2 * linux/kernel/hrtimer.c
4 * Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
5 * Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
7 * High-resolution kernel timers
9 * In contrast to the low-resolution timeout API implemented in
10 * kernel/timer.c, hrtimers provide finer resolution and accuracy
11 * depending on system configuration and capabilities.
13 * These timers are currently used for:
17 * - precise in-kernel timing
19 * Started by: Thomas Gleixner and Ingo Molnar
22 * based on kernel/timer.c
24 * Help, testing, suggestions, bugfixes, improvements were
27 * George Anzinger, Andrew Morton, Steven Rostedt, Roman Zippel
30 * For licencing details see kernel-base/COPYING
33 #include <linux/cpu.h>
34 #include <linux/module.h>
35 #include <linux/percpu.h>
36 #include <linux/hrtimer.h>
37 #include <linux/notifier.h>
38 #include <linux/syscalls.h>
39 #include <linux/interrupt.h>
41 #include <asm/uaccess.h>
44 * ktime_get - get the monotonic time in ktime_t format
46 * returns the time in ktime_t format
48 static ktime_t
ktime_get(void)
54 return timespec_to_ktime(now
);
58 * ktime_get_real - get the real (wall-) time in ktime_t format
60 * returns the time in ktime_t format
62 static ktime_t
ktime_get_real(void)
68 return timespec_to_ktime(now
);
71 EXPORT_SYMBOL_GPL(ktime_get_real
);
76 * Note: If we want to add new timer bases, we have to skip the two
77 * clock ids captured by the cpu-timers. We do this by holding empty
78 * entries rather than doing math adjustment of the clock ids.
79 * This ensures that we capture erroneous accesses to these clock ids
80 * rather than moving them into the range of valid clock id's.
83 #define MAX_HRTIMER_BASES 2
85 static DEFINE_PER_CPU(struct hrtimer_base
, hrtimer_bases
[MAX_HRTIMER_BASES
]) =
88 .index
= CLOCK_REALTIME
,
89 .get_time
= &ktime_get_real
,
90 .resolution
= KTIME_REALTIME_RES
,
93 .index
= CLOCK_MONOTONIC
,
94 .get_time
= &ktime_get
,
95 .resolution
= KTIME_MONOTONIC_RES
,
100 * ktime_get_ts - get the monotonic clock in timespec format
101 * @ts: pointer to timespec variable
103 * The function calculates the monotonic clock from the realtime
104 * clock and the wall_to_monotonic offset and stores the result
105 * in normalized timespec format in the variable pointed to by ts.
107 void ktime_get_ts(struct timespec
*ts
)
109 struct timespec tomono
;
113 seq
= read_seqbegin(&xtime_lock
);
115 tomono
= wall_to_monotonic
;
117 } while (read_seqretry(&xtime_lock
, seq
));
119 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
,
120 ts
->tv_nsec
+ tomono
.tv_nsec
);
122 EXPORT_SYMBOL_GPL(ktime_get_ts
);
125 * Get the coarse grained time at the softirq based on xtime and
128 static void hrtimer_get_softirq_time(struct hrtimer_base
*base
)
130 ktime_t xtim
, tomono
;
134 seq
= read_seqbegin(&xtime_lock
);
135 xtim
= timespec_to_ktime(xtime
);
136 tomono
= timespec_to_ktime(wall_to_monotonic
);
138 } while (read_seqretry(&xtime_lock
, seq
));
140 base
[CLOCK_REALTIME
].softirq_time
= xtim
;
141 base
[CLOCK_MONOTONIC
].softirq_time
= ktime_add(xtim
, tomono
);
145 * Functions and macros which are different for UP/SMP systems are kept in a
150 #define set_curr_timer(b, t) do { (b)->curr_timer = (t); } while (0)
153 * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
154 * means that all timers which are tied to this base via timer->base are
155 * locked, and the base itself is locked too.
157 * So __run_timers/migrate_timers can safely modify all timers which could
158 * be found on the lists/queues.
160 * When the timer's base is locked, and the timer removed from list, it is
161 * possible to set timer->base = NULL and drop the lock: the timer remains
164 static struct hrtimer_base
*lock_hrtimer_base(const struct hrtimer
*timer
,
165 unsigned long *flags
)
167 struct hrtimer_base
*base
;
171 if (likely(base
!= NULL
)) {
172 spin_lock_irqsave(&base
->lock
, *flags
);
173 if (likely(base
== timer
->base
))
175 /* The timer has migrated to another CPU: */
176 spin_unlock_irqrestore(&base
->lock
, *flags
);
183 * Switch the timer base to the current CPU when possible.
185 static inline struct hrtimer_base
*
186 switch_hrtimer_base(struct hrtimer
*timer
, struct hrtimer_base
*base
)
188 struct hrtimer_base
*new_base
;
190 new_base
= &__get_cpu_var(hrtimer_bases
[base
->index
]);
192 if (base
!= new_base
) {
194 * We are trying to schedule the timer on the local CPU.
195 * However we can't change timer's base while it is running,
196 * so we keep it on the same CPU. No hassle vs. reprogramming
197 * the event source in the high resolution case. The softirq
198 * code will take care of this when the timer function has
199 * completed. There is no conflict as we hold the lock until
200 * the timer is enqueued.
202 if (unlikely(base
->curr_timer
== timer
))
205 /* See the comment in lock_timer_base() */
207 spin_unlock(&base
->lock
);
208 spin_lock(&new_base
->lock
);
209 timer
->base
= new_base
;
214 #else /* CONFIG_SMP */
216 #define set_curr_timer(b, t) do { } while (0)
218 static inline struct hrtimer_base
*
219 lock_hrtimer_base(const struct hrtimer
*timer
, unsigned long *flags
)
221 struct hrtimer_base
*base
= timer
->base
;
223 spin_lock_irqsave(&base
->lock
, *flags
);
228 #define switch_hrtimer_base(t, b) (b)
230 #endif /* !CONFIG_SMP */
233 * Functions for the union type storage format of ktime_t which are
234 * too large for inlining:
236 #if BITS_PER_LONG < 64
237 # ifndef CONFIG_KTIME_SCALAR
239 * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
241 * @nsec: the scalar nsec value to add
243 * Returns the sum of kt and nsec in ktime_t format
245 ktime_t
ktime_add_ns(const ktime_t kt
, u64 nsec
)
249 if (likely(nsec
< NSEC_PER_SEC
)) {
252 unsigned long rem
= do_div(nsec
, NSEC_PER_SEC
);
254 tmp
= ktime_set((long)nsec
, rem
);
257 return ktime_add(kt
, tmp
);
260 #else /* CONFIG_KTIME_SCALAR */
262 # endif /* !CONFIG_KTIME_SCALAR */
265 * Divide a ktime value by a nanosecond value
267 static unsigned long ktime_divns(const ktime_t kt
, s64 div
)
272 dclc
= dns
= ktime_to_ns(kt
);
274 /* Make sure the divisor is less than 2^32: */
280 do_div(dclc
, (unsigned long) div
);
282 return (unsigned long) dclc
;
285 #else /* BITS_PER_LONG < 64 */
286 # define ktime_divns(kt, div) (unsigned long)((kt).tv64 / (div))
287 #endif /* BITS_PER_LONG >= 64 */
290 * Counterpart to lock_timer_base above:
293 void unlock_hrtimer_base(const struct hrtimer
*timer
, unsigned long *flags
)
295 spin_unlock_irqrestore(&timer
->base
->lock
, *flags
);
299 * hrtimer_forward - forward the timer expiry
300 * @timer: hrtimer to forward
301 * @now: forward past this time
302 * @interval: the interval to forward
304 * Forward the timer expiry so it will expire in the future.
305 * Returns the number of overruns.
308 hrtimer_forward(struct hrtimer
*timer
, ktime_t now
, ktime_t interval
)
310 unsigned long orun
= 1;
313 delta
= ktime_sub(now
, timer
->expires
);
318 if (interval
.tv64
< timer
->base
->resolution
.tv64
)
319 interval
.tv64
= timer
->base
->resolution
.tv64
;
321 if (unlikely(delta
.tv64
>= interval
.tv64
)) {
322 s64 incr
= ktime_to_ns(interval
);
324 orun
= ktime_divns(delta
, incr
);
325 timer
->expires
= ktime_add_ns(timer
->expires
, incr
* orun
);
326 if (timer
->expires
.tv64
> now
.tv64
)
329 * This (and the ktime_add() below) is the
330 * correction for exact:
334 timer
->expires
= ktime_add(timer
->expires
, interval
);
340 * enqueue_hrtimer - internal function to (re)start a timer
342 * The timer is inserted in expiry order. Insertion into the
343 * red black tree is O(log(n)). Must hold the base lock.
345 static void enqueue_hrtimer(struct hrtimer
*timer
, struct hrtimer_base
*base
)
347 struct rb_node
**link
= &base
->active
.rb_node
;
348 struct rb_node
*parent
= NULL
;
349 struct hrtimer
*entry
;
352 * Find the right place in the rbtree:
356 entry
= rb_entry(parent
, struct hrtimer
, node
);
358 * We dont care about collisions. Nodes with
359 * the same expiry time stay together.
361 if (timer
->expires
.tv64
< entry
->expires
.tv64
)
362 link
= &(*link
)->rb_left
;
364 link
= &(*link
)->rb_right
;
368 * Insert the timer to the rbtree and check whether it
369 * replaces the first pending timer
371 rb_link_node(&timer
->node
, parent
, link
);
372 rb_insert_color(&timer
->node
, &base
->active
);
374 if (!base
->first
|| timer
->expires
.tv64
<
375 rb_entry(base
->first
, struct hrtimer
, node
)->expires
.tv64
)
376 base
->first
= &timer
->node
;
380 * __remove_hrtimer - internal function to remove a timer
382 * Caller must hold the base lock.
384 static void __remove_hrtimer(struct hrtimer
*timer
, struct hrtimer_base
*base
)
387 * Remove the timer from the rbtree and replace the
388 * first entry pointer if necessary.
390 if (base
->first
== &timer
->node
)
391 base
->first
= rb_next(&timer
->node
);
392 rb_erase(&timer
->node
, &base
->active
);
393 rb_set_parent(&timer
->node
, &timer
->node
);
397 * remove hrtimer, called with base lock held
400 remove_hrtimer(struct hrtimer
*timer
, struct hrtimer_base
*base
)
402 if (hrtimer_active(timer
)) {
403 __remove_hrtimer(timer
, base
);
410 * hrtimer_start - (re)start an relative timer on the current CPU
411 * @timer: the timer to be added
413 * @mode: expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)
417 * 1 when the timer was active
420 hrtimer_start(struct hrtimer
*timer
, ktime_t tim
, const enum hrtimer_mode mode
)
422 struct hrtimer_base
*base
, *new_base
;
426 base
= lock_hrtimer_base(timer
, &flags
);
428 /* Remove an active timer from the queue: */
429 ret
= remove_hrtimer(timer
, base
);
431 /* Switch the timer base, if necessary: */
432 new_base
= switch_hrtimer_base(timer
, base
);
434 if (mode
== HRTIMER_REL
) {
435 tim
= ktime_add(tim
, new_base
->get_time());
437 * CONFIG_TIME_LOW_RES is a temporary way for architectures
438 * to signal that they simply return xtime in
439 * do_gettimeoffset(). In this case we want to round up by
440 * resolution when starting a relative timer, to avoid short
441 * timeouts. This will go away with the GTOD framework.
443 #ifdef CONFIG_TIME_LOW_RES
444 tim
= ktime_add(tim
, base
->resolution
);
447 timer
->expires
= tim
;
449 enqueue_hrtimer(timer
, new_base
);
451 unlock_hrtimer_base(timer
, &flags
);
455 EXPORT_SYMBOL_GPL(hrtimer_start
);
458 * hrtimer_try_to_cancel - try to deactivate a timer
459 * @timer: hrtimer to stop
462 * 0 when the timer was not active
463 * 1 when the timer was active
464 * -1 when the timer is currently excuting the callback function and
467 int hrtimer_try_to_cancel(struct hrtimer
*timer
)
469 struct hrtimer_base
*base
;
473 base
= lock_hrtimer_base(timer
, &flags
);
475 if (base
->curr_timer
!= timer
)
476 ret
= remove_hrtimer(timer
, base
);
478 unlock_hrtimer_base(timer
, &flags
);
483 EXPORT_SYMBOL_GPL(hrtimer_try_to_cancel
);
486 * hrtimer_cancel - cancel a timer and wait for the handler to finish.
487 * @timer: the timer to be cancelled
490 * 0 when the timer was not active
491 * 1 when the timer was active
493 int hrtimer_cancel(struct hrtimer
*timer
)
496 int ret
= hrtimer_try_to_cancel(timer
);
503 EXPORT_SYMBOL_GPL(hrtimer_cancel
);
506 * hrtimer_get_remaining - get remaining time for the timer
507 * @timer: the timer to read
509 ktime_t
hrtimer_get_remaining(const struct hrtimer
*timer
)
511 struct hrtimer_base
*base
;
515 base
= lock_hrtimer_base(timer
, &flags
);
516 rem
= ktime_sub(timer
->expires
, timer
->base
->get_time());
517 unlock_hrtimer_base(timer
, &flags
);
521 EXPORT_SYMBOL_GPL(hrtimer_get_remaining
);
523 #ifdef CONFIG_NO_IDLE_HZ
525 * hrtimer_get_next_event - get the time until next expiry event
527 * Returns the delta to the next expiry event or KTIME_MAX if no timer
530 ktime_t
hrtimer_get_next_event(void)
532 struct hrtimer_base
*base
= __get_cpu_var(hrtimer_bases
);
533 ktime_t delta
, mindelta
= { .tv64
= KTIME_MAX
};
537 for (i
= 0; i
< MAX_HRTIMER_BASES
; i
++, base
++) {
538 struct hrtimer
*timer
;
540 spin_lock_irqsave(&base
->lock
, flags
);
542 spin_unlock_irqrestore(&base
->lock
, flags
);
545 timer
= rb_entry(base
->first
, struct hrtimer
, node
);
546 delta
.tv64
= timer
->expires
.tv64
;
547 spin_unlock_irqrestore(&base
->lock
, flags
);
548 delta
= ktime_sub(delta
, base
->get_time());
549 if (delta
.tv64
< mindelta
.tv64
)
550 mindelta
.tv64
= delta
.tv64
;
552 if (mindelta
.tv64
< 0)
559 * hrtimer_init - initialize a timer to the given clock
560 * @timer: the timer to be initialized
561 * @clock_id: the clock to be used
562 * @mode: timer mode abs/rel
564 void hrtimer_init(struct hrtimer
*timer
, clockid_t clock_id
,
565 enum hrtimer_mode mode
)
567 struct hrtimer_base
*bases
;
569 memset(timer
, 0, sizeof(struct hrtimer
));
571 bases
= __raw_get_cpu_var(hrtimer_bases
);
573 if (clock_id
== CLOCK_REALTIME
&& mode
!= HRTIMER_ABS
)
574 clock_id
= CLOCK_MONOTONIC
;
576 timer
->base
= &bases
[clock_id
];
577 rb_set_parent(&timer
->node
, &timer
->node
);
579 EXPORT_SYMBOL_GPL(hrtimer_init
);
582 * hrtimer_get_res - get the timer resolution for a clock
583 * @which_clock: which clock to query
584 * @tp: pointer to timespec variable to store the resolution
586 * Store the resolution of the clock selected by which_clock in the
587 * variable pointed to by tp.
589 int hrtimer_get_res(const clockid_t which_clock
, struct timespec
*tp
)
591 struct hrtimer_base
*bases
;
593 bases
= __raw_get_cpu_var(hrtimer_bases
);
594 *tp
= ktime_to_timespec(bases
[which_clock
].resolution
);
598 EXPORT_SYMBOL_GPL(hrtimer_get_res
);
601 * Expire the per base hrtimer-queue:
603 static inline void run_hrtimer_queue(struct hrtimer_base
*base
)
605 struct rb_node
*node
;
610 if (base
->get_softirq_time
)
611 base
->softirq_time
= base
->get_softirq_time();
613 spin_lock_irq(&base
->lock
);
615 while ((node
= base
->first
)) {
616 struct hrtimer
*timer
;
617 int (*fn
)(struct hrtimer
*);
620 timer
= rb_entry(node
, struct hrtimer
, node
);
621 if (base
->softirq_time
.tv64
<= timer
->expires
.tv64
)
624 fn
= timer
->function
;
625 set_curr_timer(base
, timer
);
626 __remove_hrtimer(timer
, base
);
627 spin_unlock_irq(&base
->lock
);
631 spin_lock_irq(&base
->lock
);
633 if (restart
!= HRTIMER_NORESTART
) {
634 BUG_ON(hrtimer_active(timer
));
635 enqueue_hrtimer(timer
, base
);
638 set_curr_timer(base
, NULL
);
639 spin_unlock_irq(&base
->lock
);
643 * Called from timer softirq every jiffy, expire hrtimers:
645 void hrtimer_run_queues(void)
647 struct hrtimer_base
*base
= __get_cpu_var(hrtimer_bases
);
650 hrtimer_get_softirq_time(base
);
652 for (i
= 0; i
< MAX_HRTIMER_BASES
; i
++)
653 run_hrtimer_queue(&base
[i
]);
657 * Sleep related functions:
659 static int hrtimer_wakeup(struct hrtimer
*timer
)
661 struct hrtimer_sleeper
*t
=
662 container_of(timer
, struct hrtimer_sleeper
, timer
);
663 struct task_struct
*task
= t
->task
;
667 wake_up_process(task
);
669 return HRTIMER_NORESTART
;
672 void hrtimer_init_sleeper(struct hrtimer_sleeper
*sl
, struct task_struct
*task
)
674 sl
->timer
.function
= hrtimer_wakeup
;
678 static int __sched
do_nanosleep(struct hrtimer_sleeper
*t
, enum hrtimer_mode mode
)
680 hrtimer_init_sleeper(t
, current
);
683 set_current_state(TASK_INTERRUPTIBLE
);
684 hrtimer_start(&t
->timer
, t
->timer
.expires
, mode
);
688 hrtimer_cancel(&t
->timer
);
691 } while (t
->task
&& !signal_pending(current
));
693 return t
->task
== NULL
;
696 static long __sched
nanosleep_restart(struct restart_block
*restart
)
698 struct hrtimer_sleeper t
;
699 struct timespec __user
*rmtp
;
703 restart
->fn
= do_no_restart_syscall
;
705 hrtimer_init(&t
.timer
, restart
->arg3
, HRTIMER_ABS
);
706 t
.timer
.expires
.tv64
= ((u64
)restart
->arg1
<< 32) | (u64
) restart
->arg0
;
708 if (do_nanosleep(&t
, HRTIMER_ABS
))
711 rmtp
= (struct timespec __user
*) restart
->arg2
;
713 time
= ktime_sub(t
.timer
.expires
, t
.timer
.base
->get_time());
716 tu
= ktime_to_timespec(time
);
717 if (copy_to_user(rmtp
, &tu
, sizeof(tu
)))
721 restart
->fn
= nanosleep_restart
;
723 /* The other values in restart are already filled in */
724 return -ERESTART_RESTARTBLOCK
;
727 long hrtimer_nanosleep(struct timespec
*rqtp
, struct timespec __user
*rmtp
,
728 const enum hrtimer_mode mode
, const clockid_t clockid
)
730 struct restart_block
*restart
;
731 struct hrtimer_sleeper t
;
735 hrtimer_init(&t
.timer
, clockid
, mode
);
736 t
.timer
.expires
= timespec_to_ktime(*rqtp
);
737 if (do_nanosleep(&t
, mode
))
740 /* Absolute timers do not update the rmtp value and restart: */
741 if (mode
== HRTIMER_ABS
)
742 return -ERESTARTNOHAND
;
745 rem
= ktime_sub(t
.timer
.expires
, t
.timer
.base
->get_time());
748 tu
= ktime_to_timespec(rem
);
749 if (copy_to_user(rmtp
, &tu
, sizeof(tu
)))
753 restart
= ¤t_thread_info()->restart_block
;
754 restart
->fn
= nanosleep_restart
;
755 restart
->arg0
= t
.timer
.expires
.tv64
& 0xFFFFFFFF;
756 restart
->arg1
= t
.timer
.expires
.tv64
>> 32;
757 restart
->arg2
= (unsigned long) rmtp
;
758 restart
->arg3
= (unsigned long) t
.timer
.base
->index
;
760 return -ERESTART_RESTARTBLOCK
;
764 sys_nanosleep(struct timespec __user
*rqtp
, struct timespec __user
*rmtp
)
768 if (copy_from_user(&tu
, rqtp
, sizeof(tu
)))
771 if (!timespec_valid(&tu
))
774 return hrtimer_nanosleep(&tu
, rmtp
, HRTIMER_REL
, CLOCK_MONOTONIC
);
778 * Functions related to boot-time initialization:
780 static void __devinit
init_hrtimers_cpu(int cpu
)
782 struct hrtimer_base
*base
= per_cpu(hrtimer_bases
, cpu
);
785 for (i
= 0; i
< MAX_HRTIMER_BASES
; i
++, base
++) {
786 spin_lock_init(&base
->lock
);
787 lockdep_set_class(&base
->lock
, &base
->lock_key
);
791 #ifdef CONFIG_HOTPLUG_CPU
793 static void migrate_hrtimer_list(struct hrtimer_base
*old_base
,
794 struct hrtimer_base
*new_base
)
796 struct hrtimer
*timer
;
797 struct rb_node
*node
;
799 while ((node
= rb_first(&old_base
->active
))) {
800 timer
= rb_entry(node
, struct hrtimer
, node
);
801 __remove_hrtimer(timer
, old_base
);
802 timer
->base
= new_base
;
803 enqueue_hrtimer(timer
, new_base
);
807 static void migrate_hrtimers(int cpu
)
809 struct hrtimer_base
*old_base
, *new_base
;
812 BUG_ON(cpu_online(cpu
));
813 old_base
= per_cpu(hrtimer_bases
, cpu
);
814 new_base
= get_cpu_var(hrtimer_bases
);
818 for (i
= 0; i
< MAX_HRTIMER_BASES
; i
++) {
820 spin_lock(&new_base
->lock
);
821 spin_lock(&old_base
->lock
);
823 BUG_ON(old_base
->curr_timer
);
825 migrate_hrtimer_list(old_base
, new_base
);
827 spin_unlock(&old_base
->lock
);
828 spin_unlock(&new_base
->lock
);
834 put_cpu_var(hrtimer_bases
);
836 #endif /* CONFIG_HOTPLUG_CPU */
838 static int __devinit
hrtimer_cpu_notify(struct notifier_block
*self
,
839 unsigned long action
, void *hcpu
)
841 long cpu
= (long)hcpu
;
846 init_hrtimers_cpu(cpu
);
849 #ifdef CONFIG_HOTPLUG_CPU
851 migrate_hrtimers(cpu
);
862 static struct notifier_block __devinitdata hrtimers_nb
= {
863 .notifier_call
= hrtimer_cpu_notify
,
866 void __init
hrtimers_init(void)
868 hrtimer_cpu_notify(&hrtimers_nb
, (unsigned long)CPU_UP_PREPARE
,
869 (void *)(long)smp_processor_id());
870 register_cpu_notifier(&hrtimers_nb
);