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TOMOYO Linux Cross Reference
Linux/kernel/timer.c

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  1 /*
  2  *  linux/kernel/timer.c
  3  *
  4  *  Kernel internal timers, basic process system calls
  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/slab.h>
 43 
 44 #include <asm/uaccess.h>
 45 #include <asm/unistd.h>
 46 #include <asm/div64.h>
 47 #include <asm/timex.h>
 48 #include <asm/io.h>
 49 
 50 #define CREATE_TRACE_POINTS
 51 #include <trace/events/timer.h>
 52 
 53 u64 jiffies_64 __cacheline_aligned_in_smp = INITIAL_JIFFIES;
 54 
 55 EXPORT_SYMBOL(jiffies_64);
 56 
 57 /*
 58  * per-CPU timer vector definitions:
 59  */
 60 #define TVN_BITS (CONFIG_BASE_SMALL ? 4 : 6)
 61 #define TVR_BITS (CONFIG_BASE_SMALL ? 6 : 8)
 62 #define TVN_SIZE (1 << TVN_BITS)
 63 #define TVR_SIZE (1 << TVR_BITS)
 64 #define TVN_MASK (TVN_SIZE - 1)
 65 #define TVR_MASK (TVR_SIZE - 1)
 66 
 67 struct tvec {
 68         struct list_head vec[TVN_SIZE];
 69 };
 70 
 71 struct tvec_root {
 72         struct list_head vec[TVR_SIZE];
 73 };
 74 
 75 struct tvec_base {
 76         spinlock_t lock;
 77         struct timer_list *running_timer;
 78         unsigned long timer_jiffies;
 79         unsigned long next_timer;
 80         struct tvec_root tv1;
 81         struct tvec tv2;
 82         struct tvec tv3;
 83         struct tvec tv4;
 84         struct tvec tv5;
 85 } ____cacheline_aligned;
 86 
 87 struct tvec_base boot_tvec_bases;
 88 EXPORT_SYMBOL(boot_tvec_bases);
 89 static DEFINE_PER_CPU(struct tvec_base *, tvec_bases) = &boot_tvec_bases;
 90 
 91 /* Functions below help us manage 'deferrable' flag */
 92 static inline unsigned int tbase_get_deferrable(struct tvec_base *base)
 93 {
 94         return ((unsigned int)(unsigned long)base & TBASE_DEFERRABLE_FLAG);
 95 }
 96 
 97 static inline struct tvec_base *tbase_get_base(struct tvec_base *base)
 98 {
 99         return ((struct tvec_base *)((unsigned long)base & ~TBASE_DEFERRABLE_FLAG));
100 }
101 
102 static inline void timer_set_deferrable(struct timer_list *timer)
103 {
104         timer->base = TBASE_MAKE_DEFERRED(timer->base);
105 }
106 
107 static inline void
108 timer_set_base(struct timer_list *timer, struct tvec_base *new_base)
109 {
110         timer->base = (struct tvec_base *)((unsigned long)(new_base) |
111                                       tbase_get_deferrable(timer->base));
112 }
113 
114 static unsigned long round_jiffies_common(unsigned long j, int cpu,
115                 bool force_up)
116 {
117         int rem;
118         unsigned long original = j;
119 
120         /*
121          * We don't want all cpus firing their timers at once hitting the
122          * same lock or cachelines, so we skew each extra cpu with an extra
123          * 3 jiffies. This 3 jiffies came originally from the mm/ code which
124          * already did this.
125          * The skew is done by adding 3*cpunr, then round, then subtract this
126          * extra offset again.
127          */
128         j += cpu * 3;
129 
130         rem = j % HZ;
131 
132         /*
133          * If the target jiffie is just after a whole second (which can happen
134          * due to delays of the timer irq, long irq off times etc etc) then
135          * we should round down to the whole second, not up. Use 1/4th second
136          * as cutoff for this rounding as an extreme upper bound for this.
137          * But never round down if @force_up is set.
138          */
139         if (rem < HZ/4 && !force_up) /* round down */
140                 j = j - rem;
141         else /* round up */
142                 j = j - rem + HZ;
143 
144         /* now that we have rounded, subtract the extra skew again */
145         j -= cpu * 3;
146 
147         if (j <= jiffies) /* rounding ate our timeout entirely; */
148                 return original;
149         return j;
150 }
151 
152 /**
153  * __round_jiffies - function to round jiffies to a full second
154  * @j: the time in (absolute) jiffies that should be rounded
155  * @cpu: the processor number on which the timeout will happen
156  *
157  * __round_jiffies() rounds an absolute time in the future (in jiffies)
158  * up or down to (approximately) full seconds. This is useful for timers
159  * for which the exact time they fire does not matter too much, as long as
160  * they fire approximately every X seconds.
161  *
162  * By rounding these timers to whole seconds, all such timers will fire
163  * at the same time, rather than at various times spread out. The goal
164  * of this is to have the CPU wake up less, which saves power.
165  *
166  * The exact rounding is skewed for each processor to avoid all
167  * processors firing at the exact same time, which could lead
168  * to lock contention or spurious cache line bouncing.
169  *
170  * The return value is the rounded version of the @j parameter.
171  */
172 unsigned long __round_jiffies(unsigned long j, int cpu)
173 {
174         return round_jiffies_common(j, cpu, false);
175 }
176 EXPORT_SYMBOL_GPL(__round_jiffies);
177 
178 /**
179  * __round_jiffies_relative - function to round jiffies to a full second
180  * @j: the time in (relative) jiffies that should be rounded
181  * @cpu: the processor number on which the timeout will happen
182  *
183  * __round_jiffies_relative() rounds a time delta  in the future (in jiffies)
184  * up or down to (approximately) full seconds. This is useful for timers
185  * for which the exact time they fire does not matter too much, as long as
186  * they fire approximately every X seconds.
187  *
188  * By rounding these timers to whole seconds, all such timers will fire
189  * at the same time, rather than at various times spread out. The goal
190  * of this is to have the CPU wake up less, which saves power.
191  *
192  * The exact rounding is skewed for each processor to avoid all
193  * processors firing at the exact same time, which could lead
194  * to lock contention or spurious cache line bouncing.
195  *
196  * The return value is the rounded version of the @j parameter.
197  */
198 unsigned long __round_jiffies_relative(unsigned long j, int cpu)
199 {
200         unsigned long j0 = jiffies;
201 
202         /* Use j0 because jiffies might change while we run */
203         return round_jiffies_common(j + j0, cpu, false) - j0;
204 }
205 EXPORT_SYMBOL_GPL(__round_jiffies_relative);
206 
207 /**
208  * round_jiffies - function to round jiffies to a full second
209  * @j: the time in (absolute) jiffies that should be rounded
210  *
211  * round_jiffies() rounds an absolute time in the future (in jiffies)
212  * up or down to (approximately) full seconds. This is useful for timers
213  * for which the exact time they fire does not matter too much, as long as
214  * they fire approximately every X seconds.
215  *
216  * By rounding these timers to whole seconds, all such timers will fire
217  * at the same time, rather than at various times spread out. The goal
218  * of this is to have the CPU wake up less, which saves power.
219  *
220  * The return value is the rounded version of the @j parameter.
221  */
222 unsigned long round_jiffies(unsigned long j)
223 {
224         return round_jiffies_common(j, raw_smp_processor_id(), false);
225 }
226 EXPORT_SYMBOL_GPL(round_jiffies);
227 
228 /**
229  * round_jiffies_relative - function to round jiffies to a full second
230  * @j: the time in (relative) jiffies that should be rounded
231  *
232  * round_jiffies_relative() rounds a time delta  in the future (in jiffies)
233  * up or down to (approximately) full seconds. This is useful for timers
234  * for which the exact time they fire does not matter too much, as long as
235  * they fire approximately every X seconds.
236  *
237  * By rounding these timers to whole seconds, all such timers will fire
238  * at the same time, rather than at various times spread out. The goal
239  * of this is to have the CPU wake up less, which saves power.
240  *
241  * The return value is the rounded version of the @j parameter.
242  */
243 unsigned long round_jiffies_relative(unsigned long j)
244 {
245         return __round_jiffies_relative(j, raw_smp_processor_id());
246 }
247 EXPORT_SYMBOL_GPL(round_jiffies_relative);
248 
249 /**
250  * __round_jiffies_up - function to round jiffies up to a full second
251  * @j: the time in (absolute) jiffies that should be rounded
252  * @cpu: the processor number on which the timeout will happen
253  *
254  * This is the same as __round_jiffies() except that it will never
255  * round down.  This is useful for timeouts for which the exact time
256  * of firing does not matter too much, as long as they don't fire too
257  * early.
258  */
259 unsigned long __round_jiffies_up(unsigned long j, int cpu)
260 {
261         return round_jiffies_common(j, cpu, true);
262 }
263 EXPORT_SYMBOL_GPL(__round_jiffies_up);
264 
265 /**
266  * __round_jiffies_up_relative - function to round jiffies up to a full second
267  * @j: the time in (relative) jiffies that should be rounded
268  * @cpu: the processor number on which the timeout will happen
269  *
270  * This is the same as __round_jiffies_relative() except that it will never
271  * round down.  This is useful for timeouts for which the exact time
272  * of firing does not matter too much, as long as they don't fire too
273  * early.
274  */
275 unsigned long __round_jiffies_up_relative(unsigned long j, int cpu)
276 {
277         unsigned long j0 = jiffies;
278 
279         /* Use j0 because jiffies might change while we run */
280         return round_jiffies_common(j + j0, cpu, true) - j0;
281 }
282 EXPORT_SYMBOL_GPL(__round_jiffies_up_relative);
283 
284 /**
285  * round_jiffies_up - function to round jiffies up to a full second
286  * @j: the time in (absolute) jiffies that should be rounded
287  *
288  * This is the same as round_jiffies() except that it will never
289  * round down.  This is useful for timeouts for which the exact time
290  * of firing does not matter too much, as long as they don't fire too
291  * early.
292  */
293 unsigned long round_jiffies_up(unsigned long j)
294 {
295         return round_jiffies_common(j, raw_smp_processor_id(), true);
296 }
297 EXPORT_SYMBOL_GPL(round_jiffies_up);
298 
299 /**
300  * round_jiffies_up_relative - function to round jiffies up to a full second
301  * @j: the time in (relative) jiffies that should be rounded
302  *
303  * This is the same as round_jiffies_relative() except that it will never
304  * round down.  This is useful for timeouts for which the exact time
305  * of firing does not matter too much, as long as they don't fire too
306  * early.
307  */
308 unsigned long round_jiffies_up_relative(unsigned long j)
309 {
310         return __round_jiffies_up_relative(j, raw_smp_processor_id());
311 }
312 EXPORT_SYMBOL_GPL(round_jiffies_up_relative);
313 
314 /**
315  * set_timer_slack - set the allowed slack for a timer
316  * @timer: the timer to be modified
317  * @slack_hz: the amount of time (in jiffies) allowed for rounding
318  *
319  * Set the amount of time, in jiffies, that a certain timer has
320  * in terms of slack. By setting this value, the timer subsystem
321  * will schedule the actual timer somewhere between
322  * the time mod_timer() asks for, and that time plus the slack.
323  *
324  * By setting the slack to -1, a percentage of the delay is used
325  * instead.
326  */
327 void set_timer_slack(struct timer_list *timer, int slack_hz)
328 {
329         timer->slack = slack_hz;
330 }
331 EXPORT_SYMBOL_GPL(set_timer_slack);
332 
333 static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
334 {
335         unsigned long expires = timer->expires;
336         unsigned long idx = expires - base->timer_jiffies;
337         struct list_head *vec;
338 
339         if (idx < TVR_SIZE) {
340                 int i = expires & TVR_MASK;
341                 vec = base->tv1.vec + i;
342         } else if (idx < 1 << (TVR_BITS + TVN_BITS)) {
343                 int i = (expires >> TVR_BITS) & TVN_MASK;
344                 vec = base->tv2.vec + i;
345         } else if (idx < 1 << (TVR_BITS + 2 * TVN_BITS)) {
346                 int i = (expires >> (TVR_BITS + TVN_BITS)) & TVN_MASK;
347                 vec = base->tv3.vec + i;
348         } else if (idx < 1 << (TVR_BITS + 3 * TVN_BITS)) {
349                 int i = (expires >> (TVR_BITS + 2 * TVN_BITS)) & TVN_MASK;
350                 vec = base->tv4.vec + i;
351         } else if ((signed long) idx < 0) {
352                 /*
353                  * Can happen if you add a timer with expires == jiffies,
354                  * or you set a timer to go off in the past
355                  */
356                 vec = base->tv1.vec + (base->timer_jiffies & TVR_MASK);
357         } else {
358                 int i;
359                 /* If the timeout is larger than 0xffffffff on 64-bit
360                  * architectures then we use the maximum timeout:
361                  */
362                 if (idx > 0xffffffffUL) {
363                         idx = 0xffffffffUL;
364                         expires = idx + base->timer_jiffies;
365                 }
366                 i = (expires >> (TVR_BITS + 3 * TVN_BITS)) & TVN_MASK;
367                 vec = base->tv5.vec + i;
368         }
369         /*
370          * Timers are FIFO:
371          */
372         list_add_tail(&timer->entry, vec);
373 }
374 
375 #ifdef CONFIG_TIMER_STATS
376 void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr)
377 {
378         if (timer->start_site)
379                 return;
380 
381         timer->start_site = addr;
382         memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
383         timer->start_pid = current->pid;
384 }
385 
386 static void timer_stats_account_timer(struct timer_list *timer)
387 {
388         unsigned int flag = 0;
389 
390         if (likely(!timer->start_site))
391                 return;
392         if (unlikely(tbase_get_deferrable(timer->base)))
393                 flag |= TIMER_STATS_FLAG_DEFERRABLE;
394 
395         timer_stats_update_stats(timer, timer->start_pid, timer->start_site,
396                                  timer->function, timer->start_comm, flag);
397 }
398 
399 #else
400 static void timer_stats_account_timer(struct timer_list *timer) {}
401 #endif
402 
403 #ifdef CONFIG_DEBUG_OBJECTS_TIMERS
404 
405 static struct debug_obj_descr timer_debug_descr;
406 
407 static void *timer_debug_hint(void *addr)
408 {
409         return ((struct timer_list *) addr)->function;
410 }
411 
412 /*
413  * fixup_init is called when:
414  * - an active object is initialized
415  */
416 static int timer_fixup_init(void *addr, enum debug_obj_state state)
417 {
418         struct timer_list *timer = addr;
419 
420         switch (state) {
421         case ODEBUG_STATE_ACTIVE:
422                 del_timer_sync(timer);
423                 debug_object_init(timer, &timer_debug_descr);
424                 return 1;
425         default:
426                 return 0;
427         }
428 }
429 
430 /* Stub timer callback for improperly used timers. */
431 static void stub_timer(unsigned long data)
432 {
433         WARN_ON(1);
434 }
435 
436 /*
437  * fixup_activate is called when:
438  * - an active object is activated
439  * - an unknown object is activated (might be a statically initialized object)
440  */
441 static int timer_fixup_activate(void *addr, enum debug_obj_state state)
442 {
443         struct timer_list *timer = addr;
444 
445         switch (state) {
446 
447         case ODEBUG_STATE_NOTAVAILABLE:
448                 /*
449                  * This is not really a fixup. The timer was
450                  * statically initialized. We just make sure that it
451                  * is tracked in the object tracker.
452                  */
453                 if (timer->entry.next == NULL &&
454                     timer->entry.prev == TIMER_ENTRY_STATIC) {
455                         debug_object_init(timer, &timer_debug_descr);
456                         debug_object_activate(timer, &timer_debug_descr);
457                         return 0;
458                 } else {
459                         setup_timer(timer, stub_timer, 0);
460                         return 1;
461                 }
462                 return 0;
463 
464         case ODEBUG_STATE_ACTIVE:
465                 WARN_ON(1);
466 
467         default:
468                 return 0;
469         }
470 }
471 
472 /*
473  * fixup_free is called when:
474  * - an active object is freed
475  */
476 static int timer_fixup_free(void *addr, enum debug_obj_state state)
477 {
478         struct timer_list *timer = addr;
479 
480         switch (state) {
481         case ODEBUG_STATE_ACTIVE:
482                 del_timer_sync(timer);
483                 debug_object_free(timer, &timer_debug_descr);
484                 return 1;
485         default:
486                 return 0;
487         }
488 }
489 
490 /*
491  * fixup_assert_init is called when:
492  * - an untracked/uninit-ed object is found
493  */
494 static int timer_fixup_assert_init(void *addr, enum debug_obj_state state)
495 {
496         struct timer_list *timer = addr;
497 
498         switch (state) {
499         case ODEBUG_STATE_NOTAVAILABLE:
500                 if (timer->entry.prev == TIMER_ENTRY_STATIC) {
501                         /*
502                          * This is not really a fixup. The timer was
503                          * statically initialized. We just make sure that it
504                          * is tracked in the object tracker.
505                          */
506                         debug_object_init(timer, &timer_debug_descr);
507                         return 0;
508                 } else {
509                         setup_timer(timer, stub_timer, 0);
510                         return 1;
511                 }
512         default:
513                 return 0;
514         }
515 }
516 
517 static struct debug_obj_descr timer_debug_descr = {
518         .name                   = "timer_list",
519         .debug_hint             = timer_debug_hint,
520         .fixup_init             = timer_fixup_init,
521         .fixup_activate         = timer_fixup_activate,
522         .fixup_free             = timer_fixup_free,
523         .fixup_assert_init      = timer_fixup_assert_init,
524 };
525 
526 static inline void debug_timer_init(struct timer_list *timer)
527 {
528         debug_object_init(timer, &timer_debug_descr);
529 }
530 
531 static inline void debug_timer_activate(struct timer_list *timer)
532 {
533         debug_object_activate(timer, &timer_debug_descr);
534 }
535 
536 static inline void debug_timer_deactivate(struct timer_list *timer)
537 {
538         debug_object_deactivate(timer, &timer_debug_descr);
539 }
540 
541 static inline void debug_timer_free(struct timer_list *timer)
542 {
543         debug_object_free(timer, &timer_debug_descr);
544 }
545 
546 static inline void debug_timer_assert_init(struct timer_list *timer)
547 {
548         debug_object_assert_init(timer, &timer_debug_descr);
549 }
550 
551 static void __init_timer(struct timer_list *timer,
552                          const char *name,
553                          struct lock_class_key *key);
554 
555 void init_timer_on_stack_key(struct timer_list *timer,
556                              const char *name,
557                              struct lock_class_key *key)
558 {
559         debug_object_init_on_stack(timer, &timer_debug_descr);
560         __init_timer(timer, name, key);
561 }
562 EXPORT_SYMBOL_GPL(init_timer_on_stack_key);
563 
564 void destroy_timer_on_stack(struct timer_list *timer)
565 {
566         debug_object_free(timer, &timer_debug_descr);
567 }
568 EXPORT_SYMBOL_GPL(destroy_timer_on_stack);
569 
570 #else
571 static inline void debug_timer_init(struct timer_list *timer) { }
572 static inline void debug_timer_activate(struct timer_list *timer) { }
573 static inline void debug_timer_deactivate(struct timer_list *timer) { }
574 static inline void debug_timer_assert_init(struct timer_list *timer) { }
575 #endif
576 
577 static inline void debug_init(struct timer_list *timer)
578 {
579         debug_timer_init(timer);
580         trace_timer_init(timer);
581 }
582 
583 static inline void
584 debug_activate(struct timer_list *timer, unsigned long expires)
585 {
586         debug_timer_activate(timer);
587         trace_timer_start(timer, expires);
588 }
589 
590 static inline void debug_deactivate(struct timer_list *timer)
591 {
592         debug_timer_deactivate(timer);
593         trace_timer_cancel(timer);
594 }
595 
596 static inline void debug_assert_init(struct timer_list *timer)
597 {
598         debug_timer_assert_init(timer);
599 }
600 
601 static void __init_timer(struct timer_list *timer,
602                          const char *name,
603                          struct lock_class_key *key)
604 {
605         timer->entry.next = NULL;
606         timer->base = __raw_get_cpu_var(tvec_bases);
607         timer->slack = -1;
608 #ifdef CONFIG_TIMER_STATS
609         timer->start_site = NULL;
610         timer->start_pid = -1;
611         memset(timer->start_comm, 0, TASK_COMM_LEN);
612 #endif
613         lockdep_init_map(&timer->lockdep_map, name, key, 0);
614 }
615 
616 void setup_deferrable_timer_on_stack_key(struct timer_list *timer,
617                                          const char *name,
618                                          struct lock_class_key *key,
619                                          void (*function)(unsigned long),
620                                          unsigned long data)
621 {
622         timer->function = function;
623         timer->data = data;
624         init_timer_on_stack_key(timer, name, key);
625         timer_set_deferrable(timer);
626 }
627 EXPORT_SYMBOL_GPL(setup_deferrable_timer_on_stack_key);
628 
629 /**
630  * init_timer_key - initialize a timer
631  * @timer: the timer to be initialized
632  * @name: name of the timer
633  * @key: lockdep class key of the fake lock used for tracking timer
634  *       sync lock dependencies
635  *
636  * init_timer_key() must be done to a timer prior calling *any* of the
637  * other timer functions.
638  */
639 void init_timer_key(struct timer_list *timer,
640                     const char *name,
641                     struct lock_class_key *key)
642 {
643         debug_init(timer);
644         __init_timer(timer, name, key);
645 }
646 EXPORT_SYMBOL(init_timer_key);
647 
648 void init_timer_deferrable_key(struct timer_list *timer,
649                                const char *name,
650                                struct lock_class_key *key)
651 {
652         init_timer_key(timer, name, key);
653         timer_set_deferrable(timer);
654 }
655 EXPORT_SYMBOL(init_timer_deferrable_key);
656 
657 static inline void detach_timer(struct timer_list *timer,
658                                 int clear_pending)
659 {
660         struct list_head *entry = &timer->entry;
661 
662         debug_deactivate(timer);
663 
664         __list_del(entry->prev, entry->next);
665         if (clear_pending)
666                 entry->next = NULL;
667         entry->prev = LIST_POISON2;
668 }
669 
670 /*
671  * We are using hashed locking: holding per_cpu(tvec_bases).lock
672  * means that all timers which are tied to this base via timer->base are
673  * locked, and the base itself is locked too.
674  *
675  * So __run_timers/migrate_timers can safely modify all timers which could
676  * be found on ->tvX lists.
677  *
678  * When the timer's base is locked, and the timer removed from list, it is
679  * possible to set timer->base = NULL and drop the lock: the timer remains
680  * locked.
681  */
682 static struct tvec_base *lock_timer_base(struct timer_list *timer,
683                                         unsigned long *flags)
684         __acquires(timer->base->lock)
685 {
686         struct tvec_base *base;
687 
688         for (;;) {
689                 struct tvec_base *prelock_base = timer->base;
690                 base = tbase_get_base(prelock_base);
691                 if (likely(base != NULL)) {
692                         spin_lock_irqsave(&base->lock, *flags);
693                         if (likely(prelock_base == timer->base))
694                                 return base;
695                         /* The timer has migrated to another CPU */
696                         spin_unlock_irqrestore(&base->lock, *flags);
697                 }
698                 cpu_relax();
699         }
700 }
701 
702 static inline int
703 __mod_timer(struct timer_list *timer, unsigned long expires,
704                                                 bool pending_only, int pinned)
705 {
706         struct tvec_base *base, *new_base;
707         unsigned long flags;
708         int ret = 0 , cpu;
709 
710         timer_stats_timer_set_start_info(timer);
711         BUG_ON(!timer->function);
712 
713         base = lock_timer_base(timer, &flags);
714 
715         if (timer_pending(timer)) {
716                 detach_timer(timer, 0);
717                 if (timer->expires == base->next_timer &&
718                     !tbase_get_deferrable(timer->base))
719                         base->next_timer = base->timer_jiffies;
720                 ret = 1;
721         } else {
722                 if (pending_only)
723                         goto out_unlock;
724         }
725 
726         debug_activate(timer, expires);
727 
728         cpu = smp_processor_id();
729 
730 #if defined(CONFIG_NO_HZ) && defined(CONFIG_SMP)
731         if (!pinned && get_sysctl_timer_migration() && idle_cpu(cpu))
732                 cpu = get_nohz_timer_target();
733 #endif
734         new_base = per_cpu(tvec_bases, cpu);
735 
736         if (base != new_base) {
737                 /*
738                  * We are trying to schedule the timer on the local CPU.
739                  * However we can't change timer's base while it is running,
740                  * otherwise del_timer_sync() can't detect that the timer's
741                  * handler yet has not finished. This also guarantees that
742                  * the timer is serialized wrt itself.
743                  */
744                 if (likely(base->running_timer != timer)) {
745                         /* See the comment in lock_timer_base() */
746                         timer_set_base(timer, NULL);
747                         spin_unlock(&base->lock);
748                         base = new_base;
749                         spin_lock(&base->lock);
750                         timer_set_base(timer, base);
751                 }
752         }
753 
754         timer->expires = expires;
755         if (time_before(timer->expires, base->next_timer) &&
756             !tbase_get_deferrable(timer->base))
757                 base->next_timer = timer->expires;
758         internal_add_timer(base, timer);
759 
760 out_unlock:
761         spin_unlock_irqrestore(&base->lock, flags);
762 
763         return ret;
764 }
765 
766 /**
767  * mod_timer_pending - modify a pending timer's timeout
768  * @timer: the pending timer to be modified
769  * @expires: new timeout in jiffies
770  *
771  * mod_timer_pending() is the same for pending timers as mod_timer(),
772  * but will not re-activate and modify already deleted timers.
773  *
774  * It is useful for unserialized use of timers.
775  */
776 int mod_timer_pending(struct timer_list *timer, unsigned long expires)
777 {
778         return __mod_timer(timer, expires, true, TIMER_NOT_PINNED);
779 }
780 EXPORT_SYMBOL(mod_timer_pending);
781 
782 /*
783  * Decide where to put the timer while taking the slack into account
784  *
785  * Algorithm:
786  *   1) calculate the maximum (absolute) time
787  *   2) calculate the highest bit where the expires and new max are different
788  *   3) use this bit to make a mask
789  *   4) use the bitmask to round down the maximum time, so that all last
790  *      bits are zeros
791  */
792 static inline
793 unsigned long apply_slack(struct timer_list *timer, unsigned long expires)
794 {
795         unsigned long expires_limit, mask;
796         int bit;
797 
798         if (timer->slack >= 0) {
799                 expires_limit = expires + timer->slack;
800         } else {
801                 long delta = expires - jiffies;
802 
803                 if (delta < 256)
804                         return expires;
805 
806                 expires_limit = expires + delta / 256;
807         }
808         mask = expires ^ expires_limit;
809         if (mask == 0)
810                 return expires;
811 
812         bit = find_last_bit(&mask, BITS_PER_LONG);
813 
814         mask = (1 << bit) - 1;
815 
816         expires_limit = expires_limit & ~(mask);
817 
818         return expires_limit;
819 }
820 
821 /**
822  * mod_timer - modify a timer's timeout
823  * @timer: the timer to be modified
824  * @expires: new timeout in jiffies
825  *
826  * mod_timer() is a more efficient way to update the expire field of an
827  * active timer (if the timer is inactive it will be activated)
828  *
829  * mod_timer(timer, expires) is equivalent to:
830  *
831  *     del_timer(timer); timer->expires = expires; add_timer(timer);
832  *
833  * Note that if there are multiple unserialized concurrent users of the
834  * same timer, then mod_timer() is the only safe way to modify the timeout,
835  * since add_timer() cannot modify an already running timer.
836  *
837  * The function returns whether it has modified a pending timer or not.
838  * (ie. mod_timer() of an inactive timer returns 0, mod_timer() of an
839  * active timer returns 1.)
840  */
841 int mod_timer(struct timer_list *timer, unsigned long expires)
842 {
843         expires = apply_slack(timer, expires);
844 
845         /*
846          * This is a common optimization triggered by the
847          * networking code - if the timer is re-modified
848          * to be the same thing then just return:
849          */
850         if (timer_pending(timer) && timer->expires == expires)
851                 return 1;
852 
853         return __mod_timer(timer, expires, false, TIMER_NOT_PINNED);
854 }
855 EXPORT_SYMBOL(mod_timer);
856 
857 /**
858  * mod_timer_pinned - modify a timer's timeout
859  * @timer: the timer to be modified
860  * @expires: new timeout in jiffies
861  *
862  * mod_timer_pinned() is a way to update the expire field of an
863  * active timer (if the timer is inactive it will be activated)
864  * and to ensure that the timer is scheduled on the current CPU.
865  *
866  * Note that this does not prevent the timer from being migrated
867  * when the current CPU goes offline.  If this is a problem for
868  * you, use CPU-hotplug notifiers to handle it correctly, for
869  * example, cancelling the timer when the corresponding CPU goes
870  * offline.
871  *
872  * mod_timer_pinned(timer, expires) is equivalent to:
873  *
874  *     del_timer(timer); timer->expires = expires; add_timer(timer);
875  */
876 int mod_timer_pinned(struct timer_list *timer, unsigned long expires)
877 {
878         if (timer->expires == expires && timer_pending(timer))
879                 return 1;
880 
881         return __mod_timer(timer, expires, false, TIMER_PINNED);
882 }
883 EXPORT_SYMBOL(mod_timer_pinned);
884 
885 /**
886  * add_timer - start a timer
887  * @timer: the timer to be added
888  *
889  * The kernel will do a ->function(->data) callback from the
890  * timer interrupt at the ->expires point in the future. The
891  * current time is 'jiffies'.
892  *
893  * The timer's ->expires, ->function (and if the handler uses it, ->data)
894  * fields must be set prior calling this function.
895  *
896  * Timers with an ->expires field in the past will be executed in the next
897  * timer tick.
898  */
899 void add_timer(struct timer_list *timer)
900 {
901         BUG_ON(timer_pending(timer));
902         mod_timer(timer, timer->expires);
903 }
904 EXPORT_SYMBOL(add_timer);
905 
906 /**
907  * add_timer_on - start a timer on a particular CPU
908  * @timer: the timer to be added
909  * @cpu: the CPU to start it on
910  *
911  * This is not very scalable on SMP. Double adds are not possible.
912  */
913 void add_timer_on(struct timer_list *timer, int cpu)
914 {
915         struct tvec_base *base = per_cpu(tvec_bases, cpu);
916         unsigned long flags;
917 
918         timer_stats_timer_set_start_info(timer);
919         BUG_ON(timer_pending(timer) || !timer->function);
920         spin_lock_irqsave(&base->lock, flags);
921         timer_set_base(timer, base);
922         debug_activate(timer, timer->expires);
923         if (time_before(timer->expires, base->next_timer) &&
924             !tbase_get_deferrable(timer->base))
925                 base->next_timer = timer->expires;
926         internal_add_timer(base, timer);
927         /*
928          * Check whether the other CPU is idle and needs to be
929          * triggered to reevaluate the timer wheel when nohz is
930          * active. We are protected against the other CPU fiddling
931          * with the timer by holding the timer base lock. This also
932          * makes sure that a CPU on the way to idle can not evaluate
933          * the timer wheel.
934          */
935         wake_up_idle_cpu(cpu);
936         spin_unlock_irqrestore(&base->lock, flags);
937 }
938 EXPORT_SYMBOL_GPL(add_timer_on);
939 
940 /**
941  * del_timer - deactive a timer.
942  * @timer: the timer to be deactivated
943  *
944  * del_timer() deactivates a timer - this works on both active and inactive
945  * timers.
946  *
947  * The function returns whether it has deactivated a pending timer or not.
948  * (ie. del_timer() of an inactive timer returns 0, del_timer() of an
949  * active timer returns 1.)
950  */
951 int del_timer(struct timer_list *timer)
952 {
953         struct tvec_base *base;
954         unsigned long flags;
955         int ret = 0;
956 
957         debug_assert_init(timer);
958 
959         timer_stats_timer_clear_start_info(timer);
960         if (timer_pending(timer)) {
961                 base = lock_timer_base(timer, &flags);
962                 if (timer_pending(timer)) {
963                         detach_timer(timer, 1);
964                         if (timer->expires == base->next_timer &&
965                             !tbase_get_deferrable(timer->base))
966                                 base->next_timer = base->timer_jiffies;
967                         ret = 1;
968                 }
969                 spin_unlock_irqrestore(&base->lock, flags);
970         }
971 
972         return ret;
973 }
974 EXPORT_SYMBOL(del_timer);
975 
976 /**
977  * try_to_del_timer_sync - Try to deactivate a timer
978  * @timer: timer do del
979  *
980  * This function tries to deactivate a timer. Upon successful (ret >= 0)
981  * exit the timer is not queued and the handler is not running on any CPU.
982  */
983 int try_to_del_timer_sync(struct timer_list *timer)
984 {
985         struct tvec_base *base;
986         unsigned long flags;
987         int ret = -1;
988 
989         debug_assert_init(timer);
990 
991         base = lock_timer_base(timer, &flags);
992 
993         if (base->running_timer == timer)
994                 goto out;
995 
996         timer_stats_timer_clear_start_info(timer);
997         ret = 0;
998         if (timer_pending(timer)) {
999                 detach_timer(timer, 1);
1000                 if (timer->expires == base->next_timer &&
1001                     !tbase_get_deferrable(timer->base))
1002                         base->next_timer = base->timer_jiffies;
1003                 ret = 1;
1004         }
1005 out:
1006         spin_unlock_irqrestore(&base->lock, flags);
1007 
1008         return ret;
1009 }
1010 EXPORT_SYMBOL(try_to_del_timer_sync);
1011 
1012 #ifdef CONFIG_SMP
1013 /**
1014  * del_timer_sync - deactivate a timer and wait for the handler to finish.
1015  * @timer: the timer to be deactivated
1016  *
1017  * This function only differs from del_timer() on SMP: besides deactivating
1018  * the timer it also makes sure the handler has finished executing on other
1019  * CPUs.
1020  *
1021  * Synchronization rules: Callers must prevent restarting of the timer,
1022  * otherwise this function is meaningless. It must not be called from
1023  * interrupt contexts. The caller must not hold locks which would prevent
1024  * completion of the timer's handler. The timer's handler must not call
1025  * add_timer_on(). Upon exit the timer is not queued and the handler is
1026  * not running on any CPU.
1027  *
1028  * Note: You must not hold locks that are held in interrupt context
1029  *   while calling this function. Even if the lock has nothing to do
1030  *   with the timer in question.  Here's why:
1031  *
1032  *    CPU0                             CPU1
1033  *    ----                             ----
1034  *                                   <SOFTIRQ>
1035  *                                   call_timer_fn();
1036  *                                     base->running_timer = mytimer;
1037  *  spin_lock_irq(somelock);
1038  *                                     <IRQ>
1039  *                                        spin_lock(somelock);
1040  *  del_timer_sync(mytimer);
1041  *   while (base->running_timer == mytimer);
1042  *
1043  * Now del_timer_sync() will never return and never release somelock.
1044  * The interrupt on the other CPU is waiting to grab somelock but
1045  * it has interrupted the softirq that CPU0 is waiting to finish.
1046  *
1047  * The function returns whether it has deactivated a pending timer or not.
1048  */
1049 int del_timer_sync(struct timer_list *timer)
1050 {
1051 #ifdef CONFIG_LOCKDEP
1052         unsigned long flags;
1053 
1054         /*
1055          * If lockdep gives a backtrace here, please reference
1056          * the synchronization rules above.
1057          */
1058         local_irq_save(flags);
1059         lock_map_acquire(&timer->lockdep_map);
1060         lock_map_release(&timer->lockdep_map);
1061         local_irq_restore(flags);
1062 #endif
1063         /*
1064          * don't use it in hardirq context, because it
1065          * could lead to deadlock.
1066          */
1067         WARN_ON(in_irq());
1068         for (;;) {
1069                 int ret = try_to_del_timer_sync(timer);
1070                 if (ret >= 0)
1071                         return ret;
1072                 cpu_relax();
1073         }
1074 }
1075 EXPORT_SYMBOL(del_timer_sync);
1076 #endif
1077 
1078 static int cascade(struct tvec_base *base, struct tvec *tv, int index)
1079 {
1080         /* cascade all the timers from tv up one level */
1081         struct timer_list *timer, *tmp;
1082         struct list_head tv_list;
1083 
1084         list_replace_init(tv->vec + index, &tv_list);
1085 
1086         /*
1087          * We are removing _all_ timers from the list, so we
1088          * don't have to detach them individually.
1089          */
1090         list_for_each_entry_safe(timer, tmp, &tv_list, entry) {
1091                 BUG_ON(tbase_get_base(timer->base) != base);
1092                 internal_add_timer(base, timer);
1093         }
1094 
1095         return index;
1096 }
1097 
1098 static void call_timer_fn(struct timer_list *timer, void (*fn)(unsigned long),
1099                           unsigned long data)
1100 {
1101         int preempt_count = preempt_count();
1102 
1103 #ifdef CONFIG_LOCKDEP
1104         /*
1105          * It is permissible to free the timer from inside the
1106          * function that is called from it, this we need to take into
1107          * account for lockdep too. To avoid bogus "held lock freed"
1108          * warnings as well as problems when looking into
1109          * timer->lockdep_map, make a copy and use that here.
1110          */
1111         struct lockdep_map lockdep_map;
1112 
1113         lockdep_copy_map(&lockdep_map, &timer->lockdep_map);
1114 #endif
1115         /*
1116          * Couple the lock chain with the lock chain at
1117          * del_timer_sync() by acquiring the lock_map around the fn()
1118          * call here and in del_timer_sync().
1119          */
1120         lock_map_acquire(&lockdep_map);
1121 
1122         trace_timer_expire_entry(timer);
1123         fn(data);
1124         trace_timer_expire_exit(timer);
1125 
1126         lock_map_release(&lockdep_map);
1127 
1128         if (preempt_count != preempt_count()) {
1129                 WARN_ONCE(1, "timer: %pF preempt leak: %08x -> %08x\n",
1130                           fn, preempt_count, preempt_count());
1131                 /*
1132                  * Restore the preempt count. That gives us a decent
1133                  * chance to survive and extract information. If the
1134                  * callback kept a lock held, bad luck, but not worse
1135                  * than the BUG() we had.
1136                  */
1137                 preempt_count() = preempt_count;
1138         }
1139 }
1140 
1141 #define INDEX(N) ((base->timer_jiffies >> (TVR_BITS + (N) * TVN_BITS)) & TVN_MASK)
1142 
1143 /**
1144  * __run_timers - run all expired timers (if any) on this CPU.
1145  * @base: the timer vector to be processed.
1146  *
1147  * This function cascades all vectors and executes all expired timer
1148  * vectors.
1149  */
1150 static inline void __run_timers(struct tvec_base *base)
1151 {
1152         struct timer_list *timer;
1153 
1154         spin_lock_irq(&base->lock);
1155         while (time_after_eq(jiffies, base->timer_jiffies)) {
1156                 struct list_head work_list;
1157                 struct list_head *head = &work_list;
1158                 int index = base->timer_jiffies & TVR_MASK;
1159 
1160                 /*
1161                  * Cascade timers:
1162                  */
1163                 if (!index &&
1164                         (!cascade(base, &base->tv2, INDEX(0))) &&
1165                                 (!cascade(base, &base->tv3, INDEX(1))) &&
1166                                         !cascade(base, &base->tv4, INDEX(2)))
1167                         cascade(base, &base->tv5, INDEX(3));
1168                 ++base->timer_jiffies;
1169                 list_replace_init(base->tv1.vec + index, &work_list);
1170                 while (!list_empty(head)) {
1171                         void (*fn)(unsigned long);
1172                         unsigned long data;
1173 
1174                         timer = list_first_entry(head, struct timer_list,entry);
1175                         fn = timer->function;
1176                         data = timer->data;
1177 
1178                         timer_stats_account_timer(timer);
1179 
1180                         base->running_timer = timer;
1181                         detach_timer(timer, 1);
1182 
1183                         spin_unlock_irq(&base->lock);
1184                         call_timer_fn(timer, fn, data);
1185                         spin_lock_irq(&base->lock);
1186                 }
1187         }
1188         base->running_timer = NULL;
1189         spin_unlock_irq(&base->lock);
1190 }
1191 
1192 #ifdef CONFIG_NO_HZ
1193 /*
1194  * Find out when the next timer event is due to happen. This
1195  * is used on S/390 to stop all activity when a CPU is idle.
1196  * This function needs to be called with interrupts disabled.
1197  */
1198 static unsigned long __next_timer_interrupt(struct tvec_base *base)
1199 {
1200         unsigned long timer_jiffies = base->timer_jiffies;
1201         unsigned long expires = timer_jiffies + NEXT_TIMER_MAX_DELTA;
1202         int index, slot, array, found = 0;
1203         struct timer_list *nte;
1204         struct tvec *varray[4];
1205 
1206         /* Look for timer events in tv1. */
1207         index = slot = timer_jiffies & TVR_MASK;
1208         do {
1209                 list_for_each_entry(nte, base->tv1.vec + slot, entry) {
1210                         if (tbase_get_deferrable(nte->base))
1211                                 continue;
1212 
1213                         found = 1;
1214                         expires = nte->expires;
1215                         /* Look at the cascade bucket(s)? */
1216                         if (!index || slot < index)
1217                                 goto cascade;
1218                         return expires;
1219                 }
1220                 slot = (slot + 1) & TVR_MASK;
1221         } while (slot != index);
1222 
1223 cascade:
1224         /* Calculate the next cascade event */
1225         if (index)
1226                 timer_jiffies += TVR_SIZE - index;
1227         timer_jiffies >>= TVR_BITS;
1228 
1229         /* Check tv2-tv5. */
1230         varray[0] = &base->tv2;
1231         varray[1] = &base->tv3;
1232         varray[2] = &base->tv4;
1233         varray[3] = &base->tv5;
1234 
1235         for (array = 0; array < 4; array++) {
1236                 struct tvec *varp = varray[array];
1237 
1238                 index = slot = timer_jiffies & TVN_MASK;
1239                 do {
1240                         list_for_each_entry(nte, varp->vec + slot, entry) {
1241                                 if (tbase_get_deferrable(nte->base))
1242                                         continue;
1243 
1244                                 found = 1;
1245                                 if (time_before(nte->expires, expires))
1246                                         expires = nte->expires;
1247                         }
1248                         /*
1249                          * Do we still search for the first timer or are
1250                          * we looking up the cascade buckets ?
1251                          */
1252                         if (found) {
1253                                 /* Look at the cascade bucket(s)? */
1254                                 if (!index || slot < index)
1255                                         break;
1256                                 return expires;
1257                         }
1258                         slot = (slot + 1) & TVN_MASK;
1259                 } while (slot != index);
1260 
1261                 if (index)
1262                         timer_jiffies += TVN_SIZE - index;
1263                 timer_jiffies >>= TVN_BITS;
1264         }
1265         return expires;
1266 }
1267 
1268 /*
1269  * Check, if the next hrtimer event is before the next timer wheel
1270  * event:
1271  */
1272 static unsigned long cmp_next_hrtimer_event(unsigned long now,
1273                                             unsigned long expires)
1274 {
1275         ktime_t hr_delta = hrtimer_get_next_event();
1276         struct timespec tsdelta;
1277         unsigned long delta;
1278 
1279         if (hr_delta.tv64 == KTIME_MAX)
1280                 return expires;
1281 
1282         /*
1283          * Expired timer available, let it expire in the next tick
1284          */
1285         if (hr_delta.tv64 <= 0)
1286                 return now + 1;
1287 
1288         tsdelta = ktime_to_timespec(hr_delta);
1289         delta = timespec_to_jiffies(&tsdelta);
1290 
1291         /*
1292          * Limit the delta to the max value, which is checked in
1293          * tick_nohz_stop_sched_tick():
1294          */
1295         if (delta > NEXT_TIMER_MAX_DELTA)
1296                 delta = NEXT_TIMER_MAX_DELTA;
1297 
1298         /*
1299          * Take rounding errors in to account and make sure, that it
1300          * expires in the next tick. Otherwise we go into an endless
1301          * ping pong due to tick_nohz_stop_sched_tick() retriggering
1302          * the timer softirq
1303          */
1304         if (delta < 1)
1305                 delta = 1;
1306         now += delta;
1307         if (time_before(now, expires))
1308                 return now;
1309         return expires;
1310 }
1311 
1312 /**
1313  * get_next_timer_interrupt - return the jiffy of the next pending timer
1314  * @now: current time (in jiffies)
1315  */
1316 unsigned long get_next_timer_interrupt(unsigned long now)
1317 {
1318         struct tvec_base *base = __this_cpu_read(tvec_bases);
1319         unsigned long expires;
1320 
1321         /*
1322          * Pretend that there is no timer pending if the cpu is offline.
1323          * Possible pending timers will be migrated later to an active cpu.
1324          */
1325         if (cpu_is_offline(smp_processor_id()))
1326                 return now + NEXT_TIMER_MAX_DELTA;
1327         spin_lock(&base->lock);
1328         if (time_before_eq(base->next_timer, base->timer_jiffies))
1329                 base->next_timer = __next_timer_interrupt(base);
1330         expires = base->next_timer;
1331         spin_unlock(&base->lock);
1332 
1333         if (time_before_eq(expires, now))
1334                 return now;
1335 
1336         return cmp_next_hrtimer_event(now, expires);
1337 }
1338 #endif
1339 
1340 /*
1341  * Called from the timer interrupt handler to charge one tick to the current
1342  * process.  user_tick is 1 if the tick is user time, 0 for system.
1343  */
1344 void update_process_times(int user_tick)
1345 {
1346         struct task_struct *p = current;
1347         int cpu = smp_processor_id();
1348 
1349         /* Note: this timer irq context must be accounted for as well. */
1350         account_process_tick(p, user_tick);
1351         run_local_timers();
1352         rcu_check_callbacks(cpu, user_tick);
1353         printk_tick();
1354 #ifdef CONFIG_IRQ_WORK
1355         if (in_irq())
1356                 irq_work_run();
1357 #endif
1358         scheduler_tick();
1359         run_posix_cpu_timers(p);
1360 }
1361 
1362 /*
1363  * This function runs timers and the timer-tq in bottom half context.
1364  */
1365 static void run_timer_softirq(struct softirq_action *h)
1366 {
1367         struct tvec_base *base = __this_cpu_read(tvec_bases);
1368 
1369         hrtimer_run_pending();
1370 
1371         if (time_after_eq(jiffies, base->timer_jiffies))
1372                 __run_timers(base);
1373 }
1374 
1375 /*
1376  * Called by the local, per-CPU timer interrupt on SMP.
1377  */
1378 void run_local_timers(void)
1379 {
1380         hrtimer_run_queues();
1381         raise_softirq(TIMER_SOFTIRQ);
1382 }
1383 
1384 #ifdef __ARCH_WANT_SYS_ALARM
1385 
1386 /*
1387  * For backwards compatibility?  This can be done in libc so Alpha
1388  * and all newer ports shouldn't need it.
1389  */
1390 SYSCALL_DEFINE1(alarm, unsigned int, seconds)
1391 {
1392         return alarm_setitimer(seconds);
1393 }
1394 
1395 #endif
1396 
1397 #ifndef __alpha__
1398 
1399 /*
1400  * The Alpha uses getxpid, getxuid, and getxgid instead.  Maybe this
1401  * should be moved into arch/i386 instead?
1402  */
1403 
1404 /**
1405  * sys_getpid - return the thread group id of the current process
1406  *
1407  * Note, despite the name, this returns the tgid not the pid.  The tgid and
1408  * the pid are identical unless CLONE_THREAD was specified on clone() in
1409  * which case the tgid is the same in all threads of the same group.
1410  *
1411  * This is SMP safe as current->tgid does not change.
1412  */
1413 SYSCALL_DEFINE0(getpid)
1414 {
1415         return task_tgid_vnr(current);
1416 }
1417 
1418 /*
1419  * Accessing ->real_parent is not SMP-safe, it could
1420  * change from under us. However, we can use a stale
1421  * value of ->real_parent under rcu_read_lock(), see
1422  * release_task()->call_rcu(delayed_put_task_struct).
1423  */
1424 SYSCALL_DEFINE0(getppid)
1425 {
1426         int pid;
1427 
1428         rcu_read_lock();
1429         pid = task_tgid_vnr(rcu_dereference(current->real_parent));
1430         rcu_read_unlock();
1431 
1432         return pid;
1433 }
1434 
1435 SYSCALL_DEFINE0(getuid)
1436 {
1437         /* Only we change this so SMP safe */
1438         return from_kuid_munged(current_user_ns(), current_uid());
1439 }
1440 
1441 SYSCALL_DEFINE0(geteuid)
1442 {
1443         /* Only we change this so SMP safe */
1444         return from_kuid_munged(current_user_ns(), current_euid());
1445 }
1446 
1447 SYSCALL_DEFINE0(getgid)
1448 {
1449         /* Only we change this so SMP safe */
1450         return from_kgid_munged(current_user_ns(), current_gid());
1451 }
1452 
1453 SYSCALL_DEFINE0(getegid)
1454 {
1455         /* Only we change this so SMP safe */
1456         return from_kgid_munged(current_user_ns(), current_egid());
1457 }
1458 
1459 #endif
1460 
1461 static void process_timeout(unsigned long __data)
1462 {
1463         wake_up_process((struct task_struct *)__data);
1464 }
1465 
1466 /**
1467  * schedule_timeout - sleep until timeout
1468  * @timeout: timeout value in jiffies
1469  *
1470  * Make the current task sleep until @timeout jiffies have
1471  * elapsed. The routine will return immediately unless
1472  * the current task state has been set (see set_current_state()).
1473  *
1474  * You can set the task state as follows -
1475  *
1476  * %TASK_UNINTERRUPTIBLE - at least @timeout jiffies are guaranteed to
1477  * pass before the routine returns. The routine will return 0
1478  *
1479  * %TASK_INTERRUPTIBLE - the routine may return early if a signal is
1480  * delivered to the current task. In this case the remaining time
1481  * in jiffies will be returned, or 0 if the timer expired in time
1482  *
1483  * The current task state is guaranteed to be TASK_RUNNING when this
1484  * routine returns.
1485  *
1486  * Specifying a @timeout value of %MAX_SCHEDULE_TIMEOUT will schedule
1487  * the CPU away without a bound on the timeout. In this case the return
1488  * value will be %MAX_SCHEDULE_TIMEOUT.
1489  *
1490  * In all cases the return value is guaranteed to be non-negative.
1491  */
1492 signed long __sched schedule_timeout(signed long timeout)
1493 {
1494         struct timer_list timer;
1495         unsigned long expire;
1496 
1497         switch (timeout)
1498         {
1499         case MAX_SCHEDULE_TIMEOUT:
1500                 /*
1501                  * These two special cases are useful to be comfortable
1502                  * in the caller. Nothing more. We could take
1503                  * MAX_SCHEDULE_TIMEOUT from one of the negative value
1504                  * but I' d like to return a valid offset (>=0) to allow
1505                  * the caller to do everything it want with the retval.
1506                  */
1507                 schedule();
1508                 goto out;
1509         default:
1510                 /*
1511                  * Another bit of PARANOID. Note that the retval will be
1512                  * 0 since no piece of kernel is supposed to do a check
1513                  * for a negative retval of schedule_timeout() (since it
1514                  * should never happens anyway). You just have the printk()
1515                  * that will tell you if something is gone wrong and where.
1516                  */
1517                 if (timeout < 0) {
1518                         printk(KERN_ERR "schedule_timeout: wrong timeout "
1519                                 "value %lx\n", timeout);
1520                         dump_stack();
1521                         current->state = TASK_RUNNING;
1522                         goto out;
1523                 }
1524         }
1525 
1526         expire = timeout + jiffies;
1527 
1528         setup_timer_on_stack(&timer, process_timeout, (unsigned long)current);
1529         __mod_timer(&timer, expire, false, TIMER_NOT_PINNED);
1530         schedule();
1531         del_singleshot_timer_sync(&timer);
1532 
1533         /* Remove the timer from the object tracker */
1534         destroy_timer_on_stack(&timer);
1535 
1536         timeout = expire - jiffies;
1537 
1538  out:
1539         return timeout < 0 ? 0 : timeout;
1540 }
1541 EXPORT_SYMBOL(schedule_timeout);
1542 
1543 /*
1544  * We can use __set_current_state() here because schedule_timeout() calls
1545  * schedule() unconditionally.
1546  */
1547 signed long __sched schedule_timeout_interruptible(signed long timeout)
1548 {
1549         __set_current_state(TASK_INTERRUPTIBLE);
1550         return schedule_timeout(timeout);
1551 }
1552 EXPORT_SYMBOL(schedule_timeout_interruptible);
1553 
1554 signed long __sched schedule_timeout_killable(signed long timeout)
1555 {
1556         __set_current_state(TASK_KILLABLE);
1557         return schedule_timeout(timeout);
1558 }
1559 EXPORT_SYMBOL(schedule_timeout_killable);
1560 
1561 signed long __sched schedule_timeout_uninterruptible(signed long timeout)
1562 {
1563         __set_current_state(TASK_UNINTERRUPTIBLE);
1564         return schedule_timeout(timeout);
1565 }
1566 EXPORT_SYMBOL(schedule_timeout_uninterruptible);
1567 
1568 /* Thread ID - the internal kernel "pid" */
1569 SYSCALL_DEFINE0(gettid)
1570 {
1571         return task_pid_vnr(current);
1572 }
1573 
1574 /**
1575  * do_sysinfo - fill in sysinfo struct
1576  * @info: pointer to buffer to fill
1577  */
1578 int do_sysinfo(struct sysinfo *info)
1579 {
1580         unsigned long mem_total, sav_total;
1581         unsigned int mem_unit, bitcount;
1582         struct timespec tp;
1583 
1584         memset(info, 0, sizeof(struct sysinfo));
1585 
1586         ktime_get_ts(&tp);
1587         monotonic_to_bootbased(&tp);
1588         info->uptime = tp.tv_sec + (tp.tv_nsec ? 1 : 0);
1589 
1590         get_avenrun(info->loads, 0, SI_LOAD_SHIFT - FSHIFT);
1591 
1592         info->procs = nr_threads;
1593 
1594         si_meminfo(info);
1595         si_swapinfo(info);
1596 
1597         /*
1598          * If the sum of all the available memory (i.e. ram + swap)
1599          * is less than can be stored in a 32 bit unsigned long then
1600          * we can be binary compatible with 2.2.x kernels.  If not,
1601          * well, in that case 2.2.x was broken anyways...
1602          *
1603          *  -Erik Andersen <andersee@debian.org>
1604          */
1605 
1606         mem_total = info->totalram + info->totalswap;
1607         if (mem_total < info->totalram || mem_total < info->totalswap)
1608                 goto out;
1609         bitcount = 0;
1610         mem_unit = info->mem_unit;
1611         while (mem_unit > 1) {
1612                 bitcount++;
1613                 mem_unit >>= 1;
1614                 sav_total = mem_total;
1615                 mem_total <<= 1;
1616                 if (mem_total < sav_total)
1617                         goto out;
1618         }
1619 
1620         /*
1621          * If mem_total did not overflow, multiply all memory values by
1622          * info->mem_unit and set it to 1.  This leaves things compatible
1623          * with 2.2.x, and also retains compatibility with earlier 2.4.x
1624          * kernels...
1625          */
1626 
1627         info->mem_unit = 1;
1628         info->totalram <<= bitcount;
1629         info->freeram <<= bitcount;
1630         info->sharedram <<= bitcount;
1631         info->bufferram <<= bitcount;
1632         info->totalswap <<= bitcount;
1633         info->freeswap <<= bitcount;
1634         info->totalhigh <<= bitcount;
1635         info->freehigh <<= bitcount;
1636 
1637 out:
1638         return 0;
1639 }
1640 
1641 SYSCALL_DEFINE1(sysinfo, struct sysinfo __user *, info)
1642 {
1643         struct sysinfo val;
1644 
1645         do_sysinfo(&val);
1646 
1647         if (copy_to_user(info, &val, sizeof(struct sysinfo)))
1648                 return -EFAULT;
1649 
1650         return 0;
1651 }
1652 
1653 static int __cpuinit init_timers_cpu(int cpu)
1654 {
1655         int j;
1656         struct tvec_base *base;
1657         static char __cpuinitdata tvec_base_done[NR_CPUS];
1658 
1659         if (!tvec_base_done[cpu]) {
1660                 static char boot_done;
1661 
1662                 if (boot_done) {
1663                         /*
1664                          * The APs use this path later in boot
1665                          */
1666                         base = kmalloc_node(sizeof(*base),
1667                                                 GFP_KERNEL | __GFP_ZERO,
1668                                                 cpu_to_node(cpu));
1669                         if (!base)
1670                                 return -ENOMEM;
1671 
1672                         /* Make sure that tvec_base is 2 byte aligned */
1673                         if (tbase_get_deferrable(base)) {
1674                                 WARN_ON(1);
1675                                 kfree(base);
1676                                 return -ENOMEM;
1677                         }
1678                         per_cpu(tvec_bases, cpu) = base;
1679                 } else {
1680                         /*
1681                          * This is for the boot CPU - we use compile-time
1682                          * static initialisation because per-cpu memory isn't
1683                          * ready yet and because the memory allocators are not
1684                          * initialised either.
1685                          */
1686                         boot_done = 1;
1687                         base = &boot_tvec_bases;
1688                 }
1689                 tvec_base_done[cpu] = 1;
1690         } else {
1691                 base = per_cpu(tvec_bases, cpu);
1692         }
1693 
1694         spin_lock_init(&base->lock);
1695 
1696         for (j = 0; j < TVN_SIZE; j++) {
1697                 INIT_LIST_HEAD(base->tv5.vec + j);
1698                 INIT_LIST_HEAD(base->tv4.vec + j);
1699                 INIT_LIST_HEAD(base->tv3.vec + j);
1700                 INIT_LIST_HEAD(base->tv2.vec + j);
1701         }
1702         for (j = 0; j < TVR_SIZE; j++)
1703                 INIT_LIST_HEAD(base->tv1.vec + j);
1704 
1705         base->timer_jiffies = jiffies;
1706         base->next_timer = base->timer_jiffies;
1707         return 0;
1708 }
1709 
1710 #ifdef CONFIG_HOTPLUG_CPU
1711 static void migrate_timer_list(struct tvec_base *new_base, struct list_head *head)
1712 {
1713         struct timer_list *timer;
1714 
1715         while (!list_empty(head)) {
1716                 timer = list_first_entry(head, struct timer_list, entry);
1717                 detach_timer(timer, 0);
1718                 timer_set_base(timer, new_base);
1719                 if (time_before(timer->expires, new_base->next_timer) &&
1720                     !tbase_get_deferrable(timer->base))
1721                         new_base->next_timer = timer->expires;
1722                 internal_add_timer(new_base, timer);
1723         }
1724 }
1725 
1726 static void __cpuinit migrate_timers(int cpu)
1727 {
1728         struct tvec_base *old_base;
1729         struct tvec_base *new_base;
1730         int i;
1731 
1732         BUG_ON(cpu_online(cpu));
1733         old_base = per_cpu(tvec_bases, cpu);
1734         new_base = get_cpu_var(tvec_bases);
1735         /*
1736          * The caller is globally serialized and nobody else
1737          * takes two locks at once, deadlock is not possible.
1738          */
1739         spin_lock_irq(&new_base->lock);
1740         spin_lock_nested(&old_base->lock, SINGLE_DEPTH_NESTING);
1741 
1742         BUG_ON(old_base->running_timer);
1743 
1744         for (i = 0; i < TVR_SIZE; i++)
1745                 migrate_timer_list(new_base, old_base->tv1.vec + i);
1746         for (i = 0; i < TVN_SIZE; i++) {
1747                 migrate_timer_list(new_base, old_base->tv2.vec + i);
1748                 migrate_timer_list(new_base, old_base->tv3.vec + i);
1749                 migrate_timer_list(new_base, old_base->tv4.vec + i);
1750                 migrate_timer_list(new_base, old_base->tv5.vec + i);
1751         }
1752 
1753         spin_unlock(&old_base->lock);
1754         spin_unlock_irq(&new_base->lock);
1755         put_cpu_var(tvec_bases);
1756 }
1757 #endif /* CONFIG_HOTPLUG_CPU */
1758 
1759 static int __cpuinit timer_cpu_notify(struct notifier_block *self,
1760                                 unsigned long action, void *hcpu)
1761 {
1762         long cpu = (long)hcpu;
1763         int err;
1764 
1765         switch(action) {
1766         case CPU_UP_PREPARE:
1767         case CPU_UP_PREPARE_FROZEN:
1768                 err = init_timers_cpu(cpu);
1769                 if (err < 0)
1770                         return notifier_from_errno(err);
1771                 break;
1772 #ifdef CONFIG_HOTPLUG_CPU
1773         case CPU_DEAD:
1774         case CPU_DEAD_FROZEN:
1775                 migrate_timers(cpu);
1776                 break;
1777 #endif
1778         default:
1779                 break;
1780         }
1781         return NOTIFY_OK;
1782 }
1783 
1784 static struct notifier_block __cpuinitdata timers_nb = {
1785         .notifier_call  = timer_cpu_notify,
1786 };
1787 
1788 
1789 void __init init_timers(void)
1790 {
1791         int err = timer_cpu_notify(&timers_nb, (unsigned long)CPU_UP_PREPARE,
1792                                 (void *)(long)smp_processor_id());
1793 
1794         init_timer_stats();
1795 
1796         BUG_ON(err != NOTIFY_OK);
1797         register_cpu_notifier(&timers_nb);
1798         open_softirq(TIMER_SOFTIRQ, run_timer_softirq);
1799 }
1800 
1801 /**
1802  * msleep - sleep safely even with waitqueue interruptions
1803  * @msecs: Time in milliseconds to sleep for
1804  */
1805 void msleep(unsigned int msecs)
1806 {
1807         unsigned long timeout = msecs_to_jiffies(msecs) + 1;
1808 
1809         while (timeout)
1810                 timeout = schedule_timeout_uninterruptible(timeout);
1811 }
1812 
1813 EXPORT_SYMBOL(msleep);
1814 
1815 /**
1816  * msleep_interruptible - sleep waiting for signals
1817  * @msecs: Time in milliseconds to sleep for
1818  */
1819 unsigned long msleep_interruptible(unsigned int msecs)
1820 {
1821         unsigned long timeout = msecs_to_jiffies(msecs) + 1;
1822 
1823         while (timeout && !signal_pending(current))
1824                 timeout = schedule_timeout_interruptible(timeout);
1825         return jiffies_to_msecs(timeout);
1826 }
1827 
1828 EXPORT_SYMBOL(msleep_interruptible);
1829 
1830 static int __sched do_usleep_range(unsigned long min, unsigned long max)
1831 {
1832         ktime_t kmin;
1833         unsigned long delta;
1834 
1835         kmin = ktime_set(0, min * NSEC_PER_USEC);
1836         delta = (max - min) * NSEC_PER_USEC;
1837         return schedule_hrtimeout_range(&kmin, delta, HRTIMER_MODE_REL);
1838 }
1839 
1840 /**
1841  * usleep_range - Drop in replacement for udelay where wakeup is flexible
1842  * @min: Minimum time in usecs to sleep
1843  * @max: Maximum time in usecs to sleep
1844  */
1845 void usleep_range(unsigned long min, unsigned long max)
1846 {
1847         __set_current_state(TASK_UNINTERRUPTIBLE);
1848         do_usleep_range(min, max);
1849 }
1850 EXPORT_SYMBOL(usleep_range);
1851 

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