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 <linux/errno.h>
   8 #include <linux/math64.h>
   9 #include <asm/uaccess.h>
  10 #include <linux/kernel_stat.h>
  11 #include <trace/events/timer.h>
  12
  13 /*
  14  * Called after updating RLIMIT_CPU to run cpu timer and update
  15  * tsk->signal->cputime_expires expiration cache if necessary. Needs
  16  * siglock protection since other code may update expiration cache as
  17  * well.
  18  */
  19 void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
  20 {
  21         cputime_t cputime = secs_to_cputime(rlim_new);
  22
  23         spin_lock_irq(&task->sighand->siglock);
  24         set_process_cpu_timer(task, CPUCLOCK_PROF, &cputime, NULL);
  25         spin_unlock_irq(&task->sighand->siglock);
  26 }
  27
  28 static int check_clock(const clockid_t which_clock)
  29 {
  30         int error = 0;
  31         struct task_struct *p;
  32         const pid_t pid = CPUCLOCK_PID(which_clock);
  33
  34         if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
  35                 return -EINVAL;
  36
  37         if (pid == 0)
  38                 return 0;
  39
  40         rcu_read_lock();
  41         p = find_task_by_vpid(pid);
  42         if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
  43                    same_thread_group(p, current) : has_group_leader_pid(p))) {
  44                 error = -EINVAL;
  45         }
  46         rcu_read_unlock();
  47
  48         return error;
  49 }
  50
  51 static inline union cpu_time_count
  52 timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
  53 {
  54         union cpu_time_count ret;
  55         ret.sched = 0;          /* high half always zero when .cpu used */
  56         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  57                 ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
  58         } else {
  59                 ret.cpu = timespec_to_cputime(tp);
  60         }
  61         return ret;
  62 }
  63
  64 static void sample_to_timespec(const clockid_t which_clock,
  65                                union cpu_time_count cpu,
  66                                struct timespec *tp)
  67 {
  68         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
  69                 *tp = ns_to_timespec(cpu.sched);
  70         else
  71                 cputime_to_timespec(cpu.cpu, tp);
  72 }
  73
  74 static inline int cpu_time_before(const clockid_t which_clock,
  75                                   union cpu_time_count now,
  76                                   union cpu_time_count then)
  77 {
  78         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  79                 return now.sched < then.sched;
  80         }  else {
  81                 return now.cpu < then.cpu;
  82         }
  83 }
  84 static inline void cpu_time_add(const clockid_t which_clock,
  85                                 union cpu_time_count *acc,
  86                                 union cpu_time_count val)
  87 {
  88         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  89                 acc->sched += val.sched;
  90         }  else {
  91                 acc->cpu += val.cpu;
  92         }
  93 }
  94 static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
  95                                                 union cpu_time_count a,
  96                                                 union cpu_time_count b)
  97 {
  98         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  99                 a.sched -= b.sched;
 100         }  else {
 101                 a.cpu -= b.cpu;
 102         }
 103         return a;
 104 }
 105
 106 /*
 107  * Update expiry time from increment, and increase overrun count,
 108  * given the current clock sample.
 109  */
 110 static void bump_cpu_timer(struct k_itimer *timer,
 111                                   union cpu_time_count now)
 112 {
 113         int i;
 114
 115         if (timer->it.cpu.incr.sched == 0)
 116                 return;
 117
 118         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 119                 unsigned long long delta, incr;
 120
 121                 if (now.sched < timer->it.cpu.expires.sched)
 122                         return;
 123                 incr = timer->it.cpu.incr.sched;
 124                 delta = now.sched + incr - timer->it.cpu.expires.sched;
 125                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 126                 for (i = 0; incr < delta - incr; i++)
 127                         incr = incr << 1;
 128                 for (; i >= 0; incr >>= 1, i--) {
 129                         if (delta < incr)
 130                                 continue;
 131                         timer->it.cpu.expires.sched += incr;
 132                         timer->it_overrun += 1 << i;
 133                         delta -= incr;
 134                 }
 135         } else {
 136                 cputime_t delta, incr;
 137
 138                 if (now.cpu < timer->it.cpu.expires.cpu)
 139                         return;
 140                 incr = timer->it.cpu.incr.cpu;
 141                 delta = now.cpu + incr - timer->it.cpu.expires.cpu;
 142                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 143                 for (i = 0; incr < delta - incr; i++)
 144                              incr += incr;
 145                 for (; i >= 0; incr = incr >> 1, i--) {
 146                         if (delta < incr)
 147                                 continue;
 148                         timer->it.cpu.expires.cpu += incr;
 149                         timer->it_overrun += 1 << i;
 150                         delta -= incr;
 151                 }
 152         }
 153 }
 154
 155 static inline cputime_t prof_ticks(struct task_struct *p)
 156 {
 157         return p->utime + p->stime;
 158 }
 159 static inline cputime_t virt_ticks(struct task_struct *p)
 160 {
 161         return p->utime;
 162 }
 163
 164 static int
 165 posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
 166 {
 167         int error = check_clock(which_clock);
 168         if (!error) {
 169                 tp->tv_sec = 0;
 170                 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
 171                 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 172                         /*
 173                          * If sched_clock is using a cycle counter, we
 174                          * don't have any idea of its true resolution
 175                          * exported, but it is much more than 1s/HZ.
 176                          */
 177                         tp->tv_nsec = 1;
 178                 }
 179         }
 180         return error;
 181 }
 182
 183 static int
 184 posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
 185 {
 186         /*
 187          * You can never reset a CPU clock, but we check for other errors
 188          * in the call before failing with EPERM.
 189          */
 190         int error = check_clock(which_clock);
 191         if (error == 0) {
 192                 error = -EPERM;
 193         }
 194         return error;
 195 }
 196
 197
 198 /*
 199  * Sample a per-thread clock for the given task.
 200  */
 201 static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
 202                             union cpu_time_count *cpu)
 203 {
 204         switch (CPUCLOCK_WHICH(which_clock)) {
 205         default:
 206                 return -EINVAL;
 207         case CPUCLOCK_PROF:
 208                 cpu->cpu = prof_ticks(p);
 209                 break;
 210         case CPUCLOCK_VIRT:
 211                 cpu->cpu = virt_ticks(p);
 212                 break;
 213         case CPUCLOCK_SCHED:
 214                 cpu->sched = task_sched_runtime(p);
 215                 break;
 216         }
 217         return 0;
 218 }
 219
 220 void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
 221 {
 222         struct signal_struct *sig = tsk->signal;
 223         struct task_struct *t;
 224
 225         times->utime = sig->utime;
 226         times->stime = sig->stime;
 227         times->sum_exec_runtime = sig->sum_sched_runtime;
 228
 229         rcu_read_lock();
 230         /* make sure we can trust tsk->thread_group list */
 231         if (!likely(pid_alive(tsk)))
 232                 goto out;
 233
 234         t = tsk;
 235         do {
 236                 times->utime += t->utime;
 237                 times->stime += t->stime;
 238                 times->sum_exec_runtime += task_sched_runtime(t);
 239         } while_each_thread(tsk, t);
 240 out:
 241         rcu_read_unlock();
 242 }
 243
 244 static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
 245 {
 246         if (b->utime > a->utime)
 247                 a->utime = b->utime;
 248
 249         if (b->stime > a->stime)
 250                 a->stime = b->stime;
 251
 252         if (b->sum_exec_runtime > a->sum_exec_runtime)
 253                 a->sum_exec_runtime = b->sum_exec_runtime;
 254 }
 255
 256 void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
 257 {
 258         struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 259         struct task_cputime sum;
 260         unsigned long flags;
 261
 262         if (!cputimer->running) {
 263                 /*
 264                  * The POSIX timer interface allows for absolute time expiry
 265                  * values through the TIMER_ABSTIME flag, therefore we have
 266                  * to synchronize the timer to the clock every time we start
 267                  * it.
 268                  */
 269                 thread_group_cputime(tsk, &sum);
 270                 raw_spin_lock_irqsave(&cputimer->lock, flags);
 271                 cputimer->running = 1;
 272                 update_gt_cputime(&cputimer->cputime, &sum);
 273         } else
 274                 raw_spin_lock_irqsave(&cputimer->lock, flags);
 275         *times = cputimer->cputime;
 276         raw_spin_unlock_irqrestore(&cputimer->lock, flags);
 277 }
 278
 279 /*
 280  * Sample a process (thread group) clock for the given group_leader task.
 281  * Must be called with tasklist_lock held for reading.
 282  */
 283 static int cpu_clock_sample_group(const clockid_t which_clock,
 284                                   struct task_struct *p,
 285                                   union cpu_time_count *cpu)
 286 {
 287         struct task_cputime cputime;
 288
 289         switch (CPUCLOCK_WHICH(which_clock)) {
 290         default:
 291                 return -EINVAL;
 292         case CPUCLOCK_PROF:
 293                 thread_group_cputime(p, &cputime);
 294                 cpu->cpu = cputime.utime + cputime.stime;
 295                 break;
 296         case CPUCLOCK_VIRT:
 297                 thread_group_cputime(p, &cputime);
 298                 cpu->cpu = cputime.utime;
 299                 break;
 300         case CPUCLOCK_SCHED:
 301                 thread_group_cputime(p, &cputime);
 302                 cpu->sched = cputime.sum_exec_runtime;
 303                 break;
 304         }
 305         return 0;
 306 }
 307
 308
 309 static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 310 {
 311         const pid_t pid = CPUCLOCK_PID(which_clock);
 312         int error = -EINVAL;
 313         union cpu_time_count rtn;
 314
 315         if (pid == 0) {
 316                 /*
 317                  * Special case constant value for our own clocks.
 318                  * We don't have to do any lookup to find ourselves.
 319                  */
 320                 if (CPUCLOCK_PERTHREAD(which_clock)) {
 321                         /*
 322                          * Sampling just ourselves we can do with no locking.
 323                          */
 324                         error = cpu_clock_sample(which_clock,
 325                                                  current, &rtn);
 326                 } else {
 327                         read_lock(&tasklist_lock);
 328                         error = cpu_clock_sample_group(which_clock,
 329                                                        current, &rtn);
 330                         read_unlock(&tasklist_lock);
 331                 }
 332         } else {
 333                 /*
 334                  * Find the given PID, and validate that the caller
 335                  * should be able to see it.
 336                  */
 337                 struct task_struct *p;
 338                 rcu_read_lock();
 339                 p = find_task_by_vpid(pid);
 340                 if (p) {
 341                         if (CPUCLOCK_PERTHREAD(which_clock)) {
 342                                 if (same_thread_group(p, current)) {
 343                                         error = cpu_clock_sample(which_clock,
 344                                                                  p, &rtn);
 345                                 }
 346                         } else {
 347                                 read_lock(&tasklist_lock);
 348                                 if (thread_group_leader(p) && p->sighand) {
 349                                         error =
 350                                             cpu_clock_sample_group(which_clock,
 351                                                                    p, &rtn);
 352                                 }
 353                                 read_unlock(&tasklist_lock);
 354                         }
 355                 }
 356                 rcu_read_unlock();
 357         }
 358
 359         if (error)
 360                 return error;
 361         sample_to_timespec(which_clock, rtn, tp);
 362         return 0;
 363 }
 364
 365
 366 /*
 367  * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 368  * This is called from sys_timer_create() and do_cpu_nanosleep() with the
 369  * new timer already all-zeros initialized.
 370  */
 371 static int posix_cpu_timer_create(struct k_itimer *new_timer)
 372 {
 373         int ret = 0;
 374         const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
 375         struct task_struct *p;
 376
 377         if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 378                 return -EINVAL;
 379
 380         INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 381
 382         rcu_read_lock();
 383         if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
 384                 if (pid == 0) {
 385                         p = current;
 386                 } else {
 387                         p = find_task_by_vpid(pid);
 388                         if (p && !same_thread_group(p, current))
 389                                 p = NULL;
 390                 }
 391         } else {
 392                 if (pid == 0) {
 393                         p = current->group_leader;
 394                 } else {
 395                         p = find_task_by_vpid(pid);
 396                         if (p && !has_group_leader_pid(p))
 397                                 p = NULL;
 398                 }
 399         }
 400         new_timer->it.cpu.task = p;
 401         if (p) {
 402                 get_task_struct(p);
 403         } else {
 404                 ret = -EINVAL;
 405         }
 406         rcu_read_unlock();
 407
 408         return ret;
 409 }
 410
 411 /*
 412  * Clean up a CPU-clock timer that is about to be destroyed.
 413  * This is called from timer deletion with the timer already locked.
 414  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 415  * and try again.  (This happens when the timer is in the middle of firing.)
 416  */
 417 static int posix_cpu_timer_del(struct k_itimer *timer)
 418 {
 419         struct task_struct *p = timer->it.cpu.task;
 420         int ret = 0;
 421
 422         if (likely(p != NULL)) {
 423                 read_lock(&tasklist_lock);
 424                 if (unlikely(p->sighand == NULL)) {
 425                         /*
 426                          * We raced with the reaping of the task.
 427                          * The deletion should have cleared us off the list.
 428                          */
 429                         BUG_ON(!list_empty(&timer->it.cpu.entry));
 430                 } else {
 431                         spin_lock(&p->sighand->siglock);
 432                         if (timer->it.cpu.firing)
 433                                 ret = TIMER_RETRY;
 434                         else
 435                                 list_del(&timer->it.cpu.entry);
 436                         spin_unlock(&p->sighand->siglock);
 437                 }
 438                 read_unlock(&tasklist_lock);
 439
 440                 if (!ret)
 441                         put_task_struct(p);
 442         }
 443
 444         return ret;
 445 }
 446
 447 /*
 448  * Clean out CPU timers still ticking when a thread exited.  The task
 449  * pointer is cleared, and the expiry time is replaced with the residual
 450  * time for later timer_gettime calls to return.
 451  * This must be called with the siglock held.
 452  */
 453 static void cleanup_timers(struct list_head *head,
 454                            cputime_t utime, cputime_t stime,
 455                            unsigned long long sum_exec_runtime)
 456 {
 457         struct cpu_timer_list *timer, *next;
 458         cputime_t ptime = utime + stime;
 459
 460         list_for_each_entry_safe(timer, next, head, entry) {
 461                 list_del_init(&timer->entry);
 462                 if (timer->expires.cpu < ptime) {
 463                         timer->expires.cpu = 0;
 464                 } else {
 465                         timer->expires.cpu -= ptime;
 466                 }
 467         }
 468
 469         ++head;
 470         list_for_each_entry_safe(timer, next, head, entry) {
 471                 list_del_init(&timer->entry);
 472                 if (timer->expires.cpu < utime) {
 473                         timer->expires.cpu = 0;
 474                 } else {
 475                         timer->expires.cpu -= utime;
 476                 }
 477         }
 478
 479         ++head;
 480         list_for_each_entry_safe(timer, next, head, entry) {
 481                 list_del_init(&timer->entry);
 482                 if (timer->expires.sched < sum_exec_runtime) {
 483                         timer->expires.sched = 0;
 484                 } else {
 485                         timer->expires.sched -= sum_exec_runtime;
 486                 }
 487         }
 488 }
 489
 490 /*
 491  * These are both called with the siglock held, when the current thread
 492  * is being reaped.  When the final (leader) thread in the group is reaped,
 493  * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 494  */
 495 void posix_cpu_timers_exit(struct task_struct *tsk)
 496 {
 497         cleanup_timers(tsk->cpu_timers,
 498                        tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
 499
 500 }
 501 void posix_cpu_timers_exit_group(struct task_struct *tsk)
 502 {
 503         struct signal_struct *const sig = tsk->signal;
 504
 505         cleanup_timers(tsk->signal->cpu_timers,
 506                        tsk->utime + sig->utime, tsk->stime + sig->stime,
 507                        tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
 508 }
 509
 510 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 511 {
 512         /*
 513          * That's all for this thread or process.
 514          * We leave our residual in expires to be reported.
 515          */
 516         put_task_struct(timer->it.cpu.task);
 517         timer->it.cpu.task = NULL;
 518         timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
 519                                              timer->it.cpu.expires,
 520                                              now);
 521 }
 522
 523 static inline int expires_gt(cputime_t expires, cputime_t new_exp)
 524 {
 525         return expires == 0 || expires > new_exp;
 526 }
 527
 528 /*
 529  * Insert the timer on the appropriate list before any timers that
 530  * expire later.  This must be called with the tasklist_lock held
 531  * for reading, interrupts disabled and p->sighand->siglock taken.
 532  */
 533 static void arm_timer(struct k_itimer *timer)
 534 {
 535         struct task_struct *p = timer->it.cpu.task;
 536         struct list_head *head, *listpos;
 537         struct task_cputime *cputime_expires;
 538         struct cpu_timer_list *const nt = &timer->it.cpu;
 539         struct cpu_timer_list *next;
 540
 541         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 542                 head = p->cpu_timers;
 543                 cputime_expires = &p->cputime_expires;
 544         } else {
 545                 head = p->signal->cpu_timers;
 546                 cputime_expires = &p->signal->cputime_expires;
 547         }
 548         head += CPUCLOCK_WHICH(timer->it_clock);
 549
 550         listpos = head;
 551         list_for_each_entry(next, head, entry) {
 552                 if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
 553                         break;
 554                 listpos = &next->entry;
 555         }
 556         list_add(&nt->entry, listpos);
 557
 558         if (listpos == head) {
 559                 union cpu_time_count *exp = &nt->expires;
 560
 561                 /*
 562                  * We are the new earliest-expiring POSIX 1.b timer, hence
 563                  * need to update expiration cache. Take into account that
 564                  * for process timers we share expiration cache with itimers
 565                  * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
 566                  */
 567
 568                 switch (CPUCLOCK_WHICH(timer->it_clock)) {
 569                 case CPUCLOCK_PROF:
 570                         if (expires_gt(cputime_expires->prof_exp, exp->cpu))
 571                                 cputime_expires->prof_exp = exp->cpu;
 572                         break;
 573                 case CPUCLOCK_VIRT:
 574                         if (expires_gt(cputime_expires->virt_exp, exp->cpu))
 575                                 cputime_expires->virt_exp = exp->cpu;
 576                         break;
 577                 case CPUCLOCK_SCHED:
 578                         if (cputime_expires->sched_exp == 0 ||
 579                             cputime_expires->sched_exp > exp->sched)
 580                                 cputime_expires->sched_exp = exp->sched;
 581                         break;
 582                 }
 583         }
 584 }
 585
 586 /*
 587  * The timer is locked, fire it and arrange for its reload.
 588  */
 589 static void cpu_timer_fire(struct k_itimer *timer)
 590 {
 591         if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 592                 /*
 593                  * User don't want any signal.
 594                  */
 595                 timer->it.cpu.expires.sched = 0;
 596         } else if (unlikely(timer->sigq == NULL)) {
 597                 /*
 598                  * This a special case for clock_nanosleep,
 599                  * not a normal timer from sys_timer_create.
 600                  */
 601                 wake_up_process(timer->it_process);
 602                 timer->it.cpu.expires.sched = 0;
 603         } else if (timer->it.cpu.incr.sched == 0) {
 604                 /*
 605                  * One-shot timer.  Clear it as soon as it's fired.
 606                  */
 607                 posix_timer_event(timer, 0);
 608                 timer->it.cpu.expires.sched = 0;
 609         } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 610                 /*
 611                  * The signal did not get queued because the signal
 612                  * was ignored, so we won't get any callback to
 613                  * reload the timer.  But we need to keep it
 614                  * ticking in case the signal is deliverable next time.
 615                  */
 616                 posix_cpu_timer_schedule(timer);
 617         }
 618 }
 619
 620 /*
 621  * Sample a process (thread group) timer for the given group_leader task.
 622  * Must be called with tasklist_lock held for reading.
 623  */
 624 static int cpu_timer_sample_group(const clockid_t which_clock,
 625                                   struct task_struct *p,
 626                                   union cpu_time_count *cpu)
 627 {
 628         struct task_cputime cputime;
 629
 630         thread_group_cputimer(p, &cputime);
 631         switch (CPUCLOCK_WHICH(which_clock)) {
 632         default:
 633                 return -EINVAL;
 634         case CPUCLOCK_PROF:
 635                 cpu->cpu = cputime.utime + cputime.stime;
 636                 break;
 637         case CPUCLOCK_VIRT:
 638                 cpu->cpu = cputime.utime;
 639                 break;
 640         case CPUCLOCK_SCHED:
 641                 cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
 642                 break;
 643         }
 644         return 0;
 645 }
 646
 647 /*
 648  * Guts of sys_timer_settime for CPU timers.
 649  * This is called with the timer locked and interrupts disabled.
 650  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 651  * and try again.  (This happens when the timer is in the middle of firing.)
 652  */
 653 static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 654                                struct itimerspec *new, struct itimerspec *old)
 655 {
 656         struct task_struct *p = timer->it.cpu.task;
 657         union cpu_time_count old_expires, new_expires, old_incr, val;
 658         int ret;
 659
 660         if (unlikely(p == NULL)) {
 661                 /*
 662                  * Timer refers to a dead task's clock.
 663                  */
 664                 return -ESRCH;
 665         }
 666
 667         new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
 668
 669         read_lock(&tasklist_lock);
 670         /*
 671          * We need the tasklist_lock to protect against reaping that
 672          * clears p->sighand.  If p has just been reaped, we can no
 673          * longer get any information about it at all.
 674          */
 675         if (unlikely(p->sighand == NULL)) {
 676                 read_unlock(&tasklist_lock);
 677                 put_task_struct(p);
 678                 timer->it.cpu.task = NULL;
 679                 return -ESRCH;
 680         }
 681
 682         /*
 683          * Disarm any old timer after extracting its expiry time.
 684          */
 685         BUG_ON(!irqs_disabled());
 686
 687         ret = 0;
 688         old_incr = timer->it.cpu.incr;
 689         spin_lock(&p->sighand->siglock);
 690         old_expires = timer->it.cpu.expires;
 691         if (unlikely(timer->it.cpu.firing)) {
 692                 timer->it.cpu.firing = -1;
 693                 ret = TIMER_RETRY;
 694         } else
 695                 list_del_init(&timer->it.cpu.entry);
 696
 697         /*
 698          * We need to sample the current value to convert the new
 699          * value from to relative and absolute, and to convert the
 700          * old value from absolute to relative.  To set a process
 701          * timer, we need a sample to balance the thread expiry
 702          * times (in arm_timer).  With an absolute time, we must
 703          * check if it's already passed.  In short, we need a sample.
 704          */
 705         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 706                 cpu_clock_sample(timer->it_clock, p, &val);
 707         } else {
 708                 cpu_timer_sample_group(timer->it_clock, p, &val);
 709         }
 710
 711         if (old) {
 712                 if (old_expires.sched == 0) {
 713                         old->it_value.tv_sec = 0;
 714                         old->it_value.tv_nsec = 0;
 715                 } else {
 716                         /*
 717                          * Update the timer in case it has
 718                          * overrun already.  If it has,
 719                          * we'll report it as having overrun
 720                          * and with the next reloaded timer
 721                          * already ticking, though we are
 722                          * swallowing that pending
 723                          * notification here to install the
 724                          * new setting.
 725                          */
 726                         bump_cpu_timer(timer, val);
 727                         if (cpu_time_before(timer->it_clock, val,
 728                                             timer->it.cpu.expires)) {
 729                                 old_expires = cpu_time_sub(
 730                                         timer->it_clock,
 731                                         timer->it.cpu.expires, val);
 732                                 sample_to_timespec(timer->it_clock,
 733                                                    old_expires,
 734                                                    &old->it_value);
 735                         } else {
 736                                 old->it_value.tv_nsec = 1;
 737                                 old->it_value.tv_sec = 0;
 738                         }
 739                 }
 740         }
 741
 742         if (unlikely(ret)) {
 743                 /*
 744                  * We are colliding with the timer actually firing.
 745                  * Punt after filling in the timer's old value, and
 746                  * disable this firing since we are already reporting
 747                  * it as an overrun (thanks to bump_cpu_timer above).
 748                  */
 749                 spin_unlock(&p->sighand->siglock);
 750                 read_unlock(&tasklist_lock);
 751                 goto out;
 752         }
 753
 754         if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
 755                 cpu_time_add(timer->it_clock, &new_expires, val);
 756         }
 757
 758         /*
 759          * Install the new expiry time (or zero).
 760          * For a timer with no notification action, we don't actually
 761          * arm the timer (we'll just fake it for timer_gettime).
 762          */
 763         timer->it.cpu.expires = new_expires;
 764         if (new_expires.sched != 0 &&
 765             cpu_time_before(timer->it_clock, val, new_expires)) {
 766                 arm_timer(timer);
 767         }
 768
 769         spin_unlock(&p->sighand->siglock);
 770         read_unlock(&tasklist_lock);
 771
 772         /*
 773          * Install the new reload setting, and
 774          * set up the signal and overrun bookkeeping.
 775          */
 776         timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
 777                                                 &new->it_interval);
 778
 779         /*
 780          * This acts as a modification timestamp for the timer,
 781          * so any automatic reload attempt will punt on seeing
 782          * that we have reset the timer manually.
 783          */
 784         timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 785                 ~REQUEUE_PENDING;
 786         timer->it_overrun_last = 0;
 787         timer->it_overrun = -1;
 788
 789         if (new_expires.sched != 0 &&
 790             !cpu_time_before(timer->it_clock, val, new_expires)) {
 791                 /*
 792                  * The designated time already passed, so we notify
 793                  * immediately, even if the thread never runs to
 794                  * accumulate more time on this clock.
 795                  */
 796                 cpu_timer_fire(timer);
 797         }
 798
 799         ret = 0;
 800  out:
 801         if (old) {
 802                 sample_to_timespec(timer->it_clock,
 803                                    old_incr, &old->it_interval);
 804         }
 805         return ret;
 806 }
 807
 808 static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 809 {
 810         union cpu_time_count now;
 811         struct task_struct *p = timer->it.cpu.task;
 812         int clear_dead;
 813
 814         /*
 815          * Easy part: convert the reload time.
 816          */
 817         sample_to_timespec(timer->it_clock,
 818                            timer->it.cpu.incr, &itp->it_interval);
 819
 820         if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
 821                 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 822                 return;
 823         }
 824
 825         if (unlikely(p == NULL)) {
 826                 /*
 827                  * This task already died and the timer will never fire.
 828                  * In this case, expires is actually the dead value.
 829                  */
 830         dead:
 831                 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
 832                                    &itp->it_value);
 833                 return;
 834         }
 835
 836         /*
 837          * Sample the clock to take the difference with the expiry time.
 838          */
 839         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 840                 cpu_clock_sample(timer->it_clock, p, &now);
 841                 clear_dead = p->exit_state;
 842         } else {
 843                 read_lock(&tasklist_lock);
 844                 if (unlikely(p->sighand == NULL)) {
 845                         /*
 846                          * The process has been reaped.
 847                          * We can't even collect a sample any more.
 848                          * Call the timer disarmed, nothing else to do.
 849                          */
 850                         put_task_struct(p);
 851                         timer->it.cpu.task = NULL;
 852                         timer->it.cpu.expires.sched = 0;
 853                         read_unlock(&tasklist_lock);
 854                         goto dead;
 855                 } else {
 856                         cpu_timer_sample_group(timer->it_clock, p, &now);
 857                         clear_dead = (unlikely(p->exit_state) &&
 858                                       thread_group_empty(p));
 859                 }
 860                 read_unlock(&tasklist_lock);
 861         }
 862
 863         if (unlikely(clear_dead)) {
 864                 /*
 865                  * We've noticed that the thread is dead, but
 866                  * not yet reaped.  Take this opportunity to
 867                  * drop our task ref.
 868                  */
 869                 clear_dead_task(timer, now);
 870                 goto dead;
 871         }
 872
 873         if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
 874                 sample_to_timespec(timer->it_clock,
 875                                    cpu_time_sub(timer->it_clock,
 876                                                 timer->it.cpu.expires, now),
 877                                    &itp->it_value);
 878         } else {
 879                 /*
 880                  * The timer should have expired already, but the firing
 881                  * hasn't taken place yet.  Say it's just about to expire.
 882                  */
 883                 itp->it_value.tv_nsec = 1;
 884                 itp->it_value.tv_sec = 0;
 885         }
 886 }
 887
 888 /*
 889  * Check for any per-thread CPU timers that have fired and move them off
 890  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 891  * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 892  */
 893 static void check_thread_timers(struct task_struct *tsk,
 894                                 struct list_head *firing)
 895 {
 896         int maxfire;
 897         struct list_head *timers = tsk->cpu_timers;
 898         struct signal_struct *const sig = tsk->signal;
 899         unsigned long soft;
 900
 901         maxfire = 20;
 902         tsk->cputime_expires.prof_exp = 0;
 903         while (!list_empty(timers)) {
 904                 struct cpu_timer_list *t = list_first_entry(timers,
 905                                                       struct cpu_timer_list,
 906                                                       entry);
 907                 if (!--maxfire || prof_ticks(tsk) < t->expires.cpu) {
 908                         tsk->cputime_expires.prof_exp = t->expires.cpu;
 909                         break;
 910                 }
 911                 t->firing = 1;
 912                 list_move_tail(&t->entry, firing);
 913         }
 914
 915         ++timers;
 916         maxfire = 20;
 917         tsk->cputime_expires.virt_exp = 0;
 918         while (!list_empty(timers)) {
 919                 struct cpu_timer_list *t = list_first_entry(timers,
 920                                                       struct cpu_timer_list,
 921                                                       entry);
 922                 if (!--maxfire || virt_ticks(tsk) < t->expires.cpu) {
 923                         tsk->cputime_expires.virt_exp = t->expires.cpu;
 924                         break;
 925                 }
 926                 t->firing = 1;
 927                 list_move_tail(&t->entry, firing);
 928         }
 929
 930         ++timers;
 931         maxfire = 20;
 932         tsk->cputime_expires.sched_exp = 0;
 933         while (!list_empty(timers)) {
 934                 struct cpu_timer_list *t = list_first_entry(timers,
 935                                                       struct cpu_timer_list,
 936                                                       entry);
 937                 if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
 938                         tsk->cputime_expires.sched_exp = t->expires.sched;
 939                         break;
 940                 }
 941                 t->firing = 1;
 942                 list_move_tail(&t->entry, firing);
 943         }
 944
 945         /*
 946          * Check for the special case thread timers.
 947          */
 948         soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
 949         if (soft != RLIM_INFINITY) {
 950                 unsigned long hard =
 951                         ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
 952
 953                 if (hard != RLIM_INFINITY &&
 954                     tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
 955                         /*
 956                          * At the hard limit, we just die.
 957                          * No need to calculate anything else now.
 958                          */
 959                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
 960                         return;
 961                 }
 962                 if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
 963                         /*
 964                          * At the soft limit, send a SIGXCPU every second.
 965                          */
 966                         if (soft < hard) {
 967                                 soft += USEC_PER_SEC;
 968                                 sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
 969                         }
 970                         printk(KERN_INFO
 971                                 "RT Watchdog Timeout: %s[%d]\n",
 972                                 tsk->comm, task_pid_nr(tsk));
 973                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
 974                 }
 975         }
 976 }
 977
 978 static void stop_process_timers(struct signal_struct *sig)
 979 {
 980         struct thread_group_cputimer *cputimer = &sig->cputimer;
 981         unsigned long flags;
 982
 983         raw_spin_lock_irqsave(&cputimer->lock, flags);
 984         cputimer->running = 0;
 985         raw_spin_unlock_irqrestore(&cputimer->lock, flags);
 986 }
 987
 988 static u32 onecputick;
 989
 990 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
 991                              cputime_t *expires, cputime_t cur_time, int signo)
 992 {
 993         if (!it->expires)
 994                 return;
 995
 996         if (cur_time >= it->expires) {
 997                 if (it->incr) {
 998                         it->expires += it->incr;
 999                         it->error += it->incr_error;
1000                         if (it->error >= onecputick) {
1001                                 it->expires -= cputime_one_jiffy;
1002                                 it->error -= onecputick;
1003                         }
1004                 } else {
1005                         it->expires = 0;
1006                 }
1007
1008                 trace_itimer_expire(signo == SIGPROF ?
1009                                     ITIMER_PROF : ITIMER_VIRTUAL,
1010                                     tsk->signal->leader_pid, cur_time);
1011                 __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
1012         }
1013
1014         if (it->expires && (!*expires || it->expires < *expires)) {
1015                 *expires = it->expires;
1016         }
1017 }
1018
1019 /**
1020  * task_cputime_zero - Check a task_cputime struct for all zero fields.
1021  *
1022  * @cputime:    The struct to compare.
1023  *
1024  * Checks @cputime to see if all fields are zero.  Returns true if all fields
1025  * are zero, false if any field is nonzero.
1026  */
1027 static inline int task_cputime_zero(const struct task_cputime *cputime)
1028 {
1029         if (!cputime->utime && !cputime->stime && !cputime->sum_exec_runtime)
1030                 return 1;
1031         return 0;
1032 }
1033
1034 /*
1035  * Check for any per-thread CPU timers that have fired and move them
1036  * off the tsk->*_timers list onto the firing list.  Per-thread timers
1037  * have already been taken off.
1038  */
1039 static void check_process_timers(struct task_struct *tsk,
1040                                  struct list_head *firing)
1041 {
1042         int maxfire;
1043         struct signal_struct *const sig = tsk->signal;
1044         cputime_t utime, ptime, virt_expires, prof_expires;
1045         unsigned long long sum_sched_runtime, sched_expires;
1046         struct list_head *timers = sig->cpu_timers;
1047         struct task_cputime cputime;
1048         unsigned long soft;
1049
1050         /*
1051          * Collect the current process totals.
1052          */
1053         thread_group_cputimer(tsk, &cputime);
1054         utime = cputime.utime;
1055         ptime = utime + cputime.stime;
1056         sum_sched_runtime = cputime.sum_exec_runtime;
1057         maxfire = 20;
1058         prof_expires = 0;
1059         while (!list_empty(timers)) {
1060                 struct cpu_timer_list *tl = list_first_entry(timers,
1061                                                       struct cpu_timer_list,
1062                                                       entry);
1063                 if (!--maxfire || ptime < tl->expires.cpu) {
1064                         prof_expires = tl->expires.cpu;
1065                         break;
1066                 }
1067                 tl->firing = 1;
1068                 list_move_tail(&tl->entry, firing);
1069         }
1070
1071         ++timers;
1072         maxfire = 20;
1073         virt_expires = 0;
1074         while (!list_empty(timers)) {
1075                 struct cpu_timer_list *tl = list_first_entry(timers,
1076                                                       struct cpu_timer_list,
1077                                                       entry);
1078                 if (!--maxfire || utime < tl->expires.cpu) {
1079                         virt_expires = tl->expires.cpu;
1080                         break;
1081                 }
1082                 tl->firing = 1;
1083                 list_move_tail(&tl->entry, firing);
1084         }
1085
1086         ++timers;
1087         maxfire = 20;
1088         sched_expires = 0;
1089         while (!list_empty(timers)) {
1090                 struct cpu_timer_list *tl = list_first_entry(timers,
1091                                                       struct cpu_timer_list,
1092                                                       entry);
1093                 if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
1094                         sched_expires = tl->expires.sched;
1095                         break;
1096                 }
1097                 tl->firing = 1;
1098                 list_move_tail(&tl->entry, firing);
1099         }
1100
1101         /*
1102          * Check for the special case process timers.
1103          */
1104         check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
1105                          SIGPROF);
1106         check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
1107                          SIGVTALRM);
1108         soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1109         if (soft != RLIM_INFINITY) {
1110                 unsigned long psecs = cputime_to_secs(ptime);
1111                 unsigned long hard =
1112                         ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
1113                 cputime_t x;
1114                 if (psecs >= hard) {
1115                         /*
1116                          * At the hard limit, we just die.
1117                          * No need to calculate anything else now.
1118                          */
1119                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1120                         return;
1121                 }
1122                 if (psecs >= soft) {
1123                         /*
1124                          * At the soft limit, send a SIGXCPU every second.
1125                          */
1126                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1127                         if (soft < hard) {
1128                                 soft++;
1129                                 sig->rlim[RLIMIT_CPU].rlim_cur = soft;
1130                         }
1131                 }
1132                 x = secs_to_cputime(soft);
1133                 if (!prof_expires || x < prof_expires) {
1134                         prof_expires = x;
1135                 }
1136         }
1137
1138         sig->cputime_expires.prof_exp = prof_expires;
1139         sig->cputime_expires.virt_exp = virt_expires;
1140         sig->cputime_expires.sched_exp = sched_expires;
1141         if (task_cputime_zero(&sig->cputime_expires))
1142                 stop_process_timers(sig);
1143 }
1144
1145 /*
1146  * This is called from the signal code (via do_schedule_next_timer)
1147  * when the last timer signal was delivered and we have to reload the timer.
1148  */
1149 void posix_cpu_timer_schedule(struct k_itimer *timer)
1150 {
1151         struct task_struct *p = timer->it.cpu.task;
1152         union cpu_time_count now;
1153
1154         if (unlikely(p == NULL))
1155                 /*
1156                  * The task was cleaned up already, no future firings.
1157                  */
1158                 goto out;
1159
1160         /*
1161          * Fetch the current sample and update the timer's expiry time.
1162          */
1163         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1164                 cpu_clock_sample(timer->it_clock, p, &now);
1165                 bump_cpu_timer(timer, now);
1166                 if (unlikely(p->exit_state)) {
1167                         clear_dead_task(timer, now);
1168                         goto out;
1169                 }
1170                 read_lock(&tasklist_lock); /* arm_timer needs it.  */
1171                 spin_lock(&p->sighand->siglock);
1172         } else {
1173                 read_lock(&tasklist_lock);
1174                 if (unlikely(p->sighand == NULL)) {
1175                         /*
1176                          * The process has been reaped.
1177                          * We can't even collect a sample any more.
1178                          */
1179                         put_task_struct(p);
1180                         timer->it.cpu.task = p = NULL;
1181                         timer->it.cpu.expires.sched = 0;
1182                         goto out_unlock;
1183                 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1184                         /*
1185                          * We've noticed that the thread is dead, but
1186                          * not yet reaped.  Take this opportunity to
1187                          * drop our task ref.
1188                          */
1189                         clear_dead_task(timer, now);
1190                         goto out_unlock;
1191                 }
1192                 spin_lock(&p->sighand->siglock);
1193                 cpu_timer_sample_group(timer->it_clock, p, &now);
1194                 bump_cpu_timer(timer, now);
1195                 /* Leave the tasklist_lock locked for the call below.  */
1196         }
1197
1198         /*
1199          * Now re-arm for the new expiry time.
1200          */
1201         BUG_ON(!irqs_disabled());
1202         arm_timer(timer);
1203         spin_unlock(&p->sighand->siglock);
1204
1205 out_unlock:
1206         read_unlock(&tasklist_lock);
1207
1208 out:
1209         timer->it_overrun_last = timer->it_overrun;
1210         timer->it_overrun = -1;
1211         ++timer->it_requeue_pending;
1212 }
1213
1214 /**
1215  * task_cputime_expired - Compare two task_cputime entities.
1216  *
1217  * @sample:     The task_cputime structure to be checked for expiration.
1218  * @expires:    Expiration times, against which @sample will be checked.
1219  *
1220  * Checks @sample against @expires to see if any field of @sample has expired.
1221  * Returns true if any field of the former is greater than the corresponding
1222  * field of the latter if the latter field is set.  Otherwise returns false.
1223  */
1224 static inline int task_cputime_expired(const struct task_cputime *sample,
1225                                         const struct task_cputime *expires)
1226 {
1227         if (expires->utime && sample->utime >= expires->utime)
1228                 return 1;
1229         if (expires->stime && sample->utime + sample->stime >= expires->stime)
1230                 return 1;
1231         if (expires->sum_exec_runtime != 0 &&
1232             sample->sum_exec_runtime >= expires->sum_exec_runtime)
1233                 return 1;
1234         return 0;
1235 }
1236
1237 /**
1238  * fastpath_timer_check - POSIX CPU timers fast path.
1239  *
1240  * @tsk:        The task (thread) being checked.
1241  *
1242  * Check the task and thread group timers.  If both are zero (there are no
1243  * timers set) return false.  Otherwise snapshot the task and thread group
1244  * timers and compare them with the corresponding expiration times.  Return
1245  * true if a timer has expired, else return false.
1246  */
1247 static inline int fastpath_timer_check(struct task_struct *tsk)
1248 {
1249         struct signal_struct *sig;
1250
1251         if (!task_cputime_zero(&tsk->cputime_expires)) {
1252                 struct task_cputime task_sample = {
1253                         .utime = tsk->utime,
1254                         .stime = tsk->stime,
1255                         .sum_exec_runtime = tsk->se.sum_exec_runtime
1256                 };
1257
1258                 if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1259                         return 1;
1260         }
1261
1262         sig = tsk->signal;
1263         if (sig->cputimer.running) {
1264                 struct task_cputime group_sample;
1265
1266                 raw_spin_lock(&sig->cputimer.lock);
1267                 group_sample = sig->cputimer.cputime;
1268                 raw_spin_unlock(&sig->cputimer.lock);
1269
1270                 if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1271                         return 1;
1272         }
1273
1274         return 0;
1275 }
1276
1277 /*
1278  * This is called from the timer interrupt handler.  The irq handler has
1279  * already updated our counts.  We need to check if any timers fire now.
1280  * Interrupts are disabled.
1281  */
1282 void run_posix_cpu_timers(struct task_struct *tsk)
1283 {
1284         LIST_HEAD(firing);
1285         struct k_itimer *timer, *next;
1286         unsigned long flags;
1287
1288         BUG_ON(!irqs_disabled());
1289
1290         /*
1291          * The fast path checks that there are no expired thread or thread
1292          * group timers.  If that's so, just return.
1293          */
1294         if (!fastpath_timer_check(tsk))
1295                 return;
1296
1297         if (!lock_task_sighand(tsk, &flags))
1298                 return;
1299         /*
1300          * Here we take off tsk->signal->cpu_timers[N] and
1301          * tsk->cpu_timers[N] all the timers that are firing, and
1302          * put them on the firing list.
1303          */
1304         check_thread_timers(tsk, &firing);
1305         /*
1306          * If there are any active process wide timers (POSIX 1.b, itimers,
1307          * RLIMIT_CPU) cputimer must be running.
1308          */
1309         if (tsk->signal->cputimer.running)
1310                 check_process_timers(tsk, &firing);
1311
1312         /*
1313          * We must release these locks before taking any timer's lock.
1314          * There is a potential race with timer deletion here, as the
1315          * siglock now protects our private firing list.  We have set
1316          * the firing flag in each timer, so that a deletion attempt
1317          * that gets the timer lock before we do will give it up and
1318          * spin until we've taken care of that timer below.
1319          */
1320         unlock_task_sighand(tsk, &flags);
1321
1322         /*
1323          * Now that all the timers on our list have the firing flag,
1324          * no one will touch their list entries but us.  We'll take
1325          * each timer's lock before clearing its firing flag, so no
1326          * timer call will interfere.
1327          */
1328         list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1329                 int cpu_firing;
1330
1331                 spin_lock(&timer->it_lock);
1332                 list_del_init(&timer->it.cpu.entry);
1333                 cpu_firing = timer->it.cpu.firing;
1334                 timer->it.cpu.firing = 0;
1335                 /*
1336                  * The firing flag is -1 if we collided with a reset
1337                  * of the timer, which already reported this
1338                  * almost-firing as an overrun.  So don't generate an event.
1339                  */
1340                 if (likely(cpu_firing >= 0))
1341                         cpu_timer_fire(timer);
1342                 spin_unlock(&timer->it_lock);
1343         }
1344 }
1345
1346 /*
1347  * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1348  * The tsk->sighand->siglock must be held by the caller.
1349  */
1350 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1351                            cputime_t *newval, cputime_t *oldval)
1352 {
1353         union cpu_time_count now;
1354
1355         BUG_ON(clock_idx == CPUCLOCK_SCHED);
1356         cpu_timer_sample_group(clock_idx, tsk, &now);
1357
1358         if (oldval) {
1359                 /*
1360                  * We are setting itimer. The *oldval is absolute and we update
1361                  * it to be relative, *newval argument is relative and we update
1362                  * it to be absolute.
1363                  */
1364                 if (*oldval) {
1365                         if (*oldval <= now.cpu) {
1366                                 /* Just about to fire. */
1367                                 *oldval = cputime_one_jiffy;
1368                         } else {
1369                                 *oldval -= now.cpu;
1370                         }
1371                 }
1372
1373                 if (!*newval)
1374                         return;
1375                 *newval += now.cpu;
1376         }
1377
1378         /*
1379          * Update expiration cache if we are the earliest timer, or eventually
1380          * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
1381          */
1382         switch (clock_idx) {
1383         case CPUCLOCK_PROF:
1384                 if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
1385                         tsk->signal->cputime_expires.prof_exp = *newval;
1386                 break;
1387         case CPUCLOCK_VIRT:
1388                 if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
1389                         tsk->signal->cputime_expires.virt_exp = *newval;
1390                 break;
1391         }
1392 }
1393
1394 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1395                             struct timespec *rqtp, struct itimerspec *it)
1396 {
1397         struct k_itimer timer;
1398         int error;
1399
1400         /*
1401          * Set up a temporary timer and then wait for it to go off.
1402          */
1403         memset(&timer, 0, sizeof timer);
1404         spin_lock_init(&timer.it_lock);
1405         timer.it_clock = which_clock;
1406         timer.it_overrun = -1;
1407         error = posix_cpu_timer_create(&timer);
1408         timer.it_process = current;
1409         if (!error) {
1410                 static struct itimerspec zero_it;
1411
1412                 memset(it, 0, sizeof *it);
1413                 it->it_value = *rqtp;
1414
1415                 spin_lock_irq(&timer.it_lock);
1416                 error = posix_cpu_timer_set(&timer, flags, it, NULL);
1417                 if (error) {
1418                         spin_unlock_irq(&timer.it_lock);
1419                         return error;
1420                 }
1421
1422                 while (!signal_pending(current)) {
1423                         if (timer.it.cpu.expires.sched == 0) {
1424                                 /*
1425                                  * Our timer fired and was reset.
1426                                  */
1427                                 spin_unlock_irq(&timer.it_lock);
1428                                 return 0;
1429                         }
1430
1431                         /*
1432                          * Block until cpu_timer_fire (or a signal) wakes us.
1433                          */
1434                         __set_current_state(TASK_INTERRUPTIBLE);
1435                         spin_unlock_irq(&timer.it_lock);
1436                         schedule();
1437                         spin_lock_irq(&timer.it_lock);
1438                 }
1439
1440                 /*
1441                  * We were interrupted by a signal.
1442                  */
1443                 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1444                 posix_cpu_timer_set(&timer, 0, &zero_it, it);
1445                 spin_unlock_irq(&timer.it_lock);
1446
1447                 if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1448                         /*
1449                          * It actually did fire already.
1450                          */
1451                         return 0;
1452                 }
1453
1454                 error = -ERESTART_RESTARTBLOCK;
1455         }
1456
1457         return error;
1458 }
1459
1460 static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1461
1462 static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1463                             struct timespec *rqtp, struct timespec __user *rmtp)
1464 {
1465         struct restart_block *restart_block =
1466                 &current_thread_info()->restart_block;
1467         struct itimerspec it;
1468         int error;
1469
1470         /*
1471          * Diagnose required errors first.
1472          */
1473         if (CPUCLOCK_PERTHREAD(which_clock) &&
1474             (CPUCLOCK_PID(which_clock) == 0 ||
1475              CPUCLOCK_PID(which_clock) == current->pid))
1476                 return -EINVAL;
1477
1478         error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1479
1480         if (error == -ERESTART_RESTARTBLOCK) {
1481
1482                 if (flags & TIMER_ABSTIME)
1483                         return -ERESTARTNOHAND;
1484                 /*
1485                  * Report back to the user the time still remaining.
1486                  */
1487                 if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1488                         return -EFAULT;
1489
1490                 restart_block->fn = posix_cpu_nsleep_restart;
1491                 restart_block->nanosleep.clockid = which_clock;
1492                 restart_block->nanosleep.rmtp = rmtp;
1493                 restart_block->nanosleep.expires = timespec_to_ns(rqtp);
1494         }
1495         return error;
1496 }
1497
1498 static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1499 {
1500         clockid_t which_clock = restart_block->nanosleep.clockid;
1501         struct timespec t;
1502         struct itimerspec it;
1503         int error;
1504
1505         t = ns_to_timespec(restart_block->nanosleep.expires);
1506
1507         error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1508
1509         if (error == -ERESTART_RESTARTBLOCK) {
1510                 struct timespec __user *rmtp = restart_block->nanosleep.rmtp;
1511                 /*
1512                  * Report back to the user the time still remaining.
1513                  */
1514                 if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1515                         return -EFAULT;
1516
1517                 restart_block->nanosleep.expires = timespec_to_ns(&t);
1518         }
1519         return error;
1520
1521 }
1522
1523 #define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1524 #define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1525
1526 static int process_cpu_clock_getres(const clockid_t which_clock,
1527                                     struct timespec *tp)
1528 {
1529         return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1530 }
1531 static int process_cpu_clock_get(const clockid_t which_clock,
1532                                  struct timespec *tp)
1533 {
1534         return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1535 }
1536 static int process_cpu_timer_create(struct k_itimer *timer)
1537 {
1538         timer->it_clock = PROCESS_CLOCK;
1539         return posix_cpu_timer_create(timer);
1540 }
1541 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1542                               struct timespec *rqtp,
1543                               struct timespec __user *rmtp)
1544 {
1545         return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1546 }
1547 static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1548 {
1549         return -EINVAL;
1550 }
1551 static int thread_cpu_clock_getres(const clockid_t which_clock,
1552                                    struct timespec *tp)
1553 {
1554         return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1555 }
1556 static int thread_cpu_clock_get(const clockid_t which_clock,
1557                                 struct timespec *tp)
1558 {
1559         return posix_cpu_clock_get(THREAD_CLOCK, tp);
1560 }
1561 static int thread_cpu_timer_create(struct k_itimer *timer)
1562 {
1563         timer->it_clock = THREAD_CLOCK;
1564         return posix_cpu_timer_create(timer);
1565 }
1566
1567 struct k_clock clock_posix_cpu = {
1568         .clock_getres   = posix_cpu_clock_getres,
1569         .clock_set      = posix_cpu_clock_set,
1570         .clock_get      = posix_cpu_clock_get,
1571         .timer_create   = posix_cpu_timer_create,
1572         .nsleep         = posix_cpu_nsleep,
1573         .nsleep_restart = posix_cpu_nsleep_restart,
1574         .timer_set      = posix_cpu_timer_set,
1575         .timer_del      = posix_cpu_timer_del,
1576         .timer_get      = posix_cpu_timer_get,
1577 };
1578
1579 static __init int init_posix_cpu_timers(void)
1580 {
1581         struct k_clock process = {
1582                 .clock_getres   = process_cpu_clock_getres,
1583                 .clock_get      = process_cpu_clock_get,
1584                 .timer_create   = process_cpu_timer_create,
1585                 .nsleep         = process_cpu_nsleep,
1586                 .nsleep_restart = process_cpu_nsleep_restart,
1587         };
1588         struct k_clock thread = {
1589                 .clock_getres   = thread_cpu_clock_getres,
1590                 .clock_get      = thread_cpu_clock_get,
1591                 .timer_create   = thread_cpu_timer_create,
1592         };
1593         struct timespec ts;
1594
1595         posix_timers_register_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1596         posix_timers_register_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1597
1598         cputime_to_timespec(cputime_one_jiffy, &ts);
1599         onecputick = ts.tv_nsec;
1600         WARN_ON(ts.tv_sec != 0);
1601
1602         return 0;
1603 }
1604 __initcall(init_posix_cpu_timers);