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 * For licencing details see kernel-base/COPYING
27 #include <linux/cpu.h>
28 #include <linux/module.h>
29 #include <linux/percpu.h>
30 #include <linux/hrtimer.h>
31 #include <linux/notifier.h>
32 #include <linux/syscalls.h>
33 #include <linux/interrupt.h>
35 #include <asm/uaccess.h>
38 * ktime_get - get the monotonic time in ktime_t format
40 * returns the time in ktime_t format
42 static ktime_t
ktime_get(void)
48 return timespec_to_ktime(now
);
52 * ktime_get_real - get the real (wall-) time in ktime_t format
54 * returns the time in ktime_t format
56 static ktime_t
ktime_get_real(void)
62 return timespec_to_ktime(now
);
65 EXPORT_SYMBOL_GPL(ktime_get_real
);
71 #define MAX_HRTIMER_BASES 2
73 static DEFINE_PER_CPU(struct hrtimer_base
, hrtimer_bases
[MAX_HRTIMER_BASES
]) =
76 .index
= CLOCK_REALTIME
,
77 .get_time
= &ktime_get_real
,
78 .resolution
= KTIME_REALTIME_RES
,
81 .index
= CLOCK_MONOTONIC
,
82 .get_time
= &ktime_get
,
83 .resolution
= KTIME_MONOTONIC_RES
,
88 * ktime_get_ts - get the monotonic clock in timespec format
90 * @ts: pointer to timespec variable
92 * The function calculates the monotonic clock from the realtime
93 * clock and the wall_to_monotonic offset and stores the result
94 * in normalized timespec format in the variable pointed to by ts.
96 void ktime_get_ts(struct timespec
*ts
)
98 struct timespec tomono
;
102 seq
= read_seqbegin(&xtime_lock
);
104 tomono
= wall_to_monotonic
;
106 } while (read_seqretry(&xtime_lock
, seq
));
108 set_normalized_timespec(ts
, ts
->tv_sec
+ tomono
.tv_sec
,
109 ts
->tv_nsec
+ tomono
.tv_nsec
);
111 EXPORT_SYMBOL_GPL(ktime_get_ts
);
114 * Functions and macros which are different for UP/SMP systems are kept in a
119 #define set_curr_timer(b, t) do { (b)->curr_timer = (t); } while (0)
122 * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
123 * means that all timers which are tied to this base via timer->base are
124 * locked, and the base itself is locked too.
126 * So __run_timers/migrate_timers can safely modify all timers which could
127 * be found on the lists/queues.
129 * When the timer's base is locked, and the timer removed from list, it is
130 * possible to set timer->base = NULL and drop the lock: the timer remains
133 static struct hrtimer_base
*lock_hrtimer_base(const struct hrtimer
*timer
,
134 unsigned long *flags
)
136 struct hrtimer_base
*base
;
140 if (likely(base
!= NULL
)) {
141 spin_lock_irqsave(&base
->lock
, *flags
);
142 if (likely(base
== timer
->base
))
144 /* The timer has migrated to another CPU: */
145 spin_unlock_irqrestore(&base
->lock
, *flags
);
152 * Switch the timer base to the current CPU when possible.
154 static inline struct hrtimer_base
*
155 switch_hrtimer_base(struct hrtimer
*timer
, struct hrtimer_base
*base
)
157 struct hrtimer_base
*new_base
;
159 new_base
= &__get_cpu_var(hrtimer_bases
[base
->index
]);
161 if (base
!= new_base
) {
163 * We are trying to schedule the timer on the local CPU.
164 * However we can't change timer's base while it is running,
165 * so we keep it on the same CPU. No hassle vs. reprogramming
166 * the event source in the high resolution case. The softirq
167 * code will take care of this when the timer function has
168 * completed. There is no conflict as we hold the lock until
169 * the timer is enqueued.
171 if (unlikely(base
->curr_timer
== timer
))
174 /* See the comment in lock_timer_base() */
176 spin_unlock(&base
->lock
);
177 spin_lock(&new_base
->lock
);
178 timer
->base
= new_base
;
183 #else /* CONFIG_SMP */
185 #define set_curr_timer(b, t) do { } while (0)
187 static inline struct hrtimer_base
*
188 lock_hrtimer_base(const struct hrtimer
*timer
, unsigned long *flags
)
190 struct hrtimer_base
*base
= timer
->base
;
192 spin_lock_irqsave(&base
->lock
, *flags
);
197 #define switch_hrtimer_base(t, b) (b)
199 #endif /* !CONFIG_SMP */
202 * Functions for the union type storage format of ktime_t which are
203 * too large for inlining:
205 #if BITS_PER_LONG < 64
206 # ifndef CONFIG_KTIME_SCALAR
208 * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
211 * @nsec: the scalar nsec value to add
213 * Returns the sum of kt and nsec in ktime_t format
215 ktime_t
ktime_add_ns(const ktime_t kt
, u64 nsec
)
219 if (likely(nsec
< NSEC_PER_SEC
)) {
222 unsigned long rem
= do_div(nsec
, NSEC_PER_SEC
);
224 tmp
= ktime_set((long)nsec
, rem
);
227 return ktime_add(kt
, tmp
);
230 #else /* CONFIG_KTIME_SCALAR */
232 # endif /* !CONFIG_KTIME_SCALAR */
235 * Divide a ktime value by a nanosecond value
237 static unsigned long ktime_divns(const ktime_t kt
, nsec_t div
)
242 dclc
= dns
= ktime_to_ns(kt
);
244 /* Make sure the divisor is less than 2^32: */
250 do_div(dclc
, (unsigned long) div
);
252 return (unsigned long) dclc
;
255 #else /* BITS_PER_LONG < 64 */
256 # define ktime_divns(kt, div) (unsigned long)((kt).tv64 / (div))
257 #endif /* BITS_PER_LONG >= 64 */
260 * Counterpart to lock_timer_base above:
263 void unlock_hrtimer_base(const struct hrtimer
*timer
, unsigned long *flags
)
265 spin_unlock_irqrestore(&timer
->base
->lock
, *flags
);
269 * hrtimer_forward - forward the timer expiry
271 * @timer: hrtimer to forward
272 * @interval: the interval to forward
274 * Forward the timer expiry so it will expire in the future.
275 * The number of overruns is added to the overrun field.
278 hrtimer_forward(struct hrtimer
*timer
, const ktime_t interval
)
280 unsigned long orun
= 1;
283 now
= timer
->base
->get_time();
285 delta
= ktime_sub(now
, timer
->expires
);
290 if (unlikely(delta
.tv64
>= interval
.tv64
)) {
291 nsec_t incr
= ktime_to_ns(interval
);
293 orun
= ktime_divns(delta
, incr
);
294 timer
->expires
= ktime_add_ns(timer
->expires
, incr
* orun
);
295 if (timer
->expires
.tv64
> now
.tv64
)
298 * This (and the ktime_add() below) is the
299 * correction for exact:
303 timer
->expires
= ktime_add(timer
->expires
, interval
);
309 * enqueue_hrtimer - internal function to (re)start a timer
311 * The timer is inserted in expiry order. Insertion into the
312 * red black tree is O(log(n)). Must hold the base lock.
314 static void enqueue_hrtimer(struct hrtimer
*timer
, struct hrtimer_base
*base
)
316 struct rb_node
**link
= &base
->active
.rb_node
;
317 struct list_head
*prev
= &base
->pending
;
318 struct rb_node
*parent
= NULL
;
319 struct hrtimer
*entry
;
322 * Find the right place in the rbtree:
326 entry
= rb_entry(parent
, struct hrtimer
, node
);
328 * We dont care about collisions. Nodes with
329 * the same expiry time stay together.
331 if (timer
->expires
.tv64
< entry
->expires
.tv64
)
332 link
= &(*link
)->rb_left
;
334 link
= &(*link
)->rb_right
;
340 * Insert the timer to the rbtree and to the sorted list:
342 rb_link_node(&timer
->node
, parent
, link
);
343 rb_insert_color(&timer
->node
, &base
->active
);
344 list_add(&timer
->list
, prev
);
346 timer
->state
= HRTIMER_PENDING
;
351 * __remove_hrtimer - internal function to remove a timer
353 * Caller must hold the base lock.
355 static void __remove_hrtimer(struct hrtimer
*timer
, struct hrtimer_base
*base
)
358 * Remove the timer from the sorted list and from the rbtree:
360 list_del(&timer
->list
);
361 rb_erase(&timer
->node
, &base
->active
);
365 * remove hrtimer, called with base lock held
368 remove_hrtimer(struct hrtimer
*timer
, struct hrtimer_base
*base
)
370 if (hrtimer_active(timer
)) {
371 __remove_hrtimer(timer
, base
);
372 timer
->state
= HRTIMER_INACTIVE
;
379 * hrtimer_start - (re)start an relative timer on the current CPU
381 * @timer: the timer to be added
383 * @mode: expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)
387 * 1 when the timer was active
390 hrtimer_start(struct hrtimer
*timer
, ktime_t tim
, const enum hrtimer_mode mode
)
392 struct hrtimer_base
*base
, *new_base
;
396 base
= lock_hrtimer_base(timer
, &flags
);
398 /* Remove an active timer from the queue: */
399 ret
= remove_hrtimer(timer
, base
);
401 /* Switch the timer base, if necessary: */
402 new_base
= switch_hrtimer_base(timer
, base
);
404 if (mode
== HRTIMER_REL
)
405 tim
= ktime_add(tim
, new_base
->get_time());
406 timer
->expires
= tim
;
408 enqueue_hrtimer(timer
, new_base
);
410 unlock_hrtimer_base(timer
, &flags
);
416 * hrtimer_try_to_cancel - try to deactivate a timer
418 * @timer: hrtimer to stop
421 * 0 when the timer was not active
422 * 1 when the timer was active
423 * -1 when the timer is currently excuting the callback function and
426 int hrtimer_try_to_cancel(struct hrtimer
*timer
)
428 struct hrtimer_base
*base
;
432 base
= lock_hrtimer_base(timer
, &flags
);
434 if (base
->curr_timer
!= timer
)
435 ret
= remove_hrtimer(timer
, base
);
437 unlock_hrtimer_base(timer
, &flags
);
444 * hrtimer_cancel - cancel a timer and wait for the handler to finish.
446 * @timer: the timer to be cancelled
449 * 0 when the timer was not active
450 * 1 when the timer was active
452 int hrtimer_cancel(struct hrtimer
*timer
)
455 int ret
= hrtimer_try_to_cancel(timer
);
463 * hrtimer_get_remaining - get remaining time for the timer
465 * @timer: the timer to read
467 ktime_t
hrtimer_get_remaining(const struct hrtimer
*timer
)
469 struct hrtimer_base
*base
;
473 base
= lock_hrtimer_base(timer
, &flags
);
474 rem
= ktime_sub(timer
->expires
, timer
->base
->get_time());
475 unlock_hrtimer_base(timer
, &flags
);
481 * hrtimer_rebase - rebase an initialized hrtimer to a different base
483 * @timer: the timer to be rebased
484 * @clock_id: the clock to be used
486 void hrtimer_rebase(struct hrtimer
*timer
, const clockid_t clock_id
)
488 struct hrtimer_base
*bases
;
490 bases
= per_cpu(hrtimer_bases
, raw_smp_processor_id());
491 timer
->base
= &bases
[clock_id
];
495 * hrtimer_init - initialize a timer to the given clock
497 * @timer: the timer to be initialized
498 * @clock_id: the clock to be used
500 void hrtimer_init(struct hrtimer
*timer
, const clockid_t clock_id
)
502 memset(timer
, 0, sizeof(struct hrtimer
));
503 hrtimer_rebase(timer
, clock_id
);
507 * hrtimer_get_res - get the timer resolution for a clock
509 * @which_clock: which clock to query
510 * @tp: pointer to timespec variable to store the resolution
512 * Store the resolution of the clock selected by which_clock in the
513 * variable pointed to by tp.
515 int hrtimer_get_res(const clockid_t which_clock
, struct timespec
*tp
)
517 struct hrtimer_base
*bases
;
520 bases
= per_cpu(hrtimer_bases
, raw_smp_processor_id());
521 tp
->tv_nsec
= bases
[which_clock
].resolution
;
527 * Expire the per base hrtimer-queue:
529 static inline void run_hrtimer_queue(struct hrtimer_base
*base
)
531 ktime_t now
= base
->get_time();
533 spin_lock_irq(&base
->lock
);
535 while (!list_empty(&base
->pending
)) {
536 struct hrtimer
*timer
;
541 timer
= list_entry(base
->pending
.next
, struct hrtimer
, list
);
542 if (now
.tv64
<= timer
->expires
.tv64
)
545 fn
= timer
->function
;
547 set_curr_timer(base
, timer
);
548 __remove_hrtimer(timer
, base
);
549 spin_unlock_irq(&base
->lock
);
552 * fn == NULL is special case for the simplest timer
553 * variant - wake up process and do not restart:
556 wake_up_process(data
);
557 restart
= HRTIMER_NORESTART
;
561 spin_lock_irq(&base
->lock
);
563 if (restart
== HRTIMER_RESTART
)
564 enqueue_hrtimer(timer
, base
);
566 timer
->state
= HRTIMER_EXPIRED
;
568 set_curr_timer(base
, NULL
);
569 spin_unlock_irq(&base
->lock
);
573 * Called from timer softirq every jiffy, expire hrtimers:
575 void hrtimer_run_queues(void)
577 struct hrtimer_base
*base
= __get_cpu_var(hrtimer_bases
);
580 for (i
= 0; i
< MAX_HRTIMER_BASES
; i
++)
581 run_hrtimer_queue(&base
[i
]);
585 * Sleep related functions:
589 * schedule_hrtimer - sleep until timeout
591 * @timer: hrtimer variable initialized with the correct clock base
592 * @mode: timeout value is abs/rel
594 * Make the current task sleep until @timeout is
597 * You can set the task state as follows -
599 * %TASK_UNINTERRUPTIBLE - at least @timeout is guaranteed to
600 * pass before the routine returns. The routine will return 0
602 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
603 * delivered to the current task. In this case the remaining time
606 * The current task state is guaranteed to be TASK_RUNNING when this
609 static ktime_t __sched
610 schedule_hrtimer(struct hrtimer
*timer
, const enum hrtimer_mode mode
)
612 /* fn stays NULL, meaning single-shot wakeup: */
613 timer
->data
= current
;
615 hrtimer_start(timer
, timer
->expires
, mode
);
618 hrtimer_cancel(timer
);
620 /* Return the remaining time: */
621 if (timer
->state
!= HRTIMER_EXPIRED
)
622 return ktime_sub(timer
->expires
, timer
->base
->get_time());
624 return (ktime_t
) {.tv64
= 0 };
627 static inline ktime_t __sched
628 schedule_hrtimer_interruptible(struct hrtimer
*timer
,
629 const enum hrtimer_mode mode
)
631 set_current_state(TASK_INTERRUPTIBLE
);
633 return schedule_hrtimer(timer
, mode
);
637 nanosleep_restart(struct restart_block
*restart
, clockid_t clockid
)
639 struct timespec __user
*rmtp
, tu
;
640 void *rfn_save
= restart
->fn
;
641 struct hrtimer timer
;
644 restart
->fn
= do_no_restart_syscall
;
646 hrtimer_init(&timer
, clockid
);
648 timer
.expires
.tv64
= ((u64
)restart
->arg1
<< 32) | (u64
) restart
->arg0
;
650 rem
= schedule_hrtimer_interruptible(&timer
, HRTIMER_ABS
);
655 rmtp
= (struct timespec __user
*) restart
->arg2
;
656 tu
= ktime_to_timespec(rem
);
657 if (rmtp
&& copy_to_user(rmtp
, &tu
, sizeof(tu
)))
660 restart
->fn
= rfn_save
;
662 /* The other values in restart are already filled in */
663 return -ERESTART_RESTARTBLOCK
;
666 static long __sched
nanosleep_restart_mono(struct restart_block
*restart
)
668 return nanosleep_restart(restart
, CLOCK_MONOTONIC
);
671 static long __sched
nanosleep_restart_real(struct restart_block
*restart
)
673 return nanosleep_restart(restart
, CLOCK_REALTIME
);
676 long hrtimer_nanosleep(struct timespec
*rqtp
, struct timespec __user
*rmtp
,
677 const enum hrtimer_mode mode
, const clockid_t clockid
)
679 struct restart_block
*restart
;
680 struct hrtimer timer
;
684 hrtimer_init(&timer
, clockid
);
686 timer
.expires
= timespec_to_ktime(*rqtp
);
688 rem
= schedule_hrtimer_interruptible(&timer
, mode
);
692 /* Absolute timers do not update the rmtp value: */
693 if (mode
== HRTIMER_ABS
)
694 return -ERESTARTNOHAND
;
696 tu
= ktime_to_timespec(rem
);
698 if (rmtp
&& copy_to_user(rmtp
, &tu
, sizeof(tu
)))
701 restart
= ¤t_thread_info()->restart_block
;
702 restart
->fn
= (clockid
== CLOCK_MONOTONIC
) ?
703 nanosleep_restart_mono
: nanosleep_restart_real
;
704 restart
->arg0
= timer
.expires
.tv64
& 0xFFFFFFFF;
705 restart
->arg1
= timer
.expires
.tv64
>> 32;
706 restart
->arg2
= (unsigned long) rmtp
;
708 return -ERESTART_RESTARTBLOCK
;
712 sys_nanosleep(struct timespec __user
*rqtp
, struct timespec __user
*rmtp
)
716 if (copy_from_user(&tu
, rqtp
, sizeof(tu
)))
719 if (!timespec_valid(&tu
))
722 return hrtimer_nanosleep(&tu
, rmtp
, HRTIMER_REL
, CLOCK_MONOTONIC
);
726 * Functions related to boot-time initialization:
728 static void __devinit
init_hrtimers_cpu(int cpu
)
730 struct hrtimer_base
*base
= per_cpu(hrtimer_bases
, cpu
);
733 for (i
= 0; i
< MAX_HRTIMER_BASES
; i
++) {
734 spin_lock_init(&base
->lock
);
735 INIT_LIST_HEAD(&base
->pending
);
740 #ifdef CONFIG_HOTPLUG_CPU
742 static void migrate_hrtimer_list(struct hrtimer_base
*old_base
,
743 struct hrtimer_base
*new_base
)
745 struct hrtimer
*timer
;
746 struct rb_node
*node
;
748 while ((node
= rb_first(&old_base
->active
))) {
749 timer
= rb_entry(node
, struct hrtimer
, node
);
750 __remove_hrtimer(timer
, old_base
);
751 timer
->base
= new_base
;
752 enqueue_hrtimer(timer
, new_base
);
756 static void migrate_hrtimers(int cpu
)
758 struct hrtimer_base
*old_base
, *new_base
;
761 BUG_ON(cpu_online(cpu
));
762 old_base
= per_cpu(hrtimer_bases
, cpu
);
763 new_base
= get_cpu_var(hrtimer_bases
);
767 for (i
= 0; i
< MAX_HRTIMER_BASES
; i
++) {
769 spin_lock(&new_base
->lock
);
770 spin_lock(&old_base
->lock
);
772 BUG_ON(old_base
->curr_timer
);
774 migrate_hrtimer_list(old_base
, new_base
);
776 spin_unlock(&old_base
->lock
);
777 spin_unlock(&new_base
->lock
);
783 put_cpu_var(hrtimer_bases
);
785 #endif /* CONFIG_HOTPLUG_CPU */
787 static int __devinit
hrtimer_cpu_notify(struct notifier_block
*self
,
788 unsigned long action
, void *hcpu
)
790 long cpu
= (long)hcpu
;
795 init_hrtimers_cpu(cpu
);
798 #ifdef CONFIG_HOTPLUG_CPU
800 migrate_hrtimers(cpu
);
811 static struct notifier_block __devinitdata hrtimers_nb
= {
812 .notifier_call
= hrtimer_cpu_notify
,
815 void __init
hrtimers_init(void)
817 hrtimer_cpu_notify(&hrtimers_nb
, (unsigned long)CPU_UP_PREPARE
,
818 (void *)(long)smp_processor_id());
819 register_cpu_notifier(&hrtimers_nb
);