cregit-Linux how code gets into the kernel

Release 4.15 kernel/time/tick-broadcast-hrtimer.c

Directory: kernel/time
// SPDX-License-Identifier: GPL-2.0
 * linux/kernel/time/tick-broadcast-hrtimer.c
 * This file emulates a local clock event device
 * via a pseudo clock device.
#include <linux/cpu.h>
#include <linux/err.h>
#include <linux/hrtimer.h>
#include <linux/interrupt.h>
#include <linux/percpu.h>
#include <linux/profile.h>
#include <linux/clockchips.h>
#include <linux/sched.h>
#include <linux/smp.h>
#include <linux/module.h>

#include "tick-internal.h"

static struct hrtimer bctimer;

static int bc_shutdown(struct clock_event_device *evt) { /* * Note, we cannot cancel the timer here as we might * run into the following live lock scenario: * * cpu 0 cpu1 * lock(broadcast_lock); * hrtimer_interrupt() * bc_handler() * tick_handle_oneshot_broadcast(); * lock(broadcast_lock); * hrtimer_cancel() * wait_for_callback() */ hrtimer_try_to_cancel(&bctimer); return 0; }


Preeti U. Murthy1466.67%150.00%
Viresh Kumar733.33%150.00%

/* * This is called from the guts of the broadcast code when the cpu * which is about to enter idle has the earliest broadcast timer event. */
static int bc_set_next(ktime_t expires, struct clock_event_device *bc) { int bc_moved; /* * We try to cancel the timer first. If the callback is on * flight on some other cpu then we let it handle it. If we * were able to cancel the timer nothing can rearm it as we * own broadcast_lock. * * However we can also be called from the event handler of * ce_broadcast_hrtimer itself when it expires. We cannot * restart the timer because we are in the callback, but we * can set the expiry time and let the callback return * HRTIMER_RESTART. * * Since we are in the idle loop at this point and because * hrtimer_{start/cancel} functions call into tracing, * calls to these functions must be bound within RCU_NONIDLE. */ RCU_NONIDLE({ bc_moved = hrtimer_try_to_cancel(&bctimer) >= 0; if (bc_moved) hrtimer_start(&bctimer, expires, HRTIMER_MODE_ABS_PINNED);}); if (bc_moved) { /* Bind the "device" to the cpu */ bc->bound_on = smp_processor_id(); } else if (bc->bound_on == smp_processor_id()) { hrtimer_set_expires(&bctimer, expires); } return 0; }


Preeti U. Murthy5995.16%266.67%
Thomas Gleixner34.84%133.33%

static struct clock_event_device ce_broadcast_hrtimer = { .name = "bc_hrtimer", .set_state_shutdown = bc_shutdown, .set_next_ktime = bc_set_next, .features = CLOCK_EVT_FEAT_ONESHOT | CLOCK_EVT_FEAT_KTIME | CLOCK_EVT_FEAT_HRTIMER, .rating = 0, .bound_on = -1, .min_delta_ns = 1, .max_delta_ns = KTIME_MAX, .min_delta_ticks = 1, .max_delta_ticks = ULONG_MAX, .mult = 1, .shift = 0, .cpumask = cpu_all_mask, };
static enum hrtimer_restart bc_handler(struct hrtimer *t) { ce_broadcast_hrtimer.event_handler(&ce_broadcast_hrtimer); if (clockevent_state_oneshot(&ce_broadcast_hrtimer)) if (ce_broadcast_hrtimer.next_event != KTIME_MAX) return HRTIMER_RESTART; return HRTIMER_NORESTART; }


Preeti U. Murthy3173.81%133.33%
Andreas Sandberg614.29%133.33%
Viresh Kumar511.90%133.33%

void tick_setup_hrtimer_broadcast(void) { hrtimer_init(&bctimer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS); bctimer.function = bc_handler; clockevents_register_device(&ce_broadcast_hrtimer); }


Preeti U. Murthy29100.00%1100.00%

Overall Contributors

Preeti U. Murthy24389.34%337.50%
Viresh Kumar145.15%112.50%
Andreas Sandberg62.21%112.50%
JiSheng Zhang51.84%112.50%
Thomas Gleixner31.10%112.50%
Greg Kroah-Hartman10.37%112.50%
Directory: kernel/time
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