1 // SPDX-License-Identifier: GPL-2.0
3 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
4 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
5 * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner
7 * No idle tick implementation for low and high resolution timers
9 * Started by: Thomas Gleixner and Ingo Molnar
11 #include <linux/cpu.h>
12 #include <linux/err.h>
13 #include <linux/hrtimer.h>
14 #include <linux/interrupt.h>
15 #include <linux/kernel_stat.h>
16 #include <linux/percpu.h>
17 #include <linux/nmi.h>
18 #include <linux/profile.h>
19 #include <linux/sched/signal.h>
20 #include <linux/sched/clock.h>
21 #include <linux/sched/stat.h>
22 #include <linux/sched/nohz.h>
23 #include <linux/module.h>
24 #include <linux/irq_work.h>
25 #include <linux/posix-timers.h>
26 #include <linux/context_tracking.h>
29 #include <asm/irq_regs.h>
31 #include "tick-internal.h"
33 #include <trace/events/timer.h>
36 * Per-CPU nohz control structure
38 static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
40 struct tick_sched *tick_get_tick_sched(int cpu)
42 return &per_cpu(tick_cpu_sched, cpu);
45 #if defined(CONFIG_NO_HZ_COMMON) || defined(CONFIG_HIGH_RES_TIMERS)
47 * The time, when the last jiffy update happened. Protected by jiffies_lock.
49 static ktime_t last_jiffies_update;
52 * Must be called with interrupts disabled !
54 static void tick_do_update_jiffies64(ktime_t now)
56 unsigned long ticks = 0;
60 * Do a quick check without holding jiffies_lock:
62 delta = ktime_sub(now, last_jiffies_update);
63 if (delta < tick_period)
66 /* Reevaluate with jiffies_lock held */
67 write_seqlock(&jiffies_lock);
69 delta = ktime_sub(now, last_jiffies_update);
70 if (delta >= tick_period) {
72 delta = ktime_sub(delta, tick_period);
73 last_jiffies_update = ktime_add(last_jiffies_update,
76 /* Slow path for long timeouts */
77 if (unlikely(delta >= tick_period)) {
78 s64 incr = ktime_to_ns(tick_period);
80 ticks = ktime_divns(delta, incr);
82 last_jiffies_update = ktime_add_ns(last_jiffies_update,
87 /* Keep the tick_next_period variable up to date */
88 tick_next_period = ktime_add(last_jiffies_update, tick_period);
90 write_sequnlock(&jiffies_lock);
93 write_sequnlock(&jiffies_lock);
98 * Initialize and return retrieve the jiffies update.
100 static ktime_t tick_init_jiffy_update(void)
104 write_seqlock(&jiffies_lock);
105 /* Did we start the jiffies update yet ? */
106 if (last_jiffies_update == 0)
107 last_jiffies_update = tick_next_period;
108 period = last_jiffies_update;
109 write_sequnlock(&jiffies_lock);
113 static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
115 int cpu = smp_processor_id();
117 #ifdef CONFIG_NO_HZ_COMMON
119 * Check if the do_timer duty was dropped. We don't care about
120 * concurrency: This happens only when the CPU in charge went
121 * into a long sleep. If two CPUs happen to assign themselves to
122 * this duty, then the jiffies update is still serialized by
125 * If nohz_full is enabled, this should not happen because the
126 * tick_do_timer_cpu never relinquishes.
128 if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_NONE)) {
129 #ifdef CONFIG_NO_HZ_FULL
130 WARN_ON(tick_nohz_full_running);
132 tick_do_timer_cpu = cpu;
136 /* Check, if the jiffies need an update */
137 if (tick_do_timer_cpu == cpu)
138 tick_do_update_jiffies64(now);
141 ts->got_idle_tick = 1;
144 static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
146 #ifdef CONFIG_NO_HZ_COMMON
148 * When we are idle and the tick is stopped, we have to touch
149 * the watchdog as we might not schedule for a really long
150 * time. This happens on complete idle SMP systems while
151 * waiting on the login prompt. We also increment the "start of
152 * idle" jiffy stamp so the idle accounting adjustment we do
153 * when we go busy again does not account too much ticks.
155 if (ts->tick_stopped) {
156 touch_softlockup_watchdog_sched();
157 if (is_idle_task(current))
160 * In case the current tick fired too early past its expected
161 * expiration, make sure we don't bypass the next clock reprogramming
162 * to the same deadline.
167 update_process_times(user_mode(regs));
168 profile_tick(CPU_PROFILING);
172 #ifdef CONFIG_NO_HZ_FULL
173 cpumask_var_t tick_nohz_full_mask;
174 bool tick_nohz_full_running;
175 static atomic_t tick_dep_mask;
177 static bool check_tick_dependency(atomic_t *dep)
179 int val = atomic_read(dep);
181 if (val & TICK_DEP_MASK_POSIX_TIMER) {
182 trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER);
186 if (val & TICK_DEP_MASK_PERF_EVENTS) {
187 trace_tick_stop(0, TICK_DEP_MASK_PERF_EVENTS);
191 if (val & TICK_DEP_MASK_SCHED) {
192 trace_tick_stop(0, TICK_DEP_MASK_SCHED);
196 if (val & TICK_DEP_MASK_CLOCK_UNSTABLE) {
197 trace_tick_stop(0, TICK_DEP_MASK_CLOCK_UNSTABLE);
204 static bool can_stop_full_tick(int cpu, struct tick_sched *ts)
206 lockdep_assert_irqs_disabled();
208 if (unlikely(!cpu_online(cpu)))
211 if (check_tick_dependency(&tick_dep_mask))
214 if (check_tick_dependency(&ts->tick_dep_mask))
217 if (check_tick_dependency(¤t->tick_dep_mask))
220 if (check_tick_dependency(¤t->signal->tick_dep_mask))
226 static void nohz_full_kick_func(struct irq_work *work)
228 /* Empty, the tick restart happens on tick_nohz_irq_exit() */
231 static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) = {
232 .func = nohz_full_kick_func,
236 * Kick this CPU if it's full dynticks in order to force it to
237 * re-evaluate its dependency on the tick and restart it if necessary.
238 * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(),
241 static void tick_nohz_full_kick(void)
243 if (!tick_nohz_full_cpu(smp_processor_id()))
246 irq_work_queue(this_cpu_ptr(&nohz_full_kick_work));
250 * Kick the CPU if it's full dynticks in order to force it to
251 * re-evaluate its dependency on the tick and restart it if necessary.
253 void tick_nohz_full_kick_cpu(int cpu)
255 if (!tick_nohz_full_cpu(cpu))
258 irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu);
262 * Kick all full dynticks CPUs in order to force these to re-evaluate
263 * their dependency on the tick and restart it if necessary.
265 static void tick_nohz_full_kick_all(void)
269 if (!tick_nohz_full_running)
273 for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask)
274 tick_nohz_full_kick_cpu(cpu);
278 static void tick_nohz_dep_set_all(atomic_t *dep,
279 enum tick_dep_bits bit)
283 prev = atomic_fetch_or(BIT(bit), dep);
285 tick_nohz_full_kick_all();
289 * Set a global tick dependency. Used by perf events that rely on freq and
292 void tick_nohz_dep_set(enum tick_dep_bits bit)
294 tick_nohz_dep_set_all(&tick_dep_mask, bit);
297 void tick_nohz_dep_clear(enum tick_dep_bits bit)
299 atomic_andnot(BIT(bit), &tick_dep_mask);
303 * Set per-CPU tick dependency. Used by scheduler and perf events in order to
304 * manage events throttling.
306 void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit)
309 struct tick_sched *ts;
311 ts = per_cpu_ptr(&tick_cpu_sched, cpu);
313 prev = atomic_fetch_or(BIT(bit), &ts->tick_dep_mask);
316 /* Perf needs local kick that is NMI safe */
317 if (cpu == smp_processor_id()) {
318 tick_nohz_full_kick();
320 /* Remote irq work not NMI-safe */
321 if (!WARN_ON_ONCE(in_nmi()))
322 tick_nohz_full_kick_cpu(cpu);
328 void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit)
330 struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
332 atomic_andnot(BIT(bit), &ts->tick_dep_mask);
336 * Set a per-task tick dependency. Posix CPU timers need this in order to elapse
339 void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit)
342 * We could optimize this with just kicking the target running the task
343 * if that noise matters for nohz full users.
345 tick_nohz_dep_set_all(&tsk->tick_dep_mask, bit);
348 void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit)
350 atomic_andnot(BIT(bit), &tsk->tick_dep_mask);
354 * Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse
355 * per process timers.
357 void tick_nohz_dep_set_signal(struct signal_struct *sig, enum tick_dep_bits bit)
359 tick_nohz_dep_set_all(&sig->tick_dep_mask, bit);
362 void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit)
364 atomic_andnot(BIT(bit), &sig->tick_dep_mask);
368 * Re-evaluate the need for the tick as we switch the current task.
369 * It might need the tick due to per task/process properties:
370 * perf events, posix CPU timers, ...
372 void __tick_nohz_task_switch(void)
375 struct tick_sched *ts;
377 local_irq_save(flags);
379 if (!tick_nohz_full_cpu(smp_processor_id()))
382 ts = this_cpu_ptr(&tick_cpu_sched);
384 if (ts->tick_stopped) {
385 if (atomic_read(¤t->tick_dep_mask) ||
386 atomic_read(¤t->signal->tick_dep_mask))
387 tick_nohz_full_kick();
390 local_irq_restore(flags);
393 /* Get the boot-time nohz CPU list from the kernel parameters. */
394 void __init tick_nohz_full_setup(cpumask_var_t cpumask)
396 alloc_bootmem_cpumask_var(&tick_nohz_full_mask);
397 cpumask_copy(tick_nohz_full_mask, cpumask);
398 tick_nohz_full_running = true;
401 static int tick_nohz_cpu_down(unsigned int cpu)
404 * The tick_do_timer_cpu CPU handles housekeeping duty (unbound
405 * timers, workqueues, timekeeping, ...) on behalf of full dynticks
406 * CPUs. It must remain online when nohz full is enabled.
408 if (tick_nohz_full_running && tick_do_timer_cpu == cpu)
413 void __init tick_nohz_init(void)
417 if (!tick_nohz_full_running)
421 * Full dynticks uses irq work to drive the tick rescheduling on safe
422 * locking contexts. But then we need irq work to raise its own
423 * interrupts to avoid circular dependency on the tick
425 if (!arch_irq_work_has_interrupt()) {
426 pr_warn("NO_HZ: Can't run full dynticks because arch doesn't support irq work self-IPIs\n");
427 cpumask_clear(tick_nohz_full_mask);
428 tick_nohz_full_running = false;
432 if (IS_ENABLED(CONFIG_PM_SLEEP_SMP) &&
433 !IS_ENABLED(CONFIG_PM_SLEEP_SMP_NONZERO_CPU)) {
434 cpu = smp_processor_id();
436 if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) {
437 pr_warn("NO_HZ: Clearing %d from nohz_full range "
438 "for timekeeping\n", cpu);
439 cpumask_clear_cpu(cpu, tick_nohz_full_mask);
443 for_each_cpu(cpu, tick_nohz_full_mask)
444 context_tracking_cpu_set(cpu);
446 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
447 "kernel/nohz:predown", NULL,
450 pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
451 cpumask_pr_args(tick_nohz_full_mask));
456 * NOHZ - aka dynamic tick functionality
458 #ifdef CONFIG_NO_HZ_COMMON
462 bool tick_nohz_enabled __read_mostly = true;
463 unsigned long tick_nohz_active __read_mostly;
465 * Enable / Disable tickless mode
467 static int __init setup_tick_nohz(char *str)
469 return (kstrtobool(str, &tick_nohz_enabled) == 0);
472 __setup("nohz=", setup_tick_nohz);
474 bool tick_nohz_tick_stopped(void)
476 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
478 return ts->tick_stopped;
481 bool tick_nohz_tick_stopped_cpu(int cpu)
483 struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
485 return ts->tick_stopped;
489 * tick_nohz_update_jiffies - update jiffies when idle was interrupted
491 * Called from interrupt entry when the CPU was idle
493 * In case the sched_tick was stopped on this CPU, we have to check if jiffies
494 * must be updated. Otherwise an interrupt handler could use a stale jiffy
495 * value. We do this unconditionally on any CPU, as we don't know whether the
496 * CPU, which has the update task assigned is in a long sleep.
498 static void tick_nohz_update_jiffies(ktime_t now)
502 __this_cpu_write(tick_cpu_sched.idle_waketime, now);
504 local_irq_save(flags);
505 tick_do_update_jiffies64(now);
506 local_irq_restore(flags);
508 touch_softlockup_watchdog_sched();
512 * Updates the per-CPU time idle statistics counters
515 update_ts_time_stats(int cpu, struct tick_sched *ts, ktime_t now, u64 *last_update_time)
519 if (ts->idle_active) {
520 delta = ktime_sub(now, ts->idle_entrytime);
521 if (nr_iowait_cpu(cpu) > 0)
522 ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
524 ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
525 ts->idle_entrytime = now;
528 if (last_update_time)
529 *last_update_time = ktime_to_us(now);
533 static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
535 update_ts_time_stats(smp_processor_id(), ts, now, NULL);
538 sched_clock_idle_wakeup_event();
541 static void tick_nohz_start_idle(struct tick_sched *ts)
543 ts->idle_entrytime = ktime_get();
545 sched_clock_idle_sleep_event();
549 * get_cpu_idle_time_us - get the total idle time of a CPU
550 * @cpu: CPU number to query
551 * @last_update_time: variable to store update time in. Do not update
554 * Return the cumulative idle time (since boot) for a given
555 * CPU, in microseconds.
557 * This time is measured via accounting rather than sampling,
558 * and is as accurate as ktime_get() is.
560 * This function returns -1 if NOHZ is not enabled.
562 u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
564 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
567 if (!tick_nohz_active)
571 if (last_update_time) {
572 update_ts_time_stats(cpu, ts, now, last_update_time);
573 idle = ts->idle_sleeptime;
575 if (ts->idle_active && !nr_iowait_cpu(cpu)) {
576 ktime_t delta = ktime_sub(now, ts->idle_entrytime);
578 idle = ktime_add(ts->idle_sleeptime, delta);
580 idle = ts->idle_sleeptime;
584 return ktime_to_us(idle);
587 EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
590 * get_cpu_iowait_time_us - get the total iowait time of a CPU
591 * @cpu: CPU number to query
592 * @last_update_time: variable to store update time in. Do not update
595 * Return the cumulative iowait time (since boot) for a given
596 * CPU, in microseconds.
598 * This time is measured via accounting rather than sampling,
599 * and is as accurate as ktime_get() is.
601 * This function returns -1 if NOHZ is not enabled.
603 u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
605 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
608 if (!tick_nohz_active)
612 if (last_update_time) {
613 update_ts_time_stats(cpu, ts, now, last_update_time);
614 iowait = ts->iowait_sleeptime;
616 if (ts->idle_active && nr_iowait_cpu(cpu) > 0) {
617 ktime_t delta = ktime_sub(now, ts->idle_entrytime);
619 iowait = ktime_add(ts->iowait_sleeptime, delta);
621 iowait = ts->iowait_sleeptime;
625 return ktime_to_us(iowait);
627 EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
629 static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
631 hrtimer_cancel(&ts->sched_timer);
632 hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
634 /* Forward the time to expire in the future */
635 hrtimer_forward(&ts->sched_timer, now, tick_period);
637 if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
638 hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED);
640 tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
643 * Reset to make sure next tick stop doesn't get fooled by past
644 * cached clock deadline.
649 static inline bool local_timer_softirq_pending(void)
651 return local_softirq_pending() & BIT(TIMER_SOFTIRQ);
654 static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
656 u64 basemono, next_tick, next_tmr, next_rcu, delta, expires;
657 unsigned long basejiff;
660 /* Read jiffies and the time when jiffies were updated last */
662 seq = read_seqbegin(&jiffies_lock);
663 basemono = last_jiffies_update;
665 } while (read_seqretry(&jiffies_lock, seq));
666 ts->last_jiffies = basejiff;
667 ts->timer_expires_base = basemono;
670 * Keep the periodic tick, when RCU, architecture or irq_work
672 * Aside of that check whether the local timer softirq is
673 * pending. If so its a bad idea to call get_next_timer_interrupt()
674 * because there is an already expired timer, so it will request
675 * immeditate expiry, which rearms the hardware timer with a
676 * minimal delta which brings us back to this place
677 * immediately. Lather, rinse and repeat...
679 if (rcu_needs_cpu(basemono, &next_rcu) || arch_needs_cpu() ||
680 irq_work_needs_cpu() || local_timer_softirq_pending()) {
681 next_tick = basemono + TICK_NSEC;
684 * Get the next pending timer. If high resolution
685 * timers are enabled this only takes the timer wheel
686 * timers into account. If high resolution timers are
687 * disabled this also looks at the next expiring
690 next_tmr = get_next_timer_interrupt(basejiff, basemono);
691 ts->next_timer = next_tmr;
692 /* Take the next rcu event into account */
693 next_tick = next_rcu < next_tmr ? next_rcu : next_tmr;
697 * If the tick is due in the next period, keep it ticking or
698 * force prod the timer.
700 delta = next_tick - basemono;
701 if (delta <= (u64)TICK_NSEC) {
703 * Tell the timer code that the base is not idle, i.e. undo
704 * the effect of get_next_timer_interrupt():
708 * We've not stopped the tick yet, and there's a timer in the
709 * next period, so no point in stopping it either, bail.
711 if (!ts->tick_stopped) {
712 ts->timer_expires = 0;
718 * If this CPU is the one which had the do_timer() duty last, we limit
719 * the sleep time to the timekeeping max_deferment value.
720 * Otherwise we can sleep as long as we want.
722 delta = timekeeping_max_deferment();
723 if (cpu != tick_do_timer_cpu &&
724 (tick_do_timer_cpu != TICK_DO_TIMER_NONE || !ts->do_timer_last))
727 /* Calculate the next expiry time */
728 if (delta < (KTIME_MAX - basemono))
729 expires = basemono + delta;
733 ts->timer_expires = min_t(u64, expires, next_tick);
736 return ts->timer_expires;
739 static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu)
741 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
742 u64 basemono = ts->timer_expires_base;
743 u64 expires = ts->timer_expires;
744 ktime_t tick = expires;
746 /* Make sure we won't be trying to stop it twice in a row. */
747 ts->timer_expires_base = 0;
750 * If this CPU is the one which updates jiffies, then give up
751 * the assignment and let it be taken by the CPU which runs
752 * the tick timer next, which might be this CPU as well. If we
753 * don't drop this here the jiffies might be stale and
754 * do_timer() never invoked. Keep track of the fact that it
755 * was the one which had the do_timer() duty last.
757 if (cpu == tick_do_timer_cpu) {
758 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
759 ts->do_timer_last = 1;
760 } else if (tick_do_timer_cpu != TICK_DO_TIMER_NONE) {
761 ts->do_timer_last = 0;
764 /* Skip reprogram of event if its not changed */
765 if (ts->tick_stopped && (expires == ts->next_tick)) {
766 /* Sanity check: make sure clockevent is actually programmed */
767 if (tick == KTIME_MAX || ts->next_tick == hrtimer_get_expires(&ts->sched_timer))
771 printk_once("basemono: %llu ts->next_tick: %llu dev->next_event: %llu timer->active: %d timer->expires: %llu\n",
772 basemono, ts->next_tick, dev->next_event,
773 hrtimer_active(&ts->sched_timer), hrtimer_get_expires(&ts->sched_timer));
777 * nohz_stop_sched_tick can be called several times before
778 * the nohz_restart_sched_tick is called. This happens when
779 * interrupts arrive which do not cause a reschedule. In the
780 * first call we save the current tick time, so we can restart
781 * the scheduler tick in nohz_restart_sched_tick.
783 if (!ts->tick_stopped) {
784 calc_load_nohz_start();
785 cpu_load_update_nohz_start();
788 ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
789 ts->tick_stopped = 1;
790 trace_tick_stop(1, TICK_DEP_MASK_NONE);
793 ts->next_tick = tick;
796 * If the expiration time == KTIME_MAX, then we simply stop
799 if (unlikely(expires == KTIME_MAX)) {
800 if (ts->nohz_mode == NOHZ_MODE_HIGHRES)
801 hrtimer_cancel(&ts->sched_timer);
805 if (ts->nohz_mode == NOHZ_MODE_HIGHRES) {
806 hrtimer_start(&ts->sched_timer, tick, HRTIMER_MODE_ABS_PINNED);
808 hrtimer_set_expires(&ts->sched_timer, tick);
809 tick_program_event(tick, 1);
813 static void tick_nohz_retain_tick(struct tick_sched *ts)
815 ts->timer_expires_base = 0;
818 #ifdef CONFIG_NO_HZ_FULL
819 static void tick_nohz_stop_sched_tick(struct tick_sched *ts, int cpu)
821 if (tick_nohz_next_event(ts, cpu))
822 tick_nohz_stop_tick(ts, cpu);
824 tick_nohz_retain_tick(ts);
826 #endif /* CONFIG_NO_HZ_FULL */
828 static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
830 /* Update jiffies first */
831 tick_do_update_jiffies64(now);
832 cpu_load_update_nohz_stop();
835 * Clear the timer idle flag, so we avoid IPIs on remote queueing and
836 * the clock forward checks in the enqueue path:
840 calc_load_nohz_stop();
841 touch_softlockup_watchdog_sched();
843 * Cancel the scheduled timer and restore the tick
845 ts->tick_stopped = 0;
846 ts->idle_exittime = now;
848 tick_nohz_restart(ts, now);
851 static void tick_nohz_full_update_tick(struct tick_sched *ts)
853 #ifdef CONFIG_NO_HZ_FULL
854 int cpu = smp_processor_id();
856 if (!tick_nohz_full_cpu(cpu))
859 if (!ts->tick_stopped && ts->nohz_mode == NOHZ_MODE_INACTIVE)
862 if (can_stop_full_tick(cpu, ts))
863 tick_nohz_stop_sched_tick(ts, cpu);
864 else if (ts->tick_stopped)
865 tick_nohz_restart_sched_tick(ts, ktime_get());
869 static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
872 * If this CPU is offline and it is the one which updates
873 * jiffies, then give up the assignment and let it be taken by
874 * the CPU which runs the tick timer next. If we don't drop
875 * this here the jiffies might be stale and do_timer() never
878 if (unlikely(!cpu_online(cpu))) {
879 if (cpu == tick_do_timer_cpu)
880 tick_do_timer_cpu = TICK_DO_TIMER_NONE;
882 * Make sure the CPU doesn't get fooled by obsolete tick
883 * deadline if it comes back online later.
889 if (unlikely(ts->nohz_mode == NOHZ_MODE_INACTIVE))
895 if (unlikely(local_softirq_pending())) {
896 static int ratelimit;
898 if (ratelimit < 10 &&
899 (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK)) {
900 pr_warn("NOHZ: local_softirq_pending %02x\n",
901 (unsigned int) local_softirq_pending());
907 if (tick_nohz_full_enabled()) {
909 * Keep the tick alive to guarantee timekeeping progression
910 * if there are full dynticks CPUs around
912 if (tick_do_timer_cpu == cpu)
915 * Boot safety: make sure the timekeeping duty has been
916 * assigned before entering dyntick-idle mode,
917 * tick_do_timer_cpu is TICK_DO_TIMER_BOOT
919 if (unlikely(tick_do_timer_cpu == TICK_DO_TIMER_BOOT))
922 /* Should not happen for nohz-full */
923 if (WARN_ON_ONCE(tick_do_timer_cpu == TICK_DO_TIMER_NONE))
930 static void __tick_nohz_idle_stop_tick(struct tick_sched *ts)
933 int cpu = smp_processor_id();
936 * If tick_nohz_get_sleep_length() ran tick_nohz_next_event(), the
937 * tick timer expiration time is known already.
939 if (ts->timer_expires_base)
940 expires = ts->timer_expires;
941 else if (can_stop_idle_tick(cpu, ts))
942 expires = tick_nohz_next_event(ts, cpu);
949 int was_stopped = ts->tick_stopped;
951 tick_nohz_stop_tick(ts, cpu);
954 ts->idle_expires = expires;
956 if (!was_stopped && ts->tick_stopped) {
957 ts->idle_jiffies = ts->last_jiffies;
958 nohz_balance_enter_idle(cpu);
961 tick_nohz_retain_tick(ts);
966 * tick_nohz_idle_stop_tick - stop the idle tick from the idle task
968 * When the next event is more than a tick into the future, stop the idle tick
970 void tick_nohz_idle_stop_tick(void)
972 __tick_nohz_idle_stop_tick(this_cpu_ptr(&tick_cpu_sched));
975 void tick_nohz_idle_retain_tick(void)
977 tick_nohz_retain_tick(this_cpu_ptr(&tick_cpu_sched));
979 * Undo the effect of get_next_timer_interrupt() called from
980 * tick_nohz_next_event().
986 * tick_nohz_idle_enter - prepare for entering idle on the current CPU
988 * Called when we start the idle loop.
990 void tick_nohz_idle_enter(void)
992 struct tick_sched *ts;
994 lockdep_assert_irqs_enabled();
998 ts = this_cpu_ptr(&tick_cpu_sched);
1000 WARN_ON_ONCE(ts->timer_expires_base);
1003 tick_nohz_start_idle(ts);
1009 * tick_nohz_irq_exit - update next tick event from interrupt exit
1011 * When an interrupt fires while we are idle and it doesn't cause
1012 * a reschedule, it may still add, modify or delete a timer, enqueue
1013 * an RCU callback, etc...
1014 * So we need to re-calculate and reprogram the next tick event.
1016 void tick_nohz_irq_exit(void)
1018 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1021 tick_nohz_start_idle(ts);
1023 tick_nohz_full_update_tick(ts);
1027 * tick_nohz_idle_got_tick - Check whether or not the tick handler has run
1029 bool tick_nohz_idle_got_tick(void)
1031 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1033 if (ts->got_idle_tick) {
1034 ts->got_idle_tick = 0;
1041 * tick_nohz_get_next_hrtimer - return the next expiration time for the hrtimer
1042 * or the tick, whatever that expires first. Note that, if the tick has been
1043 * stopped, it returns the next hrtimer.
1045 * Called from power state control code with interrupts disabled
1047 ktime_t tick_nohz_get_next_hrtimer(void)
1049 return __this_cpu_read(tick_cpu_device.evtdev)->next_event;
1053 * tick_nohz_get_sleep_length - return the expected length of the current sleep
1054 * @delta_next: duration until the next event if the tick cannot be stopped
1056 * Called from power state control code with interrupts disabled
1058 ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next)
1060 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
1061 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1062 int cpu = smp_processor_id();
1064 * The idle entry time is expected to be a sufficient approximation of
1065 * the current time at this point.
1067 ktime_t now = ts->idle_entrytime;
1070 WARN_ON_ONCE(!ts->inidle);
1072 *delta_next = ktime_sub(dev->next_event, now);
1074 if (!can_stop_idle_tick(cpu, ts))
1077 next_event = tick_nohz_next_event(ts, cpu);
1082 * If the next highres timer to expire is earlier than next_event, the
1083 * idle governor needs to know that.
1085 next_event = min_t(u64, next_event,
1086 hrtimer_next_event_without(&ts->sched_timer));
1088 return ktime_sub(next_event, now);
1092 * tick_nohz_get_idle_calls_cpu - return the current idle calls counter value
1093 * for a particular CPU.
1095 * Called from the schedutil frequency scaling governor in scheduler context.
1097 unsigned long tick_nohz_get_idle_calls_cpu(int cpu)
1099 struct tick_sched *ts = tick_get_tick_sched(cpu);
1101 return ts->idle_calls;
1105 * tick_nohz_get_idle_calls - return the current idle calls counter value
1107 * Called from the schedutil frequency scaling governor in scheduler context.
1109 unsigned long tick_nohz_get_idle_calls(void)
1111 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1113 return ts->idle_calls;
1116 static void tick_nohz_account_idle_ticks(struct tick_sched *ts)
1118 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
1119 unsigned long ticks;
1121 if (vtime_accounting_cpu_enabled())
1124 * We stopped the tick in idle. Update process times would miss the
1125 * time we slept as update_process_times does only a 1 tick
1126 * accounting. Enforce that this is accounted to idle !
1128 ticks = jiffies - ts->idle_jiffies;
1130 * We might be one off. Do not randomly account a huge number of ticks!
1132 if (ticks && ticks < LONG_MAX)
1133 account_idle_ticks(ticks);
1137 static void __tick_nohz_idle_restart_tick(struct tick_sched *ts, ktime_t now)
1139 tick_nohz_restart_sched_tick(ts, now);
1140 tick_nohz_account_idle_ticks(ts);
1143 void tick_nohz_idle_restart_tick(void)
1145 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1147 if (ts->tick_stopped)
1148 __tick_nohz_idle_restart_tick(ts, ktime_get());
1152 * tick_nohz_idle_exit - restart the idle tick from the idle task
1154 * Restart the idle tick when the CPU is woken up from idle
1155 * This also exit the RCU extended quiescent state. The CPU
1156 * can use RCU again after this function is called.
1158 void tick_nohz_idle_exit(void)
1160 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1161 bool idle_active, tick_stopped;
1164 local_irq_disable();
1166 WARN_ON_ONCE(!ts->inidle);
1167 WARN_ON_ONCE(ts->timer_expires_base);
1170 idle_active = ts->idle_active;
1171 tick_stopped = ts->tick_stopped;
1173 if (idle_active || tick_stopped)
1177 tick_nohz_stop_idle(ts, now);
1180 __tick_nohz_idle_restart_tick(ts, now);
1186 * The nohz low res interrupt handler
1188 static void tick_nohz_handler(struct clock_event_device *dev)
1190 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1191 struct pt_regs *regs = get_irq_regs();
1192 ktime_t now = ktime_get();
1194 dev->next_event = KTIME_MAX;
1196 tick_sched_do_timer(ts, now);
1197 tick_sched_handle(ts, regs);
1199 /* No need to reprogram if we are running tickless */
1200 if (unlikely(ts->tick_stopped))
1203 hrtimer_forward(&ts->sched_timer, now, tick_period);
1204 tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
1207 static inline void tick_nohz_activate(struct tick_sched *ts, int mode)
1209 if (!tick_nohz_enabled)
1211 ts->nohz_mode = mode;
1212 /* One update is enough */
1213 if (!test_and_set_bit(0, &tick_nohz_active))
1214 timers_update_nohz();
1218 * tick_nohz_switch_to_nohz - switch to nohz mode
1220 static void tick_nohz_switch_to_nohz(void)
1222 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1225 if (!tick_nohz_enabled)
1228 if (tick_switch_to_oneshot(tick_nohz_handler))
1232 * Recycle the hrtimer in ts, so we can share the
1233 * hrtimer_forward with the highres code.
1235 hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
1236 /* Get the next period */
1237 next = tick_init_jiffy_update();
1239 hrtimer_set_expires(&ts->sched_timer, next);
1240 hrtimer_forward_now(&ts->sched_timer, tick_period);
1241 tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
1242 tick_nohz_activate(ts, NOHZ_MODE_LOWRES);
1245 static inline void tick_nohz_irq_enter(void)
1247 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1250 if (!ts->idle_active && !ts->tick_stopped)
1253 if (ts->idle_active)
1254 tick_nohz_stop_idle(ts, now);
1255 if (ts->tick_stopped)
1256 tick_nohz_update_jiffies(now);
1261 static inline void tick_nohz_switch_to_nohz(void) { }
1262 static inline void tick_nohz_irq_enter(void) { }
1263 static inline void tick_nohz_activate(struct tick_sched *ts, int mode) { }
1265 #endif /* CONFIG_NO_HZ_COMMON */
1268 * Called from irq_enter to notify about the possible interruption of idle()
1270 void tick_irq_enter(void)
1272 tick_check_oneshot_broadcast_this_cpu();
1273 tick_nohz_irq_enter();
1277 * High resolution timer specific code
1279 #ifdef CONFIG_HIGH_RES_TIMERS
1281 * We rearm the timer until we get disabled by the idle code.
1282 * Called with interrupts disabled.
1284 static enum hrtimer_restart tick_sched_timer(struct hrtimer *timer)
1286 struct tick_sched *ts =
1287 container_of(timer, struct tick_sched, sched_timer);
1288 struct pt_regs *regs = get_irq_regs();
1289 ktime_t now = ktime_get();
1291 tick_sched_do_timer(ts, now);
1294 * Do not call, when we are not in irq context and have
1295 * no valid regs pointer
1298 tick_sched_handle(ts, regs);
1302 /* No need to reprogram if we are in idle or full dynticks mode */
1303 if (unlikely(ts->tick_stopped))
1304 return HRTIMER_NORESTART;
1306 hrtimer_forward(timer, now, tick_period);
1308 return HRTIMER_RESTART;
1311 static int sched_skew_tick;
1313 static int __init skew_tick(char *str)
1315 get_option(&str, &sched_skew_tick);
1319 early_param("skew_tick", skew_tick);
1322 * tick_setup_sched_timer - setup the tick emulation timer
1324 void tick_setup_sched_timer(void)
1326 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1327 ktime_t now = ktime_get();
1330 * Emulate tick processing via per-CPU hrtimers:
1332 hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS);
1333 ts->sched_timer.function = tick_sched_timer;
1335 /* Get the next period (per-CPU) */
1336 hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
1338 /* Offset the tick to avert jiffies_lock contention. */
1339 if (sched_skew_tick) {
1340 u64 offset = ktime_to_ns(tick_period) >> 1;
1341 do_div(offset, num_possible_cpus());
1342 offset *= smp_processor_id();
1343 hrtimer_add_expires_ns(&ts->sched_timer, offset);
1346 hrtimer_forward(&ts->sched_timer, now, tick_period);
1347 hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED);
1348 tick_nohz_activate(ts, NOHZ_MODE_HIGHRES);
1350 #endif /* HIGH_RES_TIMERS */
1352 #if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
1353 void tick_cancel_sched_timer(int cpu)
1355 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
1357 # ifdef CONFIG_HIGH_RES_TIMERS
1358 if (ts->sched_timer.base)
1359 hrtimer_cancel(&ts->sched_timer);
1362 memset(ts, 0, sizeof(*ts));
1367 * Async notification about clocksource changes
1369 void tick_clock_notify(void)
1373 for_each_possible_cpu(cpu)
1374 set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks);
1378 * Async notification about clock event changes
1380 void tick_oneshot_notify(void)
1382 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1384 set_bit(0, &ts->check_clocks);
1388 * Check, if a change happened, which makes oneshot possible.
1390 * Called cyclic from the hrtimer softirq (driven by the timer
1391 * softirq) allow_nohz signals, that we can switch into low-res nohz
1392 * mode, because high resolution timers are disabled (either compile
1393 * or runtime). Called with interrupts disabled.
1395 int tick_check_oneshot_change(int allow_nohz)
1397 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1399 if (!test_and_clear_bit(0, &ts->check_clocks))
1402 if (ts->nohz_mode != NOHZ_MODE_INACTIVE)
1405 if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
1411 tick_nohz_switch_to_nohz();