Root/kernel/timer.c

1/*
2 * linux/kernel/timer.c
3 *
4 * Kernel internal timers
5 *
6 * Copyright (C) 1991, 1992 Linus Torvalds
7 *
8 * 1997-01-28 Modified by Finn Arne Gangstad to make timers scale better.
9 *
10 * 1997-09-10 Updated NTP code according to technical memorandum Jan '96
11 * "A Kernel Model for Precision Timekeeping" by Dave Mills
12 * 1998-12-24 Fixed a xtime SMP race (we need the xtime_lock rw spinlock to
13 * serialize accesses to xtime/lost_ticks).
14 * Copyright (C) 1998 Andrea Arcangeli
15 * 1999-03-10 Improved NTP compatibility by Ulrich Windl
16 * 2002-05-31 Move sys_sysinfo here and make its locking sane, Robert Love
17 * 2000-10-05 Implemented scalable SMP per-CPU timer handling.
18 * Copyright (C) 2000, 2001, 2002 Ingo Molnar
19 * Designed by David S. Miller, Alexey Kuznetsov and Ingo Molnar
20 */
21
22#include <linux/kernel_stat.h>
23#include <linux/export.h>
24#include <linux/interrupt.h>
25#include <linux/percpu.h>
26#include <linux/init.h>
27#include <linux/mm.h>
28#include <linux/swap.h>
29#include <linux/pid_namespace.h>
30#include <linux/notifier.h>
31#include <linux/thread_info.h>
32#include <linux/time.h>
33#include <linux/jiffies.h>
34#include <linux/posix-timers.h>
35#include <linux/cpu.h>
36#include <linux/syscalls.h>
37#include <linux/delay.h>
38#include <linux/tick.h>
39#include <linux/kallsyms.h>
40#include <linux/irq_work.h>
41#include <linux/sched.h>
42#include <linux/sched/sysctl.h>
43#include <linux/slab.h>
44#include <linux/compat.h>
45
46#include <asm/uaccess.h>
47#include <asm/unistd.h>
48#include <asm/div64.h>
49#include <asm/timex.h>
50#include <asm/io.h>
51
52#define CREATE_TRACE_POINTS
53#include <trace/events/timer.h>
54
55__visible u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
56
57EXPORT_SYMBOL(jiffies_64);
58
59/*
60 * per-CPU timer vector definitions:
61 */
62#define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
63#define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
64#define TVN_SIZE (1 << TVN_BITS)
65#define TVR_SIZE (1 << TVR_BITS)
66#define TVN_MASK (TVN_SIZE - 1)
67#define TVR_MASK (TVR_SIZE - 1)
68#define MAX_TVAL ((unsigned long)((1ULL << (TVR_BITS + 4*TVN_BITS)) - 1))
69
70struct tvec {
71    struct list_head vec[TVN_SIZE];
72};
73
74struct tvec_root {
75    struct list_head vec[TVR_SIZE];
76};
77
78struct tvec_base {
79    spinlock_t lock;
80    struct timer_list *running_timer;
81    unsigned long timer_jiffies;
82    unsigned long next_timer;
83    unsigned long active_timers;
84    unsigned long all_timers;
85    struct tvec_root tv1;
86    struct tvec tv2;
87    struct tvec tv3;
88    struct tvec tv4;
89    struct tvec tv5;
90} ____cacheline_aligned;
91
92struct tvec_base boot_tvec_bases;
93EXPORT_SYMBOL(boot_tvec_bases);
94static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;
95
96/* Functions below help us manage 'deferrable' flag */
97static inline unsigned int tbase_get_deferrable(struct tvec_base *base)
98{
99    return ((unsigned int)(unsigned long)base & TIMER_DEFERRABLE);
100}
101
102static inline unsigned int tbase_get_irqsafe(struct tvec_base *base)
103{
104    return ((unsigned int)(unsigned long)base & TIMER_IRQSAFE);
105}
106
107static inline struct tvec_base *tbase_get_base(struct tvec_base *base)
108{
109    return ((struct tvec_base *)((unsigned long)base & ~TIMER_FLAG_MASK));
110}
111
112static inline void
113timer_set_base(struct timer_list *timer, struct tvec_base *new_base)
114{
115    unsigned long flags = (unsigned long)timer->base & TIMER_FLAG_MASK;
116
117    timer->base = (struct tvec_base *)((unsigned long)(new_base) | flags);
118}
119
120static unsigned long round_jiffies_common(unsigned long j, int cpu,
121        bool force_up)
122{
123    int rem;
124    unsigned long original = j;
125
126    /*
127     * We don't want all cpus firing their timers at once hitting the
128     * same lock or cachelines, so we skew each extra cpu with an extra
129     * 3 jiffies. This 3 jiffies came originally from the mm/ code which
130     * already did this.
131     * The skew is done by adding 3*cpunr, then round, then subtract this
132     * extra offset again.
133     */
134    j += cpu * 3;
135
136    rem = j % HZ;
137
138    /*
139     * If the target jiffie is just after a whole second (which can happen
140     * due to delays of the timer irq, long irq off times etc etc) then
141     * we should round down to the whole second, not up. Use 1/4th second
142     * as cutoff for this rounding as an extreme upper bound for this.
143     * But never round down if @force_up is set.
144     */
145    if (rem < HZ/4 && !force_up) /* round down */
146        j = j - rem;
147    else /* round up */
148        j = j - rem + HZ;
149
150    /* now that we have rounded, subtract the extra skew again */
151    j -= cpu * 3;
152
153    /*
154     * Make sure j is still in the future. Otherwise return the
155     * unmodified value.
156     */
157    return time_is_after_jiffies(j) ? j : original;
158}
159
160/**
161 * __round_jiffies - function to round jiffies to a full second
162 * @j: the time in (absolute) jiffies that should be rounded
163 * @cpu: the processor number on which the timeout will happen
164 *
165 * __round_jiffies() rounds an absolute time in the future (in jiffies)
166 * up or down to (approximately) full seconds. This is useful for timers
167 * for which the exact time they fire does not matter too much, as long as
168 * they fire approximately every X seconds.
169 *
170 * By rounding these timers to whole seconds, all such timers will fire
171 * at the same time, rather than at various times spread out. The goal
172 * of this is to have the CPU wake up less, which saves power.
173 *
174 * The exact rounding is skewed for each processor to avoid all
175 * processors firing at the exact same time, which could lead
176 * to lock contention or spurious cache line bouncing.
177 *
178 * The return value is the rounded version of the @j parameter.
179 */
180unsigned long __round_jiffies(unsigned long j, int cpu)
181{
182    return round_jiffies_common(j, cpu, false);
183}
184EXPORT_SYMBOL_GPL(__round_jiffies);
185
186/**
187 * __round_jiffies_relative - function to round jiffies to a full second
188 * @j: the time in (relative) jiffies that should be rounded
189 * @cpu: the processor number on which the timeout will happen
190 *
191 * __round_jiffies_relative() rounds a time delta in the future (in jiffies)
192 * up or down to (approximately) full seconds. This is useful for timers
193 * for which the exact time they fire does not matter too much, as long as
194 * they fire approximately every X seconds.
195 *
196 * By rounding these timers to whole seconds, all such timers will fire
197 * at the same time, rather than at various times spread out. The goal
198 * of this is to have the CPU wake up less, which saves power.
199 *
200 * The exact rounding is skewed for each processor to avoid all
201 * processors firing at the exact same time, which could lead
202 * to lock contention or spurious cache line bouncing.
203 *
204 * The return value is the rounded version of the @j parameter.
205 */
206unsigned long __round_jiffies_relative(unsigned long j, int cpu)
207{
208    unsigned long j0 = jiffies;
209
210    /* Use j0 because jiffies might change while we run */
211    return round_jiffies_common(j + j0, cpu, false) - j0;
212}
213EXPORT_SYMBOL_GPL(__round_jiffies_relative);
214
215/**
216 * round_jiffies - function to round jiffies to a full second
217 * @j: the time in (absolute) jiffies that should be rounded
218 *
219 * round_jiffies() rounds an absolute time in the future (in jiffies)
220 * up or down to (approximately) full seconds. This is useful for timers
221 * for which the exact time they fire does not matter too much, as long as
222 * they fire approximately every X seconds.
223 *
224 * By rounding these timers to whole seconds, all such timers will fire
225 * at the same time, rather than at various times spread out. The goal
226 * of this is to have the CPU wake up less, which saves power.
227 *
228 * The return value is the rounded version of the @j parameter.
229 */
230unsigned long round_jiffies(unsigned long j)
231{
232    return round_jiffies_common(j, raw_smp_processor_id(), false);
233}
234EXPORT_SYMBOL_GPL(round_jiffies);
235
236/**
237 * round_jiffies_relative - function to round jiffies to a full second
238 * @j: the time in (relative) jiffies that should be rounded
239 *
240 * round_jiffies_relative() rounds a time delta in the future (in jiffies)
241 * up or down to (approximately) full seconds. This is useful for timers
242 * for which the exact time they fire does not matter too much, as long as
243 * they fire approximately every X seconds.
244 *
245 * By rounding these timers to whole seconds, all such timers will fire
246 * at the same time, rather than at various times spread out. The goal
247 * of this is to have the CPU wake up less, which saves power.
248 *
249 * The return value is the rounded version of the @j parameter.
250 */
251unsigned long round_jiffies_relative(unsigned long j)
252{
253    return __round_jiffies_relative(j, raw_smp_processor_id());
254}
255EXPORT_SYMBOL_GPL(round_jiffies_relative);
256
257/**
258 * __round_jiffies_up - function to round jiffies up to a full second
259 * @j: the time in (absolute) jiffies that should be rounded
260 * @cpu: the processor number on which the timeout will happen
261 *
262 * This is the same as __round_jiffies() except that it will never
263 * round down. This is useful for timeouts for which the exact time
264 * of firing does not matter too much, as long as they don't fire too
265 * early.
266 */
267unsigned long __round_jiffies_up(unsigned long j, int cpu)
268{
269    return round_jiffies_common(j, cpu, true);
270}
271EXPORT_SYMBOL_GPL(__round_jiffies_up);
272
273/**
274 * __round_jiffies_up_relative - function to round jiffies up to a full second
275 * @j: the time in (relative) jiffies that should be rounded
276 * @cpu: the processor number on which the timeout will happen
277 *
278 * This is the same as __round_jiffies_relative() except that it will never
279 * round down. This is useful for timeouts for which the exact time
280 * of firing does not matter too much, as long as they don't fire too
281 * early.
282 */
283unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
284{
285    unsigned long j0 = jiffies;
286
287    /* Use j0 because jiffies might change while we run */
288    return round_jiffies_common(j + j0, cpu, true) - j0;
289}
290EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
291
292/**
293 * round_jiffies_up - function to round jiffies up to a full second
294 * @j: the time in (absolute) jiffies that should be rounded
295 *
296 * This is the same as round_jiffies() except that it will never
297 * round down. This is useful for timeouts for which the exact time
298 * of firing does not matter too much, as long as they don't fire too
299 * early.
300 */
301unsigned long round_jiffies_up(unsigned long j)
302{
303    return round_jiffies_common(j, raw_smp_processor_id(), true);
304}
305EXPORT_SYMBOL_GPL(round_jiffies_up);
306
307/**
308 * round_jiffies_up_relative - function to round jiffies up to a full second
309 * @j: the time in (relative) jiffies that should be rounded
310 *
311 * This is the same as round_jiffies_relative() except that it will never
312 * round down. This is useful for timeouts for which the exact time
313 * of firing does not matter too much, as long as they don't fire too
314 * early.
315 */
316unsigned long round_jiffies_up_relative(unsigned long j)
317{
318    return __round_jiffies_up_relative(j, raw_smp_processor_id());
319}
320EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
321
322/**
323 * set_timer_slack - set the allowed slack for a timer
324 * @timer: the timer to be modified
325 * @slack_hz: the amount of time (in jiffies) allowed for rounding
326 *
327 * Set the amount of time, in jiffies, that a certain timer has
328 * in terms of slack. By setting this value, the timer subsystem
329 * will schedule the actual timer somewhere between
330 * the time mod_timer() asks for, and that time plus the slack.
331 *
332 * By setting the slack to -1, a percentage of the delay is used
333 * instead.
334 */
335void set_timer_slack(struct timer_list *timer, int slack_hz)
336{
337    timer->slack = slack_hz;
338}
339EXPORT_SYMBOL_GPL(set_timer_slack);
340
341/*
342 * If the list is empty, catch up ->timer_jiffies to the current time.
343 * The caller must hold the tvec_base lock. Returns true if the list
344 * was empty and therefore ->timer_jiffies was updated.
345 */
346static bool catchup_timer_jiffies(struct tvec_base *base)
347{
348    if (!base->all_timers) {
349        base->timer_jiffies = jiffies;
350        return true;
351    }
352    return false;
353}
354
355static void
356__internal_add_timer(struct tvec_base *base, struct timer_list *timer)
357{
358    unsigned long expires = timer->expires;
359    unsigned long idx = expires - base->timer_jiffies;
360    struct list_head *vec;
361
362    if (idx < TVR_SIZE) {
363        int i = expires & TVR_MASK;
364        vec = base->tv1.vec + i;
365    } else if (idx < 1 << (TVR_BITS + TVN_BITS)) {
366        int i = (expires >> TVR_BITS) & TVN_MASK;
367        vec = base->tv2.vec + i;
368    } else if (idx < 1 << (TVR_BITS + 2 * TVN_BITS)) {
369        int i = (expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
370        vec = base->tv3.vec + i;
371    } else if (idx < 1 << (TVR_BITS + 3 * TVN_BITS)) {
372        int i = (expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;
373        vec = base->tv4.vec + i;
374    } else if ((signed long) idx < 0) {
375        /*
376         * Can happen if you add a timer with expires == jiffies,
377         * or you set a timer to go off in the past
378         */
379        vec = base->tv1.vec + (base->timer_jiffies & TVR_MASK);
380    } else {
381        int i;
382        /* If the timeout is larger than MAX_TVAL (on 64-bit
383         * architectures or with CONFIG_BASE_SMALL=1) then we
384         * use the maximum timeout.
385         */
386        if (idx > MAX_TVAL) {
387            idx = MAX_TVAL;
388            expires = idx + base->timer_jiffies;
389        }
390        i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;
391        vec = base->tv5.vec + i;
392    }
393    /*
394     * Timers are FIFO:
395     */
396    list_add_tail(&timer->entry, vec);
397}
398
399static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
400{
401    (void)catchup_timer_jiffies(base);
402    __internal_add_timer(base, timer);
403    /*
404     * Update base->active_timers and base->next_timer
405     */
406    if (!tbase_get_deferrable(timer->base)) {
407        if (!base->active_timers++ ||
408            time_before(timer->expires, base->next_timer))
409            base->next_timer = timer->expires;
410    }
411    base->all_timers++;
412}
413
414#ifdef CONFIG_TIMER_STATS
415void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr)
416{
417    if (timer->start_site)
418        return;
419
420    timer->start_site = addr;
421    memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
422    timer->start_pid = current->pid;
423}
424
425static void timer_stats_account_timer(struct timer_list *timer)
426{
427    unsigned int flag = 0;
428
429    if (likely(!timer->start_site))
430        return;
431    if (unlikely(tbase_get_deferrable(timer->base)))
432        flag |= TIMER_STATS_FLAG_DEFERRABLE;
433
434    timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
435                 timer->function, timer->start_comm, flag);
436}
437
438#else
439static void timer_stats_account_timer(struct timer_list *timer) {}
440#endif
441
442#ifdef CONFIG_DEBUG_OBJECTS_TIMERS
443
444static struct debug_obj_descr timer_debug_descr;
445
446static void *timer_debug_hint(void *addr)
447{
448    return ((struct timer_list *) addr)->function;
449}
450
451/*
452 * fixup_init is called when:
453 * - an active object is initialized
454 */
455static int timer_fixup_init(void *addr, enum debug_obj_state state)
456{
457    struct timer_list *timer = addr;
458
459    switch (state) {
460    case ODEBUG_STATE_ACTIVE:
461        del_timer_sync(timer);
462        debug_object_init(timer, &timer_debug_descr);
463        return 1;
464    default:
465        return 0;
466    }
467}
468
469/* Stub timer callback for improperly used timers. */
470static void stub_timer(unsigned long data)
471{
472    WARN_ON(1);
473}
474
475/*
476 * fixup_activate is called when:
477 * - an active object is activated
478 * - an unknown object is activated (might be a statically initialized object)
479 */
480static int timer_fixup_activate(void *addr, enum debug_obj_state state)
481{
482    struct timer_list *timer = addr;
483
484    switch (state) {
485
486    case ODEBUG_STATE_NOTAVAILABLE:
487        /*
488         * This is not really a fixup. The timer was
489         * statically initialized. We just make sure that it
490         * is tracked in the object tracker.
491         */
492        if (timer->entry.next == NULL &&
493            timer->entry.prev == TIMER_ENTRY_STATIC) {
494            debug_object_init(timer, &timer_debug_descr);
495            debug_object_activate(timer, &timer_debug_descr);
496            return 0;
497        } else {
498            setup_timer(timer, stub_timer, 0);
499            return 1;
500        }
501        return 0;
502
503    case ODEBUG_STATE_ACTIVE:
504        WARN_ON(1);
505
506    default:
507        return 0;
508    }
509}
510
511/*
512 * fixup_free is called when:
513 * - an active object is freed
514 */
515static int timer_fixup_free(void *addr, enum debug_obj_state state)
516{
517    struct timer_list *timer = addr;
518
519    switch (state) {
520    case ODEBUG_STATE_ACTIVE:
521        del_timer_sync(timer);
522        debug_object_free(timer, &timer_debug_descr);
523        return 1;
524    default:
525        return 0;
526    }
527}
528
529/*
530 * fixup_assert_init is called when:
531 * - an untracked/uninit-ed object is found
532 */
533static int timer_fixup_assert_init(void *addr, enum debug_obj_state state)
534{
535    struct timer_list *timer = addr;
536
537    switch (state) {
538    case ODEBUG_STATE_NOTAVAILABLE:
539        if (timer->entry.prev == TIMER_ENTRY_STATIC) {
540            /*
541             * This is not really a fixup. The timer was
542             * statically initialized. We just make sure that it
543             * is tracked in the object tracker.
544             */
545            debug_object_init(timer, &timer_debug_descr);
546            return 0;
547        } else {
548            setup_timer(timer, stub_timer, 0);
549            return 1;
550        }
551    default:
552        return 0;
553    }
554}
555
556static struct debug_obj_descr timer_debug_descr = {
557    .name = "timer_list",
558    .debug_hint = timer_debug_hint,
559    .fixup_init = timer_fixup_init,
560    .fixup_activate = timer_fixup_activate,
561    .fixup_free = timer_fixup_free,
562    .fixup_assert_init = timer_fixup_assert_init,
563};
564
565static inline void debug_timer_init(struct timer_list *timer)
566{
567    debug_object_init(timer, &timer_debug_descr);
568}
569
570static inline void debug_timer_activate(struct timer_list *timer)
571{
572    debug_object_activate(timer, &timer_debug_descr);
573}
574
575static inline void debug_timer_deactivate(struct timer_list *timer)
576{
577    debug_object_deactivate(timer, &timer_debug_descr);
578}
579
580static inline void debug_timer_free(struct timer_list *timer)
581{
582    debug_object_free(timer, &timer_debug_descr);
583}
584
585static inline void debug_timer_assert_init(struct timer_list *timer)
586{
587    debug_object_assert_init(timer, &timer_debug_descr);
588}
589
590static void do_init_timer(struct timer_list *timer, unsigned int flags,
591              const char *name, struct lock_class_key *key);
592
593void init_timer_on_stack_key(struct timer_list *timer, unsigned int flags,
594                 const char *name, struct lock_class_key *key)
595{
596    debug_object_init_on_stack(timer, &timer_debug_descr);
597    do_init_timer(timer, flags, name, key);
598}
599EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
600
601void destroy_timer_on_stack(struct timer_list *timer)
602{
603    debug_object_free(timer, &timer_debug_descr);
604}
605EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
606
607#else
608static inline void debug_timer_init(struct timer_list *timer) { }
609static inline void debug_timer_activate(struct timer_list *timer) { }
610static inline void debug_timer_deactivate(struct timer_list *timer) { }
611static inline void debug_timer_assert_init(struct timer_list *timer) { }
612#endif
613
614static inline void debug_init(struct timer_list *timer)
615{
616    debug_timer_init(timer);
617    trace_timer_init(timer);
618}
619
620static inline void
621debug_activate(struct timer_list *timer, unsigned long expires)
622{
623    debug_timer_activate(timer);
624    trace_timer_start(timer, expires);
625}
626
627static inline void debug_deactivate(struct timer_list *timer)
628{
629    debug_timer_deactivate(timer);
630    trace_timer_cancel(timer);
631}
632
633static inline void debug_assert_init(struct timer_list *timer)
634{
635    debug_timer_assert_init(timer);
636}
637
638static void do_init_timer(struct timer_list *timer, unsigned int flags,
639              const char *name, struct lock_class_key *key)
640{
641    struct tvec_base *base = __raw_get_cpu_var(tvec_bases);
642
643    timer->entry.next = NULL;
644    timer->base = (void *)((unsigned long)base | flags);
645    timer->slack = -1;
646#ifdef CONFIG_TIMER_STATS
647    timer->start_site = NULL;
648    timer->start_pid = -1;
649    memset(timer->start_comm, 0, TASK_COMM_LEN);
650#endif
651    lockdep_init_map(&timer->lockdep_map, name, key, 0);
652}
653
654/**
655 * init_timer_key - initialize a timer
656 * @timer: the timer to be initialized
657 * @flags: timer flags
658 * @name: name of the timer
659 * @key: lockdep class key of the fake lock used for tracking timer
660 * sync lock dependencies
661 *
662 * init_timer_key() must be done to a timer prior calling *any* of the
663 * other timer functions.
664 */
665void init_timer_key(struct timer_list *timer, unsigned int flags,
666            const char *name, struct lock_class_key *key)
667{
668    debug_init(timer);
669    do_init_timer(timer, flags, name, key);
670}
671EXPORT_SYMBOL(init_timer_key);
672
673static inline void detach_timer(struct timer_list *timer, bool clear_pending)
674{
675    struct list_head *entry = &timer->entry;
676
677    debug_deactivate(timer);
678
679    __list_del(entry->prev, entry->next);
680    if (clear_pending)
681        entry->next = NULL;
682    entry->prev = LIST_POISON2;
683}
684
685static inline void
686detach_expired_timer(struct timer_list *timer, struct tvec_base *base)
687{
688    detach_timer(timer, true);
689    if (!tbase_get_deferrable(timer->base))
690        base->active_timers--;
691    base->all_timers--;
692    (void)catchup_timer_jiffies(base);
693}
694
695static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
696                 bool clear_pending)
697{
698    if (!timer_pending(timer))
699        return 0;
700
701    detach_timer(timer, clear_pending);
702    if (!tbase_get_deferrable(timer->base)) {
703        base->active_timers--;
704        if (timer->expires == base->next_timer)
705            base->next_timer = base->timer_jiffies;
706    }
707    base->all_timers--;
708    (void)catchup_timer_jiffies(base);
709    return 1;
710}
711
712/*
713 * We are using hashed locking: holding per_cpu(tvec_bases).lock
714 * means that all timers which are tied to this base via timer->base are
715 * locked, and the base itself is locked too.
716 *
717 * So __run_timers/migrate_timers can safely modify all timers which could
718 * be found on ->tvX lists.
719 *
720 * When the timer's base is locked, and the timer removed from list, it is
721 * possible to set timer->base = NULL and drop the lock: the timer remains
722 * locked.
723 */
724static struct tvec_base *lock_timer_base(struct timer_list *timer,
725                    unsigned long *flags)
726    __acquires(timer->base->lock)
727{
728    struct tvec_base *base;
729
730    for (;;) {
731        struct tvec_base *prelock_base = timer->base;
732        base = tbase_get_base(prelock_base);
733        if (likely(base != NULL)) {
734            spin_lock_irqsave(&base->lock, *flags);
735            if (likely(prelock_base == timer->base))
736                return base;
737            /* The timer has migrated to another CPU */
738            spin_unlock_irqrestore(&base->lock, *flags);
739        }
740        cpu_relax();
741    }
742}
743
744static inline int
745__mod_timer(struct timer_list *timer, unsigned long expires,
746                        bool pending_only, int pinned)
747{
748    struct tvec_base *base, *new_base;
749    unsigned long flags;
750    int ret = 0 , cpu;
751
752    timer_stats_timer_set_start_info(timer);
753    BUG_ON(!timer->function);
754
755    base = lock_timer_base(timer, &flags);
756
757    ret = detach_if_pending(timer, base, false);
758    if (!ret && pending_only)
759        goto out_unlock;
760
761    debug_activate(timer, expires);
762
763    cpu = get_nohz_timer_target(pinned);
764    new_base = per_cpu(tvec_bases, cpu);
765
766    if (base != new_base) {
767        /*
768         * We are trying to schedule the timer on the local CPU.
769         * However we can't change timer's base while it is running,
770         * otherwise del_timer_sync() can't detect that the timer's
771         * handler yet has not finished. This also guarantees that
772         * the timer is serialized wrt itself.
773         */
774        if (likely(base->running_timer != timer)) {
775            /* See the comment in lock_timer_base() */
776            timer_set_base(timer, NULL);
777            spin_unlock(&base->lock);
778            base = new_base;
779            spin_lock(&base->lock);
780            timer_set_base(timer, base);
781        }
782    }
783
784    timer->expires = expires;
785    internal_add_timer(base, timer);
786
787out_unlock:
788    spin_unlock_irqrestore(&base->lock, flags);
789
790    return ret;
791}
792
793/**
794 * mod_timer_pending - modify a pending timer's timeout
795 * @timer: the pending timer to be modified
796 * @expires: new timeout in jiffies
797 *
798 * mod_timer_pending() is the same for pending timers as mod_timer(),
799 * but will not re-activate and modify already deleted timers.
800 *
801 * It is useful for unserialized use of timers.
802 */
803int mod_timer_pending(struct timer_list *timer, unsigned long expires)
804{
805    return __mod_timer(timer, expires, true, TIMER_NOT_PINNED);
806}
807EXPORT_SYMBOL(mod_timer_pending);
808
809/*
810 * Decide where to put the timer while taking the slack into account
811 *
812 * Algorithm:
813 * 1) calculate the maximum (absolute) time
814 * 2) calculate the highest bit where the expires and new max are different
815 * 3) use this bit to make a mask
816 * 4) use the bitmask to round down the maximum time, so that all last
817 * bits are zeros
818 */
819static inline
820unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
821{
822    unsigned long expires_limit, mask;
823    int bit;
824
825    if (timer->slack >= 0) {
826        expires_limit = expires + timer->slack;
827    } else {
828        long delta = expires - jiffies;
829
830        if (delta < 256)
831            return expires;
832
833        expires_limit = expires + delta / 256;
834    }
835    mask = expires ^ expires_limit;
836    if (mask == 0)
837        return expires;
838
839    bit = find_last_bit(&mask, BITS_PER_LONG);
840
841    mask = (1UL << bit) - 1;
842
843    expires_limit = expires_limit & ~(mask);
844
845    return expires_limit;
846}
847
848/**
849 * mod_timer - modify a timer's timeout
850 * @timer: the timer to be modified
851 * @expires: new timeout in jiffies
852 *
853 * mod_timer() is a more efficient way to update the expire field of an
854 * active timer (if the timer is inactive it will be activated)
855 *
856 * mod_timer(timer, expires) is equivalent to:
857 *
858 * del_timer(timer); timer->expires = expires; add_timer(timer);
859 *
860 * Note that if there are multiple unserialized concurrent users of the
861 * same timer, then mod_timer() is the only safe way to modify the timeout,
862 * since add_timer() cannot modify an already running timer.
863 *
864 * The function returns whether it has modified a pending timer or not.
865 * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
866 * active timer returns 1.)
867 */
868int mod_timer(struct timer_list *timer, unsigned long expires)
869{
870    expires = apply_slack(timer, expires);
871
872    /*
873     * This is a common optimization triggered by the
874     * networking code - if the timer is re-modified
875     * to be the same thing then just return:
876     */
877    if (timer_pending(timer) && timer->expires == expires)
878        return 1;
879
880    return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
881}
882EXPORT_SYMBOL(mod_timer);
883
884/**
885 * mod_timer_pinned - modify a timer's timeout
886 * @timer: the timer to be modified
887 * @expires: new timeout in jiffies
888 *
889 * mod_timer_pinned() is a way to update the expire field of an
890 * active timer (if the timer is inactive it will be activated)
891 * and to ensure that the timer is scheduled on the current CPU.
892 *
893 * Note that this does not prevent the timer from being migrated
894 * when the current CPU goes offline. If this is a problem for
895 * you, use CPU-hotplug notifiers to handle it correctly, for
896 * example, cancelling the timer when the corresponding CPU goes
897 * offline.
898 *
899 * mod_timer_pinned(timer, expires) is equivalent to:
900 *
901 * del_timer(timer); timer->expires = expires; add_timer(timer);
902 */
903int mod_timer_pinned(struct timer_list *timer, unsigned long expires)
904{
905    if (timer->expires == expires && timer_pending(timer))
906        return 1;
907
908    return __mod_timer(timer, expires, false, TIMER_PINNED);
909}
910EXPORT_SYMBOL(mod_timer_pinned);
911
912/**
913 * add_timer - start a timer
914 * @timer: the timer to be added
915 *
916 * The kernel will do a ->function(->data) callback from the
917 * timer interrupt at the ->expires point in the future. The
918 * current time is 'jiffies'.
919 *
920 * The timer's ->expires, ->function (and if the handler uses it, ->data)
921 * fields must be set prior calling this function.
922 *
923 * Timers with an ->expires field in the past will be executed in the next
924 * timer tick.
925 */
926void add_timer(struct timer_list *timer)
927{
928    BUG_ON(timer_pending(timer));
929    mod_timer(timer, timer->expires);
930}
931EXPORT_SYMBOL(add_timer);
932
933/**
934 * add_timer_on - start a timer on a particular CPU
935 * @timer: the timer to be added
936 * @cpu: the CPU to start it on
937 *
938 * This is not very scalable on SMP. Double adds are not possible.
939 */
940void add_timer_on(struct timer_list *timer, int cpu)
941{
942    struct tvec_base *base = per_cpu(tvec_bases, cpu);
943    unsigned long flags;
944
945    timer_stats_timer_set_start_info(timer);
946    BUG_ON(timer_pending(timer) || !timer->function);
947    spin_lock_irqsave(&base->lock, flags);
948    timer_set_base(timer, base);
949    debug_activate(timer, timer->expires);
950    internal_add_timer(base, timer);
951    /*
952     * Check whether the other CPU is in dynticks mode and needs
953     * to be triggered to reevaluate the timer wheel.
954     * We are protected against the other CPU fiddling
955     * with the timer by holding the timer base lock. This also
956     * makes sure that a CPU on the way to stop its tick can not
957     * evaluate the timer wheel.
958     *
959     * Spare the IPI for deferrable timers on idle targets though.
960     * The next busy ticks will take care of it. Except full dynticks
961     * require special care against races with idle_cpu(), lets deal
962     * with that later.
963     */
964    if (!tbase_get_deferrable(timer->base) || tick_nohz_full_cpu(cpu))
965        wake_up_nohz_cpu(cpu);
966
967    spin_unlock_irqrestore(&base->lock, flags);
968}
969EXPORT_SYMBOL_GPL(add_timer_on);
970
971/**
972 * del_timer - deactive a timer.
973 * @timer: the timer to be deactivated
974 *
975 * del_timer() deactivates a timer - this works on both active and inactive
976 * timers.
977 *
978 * The function returns whether it has deactivated a pending timer or not.
979 * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
980 * active timer returns 1.)
981 */
982int del_timer(struct timer_list *timer)
983{
984    struct tvec_base *base;
985    unsigned long flags;
986    int ret = 0;
987
988    debug_assert_init(timer);
989
990    timer_stats_timer_clear_start_info(timer);
991    if (timer_pending(timer)) {
992        base = lock_timer_base(timer, &flags);
993        ret = detach_if_pending(timer, base, true);
994        spin_unlock_irqrestore(&base->lock, flags);
995    }
996
997    return ret;
998}
999EXPORT_SYMBOL(del_timer);
1000
1001/**
1002 * try_to_del_timer_sync - Try to deactivate a timer
1003 * @timer: timer do del
1004 *
1005 * This function tries to deactivate a timer. Upon successful (ret >= 0)
1006 * exit the timer is not queued and the handler is not running on any CPU.
1007 */
1008int try_to_del_timer_sync(struct timer_list *timer)
1009{
1010    struct tvec_base *base;
1011    unsigned long flags;
1012    int ret = -1;
1013
1014    debug_assert_init(timer);
1015
1016    base = lock_timer_base(timer, &flags);
1017
1018    if (base->running_timer != timer) {
1019        timer_stats_timer_clear_start_info(timer);
1020        ret = detach_if_pending(timer, base, true);
1021    }
1022    spin_unlock_irqrestore(&base->lock, flags);
1023
1024    return ret;
1025}
1026EXPORT_SYMBOL(try_to_del_timer_sync);
1027
1028#ifdef CONFIG_SMP
1029/**
1030 * del_timer_sync - deactivate a timer and wait for the handler to finish.
1031 * @timer: the timer to be deactivated
1032 *
1033 * This function only differs from del_timer() on SMP: besides deactivating
1034 * the timer it also makes sure the handler has finished executing on other
1035 * CPUs.
1036 *
1037 * Synchronization rules: Callers must prevent restarting of the timer,
1038 * otherwise this function is meaningless. It must not be called from
1039 * interrupt contexts unless the timer is an irqsafe one. The caller must
1040 * not hold locks which would prevent completion of the timer's
1041 * handler. The timer's handler must not call add_timer_on(). Upon exit the
1042 * timer is not queued and the handler is not running on any CPU.
1043 *
1044 * Note: For !irqsafe timers, you must not hold locks that are held in
1045 * interrupt context while calling this function. Even if the lock has
1046 * nothing to do with the timer in question. Here's why:
1047 *
1048 * CPU0 CPU1
1049 * ---- ----
1050 * <SOFTIRQ>
1051 * call_timer_fn();
1052 * base->running_timer = mytimer;
1053 * spin_lock_irq(somelock);
1054 * <IRQ>
1055 * spin_lock(somelock);
1056 * del_timer_sync(mytimer);
1057 * while (base->running_timer == mytimer);
1058 *
1059 * Now del_timer_sync() will never return and never release somelock.
1060 * The interrupt on the other CPU is waiting to grab somelock but
1061 * it has interrupted the softirq that CPU0 is waiting to finish.
1062 *
1063 * The function returns whether it has deactivated a pending timer or not.
1064 */
1065int del_timer_sync(struct timer_list *timer)
1066{
1067#ifdef CONFIG_LOCKDEP
1068    unsigned long flags;
1069
1070    /*
1071     * If lockdep gives a backtrace here, please reference
1072     * the synchronization rules above.
1073     */
1074    local_irq_save(flags);
1075    lock_map_acquire(&timer->lockdep_map);
1076    lock_map_release(&timer->lockdep_map);
1077    local_irq_restore(flags);
1078#endif
1079    /*
1080     * don't use it in hardirq context, because it
1081     * could lead to deadlock.
1082     */
1083    WARN_ON(in_irq() && !tbase_get_irqsafe(timer->base));
1084    for (;;) {
1085        int ret = try_to_del_timer_sync(timer);
1086        if (ret >= 0)
1087            return ret;
1088        cpu_relax();
1089    }
1090}
1091EXPORT_SYMBOL(del_timer_sync);
1092#endif
1093
1094static int cascade(struct tvec_base *base, struct tvec *tv, int index)
1095{
1096    /* cascade all the timers from tv up one level */
1097    struct timer_list *timer, *tmp;
1098    struct list_head tv_list;
1099
1100    list_replace_init(tv->vec + index, &tv_list);
1101
1102    /*
1103     * We are removing _all_ timers from the list, so we
1104     * don't have to detach them individually.
1105     */
1106    list_for_each_entry_safe(timer, tmp, &tv_list, entry) {
1107        BUG_ON(tbase_get_base(timer->base) != base);
1108        /* No accounting, while moving them */
1109        __internal_add_timer(base, timer);
1110    }
1111
1112    return index;
1113}
1114
1115static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
1116              unsigned long data)
1117{
1118    int count = preempt_count();
1119
1120#ifdef CONFIG_LOCKDEP
1121    /*
1122     * It is permissible to free the timer from inside the
1123     * function that is called from it, this we need to take into
1124     * account for lockdep too. To avoid bogus "held lock freed"
1125     * warnings as well as problems when looking into
1126     * timer->lockdep_map, make a copy and use that here.
1127     */
1128    struct lockdep_map lockdep_map;
1129
1130    lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
1131#endif
1132    /*
1133     * Couple the lock chain with the lock chain at
1134     * del_timer_sync() by acquiring the lock_map around the fn()
1135     * call here and in del_timer_sync().
1136     */
1137    lock_map_acquire(&lockdep_map);
1138
1139    trace_timer_expire_entry(timer);
1140    fn(data);
1141    trace_timer_expire_exit(timer);
1142
1143    lock_map_release(&lockdep_map);
1144
1145    if (count != preempt_count()) {
1146        WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
1147              fn, count, preempt_count());
1148        /*
1149         * Restore the preempt count. That gives us a decent
1150         * chance to survive and extract information. If the
1151         * callback kept a lock held, bad luck, but not worse
1152         * than the BUG() we had.
1153         */
1154        preempt_count_set(count);
1155    }
1156}
1157
1158#define INDEX(N) ((base->timer_jiffies >> (TVR_BITS + (N) * TVN_BITS)) & TVN_MASK)
1159
1160/**
1161 * __run_timers - run all expired timers (if any) on this CPU.
1162 * @base: the timer vector to be processed.
1163 *
1164 * This function cascades all vectors and executes all expired timer
1165 * vectors.
1166 */
1167static inline void __run_timers(struct tvec_base *base)
1168{
1169    struct timer_list *timer;
1170
1171    spin_lock_irq(&base->lock);
1172    if (catchup_timer_jiffies(base)) {
1173        spin_unlock_irq(&base->lock);
1174        return;
1175    }
1176    while (time_after_eq(jiffies, base->timer_jiffies)) {
1177        struct list_head work_list;
1178        struct list_head *head = &work_list;
1179        int index = base->timer_jiffies & TVR_MASK;
1180
1181        /*
1182         * Cascade timers:
1183         */
1184        if (!index &&
1185            (!cascade(base, &base->tv2, INDEX(0))) &&
1186                (!cascade(base, &base->tv3, INDEX(1))) &&
1187                    !cascade(base, &base->tv4, INDEX(2)))
1188            cascade(base, &base->tv5, INDEX(3));
1189        ++base->timer_jiffies;
1190        list_replace_init(base->tv1.vec + index, head);
1191        while (!list_empty(head)) {
1192            void (*fn)(unsigned long);
1193            unsigned long data;
1194            bool irqsafe;
1195
1196            timer = list_first_entry(head, struct timer_list,entry);
1197            fn = timer->function;
1198            data = timer->data;
1199            irqsafe = tbase_get_irqsafe(timer->base);
1200
1201            timer_stats_account_timer(timer);
1202
1203            base->running_timer = timer;
1204            detach_expired_timer(timer, base);
1205
1206            if (irqsafe) {
1207                spin_unlock(&base->lock);
1208                call_timer_fn(timer, fn, data);
1209                spin_lock(&base->lock);
1210            } else {
1211                spin_unlock_irq(&base->lock);
1212                call_timer_fn(timer, fn, data);
1213                spin_lock_irq(&base->lock);
1214            }
1215        }
1216    }
1217    base->running_timer = NULL;
1218    spin_unlock_irq(&base->lock);
1219}
1220
1221#ifdef CONFIG_NO_HZ_COMMON
1222/*
1223 * Find out when the next timer event is due to happen. This
1224 * is used on S/390 to stop all activity when a CPU is idle.
1225 * This function needs to be called with interrupts disabled.
1226 */
1227static unsigned long __next_timer_interrupt(struct tvec_base *base)
1228{
1229    unsigned long timer_jiffies = base->timer_jiffies;
1230    unsigned long expires = timer_jiffies + NEXT_TIMER_MAX_DELTA;
1231    int index, slot, array, found = 0;
1232    struct timer_list *nte;
1233    struct tvec *varray[4];
1234
1235    /* Look for timer events in tv1. */
1236    index = slot = timer_jiffies & TVR_MASK;
1237    do {
1238        list_for_each_entry(nte, base->tv1.vec + slot, entry) {
1239            if (tbase_get_deferrable(nte->base))
1240                continue;
1241
1242            found = 1;
1243            expires = nte->expires;
1244            /* Look at the cascade bucket(s)? */
1245            if (!index || slot < index)
1246                goto cascade;
1247            return expires;
1248        }
1249        slot = (slot + 1) & TVR_MASK;
1250    } while (slot != index);
1251
1252cascade:
1253    /* Calculate the next cascade event */
1254    if (index)
1255        timer_jiffies += TVR_SIZE - index;
1256    timer_jiffies >>= TVR_BITS;
1257
1258    /* Check tv2-tv5. */
1259    varray[0] = &base->tv2;
1260    varray[1] = &base->tv3;
1261    varray[2] = &base->tv4;
1262    varray[3] = &base->tv5;
1263
1264    for (array = 0; array < 4; array++) {
1265        struct tvec *varp = varray[array];
1266
1267        index = slot = timer_jiffies & TVN_MASK;
1268        do {
1269            list_for_each_entry(nte, varp->vec + slot, entry) {
1270                if (tbase_get_deferrable(nte->base))
1271                    continue;
1272
1273                found = 1;
1274                if (time_before(nte->expires, expires))
1275                    expires = nte->expires;
1276            }
1277            /*
1278             * Do we still search for the first timer or are
1279             * we looking up the cascade buckets ?
1280             */
1281            if (found) {
1282                /* Look at the cascade bucket(s)? */
1283                if (!index || slot < index)
1284                    break;
1285                return expires;
1286            }
1287            slot = (slot + 1) & TVN_MASK;
1288        } while (slot != index);
1289
1290        if (index)
1291            timer_jiffies += TVN_SIZE - index;
1292        timer_jiffies >>= TVN_BITS;
1293    }
1294    return expires;
1295}
1296
1297/*
1298 * Check, if the next hrtimer event is before the next timer wheel
1299 * event:
1300 */
1301static unsigned long cmp_next_hrtimer_event(unsigned long now,
1302                        unsigned long expires)
1303{
1304    ktime_t hr_delta = hrtimer_get_next_event();
1305    struct timespec tsdelta;
1306    unsigned long delta;
1307
1308    if (hr_delta.tv64 == KTIME_MAX)
1309        return expires;
1310
1311    /*
1312     * Expired timer available, let it expire in the next tick
1313     */
1314    if (hr_delta.tv64 <= 0)
1315        return now + 1;
1316
1317    tsdelta = ktime_to_timespec(hr_delta);
1318    delta = timespec_to_jiffies(&tsdelta);
1319
1320    /*
1321     * Limit the delta to the max value, which is checked in
1322     * tick_nohz_stop_sched_tick():
1323     */
1324    if (delta > NEXT_TIMER_MAX_DELTA)
1325        delta = NEXT_TIMER_MAX_DELTA;
1326
1327    /*
1328     * Take rounding errors in to account and make sure, that it
1329     * expires in the next tick. Otherwise we go into an endless
1330     * ping pong due to tick_nohz_stop_sched_tick() retriggering
1331     * the timer softirq
1332     */
1333    if (delta < 1)
1334        delta = 1;
1335    now += delta;
1336    if (time_before(now, expires))
1337        return now;
1338    return expires;
1339}
1340
1341/**
1342 * get_next_timer_interrupt - return the jiffy of the next pending timer
1343 * @now: current time (in jiffies)
1344 */
1345unsigned long get_next_timer_interrupt(unsigned long now)
1346{
1347    struct tvec_base *base = __this_cpu_read(tvec_bases);
1348    unsigned long expires = now + NEXT_TIMER_MAX_DELTA;
1349
1350    /*
1351     * Pretend that there is no timer pending if the cpu is offline.
1352     * Possible pending timers will be migrated later to an active cpu.
1353     */
1354    if (cpu_is_offline(smp_processor_id()))
1355        return expires;
1356
1357    spin_lock(&base->lock);
1358    if (base->active_timers) {
1359        if (time_before_eq(base->next_timer, base->timer_jiffies))
1360            base->next_timer = __next_timer_interrupt(base);
1361        expires = base->next_timer;
1362    }
1363    spin_unlock(&base->lock);
1364
1365    if (time_before_eq(expires, now))
1366        return now;
1367
1368    return cmp_next_hrtimer_event(now, expires);
1369}
1370#endif
1371
1372/*
1373 * Called from the timer interrupt handler to charge one tick to the current
1374 * process. user_tick is 1 if the tick is user time, 0 for system.
1375 */
1376void update_process_times(int user_tick)
1377{
1378    struct task_struct *p = current;
1379    int cpu = smp_processor_id();
1380
1381    /* Note: this timer irq context must be accounted for as well. */
1382    account_process_tick(p, user_tick);
1383    run_local_timers();
1384    rcu_check_callbacks(cpu, user_tick);
1385#ifdef CONFIG_IRQ_WORK
1386    if (in_irq())
1387        irq_work_run();
1388#endif
1389    scheduler_tick();
1390    run_posix_cpu_timers(p);
1391}
1392
1393/*
1394 * This function runs timers and the timer-tq in bottom half context.
1395 */
1396static void run_timer_softirq(struct softirq_action *h)
1397{
1398    struct tvec_base *base = __this_cpu_read(tvec_bases);
1399
1400    hrtimer_run_pending();
1401
1402    if (time_after_eq(jiffies, base->timer_jiffies))
1403        __run_timers(base);
1404}
1405
1406/*
1407 * Called by the local, per-CPU timer interrupt on SMP.
1408 */
1409void run_local_timers(void)
1410{
1411    hrtimer_run_queues();
1412    raise_softirq(TIMER_SOFTIRQ);
1413}
1414
1415#ifdef __ARCH_WANT_SYS_ALARM
1416
1417/*
1418 * For backwards compatibility? This can be done in libc so Alpha
1419 * and all newer ports shouldn't need it.
1420 */
1421SYSCALL_DEFINE1(alarm, unsigned int, seconds)
1422{
1423    return alarm_setitimer(seconds);
1424}
1425
1426#endif
1427
1428static void process_timeout(unsigned long __data)
1429{
1430    wake_up_process((struct task_struct *)__data);
1431}
1432
1433/**
1434 * schedule_timeout - sleep until timeout
1435 * @timeout: timeout value in jiffies
1436 *
1437 * Make the current task sleep until @timeout jiffies have
1438 * elapsed. The routine will return immediately unless
1439 * the current task state has been set (see set_current_state()).
1440 *
1441 * You can set the task state as follows -
1442 *
1443 * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1444 * pass before the routine returns. The routine will return 0
1445 *
1446 * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1447 * delivered to the current task. In this case the remaining time
1448 * in jiffies will be returned, or 0 if the timer expired in time
1449 *
1450 * The current task state is guaranteed to be TASK_RUNNING when this
1451 * routine returns.
1452 *
1453 * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1454 * the CPU away without a bound on the timeout. In this case the return
1455 * value will be %MAX_SCHEDULE_TIMEOUT.
1456 *
1457 * In all cases the return value is guaranteed to be non-negative.
1458 */
1459signed long __sched schedule_timeout(signed long timeout)
1460{
1461    struct timer_list timer;
1462    unsigned long expire;
1463
1464    switch (timeout)
1465    {
1466    case MAX_SCHEDULE_TIMEOUT:
1467        /*
1468         * These two special cases are useful to be comfortable
1469         * in the caller. Nothing more. We could take
1470         * MAX_SCHEDULE_TIMEOUT from one of the negative value
1471         * but I' d like to return a valid offset (>=0) to allow
1472         * the caller to do everything it want with the retval.
1473         */
1474        schedule();
1475        goto out;
1476    default:
1477        /*
1478         * Another bit of PARANOID. Note that the retval will be
1479         * 0 since no piece of kernel is supposed to do a check
1480         * for a negative retval of schedule_timeout() (since it
1481         * should never happens anyway). You just have the printk()
1482         * that will tell you if something is gone wrong and where.
1483         */
1484        if (timeout < 0) {
1485            printk(KERN_ERR "schedule_timeout: wrong timeout "
1486                "value %lx\n", timeout);
1487            dump_stack();
1488            current->state = TASK_RUNNING;
1489            goto out;
1490        }
1491    }
1492
1493    expire = timeout + jiffies;
1494
1495    setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);
1496    __mod_timer(&timer, expire, false, TIMER_NOT_PINNED);
1497    schedule();
1498    del_singleshot_timer_sync(&timer);
1499
1500    /* Remove the timer from the object tracker */
1501    destroy_timer_on_stack(&timer);
1502
1503    timeout = expire - jiffies;
1504
1505 out:
1506    return timeout < 0 ? 0 : timeout;
1507}
1508EXPORT_SYMBOL(schedule_timeout);
1509
1510/*
1511 * We can use __set_current_state() here because schedule_timeout() calls
1512 * schedule() unconditionally.
1513 */
1514signed long __sched schedule_timeout_interruptible(signed long timeout)
1515{
1516    __set_current_state(TASK_INTERRUPTIBLE);
1517    return schedule_timeout(timeout);
1518}
1519EXPORT_SYMBOL(schedule_timeout_interruptible);
1520
1521signed long __sched schedule_timeout_killable(signed long timeout)
1522{
1523    __set_current_state(TASK_KILLABLE);
1524    return schedule_timeout(timeout);
1525}
1526EXPORT_SYMBOL(schedule_timeout_killable);
1527
1528signed long __sched schedule_timeout_uninterruptible(signed long timeout)
1529{
1530    __set_current_state(TASK_UNINTERRUPTIBLE);
1531    return schedule_timeout(timeout);
1532}
1533EXPORT_SYMBOL(schedule_timeout_uninterruptible);
1534
1535static int init_timers_cpu(int cpu)
1536{
1537    int j;
1538    struct tvec_base *base;
1539    static char tvec_base_done[NR_CPUS];
1540
1541    if (!tvec_base_done[cpu]) {
1542        static char boot_done;
1543
1544        if (boot_done) {
1545            /*
1546             * The APs use this path later in boot
1547             */
1548            base = kzalloc_node(sizeof(*base), GFP_KERNEL,
1549                        cpu_to_node(cpu));
1550            if (!base)
1551                return -ENOMEM;
1552
1553            /* Make sure tvec_base has TIMER_FLAG_MASK bits free */
1554            if (WARN_ON(base != tbase_get_base(base))) {
1555                kfree(base);
1556                return -ENOMEM;
1557            }
1558            per_cpu(tvec_bases, cpu) = base;
1559        } else {
1560            /*
1561             * This is for the boot CPU - we use compile-time
1562             * static initialisation because per-cpu memory isn't
1563             * ready yet and because the memory allocators are not
1564             * initialised either.
1565             */
1566            boot_done = 1;
1567            base = &boot_tvec_bases;
1568        }
1569        spin_lock_init(&base->lock);
1570        tvec_base_done[cpu] = 1;
1571    } else {
1572        base = per_cpu(tvec_bases, cpu);
1573    }
1574
1575
1576    for (j = 0; j < TVN_SIZE; j++) {
1577        INIT_LIST_HEAD(base->tv5.vec + j);
1578        INIT_LIST_HEAD(base->tv4.vec + j);
1579        INIT_LIST_HEAD(base->tv3.vec + j);
1580        INIT_LIST_HEAD(base->tv2.vec + j);
1581    }
1582    for (j = 0; j < TVR_SIZE; j++)
1583        INIT_LIST_HEAD(base->tv1.vec + j);
1584
1585    base->timer_jiffies = jiffies;
1586    base->next_timer = base->timer_jiffies;
1587    base->active_timers = 0;
1588    base->all_timers = 0;
1589    return 0;
1590}
1591
1592#ifdef CONFIG_HOTPLUG_CPU
1593static void migrate_timer_list(struct tvec_base *new_base, struct list_head *head)
1594{
1595    struct timer_list *timer;
1596
1597    while (!list_empty(head)) {
1598        timer = list_first_entry(head, struct timer_list, entry);
1599        /* We ignore the accounting on the dying cpu */
1600        detach_timer(timer, false);
1601        timer_set_base(timer, new_base);
1602        internal_add_timer(new_base, timer);
1603    }
1604}
1605
1606static void migrate_timers(int cpu)
1607{
1608    struct tvec_base *old_base;
1609    struct tvec_base *new_base;
1610    int i;
1611
1612    BUG_ON(cpu_online(cpu));
1613    old_base = per_cpu(tvec_bases, cpu);
1614    new_base = get_cpu_var(tvec_bases);
1615    /*
1616     * The caller is globally serialized and nobody else
1617     * takes two locks at once, deadlock is not possible.
1618     */
1619    spin_lock_irq(&new_base->lock);
1620    spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
1621
1622    BUG_ON(old_base->running_timer);
1623
1624    for (i = 0; i < TVR_SIZE; i++)
1625        migrate_timer_list(new_base, old_base->tv1.vec + i);
1626    for (i = 0; i < TVN_SIZE; i++) {
1627        migrate_timer_list(new_base, old_base->tv2.vec + i);
1628        migrate_timer_list(new_base, old_base->tv3.vec + i);
1629        migrate_timer_list(new_base, old_base->tv4.vec + i);
1630        migrate_timer_list(new_base, old_base->tv5.vec + i);
1631    }
1632
1633    spin_unlock(&old_base->lock);
1634    spin_unlock_irq(&new_base->lock);
1635    put_cpu_var(tvec_bases);
1636}
1637#endif /* CONFIG_HOTPLUG_CPU */
1638
1639static int timer_cpu_notify(struct notifier_block *self,
1640                unsigned long action, void *hcpu)
1641{
1642    long cpu = (long)hcpu;
1643    int err;
1644
1645    switch(action) {
1646    case CPU_UP_PREPARE:
1647    case CPU_UP_PREPARE_FROZEN:
1648        err = init_timers_cpu(cpu);
1649        if (err < 0)
1650            return notifier_from_errno(err);
1651        break;
1652#ifdef CONFIG_HOTPLUG_CPU
1653    case CPU_DEAD:
1654    case CPU_DEAD_FROZEN:
1655        migrate_timers(cpu);
1656        break;
1657#endif
1658    default:
1659        break;
1660    }
1661    return NOTIFY_OK;
1662}
1663
1664static struct notifier_block timers_nb = {
1665    .notifier_call = timer_cpu_notify,
1666};
1667
1668
1669void __init init_timers(void)
1670{
1671    int err;
1672
1673    /* ensure there are enough low bits for flags in timer->base pointer */
1674    BUILD_BUG_ON(__alignof__(struct tvec_base) & TIMER_FLAG_MASK);
1675
1676    err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
1677                   (void *)(long)smp_processor_id());
1678    BUG_ON(err != NOTIFY_OK);
1679
1680    init_timer_stats();
1681    register_cpu_notifier(&timers_nb);
1682    open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
1683}
1684
1685/**
1686 * msleep - sleep safely even with waitqueue interruptions
1687 * @msecs: Time in milliseconds to sleep for
1688 */
1689void msleep(unsigned int msecs)
1690{
1691    unsigned long timeout = msecs_to_jiffies(msecs) + 1;
1692
1693    while (timeout)
1694        timeout = schedule_timeout_uninterruptible(timeout);
1695}
1696
1697EXPORT_SYMBOL(msleep);
1698
1699/**
1700 * msleep_interruptible - sleep waiting for signals
1701 * @msecs: Time in milliseconds to sleep for
1702 */
1703unsigned long msleep_interruptible(unsigned int msecs)
1704{
1705    unsigned long timeout = msecs_to_jiffies(msecs) + 1;
1706
1707    while (timeout && !signal_pending(current))
1708        timeout = schedule_timeout_interruptible(timeout);
1709    return jiffies_to_msecs(timeout);
1710}
1711
1712EXPORT_SYMBOL(msleep_interruptible);
1713
1714static int __sched do_usleep_range(unsigned long min, unsigned long max)
1715{
1716    ktime_t kmin;
1717    unsigned long delta;
1718
1719    kmin = ktime_set(0, min * NSEC_PER_USEC);
1720    delta = (max - min) * NSEC_PER_USEC;
1721    return schedule_hrtimeout_range(&kmin, delta, HRTIMER_MODE_REL);
1722}
1723
1724/**
1725 * usleep_range - Drop in replacement for udelay where wakeup is flexible
1726 * @min: Minimum time in usecs to sleep
1727 * @max: Maximum time in usecs to sleep
1728 */
1729void usleep_range(unsigned long min, unsigned long max)
1730{
1731    __set_current_state(TASK_UNINTERRUPTIBLE);
1732    do_usleep_range(min, max);
1733}
1734EXPORT_SYMBOL(usleep_range);
1735

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