[PATCH] check_process_timers: fix possible lockup
[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         if (CPUCLOCK_PERTHREAD(timer->it_clock) && (p->flags & PF_EXITING))
559                 return;
560
561         head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
562                 p->cpu_timers : p->signal->cpu_timers);
563         head += CPUCLOCK_WHICH(timer->it_clock);
564
565         BUG_ON(!irqs_disabled());
566         spin_lock(&p->sighand->siglock);
567
568         listpos = head;
569         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
570                 list_for_each_entry(next, head, entry) {
571                         if (next->expires.sched > nt->expires.sched)
572                                 break;
573                         listpos = &next->entry;
574                 }
575         } else {
576                 list_for_each_entry(next, head, entry) {
577                         if (cputime_gt(next->expires.cpu, nt->expires.cpu))
578                                 break;
579                         listpos = &next->entry;
580                 }
581         }
582         list_add(&nt->entry, listpos);
583
584         if (listpos == head) {
585                 /*
586                  * We are the new earliest-expiring timer.
587                  * If we are a thread timer, there can always
588                  * be a process timer telling us to stop earlier.
589                  */
590
591                 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
592                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
593                         default:
594                                 BUG();
595                         case CPUCLOCK_PROF:
596                                 if (cputime_eq(p->it_prof_expires,
597                                                cputime_zero) ||
598                                     cputime_gt(p->it_prof_expires,
599                                                nt->expires.cpu))
600                                         p->it_prof_expires = nt->expires.cpu;
601                                 break;
602                         case CPUCLOCK_VIRT:
603                                 if (cputime_eq(p->it_virt_expires,
604                                                cputime_zero) ||
605                                     cputime_gt(p->it_virt_expires,
606                                                nt->expires.cpu))
607                                         p->it_virt_expires = nt->expires.cpu;
608                                 break;
609                         case CPUCLOCK_SCHED:
610                                 if (p->it_sched_expires == 0 ||
611                                     p->it_sched_expires > nt->expires.sched)
612                                         p->it_sched_expires = nt->expires.sched;
613                                 break;
614                         }
615                 } else {
616                         /*
617                          * For a process timer, we must balance
618                          * all the live threads' expirations.
619                          */
620                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
621                         default:
622                                 BUG();
623                         case CPUCLOCK_VIRT:
624                                 if (!cputime_eq(p->signal->it_virt_expires,
625                                                 cputime_zero) &&
626                                     cputime_lt(p->signal->it_virt_expires,
627                                                timer->it.cpu.expires.cpu))
628                                         break;
629                                 goto rebalance;
630                         case CPUCLOCK_PROF:
631                                 if (!cputime_eq(p->signal->it_prof_expires,
632                                                 cputime_zero) &&
633                                     cputime_lt(p->signal->it_prof_expires,
634                                                timer->it.cpu.expires.cpu))
635                                         break;
636                                 i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
637                                 if (i != RLIM_INFINITY &&
638                                     i <= cputime_to_secs(timer->it.cpu.expires.cpu))
639                                         break;
640                                 goto rebalance;
641                         case CPUCLOCK_SCHED:
642                         rebalance:
643                                 process_timer_rebalance(
644                                         timer->it.cpu.task,
645                                         CPUCLOCK_WHICH(timer->it_clock),
646                                         timer->it.cpu.expires, now);
647                                 break;
648                         }
649                 }
650         }
651
652         spin_unlock(&p->sighand->siglock);
653 }
654
655 /*
656  * The timer is locked, fire it and arrange for its reload.
657  */
658 static void cpu_timer_fire(struct k_itimer *timer)
659 {
660         if (unlikely(timer->sigq == NULL)) {
661                 /*
662                  * This a special case for clock_nanosleep,
663                  * not a normal timer from sys_timer_create.
664                  */
665                 wake_up_process(timer->it_process);
666                 timer->it.cpu.expires.sched = 0;
667         } else if (timer->it.cpu.incr.sched == 0) {
668                 /*
669                  * One-shot timer.  Clear it as soon as it's fired.
670                  */
671                 posix_timer_event(timer, 0);
672                 timer->it.cpu.expires.sched = 0;
673         } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
674                 /*
675                  * The signal did not get queued because the signal
676                  * was ignored, so we won't get any callback to
677                  * reload the timer.  But we need to keep it
678                  * ticking in case the signal is deliverable next time.
679                  */
680                 posix_cpu_timer_schedule(timer);
681         }
682 }
683
684 /*
685  * Guts of sys_timer_settime for CPU timers.
686  * This is called with the timer locked and interrupts disabled.
687  * If we return TIMER_RETRY, it's necessary to release the timer's lock
688  * and try again.  (This happens when the timer is in the middle of firing.)
689  */
690 int posix_cpu_timer_set(struct k_itimer *timer, int flags,
691                         struct itimerspec *new, struct itimerspec *old)
692 {
693         struct task_struct *p = timer->it.cpu.task;
694         union cpu_time_count old_expires, new_expires, val;
695         int ret;
696
697         if (unlikely(p == NULL)) {
698                 /*
699                  * Timer refers to a dead task's clock.
700                  */
701                 return -ESRCH;
702         }
703
704         new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
705
706         read_lock(&tasklist_lock);
707         /*
708          * We need the tasklist_lock to protect against reaping that
709          * clears p->signal.  If p has just been reaped, we can no
710          * longer get any information about it at all.
711          */
712         if (unlikely(p->signal == NULL)) {
713                 read_unlock(&tasklist_lock);
714                 put_task_struct(p);
715                 timer->it.cpu.task = NULL;
716                 return -ESRCH;
717         }
718
719         /*
720          * Disarm any old timer after extracting its expiry time.
721          */
722         BUG_ON(!irqs_disabled());
723
724         ret = 0;
725         spin_lock(&p->sighand->siglock);
726         old_expires = timer->it.cpu.expires;
727         if (unlikely(timer->it.cpu.firing)) {
728                 timer->it.cpu.firing = -1;
729                 ret = TIMER_RETRY;
730         } else
731                 list_del_init(&timer->it.cpu.entry);
732         spin_unlock(&p->sighand->siglock);
733
734         /*
735          * We need to sample the current value to convert the new
736          * value from to relative and absolute, and to convert the
737          * old value from absolute to relative.  To set a process
738          * timer, we need a sample to balance the thread expiry
739          * times (in arm_timer).  With an absolute time, we must
740          * check if it's already passed.  In short, we need a sample.
741          */
742         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
743                 cpu_clock_sample(timer->it_clock, p, &val);
744         } else {
745                 cpu_clock_sample_group(timer->it_clock, p, &val);
746         }
747
748         if (old) {
749                 if (old_expires.sched == 0) {
750                         old->it_value.tv_sec = 0;
751                         old->it_value.tv_nsec = 0;
752                 } else {
753                         /*
754                          * Update the timer in case it has
755                          * overrun already.  If it has,
756                          * we'll report it as having overrun
757                          * and with the next reloaded timer
758                          * already ticking, though we are
759                          * swallowing that pending
760                          * notification here to install the
761                          * new setting.
762                          */
763                         bump_cpu_timer(timer, val);
764                         if (cpu_time_before(timer->it_clock, val,
765                                             timer->it.cpu.expires)) {
766                                 old_expires = cpu_time_sub(
767                                         timer->it_clock,
768                                         timer->it.cpu.expires, val);
769                                 sample_to_timespec(timer->it_clock,
770                                                    old_expires,
771                                                    &old->it_value);
772                         } else {
773                                 old->it_value.tv_nsec = 1;
774                                 old->it_value.tv_sec = 0;
775                         }
776                 }
777         }
778
779         if (unlikely(ret)) {
780                 /*
781                  * We are colliding with the timer actually firing.
782                  * Punt after filling in the timer's old value, and
783                  * disable this firing since we are already reporting
784                  * it as an overrun (thanks to bump_cpu_timer above).
785                  */
786                 read_unlock(&tasklist_lock);
787                 goto out;
788         }
789
790         if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
791                 cpu_time_add(timer->it_clock, &new_expires, val);
792         }
793
794         /*
795          * Install the new expiry time (or zero).
796          * For a timer with no notification action, we don't actually
797          * arm the timer (we'll just fake it for timer_gettime).
798          */
799         timer->it.cpu.expires = new_expires;
800         if (new_expires.sched != 0 &&
801             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
802             cpu_time_before(timer->it_clock, val, new_expires)) {
803                 arm_timer(timer, val);
804         }
805
806         read_unlock(&tasklist_lock);
807
808         /*
809          * Install the new reload setting, and
810          * set up the signal and overrun bookkeeping.
811          */
812         timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
813                                                 &new->it_interval);
814
815         /*
816          * This acts as a modification timestamp for the timer,
817          * so any automatic reload attempt will punt on seeing
818          * that we have reset the timer manually.
819          */
820         timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
821                 ~REQUEUE_PENDING;
822         timer->it_overrun_last = 0;
823         timer->it_overrun = -1;
824
825         if (new_expires.sched != 0 &&
826             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
827             !cpu_time_before(timer->it_clock, val, new_expires)) {
828                 /*
829                  * The designated time already passed, so we notify
830                  * immediately, even if the thread never runs to
831                  * accumulate more time on this clock.
832                  */
833                 cpu_timer_fire(timer);
834         }
835
836         ret = 0;
837  out:
838         if (old) {
839                 sample_to_timespec(timer->it_clock,
840                                    timer->it.cpu.incr, &old->it_interval);
841         }
842         return ret;
843 }
844
845 void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
846 {
847         union cpu_time_count now;
848         struct task_struct *p = timer->it.cpu.task;
849         int clear_dead;
850
851         /*
852          * Easy part: convert the reload time.
853          */
854         sample_to_timespec(timer->it_clock,
855                            timer->it.cpu.incr, &itp->it_interval);
856
857         if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
858                 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
859                 return;
860         }
861
862         if (unlikely(p == NULL)) {
863                 /*
864                  * This task already died and the timer will never fire.
865                  * In this case, expires is actually the dead value.
866                  */
867         dead:
868                 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
869                                    &itp->it_value);
870                 return;
871         }
872
873         /*
874          * Sample the clock to take the difference with the expiry time.
875          */
876         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
877                 cpu_clock_sample(timer->it_clock, p, &now);
878                 clear_dead = p->exit_state;
879         } else {
880                 read_lock(&tasklist_lock);
881                 if (unlikely(p->signal == NULL)) {
882                         /*
883                          * The process has been reaped.
884                          * We can't even collect a sample any more.
885                          * Call the timer disarmed, nothing else to do.
886                          */
887                         put_task_struct(p);
888                         timer->it.cpu.task = NULL;
889                         timer->it.cpu.expires.sched = 0;
890                         read_unlock(&tasklist_lock);
891                         goto dead;
892                 } else {
893                         cpu_clock_sample_group(timer->it_clock, p, &now);
894                         clear_dead = (unlikely(p->exit_state) &&
895                                       thread_group_empty(p));
896                 }
897                 read_unlock(&tasklist_lock);
898         }
899
900         if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
901                 if (timer->it.cpu.incr.sched == 0 &&
902                     cpu_time_before(timer->it_clock,
903                                     timer->it.cpu.expires, now)) {
904                         /*
905                          * Do-nothing timer expired and has no reload,
906                          * so it's as if it was never set.
907                          */
908                         timer->it.cpu.expires.sched = 0;
909                         itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
910                         return;
911                 }
912                 /*
913                  * Account for any expirations and reloads that should
914                  * have happened.
915                  */
916                 bump_cpu_timer(timer, now);
917         }
918
919         if (unlikely(clear_dead)) {
920                 /*
921                  * We've noticed that the thread is dead, but
922                  * not yet reaped.  Take this opportunity to
923                  * drop our task ref.
924                  */
925                 clear_dead_task(timer, now);
926                 goto dead;
927         }
928
929         if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
930                 sample_to_timespec(timer->it_clock,
931                                    cpu_time_sub(timer->it_clock,
932                                                 timer->it.cpu.expires, now),
933                                    &itp->it_value);
934         } else {
935                 /*
936                  * The timer should have expired already, but the firing
937                  * hasn't taken place yet.  Say it's just about to expire.
938                  */
939                 itp->it_value.tv_nsec = 1;
940                 itp->it_value.tv_sec = 0;
941         }
942 }
943
944 /*
945  * Check for any per-thread CPU timers that have fired and move them off
946  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
947  * tsk->it_*_expires values to reflect the remaining thread CPU timers.
948  */
949 static void check_thread_timers(struct task_struct *tsk,
950                                 struct list_head *firing)
951 {
952         int maxfire;
953         struct list_head *timers = tsk->cpu_timers;
954
955         maxfire = 20;
956         tsk->it_prof_expires = cputime_zero;
957         while (!list_empty(timers)) {
958                 struct cpu_timer_list *t = list_entry(timers->next,
959                                                       struct cpu_timer_list,
960                                                       entry);
961                 if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
962                         tsk->it_prof_expires = t->expires.cpu;
963                         break;
964                 }
965                 t->firing = 1;
966                 list_move_tail(&t->entry, firing);
967         }
968
969         ++timers;
970         maxfire = 20;
971         tsk->it_virt_expires = cputime_zero;
972         while (!list_empty(timers)) {
973                 struct cpu_timer_list *t = list_entry(timers->next,
974                                                       struct cpu_timer_list,
975                                                       entry);
976                 if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
977                         tsk->it_virt_expires = t->expires.cpu;
978                         break;
979                 }
980                 t->firing = 1;
981                 list_move_tail(&t->entry, firing);
982         }
983
984         ++timers;
985         maxfire = 20;
986         tsk->it_sched_expires = 0;
987         while (!list_empty(timers)) {
988                 struct cpu_timer_list *t = list_entry(timers->next,
989                                                       struct cpu_timer_list,
990                                                       entry);
991                 if (!--maxfire || tsk->sched_time < t->expires.sched) {
992                         tsk->it_sched_expires = t->expires.sched;
993                         break;
994                 }
995                 t->firing = 1;
996                 list_move_tail(&t->entry, firing);
997         }
998 }
999
1000 /*
1001  * Check for any per-thread CPU timers that have fired and move them
1002  * off the tsk->*_timers list onto the firing list.  Per-thread timers
1003  * have already been taken off.
1004  */
1005 static void check_process_timers(struct task_struct *tsk,
1006                                  struct list_head *firing)
1007 {
1008         int maxfire;
1009         struct signal_struct *const sig = tsk->signal;
1010         cputime_t utime, stime, ptime, virt_expires, prof_expires;
1011         unsigned long long sched_time, sched_expires;
1012         struct task_struct *t;
1013         struct list_head *timers = sig->cpu_timers;
1014
1015         /*
1016          * Don't sample the current process CPU clocks if there are no timers.
1017          */
1018         if (list_empty(&timers[CPUCLOCK_PROF]) &&
1019             cputime_eq(sig->it_prof_expires, cputime_zero) &&
1020             sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
1021             list_empty(&timers[CPUCLOCK_VIRT]) &&
1022             cputime_eq(sig->it_virt_expires, cputime_zero) &&
1023             list_empty(&timers[CPUCLOCK_SCHED]))
1024                 return;
1025
1026         /*
1027          * Collect the current process totals.
1028          */
1029         utime = sig->utime;
1030         stime = sig->stime;
1031         sched_time = sig->sched_time;
1032         t = tsk;
1033         do {
1034                 utime = cputime_add(utime, t->utime);
1035                 stime = cputime_add(stime, t->stime);
1036                 sched_time += t->sched_time;
1037                 t = next_thread(t);
1038         } while (t != tsk);
1039         ptime = cputime_add(utime, stime);
1040
1041         maxfire = 20;
1042         prof_expires = cputime_zero;
1043         while (!list_empty(timers)) {
1044                 struct cpu_timer_list *t = list_entry(timers->next,
1045                                                       struct cpu_timer_list,
1046                                                       entry);
1047                 if (!--maxfire || cputime_lt(ptime, t->expires.cpu)) {
1048                         prof_expires = t->expires.cpu;
1049                         break;
1050                 }
1051                 t->firing = 1;
1052                 list_move_tail(&t->entry, firing);
1053         }
1054
1055         ++timers;
1056         maxfire = 20;
1057         virt_expires = cputime_zero;
1058         while (!list_empty(timers)) {
1059                 struct cpu_timer_list *t = list_entry(timers->next,
1060                                                       struct cpu_timer_list,
1061                                                       entry);
1062                 if (!--maxfire || cputime_lt(utime, t->expires.cpu)) {
1063                         virt_expires = t->expires.cpu;
1064                         break;
1065                 }
1066                 t->firing = 1;
1067                 list_move_tail(&t->entry, firing);
1068         }
1069
1070         ++timers;
1071         maxfire = 20;
1072         sched_expires = 0;
1073         while (!list_empty(timers)) {
1074                 struct cpu_timer_list *t = list_entry(timers->next,
1075                                                       struct cpu_timer_list,
1076                                                       entry);
1077                 if (!--maxfire || sched_time < t->expires.sched) {
1078                         sched_expires = t->expires.sched;
1079                         break;
1080                 }
1081                 t->firing = 1;
1082                 list_move_tail(&t->entry, firing);
1083         }
1084
1085         /*
1086          * Check for the special case process timers.
1087          */
1088         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1089                 if (cputime_ge(ptime, sig->it_prof_expires)) {
1090                         /* ITIMER_PROF fires and reloads.  */
1091                         sig->it_prof_expires = sig->it_prof_incr;
1092                         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1093                                 sig->it_prof_expires = cputime_add(
1094                                         sig->it_prof_expires, ptime);
1095                         }
1096                         __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
1097                 }
1098                 if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
1099                     (cputime_eq(prof_expires, cputime_zero) ||
1100                      cputime_lt(sig->it_prof_expires, prof_expires))) {
1101                         prof_expires = sig->it_prof_expires;
1102                 }
1103         }
1104         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1105                 if (cputime_ge(utime, sig->it_virt_expires)) {
1106                         /* ITIMER_VIRTUAL fires and reloads.  */
1107                         sig->it_virt_expires = sig->it_virt_incr;
1108                         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1109                                 sig->it_virt_expires = cputime_add(
1110                                         sig->it_virt_expires, utime);
1111                         }
1112                         __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
1113                 }
1114                 if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
1115                     (cputime_eq(virt_expires, cputime_zero) ||
1116                      cputime_lt(sig->it_virt_expires, virt_expires))) {
1117                         virt_expires = sig->it_virt_expires;
1118                 }
1119         }
1120         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
1121                 unsigned long psecs = cputime_to_secs(ptime);
1122                 cputime_t x;
1123                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
1124                         /*
1125                          * At the hard limit, we just die.
1126                          * No need to calculate anything else now.
1127                          */
1128                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1129                         return;
1130                 }
1131                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
1132                         /*
1133                          * At the soft limit, send a SIGXCPU every second.
1134                          */
1135                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1136                         if (sig->rlim[RLIMIT_CPU].rlim_cur
1137                             < sig->rlim[RLIMIT_CPU].rlim_max) {
1138                                 sig->rlim[RLIMIT_CPU].rlim_cur++;
1139                         }
1140                 }
1141                 x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
1142                 if (cputime_eq(prof_expires, cputime_zero) ||
1143                     cputime_lt(x, prof_expires)) {
1144                         prof_expires = x;
1145                 }
1146         }
1147
1148         if (!cputime_eq(prof_expires, cputime_zero) ||
1149             !cputime_eq(virt_expires, cputime_zero) ||
1150             sched_expires != 0) {
1151                 /*
1152                  * Rebalance the threads' expiry times for the remaining
1153                  * process CPU timers.
1154                  */
1155
1156                 cputime_t prof_left, virt_left, ticks;
1157                 unsigned long long sched_left, sched;
1158                 const unsigned int nthreads = atomic_read(&sig->live);
1159
1160                 if (!nthreads)
1161                         return;
1162
1163                 prof_left = cputime_sub(prof_expires, utime);
1164                 prof_left = cputime_sub(prof_left, stime);
1165                 prof_left = cputime_div(prof_left, nthreads);
1166                 virt_left = cputime_sub(virt_expires, utime);
1167                 virt_left = cputime_div(virt_left, nthreads);
1168                 if (sched_expires) {
1169                         sched_left = sched_expires - sched_time;
1170                         do_div(sched_left, nthreads);
1171                 } else {
1172                         sched_left = 0;
1173                 }
1174                 t = tsk;
1175                 do {
1176                         if (unlikely(t->flags & PF_EXITING))
1177                                 continue;
1178
1179                         ticks = cputime_add(cputime_add(t->utime, t->stime),
1180                                             prof_left);
1181                         if (!cputime_eq(prof_expires, cputime_zero) &&
1182                             (cputime_eq(t->it_prof_expires, cputime_zero) ||
1183                              cputime_gt(t->it_prof_expires, ticks))) {
1184                                 t->it_prof_expires = ticks;
1185                         }
1186
1187                         ticks = cputime_add(t->utime, virt_left);
1188                         if (!cputime_eq(virt_expires, cputime_zero) &&
1189                             (cputime_eq(t->it_virt_expires, cputime_zero) ||
1190                              cputime_gt(t->it_virt_expires, ticks))) {
1191                                 t->it_virt_expires = ticks;
1192                         }
1193
1194                         sched = t->sched_time + sched_left;
1195                         if (sched_expires && (t->it_sched_expires == 0 ||
1196                                               t->it_sched_expires > sched)) {
1197                                 t->it_sched_expires = sched;
1198                         }
1199                 } while ((t = next_thread(t)) != tsk);
1200         }
1201 }
1202
1203 /*
1204  * This is called from the signal code (via do_schedule_next_timer)
1205  * when the last timer signal was delivered and we have to reload the timer.
1206  */
1207 void posix_cpu_timer_schedule(struct k_itimer *timer)
1208 {
1209         struct task_struct *p = timer->it.cpu.task;
1210         union cpu_time_count now;
1211
1212         if (unlikely(p == NULL))
1213                 /*
1214                  * The task was cleaned up already, no future firings.
1215                  */
1216                 goto out;
1217
1218         /*
1219          * Fetch the current sample and update the timer's expiry time.
1220          */
1221         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1222                 cpu_clock_sample(timer->it_clock, p, &now);
1223                 bump_cpu_timer(timer, now);
1224                 if (unlikely(p->exit_state)) {
1225                         clear_dead_task(timer, now);
1226                         goto out;
1227                 }
1228                 read_lock(&tasklist_lock); /* arm_timer needs it.  */
1229         } else {
1230                 read_lock(&tasklist_lock);
1231                 if (unlikely(p->signal == NULL)) {
1232                         /*
1233                          * The process has been reaped.
1234                          * We can't even collect a sample any more.
1235                          */
1236                         put_task_struct(p);
1237                         timer->it.cpu.task = p = NULL;
1238                         timer->it.cpu.expires.sched = 0;
1239                         goto out_unlock;
1240                 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1241                         /*
1242                          * We've noticed that the thread is dead, but
1243                          * not yet reaped.  Take this opportunity to
1244                          * drop our task ref.
1245                          */
1246                         clear_dead_task(timer, now);
1247                         goto out_unlock;
1248                 }
1249                 cpu_clock_sample_group(timer->it_clock, p, &now);
1250                 bump_cpu_timer(timer, now);
1251                 /* Leave the tasklist_lock locked for the call below.  */
1252         }
1253
1254         /*
1255          * Now re-arm for the new expiry time.
1256          */
1257         arm_timer(timer, now);
1258
1259 out_unlock:
1260         read_unlock(&tasklist_lock);
1261
1262 out:
1263         timer->it_overrun_last = timer->it_overrun;
1264         timer->it_overrun = -1;
1265         ++timer->it_requeue_pending;
1266 }
1267
1268 /*
1269  * This is called from the timer interrupt handler.  The irq handler has
1270  * already updated our counts.  We need to check if any timers fire now.
1271  * Interrupts are disabled.
1272  */
1273 void run_posix_cpu_timers(struct task_struct *tsk)
1274 {
1275         LIST_HEAD(firing);
1276         struct k_itimer *timer, *next;
1277
1278         BUG_ON(!irqs_disabled());
1279
1280 #define UNEXPIRED(clock) \
1281                 (cputime_eq(tsk->it_##clock##_expires, cputime_zero) || \
1282                  cputime_lt(clock##_ticks(tsk), tsk->it_##clock##_expires))
1283
1284         if (UNEXPIRED(prof) && UNEXPIRED(virt) &&
1285             (tsk->it_sched_expires == 0 ||
1286              tsk->sched_time < tsk->it_sched_expires))
1287                 return;
1288
1289 #undef  UNEXPIRED
1290
1291         BUG_ON(tsk->exit_state);
1292
1293         /*
1294          * Double-check with locks held.
1295          */
1296         read_lock(&tasklist_lock);
1297         spin_lock(&tsk->sighand->siglock);
1298
1299         /*
1300          * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
1301          * all the timers that are firing, and put them on the firing list.
1302          */
1303         check_thread_timers(tsk, &firing);
1304         check_process_timers(tsk, &firing);
1305
1306         /*
1307          * We must release these locks before taking any timer's lock.
1308          * There is a potential race with timer deletion here, as the
1309          * siglock now protects our private firing list.  We have set
1310          * the firing flag in each timer, so that a deletion attempt
1311          * that gets the timer lock before we do will give it up and
1312          * spin until we've taken care of that timer below.
1313          */
1314         spin_unlock(&tsk->sighand->siglock);
1315         read_unlock(&tasklist_lock);
1316
1317         /*
1318          * Now that all the timers on our list have the firing flag,
1319          * noone will touch their list entries but us.  We'll take
1320          * each timer's lock before clearing its firing flag, so no
1321          * timer call will interfere.
1322          */
1323         list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1324                 int firing;
1325                 spin_lock(&timer->it_lock);
1326                 list_del_init(&timer->it.cpu.entry);
1327                 firing = timer->it.cpu.firing;
1328                 timer->it.cpu.firing = 0;
1329                 /*
1330                  * The firing flag is -1 if we collided with a reset
1331                  * of the timer, which already reported this
1332                  * almost-firing as an overrun.  So don't generate an event.
1333                  */
1334                 if (likely(firing >= 0)) {
1335                         cpu_timer_fire(timer);
1336                 }
1337                 spin_unlock(&timer->it_lock);
1338         }
1339 }
1340
1341 /*
1342  * Set one of the process-wide special case CPU timers.
1343  * The tasklist_lock and tsk->sighand->siglock must be held by the caller.
1344  * The oldval argument is null for the RLIMIT_CPU timer, where *newval is
1345  * absolute; non-null for ITIMER_*, where *newval is relative and we update
1346  * it to be absolute, *oldval is absolute and we update it to be relative.
1347  */
1348 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1349                            cputime_t *newval, cputime_t *oldval)
1350 {
1351         union cpu_time_count now;
1352         struct list_head *head;
1353
1354         BUG_ON(clock_idx == CPUCLOCK_SCHED);
1355         cpu_clock_sample_group_locked(clock_idx, tsk, &now);
1356
1357         if (oldval) {
1358                 if (!cputime_eq(*oldval, cputime_zero)) {
1359                         if (cputime_le(*oldval, now.cpu)) {
1360                                 /* Just about to fire. */
1361                                 *oldval = jiffies_to_cputime(1);
1362                         } else {
1363                                 *oldval = cputime_sub(*oldval, now.cpu);
1364                         }
1365                 }
1366
1367                 if (cputime_eq(*newval, cputime_zero))
1368                         return;
1369                 *newval = cputime_add(*newval, now.cpu);
1370
1371                 /*
1372                  * If the RLIMIT_CPU timer will expire before the
1373                  * ITIMER_PROF timer, we have nothing else to do.
1374                  */
1375                 if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
1376                     < cputime_to_secs(*newval))
1377                         return;
1378         }
1379
1380         /*
1381          * Check whether there are any process timers already set to fire
1382          * before this one.  If so, we don't have anything more to do.
1383          */
1384         head = &tsk->signal->cpu_timers[clock_idx];
1385         if (list_empty(head) ||
1386             cputime_ge(list_entry(head->next,
1387                                   struct cpu_timer_list, entry)->expires.cpu,
1388                        *newval)) {
1389                 /*
1390                  * Rejigger each thread's expiry time so that one will
1391                  * notice before we hit the process-cumulative expiry time.
1392                  */
1393                 union cpu_time_count expires = { .sched = 0 };
1394                 expires.cpu = *newval;
1395                 process_timer_rebalance(tsk, clock_idx, expires, now);
1396         }
1397 }
1398
1399 static long posix_cpu_clock_nanosleep_restart(struct restart_block *);
1400
1401 int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1402                      struct timespec *rqtp, struct timespec __user *rmtp)
1403 {
1404         struct restart_block *restart_block =
1405             &current_thread_info()->restart_block;
1406         struct k_itimer timer;
1407         int error;
1408
1409         /*
1410          * Diagnose required errors first.
1411          */
1412         if (CPUCLOCK_PERTHREAD(which_clock) &&
1413             (CPUCLOCK_PID(which_clock) == 0 ||
1414              CPUCLOCK_PID(which_clock) == current->pid))
1415                 return -EINVAL;
1416
1417         /*
1418          * Set up a temporary timer and then wait for it to go off.
1419          */
1420         memset(&timer, 0, sizeof timer);
1421         spin_lock_init(&timer.it_lock);
1422         timer.it_clock = which_clock;
1423         timer.it_overrun = -1;
1424         error = posix_cpu_timer_create(&timer);
1425         timer.it_process = current;
1426         if (!error) {
1427                 static struct itimerspec zero_it;
1428                 struct itimerspec it = { .it_value = *rqtp,
1429                                          .it_interval = {} };
1430
1431                 spin_lock_irq(&timer.it_lock);
1432                 error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1433                 if (error) {
1434                         spin_unlock_irq(&timer.it_lock);
1435                         return error;
1436                 }
1437
1438                 while (!signal_pending(current)) {
1439                         if (timer.it.cpu.expires.sched == 0) {
1440                                 /*
1441                                  * Our timer fired and was reset.
1442                                  */
1443                                 spin_unlock_irq(&timer.it_lock);
1444                                 return 0;
1445                         }
1446
1447                         /*
1448                          * Block until cpu_timer_fire (or a signal) wakes us.
1449                          */
1450                         __set_current_state(TASK_INTERRUPTIBLE);
1451                         spin_unlock_irq(&timer.it_lock);
1452                         schedule();
1453                         spin_lock_irq(&timer.it_lock);
1454                 }
1455
1456                 /*
1457                  * We were interrupted by a signal.
1458                  */
1459                 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1460                 posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1461                 spin_unlock_irq(&timer.it_lock);
1462
1463                 if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1464                         /*
1465                          * It actually did fire already.
1466                          */
1467                         return 0;
1468                 }
1469
1470                 /*
1471                  * Report back to the user the time still remaining.
1472                  */
1473                 if (rmtp != NULL && !(flags & TIMER_ABSTIME) &&
1474                     copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1475                         return -EFAULT;
1476
1477                 restart_block->fn = posix_cpu_clock_nanosleep_restart;
1478                 /* Caller already set restart_block->arg1 */
1479                 restart_block->arg0 = which_clock;
1480                 restart_block->arg1 = (unsigned long) rmtp;
1481                 restart_block->arg2 = rqtp->tv_sec;
1482                 restart_block->arg3 = rqtp->tv_nsec;
1483
1484                 error = -ERESTART_RESTARTBLOCK;
1485         }
1486
1487         return error;
1488 }
1489
1490 static long
1491 posix_cpu_clock_nanosleep_restart(struct restart_block *restart_block)
1492 {
1493         clockid_t which_clock = restart_block->arg0;
1494         struct timespec __user *rmtp;
1495         struct timespec t;
1496
1497         rmtp = (struct timespec __user *) restart_block->arg1;
1498         t.tv_sec = restart_block->arg2;
1499         t.tv_nsec = restart_block->arg3;
1500
1501         restart_block->fn = do_no_restart_syscall;
1502         return posix_cpu_nsleep(which_clock, TIMER_ABSTIME, &t, rmtp);
1503 }
1504
1505
1506 #define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1507 #define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1508
1509 static int process_cpu_clock_getres(const clockid_t which_clock,
1510                                     struct timespec *tp)
1511 {
1512         return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1513 }
1514 static int process_cpu_clock_get(const clockid_t which_clock,
1515                                  struct timespec *tp)
1516 {
1517         return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1518 }
1519 static int process_cpu_timer_create(struct k_itimer *timer)
1520 {
1521         timer->it_clock = PROCESS_CLOCK;
1522         return posix_cpu_timer_create(timer);
1523 }
1524 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1525                               struct timespec *rqtp,
1526                               struct timespec __user *rmtp)
1527 {
1528         return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1529 }
1530 static int thread_cpu_clock_getres(const clockid_t which_clock,
1531                                    struct timespec *tp)
1532 {
1533         return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1534 }
1535 static int thread_cpu_clock_get(const clockid_t which_clock,
1536                                 struct timespec *tp)
1537 {
1538         return posix_cpu_clock_get(THREAD_CLOCK, tp);
1539 }
1540 static int thread_cpu_timer_create(struct k_itimer *timer)
1541 {
1542         timer->it_clock = THREAD_CLOCK;
1543         return posix_cpu_timer_create(timer);
1544 }
1545 static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
1546                               struct timespec *rqtp, struct timespec __user *rmtp)
1547 {
1548         return -EINVAL;
1549 }
1550
1551 static __init int init_posix_cpu_timers(void)
1552 {
1553         struct k_clock process = {
1554                 .clock_getres = process_cpu_clock_getres,
1555                 .clock_get = process_cpu_clock_get,
1556                 .clock_set = do_posix_clock_nosettime,
1557                 .timer_create = process_cpu_timer_create,
1558                 .nsleep = process_cpu_nsleep,
1559         };
1560         struct k_clock thread = {
1561                 .clock_getres = thread_cpu_clock_getres,
1562                 .clock_get = thread_cpu_clock_get,
1563                 .clock_set = do_posix_clock_nosettime,
1564                 .timer_create = thread_cpu_timer_create,
1565                 .nsleep = thread_cpu_nsleep,
1566         };
1567
1568         register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1569         register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1570
1571         return 0;
1572 }
1573 __initcall(init_posix_cpu_timers);