[PATCH] arm_timer: remove a racy and obsolete PF_EXITING check
[linux-2.6.git] / kernel / posix-cpu-timers.c
1 /*
2  * Implement CPU time clocks for the POSIX clock interface.
3  */
4
5 #include <linux/sched.h>
6 #include <linux/posix-timers.h>
7 #include <asm/uaccess.h>
8 #include <linux/errno.h>
9
10 static int check_clock(const clockid_t which_clock)
11 {
12         int error = 0;
13         struct task_struct *p;
14         const pid_t pid = CPUCLOCK_PID(which_clock);
15
16         if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
17                 return -EINVAL;
18
19         if (pid == 0)
20                 return 0;
21
22         read_lock(&tasklist_lock);
23         p = find_task_by_pid(pid);
24         if (!p || (CPUCLOCK_PERTHREAD(which_clock) ?
25                    p->tgid != current->tgid : p->tgid != pid)) {
26                 error = -EINVAL;
27         }
28         read_unlock(&tasklist_lock);
29
30         return error;
31 }
32
33 static inline union cpu_time_count
34 timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
35 {
36         union cpu_time_count ret;
37         ret.sched = 0;          /* high half always zero when .cpu used */
38         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
39                 ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
40         } else {
41                 ret.cpu = timespec_to_cputime(tp);
42         }
43         return ret;
44 }
45
46 static void sample_to_timespec(const clockid_t which_clock,
47                                union cpu_time_count cpu,
48                                struct timespec *tp)
49 {
50         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
51                 tp->tv_sec = div_long_long_rem(cpu.sched,
52                                                NSEC_PER_SEC, &tp->tv_nsec);
53         } else {
54                 cputime_to_timespec(cpu.cpu, tp);
55         }
56 }
57
58 static inline int cpu_time_before(const clockid_t which_clock,
59                                   union cpu_time_count now,
60                                   union cpu_time_count then)
61 {
62         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
63                 return now.sched < then.sched;
64         }  else {
65                 return cputime_lt(now.cpu, then.cpu);
66         }
67 }
68 static inline void cpu_time_add(const clockid_t which_clock,
69                                 union cpu_time_count *acc,
70                                 union cpu_time_count val)
71 {
72         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
73                 acc->sched += val.sched;
74         }  else {
75                 acc->cpu = cputime_add(acc->cpu, val.cpu);
76         }
77 }
78 static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
79                                                 union cpu_time_count a,
80                                                 union cpu_time_count b)
81 {
82         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
83                 a.sched -= b.sched;
84         }  else {
85                 a.cpu = cputime_sub(a.cpu, b.cpu);
86         }
87         return a;
88 }
89
90 /*
91  * Update expiry time from increment, and increase overrun count,
92  * given the current clock sample.
93  */
94 static void bump_cpu_timer(struct k_itimer *timer,
95                                   union cpu_time_count now)
96 {
97         int i;
98
99         if (timer->it.cpu.incr.sched == 0)
100                 return;
101
102         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
103                 unsigned long long delta, incr;
104
105                 if (now.sched < timer->it.cpu.expires.sched)
106                         return;
107                 incr = timer->it.cpu.incr.sched;
108                 delta = now.sched + incr - timer->it.cpu.expires.sched;
109                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
110                 for (i = 0; incr < delta - incr; i++)
111                         incr = incr << 1;
112                 for (; i >= 0; incr >>= 1, i--) {
113                         if (delta < incr)
114                                 continue;
115                         timer->it.cpu.expires.sched += incr;
116                         timer->it_overrun += 1 << i;
117                         delta -= incr;
118                 }
119         } else {
120                 cputime_t delta, incr;
121
122                 if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
123                         return;
124                 incr = timer->it.cpu.incr.cpu;
125                 delta = cputime_sub(cputime_add(now.cpu, incr),
126                                     timer->it.cpu.expires.cpu);
127                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
128                 for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
129                              incr = cputime_add(incr, incr);
130                 for (; i >= 0; incr = cputime_halve(incr), i--) {
131                         if (cputime_lt(delta, incr))
132                                 continue;
133                         timer->it.cpu.expires.cpu =
134                                 cputime_add(timer->it.cpu.expires.cpu, incr);
135                         timer->it_overrun += 1 << i;
136                         delta = cputime_sub(delta, incr);
137                 }
138         }
139 }
140
141 static inline cputime_t prof_ticks(struct task_struct *p)
142 {
143         return cputime_add(p->utime, p->stime);
144 }
145 static inline cputime_t virt_ticks(struct task_struct *p)
146 {
147         return p->utime;
148 }
149 static inline unsigned long long sched_ns(struct task_struct *p)
150 {
151         return (p == current) ? current_sched_time(p) : p->sched_time;
152 }
153
154 int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
155 {
156         int error = check_clock(which_clock);
157         if (!error) {
158                 tp->tv_sec = 0;
159                 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
160                 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
161                         /*
162                          * If sched_clock is using a cycle counter, we
163                          * don't have any idea of its true resolution
164                          * exported, but it is much more than 1s/HZ.
165                          */
166                         tp->tv_nsec = 1;
167                 }
168         }
169         return error;
170 }
171
172 int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
173 {
174         /*
175          * You can never reset a CPU clock, but we check for other errors
176          * in the call before failing with EPERM.
177          */
178         int error = check_clock(which_clock);
179         if (error == 0) {
180                 error = -EPERM;
181         }
182         return error;
183 }
184
185
186 /*
187  * Sample a per-thread clock for the given task.
188  */
189 static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
190                             union cpu_time_count *cpu)
191 {
192         switch (CPUCLOCK_WHICH(which_clock)) {
193         default:
194                 return -EINVAL;
195         case CPUCLOCK_PROF:
196                 cpu->cpu = prof_ticks(p);
197                 break;
198         case CPUCLOCK_VIRT:
199                 cpu->cpu = virt_ticks(p);
200                 break;
201         case CPUCLOCK_SCHED:
202                 cpu->sched = sched_ns(p);
203                 break;
204         }
205         return 0;
206 }
207
208 /*
209  * Sample a process (thread group) clock for the given group_leader task.
210  * Must be called with tasklist_lock held for reading.
211  * Must be called with tasklist_lock held for reading, and p->sighand->siglock.
212  */
213 static int cpu_clock_sample_group_locked(unsigned int clock_idx,
214                                          struct task_struct *p,
215                                          union cpu_time_count *cpu)
216 {
217         struct task_struct *t = p;
218         switch (clock_idx) {
219         default:
220                 return -EINVAL;
221         case CPUCLOCK_PROF:
222                 cpu->cpu = cputime_add(p->signal->utime, p->signal->stime);
223                 do {
224                         cpu->cpu = cputime_add(cpu->cpu, prof_ticks(t));
225                         t = next_thread(t);
226                 } while (t != p);
227                 break;
228         case CPUCLOCK_VIRT:
229                 cpu->cpu = p->signal->utime;
230                 do {
231                         cpu->cpu = cputime_add(cpu->cpu, virt_ticks(t));
232                         t = next_thread(t);
233                 } while (t != p);
234                 break;
235         case CPUCLOCK_SCHED:
236                 cpu->sched = p->signal->sched_time;
237                 /* Add in each other live thread.  */
238                 while ((t = next_thread(t)) != p) {
239                         cpu->sched += t->sched_time;
240                 }
241                 cpu->sched += sched_ns(p);
242                 break;
243         }
244         return 0;
245 }
246
247 /*
248  * Sample a process (thread group) clock for the given group_leader task.
249  * Must be called with tasklist_lock held for reading.
250  */
251 static int cpu_clock_sample_group(const clockid_t which_clock,
252                                   struct task_struct *p,
253                                   union cpu_time_count *cpu)
254 {
255         int ret;
256         unsigned long flags;
257         spin_lock_irqsave(&p->sighand->siglock, flags);
258         ret = cpu_clock_sample_group_locked(CPUCLOCK_WHICH(which_clock), p,
259                                             cpu);
260         spin_unlock_irqrestore(&p->sighand->siglock, flags);
261         return ret;
262 }
263
264
265 int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
266 {
267         const pid_t pid = CPUCLOCK_PID(which_clock);
268         int error = -EINVAL;
269         union cpu_time_count rtn;
270
271         if (pid == 0) {
272                 /*
273                  * Special case constant value for our own clocks.
274                  * We don't have to do any lookup to find ourselves.
275                  */
276                 if (CPUCLOCK_PERTHREAD(which_clock)) {
277                         /*
278                          * Sampling just ourselves we can do with no locking.
279                          */
280                         error = cpu_clock_sample(which_clock,
281                                                  current, &rtn);
282                 } else {
283                         read_lock(&tasklist_lock);
284                         error = cpu_clock_sample_group(which_clock,
285                                                        current, &rtn);
286                         read_unlock(&tasklist_lock);
287                 }
288         } else {
289                 /*
290                  * Find the given PID, and validate that the caller
291                  * should be able to see it.
292                  */
293                 struct task_struct *p;
294                 read_lock(&tasklist_lock);
295                 p = find_task_by_pid(pid);
296                 if (p) {
297                         if (CPUCLOCK_PERTHREAD(which_clock)) {
298                                 if (p->tgid == current->tgid) {
299                                         error = cpu_clock_sample(which_clock,
300                                                                  p, &rtn);
301                                 }
302                         } else if (p->tgid == pid && p->signal) {
303                                 error = cpu_clock_sample_group(which_clock,
304                                                                p, &rtn);
305                         }
306                 }
307                 read_unlock(&tasklist_lock);
308         }
309
310         if (error)
311                 return error;
312         sample_to_timespec(which_clock, rtn, tp);
313         return 0;
314 }
315
316
317 /*
318  * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
319  * This is called from sys_timer_create with the new timer already locked.
320  */
321 int posix_cpu_timer_create(struct k_itimer *new_timer)
322 {
323         int ret = 0;
324         const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
325         struct task_struct *p;
326
327         if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
328                 return -EINVAL;
329
330         INIT_LIST_HEAD(&new_timer->it.cpu.entry);
331         new_timer->it.cpu.incr.sched = 0;
332         new_timer->it.cpu.expires.sched = 0;
333
334         read_lock(&tasklist_lock);
335         if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
336                 if (pid == 0) {
337                         p = current;
338                 } else {
339                         p = find_task_by_pid(pid);
340                         if (p && p->tgid != current->tgid)
341                                 p = NULL;
342                 }
343         } else {
344                 if (pid == 0) {
345                         p = current->group_leader;
346                 } else {
347                         p = find_task_by_pid(pid);
348                         if (p && p->tgid != pid)
349                                 p = NULL;
350                 }
351         }
352         new_timer->it.cpu.task = p;
353         if (p) {
354                 get_task_struct(p);
355         } else {
356                 ret = -EINVAL;
357         }
358         read_unlock(&tasklist_lock);
359
360         return ret;
361 }
362
363 /*
364  * Clean up a CPU-clock timer that is about to be destroyed.
365  * This is called from timer deletion with the timer already locked.
366  * If we return TIMER_RETRY, it's necessary to release the timer's lock
367  * and try again.  (This happens when the timer is in the middle of firing.)
368  */
369 int posix_cpu_timer_del(struct k_itimer *timer)
370 {
371         struct task_struct *p = timer->it.cpu.task;
372         int ret = 0;
373
374         if (likely(p != NULL)) {
375                 read_lock(&tasklist_lock);
376                 if (unlikely(p->signal == NULL)) {
377                         /*
378                          * We raced with the reaping of the task.
379                          * The deletion should have cleared us off the list.
380                          */
381                         BUG_ON(!list_empty(&timer->it.cpu.entry));
382                 } else {
383                         spin_lock(&p->sighand->siglock);
384                         if (timer->it.cpu.firing)
385                                 ret = TIMER_RETRY;
386                         else
387                                 list_del(&timer->it.cpu.entry);
388                         spin_unlock(&p->sighand->siglock);
389                 }
390                 read_unlock(&tasklist_lock);
391
392                 if (!ret)
393                         put_task_struct(p);
394         }
395
396         return ret;
397 }
398
399 /*
400  * Clean out CPU timers still ticking when a thread exited.  The task
401  * pointer is cleared, and the expiry time is replaced with the residual
402  * time for later timer_gettime calls to return.
403  * This must be called with the siglock held.
404  */
405 static void cleanup_timers(struct list_head *head,
406                            cputime_t utime, cputime_t stime,
407                            unsigned long long sched_time)
408 {
409         struct cpu_timer_list *timer, *next;
410         cputime_t ptime = cputime_add(utime, stime);
411
412         list_for_each_entry_safe(timer, next, head, entry) {
413                 list_del_init(&timer->entry);
414                 if (cputime_lt(timer->expires.cpu, ptime)) {
415                         timer->expires.cpu = cputime_zero;
416                 } else {
417                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
418                                                          ptime);
419                 }
420         }
421
422         ++head;
423         list_for_each_entry_safe(timer, next, head, entry) {
424                 list_del_init(&timer->entry);
425                 if (cputime_lt(timer->expires.cpu, utime)) {
426                         timer->expires.cpu = cputime_zero;
427                 } else {
428                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
429                                                          utime);
430                 }
431         }
432
433         ++head;
434         list_for_each_entry_safe(timer, next, head, entry) {
435                 list_del_init(&timer->entry);
436                 if (timer->expires.sched < sched_time) {
437                         timer->expires.sched = 0;
438                 } else {
439                         timer->expires.sched -= sched_time;
440                 }
441         }
442 }
443
444 /*
445  * These are both called with the siglock held, when the current thread
446  * is being reaped.  When the final (leader) thread in the group is reaped,
447  * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
448  */
449 void posix_cpu_timers_exit(struct task_struct *tsk)
450 {
451         cleanup_timers(tsk->cpu_timers,
452                        tsk->utime, tsk->stime, tsk->sched_time);
453
454 }
455 void posix_cpu_timers_exit_group(struct task_struct *tsk)
456 {
457         cleanup_timers(tsk->signal->cpu_timers,
458                        cputime_add(tsk->utime, tsk->signal->utime),
459                        cputime_add(tsk->stime, tsk->signal->stime),
460                        tsk->sched_time + tsk->signal->sched_time);
461 }
462
463
464 /*
465  * Set the expiry times of all the threads in the process so one of them
466  * will go off before the process cumulative expiry total is reached.
467  */
468 static void process_timer_rebalance(struct task_struct *p,
469                                     unsigned int clock_idx,
470                                     union cpu_time_count expires,
471                                     union cpu_time_count val)
472 {
473         cputime_t ticks, left;
474         unsigned long long ns, nsleft;
475         struct task_struct *t = p;
476         unsigned int nthreads = atomic_read(&p->signal->live);
477
478         if (!nthreads)
479                 return;
480
481         switch (clock_idx) {
482         default:
483                 BUG();
484                 break;
485         case CPUCLOCK_PROF:
486                 left = cputime_div(cputime_sub(expires.cpu, val.cpu),
487                                    nthreads);
488                 do {
489                         if (likely(!(t->flags & PF_EXITING))) {
490                                 ticks = cputime_add(prof_ticks(t), left);
491                                 if (cputime_eq(t->it_prof_expires,
492                                                cputime_zero) ||
493                                     cputime_gt(t->it_prof_expires, ticks)) {
494                                         t->it_prof_expires = ticks;
495                                 }
496                         }
497                         t = next_thread(t);
498                 } while (t != p);
499                 break;
500         case CPUCLOCK_VIRT:
501                 left = cputime_div(cputime_sub(expires.cpu, val.cpu),
502                                    nthreads);
503                 do {
504                         if (likely(!(t->flags & PF_EXITING))) {
505                                 ticks = cputime_add(virt_ticks(t), left);
506                                 if (cputime_eq(t->it_virt_expires,
507                                                cputime_zero) ||
508                                     cputime_gt(t->it_virt_expires, ticks)) {
509                                         t->it_virt_expires = ticks;
510                                 }
511                         }
512                         t = next_thread(t);
513                 } while (t != p);
514                 break;
515         case CPUCLOCK_SCHED:
516                 nsleft = expires.sched - val.sched;
517                 do_div(nsleft, nthreads);
518                 do {
519                         if (likely(!(t->flags & PF_EXITING))) {
520                                 ns = t->sched_time + nsleft;
521                                 if (t->it_sched_expires == 0 ||
522                                     t->it_sched_expires > ns) {
523                                         t->it_sched_expires = ns;
524                                 }
525                         }
526                         t = next_thread(t);
527                 } while (t != p);
528                 break;
529         }
530 }
531
532 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
533 {
534         /*
535          * That's all for this thread or process.
536          * We leave our residual in expires to be reported.
537          */
538         put_task_struct(timer->it.cpu.task);
539         timer->it.cpu.task = NULL;
540         timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
541                                              timer->it.cpu.expires,
542                                              now);
543 }
544
545 /*
546  * Insert the timer on the appropriate list before any timers that
547  * expire later.  This must be called with the tasklist_lock held
548  * for reading, and interrupts disabled.
549  */
550 static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
551 {
552         struct task_struct *p = timer->it.cpu.task;
553         struct list_head *head, *listpos;
554         struct cpu_timer_list *const nt = &timer->it.cpu;
555         struct cpu_timer_list *next;
556         unsigned long i;
557
558         head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
559                 p->cpu_timers : p->signal->cpu_timers);
560         head += CPUCLOCK_WHICH(timer->it_clock);
561
562         BUG_ON(!irqs_disabled());
563         spin_lock(&p->sighand->siglock);
564
565         listpos = head;
566         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
567                 list_for_each_entry(next, head, entry) {
568                         if (next->expires.sched > nt->expires.sched)
569                                 break;
570                         listpos = &next->entry;
571                 }
572         } else {
573                 list_for_each_entry(next, head, entry) {
574                         if (cputime_gt(next->expires.cpu, nt->expires.cpu))
575                                 break;
576                         listpos = &next->entry;
577                 }
578         }
579         list_add(&nt->entry, listpos);
580
581         if (listpos == head) {
582                 /*
583                  * We are the new earliest-expiring timer.
584                  * If we are a thread timer, there can always
585                  * be a process timer telling us to stop earlier.
586                  */
587
588                 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
589                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
590                         default:
591                                 BUG();
592                         case CPUCLOCK_PROF:
593                                 if (cputime_eq(p->it_prof_expires,
594                                                cputime_zero) ||
595                                     cputime_gt(p->it_prof_expires,
596                                                nt->expires.cpu))
597                                         p->it_prof_expires = nt->expires.cpu;
598                                 break;
599                         case CPUCLOCK_VIRT:
600                                 if (cputime_eq(p->it_virt_expires,
601                                                cputime_zero) ||
602                                     cputime_gt(p->it_virt_expires,
603                                                nt->expires.cpu))
604                                         p->it_virt_expires = nt->expires.cpu;
605                                 break;
606                         case CPUCLOCK_SCHED:
607                                 if (p->it_sched_expires == 0 ||
608                                     p->it_sched_expires > nt->expires.sched)
609                                         p->it_sched_expires = nt->expires.sched;
610                                 break;
611                         }
612                 } else {
613                         /*
614                          * For a process timer, we must balance
615                          * all the live threads' expirations.
616                          */
617                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
618                         default:
619                                 BUG();
620                         case CPUCLOCK_VIRT:
621                                 if (!cputime_eq(p->signal->it_virt_expires,
622                                                 cputime_zero) &&
623                                     cputime_lt(p->signal->it_virt_expires,
624                                                timer->it.cpu.expires.cpu))
625                                         break;
626                                 goto rebalance;
627                         case CPUCLOCK_PROF:
628                                 if (!cputime_eq(p->signal->it_prof_expires,
629                                                 cputime_zero) &&
630                                     cputime_lt(p->signal->it_prof_expires,
631                                                timer->it.cpu.expires.cpu))
632                                         break;
633                                 i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
634                                 if (i != RLIM_INFINITY &&
635                                     i <= cputime_to_secs(timer->it.cpu.expires.cpu))
636                                         break;
637                                 goto rebalance;
638                         case CPUCLOCK_SCHED:
639                         rebalance:
640                                 process_timer_rebalance(
641                                         timer->it.cpu.task,
642                                         CPUCLOCK_WHICH(timer->it_clock),
643                                         timer->it.cpu.expires, now);
644                                 break;
645                         }
646                 }
647         }
648
649         spin_unlock(&p->sighand->siglock);
650 }
651
652 /*
653  * The timer is locked, fire it and arrange for its reload.
654  */
655 static void cpu_timer_fire(struct k_itimer *timer)
656 {
657         if (unlikely(timer->sigq == NULL)) {
658                 /*
659                  * This a special case for clock_nanosleep,
660                  * not a normal timer from sys_timer_create.
661                  */
662                 wake_up_process(timer->it_process);
663                 timer->it.cpu.expires.sched = 0;
664         } else if (timer->it.cpu.incr.sched == 0) {
665                 /*
666                  * One-shot timer.  Clear it as soon as it's fired.
667                  */
668                 posix_timer_event(timer, 0);
669                 timer->it.cpu.expires.sched = 0;
670         } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
671                 /*
672                  * The signal did not get queued because the signal
673                  * was ignored, so we won't get any callback to
674                  * reload the timer.  But we need to keep it
675                  * ticking in case the signal is deliverable next time.
676                  */
677                 posix_cpu_timer_schedule(timer);
678         }
679 }
680
681 /*
682  * Guts of sys_timer_settime for CPU timers.
683  * This is called with the timer locked and interrupts disabled.
684  * If we return TIMER_RETRY, it's necessary to release the timer's lock
685  * and try again.  (This happens when the timer is in the middle of firing.)
686  */
687 int posix_cpu_timer_set(struct k_itimer *timer, int flags,
688                         struct itimerspec *new, struct itimerspec *old)
689 {
690         struct task_struct *p = timer->it.cpu.task;
691         union cpu_time_count old_expires, new_expires, val;
692         int ret;
693
694         if (unlikely(p == NULL)) {
695                 /*
696                  * Timer refers to a dead task's clock.
697                  */
698                 return -ESRCH;
699         }
700
701         new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
702
703         read_lock(&tasklist_lock);
704         /*
705          * We need the tasklist_lock to protect against reaping that
706          * clears p->signal.  If p has just been reaped, we can no
707          * longer get any information about it at all.
708          */
709         if (unlikely(p->signal == NULL)) {
710                 read_unlock(&tasklist_lock);
711                 put_task_struct(p);
712                 timer->it.cpu.task = NULL;
713                 return -ESRCH;
714         }
715
716         /*
717          * Disarm any old timer after extracting its expiry time.
718          */
719         BUG_ON(!irqs_disabled());
720
721         ret = 0;
722         spin_lock(&p->sighand->siglock);
723         old_expires = timer->it.cpu.expires;
724         if (unlikely(timer->it.cpu.firing)) {
725                 timer->it.cpu.firing = -1;
726                 ret = TIMER_RETRY;
727         } else
728                 list_del_init(&timer->it.cpu.entry);
729         spin_unlock(&p->sighand->siglock);
730
731         /*
732          * We need to sample the current value to convert the new
733          * value from to relative and absolute, and to convert the
734          * old value from absolute to relative.  To set a process
735          * timer, we need a sample to balance the thread expiry
736          * times (in arm_timer).  With an absolute time, we must
737          * check if it's already passed.  In short, we need a sample.
738          */
739         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
740                 cpu_clock_sample(timer->it_clock, p, &val);
741         } else {
742                 cpu_clock_sample_group(timer->it_clock, p, &val);
743         }
744
745         if (old) {
746                 if (old_expires.sched == 0) {
747                         old->it_value.tv_sec = 0;
748                         old->it_value.tv_nsec = 0;
749                 } else {
750                         /*
751                          * Update the timer in case it has
752                          * overrun already.  If it has,
753                          * we'll report it as having overrun
754                          * and with the next reloaded timer
755                          * already ticking, though we are
756                          * swallowing that pending
757                          * notification here to install the
758                          * new setting.
759                          */
760                         bump_cpu_timer(timer, val);
761                         if (cpu_time_before(timer->it_clock, val,
762                                             timer->it.cpu.expires)) {
763                                 old_expires = cpu_time_sub(
764                                         timer->it_clock,
765                                         timer->it.cpu.expires, val);
766                                 sample_to_timespec(timer->it_clock,
767                                                    old_expires,
768                                                    &old->it_value);
769                         } else {
770                                 old->it_value.tv_nsec = 1;
771                                 old->it_value.tv_sec = 0;
772                         }
773                 }
774         }
775
776         if (unlikely(ret)) {
777                 /*
778                  * We are colliding with the timer actually firing.
779                  * Punt after filling in the timer's old value, and
780                  * disable this firing since we are already reporting
781                  * it as an overrun (thanks to bump_cpu_timer above).
782                  */
783                 read_unlock(&tasklist_lock);
784                 goto out;
785         }
786
787         if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
788                 cpu_time_add(timer->it_clock, &new_expires, val);
789         }
790
791         /*
792          * Install the new expiry time (or zero).
793          * For a timer with no notification action, we don't actually
794          * arm the timer (we'll just fake it for timer_gettime).
795          */
796         timer->it.cpu.expires = new_expires;
797         if (new_expires.sched != 0 &&
798             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
799             cpu_time_before(timer->it_clock, val, new_expires)) {
800                 arm_timer(timer, val);
801         }
802
803         read_unlock(&tasklist_lock);
804
805         /*
806          * Install the new reload setting, and
807          * set up the signal and overrun bookkeeping.
808          */
809         timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
810                                                 &new->it_interval);
811
812         /*
813          * This acts as a modification timestamp for the timer,
814          * so any automatic reload attempt will punt on seeing
815          * that we have reset the timer manually.
816          */
817         timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
818                 ~REQUEUE_PENDING;
819         timer->it_overrun_last = 0;
820         timer->it_overrun = -1;
821
822         if (new_expires.sched != 0 &&
823             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
824             !cpu_time_before(timer->it_clock, val, new_expires)) {
825                 /*
826                  * The designated time already passed, so we notify
827                  * immediately, even if the thread never runs to
828                  * accumulate more time on this clock.
829                  */
830                 cpu_timer_fire(timer);
831         }
832
833         ret = 0;
834  out:
835         if (old) {
836                 sample_to_timespec(timer->it_clock,
837                                    timer->it.cpu.incr, &old->it_interval);
838         }
839         return ret;
840 }
841
842 void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
843 {
844         union cpu_time_count now;
845         struct task_struct *p = timer->it.cpu.task;
846         int clear_dead;
847
848         /*
849          * Easy part: convert the reload time.
850          */
851         sample_to_timespec(timer->it_clock,
852                            timer->it.cpu.incr, &itp->it_interval);
853
854         if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
855                 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
856                 return;
857         }
858
859         if (unlikely(p == NULL)) {
860                 /*
861                  * This task already died and the timer will never fire.
862                  * In this case, expires is actually the dead value.
863                  */
864         dead:
865                 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
866                                    &itp->it_value);
867                 return;
868         }
869
870         /*
871          * Sample the clock to take the difference with the expiry time.
872          */
873         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
874                 cpu_clock_sample(timer->it_clock, p, &now);
875                 clear_dead = p->exit_state;
876         } else {
877                 read_lock(&tasklist_lock);
878                 if (unlikely(p->signal == NULL)) {
879                         /*
880                          * The process has been reaped.
881                          * We can't even collect a sample any more.
882                          * Call the timer disarmed, nothing else to do.
883                          */
884                         put_task_struct(p);
885                         timer->it.cpu.task = NULL;
886                         timer->it.cpu.expires.sched = 0;
887                         read_unlock(&tasklist_lock);
888                         goto dead;
889                 } else {
890                         cpu_clock_sample_group(timer->it_clock, p, &now);
891                         clear_dead = (unlikely(p->exit_state) &&
892                                       thread_group_empty(p));
893                 }
894                 read_unlock(&tasklist_lock);
895         }
896
897         if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
898                 if (timer->it.cpu.incr.sched == 0 &&
899                     cpu_time_before(timer->it_clock,
900                                     timer->it.cpu.expires, now)) {
901                         /*
902                          * Do-nothing timer expired and has no reload,
903                          * so it's as if it was never set.
904                          */
905                         timer->it.cpu.expires.sched = 0;
906                         itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
907                         return;
908                 }
909                 /*
910                  * Account for any expirations and reloads that should
911                  * have happened.
912                  */
913                 bump_cpu_timer(timer, now);
914         }
915
916         if (unlikely(clear_dead)) {
917                 /*
918                  * We've noticed that the thread is dead, but
919                  * not yet reaped.  Take this opportunity to
920                  * drop our task ref.
921                  */
922                 clear_dead_task(timer, now);
923                 goto dead;
924         }
925
926         if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
927                 sample_to_timespec(timer->it_clock,
928                                    cpu_time_sub(timer->it_clock,
929                                                 timer->it.cpu.expires, now),
930                                    &itp->it_value);
931         } else {
932                 /*
933                  * The timer should have expired already, but the firing
934                  * hasn't taken place yet.  Say it's just about to expire.
935                  */
936                 itp->it_value.tv_nsec = 1;
937                 itp->it_value.tv_sec = 0;
938         }
939 }
940
941 /*
942  * Check for any per-thread CPU timers that have fired and move them off
943  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
944  * tsk->it_*_expires values to reflect the remaining thread CPU timers.
945  */
946 static void check_thread_timers(struct task_struct *tsk,
947                                 struct list_head *firing)
948 {
949         int maxfire;
950         struct list_head *timers = tsk->cpu_timers;
951
952         maxfire = 20;
953         tsk->it_prof_expires = cputime_zero;
954         while (!list_empty(timers)) {
955                 struct cpu_timer_list *t = list_entry(timers->next,
956                                                       struct cpu_timer_list,
957                                                       entry);
958                 if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
959                         tsk->it_prof_expires = t->expires.cpu;
960                         break;
961                 }
962                 t->firing = 1;
963                 list_move_tail(&t->entry, firing);
964         }
965
966         ++timers;
967         maxfire = 20;
968         tsk->it_virt_expires = cputime_zero;
969         while (!list_empty(timers)) {
970                 struct cpu_timer_list *t = list_entry(timers->next,
971                                                       struct cpu_timer_list,
972                                                       entry);
973                 if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
974                         tsk->it_virt_expires = t->expires.cpu;
975                         break;
976                 }
977                 t->firing = 1;
978                 list_move_tail(&t->entry, firing);
979         }
980
981         ++timers;
982         maxfire = 20;
983         tsk->it_sched_expires = 0;
984         while (!list_empty(timers)) {
985                 struct cpu_timer_list *t = list_entry(timers->next,
986                                                       struct cpu_timer_list,
987                                                       entry);
988                 if (!--maxfire || tsk->sched_time < t->expires.sched) {
989                         tsk->it_sched_expires = t->expires.sched;
990                         break;
991                 }
992                 t->firing = 1;
993                 list_move_tail(&t->entry, firing);
994         }
995 }
996
997 /*
998  * Check for any per-thread CPU timers that have fired and move them
999  * off the tsk->*_timers list onto the firing list.  Per-thread timers
1000  * have already been taken off.
1001  */
1002 static void check_process_timers(struct task_struct *tsk,
1003                                  struct list_head *firing)
1004 {
1005         int maxfire;
1006         struct signal_struct *const sig = tsk->signal;
1007         cputime_t utime, stime, ptime, virt_expires, prof_expires;
1008         unsigned long long sched_time, sched_expires;
1009         struct task_struct *t;
1010         struct list_head *timers = sig->cpu_timers;
1011
1012         /*
1013          * Don't sample the current process CPU clocks if there are no timers.
1014          */
1015         if (list_empty(&timers[CPUCLOCK_PROF]) &&
1016             cputime_eq(sig->it_prof_expires, cputime_zero) &&
1017             sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
1018             list_empty(&timers[CPUCLOCK_VIRT]) &&
1019             cputime_eq(sig->it_virt_expires, cputime_zero) &&
1020             list_empty(&timers[CPUCLOCK_SCHED]))
1021                 return;
1022
1023         /*
1024          * Collect the current process totals.
1025          */
1026         utime = sig->utime;
1027         stime = sig->stime;
1028         sched_time = sig->sched_time;
1029         t = tsk;
1030         do {
1031                 utime = cputime_add(utime, t->utime);
1032                 stime = cputime_add(stime, t->stime);
1033                 sched_time += t->sched_time;
1034                 t = next_thread(t);
1035         } while (t != tsk);
1036         ptime = cputime_add(utime, stime);
1037
1038         maxfire = 20;
1039         prof_expires = cputime_zero;
1040         while (!list_empty(timers)) {
1041                 struct cpu_timer_list *t = list_entry(timers->next,
1042                                                       struct cpu_timer_list,
1043                                                       entry);
1044                 if (!--maxfire || cputime_lt(ptime, t->expires.cpu)) {
1045                         prof_expires = t->expires.cpu;
1046                         break;
1047                 }
1048                 t->firing = 1;
1049                 list_move_tail(&t->entry, firing);
1050         }
1051
1052         ++timers;
1053         maxfire = 20;
1054         virt_expires = cputime_zero;
1055         while (!list_empty(timers)) {
1056                 struct cpu_timer_list *t = list_entry(timers->next,
1057                                                       struct cpu_timer_list,
1058                                                       entry);
1059                 if (!--maxfire || cputime_lt(utime, t->expires.cpu)) {
1060                         virt_expires = t->expires.cpu;
1061                         break;
1062                 }
1063                 t->firing = 1;
1064                 list_move_tail(&t->entry, firing);
1065         }
1066
1067         ++timers;
1068         maxfire = 20;
1069         sched_expires = 0;
1070         while (!list_empty(timers)) {
1071                 struct cpu_timer_list *t = list_entry(timers->next,
1072                                                       struct cpu_timer_list,
1073                                                       entry);
1074                 if (!--maxfire || sched_time < t->expires.sched) {
1075                         sched_expires = t->expires.sched;
1076                         break;
1077                 }
1078                 t->firing = 1;
1079                 list_move_tail(&t->entry, firing);
1080         }
1081
1082         /*
1083          * Check for the special case process timers.
1084          */
1085         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1086                 if (cputime_ge(ptime, sig->it_prof_expires)) {
1087                         /* ITIMER_PROF fires and reloads.  */
1088                         sig->it_prof_expires = sig->it_prof_incr;
1089                         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1090                                 sig->it_prof_expires = cputime_add(
1091                                         sig->it_prof_expires, ptime);
1092                         }
1093                         __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
1094                 }
1095                 if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
1096                     (cputime_eq(prof_expires, cputime_zero) ||
1097                      cputime_lt(sig->it_prof_expires, prof_expires))) {
1098                         prof_expires = sig->it_prof_expires;
1099                 }
1100         }
1101         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1102                 if (cputime_ge(utime, sig->it_virt_expires)) {
1103                         /* ITIMER_VIRTUAL fires and reloads.  */
1104                         sig->it_virt_expires = sig->it_virt_incr;
1105                         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1106                                 sig->it_virt_expires = cputime_add(
1107                                         sig->it_virt_expires, utime);
1108                         }
1109                         __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
1110                 }
1111                 if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
1112                     (cputime_eq(virt_expires, cputime_zero) ||
1113                      cputime_lt(sig->it_virt_expires, virt_expires))) {
1114                         virt_expires = sig->it_virt_expires;
1115                 }
1116         }
1117         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
1118                 unsigned long psecs = cputime_to_secs(ptime);
1119                 cputime_t x;
1120                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
1121                         /*
1122                          * At the hard limit, we just die.
1123                          * No need to calculate anything else now.
1124                          */
1125                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1126                         return;
1127                 }
1128                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
1129                         /*
1130                          * At the soft limit, send a SIGXCPU every second.
1131                          */
1132                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1133                         if (sig->rlim[RLIMIT_CPU].rlim_cur
1134                             < sig->rlim[RLIMIT_CPU].rlim_max) {
1135                                 sig->rlim[RLIMIT_CPU].rlim_cur++;
1136                         }
1137                 }
1138                 x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
1139                 if (cputime_eq(prof_expires, cputime_zero) ||
1140                     cputime_lt(x, prof_expires)) {
1141                         prof_expires = x;
1142                 }
1143         }
1144
1145         if (!cputime_eq(prof_expires, cputime_zero) ||
1146             !cputime_eq(virt_expires, cputime_zero) ||
1147             sched_expires != 0) {
1148                 /*
1149                  * Rebalance the threads' expiry times for the remaining
1150                  * process CPU timers.
1151                  */
1152
1153                 cputime_t prof_left, virt_left, ticks;
1154                 unsigned long long sched_left, sched;
1155                 const unsigned int nthreads = atomic_read(&sig->live);
1156
1157                 if (!nthreads)
1158                         return;
1159
1160                 prof_left = cputime_sub(prof_expires, utime);
1161                 prof_left = cputime_sub(prof_left, stime);
1162                 prof_left = cputime_div(prof_left, nthreads);
1163                 virt_left = cputime_sub(virt_expires, utime);
1164                 virt_left = cputime_div(virt_left, nthreads);
1165                 if (sched_expires) {
1166                         sched_left = sched_expires - sched_time;
1167                         do_div(sched_left, nthreads);
1168                 } else {
1169                         sched_left = 0;
1170                 }
1171                 t = tsk;
1172                 do {
1173                         if (unlikely(t->flags & PF_EXITING))
1174                                 continue;
1175
1176                         ticks = cputime_add(cputime_add(t->utime, t->stime),
1177                                             prof_left);
1178                         if (!cputime_eq(prof_expires, cputime_zero) &&
1179                             (cputime_eq(t->it_prof_expires, cputime_zero) ||
1180                              cputime_gt(t->it_prof_expires, ticks))) {
1181                                 t->it_prof_expires = ticks;
1182                         }
1183
1184                         ticks = cputime_add(t->utime, virt_left);
1185                         if (!cputime_eq(virt_expires, cputime_zero) &&
1186                             (cputime_eq(t->it_virt_expires, cputime_zero) ||
1187                              cputime_gt(t->it_virt_expires, ticks))) {
1188                                 t->it_virt_expires = ticks;
1189                         }
1190
1191                         sched = t->sched_time + sched_left;
1192                         if (sched_expires && (t->it_sched_expires == 0 ||
1193                                               t->it_sched_expires > sched)) {
1194                                 t->it_sched_expires = sched;
1195                         }
1196                 } while ((t = next_thread(t)) != tsk);
1197         }
1198 }
1199
1200 /*
1201  * This is called from the signal code (via do_schedule_next_timer)
1202  * when the last timer signal was delivered and we have to reload the timer.
1203  */
1204 void posix_cpu_timer_schedule(struct k_itimer *timer)
1205 {
1206         struct task_struct *p = timer->it.cpu.task;
1207         union cpu_time_count now;
1208
1209         if (unlikely(p == NULL))
1210                 /*
1211                  * The task was cleaned up already, no future firings.
1212                  */
1213                 goto out;
1214
1215         /*
1216          * Fetch the current sample and update the timer's expiry time.
1217          */
1218         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1219                 cpu_clock_sample(timer->it_clock, p, &now);
1220                 bump_cpu_timer(timer, now);
1221                 if (unlikely(p->exit_state)) {
1222                         clear_dead_task(timer, now);
1223                         goto out;
1224                 }
1225                 read_lock(&tasklist_lock); /* arm_timer needs it.  */
1226         } else {
1227                 read_lock(&tasklist_lock);
1228                 if (unlikely(p->signal == NULL)) {
1229                         /*
1230                          * The process has been reaped.
1231                          * We can't even collect a sample any more.
1232                          */
1233                         put_task_struct(p);
1234                         timer->it.cpu.task = p = NULL;
1235                         timer->it.cpu.expires.sched = 0;
1236                         goto out_unlock;
1237                 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1238                         /*
1239                          * We've noticed that the thread is dead, but
1240                          * not yet reaped.  Take this opportunity to
1241                          * drop our task ref.
1242                          */
1243                         clear_dead_task(timer, now);
1244                         goto out_unlock;
1245                 }
1246                 cpu_clock_sample_group(timer->it_clock, p, &now);
1247                 bump_cpu_timer(timer, now);
1248                 /* Leave the tasklist_lock locked for the call below.  */
1249         }
1250
1251         /*
1252          * Now re-arm for the new expiry time.
1253          */
1254         arm_timer(timer, now);
1255
1256 out_unlock:
1257         read_unlock(&tasklist_lock);
1258
1259 out:
1260         timer->it_overrun_last = timer->it_overrun;
1261         timer->it_overrun = -1;
1262         ++timer->it_requeue_pending;
1263 }
1264
1265 /*
1266  * This is called from the timer interrupt handler.  The irq handler has
1267  * already updated our counts.  We need to check if any timers fire now.
1268  * Interrupts are disabled.
1269  */
1270 void run_posix_cpu_timers(struct task_struct *tsk)
1271 {
1272         LIST_HEAD(firing);
1273         struct k_itimer *timer, *next;
1274
1275         BUG_ON(!irqs_disabled());
1276
1277 #define UNEXPIRED(clock) \
1278                 (cputime_eq(tsk->it_##clock##_expires, cputime_zero) || \
1279                  cputime_lt(clock##_ticks(tsk), tsk->it_##clock##_expires))
1280
1281         if (UNEXPIRED(prof) && UNEXPIRED(virt) &&
1282             (tsk->it_sched_expires == 0 ||
1283              tsk->sched_time < tsk->it_sched_expires))
1284                 return;
1285
1286 #undef  UNEXPIRED
1287
1288         /*
1289          * Double-check with locks held.
1290          */
1291         read_lock(&tasklist_lock);
1292         if (likely(tsk->signal != NULL)) {
1293                 spin_lock(&tsk->sighand->siglock);
1294
1295                 /*
1296                  * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
1297                  * all the timers that are firing, and put them on the firing list.
1298                  */
1299                 check_thread_timers(tsk, &firing);
1300                 check_process_timers(tsk, &firing);
1301
1302                 /*
1303                  * We must release these locks before taking any timer's lock.
1304                  * There is a potential race with timer deletion here, as the
1305                  * siglock now protects our private firing list.  We have set
1306                  * the firing flag in each timer, so that a deletion attempt
1307                  * that gets the timer lock before we do will give it up and
1308                  * spin until we've taken care of that timer below.
1309                  */
1310                 spin_unlock(&tsk->sighand->siglock);
1311         }
1312         read_unlock(&tasklist_lock);
1313
1314         /*
1315          * Now that all the timers on our list have the firing flag,
1316          * noone will touch their list entries but us.  We'll take
1317          * each timer's lock before clearing its firing flag, so no
1318          * timer call will interfere.
1319          */
1320         list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1321                 int firing;
1322                 spin_lock(&timer->it_lock);
1323                 list_del_init(&timer->it.cpu.entry);
1324                 firing = timer->it.cpu.firing;
1325                 timer->it.cpu.firing = 0;
1326                 /*
1327                  * The firing flag is -1 if we collided with a reset
1328                  * of the timer, which already reported this
1329                  * almost-firing as an overrun.  So don't generate an event.
1330                  */
1331                 if (likely(firing >= 0)) {
1332                         cpu_timer_fire(timer);
1333                 }
1334                 spin_unlock(&timer->it_lock);
1335         }
1336 }
1337
1338 /*
1339  * Set one of the process-wide special case CPU timers.
1340  * The tasklist_lock and tsk->sighand->siglock must be held by the caller.
1341  * The oldval argument is null for the RLIMIT_CPU timer, where *newval is
1342  * absolute; non-null for ITIMER_*, where *newval is relative and we update
1343  * it to be absolute, *oldval is absolute and we update it to be relative.
1344  */
1345 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1346                            cputime_t *newval, cputime_t *oldval)
1347 {
1348         union cpu_time_count now;
1349         struct list_head *head;
1350
1351         BUG_ON(clock_idx == CPUCLOCK_SCHED);
1352         cpu_clock_sample_group_locked(clock_idx, tsk, &now);
1353
1354         if (oldval) {
1355                 if (!cputime_eq(*oldval, cputime_zero)) {
1356                         if (cputime_le(*oldval, now.cpu)) {
1357                                 /* Just about to fire. */
1358                                 *oldval = jiffies_to_cputime(1);
1359                         } else {
1360                                 *oldval = cputime_sub(*oldval, now.cpu);
1361                         }
1362                 }
1363
1364                 if (cputime_eq(*newval, cputime_zero))
1365                         return;
1366                 *newval = cputime_add(*newval, now.cpu);
1367
1368                 /*
1369                  * If the RLIMIT_CPU timer will expire before the
1370                  * ITIMER_PROF timer, we have nothing else to do.
1371                  */
1372                 if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
1373                     < cputime_to_secs(*newval))
1374                         return;
1375         }
1376
1377         /*
1378          * Check whether there are any process timers already set to fire
1379          * before this one.  If so, we don't have anything more to do.
1380          */
1381         head = &tsk->signal->cpu_timers[clock_idx];
1382         if (list_empty(head) ||
1383             cputime_ge(list_entry(head->next,
1384                                   struct cpu_timer_list, entry)->expires.cpu,
1385                        *newval)) {
1386                 /*
1387                  * Rejigger each thread's expiry time so that one will
1388                  * notice before we hit the process-cumulative expiry time.
1389                  */
1390                 union cpu_time_count expires = { .sched = 0 };
1391                 expires.cpu = *newval;
1392                 process_timer_rebalance(tsk, clock_idx, expires, now);
1393         }
1394 }
1395
1396 static long posix_cpu_clock_nanosleep_restart(struct restart_block *);
1397
1398 int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1399                      struct timespec *rqtp, struct timespec __user *rmtp)
1400 {
1401         struct restart_block *restart_block =
1402             &current_thread_info()->restart_block;
1403         struct k_itimer timer;
1404         int error;
1405
1406         /*
1407          * Diagnose required errors first.
1408          */
1409         if (CPUCLOCK_PERTHREAD(which_clock) &&
1410             (CPUCLOCK_PID(which_clock) == 0 ||
1411              CPUCLOCK_PID(which_clock) == current->pid))
1412                 return -EINVAL;
1413
1414         /*
1415          * Set up a temporary timer and then wait for it to go off.
1416          */
1417         memset(&timer, 0, sizeof timer);
1418         spin_lock_init(&timer.it_lock);
1419         timer.it_clock = which_clock;
1420         timer.it_overrun = -1;
1421         error = posix_cpu_timer_create(&timer);
1422         timer.it_process = current;
1423         if (!error) {
1424                 static struct itimerspec zero_it;
1425                 struct itimerspec it = { .it_value = *rqtp,
1426                                          .it_interval = {} };
1427
1428                 spin_lock_irq(&timer.it_lock);
1429                 error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1430                 if (error) {
1431                         spin_unlock_irq(&timer.it_lock);
1432                         return error;
1433                 }
1434
1435                 while (!signal_pending(current)) {
1436                         if (timer.it.cpu.expires.sched == 0) {
1437                                 /*
1438                                  * Our timer fired and was reset.
1439                                  */
1440                                 spin_unlock_irq(&timer.it_lock);
1441                                 return 0;
1442                         }
1443
1444                         /*
1445                          * Block until cpu_timer_fire (or a signal) wakes us.
1446                          */
1447                         __set_current_state(TASK_INTERRUPTIBLE);
1448                         spin_unlock_irq(&timer.it_lock);
1449                         schedule();
1450                         spin_lock_irq(&timer.it_lock);
1451                 }
1452
1453                 /*
1454                  * We were interrupted by a signal.
1455                  */
1456                 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1457                 posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1458                 spin_unlock_irq(&timer.it_lock);
1459
1460                 if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1461                         /*
1462                          * It actually did fire already.
1463                          */
1464                         return 0;
1465                 }
1466
1467                 /*
1468                  * Report back to the user the time still remaining.
1469                  */
1470                 if (rmtp != NULL && !(flags & TIMER_ABSTIME) &&
1471                     copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1472                         return -EFAULT;
1473
1474                 restart_block->fn = posix_cpu_clock_nanosleep_restart;
1475                 /* Caller already set restart_block->arg1 */
1476                 restart_block->arg0 = which_clock;
1477                 restart_block->arg1 = (unsigned long) rmtp;
1478                 restart_block->arg2 = rqtp->tv_sec;
1479                 restart_block->arg3 = rqtp->tv_nsec;
1480
1481                 error = -ERESTART_RESTARTBLOCK;
1482         }
1483
1484         return error;
1485 }
1486
1487 static long
1488 posix_cpu_clock_nanosleep_restart(struct restart_block *restart_block)
1489 {
1490         clockid_t which_clock = restart_block->arg0;
1491         struct timespec __user *rmtp;
1492         struct timespec t;
1493
1494         rmtp = (struct timespec __user *) restart_block->arg1;
1495         t.tv_sec = restart_block->arg2;
1496         t.tv_nsec = restart_block->arg3;
1497
1498         restart_block->fn = do_no_restart_syscall;
1499         return posix_cpu_nsleep(which_clock, TIMER_ABSTIME, &t, rmtp);
1500 }
1501
1502
1503 #define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1504 #define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1505
1506 static int process_cpu_clock_getres(const clockid_t which_clock,
1507                                     struct timespec *tp)
1508 {
1509         return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1510 }
1511 static int process_cpu_clock_get(const clockid_t which_clock,
1512                                  struct timespec *tp)
1513 {
1514         return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1515 }
1516 static int process_cpu_timer_create(struct k_itimer *timer)
1517 {
1518         timer->it_clock = PROCESS_CLOCK;
1519         return posix_cpu_timer_create(timer);
1520 }
1521 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1522                               struct timespec *rqtp,
1523                               struct timespec __user *rmtp)
1524 {
1525         return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1526 }
1527 static int thread_cpu_clock_getres(const clockid_t which_clock,
1528                                    struct timespec *tp)
1529 {
1530         return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1531 }
1532 static int thread_cpu_clock_get(const clockid_t which_clock,
1533                                 struct timespec *tp)
1534 {
1535         return posix_cpu_clock_get(THREAD_CLOCK, tp);
1536 }
1537 static int thread_cpu_timer_create(struct k_itimer *timer)
1538 {
1539         timer->it_clock = THREAD_CLOCK;
1540         return posix_cpu_timer_create(timer);
1541 }
1542 static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
1543                               struct timespec *rqtp, struct timespec __user *rmtp)
1544 {
1545         return -EINVAL;
1546 }
1547
1548 static __init int init_posix_cpu_timers(void)
1549 {
1550         struct k_clock process = {
1551                 .clock_getres = process_cpu_clock_getres,
1552                 .clock_get = process_cpu_clock_get,
1553                 .clock_set = do_posix_clock_nosettime,
1554                 .timer_create = process_cpu_timer_create,
1555                 .nsleep = process_cpu_nsleep,
1556         };
1557         struct k_clock thread = {
1558                 .clock_getres = thread_cpu_clock_getres,
1559                 .clock_get = thread_cpu_clock_get,
1560                 .clock_set = do_posix_clock_nosettime,
1561                 .timer_create = thread_cpu_timer_create,
1562                 .nsleep = thread_cpu_nsleep,
1563         };
1564
1565         register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1566         register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1567
1568         return 0;
1569 }
1570 __initcall(init_posix_cpu_timers);