| Author | Tokens | Token Proportion | Commits | Commit Proportion |
|---|---|---|---|---|
| Paul E. McKenney | 12155 | 90.42% | 454 | 83.76% |
| Byungchul Park | 262 | 1.95% | 4 | 0.74% |
| Thomas Gleixner | 191 | 1.42% | 3 | 0.55% |
| Frédéric Weisbecker | 102 | 0.76% | 9 | 1.66% |
| Joel A Fernandes | 93 | 0.69% | 6 | 1.11% |
| Steven Rostedt | 84 | 0.62% | 5 | 0.92% |
| Alexander Gordeev | 79 | 0.59% | 7 | 1.29% |
| Borislav Petkov | 63 | 0.47% | 1 | 0.18% |
| Andreea-Cristina Bernat | 59 | 0.44% | 3 | 0.55% |
| Peter Zijlstra | 57 | 0.42% | 6 | 1.11% |
| Lai Jiangshan | 51 | 0.38% | 4 | 0.74% |
| Mark Rutland | 42 | 0.31% | 1 | 0.18% |
| Boqun Feng | 40 | 0.30% | 2 | 0.37% |
| Daniel Bristot de Oliveira | 28 | 0.21% | 1 | 0.18% |
| Ingo Molnar | 16 | 0.12% | 5 | 0.92% |
| Shaohua Li | 12 | 0.09% | 1 | 0.18% |
| Christoph Lameter | 11 | 0.08% | 3 | 0.55% |
| Matthew Wilcox | 10 | 0.07% | 1 | 0.18% |
| Pranith Kumar | 9 | 0.07% | 2 | 0.37% |
| Ard Biesheuvel | 8 | 0.06% | 1 | 0.18% |
| Joe Perches | 8 | 0.06% | 1 | 0.18% |
| Eric Dumazet | 7 | 0.05% | 1 | 0.18% |
| Mike Galbraith | 6 | 0.04% | 1 | 0.18% |
| Petr Mladek | 6 | 0.04% | 1 | 0.18% |
| Daniel Wagner | 5 | 0.04% | 1 | 0.18% |
| Iulia Manda | 5 | 0.04% | 1 | 0.18% |
| Fabian Frederick | 4 | 0.03% | 1 | 0.18% |
| Dongdong Deng | 4 | 0.03% | 1 | 0.18% |
| Mathieu Desnoyers | 4 | 0.03% | 1 | 0.18% |
| Linus Torvalds | 4 | 0.03% | 2 | 0.37% |
| Paul Gortmaker | 3 | 0.02% | 2 | 0.37% |
| Shan Wei | 2 | 0.01% | 1 | 0.18% |
| Nicholas Mc Guire | 2 | 0.01% | 2 | 0.37% |
| JiSheng Zhang | 2 | 0.01% | 1 | 0.18% |
| Kees Cook | 2 | 0.01% | 1 | 0.18% |
| Himangi Saraogi | 2 | 0.01% | 1 | 0.18% |
| Alexei Starovoitov | 2 | 0.01% | 1 | 0.18% |
| Fengguang Wu | 1 | 0.01% | 1 | 0.18% |
| Masami Hiramatsu | 1 | 0.01% | 1 | 0.18% |
| Li Zhong | 1 | 0.01% | 1 | 0.18% |
| Total | 13443 | 542 |
/* * Read-Copy Update mechanism for mutual exclusion * * This program is free software; you can redistribute it and/or modify * it under the terms of the GNU General Public License as published by * the Free Software Foundation; either version 2 of the License, or * (at your option) any later version. * * This program is distributed in the hope that it will be useful, * but WITHOUT ANY WARRANTY; without even the implied warranty of * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * GNU General Public License for more details. * * You should have received a copy of the GNU General Public License * along with this program; if not, you can access it online at * http://www.gnu.org/licenses/gpl-2.0.html. * * Copyright IBM Corporation, 2008 * * Authors: Dipankar Sarma <dipankar@in.ibm.com> * Manfred Spraul <manfred@colorfullife.com> * Paul E. McKenney <paulmck@linux.vnet.ibm.com> Hierarchical version * * Based on the original work by Paul McKenney <paulmck@us.ibm.com> * and inputs from Rusty Russell, Andrea Arcangeli and Andi Kleen. * * For detailed explanation of Read-Copy Update mechanism see - * Documentation/RCU */ #define pr_fmt(fmt) "rcu: " fmt #include <linux/types.h> #include <linux/kernel.h> #include <linux/init.h> #include <linux/spinlock.h> #include <linux/smp.h> #include <linux/rcupdate_wait.h> #include <linux/interrupt.h> #include <linux/sched.h> #include <linux/sched/debug.h> #include <linux/nmi.h> #include <linux/atomic.h> #include <linux/bitops.h> #include <linux/export.h> #include <linux/completion.h> #include <linux/moduleparam.h> #include <linux/percpu.h> #include <linux/notifier.h> #include <linux/cpu.h> #include <linux/mutex.h> #include <linux/time.h> #include <linux/kernel_stat.h> #include <linux/wait.h> #include <linux/kthread.h> #include <uapi/linux/sched/types.h> #include <linux/prefetch.h> #include <linux/delay.h> #include <linux/stop_machine.h> #include <linux/random.h> #include <linux/trace_events.h> #include <linux/suspend.h> #include <linux/ftrace.h> #include <linux/tick.h> #include "tree.h" #include "rcu.h" #ifdef MODULE_PARAM_PREFIX #undef MODULE_PARAM_PREFIX #endif #define MODULE_PARAM_PREFIX "rcutree." /* Data structures. */ /* * Steal a bit from the bottom of ->dynticks for idle entry/exit * control. Initially this is for TLB flushing. */ #define RCU_DYNTICK_CTRL_MASK 0x1 #define RCU_DYNTICK_CTRL_CTR (RCU_DYNTICK_CTRL_MASK + 1) #ifndef rcu_eqs_special_exit #define rcu_eqs_special_exit() do { } while (0) #endif static DEFINE_PER_CPU_SHARED_ALIGNED(struct rcu_data, rcu_data) = { .dynticks_nesting = 1, .dynticks_nmi_nesting = DYNTICK_IRQ_NONIDLE, .dynticks = ATOMIC_INIT(RCU_DYNTICK_CTRL_CTR), }; struct rcu_state rcu_state = { .level = { &rcu_state.node[0] }, .gp_state = RCU_GP_IDLE, .gp_seq = (0UL - 300UL) << RCU_SEQ_CTR_SHIFT, .barrier_mutex = __MUTEX_INITIALIZER(rcu_state.barrier_mutex), .name = RCU_NAME, .abbr = RCU_ABBR, .exp_mutex = __MUTEX_INITIALIZER(rcu_state.exp_mutex), .exp_wake_mutex = __MUTEX_INITIALIZER(rcu_state.exp_wake_mutex), .ofl_lock = __RAW_SPIN_LOCK_UNLOCKED(rcu_state.ofl_lock), }; /* Dump rcu_node combining tree at boot to verify correct setup. */ static bool dump_tree; module_param(dump_tree, bool, 0444); /* Control rcu_node-tree auto-balancing at boot time. */ static bool rcu_fanout_exact; module_param(rcu_fanout_exact, bool, 0444); /* Increase (but not decrease) the RCU_FANOUT_LEAF at boot time. */ static int rcu_fanout_leaf = RCU_FANOUT_LEAF; module_param(rcu_fanout_leaf, int, 0444); int rcu_num_lvls __read_mostly = RCU_NUM_LVLS; /* Number of rcu_nodes at specified level. */ int num_rcu_lvl[] = NUM_RCU_LVL_INIT; int rcu_num_nodes __read_mostly = NUM_RCU_NODES; /* Total # rcu_nodes in use. */ /* panic() on RCU Stall sysctl. */ int sysctl_panic_on_rcu_stall __read_mostly; /* * The rcu_scheduler_active variable is initialized to the value * RCU_SCHEDULER_INACTIVE and transitions RCU_SCHEDULER_INIT just before the * first task is spawned. So when this variable is RCU_SCHEDULER_INACTIVE, * RCU can assume that there is but one task, allowing RCU to (for example) * optimize synchronize_rcu() to a simple barrier(). When this variable * is RCU_SCHEDULER_INIT, RCU must actually do all the hard work required * to detect real grace periods. This variable is also used to suppress * boot-time false positives from lockdep-RCU error checking. Finally, it * transitions from RCU_SCHEDULER_INIT to RCU_SCHEDULER_RUNNING after RCU * is fully initialized, including all of its kthreads having been spawned. */ int rcu_scheduler_active __read_mostly; EXPORT_SYMBOL_GPL(rcu_scheduler_active); /* * The rcu_scheduler_fully_active variable transitions from zero to one * during the early_initcall() processing, which is after the scheduler * is capable of creating new tasks. So RCU processing (for example, * creating tasks for RCU priority boosting) must be delayed until after * rcu_scheduler_fully_active transitions from zero to one. We also * currently delay invocation of any RCU callbacks until after this point. * * It might later prove better for people registering RCU callbacks during * early boot to take responsibility for these callbacks, but one step at * a time. */ static int rcu_scheduler_fully_active __read_mostly; static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp, unsigned long gps, unsigned long flags); static void rcu_init_new_rnp(struct rcu_node *rnp_leaf); static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf); static void rcu_boost_kthread_setaffinity(struct rcu_node *rnp, int outgoingcpu); static void invoke_rcu_core(void); static void invoke_rcu_callbacks(struct rcu_data *rdp); static void rcu_report_exp_rdp(struct rcu_data *rdp); static void sync_sched_exp_online_cleanup(int cpu); /* rcuc/rcub kthread realtime priority */ static int kthread_prio = IS_ENABLED(CONFIG_RCU_BOOST) ? 1 : 0; module_param(kthread_prio, int, 0644); /* Delay in jiffies for grace-period initialization delays, debug only. */ static int gp_preinit_delay; module_param(gp_preinit_delay, int, 0444); static int gp_init_delay; module_param(gp_init_delay, int, 0444); static int gp_cleanup_delay; module_param(gp_cleanup_delay, int, 0444); /* Retrieve RCU kthreads priority for rcutorture */ int rcu_get_gp_kthreads_prio(void) { return kthread_prio; } EXPORT_SYMBOL_GPL(rcu_get_gp_kthreads_prio); /* * Number of grace periods between delays, normalized by the duration of * the delay. The longer the delay, the more the grace periods between * each delay. The reason for this normalization is that it means that, * for non-zero delays, the overall slowdown of grace periods is constant * regardless of the duration of the delay. This arrangement balances * the need for long delays to increase some race probabilities with the * need for fast grace periods to increase other race probabilities. */ #define PER_RCU_NODE_PERIOD 3 /* Number of grace periods between delays. */ /* * Compute the mask of online CPUs for the specified rcu_node structure. * This will not be stable unless the rcu_node structure's ->lock is * held, but the bit corresponding to the current CPU will be stable * in most contexts. */ unsigned long rcu_rnp_online_cpus(struct rcu_node *rnp) { return READ_ONCE(rnp->qsmaskinitnext); } /* * Return true if an RCU grace period is in progress. The READ_ONCE()s * permit this function to be invoked without holding the root rcu_node * structure's ->lock, but of course results can be subject to change. */ static int rcu_gp_in_progress(void) { return rcu_seq_state(rcu_seq_current(&rcu_state.gp_seq)); } void rcu_softirq_qs(void) { rcu_qs(); rcu_preempt_deferred_qs(current); } /* * Record entry into an extended quiescent state. This is only to be * called when not already in an extended quiescent state. */ static void rcu_dynticks_eqs_enter(void) { struct rcu_data *rdp = this_cpu_ptr(&rcu_data); int seq; /* * CPUs seeing atomic_add_return() must see prior RCU read-side * critical sections, and we also must force ordering with the * next idle sojourn. */ seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); /* Better be in an extended quiescent state! */ WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & RCU_DYNTICK_CTRL_CTR)); /* Better not have special action (TLB flush) pending! */ WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && (seq & RCU_DYNTICK_CTRL_MASK)); } /* * Record exit from an extended quiescent state. This is only to be * called from an extended quiescent state. */ static void rcu_dynticks_eqs_exit(void) { struct rcu_data *rdp = this_cpu_ptr(&rcu_data); int seq; /* * CPUs seeing atomic_add_return() must see prior idle sojourns, * and we also must force ordering with the next RCU read-side * critical section. */ seq = atomic_add_return(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !(seq & RCU_DYNTICK_CTRL_CTR)); if (seq & RCU_DYNTICK_CTRL_MASK) { atomic_andnot(RCU_DYNTICK_CTRL_MASK, &rdp->dynticks); smp_mb__after_atomic(); /* _exit after clearing mask. */ /* Prefer duplicate flushes to losing a flush. */ rcu_eqs_special_exit(); } } /* * Reset the current CPU's ->dynticks counter to indicate that the * newly onlined CPU is no longer in an extended quiescent state. * This will either leave the counter unchanged, or increment it * to the next non-quiescent value. * * The non-atomic test/increment sequence works because the upper bits * of the ->dynticks counter are manipulated only by the corresponding CPU, * or when the corresponding CPU is offline. */ static void rcu_dynticks_eqs_online(void) { struct rcu_data *rdp = this_cpu_ptr(&rcu_data); if (atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR) return; atomic_add(RCU_DYNTICK_CTRL_CTR, &rdp->dynticks); } /* * Is the current CPU in an extended quiescent state? * * No ordering, as we are sampling CPU-local information. */ bool rcu_dynticks_curr_cpu_in_eqs(void) { struct rcu_data *rdp = this_cpu_ptr(&rcu_data); return !(atomic_read(&rdp->dynticks) & RCU_DYNTICK_CTRL_CTR); } /* * Snapshot the ->dynticks counter with full ordering so as to allow * stable comparison of this counter with past and future snapshots. */ int rcu_dynticks_snap(struct rcu_data *rdp) { int snap = atomic_add_return(0, &rdp->dynticks); return snap & ~RCU_DYNTICK_CTRL_MASK; } /* * Return true if the snapshot returned from rcu_dynticks_snap() * indicates that RCU is in an extended quiescent state. */ static bool rcu_dynticks_in_eqs(int snap) { return !(snap & RCU_DYNTICK_CTRL_CTR); } /* * Return true if the CPU corresponding to the specified rcu_data * structure has spent some time in an extended quiescent state since * rcu_dynticks_snap() returned the specified snapshot. */ static bool rcu_dynticks_in_eqs_since(struct rcu_data *rdp, int snap) { return snap != rcu_dynticks_snap(rdp); } /* * Set the special (bottom) bit of the specified CPU so that it * will take special action (such as flushing its TLB) on the * next exit from an extended quiescent state. Returns true if * the bit was successfully set, or false if the CPU was not in * an extended quiescent state. */ bool rcu_eqs_special_set(int cpu) { int old; int new; struct rcu_data *rdp = &per_cpu(rcu_data, cpu); do { old = atomic_read(&rdp->dynticks); if (old & RCU_DYNTICK_CTRL_CTR) return false; new = old | RCU_DYNTICK_CTRL_MASK; } while (atomic_cmpxchg(&rdp->dynticks, old, new) != old); return true; } /* * Let the RCU core know that this CPU has gone through the scheduler, * which is a quiescent state. This is called when the need for a * quiescent state is urgent, so we burn an atomic operation and full * memory barriers to let the RCU core know about it, regardless of what * this CPU might (or might not) do in the near future. * * We inform the RCU core by emulating a zero-duration dyntick-idle period. * * The caller must have disabled interrupts and must not be idle. */ static void __maybe_unused rcu_momentary_dyntick_idle(void) { int special; raw_cpu_write(rcu_data.rcu_need_heavy_qs, false); special = atomic_add_return(2 * RCU_DYNTICK_CTRL_CTR, &this_cpu_ptr(&rcu_data)->dynticks); /* It is illegal to call this from idle state. */ WARN_ON_ONCE(!(special & RCU_DYNTICK_CTRL_CTR)); rcu_preempt_deferred_qs(current); } /** * rcu_is_cpu_rrupt_from_idle - see if idle or immediately interrupted from idle * * If the current CPU is idle or running at a first-level (not nested) * interrupt from idle, return true. The caller must have at least * disabled preemption. */ static int rcu_is_cpu_rrupt_from_idle(void) { return __this_cpu_read(rcu_data.dynticks_nesting) <= 0 && __this_cpu_read(rcu_data.dynticks_nmi_nesting) <= 1; } #define DEFAULT_RCU_BLIMIT 10 /* Maximum callbacks per rcu_do_batch. */ static long blimit = DEFAULT_RCU_BLIMIT; #define DEFAULT_RCU_QHIMARK 10000 /* If this many pending, ignore blimit. */ static long qhimark = DEFAULT_RCU_QHIMARK; #define DEFAULT_RCU_QLOMARK 100 /* Once only this many pending, use blimit. */ static long qlowmark = DEFAULT_RCU_QLOMARK; module_param(blimit, long, 0444); module_param(qhimark, long, 0444); module_param(qlowmark, long, 0444); static ulong jiffies_till_first_fqs = ULONG_MAX; static ulong jiffies_till_next_fqs = ULONG_MAX; static bool rcu_kick_kthreads; /* * How long the grace period must be before we start recruiting * quiescent-state help from rcu_note_context_switch(). */ static ulong jiffies_till_sched_qs = ULONG_MAX; module_param(jiffies_till_sched_qs, ulong, 0444); static ulong jiffies_to_sched_qs; /* Adjusted version of above if not default */ module_param(jiffies_to_sched_qs, ulong, 0444); /* Display only! */ /* * Make sure that we give the grace-period kthread time to detect any * idle CPUs before taking active measures to force quiescent states. * However, don't go below 100 milliseconds, adjusted upwards for really * large systems. */ static void adjust_jiffies_till_sched_qs(void) { unsigned long j; /* If jiffies_till_sched_qs was specified, respect the request. */ if (jiffies_till_sched_qs != ULONG_MAX) { WRITE_ONCE(jiffies_to_sched_qs, jiffies_till_sched_qs); return; } j = READ_ONCE(jiffies_till_first_fqs) + 2 * READ_ONCE(jiffies_till_next_fqs); if (j < HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV) j = HZ / 10 + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; pr_info("RCU calculated value of scheduler-enlistment delay is %ld jiffies.\n", j); WRITE_ONCE(jiffies_to_sched_qs, j); } static int param_set_first_fqs_jiffies(const char *val, const struct kernel_param *kp) { ulong j; int ret = kstrtoul(val, 0, &j); if (!ret) { WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : j); adjust_jiffies_till_sched_qs(); } return ret; } static int param_set_next_fqs_jiffies(const char *val, const struct kernel_param *kp) { ulong j; int ret = kstrtoul(val, 0, &j); if (!ret) { WRITE_ONCE(*(ulong *)kp->arg, (j > HZ) ? HZ : (j ?: 1)); adjust_jiffies_till_sched_qs(); } return ret; } static struct kernel_param_ops first_fqs_jiffies_ops = { .set = param_set_first_fqs_jiffies, .get = param_get_ulong, }; static struct kernel_param_ops next_fqs_jiffies_ops = { .set = param_set_next_fqs_jiffies, .get = param_get_ulong, }; module_param_cb(jiffies_till_first_fqs, &first_fqs_jiffies_ops, &jiffies_till_first_fqs, 0644); module_param_cb(jiffies_till_next_fqs, &next_fqs_jiffies_ops, &jiffies_till_next_fqs, 0644); module_param(rcu_kick_kthreads, bool, 0644); static void force_qs_rnp(int (*f)(struct rcu_data *rdp)); static void force_quiescent_state(void); static int rcu_pending(void); /* * Return the number of RCU GPs completed thus far for debug & stats. */ unsigned long rcu_get_gp_seq(void) { return READ_ONCE(rcu_state.gp_seq); } EXPORT_SYMBOL_GPL(rcu_get_gp_seq); /* * Return the number of RCU expedited batches completed thus far for * debug & stats. Odd numbers mean that a batch is in progress, even * numbers mean idle. The value returned will thus be roughly double * the cumulative batches since boot. */ unsigned long rcu_exp_batches_completed(void) { return rcu_state.expedited_sequence; } EXPORT_SYMBOL_GPL(rcu_exp_batches_completed); /* * Force a quiescent state. */ void rcu_force_quiescent_state(void) { force_quiescent_state(); } EXPORT_SYMBOL_GPL(rcu_force_quiescent_state); /* * Show the state of the grace-period kthreads. */ void show_rcu_gp_kthreads(void) { int cpu; struct rcu_data *rdp; struct rcu_node *rnp; pr_info("%s: wait state: %d ->state: %#lx\n", rcu_state.name, rcu_state.gp_state, rcu_state.gp_kthread->state); rcu_for_each_node_breadth_first(rnp) { if (ULONG_CMP_GE(rcu_state.gp_seq, rnp->gp_seq_needed)) continue; pr_info("\trcu_node %d:%d ->gp_seq %lu ->gp_seq_needed %lu\n", rnp->grplo, rnp->grphi, rnp->gp_seq, rnp->gp_seq_needed); if (!rcu_is_leaf_node(rnp)) continue; for_each_leaf_node_possible_cpu(rnp, cpu) { rdp = per_cpu_ptr(&rcu_data, cpu); if (rdp->gpwrap || ULONG_CMP_GE(rcu_state.gp_seq, rdp->gp_seq_needed)) continue; pr_info("\tcpu %d ->gp_seq_needed %lu\n", cpu, rdp->gp_seq_needed); } } /* sched_show_task(rcu_state.gp_kthread); */ } EXPORT_SYMBOL_GPL(show_rcu_gp_kthreads); /* * Send along grace-period-related data for rcutorture diagnostics. */ void rcutorture_get_gp_data(enum rcutorture_type test_type, int *flags, unsigned long *gp_seq) { switch (test_type) { case RCU_FLAVOR: case RCU_BH_FLAVOR: case RCU_SCHED_FLAVOR: *flags = READ_ONCE(rcu_state.gp_flags); *gp_seq = rcu_seq_current(&rcu_state.gp_seq); break; default: break; } } EXPORT_SYMBOL_GPL(rcutorture_get_gp_data); /* * Return the root node of the rcu_state structure. */ static struct rcu_node *rcu_get_root(void) { return &rcu_state.node[0]; } /* * Enter an RCU extended quiescent state, which can be either the * idle loop or adaptive-tickless usermode execution. * * We crowbar the ->dynticks_nmi_nesting field to zero to allow for * the possibility of usermode upcalls having messed up our count * of interrupt nesting level during the prior busy period. */ static void rcu_eqs_enter(bool user) { struct rcu_data *rdp = this_cpu_ptr(&rcu_data); WARN_ON_ONCE(rdp->dynticks_nmi_nesting != DYNTICK_IRQ_NONIDLE); WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && rdp->dynticks_nesting == 0); if (rdp->dynticks_nesting != 1) { rdp->dynticks_nesting--; return; } lockdep_assert_irqs_disabled(); trace_rcu_dyntick(TPS("Start"), rdp->dynticks_nesting, 0, rdp->dynticks); WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); rdp = this_cpu_ptr(&rcu_data); do_nocb_deferred_wakeup(rdp); rcu_prepare_for_idle(); rcu_preempt_deferred_qs(current); WRITE_ONCE(rdp->dynticks_nesting, 0); /* Avoid irq-access tearing. */ rcu_dynticks_eqs_enter(); rcu_dynticks_task_enter(); } /** * rcu_idle_enter - inform RCU that current CPU is entering idle * * Enter idle mode, in other words, -leave- the mode in which RCU * read-side critical sections can occur. (Though RCU read-side * critical sections can occur in irq handlers in idle, a possibility * handled by irq_enter() and irq_exit().) * * If you add or remove a call to rcu_idle_enter(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ void rcu_idle_enter(void) { lockdep_assert_irqs_disabled(); rcu_eqs_enter(false); } #ifdef CONFIG_NO_HZ_FULL /** * rcu_user_enter - inform RCU that we are resuming userspace. * * Enter RCU idle mode right before resuming userspace. No use of RCU * is permitted between this call and rcu_user_exit(). This way the * CPU doesn't need to maintain the tick for RCU maintenance purposes * when the CPU runs in userspace. * * If you add or remove a call to rcu_user_enter(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ void rcu_user_enter(void) { lockdep_assert_irqs_disabled(); rcu_eqs_enter(true); } #endif /* CONFIG_NO_HZ_FULL */ /* * If we are returning from the outermost NMI handler that interrupted an * RCU-idle period, update rdp->dynticks and rdp->dynticks_nmi_nesting * to let the RCU grace-period handling know that the CPU is back to * being RCU-idle. * * If you add or remove a call to rcu_nmi_exit_common(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. */ static __always_inline void rcu_nmi_exit_common(bool irq) { struct rcu_data *rdp = this_cpu_ptr(&rcu_data); /* * Check for ->dynticks_nmi_nesting underflow and bad ->dynticks. * (We are exiting an NMI handler, so RCU better be paying attention * to us!) */ WARN_ON_ONCE(rdp->dynticks_nmi_nesting <= 0); WARN_ON_ONCE(rcu_dynticks_curr_cpu_in_eqs()); /* * If the nesting level is not 1, the CPU wasn't RCU-idle, so * leave it in non-RCU-idle state. */ if (rdp->dynticks_nmi_nesting != 1) { trace_rcu_dyntick(TPS("--="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting - 2, rdp->dynticks); WRITE_ONCE(rdp->dynticks_nmi_nesting, /* No store tearing. */ rdp->dynticks_nmi_nesting - 2); return; } /* This NMI interrupted an RCU-idle CPU, restore RCU-idleness. */ trace_rcu_dyntick(TPS("Startirq"), rdp->dynticks_nmi_nesting, 0, rdp->dynticks); WRITE_ONCE(rdp->dynticks_nmi_nesting, 0); /* Avoid store tearing. */ if (irq) rcu_prepare_for_idle(); rcu_dynticks_eqs_enter(); if (irq) rcu_dynticks_task_enter(); } /** * rcu_nmi_exit - inform RCU of exit from NMI context * @irq: Is this call from rcu_irq_exit? * * If you add or remove a call to rcu_nmi_exit(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. */ void rcu_nmi_exit(void) { rcu_nmi_exit_common(false); } /** * rcu_irq_exit - inform RCU that current CPU is exiting irq towards idle * * Exit from an interrupt handler, which might possibly result in entering * idle mode, in other words, leaving the mode in which read-side critical * sections can occur. The caller must have disabled interrupts. * * This code assumes that the idle loop never does anything that might * result in unbalanced calls to irq_enter() and irq_exit(). If your * architecture's idle loop violates this assumption, RCU will give you what * you deserve, good and hard. But very infrequently and irreproducibly. * * Use things like work queues to work around this limitation. * * You have been warned. * * If you add or remove a call to rcu_irq_exit(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ void rcu_irq_exit(void) { lockdep_assert_irqs_disabled(); rcu_nmi_exit_common(true); } /* * Wrapper for rcu_irq_exit() where interrupts are enabled. * * If you add or remove a call to rcu_irq_exit_irqson(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. */ void rcu_irq_exit_irqson(void) { unsigned long flags; local_irq_save(flags); rcu_irq_exit(); local_irq_restore(flags); } /* * Exit an RCU extended quiescent state, which can be either the * idle loop or adaptive-tickless usermode execution. * * We crowbar the ->dynticks_nmi_nesting field to DYNTICK_IRQ_NONIDLE to * allow for the possibility of usermode upcalls messing up our count of * interrupt nesting level during the busy period that is just now starting. */ static void rcu_eqs_exit(bool user) { struct rcu_data *rdp; long oldval; lockdep_assert_irqs_disabled(); rdp = this_cpu_ptr(&rcu_data); oldval = rdp->dynticks_nesting; WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && oldval < 0); if (oldval) { rdp->dynticks_nesting++; return; } rcu_dynticks_task_exit(); rcu_dynticks_eqs_exit(); rcu_cleanup_after_idle(); trace_rcu_dyntick(TPS("End"), rdp->dynticks_nesting, 1, rdp->dynticks); WARN_ON_ONCE(IS_ENABLED(CONFIG_RCU_EQS_DEBUG) && !user && !is_idle_task(current)); WRITE_ONCE(rdp->dynticks_nesting, 1); WARN_ON_ONCE(rdp->dynticks_nmi_nesting); WRITE_ONCE(rdp->dynticks_nmi_nesting, DYNTICK_IRQ_NONIDLE); } /** * rcu_idle_exit - inform RCU that current CPU is leaving idle * * Exit idle mode, in other words, -enter- the mode in which RCU * read-side critical sections can occur. * * If you add or remove a call to rcu_idle_exit(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ void rcu_idle_exit(void) { unsigned long flags; local_irq_save(flags); rcu_eqs_exit(false); local_irq_restore(flags); } #ifdef CONFIG_NO_HZ_FULL /** * rcu_user_exit - inform RCU that we are exiting userspace. * * Exit RCU idle mode while entering the kernel because it can * run a RCU read side critical section anytime. * * If you add or remove a call to rcu_user_exit(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ void rcu_user_exit(void) { rcu_eqs_exit(1); } #endif /* CONFIG_NO_HZ_FULL */ /** * rcu_nmi_enter_common - inform RCU of entry to NMI context * @irq: Is this call from rcu_irq_enter? * * If the CPU was idle from RCU's viewpoint, update rdp->dynticks and * rdp->dynticks_nmi_nesting to let the RCU grace-period handling know * that the CPU is active. This implementation permits nested NMIs, as * long as the nesting level does not overflow an int. (You will probably * run out of stack space first.) * * If you add or remove a call to rcu_nmi_enter_common(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. */ static __always_inline void rcu_nmi_enter_common(bool irq) { struct rcu_data *rdp = this_cpu_ptr(&rcu_data); long incby = 2; /* Complain about underflow. */ WARN_ON_ONCE(rdp->dynticks_nmi_nesting < 0); /* * If idle from RCU viewpoint, atomically increment ->dynticks * to mark non-idle and increment ->dynticks_nmi_nesting by one. * Otherwise, increment ->dynticks_nmi_nesting by two. This means * if ->dynticks_nmi_nesting is equal to one, we are guaranteed * to be in the outermost NMI handler that interrupted an RCU-idle * period (observation due to Andy Lutomirski). */ if (rcu_dynticks_curr_cpu_in_eqs()) { if (irq) rcu_dynticks_task_exit(); rcu_dynticks_eqs_exit(); if (irq) rcu_cleanup_after_idle(); incby = 1; } trace_rcu_dyntick(incby == 1 ? TPS("Endirq") : TPS("++="), rdp->dynticks_nmi_nesting, rdp->dynticks_nmi_nesting + incby, rdp->dynticks); WRITE_ONCE(rdp->dynticks_nmi_nesting, /* Prevent store tearing. */ rdp->dynticks_nmi_nesting + incby); barrier(); } /** * rcu_nmi_enter - inform RCU of entry to NMI context */ void rcu_nmi_enter(void) { rcu_nmi_enter_common(false); } /** * rcu_irq_enter - inform RCU that current CPU is entering irq away from idle * * Enter an interrupt handler, which might possibly result in exiting * idle mode, in other words, entering the mode in which read-side critical * sections can occur. The caller must have disabled interrupts. * * Note that the Linux kernel is fully capable of entering an interrupt * handler that it never exits, for example when doing upcalls to user mode! * This code assumes that the idle loop never does upcalls to user mode. * If your architecture's idle loop does do upcalls to user mode (or does * anything else that results in unbalanced calls to the irq_enter() and * irq_exit() functions), RCU will give you what you deserve, good and hard. * But very infrequently and irreproducibly. * * Use things like work queues to work around this limitation. * * You have been warned. * * If you add or remove a call to rcu_irq_enter(), be sure to test with * CONFIG_RCU_EQS_DEBUG=y. */ void rcu_irq_enter(void) { lockdep_assert_irqs_disabled(); rcu_nmi_enter_common(true); } /* * Wrapper for rcu_irq_enter() where interrupts are enabled. * * If you add or remove a call to rcu_irq_enter_irqson(), be sure to test * with CONFIG_RCU_EQS_DEBUG=y. */ void rcu_irq_enter_irqson(void) { unsigned long flags; local_irq_save(flags); rcu_irq_enter(); local_irq_restore(flags); } /** * rcu_is_watching - see if RCU thinks that the current CPU is idle * * Return true if RCU is watching the running CPU, which means that this * CPU can safely enter RCU read-side critical sections. In other words, * if the current CPU is in its idle loop and is neither in an interrupt * or NMI handler, return true. */ bool notrace rcu_is_watching(void) { bool ret; preempt_disable_notrace(); ret = !rcu_dynticks_curr_cpu_in_eqs(); preempt_enable_notrace(); return ret; } EXPORT_SYMBOL_GPL(rcu_is_watching); /* * If a holdout task is actually running, request an urgent quiescent * state from its CPU. This is unsynchronized, so migrations can cause * the request to go to the wrong CPU. Which is OK, all that will happen * is that the CPU's next context switch will be a bit slower and next * time around this task will generate another request. */ void rcu_request_urgent_qs_task(struct task_struct *t) { int cpu; barrier(); cpu = task_cpu(t); if (!task_curr(t)) return; /* This task is not running on that CPU. */ smp_store_release(per_cpu_ptr(&rcu_data.rcu_urgent_qs, cpu), true); } #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) /* * Is the current CPU online as far as RCU is concerned? * * Disable preemption to avoid false positives that could otherwise * happen due to the current CPU number being sampled, this task being * preempted, its old CPU being taken offline, resuming on some other CPU, * then determining that its old CPU is now offline. * * Disable checking if in an NMI handler because we cannot safely * report errors from NMI handlers anyway. In addition, it is OK to use * RCU on an offline processor during initial boot, hence the check for * rcu_scheduler_fully_active. */ bool rcu_lockdep_current_cpu_online(void) { struct rcu_data *rdp; struct rcu_node *rnp; bool ret = false; if (in_nmi() || !rcu_scheduler_fully_active) return true; preempt_disable(); rdp = this_cpu_ptr(&rcu_data); rnp = rdp->mynode; if (rdp->grpmask & rcu_rnp_online_cpus(rnp)) ret = true; preempt_enable(); return ret; } EXPORT_SYMBOL_GPL(rcu_lockdep_current_cpu_online); #endif /* #if defined(CONFIG_PROVE_RCU) && defined(CONFIG_HOTPLUG_CPU) */ /* * We are reporting a quiescent state on behalf of some other CPU, so * it is our responsibility to check for and handle potential overflow * of the rcu_node ->gp_seq counter with respect to the rcu_data counters. * After all, the CPU might be in deep idle state, and thus executing no * code whatsoever. */ static void rcu_gpnum_ovf(struct rcu_node *rnp, struct rcu_data *rdp) { raw_lockdep_assert_held_rcu_node(rnp); if (ULONG_CMP_LT(rcu_seq_current(&rdp->gp_seq) + ULONG_MAX / 4, rnp->gp_seq)) WRITE_ONCE(rdp->gpwrap, true); if (ULONG_CMP_LT(rdp->rcu_iw_gp_seq + ULONG_MAX / 4, rnp->gp_seq)) rdp->rcu_iw_gp_seq = rnp->gp_seq + ULONG_MAX / 4; } /* * Snapshot the specified CPU's dynticks counter so that we can later * credit them with an implicit quiescent state. Return 1 if this CPU * is in dynticks idle mode, which is an extended quiescent state. */ static int dyntick_save_progress_counter(struct rcu_data *rdp) { rdp->dynticks_snap = rcu_dynticks_snap(rdp); if (rcu_dynticks_in_eqs(rdp->dynticks_snap)) { trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti")); rcu_gpnum_ovf(rdp->mynode, rdp); return 1; } return 0; } /* * Handler for the irq_work request posted when a grace period has * gone on for too long, but not yet long enough for an RCU CPU * stall warning. Set state appropriately, but just complain if * there is unexpected state on entry. */ static void rcu_iw_handler(struct irq_work *iwp) { struct rcu_data *rdp; struct rcu_node *rnp; rdp = container_of(iwp, struct rcu_data, rcu_iw); rnp = rdp->mynode; raw_spin_lock_rcu_node(rnp); if (!WARN_ON_ONCE(!rdp->rcu_iw_pending)) { rdp->rcu_iw_gp_seq = rnp->gp_seq; rdp->rcu_iw_pending = false; } raw_spin_unlock_rcu_node(rnp); } /* * Return true if the specified CPU has passed through a quiescent * state by virtue of being in or having passed through an dynticks * idle state since the last call to dyntick_save_progress_counter() * for this same CPU, or by virtue of having been offline. */ static int rcu_implicit_dynticks_qs(struct rcu_data *rdp) { unsigned long jtsq; bool *rnhqp; bool *ruqp; struct rcu_node *rnp = rdp->mynode; /* * If the CPU passed through or entered a dynticks idle phase with * no active irq/NMI handlers, then we can safely pretend that the CPU * already acknowledged the request to pass through a quiescent * state. Either way, that CPU cannot possibly be in an RCU * read-side critical section that started before the beginning * of the current RCU grace period. */ if (rcu_dynticks_in_eqs_since(rdp, rdp->dynticks_snap)) { trace_rcu_fqs(rcu_state.name, rdp->gp_seq, rdp->cpu, TPS("dti")); rcu_gpnum_ovf(rnp, rdp); return 1; } /* If waiting too long on an offline CPU, complain. */ if (!(rdp->grpmask & rcu_rnp_online_cpus(rnp)) && time_after(jiffies, rcu_state.gp_start + HZ)) { bool onl; struct rcu_node *rnp1; WARN_ON(1); /* Offline CPUs are supposed to report QS! */ pr_info("%s: grp: %d-%d level: %d ->gp_seq %ld ->completedqs %ld\n", __func__, rnp->grplo, rnp->grphi, rnp->level, (long)rnp->gp_seq, (long)rnp->completedqs); for (rnp1 = rnp; rnp1; rnp1 = rnp1->parent) pr_info("%s: %d:%d ->qsmask %#lx ->qsmaskinit %#lx ->qsmaskinitnext %#lx ->rcu_gp_init_mask %#lx\n", __func__, rnp1->grplo, rnp1->grphi, rnp1->qsmask, rnp1->qsmaskinit, rnp1->qsmaskinitnext, rnp1->rcu_gp_init_mask); onl = !!(rdp->grpmask & rcu_rnp_online_cpus(rnp)); pr_info("%s %d: %c online: %ld(%d) offline: %ld(%d)\n", __func__, rdp->cpu, ".o"[onl], (long)rdp->rcu_onl_gp_seq, rdp->rcu_onl_gp_flags, (long)rdp->rcu_ofl_gp_seq, rdp->rcu_ofl_gp_flags); return 1; /* Break things loose after complaining. */ } /* * A CPU running for an extended time within the kernel can * delay RCU grace periods: (1) At age jiffies_to_sched_qs, * set .rcu_urgent_qs, (2) At age 2*jiffies_to_sched_qs, set * both .rcu_need_heavy_qs and .rcu_urgent_qs. Note that the * unsynchronized assignments to the per-CPU rcu_need_heavy_qs * variable are safe because the assignments are repeated if this * CPU failed to pass through a quiescent state. This code * also checks .jiffies_resched in case jiffies_to_sched_qs * is set way high. */ jtsq = READ_ONCE(jiffies_to_sched_qs); ruqp = per_cpu_ptr(&rcu_data.rcu_urgent_qs, rdp->cpu); rnhqp = &per_cpu(rcu_data.rcu_need_heavy_qs, rdp->cpu); if (!READ_ONCE(*rnhqp) && (time_after(jiffies, rcu_state.gp_start + jtsq * 2) || time_after(jiffies, rcu_state.jiffies_resched))) { WRITE_ONCE(*rnhqp, true); /* Store rcu_need_heavy_qs before rcu_urgent_qs. */ smp_store_release(ruqp, true); } else if (time_after(jiffies, rcu_state.gp_start + jtsq)) { WRITE_ONCE(*ruqp, true); } /* * NO_HZ_FULL CPUs can run in-kernel without rcu_check_callbacks! * The above code handles this, but only for straight cond_resched(). * And some in-kernel loops check need_resched() before calling * cond_resched(), which defeats the above code for CPUs that are * running in-kernel with scheduling-clock interrupts disabled. * So hit them over the head with the resched_cpu() hammer! */ if (tick_nohz_full_cpu(rdp->cpu) && time_after(jiffies, READ_ONCE(rdp->last_fqs_resched) + jtsq * 3)) { resched_cpu(rdp->cpu); WRITE_ONCE(rdp->last_fqs_resched, jiffies); } /* * If more than halfway to RCU CPU stall-warning time, invoke * resched_cpu() more frequently to try to loosen things up a bit. * Also check to see if the CPU is getting hammered with interrupts, * but only once per grace period, just to keep the IPIs down to * a dull roar. */ if (time_after(jiffies, rcu_state.jiffies_resched)) { if (time_after(jiffies, READ_ONCE(rdp->last_fqs_resched) + jtsq)) { resched_cpu(rdp->cpu); WRITE_ONCE(rdp->last_fqs_resched, jiffies); } if (IS_ENABLED(CONFIG_IRQ_WORK) && !rdp->rcu_iw_pending && rdp->rcu_iw_gp_seq != rnp->gp_seq && (rnp->ffmask & rdp->grpmask)) { init_irq_work(&rdp->rcu_iw, rcu_iw_handler); rdp->rcu_iw_pending = true; rdp->rcu_iw_gp_seq = rnp->gp_seq; irq_work_queue_on(&rdp->rcu_iw, rdp->cpu); } } return 0; } static void record_gp_stall_check_time(void) { unsigned long j = jiffies; unsigned long j1; rcu_state.gp_start = j; j1 = rcu_jiffies_till_stall_check(); /* Record ->gp_start before ->jiffies_stall. */ smp_store_release(&rcu_state.jiffies_stall, j + j1); /* ^^^ */ rcu_state.jiffies_resched = j + j1 / 2; rcu_state.n_force_qs_gpstart = READ_ONCE(rcu_state.n_force_qs); } /* * Convert a ->gp_state value to a character string. */ static const char *gp_state_getname(short gs) { if (gs < 0 || gs >= ARRAY_SIZE(gp_state_names)) return "???"; return gp_state_names[gs]; } /* * Complain about starvation of grace-period kthread. */ static void rcu_check_gp_kthread_starvation(void) { struct task_struct *gpk = rcu_state.gp_kthread; unsigned long j; j = jiffies - READ_ONCE(rcu_state.gp_activity); if (j > 2 * HZ) { pr_err("%s kthread starved for %ld jiffies! g%ld f%#x %s(%d) ->state=%#lx ->cpu=%d\n", rcu_state.name, j, (long)rcu_seq_current(&rcu_state.gp_seq), rcu_state.gp_flags, gp_state_getname(rcu_state.gp_state), rcu_state.gp_state, gpk ? gpk->state : ~0, gpk ? task_cpu(gpk) : -1); if (gpk) { pr_err("RCU grace-period kthread stack dump:\n"); sched_show_task(gpk); wake_up_process(gpk); } } } /* * Dump stacks of all tasks running on stalled CPUs. First try using * NMIs, but fall back to manual remote stack tracing on architectures * that don't support NMI-based stack dumps. The NMI-triggered stack * traces are more accurate because they are printed by the target CPU. */ static void rcu_dump_cpu_stacks(void) { int cpu; unsigned long flags; struct rcu_node *rnp; rcu_for_each_leaf_node(rnp) { raw_spin_lock_irqsave_rcu_node(rnp, flags); for_each_leaf_node_possible_cpu(rnp, cpu) if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) if (!trigger_single_cpu_backtrace(cpu)) dump_cpu_task(cpu); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } } /* * If too much time has passed in the current grace period, and if * so configured, go kick the relevant kthreads. */ static void rcu_stall_kick_kthreads(void) { unsigned long j; if (!rcu_kick_kthreads) return; j = READ_ONCE(rcu_state.jiffies_kick_kthreads); if (time_after(jiffies, j) && rcu_state.gp_kthread && (rcu_gp_in_progress() || READ_ONCE(rcu_state.gp_flags))) { WARN_ONCE(1, "Kicking %s grace-period kthread\n", rcu_state.name); rcu_ftrace_dump(DUMP_ALL); wake_up_process(rcu_state.gp_kthread); WRITE_ONCE(rcu_state.jiffies_kick_kthreads, j + HZ); } } static void panic_on_rcu_stall(void) { if (sysctl_panic_on_rcu_stall) panic("RCU Stall\n"); } static void print_other_cpu_stall(unsigned long gp_seq) { int cpu; unsigned long flags; unsigned long gpa; unsigned long j; int ndetected = 0; struct rcu_node *rnp = rcu_get_root(); long totqlen = 0; /* Kick and suppress, if so configured. */ rcu_stall_kick_kthreads(); if (rcu_cpu_stall_suppress) return; /* * OK, time to rat on our buddy... * See Documentation/RCU/stallwarn.txt for info on how to debug * RCU CPU stall warnings. */ pr_err("INFO: %s detected stalls on CPUs/tasks:", rcu_state.name); print_cpu_stall_info_begin(); rcu_for_each_leaf_node(rnp) { raw_spin_lock_irqsave_rcu_node(rnp, flags); ndetected += rcu_print_task_stall(rnp); if (rnp->qsmask != 0) { for_each_leaf_node_possible_cpu(rnp, cpu) if (rnp->qsmask & leaf_node_cpu_bit(rnp, cpu)) { print_cpu_stall_info(cpu); ndetected++; } } raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } print_cpu_stall_info_end(); for_each_possible_cpu(cpu) totqlen += rcu_segcblist_n_cbs(&per_cpu_ptr(&rcu_data, cpu)->cblist); pr_cont("(detected by %d, t=%ld jiffies, g=%ld, q=%lu)\n", smp_processor_id(), (long)(jiffies - rcu_state.gp_start), (long)rcu_seq_current(&rcu_state.gp_seq), totqlen); if (ndetected) { rcu_dump_cpu_stacks(); /* Complain about tasks blocking the grace period. */ rcu_print_detail_task_stall(); } else { if (rcu_seq_current(&rcu_state.gp_seq) != gp_seq) { pr_err("INFO: Stall ended before state dump start\n"); } else { j = jiffies; gpa = READ_ONCE(rcu_state.gp_activity); pr_err("All QSes seen, last %s kthread activity %ld (%ld-%ld), jiffies_till_next_fqs=%ld, root ->qsmask %#lx\n", rcu_state.name, j - gpa, j, gpa, READ_ONCE(jiffies_till_next_fqs), rcu_get_root()->qsmask); /* In this case, the current CPU might be at fault. */ sched_show_task(current); } } /* Rewrite if needed in case of slow consoles. */ if (ULONG_CMP_GE(jiffies, READ_ONCE(rcu_state.jiffies_stall))) WRITE_ONCE(rcu_state.jiffies_stall, jiffies + 3 * rcu_jiffies_till_stall_check() + 3); rcu_check_gp_kthread_starvation(); panic_on_rcu_stall(); force_quiescent_state(); /* Kick them all. */ } static void print_cpu_stall(void) { int cpu; unsigned long flags; struct rcu_data *rdp = this_cpu_ptr(&rcu_data); struct rcu_node *rnp = rcu_get_root(); long totqlen = 0; /* Kick and suppress, if so configured. */ rcu_stall_kick_kthreads(); if (rcu_cpu_stall_suppress) return; /* * OK, time to rat on ourselves... * See Documentation/RCU/stallwarn.txt for info on how to debug * RCU CPU stall warnings. */ pr_err("INFO: %s self-detected stall on CPU", rcu_state.name); print_cpu_stall_info_begin(); raw_spin_lock_irqsave_rcu_node(rdp->mynode, flags); print_cpu_stall_info(smp_processor_id()); raw_spin_unlock_irqrestore_rcu_node(rdp->mynode, flags); print_cpu_stall_info_end(); for_each_possible_cpu(cpu) totqlen += rcu_segcblist_n_cbs(&per_cpu_ptr(&rcu_data, cpu)->cblist); pr_cont(" (t=%lu jiffies g=%ld q=%lu)\n", jiffies - rcu_state.gp_start, (long)rcu_seq_current(&rcu_state.gp_seq), totqlen); rcu_check_gp_kthread_starvation(); rcu_dump_cpu_stacks(); raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Rewrite if needed in case of slow consoles. */ if (ULONG_CMP_GE(jiffies, READ_ONCE(rcu_state.jiffies_stall))) WRITE_ONCE(rcu_state.jiffies_stall, jiffies + 3 * rcu_jiffies_till_stall_check() + 3); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); panic_on_rcu_stall(); /* * Attempt to revive the RCU machinery by forcing a context switch. * * A context switch would normally allow the RCU state machine to make * progress and it could be we're stuck in kernel space without context * switches for an entirely unreasonable amount of time. */ set_tsk_need_resched(current); set_preempt_need_resched(); } static void check_cpu_stall(struct rcu_data *rdp) { unsigned long gs1; unsigned long gs2; unsigned long gps; unsigned long j; unsigned long jn; unsigned long js; struct rcu_node *rnp; if ((rcu_cpu_stall_suppress && !rcu_kick_kthreads) || !rcu_gp_in_progress()) return; rcu_stall_kick_kthreads(); j = jiffies; /* * Lots of memory barriers to reject false positives. * * The idea is to pick up rcu_state.gp_seq, then * rcu_state.jiffies_stall, then rcu_state.gp_start, and finally * another copy of rcu_state.gp_seq. These values are updated in * the opposite order with memory barriers (or equivalent) during * grace-period initialization and cleanup. Now, a false positive * can occur if we get an new value of rcu_state.gp_start and a old * value of rcu_state.jiffies_stall. But given the memory barriers, * the only way that this can happen is if one grace period ends * and another starts between these two fetches. This is detected * by comparing the second fetch of rcu_state.gp_seq with the * previous fetch from rcu_state.gp_seq. * * Given this check, comparisons of jiffies, rcu_state.jiffies_stall, * and rcu_state.gp_start suffice to forestall false positives. */ gs1 = READ_ONCE(rcu_state.gp_seq); smp_rmb(); /* Pick up ->gp_seq first... */ js = READ_ONCE(rcu_state.jiffies_stall); smp_rmb(); /* ...then ->jiffies_stall before the rest... */ gps = READ_ONCE(rcu_state.gp_start); smp_rmb(); /* ...and finally ->gp_start before ->gp_seq again. */ gs2 = READ_ONCE(rcu_state.gp_seq); if (gs1 != gs2 || ULONG_CMP_LT(j, js) || ULONG_CMP_GE(gps, js)) return; /* No stall or GP completed since entering function. */ rnp = rdp->mynode; jn = jiffies + 3 * rcu_jiffies_till_stall_check() + 3; if (rcu_gp_in_progress() && (READ_ONCE(rnp->qsmask) & rdp->grpmask) && cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) { /* We haven't checked in, so go dump stack. */ print_cpu_stall(); } else if (rcu_gp_in_progress() && ULONG_CMP_GE(j, js + RCU_STALL_RAT_DELAY) && cmpxchg(&rcu_state.jiffies_stall, js, jn) == js) { /* They had a few time units to dump stack, so complain. */ print_other_cpu_stall(gs2); } } /** * rcu_cpu_stall_reset - prevent further stall warnings in current grace period * * Set the stall-warning timeout way off into the future, thus preventing * any RCU CPU stall-warning messages from appearing in the current set of * RCU grace periods. * * The caller must disable hard irqs. */ void rcu_cpu_stall_reset(void) { WRITE_ONCE(rcu_state.jiffies_stall, jiffies + ULONG_MAX / 2); } /* Trace-event wrapper function for trace_rcu_future_grace_period. */ static void trace_rcu_this_gp(struct rcu_node *rnp, struct rcu_data *rdp, unsigned long gp_seq_req, const char *s) { trace_rcu_future_grace_period(rcu_state.name, rnp->gp_seq, gp_seq_req, rnp->level, rnp->grplo, rnp->grphi, s); } /* * rcu_start_this_gp - Request the start of a particular grace period * @rnp_start: The leaf node of the CPU from which to start. * @rdp: The rcu_data corresponding to the CPU from which to start. * @gp_seq_req: The gp_seq of the grace period to start. * * Start the specified grace period, as needed to handle newly arrived * callbacks. The required future grace periods are recorded in each * rcu_node structure's ->gp_seq_needed field. Returns true if there * is reason to awaken the grace-period kthread. * * The caller must hold the specified rcu_node structure's ->lock, which * is why the caller is responsible for waking the grace-period kthread. * * Returns true if the GP thread needs to be awakened else false. */ static bool rcu_start_this_gp(struct rcu_node *rnp_start, struct rcu_data *rdp, unsigned long gp_seq_req) { bool ret = false; struct rcu_node *rnp; /* * Use funnel locking to either acquire the root rcu_node * structure's lock or bail out if the need for this grace period * has already been recorded -- or if that grace period has in * fact already started. If there is already a grace period in * progress in a non-leaf node, no recording is needed because the * end of the grace period will scan the leaf rcu_node structures. * Note that rnp_start->lock must not be released. */ raw_lockdep_assert_held_rcu_node(rnp_start); trace_rcu_this_gp(rnp_start, rdp, gp_seq_req, TPS("Startleaf")); for (rnp = rnp_start; 1; rnp = rnp->parent) { if (rnp != rnp_start) raw_spin_lock_rcu_node(rnp); if (ULONG_CMP_GE(rnp->gp_seq_needed, gp_seq_req) || rcu_seq_started(&rnp->gp_seq, gp_seq_req) || (rnp != rnp_start && rcu_seq_state(rcu_seq_current(&rnp->gp_seq)))) { trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Prestarted")); goto unlock_out; } rnp->gp_seq_needed = gp_seq_req; if (rcu_seq_state(rcu_seq_current(&rnp->gp_seq))) { /* * We just marked the leaf or internal node, and a * grace period is in progress, which means that * rcu_gp_cleanup() will see the marking. Bail to * reduce contention. */ trace_rcu_this_gp(rnp_start, rdp, gp_seq_req, TPS("Startedleaf")); goto unlock_out; } if (rnp != rnp_start && rnp->parent != NULL) raw_spin_unlock_rcu_node(rnp); if (!rnp->parent) break; /* At root, and perhaps also leaf. */ } /* If GP already in progress, just leave, otherwise start one. */ if (rcu_gp_in_progress()) { trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedleafroot")); goto unlock_out; } trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("Startedroot")); WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags | RCU_GP_FLAG_INIT); rcu_state.gp_req_activity = jiffies; if (!rcu_state.gp_kthread) { trace_rcu_this_gp(rnp, rdp, gp_seq_req, TPS("NoGPkthread")); goto unlock_out; } trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), TPS("newreq")); ret = true; /* Caller must wake GP kthread. */ unlock_out: /* Push furthest requested GP to leaf node and rcu_data structure. */ if (ULONG_CMP_LT(gp_seq_req, rnp->gp_seq_needed)) { rnp_start->gp_seq_needed = rnp->gp_seq_needed; rdp->gp_seq_needed = rnp->gp_seq_needed; } if (rnp != rnp_start) raw_spin_unlock_rcu_node(rnp); return ret; } /* * Clean up any old requests for the just-ended grace period. Also return * whether any additional grace periods have been requested. */ static bool rcu_future_gp_cleanup(struct rcu_node *rnp) { bool needmore; struct rcu_data *rdp = this_cpu_ptr(&rcu_data); needmore = ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed); if (!needmore) rnp->gp_seq_needed = rnp->gp_seq; /* Avoid counter wrap. */ trace_rcu_this_gp(rnp, rdp, rnp->gp_seq, needmore ? TPS("CleanupMore") : TPS("Cleanup")); return needmore; } /* * Awaken the grace-period kthread. Don't do a self-awaken, and don't * bother awakening when there is nothing for the grace-period kthread * to do (as in several CPUs raced to awaken, and we lost), and finally * don't try to awaken a kthread that has not yet been created. */ static void rcu_gp_kthread_wake(void) { if (current == rcu_state.gp_kthread || !READ_ONCE(rcu_state.gp_flags) || !rcu_state.gp_kthread) return; swake_up_one(&rcu_state.gp_wq); } /* * If there is room, assign a ->gp_seq number to any callbacks on this * CPU that have not already been assigned. Also accelerate any callbacks * that were previously assigned a ->gp_seq number that has since proven * to be too conservative, which can happen if callbacks get assigned a * ->gp_seq number while RCU is idle, but with reference to a non-root * rcu_node structure. This function is idempotent, so it does not hurt * to call it repeatedly. Returns an flag saying that we should awaken * the RCU grace-period kthread. * * The caller must hold rnp->lock with interrupts disabled. */ static bool rcu_accelerate_cbs(struct rcu_node *rnp, struct rcu_data *rdp) { unsigned long gp_seq_req; bool ret = false; raw_lockdep_assert_held_rcu_node(rnp); /* If no pending (not yet ready to invoke) callbacks, nothing to do. */ if (!rcu_segcblist_pend_cbs(&rdp->cblist)) return false; /* * Callbacks are often registered with incomplete grace-period * information. Something about the fact that getting exact * information requires acquiring a global lock... RCU therefore * makes a conservative estimate of the grace period number at which * a given callback will become ready to invoke. The following * code checks this estimate and improves it when possible, thus * accelerating callback invocation to an earlier grace-period * number. */ gp_seq_req = rcu_seq_snap(&rcu_state.gp_seq); if (rcu_segcblist_accelerate(&rdp->cblist, gp_seq_req)) ret = rcu_start_this_gp(rnp, rdp, gp_seq_req); /* Trace depending on how much we were able to accelerate. */ if (rcu_segcblist_restempty(&rdp->cblist, RCU_WAIT_TAIL)) trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("AccWaitCB")); else trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("AccReadyCB")); return ret; } /* * Similar to rcu_accelerate_cbs(), but does not require that the leaf * rcu_node structure's ->lock be held. It consults the cached value * of ->gp_seq_needed in the rcu_data structure, and if that indicates * that a new grace-period request be made, invokes rcu_accelerate_cbs() * while holding the leaf rcu_node structure's ->lock. */ static void rcu_accelerate_cbs_unlocked(struct rcu_node *rnp, struct rcu_data *rdp) { unsigned long c; bool needwake; lockdep_assert_irqs_disabled(); c = rcu_seq_snap(&rcu_state.gp_seq); if (!rdp->gpwrap && ULONG_CMP_GE(rdp->gp_seq_needed, c)) { /* Old request still live, so mark recent callbacks. */ (void)rcu_segcblist_accelerate(&rdp->cblist, c); return; } raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ needwake = rcu_accelerate_cbs(rnp, rdp); raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ if (needwake) rcu_gp_kthread_wake(); } /* * Move any callbacks whose grace period has completed to the * RCU_DONE_TAIL sublist, then compact the remaining sublists and * assign ->gp_seq numbers to any callbacks in the RCU_NEXT_TAIL * sublist. This function is idempotent, so it does not hurt to * invoke it repeatedly. As long as it is not invoked -too- often... * Returns true if the RCU grace-period kthread needs to be awakened. * * The caller must hold rnp->lock with interrupts disabled. */ static bool rcu_advance_cbs(struct rcu_node *rnp, struct rcu_data *rdp) { raw_lockdep_assert_held_rcu_node(rnp); /* If no pending (not yet ready to invoke) callbacks, nothing to do. */ if (!rcu_segcblist_pend_cbs(&rdp->cblist)) return false; /* * Find all callbacks whose ->gp_seq numbers indicate that they * are ready to invoke, and put them into the RCU_DONE_TAIL sublist. */ rcu_segcblist_advance(&rdp->cblist, rnp->gp_seq); /* Classify any remaining callbacks. */ return rcu_accelerate_cbs(rnp, rdp); } /* * Update CPU-local rcu_data state to record the beginnings and ends of * grace periods. The caller must hold the ->lock of the leaf rcu_node * structure corresponding to the current CPU, and must have irqs disabled. * Returns true if the grace-period kthread needs to be awakened. */ static bool __note_gp_changes(struct rcu_node *rnp, struct rcu_data *rdp) { bool ret; bool need_gp; raw_lockdep_assert_held_rcu_node(rnp); if (rdp->gp_seq == rnp->gp_seq) return false; /* Nothing to do. */ /* Handle the ends of any preceding grace periods first. */ if (rcu_seq_completed_gp(rdp->gp_seq, rnp->gp_seq) || unlikely(READ_ONCE(rdp->gpwrap))) { ret = rcu_advance_cbs(rnp, rdp); /* Advance callbacks. */ trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuend")); } else { ret = rcu_accelerate_cbs(rnp, rdp); /* Recent callbacks. */ } /* Now handle the beginnings of any new-to-this-CPU grace periods. */ if (rcu_seq_new_gp(rdp->gp_seq, rnp->gp_seq) || unlikely(READ_ONCE(rdp->gpwrap))) { /* * If the current grace period is waiting for this CPU, * set up to detect a quiescent state, otherwise don't * go looking for one. */ trace_rcu_grace_period(rcu_state.name, rnp->gp_seq, TPS("cpustart")); need_gp = !!(rnp->qsmask & rdp->grpmask); rdp->cpu_no_qs.b.norm = need_gp; rdp->core_needs_qs = need_gp; zero_cpu_stall_ticks(rdp); } rdp->gp_seq = rnp->gp_seq; /* Remember new grace-period state. */ if (ULONG_CMP_GE(rnp->gp_seq_needed, rdp->gp_seq_needed) || rdp->gpwrap) rdp->gp_seq_needed = rnp->gp_seq_needed; WRITE_ONCE(rdp->gpwrap, false); rcu_gpnum_ovf(rnp, rdp); return ret; } static void note_gp_changes(struct rcu_data *rdp) { unsigned long flags; bool needwake; struct rcu_node *rnp; local_irq_save(flags); rnp = rdp->mynode; if ((rdp->gp_seq == rcu_seq_current(&rnp->gp_seq) && !unlikely(READ_ONCE(rdp->gpwrap))) || /* w/out lock. */ !raw_spin_trylock_rcu_node(rnp)) { /* irqs already off, so later. */ local_irq_restore(flags); return; } needwake = __note_gp_changes(rnp, rdp); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); if (needwake) rcu_gp_kthread_wake(); } static void rcu_gp_slow(int delay) { if (delay > 0 && !(rcu_seq_ctr(rcu_state.gp_seq) % (rcu_num_nodes * PER_RCU_NODE_PERIOD * delay))) schedule_timeout_uninterruptible(delay); } /* * Initialize a new grace period. Return false if no grace period required. */ static bool rcu_gp_init(void) { unsigned long flags; unsigned long oldmask; unsigned long mask; struct rcu_data *rdp; struct rcu_node *rnp = rcu_get_root(); WRITE_ONCE(rcu_state.gp_activity, jiffies); raw_spin_lock_irq_rcu_node(rnp); if (!READ_ONCE(rcu_state.gp_flags)) { /* Spurious wakeup, tell caller to go back to sleep. */ raw_spin_unlock_irq_rcu_node(rnp); return false; } WRITE_ONCE(rcu_state.gp_flags, 0); /* Clear all flags: New GP. */ if (WARN_ON_ONCE(rcu_gp_in_progress())) { /* * Grace period already in progress, don't start another. * Not supposed to be able to happen. */ raw_spin_unlock_irq_rcu_node(rnp); return false; } /* Advance to a new grace period and initialize state. */ record_gp_stall_check_time(); /* Record GP times before starting GP, hence rcu_seq_start(). */ rcu_seq_start(&rcu_state.gp_seq); trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("start")); raw_spin_unlock_irq_rcu_node(rnp); /* * Apply per-leaf buffered online and offline operations to the * rcu_node tree. Note that this new grace period need not wait * for subsequent online CPUs, and that quiescent-state forcing * will handle subsequent offline CPUs. */ rcu_state.gp_state = RCU_GP_ONOFF; rcu_for_each_leaf_node(rnp) { raw_spin_lock(&rcu_state.ofl_lock); raw_spin_lock_irq_rcu_node(rnp); if (rnp->qsmaskinit == rnp->qsmaskinitnext && !rnp->wait_blkd_tasks) { /* Nothing to do on this leaf rcu_node structure. */ raw_spin_unlock_irq_rcu_node(rnp); raw_spin_unlock(&rcu_state.ofl_lock); continue; } /* Record old state, apply changes to ->qsmaskinit field. */ oldmask = rnp->qsmaskinit; rnp->qsmaskinit = rnp->qsmaskinitnext; /* If zero-ness of ->qsmaskinit changed, propagate up tree. */ if (!oldmask != !rnp->qsmaskinit) { if (!oldmask) { /* First online CPU for rcu_node. */ if (!rnp->wait_blkd_tasks) /* Ever offline? */ rcu_init_new_rnp(rnp); } else if (rcu_preempt_has_tasks(rnp)) { rnp->wait_blkd_tasks = true; /* blocked tasks */ } else { /* Last offline CPU and can propagate. */ rcu_cleanup_dead_rnp(rnp); } } /* * If all waited-on tasks from prior grace period are * done, and if all this rcu_node structure's CPUs are * still offline, propagate up the rcu_node tree and * clear ->wait_blkd_tasks. Otherwise, if one of this * rcu_node structure's CPUs has since come back online, * simply clear ->wait_blkd_tasks. */ if (rnp->wait_blkd_tasks && (!rcu_preempt_has_tasks(rnp) || rnp->qsmaskinit)) { rnp->wait_blkd_tasks = false; if (!rnp->qsmaskinit) rcu_cleanup_dead_rnp(rnp); } raw_spin_unlock_irq_rcu_node(rnp); raw_spin_unlock(&rcu_state.ofl_lock); } rcu_gp_slow(gp_preinit_delay); /* Races with CPU hotplug. */ /* * Set the quiescent-state-needed bits in all the rcu_node * structures for all currently online CPUs in breadth-first * order, starting from the root rcu_node structure, relying on the * layout of the tree within the rcu_state.node[] array. Note that * other CPUs will access only the leaves of the hierarchy, thus * seeing that no grace period is in progress, at least until the * corresponding leaf node has been initialized. * * The grace period cannot complete until the initialization * process finishes, because this kthread handles both. */ rcu_state.gp_state = RCU_GP_INIT; rcu_for_each_node_breadth_first(rnp) { rcu_gp_slow(gp_init_delay); raw_spin_lock_irqsave_rcu_node(rnp, flags); rdp = this_cpu_ptr(&rcu_data); rcu_preempt_check_blocked_tasks(rnp); rnp->qsmask = rnp->qsmaskinit; WRITE_ONCE(rnp->gp_seq, rcu_state.gp_seq); if (rnp == rdp->mynode) (void)__note_gp_changes(rnp, rdp); rcu_preempt_boost_start_gp(rnp); trace_rcu_grace_period_init(rcu_state.name, rnp->gp_seq, rnp->level, rnp->grplo, rnp->grphi, rnp->qsmask); /* Quiescent states for tasks on any now-offline CPUs. */ mask = rnp->qsmask & ~rnp->qsmaskinitnext; rnp->rcu_gp_init_mask = mask; if ((mask || rnp->wait_blkd_tasks) && rcu_is_leaf_node(rnp)) rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); else raw_spin_unlock_irq_rcu_node(rnp); cond_resched_tasks_rcu_qs(); WRITE_ONCE(rcu_state.gp_activity, jiffies); } return true; } /* * Helper function for swait_event_idle_exclusive() wakeup at force-quiescent-state * time. */ static bool rcu_gp_fqs_check_wake(int *gfp) { struct rcu_node *rnp = rcu_get_root(); /* Someone like call_rcu() requested a force-quiescent-state scan. */ *gfp = READ_ONCE(rcu_state.gp_flags); if (*gfp & RCU_GP_FLAG_FQS) return true; /* The current grace period has completed. */ if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp)) return true; return false; } /* * Do one round of quiescent-state forcing. */ static void rcu_gp_fqs(bool first_time) { struct rcu_node *rnp = rcu_get_root(); WRITE_ONCE(rcu_state.gp_activity, jiffies); rcu_state.n_force_qs++; if (first_time) { /* Collect dyntick-idle snapshots. */ force_qs_rnp(dyntick_save_progress_counter); } else { /* Handle dyntick-idle and offline CPUs. */ force_qs_rnp(rcu_implicit_dynticks_qs); } /* Clear flag to prevent immediate re-entry. */ if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) { raw_spin_lock_irq_rcu_node(rnp); WRITE_ONCE(rcu_state.gp_flags, READ_ONCE(rcu_state.gp_flags) & ~RCU_GP_FLAG_FQS); raw_spin_unlock_irq_rcu_node(rnp); } } /* * Loop doing repeated quiescent-state forcing until the grace period ends. */ static void rcu_gp_fqs_loop(void) { bool first_gp_fqs; int gf; unsigned long j; int ret; struct rcu_node *rnp = rcu_get_root(); first_gp_fqs = true; j = READ_ONCE(jiffies_till_first_fqs); ret = 0; for (;;) { if (!ret) { rcu_state.jiffies_force_qs = jiffies + j; WRITE_ONCE(rcu_state.jiffies_kick_kthreads, jiffies + 3 * j); } trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), TPS("fqswait")); rcu_state.gp_state = RCU_GP_WAIT_FQS; ret = swait_event_idle_timeout_exclusive( rcu_state.gp_wq, rcu_gp_fqs_check_wake(&gf), j); rcu_state.gp_state = RCU_GP_DOING_FQS; /* Locking provides needed memory barriers. */ /* If grace period done, leave loop. */ if (!READ_ONCE(rnp->qsmask) && !rcu_preempt_blocked_readers_cgp(rnp)) break; /* If time for quiescent-state forcing, do it. */ if (ULONG_CMP_GE(jiffies, rcu_state.jiffies_force_qs) || (gf & RCU_GP_FLAG_FQS)) { trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), TPS("fqsstart")); rcu_gp_fqs(first_gp_fqs); first_gp_fqs = false; trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), TPS("fqsend")); cond_resched_tasks_rcu_qs(); WRITE_ONCE(rcu_state.gp_activity, jiffies); ret = 0; /* Force full wait till next FQS. */ j = READ_ONCE(jiffies_till_next_fqs); } else { /* Deal with stray signal. */ cond_resched_tasks_rcu_qs(); WRITE_ONCE(rcu_state.gp_activity, jiffies); WARN_ON(signal_pending(current)); trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), TPS("fqswaitsig")); ret = 1; /* Keep old FQS timing. */ j = jiffies; if (time_after(jiffies, rcu_state.jiffies_force_qs)) j = 1; else j = rcu_state.jiffies_force_qs - j; } } } /* * Clean up after the old grace period. */ static void rcu_gp_cleanup(void) { unsigned long gp_duration; bool needgp = false; unsigned long new_gp_seq; struct rcu_data *rdp; struct rcu_node *rnp = rcu_get_root(); struct swait_queue_head *sq; WRITE_ONCE(rcu_state.gp_activity, jiffies); raw_spin_lock_irq_rcu_node(rnp); gp_duration = jiffies - rcu_state.gp_start; if (gp_duration > rcu_state.gp_max) rcu_state.gp_max = gp_duration; /* * We know the grace period is complete, but to everyone else * it appears to still be ongoing. But it is also the case * that to everyone else it looks like there is nothing that * they can do to advance the grace period. It is therefore * safe for us to drop the lock in order to mark the grace * period as completed in all of the rcu_node structures. */ raw_spin_unlock_irq_rcu_node(rnp); /* * Propagate new ->gp_seq value to rcu_node structures so that * other CPUs don't have to wait until the start of the next grace * period to process their callbacks. This also avoids some nasty * RCU grace-period initialization races by forcing the end of * the current grace period to be completely recorded in all of * the rcu_node structures before the beginning of the next grace * period is recorded in any of the rcu_node structures. */ new_gp_seq = rcu_state.gp_seq; rcu_seq_end(&new_gp_seq); rcu_for_each_node_breadth_first(rnp) { raw_spin_lock_irq_rcu_node(rnp); if (WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp))) dump_blkd_tasks(rnp, 10); WARN_ON_ONCE(rnp->qsmask); WRITE_ONCE(rnp->gp_seq, new_gp_seq); rdp = this_cpu_ptr(&rcu_data); if (rnp == rdp->mynode) needgp = __note_gp_changes(rnp, rdp) || needgp; /* smp_mb() provided by prior unlock-lock pair. */ needgp = rcu_future_gp_cleanup(rnp) || needgp; sq = rcu_nocb_gp_get(rnp); raw_spin_unlock_irq_rcu_node(rnp); rcu_nocb_gp_cleanup(sq); cond_resched_tasks_rcu_qs(); WRITE_ONCE(rcu_state.gp_activity, jiffies); rcu_gp_slow(gp_cleanup_delay); } rnp = rcu_get_root(); raw_spin_lock_irq_rcu_node(rnp); /* GP before ->gp_seq update. */ /* Declare grace period done. */ rcu_seq_end(&rcu_state.gp_seq); trace_rcu_grace_period(rcu_state.name, rcu_state.gp_seq, TPS("end")); rcu_state.gp_state = RCU_GP_IDLE; /* Check for GP requests since above loop. */ rdp = this_cpu_ptr(&rcu_data); if (!needgp && ULONG_CMP_LT(rnp->gp_seq, rnp->gp_seq_needed)) { trace_rcu_this_gp(rnp, rdp, rnp->gp_seq_needed, TPS("CleanupMore")); needgp = true; } /* Advance CBs to reduce false positives below. */ if (!rcu_accelerate_cbs(rnp, rdp) && needgp) { WRITE_ONCE(rcu_state.gp_flags, RCU_GP_FLAG_INIT); rcu_state.gp_req_activity = jiffies; trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), TPS("newreq")); } else { WRITE_ONCE(rcu_state.gp_flags, rcu_state.gp_flags & RCU_GP_FLAG_INIT); } raw_spin_unlock_irq_rcu_node(rnp); } /* * Body of kthread that handles grace periods. */ static int __noreturn rcu_gp_kthread(void *unused) { rcu_bind_gp_kthread(); for (;;) { /* Handle grace-period start. */ for (;;) { trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), TPS("reqwait")); rcu_state.gp_state = RCU_GP_WAIT_GPS; swait_event_idle_exclusive(rcu_state.gp_wq, READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_INIT); rcu_state.gp_state = RCU_GP_DONE_GPS; /* Locking provides needed memory barrier. */ if (rcu_gp_init()) break; cond_resched_tasks_rcu_qs(); WRITE_ONCE(rcu_state.gp_activity, jiffies); WARN_ON(signal_pending(current)); trace_rcu_grace_period(rcu_state.name, READ_ONCE(rcu_state.gp_seq), TPS("reqwaitsig")); } /* Handle quiescent-state forcing. */ rcu_gp_fqs_loop(); /* Handle grace-period end. */ rcu_state.gp_state = RCU_GP_CLEANUP; rcu_gp_cleanup(); rcu_state.gp_state = RCU_GP_CLEANED; } } /* * Report a full set of quiescent states to the rcu_state data structure. * Invoke rcu_gp_kthread_wake() to awaken the grace-period kthread if * another grace period is required. Whether we wake the grace-period * kthread or it awakens itself for the next round of quiescent-state * forcing, that kthread will clean up after the just-completed grace * period. Note that the caller must hold rnp->lock, which is released * before return. */ static void rcu_report_qs_rsp(unsigned long flags) __releases(rcu_get_root()->lock) { raw_lockdep_assert_held_rcu_node(rcu_get_root()); WARN_ON_ONCE(!rcu_gp_in_progress()); WRITE_ONCE(rcu_state.gp_flags, READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); raw_spin_unlock_irqrestore_rcu_node(rcu_get_root(), flags); rcu_gp_kthread_wake(); } /* * Similar to rcu_report_qs_rdp(), for which it is a helper function. * Allows quiescent states for a group of CPUs to be reported at one go * to the specified rcu_node structure, though all the CPUs in the group * must be represented by the same rcu_node structure (which need not be a * leaf rcu_node structure, though it often will be). The gps parameter * is the grace-period snapshot, which means that the quiescent states * are valid only if rnp->gp_seq is equal to gps. That structure's lock * must be held upon entry, and it is released before return. * * As a special case, if mask is zero, the bit-already-cleared check is * disabled. This allows propagating quiescent state due to resumed tasks * during grace-period initialization. */ static void rcu_report_qs_rnp(unsigned long mask, struct rcu_node *rnp, unsigned long gps, unsigned long flags) __releases(rnp->lock) { unsigned long oldmask = 0; struct rcu_node *rnp_c; raw_lockdep_assert_held_rcu_node(rnp); /* Walk up the rcu_node hierarchy. */ for (;;) { if ((!(rnp->qsmask & mask) && mask) || rnp->gp_seq != gps) { /* * Our bit has already been cleared, or the * relevant grace period is already over, so done. */ raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return; } WARN_ON_ONCE(oldmask); /* Any child must be all zeroed! */ WARN_ON_ONCE(!rcu_is_leaf_node(rnp) && rcu_preempt_blocked_readers_cgp(rnp)); rnp->qsmask &= ~mask; trace_rcu_quiescent_state_report(rcu_state.name, rnp->gp_seq, mask, rnp->qsmask, rnp->level, rnp->grplo, rnp->grphi, !!rnp->gp_tasks); if (rnp->qsmask != 0 || rcu_preempt_blocked_readers_cgp(rnp)) { /* Other bits still set at this level, so done. */ raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return; } rnp->completedqs = rnp->gp_seq; mask = rnp->grpmask; if (rnp->parent == NULL) { /* No more levels. Exit loop holding root lock. */ break; } raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rnp_c = rnp; rnp = rnp->parent; raw_spin_lock_irqsave_rcu_node(rnp, flags); oldmask = rnp_c->qsmask; } /* * Get here if we are the last CPU to pass through a quiescent * state for this grace period. Invoke rcu_report_qs_rsp() * to clean up and start the next grace period if one is needed. */ rcu_report_qs_rsp(flags); /* releases rnp->lock. */ } /* * Record a quiescent state for all tasks that were previously queued * on the specified rcu_node structure and that were blocking the current * RCU grace period. The caller must hold the corresponding rnp->lock with * irqs disabled, and this lock is released upon return, but irqs remain * disabled. */ static void __maybe_unused rcu_report_unblock_qs_rnp(struct rcu_node *rnp, unsigned long flags) __releases(rnp->lock) { unsigned long gps; unsigned long mask; struct rcu_node *rnp_p; raw_lockdep_assert_held_rcu_node(rnp); if (WARN_ON_ONCE(!IS_ENABLED(CONFIG_PREEMPT)) || WARN_ON_ONCE(rcu_preempt_blocked_readers_cgp(rnp)) || rnp->qsmask != 0) { raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return; /* Still need more quiescent states! */ } rnp->completedqs = rnp->gp_seq; rnp_p = rnp->parent; if (rnp_p == NULL) { /* * Only one rcu_node structure in the tree, so don't * try to report up to its nonexistent parent! */ rcu_report_qs_rsp(flags); return; } /* Report up the rest of the hierarchy, tracking current ->gp_seq. */ gps = rnp->gp_seq; mask = rnp->grpmask; raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ raw_spin_lock_rcu_node(rnp_p); /* irqs already disabled. */ rcu_report_qs_rnp(mask, rnp_p, gps, flags); } /* * Record a quiescent state for the specified CPU to that CPU's rcu_data * structure. This must be called from the specified CPU. */ static void rcu_report_qs_rdp(int cpu, struct rcu_data *rdp) { unsigned long flags; unsigned long mask; bool needwake; struct rcu_node *rnp; rnp = rdp->mynode; raw_spin_lock_irqsave_rcu_node(rnp, flags); if (rdp->cpu_no_qs.b.norm || rdp->gp_seq != rnp->gp_seq || rdp->gpwrap) { /* * The grace period in which this quiescent state was * recorded has ended, so don't report it upwards. * We will instead need a new quiescent state that lies * within the current grace period. */ rdp->cpu_no_qs.b.norm = true; /* need qs for new gp. */ raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return; } mask = rdp->grpmask; if ((rnp->qsmask & mask) == 0) { raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } else { rdp->core_needs_qs = false; /* * This GP can't end until cpu checks in, so all of our * callbacks can be processed during the next GP. */ needwake = rcu_accelerate_cbs(rnp, rdp); rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); /* ^^^ Released rnp->lock */ if (needwake) rcu_gp_kthread_wake(); } } /* * Check to see if there is a new grace period of which this CPU * is not yet aware, and if so, set up local rcu_data state for it. * Otherwise, see if this CPU has just passed through its first * quiescent state for this grace period, and record that fact if so. */ static void rcu_check_quiescent_state(struct rcu_data *rdp) { /* Check for grace-period ends and beginnings. */ note_gp_changes(rdp); /* * Does this CPU still need to do its part for current grace period? * If no, return and let the other CPUs do their part as well. */ if (!rdp->core_needs_qs) return; /* * Was there a quiescent state since the beginning of the grace * period? If no, then exit and wait for the next call. */ if (rdp->cpu_no_qs.b.norm) return; /* * Tell RCU we are done (but rcu_report_qs_rdp() will be the * judge of that). */ rcu_report_qs_rdp(rdp->cpu, rdp); } /* * Near the end of the offline process. Trace the fact that this CPU * is going offline. */ int rcutree_dying_cpu(unsigned int cpu) { RCU_TRACE(bool blkd;) RCU_TRACE(struct rcu_data *rdp = this_cpu_ptr(&rcu_data);) RCU_TRACE(struct rcu_node *rnp = rdp->mynode;) if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) return 0; RCU_TRACE(blkd = !!(rnp->qsmask & rdp->grpmask);) trace_rcu_grace_period(rcu_state.name, rnp->gp_seq, blkd ? TPS("cpuofl") : TPS("cpuofl-bgp")); return 0; } /* * All CPUs for the specified rcu_node structure have gone offline, * and all tasks that were preempted within an RCU read-side critical * section while running on one of those CPUs have since exited their RCU * read-side critical section. Some other CPU is reporting this fact with * the specified rcu_node structure's ->lock held and interrupts disabled. * This function therefore goes up the tree of rcu_node structures, * clearing the corresponding bits in the ->qsmaskinit fields. Note that * the leaf rcu_node structure's ->qsmaskinit field has already been * updated. * * This function does check that the specified rcu_node structure has * all CPUs offline and no blocked tasks, so it is OK to invoke it * prematurely. That said, invoking it after the fact will cost you * a needless lock acquisition. So once it has done its work, don't * invoke it again. */ static void rcu_cleanup_dead_rnp(struct rcu_node *rnp_leaf) { long mask; struct rcu_node *rnp = rnp_leaf; raw_lockdep_assert_held_rcu_node(rnp_leaf); if (!IS_ENABLED(CONFIG_HOTPLUG_CPU) || WARN_ON_ONCE(rnp_leaf->qsmaskinit) || WARN_ON_ONCE(rcu_preempt_has_tasks(rnp_leaf))) return; for (;;) { mask = rnp->grpmask; rnp = rnp->parent; if (!rnp) break; raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ rnp->qsmaskinit &= ~mask; /* Between grace periods, so better already be zero! */ WARN_ON_ONCE(rnp->qsmask); if (rnp->qsmaskinit) { raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ return; } raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ } } /* * The CPU has been completely removed, and some other CPU is reporting * this fact from process context. Do the remainder of the cleanup. * There can only be one CPU hotplug operation at a time, so no need for * explicit locking. */ int rcutree_dead_cpu(unsigned int cpu) { struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ if (!IS_ENABLED(CONFIG_HOTPLUG_CPU)) return 0; /* Adjust any no-longer-needed kthreads. */ rcu_boost_kthread_setaffinity(rnp, -1); /* Do any needed no-CB deferred wakeups from this CPU. */ do_nocb_deferred_wakeup(per_cpu_ptr(&rcu_data, cpu)); return 0; } /* * Invoke any RCU callbacks that have made it to the end of their grace * period. Thottle as specified by rdp->blimit. */ static void rcu_do_batch(struct rcu_data *rdp) { unsigned long flags; struct rcu_head *rhp; struct rcu_cblist rcl = RCU_CBLIST_INITIALIZER(rcl); long bl, count; /* If no callbacks are ready, just return. */ if (!rcu_segcblist_ready_cbs(&rdp->cblist)) { trace_rcu_batch_start(rcu_state.name, rcu_segcblist_n_lazy_cbs(&rdp->cblist), rcu_segcblist_n_cbs(&rdp->cblist), 0); trace_rcu_batch_end(rcu_state.name, 0, !rcu_segcblist_empty(&rdp->cblist), need_resched(), is_idle_task(current), rcu_is_callbacks_kthread()); return; } /* * Extract the list of ready callbacks, disabling to prevent * races with call_rcu() from interrupt handlers. Leave the * callback counts, as rcu_barrier() needs to be conservative. */ local_irq_save(flags); WARN_ON_ONCE(cpu_is_offline(smp_processor_id())); bl = rdp->blimit; trace_rcu_batch_start(rcu_state.name, rcu_segcblist_n_lazy_cbs(&rdp->cblist), rcu_segcblist_n_cbs(&rdp->cblist), bl); rcu_segcblist_extract_done_cbs(&rdp->cblist, &rcl); local_irq_restore(flags); /* Invoke callbacks. */ rhp = rcu_cblist_dequeue(&rcl); for (; rhp; rhp = rcu_cblist_dequeue(&rcl)) { debug_rcu_head_unqueue(rhp); if (__rcu_reclaim(rcu_state.name, rhp)) rcu_cblist_dequeued_lazy(&rcl); /* * Stop only if limit reached and CPU has something to do. * Note: The rcl structure counts down from zero. */ if (-rcl.len >= bl && (need_resched() || (!is_idle_task(current) && !rcu_is_callbacks_kthread()))) break; } local_irq_save(flags); count = -rcl.len; trace_rcu_batch_end(rcu_state.name, count, !!rcl.head, need_resched(), is_idle_task(current), rcu_is_callbacks_kthread()); /* Update counts and requeue any remaining callbacks. */ rcu_segcblist_insert_done_cbs(&rdp->cblist, &rcl); smp_mb(); /* List handling before counting for rcu_barrier(). */ rcu_segcblist_insert_count(&rdp->cblist, &rcl); /* Reinstate batch limit if we have worked down the excess. */ count = rcu_segcblist_n_cbs(&rdp->cblist); if (rdp->blimit == LONG_MAX && count <= qlowmark) rdp->blimit = blimit; /* Reset ->qlen_last_fqs_check trigger if enough CBs have drained. */ if (count == 0 && rdp->qlen_last_fqs_check != 0) { rdp->qlen_last_fqs_check = 0; rdp->n_force_qs_snap = rcu_state.n_force_qs; } else if (count < rdp->qlen_last_fqs_check - qhimark) rdp->qlen_last_fqs_check = count; /* * The following usually indicates a double call_rcu(). To track * this down, try building with CONFIG_DEBUG_OBJECTS_RCU_HEAD=y. */ WARN_ON_ONCE(rcu_segcblist_empty(&rdp->cblist) != (count == 0)); local_irq_restore(flags); /* Re-invoke RCU core processing if there are callbacks remaining. */ if (rcu_segcblist_ready_cbs(&rdp->cblist)) invoke_rcu_core(); } /* * Check to see if this CPU is in a non-context-switch quiescent state * (user mode or idle loop for rcu, non-softirq execution for rcu_bh). * Also schedule RCU core processing. * * This function must be called from hardirq context. It is normally * invoked from the scheduling-clock interrupt. */ void rcu_check_callbacks(int user) { trace_rcu_utilization(TPS("Start scheduler-tick")); raw_cpu_inc(rcu_data.ticks_this_gp); /* The load-acquire pairs with the store-release setting to true. */ if (smp_load_acquire(this_cpu_ptr(&rcu_data.rcu_urgent_qs))) { /* Idle and userspace execution already are quiescent states. */ if (!rcu_is_cpu_rrupt_from_idle() && !user) { set_tsk_need_resched(current); set_preempt_need_resched(); } __this_cpu_write(rcu_data.rcu_urgent_qs, false); } rcu_flavor_check_callbacks(user); if (rcu_pending()) invoke_rcu_core(); trace_rcu_utilization(TPS("End scheduler-tick")); } /* * Scan the leaf rcu_node structures, processing dyntick state for any that * have not yet encountered a quiescent state, using the function specified. * Also initiate boosting for any threads blocked on the root rcu_node. * * The caller must have suppressed start of new grace periods. */ static void force_qs_rnp(int (*f)(struct rcu_data *rdp)) { int cpu; unsigned long flags; unsigned long mask; struct rcu_node *rnp; rcu_for_each_leaf_node(rnp) { cond_resched_tasks_rcu_qs(); mask = 0; raw_spin_lock_irqsave_rcu_node(rnp, flags); if (rnp->qsmask == 0) { if (!IS_ENABLED(CONFIG_PREEMPT) || rcu_preempt_blocked_readers_cgp(rnp)) { /* * No point in scanning bits because they * are all zero. But we might need to * priority-boost blocked readers. */ rcu_initiate_boost(rnp, flags); /* rcu_initiate_boost() releases rnp->lock */ continue; } raw_spin_unlock_irqrestore_rcu_node(rnp, flags); continue; } for_each_leaf_node_possible_cpu(rnp, cpu) { unsigned long bit = leaf_node_cpu_bit(rnp, cpu); if ((rnp->qsmask & bit) != 0) { if (f(per_cpu_ptr(&rcu_data, cpu))) mask |= bit; } } if (mask != 0) { /* Idle/offline CPUs, report (releases rnp->lock). */ rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); } else { /* Nothing to do here, so just drop the lock. */ raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } } } /* * Force quiescent states on reluctant CPUs, and also detect which * CPUs are in dyntick-idle mode. */ static void force_quiescent_state(void) { unsigned long flags; bool ret; struct rcu_node *rnp; struct rcu_node *rnp_old = NULL; /* Funnel through hierarchy to reduce memory contention. */ rnp = __this_cpu_read(rcu_data.mynode); for (; rnp != NULL; rnp = rnp->parent) { ret = (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) || !raw_spin_trylock(&rnp->fqslock); if (rnp_old != NULL) raw_spin_unlock(&rnp_old->fqslock); if (ret) return; rnp_old = rnp; } /* rnp_old == rcu_get_root(), rnp == NULL. */ /* Reached the root of the rcu_node tree, acquire lock. */ raw_spin_lock_irqsave_rcu_node(rnp_old, flags); raw_spin_unlock(&rnp_old->fqslock); if (READ_ONCE(rcu_state.gp_flags) & RCU_GP_FLAG_FQS) { raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); return; /* Someone beat us to it. */ } WRITE_ONCE(rcu_state.gp_flags, READ_ONCE(rcu_state.gp_flags) | RCU_GP_FLAG_FQS); raw_spin_unlock_irqrestore_rcu_node(rnp_old, flags); rcu_gp_kthread_wake(); } /* * This function checks for grace-period requests that fail to motivate * RCU to come out of its idle mode. */ static void rcu_check_gp_start_stall(struct rcu_node *rnp, struct rcu_data *rdp) { const unsigned long gpssdelay = rcu_jiffies_till_stall_check() * HZ; unsigned long flags; unsigned long j; struct rcu_node *rnp_root = rcu_get_root(); static atomic_t warned = ATOMIC_INIT(0); if (!IS_ENABLED(CONFIG_PROVE_RCU) || rcu_gp_in_progress() || ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed)) return; j = jiffies; /* Expensive access, and in common case don't get here. */ if (time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) || time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) || atomic_read(&warned)) return; raw_spin_lock_irqsave_rcu_node(rnp, flags); j = jiffies; if (rcu_gp_in_progress() || ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) || time_before(j, READ_ONCE(rcu_state.gp_req_activity) + gpssdelay) || time_before(j, READ_ONCE(rcu_state.gp_activity) + gpssdelay) || atomic_read(&warned)) { raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return; } /* Hold onto the leaf lock to make others see warned==1. */ if (rnp_root != rnp) raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */ j = jiffies; if (rcu_gp_in_progress() || ULONG_CMP_GE(rnp_root->gp_seq, rnp_root->gp_seq_needed) || time_before(j, rcu_state.gp_req_activity + gpssdelay) || time_before(j, rcu_state.gp_activity + gpssdelay) || atomic_xchg(&warned, 1)) { raw_spin_unlock_rcu_node(rnp_root); /* irqs remain disabled. */ raw_spin_unlock_irqrestore_rcu_node(rnp, flags); return; } pr_alert("%s: g%ld->%ld gar:%lu ga:%lu f%#x gs:%d %s->state:%#lx\n", __func__, (long)READ_ONCE(rcu_state.gp_seq), (long)READ_ONCE(rnp_root->gp_seq_needed), j - rcu_state.gp_req_activity, j - rcu_state.gp_activity, rcu_state.gp_flags, rcu_state.gp_state, rcu_state.name, rcu_state.gp_kthread ? rcu_state.gp_kthread->state : 0x1ffffL); WARN_ON(1); if (rnp_root != rnp) raw_spin_unlock_rcu_node(rnp_root); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } /* * This does the RCU core processing work for the specified rcu_data * structures. This may be called only from the CPU to whom the rdp * belongs. */ static __latent_entropy void rcu_process_callbacks(struct softirq_action *unused) { unsigned long flags; struct rcu_data *rdp = raw_cpu_ptr(&rcu_data); struct rcu_node *rnp = rdp->mynode; if (cpu_is_offline(smp_processor_id())) return; trace_rcu_utilization(TPS("Start RCU core")); WARN_ON_ONCE(!rdp->beenonline); /* Report any deferred quiescent states if preemption enabled. */ if (!(preempt_count() & PREEMPT_MASK)) { rcu_preempt_deferred_qs(current); } else if (rcu_preempt_need_deferred_qs(current)) { set_tsk_need_resched(current); set_preempt_need_resched(); } /* Update RCU state based on any recent quiescent states. */ rcu_check_quiescent_state(rdp); /* No grace period and unregistered callbacks? */ if (!rcu_gp_in_progress() && rcu_segcblist_is_enabled(&rdp->cblist)) { local_irq_save(flags); if (!rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) rcu_accelerate_cbs_unlocked(rnp, rdp); local_irq_restore(flags); } rcu_check_gp_start_stall(rnp, rdp); /* If there are callbacks ready, invoke them. */ if (rcu_segcblist_ready_cbs(&rdp->cblist)) invoke_rcu_callbacks(rdp); /* Do any needed deferred wakeups of rcuo kthreads. */ do_nocb_deferred_wakeup(rdp); trace_rcu_utilization(TPS("End RCU core")); } /* * Schedule RCU callback invocation. If the running implementation of RCU * does not support RCU priority boosting, just do a direct call, otherwise * wake up the per-CPU kernel kthread. Note that because we are running * on the current CPU with softirqs disabled, the rcu_cpu_kthread_task * cannot disappear out from under us. */ static void invoke_rcu_callbacks(struct rcu_data *rdp) { if (unlikely(!READ_ONCE(rcu_scheduler_fully_active))) return; if (likely(!rcu_state.boost)) { rcu_do_batch(rdp); return; } invoke_rcu_callbacks_kthread(); } static void invoke_rcu_core(void) { if (cpu_online(smp_processor_id())) raise_softirq(RCU_SOFTIRQ); } /* * Handle any core-RCU processing required by a call_rcu() invocation. */ static void __call_rcu_core(struct rcu_data *rdp, struct rcu_head *head, unsigned long flags) { /* * If called from an extended quiescent state, invoke the RCU * core in order to force a re-evaluation of RCU's idleness. */ if (!rcu_is_watching()) invoke_rcu_core(); /* If interrupts were disabled or CPU offline, don't invoke RCU core. */ if (irqs_disabled_flags(flags) || cpu_is_offline(smp_processor_id())) return; /* * Force the grace period if too many callbacks or too long waiting. * Enforce hysteresis, and don't invoke force_quiescent_state() * if some other CPU has recently done so. Also, don't bother * invoking force_quiescent_state() if the newly enqueued callback * is the only one waiting for a grace period to complete. */ if (unlikely(rcu_segcblist_n_cbs(&rdp->cblist) > rdp->qlen_last_fqs_check + qhimark)) { /* Are we ignoring a completed grace period? */ note_gp_changes(rdp); /* Start a new grace period if one not already started. */ if (!rcu_gp_in_progress()) { rcu_accelerate_cbs_unlocked(rdp->mynode, rdp); } else { /* Give the grace period a kick. */ rdp->blimit = LONG_MAX; if (rcu_state.n_force_qs == rdp->n_force_qs_snap && rcu_segcblist_first_pend_cb(&rdp->cblist) != head) force_quiescent_state(); rdp->n_force_qs_snap = rcu_state.n_force_qs; rdp->qlen_last_fqs_check = rcu_segcblist_n_cbs(&rdp->cblist); } } } /* * RCU callback function to leak a callback. */ static void rcu_leak_callback(struct rcu_head *rhp) { } /* * Helper function for call_rcu() and friends. The cpu argument will * normally be -1, indicating "currently running CPU". It may specify * a CPU only if that CPU is a no-CBs CPU. Currently, only rcu_barrier() * is expected to specify a CPU. */ static void __call_rcu(struct rcu_head *head, rcu_callback_t func, int cpu, bool lazy) { unsigned long flags; struct rcu_data *rdp; /* Misaligned rcu_head! */ WARN_ON_ONCE((unsigned long)head & (sizeof(void *) - 1)); if (debug_rcu_head_queue(head)) { /* * Probable double call_rcu(), so leak the callback. * Use rcu:rcu_callback trace event to find the previous * time callback was passed to __call_rcu(). */ WARN_ONCE(1, "__call_rcu(): Double-freed CB %p->%pF()!!!\n", head, head->func); WRITE_ONCE(head->func, rcu_leak_callback); return; } head->func = func; head->next = NULL; local_irq_save(flags); rdp = this_cpu_ptr(&rcu_data); /* Add the callback to our list. */ if (unlikely(!rcu_segcblist_is_enabled(&rdp->cblist)) || cpu != -1) { int offline; if (cpu != -1) rdp = per_cpu_ptr(&rcu_data, cpu); if (likely(rdp->mynode)) { /* Post-boot, so this should be for a no-CBs CPU. */ offline = !__call_rcu_nocb(rdp, head, lazy, flags); WARN_ON_ONCE(offline); /* Offline CPU, _call_rcu() illegal, leak callback. */ local_irq_restore(flags); return; } /* * Very early boot, before rcu_init(). Initialize if needed * and then drop through to queue the callback. */ BUG_ON(cpu != -1); WARN_ON_ONCE(!rcu_is_watching()); if (rcu_segcblist_empty(&rdp->cblist)) rcu_segcblist_init(&rdp->cblist); } rcu_segcblist_enqueue(&rdp->cblist, head, lazy); if (!lazy) rcu_idle_count_callbacks_posted(); if (__is_kfree_rcu_offset((unsigned long)func)) trace_rcu_kfree_callback(rcu_state.name, head, (unsigned long)func, rcu_segcblist_n_lazy_cbs(&rdp->cblist), rcu_segcblist_n_cbs(&rdp->cblist)); else trace_rcu_callback(rcu_state.name, head, rcu_segcblist_n_lazy_cbs(&rdp->cblist), rcu_segcblist_n_cbs(&rdp->cblist)); /* Go handle any RCU core processing required. */ __call_rcu_core(rdp, head, flags); local_irq_restore(flags); } /** * call_rcu() - Queue an RCU callback for invocation after a grace period. * @head: structure to be used for queueing the RCU updates. * @func: actual callback function to be invoked after the grace period * * The callback function will be invoked some time after a full grace * period elapses, in other words after all pre-existing RCU read-side * critical sections have completed. However, the callback function * might well execute concurrently with RCU read-side critical sections * that started after call_rcu() was invoked. RCU read-side critical * sections are delimited by rcu_read_lock() and rcu_read_unlock(), and * may be nested. In addition, regions of code across which interrupts, * preemption, or softirqs have been disabled also serve as RCU read-side * critical sections. This includes hardware interrupt handlers, softirq * handlers, and NMI handlers. * * Note that all CPUs must agree that the grace period extended beyond * all pre-existing RCU read-side critical section. On systems with more * than one CPU, this means that when "func()" is invoked, each CPU is * guaranteed to have executed a full memory barrier since the end of its * last RCU read-side critical section whose beginning preceded the call * to call_rcu(). It also means that each CPU executing an RCU read-side * critical section that continues beyond the start of "func()" must have * executed a memory barrier after the call_rcu() but before the beginning * of that RCU read-side critical section. Note that these guarantees * include CPUs that are offline, idle, or executing in user mode, as * well as CPUs that are executing in the kernel. * * Furthermore, if CPU A invoked call_rcu() and CPU B invoked the * resulting RCU callback function "func()", then both CPU A and CPU B are * guaranteed to execute a full memory barrier during the time interval * between the call to call_rcu() and the invocation of "func()" -- even * if CPU A and CPU B are the same CPU (but again only if the system has * more than one CPU). */ void call_rcu(struct rcu_head *head, rcu_callback_t func) { __call_rcu(head, func, -1, 0); } EXPORT_SYMBOL_GPL(call_rcu); /* * Queue an RCU callback for lazy invocation after a grace period. * This will likely be later named something like "call_rcu_lazy()", * but this change will require some way of tagging the lazy RCU * callbacks in the list of pending callbacks. Until then, this * function may only be called from __kfree_rcu(). */ void kfree_call_rcu(struct rcu_head *head, rcu_callback_t func) { __call_rcu(head, func, -1, 1); } EXPORT_SYMBOL_GPL(kfree_call_rcu); /** * get_state_synchronize_rcu - Snapshot current RCU state * * Returns a cookie that is used by a later call to cond_synchronize_rcu() * to determine whether or not a full grace period has elapsed in the * meantime. */ unsigned long get_state_synchronize_rcu(void) { /* * Any prior manipulation of RCU-protected data must happen * before the load from ->gp_seq. */ smp_mb(); /* ^^^ */ return rcu_seq_snap(&rcu_state.gp_seq); } EXPORT_SYMBOL_GPL(get_state_synchronize_rcu); /** * cond_synchronize_rcu - Conditionally wait for an RCU grace period * * @oldstate: return value from earlier call to get_state_synchronize_rcu() * * If a full RCU grace period has elapsed since the earlier call to * get_state_synchronize_rcu(), just return. Otherwise, invoke * synchronize_rcu() to wait for a full grace period. * * Yes, this function does not take counter wrap into account. But * counter wrap is harmless. If the counter wraps, we have waited for * more than 2 billion grace periods (and way more on a 64-bit system!), * so waiting for one additional grace period should be just fine. */ void cond_synchronize_rcu(unsigned long oldstate) { if (!rcu_seq_done(&rcu_state.gp_seq, oldstate)) synchronize_rcu(); else smp_mb(); /* Ensure GP ends before subsequent accesses. */ } EXPORT_SYMBOL_GPL(cond_synchronize_rcu); /* * Check to see if there is any immediate RCU-related work to be done by * the current CPU, returning 1 if so and zero otherwise. The checks are * in order of increasing expense: checks that can be carried out against * CPU-local state are performed first. However, we must check for CPU * stalls first, else we might not get a chance. */ static int rcu_pending(void) { struct rcu_data *rdp = this_cpu_ptr(&rcu_data); struct rcu_node *rnp = rdp->mynode; /* Check for CPU stalls, if enabled. */ check_cpu_stall(rdp); /* Is this CPU a NO_HZ_FULL CPU that should ignore RCU? */ if (rcu_nohz_full_cpu()) return 0; /* Is the RCU core waiting for a quiescent state from this CPU? */ if (rdp->core_needs_qs && !rdp->cpu_no_qs.b.norm) return 1; /* Does this CPU have callbacks ready to invoke? */ if (rcu_segcblist_ready_cbs(&rdp->cblist)) return 1; /* Has RCU gone idle with this CPU needing another grace period? */ if (!rcu_gp_in_progress() && rcu_segcblist_is_enabled(&rdp->cblist) && !rcu_segcblist_restempty(&rdp->cblist, RCU_NEXT_READY_TAIL)) return 1; /* Have RCU grace period completed or started? */ if (rcu_seq_current(&rnp->gp_seq) != rdp->gp_seq || unlikely(READ_ONCE(rdp->gpwrap))) /* outside lock */ return 1; /* Does this CPU need a deferred NOCB wakeup? */ if (rcu_nocb_need_deferred_wakeup(rdp)) return 1; /* nothing to do */ return 0; } /* * Return true if the specified CPU has any callback. If all_lazy is * non-NULL, store an indication of whether all callbacks are lazy. * (If there are no callbacks, all of them are deemed to be lazy.) */ static bool rcu_cpu_has_callbacks(bool *all_lazy) { bool al = true; bool hc = false; struct rcu_data *rdp; rdp = this_cpu_ptr(&rcu_data); if (!rcu_segcblist_empty(&rdp->cblist)) { hc = true; if (rcu_segcblist_n_nonlazy_cbs(&rdp->cblist)) al = false; } if (all_lazy) *all_lazy = al; return hc; } /* * Helper function for rcu_barrier() tracing. If tracing is disabled, * the compiler is expected to optimize this away. */ static void rcu_barrier_trace(const char *s, int cpu, unsigned long done) { trace_rcu_barrier(rcu_state.name, s, cpu, atomic_read(&rcu_state.barrier_cpu_count), done); } /* * RCU callback function for rcu_barrier(). If we are last, wake * up the task executing rcu_barrier(). */ static void rcu_barrier_callback(struct rcu_head *rhp) { if (atomic_dec_and_test(&rcu_state.barrier_cpu_count)) { rcu_barrier_trace(TPS("LastCB"), -1, rcu_state.barrier_sequence); complete(&rcu_state.barrier_completion); } else { rcu_barrier_trace(TPS("CB"), -1, rcu_state.barrier_sequence); } } /* * Called with preemption disabled, and from cross-cpu IRQ context. */ static void rcu_barrier_func(void *unused) { struct rcu_data *rdp = raw_cpu_ptr(&rcu_data); rcu_barrier_trace(TPS("IRQ"), -1, rcu_state.barrier_sequence); rdp->barrier_head.func = rcu_barrier_callback; debug_rcu_head_queue(&rdp->barrier_head); if (rcu_segcblist_entrain(&rdp->cblist, &rdp->barrier_head, 0)) { atomic_inc(&rcu_state.barrier_cpu_count); } else { debug_rcu_head_unqueue(&rdp->barrier_head); rcu_barrier_trace(TPS("IRQNQ"), -1, rcu_state.barrier_sequence); } } /** * rcu_barrier - Wait until all in-flight call_rcu() callbacks complete. * * Note that this primitive does not necessarily wait for an RCU grace period * to complete. For example, if there are no RCU callbacks queued anywhere * in the system, then rcu_barrier() is within its rights to return * immediately, without waiting for anything, much less an RCU grace period. */ void rcu_barrier(void) { int cpu; struct rcu_data *rdp; unsigned long s = rcu_seq_snap(&rcu_state.barrier_sequence); rcu_barrier_trace(TPS("Begin"), -1, s); /* Take mutex to serialize concurrent rcu_barrier() requests. */ mutex_lock(&rcu_state.barrier_mutex); /* Did someone else do our work for us? */ if (rcu_seq_done(&rcu_state.barrier_sequence, s)) { rcu_barrier_trace(TPS("EarlyExit"), -1, rcu_state.barrier_sequence); smp_mb(); /* caller's subsequent code after above check. */ mutex_unlock(&rcu_state.barrier_mutex); return; } /* Mark the start of the barrier operation. */ rcu_seq_start(&rcu_state.barrier_sequence); rcu_barrier_trace(TPS("Inc1"), -1, rcu_state.barrier_sequence); /* * Initialize the count to one rather than to zero in order to * avoid a too-soon return to zero in case of a short grace period * (or preemption of this task). Exclude CPU-hotplug operations * to ensure that no offline CPU has callbacks queued. */ init_completion(&rcu_state.barrier_completion); atomic_set(&rcu_state.barrier_cpu_count, 1); get_online_cpus(); /* * Force each CPU with callbacks to register a new callback. * When that callback is invoked, we will know that all of the * corresponding CPU's preceding callbacks have been invoked. */ for_each_possible_cpu(cpu) { if (!cpu_online(cpu) && !rcu_is_nocb_cpu(cpu)) continue; rdp = per_cpu_ptr(&rcu_data, cpu); if (rcu_is_nocb_cpu(cpu)) { if (!rcu_nocb_cpu_needs_barrier(cpu)) { rcu_barrier_trace(TPS("OfflineNoCB"), cpu, rcu_state.barrier_sequence); } else { rcu_barrier_trace(TPS("OnlineNoCB"), cpu, rcu_state.barrier_sequence); smp_mb__before_atomic(); atomic_inc(&rcu_state.barrier_cpu_count); __call_rcu(&rdp->barrier_head, rcu_barrier_callback, cpu, 0); } } else if (rcu_segcblist_n_cbs(&rdp->cblist)) { rcu_barrier_trace(TPS("OnlineQ"), cpu, rcu_state.barrier_sequence); smp_call_function_single(cpu, rcu_barrier_func, NULL, 1); } else { rcu_barrier_trace(TPS("OnlineNQ"), cpu, rcu_state.barrier_sequence); } } put_online_cpus(); /* * Now that we have an rcu_barrier_callback() callback on each * CPU, and thus each counted, remove the initial count. */ if (atomic_dec_and_test(&rcu_state.barrier_cpu_count)) complete(&rcu_state.barrier_completion); /* Wait for all rcu_barrier_callback() callbacks to be invoked. */ wait_for_completion(&rcu_state.barrier_completion); /* Mark the end of the barrier operation. */ rcu_barrier_trace(TPS("Inc2"), -1, rcu_state.barrier_sequence); rcu_seq_end(&rcu_state.barrier_sequence); /* Other rcu_barrier() invocations can now safely proceed. */ mutex_unlock(&rcu_state.barrier_mutex); } EXPORT_SYMBOL_GPL(rcu_barrier); /* * Propagate ->qsinitmask bits up the rcu_node tree to account for the * first CPU in a given leaf rcu_node structure coming online. The caller * must hold the corresponding leaf rcu_node ->lock with interrrupts * disabled. */ static void rcu_init_new_rnp(struct rcu_node *rnp_leaf) { long mask; long oldmask; struct rcu_node *rnp = rnp_leaf; raw_lockdep_assert_held_rcu_node(rnp_leaf); WARN_ON_ONCE(rnp->wait_blkd_tasks); for (;;) { mask = rnp->grpmask; rnp = rnp->parent; if (rnp == NULL) return; raw_spin_lock_rcu_node(rnp); /* Interrupts already disabled. */ oldmask = rnp->qsmaskinit; rnp->qsmaskinit |= mask; raw_spin_unlock_rcu_node(rnp); /* Interrupts remain disabled. */ if (oldmask) return; } } /* * Do boot-time initialization of a CPU's per-CPU RCU data. */ static void __init rcu_boot_init_percpu_data(int cpu) { struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); /* Set up local state, ensuring consistent view of global state. */ rdp->grpmask = leaf_node_cpu_bit(rdp->mynode, cpu); WARN_ON_ONCE(rdp->dynticks_nesting != 1); WARN_ON_ONCE(rcu_dynticks_in_eqs(rcu_dynticks_snap(rdp))); rdp->rcu_ofl_gp_seq = rcu_state.gp_seq; rdp->rcu_ofl_gp_flags = RCU_GP_CLEANED; rdp->rcu_onl_gp_seq = rcu_state.gp_seq; rdp->rcu_onl_gp_flags = RCU_GP_CLEANED; rdp->cpu = cpu; rcu_boot_init_nocb_percpu_data(rdp); } /* * Invoked early in the CPU-online process, when pretty much all services * are available. The incoming CPU is not present. * * Initializes a CPU's per-CPU RCU data. Note that only one online or * offline event can be happening at a given time. Note also that we can * accept some slop in the rsp->gp_seq access due to the fact that this * CPU cannot possibly have any RCU callbacks in flight yet. */ int rcutree_prepare_cpu(unsigned int cpu) { unsigned long flags; struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); struct rcu_node *rnp = rcu_get_root(); /* Set up local state, ensuring consistent view of global state. */ raw_spin_lock_irqsave_rcu_node(rnp, flags); rdp->qlen_last_fqs_check = 0; rdp->n_force_qs_snap = rcu_state.n_force_qs; rdp->blimit = blimit; if (rcu_segcblist_empty(&rdp->cblist) && /* No early-boot CBs? */ !init_nocb_callback_list(rdp)) rcu_segcblist_init(&rdp->cblist); /* Re-enable callbacks. */ rdp->dynticks_nesting = 1; /* CPU not up, no tearing. */ rcu_dynticks_eqs_online(); raw_spin_unlock_rcu_node(rnp); /* irqs remain disabled. */ /* * Add CPU to leaf rcu_node pending-online bitmask. Any needed * propagation up the rcu_node tree will happen at the beginning * of the next grace period. */ rnp = rdp->mynode; raw_spin_lock_rcu_node(rnp); /* irqs already disabled. */ rdp->beenonline = true; /* We have now been online. */ rdp->gp_seq = rnp->gp_seq; rdp->gp_seq_needed = rnp->gp_seq; rdp->cpu_no_qs.b.norm = true; rdp->core_needs_qs = false; rdp->rcu_iw_pending = false; rdp->rcu_iw_gp_seq = rnp->gp_seq - 1; trace_rcu_grace_period(rcu_state.name, rdp->gp_seq, TPS("cpuonl")); raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rcu_prepare_kthreads(cpu); rcu_spawn_all_nocb_kthreads(cpu); return 0; } /* * Update RCU priority boot kthread affinity for CPU-hotplug changes. */ static void rcutree_affinity_setting(unsigned int cpu, int outgoing) { struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); rcu_boost_kthread_setaffinity(rdp->mynode, outgoing); } /* * Near the end of the CPU-online process. Pretty much all services * enabled, and the CPU is now very much alive. */ int rcutree_online_cpu(unsigned int cpu) { unsigned long flags; struct rcu_data *rdp; struct rcu_node *rnp; rdp = per_cpu_ptr(&rcu_data, cpu); rnp = rdp->mynode; raw_spin_lock_irqsave_rcu_node(rnp, flags); rnp->ffmask |= rdp->grpmask; raw_spin_unlock_irqrestore_rcu_node(rnp, flags); if (IS_ENABLED(CONFIG_TREE_SRCU)) srcu_online_cpu(cpu); if (rcu_scheduler_active == RCU_SCHEDULER_INACTIVE) return 0; /* Too early in boot for scheduler work. */ sync_sched_exp_online_cleanup(cpu); rcutree_affinity_setting(cpu, -1); return 0; } /* * Near the beginning of the process. The CPU is still very much alive * with pretty much all services enabled. */ int rcutree_offline_cpu(unsigned int cpu) { unsigned long flags; struct rcu_data *rdp; struct rcu_node *rnp; rdp = per_cpu_ptr(&rcu_data, cpu); rnp = rdp->mynode; raw_spin_lock_irqsave_rcu_node(rnp, flags); rnp->ffmask &= ~rdp->grpmask; raw_spin_unlock_irqrestore_rcu_node(rnp, flags); rcutree_affinity_setting(cpu, cpu); if (IS_ENABLED(CONFIG_TREE_SRCU)) srcu_offline_cpu(cpu); return 0; } static DEFINE_PER_CPU(int, rcu_cpu_started); /* * Mark the specified CPU as being online so that subsequent grace periods * (both expedited and normal) will wait on it. Note that this means that * incoming CPUs are not allowed to use RCU read-side critical sections * until this function is called. Failing to observe this restriction * will result in lockdep splats. * * Note that this function is special in that it is invoked directly * from the incoming CPU rather than from the cpuhp_step mechanism. * This is because this function must be invoked at a precise location. */ void rcu_cpu_starting(unsigned int cpu) { unsigned long flags; unsigned long mask; int nbits; unsigned long oldmask; struct rcu_data *rdp; struct rcu_node *rnp; if (per_cpu(rcu_cpu_started, cpu)) return; per_cpu(rcu_cpu_started, cpu) = 1; rdp = per_cpu_ptr(&rcu_data, cpu); rnp = rdp->mynode; mask = rdp->grpmask; raw_spin_lock_irqsave_rcu_node(rnp, flags); rnp->qsmaskinitnext |= mask; oldmask = rnp->expmaskinitnext; rnp->expmaskinitnext |= mask; oldmask ^= rnp->expmaskinitnext; nbits = bitmap_weight(&oldmask, BITS_PER_LONG); /* Allow lockless access for expedited grace periods. */ smp_store_release(&rcu_state.ncpus, rcu_state.ncpus + nbits); /* ^^^ */ rcu_gpnum_ovf(rnp, rdp); /* Offline-induced counter wrap? */ rdp->rcu_onl_gp_seq = READ_ONCE(rcu_state.gp_seq); rdp->rcu_onl_gp_flags = READ_ONCE(rcu_state.gp_flags); if (rnp->qsmask & mask) { /* RCU waiting on incoming CPU? */ /* Report QS -after- changing ->qsmaskinitnext! */ rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); } else { raw_spin_unlock_irqrestore_rcu_node(rnp, flags); } smp_mb(); /* Ensure RCU read-side usage follows above initialization. */ } #ifdef CONFIG_HOTPLUG_CPU /* * The outgoing function has no further need of RCU, so remove it from * the rcu_node tree's ->qsmaskinitnext bit masks. * * Note that this function is special in that it is invoked directly * from the outgoing CPU rather than from the cpuhp_step mechanism. * This is because this function must be invoked at a precise location. */ void rcu_report_dead(unsigned int cpu) { unsigned long flags; unsigned long mask; struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); struct rcu_node *rnp = rdp->mynode; /* Outgoing CPU's rdp & rnp. */ /* QS for any half-done expedited grace period. */ preempt_disable(); rcu_report_exp_rdp(this_cpu_ptr(&rcu_data)); preempt_enable(); rcu_preempt_deferred_qs(current); /* Remove outgoing CPU from mask in the leaf rcu_node structure. */ mask = rdp->grpmask; raw_spin_lock(&rcu_state.ofl_lock); raw_spin_lock_irqsave_rcu_node(rnp, flags); /* Enforce GP memory-order guarantee. */ rdp->rcu_ofl_gp_seq = READ_ONCE(rcu_state.gp_seq); rdp->rcu_ofl_gp_flags = READ_ONCE(rcu_state.gp_flags); if (rnp->qsmask & mask) { /* RCU waiting on outgoing CPU? */ /* Report quiescent state -before- changing ->qsmaskinitnext! */ rcu_report_qs_rnp(mask, rnp, rnp->gp_seq, flags); raw_spin_lock_irqsave_rcu_node(rnp, flags); } rnp->qsmaskinitnext &= ~mask; raw_spin_unlock_irqrestore_rcu_node(rnp, flags); raw_spin_unlock(&rcu_state.ofl_lock); per_cpu(rcu_cpu_started, cpu) = 0; } /* * The outgoing CPU has just passed through the dying-idle state, and we * are being invoked from the CPU that was IPIed to continue the offline * operation. Migrate the outgoing CPU's callbacks to the current CPU. */ void rcutree_migrate_callbacks(int cpu) { unsigned long flags; struct rcu_data *my_rdp; struct rcu_data *rdp = per_cpu_ptr(&rcu_data, cpu); struct rcu_node *rnp_root = rcu_get_root(); bool needwake; if (rcu_is_nocb_cpu(cpu) || rcu_segcblist_empty(&rdp->cblist)) return; /* No callbacks to migrate. */ local_irq_save(flags); my_rdp = this_cpu_ptr(&rcu_data); if (rcu_nocb_adopt_orphan_cbs(my_rdp, rdp, flags)) { local_irq_restore(flags); return; } raw_spin_lock_rcu_node(rnp_root); /* irqs already disabled. */ /* Leverage recent GPs and set GP for new callbacks. */ needwake = rcu_advance_cbs(rnp_root, rdp) || rcu_advance_cbs(rnp_root, my_rdp); rcu_segcblist_merge(&my_rdp->cblist, &rdp->cblist); WARN_ON_ONCE(rcu_segcblist_empty(&my_rdp->cblist) != !rcu_segcblist_n_cbs(&my_rdp->cblist)); raw_spin_unlock_irqrestore_rcu_node(rnp_root, flags); if (needwake) rcu_gp_kthread_wake(); WARN_ONCE(rcu_segcblist_n_cbs(&rdp->cblist) != 0 || !rcu_segcblist_empty(&rdp->cblist), "rcu_cleanup_dead_cpu: Callbacks on offline CPU %d: qlen=%lu, 1stCB=%p\n", cpu, rcu_segcblist_n_cbs(&rdp->cblist), rcu_segcblist_first_cb(&rdp->cblist)); } #endif /* * On non-huge systems, use expedited RCU grace periods to make suspend * and hibernation run faster. */ static int rcu_pm_notify(struct notifier_block *self, unsigned long action, void *hcpu) { switch (action) { case PM_HIBERNATION_PREPARE: case PM_SUSPEND_PREPARE: if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ rcu_expedite_gp(); break; case PM_POST_HIBERNATION: case PM_POST_SUSPEND: if (nr_cpu_ids <= 256) /* Expediting bad for large systems. */ rcu_unexpedite_gp(); break; default: break; } return NOTIFY_OK; } /* * Spawn the kthreads that handle RCU's grace periods. */ static int __init rcu_spawn_gp_kthread(void) { unsigned long flags; int kthread_prio_in = kthread_prio; struct rcu_node *rnp; struct sched_param sp; struct task_struct *t; /* Force priority into range. */ if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 2 && IS_BUILTIN(CONFIG_RCU_TORTURE_TEST)) kthread_prio = 2; else if (IS_ENABLED(CONFIG_RCU_BOOST) && kthread_prio < 1) kthread_prio = 1; else if (kthread_prio < 0) kthread_prio = 0; else if (kthread_prio > 99) kthread_prio = 99; if (kthread_prio != kthread_prio_in) pr_alert("rcu_spawn_gp_kthread(): Limited prio to %d from %d\n", kthread_prio, kthread_prio_in); rcu_scheduler_fully_active = 1; t = kthread_create(rcu_gp_kthread, NULL, "%s", rcu_state.name); BUG_ON(IS_ERR(t)); rnp = rcu_get_root(); raw_spin_lock_irqsave_rcu_node(rnp, flags); rcu_state.gp_kthread = t; if (kthread_prio) { sp.sched_priority = kthread_prio; sched_setscheduler_nocheck(t, SCHED_FIFO, &sp); } raw_spin_unlock_irqrestore_rcu_node(rnp, flags); wake_up_process(t); rcu_spawn_nocb_kthreads(); rcu_spawn_boost_kthreads(); return 0; } early_initcall(rcu_spawn_gp_kthread); /* * This function is invoked towards the end of the scheduler's * initialization process. Before this is called, the idle task might * contain synchronous grace-period primitives (during which time, this idle * task is booting the system, and such primitives are no-ops). After this * function is called, any synchronous grace-period primitives are run as * expedited, with the requesting task driving the grace period forward. * A later core_initcall() rcu_set_runtime_mode() will switch to full * runtime RCU functionality. */ void rcu_scheduler_starting(void) { WARN_ON(num_online_cpus() != 1); WARN_ON(nr_context_switches() > 0); rcu_test_sync_prims(); rcu_scheduler_active = RCU_SCHEDULER_INIT; rcu_test_sync_prims(); } /* * Helper function for rcu_init() that initializes the rcu_state structure. */ static void __init rcu_init_one(void) { static const char * const buf[] = RCU_NODE_NAME_INIT; static const char * const fqs[] = RCU_FQS_NAME_INIT; static struct lock_class_key rcu_node_class[RCU_NUM_LVLS]; static struct lock_class_key rcu_fqs_class[RCU_NUM_LVLS]; int levelspread[RCU_NUM_LVLS]; /* kids/node in each level. */ int cpustride = 1; int i; int j; struct rcu_node *rnp; BUILD_BUG_ON(RCU_NUM_LVLS > ARRAY_SIZE(buf)); /* Fix buf[] init! */ /* Silence gcc 4.8 false positive about array index out of range. */ if (rcu_num_lvls <= 0 || rcu_num_lvls > RCU_NUM_LVLS) panic("rcu_init_one: rcu_num_lvls out of range"); /* Initialize the level-tracking arrays. */ for (i = 1; i < rcu_num_lvls; i++) rcu_state.level[i] = rcu_state.level[i - 1] + num_rcu_lvl[i - 1]; rcu_init_levelspread(levelspread, num_rcu_lvl); /* Initialize the elements themselves, starting from the leaves. */ for (i = rcu_num_lvls - 1; i >= 0; i--) { cpustride *= levelspread[i]; rnp = rcu_state.level[i]; for (j = 0; j < num_rcu_lvl[i]; j++, rnp++) { raw_spin_lock_init(&ACCESS_PRIVATE(rnp, lock)); lockdep_set_class_and_name(&ACCESS_PRIVATE(rnp, lock), &rcu_node_class[i], buf[i]); raw_spin_lock_init(&rnp->fqslock); lockdep_set_class_and_name(&rnp->fqslock, &rcu_fqs_class[i], fqs[i]); rnp->gp_seq = rcu_state.gp_seq; rnp->gp_seq_needed = rcu_state.gp_seq; rnp->completedqs = rcu_state.gp_seq; rnp->qsmask = 0; rnp->qsmaskinit = 0; rnp->grplo = j * cpustride; rnp->grphi = (j + 1) * cpustride - 1; if (rnp->grphi >= nr_cpu_ids) rnp->grphi = nr_cpu_ids - 1; if (i == 0) { rnp->grpnum = 0; rnp->grpmask = 0; rnp->parent = NULL; } else { rnp->grpnum = j % levelspread[i - 1]; rnp->grpmask = BIT(rnp->grpnum); rnp->parent = rcu_state.level[i - 1] + j / levelspread[i - 1]; } rnp->level = i; INIT_LIST_HEAD(&rnp->blkd_tasks); rcu_init_one_nocb(rnp); init_waitqueue_head(&rnp->exp_wq[0]); init_waitqueue_head(&rnp->exp_wq[1]); init_waitqueue_head(&rnp->exp_wq[2]); init_waitqueue_head(&rnp->exp_wq[3]); spin_lock_init(&rnp->exp_lock); } } init_swait_queue_head(&rcu_state.gp_wq); init_swait_queue_head(&rcu_state.expedited_wq); rnp = rcu_first_leaf_node(); for_each_possible_cpu(i) { while (i > rnp->grphi) rnp++; per_cpu_ptr(&rcu_data, i)->mynode = rnp; rcu_boot_init_percpu_data(i); } } /* * Compute the rcu_node tree geometry from kernel parameters. This cannot * replace the definitions in tree.h because those are needed to size * the ->node array in the rcu_state structure. */ static void __init rcu_init_geometry(void) { ulong d; int i; int rcu_capacity[RCU_NUM_LVLS]; /* * Initialize any unspecified boot parameters. * The default values of jiffies_till_first_fqs and * jiffies_till_next_fqs are set to the RCU_JIFFIES_TILL_FORCE_QS * value, which is a function of HZ, then adding one for each * RCU_JIFFIES_FQS_DIV CPUs that might be on the system. */ d = RCU_JIFFIES_TILL_FORCE_QS + nr_cpu_ids / RCU_JIFFIES_FQS_DIV; if (jiffies_till_first_fqs == ULONG_MAX) jiffies_till_first_fqs = d; if (jiffies_till_next_fqs == ULONG_MAX) jiffies_till_next_fqs = d; if (jiffies_till_sched_qs == ULONG_MAX) adjust_jiffies_till_sched_qs(); /* If the compile-time values are accurate, just leave. */ if (rcu_fanout_leaf == RCU_FANOUT_LEAF && nr_cpu_ids == NR_CPUS) return; pr_info("Adjusting geometry for rcu_fanout_leaf=%d, nr_cpu_ids=%u\n", rcu_fanout_leaf, nr_cpu_ids); /* * The boot-time rcu_fanout_leaf parameter must be at least two * and cannot exceed the number of bits in the rcu_node masks. * Complain and fall back to the compile-time values if this * limit is exceeded. */ if (rcu_fanout_leaf < 2 || rcu_fanout_leaf > sizeof(unsigned long) * 8) { rcu_fanout_leaf = RCU_FANOUT_LEAF; WARN_ON(1); return; } /* * Compute number of nodes that can be handled an rcu_node tree * with the given number of levels. */ rcu_capacity[0] = rcu_fanout_leaf; for (i = 1; i < RCU_NUM_LVLS; i++) rcu_capacity[i] = rcu_capacity[i - 1] * RCU_FANOUT; /* * The tree must be able to accommodate the configured number of CPUs. * If this limit is exceeded, fall back to the compile-time values. */ if (nr_cpu_ids > rcu_capacity[RCU_NUM_LVLS - 1]) { rcu_fanout_leaf = RCU_FANOUT_LEAF; WARN_ON(1); return; } /* Calculate the number of levels in the tree. */ for (i = 0; nr_cpu_ids > rcu_capacity[i]; i++) { } rcu_num_lvls = i + 1; /* Calculate the number of rcu_nodes at each level of the tree. */ for (i = 0; i < rcu_num_lvls; i++) { int cap = rcu_capacity[(rcu_num_lvls - 1) - i]; num_rcu_lvl[i] = DIV_ROUND_UP(nr_cpu_ids, cap); } /* Calculate the total number of rcu_node structures. */ rcu_num_nodes = 0; for (i = 0; i < rcu_num_lvls; i++) rcu_num_nodes += num_rcu_lvl[i]; } /* * Dump out the structure of the rcu_node combining tree associated * with the rcu_state structure. */ static void __init rcu_dump_rcu_node_tree(void) { int level = 0; struct rcu_node *rnp; pr_info("rcu_node tree layout dump\n"); pr_info(" "); rcu_for_each_node_breadth_first(rnp) { if (rnp->level != level) { pr_cont("\n"); pr_info(" "); level = rnp->level; } pr_cont("%d:%d ^%d ", rnp->grplo, rnp->grphi, rnp->grpnum); } pr_cont("\n"); } struct workqueue_struct *rcu_gp_wq; struct workqueue_struct *rcu_par_gp_wq; void __init rcu_init(void) { int cpu; rcu_early_boot_tests(); rcu_bootup_announce(); rcu_init_geometry(); rcu_init_one(); if (dump_tree) rcu_dump_rcu_node_tree(); open_softirq(RCU_SOFTIRQ, rcu_process_callbacks); /* * We don't need protection against CPU-hotplug here because * this is called early in boot, before either interrupts * or the scheduler are operational. */ pm_notifier(rcu_pm_notify, 0); for_each_online_cpu(cpu) { rcutree_prepare_cpu(cpu); rcu_cpu_starting(cpu); rcutree_online_cpu(cpu); } /* Create workqueue for expedited GPs and for Tree SRCU. */ rcu_gp_wq = alloc_workqueue("rcu_gp", WQ_MEM_RECLAIM, 0); WARN_ON(!rcu_gp_wq); rcu_par_gp_wq = alloc_workqueue("rcu_par_gp", WQ_MEM_RECLAIM, 0); WARN_ON(!rcu_par_gp_wq); srcu_init(); } #include "tree_exp.h" #include "tree_plugin.h"
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