.24% |
| Yacine Belkadi | 10 | 0.03% | 1 | 0.08% |
| Yang Yang | 9 | 0.02% | 1 | 0.08% |
| David Howells | 9 | 0.02% | 2 | 0.16% |
| Catalin Marinas | 9 | 0.02% | 2 | 0.16% |
| Robert Love | 9 | 0.02% | 1 | 0.08% |
| Con Kolivas | 9 | 0.02% | 1 | 0.08% |
| Rick Lindsley | 9 | 0.02% | 1 | 0.08% |
| Milton D. Miller II | 9 | 0.02% | 2 | 0.16% |
| Vatika Harlalka | 9 | 0.02% | 1 | 0.08% |
| Yair Podemsky | 9 | 0.02% | 1 | 0.08% |
| John Keeping | 8 | 0.02% | 1 | 0.08% |
| Alex Shi | 8 | 0.02% | 1 | 0.08% |
| Arnaldo Carvalho de Melo | 8 | 0.02% | 1 | 0.08% |
| Cheng Chao | 8 | 0.02% | 1 | 0.08% |
| Dmitry Adamushko | 8 | 0.02% | 2 | 0.16% |
| Jason Wessel | 8 | 0.02% | 1 | 0.08% |
| Brian Silverman | 7 | 0.02% | 1 | 0.08% |
| Clark Williams | 7 | 0.02% | 1 | 0.08% |
| Chris Wright | 7 | 0.02% | 1 | 0.08% |
| Stanislaw Gruszka | 7 | 0.02% | 1 | 0.08% |
| Yu Zhao | 7 | 0.02% | 1 | 0.08% |
| Michael S. Tsirkin | 7 | 0.02% | 1 | 0.08% |
| Maksim Krasnyanskiy | 7 | 0.02% | 3 | 0.24% |
| Arnd Bergmann | 7 | 0.02% | 3 | 0.24% |
| Matt Mackall | 6 | 0.02% | 1 | 0.08% |
| Andrey Vagin | 6 | 0.02% | 2 | 0.16% |
| Randy Dunlap | 6 | 0.02% | 3 | 0.24% |
| Matthew Wilcox | 6 | 0.02% | 2 | 0.16% |
| Daniel Bristot de Oliveira | 6 | 0.02% | 2 | 0.16% |
| Dmitry Safonov | 6 | 0.02% | 3 | 0.24% |
| Yajun Deng | 6 | 0.02% | 1 | 0.08% |
| Jason Low | 6 | 0.02% | 2 | 0.16% |
| Motohiro Kosaki | 6 | 0.02% | 2 | 0.16% |
| Lennart Poettering | 6 | 0.02% | 1 | 0.08% |
| Balbir Singh | 6 | 0.02% | 2 | 0.16% |
| Wang Jinchao | 6 | 0.02% | 1 | 0.08% |
| Anna-Maria Gleixner | 6 | 0.02% | 1 | 0.08% |
| Andrea Arcangeli | 5 | 0.01% | 1 | 0.08% |
| Christian Ehrhardt | 5 | 0.01% | 2 | 0.16% |
| Christoph Lameter | 5 | 0.01% | 3 | 0.24% |
| Rabin Vincent | 5 | 0.01% | 1 | 0.08% |
| Pavel Machek | 5 | 0.01% | 1 | 0.08% |
| Eric Sandeen | 5 | 0.01% | 1 | 0.08% |
| Jann Horn | 5 | 0.01% | 1 | 0.08% |
| Qian Cai | 5 | 0.01% | 1 | 0.08% |
| Dinakar Guniguntala | 5 | 0.01% | 1 | 0.08% |
| Namhyung Kim | 5 | 0.01% | 1 | 0.08% |
| David P. Quigley | 5 | 0.01% | 1 | 0.08% |
| Dongsheng Yang | 5 | 0.01% | 3 | 0.24% |
| Morten Rasmussen | 5 | 0.01% | 1 | 0.08% |
| Andrea Parri | 5 | 0.01% | 4 | 0.32% |
| Alex Kelly | 4 | 0.01% | 1 | 0.08% |
| Alexei Starovoitov | 4 | 0.01% | 1 | 0.08% |
| Nathan T. Lynch | 4 | 0.01% | 2 | 0.16% |
| Andrey Ryabinin | 4 | 0.01% | 1 | 0.08% |
| Mike Waychison | 4 | 0.01% | 1 | 0.08% |
| Ankita Garg | 4 | 0.01% | 1 | 0.08% |
| Libing Zhou | 4 | 0.01% | 1 | 0.08% |
| Yong Zhang | 4 | 0.01% | 2 | 0.16% |
| Måns Rullgård | 4 | 0.01% | 1 | 0.08% |
| Rakib Mullick | 3 | 0.01% | 2 | 0.16% |
| Matteo Croce | 3 | 0.01% | 1 | 0.08% |
| Elliot Berman | 3 | 0.01% | 1 | 0.08% |
| Patrick Mochel | 3 | 0.01% | 1 | 0.08% |
| Kirill Korotaev | 3 | 0.01% | 1 | 0.08% |
| Paul Mackerras | 3 | 0.01% | 1 | 0.08% |
| Harvey Harrison | 3 | 0.01% | 1 | 0.08% |
| Masami Hiramatsu | 3 | 0.01% | 2 | 0.16% |
| Dmitriy Vyukov | 3 | 0.01% | 1 | 0.08% |
| Tim Chen | 3 | 0.01% | 1 | 0.08% |
| Nadia Yvette Chambers | 3 | 0.01% | 1 | 0.08% |
| Xie XiuQi | 3 | 0.01% | 1 | 0.08% |
| Frank Mayhar | 3 | 0.01% | 1 | 0.08% |
| Xiaotian Feng | 3 | 0.01% | 1 | 0.08% |
| Laurent Vivier | 3 | 0.01% | 1 | 0.08% |
| Paul Burton | 3 | 0.01% | 1 | 0.08% |
| Neil Brown | 3 | 0.01% | 1 | 0.08% |
| Steven Cole | 2 | 0.01% | 1 | 0.08% |
| Ard Biesheuvel | 2 | 0.01% | 1 | 0.08% |
| Jeremy Fitzhardinge | 2 | 0.01% | 2 | 0.16% |
| Gustavo A. R. Silva | 2 | 0.01% | 1 | 0.08% |
| Olivier Croquette | 2 | 0.01% | 1 | 0.08% |
| Carsten Emde | 2 | 0.01% | 1 | 0.08% |
| Alan Cox | 2 | 0.01% | 1 | 0.08% |
| Jessica Yu | 2 | 0.01% | 1 | 0.08% |
| Miao Xie | 2 | 0.01% | 1 | 0.08% |
| Shigeru Yoshida | 2 | 0.01% | 1 | 0.08% |
| Joe Korty | 2 | 0.01% | 1 | 0.08% |
| Jack Steiner | 2 | 0.01% | 1 | 0.08% |
| Hitoshi Mitake | 2 | 0.01% | 1 | 0.08% |
| Jiri Kosina | 2 | 0.01% | 1 | 0.08% |
| Tadeusz Struk | 2 | 0.01% | 1 | 0.08% |
| Josh Snyder | 2 | 0.01% | 1 | 0.08% |
| Arjan van de Ven | 2 | 0.01% | 1 | 0.08% |
| David Rientjes | 2 | 0.01% | 1 | 0.08% |
| Delyan Kratunov | 2 | 0.01% | 1 | 0.08% |
| Eduard - Gabriel Munteanu | 2 | 0.01% | 1 | 0.08% |
| Darren Hart | 2 | 0.01% | 1 | 0.08% |
| Marcelo Tosatti | 2 | 0.01% | 1 | 0.08% |
| Aaron Tomlin | 2 | 0.01% | 1 | 0.08% |
| Ryota Ozaki | 2 | 0.01% | 1 | 0.08% |
| Bron Gondwana | 2 | 0.01% | 1 | 0.08% |
| Zhihui Zhang | 2 | 0.01% | 1 | 0.08% |
| Gautham R. Shenoy | 2 | 0.01% | 2 | 0.16% |
| Pavel Emelyanov | 1 | 0.00% | 1 | 0.08% |
| Masahiro Yamada | 1 | 0.00% | 1 | 0.08% |
| Christian Bornträger | 1 | 0.00% | 1 | 0.08% |
| Luis Henriques | 1 | 0.00% | 1 | 0.08% |
| Richard Weinberger | 1 | 0.00% | 1 | 0.08% |
| Satyam Sharma | 1 | 0.00% | 1 | 0.08% |
| Masanari Iida | 1 | 0.00% | 1 | 0.08% |
| Yury Norov | 1 | 0.00% | 1 | 0.08% |
| Simon Kågström | 1 | 0.00% | 1 | 0.08% |
| Harald Gustafsson | 1 | 0.00% | 1 | 0.08% |
| Kazuto Miyoshi | 1 | 0.00% | 1 | 0.08% |
| Shailabh Nagar | 1 | 0.00% | 1 | 0.08% |
| Hsiang Kao | 1 | 0.00% | 1 | 0.08% |
| Sha Zhengju | 1 | 0.00% | 1 | 0.08% |
| Dominik Dingel | 1 | 0.00% | 1 | 0.08% |
| Davide Libenzi | 1 | 0.00% | 1 | 0.08% |
| Geliang Tang | 1 | 0.00% | 1 | 0.08% |
| Mirco Tischler | 1 | 0.00% | 1 | 0.08% |
| Shrikanth Hegde | 1 | 0.00% | 1 | 0.08% |
| Alex Thorlton | 1 | 0.00% | 1 | 0.08% |
| Peter Xu | 1 | 0.00% | 1 | 0.08% |
| Octavian Purdila | 1 | 0.00% | 1 | 0.08% |
| Joel Savitz | 1 | 0.00% | 1 | 0.08% |
| Zachary Amsden | 1 | 0.00% | 1 | 0.08% |
| Yanmin Zhang | 1 | 0.00% | 1 | 0.08% |
| Peter Oskolkov | 1 | 0.00% | 1 | 0.08% |
| Total | 38579 | 1264 |
// SPDX-License-Identifier: GPL-2.0-only /* * kernel/sched/core.c * * Core kernel scheduler code and related syscalls * * Copyright (C) 1991-2002 Linus Torvalds */ #include <linux/highmem.h> #include <linux/hrtimer_api.h> #include <linux/ktime_api.h> #include <linux/sched/signal.h> #include <linux/syscalls_api.h> #include <linux/debug_locks.h> #include <linux/prefetch.h> #include <linux/capability.h> #include <linux/pgtable_api.h> #include <linux/wait_bit.h> #include <linux/jiffies.h> #include <linux/spinlock_api.h> #include <linux/cpumask_api.h> #include <linux/lockdep_api.h> #include <linux/hardirq.h> #include <linux/softirq.h> #include <linux/refcount_api.h> #include <linux/topology.h> #include <linux/sched/clock.h> #include <linux/sched/cond_resched.h> #include <linux/sched/cputime.h> #include <linux/sched/debug.h> #include <linux/sched/hotplug.h> #include <linux/sched/init.h> #include <linux/sched/isolation.h> #include <linux/sched/loadavg.h> #include <linux/sched/mm.h> #include <linux/sched/nohz.h> #include <linux/sched/rseq_api.h> #include <linux/sched/rt.h> #include <linux/blkdev.h> #include <linux/context_tracking.h> #include <linux/cpuset.h> #include <linux/delayacct.h> #include <linux/init_task.h> #include <linux/interrupt.h> #include <linux/ioprio.h> #include <linux/kallsyms.h> #include <linux/kcov.h> #include <linux/kprobes.h> #include <linux/llist_api.h> #include <linux/mmu_context.h> #include <linux/mmzone.h> #include <linux/mutex_api.h> #include <linux/nmi.h> #include <linux/nospec.h> #include <linux/perf_event_api.h> #include <linux/profile.h> #include <linux/psi.h> #include <linux/rcuwait_api.h> #include <linux/rseq.h> #include <linux/sched/wake_q.h> #include <linux/scs.h> #include <linux/slab.h> #include <linux/syscalls.h> #include <linux/vtime.h> #include <linux/wait_api.h> #include <linux/workqueue_api.h> #ifdef CONFIG_PREEMPT_DYNAMIC # ifdef CONFIG_GENERIC_ENTRY # include <linux/entry-common.h> # endif #endif #include <uapi/linux/sched/types.h> #include <asm/irq_regs.h> #include <asm/switch_to.h> #include <asm/tlb.h> #define CREATE_TRACE_POINTS #include <linux/sched/rseq_api.h> #include <trace/events/sched.h> #include <trace/events/ipi.h> #undef CREATE_TRACE_POINTS #include "sched.h" #include "stats.h" #include "autogroup.h" #include "pelt.h" #include "smp.h" #include "stats.h" #include "../workqueue_internal.h" #include "../../io_uring/io-wq.h" #include "../smpboot.h" EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpu); EXPORT_TRACEPOINT_SYMBOL_GPL(ipi_send_cpumask); /* * Export tracepoints that act as a bare tracehook (ie: have no trace event * associated with them) to allow external modules to probe them. */ EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_cfs_tp); EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_rt_tp); EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_dl_tp); EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_irq_tp); EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_se_tp); EXPORT_TRACEPOINT_SYMBOL_GPL(pelt_thermal_tp); EXPORT_TRACEPOINT_SYMBOL_GPL(sched_cpu_capacity_tp); EXPORT_TRACEPOINT_SYMBOL_GPL(sched_overutilized_tp); EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_cfs_tp); EXPORT_TRACEPOINT_SYMBOL_GPL(sched_util_est_se_tp); EXPORT_TRACEPOINT_SYMBOL_GPL(sched_update_nr_running_tp); EXPORT_TRACEPOINT_SYMBOL_GPL(sched_compute_energy_tp); DEFINE_PER_CPU_SHARED_ALIGNED(struct rq, runqueues); #ifdef CONFIG_SCHED_DEBUG /* * Debugging: various feature bits * * If SCHED_DEBUG is disabled, each compilation unit has its own copy of * sysctl_sched_features, defined in sched.h, to allow constants propagation * at compile time and compiler optimization based on features default. */ #define SCHED_FEAT(name, enabled) \ (1UL << __SCHED_FEAT_##name) * enabled | const_debug unsigned int sysctl_sched_features = #include "features.h" 0; #undef SCHED_FEAT /* * Print a warning if need_resched is set for the given duration (if * LATENCY_WARN is enabled). * * If sysctl_resched_latency_warn_once is set, only one warning will be shown * per boot. */ __read_mostly int sysctl_resched_latency_warn_ms = 100; __read_mostly int sysctl_resched_latency_warn_once = 1; #endif /* CONFIG_SCHED_DEBUG */ /* * Number of tasks to iterate in a single balance run. * Limited because this is done with IRQs disabled. */ const_debug unsigned int sysctl_sched_nr_migrate = SCHED_NR_MIGRATE_BREAK; __read_mostly int scheduler_running; #ifdef CONFIG_SCHED_CORE DEFINE_STATIC_KEY_FALSE(__sched_core_enabled); /* kernel prio, less is more */ static inline int __task_prio(const struct task_struct *p) { if (p->sched_class == &stop_sched_class) /* trumps deadline */ return -2; if (rt_prio(p->prio)) /* includes deadline */ return p->prio; /* [-1, 99] */ if (p->sched_class == &idle_sched_class) return MAX_RT_PRIO + NICE_WIDTH; /* 140 */ return MAX_RT_PRIO + MAX_NICE; /* 120, squash fair */ } /* * l(a,b) * le(a,b) := !l(b,a) * g(a,b) := l(b,a) * ge(a,b) := !l(a,b) */ /* real prio, less is less */ static inline bool prio_less(const struct task_struct *a, const struct task_struct *b, bool in_fi) { int pa = __task_prio(a), pb = __task_prio(b); if (-pa < -pb) return true; if (-pb < -pa) return false; if (pa == -1) /* dl_prio() doesn't work because of stop_class above */ return !dl_time_before(a->dl.deadline, b->dl.deadline); if (pa == MAX_RT_PRIO + MAX_NICE) /* fair */ return cfs_prio_less(a, b, in_fi); return false; } static inline bool __sched_core_less(const struct task_struct *a, const struct task_struct *b) { if (a->core_cookie < b->core_cookie) return true; if (a->core_cookie > b->core_cookie) return false; /* flip prio, so high prio is leftmost */ if (prio_less(b, a, !!task_rq(a)->core->core_forceidle_count)) return true; return false; } #define __node_2_sc(node) rb_entry((node), struct task_struct, core_node) static inline bool rb_sched_core_less(struct rb_node *a, const struct rb_node *b) { return __sched_core_less(__node_2_sc(a), __node_2_sc(b)); } static inline int rb_sched_core_cmp(const void *key, const struct rb_node *node) { const struct task_struct *p = __node_2_sc(node); unsigned long cookie = (unsigned long)key; if (cookie < p->core_cookie) return -1; if (cookie > p->core_cookie) return 1; return 0; } void sched_core_enqueue(struct rq *rq, struct task_struct *p) { rq->core->core_task_seq++; if (!p->core_cookie) return; rb_add(&p->core_node, &rq->core_tree, rb_sched_core_less); } void sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { rq->core->core_task_seq++; if (sched_core_enqueued(p)) { rb_erase(&p->core_node, &rq->core_tree); RB_CLEAR_NODE(&p->core_node); } /* * Migrating the last task off the cpu, with the cpu in forced idle * state. Reschedule to create an accounting edge for forced idle, * and re-examine whether the core is still in forced idle state. */ if (!(flags & DEQUEUE_SAVE) && rq->nr_running == 1 && rq->core->core_forceidle_count && rq->curr == rq->idle) resched_curr(rq); } static int sched_task_is_throttled(struct task_struct *p, int cpu) { if (p->sched_class->task_is_throttled) return p->sched_class->task_is_throttled(p, cpu); return 0; } static struct task_struct *sched_core_next(struct task_struct *p, unsigned long cookie) { struct rb_node *node = &p->core_node; int cpu = task_cpu(p); do { node = rb_next(node); if (!node) return NULL; p = __node_2_sc(node); if (p->core_cookie != cookie) return NULL; } while (sched_task_is_throttled(p, cpu)); return p; } /* * Find left-most (aka, highest priority) and unthrottled task matching @cookie. * If no suitable task is found, NULL will be returned. */ static struct task_struct *sched_core_find(struct rq *rq, unsigned long cookie) { struct task_struct *p; struct rb_node *node; node = rb_find_first((void *)cookie, &rq->core_tree, rb_sched_core_cmp); if (!node) return NULL; p = __node_2_sc(node); if (!sched_task_is_throttled(p, rq->cpu)) return p; return sched_core_next(p, cookie); } /* * Magic required such that: * * raw_spin_rq_lock(rq); * ... * raw_spin_rq_unlock(rq); * * ends up locking and unlocking the _same_ lock, and all CPUs * always agree on what rq has what lock. * * XXX entirely possible to selectively enable cores, don't bother for now. */ static DEFINE_MUTEX(sched_core_mutex); static atomic_t sched_core_count; static struct cpumask sched_core_mask; static void sched_core_lock(int cpu, unsigned long *flags) { const struct cpumask *smt_mask = cpu_smt_mask(cpu); int t, i = 0; local_irq_save(*flags); for_each_cpu(t, smt_mask) raw_spin_lock_nested(&cpu_rq(t)->__lock, i++); } static void sched_core_unlock(int cpu, unsigned long *flags) { const struct cpumask *smt_mask = cpu_smt_mask(cpu); int t; for_each_cpu(t, smt_mask) raw_spin_unlock(&cpu_rq(t)->__lock); local_irq_restore(*flags); } static void __sched_core_flip(bool enabled) { unsigned long flags; int cpu, t; cpus_read_lock(); /* * Toggle the online cores, one by one. */ cpumask_copy(&sched_core_mask, cpu_online_mask); for_each_cpu(cpu, &sched_core_mask) { const struct cpumask *smt_mask = cpu_smt_mask(cpu); sched_core_lock(cpu, &flags); for_each_cpu(t, smt_mask) cpu_rq(t)->core_enabled = enabled; cpu_rq(cpu)->core->core_forceidle_start = 0; sched_core_unlock(cpu, &flags); cpumask_andnot(&sched_core_mask, &sched_core_mask, smt_mask); } /* * Toggle the offline CPUs. */ for_each_cpu_andnot(cpu, cpu_possible_mask, cpu_online_mask) cpu_rq(cpu)->core_enabled = enabled; cpus_read_unlock(); } static void sched_core_assert_empty(void) { int cpu; for_each_possible_cpu(cpu) WARN_ON_ONCE(!RB_EMPTY_ROOT(&cpu_rq(cpu)->core_tree)); } static void __sched_core_enable(void) { static_branch_enable(&__sched_core_enabled); /* * Ensure all previous instances of raw_spin_rq_*lock() have finished * and future ones will observe !sched_core_disabled(). */ synchronize_rcu(); __sched_core_flip(true); sched_core_assert_empty(); } static void __sched_core_disable(void) { sched_core_assert_empty(); __sched_core_flip(false); static_branch_disable(&__sched_core_enabled); } void sched_core_get(void) { if (atomic_inc_not_zero(&sched_core_count)) return; mutex_lock(&sched_core_mutex); if (!atomic_read(&sched_core_count)) __sched_core_enable(); smp_mb__before_atomic(); atomic_inc(&sched_core_count); mutex_unlock(&sched_core_mutex); } static void __sched_core_put(struct work_struct *work) { if (atomic_dec_and_mutex_lock(&sched_core_count, &sched_core_mutex)) { __sched_core_disable(); mutex_unlock(&sched_core_mutex); } } void sched_core_put(void) { static DECLARE_WORK(_work, __sched_core_put); /* * "There can be only one" * * Either this is the last one, or we don't actually need to do any * 'work'. If it is the last *again*, we rely on * WORK_STRUCT_PENDING_BIT. */ if (!atomic_add_unless(&sched_core_count, -1, 1)) schedule_work(&_work); } #else /* !CONFIG_SCHED_CORE */ static inline void sched_core_enqueue(struct rq *rq, struct task_struct *p) { } static inline void sched_core_dequeue(struct rq *rq, struct task_struct *p, int flags) { } #endif /* CONFIG_SCHED_CORE */ /* * Serialization rules: * * Lock order: * * p->pi_lock * rq->lock * hrtimer_cpu_base->lock (hrtimer_start() for bandwidth controls) * * rq1->lock * rq2->lock where: rq1 < rq2 * * Regular state: * * Normal scheduling state is serialized by rq->lock. __schedule() takes the * local CPU's rq->lock, it optionally removes the task from the runqueue and * always looks at the local rq data structures to find the most eligible task * to run next. * * Task enqueue is also under rq->lock, possibly taken from another CPU. * Wakeups from another LLC domain might use an IPI to transfer the enqueue to * the local CPU to avoid bouncing the runqueue state around [ see * ttwu_queue_wakelist() ] * * Task wakeup, specifically wakeups that involve migration, are horribly * complicated to avoid having to take two rq->locks. * * Special state: * * System-calls and anything external will use task_rq_lock() which acquires * both p->pi_lock and rq->lock. As a consequence the state they change is * stable while holding either lock: * * - sched_setaffinity()/ * set_cpus_allowed_ptr(): p->cpus_ptr, p->nr_cpus_allowed * - set_user_nice(): p->se.load, p->*prio * - __sched_setscheduler(): p->sched_class, p->policy, p->*prio, * p->se.load, p->rt_priority, * p->dl.dl_{runtime, deadline, period, flags, bw, density} * - sched_setnuma(): p->numa_preferred_nid * - sched_move_task(): p->sched_task_group * - uclamp_update_active() p->uclamp* * * p->state <- TASK_*: * * is changed locklessly using set_current_state(), __set_current_state() or * set_special_state(), see their respective comments, or by * try_to_wake_up(). This latter uses p->pi_lock to serialize against * concurrent self. * * p->on_rq <- { 0, 1 = TASK_ON_RQ_QUEUED, 2 = TASK_ON_RQ_MIGRATING }: * * is set by activate_task() and cleared by deactivate_task(), under * rq->lock. Non-zero indicates the task is runnable, the special * ON_RQ_MIGRATING state is used for migration without holding both * rq->locks. It indicates task_cpu() is not stable, see task_rq_lock(). * * p->on_cpu <- { 0, 1 }: * * is set by prepare_task() and cleared by finish_task() such that it will be * set before p is scheduled-in and cleared after p is scheduled-out, both * under rq->lock. Non-zero indicates the task is running on its CPU. * * [ The astute reader will observe that it is possible for two tasks on one * CPU to have ->on_cpu = 1 at the same time. ] * * task_cpu(p): is changed by set_task_cpu(), the rules are: * * - Don't call set_task_cpu() on a blocked task: * * We don't care what CPU we're not running on, this simplifies hotplug, * the CPU assignment of blocked tasks isn't required to be valid. * * - for try_to_wake_up(), called under p->pi_lock: * * This allows try_to_wake_up() to only take one rq->lock, see its comment. * * - for migration called under rq->lock: * [ see task_on_rq_migrating() in task_rq_lock() ] * * o move_queued_task() * o detach_task() * * - for migration called under double_rq_lock(): * * o __migrate_swap_task() * o push_rt_task() / pull_rt_task() * o push_dl_task() / pull_dl_task() * o dl_task_offline_migration() * */ void raw_spin_rq_lock_nested(struct rq *rq, int subclass) { raw_spinlock_t *lock; /* Matches synchronize_rcu() in __sched_core_enable() */ preempt_disable(); if (sched_core_disabled()) { raw_spin_lock_nested(&rq->__lock, subclass); /* preempt_count *MUST* be > 1 */ preempt_enable_no_resched(); return; } for (;;) { lock = __rq_lockp(rq); raw_spin_lock_nested(lock, subclass); if (likely(lock == __rq_lockp(rq))) { /* preempt_count *MUST* be > 1 */ preempt_enable_no_resched(); return; } raw_spin_unlock(lock); } } bool raw_spin_rq_trylock(struct rq *rq) { raw_spinlock_t *lock; bool ret; /* Matches synchronize_rcu() in __sched_core_enable() */ preempt_disable(); if (sched_core_disabled()) { ret = raw_spin_trylock(&rq->__lock); preempt_enable(); return ret; } for (;;) { lock = __rq_lockp(rq); ret = raw_spin_trylock(lock); if (!ret || (likely(lock == __rq_lockp(rq)))) { preempt_enable(); return ret; } raw_spin_unlock(lock); } } void raw_spin_rq_unlock(struct rq *rq) { raw_spin_unlock(rq_lockp(rq)); } #ifdef CONFIG_SMP /* * double_rq_lock - safely lock two runqueues */ void double_rq_lock(struct rq *rq1, struct rq *rq2) { lockdep_assert_irqs_disabled(); if (rq_order_less(rq2, rq1)) swap(rq1, rq2); raw_spin_rq_lock(rq1); if (__rq_lockp(rq1) != __rq_lockp(rq2)) raw_spin_rq_lock_nested(rq2, SINGLE_DEPTH_NESTING); double_rq_clock_clear_update(rq1, rq2); } #endif /* * __task_rq_lock - lock the rq @p resides on. */ struct rq *__task_rq_lock(struct task_struct *p, struct rq_flags *rf) __acquires(rq->lock) { struct rq *rq; lockdep_assert_held(&p->pi_lock); for (;;) { rq = task_rq(p); raw_spin_rq_lock(rq); if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) { rq_pin_lock(rq, rf); return rq; } raw_spin_rq_unlock(rq); while (unlikely(task_on_rq_migrating(p))) cpu_relax(); } } /* * task_rq_lock - lock p->pi_lock and lock the rq @p resides on. */ struct rq *task_rq_lock(struct task_struct *p, struct rq_flags *rf) __acquires(p->pi_lock) __acquires(rq->lock) { struct rq *rq; for (;;) { raw_spin_lock_irqsave(&p->pi_lock, rf->flags); rq = task_rq(p); raw_spin_rq_lock(rq); /* * move_queued_task() task_rq_lock() * * ACQUIRE (rq->lock) * [S] ->on_rq = MIGRATING [L] rq = task_rq() * WMB (__set_task_cpu()) ACQUIRE (rq->lock); * [S] ->cpu = new_cpu [L] task_rq() * [L] ->on_rq * RELEASE (rq->lock) * * If we observe the old CPU in task_rq_lock(), the acquire of * the old rq->lock will fully serialize against the stores. * * If we observe the new CPU in task_rq_lock(), the address * dependency headed by '[L] rq = task_rq()' and the acquire * will pair with the WMB to ensure we then also see migrating. */ if (likely(rq == task_rq(p) && !task_on_rq_migrating(p))) { rq_pin_lock(rq, rf); return rq; } raw_spin_rq_unlock(rq); raw_spin_unlock_irqrestore(&p->pi_lock, rf->flags); while (unlikely(task_on_rq_migrating(p))) cpu_relax(); } } /* * RQ-clock updating methods: */ static void update_rq_clock_task(struct rq *rq, s64 delta) { /* * In theory, the compile should just see 0 here, and optimize out the call * to sched_rt_avg_update. But I don't trust it... */ s64 __maybe_unused steal = 0, irq_delta = 0; #ifdef CONFIG_IRQ_TIME_ACCOUNTING irq_delta = irq_time_read(cpu_of(rq)) - rq->prev_irq_time; /* * Since irq_time is only updated on {soft,}irq_exit, we might run into * this case when a previous update_rq_clock() happened inside a * {soft,}irq region. * * When this happens, we stop ->clock_task and only update the * prev_irq_time stamp to account for the part that fit, so that a next * update will consume the rest. This ensures ->clock_task is * monotonic. * * It does however cause some slight miss-attribution of {soft,}irq * time, a more accurate solution would be to update the irq_time using * the current rq->clock timestamp, except that would require using * atomic ops. */ if (irq_delta > delta) irq_delta = delta; rq->prev_irq_time += irq_delta; delta -= irq_delta; psi_account_irqtime(rq->curr, irq_delta); delayacct_irq(rq->curr, irq_delta); #endif #ifdef CONFIG_PARAVIRT_TIME_ACCOUNTING if (static_key_false((¶virt_steal_rq_enabled))) { steal = paravirt_steal_clock(cpu_of(rq)); steal -= rq->prev_steal_time_rq; if (unlikely(steal > delta)) steal = delta; rq->prev_steal_time_rq += steal; delta -= steal; } #endif rq->clock_task += delta; #ifdef CONFIG_HAVE_SCHED_AVG_IRQ if ((irq_delta + steal) && sched_feat(NONTASK_CAPACITY)) update_irq_load_avg(rq, irq_delta + steal); #endif update_rq_clock_pelt(rq, delta); } void update_rq_clock(struct rq *rq) { s64 delta; lockdep_assert_rq_held(rq); if (rq->clock_update_flags & RQCF_ACT_SKIP) return; #ifdef CONFIG_SCHED_DEBUG if (sched_feat(WARN_DOUBLE_CLOCK)) SCHED_WARN_ON(rq->clock_update_flags & RQCF_UPDATED); rq->clock_update_flags |= RQCF_UPDATED; #endif delta = sched_clock_cpu(cpu_of(rq)) - rq->clock; if (delta < 0) return; rq->clock += delta; update_rq_clock_task(rq, delta); } #ifdef CONFIG_SCHED_HRTICK /* * Use HR-timers to deliver accurate preemption points. */ static void hrtick_clear(struct rq *rq) { if (hrtimer_active(&rq->hrtick_timer)) hrtimer_cancel(&rq->hrtick_timer); } /* * High-resolution timer tick. * Runs from hardirq context with interrupts disabled. */ static enum hrtimer_restart hrtick(struct hrtimer *timer) { struct rq *rq = container_of(timer, struct rq, hrtick_timer); struct rq_flags rf; WARN_ON_ONCE(cpu_of(rq) != smp_processor_id()); rq_lock(rq, &rf); update_rq_clock(rq); rq->curr->sched_class->task_tick(rq, rq->curr, 1); rq_unlock(rq, &rf); return HRTIMER_NORESTART; } #ifdef CONFIG_SMP static void __hrtick_restart(struct rq *rq) { struct hrtimer *timer = &rq->hrtick_timer; ktime_t time = rq->hrtick_time; hrtimer_start(timer, time, HRTIMER_MODE_ABS_PINNED_HARD); } /* * called from hardirq (IPI) context */ static void __hrtick_start(void *arg) { struct rq *rq = arg; struct rq_flags rf; rq_lock(rq, &rf); __hrtick_restart(rq); rq_unlock(rq, &rf); } /* * Called to set the hrtick timer state. * * called with rq->lock held and irqs disabled */ void hrtick_start(struct rq *rq, u64 delay) { struct hrtimer *timer = &rq->hrtick_timer; s64 delta; /* * Don't schedule slices shorter than 10000ns, that just * doesn't make sense and can cause timer DoS. */ delta = max_t(s64, delay, 10000LL); rq->hrtick_time = ktime_add_ns(timer->base->get_time(), delta); if (rq == this_rq()) __hrtick_restart(rq); else smp_call_function_single_async(cpu_of(rq), &rq->hrtick_csd); } #else /* * Called to set the hrtick timer state. * * called with rq->lock held and irqs disabled */ void hrtick_start(struct rq *rq, u64 delay) { /* * Don't schedule slices shorter than 10000ns, that just * doesn't make sense. Rely on vruntime for fairness. */ delay = max_t(u64, delay, 10000LL); hrtimer_start(&rq->hrtick_timer, ns_to_ktime(delay), HRTIMER_MODE_REL_PINNED_HARD); } #endif /* CONFIG_SMP */ static void hrtick_rq_init(struct rq *rq) { #ifdef CONFIG_SMP INIT_CSD(&rq->hrtick_csd, __hrtick_start, rq); #endif hrtimer_init(&rq->hrtick_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL_HARD); rq->hrtick_timer.function = hrtick; } #else /* CONFIG_SCHED_HRTICK */ static inline void hrtick_clear(struct rq *rq) { } static inline void hrtick_rq_init(struct rq *rq) { } #endif /* CONFIG_SCHED_HRTICK */ /* * cmpxchg based fetch_or, macro so it works for different integer types */ #define fetch_or(ptr, mask) \ ({ \ typeof(ptr) _ptr = (ptr); \ typeof(mask) _mask = (mask); \ typeof(*_ptr) _val = *_ptr; \ \ do { \ } while (!try_cmpxchg(_ptr, &_val, _val | _mask)); \ _val; \ }) #if defined(CONFIG_SMP) && defined(TIF_POLLING_NRFLAG) /* * Atomically set TIF_NEED_RESCHED and test for TIF_POLLING_NRFLAG, * this avoids any races wrt polling state changes and thereby avoids * spurious IPIs. */ static inline bool set_nr_and_not_polling(struct task_struct *p) { struct thread_info *ti = task_thread_info(p); return !(fetch_or(&ti->flags, _TIF_NEED_RESCHED) & _TIF_POLLING_NRFLAG); } /* * Atomically set TIF_NEED_RESCHED if TIF_POLLING_NRFLAG is set. * * If this returns true, then the idle task promises to call * sched_ttwu_pending() and reschedule soon. */ static bool set_nr_if_polling(struct task_struct *p) { struct thread_info *ti = task_thread_info(p); typeof(ti->flags) val = READ_ONCE(ti->flags); do { if (!(val & _TIF_POLLING_NRFLAG)) return false; if (val & _TIF_NEED_RESCHED) return true; } while (!try_cmpxchg(&ti->flags, &val, val | _TIF_NEED_RESCHED)); return true; } #else static inline bool set_nr_and_not_polling(struct task_struct *p) { set_tsk_need_resched(p); return true; } #ifdef CONFIG_SMP static inline bool set_nr_if_polling(struct task_struct *p) { return false; } #endif #endif static bool __wake_q_add(struct wake_q_head *head, struct task_struct *task) { struct wake_q_node *node = &task->wake_q; /* * Atomically grab the task, if ->wake_q is !nil already it means * it's already queued (either by us or someone else) and will get the * wakeup due to that. * * In order to ensure that a pending wakeup will observe our pending * state, even in the failed case, an explicit smp_mb() must be used. */ smp_mb__before_atomic(); if (unlikely(cmpxchg_relaxed(&node->next, NULL, WAKE_Q_TAIL))) return false; /* * The head is context local, there can be no concurrency. */ *head->lastp = node; head->lastp = &node->next; return true; } /** * wake_q_add() - queue a wakeup for 'later' waking. * @head: the wake_q_head to add @task to * @task: the task to queue for 'later' wakeup * * Queue a task for later wakeup, most likely by the wake_up_q() call in the * same context, _HOWEVER_ this is not guaranteed, the wakeup can come * instantly. * * This function must be used as-if it were wake_up_process(); IOW the task * must be ready to be woken at this location. */ void wake_q_add(struct wake_q_head *head, struct task_struct *task) { if (__wake_q_add(head, task)) get_task_struct(task); } /** * wake_q_add_safe() - safely queue a wakeup for 'later' waking. * @head: the wake_q_head to add @task to * @task: the task to queue for 'later' wakeup * * Queue a task for later wakeup, most likely by the wake_up_q() call in the * same context, _HOWEVER_ this is not guaranteed, the wakeup can come * instantly. * * This function must be used as-if it were wake_up_process(); IOW the task * must be ready to be woken at this location. * * This function is essentially a task-safe equivalent to wake_q_add(). Callers * that already hold reference to @task can call the 'safe' version and trust * wake_q to do the right thing depending whether or not the @task is already * queued for wakeup. */ void wake_q_add_safe(struct wake_q_head *head, struct task_struct *task) { if (!__wake_q_add(head, task)) put_task_struct(task); } void wake_up_q(struct wake_q_head *head) { struct wake_q_node *node = head->first; while (node != WAKE_Q_TAIL) { struct task_struct *task; task = container_of(node, struct task_struct, wake_q); /* Task can safely be re-inserted now: */ node = node->next; task->wake_q.next = NULL; /* * wake_up_process() executes a full barrier, which pairs with * the queueing in wake_q_add() so as not to miss wakeups. */ wake_up_process(task); put_task_struct(task); } } /* * resched_curr - mark rq's current task 'to be rescheduled now'. * * On UP this means the setting of the need_resched flag, on SMP it * might also involve a cross-CPU call to trigger the scheduler on * the target CPU. */ void resched_curr(struct rq *rq) { struct task_struct *curr = rq->curr; int cpu; lockdep_assert_rq_held(rq); if (test_tsk_need_resched(curr)) return; cpu = cpu_of(rq); if (cpu == smp_processor_id()) { set_tsk_need_resched(curr); set_preempt_need_resched(); return; } if (set_nr_and_not_polling(curr)) smp_send_reschedule(cpu); else trace_sched_wake_idle_without_ipi(cpu); } void resched_cpu(int cpu) { struct rq *rq = cpu_rq(cpu); unsigned long flags; raw_spin_rq_lock_irqsave(rq, flags); if (cpu_online(cpu) || cpu == smp_processor_id()) resched_curr(rq); raw_spin_rq_unlock_irqrestore(rq, flags); } #ifdef CONFIG_SMP #ifdef CONFIG_NO_HZ_COMMON /* * In the semi idle case, use the nearest busy CPU for migrating timers * from an idle CPU. This is good for power-savings. * * We don't do similar optimization for completely idle system, as * selecting an idle CPU will add more delays to the timers than intended * (as that CPU's timer base may not be uptodate wrt jiffies etc). */ int get_nohz_timer_target(void) { int i, cpu = smp_processor_id(), default_cpu = -1; struct sched_domain *sd; const struct cpumask *hk_mask; if (housekeeping_cpu(cpu, HK_TYPE_TIMER)) { if (!idle_cpu(cpu)) return cpu; default_cpu = cpu; } hk_mask = housekeeping_cpumask(HK_TYPE_TIMER); guard(rcu)(); for_each_domain(cpu, sd) { for_each_cpu_and(i, sched_domain_span(sd), hk_mask) { if (cpu == i) continue; if (!idle_cpu(i)) return i; } } if (default_cpu == -1) default_cpu = housekeeping_any_cpu(HK_TYPE_TIMER); return default_cpu; } /* * When add_timer_on() enqueues a timer into the timer wheel of an * idle CPU then this timer might expire before the next timer event * which is scheduled to wake up that CPU. In case of a completely * idle system the next event might even be infinite time into the * future. wake_up_idle_cpu() ensures that the CPU is woken up and * leaves the inner idle loop so the newly added timer is taken into * account when the CPU goes back to idle and evaluates the timer * wheel for the next timer event. */ static void wake_up_idle_cpu(int cpu) { struct rq *rq = cpu_rq(cpu); if (cpu == smp_processor_id()) return; /* * Set TIF_NEED_RESCHED and send an IPI if in the non-polling * part of the idle loop. This forces an exit from the idle loop * and a round trip to schedule(). Now this could be optimized * because a simple new idle loop iteration is enough to * re-evaluate the next tick. Provided some re-ordering of tick * nohz functions that would need to follow TIF_NR_POLLING * clearing: * * - On most archs, a simple fetch_or on ti::flags with a * "0" value would be enough to know if an IPI needs to be sent. * * - x86 needs to perform a last need_resched() check between * monitor and mwait which doesn't take timers into account. * There a dedicated TIF_TIMER flag would be required to * fetch_or here and be checked along with TIF_NEED_RESCHED * before mwait(). * * However, remote timer enqueue is not such a frequent event * and testing of the above solutions didn't appear to report * much benefits. */ if (set_nr_and_not_polling(rq->idle)) smp_send_reschedule(cpu); else trace_sched_wake_idle_without_ipi(cpu); } static bool wake_up_full_nohz_cpu(int cpu) { /* * We just need the target to call irq_exit() and re-evaluate * the next tick. The nohz full kick at least implies that. * If needed we can still optimize that later with an * empty IRQ. */ if (cpu_is_offline(cpu)) return true; /* Don't try to wake offline CPUs. */ if (tick_nohz_full_cpu(cpu)) { if (cpu != smp_processor_id() || tick_nohz_tick_stopped()) tick_nohz_full_kick_cpu(cpu); return true; } return false; } /* * Wake up the specified CPU. If the CPU is going offline, it is the * caller's responsibility to deal with the lost wakeup, for example, * by hooking into the CPU_DEAD notifier like timers and hrtimers do. */ void wake_up_nohz_cpu(int cpu) { if (!wake_up_full_nohz_cpu(cpu)) wake_up_idle_cpu(cpu); } static void nohz_csd_func(void *info) { struct rq *rq = info; int cpu = cpu_of(rq); unsigned int flags; /* * Release the rq::nohz_csd. */ flags = atomic_fetch_andnot(NOHZ_KICK_MASK | NOHZ_NEWILB_KICK, nohz_flags(cpu)); WARN_ON(!(flags & NOHZ_KICK_MASK)); rq->idle_balance = idle_cpu(cpu); if (rq->idle_balance && !need_resched()) { rq->nohz_idle_balance = flags; raise_softirq_irqoff(SCHED_SOFTIRQ); } } #endif /* CONFIG_NO_HZ_COMMON */ #ifdef CONFIG_NO_HZ_FULL static inline bool __need_bw_check(struct rq *rq, struct task_struct *p) { if (rq->nr_running != 1) return false; if (p->sched_class != &fair_sched_class) return false; if (!task_on_rq_queued(p)) return false; return true; } bool sched_can_stop_tick(struct rq *rq) { int fifo_nr_running; /* Deadline tasks, even if single, need the tick */ if (rq->dl.dl_nr_running) return false; /* * If there are more than one RR tasks, we need the tick to affect the * actual RR behaviour. */ if (rq->rt.rr_nr_running) { if (rq->rt.rr_nr_running == 1) return true; else return false; } /* * If there's no RR tasks, but FIFO tasks, we can skip the tick, no * forced preemption between FIFO tasks. */ fifo_nr_running = rq->rt.rt_nr_running - rq->rt.rr_nr_running; if (fifo_nr_running) return true; /* * If there are no DL,RR/FIFO tasks, there must only be CFS tasks left; * if there's more than one we need the tick for involuntary * preemption. */ if (rq->nr_running > 1) return false; /* * If there is one task and it has CFS runtime bandwidth constraints * and it's on the cpu now we don't want to stop the tick. * This check prevents clearing the bit if a newly enqueued task here is * dequeued by migrating while the constrained task continues to run. * E.g. going from 2->1 without going through pick_next_task(). */ if (sched_feat(HZ_BW) && __need_bw_check(rq, rq->curr)) { if (cfs_task_bw_constrained(rq->curr)) return false; } return true; } #endif /* CONFIG_NO_HZ_FULL */ #endif /* CONFIG_SMP */ #if defined(CONFIG_RT_GROUP_SCHED) || (defined(CONFIG_FAIR_GROUP_SCHED) && \ (defined(CONFIG_SMP) || defined(CONFIG_CFS_BANDWIDTH))) /* * Iterate task_group tree rooted at *from, calling @down when first entering a * node and @up when leaving it for the final time. * * Caller must hold rcu_lock or sufficient equivalent. */ int walk_tg_tree_from(struct task_group *from, tg_visitor down, tg_visitor up, void *data) { struct task_group *parent, *child; int ret; parent = from; down: ret = (*down)(parent, data); if (ret) goto out; list_for_each_entry_rcu(child, &parent->children, siblings) { parent = child; goto down; up: continue; } ret = (*up)(parent, data); if (ret || parent == from) goto out; child = parent; parent = parent->parent; if (parent) goto up; out: return ret; } int tg_nop(struct task_group *tg, void *data) { return 0; } #endif static void set_load_weight(struct task_struct *p, bool update_load) { int prio = p->static_prio - MAX_RT_PRIO; struct load_weight *load = &p->se.load; /* * SCHED_IDLE tasks get minimal weight: */ if (task_has_idle_policy(p)) { load->weight = scale_load(WEIGHT_IDLEPRIO); load->inv_weight = WMULT_IDLEPRIO; return; } /* * SCHED_OTHER tasks have to update their load when changing their * weight */ if (update_load && p->sched_class == &fair_sched_class) { reweight_task(p, prio); } else { load->weight = scale_load(sched_prio_to_weight[prio]); load->inv_weight = sched_prio_to_wmult[prio]; } } #ifdef CONFIG_UCLAMP_TASK /* * Serializes updates of utilization clamp values * * The (slow-path) user-space triggers utilization clamp value updates which * can require updates on (fast-path) scheduler's data structures used to * support enqueue/dequeue operations. * While the per-CPU rq lock protects fast-path update operations, user-space * requests are serialized using a mutex to reduce the risk of conflicting * updates or API abuses. */ static DEFINE_MUTEX(uclamp_mutex); /* Max allowed minimum utilization */ static unsigned int __maybe_unused sysctl_sched_uclamp_util_min = SCHED_CAPACITY_SCALE; /* Max allowed maximum utilization */ static unsigned int __maybe_unused sysctl_sched_uclamp_util_max = SCHED_CAPACITY_SCALE; /* * By default RT tasks run at the maximum performance point/capacity of the * system. Uclamp enforces this by always setting UCLAMP_MIN of RT tasks to * SCHED_CAPACITY_SCALE. * * This knob allows admins to change the default behavior when uclamp is being * used. In battery powered devices, particularly, running at the maximum * capacity and frequency will increase energy consumption and shorten the * battery life. * * This knob only affects RT tasks that their uclamp_se->user_defined == false. * * This knob will not override the system default sched_util_clamp_min defined * above. */ static unsigned int sysctl_sched_uclamp_util_min_rt_default = SCHED_CAPACITY_SCALE; /* All clamps are required to be less or equal than these values */ static struct uclamp_se uclamp_default[UCLAMP_CNT]; /* * This static key is used to reduce the uclamp overhead in the fast path. It * primarily disables the call to uclamp_rq_{inc, dec}() in * enqueue/dequeue_task(). * * This allows users to continue to enable uclamp in their kernel config with * minimum uclamp overhead in the fast path. * * As soon as userspace modifies any of the uclamp knobs, the static key is * enabled, since we have an actual users that make use of uclamp * functionality. * * The knobs that would enable this static key are: * * * A task modifying its uclamp value with sched_setattr(). * * An admin modifying the sysctl_sched_uclamp_{min, max} via procfs. * * An admin modifying the cgroup cpu.uclamp.{min, max} */ DEFINE_STATIC_KEY_FALSE(sched_uclamp_used); /* Integer rounded range for each bucket */ #define UCLAMP_BUCKET_DELTA DIV_ROUND_CLOSEST(SCHED_CAPACITY_SCALE, UCLAMP_BUCKETS) #define for_each_clamp_id(clamp_id) \ for ((clamp_id) = 0; (clamp_id) < UCLAMP_CNT; (clamp_id)++) static inline unsigned int uclamp_bucket_id(unsigned int clamp_value) { return min_t(unsigned int, clamp_value / UCLAMP_BUCKET_DELTA, UCLAMP_BUCKETS - 1); } static inline unsigned int uclamp_none(enum uclamp_id clamp_id) { if (clamp_id == UCLAMP_MIN) return 0; return SCHED_CAPACITY_SCALE; } static inline void uclamp_se_set(struct uclamp_se *uc_se, unsigned int value, bool user_defined) { uc_se->value = value; uc_se->bucket_id = uclamp_bucket_id(value); uc_se->user_defined = user_defined; } static inline unsigned int uclamp_idle_value(struct rq *rq, enum uclamp_id clamp_id, unsigned int clamp_value) { /* * Avoid blocked utilization pushing up the frequency when we go * idle (which drops the max-clamp) by retaining the last known * max-clamp. */ if (clamp_id == UCLAMP_MAX) { rq->uclamp_flags |= UCLAMP_FLAG_IDLE; return clamp_value; } return uclamp_none(UCLAMP_MIN); } static inline void uclamp_idle_reset(struct rq *rq, enum uclamp_id clamp_id, unsigned int clamp_value) { /* Reset max-clamp retention only on idle exit */ if (!(rq->uclamp_flags & UCLAMP_FLAG_IDLE)) return; uclamp_rq_set(rq, clamp_id, clamp_value); } static inline unsigned int uclamp_rq_max_value(struct rq *rq, enum uclamp_id clamp_id, unsigned int clamp_value) { struct uclamp_bucket *bucket = rq->uclamp[clamp_id].bucket; int bucket_id = UCLAMP_BUCKETS - 1; /* * Since both min and max clamps are max aggregated, find the * top most bucket with tasks in. */ for ( ; bucket_id >= 0; bucket_id--) { if (!bucket[bucket_id].tasks) continue; return bucket[bucket_id].value; } /* No tasks -- default clamp values */ return uclamp_idle_value(rq, clamp_id, clamp_value); } static void __uclamp_update_util_min_rt_default(struct task_struct *p) { unsigned int default_util_min; struct uclamp_se *uc_se; lockdep_assert_held(&p->pi_lock); uc_se = &p->uclamp_req[UCLAMP_MIN]; /* Only sync if user didn't override the default */ if (uc_se->user_defined) return; default_util_min = sysctl_sched_uclamp_util_min_rt_default; uclamp_se_set(uc_se, default_util_min, false); } static void uclamp_update_util_min_rt_default(struct task_struct *p) { if (!rt_task(p)) return; /* Protect updates to p->uclamp_* */ guard(task_rq_lock)(p); __uclamp_update_util_min_rt_default(p); } static inline struct uclamp_se uclamp_tg_restrict(struct task_struct *p, enum uclamp_id clamp_id) { /* Copy by value as we could modify it */ struct uclamp_se uc_req = p->uclamp_req[clamp_id]; #ifdef CONFIG_UCLAMP_TASK_GROUP unsigned int tg_min, tg_max, value; /* * Tasks in autogroups or root task group will be * restricted by system defaults. */ if (task_group_is_autogroup(task_group(p))) return uc_req; if (task_group(p) == &root_task_group) return uc_req; tg_min = task_group(p)->uclamp[UCLAMP_MIN].value; tg_max = task_group(p)->uclamp[UCLAMP_MAX].value; value = uc_req.value; value = clamp(value, tg_min, tg_max); uclamp_se_set(&uc_req, value, false); #endif return uc_req; } /* * The effective clamp bucket index of a task depends on, by increasing * priority: * - the task specific clamp value, when explicitly requested from userspace * - the task group effective clamp value, for tasks not either in the root * group or in an autogroup * - the system default clamp value, defined by the sysadmin */ static inline struct uclamp_se uclamp_eff_get(struct task_struct *p, enum uclamp_id clamp_id) { struct uclamp_se uc_req = uclamp_tg_restrict(p, clamp_id); struct uclamp_se uc_max = uclamp_default[clamp_id]; /* System default restrictions always apply */ if (unlikely(uc_req.value > uc_max.value)) return uc_max; return uc_req; } unsigned long uclamp_eff_value(struct task_struct *p, enum uclamp_id clamp_id) { struct uclamp_se uc_eff; /* Task currently refcounted: use back-annotated (effective) value */ if (p->uclamp[clamp_id].active) return (unsigned long)p->uclamp[clamp_id].value; uc_eff = uclamp_eff_get(p, clamp_id); return (unsigned long)uc_eff.value; } /* * When a task is enqueued on a rq, the clamp bucket currently defined by the * task's uclamp::bucket_id is refcounted on that rq. This also immediately * updates the rq's clamp value if required. * * Tasks can have a task-specific value requested from user-space, track * within each bucket the maximum value for tasks refcounted in it. * This "local max aggregation" allows to track the exact "requested" value * for each bucket when all its RUNNABLE tasks require the same clamp. */ static inline void uclamp_rq_inc_id(struct rq *rq, struct task_struct *p, enum uclamp_id clamp_id) { struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id]; struct uclamp_se *uc_se = &p->uclamp[clamp_id]; struct uclamp_bucket *bucket; lockdep_assert_rq_held(rq); /* Update task effective clamp */ p->uclamp[clamp_id] = uclamp_eff_get(p, clamp_id); bucket = &uc_rq->bucket[uc_se->bucket_id]; bucket->tasks++; uc_se->active = true; uclamp_idle_reset(rq, clamp_id, uc_se->value); /* * Local max aggregation: rq buckets always track the max * "requested" clamp value of its RUNNABLE tasks. */ if (bucket->tasks == 1 || uc_se->value > bucket->value) bucket->value = uc_se->value; if (uc_se->value > uclamp_rq_get(rq, clamp_id)) uclamp_rq_set(rq, clamp_id, uc_se->value); } /* * When a task is dequeued from a rq, the clamp bucket refcounted by the task * is released. If this is the last task reference counting the rq's max * active clamp value, then the rq's clamp value is updated. * * Both refcounted tasks and rq's cached clamp values are expected to be * always valid. If it's detected they are not, as defensive programming, * enforce the expected state and warn. */ static inline void uclamp_rq_dec_id(struct rq *rq, struct task_struct *p, enum uclamp_id clamp_id) { struct uclamp_rq *uc_rq = &rq->uclamp[clamp_id]; struct uclamp_se *uc_se = &p->uclamp[clamp_id]; struct uclamp_bucket *bucket; unsigned int bkt_clamp; unsigned int rq_clamp; lockdep_assert_rq_held(rq); /* * If sched_uclamp_used was enabled after task @p was enqueued, * we could end up with unbalanced call to uclamp_rq_dec_id(). * * In this case the uc_se->active flag should be false since no uclamp * accounting was performed at enqueue time and we can just return * here. * * Need to be careful of the following enqueue/dequeue ordering * problem too * * enqueue(taskA) * // sched_uclamp_used gets enabled * enqueue(taskB) * dequeue(taskA) * // Must not decrement bucket->tasks here * dequeue(taskB) * * where we could end up with stale data in uc_se and * bucket[uc_se->bucket_id]. * * The following check here eliminates the possibility of such race. */ if (unlikely(!uc_se->active)) return; bucket = &uc_rq->bucket[uc_se->bucket_id]; SCHED_WARN_ON(!bucket->tasks); if (likely(bucket->tasks)) bucket->tasks--; uc_se->active = false; /* * Keep "local max aggregation" simple and accept to (possibly) * overboost some RUNNABLE tasks in the same bucket. * The rq clamp bucket value is reset to its base value whenever * there are no more RUNNABLE tasks refcounting it. */ if (likely(bucket->tasks)) return; rq_clamp = uclamp_rq_get(rq, clamp_id); /* * Defensive programming: this should never happen. If it happens, * e.g. due to future modification, warn and fixup the expected value. */ SCHED_WARN_ON(bucket->value > rq_clamp); if (bucket->value >= rq_clamp) { bkt_clamp = uclamp_rq_max_value(rq, clamp_id, uc_se->value); uclamp_rq_set(rq, clamp_id, bkt_clamp); } } static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { enum uclamp_id clamp_id; /* * Avoid any overhead until uclamp is actually used by the userspace. * * The condition is constructed such that a NOP is generated when * sched_uclamp_used is disabled. */ if (!static_branch_unlikely(&sched_uclamp_used)) return; if (unlikely(!p->sched_class->uclamp_enabled)) return; for_each_clamp_id(clamp_id) uclamp_rq_inc_id(rq, p, clamp_id); /* Reset clamp idle holding when there is one RUNNABLE task */ if (rq->uclamp_flags & UCLAMP_FLAG_IDLE) rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE; } static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { enum uclamp_id clamp_id; /* * Avoid any overhead until uclamp is actually used by the userspace. * * The condition is constructed such that a NOP is generated when * sched_uclamp_used is disabled. */ if (!static_branch_unlikely(&sched_uclamp_used)) return; if (unlikely(!p->sched_class->uclamp_enabled)) return; for_each_clamp_id(clamp_id) uclamp_rq_dec_id(rq, p, clamp_id); } static inline void uclamp_rq_reinc_id(struct rq *rq, struct task_struct *p, enum uclamp_id clamp_id) { if (!p->uclamp[clamp_id].active) return; uclamp_rq_dec_id(rq, p, clamp_id); uclamp_rq_inc_id(rq, p, clamp_id); /* * Make sure to clear the idle flag if we've transiently reached 0 * active tasks on rq. */ if (clamp_id == UCLAMP_MAX && (rq->uclamp_flags & UCLAMP_FLAG_IDLE)) rq->uclamp_flags &= ~UCLAMP_FLAG_IDLE; } static inline void uclamp_update_active(struct task_struct *p) { enum uclamp_id clamp_id; struct rq_flags rf; struct rq *rq; /* * Lock the task and the rq where the task is (or was) queued. * * We might lock the (previous) rq of a !RUNNABLE task, but that's the * price to pay to safely serialize util_{min,max} updates with * enqueues, dequeues and migration operations. * This is the same locking schema used by __set_cpus_allowed_ptr(). */ rq = task_rq_lock(p, &rf); /* * Setting the clamp bucket is serialized by task_rq_lock(). * If the task is not yet RUNNABLE and its task_struct is not * affecting a valid clamp bucket, the next time it's enqueued, * it will already see the updated clamp bucket value. */ for_each_clamp_id(clamp_id) uclamp_rq_reinc_id(rq, p, clamp_id); task_rq_unlock(rq, p, &rf); } #ifdef CONFIG_UCLAMP_TASK_GROUP static inline void uclamp_update_active_tasks(struct cgroup_subsys_state *css) { struct css_task_iter it; struct task_struct *p; css_task_iter_start(css, 0, &it); while ((p = css_task_iter_next(&it))) uclamp_update_active(p); css_task_iter_end(&it); } static void cpu_util_update_eff(struct cgroup_subsys_state *css); #endif #ifdef CONFIG_SYSCTL #ifdef CONFIG_UCLAMP_TASK_GROUP static void uclamp_update_root_tg(void) { struct task_group *tg = &root_task_group; uclamp_se_set(&tg->uclamp_req[UCLAMP_MIN], sysctl_sched_uclamp_util_min, false); uclamp_se_set(&tg->uclamp_req[UCLAMP_MAX], sysctl_sched_uclamp_util_max, false); guard(rcu)(); cpu_util_update_eff(&root_task_group.css); } #else static void uclamp_update_root_tg(void) { } #endif static void uclamp_sync_util_min_rt_default(void) { struct task_struct *g, *p; /* * copy_process() sysctl_uclamp * uclamp_min_rt = X; * write_lock(&tasklist_lock) read_lock(&tasklist_lock) * // link thread smp_mb__after_spinlock() * write_unlock(&tasklist_lock) read_unlock(&tasklist_lock); * sched_post_fork() for_each_process_thread() * __uclamp_sync_rt() __uclamp_sync_rt() * * Ensures that either sched_post_fork() will observe the new * uclamp_min_rt or for_each_process_thread() will observe the new * task. */ read_lock(&tasklist_lock); smp_mb__after_spinlock(); read_unlock(&tasklist_lock); guard(rcu)(); for_each_process_thread(g, p) uclamp_update_util_min_rt_default(p); } static int sysctl_sched_uclamp_handler(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { bool update_root_tg = false; int old_min, old_max, old_min_rt; int result; guard(mutex)(&uclamp_mutex); old_min = sysctl_sched_uclamp_util_min; old_max = sysctl_sched_uclamp_util_max; old_min_rt = sysctl_sched_uclamp_util_min_rt_default; result = proc_dointvec(table, write, buffer, lenp, ppos); if (result) goto undo; if (!write) return 0; if (sysctl_sched_uclamp_util_min > sysctl_sched_uclamp_util_max || sysctl_sched_uclamp_util_max > SCHED_CAPACITY_SCALE || sysctl_sched_uclamp_util_min_rt_default > SCHED_CAPACITY_SCALE) { result = -EINVAL; goto undo; } if (old_min != sysctl_sched_uclamp_util_min) { uclamp_se_set(&uclamp_default[UCLAMP_MIN], sysctl_sched_uclamp_util_min, false); update_root_tg = true; } if (old_max != sysctl_sched_uclamp_util_max) { uclamp_se_set(&uclamp_default[UCLAMP_MAX], sysctl_sched_uclamp_util_max, false); update_root_tg = true; } if (update_root_tg) { static_branch_enable(&sched_uclamp_used); uclamp_update_root_tg(); } if (old_min_rt != sysctl_sched_uclamp_util_min_rt_default) { static_branch_enable(&sched_uclamp_used); uclamp_sync_util_min_rt_default(); } /* * We update all RUNNABLE tasks only when task groups are in use. * Otherwise, keep it simple and do just a lazy update at each next * task enqueue time. */ return 0; undo: sysctl_sched_uclamp_util_min = old_min; sysctl_sched_uclamp_util_max = old_max; sysctl_sched_uclamp_util_min_rt_default = old_min_rt; return result; } #endif static int uclamp_validate(struct task_struct *p, const struct sched_attr *attr) { int util_min = p->uclamp_req[UCLAMP_MIN].value; int util_max = p->uclamp_req[UCLAMP_MAX].value; if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN) { util_min = attr->sched_util_min; if (util_min + 1 > SCHED_CAPACITY_SCALE + 1) return -EINVAL; } if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX) { util_max = attr->sched_util_max; if (util_max + 1 > SCHED_CAPACITY_SCALE + 1) return -EINVAL; } if (util_min != -1 && util_max != -1 && util_min > util_max) return -EINVAL; /* * We have valid uclamp attributes; make sure uclamp is enabled. * * We need to do that here, because enabling static branches is a * blocking operation which obviously cannot be done while holding * scheduler locks. */ static_branch_enable(&sched_uclamp_used); return 0; } static bool uclamp_reset(const struct sched_attr *attr, enum uclamp_id clamp_id, struct uclamp_se *uc_se) { /* Reset on sched class change for a non user-defined clamp value. */ if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP)) && !uc_se->user_defined) return true; /* Reset on sched_util_{min,max} == -1. */ if (clamp_id == UCLAMP_MIN && attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN && attr->sched_util_min == -1) { return true; } if (clamp_id == UCLAMP_MAX && attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX && attr->sched_util_max == -1) { return true; } return false; } static void __setscheduler_uclamp(struct task_struct *p, const struct sched_attr *attr) { enum uclamp_id clamp_id; for_each_clamp_id(clamp_id) { struct uclamp_se *uc_se = &p->uclamp_req[clamp_id]; unsigned int value; if (!uclamp_reset(attr, clamp_id, uc_se)) continue; /* * RT by default have a 100% boost value that could be modified * at runtime. */ if (unlikely(rt_task(p) && clamp_id == UCLAMP_MIN)) value = sysctl_sched_uclamp_util_min_rt_default; else value = uclamp_none(clamp_id); uclamp_se_set(uc_se, value, false); } if (likely(!(attr->sched_flags & SCHED_FLAG_UTIL_CLAMP))) return; if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MIN && attr->sched_util_min != -1) { uclamp_se_set(&p->uclamp_req[UCLAMP_MIN], attr->sched_util_min, true); } if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP_MAX && attr->sched_util_max != -1) { uclamp_se_set(&p->uclamp_req[UCLAMP_MAX], attr->sched_util_max, true); } } static void uclamp_fork(struct task_struct *p) { enum uclamp_id clamp_id; /* * We don't need to hold task_rq_lock() when updating p->uclamp_* here * as the task is still at its early fork stages. */ for_each_clamp_id(clamp_id) p->uclamp[clamp_id].active = false; if (likely(!p->sched_reset_on_fork)) return; for_each_clamp_id(clamp_id) { uclamp_se_set(&p->uclamp_req[clamp_id], uclamp_none(clamp_id), false); } } static void uclamp_post_fork(struct task_struct *p) { uclamp_update_util_min_rt_default(p); } static void __init init_uclamp_rq(struct rq *rq) { enum uclamp_id clamp_id; struct uclamp_rq *uc_rq = rq->uclamp; for_each_clamp_id(clamp_id) { uc_rq[clamp_id] = (struct uclamp_rq) { .value = uclamp_none(clamp_id) }; } rq->uclamp_flags = UCLAMP_FLAG_IDLE; } static void __init init_uclamp(void) { struct uclamp_se uc_max = {}; enum uclamp_id clamp_id; int cpu; for_each_possible_cpu(cpu) init_uclamp_rq(cpu_rq(cpu)); for_each_clamp_id(clamp_id) { uclamp_se_set(&init_task.uclamp_req[clamp_id], uclamp_none(clamp_id), false); } /* System defaults allow max clamp values for both indexes */ uclamp_se_set(&uc_max, uclamp_none(UCLAMP_MAX), false); for_each_clamp_id(clamp_id) { uclamp_default[clamp_id] = uc_max; #ifdef CONFIG_UCLAMP_TASK_GROUP root_task_group.uclamp_req[clamp_id] = uc_max; root_task_group.uclamp[clamp_id] = uc_max; #endif } } #else /* !CONFIG_UCLAMP_TASK */ static inline void uclamp_rq_inc(struct rq *rq, struct task_struct *p) { } static inline void uclamp_rq_dec(struct rq *rq, struct task_struct *p) { } static inline int uclamp_validate(struct task_struct *p, const struct sched_attr *attr) { return -EOPNOTSUPP; } static void __setscheduler_uclamp(struct task_struct *p, const struct sched_attr *attr) { } static inline void uclamp_fork(struct task_struct *p) { } static inline void uclamp_post_fork(struct task_struct *p) { } static inline void init_uclamp(void) { } #endif /* CONFIG_UCLAMP_TASK */ bool sched_task_on_rq(struct task_struct *p) { return task_on_rq_queued(p); } unsigned long get_wchan(struct task_struct *p) { unsigned long ip = 0; unsigned int state; if (!p || p == current) return 0; /* Only get wchan if task is blocked and we can keep it that way. */ raw_spin_lock_irq(&p->pi_lock); state = READ_ONCE(p->__state); smp_rmb(); /* see try_to_wake_up() */ if (state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq) ip = __get_wchan(p); raw_spin_unlock_irq(&p->pi_lock); return ip; } static inline void enqueue_task(struct rq *rq, struct task_struct *p, int flags) { if (!(flags & ENQUEUE_NOCLOCK)) update_rq_clock(rq); if (!(flags & ENQUEUE_RESTORE)) { sched_info_enqueue(rq, p); psi_enqueue(p, (flags & ENQUEUE_WAKEUP) && !(flags & ENQUEUE_MIGRATED)); } uclamp_rq_inc(rq, p); p->sched_class->enqueue_task(rq, p, flags); if (sched_core_enabled(rq)) sched_core_enqueue(rq, p); } static inline void dequeue_task(struct rq *rq, struct task_struct *p, int flags) { if (sched_core_enabled(rq)) sched_core_dequeue(rq, p, flags); if (!(flags & DEQUEUE_NOCLOCK)) update_rq_clock(rq); if (!(flags & DEQUEUE_SAVE)) { sched_info_dequeue(rq, p); psi_dequeue(p, flags & DEQUEUE_SLEEP); } uclamp_rq_dec(rq, p); p->sched_class->dequeue_task(rq, p, flags); } void activate_task(struct rq *rq, struct task_struct *p, int flags) { if (task_on_rq_migrating(p)) flags |= ENQUEUE_MIGRATED; if (flags & ENQUEUE_MIGRATED) sched_mm_cid_migrate_to(rq, p); enqueue_task(rq, p, flags); WRITE_ONCE(p->on_rq, TASK_ON_RQ_QUEUED); ASSERT_EXCLUSIVE_WRITER(p->on_rq); } void deactivate_task(struct rq *rq, struct task_struct *p, int flags) { WRITE_ONCE(p->on_rq, (flags & DEQUEUE_SLEEP) ? 0 : TASK_ON_RQ_MIGRATING); ASSERT_EXCLUSIVE_WRITER(p->on_rq); dequeue_task(rq, p, flags); } static inline int __normal_prio(int policy, int rt_prio, int nice) { int prio; if (dl_policy(policy)) prio = MAX_DL_PRIO - 1; else if (rt_policy(policy)) prio = MAX_RT_PRIO - 1 - rt_prio; else prio = NICE_TO_PRIO(nice); return prio; } /* * Calculate the expected normal priority: i.e. priority * without taking RT-inheritance into account. Might be * boosted by interactivity modifiers. Changes upon fork, * setprio syscalls, and whenever the interactivity * estimator recalculates. */ static inline int normal_prio(struct task_struct *p) { return __normal_prio(p->policy, p->rt_priority, PRIO_TO_NICE(p->static_prio)); } /* * Calculate the current priority, i.e. the priority * taken into account by the scheduler. This value might * be boosted by RT tasks, or might be boosted by * interactivity modifiers. Will be RT if the task got * RT-boosted. If not then it returns p->normal_prio. */ static int effective_prio(struct task_struct *p) { p->normal_prio = normal_prio(p); /* * If we are RT tasks or we were boosted to RT priority, * keep the priority unchanged. Otherwise, update priority * to the normal priority: */ if (!rt_prio(p->prio)) return p->normal_prio; return p->prio; } /** * task_curr - is this task currently executing on a CPU? * @p: the task in question. * * Return: 1 if the task is currently executing. 0 otherwise. */ inline int task_curr(const struct task_struct *p) { return cpu_curr(task_cpu(p)) == p; } /* * switched_from, switched_to and prio_changed must _NOT_ drop rq->lock, * use the balance_callback list if you want balancing. * * this means any call to check_class_changed() must be followed by a call to * balance_callback(). */ static inline void check_class_changed(struct rq *rq, struct task_struct *p, const struct sched_class *prev_class, int oldprio) { if (prev_class != p->sched_class) { if (prev_class->switched_from) prev_class->switched_from(rq, p); p->sched_class->switched_to(rq, p); } else if (oldprio != p->prio || dl_task(p)) p->sched_class->prio_changed(rq, p, oldprio); } void wakeup_preempt(struct rq *rq, struct task_struct *p, int flags) { if (p->sched_class == rq->curr->sched_class) rq->curr->sched_class->wakeup_preempt(rq, p, flags); else if (sched_class_above(p->sched_class, rq->curr->sched_class)) resched_curr(rq); /* * A queue event has occurred, and we're going to schedule. In * this case, we can save a useless back to back clock update. */ if (task_on_rq_queued(rq->curr) && test_tsk_need_resched(rq->curr)) rq_clock_skip_update(rq); } static __always_inline int __task_state_match(struct task_struct *p, unsigned int state) { if (READ_ONCE(p->__state) & state) return 1; if (READ_ONCE(p->saved_state) & state) return -1; return 0; } static __always_inline int task_state_match(struct task_struct *p, unsigned int state) { /* * Serialize against current_save_and_set_rtlock_wait_state(), * current_restore_rtlock_saved_state(), and __refrigerator(). */ guard(raw_spinlock_irq)(&p->pi_lock); return __task_state_match(p, state); } /* * wait_task_inactive - wait for a thread to unschedule. * * Wait for the thread to block in any of the states set in @match_state. * If it changes, i.e. @p might have woken up, then return zero. When we * succeed in waiting for @p to be off its CPU, we return a positive number * (its total switch count). If a second call a short while later returns the * same number, the caller can be sure that @p has remained unscheduled the * whole time. * * The caller must ensure that the task *will* unschedule sometime soon, * else this function might spin for a *long* time. This function can't * be called with interrupts off, or it may introduce deadlock with * smp_call_function() if an IPI is sent by the same process we are * waiting to become inactive. */ unsigned long wait_task_inactive(struct task_struct *p, unsigned int match_state) { int running, queued, match; struct rq_flags rf; unsigned long ncsw; struct rq *rq; for (;;) { /* * We do the initial early heuristics without holding * any task-queue locks at all. We'll only try to get * the runqueue lock when things look like they will * work out! */ rq = task_rq(p); /* * If the task is actively running on another CPU * still, just relax and busy-wait without holding * any locks. * * NOTE! Since we don't hold any locks, it's not * even sure that "rq" stays as the right runqueue! * But we don't care, since "task_on_cpu()" will * return false if the runqueue has changed and p * is actually now running somewhere else! */ while (task_on_cpu(rq, p)) { if (!task_state_match(p, match_state)) return 0; cpu_relax(); } /* * Ok, time to look more closely! We need the rq * lock now, to be *sure*. If we're wrong, we'll * just go back and repeat. */ rq = task_rq_lock(p, &rf); trace_sched_wait_task(p); running = task_on_cpu(rq, p); queued = task_on_rq_queued(p); ncsw = 0; if ((match = __task_state_match(p, match_state))) { /* * When matching on p->saved_state, consider this task * still queued so it will wait. */ if (match < 0) queued = 1; ncsw = p->nvcsw | LONG_MIN; /* sets MSB */ } task_rq_unlock(rq, p, &rf); /* * If it changed from the expected state, bail out now. */ if (unlikely(!ncsw)) break; /* * Was it really running after all now that we * checked with the proper locks actually held? * * Oops. Go back and try again.. */ if (unlikely(running)) { cpu_relax(); continue; } /* * It's not enough that it's not actively running, * it must be off the runqueue _entirely_, and not * preempted! * * So if it was still runnable (but just not actively * running right now), it's preempted, and we should * yield - it could be a while. */ if (unlikely(queued)) { ktime_t to = NSEC_PER_SEC / HZ; set_current_state(TASK_UNINTERRUPTIBLE); schedule_hrtimeout(&to, HRTIMER_MODE_REL_HARD); continue; } /* * Ahh, all good. It wasn't running, and it wasn't * runnable, which means that it will never become * running in the future either. We're all done! */ break; } return ncsw; } #ifdef CONFIG_SMP static void __do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx); static int __set_cpus_allowed_ptr(struct task_struct *p, struct affinity_context *ctx); static void migrate_disable_switch(struct rq *rq, struct task_struct *p) { struct affinity_context ac = { .new_mask = cpumask_of(rq->cpu), .flags = SCA_MIGRATE_DISABLE, }; if (likely(!p->migration_disabled)) return; if (p->cpus_ptr != &p->cpus_mask) return; /* * Violates locking rules! see comment in __do_set_cpus_allowed(). */ __do_set_cpus_allowed(p, &ac); } void migrate_disable(void) { struct task_struct *p = current; if (p->migration_disabled) { p->migration_disabled++; return; } guard(preempt)(); this_rq()->nr_pinned++; p->migration_disabled = 1; } EXPORT_SYMBOL_GPL(migrate_disable); void migrate_enable(void) { struct task_struct *p = current; struct affinity_context ac = { .new_mask = &p->cpus_mask, .flags = SCA_MIGRATE_ENABLE, }; if (p->migration_disabled > 1) { p->migration_disabled--; return; } if (WARN_ON_ONCE(!p->migration_disabled)) return; /* * Ensure stop_task runs either before or after this, and that * __set_cpus_allowed_ptr(SCA_MIGRATE_ENABLE) doesn't schedule(). */ guard(preempt)(); if (p->cpus_ptr != &p->cpus_mask) __set_cpus_allowed_ptr(p, &ac); /* * Mustn't clear migration_disabled() until cpus_ptr points back at the * regular cpus_mask, otherwise things that race (eg. * select_fallback_rq) get confused. */ barrier(); p->migration_disabled = 0; this_rq()->nr_pinned--; } EXPORT_SYMBOL_GPL(migrate_enable); static inline bool rq_has_pinned_tasks(struct rq *rq) { return rq->nr_pinned; } /* * Per-CPU kthreads are allowed to run on !active && online CPUs, see * __set_cpus_allowed_ptr() and select_fallback_rq(). */ static inline bool is_cpu_allowed(struct task_struct *p, int cpu) { /* When not in the task's cpumask, no point in looking further. */ if (!cpumask_test_cpu(cpu, p->cpus_ptr)) return false; /* migrate_disabled() must be allowed to finish. */ if (is_migration_disabled(p)) return cpu_online(cpu); /* Non kernel threads are not allowed during either online or offline. */ if (!(p->flags & PF_KTHREAD)) return cpu_active(cpu) && task_cpu_possible(cpu, p); /* KTHREAD_IS_PER_CPU is always allowed. */ if (kthread_is_per_cpu(p)) return cpu_online(cpu); /* Regular kernel threads don't get to stay during offline. */ if (cpu_dying(cpu)) return false; /* But are allowed during online. */ return cpu_online(cpu); } /* * This is how migration works: * * 1) we invoke migration_cpu_stop() on the target CPU using * stop_one_cpu(). * 2) stopper starts to run (implicitly forcing the migrated thread * off the CPU) * 3) it checks whether the migrated task is still in the wrong runqueue. * 4) if it's in the wrong runqueue then the migration thread removes * it and puts it into the right queue. * 5) stopper completes and stop_one_cpu() returns and the migration * is done. */ /* * move_queued_task - move a queued task to new rq. * * Returns (locked) new rq. Old rq's lock is released. */ static struct rq *move_queued_task(struct rq *rq, struct rq_flags *rf, struct task_struct *p, int new_cpu) { lockdep_assert_rq_held(rq); deactivate_task(rq, p, DEQUEUE_NOCLOCK); set_task_cpu(p, new_cpu); rq_unlock(rq, rf); rq = cpu_rq(new_cpu); rq_lock(rq, rf); WARN_ON_ONCE(task_cpu(p) != new_cpu); activate_task(rq, p, 0); wakeup_preempt(rq, p, 0); return rq; } struct migration_arg { struct task_struct *task; int dest_cpu; struct set_affinity_pending *pending; }; /* * @refs: number of wait_for_completion() * @stop_pending: is @stop_work in use */ struct set_affinity_pending { refcount_t refs; unsigned int stop_pending; struct completion done; struct cpu_stop_work stop_work; struct migration_arg arg; }; /* * Move (not current) task off this CPU, onto the destination CPU. We're doing * this because either it can't run here any more (set_cpus_allowed() * away from this CPU, or CPU going down), or because we're * attempting to rebalance this task on exec (sched_exec). * * So we race with normal scheduler movements, but that's OK, as long * as the task is no longer on this CPU. */ static struct rq *__migrate_task(struct rq *rq, struct rq_flags *rf, struct task_struct *p, int dest_cpu) { /* Affinity changed (again). */ if (!is_cpu_allowed(p, dest_cpu)) return rq; rq = move_queued_task(rq, rf, p, dest_cpu); return rq; } /* * migration_cpu_stop - this will be executed by a highprio stopper thread * and performs thread migration by bumping thread off CPU then * 'pushing' onto another runqueue. */ static int migration_cpu_stop(void *data) { struct migration_arg *arg = data; struct set_affinity_pending *pending = arg->pending; struct task_struct *p = arg->task; struct rq *rq = this_rq(); bool complete = false; struct rq_flags rf; /* * The original target CPU might have gone down and we might * be on another CPU but it doesn't matter. */ local_irq_save(rf.flags); /* * We need to explicitly wake pending tasks before running * __migrate_task() such that we will not miss enforcing cpus_ptr * during wakeups, see set_cpus_allowed_ptr()'s TASK_WAKING test. */ flush_smp_call_function_queue(); raw_spin_lock(&p->pi_lock); rq_lock(rq, &rf); /* * If we were passed a pending, then ->stop_pending was set, thus * p->migration_pending must have remained stable. */ WARN_ON_ONCE(pending && pending != p->migration_pending); /* * If task_rq(p) != rq, it cannot be migrated here, because we're * holding rq->lock, if p->on_rq == 0 it cannot get enqueued because * we're holding p->pi_lock. */ if (task_rq(p) == rq) { if (is_migration_disabled(p)) goto out; if (pending) { p->migration_pending = NULL; complete = true; if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) goto out; } if (task_on_rq_queued(p)) { update_rq_clock(rq); rq = __migrate_task(rq, &rf, p, arg->dest_cpu); } else { p->wake_cpu = arg->dest_cpu; } /* * XXX __migrate_task() can fail, at which point we might end * up running on a dodgy CPU, AFAICT this can only happen * during CPU hotplug, at which point we'll get pushed out * anyway, so it's probably not a big deal. */ } else if (pending) { /* * This happens when we get migrated between migrate_enable()'s * preempt_enable() and scheduling the stopper task. At that * point we're a regular task again and not current anymore. * * A !PREEMPT kernel has a giant hole here, which makes it far * more likely. */ /* * The task moved before the stopper got to run. We're holding * ->pi_lock, so the allowed mask is stable - if it got * somewhere allowed, we're done. */ if (cpumask_test_cpu(task_cpu(p), p->cpus_ptr)) { p->migration_pending = NULL; complete = true; goto out; } /* * When migrate_enable() hits a rq mis-match we can't reliably * determine is_migration_disabled() and so have to chase after * it. */ WARN_ON_ONCE(!pending->stop_pending); preempt_disable(); task_rq_unlock(rq, p, &rf); stop_one_cpu_nowait(task_cpu(p), migration_cpu_stop, &pending->arg, &pending->stop_work); preempt_enable(); return 0; } out: if (pending) pending->stop_pending = false; task_rq_unlock(rq, p, &rf); if (complete) complete_all(&pending->done); return 0; } int push_cpu_stop(void *arg) { struct rq *lowest_rq = NULL, *rq = this_rq(); struct task_struct *p = arg; raw_spin_lock_irq(&p->pi_lock); raw_spin_rq_lock(rq); if (task_rq(p) != rq) goto out_unlock; if (is_migration_disabled(p)) { p->migration_flags |= MDF_PUSH; goto out_unlock; } p->migration_flags &= ~MDF_PUSH; if (p->sched_class->find_lock_rq) lowest_rq = p->sched_class->find_lock_rq(p, rq); if (!lowest_rq) goto out_unlock; // XXX validate p is still the highest prio task if (task_rq(p) == rq) { deactivate_task(rq, p, 0); set_task_cpu(p, lowest_rq->cpu); activate_task(lowest_rq, p, 0); resched_curr(lowest_rq); } double_unlock_balance(rq, lowest_rq); out_unlock: rq->push_busy = false; raw_spin_rq_unlock(rq); raw_spin_unlock_irq(&p->pi_lock); put_task_struct(p); return 0; } /* * sched_class::set_cpus_allowed must do the below, but is not required to * actually call this function. */ void set_cpus_allowed_common(struct task_struct *p, struct affinity_context *ctx) { if (ctx->flags & (SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) { p->cpus_ptr = ctx->new_mask; return; } cpumask_copy(&p->cpus_mask, ctx->new_mask); p->nr_cpus_allowed = cpumask_weight(ctx->new_mask); /* * Swap in a new user_cpus_ptr if SCA_USER flag set */ if (ctx->flags & SCA_USER) swap(p->user_cpus_ptr, ctx->user_mask); } static void __do_set_cpus_allowed(struct task_struct *p, struct affinity_context *ctx) { struct rq *rq = task_rq(p); bool queued, running; /* * This here violates the locking rules for affinity, since we're only * supposed to change these variables while holding both rq->lock and * p->pi_lock. * * HOWEVER, it magically works, because ttwu() is the only code that * accesses these variables under p->pi_lock and only does so after * smp_cond_load_acquire(&p->on_cpu, !VAL), and we're in __schedule() * before finish_task(). * * XXX do further audits, this smells like something putrid. */ if (ctx->flags & SCA_MIGRATE_DISABLE) SCHED_WARN_ON(!p->on_cpu); else lockdep_assert_held(&p->pi_lock); queued = task_on_rq_queued(p); running = task_current(rq, p); if (queued) { /* * Because __kthread_bind() calls this on blocked tasks without * holding rq->lock. */ lockdep_assert_rq_held(rq); dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK); } if (running) put_prev_task(rq, p); p->sched_class->set_cpus_allowed(p, ctx); if (queued) enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); if (running) set_next_task(rq, p); } /* * Used for kthread_bind() and select_fallback_rq(), in both cases the user * affinity (if any) should be destroyed too. */ void do_set_cpus_allowed(struct task_struct *p, const struct cpumask *new_mask) { struct affinity_context ac = { .new_mask = new_mask, .user_mask = NULL, .flags = SCA_USER, /* clear the user requested mask */ }; union cpumask_rcuhead { cpumask_t cpumask; struct rcu_head rcu; }; __do_set_cpus_allowed(p, &ac); /* * Because this is called with p->pi_lock held, it is not possible * to use kfree() here (when PREEMPT_RT=y), therefore punt to using * kfree_rcu(). */ kfree_rcu((union cpumask_rcuhead *)ac.user_mask, rcu); } static cpumask_t *alloc_user_cpus_ptr(int node) { /* * See do_set_cpus_allowed() above for the rcu_head usage. */ int size = max_t(int, cpumask_size(), sizeof(struct rcu_head)); return kmalloc_node(size, GFP_KERNEL, node); } int dup_user_cpus_ptr(struct task_struct *dst, struct task_struct *src, int node) { cpumask_t *user_mask; unsigned long flags; /* * Always clear dst->user_cpus_ptr first as their user_cpus_ptr's * may differ by now due to racing. */ dst->user_cpus_ptr = NULL; /* * This check is racy and losing the race is a valid situation. * It is not worth the extra overhead of taking the pi_lock on * every fork/clone. */ if (data_race(!src->user_cpus_ptr)) return 0; user_mask = alloc_user_cpus_ptr(node); if (!user_mask) return -ENOMEM; /* * Use pi_lock to protect content of user_cpus_ptr * * Though unlikely, user_cpus_ptr can be reset to NULL by a concurrent * do_set_cpus_allowed(). */ raw_spin_lock_irqsave(&src->pi_lock, flags); if (src->user_cpus_ptr) { swap(dst->user_cpus_ptr, user_mask); cpumask_copy(dst->user_cpus_ptr, src->user_cpus_ptr); } raw_spin_unlock_irqrestore(&src->pi_lock, flags); if (unlikely(user_mask)) kfree(user_mask); return 0; } static inline struct cpumask *clear_user_cpus_ptr(struct task_struct *p) { struct cpumask *user_mask = NULL; swap(p->user_cpus_ptr, user_mask); return user_mask; } void release_user_cpus_ptr(struct task_struct *p) { kfree(clear_user_cpus_ptr(p)); } /* * This function is wildly self concurrent; here be dragons. * * * When given a valid mask, __set_cpus_allowed_ptr() must block until the * designated task is enqueued on an allowed CPU. If that task is currently * running, we have to kick it out using the CPU stopper. * * Migrate-Disable comes along and tramples all over our nice sandcastle. * Consider: * * Initial conditions: P0->cpus_mask = [0, 1] * * P0@CPU0 P1 * * migrate_disable(); * <preempted> * set_cpus_allowed_ptr(P0, [1]); * * P1 *cannot* return from this set_cpus_allowed_ptr() call until P0 executes * its outermost migrate_enable() (i.e. it exits its Migrate-Disable region). * This means we need the following scheme: * * P0@CPU0 P1 * * migrate_disable(); * <preempted> * set_cpus_allowed_ptr(P0, [1]); * <blocks> * <resumes> * migrate_enable(); * __set_cpus_allowed_ptr(); * <wakes local stopper> * `--> <woken on migration completion> * * Now the fun stuff: there may be several P1-like tasks, i.e. multiple * concurrent set_cpus_allowed_ptr(P0, [*]) calls. CPU affinity changes of any * task p are serialized by p->pi_lock, which we can leverage: the one that * should come into effect at the end of the Migrate-Disable region is the last * one. This means we only need to track a single cpumask (i.e. p->cpus_mask), * but we still need to properly signal those waiting tasks at the appropriate * moment. * * This is implemented using struct set_affinity_pending. The first * __set_cpus_allowed_ptr() caller within a given Migrate-Disable region will * setup an instance of that struct and install it on the targeted task_struct. * Any and all further callers will reuse that instance. Those then wait for * a completion signaled at the tail of the CPU stopper callback (1), triggered * on the end of the Migrate-Disable region (i.e. outermost migrate_enable()). * * * (1) In the cases covered above. There is one more where the completion is * signaled within affine_move_task() itself: when a subsequent affinity request * occurs after the stopper bailed out due to the targeted task still being * Migrate-Disable. Consider: * * Initial conditions: P0->cpus_mask = [0, 1] * * CPU0 P1 P2 * <P0> * migrate_disable(); * <preempted> * set_cpus_allowed_ptr(P0, [1]); * <blocks> * <migration/0> * migration_cpu_stop() * is_migration_disabled() * <bails> * set_cpus_allowed_ptr(P0, [0, 1]); * <signal completion> * <awakes> * * Note that the above is safe vs a concurrent migrate_enable(), as any * pending affinity completion is preceded by an uninstallation of * p->migration_pending done with p->pi_lock held. */ static int affine_move_task(struct rq *rq, struct task_struct *p, struct rq_flags *rf, int dest_cpu, unsigned int flags) __releases(rq->lock) __releases(p->pi_lock) { struct set_affinity_pending my_pending = { }, *pending = NULL; bool stop_pending, complete = false; /* Can the task run on the task's current CPU? If so, we're done */ if (cpumask_test_cpu(task_cpu(p), &p->cpus_mask)) { struct task_struct *push_task = NULL; if ((flags & SCA_MIGRATE_ENABLE) && (p->migration_flags & MDF_PUSH) && !rq->push_busy) { rq->push_busy = true; push_task = get_task_struct(p); } /* * If there are pending waiters, but no pending stop_work, * then complete now. */ pending = p->migration_pending; if (pending && !pending->stop_pending) { p->migration_pending = NULL; complete = true; } preempt_disable(); task_rq_unlock(rq, p, rf); if (push_task) { stop_one_cpu_nowait(rq->cpu, push_cpu_stop, p, &rq->push_work); } preempt_enable(); if (complete) complete_all(&pending->done); return 0; } if (!(flags & SCA_MIGRATE_ENABLE)) { /* serialized by p->pi_lock */ if (!p->migration_pending) { /* Install the request */ refcount_set(&my_pending.refs, 1); init_completion(&my_pending.done); my_pending.arg = (struct migration_arg) { .task = p, .dest_cpu = dest_cpu, .pending = &my_pending, }; p->migration_pending = &my_pending; } else { pending = p->migration_pending; refcount_inc(&pending->refs); /* * Affinity has changed, but we've already installed a * pending. migration_cpu_stop() *must* see this, else * we risk a completion of the pending despite having a * task on a disallowed CPU. * * Serialized by p->pi_lock, so this is safe. */ pending->arg.dest_cpu = dest_cpu; } } pending = p->migration_pending; /* * - !MIGRATE_ENABLE: * we'll have installed a pending if there wasn't one already. * * - MIGRATE_ENABLE: * we're here because the current CPU isn't matching anymore, * the only way that can happen is because of a concurrent * set_cpus_allowed_ptr() call, which should then still be * pending completion. * * Either way, we really should have a @pending here. */ if (WARN_ON_ONCE(!pending)) { task_rq_unlock(rq, p, rf); return -EINVAL; } if (task_on_cpu(rq, p) || READ_ONCE(p->__state) == TASK_WAKING) { /* * MIGRATE_ENABLE gets here because 'p == current', but for * anything else we cannot do is_migration_disabled(), punt * and have the stopper function handle it all race-free. */ stop_pending = pending->stop_pending; if (!stop_pending) pending->stop_pending = true; if (flags & SCA_MIGRATE_ENABLE) p->migration_flags &= ~MDF_PUSH; preempt_disable(); task_rq_unlock(rq, p, rf); if (!stop_pending) { stop_one_cpu_nowait(cpu_of(rq), migration_cpu_stop, &pending->arg, &pending->stop_work); } preempt_enable(); if (flags & SCA_MIGRATE_ENABLE) return 0; } else { if (!is_migration_disabled(p)) { if (task_on_rq_queued(p)) rq = move_queued_task(rq, rf, p, dest_cpu); if (!pending->stop_pending) { p->migration_pending = NULL; complete = true; } } task_rq_unlock(rq, p, rf); if (complete) complete_all(&pending->done); } wait_for_completion(&pending->done); if (refcount_dec_and_test(&pending->refs)) wake_up_var(&pending->refs); /* No UaF, just an address */ /* * Block the original owner of &pending until all subsequent callers * have seen the completion and decremented the refcount */ wait_var_event(&my_pending.refs, !refcount_read(&my_pending.refs)); /* ARGH */ WARN_ON_ONCE(my_pending.stop_pending); return 0; } /* * Called with both p->pi_lock and rq->lock held; drops both before returning. */ static int __set_cpus_allowed_ptr_locked(struct task_struct *p, struct affinity_context *ctx, struct rq *rq, struct rq_flags *rf) __releases(rq->lock) __releases(p->pi_lock) { const struct cpumask *cpu_allowed_mask = task_cpu_possible_mask(p); const struct cpumask *cpu_valid_mask = cpu_active_mask; bool kthread = p->flags & PF_KTHREAD; unsigned int dest_cpu; int ret = 0; update_rq_clock(rq); if (kthread || is_migration_disabled(p)) { /* * Kernel threads are allowed on online && !active CPUs, * however, during cpu-hot-unplug, even these might get pushed * away if not KTHREAD_IS_PER_CPU. * * Specifically, migration_disabled() tasks must not fail the * cpumask_any_and_distribute() pick below, esp. so on * SCA_MIGRATE_ENABLE, otherwise we'll not call * set_cpus_allowed_common() and actually reset p->cpus_ptr. */ cpu_valid_mask = cpu_online_mask; } if (!kthread && !cpumask_subset(ctx->new_mask, cpu_allowed_mask)) { ret = -EINVAL; goto out; } /* * Must re-check here, to close a race against __kthread_bind(), * sched_setaffinity() is not guaranteed to observe the flag. */ if ((ctx->flags & SCA_CHECK) && (p->flags & PF_NO_SETAFFINITY)) { ret = -EINVAL; goto out; } if (!(ctx->flags & SCA_MIGRATE_ENABLE)) { if (cpumask_equal(&p->cpus_mask, ctx->new_mask)) { if (ctx->flags & SCA_USER) swap(p->user_cpus_ptr, ctx->user_mask); goto out; } if (WARN_ON_ONCE(p == current && is_migration_disabled(p) && !cpumask_test_cpu(task_cpu(p), ctx->new_mask))) { ret = -EBUSY; goto out; } } /* * Picking a ~random cpu helps in cases where we are changing affinity * for groups of tasks (ie. cpuset), so that load balancing is not * immediately required to distribute the tasks within their new mask. */ dest_cpu = cpumask_any_and_distribute(cpu_valid_mask, ctx->new_mask); if (dest_cpu >= nr_cpu_ids) { ret = -EINVAL; goto out; } __do_set_cpus_allowed(p, ctx); return affine_move_task(rq, p, rf, dest_cpu, ctx->flags); out: task_rq_unlock(rq, p, rf); return ret; } /* * Change a given task's CPU affinity. Migrate the thread to a * proper CPU and schedule it away if the CPU it's executing on * is removed from the allowed bitmask. * * NOTE: the caller must have a valid reference to the task, the * task must not exit() & deallocate itself prematurely. The * call is not atomic; no spinlocks may be held. */ static int __set_cpus_allowed_ptr(struct task_struct *p, struct affinity_context *ctx) { struct rq_flags rf; struct rq *rq; rq = task_rq_lock(p, &rf); /* * Masking should be skipped if SCA_USER or any of the SCA_MIGRATE_* * flags are set. */ if (p->user_cpus_ptr && !(ctx->flags & (SCA_USER | SCA_MIGRATE_ENABLE | SCA_MIGRATE_DISABLE)) && cpumask_and(rq->scratch_mask, ctx->new_mask, p->user_cpus_ptr)) ctx->new_mask = rq->scratch_mask; return __set_cpus_allowed_ptr_locked(p, ctx, rq, &rf); } int set_cpus_allowed_ptr(struct task_struct *p, const struct cpumask *new_mask) { struct affinity_context ac = { .new_mask = new_mask, .flags = 0, }; return __set_cpus_allowed_ptr(p, &ac); } EXPORT_SYMBOL_GPL(set_cpus_allowed_ptr); /* * Change a given task's CPU affinity to the intersection of its current * affinity mask and @subset_mask, writing the resulting mask to @new_mask. * If user_cpus_ptr is defined, use it as the basis for restricting CPU * affinity or use cpu_online_mask instead. * * If the resulting mask is empty, leave the affinity unchanged and return * -EINVAL. */ static int restrict_cpus_allowed_ptr(struct task_struct *p, struct cpumask *new_mask, const struct cpumask *subset_mask) { struct affinity_context ac = { .new_mask = new_mask, .flags = 0, }; struct rq_flags rf; struct rq *rq; int err; rq = task_rq_lock(p, &rf); /* * Forcefully restricting the affinity of a deadline task is * likely to cause problems, so fail and noisily override the * mask entirely. */ if (task_has_dl_policy(p) && dl_bandwidth_enabled()) { err = -EPERM; goto err_unlock; } if (!cpumask_and(new_mask, task_user_cpus(p), subset_mask)) { err = -EINVAL; goto err_unlock; } return __set_cpus_allowed_ptr_locked(p, &ac, rq, &rf); err_unlock: task_rq_unlock(rq, p, &rf); return err; } /* * Restrict the CPU affinity of task @p so that it is a subset of * task_cpu_possible_mask() and point @p->user_cpus_ptr to a copy of the * old affinity mask. If the resulting mask is empty, we warn and walk * up the cpuset hierarchy until we find a suitable mask. */ void force_compatible_cpus_allowed_ptr(struct task_struct *p) { cpumask_var_t new_mask; const struct cpumask *override_mask = task_cpu_possible_mask(p); alloc_cpumask_var(&new_mask, GFP_KERNEL); /* * __migrate_task() can fail silently in the face of concurrent * offlining of the chosen destination CPU, so take the hotplug * lock to ensure that the migration succeeds. */ cpus_read_lock(); if (!cpumask_available(new_mask)) goto out_set_mask; if (!restrict_cpus_allowed_ptr(p, new_mask, override_mask)) goto out_free_mask; /* * We failed to find a valid subset of the affinity mask for the * task, so override it based on its cpuset hierarchy. */ cpuset_cpus_allowed(p, new_mask); override_mask = new_mask; out_set_mask: if (printk_ratelimit()) { printk_deferred("Overriding affinity for process %d (%s) to CPUs %*pbl\n", task_pid_nr(p), p->comm, cpumask_pr_args(override_mask)); } WARN_ON(set_cpus_allowed_ptr(p, override_mask)); out_free_mask: cpus_read_unlock(); free_cpumask_var(new_mask); } static int __sched_setaffinity(struct task_struct *p, struct affinity_context *ctx); /* * Restore the affinity of a task @p which was previously restricted by a * call to force_compatible_cpus_allowed_ptr(). * * It is the caller's responsibility to serialise this with any calls to * force_compatible_cpus_allowed_ptr(@p). */ void relax_compatible_cpus_allowed_ptr(struct task_struct *p) { struct affinity_context ac = { .new_mask = task_user_cpus(p), .flags = 0, }; int ret; /* * Try to restore the old affinity mask with __sched_setaffinity(). * Cpuset masking will be done there too. */ ret = __sched_setaffinity(p, &ac); WARN_ON_ONCE(ret); } void set_task_cpu(struct task_struct *p, unsigned int new_cpu) { #ifdef CONFIG_SCHED_DEBUG unsigned int state = READ_ONCE(p->__state); /* * We should never call set_task_cpu() on a blocked task, * ttwu() will sort out the placement. */ WARN_ON_ONCE(state != TASK_RUNNING && state != TASK_WAKING && !p->on_rq); /* * Migrating fair class task must have p->on_rq = TASK_ON_RQ_MIGRATING, * because schedstat_wait_{start,end} rebase migrating task's wait_start * time relying on p->on_rq. */ WARN_ON_ONCE(state == TASK_RUNNING && p->sched_class == &fair_sched_class && (p->on_rq && !task_on_rq_migrating(p))); #ifdef CONFIG_LOCKDEP /* * The caller should hold either p->pi_lock or rq->lock, when changing * a task's CPU. ->pi_lock for waking tasks, rq->lock for runnable tasks. * * sched_move_task() holds both and thus holding either pins the cgroup, * see task_group(). * * Furthermore, all task_rq users should acquire both locks, see * task_rq_lock(). */ WARN_ON_ONCE(debug_locks && !(lockdep_is_held(&p->pi_lock) || lockdep_is_held(__rq_lockp(task_rq(p))))); #endif /* * Clearly, migrating tasks to offline CPUs is a fairly daft thing. */ WARN_ON_ONCE(!cpu_online(new_cpu)); WARN_ON_ONCE(is_migration_disabled(p)); #endif trace_sched_migrate_task(p, new_cpu); if (task_cpu(p) != new_cpu) { if (p->sched_class->migrate_task_rq) p->sched_class->migrate_task_rq(p, new_cpu); p->se.nr_migrations++; rseq_migrate(p); sched_mm_cid_migrate_from(p); perf_event_task_migrate(p); } __set_task_cpu(p, new_cpu); } #ifdef CONFIG_NUMA_BALANCING static void __migrate_swap_task(struct task_struct *p, int cpu) { if (task_on_rq_queued(p)) { struct rq *src_rq, *dst_rq; struct rq_flags srf, drf; src_rq = task_rq(p); dst_rq = cpu_rq(cpu); rq_pin_lock(src_rq, &srf); rq_pin_lock(dst_rq, &drf); deactivate_task(src_rq, p, 0); set_task_cpu(p, cpu); activate_task(dst_rq, p, 0); wakeup_preempt(dst_rq, p, 0); rq_unpin_lock(dst_rq, &drf); rq_unpin_lock(src_rq, &srf); } else { /* * Task isn't running anymore; make it appear like we migrated * it before it went to sleep. This means on wakeup we make the * previous CPU our target instead of where it really is. */ p->wake_cpu = cpu; } } struct migration_swap_arg { struct task_struct *src_task, *dst_task; int src_cpu, dst_cpu; }; static int migrate_swap_stop(void *data) { struct migration_swap_arg *arg = data; struct rq *src_rq, *dst_rq; if (!cpu_active(arg->src_cpu) || !cpu_active(arg->dst_cpu)) return -EAGAIN; src_rq = cpu_rq(arg->src_cpu); dst_rq = cpu_rq(arg->dst_cpu); guard(double_raw_spinlock)(&arg->src_task->pi_lock, &arg->dst_task->pi_lock); guard(double_rq_lock)(src_rq, dst_rq); if (task_cpu(arg->dst_task) != arg->dst_cpu) return -EAGAIN; if (task_cpu(arg->src_task) != arg->src_cpu) return -EAGAIN; if (!cpumask_test_cpu(arg->dst_cpu, arg->src_task->cpus_ptr)) return -EAGAIN; if (!cpumask_test_cpu(arg->src_cpu, arg->dst_task->cpus_ptr)) return -EAGAIN; __migrate_swap_task(arg->src_task, arg->dst_cpu); __migrate_swap_task(arg->dst_task, arg->src_cpu); return 0; } /* * Cross migrate two tasks */ int migrate_swap(struct task_struct *cur, struct task_struct *p, int target_cpu, int curr_cpu) { struct migration_swap_arg arg; int ret = -EINVAL; arg = (struct migration_swap_arg){ .src_task = cur, .src_cpu = curr_cpu, .dst_task = p, .dst_cpu = target_cpu, }; if (arg.src_cpu == arg.dst_cpu) goto out; /* * These three tests are all lockless; this is OK since all of them * will be re-checked with proper locks held further down the line. */ if (!cpu_active(arg.src_cpu) || !cpu_active(arg.dst_cpu)) goto out; if (!cpumask_test_cpu(arg.dst_cpu, arg.src_task->cpus_ptr)) goto out; if (!cpumask_test_cpu(arg.src_cpu, arg.dst_task->cpus_ptr)) goto out; trace_sched_swap_numa(cur, arg.src_cpu, p, arg.dst_cpu); ret = stop_two_cpus(arg.dst_cpu, arg.src_cpu, migrate_swap_stop, &arg); out: return ret; } #endif /* CONFIG_NUMA_BALANCING */ /*** * kick_process - kick a running thread to enter/exit the kernel * @p: the to-be-kicked thread * * Cause a process which is running on another CPU to enter * kernel-mode, without any delay. (to get signals handled.) * * NOTE: this function doesn't have to take the runqueue lock, * because all it wants to ensure is that the remote task enters * the kernel. If the IPI races and the task has been migrated * to another CPU then no harm is done and the purpose has been * achieved as well. */ void kick_process(struct task_struct *p) { guard(preempt)(); int cpu = task_cpu(p); if ((cpu != smp_processor_id()) && task_curr(p)) smp_send_reschedule(cpu); } EXPORT_SYMBOL_GPL(kick_process); /* * ->cpus_ptr is protected by both rq->lock and p->pi_lock * * A few notes on cpu_active vs cpu_online: * * - cpu_active must be a subset of cpu_online * * - on CPU-up we allow per-CPU kthreads on the online && !active CPU, * see __set_cpus_allowed_ptr(). At this point the newly online * CPU isn't yet part of the sched domains, and balancing will not * see it. * * - on CPU-down we clear cpu_active() to mask the sched domains and * avoid the load balancer to place new tasks on the to be removed * CPU. Existing tasks will remain running there and will be taken * off. * * This means that fallback selection must not select !active CPUs. * And can assume that any active CPU must be online. Conversely * select_task_rq() below may allow selection of !active CPUs in order * to satisfy the above rules. */ static int select_fallback_rq(int cpu, struct task_struct *p) { int nid = cpu_to_node(cpu); const struct cpumask *nodemask = NULL; enum { cpuset, possible, fail } state = cpuset; int dest_cpu; /* * If the node that the CPU is on has been offlined, cpu_to_node() * will return -1. There is no CPU on the node, and we should * select the CPU on the other node. */ if (nid != -1) { nodemask = cpumask_of_node(nid); /* Look for allowed, online CPU in same node. */ for_each_cpu(dest_cpu, nodemask) { if (is_cpu_allowed(p, dest_cpu)) return dest_cpu; } } for (;;) { /* Any allowed, online CPU? */ for_each_cpu(dest_cpu, p->cpus_ptr) { if (!is_cpu_allowed(p, dest_cpu)) continue; goto out; } /* No more Mr. Nice Guy. */ switch (state) { case cpuset: if (cpuset_cpus_allowed_fallback(p)) { state = possible; break; } fallthrough; case possible: /* * XXX When called from select_task_rq() we only * hold p->pi_lock and again violate locking order. * * More yuck to audit. */ do_set_cpus_allowed(p, task_cpu_possible_mask(p)); state = fail; break; case fail: BUG(); break; } } out: if (state != cpuset) { /* * Don't tell them about moving exiting tasks or * kernel threads (both mm NULL), since they never * leave kernel. */ if (p->mm && printk_ratelimit()) { printk_deferred("process %d (%s) no longer affine to cpu%d\n", task_pid_nr(p), p->comm, cpu); } } return dest_cpu; } /* * The caller (fork, wakeup) owns p->pi_lock, ->cpus_ptr is stable. */ static inline int select_task_rq(struct task_struct *p, int cpu, int wake_flags) { lockdep_assert_held(&p->pi_lock); if (p->nr_cpus_allowed > 1 && !is_migration_disabled(p)) cpu = p->sched_class->select_task_rq(p, cpu, wake_flags); else cpu = cpumask_any(p->cpus_ptr); /* * In order not to call set_task_cpu() on a blocking task we need * to rely on ttwu() to place the task on a valid ->cpus_ptr * CPU. * * Since this is common to all placement strategies, this lives here. * * [ this allows ->select_task() to simply return task_cpu(p) and * not worry about this generic constraint ] */ if (unlikely(!is_cpu_allowed(p, cpu))) cpu = select_fallback_rq(task_cpu(p), p); return cpu; } void sched_set_stop_task(int cpu, struct task_struct *stop) { static struct lock_class_key stop_pi_lock; struct sched_param param = { .sched_priority = MAX_RT_PRIO - 1 }; struct task_struct *old_stop = cpu_rq(cpu)->stop; if (stop) { /* * Make it appear like a SCHED_FIFO task, its something * userspace knows about and won't get confused about. * * Also, it will make PI more or less work without too * much confusion -- but then, stop work should not * rely on PI working anyway. */ sched_setscheduler_nocheck(stop, SCHED_FIFO, ¶m); stop->sched_class = &stop_sched_class; /* * The PI code calls rt_mutex_setprio() with ->pi_lock held to * adjust the effective priority of a task. As a result, * rt_mutex_setprio() can trigger (RT) balancing operations, * which can then trigger wakeups of the stop thread to push * around the current task. * * The stop task itself will never be part of the PI-chain, it * never blocks, therefore that ->pi_lock recursion is safe. * Tell lockdep about this by placing the stop->pi_lock in its * own class. */ lockdep_set_class(&stop->pi_lock, &stop_pi_lock); } cpu_rq(cpu)->stop = stop; if (old_stop) { /* * Reset it back to a normal scheduling class so that * it can die in pieces. */ old_stop->sched_class = &rt_sched_class; } } #else /* CONFIG_SMP */ static inline int __set_cpus_allowed_ptr(struct task_struct *p, struct affinity_context *ctx) { return set_cpus_allowed_ptr(p, ctx->new_mask); } static inline void migrate_disable_switch(struct rq *rq, struct task_struct *p) { } static inline bool rq_has_pinned_tasks(struct rq *rq) { return false; } static inline cpumask_t *alloc_user_cpus_ptr(int node) { return NULL; } #endif /* !CONFIG_SMP */ static void ttwu_stat(struct task_struct *p, int cpu, int wake_flags) { struct rq *rq; if (!schedstat_enabled()) return; rq = this_rq(); #ifdef CONFIG_SMP if (cpu == rq->cpu) { __schedstat_inc(rq->ttwu_local); __schedstat_inc(p->stats.nr_wakeups_local); } else { struct sched_domain *sd; __schedstat_inc(p->stats.nr_wakeups_remote); guard(rcu)(); for_each_domain(rq->cpu, sd) { if (cpumask_test_cpu(cpu, sched_domain_span(sd))) { __schedstat_inc(sd->ttwu_wake_remote); break; } } } if (wake_flags & WF_MIGRATED) __schedstat_inc(p->stats.nr_wakeups_migrate); #endif /* CONFIG_SMP */ __schedstat_inc(rq->ttwu_count); __schedstat_inc(p->stats.nr_wakeups); if (wake_flags & WF_SYNC) __schedstat_inc(p->stats.nr_wakeups_sync); } /* * Mark the task runnable. */ static inline void ttwu_do_wakeup(struct task_struct *p) { WRITE_ONCE(p->__state, TASK_RUNNING); trace_sched_wakeup(p); } static void ttwu_do_activate(struct rq *rq, struct task_struct *p, int wake_flags, struct rq_flags *rf) { int en_flags = ENQUEUE_WAKEUP | ENQUEUE_NOCLOCK; lockdep_assert_rq_held(rq); if (p->sched_contributes_to_load) rq->nr_uninterruptible--; #ifdef CONFIG_SMP if (wake_flags & WF_MIGRATED) en_flags |= ENQUEUE_MIGRATED; else #endif if (p->in_iowait) { delayacct_blkio_end(p); atomic_dec(&task_rq(p)->nr_iowait); } activate_task(rq, p, en_flags); wakeup_preempt(rq, p, wake_flags); ttwu_do_wakeup(p); #ifdef CONFIG_SMP if (p->sched_class->task_woken) { /* * Our task @p is fully woken up and running; so it's safe to * drop the rq->lock, hereafter rq is only used for statistics. */ rq_unpin_lock(rq, rf); p->sched_class->task_woken(rq, p); rq_repin_lock(rq, rf); } if (rq->idle_stamp) { u64 delta = rq_clock(rq) - rq->idle_stamp; u64 max = 2*rq->max_idle_balance_cost; update_avg(&rq->avg_idle, delta); if (rq->avg_idle > max) rq->avg_idle = max; rq->idle_stamp = 0; } #endif p->dl_server = NULL; } /* * Consider @p being inside a wait loop: * * for (;;) { * set_current_state(TASK_UNINTERRUPTIBLE); * * if (CONDITION) * break; * * schedule(); * } * __set_current_state(TASK_RUNNING); * * between set_current_state() and schedule(). In this case @p is still * runnable, so all that needs doing is change p->state back to TASK_RUNNING in * an atomic manner. * * By taking task_rq(p)->lock we serialize against schedule(), if @p->on_rq * then schedule() must still happen and p->state can be changed to * TASK_RUNNING. Otherwise we lost the race, schedule() has happened, and we * need to do a full wakeup with enqueue. * * Returns: %true when the wakeup is done, * %false otherwise. */ static int ttwu_runnable(struct task_struct *p, int wake_flags) { struct rq_flags rf; struct rq *rq; int ret = 0; rq = __task_rq_lock(p, &rf); if (task_on_rq_queued(p)) { if (!task_on_cpu(rq, p)) { /* * When on_rq && !on_cpu the task is preempted, see if * it should preempt the task that is current now. */ update_rq_clock(rq); wakeup_preempt(rq, p, wake_flags); } ttwu_do_wakeup(p); ret = 1; } __task_rq_unlock(rq, &rf); return ret; } #ifdef CONFIG_SMP void sched_ttwu_pending(void *arg) { struct llist_node *llist = arg; struct rq *rq = this_rq(); struct task_struct *p, *t; struct rq_flags rf; if (!llist) return; rq_lock_irqsave(rq, &rf); update_rq_clock(rq); llist_for_each_entry_safe(p, t, llist, wake_entry.llist) { if (WARN_ON_ONCE(p->on_cpu)) smp_cond_load_acquire(&p->on_cpu, !VAL); if (WARN_ON_ONCE(task_cpu(p) != cpu_of(rq))) set_task_cpu(p, cpu_of(rq)); ttwu_do_activate(rq, p, p->sched_remote_wakeup ? WF_MIGRATED : 0, &rf); } /* * Must be after enqueueing at least once task such that * idle_cpu() does not observe a false-negative -- if it does, * it is possible for select_idle_siblings() to stack a number * of tasks on this CPU during that window. * * It is ok to clear ttwu_pending when another task pending. * We will receive IPI after local irq enabled and then enqueue it. * Since now nr_running > 0, idle_cpu() will always get correct result. */ WRITE_ONCE(rq->ttwu_pending, 0); rq_unlock_irqrestore(rq, &rf); } /* * Prepare the scene for sending an IPI for a remote smp_call * * Returns true if the caller can proceed with sending the IPI. * Returns false otherwise. */ bool call_function_single_prep_ipi(int cpu) { if (set_nr_if_polling(cpu_rq(cpu)->idle)) { trace_sched_wake_idle_without_ipi(cpu); return false; } return true; } /* * Queue a task on the target CPUs wake_list and wake the CPU via IPI if * necessary. The wakee CPU on receipt of the IPI will queue the task * via sched_ttwu_wakeup() for activation so the wakee incurs the cost * of the wakeup instead of the waker. */ static void __ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags) { struct rq *rq = cpu_rq(cpu); p->sched_remote_wakeup = !!(wake_flags & WF_MIGRATED); WRITE_ONCE(rq->ttwu_pending, 1); __smp_call_single_queue(cpu, &p->wake_entry.llist); } void wake_up_if_idle(int cpu) { struct rq *rq = cpu_rq(cpu); guard(rcu)(); if (is_idle_task(rcu_dereference(rq->curr))) { guard(rq_lock_irqsave)(rq); if (is_idle_task(rq->curr)) resched_curr(rq); } } bool cpus_equal_capacity(int this_cpu, int that_cpu) { if (!sched_asym_cpucap_active()) return true; if (this_cpu == that_cpu) return true; return arch_scale_cpu_capacity(this_cpu) == arch_scale_cpu_capacity(that_cpu); } bool cpus_share_cache(int this_cpu, int that_cpu) { if (this_cpu == that_cpu) return true; return per_cpu(sd_llc_id, this_cpu) == per_cpu(sd_llc_id, that_cpu); } /* * Whether CPUs are share cache resources, which means LLC on non-cluster * machines and LLC tag or L2 on machines with clusters. */ bool cpus_share_resources(int this_cpu, int that_cpu) { if (this_cpu == that_cpu) return true; return per_cpu(sd_share_id, this_cpu) == per_cpu(sd_share_id, that_cpu); } static inline bool ttwu_queue_cond(struct task_struct *p, int cpu) { /* * Do not complicate things with the async wake_list while the CPU is * in hotplug state. */ if (!cpu_active(cpu)) return false; /* Ensure the task will still be allowed to run on the CPU. */ if (!cpumask_test_cpu(cpu, p->cpus_ptr)) return false; /* * If the CPU does not share cache, then queue the task on the * remote rqs wakelist to avoid accessing remote data. */ if (!cpus_share_cache(smp_processor_id(), cpu)) return true; if (cpu == smp_processor_id()) return false; /* * If the wakee cpu is idle, or the task is descheduling and the * only running task on the CPU, then use the wakelist to offload * the task activation to the idle (or soon-to-be-idle) CPU as * the current CPU is likely busy. nr_running is checked to * avoid unnecessary task stacking. * * Note that we can only get here with (wakee) p->on_rq=0, * p->on_cpu can be whatever, we've done the dequeue, so * the wakee has been accounted out of ->nr_running. */ if (!cpu_rq(cpu)->nr_running) return true; return false; } static bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags) { if (sched_feat(TTWU_QUEUE) && ttwu_queue_cond(p, cpu)) { sched_clock_cpu(cpu); /* Sync clocks across CPUs */ __ttwu_queue_wakelist(p, cpu, wake_flags); return true; } return false; } #else /* !CONFIG_SMP */ static inline bool ttwu_queue_wakelist(struct task_struct *p, int cpu, int wake_flags) { return false; } #endif /* CONFIG_SMP */ static void ttwu_queue(struct task_struct *p, int cpu, int wake_flags) { struct rq *rq = cpu_rq(cpu); struct rq_flags rf; if (ttwu_queue_wakelist(p, cpu, wake_flags)) return; rq_lock(rq, &rf); update_rq_clock(rq); ttwu_do_activate(rq, p, wake_flags, &rf); rq_unlock(rq, &rf); } /* * Invoked from try_to_wake_up() to check whether the task can be woken up. * * The caller holds p::pi_lock if p != current or has preemption * disabled when p == current. * * The rules of saved_state: * * The related locking code always holds p::pi_lock when updating * p::saved_state, which means the code is fully serialized in both cases. * * For PREEMPT_RT, the lock wait and lock wakeups happen via TASK_RTLOCK_WAIT. * No other bits set. This allows to distinguish all wakeup scenarios. * * For FREEZER, the wakeup happens via TASK_FROZEN. No other bits set. This * allows us to prevent early wakeup of tasks before they can be run on * asymmetric ISA architectures (eg ARMv9). */ static __always_inline bool ttwu_state_match(struct task_struct *p, unsigned int state, int *success) { int match; if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) { WARN_ON_ONCE((state & TASK_RTLOCK_WAIT) && state != TASK_RTLOCK_WAIT); } *success = !!(match = __task_state_match(p, state)); /* * Saved state preserves the task state across blocking on * an RT lock or TASK_FREEZABLE tasks. If the state matches, * set p::saved_state to TASK_RUNNING, but do not wake the task * because it waits for a lock wakeup or __thaw_task(). Also * indicate success because from the regular waker's point of * view this has succeeded. * * After acquiring the lock the task will restore p::__state * from p::saved_state which ensures that the regular * wakeup is not lost. The restore will also set * p::saved_state to TASK_RUNNING so any further tests will * not result in false positives vs. @success */ if (match < 0) p->saved_state = TASK_RUNNING; return match > 0; } /* * Notes on Program-Order guarantees on SMP systems. * * MIGRATION * * The basic program-order guarantee on SMP systems is that when a task [t] * migrates, all its activity on its old CPU [c0] happens-before any subsequent * execution on its new CPU [c1]. * * For migration (of runnable tasks) this is provided by the following means: * * A) UNLOCK of the rq(c0)->lock scheduling out task t * B) migration for t is required to synchronize *both* rq(c0)->lock and * rq(c1)->lock (if not at the same time, then in that order). * C) LOCK of the rq(c1)->lock scheduling in task * * Release/acquire chaining guarantees that B happens after A and C after B. * Note: the CPU doing B need not be c0 or c1 * * Example: * * CPU0 CPU1 CPU2 * * LOCK rq(0)->lock * sched-out X * sched-in Y * UNLOCK rq(0)->lock * * LOCK rq(0)->lock // orders against CPU0 * dequeue X * UNLOCK rq(0)->lock * * LOCK rq(1)->lock * enqueue X * UNLOCK rq(1)->lock * * LOCK rq(1)->lock // orders against CPU2 * sched-out Z * sched-in X * UNLOCK rq(1)->lock * * * BLOCKING -- aka. SLEEP + WAKEUP * * For blocking we (obviously) need to provide the same guarantee as for * migration. However the means are completely different as there is no lock * chain to provide order. Instead we do: * * 1) smp_store_release(X->on_cpu, 0) -- finish_task() * 2) smp_cond_load_acquire(!X->on_cpu) -- try_to_wake_up() * * Example: * * CPU0 (schedule) CPU1 (try_to_wake_up) CPU2 (schedule) * * LOCK rq(0)->lock LOCK X->pi_lock * dequeue X * sched-out X * smp_store_release(X->on_cpu, 0); * * smp_cond_load_acquire(&X->on_cpu, !VAL); * X->state = WAKING * set_task_cpu(X,2) * * LOCK rq(2)->lock * enqueue X * X->state = RUNNING * UNLOCK rq(2)->lock * * LOCK rq(2)->lock // orders against CPU1 * sched-out Z * sched-in X * UNLOCK rq(2)->lock * * UNLOCK X->pi_lock * UNLOCK rq(0)->lock * * * However, for wakeups there is a second guarantee we must provide, namely we * must ensure that CONDITION=1 done by the caller can not be reordered with * accesses to the task state; see try_to_wake_up() and set_current_state(). */ /** * try_to_wake_up - wake up a thread * @p: the thread to be awakened * @state: the mask of task states that can be woken * @wake_flags: wake modifier flags (WF_*) * * Conceptually does: * * If (@state & @p->state) @p->state = TASK_RUNNING. * * If the task was not queued/runnable, also place it back on a runqueue. * * This function is atomic against schedule() which would dequeue the task. * * It issues a full memory barrier before accessing @p->state, see the comment * with set_current_state(). * * Uses p->pi_lock to serialize against concurrent wake-ups. * * Relies on p->pi_lock stabilizing: * - p->sched_class * - p->cpus_ptr * - p->sched_task_group * in order to do migration, see its use of select_task_rq()/set_task_cpu(). * * Tries really hard to only take one task_rq(p)->lock for performance. * Takes rq->lock in: * - ttwu_runnable() -- old rq, unavoidable, see comment there; * - ttwu_queue() -- new rq, for enqueue of the task; * - psi_ttwu_dequeue() -- much sadness :-( accounting will kill us. * * As a consequence we race really badly with just about everything. See the * many memory barriers and their comments for details. * * Return: %true if @p->state changes (an actual wakeup was done), * %false otherwise. */ int try_to_wake_up(struct task_struct *p, unsigned int state, int wake_flags) { guard(preempt)(); int cpu, success = 0; if (p == current) { /* * We're waking current, this means 'p->on_rq' and 'task_cpu(p) * == smp_processor_id()'. Together this means we can special * case the whole 'p->on_rq && ttwu_runnable()' case below * without taking any locks. * * In particular: * - we rely on Program-Order guarantees for all the ordering, * - we're serialized against set_special_state() by virtue of * it disabling IRQs (this allows not taking ->pi_lock). */ if (!ttwu_state_match(p, state, &success)) goto out; trace_sched_waking(p); ttwu_do_wakeup(p); goto out; } /* * If we are going to wake up a thread waiting for CONDITION we * need to ensure that CONDITION=1 done by the caller can not be * reordered with p->state check below. This pairs with smp_store_mb() * in set_current_state() that the waiting thread does. */ scoped_guard (raw_spinlock_irqsave, &p->pi_lock) { smp_mb__after_spinlock(); if (!ttwu_state_match(p, state, &success)) break; trace_sched_waking(p); /* * Ensure we load p->on_rq _after_ p->state, otherwise it would * be possible to, falsely, observe p->on_rq == 0 and get stuck * in smp_cond_load_acquire() below. * * sched_ttwu_pending() try_to_wake_up() * STORE p->on_rq = 1 LOAD p->state * UNLOCK rq->lock * * __schedule() (switch to task 'p') * LOCK rq->lock smp_rmb(); * smp_mb__after_spinlock(); * UNLOCK rq->lock * * [task p] * STORE p->state = UNINTERRUPTIBLE LOAD p->on_rq * * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in * __schedule(). See the comment for smp_mb__after_spinlock(). * * A similar smp_rmb() lives in __task_needs_rq_lock(). */ smp_rmb(); if (READ_ONCE(p->on_rq) && ttwu_runnable(p, wake_flags)) break; #ifdef CONFIG_SMP /* * Ensure we load p->on_cpu _after_ p->on_rq, otherwise it would be * possible to, falsely, observe p->on_cpu == 0. * * One must be running (->on_cpu == 1) in order to remove oneself * from the runqueue. * * __schedule() (switch to task 'p') try_to_wake_up() * STORE p->on_cpu = 1 LOAD p->on_rq * UNLOCK rq->lock * * __schedule() (put 'p' to sleep) * LOCK rq->lock smp_rmb(); * smp_mb__after_spinlock(); * STORE p->on_rq = 0 LOAD p->on_cpu * * Pairs with the LOCK+smp_mb__after_spinlock() on rq->lock in * __schedule(). See the comment for smp_mb__after_spinlock(). * * Form a control-dep-acquire with p->on_rq == 0 above, to ensure * schedule()'s deactivate_task() has 'happened' and p will no longer * care about it's own p->state. See the comment in __schedule(). */ smp_acquire__after_ctrl_dep(); /* * We're doing the wakeup (@success == 1), they did a dequeue (p->on_rq * == 0), which means we need to do an enqueue, change p->state to * TASK_WAKING such that we can unlock p->pi_lock before doing the * enqueue, such as ttwu_queue_wakelist(). */ WRITE_ONCE(p->__state, TASK_WAKING); /* * If the owning (remote) CPU is still in the middle of schedule() with * this task as prev, considering queueing p on the remote CPUs wake_list * which potentially sends an IPI instead of spinning on p->on_cpu to * let the waker make forward progress. This is safe because IRQs are * disabled and the IPI will deliver after on_cpu is cleared. * * Ensure we load task_cpu(p) after p->on_cpu: * * set_task_cpu(p, cpu); * STORE p->cpu = @cpu * __schedule() (switch to task 'p') * LOCK rq->lock * smp_mb__after_spin_lock() smp_cond_load_acquire(&p->on_cpu) * STORE p->on_cpu = 1 LOAD p->cpu * * to ensure we observe the correct CPU on which the task is currently * scheduling. */ if (smp_load_acquire(&p->on_cpu) && ttwu_queue_wakelist(p, task_cpu(p), wake_flags)) break; /* * If the owning (remote) CPU is still in the middle of schedule() with * this task as prev, wait until it's done referencing the task. * * Pairs with the smp_store_release() in finish_task(). * * This ensures that tasks getting woken will be fully ordered against * their previous state and preserve Program Order. */ smp_cond_load_acquire(&p->on_cpu, !VAL); cpu = select_task_rq(p, p->wake_cpu, wake_flags | WF_TTWU); if (task_cpu(p) != cpu) { if (p->in_iowait) { delayacct_blkio_end(p); atomic_dec(&task_rq(p)->nr_iowait); } wake_flags |= WF_MIGRATED; psi_ttwu_dequeue(p); set_task_cpu(p, cpu); } #else cpu = task_cpu(p); #endif /* CONFIG_SMP */ ttwu_queue(p, cpu, wake_flags); } out: if (success) ttwu_stat(p, task_cpu(p), wake_flags); return success; } static bool __task_needs_rq_lock(struct task_struct *p) { unsigned int state = READ_ONCE(p->__state); /* * Since pi->lock blocks try_to_wake_up(), we don't need rq->lock when * the task is blocked. Make sure to check @state since ttwu() can drop * locks at the end, see ttwu_queue_wakelist(). */ if (state == TASK_RUNNING || state == TASK_WAKING) return true; /* * Ensure we load p->on_rq after p->__state, otherwise it would be * possible to, falsely, observe p->on_rq == 0. * * See try_to_wake_up() for a longer comment. */ smp_rmb(); if (p->on_rq) return true; #ifdef CONFIG_SMP /* * Ensure the task has finished __schedule() and will not be referenced * anymore. Again, see try_to_wake_up() for a longer comment. */ smp_rmb(); smp_cond_load_acquire(&p->on_cpu, !VAL); #endif return false; } /** * task_call_func - Invoke a function on task in fixed state * @p: Process for which the function is to be invoked, can be @current. * @func: Function to invoke. * @arg: Argument to function. * * Fix the task in it's current state by avoiding wakeups and or rq operations * and call @func(@arg) on it. This function can use ->on_rq and task_curr() * to work out what the state is, if required. Given that @func can be invoked * with a runqueue lock held, it had better be quite lightweight. * * Returns: * Whatever @func returns */ int task_call_func(struct task_struct *p, task_call_f func, void *arg) { struct rq *rq = NULL; struct rq_flags rf; int ret; raw_spin_lock_irqsave(&p->pi_lock, rf.flags); if (__task_needs_rq_lock(p)) rq = __task_rq_lock(p, &rf); /* * At this point the task is pinned; either: * - blocked and we're holding off wakeups (pi->lock) * - woken, and we're holding off enqueue (rq->lock) * - queued, and we're holding off schedule (rq->lock) * - running, and we're holding off de-schedule (rq->lock) * * The called function (@func) can use: task_curr(), p->on_rq and * p->__state to differentiate between these states. */ ret = func(p, arg); if (rq) rq_unlock(rq, &rf); raw_spin_unlock_irqrestore(&p->pi_lock, rf.flags); return ret; } /** * cpu_curr_snapshot - Return a snapshot of the currently running task * @cpu: The CPU on which to snapshot the task. * * Returns the task_struct pointer of the task "currently" running on * the specified CPU. If the same task is running on that CPU throughout, * the return value will be a pointer to that task's task_struct structure. * If the CPU did any context switches even vaguely concurrently with the * execution of this function, the return value will be a pointer to the * task_struct structure of a randomly chosen task that was running on * that CPU somewhere around the time that this function was executing. * * If the specified CPU was offline, the return value is whatever it * is, perhaps a pointer to the task_struct structure of that CPU's idle * task, but there is no guarantee. Callers wishing a useful return * value must take some action to ensure that the specified CPU remains * online throughout. * * This function executes full memory barriers before and after fetching * the pointer, which permits the caller to confine this function's fetch * with respect to the caller's accesses to other shared variables. */ struct task_struct *cpu_curr_snapshot(int cpu) { struct task_struct *t; smp_mb(); /* Pairing determined by caller's synchronization design. */ t = rcu_dereference(cpu_curr(cpu)); smp_mb(); /* Pairing determined by caller's synchronization design. */ return t; } /** * wake_up_process - Wake up a specific process * @p: The process to be woken up. * * Attempt to wake up the nominated process and move it to the set of runnable * processes. * * Return: 1 if the process was woken up, 0 if it was already running. * * This function executes a full memory barrier before accessing the task state. */ int wake_up_process(struct task_struct *p) { return try_to_wake_up(p, TASK_NORMAL, 0); } EXPORT_SYMBOL(wake_up_process); int wake_up_state(struct task_struct *p, unsigned int state) { return try_to_wake_up(p, state, 0); } /* * Perform scheduler related setup for a newly forked process p. * p is forked by current. * * __sched_fork() is basic setup used by init_idle() too: */ static void __sched_fork(unsigned long clone_flags, struct task_struct *p) { p->on_rq = 0; p->se.on_rq = 0; p->se.exec_start = 0; p->se.sum_exec_runtime = 0; p->se.prev_sum_exec_runtime = 0; p->se.nr_migrations = 0; p->se.vruntime = 0; p->se.vlag = 0; p->se.slice = sysctl_sched_base_slice; INIT_LIST_HEAD(&p->se.group_node); #ifdef CONFIG_FAIR_GROUP_SCHED p->se.cfs_rq = NULL; #endif #ifdef CONFIG_SCHEDSTATS /* Even if schedstat is disabled, there should not be garbage */ memset(&p->stats, 0, sizeof(p->stats)); #endif init_dl_entity(&p->dl); INIT_LIST_HEAD(&p->rt.run_list); p->rt.timeout = 0; p->rt.time_slice = sched_rr_timeslice; p->rt.on_rq = 0; p->rt.on_list = 0; #ifdef CONFIG_PREEMPT_NOTIFIERS INIT_HLIST_HEAD(&p->preempt_notifiers); #endif #ifdef CONFIG_COMPACTION p->capture_control = NULL; #endif init_numa_balancing(clone_flags, p); #ifdef CONFIG_SMP p->wake_entry.u_flags = CSD_TYPE_TTWU; p->migration_pending = NULL; #endif init_sched_mm_cid(p); } DEFINE_STATIC_KEY_FALSE(sched_numa_balancing); #ifdef CONFIG_NUMA_BALANCING int sysctl_numa_balancing_mode; static void __set_numabalancing_state(bool enabled) { if (enabled) static_branch_enable(&sched_numa_balancing); else static_branch_disable(&sched_numa_balancing); } void set_numabalancing_state(bool enabled) { if (enabled) sysctl_numa_balancing_mode = NUMA_BALANCING_NORMAL; else sysctl_numa_balancing_mode = NUMA_BALANCING_DISABLED; __set_numabalancing_state(enabled); } #ifdef CONFIG_PROC_SYSCTL static void reset_memory_tiering(void) { struct pglist_data *pgdat; for_each_online_pgdat(pgdat) { pgdat->nbp_threshold = 0; pgdat->nbp_th_nr_cand = node_page_state(pgdat, PGPROMOTE_CANDIDATE); pgdat->nbp_th_start = jiffies_to_msecs(jiffies); } } static int sysctl_numa_balancing(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { struct ctl_table t; int err; int state = sysctl_numa_balancing_mode; if (write && !capable(CAP_SYS_ADMIN)) return -EPERM; t = *table; t.data = &state; err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); if (err < 0) return err; if (write) { if (!(sysctl_numa_balancing_mode & NUMA_BALANCING_MEMORY_TIERING) && (state & NUMA_BALANCING_MEMORY_TIERING)) reset_memory_tiering(); sysctl_numa_balancing_mode = state; __set_numabalancing_state(state); } return err; } #endif #endif #ifdef CONFIG_SCHEDSTATS DEFINE_STATIC_KEY_FALSE(sched_schedstats); static void set_schedstats(bool enabled) { if (enabled) static_branch_enable(&sched_schedstats); else static_branch_disable(&sched_schedstats); } void force_schedstat_enabled(void) { if (!schedstat_enabled()) { pr_info("kernel profiling enabled schedstats, disable via kernel.sched_schedstats.\n"); static_branch_enable(&sched_schedstats); } } static int __init setup_schedstats(char *str) { int ret = 0; if (!str) goto out; if (!strcmp(str, "enable")) { set_schedstats(true); ret = 1; } else if (!strcmp(str, "disable")) { set_schedstats(false); ret = 1; } out: if (!ret) pr_warn("Unable to parse schedstats=\n"); return ret; } __setup("schedstats=", setup_schedstats); #ifdef CONFIG_PROC_SYSCTL static int sysctl_schedstats(struct ctl_table *table, int write, void *buffer, size_t *lenp, loff_t *ppos) { struct ctl_table t; int err; int state = static_branch_likely(&sched_schedstats); if (write && !capable(CAP_SYS_ADMIN)) return -EPERM; t = *table; t.data = &state; err = proc_dointvec_minmax(&t, write, buffer, lenp, ppos); if (err < 0) return err; if (write) set_schedstats(state); return err; } #endif /* CONFIG_PROC_SYSCTL */ #endif /* CONFIG_SCHEDSTATS */ #ifdef CONFIG_SYSCTL static struct ctl_table sched_core_sysctls[] = { #ifdef CONFIG_SCHEDSTATS { .procname = "sched_schedstats", .data = NULL, .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = sysctl_schedstats, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_ONE, }, #endif /* CONFIG_SCHEDSTATS */ #ifdef CONFIG_UCLAMP_TASK { .procname = "sched_util_clamp_min", .data = &sysctl_sched_uclamp_util_min, .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = sysctl_sched_uclamp_handler, }, { .procname = "sched_util_clamp_max", .data = &sysctl_sched_uclamp_util_max, .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = sysctl_sched_uclamp_handler, }, { .procname = "sched_util_clamp_min_rt_default", .data = &sysctl_sched_uclamp_util_min_rt_default, .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = sysctl_sched_uclamp_handler, }, #endif /* CONFIG_UCLAMP_TASK */ #ifdef CONFIG_NUMA_BALANCING { .procname = "numa_balancing", .data = NULL, /* filled in by handler */ .maxlen = sizeof(unsigned int), .mode = 0644, .proc_handler = sysctl_numa_balancing, .extra1 = SYSCTL_ZERO, .extra2 = SYSCTL_FOUR, }, #endif /* CONFIG_NUMA_BALANCING */ {} }; static int __init sched_core_sysctl_init(void) { register_sysctl_init("kernel", sched_core_sysctls); return 0; } late_initcall(sched_core_sysctl_init); #endif /* CONFIG_SYSCTL */ /* * fork()/clone()-time setup: */ int sched_fork(unsigned long clone_flags, struct task_struct *p) { __sched_fork(clone_flags, p); /* * We mark the process as NEW here. This guarantees that * nobody will actually run it, and a signal or other external * event cannot wake it up and insert it on the runqueue either. */ p->__state = TASK_NEW; /* * Make sure we do not leak PI boosting priority to the child. */ p->prio = current->normal_prio; uclamp_fork(p); /* * Revert to default priority/policy on fork if requested. */ if (unlikely(p->sched_reset_on_fork)) { if (task_has_dl_policy(p) || task_has_rt_policy(p)) { p->policy = SCHED_NORMAL; p->static_prio = NICE_TO_PRIO(0); p->rt_priority = 0; } else if (PRIO_TO_NICE(p->static_prio) < 0) p->static_prio = NICE_TO_PRIO(0); p->prio = p->normal_prio = p->static_prio; set_load_weight(p, false); /* * We don't need the reset flag anymore after the fork. It has * fulfilled its duty: */ p->sched_reset_on_fork = 0; } if (dl_prio(p->prio)) return -EAGAIN; else if (rt_prio(p->prio)) p->sched_class = &rt_sched_class; else p->sched_class = &fair_sched_class; init_entity_runnable_average(&p->se); #ifdef CONFIG_SCHED_INFO if (likely(sched_info_on())) memset(&p->sched_info, 0, sizeof(p->sched_info)); #endif #if defined(CONFIG_SMP) p->on_cpu = 0; #endif init_task_preempt_count(p); #ifdef CONFIG_SMP plist_node_init(&p->pushable_tasks, MAX_PRIO); RB_CLEAR_NODE(&p->pushable_dl_tasks); #endif return 0; } void sched_cgroup_fork(struct task_struct *p, struct kernel_clone_args *kargs) { unsigned long flags; /* * Because we're not yet on the pid-hash, p->pi_lock isn't strictly * required yet, but lockdep gets upset if rules are violated. */ raw_spin_lock_irqsave(&p->pi_lock, flags); #ifdef CONFIG_CGROUP_SCHED if (1) { struct task_group *tg; tg = container_of(kargs->cset->subsys[cpu_cgrp_id], struct task_group, css); tg = autogroup_task_group(p, tg); p->sched_task_group = tg; } #endif rseq_migrate(p); /* * We're setting the CPU for the first time, we don't migrate, * so use __set_task_cpu(). */ __set_task_cpu(p, smp_processor_id()); if (p->sched_class->task_fork) p->sched_class->task_fork(p); raw_spin_unlock_irqrestore(&p->pi_lock, flags); } void sched_post_fork(struct task_struct *p) { uclamp_post_fork(p); } unsigned long to_ratio(u64 period, u64 runtime) { if (runtime == RUNTIME_INF) return BW_UNIT; /* * Doing this here saves a lot of checks in all * the calling paths, and returning zero seems * safe for them anyway. */ if (period == 0) return 0; return div64_u64(runtime << BW_SHIFT, period); } /* * wake_up_new_task - wake up a newly created task for the first time. * * This function will do some initial scheduler statistics housekeeping * that must be done for every newly created context, then puts the task * on the runqueue and wakes it. */ void wake_up_new_task(struct task_struct *p) { struct rq_flags rf; struct rq *rq; raw_spin_lock_irqsave(&p->pi_lock, rf.flags); WRITE_ONCE(p->__state, TASK_RUNNING); #ifdef CONFIG_SMP /* * Fork balancing, do it here and not earlier because: * - cpus_ptr can change in the fork path * - any previously selected CPU might disappear through hotplug * * Use __set_task_cpu() to avoid calling sched_class::migrate_task_rq, * as we're not fully set-up yet. */ p->recent_used_cpu = task_cpu(p); rseq_migrate(p); __set_task_cpu(p, select_task_rq(p, task_cpu(p), WF_FORK)); #endif rq = __task_rq_lock(p, &rf); update_rq_clock(rq); post_init_entity_util_avg(p); activate_task(rq, p, ENQUEUE_NOCLOCK); trace_sched_wakeup_new(p); wakeup_preempt(rq, p, WF_FORK); #ifdef CONFIG_SMP if (p->sched_class->task_woken) { /* * Nothing relies on rq->lock after this, so it's fine to * drop it. */ rq_unpin_lock(rq, &rf); p->sched_class->task_woken(rq, p); rq_repin_lock(rq, &rf); } #endif task_rq_unlock(rq, p, &rf); } #ifdef CONFIG_PREEMPT_NOTIFIERS static DEFINE_STATIC_KEY_FALSE(preempt_notifier_key); void preempt_notifier_inc(void) { static_branch_inc(&preempt_notifier_key); } EXPORT_SYMBOL_GPL(preempt_notifier_inc); void preempt_notifier_dec(void) { static_branch_dec(&preempt_notifier_key); } EXPORT_SYMBOL_GPL(preempt_notifier_dec); /** * preempt_notifier_register - tell me when current is being preempted & rescheduled * @notifier: notifier struct to register */ void preempt_notifier_register(struct preempt_notifier *notifier) { if (!static_branch_unlikely(&preempt_notifier_key)) WARN(1, "registering preempt_notifier while notifiers disabled\n"); hlist_add_head(¬ifier->link, ¤t->preempt_notifiers); } EXPORT_SYMBOL_GPL(preempt_notifier_register); /** * preempt_notifier_unregister - no longer interested in preemption notifications * @notifier: notifier struct to unregister * * This is *not* safe to call from within a preemption notifier. */ void preempt_notifier_unregister(struct preempt_notifier *notifier) { hlist_del(¬ifier->link); } EXPORT_SYMBOL_GPL(preempt_notifier_unregister); static void __fire_sched_in_preempt_notifiers(struct task_struct *curr) { struct preempt_notifier *notifier; hlist_for_each_entry(notifier, &curr->preempt_notifiers, link) notifier->ops->sched_in(notifier, raw_smp_processor_id()); } static __always_inline void fire_sched_in_preempt_notifiers(struct task_struct *curr) { if (static_branch_unlikely(&preempt_notifier_key)) __fire_sched_in_preempt_notifiers(curr); } static void __fire_sched_out_preempt_notifiers(struct task_struct *curr, struct task_struct *next) { struct preempt_notifier *notifier; hlist_for_each_entry(notifier, &curr->preempt_notifiers, link) notifier->ops->sched_out(notifier, next); } static __always_inline void fire_sched_out_preempt_notifiers(struct task_struct *curr, struct task_struct *next) { if (static_branch_unlikely(&preempt_notifier_key)) __fire_sched_out_preempt_notifiers(curr, next); } #else /* !CONFIG_PREEMPT_NOTIFIERS */ static inline void fire_sched_in_preempt_notifiers(struct task_struct *curr) { } static inline void fire_sched_out_preempt_notifiers(struct task_struct *curr, struct task_struct *next) { } #endif /* CONFIG_PREEMPT_NOTIFIERS */ static inline void prepare_task(struct task_struct *next) { #ifdef CONFIG_SMP /* * Claim the task as running, we do this before switching to it * such that any running task will have this set. * * See the smp_load_acquire(&p->on_cpu) case in ttwu() and * its ordering comment. */ WRITE_ONCE(next->on_cpu, 1); #endif } static inline void finish_task(struct task_struct *prev) { #ifdef CONFIG_SMP /* * This must be the very last reference to @prev from this CPU. After * p->on_cpu is cleared, the task can be moved to a different CPU. We * must ensure this doesn't happen until the switch is completely * finished. * * In particular, the load of prev->state in finish_task_switch() must * happen before this. * * Pairs with the smp_cond_load_acquire() in try_to_wake_up(). */ smp_store_release(&prev->on_cpu, 0); #endif } #ifdef CONFIG_SMP static void do_balance_callbacks(struct rq *rq, struct balance_callback *head) { void (*func)(struct rq *rq); struct balance_callback *next; lockdep_assert_rq_held(rq); while (head) { func = (void (*)(struct rq *))head->func; next = head->next; head->next = NULL; head = next; func(rq); } } static void balance_push(struct rq *rq); /* * balance_push_callback is a right abuse of the callback interface and plays * by significantly different rules. * * Where the normal balance_callback's purpose is to be ran in the same context * that queued it (only later, when it's safe to drop rq->lock again), * balance_push_callback is specifically targeted at __schedule(). * * This abuse is tolerated because it places all the unlikely/odd cases behind * a single test, namely: rq->balance_callback == NULL. */ struct balance_callback balance_push_callback = { .next = NULL, .func = balance_push, }; static inline struct balance_callback * __splice_balance_callbacks(struct rq *rq, bool split) { struct balance_callback *head = rq->balance_callback; if (likely(!head)) return NULL; lockdep_assert_rq_held(rq); /* * Must not take balance_push_callback off the list when * splice_balance_callbacks() and balance_callbacks() are not * in the same rq->lock section. * * In that case it would be possible for __schedule() to interleave * and observe the list empty. */ if (split && head == &balance_push_callback) head = NULL; else rq->balance_callback = NULL; return head; } static inline struct balance_callback *splice_balance_callbacks(struct rq *rq) { return __splice_balance_callbacks(rq, true); } static void __balance_callbacks(struct rq *rq) { do_balance_callbacks(rq, __splice_balance_callbacks(rq, false)); } static inline void balance_callbacks(struct rq *rq, struct balance_callback *head) { unsigned long flags; if (unlikely(head)) { raw_spin_rq_lock_irqsave(rq, flags); do_balance_callbacks(rq, head); raw_spin_rq_unlock_irqrestore(rq, flags); } } #else static inline void __balance_callbacks(struct rq *rq) { } static inline struct balance_callback *splice_balance_callbacks(struct rq *rq) { return NULL; } static inline void balance_callbacks(struct rq *rq, struct balance_callback *head) { } #endif static inline void prepare_lock_switch(struct rq *rq, struct task_struct *next, struct rq_flags *rf) { /* * Since the runqueue lock will be released by the next * task (which is an invalid locking op but in the case * of the scheduler it's an obvious special-case), so we * do an early lockdep release here: */ rq_unpin_lock(rq, rf); spin_release(&__rq_lockp(rq)->dep_map, _THIS_IP_); #ifdef CONFIG_DEBUG_SPINLOCK /* this is a valid case when another task releases the spinlock */ rq_lockp(rq)->owner = next; #endif } static inline void finish_lock_switch(struct rq *rq) { /* * If we are tracking spinlock dependencies then we have to * fix up the runqueue lock - which gets 'carried over' from * prev into current: */ spin_acquire(&__rq_lockp(rq)->dep_map, 0, 0, _THIS_IP_); __balance_callbacks(rq); raw_spin_rq_unlock_irq(rq); } /* * NOP if the arch has not defined these: */ #ifndef prepare_arch_switch # define prepare_arch_switch(next) do { } while (0) #endif #ifndef finish_arch_post_lock_switch # define finish_arch_post_lock_switch() do { } while (0) #endif static inline void kmap_local_sched_out(void) { #ifdef CONFIG_KMAP_LOCAL if (unlikely(current->kmap_ctrl.idx)) __kmap_local_sched_out(); #endif } static inline void kmap_local_sched_in(void) { #ifdef CONFIG_KMAP_LOCAL if (unlikely(current->kmap_ctrl.idx)) __kmap_local_sched_in(); #endif } /** * prepare_task_switch - prepare to switch tasks * @rq: the runqueue preparing to switch * @prev: the current task that is being switched out * @next: the task we are going to switch to. * * This is called with the rq lock held and interrupts off. It must * be paired with a subsequent finish_task_switch after the context * switch. * * prepare_task_switch sets up locking and calls architecture specific * hooks. */ static inline void prepare_task_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next) { kcov_prepare_switch(prev); sched_info_switch(rq, prev, next); perf_event_task_sched_out(prev, next); rseq_preempt(prev); fire_sched_out_preempt_notifiers(prev, next); kmap_local_sched_out(); prepare_task(next); prepare_arch_switch(next); } /** * finish_task_switch - clean up after a task-switch * @prev: the thread we just switched away from. * * finish_task_switch must be called after the context switch, paired * with a prepare_task_switch call before the context switch. * finish_task_switch will reconcile locking set up by prepare_task_switch, * and do any other architecture-specific cleanup actions. * * Note that we may have delayed dropping an mm in context_switch(). If * so, we finish that here outside of the runqueue lock. (Doing it * with the lock held can cause deadlocks; see schedule() for * details.) * * The context switch have flipped the stack from under us and restored the * local variables which were saved when this task called schedule() in the * past. prev == current is still correct but we need to recalculate this_rq * because prev may have moved to another CPU. */ static struct rq *finish_task_switch(struct task_struct *prev) __releases(rq->lock) { struct rq *rq = this_rq(); struct mm_struct *mm = rq->prev_mm; unsigned int prev_state; /* * The previous task will have left us with a preempt_count of 2 * because it left us after: * * schedule() * preempt_disable(); // 1 * __schedule() * raw_spin_lock_irq(&rq->lock) // 2 * * Also, see FORK_PREEMPT_COUNT. */ if (WARN_ONCE(preempt_count() != 2*PREEMPT_DISABLE_OFFSET, "corrupted preempt_count: %s/%d/0x%x\n", current->comm, current->pid, preempt_count())) preempt_count_set(FORK_PREEMPT_COUNT); rq->prev_mm = NULL; /* * A task struct has one reference for the use as "current". * If a task dies, then it sets TASK_DEAD in tsk->state and calls * schedule one last time. The schedule call will never return, and * the scheduled task must drop that reference. * * We must observe prev->state before clearing prev->on_cpu (in * finish_task), otherwise a concurrent wakeup can get prev * running on another CPU and we could rave with its RUNNING -> DEAD * transition, resulting in a double drop. */ prev_state = READ_ONCE(prev->__state); vtime_task_switch(prev); perf_event_task_sched_in(prev, current); finish_task(prev); tick_nohz_task_switch(); finish_lock_switch(rq); finish_arch_post_lock_switch(); kcov_finish_switch(current); /* * kmap_local_sched_out() is invoked with rq::lock held and * interrupts disabled. There is no requirement for that, but the * sched out code does not have an interrupt enabled section. * Restoring the maps on sched in does not require interrupts being * disabled either. */ kmap_local_sched_in(); fire_sched_in_preempt_notifiers(current); /* * When switching through a kernel thread, the loop in * membarrier_{private,global}_expedited() may have observed that * kernel thread and not issued an IPI. It is therefore possible to * schedule between user->kernel->user threads without passing though * switch_mm(). Membarrier requires a barrier after storing to * rq->curr, before returning to userspace, so provide them here: * * - a full memory barrier for {PRIVATE,GLOBAL}_EXPEDITED, implicitly * provided by mmdrop_lazy_tlb(), * - a sync_core for SYNC_CORE. */ if (mm) { membarrier_mm_sync_core_before_usermode(mm); mmdrop_lazy_tlb_sched(mm); } if (unlikely(prev_state == TASK_DEAD)) { if (prev->sched_class->task_dead) prev->sched_class->task_dead(prev); /* Task is done with its stack. */ put_task_stack(prev); put_task_struct_rcu_user(prev); } return rq; } /** * schedule_tail - first thing a freshly forked thread must call. * @prev: the thread we just switched away from. */ asmlinkage __visible void schedule_tail(struct task_struct *prev) __releases(rq->lock) { /* * New tasks start with FORK_PREEMPT_COUNT, see there and * finish_task_switch() for details. * * finish_task_switch() will drop rq->lock() and lower preempt_count * and the preempt_enable() will end up enabling preemption (on * PREEMPT_COUNT kernels). */ finish_task_switch(prev); preempt_enable(); if (current->set_child_tid) put_user(task_pid_vnr(current), current->set_child_tid); calculate_sigpending(); } /* * context_switch - switch to the new MM and the new thread's register state. */ static __always_inline struct rq * context_switch(struct rq *rq, struct task_struct *prev, struct task_struct *next, struct rq_flags *rf) { prepare_task_switch(rq, prev, next); /* * For paravirt, this is coupled with an exit in switch_to to * combine the page table reload and the switch backend into * one hypercall. */ arch_start_context_switch(prev); /* * kernel -> kernel lazy + transfer active * user -> kernel lazy + mmgrab_lazy_tlb() active * * kernel -> user switch + mmdrop_lazy_tlb() active * user -> user switch * * switch_mm_cid() needs to be updated if the barriers provided * by context_switch() are modified. */ if (!next->mm) { // to kernel enter_lazy_tlb(prev->active_mm, next); next->active_mm = prev->active_mm; if (prev->mm) // from user mmgrab_lazy_tlb(prev->active_mm); else prev->active_mm = NULL; } else { // to user membarrier_switch_mm(rq, prev->active_mm, next->mm); /* * sys_membarrier() requires an smp_mb() between setting * rq->curr / membarrier_switch_mm() and returning to userspace. * * The below provides this either through switch_mm(), or in * case 'prev->active_mm == next->mm' through * finish_task_switch()'s mmdrop(). */ switch_mm_irqs_off(prev->active_mm, next->mm, next); lru_gen_use_mm(next->mm); if (!prev->mm) { // from kernel /* will mmdrop_lazy_tlb() in finish_task_switch(). */ rq->prev_mm = prev->active_mm; prev->active_mm = NULL; } } /* switch_mm_cid() requires the memory barriers above. */ switch_mm_cid(rq, prev, next); prepare_lock_switch(rq, next, rf); /* Here we just switch the register state and the stack. */ switch_to(prev, next, prev); barrier(); return finish_task_switch(prev); } /* * nr_running and nr_context_switches: * * externally visible scheduler statistics: current number of runnable * threads, total number of context switches performed since bootup. */ unsigned int nr_running(void) { unsigned int i, sum = 0; for_each_online_cpu(i) sum += cpu_rq(i)->nr_running; return sum; } /* * Check if only the current task is running on the CPU. * * Caution: this function does not check that the caller has disabled * preemption, thus the result might have a time-of-check-to-time-of-use * race. The caller is responsible to use it correctly, for example: * * - from a non-preemptible section (of course) * * - from a thread that is bound to a single CPU * * - in a loop with very short iterations (e.g. a polling loop) */ bool single_task_running(void) { return raw_rq()->nr_running == 1; } EXPORT_SYMBOL(single_task_running); unsigned long long nr_context_switches_cpu(int cpu) { return cpu_rq(cpu)->nr_switches; } unsigned long long nr_context_switches(void) { int i; unsigned long long sum = 0; for_each_possible_cpu(i) sum += cpu_rq(i)->nr_switches; return sum; } /* * Consumers of these two interfaces, like for example the cpuidle menu * governor, are using nonsensical data. Preferring shallow idle state selection * for a CPU that has IO-wait which might not even end up running the task when * it does become runnable. */ unsigned int nr_iowait_cpu(int cpu) { return atomic_read(&cpu_rq(cpu)->nr_iowait); } /* * IO-wait accounting, and how it's mostly bollocks (on SMP). * * The idea behind IO-wait account is to account the idle time that we could * have spend running if it were not for IO. That is, if we were to improve the * storage performance, we'd have a proportional reduction in IO-wait time. * * This all works nicely on UP, where, when a task blocks on IO, we account * idle time as IO-wait, because if the storage were faster, it could've been * running and we'd not be idle. * * This has been extended to SMP, by doing the same for each CPU. This however * is broken. * * Imagine for instance the case where two tasks block on one CPU, only the one * CPU will have IO-wait accounted, while the other has regular idle. Even * though, if the storage were faster, both could've ran at the same time, * utilising both CPUs. * * This means, that when looking globally, the current IO-wait accounting on * SMP is a lower bound, by reason of under accounting. * * Worse, since the numbers are provided per CPU, they are sometimes * interpreted per CPU, and that is nonsensical. A blocked task isn't strictly * associated with any one particular CPU, it can wake to another CPU than it * blocked on. This means the per CPU IO-wait number is meaningless. * * Task CPU affinities can make all that even more 'interesting'. */ unsigned int nr_iowait(void) { unsigned int i, sum = 0; for_each_possible_cpu(i) sum += nr_iowait_cpu(i); return sum; } #ifdef CONFIG_SMP /* * sched_exec - execve() is a valuable balancing opportunity, because at * this point the task has the smallest effective memory and cache footprint. */ void sched_exec(void) { struct task_struct *p = current; struct migration_arg arg; int dest_cpu; scoped_guard (raw_spinlock_irqsave, &p->pi_lock) { dest_cpu = p->sched_class->select_task_rq(p, task_cpu(p), WF_EXEC); if (dest_cpu == smp_processor_id()) return; if (unlikely(!cpu_active(dest_cpu))) return; arg = (struct migration_arg){ p, dest_cpu }; } stop_one_cpu(task_cpu(p), migration_cpu_stop, &arg); } #endif DEFINE_PER_CPU(struct kernel_stat, kstat); DEFINE_PER_CPU(struct kernel_cpustat, kernel_cpustat); EXPORT_PER_CPU_SYMBOL(kstat); EXPORT_PER_CPU_SYMBOL(kernel_cpustat); /* * The function fair_sched_class.update_curr accesses the struct curr * and its field curr->exec_start; when called from task_sched_runtime(), * we observe a high rate of cache misses in practice. * Prefetching this data results in improved performance. */ static inline void prefetch_curr_exec_start(struct task_struct *p) { #ifdef CONFIG_FAIR_GROUP_SCHED struct sched_entity *curr = (&p->se)->cfs_rq->curr; #else struct sched_entity *curr = (&task_rq(p)->cfs)->curr; #endif prefetch(curr); prefetch(&curr->exec_start); } /* * Return accounted runtime for the task. * In case the task is currently running, return the runtime plus current's * pending runtime that have not been accounted yet. */ unsigned long long task_sched_runtime(struct task_struct *p) { struct rq_flags rf; struct rq *rq; u64 ns; #if defined(CONFIG_64BIT) && defined(CONFIG_SMP) /* * 64-bit doesn't need locks to atomically read a 64-bit value. * So we have a optimization chance when the task's delta_exec is 0. * Reading ->on_cpu is racy, but this is ok. * * If we race with it leaving CPU, we'll take a lock. So we're correct. * If we race with it entering CPU, unaccounted time is 0. This is * indistinguishable from the read occurring a few cycles earlier. * If we see ->on_cpu without ->on_rq, the task is leaving, and has * been accounted, so we're correct here as well. */ if (!p->on_cpu || !task_on_rq_queued(p)) return p->se.sum_exec_runtime; #endif rq = task_rq_lock(p, &rf); /* * Must be ->curr _and_ ->on_rq. If dequeued, we would * project cycles that may never be accounted to this * thread, breaking clock_gettime(). */ if (task_current(rq, p) && task_on_rq_queued(p)) { prefetch_curr_exec_start(p); update_rq_clock(rq); p->sched_class->update_curr(rq); } ns = p->se.sum_exec_runtime; task_rq_unlock(rq, p, &rf); return ns; } #ifdef CONFIG_SCHED_DEBUG static u64 cpu_resched_latency(struct rq *rq) { int latency_warn_ms = READ_ONCE(sysctl_resched_latency_warn_ms); u64 resched_latency, now = rq_clock(rq); static bool warned_once; if (sysctl_resched_latency_warn_once && warned_once) return 0; if (!need_resched() || !latency_warn_ms) return 0; if (system_state == SYSTEM_BOOTING) return 0; if (!rq->last_seen_need_resched_ns) { rq->last_seen_need_resched_ns = now; rq->ticks_without_resched = 0; return 0; } rq->ticks_without_resched++; resched_latency = now - rq->last_seen_need_resched_ns; if (resched_latency <= latency_warn_ms * NSEC_PER_MSEC) return 0; warned_once = true; return resched_latency; } static int __init setup_resched_latency_warn_ms(char *str) { long val; if ((kstrtol(str, 0, &val))) { pr_warn("Unable to set resched_latency_warn_ms\n"); return 1; } sysctl_resched_latency_warn_ms = val; return 1; } __setup("resched_latency_warn_ms=", setup_resched_latency_warn_ms); #else static inline u64 cpu_resched_latency(struct rq *rq) { return 0; } #endif /* CONFIG_SCHED_DEBUG */ /* * This function gets called by the timer code, with HZ frequency. * We call it with interrupts disabled. */ void scheduler_tick(void) { int cpu = smp_processor_id(); struct rq *rq = cpu_rq(cpu); struct task_struct *curr = rq->curr; struct rq_flags rf; unsigned long thermal_pressure; u64 resched_latency; if (housekeeping_cpu(cpu, HK_TYPE_TICK)) arch_scale_freq_tick(); sched_clock_tick(); rq_lock(rq, &rf); update_rq_clock(rq); thermal_pressure = arch_scale_thermal_pressure(cpu_of(rq)); update_thermal_load_avg(rq_clock_thermal(rq), rq, thermal_pressure); curr->sched_class->task_tick(rq, curr, 0); if (sched_feat(LATENCY_WARN)) resched_latency = cpu_resched_latency(rq); calc_global_load_tick(rq); sched_core_tick(rq); task_tick_mm_cid(rq, curr); rq_unlock(rq, &rf); if (sched_feat(LATENCY_WARN) && resched_latency) resched_latency_warn(cpu, resched_latency); perf_event_task_tick(); if (curr->flags & PF_WQ_WORKER) wq_worker_tick(curr); #ifdef CONFIG_SMP rq->idle_balance = idle_cpu(cpu); trigger_load_balance(rq); #endif } #ifdef CONFIG_NO_HZ_FULL struct tick_work { int cpu; atomic_t state; struct delayed_work work; }; /* Values for ->state, see diagram below. */ #define TICK_SCHED_REMOTE_OFFLINE 0 #define TICK_SCHED_REMOTE_OFFLINING 1 #define TICK_SCHED_REMOTE_RUNNING 2 /* * State diagram for ->state: * * * TICK_SCHED_REMOTE_OFFLINE * | ^ * | | * | | sched_tick_remote() * | | * | | * +--TICK_SCHED_REMOTE_OFFLINING * | ^ * | | * sched_tick_start() | | sched_tick_stop() * | | * V | * TICK_SCHED_REMOTE_RUNNING * * * Other transitions get WARN_ON_ONCE(), except that sched_tick_remote() * and sched_tick_start() are happy to leave the state in RUNNING. */ static struct tick_work __percpu *tick_work_cpu; static void sched_tick_remote(struct work_struct *work) { struct delayed_work *dwork = to_delayed_work(work); struct tick_work *twork = container_of(dwork, struct tick_work, work); int cpu = twork->cpu; struct rq *rq = cpu_rq(cpu); int os; /* * Handle the tick only if it appears the remote CPU is running in full * dynticks mode. The check is racy by nature, but missing a tick or * having one too much is no big deal because the scheduler tick updates * statistics and checks timeslices in a time-independent way, regardless * of when exactly it is running. */ if (tick_nohz_tick_stopped_cpu(cpu)) { guard(rq_lock_irq)(rq); struct task_struct *curr = rq->curr; if (cpu_online(cpu)) { update_rq_clock(rq); if (!is_idle_task(curr)) { /* * Make sure the next tick runs within a * reasonable amount of time. */ u64 delta = rq_clock_task(rq) - curr->se.exec_start; WARN_ON_ONCE(delta > (u64)NSEC_PER_SEC * 3); } curr->sched_class->task_tick(rq, curr, 0); calc_load_nohz_remote(rq); } } /* * Run the remote tick once per second (1Hz). This arbitrary * frequency is large enough to avoid overload but short enough * to keep scheduler internal stats reasonably up to date. But * first update state to reflect hotplug activity if required. */ os = atomic_fetch_add_unless(&twork->state, -1, TICK_SCHED_REMOTE_RUNNING); WARN_ON_ONCE(os == TICK_SCHED_REMOTE_OFFLINE); if (os == TICK_SCHED_REMOTE_RUNNING) queue_delayed_work(system_unbound_wq, dwork, HZ); } static void sched_tick_start(int cpu) { int os; struct tick_work *twork; if (housekeeping_cpu(cpu, HK_TYPE_TICK)) return; WARN_ON_ONCE(!tick_work_cpu); twork = per_cpu_ptr(tick_work_cpu, cpu); os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_RUNNING); WARN_ON_ONCE(os == TICK_SCHED_REMOTE_RUNNING); if (os == TICK_SCHED_REMOTE_OFFLINE) { twork->cpu = cpu; INIT_DELAYED_WORK(&twork->work, sched_tick_remote); queue_delayed_work(system_unbound_wq, &twork->work, HZ); } } #ifdef CONFIG_HOTPLUG_CPU static void sched_tick_stop(int cpu) { struct tick_work *twork; int os; if (housekeeping_cpu(cpu, HK_TYPE_TICK)) return; WARN_ON_ONCE(!tick_work_cpu); twork = per_cpu_ptr(tick_work_cpu, cpu); /* There cannot be competing actions, but don't rely on stop-machine. */ os = atomic_xchg(&twork->state, TICK_SCHED_REMOTE_OFFLINING); WARN_ON_ONCE(os != TICK_SCHED_REMOTE_RUNNING); /* Don't cancel, as this would mess up the state machine. */ } #endif /* CONFIG_HOTPLUG_CPU */ int __init sched_tick_offload_init(void) { tick_work_cpu = alloc_percpu(struct tick_work); BUG_ON(!tick_work_cpu); return 0; } #else /* !CONFIG_NO_HZ_FULL */ static inline void sched_tick_start(int cpu) { } static inline void sched_tick_stop(int cpu) { } #endif #if defined(CONFIG_PREEMPTION) && (defined(CONFIG_DEBUG_PREEMPT) || \ defined(CONFIG_TRACE_PREEMPT_TOGGLE)) /* * If the value passed in is equal to the current preempt count * then we just disabled preemption. Start timing the latency. */ static inline void preempt_latency_start(int val) { if (preempt_count() == val) { unsigned long ip = get_lock_parent_ip(); #ifdef CONFIG_DEBUG_PREEMPT current->preempt_disable_ip = ip; #endif trace_preempt_off(CALLER_ADDR0, ip); } } void preempt_count_add(int val) { #ifdef CONFIG_DEBUG_PREEMPT /* * Underflow? */ if (DEBUG_LOCKS_WARN_ON((preempt_count() < 0))) return; #endif __preempt_count_add(val); #ifdef CONFIG_DEBUG_PREEMPT /* * Spinlock count overflowing soon? */ DEBUG_LOCKS_WARN_ON((preempt_count() & PREEMPT_MASK) >= PREEMPT_MASK - 10); #endif preempt_latency_start(val); } EXPORT_SYMBOL(preempt_count_add); NOKPROBE_SYMBOL(preempt_count_add); /* * If the value passed in equals to the current preempt count * then we just enabled preemption. Stop timing the latency. */ static inline void preempt_latency_stop(int val) { if (preempt_count() == val) trace_preempt_on(CALLER_ADDR0, get_lock_parent_ip()); } void preempt_count_sub(int val) { #ifdef CONFIG_DEBUG_PREEMPT /* * Underflow? */ if (DEBUG_LOCKS_WARN_ON(val > preempt_count())) return; /* * Is the spinlock portion underflowing? */ if (DEBUG_LOCKS_WARN_ON((val < PREEMPT_MASK) && !(preempt_count() & PREEMPT_MASK))) return; #endif preempt_latency_stop(val); __preempt_count_sub(val); } EXPORT_SYMBOL(preempt_count_sub); NOKPROBE_SYMBOL(preempt_count_sub); #else static inline void preempt_latency_start(int val) { } static inline void preempt_latency_stop(int val) { } #endif static inline unsigned long get_preempt_disable_ip(struct task_struct *p) { #ifdef CONFIG_DEBUG_PREEMPT return p->preempt_disable_ip; #else return 0; #endif } /* * Print scheduling while atomic bug: */ static noinline void __schedule_bug(struct task_struct *prev) { /* Save this before calling printk(), since that will clobber it */ unsigned long preempt_disable_ip = get_preempt_disable_ip(current); if (oops_in_progress) return; printk(KERN_ERR "BUG: scheduling while atomic: %s/%d/0x%08x\n", prev->comm, prev->pid, preempt_count()); debug_show_held_locks(prev); print_modules(); if (irqs_disabled()) print_irqtrace_events(prev); if (IS_ENABLED(CONFIG_DEBUG_PREEMPT)) { pr_err("Preemption disabled at:"); print_ip_sym(KERN_ERR, preempt_disable_ip); } check_panic_on_warn("scheduling while atomic"); dump_stack(); add_taint(TAINT_WARN, LOCKDEP_STILL_OK); } /* * Various schedule()-time debugging checks and statistics: */ static inline void schedule_debug(struct task_struct *prev, bool preempt) { #ifdef CONFIG_SCHED_STACK_END_CHECK if (task_stack_end_corrupted(prev)) panic("corrupted stack end detected inside scheduler\n"); if (task_scs_end_corrupted(prev)) panic("corrupted shadow stack detected inside scheduler\n"); #endif #ifdef CONFIG_DEBUG_ATOMIC_SLEEP if (!preempt && READ_ONCE(prev->__state) && prev->non_block_count) { printk(KERN_ERR "BUG: scheduling in a non-blocking section: %s/%d/%i\n", prev->comm, prev->pid, prev->non_block_count); dump_stack(); add_taint(TAINT_WARN, LOCKDEP_STILL_OK); } #endif if (unlikely(in_atomic_preempt_off())) { __schedule_bug(prev); preempt_count_set(PREEMPT_DISABLED); } rcu_sleep_check(); SCHED_WARN_ON(ct_state() == CONTEXT_USER); profile_hit(SCHED_PROFILING, __builtin_return_address(0)); schedstat_inc(this_rq()->sched_count); } static void put_prev_task_balance(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { #ifdef CONFIG_SMP const struct sched_class *class; /* * We must do the balancing pass before put_prev_task(), such * that when we release the rq->lock the task is in the same * state as before we took rq->lock. * * We can terminate the balance pass as soon as we know there is * a runnable task of @class priority or higher. */ for_class_range(class, prev->sched_class, &idle_sched_class) { if (class->balance(rq, prev, rf)) break; } #endif put_prev_task(rq, prev); } /* * Pick up the highest-prio task: */ static inline struct task_struct * __pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { const struct sched_class *class; struct task_struct *p; /* * Optimization: we know that if all tasks are in the fair class we can * call that function directly, but only if the @prev task wasn't of a * higher scheduling class, because otherwise those lose the * opportunity to pull in more work from other CPUs. */ if (likely(!sched_class_above(prev->sched_class, &fair_sched_class) && rq->nr_running == rq->cfs.h_nr_running)) { p = pick_next_task_fair(rq, prev, rf); if (unlikely(p == RETRY_TASK)) goto restart; /* Assume the next prioritized class is idle_sched_class */ if (!p) { put_prev_task(rq, prev); p = pick_next_task_idle(rq); } /* * This is the fast path; it cannot be a DL server pick; * therefore even if @p == @prev, ->dl_server must be NULL. */ if (p->dl_server) p->dl_server = NULL; return p; } restart: put_prev_task_balance(rq, prev, rf); /* * We've updated @prev and no longer need the server link, clear it. * Must be done before ->pick_next_task() because that can (re)set * ->dl_server. */ if (prev->dl_server) prev->dl_server = NULL; for_each_class(class) { p = class->pick_next_task(rq); if (p) return p; } BUG(); /* The idle class should always have a runnable task. */ } #ifdef CONFIG_SCHED_CORE static inline bool is_task_rq_idle(struct task_struct *t) { return (task_rq(t)->idle == t); } static inline bool cookie_equals(struct task_struct *a, unsigned long cookie) { return is_task_rq_idle(a) || (a->core_cookie == cookie); } static inline bool cookie_match(struct task_struct *a, struct task_struct *b) { if (is_task_rq_idle(a) || is_task_rq_idle(b)) return true; return a->core_cookie == b->core_cookie; } static inline struct task_struct *pick_task(struct rq *rq) { const struct sched_class *class; struct task_struct *p; for_each_class(class) { p = class->pick_task(rq); if (p) return p; } BUG(); /* The idle class should always have a runnable task. */ } extern void task_vruntime_update(struct rq *rq, struct task_struct *p, bool in_fi); static void queue_core_balance(struct rq *rq); static struct task_struct * pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { struct task_struct *next, *p, *max = NULL; const struct cpumask *smt_mask; bool fi_before = false; bool core_clock_updated = (rq == rq->core); unsigned long cookie; int i, cpu, occ = 0; struct rq *rq_i; bool need_sync; if (!sched_core_enabled(rq)) return __pick_next_task(rq, prev, rf); cpu = cpu_of(rq); /* Stopper task is switching into idle, no need core-wide selection. */ if (cpu_is_offline(cpu)) { /* * Reset core_pick so that we don't enter the fastpath when * coming online. core_pick would already be migrated to * another cpu during offline. */ rq->core_pick = NULL; return __pick_next_task(rq, prev, rf); } /* * If there were no {en,de}queues since we picked (IOW, the task * pointers are all still valid), and we haven't scheduled the last * pick yet, do so now. * * rq->core_pick can be NULL if no selection was made for a CPU because * it was either offline or went offline during a sibling's core-wide * selection. In this case, do a core-wide selection. */ if (rq->core->core_pick_seq == rq->core->core_task_seq && rq->core->core_pick_seq != rq->core_sched_seq && rq->core_pick) { WRITE_ONCE(rq->core_sched_seq, rq->core->core_pick_seq); next = rq->core_pick; if (next != prev) { put_prev_task(rq, prev); set_next_task(rq, next); } rq->core_pick = NULL; goto out; } put_prev_task_balance(rq, prev, rf); smt_mask = cpu_smt_mask(cpu); need_sync = !!rq->core->core_cookie; /* reset state */ rq->core->core_cookie = 0UL; if (rq->core->core_forceidle_count) { if (!core_clock_updated) { update_rq_clock(rq->core); core_clock_updated = true; } sched_core_account_forceidle(rq); /* reset after accounting force idle */ rq->core->core_forceidle_start = 0; rq->core->core_forceidle_count = 0; rq->core->core_forceidle_occupation = 0; need_sync = true; fi_before = true; } /* * core->core_task_seq, core->core_pick_seq, rq->core_sched_seq * * @task_seq guards the task state ({en,de}queues) * @pick_seq is the @task_seq we did a selection on * @sched_seq is the @pick_seq we scheduled * * However, preemptions can cause multiple picks on the same task set. * 'Fix' this by also increasing @task_seq for every pick. */ rq->core->core_task_seq++; /* * Optimize for common case where this CPU has no cookies * and there are no cookied tasks running on siblings. */ if (!need_sync) { next = pick_task(rq); if (!next->core_cookie) { rq->core_pick = NULL; /* * For robustness, update the min_vruntime_fi for * unconstrained picks as well. */ WARN_ON_ONCE(fi_before); task_vruntime_update(rq, next, false); goto out_set_next; } } /* * For each thread: do the regular task pick and find the max prio task * amongst them. * * Tie-break prio towards the current CPU */ for_each_cpu_wrap(i, smt_mask, cpu) { rq_i = cpu_rq(i); /* * Current cpu always has its clock updated on entrance to * pick_next_task(). If the current cpu is not the core, * the core may also have been updated above. */ if (i != cpu && (rq_i != rq->core || !core_clock_updated)) update_rq_clock(rq_i); p = rq_i->core_pick = pick_task(rq_i); if (!max || prio_less(max, p, fi_before)) max = p; } cookie = rq->core->core_cookie = max->core_cookie; /* * For each thread: try and find a runnable task that matches @max or * force idle. */ for_each_cpu(i, smt_mask) { rq_i = cpu_rq(i); p = rq_i->core_pick; if (!cookie_equals(p, cookie)) { p = NULL; if (cookie) p = sched_core_find(rq_i, cookie); if (!p) p = idle_sched_class.pick_task(rq_i); } rq_i->core_pick = p; if (p == rq_i->idle) { if (rq_i->nr_running) { rq->core->core_forceidle_count++; if (!fi_before) rq->core->core_forceidle_seq++; } } else { occ++; } } if (schedstat_enabled() && rq->core->core_forceidle_count) { rq->core->core_forceidle_start = rq_clock(rq->core); rq->core->core_forceidle_occupation = occ; } rq->core->core_pick_seq = rq->core->core_task_seq; next = rq->core_pick; rq->core_sched_seq = rq->core->core_pick_seq; /* Something should have been selected for current CPU */ WARN_ON_ONCE(!next); /* * Reschedule siblings * * NOTE: L1TF -- at this point we're no longer running the old task and * sending an IPI (below) ensures the sibling will no longer be running * their task. This ensures there is no inter-sibling overlap between * non-matching user state. */ for_each_cpu(i, smt_mask) { rq_i = cpu_rq(i); /* * An online sibling might have gone offline before a task * could be picked for it, or it might be offline but later * happen to come online, but its too late and nothing was * picked for it. That's Ok - it will pick tasks for itself, * so ignore it. */ if (!rq_i->core_pick) continue; /* * Update for new !FI->FI transitions, or if continuing to be in !FI: * fi_before fi update? * 0 0 1 * 0 1 1 * 1 0 1 * 1 1 0 */ if (!(fi_before && rq->core->core_forceidle_count)) task_vruntime_update(rq_i, rq_i->core_pick, !!rq->core->core_forceidle_count); rq_i->core_pick->core_occupation = occ; if (i == cpu) { rq_i->core_pick = NULL; continue; } /* Did we break L1TF mitigation requirements? */ WARN_ON_ONCE(!cookie_match(next, rq_i->core_pick)); if (rq_i->curr == rq_i->core_pick) { rq_i->core_pick = NULL; continue; } resched_curr(rq_i); } out_set_next: set_next_task(rq, next); out: if (rq->core->core_forceidle_count && next == rq->idle) queue_core_balance(rq); return next; } static bool try_steal_cookie(int this, int that) { struct rq *dst = cpu_rq(this), *src = cpu_rq(that); struct task_struct *p; unsigned long cookie; bool success = false; guard(irq)(); guard(double_rq_lock)(dst, src); cookie = dst->core->core_cookie; if (!cookie) return false; if (dst->curr != dst->idle) return false; p = sched_core_find(src, cookie); if (!p) return false; do { if (p == src->core_pick || p == src->curr) goto next; if (!is_cpu_allowed(p, this)) goto next; if (p->core_occupation > dst->idle->core_occupation) goto next; /* * sched_core_find() and sched_core_next() will ensure * that task @p is not throttled now, we also need to * check whether the runqueue of the destination CPU is * being throttled. */ if (sched_task_is_throttled(p, this)) goto next; deactivate_task(src, p, 0); set_task_cpu(p, this); activate_task(dst, p, 0); resched_curr(dst); success = true; break; next: p = sched_core_next(p, cookie); } while (p); return success; } static bool steal_cookie_task(int cpu, struct sched_domain *sd) { int i; for_each_cpu_wrap(i, sched_domain_span(sd), cpu + 1) { if (i == cpu) continue; if (need_resched()) break; if (try_steal_cookie(cpu, i)) return true; } return false; } static void sched_core_balance(struct rq *rq) { struct sched_domain *sd; int cpu = cpu_of(rq); guard(preempt)(); guard(rcu)(); raw_spin_rq_unlock_irq(rq); for_each_domain(cpu, sd) { if (need_resched()) break; if (steal_cookie_task(cpu, sd)) break; } raw_spin_rq_lock_irq(rq); } static DEFINE_PER_CPU(struct balance_callback, core_balance_head); static void queue_core_balance(struct rq *rq) { if (!sched_core_enabled(rq)) return; if (!rq->core->core_cookie) return; if (!rq->nr_running) /* not forced idle */ return; queue_balance_callback(rq, &per_cpu(core_balance_head, rq->cpu), sched_core_balance); } DEFINE_LOCK_GUARD_1(core_lock, int, sched_core_lock(*_T->lock, &_T->flags), sched_core_unlock(*_T->lock, &_T->flags), unsigned long flags) static void sched_core_cpu_starting(unsigned int cpu) { const struct cpumask *smt_mask = cpu_smt_mask(cpu); struct rq *rq = cpu_rq(cpu), *core_rq = NULL; int t; guard(core_lock)(&cpu); WARN_ON_ONCE(rq->core != rq); /* if we're the first, we'll be our own leader */ if (cpumask_weight(smt_mask) == 1) return; /* find the leader */ for_each_cpu(t, smt_mask) { if (t == cpu) continue; rq = cpu_rq(t); if (rq->core == rq) { core_rq = rq; break; } } if (WARN_ON_ONCE(!core_rq)) /* whoopsie */ return; /* install and validate core_rq */ for_each_cpu(t, smt_mask) { rq = cpu_rq(t); if (t == cpu) rq->core = core_rq; WARN_ON_ONCE(rq->core != core_rq); } } static void sched_core_cpu_deactivate(unsigned int cpu) { const struct cpumask *smt_mask = cpu_smt_mask(cpu); struct rq *rq = cpu_rq(cpu), *core_rq = NULL; int t; guard(core_lock)(&cpu); /* if we're the last man standing, nothing to do */ if (cpumask_weight(smt_mask) == 1) { WARN_ON_ONCE(rq->core != rq); return; } /* if we're not the leader, nothing to do */ if (rq->core != rq) return; /* find a new leader */ for_each_cpu(t, smt_mask) { if (t == cpu) continue; core_rq = cpu_rq(t); break; } if (WARN_ON_ONCE(!core_rq)) /* impossible */ return; /* copy the shared state to the new leader */ core_rq->core_task_seq = rq->core_task_seq; core_rq->core_pick_seq = rq->core_pick_seq; core_rq->core_cookie = rq->core_cookie; core_rq->core_forceidle_count = rq->core_forceidle_count; core_rq->core_forceidle_seq = rq->core_forceidle_seq; core_rq->core_forceidle_occupation = rq->core_forceidle_occupation; /* * Accounting edge for forced idle is handled in pick_next_task(). * Don't need another one here, since the hotplug thread shouldn't * have a cookie. */ core_rq->core_forceidle_start = 0; /* install new leader */ for_each_cpu(t, smt_mask) { rq = cpu_rq(t); rq->core = core_rq; } } static inline void sched_core_cpu_dying(unsigned int cpu) { struct rq *rq = cpu_rq(cpu); if (rq->core != rq) rq->core = rq; } #else /* !CONFIG_SCHED_CORE */ static inline void sched_core_cpu_starting(unsigned int cpu) {} static inline void sched_core_cpu_deactivate(unsigned int cpu) {} static inline void sched_core_cpu_dying(unsigned int cpu) {} static struct task_struct * pick_next_task(struct rq *rq, struct task_struct *prev, struct rq_flags *rf) { return __pick_next_task(rq, prev, rf); } #endif /* CONFIG_SCHED_CORE */ /* * Constants for the sched_mode argument of __schedule(). * * The mode argument allows RT enabled kernels to differentiate a * preemption from blocking on an 'sleeping' spin/rwlock. Note that * SM_MASK_PREEMPT for !RT has all bits set, which allows the compiler to * optimize the AND operation out and just check for zero. */ #define SM_NONE 0x0 #define SM_PREEMPT 0x1 #define SM_RTLOCK_WAIT 0x2 #ifndef CONFIG_PREEMPT_RT # define SM_MASK_PREEMPT (~0U) #else # define SM_MASK_PREEMPT SM_PREEMPT #endif /* * __schedule() is the main scheduler function. * * The main means of driving the scheduler and thus entering this function are: * * 1. Explicit blocking: mutex, semaphore, waitqueue, etc. * * 2. TIF_NEED_RESCHED flag is checked on interrupt and userspace return * paths. For example, see arch/x86/entry_64.S. * * To drive preemption between tasks, the scheduler sets the flag in timer * interrupt handler scheduler_tick(). * * 3. Wakeups don't really cause entry into schedule(). They add a * task to the run-queue and that's it. * * Now, if the new task added to the run-queue preempts the current * task, then the wakeup sets TIF_NEED_RESCHED and schedule() gets * called on the nearest possible occasion: * * - If the kernel is preemptible (CONFIG_PREEMPTION=y): * * - in syscall or exception context, at the next outmost * preempt_enable(). (this might be as soon as the wake_up()'s * spin_unlock()!) * * - in IRQ context, return from interrupt-handler to * preemptible context * * - If the kernel is not preemptible (CONFIG_PREEMPTION is not set) * then at the next: * * - cond_resched() call * - explicit schedule() call * - return from syscall or exception to user-space * - return from interrupt-handler to user-space * * WARNING: must be called with preemption disabled! */ static void __sched notrace __schedule(unsigned int sched_mode) { struct task_struct *prev, *next; unsigned long *switch_count; unsigned long prev_state; struct rq_flags rf; struct rq *rq; int cpu; cpu = smp_processor_id(); rq = cpu_rq(cpu); prev = rq->curr; schedule_debug(prev, !!sched_mode); if (sched_feat(HRTICK) || sched_feat(HRTICK_DL)) hrtick_clear(rq); local_irq_disable(); rcu_note_context_switch(!!sched_mode); /* * Make sure that signal_pending_state()->signal_pending() below * can't be reordered with __set_current_state(TASK_INTERRUPTIBLE) * done by the caller to avoid the race with signal_wake_up(): * * __set_current_state(@state) signal_wake_up() * schedule() set_tsk_thread_flag(p, TIF_SIGPENDING) * wake_up_state(p, state) * LOCK rq->lock LOCK p->pi_state * smp_mb__after_spinlock() smp_mb__after_spinlock() * if (signal_pending_state()) if (p->state & @state) * * Also, the membarrier system call requires a full memory barrier * after coming from user-space, before storing to rq->curr; this * barrier matches a full barrier in the proximity of the membarrier * system call exit. */ rq_lock(rq, &rf); smp_mb__after_spinlock(); /* Promote REQ to ACT */ rq->clock_update_flags <<= 1; update_rq_clock(rq); rq->clock_update_flags = RQCF_UPDATED; switch_count = &prev->nivcsw; /* * We must load prev->state once (task_struct::state is volatile), such * that we form a control dependency vs deactivate_task() below. */ prev_state = READ_ONCE(prev->__state); if (!(sched_mode & SM_MASK_PREEMPT) && prev_state) { if (signal_pending_state(prev_state, prev)) { WRITE_ONCE(prev->__state, TASK_RUNNING); } else { prev->sched_contributes_to_load = (prev_state & TASK_UNINTERRUPTIBLE) && !(prev_state & TASK_NOLOAD) && !(prev_state & TASK_FROZEN); if (prev->sched_contributes_to_load) rq->nr_uninterruptible++; /* * __schedule() ttwu() * prev_state = prev->state; if (p->on_rq && ...) * if (prev_state) goto out; * p->on_rq = 0; smp_acquire__after_ctrl_dep(); * p->state = TASK_WAKING * * Where __schedule() and ttwu() have matching control dependencies. * * After this, schedule() must not care about p->state any more. */ deactivate_task(rq, prev, DEQUEUE_SLEEP | DEQUEUE_NOCLOCK); if (prev->in_iowait) { atomic_inc(&rq->nr_iowait); delayacct_blkio_start(); } } switch_count = &prev->nvcsw; } next = pick_next_task(rq, prev, &rf); clear_tsk_need_resched(prev); clear_preempt_need_resched(); #ifdef CONFIG_SCHED_DEBUG rq->last_seen_need_resched_ns = 0; #endif if (likely(prev != next)) { rq->nr_switches++; /* * RCU users of rcu_dereference(rq->curr) may not see * changes to task_struct made by pick_next_task(). */ RCU_INIT_POINTER(rq->curr, next); /* * The membarrier system call requires each architecture * to have a full memory barrier after updating * rq->curr, before returning to user-space. * * Here are the schemes providing that barrier on the * various architectures: * - mm ? switch_mm() : mmdrop() for x86, s390, sparc, PowerPC, * RISC-V. switch_mm() relies on membarrier_arch_switch_mm() * on PowerPC and on RISC-V. * - finish_lock_switch() for weakly-ordered * architectures where spin_unlock is a full barrier, * - switch_to() for arm64 (weakly-ordered, spin_unlock * is a RELEASE barrier), * * The barrier matches a full barrier in the proximity of * the membarrier system call entry. * * On RISC-V, this barrier pairing is also needed for the * SYNC_CORE command when switching between processes, cf. * the inline comments in membarrier_arch_switch_mm(). */ ++*switch_count; migrate_disable_switch(rq, prev); psi_sched_switch(prev, next, !task_on_rq_queued(prev)); trace_sched_switch(sched_mode & SM_MASK_PREEMPT, prev, next, prev_state); /* Also unlocks the rq: */ rq = context_switch(rq, prev, next, &rf); } else { rq_unpin_lock(rq, &rf); __balance_callbacks(rq); raw_spin_rq_unlock_irq(rq); } } void __noreturn do_task_dead(void) { /* Causes final put_task_struct in finish_task_switch(): */ set_special_state(TASK_DEAD); /* Tell freezer to ignore us: */ current->flags |= PF_NOFREEZE; __schedule(SM_NONE); BUG(); /* Avoid "noreturn function does return" - but don't continue if BUG() is a NOP: */ for (;;) cpu_relax(); } static inline void sched_submit_work(struct task_struct *tsk) { static DEFINE_WAIT_OVERRIDE_MAP(sched_map, LD_WAIT_CONFIG); unsigned int task_flags; /* * Establish LD_WAIT_CONFIG context to ensure none of the code called * will use a blocking primitive -- which would lead to recursion. */ lock_map_acquire_try(&sched_map); task_flags = tsk->flags; /* * If a worker goes to sleep, notify and ask workqueue whether it * wants to wake up a task to maintain concurrency. */ if (task_flags & PF_WQ_WORKER) wq_worker_sleeping(tsk); else if (task_flags & PF_IO_WORKER) io_wq_worker_sleeping(tsk); /* * spinlock and rwlock must not flush block requests. This will * deadlock if the callback attempts to acquire a lock which is * already acquired. */ SCHED_WARN_ON(current->__state & TASK_RTLOCK_WAIT); /* * If we are going to sleep and we have plugged IO queued, * make sure to submit it to avoid deadlocks. */ blk_flush_plug(tsk->plug, true); lock_map_release(&sched_map); } static void sched_update_worker(struct task_struct *tsk) { if (tsk->flags & (PF_WQ_WORKER | PF_IO_WORKER | PF_BLOCK_TS)) { if (tsk->flags & PF_BLOCK_TS) blk_plug_invalidate_ts(tsk); if (tsk->flags & PF_WQ_WORKER) wq_worker_running(tsk); else if (tsk->flags & PF_IO_WORKER) io_wq_worker_running(tsk); } } static __always_inline void __schedule_loop(unsigned int sched_mode) { do { preempt_disable(); __schedule(sched_mode); sched_preempt_enable_no_resched(); } while (need_resched()); } asmlinkage __visible void __sched schedule(void) { struct task_struct *tsk = current; #ifdef CONFIG_RT_MUTEXES lockdep_assert(!tsk->sched_rt_mutex); #endif if (!task_is_running(tsk)) sched_submit_work(tsk); __schedule_loop(SM_NONE); sched_update_worker(tsk); } EXPORT_SYMBOL(schedule); /* * synchronize_rcu_tasks() makes sure that no task is stuck in preempted * state (have scheduled out non-voluntarily) by making sure that all * tasks have either left the run queue or have gone into user space. * As idle tasks do not do either, they must not ever be preempted * (schedule out non-voluntarily). * * schedule_idle() is similar to schedule_preempt_disable() except that it * never enables preemption because it does not call sched_submit_work(). */ void __sched schedule_idle(void) { /* * As this skips calling sched_submit_work(), which the idle task does * regardless because that function is a nop when the task is in a * TASK_RUNNING state, make sure this isn't used someplace that the * current task can be in any other state. Note, idle is always in the * TASK_RUNNING state. */ WARN_ON_ONCE(current->__state); do { __schedule(SM_NONE); } while (need_resched()); } #if defined(CONFIG_CONTEXT_TRACKING_USER) && !defined(CONFIG_HAVE_CONTEXT_TRACKING_USER_OFFSTACK) asmlinkage __visible void __sched schedule_user(void) { /* * If we come here after a random call to set_need_resched(), * or we have been woken up remotely but the IPI has not yet arrived, * we haven't yet exited the RCU idle mode. Do it here manually until * we find a better solution. * * NB: There are buggy callers of this function. Ideally we * should warn if prev_state != CONTEXT_USER, but that will trigger * too frequently to make sense yet. */ enum ctx_state prev_state = exception_enter(); schedule(); exception_exit(prev_state); } #endif /** * schedule_preempt_disabled - called with preemption disabled * * Returns with preemption disabled. Note: preempt_count must be 1 */ void __sched schedule_preempt_disabled(void) { sched_preempt_enable_no_resched(); schedule(); preempt_disable(); } #ifdef CONFIG_PREEMPT_RT void __sched notrace schedule_rtlock(void) { __schedule_loop(SM_RTLOCK_WAIT); } NOKPROBE_SYMBOL(schedule_rtlock); #endif static void __sched notrace preempt_schedule_common(void) { do { /* * Because the function tracer can trace preempt_count_sub() * and it also uses preempt_enable/disable_notrace(), if * NEED_RESCHED is set, the preempt_enable_notrace() called * by the function tracer will call this function again and * cause infinite recursion. * * Preemption must be disabled here before the function * tracer can trace. Break up preempt_disable() into two * calls. One to disable preemption without fear of being * traced. The other to still record the preemption latency, * which can also be traced by the function tracer. */ preempt_disable_notrace(); preempt_latency_start(1); __schedule(SM_PREEMPT); preempt_latency_stop(1); preempt_enable_no_resched_notrace(); /* * Check again in case we missed a preemption opportunity * between schedule and now. */ } while (need_resched()); } #ifdef CONFIG_PREEMPTION /* * This is the entry point to schedule() from in-kernel preemption * off of preempt_enable. */ asmlinkage __visible void __sched notrace preempt_schedule(void) { /* * If there is a non-zero preempt_count or interrupts are disabled, * we do not want to preempt the current task. Just return.. */ if (likely(!preemptible())) return; preempt_schedule_common(); } NOKPROBE_SYMBOL(preempt_schedule); EXPORT_SYMBOL(preempt_schedule); #ifdef CONFIG_PREEMPT_DYNAMIC #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) #ifndef preempt_schedule_dynamic_enabled #define preempt_schedule_dynamic_enabled preempt_schedule #define preempt_schedule_dynamic_disabled NULL #endif DEFINE_STATIC_CALL(preempt_schedule, preempt_schedule_dynamic_enabled); EXPORT_STATIC_CALL_TRAMP(preempt_schedule); #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule); void __sched notrace dynamic_preempt_schedule(void) { if (!static_branch_unlikely(&sk_dynamic_preempt_schedule)) return; preempt_schedule(); } NOKPROBE_SYMBOL(dynamic_preempt_schedule); EXPORT_SYMBOL(dynamic_preempt_schedule); #endif #endif /** * preempt_schedule_notrace - preempt_schedule called by tracing * * The tracing infrastructure uses preempt_enable_notrace to prevent * recursion and tracing preempt enabling caused by the tracing * infrastructure itself. But as tracing can happen in areas coming * from userspace or just about to enter userspace, a preempt enable * can occur before user_exit() is called. This will cause the scheduler * to be called when the system is still in usermode. * * To prevent this, the preempt_enable_notrace will use this function * instead of preempt_schedule() to exit user context if needed before * calling the scheduler. */ asmlinkage __visible void __sched notrace preempt_schedule_notrace(void) { enum ctx_state prev_ctx; if (likely(!preemptible())) return; do { /* * Because the function tracer can trace preempt_count_sub() * and it also uses preempt_enable/disable_notrace(), if * NEED_RESCHED is set, the preempt_enable_notrace() called * by the function tracer will call this function again and * cause infinite recursion. * * Preemption must be disabled here before the function * tracer can trace. Break up preempt_disable() into two * calls. One to disable preemption without fear of being * traced. The other to still record the preemption latency, * which can also be traced by the function tracer. */ preempt_disable_notrace(); preempt_latency_start(1); /* * Needs preempt disabled in case user_exit() is traced * and the tracer calls preempt_enable_notrace() causing * an infinite recursion. */ prev_ctx = exception_enter(); __schedule(SM_PREEMPT); exception_exit(prev_ctx); preempt_latency_stop(1); preempt_enable_no_resched_notrace(); } while (need_resched()); } EXPORT_SYMBOL_GPL(preempt_schedule_notrace); #ifdef CONFIG_PREEMPT_DYNAMIC #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) #ifndef preempt_schedule_notrace_dynamic_enabled #define preempt_schedule_notrace_dynamic_enabled preempt_schedule_notrace #define preempt_schedule_notrace_dynamic_disabled NULL #endif DEFINE_STATIC_CALL(preempt_schedule_notrace, preempt_schedule_notrace_dynamic_enabled); EXPORT_STATIC_CALL_TRAMP(preempt_schedule_notrace); #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) static DEFINE_STATIC_KEY_TRUE(sk_dynamic_preempt_schedule_notrace); void __sched notrace dynamic_preempt_schedule_notrace(void) { if (!static_branch_unlikely(&sk_dynamic_preempt_schedule_notrace)) return; preempt_schedule_notrace(); } NOKPROBE_SYMBOL(dynamic_preempt_schedule_notrace); EXPORT_SYMBOL(dynamic_preempt_schedule_notrace); #endif #endif #endif /* CONFIG_PREEMPTION */ /* * This is the entry point to schedule() from kernel preemption * off of irq context. * Note, that this is called and return with irqs disabled. This will * protect us against recursive calling from irq. */ asmlinkage __visible void __sched preempt_schedule_irq(void) { enum ctx_state prev_state; /* Catch callers which need to be fixed */ BUG_ON(preempt_count() || !irqs_disabled()); prev_state = exception_enter(); do { preempt_disable(); local_irq_enable(); __schedule(SM_PREEMPT); local_irq_disable(); sched_preempt_enable_no_resched(); } while (need_resched()); exception_exit(prev_state); } int default_wake_function(wait_queue_entry_t *curr, unsigned mode, int wake_flags, void *key) { WARN_ON_ONCE(IS_ENABLED(CONFIG_SCHED_DEBUG) && wake_flags & ~(WF_SYNC|WF_CURRENT_CPU)); return try_to_wake_up(curr->private, mode, wake_flags); } EXPORT_SYMBOL(default_wake_function); static void __setscheduler_prio(struct task_struct *p, int prio) { if (dl_prio(prio)) p->sched_class = &dl_sched_class; else if (rt_prio(prio)) p->sched_class = &rt_sched_class; else p->sched_class = &fair_sched_class; p->prio = prio; } #ifdef CONFIG_RT_MUTEXES /* * Would be more useful with typeof()/auto_type but they don't mix with * bit-fields. Since it's a local thing, use int. Keep the generic sounding * name such that if someone were to implement this function we get to compare * notes. */ #define fetch_and_set(x, v) ({ int _x = (x); (x) = (v); _x; }) void rt_mutex_pre_schedule(void) { lockdep_assert(!fetch_and_set(current->sched_rt_mutex, 1)); sched_submit_work(current); } void rt_mutex_schedule(void) { lockdep_assert(current->sched_rt_mutex); __schedule_loop(SM_NONE); } void rt_mutex_post_schedule(void) { sched_update_worker(current); lockdep_assert(fetch_and_set(current->sched_rt_mutex, 0)); } static inline int __rt_effective_prio(struct task_struct *pi_task, int prio) { if (pi_task) prio = min(prio, pi_task->prio); return prio; } static inline int rt_effective_prio(struct task_struct *p, int prio) { struct task_struct *pi_task = rt_mutex_get_top_task(p); return __rt_effective_prio(pi_task, prio); } /* * rt_mutex_setprio - set the current priority of a task * @p: task to boost * @pi_task: donor task * * This function changes the 'effective' priority of a task. It does * not touch ->normal_prio like __setscheduler(). * * Used by the rt_mutex code to implement priority inheritance * logic. Call site only calls if the priority of the task changed. */ void rt_mutex_setprio(struct task_struct *p, struct task_struct *pi_task) { int prio, oldprio, queued, running, queue_flag = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; const struct sched_class *prev_class; struct rq_flags rf; struct rq *rq; /* XXX used to be waiter->prio, not waiter->task->prio */ prio = __rt_effective_prio(pi_task, p->normal_prio); /* * If nothing changed; bail early. */ if (p->pi_top_task == pi_task && prio == p->prio && !dl_prio(prio)) return; rq = __task_rq_lock(p, &rf); update_rq_clock(rq); /* * Set under pi_lock && rq->lock, such that the value can be used under * either lock. * * Note that there is loads of tricky to make this pointer cache work * right. rt_mutex_slowunlock()+rt_mutex_postunlock() work together to * ensure a task is de-boosted (pi_task is set to NULL) before the * task is allowed to run again (and can exit). This ensures the pointer * points to a blocked task -- which guarantees the task is present. */ p->pi_top_task = pi_task; /* * For FIFO/RR we only need to set prio, if that matches we're done. */ if (prio == p->prio && !dl_prio(prio)) goto out_unlock; /* * Idle task boosting is a nono in general. There is one * exception, when PREEMPT_RT and NOHZ is active: * * The idle task calls get_next_timer_interrupt() and holds * the timer wheel base->lock on the CPU and another CPU wants * to access the timer (probably to cancel it). We can safely * ignore the boosting request, as the idle CPU runs this code * with interrupts disabled and will complete the lock * protected section without being interrupted. So there is no * real need to boost. */ if (unlikely(p == rq->idle)) { WARN_ON(p != rq->curr); WARN_ON(p->pi_blocked_on); goto out_unlock; } trace_sched_pi_setprio(p, pi_task); oldprio = p->prio; if (oldprio == prio) queue_flag &= ~DEQUEUE_MOVE; prev_class = p->sched_class; queued = task_on_rq_queued(p); running = task_current(rq, p); if (queued) dequeue_task(rq, p, queue_flag); if (running) put_prev_task(rq, p); /* * Boosting condition are: * 1. -rt task is running and holds mutex A * --> -dl task blocks on mutex A * * 2. -dl task is running and holds mutex A * --> -dl task blocks on mutex A and could preempt the * running task */ if (dl_prio(prio)) { if (!dl_prio(p->normal_prio) || (pi_task && dl_prio(pi_task->prio) && dl_entity_preempt(&pi_task->dl, &p->dl))) { p->dl.pi_se = pi_task->dl.pi_se; queue_flag |= ENQUEUE_REPLENISH; } else { p->dl.pi_se = &p->dl; } } else if (rt_prio(prio)) { if (dl_prio(oldprio)) p->dl.pi_se = &p->dl; if (oldprio < prio) queue_flag |= ENQUEUE_HEAD; } else { if (dl_prio(oldprio)) p->dl.pi_se = &p->dl; if (rt_prio(oldprio)) p->rt.timeout = 0; } __setscheduler_prio(p, prio); if (queued) enqueue_task(rq, p, queue_flag); if (running) set_next_task(rq, p); check_class_changed(rq, p, prev_class, oldprio); out_unlock: /* Avoid rq from going away on us: */ preempt_disable(); rq_unpin_lock(rq, &rf); __balance_callbacks(rq); raw_spin_rq_unlock(rq); preempt_enable(); } #else static inline int rt_effective_prio(struct task_struct *p, int prio) { return prio; } #endif void set_user_nice(struct task_struct *p, long nice) { bool queued, running; struct rq *rq; int old_prio; if (task_nice(p) == nice || nice < MIN_NICE || nice > MAX_NICE) return; /* * We have to be careful, if called from sys_setpriority(), * the task might be in the middle of scheduling on another CPU. */ CLASS(task_rq_lock, rq_guard)(p); rq = rq_guard.rq; update_rq_clock(rq); /* * The RT priorities are set via sched_setscheduler(), but we still * allow the 'normal' nice value to be set - but as expected * it won't have any effect on scheduling until the task is * SCHED_DEADLINE, SCHED_FIFO or SCHED_RR: */ if (task_has_dl_policy(p) || task_has_rt_policy(p)) { p->static_prio = NICE_TO_PRIO(nice); return; } queued = task_on_rq_queued(p); running = task_current(rq, p); if (queued) dequeue_task(rq, p, DEQUEUE_SAVE | DEQUEUE_NOCLOCK); if (running) put_prev_task(rq, p); p->static_prio = NICE_TO_PRIO(nice); set_load_weight(p, true); old_prio = p->prio; p->prio = effective_prio(p); if (queued) enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); if (running) set_next_task(rq, p); /* * If the task increased its priority or is running and * lowered its priority, then reschedule its CPU: */ p->sched_class->prio_changed(rq, p, old_prio); } EXPORT_SYMBOL(set_user_nice); /* * is_nice_reduction - check if nice value is an actual reduction * * Similar to can_nice() but does not perform a capability check. * * @p: task * @nice: nice value */ static bool is_nice_reduction(const struct task_struct *p, const int nice) { /* Convert nice value [19,-20] to rlimit style value [1,40]: */ int nice_rlim = nice_to_rlimit(nice); return (nice_rlim <= task_rlimit(p, RLIMIT_NICE)); } /* * can_nice - check if a task can reduce its nice value * @p: task * @nice: nice value */ int can_nice(const struct task_struct *p, const int nice) { return is_nice_reduction(p, nice) || capable(CAP_SYS_NICE); } #ifdef __ARCH_WANT_SYS_NICE /* * sys_nice - change the priority of the current process. * @increment: priority increment * * sys_setpriority is a more generic, but much slower function that * does similar things. */ SYSCALL_DEFINE1(nice, int, increment) { long nice, retval; /* * Setpriority might change our priority at the same moment. * We don't have to worry. Conceptually one call occurs first * and we have a single winner. */ increment = clamp(increment, -NICE_WIDTH, NICE_WIDTH); nice = task_nice(current) + increment; nice = clamp_val(nice, MIN_NICE, MAX_NICE); if (increment < 0 && !can_nice(current, nice)) return -EPERM; retval = security_task_setnice(current, nice); if (retval) return retval; set_user_nice(current, nice); return 0; } #endif /** * task_prio - return the priority value of a given task. * @p: the task in question. * * Return: The priority value as seen by users in /proc. * * sched policy return value kernel prio user prio/nice * * normal, batch, idle [0 ... 39] [100 ... 139] 0/[-20 ... 19] * fifo, rr [-2 ... -100] [98 ... 0] [1 ... 99] * deadline -101 -1 0 */ int task_prio(const struct task_struct *p) { return p->prio - MAX_RT_PRIO; } /** * idle_cpu - is a given CPU idle currently? * @cpu: the processor in question. * * Return: 1 if the CPU is currently idle. 0 otherwise. */ int idle_cpu(int cpu) { struct rq *rq = cpu_rq(cpu); if (rq->curr != rq->idle) return 0; if (rq->nr_running) return 0; #ifdef CONFIG_SMP if (rq->ttwu_pending) return 0; #endif return 1; } /** * available_idle_cpu - is a given CPU idle for enqueuing work. * @cpu: the CPU in question. * * Return: 1 if the CPU is currently idle. 0 otherwise. */ int available_idle_cpu(int cpu) { if (!idle_cpu(cpu)) return 0; if (vcpu_is_preempted(cpu)) return 0; return 1; } /** * idle_task - return the idle task for a given CPU. * @cpu: the processor in question. * * Return: The idle task for the CPU @cpu. */ struct task_struct *idle_task(int cpu) { return cpu_rq(cpu)->idle; } #ifdef CONFIG_SCHED_CORE int sched_core_idle_cpu(int cpu) { struct rq *rq = cpu_rq(cpu); if (sched_core_enabled(rq) && rq->curr == rq->idle) return 1; return idle_cpu(cpu); } #endif #ifdef CONFIG_SMP /* * This function computes an effective utilization for the given CPU, to be * used for frequency selection given the linear relation: f = u * f_max. * * The scheduler tracks the following metrics: * * cpu_util_{cfs,rt,dl,irq}() * cpu_bw_dl() * * Where the cfs,rt and dl util numbers are tracked with the same metric and * synchronized windows and are thus directly comparable. * * The cfs,rt,dl utilization are the running times measured with rq->clock_task * which excludes things like IRQ and steal-time. These latter are then accrued * in the irq utilization. * * The DL bandwidth number otoh is not a measured metric but a value computed * based on the task model parameters and gives the minimal utilization * required to meet deadlines. */ unsigned long effective_cpu_util(int cpu, unsigned long util_cfs, unsigned long *min, unsigned long *max) { unsigned long util, irq, scale; struct rq *rq = cpu_rq(cpu); scale = arch_scale_cpu_capacity(cpu); /* * Early check to see if IRQ/steal time saturates the CPU, can be * because of inaccuracies in how we track these -- see * update_irq_load_avg(). */ irq = cpu_util_irq(rq); if (unlikely(irq >= scale)) { if (min) *min = scale; if (max) *max = scale; return scale; } if (min) { /* * The minimum utilization returns the highest level between: * - the computed DL bandwidth needed with the IRQ pressure which * steals time to the deadline task. * - The minimum performance requirement for CFS and/or RT. */ *min = max(irq + cpu_bw_dl(rq), uclamp_rq_get(rq, UCLAMP_MIN)); /* * When an RT task is runnable and uclamp is not used, we must * ensure that the task will run at maximum compute capacity. */ if (!uclamp_is_used() && rt_rq_is_runnable(&rq->rt)) *min = max(*min, scale); } /* * Because the time spend on RT/DL tasks is visible as 'lost' time to * CFS tasks and we use the same metric to track the effective * utilization (PELT windows are synchronized) we can directly add them * to obtain the CPU's actual utilization. */ util = util_cfs + cpu_util_rt(rq); util += cpu_util_dl(rq); /* * The maximum hint is a soft bandwidth requirement, which can be lower * than the actual utilization because of uclamp_max requirements. */ if (max) *max = min(scale, uclamp_rq_get(rq, UCLAMP_MAX)); if (util >= scale) return scale; /* * There is still idle time; further improve the number by using the * irq metric. Because IRQ/steal time is hidden from the task clock we * need to scale the task numbers: * * max - irq * U' = irq + --------- * U * max */ util = scale_irq_capacity(util, irq, scale); util += irq; return min(scale, util); } unsigned long sched_cpu_util(int cpu) { return effective_cpu_util(cpu, cpu_util_cfs(cpu), NULL, NULL); } #endif /* CONFIG_SMP */ /** * find_process_by_pid - find a process with a matching PID value. * @pid: the pid in question. * * The task of @pid, if found. %NULL otherwise. */ static struct task_struct *find_process_by_pid(pid_t pid) { return pid ? find_task_by_vpid(pid) : current; } static struct task_struct *find_get_task(pid_t pid) { struct task_struct *p; guard(rcu)(); p = find_process_by_pid(pid); if (likely(p)) get_task_struct(p); return p; } DEFINE_CLASS(find_get_task, struct task_struct *, if (_T) put_task_struct(_T), find_get_task(pid), pid_t pid) /* * sched_setparam() passes in -1 for its policy, to let the functions * it calls know not to change it. */ #define SETPARAM_POLICY -1 static void __setscheduler_params(struct task_struct *p, const struct sched_attr *attr) { int policy = attr->sched_policy; if (policy == SETPARAM_POLICY) policy = p->policy; p->policy = policy; if (dl_policy(policy)) __setparam_dl(p, attr); else if (fair_policy(policy)) p->static_prio = NICE_TO_PRIO(attr->sched_nice); /* * __sched_setscheduler() ensures attr->sched_priority == 0 when * !rt_policy. Always setting this ensures that things like * getparam()/getattr() don't report silly values for !rt tasks. */ p->rt_priority = attr->sched_priority; p->normal_prio = normal_prio(p); set_load_weight(p, true); } /* * Check the target process has a UID that matches the current process's: */ static bool check_same_owner(struct task_struct *p) { const struct cred *cred = current_cred(), *pcred; guard(rcu)(); pcred = __task_cred(p); return (uid_eq(cred->euid, pcred->euid) || uid_eq(cred->euid, pcred->uid)); } /* * Allow unprivileged RT tasks to decrease priority. * Only issue a capable test if needed and only once to avoid an audit * event on permitted non-privileged operations: */ static int user_check_sched_setscheduler(struct task_struct *p, const struct sched_attr *attr, int policy, int reset_on_fork) { if (fair_policy(policy)) { if (attr->sched_nice < task_nice(p) && !is_nice_reduction(p, attr->sched_nice)) goto req_priv; } if (rt_policy(policy)) { unsigned long rlim_rtprio = task_rlimit(p, RLIMIT_RTPRIO); /* Can't set/change the rt policy: */ if (policy != p->policy && !rlim_rtprio) goto req_priv; /* Can't increase priority: */ if (attr->sched_priority > p->rt_priority && attr->sched_priority > rlim_rtprio) goto req_priv; } /* * Can't set/change SCHED_DEADLINE policy at all for now * (safest behavior); in the future we would like to allow * unprivileged DL tasks to increase their relative deadline * or reduce their runtime (both ways reducing utilization) */ if (dl_policy(policy)) goto req_priv; /* * Treat SCHED_IDLE as nice 20. Only allow a switch to * SCHED_NORMAL if the RLIMIT_NICE would normally permit it. */ if (task_has_idle_policy(p) && !idle_policy(policy)) { if (!is_nice_reduction(p, task_nice(p))) goto req_priv; } /* Can't change other user's priorities: */ if (!check_same_owner(p)) goto req_priv; /* Normal users shall not reset the sched_reset_on_fork flag: */ if (p->sched_reset_on_fork && !reset_on_fork) goto req_priv; return 0; req_priv: if (!capable(CAP_SYS_NICE)) return -EPERM; return 0; } static int __sched_setscheduler(struct task_struct *p, const struct sched_attr *attr, bool user, bool pi) { int oldpolicy = -1, policy = attr->sched_policy; int retval, oldprio, newprio, queued, running; const struct sched_class *prev_class; struct balance_callback *head; struct rq_flags rf; int reset_on_fork; int queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; struct rq *rq; bool cpuset_locked = false; /* The pi code expects interrupts enabled */ BUG_ON(pi && in_interrupt()); recheck: /* Double check policy once rq lock held: */ if (policy < 0) { reset_on_fork = p->sched_reset_on_fork; policy = oldpolicy = p->policy; } else { reset_on_fork = !!(attr->sched_flags & SCHED_FLAG_RESET_ON_FORK); if (!valid_policy(policy)) return -EINVAL; } if (attr->sched_flags & ~(SCHED_FLAG_ALL | SCHED_FLAG_SUGOV)) return -EINVAL; /* * Valid priorities for SCHED_FIFO and SCHED_RR are * 1..MAX_RT_PRIO-1, valid priority for SCHED_NORMAL, * SCHED_BATCH and SCHED_IDLE is 0. */ if (attr->sched_priority > MAX_RT_PRIO-1) return -EINVAL; if ((dl_policy(policy) && !__checkparam_dl(attr)) || (rt_policy(policy) != (attr->sched_priority != 0))) return -EINVAL; if (user) { retval = user_check_sched_setscheduler(p, attr, policy, reset_on_fork); if (retval) return retval; if (attr->sched_flags & SCHED_FLAG_SUGOV) return -EINVAL; retval = security_task_setscheduler(p); if (retval) return retval; } /* Update task specific "requested" clamps */ if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) { retval = uclamp_validate(p, attr); if (retval) return retval; } /* * SCHED_DEADLINE bandwidth accounting relies on stable cpusets * information. */ if (dl_policy(policy) || dl_policy(p->policy)) { cpuset_locked = true; cpuset_lock(); } /* * Make sure no PI-waiters arrive (or leave) while we are * changing the priority of the task: * * To be able to change p->policy safely, the appropriate * runqueue lock must be held. */ rq = task_rq_lock(p, &rf); update_rq_clock(rq); /* * Changing the policy of the stop threads its a very bad idea: */ if (p == rq->stop) { retval = -EINVAL; goto unlock; } /* * If not changing anything there's no need to proceed further, * but store a possible modification of reset_on_fork. */ if (unlikely(policy == p->policy)) { if (fair_policy(policy) && attr->sched_nice != task_nice(p)) goto change; if (rt_policy(policy) && attr->sched_priority != p->rt_priority) goto change; if (dl_policy(policy) && dl_param_changed(p, attr)) goto change; if (attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) goto change; p->sched_reset_on_fork = reset_on_fork; retval = 0; goto unlock; } change: if (user) { #ifdef CONFIG_RT_GROUP_SCHED /* * Do not allow realtime tasks into groups that have no runtime * assigned. */ if (rt_bandwidth_enabled() && rt_policy(policy) && task_group(p)->rt_bandwidth.rt_runtime == 0 && !task_group_is_autogroup(task_group(p))) { retval = -EPERM; goto unlock; } #endif #ifdef CONFIG_SMP if (dl_bandwidth_enabled() && dl_policy(policy) && !(attr->sched_flags & SCHED_FLAG_SUGOV)) { cpumask_t *span = rq->rd->span; /* * Don't allow tasks with an affinity mask smaller than * the entire root_domain to become SCHED_DEADLINE. We * will also fail if there's no bandwidth available. */ if (!cpumask_subset(span, p->cpus_ptr) || rq->rd->dl_bw.bw == 0) { retval = -EPERM; goto unlock; } } #endif } /* Re-check policy now with rq lock held: */ if (unlikely(oldpolicy != -1 && oldpolicy != p->policy)) { policy = oldpolicy = -1; task_rq_unlock(rq, p, &rf); if (cpuset_locked) cpuset_unlock(); goto recheck; } /* * If setscheduling to SCHED_DEADLINE (or changing the parameters * of a SCHED_DEADLINE task) we need to check if enough bandwidth * is available. */ if ((dl_policy(policy) || dl_task(p)) && sched_dl_overflow(p, policy, attr)) { retval = -EBUSY; goto unlock; } p->sched_reset_on_fork = reset_on_fork; oldprio = p->prio; newprio = __normal_prio(policy, attr->sched_priority, attr->sched_nice); if (pi) { /* * Take priority boosted tasks into account. If the new * effective priority is unchanged, we just store the new * normal parameters and do not touch the scheduler class and * the runqueue. This will be done when the task deboost * itself. */ newprio = rt_effective_prio(p, newprio); if (newprio == oldprio) queue_flags &= ~DEQUEUE_MOVE; } queued = task_on_rq_queued(p); running = task_current(rq, p); if (queued) dequeue_task(rq, p, queue_flags); if (running) put_prev_task(rq, p); prev_class = p->sched_class; if (!(attr->sched_flags & SCHED_FLAG_KEEP_PARAMS)) { __setscheduler_params(p, attr); __setscheduler_prio(p, newprio); } __setscheduler_uclamp(p, attr); if (queued) { /* * We enqueue to tail when the priority of a task is * increased (user space view). */ if (oldprio < p->prio) queue_flags |= ENQUEUE_HEAD; enqueue_task(rq, p, queue_flags); } if (running) set_next_task(rq, p); check_class_changed(rq, p, prev_class, oldprio); /* Avoid rq from going away on us: */ preempt_disable(); head = splice_balance_callbacks(rq); task_rq_unlock(rq, p, &rf); if (pi) { if (cpuset_locked) cpuset_unlock(); rt_mutex_adjust_pi(p); } /* Run balance callbacks after we've adjusted the PI chain: */ balance_callbacks(rq, head); preempt_enable(); return 0; unlock: task_rq_unlock(rq, p, &rf); if (cpuset_locked) cpuset_unlock(); return retval; } static int _sched_setscheduler(struct task_struct *p, int policy, const struct sched_param *param, bool check) { struct sched_attr attr = { .sched_policy = policy, .sched_priority = param->sched_priority, .sched_nice = PRIO_TO_NICE(p->static_prio), }; /* Fixup the legacy SCHED_RESET_ON_FORK hack. */ if ((policy != SETPARAM_POLICY) && (policy & SCHED_RESET_ON_FORK)) { attr.sched_flags |= SCHED_FLAG_RESET_ON_FORK; policy &= ~SCHED_RESET_ON_FORK; attr.sched_policy = policy; } return __sched_setscheduler(p, &attr, check, true); } /** * sched_setscheduler - change the scheduling policy and/or RT priority of a thread. * @p: the task in question. * @policy: new policy. * @param: structure containing the new RT priority. * * Use sched_set_fifo(), read its comment. * * Return: 0 on success. An error code otherwise. * * NOTE that the task may be already dead. */ int sched_setscheduler(struct task_struct *p, int policy, const struct sched_param *param) { return _sched_setscheduler(p, policy, param, true); } int sched_setattr(struct task_struct *p, const struct sched_attr *attr) { return __sched_setscheduler(p, attr, true, true); } int sched_setattr_nocheck(struct task_struct *p, const struct sched_attr *attr) { return __sched_setscheduler(p, attr, false, true); } EXPORT_SYMBOL_GPL(sched_setattr_nocheck); /** * sched_setscheduler_nocheck - change the scheduling policy and/or RT priority of a thread from kernelspace. * @p: the task in question. * @policy: new policy. * @param: structure containing the new RT priority. * * Just like sched_setscheduler, only don't bother checking if the * current context has permission. For example, this is needed in * stop_machine(): we create temporary high priority worker threads, * but our caller might not have that capability. * * Return: 0 on success. An error code otherwise. */ int sched_setscheduler_nocheck(struct task_struct *p, int policy, const struct sched_param *param) { return _sched_setscheduler(p, policy, param, false); } /* * SCHED_FIFO is a broken scheduler model; that is, it is fundamentally * incapable of resource management, which is the one thing an OS really should * be doing. * * This is of course the reason it is limited to privileged users only. * * Worse still; it is fundamentally impossible to compose static priority * workloads. You cannot take two correctly working static prio workloads * and smash them together and still expect them to work. * * For this reason 'all' FIFO tasks the kernel creates are basically at: * * MAX_RT_PRIO / 2 * * The administrator _MUST_ configure the system, the kernel simply doesn't * know enough information to make a sensible choice. */ void sched_set_fifo(struct task_struct *p) { struct sched_param sp = { .sched_priority = MAX_RT_PRIO / 2 }; WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0); } EXPORT_SYMBOL_GPL(sched_set_fifo); /* * For when you don't much care about FIFO, but want to be above SCHED_NORMAL. */ void sched_set_fifo_low(struct task_struct *p) { struct sched_param sp = { .sched_priority = 1 }; WARN_ON_ONCE(sched_setscheduler_nocheck(p, SCHED_FIFO, &sp) != 0); } EXPORT_SYMBOL_GPL(sched_set_fifo_low); void sched_set_normal(struct task_struct *p, int nice) { struct sched_attr attr = { .sched_policy = SCHED_NORMAL, .sched_nice = nice, }; WARN_ON_ONCE(sched_setattr_nocheck(p, &attr) != 0); } EXPORT_SYMBOL_GPL(sched_set_normal); static int do_sched_setscheduler(pid_t pid, int policy, struct sched_param __user *param) { struct sched_param lparam; if (!param || pid < 0) return -EINVAL; if (copy_from_user(&lparam, param, sizeof(struct sched_param))) return -EFAULT; CLASS(find_get_task, p)(pid); if (!p) return -ESRCH; return sched_setscheduler(p, policy, &lparam); } /* * Mimics kernel/events/core.c perf_copy_attr(). */ static int sched_copy_attr(struct sched_attr __user *uattr, struct sched_attr *attr) { u32 size; int ret; /* Zero the full structure, so that a short copy will be nice: */ memset(attr, 0, sizeof(*attr)); ret = get_user(size, &uattr->size); if (ret) return ret; /* ABI compatibility quirk: */ if (!size) size = SCHED_ATTR_SIZE_VER0; if (size < SCHED_ATTR_SIZE_VER0 || size > PAGE_SIZE) goto err_size; ret = copy_struct_from_user(attr, sizeof(*attr), uattr, size); if (ret) { if (ret == -E2BIG) goto err_size; return ret; } if ((attr->sched_flags & SCHED_FLAG_UTIL_CLAMP) && size < SCHED_ATTR_SIZE_VER1) return -EINVAL; /* * XXX: Do we want to be lenient like existing syscalls; or do we want * to be strict and return an error on out-of-bounds values? */ attr->sched_nice = clamp(attr->sched_nice, MIN_NICE, MAX_NICE); return 0; err_size: put_user(sizeof(*attr), &uattr->size); return -E2BIG; } static void get_params(struct task_struct *p, struct sched_attr *attr) { if (task_has_dl_policy(p)) __getparam_dl(p, attr); else if (task_has_rt_policy(p)) attr->sched_priority = p->rt_priority; else attr->sched_nice = task_nice(p); } /** * sys_sched_setscheduler - set/change the scheduler policy and RT priority * @pid: the pid in question. * @policy: new policy. * @param: structure containing the new RT priority. * * Return: 0 on success. An error code otherwise. */ SYSCALL_DEFINE3(sched_setscheduler, pid_t, pid, int, policy, struct sched_param __user *, param) { if (policy < 0) return -EINVAL; return do_sched_setscheduler(pid, policy, param); } /** * sys_sched_setparam - set/change the RT priority of a thread * @pid: the pid in question. * @param: structure containing the new RT priority. * * Return: 0 on success. An error code otherwise. */ SYSCALL_DEFINE2(sched_setparam, pid_t, pid, struct sched_param __user *, param) { return do_sched_setscheduler(pid, SETPARAM_POLICY, param); } /** * sys_sched_setattr - same as above, but with extended sched_attr * @pid: the pid in question. * @uattr: structure containing the extended parameters. * @flags: for future extension. */ SYSCALL_DEFINE3(sched_setattr, pid_t, pid, struct sched_attr __user *, uattr, unsigned int, flags) { struct sched_attr attr; int retval; if (!uattr || pid < 0 || flags) return -EINVAL; retval = sched_copy_attr(uattr, &attr); if (retval) return retval; if ((int)attr.sched_policy < 0) return -EINVAL; if (attr.sched_flags & SCHED_FLAG_KEEP_POLICY) attr.sched_policy = SETPARAM_POLICY; CLASS(find_get_task, p)(pid); if (!p) return -ESRCH; if (attr.sched_flags & SCHED_FLAG_KEEP_PARAMS) get_params(p, &attr); return sched_setattr(p, &attr); } /** * sys_sched_getscheduler - get the policy (scheduling class) of a thread * @pid: the pid in question. * * Return: On success, the policy of the thread. Otherwise, a negative error * code. */ SYSCALL_DEFINE1(sched_getscheduler, pid_t, pid) { struct task_struct *p; int retval; if (pid < 0) return -EINVAL; guard(rcu)(); p = find_process_by_pid(pid); if (!p) return -ESRCH; retval = security_task_getscheduler(p); if (!retval) { retval = p->policy; if (p->sched_reset_on_fork) retval |= SCHED_RESET_ON_FORK; } return retval; } /** * sys_sched_getparam - get the RT priority of a thread * @pid: the pid in question. * @param: structure containing the RT priority. * * Return: On success, 0 and the RT priority is in @param. Otherwise, an error * code. */ SYSCALL_DEFINE2(sched_getparam, pid_t, pid, struct sched_param __user *, param) { struct sched_param lp = { .sched_priority = 0 }; struct task_struct *p; int retval; if (!param || pid < 0) return -EINVAL; scoped_guard (rcu) { p = find_process_by_pid(pid); if (!p) return -ESRCH; retval = security_task_getscheduler(p); if (retval) return retval; if (task_has_rt_policy(p)) lp.sched_priority = p->rt_priority; } /* * This one might sleep, we cannot do it with a spinlock held ... */ return copy_to_user(param, &lp, sizeof(*param)) ? -EFAULT : 0; } /* * Copy the kernel size attribute structure (which might be larger * than what user-space knows about) to user-space. * * Note that all cases are valid: user-space buffer can be larger or * smaller than the kernel-space buffer. The usual case is that both * have the same size. */ static int sched_attr_copy_to_user(struct sched_attr __user *uattr, struct sched_attr *kattr, unsigned int usize) { unsigned int ksize = sizeof(*kattr); if (!access_ok(uattr, usize)) return -EFAULT; /* * sched_getattr() ABI forwards and backwards compatibility: * * If usize == ksize then we just copy everything to user-space and all is good. * * If usize < ksize then we only copy as much as user-space has space for, * this keeps ABI compatibility as well. We skip the rest. * * If usize > ksize then user-space is using a newer version of the ABI, * which part the kernel doesn't know about. Just ignore it - tooling can * detect the kernel's knowledge of attributes from the attr->size value * which is set to ksize in this case. */ kattr->size = min(usize, ksize); if (copy_to_user(uattr, kattr, kattr->size)) return -EFAULT; return 0; } /** * sys_sched_getattr - similar to sched_getparam, but with sched_attr * @pid: the pid in question. * @uattr: structure containing the extended parameters. * @usize: sizeof(attr) for fwd/bwd comp. * @flags: for future extension. */ SYSCALL_DEFINE4(sched_getattr, pid_t, pid, struct sched_attr __user *, uattr, unsigned int, usize, unsigned int, flags) { struct sched_attr kattr = { }; struct task_struct *p; int retval; if (!uattr || pid < 0 || usize > PAGE_SIZE || usize < SCHED_ATTR_SIZE_VER0 || flags) return -EINVAL; scoped_guard (rcu) { p = find_process_by_pid(pid); if (!p) return -ESRCH; retval = security_task_getscheduler(p); if (retval) return retval; kattr.sched_policy = p->policy; if (p->sched_reset_on_fork) kattr.sched_flags |= SCHED_FLAG_RESET_ON_FORK; get_params(p, &kattr); kattr.sched_flags &= SCHED_FLAG_ALL; #ifdef CONFIG_UCLAMP_TASK /* * This could race with another potential updater, but this is fine * because it'll correctly read the old or the new value. We don't need * to guarantee who wins the race as long as it doesn't return garbage. */ kattr.sched_util_min = p->uclamp_req[UCLAMP_MIN].value; kattr.sched_util_max = p->uclamp_req[UCLAMP_MAX].value; #endif } return sched_attr_copy_to_user(uattr, &kattr, usize); } #ifdef CONFIG_SMP int dl_task_check_affinity(struct task_struct *p, const struct cpumask *mask) { /* * If the task isn't a deadline task or admission control is * disabled then we don't care about affinity changes. */ if (!task_has_dl_policy(p) || !dl_bandwidth_enabled()) return 0; /* * Since bandwidth control happens on root_domain basis, * if admission test is enabled, we only admit -deadline * tasks allowed to run on all the CPUs in the task's * root_domain. */ guard(rcu)(); if (!cpumask_subset(task_rq(p)->rd->span, mask)) return -EBUSY; return 0; } #endif static int __sched_setaffinity(struct task_struct *p, struct affinity_context *ctx) { int retval; cpumask_var_t cpus_allowed, new_mask; if (!alloc_cpumask_var(&cpus_allowed, GFP_KERNEL)) return -ENOMEM; if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) { retval = -ENOMEM; goto out_free_cpus_allowed; } cpuset_cpus_allowed(p, cpus_allowed); cpumask_and(new_mask, ctx->new_mask, cpus_allowed); ctx->new_mask = new_mask; ctx->flags |= SCA_CHECK; retval = dl_task_check_affinity(p, new_mask); if (retval) goto out_free_new_mask; retval = __set_cpus_allowed_ptr(p, ctx); if (retval) goto out_free_new_mask; cpuset_cpus_allowed(p, cpus_allowed); if (!cpumask_subset(new_mask, cpus_allowed)) { /* * We must have raced with a concurrent cpuset update. * Just reset the cpumask to the cpuset's cpus_allowed. */ cpumask_copy(new_mask, cpus_allowed); /* * If SCA_USER is set, a 2nd call to __set_cpus_allowed_ptr() * will restore the previous user_cpus_ptr value. * * In the unlikely event a previous user_cpus_ptr exists, * we need to further restrict the mask to what is allowed * by that old user_cpus_ptr. */ if (unlikely((ctx->flags & SCA_USER) && ctx->user_mask)) { bool empty = !cpumask_and(new_mask, new_mask, ctx->user_mask); if (WARN_ON_ONCE(empty)) cpumask_copy(new_mask, cpus_allowed); } __set_cpus_allowed_ptr(p, ctx); retval = -EINVAL; } out_free_new_mask: free_cpumask_var(new_mask); out_free_cpus_allowed: free_cpumask_var(cpus_allowed); return retval; } long sched_setaffinity(pid_t pid, const struct cpumask *in_mask) { struct affinity_context ac; struct cpumask *user_mask; int retval; CLASS(find_get_task, p)(pid); if (!p) return -ESRCH; if (p->flags & PF_NO_SETAFFINITY) return -EINVAL; if (!check_same_owner(p)) { guard(rcu)(); if (!ns_capable(__task_cred(p)->user_ns, CAP_SYS_NICE)) return -EPERM; } retval = security_task_setscheduler(p); if (retval) return retval; /* * With non-SMP configs, user_cpus_ptr/user_mask isn't used and * alloc_user_cpus_ptr() returns NULL. */ user_mask = alloc_user_cpus_ptr(NUMA_NO_NODE); if (user_mask) { cpumask_copy(user_mask, in_mask); } else if (IS_ENABLED(CONFIG_SMP)) { return -ENOMEM; } ac = (struct affinity_context){ .new_mask = in_mask, .user_mask = user_mask, .flags = SCA_USER, }; retval = __sched_setaffinity(p, &ac); kfree(ac.user_mask); return retval; } static int get_user_cpu_mask(unsigned long __user *user_mask_ptr, unsigned len, struct cpumask *new_mask) { if (len < cpumask_size()) cpumask_clear(new_mask); else if (len > cpumask_size()) len = cpumask_size(); return copy_from_user(new_mask, user_mask_ptr, len) ? -EFAULT : 0; } /** * sys_sched_setaffinity - set the CPU affinity of a process * @pid: pid of the process * @len: length in bytes of the bitmask pointed to by user_mask_ptr * @user_mask_ptr: user-space pointer to the new CPU mask * * Return: 0 on success. An error code otherwise. */ SYSCALL_DEFINE3(sched_setaffinity, pid_t, pid, unsigned int, len, unsigned long __user *, user_mask_ptr) { cpumask_var_t new_mask; int retval; if (!alloc_cpumask_var(&new_mask, GFP_KERNEL)) return -ENOMEM; retval = get_user_cpu_mask(user_mask_ptr, len, new_mask); if (retval == 0) retval = sched_setaffinity(pid, new_mask); free_cpumask_var(new_mask); return retval; } long sched_getaffinity(pid_t pid, struct cpumask *mask) { struct task_struct *p; int retval; guard(rcu)(); p = find_process_by_pid(pid); if (!p) return -ESRCH; retval = security_task_getscheduler(p); if (retval) return retval; guard(raw_spinlock_irqsave)(&p->pi_lock); cpumask_and(mask, &p->cpus_mask, cpu_active_mask); return 0; } /** * sys_sched_getaffinity - get the CPU affinity of a process * @pid: pid of the process * @len: length in bytes of the bitmask pointed to by user_mask_ptr * @user_mask_ptr: user-space pointer to hold the current CPU mask * * Return: size of CPU mask copied to user_mask_ptr on success. An * error code otherwise. */ SYSCALL_DEFINE3(sched_getaffinity, pid_t, pid, unsigned int, len, unsigned long __user *, user_mask_ptr) { int ret; cpumask_var_t mask; if ((len * BITS_PER_BYTE) < nr_cpu_ids) return -EINVAL; if (len & (sizeof(unsigned long)-1)) return -EINVAL; if (!zalloc_cpumask_var(&mask, GFP_KERNEL)) return -ENOMEM; ret = sched_getaffinity(pid, mask); if (ret == 0) { unsigned int retlen = min(len, cpumask_size()); if (copy_to_user(user_mask_ptr, cpumask_bits(mask), retlen)) ret = -EFAULT; else ret = retlen; } free_cpumask_var(mask); return ret; } static void do_sched_yield(void) { struct rq_flags rf; struct rq *rq; rq = this_rq_lock_irq(&rf); schedstat_inc(rq->yld_count); current->sched_class->yield_task(rq); preempt_disable(); rq_unlock_irq(rq, &rf); sched_preempt_enable_no_resched(); schedule(); } /** * sys_sched_yield - yield the current processor to other threads. * * This function yields the current CPU to other tasks. If there are no * other threads running on this CPU then this function will return. * * Return: 0. */ SYSCALL_DEFINE0(sched_yield) { do_sched_yield(); return 0; } #if !defined(CONFIG_PREEMPTION) || defined(CONFIG_PREEMPT_DYNAMIC) int __sched __cond_resched(void) { if (should_resched(0)) { preempt_schedule_common(); return 1; } /* * In preemptible kernels, ->rcu_read_lock_nesting tells the tick * whether the current CPU is in an RCU read-side critical section, * so the tick can report quiescent states even for CPUs looping * in kernel context. In contrast, in non-preemptible kernels, * RCU readers leave no in-memory hints, which means that CPU-bound * processes executing in kernel context might never report an * RCU quiescent state. Therefore, the following code causes * cond_resched() to report a quiescent state, but only when RCU * is in urgent need of one. */ #ifndef CONFIG_PREEMPT_RCU rcu_all_qs(); #endif return 0; } EXPORT_SYMBOL(__cond_resched); #endif #ifdef CONFIG_PREEMPT_DYNAMIC #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) #define cond_resched_dynamic_enabled __cond_resched #define cond_resched_dynamic_disabled ((void *)&__static_call_return0) DEFINE_STATIC_CALL_RET0(cond_resched, __cond_resched); EXPORT_STATIC_CALL_TRAMP(cond_resched); #define might_resched_dynamic_enabled __cond_resched #define might_resched_dynamic_disabled ((void *)&__static_call_return0) DEFINE_STATIC_CALL_RET0(might_resched, __cond_resched); EXPORT_STATIC_CALL_TRAMP(might_resched); #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) static DEFINE_STATIC_KEY_FALSE(sk_dynamic_cond_resched); int __sched dynamic_cond_resched(void) { klp_sched_try_switch(); if (!static_branch_unlikely(&sk_dynamic_cond_resched)) return 0; return __cond_resched(); } EXPORT_SYMBOL(dynamic_cond_resched); static DEFINE_STATIC_KEY_FALSE(sk_dynamic_might_resched); int __sched dynamic_might_resched(void) { if (!static_branch_unlikely(&sk_dynamic_might_resched)) return 0; return __cond_resched(); } EXPORT_SYMBOL(dynamic_might_resched); #endif #endif /* * __cond_resched_lock() - if a reschedule is pending, drop the given lock, * call schedule, and on return reacquire the lock. * * This works OK both with and without CONFIG_PREEMPTION. We do strange low-level * operations here to prevent schedule() from being called twice (once via * spin_unlock(), once by hand). */ int __cond_resched_lock(spinlock_t *lock) { int resched = should_resched(PREEMPT_LOCK_OFFSET); int ret = 0; lockdep_assert_held(lock); if (spin_needbreak(lock) || resched) { spin_unlock(lock); if (!_cond_resched()) cpu_relax(); ret = 1; spin_lock(lock); } return ret; } EXPORT_SYMBOL(__cond_resched_lock); int __cond_resched_rwlock_read(rwlock_t *lock) { int resched = should_resched(PREEMPT_LOCK_OFFSET); int ret = 0; lockdep_assert_held_read(lock); if (rwlock_needbreak(lock) || resched) { read_unlock(lock); if (!_cond_resched()) cpu_relax(); ret = 1; read_lock(lock); } return ret; } EXPORT_SYMBOL(__cond_resched_rwlock_read); int __cond_resched_rwlock_write(rwlock_t *lock) { int resched = should_resched(PREEMPT_LOCK_OFFSET); int ret = 0; lockdep_assert_held_write(lock); if (rwlock_needbreak(lock) || resched) { write_unlock(lock); if (!_cond_resched()) cpu_relax(); ret = 1; write_lock(lock); } return ret; } EXPORT_SYMBOL(__cond_resched_rwlock_write); #ifdef CONFIG_PREEMPT_DYNAMIC #ifdef CONFIG_GENERIC_ENTRY #include <linux/entry-common.h> #endif /* * SC:cond_resched * SC:might_resched * SC:preempt_schedule * SC:preempt_schedule_notrace * SC:irqentry_exit_cond_resched * * * NONE: * cond_resched <- __cond_resched * might_resched <- RET0 * preempt_schedule <- NOP * preempt_schedule_notrace <- NOP * irqentry_exit_cond_resched <- NOP * * VOLUNTARY: * cond_resched <- __cond_resched * might_resched <- __cond_resched * preempt_schedule <- NOP * preempt_schedule_notrace <- NOP * irqentry_exit_cond_resched <- NOP * * FULL: * cond_resched <- RET0 * might_resched <- RET0 * preempt_schedule <- preempt_schedule * preempt_schedule_notrace <- preempt_schedule_notrace * irqentry_exit_cond_resched <- irqentry_exit_cond_resched */ enum { preempt_dynamic_undefined = -1, preempt_dynamic_none, preempt_dynamic_voluntary, preempt_dynamic_full, }; int preempt_dynamic_mode = preempt_dynamic_undefined; int sched_dynamic_mode(const char *str) { if (!strcmp(str, "none")) return preempt_dynamic_none; if (!strcmp(str, "voluntary")) return preempt_dynamic_voluntary; if (!strcmp(str, "full")) return preempt_dynamic_full; return -EINVAL; } #if defined(CONFIG_HAVE_PREEMPT_DYNAMIC_CALL) #define preempt_dynamic_enable(f) static_call_update(f, f##_dynamic_enabled) #define preempt_dynamic_disable(f) static_call_update(f, f##_dynamic_disabled) #elif defined(CONFIG_HAVE_PREEMPT_DYNAMIC_KEY) #define preempt_dynamic_enable(f) static_key_enable(&sk_dynamic_##f.key) #define preempt_dynamic_disable(f) static_key_disable(&sk_dynamic_##f.key) #else #error "Unsupported PREEMPT_DYNAMIC mechanism" #endif static DEFINE_MUTEX(sched_dynamic_mutex); static bool klp_override; static void __sched_dynamic_update(int mode) { /* * Avoid {NONE,VOLUNTARY} -> FULL transitions from ever ending up in * the ZERO state, which is invalid. */ if (!klp_override) preempt_dynamic_enable(cond_resched); preempt_dynamic_enable(might_resched); preempt_dynamic_enable(preempt_schedule); preempt_dynamic_enable(preempt_schedule_notrace); preempt_dynamic_enable(irqentry_exit_cond_resched); switch (mode) { case preempt_dynamic_none: if (!klp_override) preempt_dynamic_enable(cond_resched); preempt_dynamic_disable(might_resched); preempt_dynamic_disable(preempt_schedule); preempt_dynamic_disable(preempt_schedule_notrace); preempt_dynamic_disable(irqentry_exit_cond_resched); if (mode != preempt_dynamic_mode) pr_info("Dynamic Preempt: none\n"); break; case preempt_dynamic_voluntary: if (!klp_override) preempt_dynamic_enable(cond_resched); preempt_dynamic_enable(might_resched); preempt_dynamic_disable(preempt_schedule); preempt_dynamic_disable(preempt_schedule_notrace); preempt_dynamic_disable(irqentry_exit_cond_resched); if (mode != preempt_dynamic_mode) pr_info("Dynamic Preempt: voluntary\n"); break; case preempt_dynamic_full: if (!klp_override) preempt_dynamic_disable(cond_resched); preempt_dynamic_disable(might_resched); preempt_dynamic_enable(preempt_schedule); preempt_dynamic_enable(preempt_schedule_notrace); preempt_dynamic_enable(irqentry_exit_cond_resched); if (mode != preempt_dynamic_mode) pr_info("Dynamic Preempt: full\n"); break; } preempt_dynamic_mode = mode; } void sched_dynamic_update(int mode) { mutex_lock(&sched_dynamic_mutex); __sched_dynamic_update(mode); mutex_unlock(&sched_dynamic_mutex); } #ifdef CONFIG_HAVE_PREEMPT_DYNAMIC_CALL static int klp_cond_resched(void) { __klp_sched_try_switch(); return __cond_resched(); } void sched_dynamic_klp_enable(void) { mutex_lock(&sched_dynamic_mutex); klp_override = true; static_call_update(cond_resched, klp_cond_resched); mutex_unlock(&sched_dynamic_mutex); } void sched_dynamic_klp_disable(void) { mutex_lock(&sched_dynamic_mutex); klp_override = false; __sched_dynamic_update(preempt_dynamic_mode); mutex_unlock(&sched_dynamic_mutex); } #endif /* CONFIG_HAVE_PREEMPT_DYNAMIC_CALL */ static int __init setup_preempt_mode(char *str) { int mode = sched_dynamic_mode(str); if (mode < 0) { pr_warn("Dynamic Preempt: unsupported mode: %s\n", str); return 0; } sched_dynamic_update(mode); return 1; } __setup("preempt=", setup_preempt_mode); static void __init preempt_dynamic_init(void) { if (preempt_dynamic_mode == preempt_dynamic_undefined) { if (IS_ENABLED(CONFIG_PREEMPT_NONE)) { sched_dynamic_update(preempt_dynamic_none); } else if (IS_ENABLED(CONFIG_PREEMPT_VOLUNTARY)) { sched_dynamic_update(preempt_dynamic_voluntary); } else { /* Default static call setting, nothing to do */ WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT)); preempt_dynamic_mode = preempt_dynamic_full; pr_info("Dynamic Preempt: full\n"); } } } #define PREEMPT_MODEL_ACCESSOR(mode) \ bool preempt_model_##mode(void) \ { \ WARN_ON_ONCE(preempt_dynamic_mode == preempt_dynamic_undefined); \ return preempt_dynamic_mode == preempt_dynamic_##mode; \ } \ EXPORT_SYMBOL_GPL(preempt_model_##mode) PREEMPT_MODEL_ACCESSOR(none); PREEMPT_MODEL_ACCESSOR(voluntary); PREEMPT_MODEL_ACCESSOR(full); #else /* !CONFIG_PREEMPT_DYNAMIC */ static inline void preempt_dynamic_init(void) { } #endif /* #ifdef CONFIG_PREEMPT_DYNAMIC */ /** * yield - yield the current processor to other threads. * * Do not ever use this function, there's a 99% chance you're doing it wrong. * * The scheduler is at all times free to pick the calling task as the most * eligible task to run, if removing the yield() call from your code breaks * it, it's already broken. * * Typical broken usage is: * * while (!event) * yield(); * * where one assumes that yield() will let 'the other' process run that will * make event true. If the current task is a SCHED_FIFO task that will never * happen. Never use yield() as a progress guarantee!! * * If you want to use yield() to wait for something, use wait_event(). * If you want to use yield() to be 'nice' for others, use cond_resched(). * If you still want to use yield(), do not! */ void __sched yield(void) { set_current_state(TASK_RUNNING); do_sched_yield(); } EXPORT_SYMBOL(yield); /** * yield_to - yield the current processor to another thread in * your thread group, or accelerate that thread toward the * processor it's on. * @p: target task * @preempt: whether task preemption is allowed or not * * It's the caller's job to ensure that the target task struct * can't go away on us before we can do any checks. * * Return: * true (>0) if we indeed boosted the target task. * false (0) if we failed to boost the target. * -ESRCH if there's no task to yield to. */ int __sched yield_to(struct task_struct *p, bool preempt) { struct task_struct *curr = current; struct rq *rq, *p_rq; int yielded = 0; scoped_guard (irqsave) { rq = this_rq(); again: p_rq = task_rq(p); /* * If we're the only runnable task on the rq and target rq also * has only one task, there's absolutely no point in yielding. */ if (rq->nr_running == 1 && p_rq->nr_running == 1) return -ESRCH; guard(double_rq_lock)(rq, p_rq); if (task_rq(p) != p_rq) goto again; if (!curr->sched_class->yield_to_task) return 0; if (curr->sched_class != p->sched_class) return 0; if (task_on_cpu(p_rq, p) || !task_is_running(p)) return 0; yielded = curr->sched_class->yield_to_task(rq, p); if (yielded) { schedstat_inc(rq->yld_count); /* * Make p's CPU reschedule; pick_next_entity * takes care of fairness. */ if (preempt && rq != p_rq) resched_curr(p_rq); } } if (yielded) schedule(); return yielded; } EXPORT_SYMBOL_GPL(yield_to); int io_schedule_prepare(void) { int old_iowait = current->in_iowait; current->in_iowait = 1; blk_flush_plug(current->plug, true); return old_iowait; } void io_schedule_finish(int token) { current->in_iowait = token; } /* * This task is about to go to sleep on IO. Increment rq->nr_iowait so * that process accounting knows that this is a task in IO wait state. */ long __sched io_schedule_timeout(long timeout) { int token; long ret; token = io_schedule_prepare(); ret = schedule_timeout(timeout); io_schedule_finish(token); return ret; } EXPORT_SYMBOL(io_schedule_timeout); void __sched io_schedule(void) { int token; token = io_schedule_prepare(); schedule(); io_schedule_finish(token); } EXPORT_SYMBOL(io_schedule); /** * sys_sched_get_priority_max - return maximum RT priority. * @policy: scheduling class. * * Return: On success, this syscall returns the maximum * rt_priority that can be used by a given scheduling class. * On failure, a negative error code is returned. */ SYSCALL_DEFINE1(sched_get_priority_max, int, policy) { int ret = -EINVAL; switch (policy) { case SCHED_FIFO: case SCHED_RR: ret = MAX_RT_PRIO-1; break; case SCHED_DEADLINE: case SCHED_NORMAL: case SCHED_BATCH: case SCHED_IDLE: ret = 0; break; } return ret; } /** * sys_sched_get_priority_min - return minimum RT priority. * @policy: scheduling class. * * Return: On success, this syscall returns the minimum * rt_priority that can be used by a given scheduling class. * On failure, a negative error code is returned. */ SYSCALL_DEFINE1(sched_get_priority_min, int, policy) { int ret = -EINVAL; switch (policy) { case SCHED_FIFO: case SCHED_RR: ret = 1; break; case SCHED_DEADLINE: case SCHED_NORMAL: case SCHED_BATCH: case SCHED_IDLE: ret = 0; } return ret; } static int sched_rr_get_interval(pid_t pid, struct timespec64 *t) { unsigned int time_slice = 0; int retval; if (pid < 0) return -EINVAL; scoped_guard (rcu) { struct task_struct *p = find_process_by_pid(pid); if (!p) return -ESRCH; retval = security_task_getscheduler(p); if (retval) return retval; scoped_guard (task_rq_lock, p) { struct rq *rq = scope.rq; if (p->sched_class->get_rr_interval) time_slice = p->sched_class->get_rr_interval(rq, p); } } jiffies_to_timespec64(time_slice, t); return 0; } /** * sys_sched_rr_get_interval - return the default timeslice of a process. * @pid: pid of the process. * @interval: userspace pointer to the timeslice value. * * this syscall writes the default timeslice value of a given process * into the user-space timespec buffer. A value of '0' means infinity. * * Return: On success, 0 and the timeslice is in @interval. Otherwise, * an error code. */ SYSCALL_DEFINE2(sched_rr_get_interval, pid_t, pid, struct __kernel_timespec __user *, interval) { struct timespec64 t; int retval = sched_rr_get_interval(pid, &t); if (retval == 0) retval = put_timespec64(&t, interval); return retval; } #ifdef CONFIG_COMPAT_32BIT_TIME SYSCALL_DEFINE2(sched_rr_get_interval_time32, pid_t, pid, struct old_timespec32 __user *, interval) { struct timespec64 t; int retval = sched_rr_get_interval(pid, &t); if (retval == 0) retval = put_old_timespec32(&t, interval); return retval; } #endif void sched_show_task(struct task_struct *p) { unsigned long free = 0; int ppid; if (!try_get_task_stack(p)) return; pr_info("task:%-15.15s state:%c", p->comm, task_state_to_char(p)); if (task_is_running(p)) pr_cont(" running task "); #ifdef CONFIG_DEBUG_STACK_USAGE free = stack_not_used(p); #endif ppid = 0; rcu_read_lock(); if (pid_alive(p)) ppid = task_pid_nr(rcu_dereference(p->real_parent)); rcu_read_unlock(); pr_cont(" stack:%-5lu pid:%-5d tgid:%-5d ppid:%-6d flags:0x%08lx\n", free, task_pid_nr(p), task_tgid_nr(p), ppid, read_task_thread_flags(p)); print_worker_info(KERN_INFO, p); print_stop_info(KERN_INFO, p); show_stack(p, NULL, KERN_INFO); put_task_stack(p); } EXPORT_SYMBOL_GPL(sched_show_task); static inline bool state_filter_match(unsigned long state_filter, struct task_struct *p) { unsigned int state = READ_ONCE(p->__state); /* no filter, everything matches */ if (!state_filter) return true; /* filter, but doesn't match */ if (!(state & state_filter)) return false; /* * When looking for TASK_UNINTERRUPTIBLE skip TASK_IDLE (allows * TASK_KILLABLE). */ if (state_filter == TASK_UNINTERRUPTIBLE && (state & TASK_NOLOAD)) return false; return true; } void show_state_filter(unsigned int state_filter) { struct task_struct *g, *p; rcu_read_lock(); for_each_process_thread(g, p) { /* * reset the NMI-timeout, listing all files on a slow * console might take a lot of time: * Also, reset softlockup watchdogs on all CPUs, because * another CPU might be blocked waiting for us to process * an IPI. */ touch_nmi_watchdog(); touch_all_softlockup_watchdogs(); if (state_filter_match(state_filter, p)) sched_show_task(p); } #ifdef CONFIG_SCHED_DEBUG if (!state_filter) sysrq_sched_debug_show(); #endif rcu_read_unlock(); /* * Only show locks if all tasks are dumped: */ if (!state_filter) debug_show_all_locks(); } /** * init_idle - set up an idle thread for a given CPU * @idle: task in question * @cpu: CPU the idle task belongs to * * NOTE: this function does not set the idle thread's NEED_RESCHED * flag, to make booting more robust. */ void __init init_idle(struct task_struct *idle, int cpu) { #ifdef CONFIG_SMP struct affinity_context ac = (struct affinity_context) { .new_mask = cpumask_of(cpu), .flags = 0, }; #endif struct rq *rq = cpu_rq(cpu); unsigned long flags; __sched_fork(0, idle); raw_spin_lock_irqsave(&idle->pi_lock, flags); raw_spin_rq_lock(rq); idle->__state = TASK_RUNNING; idle->se.exec_start = sched_clock(); /* * PF_KTHREAD should already be set at this point; regardless, make it * look like a proper per-CPU kthread. */ idle->flags |= PF_KTHREAD | PF_NO_SETAFFINITY; kthread_set_per_cpu(idle, cpu); #ifdef CONFIG_SMP /* * It's possible that init_idle() gets called multiple times on a task, * in that case do_set_cpus_allowed() will not do the right thing. * * And since this is boot we can forgo the serialization. */ set_cpus_allowed_common(idle, &ac); #endif /* * We're having a chicken and egg problem, even though we are * holding rq->lock, the CPU isn't yet set to this CPU so the * lockdep check in task_group() will fail. * * Similar case to sched_fork(). / Alternatively we could * use task_rq_lock() here and obtain the other rq->lock. * * Silence PROVE_RCU */ rcu_read_lock(); __set_task_cpu(idle, cpu); rcu_read_unlock(); rq->idle = idle; rcu_assign_pointer(rq->curr, idle); idle->on_rq = TASK_ON_RQ_QUEUED; #ifdef CONFIG_SMP idle->on_cpu = 1; #endif raw_spin_rq_unlock(rq); raw_spin_unlock_irqrestore(&idle->pi_lock, flags); /* Set the preempt count _outside_ the spinlocks! */ init_idle_preempt_count(idle, cpu); /* * The idle tasks have their own, simple scheduling class: */ idle->sched_class = &idle_sched_class; ftrace_graph_init_idle_task(idle, cpu); vtime_init_idle(idle, cpu); #ifdef CONFIG_SMP sprintf(idle->comm, "%s/%d", INIT_TASK_COMM, cpu); #endif } #ifdef CONFIG_SMP int cpuset_cpumask_can_shrink(const struct cpumask *cur, const struct cpumask *trial) { int ret = 1; if (cpumask_empty(cur)) return ret; ret = dl_cpuset_cpumask_can_shrink(cur, trial); return ret; } int task_can_attach(struct task_struct *p) { int ret = 0; /* * Kthreads which disallow setaffinity shouldn't be moved * to a new cpuset; we don't want to change their CPU * affinity and isolating such threads by their set of * allowed nodes is unnecessary. Thus, cpusets are not * applicable for such threads. This prevents checking for * success of set_cpus_allowed_ptr() on all attached tasks * before cpus_mask may be changed. */ if (p->flags & PF_NO_SETAFFINITY) ret = -EINVAL; return ret; } bool sched_smp_initialized __read_mostly; #ifdef CONFIG_NUMA_BALANCING /* Migrate current task p to target_cpu */ int migrate_task_to(struct task_struct *p, int target_cpu) { struct migration_arg arg = { p, target_cpu }; int curr_cpu = task_cpu(p); if (curr_cpu == target_cpu) return 0; if (!cpumask_test_cpu(target_cpu, p->cpus_ptr)) return -EINVAL; /* TODO: This is not properly updating schedstats */ trace_sched_move_numa(p, curr_cpu, target_cpu); return stop_one_cpu(curr_cpu, migration_cpu_stop, &arg); } /* * Requeue a task on a given node and accurately track the number of NUMA * tasks on the runqueues */ void sched_setnuma(struct task_struct *p, int nid) { bool queued, running; struct rq_flags rf; struct rq *rq; rq = task_rq_lock(p, &rf); queued = task_on_rq_queued(p); running = task_current(rq, p); if (queued) dequeue_task(rq, p, DEQUEUE_SAVE); if (running) put_prev_task(rq, p); p->numa_preferred_nid = nid; if (queued) enqueue_task(rq, p, ENQUEUE_RESTORE | ENQUEUE_NOCLOCK); if (running) set_next_task(rq, p); task_rq_unlock(rq, p, &rf); } #endif /* CONFIG_NUMA_BALANCING */ #ifdef CONFIG_HOTPLUG_CPU /* * Ensure that the idle task is using init_mm right before its CPU goes * offline. */ void idle_task_exit(void) { struct mm_struct *mm = current->active_mm; BUG_ON(cpu_online(smp_processor_id())); BUG_ON(current != this_rq()->idle); if (mm != &init_mm) { switch_mm(mm, &init_mm, current); finish_arch_post_lock_switch(); } /* finish_cpu(), as ran on the BP, will clean up the active_mm state */ } static int __balance_push_cpu_stop(void *arg) { struct task_struct *p = arg; struct rq *rq = this_rq(); struct rq_flags rf; int cpu; raw_spin_lock_irq(&p->pi_lock); rq_lock(rq, &rf); update_rq_clock(rq); if (task_rq(p) == rq && task_on_rq_queued(p)) { cpu = select_fallback_rq(rq->cpu, p); rq = __migrate_task(rq, &rf, p, cpu); } rq_unlock(rq, &rf); raw_spin_unlock_irq(&p->pi_lock); put_task_struct(p); return 0; } static DEFINE_PER_CPU(struct cpu_stop_work, push_work); /* * Ensure we only run per-cpu kthreads once the CPU goes !active. * * This is enabled below SCHED_AP_ACTIVE; when !cpu_active(), but only * effective when the hotplug motion is down. */ static void balance_push(struct rq *rq) { struct task_struct *push_task = rq->curr; lockdep_assert_rq_held(rq); /* * Ensure the thing is persistent until balance_push_set(.on = false); */ rq->balance_callback = &balance_push_callback; /* * Only active while going offline and when invoked on the outgoing * CPU. */ if (!cpu_dying(rq->cpu) || rq != this_rq()) return; /* * Both the cpu-hotplug and stop task are in this case and are * required to complete the hotplug process. */ if (kthread_is_per_cpu(push_task) || is_migration_disabled(push_task)) { /* * If this is the idle task on the outgoing CPU try to wake * up the hotplug control thread which might wait for the * last task to vanish. The rcuwait_active() check is * accurate here because the waiter is pinned on this CPU * and can't obviously be running in parallel. * * On RT kernels this also has to check whether there are * pinned and scheduled out tasks on the runqueue. They * need to leave the migrate disabled section first. */ if (!rq->nr_running && !rq_has_pinned_tasks(rq) && rcuwait_active(&rq->hotplug_wait)) { raw_spin_rq_unlock(rq); rcuwait_wake_up(&rq->hotplug_wait); raw_spin_rq_lock(rq); } return; } get_task_struct(push_task); /* * Temporarily drop rq->lock such that we can wake-up the stop task. * Both preemption and IRQs are still disabled. */ preempt_disable(); raw_spin_rq_unlock(rq); stop_one_cpu_nowait(rq->cpu, __balance_push_cpu_stop, push_task, this_cpu_ptr(&push_work)); preempt_enable(); /* * At this point need_resched() is true and we'll take the loop in * schedule(). The next pick is obviously going to be the stop task * which kthread_is_per_cpu() and will push this task away. */ raw_spin_rq_lock(rq); } static void balance_push_set(int cpu, bool on) { struct rq *rq = cpu_rq(cpu); struct rq_flags rf; rq_lock_irqsave(rq, &rf); if (on) { WARN_ON_ONCE(rq->balance_callback); rq->balance_callback = &balance_push_callback; } else if (rq->balance_callback == &balance_push_callback) { rq->balance_callback = NULL; } rq_unlock_irqrestore(rq, &rf); } /* * Invoked from a CPUs hotplug control thread after the CPU has been marked * inactive. All tasks which are not per CPU kernel threads are either * pushed off this CPU now via balance_push() or placed on a different CPU * during wakeup. Wait until the CPU is quiescent. */ static void balance_hotplug_wait(void) { struct rq *rq = this_rq(); rcuwait_wait_event(&rq->hotplug_wait, rq->nr_running == 1 && !rq_has_pinned_tasks(rq), TASK_UNINTERRUPTIBLE); } #else static inline void balance_push(struct rq *rq) { } static inline void balance_push_set(int cpu, bool on) { } static inline void balance_hotplug_wait(void) { } #endif /* CONFIG_HOTPLUG_CPU */ void set_rq_online(struct rq *rq) { if (!rq->online) { const struct sched_class *class; cpumask_set_cpu(rq->cpu, rq->rd->online); rq->online = 1; for_each_class(class) { if (class->rq_online) class->rq_online(rq); } } } void set_rq_offline(struct rq *rq) { if (rq->online) { const struct sched_class *class; update_rq_clock(rq); for_each_class(class) { if (class->rq_offline) class->rq_offline(rq); } cpumask_clear_cpu(rq->cpu, rq->rd->online); rq->online = 0; } } /* * used to mark begin/end of suspend/resume: */ static int num_cpus_frozen; /* * Update cpusets according to cpu_active mask. If cpusets are * disabled, cpuset_update_active_cpus() becomes a simple wrapper * around partition_sched_domains(). * * If we come here as part of a suspend/resume, don't touch cpusets because we * want to restore it back to its original state upon resume anyway. */ static void cpuset_cpu_active(void) { if (cpuhp_tasks_frozen) { /* * num_cpus_frozen tracks how many CPUs are involved in suspend * resume sequence. As long as this is not the last online * operation in the resume sequence, just build a single sched * domain, ignoring cpusets. */ partition_sched_domains(1, NULL, NULL); if (--num_cpus_frozen) return; /* * This is the last CPU online operation. So fall through and * restore the original sched domains by considering the * cpuset configurations. */ cpuset_force_rebuild(); } cpuset_update_active_cpus(); } static int cpuset_cpu_inactive(unsigned int cpu) { if (!cpuhp_tasks_frozen) { int ret = dl_bw_check_overflow(cpu); if (ret) return ret; cpuset_update_active_cpus(); } else { num_cpus_frozen++; partition_sched_domains(1, NULL, NULL); } return 0; } int sched_cpu_activate(unsigned int cpu) { struct rq *rq = cpu_rq(cpu); struct rq_flags rf; /* * Clear the balance_push callback and prepare to schedule * regular tasks. */ balance_push_set(cpu, false); #ifdef CONFIG_SCHED_SMT /* * When going up, increment the number of cores with SMT present. */ if (cpumask_weight(cpu_smt_mask(cpu)) == 2) static_branch_inc_cpuslocked(&sched_smt_present); #endif set_cpu_active(cpu, true); if (sched_smp_initialized) { sched_update_numa(cpu, true); sched_domains_numa_masks_set(cpu); cpuset_cpu_active(); } /* * Put the rq online, if not already. This happens: * * 1) In the early boot process, because we build the real domains * after all CPUs have been brought up. * * 2) At runtime, if cpuset_cpu_active() fails to rebuild the * domains. */ rq_lock_irqsave(rq, &rf); if (rq->rd) { BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); set_rq_online(rq); } rq_unlock_irqrestore(rq, &rf); return 0; } int sched_cpu_deactivate(unsigned int cpu) { struct rq *rq = cpu_rq(cpu); struct rq_flags rf; int ret; /* * Remove CPU from nohz.idle_cpus_mask to prevent participating in * load balancing when not active */ nohz_balance_exit_idle(rq); set_cpu_active(cpu, false); /* * From this point forward, this CPU will refuse to run any task that * is not: migrate_disable() or KTHREAD_IS_PER_CPU, and will actively * push those tasks away until this gets cleared, see * sched_cpu_dying(). */ balance_push_set(cpu, true); /* * We've cleared cpu_active_mask / set balance_push, wait for all * preempt-disabled and RCU users of this state to go away such that * all new such users will observe it. * * Specifically, we rely on ttwu to no longer target this CPU, see * ttwu_queue_cond() and is_cpu_allowed(). * * Do sync before park smpboot threads to take care the rcu boost case. */ synchronize_rcu(); rq_lock_irqsave(rq, &rf); if (rq->rd) { BUG_ON(!cpumask_test_cpu(cpu, rq->rd->span)); set_rq_offline(rq); } rq_unlock_irqrestore(rq, &rf); #ifdef CONFIG_SCHED_SMT /* * When going down, decrement the number of cores with SMT present. */ if (cpumask_weight(cpu_smt_mask(cpu)) == 2) static_branch_dec_cpuslocked(&sched_smt_present); sched_core_cpu_deactivate(cpu); #endif if (!sched_smp_initialized) return 0; sched_update_numa(cpu, false); ret = cpuset_cpu_inactive(cpu); if (ret) { balance_push_set(cpu, false); set_cpu_active(cpu, true); sched_update_numa(cpu, true); return ret; } sched_domains_numa_masks_clear(cpu); return 0; } static void sched_rq_cpu_starting(unsigned int cpu) { struct rq *rq = cpu_rq(cpu); rq->calc_load_update = calc_load_update; update_max_interval(); } int sched_cpu_starting(unsigned int cpu) { sched_core_cpu_starting(cpu); sched_rq_cpu_starting(cpu); sched_tick_start(cpu); return 0; } #ifdef CONFIG_HOTPLUG_CPU /* * Invoked immediately before the stopper thread is invoked to bring the * CPU down completely. At this point all per CPU kthreads except the * hotplug thread (current) and the stopper thread (inactive) have been * either parked or have been unbound from the outgoing CPU. Ensure that * any of those which might be on the way out are gone. * * If after this point a bound task is being woken on this CPU then the * responsible hotplug callback has failed to do it's job. * sched_cpu_dying() will catch it with the appropriate fireworks. */ int sched_cpu_wait_empty(unsigned int cpu) { balance_hotplug_wait(); return 0; } /* * Since this CPU is going 'away' for a while, fold any nr_active delta we * might have. Called from the CPU stopper task after ensuring that the * stopper is the last running task on the CPU, so nr_active count is * stable. We need to take the teardown thread which is calling this into * account, so we hand in adjust = 1 to the load calculation. * * Also see the comment "Global load-average calculations". */ static void calc_load_migrate(struct rq *rq) { long delta = calc_load_fold_active(rq, 1); if (delta) atomic_long_add(delta, &calc_load_tasks); } static void dump_rq_tasks(struct rq *rq, const char *loglvl) { struct task_struct *g, *p; int cpu = cpu_of(rq); lockdep_assert_rq_held(rq); printk("%sCPU%d enqueued tasks (%u total):\n", loglvl, cpu, rq->nr_running); for_each_process_thread(g, p) { if (task_cpu(p) != cpu) continue; if (!task_on_rq_queued(p)) continue; printk("%s\tpid: %d, name: %s\n", loglvl, p->pid, p->comm); } } int sched_cpu_dying(unsigned int cpu) { struct rq *rq = cpu_rq(cpu); struct rq_flags rf; /* Handle pending wakeups and then migrate everything off */ sched_tick_stop(cpu); rq_lock_irqsave(rq, &rf); if (rq->nr_running != 1 || rq_has_pinned_tasks(rq)) { WARN(true, "Dying CPU not properly vacated!"); dump_rq_tasks(rq, KERN_WARNING); } rq_unlock_irqrestore(rq, &rf); calc_load_migrate(rq); update_max_interval(); hrtick_clear(rq); sched_core_cpu_dying(cpu); return 0; } #endif void __init sched_init_smp(void) { sched_init_numa(NUMA_NO_NODE); /* * There's no userspace yet to cause hotplug operations; hence all the * CPU masks are stable and all blatant races in the below code cannot * happen. */ mutex_lock(&sched_domains_mutex); sched_init_domains(cpu_active_mask); mutex_unlock(&sched_domains_mutex); /* Move init over to a non-isolated CPU */ if (set_cpus_allowed_ptr(current, housekeeping_cpumask(HK_TYPE_DOMAIN)) < 0) BUG(); current->flags &= ~PF_NO_SETAFFINITY; sched_init_granularity(); init_sched_rt_class(); init_sched_dl_class(); sched_smp_initialized = true; } static int __init migration_init(void) { sched_cpu_starting(smp_processor_id()); return 0; } early_initcall(migration_init); #else void __init sched_init_smp(void) { sched_init_granularity(); } #endif /* CONFIG_SMP */ int in_sched_functions(unsigned long addr) { return in_lock_functions(addr) || (addr >= (unsigned long)__sched_text_start && addr < (unsigned long)__sched_text_end); } #ifdef CONFIG_CGROUP_SCHED /* * Default task group. * Every task in system belongs to this group at bootup. */ struct task_group root_task_group; LIST_HEAD(task_groups); /* Cacheline aligned slab cache for task_group */ static struct kmem_cache *task_group_cache __ro_after_init; #endif void __init sched_init(void) { unsigned long ptr = 0; int i; /* Make sure the linker didn't screw up */ BUG_ON(&idle_sched_class != &fair_sched_class + 1 || &fair_sched_class != &rt_sched_class + 1 || &rt_sched_class != &dl_sched_class + 1); #ifdef CONFIG_SMP BUG_ON(&dl_sched_class != &stop_sched_class + 1); #endif wait_bit_init(); #ifdef CONFIG_FAIR_GROUP_SCHED ptr += 2 * nr_cpu_ids * sizeof(void **); #endif #ifdef CONFIG_RT_GROUP_SCHED ptr += 2 * nr_cpu_ids * sizeof(void **); #endif if (ptr) { ptr = (unsigned long)kzalloc(ptr, GFP_NOWAIT); #ifdef CONFIG_FAIR_GROUP_SCHED root_task_group.se = (struct sched_entity **)ptr; ptr += nr_cpu_ids * sizeof(void **); root_task_group.cfs_rq = (struct cfs_rq **)ptr; ptr += nr_cpu_ids * sizeof(void **); root_task_group.shares = ROOT_TASK_GROUP_LOAD; init_cfs_bandwidth(&root_task_group.cfs_bandwidth, NULL); #endif /* CONFIG_FAIR_GROUP_SCHED */ #ifdef CONFIG_RT_GROUP_SCHED root_task_group.rt_se = (struct sched_rt_entity **)ptr; ptr += nr_cpu_ids * sizeof(void **); root_task_group.rt_rq = (struct rt_rq **)ptr; ptr += nr_cpu_ids * sizeof(void **); #endif /* CONFIG_RT_GROUP_SCHED */ } init_rt_bandwidth(&def_rt_bandwidth, global_rt_period(), global_rt_runtime()); #ifdef CONFIG_SMP init_defrootdomain(); #endif #ifdef CONFIG_RT_GROUP_SCHED init_rt_bandwidth(&root_task_group.rt_bandwidth, global_rt_period(), global_rt_runtime()); #endif /* CONFIG_RT_GROUP_SCHED */ #ifdef CONFIG_CGROUP_SCHED task_group_cache = KMEM_CACHE(task_group, 0); list_add(&root_task_group.list, &task_groups); INIT_LIST_HEAD(&root_task_group.children); INIT_LIST_HEAD(&root_task_group.siblings); autogroup_init(&init_task); #endif /* CONFIG_CGROUP_SCHED */ for_each_possible_cpu(i) { struct rq *rq; rq = cpu_rq(i); raw_spin_lock_init(&rq->__lock); rq->nr_running = 0; rq->calc_load_active = 0; rq->calc_load_update = jiffies + LOAD_FREQ; init_cfs_rq(&rq->cfs); init_rt_rq(&rq->rt); init_dl_rq(&rq->dl); #ifdef CONFIG_FAIR_GROUP_SCHED INIT_LIST_HEAD(&rq->leaf_cfs_rq_list); rq->tmp_alone_branch = &rq->leaf_cfs_rq_list; /* * How much CPU bandwidth does root_task_group get? * * In case of task-groups formed thr' the cgroup filesystem, it * gets 100% of the CPU resources in the system. This overall * system CPU resource is divided among the tasks of * root_task_group and its child task-groups in a fair manner, * based on each entity's (task or task-group's) weight * (se->load.weight). * * In other words, if root_task_group has 10 tasks of weight * 1024) and two child groups A0 and A1 (of weight 1024 each), * then A0's share of the CPU resource is: * * A0's bandwidth = 1024 / (10*1024 + 1024 + 1024) = 8.33% * * We achieve this by letting root_task_group's tasks sit * directly in rq->cfs (i.e root_task_group->se[] = NULL). */ init_tg_cfs_entry(&root_task_group, &rq->cfs, NULL, i, NULL); #endif /* CONFIG_FAIR_GROUP_SCHED */ rq->rt.rt_runtime = def_rt_bandwidth.rt_runtime; #ifdef CONFIG_RT_GROUP_SCHED init_tg_rt_entry(&root_task_group, &rq->rt, NULL, i, NULL); #endif #ifdef CONFIG_SMP rq->sd = NULL; rq->rd = NULL; rq->cpu_capacity = SCHED_CAPACITY_SCALE; rq->balance_callback = &balance_push_callback; rq->active_balance = 0; rq->next_balance = jiffies; rq->push_cpu = 0; rq->cpu = i; rq->online = 0; rq->idle_stamp = 0; rq->avg_idle = 2*sysctl_sched_migration_cost; rq->max_idle_balance_cost = sysctl_sched_migration_cost; INIT_LIST_HEAD(&rq->cfs_tasks); rq_attach_root(rq, &def_root_domain); #ifdef CONFIG_NO_HZ_COMMON rq->last_blocked_load_update_tick = jiffies; atomic_set(&rq->nohz_flags, 0); INIT_CSD(&rq->nohz_csd, nohz_csd_func, rq); #endif #ifdef CONFIG_HOTPLUG_CPU rcuwait_init(&rq->hotplug_wait); #endif #endif /* CONFIG_SMP */ hrtick_rq_init(rq); atomic_set(&rq->nr_iowait, 0); #ifdef CONFIG_SCHED_CORE rq->core = rq; rq->core_pick = NULL; rq->core_enabled = 0; rq->core_tree = RB_ROOT; rq->core_forceidle_count = 0; rq->core_forceidle_occupation = 0; rq->core_forceidle_start = 0; rq->core_cookie = 0UL; #endif zalloc_cpumask_var_node(&rq->scratch_mask, GFP_KERNEL, cpu_to_node(i)); } set_load_weight(&init_task, false); /* * The boot idle thread does lazy MMU switching as well: */ mmgrab_lazy_tlb(&init_mm); enter_lazy_tlb(&init_mm, current); /* * The idle task doesn't need the kthread struct to function, but it * is dressed up as a per-CPU kthread and thus needs to play the part * if we want to avoid special-casing it in code that deals with per-CPU * kthreads. */ WARN_ON(!set_kthread_struct(current)); /* * Make us the idle thread. Technically, schedule() should not be * called from this thread, however somewhere below it might be, * but because we are the idle thread, we just pick up running again * when this runqueue becomes "idle". */ init_idle(current, smp_processor_id()); calc_load_update = jiffies + LOAD_FREQ; #ifdef CONFIG_SMP idle_thread_set_boot_cpu(); balance_push_set(smp_processor_id(), false); #endif init_sched_fair_class(); psi_init(); init_uclamp(); preempt_dynamic_init(); scheduler_running = 1; } #ifdef CONFIG_DEBUG_ATOMIC_SLEEP void __might_sleep(const char *file, int line) { unsigned int state = get_current_state(); /* * Blocking primitives will set (and therefore destroy) current->state, * since we will exit with TASK_RUNNING make sure we enter with it, * otherwise we will destroy state. */ WARN_ONCE(state != TASK_RUNNING && current->task_state_change, "do not call blocking ops when !TASK_RUNNING; " "state=%x set at [<%p>] %pS\n", state, (void *)current->task_state_change, (void *)current->task_state_change); __might_resched(file, line, 0); } EXPORT_SYMBOL(__might_sleep); static void print_preempt_disable_ip(int preempt_offset, unsigned long ip) { if (!IS_ENABLED(CONFIG_DEBUG_PREEMPT)) return; if (preempt_count() == preempt_offset) return; pr_err("Preemption disabled at:"); print_ip_sym(KERN_ERR, ip); } static inline bool resched_offsets_ok(unsigned int offsets) { unsigned int nested = preempt_count(); nested += rcu_preempt_depth() << MIGHT_RESCHED_RCU_SHIFT; return nested == offsets; } void __might_resched(const char *file, int line, unsigned int offsets) { /* Ratelimiting timestamp: */ static unsigned long prev_jiffy; unsigned long preempt_disable_ip; /* WARN_ON_ONCE() by default, no rate limit required: */ rcu_sleep_check(); if ((resched_offsets_ok(offsets) && !irqs_disabled() && !is_idle_task(current) && !current->non_block_count) || system_state == SYSTEM_BOOTING || system_state > SYSTEM_RUNNING || oops_in_progress) return; if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy) return; prev_jiffy = jiffies; /* Save this before calling printk(), since that will clobber it: */ preempt_disable_ip = get_preempt_disable_ip(current); pr_err("BUG: sleeping function called from invalid context at %s:%d\n", file, line); pr_err("in_atomic(): %d, irqs_disabled(): %d, non_block: %d, pid: %d, name: %s\n", in_atomic(), irqs_disabled(), current->non_block_count, current->pid, current->comm); pr_err("preempt_count: %x, expected: %x\n", preempt_count(), offsets & MIGHT_RESCHED_PREEMPT_MASK); if (IS_ENABLED(CONFIG_PREEMPT_RCU)) { pr_err("RCU nest depth: %d, expected: %u\n", rcu_preempt_depth(), offsets >> MIGHT_RESCHED_RCU_SHIFT); } if (task_stack_end_corrupted(current)) pr_emerg("Thread overran stack, or stack corrupted\n"); debug_show_held_locks(current); if (irqs_disabled()) print_irqtrace_events(current); print_preempt_disable_ip(offsets & MIGHT_RESCHED_PREEMPT_MASK, preempt_disable_ip); dump_stack(); add_taint(TAINT_WARN, LOCKDEP_STILL_OK); } EXPORT_SYMBOL(__might_resched); void __cant_sleep(const char *file, int line, int preempt_offset) { static unsigned long prev_jiffy; if (irqs_disabled()) return; if (!IS_ENABLED(CONFIG_PREEMPT_COUNT)) return; if (preempt_count() > preempt_offset) return; if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy) return; prev_jiffy = jiffies; printk(KERN_ERR "BUG: assuming atomic context at %s:%d\n", file, line); printk(KERN_ERR "in_atomic(): %d, irqs_disabled(): %d, pid: %d, name: %s\n", in_atomic(), irqs_disabled(), current->pid, current->comm); debug_show_held_locks(current); dump_stack(); add_taint(TAINT_WARN, LOCKDEP_STILL_OK); } EXPORT_SYMBOL_GPL(__cant_sleep); #ifdef CONFIG_SMP void __cant_migrate(const char *file, int line) { static unsigned long prev_jiffy; if (irqs_disabled()) return; if (is_migration_disabled(current)) return; if (!IS_ENABLED(CONFIG_PREEMPT_COUNT)) return; if (preempt_count() > 0) return; if (time_before(jiffies, prev_jiffy + HZ) && prev_jiffy) return; prev_jiffy = jiffies; pr_err("BUG: assuming non migratable context at %s:%d\n", file, line); pr_err("in_atomic(): %d, irqs_disabled(): %d, migration_disabled() %u pid: %d, name: %s\n", in_atomic(), irqs_disabled(), is_migration_disabled(current), current->pid, current->comm); debug_show_held_locks(current); dump_stack(); add_taint(TAINT_WARN, LOCKDEP_STILL_OK); } EXPORT_SYMBOL_GPL(__cant_migrate); #endif #endif #ifdef CONFIG_MAGIC_SYSRQ void normalize_rt_tasks(void) { struct task_struct *g, *p; struct sched_attr attr = { .sched_policy = SCHED_NORMAL, }; read_lock(&tasklist_lock); for_each_process_thread(g, p) { /* * Only normalize user tasks: */ if (p->flags & PF_KTHREAD) continue; p->se.exec_start = 0; schedstat_set(p->stats.wait_start, 0); schedstat_set(p->stats.sleep_start, 0); schedstat_set(p->stats.block_start, 0); if (!dl_task(p) && !rt_task(p)) { /* * Renice negative nice level userspace * tasks back to 0: */ if (task_nice(p) < 0) set_user_nice(p, 0); continue; } __sched_setscheduler(p, &attr, false, false); } read_unlock(&tasklist_lock); } #endif /* CONFIG_MAGIC_SYSRQ */ #if defined(CONFIG_KGDB_KDB) /* * These functions are only useful for kdb. * * They can only be called when the whole system has been * stopped - every CPU needs to be quiescent, and no scheduling * activity can take place. Using them for anything else would * be a serious bug, and as a result, they aren't even visible * under any other configuration. */ /** * curr_task - return the current task for a given CPU. * @cpu: the processor in question. * * ONLY VALID WHEN THE WHOLE SYSTEM IS STOPPED! * * Return: The current task for @cpu. */ struct task_struct *curr_task(int cpu) { return cpu_curr(cpu); } #endif /* defined(CONFIG_KGDB_KDB) */ #ifdef CONFIG_CGROUP_SCHED /* task_group_lock serializes the addition/removal of task groups */ static DEFINE_SPINLOCK(task_group_lock); static inline void alloc_uclamp_sched_group(struct task_group *tg, struct task_group *parent) { #ifdef CONFIG_UCLAMP_TASK_GROUP enum uclamp_id clamp_id; for_each_clamp_id(clamp_id) { uclamp_se_set(&tg->uclamp_req[clamp_id], uclamp_none(clamp_id), false); tg->uclamp[clamp_id] = parent->uclamp[clamp_id]; } #endif } static void sched_free_group(struct task_group *tg) { free_fair_sched_group(tg); free_rt_sched_group(tg); autogroup_free(tg); kmem_cache_free(task_group_cache, tg); } static void sched_free_group_rcu(struct rcu_head *rcu) { sched_free_group(container_of(rcu, struct task_group, rcu)); } static void sched_unregister_group(struct task_group *tg) { unregister_fair_sched_group(tg); unregister_rt_sched_group(tg); /* * We have to wait for yet another RCU grace period to expire, as * print_cfs_stats() might run concurrently. */ call_rcu(&tg->rcu, sched_free_group_rcu); } /* allocate runqueue etc for a new task group */ struct task_group *sched_create_group(struct task_group *parent) { struct task_group *tg; tg = kmem_cache_alloc(task_group_cache, GFP_KERNEL | __GFP_ZERO); if (!tg) return ERR_PTR(-ENOMEM); if (!alloc_fair_sched_group(tg, parent)) goto err; if (!alloc_rt_sched_group(tg, parent)) goto err; alloc_uclamp_sched_group(tg, parent); return tg; err: sched_free_group(tg); return ERR_PTR(-ENOMEM); } void sched_online_group(struct task_group *tg, struct task_group *parent) { unsigned long flags; spin_lock_irqsave(&task_group_lock, flags); list_add_rcu(&tg->list, &task_groups); /* Root should already exist: */ WARN_ON(!parent); tg->parent = parent; INIT_LIST_HEAD(&tg->children); list_add_rcu(&tg->siblings, &parent->children); spin_unlock_irqrestore(&task_group_lock, flags); online_fair_sched_group(tg); } /* rcu callback to free various structures associated with a task group */ static void sched_unregister_group_rcu(struct rcu_head *rhp) { /* Now it should be safe to free those cfs_rqs: */ sched_unregister_group(container_of(rhp, struct task_group, rcu)); } void sched_destroy_group(struct task_group *tg) { /* Wait for possible concurrent references to cfs_rqs complete: */ call_rcu(&tg->rcu, sched_unregister_group_rcu); } void sched_release_group(struct task_group *tg) { unsigned long flags; /* * Unlink first, to avoid walk_tg_tree_from() from finding us (via * sched_cfs_period_timer()). * * For this to be effective, we have to wait for all pending users of * this task group to leave their RCU critical section to ensure no new * user will see our dying task group any more. Specifically ensure * that tg_unthrottle_up() won't add decayed cfs_rq's to it. * * We therefore defer calling unregister_fair_sched_group() to * sched_unregister_group() which is guarantied to get called only after the * current RCU grace period has expired. */ spin_lock_irqsave(&task_group_lock, flags); list_del_rcu(&tg->list); list_del_rcu(&tg->siblings); spin_unlock_irqrestore(&task_group_lock, flags); } static struct task_group *sched_get_task_group(struct task_struct *tsk) { struct task_group *tg; /* * All callers are synchronized by task_rq_lock(); we do not use RCU * which is pointless here. Thus, we pass "true" to task_css_check() * to prevent lockdep warnings. */ tg = container_of(task_css_check(tsk, cpu_cgrp_id, true), struct task_group, css); tg = autogroup_task_group(tsk, tg); return tg; } static void sched_change_group(struct task_struct *tsk, struct task_group *group) { tsk->sched_task_group = group; #ifdef CONFIG_FAIR_GROUP_SCHED if (tsk->sched_class->task_change_group) tsk->sched_class->task_change_group(tsk); else #endif set_task_rq(tsk, task_cpu(tsk)); } /* * Change task's runqueue when it moves between groups. * * The caller of this function should have put the task in its new group by * now. This function just updates tsk->se.cfs_rq and tsk->se.parent to reflect * its new group. */ void sched_move_task(struct task_struct *tsk) { int queued, running, queue_flags = DEQUEUE_SAVE | DEQUEUE_MOVE | DEQUEUE_NOCLOCK; struct task_group *group; struct rq *rq; CLASS(task_rq_lock, rq_guard)(tsk); rq = rq_guard.rq; /* * Esp. with SCHED_AUTOGROUP enabled it is possible to get superfluous * group changes. */ group = sched_get_task_group(tsk); if (group == tsk->sched_task_group) return; update_rq_clock(rq); running = task_current(rq, tsk); queued = task_on_rq_queued(tsk); if (queued) dequeue_task(rq, tsk, queue_flags); if (running) put_prev_task(rq, tsk); sched_change_group(tsk, group); if (queued) enqueue_task(rq, tsk, queue_flags); if (running) { set_next_task(rq, tsk); /* * After changing group, the running task may have joined a * throttled one but it's still the running task. Trigger a * resched to make sure that task can still run. */ resched_curr(rq); } } static inline struct task_group *css_tg(struct cgroup_subsys_state *css) { return css ? container_of(css, struct task_group, css) : NULL; } static struct cgroup_subsys_state * cpu_cgroup_css_alloc(struct cgroup_subsys_state *parent_css) { struct task_group *parent = css_tg(parent_css); struct task_group *tg; if (!parent) { /* This is early initialization for the top cgroup */ return &root_task_group.css; } tg = sched_create_group(parent); if (IS_ERR(tg)) return ERR_PTR(-ENOMEM); return &tg->css; } /* Expose task group only after completing cgroup initialization */ static int cpu_cgroup_css_online(struct cgroup_subsys_state *css) { struct task_group *tg = css_tg(css); struct task_group *parent = css_tg(css->parent); if (parent) sched_online_group(tg, parent); #ifdef CONFIG_UCLAMP_TASK_GROUP /* Propagate the effective uclamp value for the new group */ guard(mutex)(&uclamp_mutex); guard(rcu)(); cpu_util_update_eff(css); #endif return 0; } static void cpu_cgroup_css_released(struct cgroup_subsys_state *css) { struct task_group *tg = css_tg(css); sched_release_group(tg); } static void cpu_cgroup_css_free(struct cgroup_subsys_state *css) { struct task_group *tg = css_tg(css); /* * Relies on the RCU grace period between css_released() and this. */ sched_unregister_group(tg); } #ifdef CONFIG_RT_GROUP_SCHED static int cpu_cgroup_can_attach(struct cgroup_taskset *tset) { struct task_struct *task; struct cgroup_subsys_state *css; cgroup_taskset_for_each(task, css, tset) { if (!sched_rt_can_attach(css_tg(css), task)) return -EINVAL; } return 0; } #endif static void cpu_cgroup_attach(struct cgroup_taskset *tset) { struct task_struct *task; struct cgroup_subsys_state *css; cgroup_taskset_for_each(task, css, tset) sched_move_task(task); } #ifdef CONFIG_UCLAMP_TASK_GROUP static void cpu_util_update_eff(struct cgroup_subsys_state *css) { struct cgroup_subsys_state *top_css = css; struct uclamp_se *uc_parent = NULL; struct uclamp_se *uc_se = NULL; unsigned int eff[UCLAMP_CNT]; enum uclamp_id clamp_id; unsigned int clamps; lockdep_assert_held(&uclamp_mutex); SCHED_WARN_ON(!rcu_read_lock_held()); css_for_each_descendant_pre(css, top_css) { uc_parent = css_tg(css)->parent ? css_tg(css)->parent->uclamp : NULL; for_each_clamp_id(clamp_id) { /* Assume effective clamps matches requested clamps */ eff[clamp_id] = css_tg(css)->uclamp_req[clamp_id].value; /* Cap effective clamps with parent's effective clamps */ if (uc_parent && eff[clamp_id] > uc_parent[clamp_id].value) { eff[clamp_id] = uc_parent[clamp_id].value; } } /* Ensure protection is always capped by limit */ eff[UCLAMP_MIN] = min(eff[UCLAMP_MIN], eff[UCLAMP_MAX]); /* Propagate most restrictive effective clamps */ clamps = 0x0; uc_se = css_tg(css)->uclamp; for_each_clamp_id(clamp_id) { if (eff[clamp_id] == uc_se[clamp_id].value) continue; uc_se[clamp_id].value = eff[clamp_id]; uc_se[clamp_id].bucket_id = uclamp_bucket_id(eff[clamp_id]); clamps |= (0x1 << clamp_id); } if (!clamps) { css = css_rightmost_descendant(css); continue; } /* Immediately update descendants RUNNABLE tasks */ uclamp_update_active_tasks(css); } } /* * Integer 10^N with a given N exponent by casting to integer the literal "1eN" * C expression. Since there is no way to convert a macro argument (N) into a * character constant, use two levels of macros. */ #define _POW10(exp) ((unsigned int)1e##exp) #define POW10(exp) _POW10(exp) struct uclamp_request { #define UCLAMP_PERCENT_SHIFT 2 #define UCLAMP_PERCENT_SCALE (100 * POW10(UCLAMP_PERCENT_SHIFT)) s64 percent; u64 util; int ret; }; static inline struct uclamp_request capacity_from_percent(char *buf) { struct uclamp_request req = { .percent = UCLAMP_PERCENT_SCALE, .util = SCHED_CAPACITY_SCALE, .ret = 0, }; buf = strim(buf); if (strcmp(buf, "max")) { req.ret = cgroup_parse_float(buf, UCLAMP_PERCENT_SHIFT, &req.percent); if (req.ret) return req; if ((u64)req.percent > UCLAMP_PERCENT_SCALE) { req.ret = -ERANGE; return req; } req.util = req.percent << SCHED_CAPACITY_SHIFT; req.util = DIV_ROUND_CLOSEST_ULL(req.util, UCLAMP_PERCENT_SCALE); } return req; } static ssize_t cpu_uclamp_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off, enum uclamp_id clamp_id) { struct uclamp_request req; struct task_group *tg; req = capacity_from_percent(buf); if (req.ret) return req.ret; static_branch_enable(&sched_uclamp_used); guard(mutex)(&uclamp_mutex); guard(rcu)(); tg = css_tg(of_css(of)); if (tg->uclamp_req[clamp_id].value != req.util) uclamp_se_set(&tg->uclamp_req[clamp_id], req.util, false); /* * Because of not recoverable conversion rounding we keep track of the * exact requested value */ tg->uclamp_pct[clamp_id] = req.percent; /* Update effective clamps to track the most restrictive value */ cpu_util_update_eff(of_css(of)); return nbytes; } static ssize_t cpu_uclamp_min_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MIN); } static ssize_t cpu_uclamp_max_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { return cpu_uclamp_write(of, buf, nbytes, off, UCLAMP_MAX); } static inline void cpu_uclamp_print(struct seq_file *sf, enum uclamp_id clamp_id) { struct task_group *tg; u64 util_clamp; u64 percent; u32 rem; scoped_guard (rcu) { tg = css_tg(seq_css(sf)); util_clamp = tg->uclamp_req[clamp_id].value; } if (util_clamp == SCHED_CAPACITY_SCALE) { seq_puts(sf, "max\n"); return; } percent = tg->uclamp_pct[clamp_id]; percent = div_u64_rem(percent, POW10(UCLAMP_PERCENT_SHIFT), &rem); seq_printf(sf, "%llu.%0*u\n", percent, UCLAMP_PERCENT_SHIFT, rem); } static int cpu_uclamp_min_show(struct seq_file *sf, void *v) { cpu_uclamp_print(sf, UCLAMP_MIN); return 0; } static int cpu_uclamp_max_show(struct seq_file *sf, void *v) { cpu_uclamp_print(sf, UCLAMP_MAX); return 0; } #endif /* CONFIG_UCLAMP_TASK_GROUP */ #ifdef CONFIG_FAIR_GROUP_SCHED static int cpu_shares_write_u64(struct cgroup_subsys_state *css, struct cftype *cftype, u64 shareval) { if (shareval > scale_load_down(ULONG_MAX)) shareval = MAX_SHARES; return sched_group_set_shares(css_tg(css), scale_load(shareval)); } static u64 cpu_shares_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { struct task_group *tg = css_tg(css); return (u64) scale_load_down(tg->shares); } #ifdef CONFIG_CFS_BANDWIDTH static DEFINE_MUTEX(cfs_constraints_mutex); const u64 max_cfs_quota_period = 1 * NSEC_PER_SEC; /* 1s */ static const u64 min_cfs_quota_period = 1 * NSEC_PER_MSEC; /* 1ms */ /* More than 203 days if BW_SHIFT equals 20. */ static const u64 max_cfs_runtime = MAX_BW * NSEC_PER_USEC; static int __cfs_schedulable(struct task_group *tg, u64 period, u64 runtime); static int tg_set_cfs_bandwidth(struct task_group *tg, u64 period, u64 quota, u64 burst) { int i, ret = 0, runtime_enabled, runtime_was_enabled; struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; if (tg == &root_task_group) return -EINVAL; /* * Ensure we have at some amount of bandwidth every period. This is * to prevent reaching a state of large arrears when throttled via * entity_tick() resulting in prolonged exit starvation. */ if (quota < min_cfs_quota_period || period < min_cfs_quota_period) return -EINVAL; /* * Likewise, bound things on the other side by preventing insane quota * periods. This also allows us to normalize in computing quota * feasibility. */ if (period > max_cfs_quota_period) return -EINVAL; /* * Bound quota to defend quota against overflow during bandwidth shift. */ if (quota != RUNTIME_INF && quota > max_cfs_runtime) return -EINVAL; if (quota != RUNTIME_INF && (burst > quota || burst + quota > max_cfs_runtime)) return -EINVAL; /* * Prevent race between setting of cfs_rq->runtime_enabled and * unthrottle_offline_cfs_rqs(). */ guard(cpus_read_lock)(); guard(mutex)(&cfs_constraints_mutex); ret = __cfs_schedulable(tg, period, quota); if (ret) return ret; runtime_enabled = quota != RUNTIME_INF; runtime_was_enabled = cfs_b->quota != RUNTIME_INF; /* * If we need to toggle cfs_bandwidth_used, off->on must occur * before making related changes, and on->off must occur afterwards */ if (runtime_enabled && !runtime_was_enabled) cfs_bandwidth_usage_inc(); scoped_guard (raw_spinlock_irq, &cfs_b->lock) { cfs_b->period = ns_to_ktime(period); cfs_b->quota = quota; cfs_b->burst = burst; __refill_cfs_bandwidth_runtime(cfs_b); /* * Restart the period timer (if active) to handle new * period expiry: */ if (runtime_enabled) start_cfs_bandwidth(cfs_b); } for_each_online_cpu(i) { struct cfs_rq *cfs_rq = tg->cfs_rq[i]; struct rq *rq = cfs_rq->rq; guard(rq_lock_irq)(rq); cfs_rq->runtime_enabled = runtime_enabled; cfs_rq->runtime_remaining = 0; if (cfs_rq->throttled) unthrottle_cfs_rq(cfs_rq); } if (runtime_was_enabled && !runtime_enabled) cfs_bandwidth_usage_dec(); return 0; } static int tg_set_cfs_quota(struct task_group *tg, long cfs_quota_us) { u64 quota, period, burst; period = ktime_to_ns(tg->cfs_bandwidth.period); burst = tg->cfs_bandwidth.burst; if (cfs_quota_us < 0) quota = RUNTIME_INF; else if ((u64)cfs_quota_us <= U64_MAX / NSEC_PER_USEC) quota = (u64)cfs_quota_us * NSEC_PER_USEC; else return -EINVAL; return tg_set_cfs_bandwidth(tg, period, quota, burst); } static long tg_get_cfs_quota(struct task_group *tg) { u64 quota_us; if (tg->cfs_bandwidth.quota == RUNTIME_INF) return -1; quota_us = tg->cfs_bandwidth.quota; do_div(quota_us, NSEC_PER_USEC); return quota_us; } static int tg_set_cfs_period(struct task_group *tg, long cfs_period_us) { u64 quota, period, burst; if ((u64)cfs_period_us > U64_MAX / NSEC_PER_USEC) return -EINVAL; period = (u64)cfs_period_us * NSEC_PER_USEC; quota = tg->cfs_bandwidth.quota; burst = tg->cfs_bandwidth.burst; return tg_set_cfs_bandwidth(tg, period, quota, burst); } static long tg_get_cfs_period(struct task_group *tg) { u64 cfs_period_us; cfs_period_us = ktime_to_ns(tg->cfs_bandwidth.period); do_div(cfs_period_us, NSEC_PER_USEC); return cfs_period_us; } static int tg_set_cfs_burst(struct task_group *tg, long cfs_burst_us) { u64 quota, period, burst; if ((u64)cfs_burst_us > U64_MAX / NSEC_PER_USEC) return -EINVAL; burst = (u64)cfs_burst_us * NSEC_PER_USEC; period = ktime_to_ns(tg->cfs_bandwidth.period); quota = tg->cfs_bandwidth.quota; return tg_set_cfs_bandwidth(tg, period, quota, burst); } static long tg_get_cfs_burst(struct task_group *tg) { u64 burst_us; burst_us = tg->cfs_bandwidth.burst; do_div(burst_us, NSEC_PER_USEC); return burst_us; } static s64 cpu_cfs_quota_read_s64(struct cgroup_subsys_state *css, struct cftype *cft) { return tg_get_cfs_quota(css_tg(css)); } static int cpu_cfs_quota_write_s64(struct cgroup_subsys_state *css, struct cftype *cftype, s64 cfs_quota_us) { return tg_set_cfs_quota(css_tg(css), cfs_quota_us); } static u64 cpu_cfs_period_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { return tg_get_cfs_period(css_tg(css)); } static int cpu_cfs_period_write_u64(struct cgroup_subsys_state *css, struct cftype *cftype, u64 cfs_period_us) { return tg_set_cfs_period(css_tg(css), cfs_period_us); } static u64 cpu_cfs_burst_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { return tg_get_cfs_burst(css_tg(css)); } static int cpu_cfs_burst_write_u64(struct cgroup_subsys_state *css, struct cftype *cftype, u64 cfs_burst_us) { return tg_set_cfs_burst(css_tg(css), cfs_burst_us); } struct cfs_schedulable_data { struct task_group *tg; u64 period, quota; }; /* * normalize group quota/period to be quota/max_period * note: units are usecs */ static u64 normalize_cfs_quota(struct task_group *tg, struct cfs_schedulable_data *d) { u64 quota, period; if (tg == d->tg) { period = d->period; quota = d->quota; } else { period = tg_get_cfs_period(tg); quota = tg_get_cfs_quota(tg); } /* note: these should typically be equivalent */ if (quota == RUNTIME_INF || quota == -1) return RUNTIME_INF; return to_ratio(period, quota); } static int tg_cfs_schedulable_down(struct task_group *tg, void *data) { struct cfs_schedulable_data *d = data; struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; s64 quota = 0, parent_quota = -1; if (!tg->parent) { quota = RUNTIME_INF; } else { struct cfs_bandwidth *parent_b = &tg->parent->cfs_bandwidth; quota = normalize_cfs_quota(tg, d); parent_quota = parent_b->hierarchical_quota; /* * Ensure max(child_quota) <= parent_quota. On cgroup2, * always take the non-RUNTIME_INF min. On cgroup1, only * inherit when no limit is set. In both cases this is used * by the scheduler to determine if a given CFS task has a * bandwidth constraint at some higher level. */ if (cgroup_subsys_on_dfl(cpu_cgrp_subsys)) { if (quota == RUNTIME_INF) quota = parent_quota; else if (parent_quota != RUNTIME_INF) quota = min(quota, parent_quota); } else { if (quota == RUNTIME_INF) quota = parent_quota; else if (parent_quota != RUNTIME_INF && quota > parent_quota) return -EINVAL; } } cfs_b->hierarchical_quota = quota; return 0; } static int __cfs_schedulable(struct task_group *tg, u64 period, u64 quota) { struct cfs_schedulable_data data = { .tg = tg, .period = period, .quota = quota, }; if (quota != RUNTIME_INF) { do_div(data.period, NSEC_PER_USEC); do_div(data.quota, NSEC_PER_USEC); } guard(rcu)(); return walk_tg_tree(tg_cfs_schedulable_down, tg_nop, &data); } static int cpu_cfs_stat_show(struct seq_file *sf, void *v) { struct task_group *tg = css_tg(seq_css(sf)); struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; seq_printf(sf, "nr_periods %d\n", cfs_b->nr_periods); seq_printf(sf, "nr_throttled %d\n", cfs_b->nr_throttled); seq_printf(sf, "throttled_time %llu\n", cfs_b->throttled_time); if (schedstat_enabled() && tg != &root_task_group) { struct sched_statistics *stats; u64 ws = 0; int i; for_each_possible_cpu(i) { stats = __schedstats_from_se(tg->se[i]); ws += schedstat_val(stats->wait_sum); } seq_printf(sf, "wait_sum %llu\n", ws); } seq_printf(sf, "nr_bursts %d\n", cfs_b->nr_burst); seq_printf(sf, "burst_time %llu\n", cfs_b->burst_time); return 0; } static u64 throttled_time_self(struct task_group *tg) { int i; u64 total = 0; for_each_possible_cpu(i) { total += READ_ONCE(tg->cfs_rq[i]->throttled_clock_self_time); } return total; } static int cpu_cfs_local_stat_show(struct seq_file *sf, void *v) { struct task_group *tg = css_tg(seq_css(sf)); seq_printf(sf, "throttled_time %llu\n", throttled_time_self(tg)); return 0; } #endif /* CONFIG_CFS_BANDWIDTH */ #endif /* CONFIG_FAIR_GROUP_SCHED */ #ifdef CONFIG_RT_GROUP_SCHED static int cpu_rt_runtime_write(struct cgroup_subsys_state *css, struct cftype *cft, s64 val) { return sched_group_set_rt_runtime(css_tg(css), val); } static s64 cpu_rt_runtime_read(struct cgroup_subsys_state *css, struct cftype *cft) { return sched_group_rt_runtime(css_tg(css)); } static int cpu_rt_period_write_uint(struct cgroup_subsys_state *css, struct cftype *cftype, u64 rt_period_us) { return sched_group_set_rt_period(css_tg(css), rt_period_us); } static u64 cpu_rt_period_read_uint(struct cgroup_subsys_state *css, struct cftype *cft) { return sched_group_rt_period(css_tg(css)); } #endif /* CONFIG_RT_GROUP_SCHED */ #ifdef CONFIG_FAIR_GROUP_SCHED static s64 cpu_idle_read_s64(struct cgroup_subsys_state *css, struct cftype *cft) { return css_tg(css)->idle; } static int cpu_idle_write_s64(struct cgroup_subsys_state *css, struct cftype *cft, s64 idle) { return sched_group_set_idle(css_tg(css), idle); } #endif static struct cftype cpu_legacy_files[] = { #ifdef CONFIG_FAIR_GROUP_SCHED { .name = "shares", .read_u64 = cpu_shares_read_u64, .write_u64 = cpu_shares_write_u64, }, { .name = "idle", .read_s64 = cpu_idle_read_s64, .write_s64 = cpu_idle_write_s64, }, #endif #ifdef CONFIG_CFS_BANDWIDTH { .name = "cfs_quota_us", .read_s64 = cpu_cfs_quota_read_s64, .write_s64 = cpu_cfs_quota_write_s64, }, { .name = "cfs_period_us", .read_u64 = cpu_cfs_period_read_u64, .write_u64 = cpu_cfs_period_write_u64, }, { .name = "cfs_burst_us", .read_u64 = cpu_cfs_burst_read_u64, .write_u64 = cpu_cfs_burst_write_u64, }, { .name = "stat", .seq_show = cpu_cfs_stat_show, }, { .name = "stat.local", .seq_show = cpu_cfs_local_stat_show, }, #endif #ifdef CONFIG_RT_GROUP_SCHED { .name = "rt_runtime_us", .read_s64 = cpu_rt_runtime_read, .write_s64 = cpu_rt_runtime_write, }, { .name = "rt_period_us", .read_u64 = cpu_rt_period_read_uint, .write_u64 = cpu_rt_period_write_uint, }, #endif #ifdef CONFIG_UCLAMP_TASK_GROUP { .name = "uclamp.min", .flags = CFTYPE_NOT_ON_ROOT, .seq_show = cpu_uclamp_min_show, .write = cpu_uclamp_min_write, }, { .name = "uclamp.max", .flags = CFTYPE_NOT_ON_ROOT, .seq_show = cpu_uclamp_max_show, .write = cpu_uclamp_max_write, }, #endif { } /* Terminate */ }; static int cpu_extra_stat_show(struct seq_file *sf, struct cgroup_subsys_state *css) { #ifdef CONFIG_CFS_BANDWIDTH { struct task_group *tg = css_tg(css); struct cfs_bandwidth *cfs_b = &tg->cfs_bandwidth; u64 throttled_usec, burst_usec; throttled_usec = cfs_b->throttled_time; do_div(throttled_usec, NSEC_PER_USEC); burst_usec = cfs_b->burst_time; do_div(burst_usec, NSEC_PER_USEC); seq_printf(sf, "nr_periods %d\n" "nr_throttled %d\n" "throttled_usec %llu\n" "nr_bursts %d\n" "burst_usec %llu\n", cfs_b->nr_periods, cfs_b->nr_throttled, throttled_usec, cfs_b->nr_burst, burst_usec); } #endif return 0; } static int cpu_local_stat_show(struct seq_file *sf, struct cgroup_subsys_state *css) { #ifdef CONFIG_CFS_BANDWIDTH { struct task_group *tg = css_tg(css); u64 throttled_self_usec; throttled_self_usec = throttled_time_self(tg); do_div(throttled_self_usec, NSEC_PER_USEC); seq_printf(sf, "throttled_usec %llu\n", throttled_self_usec); } #endif return 0; } #ifdef CONFIG_FAIR_GROUP_SCHED static u64 cpu_weight_read_u64(struct cgroup_subsys_state *css, struct cftype *cft) { struct task_group *tg = css_tg(css); u64 weight = scale_load_down(tg->shares); return DIV_ROUND_CLOSEST_ULL(weight * CGROUP_WEIGHT_DFL, 1024); } static int cpu_weight_write_u64(struct cgroup_subsys_state *css, struct cftype *cft, u64 weight) { /* * cgroup weight knobs should use the common MIN, DFL and MAX * values which are 1, 100 and 10000 respectively. While it loses * a bit of range on both ends, it maps pretty well onto the shares * value used by scheduler and the round-trip conversions preserve * the original value over the entire range. */ if (weight < CGROUP_WEIGHT_MIN || weight > CGROUP_WEIGHT_MAX) return -ERANGE; weight = DIV_ROUND_CLOSEST_ULL(weight * 1024, CGROUP_WEIGHT_DFL); return sched_group_set_shares(css_tg(css), scale_load(weight)); } static s64 cpu_weight_nice_read_s64(struct cgroup_subsys_state *css, struct cftype *cft) { unsigned long weight = scale_load_down(css_tg(css)->shares); int last_delta = INT_MAX; int prio, delta; /* find the closest nice value to the current weight */ for (prio = 0; prio < ARRAY_SIZE(sched_prio_to_weight); prio++) { delta = abs(sched_prio_to_weight[prio] - weight); if (delta >= last_delta) break; last_delta = delta; } return PRIO_TO_NICE(prio - 1 + MAX_RT_PRIO); } static int cpu_weight_nice_write_s64(struct cgroup_subsys_state *css, struct cftype *cft, s64 nice) { unsigned long weight; int idx; if (nice < MIN_NICE || nice > MAX_NICE) return -ERANGE; idx = NICE_TO_PRIO(nice) - MAX_RT_PRIO; idx = array_index_nospec(idx, 40); weight = sched_prio_to_weight[idx]; return sched_group_set_shares(css_tg(css), scale_load(weight)); } #endif static void __maybe_unused cpu_period_quota_print(struct seq_file *sf, long period, long quota) { if (quota < 0) seq_puts(sf, "max"); else seq_printf(sf, "%ld", quota); seq_printf(sf, " %ld\n", period); } /* caller should put the current value in *@periodp before calling */ static int __maybe_unused cpu_period_quota_parse(char *buf, u64 *periodp, u64 *quotap) { char tok[21]; /* U64_MAX */ if (sscanf(buf, "%20s %llu", tok, periodp) < 1) return -EINVAL; *periodp *= NSEC_PER_USEC; if (sscanf(tok, "%llu", quotap)) *quotap *= NSEC_PER_USEC; else if (!strcmp(tok, "max")) *quotap = RUNTIME_INF; else return -EINVAL; return 0; } #ifdef CONFIG_CFS_BANDWIDTH static int cpu_max_show(struct seq_file *sf, void *v) { struct task_group *tg = css_tg(seq_css(sf)); cpu_period_quota_print(sf, tg_get_cfs_period(tg), tg_get_cfs_quota(tg)); return 0; } static ssize_t cpu_max_write(struct kernfs_open_file *of, char *buf, size_t nbytes, loff_t off) { struct task_group *tg = css_tg(of_css(of)); u64 period = tg_get_cfs_period(tg); u64 burst = tg_get_cfs_burst(tg); u64 quota; int ret; ret = cpu_period_quota_parse(buf, &period, "a); if (!ret) ret = tg_set_cfs_bandwidth(tg, period, quota, burst); return ret ?: nbytes; } #endif static struct cftype cpu_files[] = { #ifdef CONFIG_FAIR_GROUP_SCHED { .name = "weight", .flags = CFTYPE_NOT_ON_ROOT, .read_u64 = cpu_weight_read_u64, .write_u64 = cpu_weight_write_u64, }, { .name = "weight.nice", .flags = CFTYPE_NOT_ON_ROOT, .read_s64 = cpu_weight_nice_read_s64, .write_s64 = cpu_weight_nice_write_s64, }, { .name = "idle", .flags = CFTYPE_NOT_ON_ROOT, .read_s64 = cpu_idle_read_s64, .write_s64 = cpu_idle_write_s64, }, #endif #ifdef CONFIG_CFS_BANDWIDTH { .name = "max", .flags = CFTYPE_NOT_ON_ROOT, .seq_show = cpu_max_show, .write = cpu_max_write, }, { .name = "max.burst", .flags = CFTYPE_NOT_ON_ROOT, .read_u64 = cpu_cfs_burst_read_u64, .write_u64 = cpu_cfs_burst_write_u64, }, #endif #ifdef CONFIG_UCLAMP_TASK_GROUP { .name = "uclamp.min", .flags = CFTYPE_NOT_ON_ROOT, .seq_show = cpu_uclamp_min_show, .write = cpu_uclamp_min_write, }, { .name = "uclamp.max", .flags = CFTYPE_NOT_ON_ROOT, .seq_show = cpu_uclamp_max_show, .write = cpu_uclamp_max_write, }, #endif { } /* terminate */ }; struct cgroup_subsys cpu_cgrp_subsys = { .css_alloc = cpu_cgroup_css_alloc, .css_online = cpu_cgroup_css_online, .css_released = cpu_cgroup_css_released, .css_free = cpu_cgroup_css_free, .css_extra_stat_show = cpu_extra_stat_show, .css_local_stat_show = cpu_local_stat_show, #ifdef CONFIG_RT_GROUP_SCHED .can_attach = cpu_cgroup_can_attach, #endif .attach = cpu_cgroup_attach, .legacy_cftypes = cpu_legacy_files, .dfl_cftypes = cpu_files, .early_init = true, .threaded = true, }; #endif /* CONFIG_CGROUP_SCHED */ void dump_cpu_task(int cpu) { if (cpu == smp_processor_id() && in_hardirq()) { struct pt_regs *regs; regs = get_irq_regs(); if (regs) { show_regs(regs); return; } } if (trigger_single_cpu_backtrace(cpu)) return; pr_info("Task dump for CPU %d:\n", cpu); sched_show_task(cpu_curr(cpu)); } /* * Nice levels are multiplicative, with a gentle 10% change for every * nice level changed. I.e. when a CPU-bound task goes from nice 0 to * nice 1, it will get ~10% less CPU time than another CPU-bound task * that remained on nice 0. * * The "10% effect" is relative and cumulative: from _any_ nice level, * if you go up 1 level, it's -10% CPU usage, if you go down 1 level * it's +10% CPU usage. (to achieve that we use a multiplier of 1.25. * If a task goes up by ~10% and another task goes down by ~10% then * the relative distance between them is ~25%.) */ const int sched_prio_to_weight[40] = { /* -20 */ 88761, 71755, 56483, 46273, 36291, /* -15 */ 29154, 23254, 18705, 14949, 11916, /* -10 */ 9548, 7620, 6100, 4904, 3906, /* -5 */ 3121, 2501, 1991, 1586, 1277, /* 0 */ 1024, 820, 655, 526, 423, /* 5 */ 335, 272, 215, 172, 137, /* 10 */ 110, 87, 70, 56, 45, /* 15 */ 36, 29, 23, 18, 15, }; /* * Inverse (2^32/x) values of the sched_prio_to_weight[] array, precalculated. * * In cases where the weight does not change often, we can use the * precalculated inverse to speed up arithmetics by turning divisions * into multiplications: */ const u32 sched_prio_to_wmult[40] = { /* -20 */ 48388, 59856, 76040, 92818, 118348, /* -15 */ 147320, 184698, 229616, 287308, 360437, /* -10 */ 449829, 563644, 704093, 875809, 1099582, /* -5 */ 1376151, 1717300, 2157191, 2708050, 3363326, /* 0 */ 4194304, 5237765, 6557202, 8165337, 10153587, /* 5 */ 12820798, 15790321, 19976592, 24970740, 31350126, /* 10 */ 39045157, 49367440, 61356676, 76695844, 95443717, /* 15 */ 119304647, 148102320, 186737708, 238609294, 286331153, }; void call_trace_sched_update_nr_running(struct rq *rq, int count) { trace_sched_update_nr_running_tp(rq, count); } #ifdef CONFIG_SCHED_MM_CID /* * @cid_lock: Guarantee forward-progress of cid allocation. * * Concurrency ID allocation within a bitmap is mostly lock-free. The cid_lock * is only used when contention is detected by the lock-free allocation so * forward progress can be guaranteed. */ DEFINE_RAW_SPINLOCK(cid_lock); /* * @use_cid_lock: Select cid allocation behavior: lock-free vs spinlock. * * When @use_cid_lock is 0, the cid allocation is lock-free. When contention is * detected, it is set to 1 to ensure that all newly coming allocations are * serialized by @cid_lock until the allocation which detected contention * completes and sets @use_cid_lock back to 0. This guarantees forward progress * of a cid allocation. */ int use_cid_lock; /* * mm_cid remote-clear implements a lock-free algorithm to clear per-mm/cpu cid * concurrently with respect to the execution of the source runqueue context * switch. * * There is one basic properties we want to guarantee here: * * (1) Remote-clear should _never_ mark a per-cpu cid UNSET when it is actively * used by a task. That would lead to concurrent allocation of the cid and * userspace corruption. * * Provide this guarantee by introducing a Dekker memory ordering to guarantee * that a pair of loads observe at least one of a pair of stores, which can be * shown as: * * X = Y = 0 * * w[X]=1 w[Y]=1 * MB MB * r[Y]=y r[X]=x * * Which guarantees that x==0 && y==0 is impossible. But rather than using * values 0 and 1, this algorithm cares about specific state transitions of the * runqueue current task (as updated by the scheduler context switch), and the * per-mm/cpu cid value. * * Let's introduce task (Y) which has task->mm == mm and task (N) which has * task->mm != mm for the rest of the discussion. There are two scheduler state * transitions on context switch we care about: * * (TSA) Store to rq->curr with transition from (N) to (Y) * * (TSB) Store to rq->curr with transition from (Y) to (N) * * On the remote-clear side, there is one transition we care about: * * (TMA) cmpxchg to *pcpu_cid to set the LAZY flag * * There is also a transition to UNSET state which can be performed from all * sides (scheduler, remote-clear). It is always performed with a cmpxchg which * guarantees that only a single thread will succeed: * * (TMB) cmpxchg to *pcpu_cid to mark UNSET * * Just to be clear, what we do _not_ want to happen is a transition to UNSET * when a thread is actively using the cid (property (1)). * * Let's looks at the relevant combinations of TSA/TSB, and TMA transitions. * * Scenario A) (TSA)+(TMA) (from next task perspective) * * CPU0 CPU1 * * Context switch CS-1 Remote-clear * - store to rq->curr: (N)->(Y) (TSA) - cmpxchg to *pcpu_id to LAZY (TMA) * (implied barrier after cmpxchg) * - switch_mm_cid() * - memory barrier (see switch_mm_cid() * comment explaining how this barrier * is combined with other scheduler * barriers) * - mm_cid_get (next) * - READ_ONCE(*pcpu_cid) - rcu_dereference(src_rq->curr) * * This Dekker ensures that either task (Y) is observed by the * rcu_dereference() or the LAZY flag is observed by READ_ONCE(), or both are * observed. * * If task (Y) store is observed by rcu_dereference(), it means that there is * still an active task on the cpu. Remote-clear will therefore not transition * to UNSET, which fulfills property (1). * * If task (Y) is not observed, but the lazy flag is observed by READ_ONCE(), * it will move its state to UNSET, which clears the percpu cid perhaps * uselessly (which is not an issue for correctness). Because task (Y) is not * observed, CPU1 can move ahead to set the state to UNSET. Because moving * state to UNSET is done with a cmpxchg expecting that the old state has the * LAZY flag set, only one thread will successfully UNSET. * * If both states (LAZY flag and task (Y)) are observed, the thread on CPU0 * will observe the LAZY flag and transition to UNSET (perhaps uselessly), and * CPU1 will observe task (Y) and do nothing more, which is fine. * * What we are effectively preventing with this Dekker is a scenario where * neither LAZY flag nor store (Y) are observed, which would fail property (1) * because this would UNSET a cid which is actively used. */ void sched_mm_cid_migrate_from(struct task_struct *t) { t->migrate_from_cpu = task_cpu(t); } static int __sched_mm_cid_migrate_from_fetch_cid(struct rq *src_rq, struct task_struct *t, struct mm_cid *src_pcpu_cid) { struct mm_struct *mm = t->mm; struct task_struct *src_task; int src_cid, last_mm_cid; if (!mm) return -1; last_mm_cid = t->last_mm_cid; /* * If the migrated task has no last cid, or if the current * task on src rq uses the cid, it means the source cid does not need * to be moved to the destination cpu. */ if (last_mm_cid == -1) return -1; src_cid = READ_ONCE(src_pcpu_cid->cid); if (!mm_cid_is_valid(src_cid) || last_mm_cid != src_cid) return -1; /* * If we observe an active task using the mm on this rq, it means we * are not the last task to be migrated from this cpu for this mm, so * there is no need to move src_cid to the destination cpu. */ guard(rcu)(); src_task = rcu_dereference(src_rq->curr); if (READ_ONCE(src_task->mm_cid_active) && src_task->mm == mm) { t->last_mm_cid = -1; return -1; } return src_cid; } static int __sched_mm_cid_migrate_from_try_steal_cid(struct rq *src_rq, struct task_struct *t, struct mm_cid *src_pcpu_cid, int src_cid) { struct task_struct *src_task; struct mm_struct *mm = t->mm; int lazy_cid; if (src_cid == -1) return -1; /* * Attempt to clear the source cpu cid to move it to the destination * cpu. */ lazy_cid = mm_cid_set_lazy_put(src_cid); if (!try_cmpxchg(&src_pcpu_cid->cid, &src_cid, lazy_cid)) return -1; /* * The implicit barrier after cmpxchg per-mm/cpu cid before loading * rq->curr->mm matches the scheduler barrier in context_switch() * between store to rq->curr and load of prev and next task's * per-mm/cpu cid. * * The implicit barrier after cmpxchg per-mm/cpu cid before loading * rq->curr->mm_cid_active matches the barrier in * sched_mm_cid_exit_signals(), sched_mm_cid_before_execve(), and * sched_mm_cid_after_execve() between store to t->mm_cid_active and * load of per-mm/cpu cid. */ /* * If we observe an active task using the mm on this rq after setting * the lazy-put flag, this task will be responsible for transitioning * from lazy-put flag set to MM_CID_UNSET. */ scoped_guard (rcu) { src_task = rcu_dereference(src_rq->curr); if (READ_ONCE(src_task->mm_cid_active) && src_task->mm == mm) { /* * We observed an active task for this mm, there is therefore * no point in moving this cid to the destination cpu. */ t->last_mm_cid = -1; return -1; } } /* * The src_cid is unused, so it can be unset. */ if (!try_cmpxchg(&src_pcpu_cid->cid, &lazy_cid, MM_CID_UNSET)) return -1; return src_cid; } /* * Migration to dst cpu. Called with dst_rq lock held. * Interrupts are disabled, which keeps the window of cid ownership without the * source rq lock held small. */ void sched_mm_cid_migrate_to(struct rq *dst_rq, struct task_struct *t) { struct mm_cid *src_pcpu_cid, *dst_pcpu_cid; struct mm_struct *mm = t->mm; int src_cid, dst_cid, src_cpu; struct rq *src_rq; lockdep_assert_rq_held(dst_rq); if (!mm) return; src_cpu = t->migrate_from_cpu; if (src_cpu == -1) { t->last_mm_cid = -1; return; } /* * Move the src cid if the dst cid is unset. This keeps id * allocation closest to 0 in cases where few threads migrate around * many cpus. * * If destination cid is already set, we may have to just clear * the src cid to ensure compactness in frequent migrations * scenarios. * * It is not useful to clear the src cid when the number of threads is * greater or equal to the number of allowed cpus, because user-space * can expect that the number of allowed cids can reach the number of * allowed cpus. */ dst_pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu_of(dst_rq)); dst_cid = READ_ONCE(dst_pcpu_cid->cid); if (!mm_cid_is_unset(dst_cid) && atomic_read(&mm->mm_users) >= t->nr_cpus_allowed) return; src_pcpu_cid = per_cpu_ptr(mm->pcpu_cid, src_cpu); src_rq = cpu_rq(src_cpu); src_cid = __sched_mm_cid_migrate_from_fetch_cid(src_rq, t, src_pcpu_cid); if (src_cid == -1) return; src_cid = __sched_mm_cid_migrate_from_try_steal_cid(src_rq, t, src_pcpu_cid, src_cid); if (src_cid == -1) return; if (!mm_cid_is_unset(dst_cid)) { __mm_cid_put(mm, src_cid); return; } /* Move src_cid to dst cpu. */ mm_cid_snapshot_time(dst_rq, mm); WRITE_ONCE(dst_pcpu_cid->cid, src_cid); } static void sched_mm_cid_remote_clear(struct mm_struct *mm, struct mm_cid *pcpu_cid, int cpu) { struct rq *rq = cpu_rq(cpu); struct task_struct *t; int cid, lazy_cid; cid = READ_ONCE(pcpu_cid->cid); if (!mm_cid_is_valid(cid)) return; /* * Clear the cpu cid if it is set to keep cid allocation compact. If * there happens to be other tasks left on the source cpu using this * mm, the next task using this mm will reallocate its cid on context * switch. */ lazy_cid = mm_cid_set_lazy_put(cid); if (!try_cmpxchg(&pcpu_cid->cid, &cid, lazy_cid)) return; /* * The implicit barrier after cmpxchg per-mm/cpu cid before loading * rq->curr->mm matches the scheduler barrier in context_switch() * between store to rq->curr and load of prev and next task's * per-mm/cpu cid. * * The implicit barrier after cmpxchg per-mm/cpu cid before loading * rq->curr->mm_cid_active matches the barrier in * sched_mm_cid_exit_signals(), sched_mm_cid_before_execve(), and * sched_mm_cid_after_execve() between store to t->mm_cid_active and * load of per-mm/cpu cid. */ /* * If we observe an active task using the mm on this rq after setting * the lazy-put flag, that task will be responsible for transitioning * from lazy-put flag set to MM_CID_UNSET. */ scoped_guard (rcu) { t = rcu_dereference(rq->curr); if (READ_ONCE(t->mm_cid_active) && t->mm == mm) return; } /* * The cid is unused, so it can be unset. * Disable interrupts to keep the window of cid ownership without rq * lock small. */ scoped_guard (irqsave) { if (try_cmpxchg(&pcpu_cid->cid, &lazy_cid, MM_CID_UNSET)) __mm_cid_put(mm, cid); } } static void sched_mm_cid_remote_clear_old(struct mm_struct *mm, int cpu) { struct rq *rq = cpu_rq(cpu); struct mm_cid *pcpu_cid; struct task_struct *curr; u64 rq_clock; /* * rq->clock load is racy on 32-bit but one spurious clear once in a * while is irrelevant. */ rq_clock = READ_ONCE(rq->clock); pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu); /* * In order to take care of infrequently scheduled tasks, bump the time * snapshot associated with this cid if an active task using the mm is * observed on this rq. */ scoped_guard (rcu) { curr = rcu_dereference(rq->curr); if (READ_ONCE(curr->mm_cid_active) && curr->mm == mm) { WRITE_ONCE(pcpu_cid->time, rq_clock); return; } } if (rq_clock < pcpu_cid->time + SCHED_MM_CID_PERIOD_NS) return; sched_mm_cid_remote_clear(mm, pcpu_cid, cpu); } static void sched_mm_cid_remote_clear_weight(struct mm_struct *mm, int cpu, int weight) { struct mm_cid *pcpu_cid; int cid; pcpu_cid = per_cpu_ptr(mm->pcpu_cid, cpu); cid = READ_ONCE(pcpu_cid->cid); if (!mm_cid_is_valid(cid) || cid < weight) return; sched_mm_cid_remote_clear(mm, pcpu_cid, cpu); } static void task_mm_cid_work(struct callback_head *work) { unsigned long now = jiffies, old_scan, next_scan; struct task_struct *t = current; struct cpumask *cidmask; struct mm_struct *mm; int weight, cpu; SCHED_WARN_ON(t != container_of(work, struct task_struct, cid_work)); work->next = work; /* Prevent double-add */ if (t->flags & PF_EXITING) return; mm = t->mm; if (!mm) return; old_scan = READ_ONCE(mm->mm_cid_next_scan); next_scan = now + msecs_to_jiffies(MM_CID_SCAN_DELAY); if (!old_scan) { unsigned long res; res = cmpxchg(&mm->mm_cid_next_scan, old_scan, next_scan); if (res != old_scan) old_scan = res; else old_scan = next_scan; } if (time_before(now, old_scan)) return; if (!try_cmpxchg(&mm->mm_cid_next_scan, &old_scan, next_scan)) return; cidmask = mm_cidmask(mm); /* Clear cids that were not recently used. */ for_each_possible_cpu(cpu) sched_mm_cid_remote_clear_old(mm, cpu); weight = cpumask_weight(cidmask); /* * Clear cids that are greater or equal to the cidmask weight to * recompact it. */ for_each_possible_cpu(cpu) sched_mm_cid_remote_clear_weight(mm, cpu, weight); } void init_sched_mm_cid(struct task_struct *t) { struct mm_struct *mm = t->mm; int mm_users = 0; if (mm) { mm_users = atomic_read(&mm->mm_users); if (mm_users == 1) mm->mm_cid_next_scan = jiffies + msecs_to_jiffies(MM_CID_SCAN_DELAY); } t->cid_work.next = &t->cid_work; /* Protect against double add */ init_task_work(&t->cid_work, task_mm_cid_work); } void task_tick_mm_cid(struct rq *rq, struct task_struct *curr) { struct callback_head *work = &curr->cid_work; unsigned long now = jiffies; if (!curr->mm || (curr->flags & (PF_EXITING | PF_KTHREAD)) || work->next != work) return; if (time_before(now, READ_ONCE(curr->mm->mm_cid_next_scan))) return; task_work_add(curr, work, TWA_RESUME); } void sched_mm_cid_exit_signals(struct task_struct *t) { struct mm_struct *mm = t->mm; struct rq *rq; if (!mm) return; preempt_disable(); rq = this_rq(); guard(rq_lock_irqsave)(rq); preempt_enable_no_resched(); /* holding spinlock */ WRITE_ONCE(t->mm_cid_active, 0); /* * Store t->mm_cid_active before loading per-mm/cpu cid. * Matches barrier in sched_mm_cid_remote_clear_old(). */ smp_mb(); mm_cid_put(mm); t->last_mm_cid = t->mm_cid = -1; } void sched_mm_cid_before_execve(struct task_struct *t) { struct mm_struct *mm = t->mm; struct rq *rq; if (!mm) return; preempt_disable(); rq = this_rq(); guard(rq_lock_irqsave)(rq); preempt_enable_no_resched(); /* holding spinlock */ WRITE_ONCE(t->mm_cid_active, 0); /* * Store t->mm_cid_active before loading per-mm/cpu cid. * Matches barrier in sched_mm_cid_remote_clear_old(). */ smp_mb(); mm_cid_put(mm); t->last_mm_cid = t->mm_cid = -1; } void sched_mm_cid_after_execve(struct task_struct *t) { struct mm_struct *mm = t->mm; struct rq *rq; if (!mm) return; preempt_disable(); rq = this_rq(); scoped_guard (rq_lock_irqsave, rq) { preempt_enable_no_resched(); /* holding spinlock */ WRITE_ONCE(t->mm_cid_active, 1); /* * Store t->mm_cid_active before loading per-mm/cpu cid. * Matches barrier in sched_mm_cid_remote_clear_old(). */ smp_mb(); t->last_mm_cid = t->mm_cid = mm_cid_get(rq, mm); } rseq_set_notify_resume(t); } void sched_mm_cid_fork(struct task_struct *t) { WARN_ON_ONCE(!t->mm || t->mm_cid != -1); t->mm_cid_active = 1; } #endif
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