[MIPS] Fix non-linear memory mapping on MIPS
[linux-2.6/kvm.git] / kernel / hrtimer.c
blob01fa2ae98a8571d7e2d7a4e71c03a423792a0d67
1 /*
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:
14 * - itimers
15 * - POSIX timers
16 * - nanosleep
17 * - precise in-kernel timing
19 * Started by: Thomas Gleixner and Ingo Molnar
21 * Credits:
22 * based on kernel/timer.c
24 * Help, testing, suggestions, bugfixes, improvements were
25 * provided by:
27 * George Anzinger, Andrew Morton, Steven Rostedt, Roman Zippel
28 * et. al.
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>
43 /**
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)
50 struct timespec now;
52 ktime_get_ts(&now);
54 return timespec_to_ktime(now);
57 /**
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)
64 struct timespec now;
66 getnstimeofday(&now);
68 return timespec_to_ktime(now);
71 EXPORT_SYMBOL_GPL(ktime_get_real);
74 * The timer bases:
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,
99 /**
100 * ktime_get_ts - get the monotonic clock in timespec format
102 * @ts: pointer to timespec variable
104 * The function calculates the monotonic clock from the realtime
105 * clock and the wall_to_monotonic offset and stores the result
106 * in normalized timespec format in the variable pointed to by ts.
108 void ktime_get_ts(struct timespec *ts)
110 struct timespec tomono;
111 unsigned long seq;
113 do {
114 seq = read_seqbegin(&xtime_lock);
115 getnstimeofday(ts);
116 tomono = wall_to_monotonic;
118 } while (read_seqretry(&xtime_lock, seq));
120 set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
121 ts->tv_nsec + tomono.tv_nsec);
123 EXPORT_SYMBOL_GPL(ktime_get_ts);
126 * Get the coarse grained time at the softirq based on xtime and
127 * wall_to_monotonic.
129 static void hrtimer_get_softirq_time(struct hrtimer_base *base)
131 ktime_t xtim, tomono;
132 unsigned long seq;
134 do {
135 seq = read_seqbegin(&xtime_lock);
136 xtim = timespec_to_ktime(xtime);
137 tomono = timespec_to_ktime(wall_to_monotonic);
139 } while (read_seqretry(&xtime_lock, seq));
141 base[CLOCK_REALTIME].softirq_time = xtim;
142 base[CLOCK_MONOTONIC].softirq_time = ktime_add(xtim, tomono);
146 * Functions and macros which are different for UP/SMP systems are kept in a
147 * single place
149 #ifdef CONFIG_SMP
151 #define set_curr_timer(b, t) do { (b)->curr_timer = (t); } while (0)
154 * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
155 * means that all timers which are tied to this base via timer->base are
156 * locked, and the base itself is locked too.
158 * So __run_timers/migrate_timers can safely modify all timers which could
159 * be found on the lists/queues.
161 * When the timer's base is locked, and the timer removed from list, it is
162 * possible to set timer->base = NULL and drop the lock: the timer remains
163 * locked.
165 static struct hrtimer_base *lock_hrtimer_base(const struct hrtimer *timer,
166 unsigned long *flags)
168 struct hrtimer_base *base;
170 for (;;) {
171 base = timer->base;
172 if (likely(base != NULL)) {
173 spin_lock_irqsave(&base->lock, *flags);
174 if (likely(base == timer->base))
175 return base;
176 /* The timer has migrated to another CPU: */
177 spin_unlock_irqrestore(&base->lock, *flags);
179 cpu_relax();
184 * Switch the timer base to the current CPU when possible.
186 static inline struct hrtimer_base *
187 switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_base *base)
189 struct hrtimer_base *new_base;
191 new_base = &__get_cpu_var(hrtimer_bases[base->index]);
193 if (base != new_base) {
195 * We are trying to schedule the timer on the local CPU.
196 * However we can't change timer's base while it is running,
197 * so we keep it on the same CPU. No hassle vs. reprogramming
198 * the event source in the high resolution case. The softirq
199 * code will take care of this when the timer function has
200 * completed. There is no conflict as we hold the lock until
201 * the timer is enqueued.
203 if (unlikely(base->curr_timer == timer))
204 return base;
206 /* See the comment in lock_timer_base() */
207 timer->base = NULL;
208 spin_unlock(&base->lock);
209 spin_lock(&new_base->lock);
210 timer->base = new_base;
212 return new_base;
215 #else /* CONFIG_SMP */
217 #define set_curr_timer(b, t) do { } while (0)
219 static inline struct hrtimer_base *
220 lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
222 struct hrtimer_base *base = timer->base;
224 spin_lock_irqsave(&base->lock, *flags);
226 return base;
229 #define switch_hrtimer_base(t, b) (b)
231 #endif /* !CONFIG_SMP */
234 * Functions for the union type storage format of ktime_t which are
235 * too large for inlining:
237 #if BITS_PER_LONG < 64
238 # ifndef CONFIG_KTIME_SCALAR
240 * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
242 * @kt: addend
243 * @nsec: the scalar nsec value to add
245 * Returns the sum of kt and nsec in ktime_t format
247 ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
249 ktime_t tmp;
251 if (likely(nsec < NSEC_PER_SEC)) {
252 tmp.tv64 = nsec;
253 } else {
254 unsigned long rem = do_div(nsec, NSEC_PER_SEC);
256 tmp = ktime_set((long)nsec, rem);
259 return ktime_add(kt, tmp);
262 #else /* CONFIG_KTIME_SCALAR */
264 # endif /* !CONFIG_KTIME_SCALAR */
267 * Divide a ktime value by a nanosecond value
269 static unsigned long ktime_divns(const ktime_t kt, s64 div)
271 u64 dclc, inc, dns;
272 int sft = 0;
274 dclc = dns = ktime_to_ns(kt);
275 inc = div;
276 /* Make sure the divisor is less than 2^32: */
277 while (div >> 32) {
278 sft++;
279 div >>= 1;
281 dclc >>= sft;
282 do_div(dclc, (unsigned long) div);
284 return (unsigned long) dclc;
287 #else /* BITS_PER_LONG < 64 */
288 # define ktime_divns(kt, div) (unsigned long)((kt).tv64 / (div))
289 #endif /* BITS_PER_LONG >= 64 */
292 * Counterpart to lock_timer_base above:
294 static inline
295 void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
297 spin_unlock_irqrestore(&timer->base->lock, *flags);
301 * hrtimer_forward - forward the timer expiry
303 * @timer: hrtimer to forward
304 * @now: forward past this time
305 * @interval: the interval to forward
307 * Forward the timer expiry so it will expire in the future.
308 * Returns the number of overruns.
310 unsigned long
311 hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
313 unsigned long orun = 1;
314 ktime_t delta;
316 delta = ktime_sub(now, timer->expires);
318 if (delta.tv64 < 0)
319 return 0;
321 if (interval.tv64 < timer->base->resolution.tv64)
322 interval.tv64 = timer->base->resolution.tv64;
324 if (unlikely(delta.tv64 >= interval.tv64)) {
325 s64 incr = ktime_to_ns(interval);
327 orun = ktime_divns(delta, incr);
328 timer->expires = ktime_add_ns(timer->expires, incr * orun);
329 if (timer->expires.tv64 > now.tv64)
330 return orun;
332 * This (and the ktime_add() below) is the
333 * correction for exact:
335 orun++;
337 timer->expires = ktime_add(timer->expires, interval);
339 return orun;
343 * enqueue_hrtimer - internal function to (re)start a timer
345 * The timer is inserted in expiry order. Insertion into the
346 * red black tree is O(log(n)). Must hold the base lock.
348 static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
350 struct rb_node **link = &base->active.rb_node;
351 struct rb_node *parent = NULL;
352 struct hrtimer *entry;
355 * Find the right place in the rbtree:
357 while (*link) {
358 parent = *link;
359 entry = rb_entry(parent, struct hrtimer, node);
361 * We dont care about collisions. Nodes with
362 * the same expiry time stay together.
364 if (timer->expires.tv64 < entry->expires.tv64)
365 link = &(*link)->rb_left;
366 else
367 link = &(*link)->rb_right;
371 * Insert the timer to the rbtree and check whether it
372 * replaces the first pending timer
374 rb_link_node(&timer->node, parent, link);
375 rb_insert_color(&timer->node, &base->active);
377 if (!base->first || timer->expires.tv64 <
378 rb_entry(base->first, struct hrtimer, node)->expires.tv64)
379 base->first = &timer->node;
383 * __remove_hrtimer - internal function to remove a timer
385 * Caller must hold the base lock.
387 static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
390 * Remove the timer from the rbtree and replace the
391 * first entry pointer if necessary.
393 if (base->first == &timer->node)
394 base->first = rb_next(&timer->node);
395 rb_erase(&timer->node, &base->active);
396 timer->node.rb_parent = HRTIMER_INACTIVE;
400 * remove hrtimer, called with base lock held
402 static inline int
403 remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
405 if (hrtimer_active(timer)) {
406 __remove_hrtimer(timer, base);
407 return 1;
409 return 0;
413 * hrtimer_start - (re)start an relative timer on the current CPU
415 * @timer: the timer to be added
416 * @tim: expiry time
417 * @mode: expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)
419 * Returns:
420 * 0 on success
421 * 1 when the timer was active
424 hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
426 struct hrtimer_base *base, *new_base;
427 unsigned long flags;
428 int ret;
430 base = lock_hrtimer_base(timer, &flags);
432 /* Remove an active timer from the queue: */
433 ret = remove_hrtimer(timer, base);
435 /* Switch the timer base, if necessary: */
436 new_base = switch_hrtimer_base(timer, base);
438 if (mode == HRTIMER_REL) {
439 tim = ktime_add(tim, new_base->get_time());
441 * CONFIG_TIME_LOW_RES is a temporary way for architectures
442 * to signal that they simply return xtime in
443 * do_gettimeoffset(). In this case we want to round up by
444 * resolution when starting a relative timer, to avoid short
445 * timeouts. This will go away with the GTOD framework.
447 #ifdef CONFIG_TIME_LOW_RES
448 tim = ktime_add(tim, base->resolution);
449 #endif
451 timer->expires = tim;
453 enqueue_hrtimer(timer, new_base);
455 unlock_hrtimer_base(timer, &flags);
457 return ret;
459 EXPORT_SYMBOL_GPL(hrtimer_start);
462 * hrtimer_try_to_cancel - try to deactivate a timer
464 * @timer: hrtimer to stop
466 * Returns:
467 * 0 when the timer was not active
468 * 1 when the timer was active
469 * -1 when the timer is currently excuting the callback function and
470 * can not be stopped
472 int hrtimer_try_to_cancel(struct hrtimer *timer)
474 struct hrtimer_base *base;
475 unsigned long flags;
476 int ret = -1;
478 base = lock_hrtimer_base(timer, &flags);
480 if (base->curr_timer != timer)
481 ret = remove_hrtimer(timer, base);
483 unlock_hrtimer_base(timer, &flags);
485 return ret;
488 EXPORT_SYMBOL_GPL(hrtimer_try_to_cancel);
491 * hrtimer_cancel - cancel a timer and wait for the handler to finish.
493 * @timer: the timer to be cancelled
495 * Returns:
496 * 0 when the timer was not active
497 * 1 when the timer was active
499 int hrtimer_cancel(struct hrtimer *timer)
501 for (;;) {
502 int ret = hrtimer_try_to_cancel(timer);
504 if (ret >= 0)
505 return ret;
506 cpu_relax();
509 EXPORT_SYMBOL_GPL(hrtimer_cancel);
512 * hrtimer_get_remaining - get remaining time for the timer
514 * @timer: the timer to read
516 ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
518 struct hrtimer_base *base;
519 unsigned long flags;
520 ktime_t rem;
522 base = lock_hrtimer_base(timer, &flags);
523 rem = ktime_sub(timer->expires, timer->base->get_time());
524 unlock_hrtimer_base(timer, &flags);
526 return rem;
528 EXPORT_SYMBOL_GPL(hrtimer_get_remaining);
530 #ifdef CONFIG_NO_IDLE_HZ
532 * hrtimer_get_next_event - get the time until next expiry event
534 * Returns the delta to the next expiry event or KTIME_MAX if no timer
535 * is pending.
537 ktime_t hrtimer_get_next_event(void)
539 struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
540 ktime_t delta, mindelta = { .tv64 = KTIME_MAX };
541 unsigned long flags;
542 int i;
544 for (i = 0; i < MAX_HRTIMER_BASES; i++, base++) {
545 struct hrtimer *timer;
547 spin_lock_irqsave(&base->lock, flags);
548 if (!base->first) {
549 spin_unlock_irqrestore(&base->lock, flags);
550 continue;
552 timer = rb_entry(base->first, struct hrtimer, node);
553 delta.tv64 = timer->expires.tv64;
554 spin_unlock_irqrestore(&base->lock, flags);
555 delta = ktime_sub(delta, base->get_time());
556 if (delta.tv64 < mindelta.tv64)
557 mindelta.tv64 = delta.tv64;
559 if (mindelta.tv64 < 0)
560 mindelta.tv64 = 0;
561 return mindelta;
563 #endif
566 * hrtimer_init - initialize a timer to the given clock
568 * @timer: the timer to be initialized
569 * @clock_id: the clock to be used
570 * @mode: timer mode abs/rel
572 void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
573 enum hrtimer_mode mode)
575 struct hrtimer_base *bases;
577 memset(timer, 0, sizeof(struct hrtimer));
579 bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
581 if (clock_id == CLOCK_REALTIME && mode != HRTIMER_ABS)
582 clock_id = CLOCK_MONOTONIC;
584 timer->base = &bases[clock_id];
585 timer->node.rb_parent = HRTIMER_INACTIVE;
587 EXPORT_SYMBOL_GPL(hrtimer_init);
590 * hrtimer_get_res - get the timer resolution for a clock
592 * @which_clock: which clock to query
593 * @tp: pointer to timespec variable to store the resolution
595 * Store the resolution of the clock selected by which_clock in the
596 * variable pointed to by tp.
598 int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
600 struct hrtimer_base *bases;
602 bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
603 *tp = ktime_to_timespec(bases[which_clock].resolution);
605 return 0;
607 EXPORT_SYMBOL_GPL(hrtimer_get_res);
610 * Expire the per base hrtimer-queue:
612 static inline void run_hrtimer_queue(struct hrtimer_base *base)
614 struct rb_node *node;
616 if (!base->first)
617 return;
619 if (base->get_softirq_time)
620 base->softirq_time = base->get_softirq_time();
622 spin_lock_irq(&base->lock);
624 while ((node = base->first)) {
625 struct hrtimer *timer;
626 int (*fn)(struct hrtimer *);
627 int restart;
629 timer = rb_entry(node, struct hrtimer, node);
630 if (base->softirq_time.tv64 <= timer->expires.tv64)
631 break;
633 fn = timer->function;
634 set_curr_timer(base, timer);
635 __remove_hrtimer(timer, base);
636 spin_unlock_irq(&base->lock);
638 restart = fn(timer);
640 spin_lock_irq(&base->lock);
642 if (restart != HRTIMER_NORESTART) {
643 BUG_ON(hrtimer_active(timer));
644 enqueue_hrtimer(timer, base);
647 set_curr_timer(base, NULL);
648 spin_unlock_irq(&base->lock);
652 * Called from timer softirq every jiffy, expire hrtimers:
654 void hrtimer_run_queues(void)
656 struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
657 int i;
659 hrtimer_get_softirq_time(base);
661 for (i = 0; i < MAX_HRTIMER_BASES; i++)
662 run_hrtimer_queue(&base[i]);
666 * Sleep related functions:
668 static int hrtimer_wakeup(struct hrtimer *timer)
670 struct hrtimer_sleeper *t =
671 container_of(timer, struct hrtimer_sleeper, timer);
672 struct task_struct *task = t->task;
674 t->task = NULL;
675 if (task)
676 wake_up_process(task);
678 return HRTIMER_NORESTART;
681 void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, task_t *task)
683 sl->timer.function = hrtimer_wakeup;
684 sl->task = task;
687 static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
689 hrtimer_init_sleeper(t, current);
691 do {
692 set_current_state(TASK_INTERRUPTIBLE);
693 hrtimer_start(&t->timer, t->timer.expires, mode);
695 schedule();
697 hrtimer_cancel(&t->timer);
698 mode = HRTIMER_ABS;
700 } while (t->task && !signal_pending(current));
702 return t->task == NULL;
705 static long __sched nanosleep_restart(struct restart_block *restart)
707 struct hrtimer_sleeper t;
708 struct timespec __user *rmtp;
709 struct timespec tu;
710 ktime_t time;
712 restart->fn = do_no_restart_syscall;
714 hrtimer_init(&t.timer, restart->arg3, HRTIMER_ABS);
715 t.timer.expires.tv64 = ((u64)restart->arg1 << 32) | (u64) restart->arg0;
717 if (do_nanosleep(&t, HRTIMER_ABS))
718 return 0;
720 rmtp = (struct timespec __user *) restart->arg2;
721 if (rmtp) {
722 time = ktime_sub(t.timer.expires, t.timer.base->get_time());
723 if (time.tv64 <= 0)
724 return 0;
725 tu = ktime_to_timespec(time);
726 if (copy_to_user(rmtp, &tu, sizeof(tu)))
727 return -EFAULT;
730 restart->fn = nanosleep_restart;
732 /* The other values in restart are already filled in */
733 return -ERESTART_RESTARTBLOCK;
736 long hrtimer_nanosleep(struct timespec *rqtp, struct timespec __user *rmtp,
737 const enum hrtimer_mode mode, const clockid_t clockid)
739 struct restart_block *restart;
740 struct hrtimer_sleeper t;
741 struct timespec tu;
742 ktime_t rem;
744 hrtimer_init(&t.timer, clockid, mode);
745 t.timer.expires = timespec_to_ktime(*rqtp);
746 if (do_nanosleep(&t, mode))
747 return 0;
749 /* Absolute timers do not update the rmtp value and restart: */
750 if (mode == HRTIMER_ABS)
751 return -ERESTARTNOHAND;
753 if (rmtp) {
754 rem = ktime_sub(t.timer.expires, t.timer.base->get_time());
755 if (rem.tv64 <= 0)
756 return 0;
757 tu = ktime_to_timespec(rem);
758 if (copy_to_user(rmtp, &tu, sizeof(tu)))
759 return -EFAULT;
762 restart = &current_thread_info()->restart_block;
763 restart->fn = nanosleep_restart;
764 restart->arg0 = t.timer.expires.tv64 & 0xFFFFFFFF;
765 restart->arg1 = t.timer.expires.tv64 >> 32;
766 restart->arg2 = (unsigned long) rmtp;
767 restart->arg3 = (unsigned long) t.timer.base->index;
769 return -ERESTART_RESTARTBLOCK;
772 asmlinkage long
773 sys_nanosleep(struct timespec __user *rqtp, struct timespec __user *rmtp)
775 struct timespec tu;
777 if (copy_from_user(&tu, rqtp, sizeof(tu)))
778 return -EFAULT;
780 if (!timespec_valid(&tu))
781 return -EINVAL;
783 return hrtimer_nanosleep(&tu, rmtp, HRTIMER_REL, CLOCK_MONOTONIC);
787 * Functions related to boot-time initialization:
789 static void __devinit init_hrtimers_cpu(int cpu)
791 struct hrtimer_base *base = per_cpu(hrtimer_bases, cpu);
792 int i;
794 for (i = 0; i < MAX_HRTIMER_BASES; i++, base++)
795 spin_lock_init(&base->lock);
798 #ifdef CONFIG_HOTPLUG_CPU
800 static void migrate_hrtimer_list(struct hrtimer_base *old_base,
801 struct hrtimer_base *new_base)
803 struct hrtimer *timer;
804 struct rb_node *node;
806 while ((node = rb_first(&old_base->active))) {
807 timer = rb_entry(node, struct hrtimer, node);
808 __remove_hrtimer(timer, old_base);
809 timer->base = new_base;
810 enqueue_hrtimer(timer, new_base);
814 static void migrate_hrtimers(int cpu)
816 struct hrtimer_base *old_base, *new_base;
817 int i;
819 BUG_ON(cpu_online(cpu));
820 old_base = per_cpu(hrtimer_bases, cpu);
821 new_base = get_cpu_var(hrtimer_bases);
823 local_irq_disable();
825 for (i = 0; i < MAX_HRTIMER_BASES; i++) {
827 spin_lock(&new_base->lock);
828 spin_lock(&old_base->lock);
830 BUG_ON(old_base->curr_timer);
832 migrate_hrtimer_list(old_base, new_base);
834 spin_unlock(&old_base->lock);
835 spin_unlock(&new_base->lock);
836 old_base++;
837 new_base++;
840 local_irq_enable();
841 put_cpu_var(hrtimer_bases);
843 #endif /* CONFIG_HOTPLUG_CPU */
845 static int hrtimer_cpu_notify(struct notifier_block *self,
846 unsigned long action, void *hcpu)
848 long cpu = (long)hcpu;
850 switch (action) {
852 case CPU_UP_PREPARE:
853 init_hrtimers_cpu(cpu);
854 break;
856 #ifdef CONFIG_HOTPLUG_CPU
857 case CPU_DEAD:
858 migrate_hrtimers(cpu);
859 break;
860 #endif
862 default:
863 break;
866 return NOTIFY_OK;
869 static struct notifier_block hrtimers_nb = {
870 .notifier_call = hrtimer_cpu_notify,
873 void __init hrtimers_init(void)
875 hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE,
876 (void *)(long)smp_processor_id());
877 register_cpu_notifier(&hrtimers_nb);