2 * linux/kernel/time/tick-sched.c
4 * Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
5 * Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
6 * Copyright(C) 2006-2007 Timesys Corp., Thomas Gleixner
8 * No idle tick implementation for low and high resolution timers
10 * Started by: Thomas Gleixner and Ingo Molnar
12 * Distribute under GPLv2.
14 #include <linux/cpu.h>
15 #include <linux/err.h>
16 #include <linux/hrtimer.h>
17 #include <linux/interrupt.h>
18 #include <linux/kernel_stat.h>
19 #include <linux/percpu.h>
20 #include <linux/profile.h>
21 #include <linux/sched.h>
22 #include <linux/module.h>
23 #include <linux/irq_work.h>
24 #include <linux/posix-timers.h>
25 #include <linux/perf_event.h>
26 #include <linux/context_tracking.h>
28 #include <asm/irq_regs.h>
30 #include "tick-internal.h"
32 #include <trace/events/timer.h>
35 * Per cpu nohz control structure
37 static DEFINE_PER_CPU(struct tick_sched
, tick_cpu_sched
);
40 * The time, when the last jiffy update happened. Protected by jiffies_lock.
42 static ktime_t last_jiffies_update
;
44 struct tick_sched
*tick_get_tick_sched(int cpu
)
46 return &per_cpu(tick_cpu_sched
, cpu
);
50 * Must be called with interrupts disabled !
52 static void tick_do_update_jiffies64(ktime_t now
)
54 unsigned long ticks
= 0;
58 * Do a quick check without holding jiffies_lock:
60 delta
= ktime_sub(now
, last_jiffies_update
);
61 if (delta
.tv64
< tick_period
.tv64
)
64 /* Reevalute with jiffies_lock held */
65 write_seqlock(&jiffies_lock
);
67 delta
= ktime_sub(now
, last_jiffies_update
);
68 if (delta
.tv64
>= tick_period
.tv64
) {
70 delta
= ktime_sub(delta
, tick_period
);
71 last_jiffies_update
= ktime_add(last_jiffies_update
,
74 /* Slow path for long timeouts */
75 if (unlikely(delta
.tv64
>= tick_period
.tv64
)) {
76 s64 incr
= ktime_to_ns(tick_period
);
78 ticks
= ktime_divns(delta
, incr
);
80 last_jiffies_update
= ktime_add_ns(last_jiffies_update
,
85 /* Keep the tick_next_period variable up to date */
86 tick_next_period
= ktime_add(last_jiffies_update
, tick_period
);
88 write_sequnlock(&jiffies_lock
);
91 write_sequnlock(&jiffies_lock
);
96 * Initialize and return retrieve the jiffies update.
98 static ktime_t
tick_init_jiffy_update(void)
102 write_seqlock(&jiffies_lock
);
103 /* Did we start the jiffies update yet ? */
104 if (last_jiffies_update
.tv64
== 0)
105 last_jiffies_update
= tick_next_period
;
106 period
= last_jiffies_update
;
107 write_sequnlock(&jiffies_lock
);
112 static void tick_sched_do_timer(ktime_t now
)
114 int cpu
= smp_processor_id();
116 #ifdef CONFIG_NO_HZ_COMMON
118 * Check if the do_timer duty was dropped. We don't care about
119 * concurrency: This happens only when the cpu in charge went
120 * into a long sleep. If two cpus happen to assign themself to
121 * this duty, then the jiffies update is still serialized by
124 if (unlikely(tick_do_timer_cpu
== TICK_DO_TIMER_NONE
)
125 && !tick_nohz_full_cpu(cpu
))
126 tick_do_timer_cpu
= cpu
;
129 /* Check, if the jiffies need an update */
130 if (tick_do_timer_cpu
== cpu
)
131 tick_do_update_jiffies64(now
);
134 static void tick_sched_handle(struct tick_sched
*ts
, struct pt_regs
*regs
)
136 #ifdef CONFIG_NO_HZ_COMMON
138 * When we are idle and the tick is stopped, we have to touch
139 * the watchdog as we might not schedule for a really long
140 * time. This happens on complete idle SMP systems while
141 * waiting on the login prompt. We also increment the "start of
142 * idle" jiffy stamp so the idle accounting adjustment we do
143 * when we go busy again does not account too much ticks.
145 if (ts
->tick_stopped
) {
146 touch_softlockup_watchdog();
147 if (is_idle_task(current
))
151 update_process_times(user_mode(regs
));
152 profile_tick(CPU_PROFILING
);
155 #ifdef CONFIG_NO_HZ_FULL
156 cpumask_var_t tick_nohz_full_mask
;
157 cpumask_var_t housekeeping_mask
;
158 bool tick_nohz_full_running
;
160 static bool can_stop_full_tick(void)
162 WARN_ON_ONCE(!irqs_disabled());
164 if (!sched_can_stop_tick()) {
165 trace_tick_stop(0, "more than 1 task in runqueue\n");
169 if (!posix_cpu_timers_can_stop_tick(current
)) {
170 trace_tick_stop(0, "posix timers running\n");
174 if (!perf_event_can_stop_tick()) {
175 trace_tick_stop(0, "perf events running\n");
179 /* sched_clock_tick() needs us? */
180 #ifdef CONFIG_HAVE_UNSTABLE_SCHED_CLOCK
182 * TODO: kick full dynticks CPUs when
183 * sched_clock_stable is set.
185 if (!sched_clock_stable()) {
186 trace_tick_stop(0, "unstable sched clock\n");
188 * Don't allow the user to think they can get
189 * full NO_HZ with this machine.
191 WARN_ONCE(tick_nohz_full_running
,
192 "NO_HZ FULL will not work with unstable sched clock");
200 static void tick_nohz_restart_sched_tick(struct tick_sched
*ts
, ktime_t now
);
203 * Re-evaluate the need for the tick on the current CPU
204 * and restart it if necessary.
206 void __tick_nohz_full_check(void)
208 struct tick_sched
*ts
= this_cpu_ptr(&tick_cpu_sched
);
210 if (tick_nohz_full_cpu(smp_processor_id())) {
211 if (ts
->tick_stopped
&& !is_idle_task(current
)) {
212 if (!can_stop_full_tick())
213 tick_nohz_restart_sched_tick(ts
, ktime_get());
218 static void nohz_full_kick_work_func(struct irq_work
*work
)
220 __tick_nohz_full_check();
223 static DEFINE_PER_CPU(struct irq_work
, nohz_full_kick_work
) = {
224 .func
= nohz_full_kick_work_func
,
228 * Kick this CPU if it's full dynticks in order to force it to
229 * re-evaluate its dependency on the tick and restart it if necessary.
230 * This kick, unlike tick_nohz_full_kick_cpu() and tick_nohz_full_kick_all(),
233 void tick_nohz_full_kick(void)
235 if (!tick_nohz_full_cpu(smp_processor_id()))
238 irq_work_queue(this_cpu_ptr(&nohz_full_kick_work
));
242 * Kick the CPU if it's full dynticks in order to force it to
243 * re-evaluate its dependency on the tick and restart it if necessary.
245 void tick_nohz_full_kick_cpu(int cpu
)
247 if (!tick_nohz_full_cpu(cpu
))
250 irq_work_queue_on(&per_cpu(nohz_full_kick_work
, cpu
), cpu
);
253 static void nohz_full_kick_ipi(void *info
)
255 __tick_nohz_full_check();
259 * Kick all full dynticks CPUs in order to force these to re-evaluate
260 * their dependency on the tick and restart it if necessary.
262 void tick_nohz_full_kick_all(void)
264 if (!tick_nohz_full_running
)
268 smp_call_function_many(tick_nohz_full_mask
,
269 nohz_full_kick_ipi
, NULL
, false);
270 tick_nohz_full_kick();
275 * Re-evaluate the need for the tick as we switch the current task.
276 * It might need the tick due to per task/process properties:
277 * perf events, posix cpu timers, ...
279 void __tick_nohz_task_switch(struct task_struct
*tsk
)
283 local_irq_save(flags
);
285 if (!tick_nohz_full_cpu(smp_processor_id()))
288 if (tick_nohz_tick_stopped() && !can_stop_full_tick())
289 tick_nohz_full_kick();
292 local_irq_restore(flags
);
295 /* Parse the boot-time nohz CPU list from the kernel parameters. */
296 static int __init
tick_nohz_full_setup(char *str
)
298 alloc_bootmem_cpumask_var(&tick_nohz_full_mask
);
299 if (cpulist_parse(str
, tick_nohz_full_mask
) < 0) {
300 pr_warning("NOHZ: Incorrect nohz_full cpumask\n");
301 free_bootmem_cpumask_var(tick_nohz_full_mask
);
304 tick_nohz_full_running
= true;
308 __setup("nohz_full=", tick_nohz_full_setup
);
310 static int tick_nohz_cpu_down_callback(struct notifier_block
*nfb
,
311 unsigned long action
,
314 unsigned int cpu
= (unsigned long)hcpu
;
316 switch (action
& ~CPU_TASKS_FROZEN
) {
317 case CPU_DOWN_PREPARE
:
319 * If we handle the timekeeping duty for full dynticks CPUs,
320 * we can't safely shutdown that CPU.
322 if (tick_nohz_full_running
&& tick_do_timer_cpu
== cpu
)
329 static int tick_nohz_init_all(void)
333 #ifdef CONFIG_NO_HZ_FULL_ALL
334 if (!alloc_cpumask_var(&tick_nohz_full_mask
, GFP_KERNEL
)) {
335 WARN(1, "NO_HZ: Can't allocate full dynticks cpumask\n");
339 cpumask_setall(tick_nohz_full_mask
);
340 tick_nohz_full_running
= true;
345 void __init
tick_nohz_init(void)
349 if (!tick_nohz_full_running
) {
350 if (tick_nohz_init_all() < 0)
354 if (!alloc_cpumask_var(&housekeeping_mask
, GFP_KERNEL
)) {
355 WARN(1, "NO_HZ: Can't allocate not-full dynticks cpumask\n");
356 cpumask_clear(tick_nohz_full_mask
);
357 tick_nohz_full_running
= false;
362 * Full dynticks uses irq work to drive the tick rescheduling on safe
363 * locking contexts. But then we need irq work to raise its own
364 * interrupts to avoid circular dependency on the tick
366 if (!arch_irq_work_has_interrupt()) {
367 pr_warning("NO_HZ: Can't run full dynticks because arch doesn't "
368 "support irq work self-IPIs\n");
369 cpumask_clear(tick_nohz_full_mask
);
370 cpumask_copy(housekeeping_mask
, cpu_possible_mask
);
371 tick_nohz_full_running
= false;
375 cpu
= smp_processor_id();
377 if (cpumask_test_cpu(cpu
, tick_nohz_full_mask
)) {
378 pr_warning("NO_HZ: Clearing %d from nohz_full range for timekeeping\n", cpu
);
379 cpumask_clear_cpu(cpu
, tick_nohz_full_mask
);
382 cpumask_andnot(housekeeping_mask
,
383 cpu_possible_mask
, tick_nohz_full_mask
);
385 for_each_cpu(cpu
, tick_nohz_full_mask
)
386 context_tracking_cpu_set(cpu
);
388 cpu_notifier(tick_nohz_cpu_down_callback
, 0);
389 pr_info("NO_HZ: Full dynticks CPUs: %*pbl.\n",
390 cpumask_pr_args(tick_nohz_full_mask
));
395 * NOHZ - aka dynamic tick functionality
397 #ifdef CONFIG_NO_HZ_COMMON
401 static int tick_nohz_enabled __read_mostly
= 1;
402 int tick_nohz_active __read_mostly
;
404 * Enable / Disable tickless mode
406 static int __init
setup_tick_nohz(char *str
)
408 if (!strcmp(str
, "off"))
409 tick_nohz_enabled
= 0;
410 else if (!strcmp(str
, "on"))
411 tick_nohz_enabled
= 1;
417 __setup("nohz=", setup_tick_nohz
);
419 int tick_nohz_tick_stopped(void)
421 return __this_cpu_read(tick_cpu_sched
.tick_stopped
);
425 * tick_nohz_update_jiffies - update jiffies when idle was interrupted
427 * Called from interrupt entry when the CPU was idle
429 * In case the sched_tick was stopped on this CPU, we have to check if jiffies
430 * must be updated. Otherwise an interrupt handler could use a stale jiffy
431 * value. We do this unconditionally on any cpu, as we don't know whether the
432 * cpu, which has the update task assigned is in a long sleep.
434 static void tick_nohz_update_jiffies(ktime_t now
)
438 __this_cpu_write(tick_cpu_sched
.idle_waketime
, now
);
440 local_irq_save(flags
);
441 tick_do_update_jiffies64(now
);
442 local_irq_restore(flags
);
444 touch_softlockup_watchdog();
448 * Updates the per cpu time idle statistics counters
451 update_ts_time_stats(int cpu
, struct tick_sched
*ts
, ktime_t now
, u64
*last_update_time
)
455 if (ts
->idle_active
) {
456 delta
= ktime_sub(now
, ts
->idle_entrytime
);
457 if (nr_iowait_cpu(cpu
) > 0)
458 ts
->iowait_sleeptime
= ktime_add(ts
->iowait_sleeptime
, delta
);
460 ts
->idle_sleeptime
= ktime_add(ts
->idle_sleeptime
, delta
);
461 ts
->idle_entrytime
= now
;
464 if (last_update_time
)
465 *last_update_time
= ktime_to_us(now
);
469 static void tick_nohz_stop_idle(struct tick_sched
*ts
, ktime_t now
)
471 update_ts_time_stats(smp_processor_id(), ts
, now
, NULL
);
474 sched_clock_idle_wakeup_event(0);
477 static ktime_t
tick_nohz_start_idle(struct tick_sched
*ts
)
479 ktime_t now
= ktime_get();
481 ts
->idle_entrytime
= now
;
483 sched_clock_idle_sleep_event();
488 * get_cpu_idle_time_us - get the total idle time of a cpu
489 * @cpu: CPU number to query
490 * @last_update_time: variable to store update time in. Do not update
493 * Return the cummulative idle time (since boot) for a given
494 * CPU, in microseconds.
496 * This time is measured via accounting rather than sampling,
497 * and is as accurate as ktime_get() is.
499 * This function returns -1 if NOHZ is not enabled.
501 u64
get_cpu_idle_time_us(int cpu
, u64
*last_update_time
)
503 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
506 if (!tick_nohz_active
)
510 if (last_update_time
) {
511 update_ts_time_stats(cpu
, ts
, now
, last_update_time
);
512 idle
= ts
->idle_sleeptime
;
514 if (ts
->idle_active
&& !nr_iowait_cpu(cpu
)) {
515 ktime_t delta
= ktime_sub(now
, ts
->idle_entrytime
);
517 idle
= ktime_add(ts
->idle_sleeptime
, delta
);
519 idle
= ts
->idle_sleeptime
;
523 return ktime_to_us(idle
);
526 EXPORT_SYMBOL_GPL(get_cpu_idle_time_us
);
529 * get_cpu_iowait_time_us - get the total iowait time of a cpu
530 * @cpu: CPU number to query
531 * @last_update_time: variable to store update time in. Do not update
534 * Return the cummulative iowait time (since boot) for a given
535 * CPU, in microseconds.
537 * This time is measured via accounting rather than sampling,
538 * and is as accurate as ktime_get() is.
540 * This function returns -1 if NOHZ is not enabled.
542 u64
get_cpu_iowait_time_us(int cpu
, u64
*last_update_time
)
544 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
547 if (!tick_nohz_active
)
551 if (last_update_time
) {
552 update_ts_time_stats(cpu
, ts
, now
, last_update_time
);
553 iowait
= ts
->iowait_sleeptime
;
555 if (ts
->idle_active
&& nr_iowait_cpu(cpu
) > 0) {
556 ktime_t delta
= ktime_sub(now
, ts
->idle_entrytime
);
558 iowait
= ktime_add(ts
->iowait_sleeptime
, delta
);
560 iowait
= ts
->iowait_sleeptime
;
564 return ktime_to_us(iowait
);
566 EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us
);
568 static ktime_t
tick_nohz_stop_sched_tick(struct tick_sched
*ts
,
569 ktime_t now
, int cpu
)
571 unsigned long seq
, last_jiffies
, next_jiffies
, delta_jiffies
;
572 ktime_t last_update
, expires
, ret
= { .tv64
= 0 };
573 unsigned long rcu_delta_jiffies
;
574 struct clock_event_device
*dev
= __this_cpu_read(tick_cpu_device
.evtdev
);
577 time_delta
= timekeeping_max_deferment();
579 /* Read jiffies and the time when jiffies were updated last */
581 seq
= read_seqbegin(&jiffies_lock
);
582 last_update
= last_jiffies_update
;
583 last_jiffies
= jiffies
;
584 } while (read_seqretry(&jiffies_lock
, seq
));
586 if (rcu_needs_cpu(&rcu_delta_jiffies
) ||
587 arch_needs_cpu() || irq_work_needs_cpu()) {
588 next_jiffies
= last_jiffies
+ 1;
591 /* Get the next timer wheel timer */
592 next_jiffies
= get_next_timer_interrupt(last_jiffies
);
593 delta_jiffies
= next_jiffies
- last_jiffies
;
594 if (rcu_delta_jiffies
< delta_jiffies
) {
595 next_jiffies
= last_jiffies
+ rcu_delta_jiffies
;
596 delta_jiffies
= rcu_delta_jiffies
;
601 * Do not stop the tick, if we are only one off (or less)
602 * or if the cpu is required for RCU:
604 if (!ts
->tick_stopped
&& delta_jiffies
<= 1)
607 /* Schedule the tick, if we are at least one jiffie off */
608 if ((long)delta_jiffies
>= 1) {
611 * If this cpu is the one which updates jiffies, then
612 * give up the assignment and let it be taken by the
613 * cpu which runs the tick timer next, which might be
614 * this cpu as well. If we don't drop this here the
615 * jiffies might be stale and do_timer() never
616 * invoked. Keep track of the fact that it was the one
617 * which had the do_timer() duty last. If this cpu is
618 * the one which had the do_timer() duty last, we
619 * limit the sleep time to the timekeeping
620 * max_deferement value which we retrieved
621 * above. Otherwise we can sleep as long as we want.
623 if (cpu
== tick_do_timer_cpu
) {
624 tick_do_timer_cpu
= TICK_DO_TIMER_NONE
;
625 ts
->do_timer_last
= 1;
626 } else if (tick_do_timer_cpu
!= TICK_DO_TIMER_NONE
) {
627 time_delta
= KTIME_MAX
;
628 ts
->do_timer_last
= 0;
629 } else if (!ts
->do_timer_last
) {
630 time_delta
= KTIME_MAX
;
633 #ifdef CONFIG_NO_HZ_FULL
635 time_delta
= min(time_delta
,
636 scheduler_tick_max_deferment());
641 * calculate the expiry time for the next timer wheel
642 * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals
643 * that there is no timer pending or at least extremely
644 * far into the future (12 days for HZ=1000). In this
645 * case we set the expiry to the end of time.
647 if (likely(delta_jiffies
< NEXT_TIMER_MAX_DELTA
)) {
649 * Calculate the time delta for the next timer event.
650 * If the time delta exceeds the maximum time delta
651 * permitted by the current clocksource then adjust
652 * the time delta accordingly to ensure the
653 * clocksource does not wrap.
655 time_delta
= min_t(u64
, time_delta
,
656 tick_period
.tv64
* delta_jiffies
);
659 if (time_delta
< KTIME_MAX
)
660 expires
= ktime_add_ns(last_update
, time_delta
);
662 expires
.tv64
= KTIME_MAX
;
664 /* Skip reprogram of event if its not changed */
665 if (ts
->tick_stopped
&& ktime_equal(expires
, dev
->next_event
))
671 * nohz_stop_sched_tick can be called several times before
672 * the nohz_restart_sched_tick is called. This happens when
673 * interrupts arrive which do not cause a reschedule. In the
674 * first call we save the current tick time, so we can restart
675 * the scheduler tick in nohz_restart_sched_tick.
677 if (!ts
->tick_stopped
) {
678 nohz_balance_enter_idle(cpu
);
679 calc_load_enter_idle();
681 ts
->last_tick
= hrtimer_get_expires(&ts
->sched_timer
);
682 ts
->tick_stopped
= 1;
683 trace_tick_stop(1, " ");
687 * If the expiration time == KTIME_MAX, then
688 * in this case we simply stop the tick timer.
690 if (unlikely(expires
.tv64
== KTIME_MAX
)) {
691 if (ts
->nohz_mode
== NOHZ_MODE_HIGHRES
)
692 hrtimer_cancel(&ts
->sched_timer
);
696 if (ts
->nohz_mode
== NOHZ_MODE_HIGHRES
) {
697 hrtimer_start(&ts
->sched_timer
, expires
,
698 HRTIMER_MODE_ABS_PINNED
);
699 /* Check, if the timer was already in the past */
700 if (hrtimer_active(&ts
->sched_timer
))
702 } else if (!tick_program_event(expires
, 0))
705 * We are past the event already. So we crossed a
706 * jiffie boundary. Update jiffies and raise the
709 tick_do_update_jiffies64(ktime_get());
711 raise_softirq_irqoff(TIMER_SOFTIRQ
);
713 ts
->next_jiffies
= next_jiffies
;
714 ts
->last_jiffies
= last_jiffies
;
715 ts
->sleep_length
= ktime_sub(dev
->next_event
, now
);
720 static void tick_nohz_full_stop_tick(struct tick_sched
*ts
)
722 #ifdef CONFIG_NO_HZ_FULL
723 int cpu
= smp_processor_id();
725 if (!tick_nohz_full_cpu(cpu
) || is_idle_task(current
))
728 if (!ts
->tick_stopped
&& ts
->nohz_mode
== NOHZ_MODE_INACTIVE
)
731 if (!can_stop_full_tick())
734 tick_nohz_stop_sched_tick(ts
, ktime_get(), cpu
);
738 static bool can_stop_idle_tick(int cpu
, struct tick_sched
*ts
)
741 * If this cpu is offline and it is the one which updates
742 * jiffies, then give up the assignment and let it be taken by
743 * the cpu which runs the tick timer next. If we don't drop
744 * this here the jiffies might be stale and do_timer() never
747 if (unlikely(!cpu_online(cpu
))) {
748 if (cpu
== tick_do_timer_cpu
)
749 tick_do_timer_cpu
= TICK_DO_TIMER_NONE
;
753 if (unlikely(ts
->nohz_mode
== NOHZ_MODE_INACTIVE
)) {
754 ts
->sleep_length
= (ktime_t
) { .tv64
= NSEC_PER_SEC
/HZ
};
761 if (unlikely(local_softirq_pending() && cpu_online(cpu
))) {
762 static int ratelimit
;
764 if (ratelimit
< 10 &&
765 (local_softirq_pending() & SOFTIRQ_STOP_IDLE_MASK
)) {
766 pr_warn("NOHZ: local_softirq_pending %02x\n",
767 (unsigned int) local_softirq_pending());
773 if (tick_nohz_full_enabled()) {
775 * Keep the tick alive to guarantee timekeeping progression
776 * if there are full dynticks CPUs around
778 if (tick_do_timer_cpu
== cpu
)
781 * Boot safety: make sure the timekeeping duty has been
782 * assigned before entering dyntick-idle mode,
784 if (tick_do_timer_cpu
== TICK_DO_TIMER_NONE
)
791 static void __tick_nohz_idle_enter(struct tick_sched
*ts
)
793 ktime_t now
, expires
;
794 int cpu
= smp_processor_id();
796 now
= tick_nohz_start_idle(ts
);
798 if (can_stop_idle_tick(cpu
, ts
)) {
799 int was_stopped
= ts
->tick_stopped
;
803 expires
= tick_nohz_stop_sched_tick(ts
, now
, cpu
);
804 if (expires
.tv64
> 0LL) {
806 ts
->idle_expires
= expires
;
809 if (!was_stopped
&& ts
->tick_stopped
)
810 ts
->idle_jiffies
= ts
->last_jiffies
;
815 * tick_nohz_idle_enter - stop the idle tick from the idle task
817 * When the next event is more than a tick into the future, stop the idle tick
818 * Called when we start the idle loop.
820 * The arch is responsible of calling:
822 * - rcu_idle_enter() after its last use of RCU before the CPU is put
824 * - rcu_idle_exit() before the first use of RCU after the CPU is woken up.
826 void tick_nohz_idle_enter(void)
828 struct tick_sched
*ts
;
830 WARN_ON_ONCE(irqs_disabled());
833 * Update the idle state in the scheduler domain hierarchy
834 * when tick_nohz_stop_sched_tick() is called from the idle loop.
835 * State will be updated to busy during the first busy tick after
838 set_cpu_sd_state_idle();
842 ts
= this_cpu_ptr(&tick_cpu_sched
);
844 __tick_nohz_idle_enter(ts
);
850 * tick_nohz_irq_exit - update next tick event from interrupt exit
852 * When an interrupt fires while we are idle and it doesn't cause
853 * a reschedule, it may still add, modify or delete a timer, enqueue
854 * an RCU callback, etc...
855 * So we need to re-calculate and reprogram the next tick event.
857 void tick_nohz_irq_exit(void)
859 struct tick_sched
*ts
= this_cpu_ptr(&tick_cpu_sched
);
862 __tick_nohz_idle_enter(ts
);
864 tick_nohz_full_stop_tick(ts
);
868 * tick_nohz_get_sleep_length - return the length of the current sleep
870 * Called from power state control code with interrupts disabled
872 ktime_t
tick_nohz_get_sleep_length(void)
874 struct tick_sched
*ts
= this_cpu_ptr(&tick_cpu_sched
);
876 return ts
->sleep_length
;
879 static void tick_nohz_restart(struct tick_sched
*ts
, ktime_t now
)
881 hrtimer_cancel(&ts
->sched_timer
);
882 hrtimer_set_expires(&ts
->sched_timer
, ts
->last_tick
);
885 /* Forward the time to expire in the future */
886 hrtimer_forward(&ts
->sched_timer
, now
, tick_period
);
888 if (ts
->nohz_mode
== NOHZ_MODE_HIGHRES
) {
889 hrtimer_start_expires(&ts
->sched_timer
,
890 HRTIMER_MODE_ABS_PINNED
);
891 /* Check, if the timer was already in the past */
892 if (hrtimer_active(&ts
->sched_timer
))
895 if (!tick_program_event(
896 hrtimer_get_expires(&ts
->sched_timer
), 0))
899 /* Reread time and update jiffies */
901 tick_do_update_jiffies64(now
);
905 static void tick_nohz_restart_sched_tick(struct tick_sched
*ts
, ktime_t now
)
907 /* Update jiffies first */
908 tick_do_update_jiffies64(now
);
909 update_cpu_load_nohz();
911 calc_load_exit_idle();
912 touch_softlockup_watchdog();
914 * Cancel the scheduled timer and restore the tick
916 ts
->tick_stopped
= 0;
917 ts
->idle_exittime
= now
;
919 tick_nohz_restart(ts
, now
);
922 static void tick_nohz_account_idle_ticks(struct tick_sched
*ts
)
924 #ifndef CONFIG_VIRT_CPU_ACCOUNTING_NATIVE
927 if (vtime_accounting_enabled())
930 * We stopped the tick in idle. Update process times would miss the
931 * time we slept as update_process_times does only a 1 tick
932 * accounting. Enforce that this is accounted to idle !
934 ticks
= jiffies
- ts
->idle_jiffies
;
936 * We might be one off. Do not randomly account a huge number of ticks!
938 if (ticks
&& ticks
< LONG_MAX
)
939 account_idle_ticks(ticks
);
944 * tick_nohz_idle_exit - restart the idle tick from the idle task
946 * Restart the idle tick when the CPU is woken up from idle
947 * This also exit the RCU extended quiescent state. The CPU
948 * can use RCU again after this function is called.
950 void tick_nohz_idle_exit(void)
952 struct tick_sched
*ts
= this_cpu_ptr(&tick_cpu_sched
);
957 WARN_ON_ONCE(!ts
->inidle
);
961 if (ts
->idle_active
|| ts
->tick_stopped
)
965 tick_nohz_stop_idle(ts
, now
);
967 if (ts
->tick_stopped
) {
968 tick_nohz_restart_sched_tick(ts
, now
);
969 tick_nohz_account_idle_ticks(ts
);
975 static int tick_nohz_reprogram(struct tick_sched
*ts
, ktime_t now
)
977 hrtimer_forward(&ts
->sched_timer
, now
, tick_period
);
978 return tick_program_event(hrtimer_get_expires(&ts
->sched_timer
), 0);
982 * The nohz low res interrupt handler
984 static void tick_nohz_handler(struct clock_event_device
*dev
)
986 struct tick_sched
*ts
= this_cpu_ptr(&tick_cpu_sched
);
987 struct pt_regs
*regs
= get_irq_regs();
988 ktime_t now
= ktime_get();
990 dev
->next_event
.tv64
= KTIME_MAX
;
992 tick_sched_do_timer(now
);
993 tick_sched_handle(ts
, regs
);
995 /* No need to reprogram if we are running tickless */
996 if (unlikely(ts
->tick_stopped
))
999 while (tick_nohz_reprogram(ts
, now
)) {
1001 tick_do_update_jiffies64(now
);
1006 * tick_nohz_switch_to_nohz - switch to nohz mode
1008 static void tick_nohz_switch_to_nohz(void)
1010 struct tick_sched
*ts
= this_cpu_ptr(&tick_cpu_sched
);
1013 if (!tick_nohz_enabled
)
1016 local_irq_disable();
1017 if (tick_switch_to_oneshot(tick_nohz_handler
)) {
1021 tick_nohz_active
= 1;
1022 ts
->nohz_mode
= NOHZ_MODE_LOWRES
;
1025 * Recycle the hrtimer in ts, so we can share the
1026 * hrtimer_forward with the highres code.
1028 hrtimer_init(&ts
->sched_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS
);
1029 /* Get the next period */
1030 next
= tick_init_jiffy_update();
1033 hrtimer_set_expires(&ts
->sched_timer
, next
);
1034 if (!tick_program_event(next
, 0))
1036 next
= ktime_add(next
, tick_period
);
1042 * When NOHZ is enabled and the tick is stopped, we need to kick the
1043 * tick timer from irq_enter() so that the jiffies update is kept
1044 * alive during long running softirqs. That's ugly as hell, but
1045 * correctness is key even if we need to fix the offending softirq in
1048 * Note, this is different to tick_nohz_restart. We just kick the
1049 * timer and do not touch the other magic bits which need to be done
1050 * when idle is left.
1052 static void tick_nohz_kick_tick(struct tick_sched
*ts
, ktime_t now
)
1055 /* Switch back to 2.6.27 behaviour */
1059 * Do not touch the tick device, when the next expiry is either
1060 * already reached or less/equal than the tick period.
1062 delta
= ktime_sub(hrtimer_get_expires(&ts
->sched_timer
), now
);
1063 if (delta
.tv64
<= tick_period
.tv64
)
1066 tick_nohz_restart(ts
, now
);
1070 static inline void tick_nohz_irq_enter(void)
1072 struct tick_sched
*ts
= this_cpu_ptr(&tick_cpu_sched
);
1075 if (!ts
->idle_active
&& !ts
->tick_stopped
)
1078 if (ts
->idle_active
)
1079 tick_nohz_stop_idle(ts
, now
);
1080 if (ts
->tick_stopped
) {
1081 tick_nohz_update_jiffies(now
);
1082 tick_nohz_kick_tick(ts
, now
);
1088 static inline void tick_nohz_switch_to_nohz(void) { }
1089 static inline void tick_nohz_irq_enter(void) { }
1091 #endif /* CONFIG_NO_HZ_COMMON */
1094 * Called from irq_enter to notify about the possible interruption of idle()
1096 void tick_irq_enter(void)
1098 tick_check_oneshot_broadcast_this_cpu();
1099 tick_nohz_irq_enter();
1103 * High resolution timer specific code
1105 #ifdef CONFIG_HIGH_RES_TIMERS
1107 * We rearm the timer until we get disabled by the idle code.
1108 * Called with interrupts disabled.
1110 static enum hrtimer_restart
tick_sched_timer(struct hrtimer
*timer
)
1112 struct tick_sched
*ts
=
1113 container_of(timer
, struct tick_sched
, sched_timer
);
1114 struct pt_regs
*regs
= get_irq_regs();
1115 ktime_t now
= ktime_get();
1117 tick_sched_do_timer(now
);
1120 * Do not call, when we are not in irq context and have
1121 * no valid regs pointer
1124 tick_sched_handle(ts
, regs
);
1126 /* No need to reprogram if we are in idle or full dynticks mode */
1127 if (unlikely(ts
->tick_stopped
))
1128 return HRTIMER_NORESTART
;
1130 hrtimer_forward(timer
, now
, tick_period
);
1132 return HRTIMER_RESTART
;
1135 static int sched_skew_tick
;
1137 static int __init
skew_tick(char *str
)
1139 get_option(&str
, &sched_skew_tick
);
1143 early_param("skew_tick", skew_tick
);
1146 * tick_setup_sched_timer - setup the tick emulation timer
1148 void tick_setup_sched_timer(void)
1150 struct tick_sched
*ts
= this_cpu_ptr(&tick_cpu_sched
);
1151 ktime_t now
= ktime_get();
1154 * Emulate tick processing via per-CPU hrtimers:
1156 hrtimer_init(&ts
->sched_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS
);
1157 ts
->sched_timer
.function
= tick_sched_timer
;
1159 /* Get the next period (per cpu) */
1160 hrtimer_set_expires(&ts
->sched_timer
, tick_init_jiffy_update());
1162 /* Offset the tick to avert jiffies_lock contention. */
1163 if (sched_skew_tick
) {
1164 u64 offset
= ktime_to_ns(tick_period
) >> 1;
1165 do_div(offset
, num_possible_cpus());
1166 offset
*= smp_processor_id();
1167 hrtimer_add_expires_ns(&ts
->sched_timer
, offset
);
1171 hrtimer_forward(&ts
->sched_timer
, now
, tick_period
);
1172 hrtimer_start_expires(&ts
->sched_timer
,
1173 HRTIMER_MODE_ABS_PINNED
);
1174 /* Check, if the timer was already in the past */
1175 if (hrtimer_active(&ts
->sched_timer
))
1180 #ifdef CONFIG_NO_HZ_COMMON
1181 if (tick_nohz_enabled
) {
1182 ts
->nohz_mode
= NOHZ_MODE_HIGHRES
;
1183 tick_nohz_active
= 1;
1187 #endif /* HIGH_RES_TIMERS */
1189 #if defined CONFIG_NO_HZ_COMMON || defined CONFIG_HIGH_RES_TIMERS
1190 void tick_cancel_sched_timer(int cpu
)
1192 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
1194 # ifdef CONFIG_HIGH_RES_TIMERS
1195 if (ts
->sched_timer
.base
)
1196 hrtimer_cancel(&ts
->sched_timer
);
1199 memset(ts
, 0, sizeof(*ts
));
1204 * Async notification about clocksource changes
1206 void tick_clock_notify(void)
1210 for_each_possible_cpu(cpu
)
1211 set_bit(0, &per_cpu(tick_cpu_sched
, cpu
).check_clocks
);
1215 * Async notification about clock event changes
1217 void tick_oneshot_notify(void)
1219 struct tick_sched
*ts
= this_cpu_ptr(&tick_cpu_sched
);
1221 set_bit(0, &ts
->check_clocks
);
1225 * Check, if a change happened, which makes oneshot possible.
1227 * Called cyclic from the hrtimer softirq (driven by the timer
1228 * softirq) allow_nohz signals, that we can switch into low-res nohz
1229 * mode, because high resolution timers are disabled (either compile
1232 int tick_check_oneshot_change(int allow_nohz
)
1234 struct tick_sched
*ts
= this_cpu_ptr(&tick_cpu_sched
);
1236 if (!test_and_clear_bit(0, &ts
->check_clocks
))
1239 if (ts
->nohz_mode
!= NOHZ_MODE_INACTIVE
)
1242 if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
1248 tick_nohz_switch_to_nohz();