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);
70 * Note: If we want to add new timer bases, we have to skip the two
71 * clock ids captured by the cpu-timers. We do this by holding empty
72 * entries rather than doing math adjustment of the clock ids.
73 * This ensures that we capture erroneous accesses to these clock ids
74 * rather than moving them into the range of valid clock id's.
77 #define MAX_HRTIMER_BASES 2
79 static DEFINE_PER_CPU(struct hrtimer_base, hrtimer_bases[MAX_HRTIMER_BASES]) =
82 .index = CLOCK_REALTIME,
83 .get_time = &ktime_get_real,
84 .resolution = KTIME_REALTIME_RES,
87 .index = CLOCK_MONOTONIC,
88 .get_time = &ktime_get,
89 .resolution = KTIME_MONOTONIC_RES,
94 * ktime_get_ts - get the monotonic clock in timespec format
96 * @ts: pointer to timespec variable
98 * The function calculates the monotonic clock from the realtime
99 * clock and the wall_to_monotonic offset and stores the result
100 * in normalized timespec format in the variable pointed to by ts.
102 void ktime_get_ts(struct timespec *ts)
104 struct timespec tomono;
108 seq = read_seqbegin(&xtime_lock);
110 tomono = wall_to_monotonic;
112 } while (read_seqretry(&xtime_lock, seq));
114 set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
115 ts->tv_nsec + tomono.tv_nsec);
117 EXPORT_SYMBOL_GPL(ktime_get_ts);
120 * Functions and macros which are different for UP/SMP systems are kept in a
125 #define set_curr_timer(b, t) do { (b)->curr_timer = (t); } while (0)
128 * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
129 * means that all timers which are tied to this base via timer->base are
130 * locked, and the base itself is locked too.
132 * So __run_timers/migrate_timers can safely modify all timers which could
133 * be found on the lists/queues.
135 * When the timer's base is locked, and the timer removed from list, it is
136 * possible to set timer->base = NULL and drop the lock: the timer remains
139 static struct hrtimer_base *lock_hrtimer_base(const struct hrtimer *timer,
140 unsigned long *flags)
142 struct hrtimer_base *base;
146 if (likely(base != NULL)) {
147 spin_lock_irqsave(&base->lock, *flags);
148 if (likely(base == timer->base))
150 /* The timer has migrated to another CPU: */
151 spin_unlock_irqrestore(&base->lock, *flags);
158 * Switch the timer base to the current CPU when possible.
160 static inline struct hrtimer_base *
161 switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_base *base)
163 struct hrtimer_base *new_base;
165 new_base = &__get_cpu_var(hrtimer_bases[base->index]);
167 if (base != new_base) {
169 * We are trying to schedule the timer on the local CPU.
170 * However we can't change timer's base while it is running,
171 * so we keep it on the same CPU. No hassle vs. reprogramming
172 * the event source in the high resolution case. The softirq
173 * code will take care of this when the timer function has
174 * completed. There is no conflict as we hold the lock until
175 * the timer is enqueued.
177 if (unlikely(base->curr_timer == timer))
180 /* See the comment in lock_timer_base() */
182 spin_unlock(&base->lock);
183 spin_lock(&new_base->lock);
184 timer->base = new_base;
189 #else /* CONFIG_SMP */
191 #define set_curr_timer(b, t) do { } while (0)
193 static inline struct hrtimer_base *
194 lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
196 struct hrtimer_base *base = timer->base;
198 spin_lock_irqsave(&base->lock, *flags);
203 #define switch_hrtimer_base(t, b) (b)
205 #endif /* !CONFIG_SMP */
208 * Functions for the union type storage format of ktime_t which are
209 * too large for inlining:
211 #if BITS_PER_LONG < 64
212 # ifndef CONFIG_KTIME_SCALAR
214 * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
217 * @nsec: the scalar nsec value to add
219 * Returns the sum of kt and nsec in ktime_t format
221 ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
225 if (likely(nsec < NSEC_PER_SEC)) {
228 unsigned long rem = do_div(nsec, NSEC_PER_SEC);
230 tmp = ktime_set((long)nsec, rem);
233 return ktime_add(kt, tmp);
236 #else /* CONFIG_KTIME_SCALAR */
238 # endif /* !CONFIG_KTIME_SCALAR */
241 * Divide a ktime value by a nanosecond value
243 static unsigned long ktime_divns(const ktime_t kt, nsec_t div)
248 dclc = dns = ktime_to_ns(kt);
250 /* Make sure the divisor is less than 2^32: */
256 do_div(dclc, (unsigned long) div);
258 return (unsigned long) dclc;
261 #else /* BITS_PER_LONG < 64 */
262 # define ktime_divns(kt, div) (unsigned long)((kt).tv64 / (div))
263 #endif /* BITS_PER_LONG >= 64 */
266 * Counterpart to lock_timer_base above:
269 void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
271 spin_unlock_irqrestore(&timer->base->lock, *flags);
275 * hrtimer_forward - forward the timer expiry
277 * @timer: hrtimer to forward
278 * @interval: the interval to forward
280 * Forward the timer expiry so it will expire in the future.
281 * Returns the number of overruns.
284 hrtimer_forward(struct hrtimer *timer, ktime_t interval)
286 unsigned long orun = 1;
289 now = timer->base->get_time();
291 delta = ktime_sub(now, timer->expires);
296 if (interval.tv64 < timer->base->resolution.tv64)
297 interval.tv64 = timer->base->resolution.tv64;
299 if (unlikely(delta.tv64 >= interval.tv64)) {
300 nsec_t incr = ktime_to_ns(interval);
302 orun = ktime_divns(delta, incr);
303 timer->expires = ktime_add_ns(timer->expires, incr * orun);
304 if (timer->expires.tv64 > now.tv64)
307 * This (and the ktime_add() below) is the
308 * correction for exact:
312 timer->expires = ktime_add(timer->expires, interval);
318 * enqueue_hrtimer - internal function to (re)start a timer
320 * The timer is inserted in expiry order. Insertion into the
321 * red black tree is O(log(n)). Must hold the base lock.
323 static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
325 struct rb_node **link = &base->active.rb_node;
326 struct rb_node *parent = NULL;
327 struct hrtimer *entry;
330 * Find the right place in the rbtree:
334 entry = rb_entry(parent, struct hrtimer, node);
336 * We dont care about collisions. Nodes with
337 * the same expiry time stay together.
339 if (timer->expires.tv64 < entry->expires.tv64)
340 link = &(*link)->rb_left;
342 link = &(*link)->rb_right;
346 * Insert the timer to the rbtree and check whether it
347 * replaces the first pending timer
349 rb_link_node(&timer->node, parent, link);
350 rb_insert_color(&timer->node, &base->active);
352 timer->state = HRTIMER_PENDING;
354 if (!base->first || timer->expires.tv64 <
355 rb_entry(base->first, struct hrtimer, node)->expires.tv64)
356 base->first = &timer->node;
360 * __remove_hrtimer - internal function to remove a timer
362 * Caller must hold the base lock.
364 static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
367 * Remove the timer from the rbtree and replace the
368 * first entry pointer if necessary.
370 if (base->first == &timer->node)
371 base->first = rb_next(&timer->node);
372 rb_erase(&timer->node, &base->active);
376 * remove hrtimer, called with base lock held
379 remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
381 if (hrtimer_active(timer)) {
382 __remove_hrtimer(timer, base);
383 timer->state = HRTIMER_INACTIVE;
390 * hrtimer_start - (re)start an relative timer on the current CPU
392 * @timer: the timer to be added
394 * @mode: expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)
398 * 1 when the timer was active
401 hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
403 struct hrtimer_base *base, *new_base;
407 base = lock_hrtimer_base(timer, &flags);
409 /* Remove an active timer from the queue: */
410 ret = remove_hrtimer(timer, base);
412 /* Switch the timer base, if necessary: */
413 new_base = switch_hrtimer_base(timer, base);
415 if (mode == HRTIMER_REL)
416 tim = ktime_add(tim, new_base->get_time());
417 timer->expires = tim;
419 enqueue_hrtimer(timer, new_base);
421 unlock_hrtimer_base(timer, &flags);
427 * hrtimer_try_to_cancel - try to deactivate a timer
429 * @timer: hrtimer to stop
432 * 0 when the timer was not active
433 * 1 when the timer was active
434 * -1 when the timer is currently excuting the callback function and
437 int hrtimer_try_to_cancel(struct hrtimer *timer)
439 struct hrtimer_base *base;
443 base = lock_hrtimer_base(timer, &flags);
445 if (base->curr_timer != timer)
446 ret = remove_hrtimer(timer, base);
448 unlock_hrtimer_base(timer, &flags);
455 * hrtimer_cancel - cancel a timer and wait for the handler to finish.
457 * @timer: the timer to be cancelled
460 * 0 when the timer was not active
461 * 1 when the timer was active
463 int hrtimer_cancel(struct hrtimer *timer)
466 int ret = hrtimer_try_to_cancel(timer);
474 * hrtimer_get_remaining - get remaining time for the timer
476 * @timer: the timer to read
478 ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
480 struct hrtimer_base *base;
484 base = lock_hrtimer_base(timer, &flags);
485 rem = ktime_sub(timer->expires, timer->base->get_time());
486 unlock_hrtimer_base(timer, &flags);
492 * hrtimer_init - initialize a timer to the given clock
494 * @timer: the timer to be initialized
495 * @clock_id: the clock to be used
496 * @mode: timer mode abs/rel
498 void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
499 enum hrtimer_mode mode)
501 struct hrtimer_base *bases;
503 memset(timer, 0, sizeof(struct hrtimer));
505 bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
507 if (clock_id == CLOCK_REALTIME && mode != HRTIMER_ABS)
508 clock_id = CLOCK_MONOTONIC;
510 timer->base = &bases[clock_id];
514 * hrtimer_get_res - get the timer resolution for a clock
516 * @which_clock: which clock to query
517 * @tp: pointer to timespec variable to store the resolution
519 * Store the resolution of the clock selected by which_clock in the
520 * variable pointed to by tp.
522 int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
524 struct hrtimer_base *bases;
526 bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
527 *tp = ktime_to_timespec(bases[which_clock].resolution);
533 * Expire the per base hrtimer-queue:
535 static inline void run_hrtimer_queue(struct hrtimer_base *base)
537 ktime_t now = base->get_time();
538 struct rb_node *node;
540 spin_lock_irq(&base->lock);
542 while ((node = base->first)) {
543 struct hrtimer *timer;
548 timer = rb_entry(node, struct hrtimer, node);
549 if (now.tv64 <= timer->expires.tv64)
552 fn = timer->function;
554 set_curr_timer(base, timer);
555 timer->state = HRTIMER_RUNNING;
556 __remove_hrtimer(timer, base);
557 spin_unlock_irq(&base->lock);
560 * fn == NULL is special case for the simplest timer
561 * variant - wake up process and do not restart:
564 wake_up_process(data);
565 restart = HRTIMER_NORESTART;
569 spin_lock_irq(&base->lock);
571 /* Another CPU has added back the timer */
572 if (timer->state != HRTIMER_RUNNING)
575 if (restart == HRTIMER_RESTART)
576 enqueue_hrtimer(timer, base);
578 timer->state = HRTIMER_EXPIRED;
580 set_curr_timer(base, NULL);
581 spin_unlock_irq(&base->lock);
585 * Called from timer softirq every jiffy, expire hrtimers:
587 void hrtimer_run_queues(void)
589 struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
592 for (i = 0; i < MAX_HRTIMER_BASES; i++)
593 run_hrtimer_queue(&base[i]);
597 * Sleep related functions:
601 * schedule_hrtimer - sleep until timeout
603 * @timer: hrtimer variable initialized with the correct clock base
604 * @mode: timeout value is abs/rel
606 * Make the current task sleep until @timeout is
609 * You can set the task state as follows -
611 * %TASK_UNINTERRUPTIBLE - at least @timeout is guaranteed to
612 * pass before the routine returns. The routine will return 0
614 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
615 * delivered to the current task. In this case the remaining time
618 * The current task state is guaranteed to be TASK_RUNNING when this
621 static ktime_t __sched
622 schedule_hrtimer(struct hrtimer *timer, const enum hrtimer_mode mode)
624 /* fn stays NULL, meaning single-shot wakeup: */
625 timer->data = current;
627 hrtimer_start(timer, timer->expires, mode);
630 hrtimer_cancel(timer);
632 /* Return the remaining time: */
633 if (timer->state != HRTIMER_EXPIRED)
634 return ktime_sub(timer->expires, timer->base->get_time());
636 return (ktime_t) {.tv64 = 0 };
639 static inline ktime_t __sched
640 schedule_hrtimer_interruptible(struct hrtimer *timer,
641 const enum hrtimer_mode mode)
643 set_current_state(TASK_INTERRUPTIBLE);
645 return schedule_hrtimer(timer, mode);
648 static long __sched nanosleep_restart(struct restart_block *restart)
650 struct timespec __user *rmtp;
652 void *rfn_save = restart->fn;
653 struct hrtimer timer;
656 restart->fn = do_no_restart_syscall;
658 hrtimer_init(&timer, (clockid_t) restart->arg3, HRTIMER_ABS);
660 timer.expires.tv64 = ((u64)restart->arg1 << 32) | (u64) restart->arg0;
662 rem = schedule_hrtimer_interruptible(&timer, HRTIMER_ABS);
667 rmtp = (struct timespec __user *) restart->arg2;
668 tu = ktime_to_timespec(rem);
669 if (rmtp && copy_to_user(rmtp, &tu, sizeof(tu)))
672 restart->fn = rfn_save;
674 /* The other values in restart are already filled in */
675 return -ERESTART_RESTARTBLOCK;
678 long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
679 const enum hrtimer_mode mode, const clockid_t clockid)
681 struct restart_block *restart;
682 struct hrtimer timer;
686 hrtimer_init(&timer, clockid, mode);
688 timer.expires = timespec_to_ktime(*rqtp);
690 rem = schedule_hrtimer_interruptible(&timer, mode);
694 /* Absolute timers do not update the rmtp value and restart: */
695 if (mode == HRTIMER_ABS)
696 return -ERESTARTNOHAND;
698 tu = ktime_to_timespec(rem);
700 if (rmtp && copy_to_user(rmtp, &tu, sizeof(tu)))
703 restart = ¤t_thread_info()->restart_block;
704 restart->fn = nanosleep_restart;
705 restart->arg0 = timer.expires.tv64 & 0xFFFFFFFF;
706 restart->arg1 = timer.expires.tv64 >> 32;
707 restart->arg2 = (unsigned long) rmtp;
708 restart->arg3 = (unsigned long) timer.base->index;
710 return -ERESTART_RESTARTBLOCK;
714 sys_nanosleep(struct timespec __user *rqtp, struct timespec __user *rmtp)
718 if (copy_from_user(&tu, rqtp, sizeof(tu)))
721 if (!timespec_valid(&tu))
724 return hrtimer_nanosleep(&tu, rmtp, HRTIMER_REL, CLOCK_MONOTONIC);
728 * Functions related to boot-time initialization:
730 static void __devinit init_hrtimers_cpu(int cpu)
732 struct hrtimer_base *base = per_cpu(hrtimer_bases, cpu);
735 for (i = 0; i < MAX_HRTIMER_BASES; i++, base++)
736 spin_lock_init(&base->lock);
739 #ifdef CONFIG_HOTPLUG_CPU
741 static void migrate_hrtimer_list(struct hrtimer_base *old_base,
742 struct hrtimer_base *new_base)
744 struct hrtimer *timer;
745 struct rb_node *node;
747 while ((node = rb_first(&old_base->active))) {
748 timer = rb_entry(node, struct hrtimer, node);
749 __remove_hrtimer(timer, old_base);
750 timer->base = new_base;
751 enqueue_hrtimer(timer, new_base);
755 static void migrate_hrtimers(int cpu)
757 struct hrtimer_base *old_base, *new_base;
760 BUG_ON(cpu_online(cpu));
761 old_base = per_cpu(hrtimer_bases, cpu);
762 new_base = get_cpu_var(hrtimer_bases);
766 for (i = 0; i < MAX_HRTIMER_BASES; i++) {
768 spin_lock(&new_base->lock);
769 spin_lock(&old_base->lock);
771 BUG_ON(old_base->curr_timer);
773 migrate_hrtimer_list(old_base, new_base);
775 spin_unlock(&old_base->lock);
776 spin_unlock(&new_base->lock);
782 put_cpu_var(hrtimer_bases);
784 #endif /* CONFIG_HOTPLUG_CPU */
786 static int __devinit hrtimer_cpu_notify(struct notifier_block *self,
787 unsigned long action, void *hcpu)
789 long cpu = (long)hcpu;
794 init_hrtimers_cpu(cpu);
797 #ifdef CONFIG_HOTPLUG_CPU
799 migrate_hrtimers(cpu);
810 static struct notifier_block __devinitdata hrtimers_nb = {
811 .notifier_call = hrtimer_cpu_notify,
814 void __init hrtimers_init(void)
816 hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE,
817 (void *)(long)smp_processor_id());
818 register_cpu_notifier(&hrtimers_nb);