1 // SPDX-License-Identifier: GPL-2.0
4 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
5 * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner
7 * NOHZ implementation for low and high resolution timers
9 * Started by: Thomas Gleixner and Ingo Molnar
11 #include <linux/compiler.h>
12 #include <linux/cpu.h>
13 #include <linux/err.h>
14 #include <linux/hrtimer.h>
15 #include <linux/interrupt.h>
16 #include <linux/kernel_stat.h>
17 #include <linux/percpu.h>
18 #include <linux/nmi.h>
19 #include <linux/profile.h>
20 #include <linux/sched/signal.h>
21 #include <linux/sched/clock.h>
22 #include <linux/sched/stat.h>
23 #include <linux/sched/nohz.h>
24 #include <linux/sched/loadavg.h>
25 #include <linux/module.h>
26 #include <linux/irq_work.h>
27 #include <linux/posix-timers.h>
28 #include <linux/context_tracking.h>
31 #include <asm/irq_regs.h>
33 #include "tick-internal.h"
35 #include <trace/events/timer.h>
38 * Per-CPU nohz control structure
40 static DEFINE_PER_CPU(struct tick_sched, tick_cpu_sched);
42 struct tick_sched *tick_get_tick_sched(int cpu)
44 return &per_cpu(tick_cpu_sched, cpu);
48 * The time when the last jiffy update happened. Write access must hold
49 * jiffies_lock and jiffies_seq. tick_nohz_next_event() needs to get a
50 * consistent view of jiffies and last_jiffies_update.
52 static ktime_t last_jiffies_update;
55 * Must be called with interrupts disabled !
57 static void tick_do_update_jiffies64(ktime_t now)
59 unsigned long ticks = 1;
63 * 64-bit can do a quick check without holding the jiffies lock and
64 * without looking at the sequence count. The smp_load_acquire()
65 * pairs with the update done later in this function.
67 * 32-bit cannot do that because the store of 'tick_next_period'
68 * consists of two 32-bit stores, and the first store could be
69 * moved by the CPU to a random point in the future.
71 if (IS_ENABLED(CONFIG_64BIT)) {
72 if (ktime_before(now, smp_load_acquire(&tick_next_period)))
78 * Avoid contention on 'jiffies_lock' and protect the quick
79 * check with the sequence count.
82 seq = read_seqcount_begin(&jiffies_seq);
83 nextp = tick_next_period;
84 } while (read_seqcount_retry(&jiffies_seq, seq));
86 if (ktime_before(now, nextp))
90 /* Quick check failed, i.e. update is required. */
91 raw_spin_lock(&jiffies_lock);
93 * Re-evaluate with the lock held. Another CPU might have done the
96 if (ktime_before(now, tick_next_period)) {
97 raw_spin_unlock(&jiffies_lock);
101 write_seqcount_begin(&jiffies_seq);
103 delta = ktime_sub(now, tick_next_period);
104 if (unlikely(delta >= TICK_NSEC)) {
105 /* Slow path for long idle sleep times */
106 s64 incr = TICK_NSEC;
108 ticks += ktime_divns(delta, incr);
110 last_jiffies_update = ktime_add_ns(last_jiffies_update,
113 last_jiffies_update = ktime_add_ns(last_jiffies_update,
117 /* Advance jiffies to complete the 'jiffies_seq' protected job */
120 /* Keep the tick_next_period variable up to date */
121 nextp = ktime_add_ns(last_jiffies_update, TICK_NSEC);
123 if (IS_ENABLED(CONFIG_64BIT)) {
125 * Pairs with smp_load_acquire() in the lockless quick
126 * check above, and ensures that the update to 'jiffies_64' is
127 * not reordered vs. the store to 'tick_next_period', neither
128 * by the compiler nor by the CPU.
130 smp_store_release(&tick_next_period, nextp);
133 * A plain store is good enough on 32-bit, as the quick check
134 * above is protected by the sequence count.
136 tick_next_period = nextp;
140 * Release the sequence count. calc_global_load() below is not
141 * protected by it, but 'jiffies_lock' needs to be held to prevent
142 * concurrent invocations.
144 write_seqcount_end(&jiffies_seq);
148 raw_spin_unlock(&jiffies_lock);
153 * Initialize and return retrieve the jiffies update.
155 static ktime_t tick_init_jiffy_update(void)
159 raw_spin_lock(&jiffies_lock);
160 write_seqcount_begin(&jiffies_seq);
162 /* Have we started the jiffies update yet ? */
163 if (last_jiffies_update == 0) {
167 * Ensure that the tick is aligned to a multiple of
170 div_u64_rem(tick_next_period, TICK_NSEC, &rem);
172 tick_next_period += TICK_NSEC - rem;
174 last_jiffies_update = tick_next_period;
176 period = last_jiffies_update;
178 write_seqcount_end(&jiffies_seq);
179 raw_spin_unlock(&jiffies_lock);
184 static inline int tick_sched_flag_test(struct tick_sched *ts,
187 return !!(ts->flags & flag);
190 static inline void tick_sched_flag_set(struct tick_sched *ts,
193 lockdep_assert_irqs_disabled();
197 static inline void tick_sched_flag_clear(struct tick_sched *ts,
200 lockdep_assert_irqs_disabled();
204 #define MAX_STALLED_JIFFIES 5
206 static void tick_sched_do_timer(struct tick_sched *ts, ktime_t now)
208 int tick_cpu, cpu = smp_processor_id();
211 * Check if the do_timer duty was dropped. We don't care about
212 * concurrency: This happens only when the CPU in charge went
213 * into a long sleep. If two CPUs happen to assign themselves to
214 * this duty, then the jiffies update is still serialized by
217 * If nohz_full is enabled, this should not happen because the
218 * 'tick_do_timer_cpu' CPU never relinquishes.
220 tick_cpu = READ_ONCE(tick_do_timer_cpu);
222 if (IS_ENABLED(CONFIG_NO_HZ_COMMON) && unlikely(tick_cpu == TICK_DO_TIMER_NONE)) {
223 #ifdef CONFIG_NO_HZ_FULL
224 WARN_ON_ONCE(tick_nohz_full_running);
226 WRITE_ONCE(tick_do_timer_cpu, cpu);
230 /* Check if jiffies need an update */
232 tick_do_update_jiffies64(now);
235 * If the jiffies update stalled for too long (timekeeper in stop_machine()
236 * or VMEXIT'ed for several msecs), force an update.
238 if (ts->last_tick_jiffies != jiffies) {
239 ts->stalled_jiffies = 0;
240 ts->last_tick_jiffies = READ_ONCE(jiffies);
242 if (++ts->stalled_jiffies == MAX_STALLED_JIFFIES) {
243 tick_do_update_jiffies64(now);
244 ts->stalled_jiffies = 0;
245 ts->last_tick_jiffies = READ_ONCE(jiffies);
249 if (tick_sched_flag_test(ts, TS_FLAG_INIDLE))
250 ts->got_idle_tick = 1;
253 static void tick_sched_handle(struct tick_sched *ts, struct pt_regs *regs)
256 * When we are idle and the tick is stopped, we have to touch
257 * the watchdog as we might not schedule for a really long
258 * time. This happens on completely idle SMP systems while
259 * waiting on the login prompt. We also increment the "start of
260 * idle" jiffy stamp so the idle accounting adjustment we do
261 * when we go busy again does not account too many ticks.
263 if (IS_ENABLED(CONFIG_NO_HZ_COMMON) &&
264 tick_sched_flag_test(ts, TS_FLAG_STOPPED)) {
265 touch_softlockup_watchdog_sched();
266 if (is_idle_task(current))
269 * In case the current tick fired too early past its expected
270 * expiration, make sure we don't bypass the next clock reprogramming
271 * to the same deadline.
276 update_process_times(user_mode(regs));
277 profile_tick(CPU_PROFILING);
281 * We rearm the timer until we get disabled by the idle code.
282 * Called with interrupts disabled.
284 static enum hrtimer_restart tick_nohz_handler(struct hrtimer *timer)
286 struct tick_sched *ts = container_of(timer, struct tick_sched, sched_timer);
287 struct pt_regs *regs = get_irq_regs();
288 ktime_t now = ktime_get();
290 tick_sched_do_timer(ts, now);
293 * Do not call when we are not in IRQ context and have
294 * no valid 'regs' pointer
297 tick_sched_handle(ts, regs);
302 * In dynticks mode, tick reprogram is deferred:
303 * - to the idle task if in dynticks-idle
304 * - to IRQ exit if in full-dynticks.
306 if (unlikely(tick_sched_flag_test(ts, TS_FLAG_STOPPED)))
307 return HRTIMER_NORESTART;
309 hrtimer_forward(timer, now, TICK_NSEC);
311 return HRTIMER_RESTART;
314 static void tick_sched_timer_cancel(struct tick_sched *ts)
316 if (tick_sched_flag_test(ts, TS_FLAG_HIGHRES))
317 hrtimer_cancel(&ts->sched_timer);
318 else if (tick_sched_flag_test(ts, TS_FLAG_NOHZ))
319 tick_program_event(KTIME_MAX, 1);
322 #ifdef CONFIG_NO_HZ_FULL
323 cpumask_var_t tick_nohz_full_mask;
324 EXPORT_SYMBOL_GPL(tick_nohz_full_mask);
325 bool tick_nohz_full_running;
326 EXPORT_SYMBOL_GPL(tick_nohz_full_running);
327 static atomic_t tick_dep_mask;
329 static bool check_tick_dependency(atomic_t *dep)
331 int val = atomic_read(dep);
333 if (val & TICK_DEP_MASK_POSIX_TIMER) {
334 trace_tick_stop(0, TICK_DEP_MASK_POSIX_TIMER);
338 if (val & TICK_DEP_MASK_PERF_EVENTS) {
339 trace_tick_stop(0, TICK_DEP_MASK_PERF_EVENTS);
343 if (val & TICK_DEP_MASK_SCHED) {
344 trace_tick_stop(0, TICK_DEP_MASK_SCHED);
348 if (val & TICK_DEP_MASK_CLOCK_UNSTABLE) {
349 trace_tick_stop(0, TICK_DEP_MASK_CLOCK_UNSTABLE);
353 if (val & TICK_DEP_MASK_RCU) {
354 trace_tick_stop(0, TICK_DEP_MASK_RCU);
358 if (val & TICK_DEP_MASK_RCU_EXP) {
359 trace_tick_stop(0, TICK_DEP_MASK_RCU_EXP);
366 static bool can_stop_full_tick(int cpu, struct tick_sched *ts)
368 lockdep_assert_irqs_disabled();
370 if (unlikely(!cpu_online(cpu)))
373 if (check_tick_dependency(&tick_dep_mask))
376 if (check_tick_dependency(&ts->tick_dep_mask))
379 if (check_tick_dependency(¤t->tick_dep_mask))
382 if (check_tick_dependency(¤t->signal->tick_dep_mask))
388 static void nohz_full_kick_func(struct irq_work *work)
390 /* Empty, the tick restart happens on tick_nohz_irq_exit() */
393 static DEFINE_PER_CPU(struct irq_work, nohz_full_kick_work) =
394 IRQ_WORK_INIT_HARD(nohz_full_kick_func);
397 * Kick this CPU if it's full dynticks in order to force it to
398 * re-evaluate its dependency on the tick and restart it if necessary.
399 * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(),
402 static void tick_nohz_full_kick(void)
404 if (!tick_nohz_full_cpu(smp_processor_id()))
407 irq_work_queue(this_cpu_ptr(&nohz_full_kick_work));
411 * Kick the CPU if it's full dynticks in order to force it to
412 * re-evaluate its dependency on the tick and restart it if necessary.
414 void tick_nohz_full_kick_cpu(int cpu)
416 if (!tick_nohz_full_cpu(cpu))
419 irq_work_queue_on(&per_cpu(nohz_full_kick_work, cpu), cpu);
422 static void tick_nohz_kick_task(struct task_struct *tsk)
427 * If the task is not running, run_posix_cpu_timers()
428 * has nothing to elapse, and an IPI can then be optimized out.
430 * activate_task() STORE p->tick_dep_mask
432 * __schedule() (switch to task 'p') smp_mb() (atomic_fetch_or())
433 * LOCK rq->lock LOAD p->on_rq
434 * smp_mb__after_spin_lock()
435 * tick_nohz_task_switch()
436 * LOAD p->tick_dep_mask
438 if (!sched_task_on_rq(tsk))
442 * If the task concurrently migrates to another CPU,
443 * we guarantee it sees the new tick dependency upon
446 * set_task_cpu(p, cpu);
447 * STORE p->cpu = @cpu
448 * __schedule() (switch to task 'p')
450 * smp_mb__after_spin_lock() STORE p->tick_dep_mask
451 * tick_nohz_task_switch() smp_mb() (atomic_fetch_or())
452 * LOAD p->tick_dep_mask LOAD p->cpu
458 tick_nohz_full_kick_cpu(cpu);
463 * Kick all full dynticks CPUs in order to force these to re-evaluate
464 * their dependency on the tick and restart it if necessary.
466 static void tick_nohz_full_kick_all(void)
470 if (!tick_nohz_full_running)
474 for_each_cpu_and(cpu, tick_nohz_full_mask, cpu_online_mask)
475 tick_nohz_full_kick_cpu(cpu);
479 static void tick_nohz_dep_set_all(atomic_t *dep,
480 enum tick_dep_bits bit)
484 prev = atomic_fetch_or(BIT(bit), dep);
486 tick_nohz_full_kick_all();
490 * Set a global tick dependency. Used by perf events that rely on freq and
493 void tick_nohz_dep_set(enum tick_dep_bits bit)
495 tick_nohz_dep_set_all(&tick_dep_mask, bit);
498 void tick_nohz_dep_clear(enum tick_dep_bits bit)
500 atomic_andnot(BIT(bit), &tick_dep_mask);
504 * Set per-CPU tick dependency. Used by scheduler and perf events in order to
505 * manage event-throttling.
507 void tick_nohz_dep_set_cpu(int cpu, enum tick_dep_bits bit)
510 struct tick_sched *ts;
512 ts = per_cpu_ptr(&tick_cpu_sched, cpu);
514 prev = atomic_fetch_or(BIT(bit), &ts->tick_dep_mask);
517 /* Perf needs local kick that is NMI safe */
518 if (cpu == smp_processor_id()) {
519 tick_nohz_full_kick();
521 /* Remote IRQ work not NMI-safe */
522 if (!WARN_ON_ONCE(in_nmi()))
523 tick_nohz_full_kick_cpu(cpu);
528 EXPORT_SYMBOL_GPL(tick_nohz_dep_set_cpu);
530 void tick_nohz_dep_clear_cpu(int cpu, enum tick_dep_bits bit)
532 struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
534 atomic_andnot(BIT(bit), &ts->tick_dep_mask);
536 EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_cpu);
539 * Set a per-task tick dependency. RCU needs this. Also posix CPU timers
540 * in order to elapse per task timers.
542 void tick_nohz_dep_set_task(struct task_struct *tsk, enum tick_dep_bits bit)
544 if (!atomic_fetch_or(BIT(bit), &tsk->tick_dep_mask))
545 tick_nohz_kick_task(tsk);
547 EXPORT_SYMBOL_GPL(tick_nohz_dep_set_task);
549 void tick_nohz_dep_clear_task(struct task_struct *tsk, enum tick_dep_bits bit)
551 atomic_andnot(BIT(bit), &tsk->tick_dep_mask);
553 EXPORT_SYMBOL_GPL(tick_nohz_dep_clear_task);
556 * Set a per-taskgroup tick dependency. Posix CPU timers need this in order to elapse
557 * per process timers.
559 void tick_nohz_dep_set_signal(struct task_struct *tsk,
560 enum tick_dep_bits bit)
563 struct signal_struct *sig = tsk->signal;
565 prev = atomic_fetch_or(BIT(bit), &sig->tick_dep_mask);
567 struct task_struct *t;
569 lockdep_assert_held(&tsk->sighand->siglock);
570 __for_each_thread(sig, t)
571 tick_nohz_kick_task(t);
575 void tick_nohz_dep_clear_signal(struct signal_struct *sig, enum tick_dep_bits bit)
577 atomic_andnot(BIT(bit), &sig->tick_dep_mask);
581 * Re-evaluate the need for the tick as we switch the current task.
582 * It might need the tick due to per task/process properties:
583 * perf events, posix CPU timers, ...
585 void __tick_nohz_task_switch(void)
587 struct tick_sched *ts;
589 if (!tick_nohz_full_cpu(smp_processor_id()))
592 ts = this_cpu_ptr(&tick_cpu_sched);
594 if (tick_sched_flag_test(ts, TS_FLAG_STOPPED)) {
595 if (atomic_read(¤t->tick_dep_mask) ||
596 atomic_read(¤t->signal->tick_dep_mask))
597 tick_nohz_full_kick();
601 /* Get the boot-time nohz CPU list from the kernel parameters. */
602 void __init tick_nohz_full_setup(cpumask_var_t cpumask)
604 alloc_bootmem_cpumask_var(&tick_nohz_full_mask);
605 cpumask_copy(tick_nohz_full_mask, cpumask);
606 tick_nohz_full_running = true;
609 bool tick_nohz_cpu_hotpluggable(unsigned int cpu)
612 * The 'tick_do_timer_cpu' CPU handles housekeeping duty (unbound
613 * timers, workqueues, timekeeping, ...) on behalf of full dynticks
614 * CPUs. It must remain online when nohz full is enabled.
616 if (tick_nohz_full_running && READ_ONCE(tick_do_timer_cpu) == cpu)
621 static int tick_nohz_cpu_down(unsigned int cpu)
623 return tick_nohz_cpu_hotpluggable(cpu) ? 0 : -EBUSY;
626 void __init tick_nohz_init(void)
630 if (!tick_nohz_full_running)
634 * Full dynticks uses IRQ work to drive the tick rescheduling on safe
635 * locking contexts. But then we need IRQ work to raise its own
636 * interrupts to avoid circular dependency on the tick.
638 if (!arch_irq_work_has_interrupt()) {
639 pr_warn("NO_HZ: Can't run full dynticks because arch doesn't support IRQ work self-IPIs\n");
640 cpumask_clear(tick_nohz_full_mask);
641 tick_nohz_full_running = false;
645 if (IS_ENABLED(CONFIG_PM_SLEEP_SMP) &&
646 !IS_ENABLED(CONFIG_PM_SLEEP_SMP_NONZERO_CPU)) {
647 cpu = smp_processor_id();
649 if (cpumask_test_cpu(cpu, tick_nohz_full_mask)) {
650 pr_warn("NO_HZ: Clearing %d from nohz_full range "
651 "for timekeeping\n", cpu);
652 cpumask_clear_cpu(cpu, tick_nohz_full_mask);
656 for_each_cpu(cpu, tick_nohz_full_mask)
657 ct_cpu_track_user(cpu);
659 ret = cpuhp_setup_state_nocalls(CPUHP_AP_ONLINE_DYN,
660 "kernel/nohz:predown", NULL,
663 pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
664 cpumask_pr_args(tick_nohz_full_mask));
666 #endif /* #ifdef CONFIG_NO_HZ_FULL */
669 * NOHZ - aka dynamic tick functionality
671 #ifdef CONFIG_NO_HZ_COMMON
675 bool tick_nohz_enabled __read_mostly = true;
676 unsigned long tick_nohz_active __read_mostly;
678 * Enable / Disable tickless mode
680 static int __init setup_tick_nohz(char *str)
682 return (kstrtobool(str, &tick_nohz_enabled) == 0);
685 __setup("nohz=", setup_tick_nohz);
687 bool tick_nohz_tick_stopped(void)
689 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
691 return tick_sched_flag_test(ts, TS_FLAG_STOPPED);
694 bool tick_nohz_tick_stopped_cpu(int cpu)
696 struct tick_sched *ts = per_cpu_ptr(&tick_cpu_sched, cpu);
698 return tick_sched_flag_test(ts, TS_FLAG_STOPPED);
702 * tick_nohz_update_jiffies - update jiffies when idle was interrupted
703 * @now: current ktime_t
705 * Called from interrupt entry when the CPU was idle
707 * In case the sched_tick was stopped on this CPU, we have to check if jiffies
708 * must be updated. Otherwise an interrupt handler could use a stale jiffy
709 * value. We do this unconditionally on any CPU, as we don't know whether the
710 * CPU, which has the update task assigned, is in a long sleep.
712 static void tick_nohz_update_jiffies(ktime_t now)
716 __this_cpu_write(tick_cpu_sched.idle_waketime, now);
718 local_irq_save(flags);
719 tick_do_update_jiffies64(now);
720 local_irq_restore(flags);
722 touch_softlockup_watchdog_sched();
725 static void tick_nohz_stop_idle(struct tick_sched *ts, ktime_t now)
729 if (WARN_ON_ONCE(!tick_sched_flag_test(ts, TS_FLAG_IDLE_ACTIVE)))
732 delta = ktime_sub(now, ts->idle_entrytime);
734 write_seqcount_begin(&ts->idle_sleeptime_seq);
735 if (nr_iowait_cpu(smp_processor_id()) > 0)
736 ts->iowait_sleeptime = ktime_add(ts->iowait_sleeptime, delta);
738 ts->idle_sleeptime = ktime_add(ts->idle_sleeptime, delta);
740 ts->idle_entrytime = now;
741 tick_sched_flag_clear(ts, TS_FLAG_IDLE_ACTIVE);
742 write_seqcount_end(&ts->idle_sleeptime_seq);
744 sched_clock_idle_wakeup_event();
747 static void tick_nohz_start_idle(struct tick_sched *ts)
749 write_seqcount_begin(&ts->idle_sleeptime_seq);
750 ts->idle_entrytime = ktime_get();
751 tick_sched_flag_set(ts, TS_FLAG_IDLE_ACTIVE);
752 write_seqcount_end(&ts->idle_sleeptime_seq);
754 sched_clock_idle_sleep_event();
757 static u64 get_cpu_sleep_time_us(struct tick_sched *ts, ktime_t *sleeptime,
758 bool compute_delta, u64 *last_update_time)
763 if (!tick_nohz_active)
767 if (last_update_time)
768 *last_update_time = ktime_to_us(now);
771 seq = read_seqcount_begin(&ts->idle_sleeptime_seq);
773 if (tick_sched_flag_test(ts, TS_FLAG_IDLE_ACTIVE) && compute_delta) {
774 ktime_t delta = ktime_sub(now, ts->idle_entrytime);
776 idle = ktime_add(*sleeptime, delta);
780 } while (read_seqcount_retry(&ts->idle_sleeptime_seq, seq));
782 return ktime_to_us(idle);
787 * get_cpu_idle_time_us - get the total idle time of a CPU
788 * @cpu: CPU number to query
789 * @last_update_time: variable to store update time in. Do not update
792 * Return the cumulative idle time (since boot) for a given
793 * CPU, in microseconds. Note that this is partially broken due to
794 * the counter of iowait tasks that can be remotely updated without
795 * any synchronization. Therefore it is possible to observe backward
796 * values within two consecutive reads.
798 * This time is measured via accounting rather than sampling,
799 * and is as accurate as ktime_get() is.
801 * Return: -1 if NOHZ is not enabled, else total idle time of the @cpu
803 u64 get_cpu_idle_time_us(int cpu, u64 *last_update_time)
805 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
807 return get_cpu_sleep_time_us(ts, &ts->idle_sleeptime,
808 !nr_iowait_cpu(cpu), last_update_time);
810 EXPORT_SYMBOL_GPL(get_cpu_idle_time_us);
813 * get_cpu_iowait_time_us - get the total iowait time of a CPU
814 * @cpu: CPU number to query
815 * @last_update_time: variable to store update time in. Do not update
818 * Return the cumulative iowait time (since boot) for a given
819 * CPU, in microseconds. Note this is partially broken due to
820 * the counter of iowait tasks that can be remotely updated without
821 * any synchronization. Therefore it is possible to observe backward
822 * values within two consecutive reads.
824 * This time is measured via accounting rather than sampling,
825 * and is as accurate as ktime_get() is.
827 * Return: -1 if NOHZ is not enabled, else total iowait time of @cpu
829 u64 get_cpu_iowait_time_us(int cpu, u64 *last_update_time)
831 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
833 return get_cpu_sleep_time_us(ts, &ts->iowait_sleeptime,
834 nr_iowait_cpu(cpu), last_update_time);
836 EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us);
838 static void tick_nohz_restart(struct tick_sched *ts, ktime_t now)
840 hrtimer_cancel(&ts->sched_timer);
841 hrtimer_set_expires(&ts->sched_timer, ts->last_tick);
843 /* Forward the time to expire in the future */
844 hrtimer_forward(&ts->sched_timer, now, TICK_NSEC);
846 if (tick_sched_flag_test(ts, TS_FLAG_HIGHRES)) {
847 hrtimer_start_expires(&ts->sched_timer,
848 HRTIMER_MODE_ABS_PINNED_HARD);
850 tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
854 * Reset to make sure the next tick stop doesn't get fooled by past
855 * cached clock deadline.
860 static inline bool local_timer_softirq_pending(void)
862 return local_softirq_pending() & BIT(TIMER_SOFTIRQ);
866 * Read jiffies and the time when jiffies were updated last
868 u64 get_jiffies_update(unsigned long *basej)
870 unsigned long basejiff;
875 seq = read_seqcount_begin(&jiffies_seq);
876 basemono = last_jiffies_update;
878 } while (read_seqcount_retry(&jiffies_seq, seq));
884 * tick_nohz_next_event() - return the clock monotonic based next event
885 * @ts: pointer to tick_sched struct
889 * *%0 - When the next event is a maximum of TICK_NSEC in the future
890 * and the tick is not stopped yet
891 * *%next_event - Next event based on clock monotonic
893 static ktime_t tick_nohz_next_event(struct tick_sched *ts, int cpu)
895 u64 basemono, next_tick, delta, expires;
896 unsigned long basejiff;
899 basemono = get_jiffies_update(&basejiff);
900 ts->last_jiffies = basejiff;
901 ts->timer_expires_base = basemono;
904 * Keep the periodic tick, when RCU, architecture or irq_work
906 * Aside of that, check whether the local timer softirq is
907 * pending. If so, its a bad idea to call get_next_timer_interrupt(),
908 * because there is an already expired timer, so it will request
909 * immediate expiry, which rearms the hardware timer with a
910 * minimal delta, which brings us back to this place
911 * immediately. Lather, rinse and repeat...
913 if (rcu_needs_cpu() || arch_needs_cpu() ||
914 irq_work_needs_cpu() || local_timer_softirq_pending()) {
915 next_tick = basemono + TICK_NSEC;
918 * Get the next pending timer. If high resolution
919 * timers are enabled this only takes the timer wheel
920 * timers into account. If high resolution timers are
921 * disabled this also looks at the next expiring
924 next_tick = get_next_timer_interrupt(basejiff, basemono);
925 ts->next_timer = next_tick;
928 /* Make sure next_tick is never before basemono! */
929 if (WARN_ON_ONCE(basemono > next_tick))
930 next_tick = basemono;
933 * If the tick is due in the next period, keep it ticking or
934 * force prod the timer.
936 delta = next_tick - basemono;
937 if (delta <= (u64)TICK_NSEC) {
939 * We've not stopped the tick yet, and there's a timer in the
940 * next period, so no point in stopping it either, bail.
942 if (!tick_sched_flag_test(ts, TS_FLAG_STOPPED)) {
943 ts->timer_expires = 0;
949 * If this CPU is the one which had the do_timer() duty last, we limit
950 * the sleep time to the timekeeping 'max_deferment' value.
951 * Otherwise we can sleep as long as we want.
953 delta = timekeeping_max_deferment();
954 tick_cpu = READ_ONCE(tick_do_timer_cpu);
955 if (tick_cpu != cpu &&
956 (tick_cpu != TICK_DO_TIMER_NONE || !tick_sched_flag_test(ts, TS_FLAG_DO_TIMER_LAST)))
959 /* Calculate the next expiry time */
960 if (delta < (KTIME_MAX - basemono))
961 expires = basemono + delta;
965 ts->timer_expires = min_t(u64, expires, next_tick);
968 return ts->timer_expires;
971 static void tick_nohz_stop_tick(struct tick_sched *ts, int cpu)
973 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
974 unsigned long basejiff = ts->last_jiffies;
975 u64 basemono = ts->timer_expires_base;
976 bool timer_idle = tick_sched_flag_test(ts, TS_FLAG_STOPPED);
980 /* Make sure we won't be trying to stop it twice in a row. */
981 ts->timer_expires_base = 0;
984 * Now the tick should be stopped definitely - so the timer base needs
985 * to be marked idle as well to not miss a newly queued timer.
987 expires = timer_base_try_to_set_idle(basejiff, basemono, &timer_idle);
988 if (expires > ts->timer_expires) {
990 * This path could only happen when the first timer was removed
991 * between calculating the possible sleep length and now (when
992 * high resolution mode is not active, timer could also be a
995 * We have to stick to the original calculated expiry value to
996 * not stop the tick for too long with a shallow C-state (which
997 * was programmed by cpuidle because of an early next expiration
1000 expires = ts->timer_expires;
1003 /* If the timer base is not idle, retain the not yet stopped tick. */
1008 * If this CPU is the one which updates jiffies, then give up
1009 * the assignment and let it be taken by the CPU which runs
1010 * the tick timer next, which might be this CPU as well. If we
1011 * don't drop this here, the jiffies might be stale and
1012 * do_timer() never gets invoked. Keep track of the fact that it
1013 * was the one which had the do_timer() duty last.
1015 tick_cpu = READ_ONCE(tick_do_timer_cpu);
1016 if (tick_cpu == cpu) {
1017 WRITE_ONCE(tick_do_timer_cpu, TICK_DO_TIMER_NONE);
1018 tick_sched_flag_set(ts, TS_FLAG_DO_TIMER_LAST);
1019 } else if (tick_cpu != TICK_DO_TIMER_NONE) {
1020 tick_sched_flag_clear(ts, TS_FLAG_DO_TIMER_LAST);
1023 /* Skip reprogram of event if it's not changed */
1024 if (tick_sched_flag_test(ts, TS_FLAG_STOPPED) && (expires == ts->next_tick)) {
1025 /* Sanity check: make sure clockevent is actually programmed */
1026 if (expires == KTIME_MAX || ts->next_tick == hrtimer_get_expires(&ts->sched_timer))
1030 printk_once("basemono: %llu ts->next_tick: %llu dev->next_event: %llu timer->active: %d timer->expires: %llu\n",
1031 basemono, ts->next_tick, dev->next_event,
1032 hrtimer_active(&ts->sched_timer), hrtimer_get_expires(&ts->sched_timer));
1036 * tick_nohz_stop_tick() can be called several times before
1037 * tick_nohz_restart_sched_tick() is called. This happens when
1038 * interrupts arrive which do not cause a reschedule. In the first
1039 * call we save the current tick time, so we can restart the
1040 * scheduler tick in tick_nohz_restart_sched_tick().
1042 if (!tick_sched_flag_test(ts, TS_FLAG_STOPPED)) {
1043 calc_load_nohz_start();
1046 ts->last_tick = hrtimer_get_expires(&ts->sched_timer);
1047 tick_sched_flag_set(ts, TS_FLAG_STOPPED);
1048 trace_tick_stop(1, TICK_DEP_MASK_NONE);
1051 ts->next_tick = expires;
1054 * If the expiration time == KTIME_MAX, then we simply stop
1057 if (unlikely(expires == KTIME_MAX)) {
1058 tick_sched_timer_cancel(ts);
1062 if (tick_sched_flag_test(ts, TS_FLAG_HIGHRES)) {
1063 hrtimer_start(&ts->sched_timer, expires,
1064 HRTIMER_MODE_ABS_PINNED_HARD);
1066 hrtimer_set_expires(&ts->sched_timer, expires);
1067 tick_program_event(expires, 1);
1071 static void tick_nohz_retain_tick(struct tick_sched *ts)
1073 ts->timer_expires_base = 0;
1076 #ifdef CONFIG_NO_HZ_FULL
1077 static void tick_nohz_full_stop_tick(struct tick_sched *ts, int cpu)
1079 if (tick_nohz_next_event(ts, cpu))
1080 tick_nohz_stop_tick(ts, cpu);
1082 tick_nohz_retain_tick(ts);
1084 #endif /* CONFIG_NO_HZ_FULL */
1086 static void tick_nohz_restart_sched_tick(struct tick_sched *ts, ktime_t now)
1088 /* Update jiffies first */
1089 tick_do_update_jiffies64(now);
1092 * Clear the timer idle flag, so we avoid IPIs on remote queueing and
1093 * the clock forward checks in the enqueue path:
1097 calc_load_nohz_stop();
1098 touch_softlockup_watchdog_sched();
1100 /* Cancel the scheduled timer and restore the tick: */
1101 tick_sched_flag_clear(ts, TS_FLAG_STOPPED);
1102 tick_nohz_restart(ts, now);
1105 static void __tick_nohz_full_update_tick(struct tick_sched *ts,
1108 #ifdef CONFIG_NO_HZ_FULL
1109 int cpu = smp_processor_id();
1111 if (can_stop_full_tick(cpu, ts))
1112 tick_nohz_full_stop_tick(ts, cpu);
1113 else if (tick_sched_flag_test(ts, TS_FLAG_STOPPED))
1114 tick_nohz_restart_sched_tick(ts, now);
1118 static void tick_nohz_full_update_tick(struct tick_sched *ts)
1120 if (!tick_nohz_full_cpu(smp_processor_id()))
1123 if (!tick_sched_flag_test(ts, TS_FLAG_NOHZ))
1126 __tick_nohz_full_update_tick(ts, ktime_get());
1130 * A pending softirq outside an IRQ (or softirq disabled section) context
1131 * should be waiting for ksoftirqd to handle it. Therefore we shouldn't
1132 * reach this code due to the need_resched() early check in can_stop_idle_tick().
1134 * However if we are between CPUHP_AP_SMPBOOT_THREADS and CPU_TEARDOWN_CPU on the
1135 * cpu_down() process, softirqs can still be raised while ksoftirqd is parked,
1136 * triggering the code below, since wakep_softirqd() is ignored.
1139 static bool report_idle_softirq(void)
1141 static int ratelimit;
1142 unsigned int pending = local_softirq_pending();
1144 if (likely(!pending))
1147 /* Some softirqs claim to be safe against hotplug and ksoftirqd parking */
1148 if (!cpu_active(smp_processor_id())) {
1149 pending &= ~SOFTIRQ_HOTPLUG_SAFE_MASK;
1154 if (ratelimit >= 10)
1157 /* On RT, softirq handling may be waiting on some lock */
1158 if (local_bh_blocked())
1161 pr_warn("NOHZ tick-stop error: local softirq work is pending, handler #%02x!!!\n",
1168 static bool can_stop_idle_tick(int cpu, struct tick_sched *ts)
1170 WARN_ON_ONCE(cpu_is_offline(cpu));
1172 if (unlikely(!tick_sched_flag_test(ts, TS_FLAG_NOHZ)))
1178 if (unlikely(report_idle_softirq()))
1181 if (tick_nohz_full_enabled()) {
1182 int tick_cpu = READ_ONCE(tick_do_timer_cpu);
1185 * Keep the tick alive to guarantee timekeeping progression
1186 * if there are full dynticks CPUs around
1188 if (tick_cpu == cpu)
1191 /* Should not happen for nohz-full */
1192 if (WARN_ON_ONCE(tick_cpu == TICK_DO_TIMER_NONE))
1200 * tick_nohz_idle_stop_tick - stop the idle tick from the idle task
1202 * When the next event is more than a tick into the future, stop the idle tick
1204 void tick_nohz_idle_stop_tick(void)
1206 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1207 int cpu = smp_processor_id();
1211 * If tick_nohz_get_sleep_length() ran tick_nohz_next_event(), the
1212 * tick timer expiration time is known already.
1214 if (ts->timer_expires_base)
1215 expires = ts->timer_expires;
1216 else if (can_stop_idle_tick(cpu, ts))
1217 expires = tick_nohz_next_event(ts, cpu);
1223 if (expires > 0LL) {
1224 int was_stopped = tick_sched_flag_test(ts, TS_FLAG_STOPPED);
1226 tick_nohz_stop_tick(ts, cpu);
1229 ts->idle_expires = expires;
1231 if (!was_stopped && tick_sched_flag_test(ts, TS_FLAG_STOPPED)) {
1232 ts->idle_jiffies = ts->last_jiffies;
1233 nohz_balance_enter_idle(cpu);
1236 tick_nohz_retain_tick(ts);
1240 void tick_nohz_idle_retain_tick(void)
1242 tick_nohz_retain_tick(this_cpu_ptr(&tick_cpu_sched));
1246 * tick_nohz_idle_enter - prepare for entering idle on the current CPU
1248 * Called when we start the idle loop.
1250 void tick_nohz_idle_enter(void)
1252 struct tick_sched *ts;
1254 lockdep_assert_irqs_enabled();
1256 local_irq_disable();
1258 ts = this_cpu_ptr(&tick_cpu_sched);
1260 WARN_ON_ONCE(ts->timer_expires_base);
1262 tick_sched_flag_set(ts, TS_FLAG_INIDLE);
1263 tick_nohz_start_idle(ts);
1269 * tick_nohz_irq_exit - Notify the tick about IRQ exit
1271 * A timer may have been added/modified/deleted either by the current IRQ,
1272 * or by another place using this IRQ as a notification. This IRQ may have
1273 * also updated the RCU callback list. These events may require a
1274 * re-evaluation of the next tick. Depending on the context:
1276 * 1) If the CPU is idle and no resched is pending, just proceed with idle
1277 * time accounting. The next tick will be re-evaluated on the next idle
1280 * 2) If the CPU is nohz_full:
1282 * 2.1) If there is any tick dependency, restart the tick if stopped.
1284 * 2.2) If there is no tick dependency, (re-)evaluate the next tick and
1285 * stop/update it accordingly.
1287 void tick_nohz_irq_exit(void)
1289 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1291 if (tick_sched_flag_test(ts, TS_FLAG_INIDLE))
1292 tick_nohz_start_idle(ts);
1294 tick_nohz_full_update_tick(ts);
1298 * tick_nohz_idle_got_tick - Check whether or not the tick handler has run
1300 * Return: %true if the tick handler has run, otherwise %false
1302 bool tick_nohz_idle_got_tick(void)
1304 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1306 if (ts->got_idle_tick) {
1307 ts->got_idle_tick = 0;
1314 * tick_nohz_get_next_hrtimer - return the next expiration time for the hrtimer
1315 * or the tick, whichever expires first. Note that, if the tick has been
1316 * stopped, it returns the next hrtimer.
1318 * Called from power state control code with interrupts disabled
1320 * Return: the next expiration time
1322 ktime_t tick_nohz_get_next_hrtimer(void)
1324 return __this_cpu_read(tick_cpu_device.evtdev)->next_event;
1328 * tick_nohz_get_sleep_length - return the expected length of the current sleep
1329 * @delta_next: duration until the next event if the tick cannot be stopped
1331 * Called from power state control code with interrupts disabled.
1333 * The return value of this function and/or the value returned by it through the
1334 * @delta_next pointer can be negative which must be taken into account by its
1337 * Return: the expected length of the current sleep
1339 ktime_t tick_nohz_get_sleep_length(ktime_t *delta_next)
1341 struct clock_event_device *dev = __this_cpu_read(tick_cpu_device.evtdev);
1342 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1343 int cpu = smp_processor_id();
1345 * The idle entry time is expected to be a sufficient approximation of
1346 * the current time at this point.
1348 ktime_t now = ts->idle_entrytime;
1351 WARN_ON_ONCE(!tick_sched_flag_test(ts, TS_FLAG_INIDLE));
1353 *delta_next = ktime_sub(dev->next_event, now);
1355 if (!can_stop_idle_tick(cpu, ts))
1358 next_event = tick_nohz_next_event(ts, cpu);
1363 * If the next highres timer to expire is earlier than 'next_event', the
1364 * idle governor needs to know that.
1366 next_event = min_t(u64, next_event,
1367 hrtimer_next_event_without(&ts->sched_timer));
1369 return ktime_sub(next_event, now);
1373 * tick_nohz_get_idle_calls_cpu - return the current idle calls counter value
1374 * for a particular CPU.
1375 * @cpu: target CPU number
1377 * Called from the schedutil frequency scaling governor in scheduler context.
1379 * Return: the current idle calls counter value for @cpu
1381 unsigned long tick_nohz_get_idle_calls_cpu(int cpu)
1383 struct tick_sched *ts = tick_get_tick_sched(cpu);
1385 return ts->idle_calls;
1389 * tick_nohz_get_idle_calls - return the current idle calls counter value
1391 * Called from the schedutil frequency scaling governor in scheduler context.
1393 * Return: the current idle calls counter value for the current CPU
1395 unsigned long tick_nohz_get_idle_calls(void)
1397 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1399 return ts->idle_calls;
1402 static void tick_nohz_account_idle_time(struct tick_sched *ts,
1405 unsigned long ticks;
1407 ts->idle_exittime = now;
1409 if (vtime_accounting_enabled_this_cpu())
1412 * We stopped the tick in idle. update_process_times() would miss the
1413 * time we slept, as it does only a 1 tick accounting.
1414 * Enforce that this is accounted to idle !
1416 ticks = jiffies - ts->idle_jiffies;
1418 * We might be one off. Do not randomly account a huge number of ticks!
1420 if (ticks && ticks < LONG_MAX)
1421 account_idle_ticks(ticks);
1424 void tick_nohz_idle_restart_tick(void)
1426 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1428 if (tick_sched_flag_test(ts, TS_FLAG_STOPPED)) {
1429 ktime_t now = ktime_get();
1430 tick_nohz_restart_sched_tick(ts, now);
1431 tick_nohz_account_idle_time(ts, now);
1435 static void tick_nohz_idle_update_tick(struct tick_sched *ts, ktime_t now)
1437 if (tick_nohz_full_cpu(smp_processor_id()))
1438 __tick_nohz_full_update_tick(ts, now);
1440 tick_nohz_restart_sched_tick(ts, now);
1442 tick_nohz_account_idle_time(ts, now);
1446 * tick_nohz_idle_exit - Update the tick upon idle task exit
1448 * When the idle task exits, update the tick depending on the
1449 * following situations:
1451 * 1) If the CPU is not in nohz_full mode (most cases), then
1454 * 2) If the CPU is in nohz_full mode (corner case):
1455 * 2.1) If the tick can be kept stopped (no tick dependencies)
1456 * then re-evaluate the next tick and try to keep it stopped
1457 * as long as possible.
1458 * 2.2) If the tick has dependencies, restart the tick.
1461 void tick_nohz_idle_exit(void)
1463 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1464 bool idle_active, tick_stopped;
1467 local_irq_disable();
1469 WARN_ON_ONCE(!tick_sched_flag_test(ts, TS_FLAG_INIDLE));
1470 WARN_ON_ONCE(ts->timer_expires_base);
1472 tick_sched_flag_clear(ts, TS_FLAG_INIDLE);
1473 idle_active = tick_sched_flag_test(ts, TS_FLAG_IDLE_ACTIVE);
1474 tick_stopped = tick_sched_flag_test(ts, TS_FLAG_STOPPED);
1476 if (idle_active || tick_stopped)
1480 tick_nohz_stop_idle(ts, now);
1483 tick_nohz_idle_update_tick(ts, now);
1489 * In low-resolution mode, the tick handler must be implemented directly
1490 * at the clockevent level. hrtimer can't be used instead, because its
1491 * infrastructure actually relies on the tick itself as a backend in
1492 * low-resolution mode (see hrtimer_run_queues()).
1494 static void tick_nohz_lowres_handler(struct clock_event_device *dev)
1496 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1498 dev->next_event = KTIME_MAX;
1500 if (likely(tick_nohz_handler(&ts->sched_timer) == HRTIMER_RESTART))
1501 tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
1504 static inline void tick_nohz_activate(struct tick_sched *ts)
1506 if (!tick_nohz_enabled)
1508 tick_sched_flag_set(ts, TS_FLAG_NOHZ);
1509 /* One update is enough */
1510 if (!test_and_set_bit(0, &tick_nohz_active))
1511 timers_update_nohz();
1515 * tick_nohz_switch_to_nohz - switch to NOHZ mode
1517 static void tick_nohz_switch_to_nohz(void)
1519 if (!tick_nohz_enabled)
1522 if (tick_switch_to_oneshot(tick_nohz_lowres_handler))
1526 * Recycle the hrtimer in 'ts', so we can share the
1529 tick_setup_sched_timer(false);
1532 static inline void tick_nohz_irq_enter(void)
1534 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1537 if (!tick_sched_flag_test(ts, TS_FLAG_STOPPED | TS_FLAG_IDLE_ACTIVE))
1540 if (tick_sched_flag_test(ts, TS_FLAG_IDLE_ACTIVE))
1541 tick_nohz_stop_idle(ts, now);
1543 * If all CPUs are idle we may need to update a stale jiffies value.
1544 * Note nohz_full is a special case: a timekeeper is guaranteed to stay
1545 * alive but it might be busy looping with interrupts disabled in some
1546 * rare case (typically stop machine). So we must make sure we have a
1549 if (tick_sched_flag_test(ts, TS_FLAG_STOPPED))
1550 tick_nohz_update_jiffies(now);
1555 static inline void tick_nohz_switch_to_nohz(void) { }
1556 static inline void tick_nohz_irq_enter(void) { }
1557 static inline void tick_nohz_activate(struct tick_sched *ts) { }
1559 #endif /* CONFIG_NO_HZ_COMMON */
1562 * Called from irq_enter() to notify about the possible interruption of idle()
1564 void tick_irq_enter(void)
1566 tick_check_oneshot_broadcast_this_cpu();
1567 tick_nohz_irq_enter();
1570 static int sched_skew_tick;
1572 static int __init skew_tick(char *str)
1574 get_option(&str, &sched_skew_tick);
1578 early_param("skew_tick", skew_tick);
1581 * tick_setup_sched_timer - setup the tick emulation timer
1582 * @hrtimer: whether to use the hrtimer or not
1584 void tick_setup_sched_timer(bool hrtimer)
1586 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1588 /* Emulate tick processing via per-CPU hrtimers: */
1589 hrtimer_init(&ts->sched_timer, CLOCK_MONOTONIC, HRTIMER_MODE_ABS_HARD);
1591 if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && hrtimer) {
1592 tick_sched_flag_set(ts, TS_FLAG_HIGHRES);
1593 ts->sched_timer.function = tick_nohz_handler;
1596 /* Get the next period (per-CPU) */
1597 hrtimer_set_expires(&ts->sched_timer, tick_init_jiffy_update());
1599 /* Offset the tick to avert 'jiffies_lock' contention. */
1600 if (sched_skew_tick) {
1601 u64 offset = TICK_NSEC >> 1;
1602 do_div(offset, num_possible_cpus());
1603 offset *= smp_processor_id();
1604 hrtimer_add_expires_ns(&ts->sched_timer, offset);
1607 hrtimer_forward_now(&ts->sched_timer, TICK_NSEC);
1608 if (IS_ENABLED(CONFIG_HIGH_RES_TIMERS) && hrtimer)
1609 hrtimer_start_expires(&ts->sched_timer, HRTIMER_MODE_ABS_PINNED_HARD);
1611 tick_program_event(hrtimer_get_expires(&ts->sched_timer), 1);
1612 tick_nohz_activate(ts);
1616 * Shut down the tick and make sure the CPU won't try to retake the timekeeping
1617 * duty before disabling IRQs in idle for the last time.
1619 void tick_sched_timer_dying(int cpu)
1621 struct tick_device *td = &per_cpu(tick_cpu_device, cpu);
1622 struct tick_sched *ts = &per_cpu(tick_cpu_sched, cpu);
1623 struct clock_event_device *dev = td->evtdev;
1624 ktime_t idle_sleeptime, iowait_sleeptime;
1625 unsigned long idle_calls, idle_sleeps;
1627 /* This must happen before hrtimers are migrated! */
1628 tick_sched_timer_cancel(ts);
1631 * If the clockevents doesn't support CLOCK_EVT_STATE_ONESHOT_STOPPED,
1632 * make sure not to call low-res tick handler.
1634 if (tick_sched_flag_test(ts, TS_FLAG_NOHZ))
1635 dev->event_handler = clockevents_handle_noop;
1637 idle_sleeptime = ts->idle_sleeptime;
1638 iowait_sleeptime = ts->iowait_sleeptime;
1639 idle_calls = ts->idle_calls;
1640 idle_sleeps = ts->idle_sleeps;
1641 memset(ts, 0, sizeof(*ts));
1642 ts->idle_sleeptime = idle_sleeptime;
1643 ts->iowait_sleeptime = iowait_sleeptime;
1644 ts->idle_calls = idle_calls;
1645 ts->idle_sleeps = idle_sleeps;
1649 * Async notification about clocksource changes
1651 void tick_clock_notify(void)
1655 for_each_possible_cpu(cpu)
1656 set_bit(0, &per_cpu(tick_cpu_sched, cpu).check_clocks);
1660 * Async notification about clock event changes
1662 void tick_oneshot_notify(void)
1664 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1666 set_bit(0, &ts->check_clocks);
1670 * Check if a change happened, which makes oneshot possible.
1672 * Called cyclically from the hrtimer softirq (driven by the timer
1673 * softirq). 'allow_nohz' signals that we can switch into low-res NOHZ
1674 * mode, because high resolution timers are disabled (either compile
1675 * or runtime). Called with interrupts disabled.
1677 int tick_check_oneshot_change(int allow_nohz)
1679 struct tick_sched *ts = this_cpu_ptr(&tick_cpu_sched);
1681 if (!test_and_clear_bit(0, &ts->check_clocks))
1684 if (tick_sched_flag_test(ts, TS_FLAG_NOHZ))
1687 if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
1693 tick_nohz_switch_to_nohz();