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 ts
->idle_waketime
= now
;
144 local_irq_save(flags
);
145 tick_do_update_jiffies64(now
);
146 local_irq_restore(flags
);
148 touch_softlockup_watchdog();
152 * Updates the per cpu time idle statistics counters
155 update_ts_time_stats(int cpu
, struct tick_sched
*ts
, ktime_t now
, u64
*last_update_time
)
159 if (ts
->idle_active
) {
160 delta
= ktime_sub(now
, ts
->idle_entrytime
);
161 if (nr_iowait_cpu(cpu
) > 0)
162 ts
->iowait_sleeptime
= ktime_add(ts
->iowait_sleeptime
, delta
);
164 ts
->idle_sleeptime
= ktime_add(ts
->idle_sleeptime
, delta
);
165 ts
->idle_entrytime
= now
;
168 if (last_update_time
)
169 *last_update_time
= ktime_to_us(now
);
173 static void tick_nohz_stop_idle(int cpu
, ktime_t now
)
175 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
177 update_ts_time_stats(cpu
, ts
, now
, NULL
);
180 sched_clock_idle_wakeup_event(0);
183 static ktime_t
tick_nohz_start_idle(int cpu
, struct tick_sched
*ts
)
185 ktime_t now
= ktime_get();
187 ts
->idle_entrytime
= now
;
189 sched_clock_idle_sleep_event();
194 * get_cpu_idle_time_us - get the total idle time of a cpu
195 * @cpu: CPU number to query
196 * @last_update_time: variable to store update time in. Do not update
199 * Return the cummulative idle time (since boot) for a given
200 * CPU, in microseconds.
202 * This time is measured via accounting rather than sampling,
203 * and is as accurate as ktime_get() is.
205 * This function returns -1 if NOHZ is not enabled.
207 u64
get_cpu_idle_time_us(int cpu
, u64
*last_update_time
)
209 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
212 if (!tick_nohz_enabled
)
216 if (last_update_time
) {
217 update_ts_time_stats(cpu
, ts
, now
, last_update_time
);
218 idle
= ts
->idle_sleeptime
;
220 if (ts
->idle_active
&& !nr_iowait_cpu(cpu
)) {
221 ktime_t delta
= ktime_sub(now
, ts
->idle_entrytime
);
223 idle
= ktime_add(ts
->idle_sleeptime
, delta
);
225 idle
= ts
->idle_sleeptime
;
229 return ktime_to_us(idle
);
232 EXPORT_SYMBOL_GPL(get_cpu_idle_time_us
);
235 * get_cpu_iowait_time_us - get the total iowait time of a cpu
236 * @cpu: CPU number to query
237 * @last_update_time: variable to store update time in. Do not update
240 * Return the cummulative iowait time (since boot) for a given
241 * CPU, in microseconds.
243 * This time is measured via accounting rather than sampling,
244 * and is as accurate as ktime_get() is.
246 * This function returns -1 if NOHZ is not enabled.
248 u64
get_cpu_iowait_time_us(int cpu
, u64
*last_update_time
)
250 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
253 if (!tick_nohz_enabled
)
257 if (last_update_time
) {
258 update_ts_time_stats(cpu
, ts
, now
, last_update_time
);
259 iowait
= ts
->iowait_sleeptime
;
261 if (ts
->idle_active
&& nr_iowait_cpu(cpu
) > 0) {
262 ktime_t delta
= ktime_sub(now
, ts
->idle_entrytime
);
264 iowait
= ktime_add(ts
->iowait_sleeptime
, delta
);
266 iowait
= ts
->iowait_sleeptime
;
270 return ktime_to_us(iowait
);
272 EXPORT_SYMBOL_GPL(get_cpu_iowait_time_us
);
274 static void tick_nohz_stop_sched_tick(struct tick_sched
*ts
)
276 unsigned long seq
, last_jiffies
, next_jiffies
, delta_jiffies
;
277 ktime_t last_update
, expires
, now
;
278 struct clock_event_device
*dev
= __get_cpu_var(tick_cpu_device
).evtdev
;
282 cpu
= smp_processor_id();
283 ts
= &per_cpu(tick_cpu_sched
, cpu
);
285 now
= tick_nohz_start_idle(cpu
, ts
);
288 * If this cpu is offline and it is the one which updates
289 * jiffies, then give up the assignment and let it be taken by
290 * the cpu which runs the tick timer next. If we don't drop
291 * this here the jiffies might be stale and do_timer() never
294 if (unlikely(!cpu_online(cpu
))) {
295 if (cpu
== tick_do_timer_cpu
)
296 tick_do_timer_cpu
= TICK_DO_TIMER_NONE
;
299 if (unlikely(ts
->nohz_mode
== NOHZ_MODE_INACTIVE
))
305 if (unlikely(local_softirq_pending() && cpu_online(cpu
))) {
306 static int ratelimit
;
308 if (ratelimit
< 10) {
309 printk(KERN_ERR
"NOHZ: local_softirq_pending %02x\n",
310 (unsigned int) local_softirq_pending());
317 /* Read jiffies and the time when jiffies were updated last */
319 seq
= read_seqbegin(&xtime_lock
);
320 last_update
= last_jiffies_update
;
321 last_jiffies
= jiffies
;
322 time_delta
= timekeeping_max_deferment();
323 } while (read_seqretry(&xtime_lock
, seq
));
325 if (rcu_needs_cpu(cpu
) || printk_needs_cpu(cpu
) ||
326 arch_needs_cpu(cpu
)) {
327 next_jiffies
= last_jiffies
+ 1;
330 /* Get the next timer wheel timer */
331 next_jiffies
= get_next_timer_interrupt(last_jiffies
);
332 delta_jiffies
= next_jiffies
- last_jiffies
;
335 * Do not stop the tick, if we are only one off
336 * or if the cpu is required for rcu
338 if (!ts
->tick_stopped
&& delta_jiffies
== 1)
341 /* Schedule the tick, if we are at least one jiffie off */
342 if ((long)delta_jiffies
>= 1) {
345 * If this cpu is the one which updates jiffies, then
346 * give up the assignment and let it be taken by the
347 * cpu which runs the tick timer next, which might be
348 * this cpu as well. If we don't drop this here the
349 * jiffies might be stale and do_timer() never
350 * invoked. Keep track of the fact that it was the one
351 * which had the do_timer() duty last. If this cpu is
352 * the one which had the do_timer() duty last, we
353 * limit the sleep time to the timekeeping
354 * max_deferement value which we retrieved
355 * above. Otherwise we can sleep as long as we want.
357 if (cpu
== tick_do_timer_cpu
) {
358 tick_do_timer_cpu
= TICK_DO_TIMER_NONE
;
359 ts
->do_timer_last
= 1;
360 } else if (tick_do_timer_cpu
!= TICK_DO_TIMER_NONE
) {
361 time_delta
= KTIME_MAX
;
362 ts
->do_timer_last
= 0;
363 } else if (!ts
->do_timer_last
) {
364 time_delta
= KTIME_MAX
;
368 * calculate the expiry time for the next timer wheel
369 * timer. delta_jiffies >= NEXT_TIMER_MAX_DELTA signals
370 * that there is no timer pending or at least extremely
371 * far into the future (12 days for HZ=1000). In this
372 * case we set the expiry to the end of time.
374 if (likely(delta_jiffies
< NEXT_TIMER_MAX_DELTA
)) {
376 * Calculate the time delta for the next timer event.
377 * If the time delta exceeds the maximum time delta
378 * permitted by the current clocksource then adjust
379 * the time delta accordingly to ensure the
380 * clocksource does not wrap.
382 time_delta
= min_t(u64
, time_delta
,
383 tick_period
.tv64
* delta_jiffies
);
386 if (time_delta
< KTIME_MAX
)
387 expires
= ktime_add_ns(last_update
, time_delta
);
389 expires
.tv64
= KTIME_MAX
;
391 /* Skip reprogram of event if its not changed */
392 if (ts
->tick_stopped
&& ktime_equal(expires
, dev
->next_event
))
396 * nohz_stop_sched_tick can be called several times before
397 * the nohz_restart_sched_tick is called. This happens when
398 * interrupts arrive which do not cause a reschedule. In the
399 * first call we save the current tick time, so we can restart
400 * the scheduler tick in nohz_restart_sched_tick.
402 if (!ts
->tick_stopped
) {
403 select_nohz_load_balancer(1);
405 ts
->idle_tick
= hrtimer_get_expires(&ts
->sched_timer
);
406 ts
->tick_stopped
= 1;
407 ts
->idle_jiffies
= last_jiffies
;
413 ts
->idle_expires
= expires
;
416 * If the expiration time == KTIME_MAX, then
417 * in this case we simply stop the tick timer.
419 if (unlikely(expires
.tv64
== KTIME_MAX
)) {
420 if (ts
->nohz_mode
== NOHZ_MODE_HIGHRES
)
421 hrtimer_cancel(&ts
->sched_timer
);
425 if (ts
->nohz_mode
== NOHZ_MODE_HIGHRES
) {
426 hrtimer_start(&ts
->sched_timer
, expires
,
427 HRTIMER_MODE_ABS_PINNED
);
428 /* Check, if the timer was already in the past */
429 if (hrtimer_active(&ts
->sched_timer
))
431 } else if (!tick_program_event(expires
, 0))
434 * We are past the event already. So we crossed a
435 * jiffie boundary. Update jiffies and raise the
438 tick_do_update_jiffies64(ktime_get());
440 raise_softirq_irqoff(TIMER_SOFTIRQ
);
442 ts
->next_jiffies
= next_jiffies
;
443 ts
->last_jiffies
= last_jiffies
;
444 ts
->sleep_length
= ktime_sub(dev
->next_event
, now
);
448 * tick_nohz_idle_enter - stop the idle tick from the idle task
450 * When the next event is more than a tick into the future, stop the idle tick
451 * Called when we start the idle loop.
453 * The arch is responsible of calling:
455 * - rcu_idle_enter() after its last use of RCU before the CPU is put
457 * - rcu_idle_exit() before the first use of RCU after the CPU is woken up.
459 void tick_nohz_idle_enter(void)
461 struct tick_sched
*ts
;
463 WARN_ON_ONCE(irqs_disabled());
466 * Update the idle state in the scheduler domain hierarchy
467 * when tick_nohz_stop_sched_tick() is called from the idle loop.
468 * State will be updated to busy during the first busy tick after
471 set_cpu_sd_state_idle();
475 ts
= &__get_cpu_var(tick_cpu_sched
);
477 * set ts->inidle unconditionally. even if the system did not
478 * switch to nohz mode the cpu frequency governers rely on the
479 * update of the idle time accounting in tick_nohz_start_idle().
482 tick_nohz_stop_sched_tick(ts
);
488 * tick_nohz_irq_exit - update next tick event from interrupt exit
490 * When an interrupt fires while we are idle and it doesn't cause
491 * a reschedule, it may still add, modify or delete a timer, enqueue
492 * an RCU callback, etc...
493 * So we need to re-calculate and reprogram the next tick event.
495 void tick_nohz_irq_exit(void)
497 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
502 tick_nohz_stop_sched_tick(ts
);
506 * tick_nohz_get_sleep_length - return the length of the current sleep
508 * Called from power state control code with interrupts disabled
510 ktime_t
tick_nohz_get_sleep_length(void)
512 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
514 return ts
->sleep_length
;
517 static void tick_nohz_restart(struct tick_sched
*ts
, ktime_t now
)
519 hrtimer_cancel(&ts
->sched_timer
);
520 hrtimer_set_expires(&ts
->sched_timer
, ts
->idle_tick
);
523 /* Forward the time to expire in the future */
524 hrtimer_forward(&ts
->sched_timer
, now
, tick_period
);
526 if (ts
->nohz_mode
== NOHZ_MODE_HIGHRES
) {
527 hrtimer_start_expires(&ts
->sched_timer
,
528 HRTIMER_MODE_ABS_PINNED
);
529 /* Check, if the timer was already in the past */
530 if (hrtimer_active(&ts
->sched_timer
))
533 if (!tick_program_event(
534 hrtimer_get_expires(&ts
->sched_timer
), 0))
537 /* Reread time and update jiffies */
539 tick_do_update_jiffies64(now
);
544 * tick_nohz_idle_exit - restart the idle tick from the idle task
546 * Restart the idle tick when the CPU is woken up from idle
547 * This also exit the RCU extended quiescent state. The CPU
548 * can use RCU again after this function is called.
550 void tick_nohz_idle_exit(void)
552 int cpu
= smp_processor_id();
553 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
554 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
561 WARN_ON_ONCE(!ts
->inidle
);
565 if (ts
->idle_active
|| ts
->tick_stopped
)
569 tick_nohz_stop_idle(cpu
, now
);
571 if (!ts
->tick_stopped
) {
576 /* Update jiffies first */
577 select_nohz_load_balancer(0);
578 tick_do_update_jiffies64(now
);
580 #ifndef CONFIG_VIRT_CPU_ACCOUNTING
582 * We stopped the tick in idle. Update process times would miss the
583 * time we slept as update_process_times does only a 1 tick
584 * accounting. Enforce that this is accounted to idle !
586 ticks
= jiffies
- ts
->idle_jiffies
;
588 * We might be one off. Do not randomly account a huge number of ticks!
590 if (ticks
&& ticks
< LONG_MAX
)
591 account_idle_ticks(ticks
);
594 touch_softlockup_watchdog();
596 * Cancel the scheduled timer and restore the tick
598 ts
->tick_stopped
= 0;
599 ts
->idle_exittime
= now
;
601 tick_nohz_restart(ts
, now
);
606 static int tick_nohz_reprogram(struct tick_sched
*ts
, ktime_t now
)
608 hrtimer_forward(&ts
->sched_timer
, now
, tick_period
);
609 return tick_program_event(hrtimer_get_expires(&ts
->sched_timer
), 0);
613 * The nohz low res interrupt handler
615 static void tick_nohz_handler(struct clock_event_device
*dev
)
617 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
618 struct pt_regs
*regs
= get_irq_regs();
619 int cpu
= smp_processor_id();
620 ktime_t now
= ktime_get();
622 dev
->next_event
.tv64
= KTIME_MAX
;
625 * Check if the do_timer duty was dropped. We don't care about
626 * concurrency: This happens only when the cpu in charge went
627 * into a long sleep. If two cpus happen to assign themself to
628 * this duty, then the jiffies update is still serialized by
631 if (unlikely(tick_do_timer_cpu
== TICK_DO_TIMER_NONE
))
632 tick_do_timer_cpu
= cpu
;
634 /* Check, if the jiffies need an update */
635 if (tick_do_timer_cpu
== cpu
)
636 tick_do_update_jiffies64(now
);
639 * When we are idle and the tick is stopped, we have to touch
640 * the watchdog as we might not schedule for a really long
641 * time. This happens on complete idle SMP systems while
642 * waiting on the login prompt. We also increment the "start
643 * of idle" jiffy stamp so the idle accounting adjustment we
644 * do when we go busy again does not account too much ticks.
646 if (ts
->tick_stopped
) {
647 touch_softlockup_watchdog();
651 update_process_times(user_mode(regs
));
652 profile_tick(CPU_PROFILING
);
654 while (tick_nohz_reprogram(ts
, now
)) {
656 tick_do_update_jiffies64(now
);
661 * tick_nohz_switch_to_nohz - switch to nohz mode
663 static void tick_nohz_switch_to_nohz(void)
665 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
668 if (!tick_nohz_enabled
)
672 if (tick_switch_to_oneshot(tick_nohz_handler
)) {
677 ts
->nohz_mode
= NOHZ_MODE_LOWRES
;
680 * Recycle the hrtimer in ts, so we can share the
681 * hrtimer_forward with the highres code.
683 hrtimer_init(&ts
->sched_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS
);
684 /* Get the next period */
685 next
= tick_init_jiffy_update();
688 hrtimer_set_expires(&ts
->sched_timer
, next
);
689 if (!tick_program_event(next
, 0))
691 next
= ktime_add(next
, tick_period
);
697 * When NOHZ is enabled and the tick is stopped, we need to kick the
698 * tick timer from irq_enter() so that the jiffies update is kept
699 * alive during long running softirqs. That's ugly as hell, but
700 * correctness is key even if we need to fix the offending softirq in
703 * Note, this is different to tick_nohz_restart. We just kick the
704 * timer and do not touch the other magic bits which need to be done
707 static void tick_nohz_kick_tick(int cpu
, ktime_t now
)
710 /* Switch back to 2.6.27 behaviour */
712 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
716 * Do not touch the tick device, when the next expiry is either
717 * already reached or less/equal than the tick period.
719 delta
= ktime_sub(hrtimer_get_expires(&ts
->sched_timer
), now
);
720 if (delta
.tv64
<= tick_period
.tv64
)
723 tick_nohz_restart(ts
, now
);
727 static inline void tick_check_nohz(int cpu
)
729 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
732 if (!ts
->idle_active
&& !ts
->tick_stopped
)
736 tick_nohz_stop_idle(cpu
, now
);
737 if (ts
->tick_stopped
) {
738 tick_nohz_update_jiffies(now
);
739 tick_nohz_kick_tick(cpu
, now
);
745 static inline void tick_nohz_switch_to_nohz(void) { }
746 static inline void tick_check_nohz(int cpu
) { }
751 * Called from irq_enter to notify about the possible interruption of idle()
753 void tick_check_idle(int cpu
)
755 tick_check_oneshot_broadcast(cpu
);
756 tick_check_nohz(cpu
);
760 * High resolution timer specific code
762 #ifdef CONFIG_HIGH_RES_TIMERS
764 * We rearm the timer until we get disabled by the idle code.
765 * Called with interrupts disabled and timer->base->cpu_base->lock held.
767 static enum hrtimer_restart
tick_sched_timer(struct hrtimer
*timer
)
769 struct tick_sched
*ts
=
770 container_of(timer
, struct tick_sched
, sched_timer
);
771 struct pt_regs
*regs
= get_irq_regs();
772 ktime_t now
= ktime_get();
773 int cpu
= smp_processor_id();
777 * Check if the do_timer duty was dropped. We don't care about
778 * concurrency: This happens only when the cpu in charge went
779 * into a long sleep. If two cpus happen to assign themself to
780 * this duty, then the jiffies update is still serialized by
783 if (unlikely(tick_do_timer_cpu
== TICK_DO_TIMER_NONE
))
784 tick_do_timer_cpu
= cpu
;
787 /* Check, if the jiffies need an update */
788 if (tick_do_timer_cpu
== cpu
)
789 tick_do_update_jiffies64(now
);
792 * Do not call, when we are not in irq context and have
793 * no valid regs pointer
797 * When we are idle and the tick is stopped, we have to touch
798 * the watchdog as we might not schedule for a really long
799 * time. This happens on complete idle SMP systems while
800 * waiting on the login prompt. We also increment the "start of
801 * idle" jiffy stamp so the idle accounting adjustment we do
802 * when we go busy again does not account too much ticks.
804 if (ts
->tick_stopped
) {
805 touch_softlockup_watchdog();
808 update_process_times(user_mode(regs
));
809 profile_tick(CPU_PROFILING
);
812 hrtimer_forward(timer
, now
, tick_period
);
814 return HRTIMER_RESTART
;
818 * tick_setup_sched_timer - setup the tick emulation timer
820 void tick_setup_sched_timer(void)
822 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
823 ktime_t now
= ktime_get();
826 * Emulate tick processing via per-CPU hrtimers:
828 hrtimer_init(&ts
->sched_timer
, CLOCK_MONOTONIC
, HRTIMER_MODE_ABS
);
829 ts
->sched_timer
.function
= tick_sched_timer
;
831 /* Get the next period (per cpu) */
832 hrtimer_set_expires(&ts
->sched_timer
, tick_init_jiffy_update());
835 hrtimer_forward(&ts
->sched_timer
, now
, tick_period
);
836 hrtimer_start_expires(&ts
->sched_timer
,
837 HRTIMER_MODE_ABS_PINNED
);
838 /* Check, if the timer was already in the past */
839 if (hrtimer_active(&ts
->sched_timer
))
845 if (tick_nohz_enabled
)
846 ts
->nohz_mode
= NOHZ_MODE_HIGHRES
;
849 #endif /* HIGH_RES_TIMERS */
851 #if defined CONFIG_NO_HZ || defined CONFIG_HIGH_RES_TIMERS
852 void tick_cancel_sched_timer(int cpu
)
854 struct tick_sched
*ts
= &per_cpu(tick_cpu_sched
, cpu
);
856 # ifdef CONFIG_HIGH_RES_TIMERS
857 if (ts
->sched_timer
.base
)
858 hrtimer_cancel(&ts
->sched_timer
);
861 ts
->nohz_mode
= NOHZ_MODE_INACTIVE
;
866 * Async notification about clocksource changes
868 void tick_clock_notify(void)
872 for_each_possible_cpu(cpu
)
873 set_bit(0, &per_cpu(tick_cpu_sched
, cpu
).check_clocks
);
877 * Async notification about clock event changes
879 void tick_oneshot_notify(void)
881 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
883 set_bit(0, &ts
->check_clocks
);
887 * Check, if a change happened, which makes oneshot possible.
889 * Called cyclic from the hrtimer softirq (driven by the timer
890 * softirq) allow_nohz signals, that we can switch into low-res nohz
891 * mode, because high resolution timers are disabled (either compile
894 int tick_check_oneshot_change(int allow_nohz
)
896 struct tick_sched
*ts
= &__get_cpu_var(tick_cpu_sched
);
898 if (!test_and_clear_bit(0, &ts
->check_clocks
))
901 if (ts
->nohz_mode
!= NOHZ_MODE_INACTIVE
)
904 if (!timekeeping_valid_for_hres() || !tick_is_oneshot_available())
910 tick_nohz_switch_to_nohz();