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-rw-r--r--kernel/hrtimer.c679
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diff --git a/kernel/hrtimer.c b/kernel/hrtimer.c
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1/*
2 * linux/kernel/hrtimer.c
3 *
4 * Copyright(C) 2005, Thomas Gleixner <tglx@linutronix.de>
5 * Copyright(C) 2005, Red Hat, Inc., Ingo Molnar
6 *
7 * High-resolution kernel timers
8 *
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.
12 *
13 * These timers are currently used for:
14 * - itimers
15 * - POSIX timers
16 * - nanosleep
17 * - precise in-kernel timing
18 *
19 * Started by: Thomas Gleixner and Ingo Molnar
20 *
21 * Credits:
22 * based on kernel/timer.c
23 *
24 * For licencing details see kernel-base/COPYING
25 */
26
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>
34
35#include <asm/uaccess.h>
36
37/**
38 * ktime_get - get the monotonic time in ktime_t format
39 *
40 * returns the time in ktime_t format
41 */
42static ktime_t ktime_get(void)
43{
44 struct timespec now;
45
46 ktime_get_ts(&now);
47
48 return timespec_to_ktime(now);
49}
50
51/**
52 * ktime_get_real - get the real (wall-) time in ktime_t format
53 *
54 * returns the time in ktime_t format
55 */
56static ktime_t ktime_get_real(void)
57{
58 struct timespec now;
59
60 getnstimeofday(&now);
61
62 return timespec_to_ktime(now);
63}
64
65EXPORT_SYMBOL_GPL(ktime_get_real);
66
67/*
68 * The timer bases:
69 */
70
71#define MAX_HRTIMER_BASES 2
72
73static DEFINE_PER_CPU(struct hrtimer_base, hrtimer_bases[MAX_HRTIMER_BASES]) =
74{
75 {
76 .index = CLOCK_REALTIME,
77 .get_time = &ktime_get_real,
78 .resolution = KTIME_REALTIME_RES,
79 },
80 {
81 .index = CLOCK_MONOTONIC,
82 .get_time = &ktime_get,
83 .resolution = KTIME_MONOTONIC_RES,
84 },
85};
86
87/**
88 * ktime_get_ts - get the monotonic clock in timespec format
89 *
90 * @ts: pointer to timespec variable
91 *
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.
95 */
96void ktime_get_ts(struct timespec *ts)
97{
98 struct timespec tomono;
99 unsigned long seq;
100
101 do {
102 seq = read_seqbegin(&xtime_lock);
103 getnstimeofday(ts);
104 tomono = wall_to_monotonic;
105
106 } while (read_seqretry(&xtime_lock, seq));
107
108 set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
109 ts->tv_nsec + tomono.tv_nsec);
110}
111
112/*
113 * Functions and macros which are different for UP/SMP systems are kept in a
114 * single place
115 */
116#ifdef CONFIG_SMP
117
118#define set_curr_timer(b, t) do { (b)->curr_timer = (t); } while (0)
119
120/*
121 * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
122 * means that all timers which are tied to this base via timer->base are
123 * locked, and the base itself is locked too.
124 *
125 * So __run_timers/migrate_timers can safely modify all timers which could
126 * be found on the lists/queues.
127 *
128 * When the timer's base is locked, and the timer removed from list, it is
129 * possible to set timer->base = NULL and drop the lock: the timer remains
130 * locked.
131 */
132static struct hrtimer_base *lock_hrtimer_base(const struct hrtimer *timer,
133 unsigned long *flags)
134{
135 struct hrtimer_base *base;
136
137 for (;;) {
138 base = timer->base;
139 if (likely(base != NULL)) {
140 spin_lock_irqsave(&base->lock, *flags);
141 if (likely(base == timer->base))
142 return base;
143 /* The timer has migrated to another CPU: */
144 spin_unlock_irqrestore(&base->lock, *flags);
145 }
146 cpu_relax();
147 }
148}
149
150/*
151 * Switch the timer base to the current CPU when possible.
152 */
153static inline struct hrtimer_base *
154switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_base *base)
155{
156 struct hrtimer_base *new_base;
157
158 new_base = &__get_cpu_var(hrtimer_bases[base->index]);
159
160 if (base != new_base) {
161 /*
162 * We are trying to schedule the timer on the local CPU.
163 * However we can't change timer's base while it is running,
164 * so we keep it on the same CPU. No hassle vs. reprogramming
165 * the event source in the high resolution case. The softirq
166 * code will take care of this when the timer function has
167 * completed. There is no conflict as we hold the lock until
168 * the timer is enqueued.
169 */
170 if (unlikely(base->curr_timer == timer))
171 return base;
172
173 /* See the comment in lock_timer_base() */
174 timer->base = NULL;
175 spin_unlock(&base->lock);
176 spin_lock(&new_base->lock);
177 timer->base = new_base;
178 }
179 return new_base;
180}
181
182#else /* CONFIG_SMP */
183
184#define set_curr_timer(b, t) do { } while (0)
185
186static inline struct hrtimer_base *
187lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
188{
189 struct hrtimer_base *base = timer->base;
190
191 spin_lock_irqsave(&base->lock, *flags);
192
193 return base;
194}
195
196#define switch_hrtimer_base(t, b) (b)
197
198#endif /* !CONFIG_SMP */
199
200/*
201 * Functions for the union type storage format of ktime_t which are
202 * too large for inlining:
203 */
204#if BITS_PER_LONG < 64
205# ifndef CONFIG_KTIME_SCALAR
206/**
207 * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
208 *
209 * @kt: addend
210 * @nsec: the scalar nsec value to add
211 *
212 * Returns the sum of kt and nsec in ktime_t format
213 */
214ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
215{
216 ktime_t tmp;
217
218 if (likely(nsec < NSEC_PER_SEC)) {
219 tmp.tv64 = nsec;
220 } else {
221 unsigned long rem = do_div(nsec, NSEC_PER_SEC);
222
223 tmp = ktime_set((long)nsec, rem);
224 }
225
226 return ktime_add(kt, tmp);
227}
228
229#else /* CONFIG_KTIME_SCALAR */
230
231# endif /* !CONFIG_KTIME_SCALAR */
232
233/*
234 * Divide a ktime value by a nanosecond value
235 */
236static unsigned long ktime_divns(const ktime_t kt, nsec_t div)
237{
238 u64 dclc, inc, dns;
239 int sft = 0;
240
241 dclc = dns = ktime_to_ns(kt);
242 inc = div;
243 /* Make sure the divisor is less than 2^32: */
244 while (div >> 32) {
245 sft++;
246 div >>= 1;
247 }
248 dclc >>= sft;
249 do_div(dclc, (unsigned long) div);
250
251 return (unsigned long) dclc;
252}
253
254#else /* BITS_PER_LONG < 64 */
255# define ktime_divns(kt, div) (unsigned long)((kt).tv64 / (div))
256#endif /* BITS_PER_LONG >= 64 */
257
258/*
259 * Counterpart to lock_timer_base above:
260 */
261static inline
262void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
263{
264 spin_unlock_irqrestore(&timer->base->lock, *flags);
265}
266
267/**
268 * hrtimer_forward - forward the timer expiry
269 *
270 * @timer: hrtimer to forward
271 * @interval: the interval to forward
272 *
273 * Forward the timer expiry so it will expire in the future.
274 * The number of overruns is added to the overrun field.
275 */
276unsigned long
277hrtimer_forward(struct hrtimer *timer, const ktime_t interval)
278{
279 unsigned long orun = 1;
280 ktime_t delta, now;
281
282 now = timer->base->get_time();
283
284 delta = ktime_sub(now, timer->expires);
285
286 if (delta.tv64 < 0)
287 return 0;
288
289 if (unlikely(delta.tv64 >= interval.tv64)) {
290 nsec_t incr = ktime_to_ns(interval);
291
292 orun = ktime_divns(delta, incr);
293 timer->expires = ktime_add_ns(timer->expires, incr * orun);
294 if (timer->expires.tv64 > now.tv64)
295 return orun;
296 /*
297 * This (and the ktime_add() below) is the
298 * correction for exact:
299 */
300 orun++;
301 }
302 timer->expires = ktime_add(timer->expires, interval);
303
304 return orun;
305}
306
307/*
308 * enqueue_hrtimer - internal function to (re)start a timer
309 *
310 * The timer is inserted in expiry order. Insertion into the
311 * red black tree is O(log(n)). Must hold the base lock.
312 */
313static void enqueue_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
314{
315 struct rb_node **link = &base->active.rb_node;
316 struct list_head *prev = &base->pending;
317 struct rb_node *parent = NULL;
318 struct hrtimer *entry;
319
320 /*
321 * Find the right place in the rbtree:
322 */
323 while (*link) {
324 parent = *link;
325 entry = rb_entry(parent, struct hrtimer, node);
326 /*
327 * We dont care about collisions. Nodes with
328 * the same expiry time stay together.
329 */
330 if (timer->expires.tv64 < entry->expires.tv64)
331 link = &(*link)->rb_left;
332 else {
333 link = &(*link)->rb_right;
334 prev = &entry->list;
335 }
336 }
337
338 /*
339 * Insert the timer to the rbtree and to the sorted list:
340 */
341 rb_link_node(&timer->node, parent, link);
342 rb_insert_color(&timer->node, &base->active);
343 list_add(&timer->list, prev);
344
345 timer->state = HRTIMER_PENDING;
346}
347
348
349/*
350 * __remove_hrtimer - internal function to remove a timer
351 *
352 * Caller must hold the base lock.
353 */
354static void __remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
355{
356 /*
357 * Remove the timer from the sorted list and from the rbtree:
358 */
359 list_del(&timer->list);
360 rb_erase(&timer->node, &base->active);
361}
362
363/*
364 * remove hrtimer, called with base lock held
365 */
366static inline int
367remove_hrtimer(struct hrtimer *timer, struct hrtimer_base *base)
368{
369 if (hrtimer_active(timer)) {
370 __remove_hrtimer(timer, base);
371 timer->state = HRTIMER_INACTIVE;
372 return 1;
373 }
374 return 0;
375}
376
377/**
378 * hrtimer_start - (re)start an relative timer on the current CPU
379 *
380 * @timer: the timer to be added
381 * @tim: expiry time
382 * @mode: expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)
383 *
384 * Returns:
385 * 0 on success
386 * 1 when the timer was active
387 */
388int
389hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
390{
391 struct hrtimer_base *base, *new_base;
392 unsigned long flags;
393 int ret;
394
395 base = lock_hrtimer_base(timer, &flags);
396
397 /* Remove an active timer from the queue: */
398 ret = remove_hrtimer(timer, base);
399
400 /* Switch the timer base, if necessary: */
401 new_base = switch_hrtimer_base(timer, base);
402
403 if (mode == HRTIMER_REL)
404 tim = ktime_add(tim, new_base->get_time());
405 timer->expires = tim;
406
407 enqueue_hrtimer(timer, new_base);
408
409 unlock_hrtimer_base(timer, &flags);
410
411 return ret;
412}
413
414/**
415 * hrtimer_try_to_cancel - try to deactivate a timer
416 *
417 * @timer: hrtimer to stop
418 *
419 * Returns:
420 * 0 when the timer was not active
421 * 1 when the timer was active
422 * -1 when the timer is currently excuting the callback function and
423 * can not be stopped
424 */
425int hrtimer_try_to_cancel(struct hrtimer *timer)
426{
427 struct hrtimer_base *base;
428 unsigned long flags;
429 int ret = -1;
430
431 base = lock_hrtimer_base(timer, &flags);
432
433 if (base->curr_timer != timer)
434 ret = remove_hrtimer(timer, base);
435
436 unlock_hrtimer_base(timer, &flags);
437
438 return ret;
439
440}
441
442/**
443 * hrtimer_cancel - cancel a timer and wait for the handler to finish.
444 *
445 * @timer: the timer to be cancelled
446 *
447 * Returns:
448 * 0 when the timer was not active
449 * 1 when the timer was active
450 */
451int hrtimer_cancel(struct hrtimer *timer)
452{
453 for (;;) {
454 int ret = hrtimer_try_to_cancel(timer);
455
456 if (ret >= 0)
457 return ret;
458 }
459}
460
461/**
462 * hrtimer_get_remaining - get remaining time for the timer
463 *
464 * @timer: the timer to read
465 */
466ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
467{
468 struct hrtimer_base *base;
469 unsigned long flags;
470 ktime_t rem;
471
472 base = lock_hrtimer_base(timer, &flags);
473 rem = ktime_sub(timer->expires, timer->base->get_time());
474 unlock_hrtimer_base(timer, &flags);
475
476 return rem;
477}
478
479/**
480 * hrtimer_rebase - rebase an initialized hrtimer to a different base
481 *
482 * @timer: the timer to be rebased
483 * @clock_id: the clock to be used
484 */
485void hrtimer_rebase(struct hrtimer *timer, const clockid_t clock_id)
486{
487 struct hrtimer_base *bases;
488
489 bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
490 timer->base = &bases[clock_id];
491}
492
493/**
494 * hrtimer_init - initialize a timer to the given clock
495 *
496 * @timer: the timer to be initialized
497 * @clock_id: the clock to be used
498 */
499void hrtimer_init(struct hrtimer *timer, const clockid_t clock_id)
500{
501 memset(timer, 0, sizeof(struct hrtimer));
502 hrtimer_rebase(timer, clock_id);
503}
504
505/**
506 * hrtimer_get_res - get the timer resolution for a clock
507 *
508 * @which_clock: which clock to query
509 * @tp: pointer to timespec variable to store the resolution
510 *
511 * Store the resolution of the clock selected by which_clock in the
512 * variable pointed to by tp.
513 */
514int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
515{
516 struct hrtimer_base *bases;
517
518 tp->tv_sec = 0;
519 bases = per_cpu(hrtimer_bases, raw_smp_processor_id());
520 tp->tv_nsec = bases[which_clock].resolution;
521
522 return 0;
523}
524
525/*
526 * Expire the per base hrtimer-queue:
527 */
528static inline void run_hrtimer_queue(struct hrtimer_base *base)
529{
530 ktime_t now = base->get_time();
531
532 spin_lock_irq(&base->lock);
533
534 while (!list_empty(&base->pending)) {
535 struct hrtimer *timer;
536 int (*fn)(void *);
537 int restart;
538 void *data;
539
540 timer = list_entry(base->pending.next, struct hrtimer, list);
541 if (now.tv64 <= timer->expires.tv64)
542 break;
543
544 fn = timer->function;
545 data = timer->data;
546 set_curr_timer(base, timer);
547 __remove_hrtimer(timer, base);
548 spin_unlock_irq(&base->lock);
549
550 /*
551 * fn == NULL is special case for the simplest timer
552 * variant - wake up process and do not restart:
553 */
554 if (!fn) {
555 wake_up_process(data);
556 restart = HRTIMER_NORESTART;
557 } else
558 restart = fn(data);
559
560 spin_lock_irq(&base->lock);
561
562 if (restart == HRTIMER_RESTART)
563 enqueue_hrtimer(timer, base);
564 else
565 timer->state = HRTIMER_EXPIRED;
566 }
567 set_curr_timer(base, NULL);
568 spin_unlock_irq(&base->lock);
569}
570
571/*
572 * Called from timer softirq every jiffy, expire hrtimers:
573 */
574void hrtimer_run_queues(void)
575{
576 struct hrtimer_base *base = __get_cpu_var(hrtimer_bases);
577 int i;
578
579 for (i = 0; i < MAX_HRTIMER_BASES; i++)
580 run_hrtimer_queue(&base[i]);
581}
582
583/*
584 * Functions related to boot-time initialization:
585 */
586static void __devinit init_hrtimers_cpu(int cpu)
587{
588 struct hrtimer_base *base = per_cpu(hrtimer_bases, cpu);
589 int i;
590
591 for (i = 0; i < MAX_HRTIMER_BASES; i++) {
592 spin_lock_init(&base->lock);
593 INIT_LIST_HEAD(&base->pending);
594 base++;
595 }
596}
597
598#ifdef CONFIG_HOTPLUG_CPU
599
600static void migrate_hrtimer_list(struct hrtimer_base *old_base,
601 struct hrtimer_base *new_base)
602{
603 struct hrtimer *timer;
604 struct rb_node *node;
605
606 while ((node = rb_first(&old_base->active))) {
607 timer = rb_entry(node, struct hrtimer, node);
608 __remove_hrtimer(timer, old_base);
609 timer->base = new_base;
610 enqueue_hrtimer(timer, new_base);
611 }
612}
613
614static void migrate_hrtimers(int cpu)
615{
616 struct hrtimer_base *old_base, *new_base;
617 int i;
618
619 BUG_ON(cpu_online(cpu));
620 old_base = per_cpu(hrtimer_bases, cpu);
621 new_base = get_cpu_var(hrtimer_bases);
622
623 local_irq_disable();
624
625 for (i = 0; i < MAX_HRTIMER_BASES; i++) {
626
627 spin_lock(&new_base->lock);
628 spin_lock(&old_base->lock);
629
630 BUG_ON(old_base->curr_timer);
631
632 migrate_hrtimer_list(old_base, new_base);
633
634 spin_unlock(&old_base->lock);
635 spin_unlock(&new_base->lock);
636 old_base++;
637 new_base++;
638 }
639
640 local_irq_enable();
641 put_cpu_var(hrtimer_bases);
642}
643#endif /* CONFIG_HOTPLUG_CPU */
644
645static int __devinit hrtimer_cpu_notify(struct notifier_block *self,
646 unsigned long action, void *hcpu)
647{
648 long cpu = (long)hcpu;
649
650 switch (action) {
651
652 case CPU_UP_PREPARE:
653 init_hrtimers_cpu(cpu);
654 break;
655
656#ifdef CONFIG_HOTPLUG_CPU
657 case CPU_DEAD:
658 migrate_hrtimers(cpu);
659 break;
660#endif
661
662 default:
663 break;
664 }
665
666 return NOTIFY_OK;
667}
668
669static struct notifier_block __devinitdata hrtimers_nb = {
670 .notifier_call = hrtimer_cpu_notify,
671};
672
673void __init hrtimers_init(void)
674{
675 hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE,
676 (void *)(long)smp_processor_id());
677 register_cpu_notifier(&hrtimers_nb);
678}
679