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>
24 #include <asm/irq_regs.h>
26 #include "tick-internal.h"
29 * Per cpu nohz control structure
31 static DEFINE_PER_CPU(struct tick_sched
, tick_cpu_sched
);
34 * The time, when the last jiffy update happened. Protected by xtime_lock.
36 static ktime_t last_jiffies_update
;
38 struct tick_sched
*tick_get_tick_sched(int cpu
)
40 return &per_cpu(tick_cpu_sched
, cpu
);
44 * Must be called with interrupts disabled !
46 static void tick_do_update_jiffies64(ktime_t now
)
48 unsigned long ticks
= 0;
52 * Do a quick check without holding xtime_lock:
54 delta
= ktime_sub(now
, last_jiffies_update
);
55 if (delta
.tv64
< tick_period
.tv64
)
58 /* Reevalute with xtime_lock held */
59 write_seqlock(&xtime_lock
);
61 delta
= ktime_sub(now
, last_jiffies_update
);
62 if (delta
.tv64
>= tick_period
.tv64
) {
64 delta
= ktime_sub(delta
, tick_period
);
65 last_jiffies_update
= ktime_add(last_jiffies_update
,
68 /* Slow path for long timeouts */
69 if (unlikely(delta
.tv64
>= tick_period
.tv64
)) {
70 s64 incr
= ktime_to_ns(tick_period
);
72 ticks
= ktime_divns(delta
, incr
);
74 last_jiffies_update
= ktime_add_ns(last_jiffies_update
,
79 /* Keep the tick_next_period variable up to date */
80 tick_next_period
= ktime_add(last_jiffies_update
, tick_period
);
82 write_sequnlock(&xtime_lock
);
86 * Initialize and return retrieve the jiffies update.
88 static ktime_t
tick_init_jiffy_update(void)
92 write_seqlock(&xtime_lock
);
93 /* Did we start the jiffies update yet ? */
94 if (last_jiffies_update
.tv64
== 0)
95 last_jiffies_update
= tick_next_period
;
96 period
= last_jiffies_update
;
97 write_sequnlock(&xtime_lock
);
102 * NOHZ - aka dynamic tick functionality
108 static int tick_nohz_enabled __read_mostly
= 1;
111 * Enable / Disable tickless mode
113 static int __init
setup_tick_nohz(char *str
)
115 if (!strcmp(str
, "off"))
116 tick_nohz_enabled
= 0;
117 else if (!strcmp(str
, "on"))
118 tick_nohz_enabled
= 1;
124 __setup("nohz=", setup_tick_nohz
);
127 * tick_nohz_update_jiffies - update jiffies when idle was interrupted
129 * Called from interrupt entry when the CPU was idle
131 * In case the sched_tick was stopped on this CPU, we have to check if jiffies
132 * must be updated. Otherwise an interrupt handler could use a stale jiffy
133 * value. We do this unconditionally on any cpu, as we don't know whether the
134 * cpu, which has the update task assigned is in a long sleep.
136 static void tick_nohz_update_jiffies(ktime_t now
)
138 int cpu
= smp_processor_id();
139 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
142 cpumask_clear_cpu(cpu
, nohz_cpu_mask
);
143 ts
->idle_waketime
= now
;
145 local_irq_save(flags
);
146 tick_do_update_jiffies64(now
);
147 local_irq_restore(flags
);
149 touch_softlockup_watchdog();
153 * Updates the per cpu time idle statistics counters
156 update_ts_time_stats(int cpu
, struct tick_sched
*ts
, ktime_t now
, u64
*last_update_time
)
160 if (ts
->idle_active
) {
161 delta
= ktime_sub(now
, ts
->idle_entrytime
);
162 if (nr_iowait_cpu(cpu
) > 0)
163 ts
->iowait_sleeptime
= ktime_add(ts
->iowait_sleeptime
, delta
);
165 ts
->idle_sleeptime
= ktime_add(ts
->idle_sleeptime
, delta
);
166 ts
->idle_entrytime
= now
;
169 if (last_update_time
)
170 *last_update_time
= ktime_to_us(now
);
174 static void tick_nohz_stop_idle(int cpu
, ktime_t now
)
176 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
178 update_ts_time_stats(cpu
, ts
, now
, NULL
);
181 sched_clock_idle_wakeup_event(0);
184 static ktime_t
tick_nohz_start_idle(int cpu
, struct tick_sched
*ts
)
190 update_ts_time_stats(cpu
, ts
, now
, NULL
);
192 ts
->idle_entrytime
= now
;
194 sched_clock_idle_sleep_event();
199 * get_cpu_idle_time_us - get the total idle time of a cpu
200 * @cpu: CPU number to query
201 * @last_update_time: variable to store update time in. Do not update
204 * Return the cummulative idle time (since boot) for a given
205 * CPU, in microseconds.
207 * This time is measured via accounting rather than sampling,
208 * and is as accurate as ktime_get() is.
210 * This function returns -1 if NOHZ is not enabled.
212 u64
get_cpu_idle_time_us(int cpu
, u64
*last_update_time
)
214 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
217 if (!tick_nohz_enabled
)
221 if (last_update_time
) {
222 update_ts_time_stats(cpu
, ts
, now
, last_update_time
);
223 idle
= ts
->idle_sleeptime
;
225 if (ts
->idle_active
&& !nr_iowait_cpu(cpu
)) {
226 ktime_t delta
= ktime_sub(now
, ts
->idle_entrytime
);
228 idle
= ktime_add(ts
->idle_sleeptime
, delta
);
230 idle
= ts
->idle_sleeptime
;
234 return ktime_to_us(idle
);
237 EXPORT_SYMBOL_GPL(get_cpu_idle_time_us
);
240 * get_cpu_iowait_time_us - get the total iowait time of a cpu
241 * @cpu: CPU number to query
242 * @last_update_time: variable to store update time in. Do not update
245 * Return the cummulative iowait time (since boot) for a given
246 * CPU, in microseconds.
248 * This time is measured via accounting rather than sampling,
249 * and is as accurate as ktime_get() is.
251 * This function returns -1 if NOHZ is not enabled.
253 u64
get_cpu_iowait_time_us(int cpu
, u64
*last_update_time
)
255 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
258 if (!tick_nohz_enabled
)
262 if (last_update_time
) {
263 update_ts_time_stats(cpu
, ts
, now
, last_update_time
);
264 iowait
= ts
->iowait_sleeptime
;
266 if (ts
->idle_active
&& nr_iowait_cpu(cpu
) > 0) {
267 ktime_t delta
= ktime_sub(now
, ts
->idle_entrytime
);
269 iowait
= ktime_add(ts
->iowait_sleeptime
, delta
);
271 iowait
= ts
->iowait_sleeptime
;
275 return ktime_to_us(iowait
);
277 EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us
);
280 * tick_nohz_stop_sched_tick - stop the idle tick from the idle task
282 * When the next event is more than a tick into the future, stop the idle tick
283 * Called either from the idle loop or from irq_exit() when an idle period was
284 * just interrupted by an interrupt which did not cause a reschedule.
286 void tick_nohz_stop_sched_tick(int inidle
)
288 unsigned long seq
, last_jiffies
, next_jiffies
, delta_jiffies
, flags
;
289 struct tick_sched
*ts
;
290 ktime_t last_update
, expires
, now
;
291 struct clock_event_device
*dev
= __get_cpu_var(tick_cpu_device
).evtdev
;
295 local_irq_save(flags
);
297 cpu
= smp_processor_id();
298 ts
= &per_cpu(tick_cpu_sched
, cpu
);
301 * Call to tick_nohz_start_idle stops the last_update_time from being
302 * updated. Thus, it must not be called in the event we are called from
303 * irq_exit() with the prior state different than idle.
305 if (!inidle
&& !ts
->inidle
)
309 * Set ts->inidle unconditionally. Even if the system did not
310 * switch to NOHZ mode the cpu frequency governers rely on the
311 * update of the idle time accounting in tick_nohz_start_idle().
315 now
= tick_nohz_start_idle(cpu
, ts
);
318 * If this cpu is offline and it is the one which updates
319 * jiffies, then give up the assignment and let it be taken by
320 * the cpu which runs the tick timer next. If we don't drop
321 * this here the jiffies might be stale and do_timer() never
324 if (unlikely(!cpu_online(cpu
))) {
325 if (cpu
== tick_do_timer_cpu
)
326 tick_do_timer_cpu
= TICK_DO_TIMER_NONE
;
329 if (unlikely(ts
->nohz_mode
== NOHZ_MODE_INACTIVE
))
335 if (unlikely(local_softirq_pending() && cpu_online(cpu
))) {
336 static int ratelimit
;
338 if (ratelimit
< 10) {
339 printk(KERN_ERR
"NOHZ: local_softirq_pending %02x\n",
340 (unsigned int) local_softirq_pending());
347 /* Read jiffies and the time when jiffies were updated last */
349 seq
= read_seqbegin(&xtime_lock
);
350 last_update
= last_jiffies_update
;
351 last_jiffies
= jiffies
;
352 time_delta
= timekeeping_max_deferment();
353 } while (read_seqretry(&xtime_lock
, seq
));
355 if (rcu_needs_cpu(cpu
) || printk_needs_cpu(cpu
) ||
356 arch_needs_cpu(cpu
)) {
357 next_jiffies
= last_jiffies
+ 1;
360 /* Get the next timer wheel timer */
361 next_jiffies
= get_next_timer_interrupt(last_jiffies
);
362 delta_jiffies
= next_jiffies
- last_jiffies
;
365 * Do not stop the tick, if we are only one off
366 * or if the cpu is required for rcu
368 if (!ts
->tick_stopped
&& delta_jiffies
== 1)
371 /* Schedule the tick, if we are at least one jiffie off */
372 if ((long)delta_jiffies
>= 1) {
375 * If this cpu is the one which updates jiffies, then
376 * give up the assignment and let it be taken by the
377 * cpu which runs the tick timer next, which might be
378 * this cpu as well. If we don't drop this here the
379 * jiffies might be stale and do_timer() never
380 * invoked. Keep track of the fact that it was the one
381 * which had the do_timer() duty last. If this cpu is
382 * the one which had the do_timer() duty last, we
383 * limit the sleep time to the timekeeping
384 * max_deferement value which we retrieved
385 * above. Otherwise we can sleep as long as we want.
387 if (cpu
== tick_do_timer_cpu
) {
388 tick_do_timer_cpu
= TICK_DO_TIMER_NONE
;
389 ts
->do_timer_last
= 1;
390 } else if (tick_do_timer_cpu
!= TICK_DO_TIMER_NONE
) {
391 time_delta
= KTIME_MAX
;
392 ts
->do_timer_last
= 0;
393 } else if (!ts
->do_timer_last
) {
394 time_delta
= KTIME_MAX
;
398 * calculate the expiry time for the next timer wheel
399 * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals
400 * that there is no timer pending or at least extremely
401 * far into the future (12 days for HZ=1000). In this
402 * case we set the expiry to the end of time.
404 if (likely(delta_jiffies
< NEXT_TIMER_MAX_DELTA
)) {
406 * Calculate the time delta for the next timer event.
407 * If the time delta exceeds the maximum time delta
408 * permitted by the current clocksource then adjust
409 * the time delta accordingly to ensure the
410 * clocksource does not wrap.
412 time_delta
= min_t(u64
, time_delta
,
413 tick_period
.tv64
* delta_jiffies
);
416 if (time_delta
< KTIME_MAX
)
417 expires
= ktime_add_ns(last_update
, time_delta
);
419 expires
.tv64
= KTIME_MAX
;
421 if (delta_jiffies
> 1)
422 cpumask_set_cpu(cpu
, nohz_cpu_mask
);
424 /* Skip reprogram of event if its not changed */
425 if (ts
->tick_stopped
&& ktime_equal(expires
, dev
->next_event
))
429 * nohz_stop_sched_tick can be called several times before
430 * the nohz_restart_sched_tick is called. This happens when
431 * interrupts arrive which do not cause a reschedule. In the
432 * first call we save the current tick time, so we can restart
433 * the scheduler tick in nohz_restart_sched_tick.
435 if (!ts
->tick_stopped
) {
436 select_nohz_load_balancer(1);
438 ts
->idle_tick
= hrtimer_get_expires(&ts
->sched_timer
);
439 ts
->tick_stopped
= 1;
440 ts
->idle_jiffies
= last_jiffies
;
447 ts
->idle_expires
= expires
;
450 * If the expiration time == KTIME_MAX, then
451 * in this case we simply stop the tick timer.
453 if (unlikely(expires
.tv64
== KTIME_MAX
)) {
454 if (ts
->nohz_mode
== NOHZ_MODE_HIGHRES
)
455 hrtimer_cancel(&ts
->sched_timer
);
459 if (ts
->nohz_mode
== NOHZ_MODE_HIGHRES
) {
460 hrtimer_start(&ts
->sched_timer
, expires
,
461 HRTIMER_MODE_ABS_PINNED
);
462 /* Check, if the timer was already in the past */
463 if (hrtimer_active(&ts
->sched_timer
))
465 } else if (!tick_program_event(expires
, 0))
468 * We are past the event already. So we crossed a
469 * jiffie boundary. Update jiffies and raise the
472 tick_do_update_jiffies64(ktime_get());
473 cpumask_clear_cpu(cpu
, nohz_cpu_mask
);
475 raise_softirq_irqoff(TIMER_SOFTIRQ
);
477 ts
->next_jiffies
= next_jiffies
;
478 ts
->last_jiffies
= last_jiffies
;
479 ts
->sleep_length
= ktime_sub(dev
->next_event
, now
);
481 local_irq_restore(flags
);
485 * tick_nohz_get_sleep_length - return the length of the current sleep
487 * Called from power state control code with interrupts disabled
489 ktime_t
tick_nohz_get_sleep_length(void)
491 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
493 return ts
->sleep_length
;
496 static void tick_nohz_restart(struct tick_sched
*ts
, ktime_t now
)
498 hrtimer_cancel(&ts
->sched_timer
);
499 hrtimer_set_expires(&ts
->sched_timer
, ts
->idle_tick
);
502 /* Forward the time to expire in the future */
503 hrtimer_forward(&ts
->sched_timer
, now
, tick_period
);
505 if (ts
->nohz_mode
== NOHZ_MODE_HIGHRES
) {
506 hrtimer_start_expires(&ts
->sched_timer
,
507 HRTIMER_MODE_ABS_PINNED
);
508 /* Check, if the timer was already in the past */
509 if (hrtimer_active(&ts
->sched_timer
))
512 if (!tick_program_event(
513 hrtimer_get_expires(&ts
->sched_timer
), 0))
516 /* Update jiffies and reread time */
517 tick_do_update_jiffies64(now
);
523 * tick_nohz_restart_sched_tick - restart the idle tick from the idle task
525 * Restart the idle tick when the CPU is woken up from idle
527 void tick_nohz_restart_sched_tick(void)
529 int cpu
= smp_processor_id();
530 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
531 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
537 if (ts
->idle_active
|| (ts
->inidle
&& ts
->tick_stopped
))
541 tick_nohz_stop_idle(cpu
, now
);
543 if (!ts
->inidle
|| !ts
->tick_stopped
) {
553 /* Update jiffies first */
554 select_nohz_load_balancer(0);
555 tick_do_update_jiffies64(now
);
556 cpumask_clear_cpu(cpu
, nohz_cpu_mask
);
558 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
560 * We stopped the tick in idle. Update process times would miss the
561 * time we slept as update_process_times does only a 1 tick
562 * accounting. Enforce that this is accounted to idle !
564 ticks
= jiffies
- ts
->idle_jiffies
;
566 * We might be one off. Do not randomly account a huge number of ticks!
568 if (ticks
&& ticks
< LONG_MAX
)
569 account_idle_ticks(ticks
);
572 touch_softlockup_watchdog();
574 * Cancel the scheduled timer and restore the tick
576 ts
->tick_stopped
= 0;
577 ts
->idle_exittime
= now
;
579 tick_nohz_restart(ts
, now
);
584 static int tick_nohz_reprogram(struct tick_sched
*ts
, ktime_t now
)
586 hrtimer_forward(&ts
->sched_timer
, now
, tick_period
);
587 return tick_program_event(hrtimer_get_expires(&ts
->sched_timer
), 0);
591 * The nohz low res interrupt handler
593 static void tick_nohz_handler(struct clock_event_device
*dev
)
595 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
596 struct pt_regs
*regs
= get_irq_regs();
597 int cpu
= smp_processor_id();
598 ktime_t now
= ktime_get();
600 dev
->next_event
.tv64
= KTIME_MAX
;
603 * Check if the do_timer duty was dropped. We don't care about
604 * concurrency: This happens only when the cpu in charge went
605 * into a long sleep. If two cpus happen to assign themself to
606 * this duty, then the jiffies update is still serialized by
609 if (unlikely(tick_do_timer_cpu
== TICK_DO_TIMER_NONE
))
610 tick_do_timer_cpu
= cpu
;
612 /* Check, if the jiffies need an update */
613 if (tick_do_timer_cpu
== cpu
)
614 tick_do_update_jiffies64(now
);
617 * When we are idle and the tick is stopped, we have to touch
618 * the watchdog as we might not schedule for a really long
619 * time. This happens on complete idle SMP systems while
620 * waiting on the login prompt. We also increment the "start
621 * of idle" jiffy stamp so the idle accounting adjustment we
622 * do when we go busy again does not account too much ticks.
624 if (ts
->tick_stopped
) {
625 touch_softlockup_watchdog();
629 update_process_times(user_mode(regs
));
630 profile_tick(CPU_PROFILING
);
632 while (tick_nohz_reprogram(ts
, now
)) {
634 tick_do_update_jiffies64(now
);
639 * tick_nohz_switch_to_nohz - switch to nohz mode
641 static void tick_nohz_switch_to_nohz(void)
643 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
646 if (!tick_nohz_enabled
)
650 if (tick_switch_to_oneshot(tick_nohz_handler
)) {
655 ts
->nohz_mode
= NOHZ_MODE_LOWRES
;
658 * Recycle the hrtimer in ts, so we can share the
659 * hrtimer_forward with the highres code.
661 hrtimer_init(&ts
->sched_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS
);
662 /* Get the next period */
663 next
= tick_init_jiffy_update();
666 hrtimer_set_expires(&ts
->sched_timer
, next
);
667 if (!tick_program_event(next
, 0))
669 next
= ktime_add(next
, tick_period
);
673 printk(KERN_INFO
"Switched to NOHz mode on CPU #%d\n", smp_processor_id());
677 * When NOHZ is enabled and the tick is stopped, we need to kick the
678 * tick timer from irq_enter() so that the jiffies update is kept
679 * alive during long running softirqs. That's ugly as hell, but
680 * correctness is key even if we need to fix the offending softirq in
683 * Note, this is different to tick_nohz_restart. We just kick the
684 * timer and do not touch the other magic bits which need to be done
687 static void tick_nohz_kick_tick(int cpu
, ktime_t now
)
690 /* Switch back to 2.6.27 behaviour */
692 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
696 * Do not touch the tick device, when the next expiry is either
697 * already reached or less/equal than the tick period.
699 delta
= ktime_sub(hrtimer_get_expires(&ts
->sched_timer
), now
);
700 if (delta
.tv64
<= tick_period
.tv64
)
703 tick_nohz_restart(ts
, now
);
707 static inline void tick_check_nohz(int cpu
)
709 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
712 if (!ts
->idle_active
&& !ts
->tick_stopped
)
716 tick_nohz_stop_idle(cpu
, now
);
717 if (ts
->tick_stopped
) {
718 tick_nohz_update_jiffies(now
);
719 tick_nohz_kick_tick(cpu
, now
);
725 static inline void tick_nohz_switch_to_nohz(void) { }
726 static inline void tick_check_nohz(int cpu
) { }
731 * Called from irq_enter to notify about the possible interruption of idle()
733 void tick_check_idle(int cpu
)
735 tick_check_oneshot_broadcast(cpu
);
736 tick_check_nohz(cpu
);
740 * High resolution timer specific code
742 #ifdef CONFIG_HIGH_RES_TIMERS
744 * We rearm the timer until we get disabled by the idle code.
745 * Called with interrupts disabled and timer->base->cpu_base->lock held.
747 static enum hrtimer_restart
tick_sched_timer(struct hrtimer
*timer
)
749 struct tick_sched
*ts
=
750 container_of(timer
, struct tick_sched
, sched_timer
);
751 struct pt_regs
*regs
= get_irq_regs();
752 ktime_t now
= ktime_get();
753 int cpu
= smp_processor_id();
757 * Check if the do_timer duty was dropped. We don't care about
758 * concurrency: This happens only when the cpu in charge went
759 * into a long sleep. If two cpus happen to assign themself to
760 * this duty, then the jiffies update is still serialized by
763 if (unlikely(tick_do_timer_cpu
== TICK_DO_TIMER_NONE
))
764 tick_do_timer_cpu
= cpu
;
767 /* Check, if the jiffies need an update */
768 if (tick_do_timer_cpu
== cpu
)
769 tick_do_update_jiffies64(now
);
772 * Do not call, when we are not in irq context and have
773 * no valid regs pointer
777 * When we are idle and the tick is stopped, we have to touch
778 * the watchdog as we might not schedule for a really long
779 * time. This happens on complete idle SMP systems while
780 * waiting on the login prompt. We also increment the "start of
781 * idle" jiffy stamp so the idle accounting adjustment we do
782 * when we go busy again does not account too much ticks.
784 if (ts
->tick_stopped
) {
785 touch_softlockup_watchdog();
788 update_process_times(user_mode(regs
));
789 profile_tick(CPU_PROFILING
);
792 hrtimer_forward(timer
, now
, tick_period
);
794 return HRTIMER_RESTART
;
798 * tick_setup_sched_timer - setup the tick emulation timer
800 void tick_setup_sched_timer(void)
802 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
803 ktime_t now
= ktime_get();
806 * Emulate tick processing via per-CPU hrtimers:
808 hrtimer_init(&ts
->sched_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS
);
809 ts
->sched_timer
.function
= tick_sched_timer
;
811 /* Get the next period (per cpu) */
812 hrtimer_set_expires(&ts
->sched_timer
, tick_init_jiffy_update());
815 hrtimer_forward(&ts
->sched_timer
, now
, tick_period
);
816 hrtimer_start_expires(&ts
->sched_timer
,
817 HRTIMER_MODE_ABS_PINNED
);
818 /* Check, if the timer was already in the past */
819 if (hrtimer_active(&ts
->sched_timer
))
825 if (tick_nohz_enabled
) {
826 ts
->nohz_mode
= NOHZ_MODE_HIGHRES
;
827 printk(KERN_INFO
"Switched to NOHz mode on CPU #%d\n", smp_processor_id());
831 #endif /* HIGH_RES_TIMERS */
833 #if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS
834 void tick_cancel_sched_timer(int cpu
)
836 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
838 # ifdef CONFIG_HIGH_RES_TIMERS
839 if (ts
->sched_timer
.base
)
840 hrtimer_cancel(&ts
->sched_timer
);
843 ts
->nohz_mode
= NOHZ_MODE_INACTIVE
;
848 * Async notification about clocksource changes
850 void tick_clock_notify(void)
854 for_each_possible_cpu(cpu
)
855 set_bit(0, &per_cpu(tick_cpu_sched
, cpu
).check_clocks
);
859 * Async notification about clock event changes
861 void tick_oneshot_notify(void)
863 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
865 set_bit(0, &ts
->check_clocks
);
869 * Check, if a change happened, which makes oneshot possible.
871 * Called cyclic from the hrtimer softirq (driven by the timer
872 * softirq) allow_nohz signals, that we can switch into low-res nohz
873 * mode, because high resolution timers are disabled (either compile
876 int tick_check_oneshot_change(int allow_nohz
)
878 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
880 if (!test_and_clear_bit(0, &ts
->check_clocks
))
883 if (ts
->nohz_mode
!= NOHZ_MODE_INACTIVE
)
886 if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
892 tick_nohz_switch_to_nohz();