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(unsigned long rlim_new)
  20 {
  21         cputime_t cputime = secs_to_cputime(rlim_new);
  22
  23         spin_lock_irq(&current->sighand->siglock);
  24         set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
  25         spin_unlock_irq(&current->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         read_lock(&tasklist_lock);
  41         p = find_task_by_vpid(pid);
  42         if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
  43                    same_thread_group(p, current) : thread_group_leader(p))) {
  44                 error = -EINVAL;
  45         }
  46         read_unlock(&tasklist_lock);
  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 cputime_lt(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 = cputime_add(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 = cputime_sub(a.cpu, b.cpu);
 102         }
 103         return a;
 104 }
 105
 106 /*
 107  * Divide and limit the result to res >= 1
 108  *
 109  * This is necessary to prevent signal delivery starvation, when the result of
 110  * the division would be rounded down to 0.
 111  */
 112 static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
 113 {
 114         cputime_t res = cputime_div(time, div);
 115
 116         return max_t(cputime_t, res, 1);
 117 }
 118
 119 /*
 120  * Update expiry time from increment, and increase overrun count,
 121  * given the current clock sample.
 122  */
 123 static void bump_cpu_timer(struct k_itimer *timer,
 124                                   union cpu_time_count now)
 125 {
 126         int i;
 127
 128         if (timer->it.cpu.incr.sched == 0)
 129                 return;
 130
 131         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 132                 unsigned long long delta, incr;
 133
 134                 if (now.sched < timer->it.cpu.expires.sched)
 135                         return;
 136                 incr = timer->it.cpu.incr.sched;
 137                 delta = now.sched + incr - timer->it.cpu.expires.sched;
 138                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 139                 for (i = 0; incr < delta - incr; i++)
 140                         incr = incr << 1;
 141                 for (; i >= 0; incr >>= 1, i--) {
 142                         if (delta < incr)
 143                                 continue;
 144                         timer->it.cpu.expires.sched += incr;
 145                         timer->it_overrun += 1 << i;
 146                         delta -= incr;
 147                 }
 148         } else {
 149                 cputime_t delta, incr;
 150
 151                 if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
 152                         return;
 153                 incr = timer->it.cpu.incr.cpu;
 154                 delta = cputime_sub(cputime_add(now.cpu, incr),
 155                                     timer->it.cpu.expires.cpu);
 156                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 157                 for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
 158                              incr = cputime_add(incr, incr);
 159                 for (; i >= 0; incr = cputime_halve(incr), i--) {
 160                         if (cputime_lt(delta, incr))
 161                                 continue;
 162                         timer->it.cpu.expires.cpu =
 163                                 cputime_add(timer->it.cpu.expires.cpu, incr);
 164                         timer->it_overrun += 1 << i;
 165                         delta = cputime_sub(delta, incr);
 166                 }
 167         }
 168 }
 169
 170 static inline cputime_t prof_ticks(struct task_struct *p)
 171 {
 172         return cputime_add(p->utime, p->stime);
 173 }
 174 static inline cputime_t virt_ticks(struct task_struct *p)
 175 {
 176         return p->utime;
 177 }
 178
 179 int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
 180 {
 181         int error = check_clock(which_clock);
 182         if (!error) {
 183                 tp->tv_sec = 0;
 184                 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
 185                 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 186                         /*
 187                          * If sched_clock is using a cycle counter, we
 188                          * don't have any idea of its true resolution
 189                          * exported, but it is much more than 1s/HZ.
 190                          */
 191                         tp->tv_nsec = 1;
 192                 }
 193         }
 194         return error;
 195 }
 196
 197 int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
 198 {
 199         /*
 200          * You can never reset a CPU clock, but we check for other errors
 201          * in the call before failing with EPERM.
 202          */
 203         int error = check_clock(which_clock);
 204         if (error == 0) {
 205                 error = -EPERM;
 206         }
 207         return error;
 208 }
 209
 210
 211 /*
 212  * Sample a per-thread clock for the given task.
 213  */
 214 static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
 215                             union cpu_time_count *cpu)
 216 {
 217         switch (CPUCLOCK_WHICH(which_clock)) {
 218         default:
 219                 return -EINVAL;
 220         case CPUCLOCK_PROF:
 221                 cpu->cpu = prof_ticks(p);
 222                 break;
 223         case CPUCLOCK_VIRT:
 224                 cpu->cpu = virt_ticks(p);
 225                 break;
 226         case CPUCLOCK_SCHED:
 227                 cpu->sched = task_sched_runtime(p);
 228                 break;
 229         }
 230         return 0;
 231 }
 232
 233 void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
 234 {
 235         struct sighand_struct *sighand;
 236         struct signal_struct *sig;
 237         struct task_struct *t;
 238
 239         *times = INIT_CPUTIME;
 240
 241         rcu_read_lock();
 242         sighand = rcu_dereference(tsk->sighand);
 243         if (!sighand)
 244                 goto out;
 245
 246         sig = tsk->signal;
 247
 248         t = tsk;
 249         do {
 250                 times->utime = cputime_add(times->utime, t->utime);
 251                 times->stime = cputime_add(times->stime, t->stime);
 252                 times->sum_exec_runtime += t->se.sum_exec_runtime;
 253
 254                 t = next_thread(t);
 255         } while (t != tsk);
 256
 257         times->utime = cputime_add(times->utime, sig->utime);
 258         times->stime = cputime_add(times->stime, sig->stime);
 259         times->sum_exec_runtime += sig->sum_sched_runtime;
 260 out:
 261         rcu_read_unlock();
 262 }
 263
 264 static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
 265 {
 266         if (cputime_gt(b->utime, a->utime))
 267                 a->utime = b->utime;
 268
 269         if (cputime_gt(b->stime, a->stime))
 270                 a->stime = b->stime;
 271
 272         if (b->sum_exec_runtime > a->sum_exec_runtime)
 273                 a->sum_exec_runtime = b->sum_exec_runtime;
 274 }
 275
 276 void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
 277 {
 278         struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 279         struct task_cputime sum;
 280         unsigned long flags;
 281
 282         spin_lock_irqsave(&cputimer->lock, flags);
 283         if (!cputimer->running) {
 284                 cputimer->running = 1;
 285                 /*
 286                  * The POSIX timer interface allows for absolute time expiry
 287                  * values through the TIMER_ABSTIME flag, therefore we have
 288                  * to synchronize the timer to the clock every time we start
 289                  * it.
 290                  */
 291                 thread_group_cputime(tsk, &sum);
 292                 update_gt_cputime(&cputimer->cputime, &sum);
 293         }
 294         *times = cputimer->cputime;
 295         spin_unlock_irqrestore(&cputimer->lock, flags);
 296 }
 297
 298 /*
 299  * Sample a process (thread group) clock for the given group_leader task.
 300  * Must be called with tasklist_lock held for reading.
 301  */
 302 static int cpu_clock_sample_group(const clockid_t which_clock,
 303                                   struct task_struct *p,
 304                                   union cpu_time_count *cpu)
 305 {
 306         struct task_cputime cputime;
 307
 308         switch (CPUCLOCK_WHICH(which_clock)) {
 309         default:
 310                 return -EINVAL;
 311         case CPUCLOCK_PROF:
 312                 thread_group_cputime(p, &cputime);
 313                 cpu->cpu = cputime_add(cputime.utime, cputime.stime);
 314                 break;
 315         case CPUCLOCK_VIRT:
 316                 thread_group_cputime(p, &cputime);
 317                 cpu->cpu = cputime.utime;
 318                 break;
 319         case CPUCLOCK_SCHED:
 320                 cpu->sched = thread_group_sched_runtime(p);
 321                 break;
 322         }
 323         return 0;
 324 }
 325
 326
 327 int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 328 {
 329         const pid_t pid = CPUCLOCK_PID(which_clock);
 330         int error = -EINVAL;
 331         union cpu_time_count rtn;
 332
 333         if (pid == 0) {
 334                 /*
 335                  * Special case constant value for our own clocks.
 336                  * We don't have to do any lookup to find ourselves.
 337                  */
 338                 if (CPUCLOCK_PERTHREAD(which_clock)) {
 339                         /*
 340                          * Sampling just ourselves we can do with no locking.
 341                          */
 342                         error = cpu_clock_sample(which_clock,
 343                                                  current, &rtn);
 344                 } else {
 345                         read_lock(&tasklist_lock);
 346                         error = cpu_clock_sample_group(which_clock,
 347                                                        current, &rtn);
 348                         read_unlock(&tasklist_lock);
 349                 }
 350         } else {
 351                 /*
 352                  * Find the given PID, and validate that the caller
 353                  * should be able to see it.
 354                  */
 355                 struct task_struct *p;
 356                 rcu_read_lock();
 357                 p = find_task_by_vpid(pid);
 358                 if (p) {
 359                         if (CPUCLOCK_PERTHREAD(which_clock)) {
 360                                 if (same_thread_group(p, current)) {
 361                                         error = cpu_clock_sample(which_clock,
 362                                                                  p, &rtn);
 363                                 }
 364                         } else {
 365                                 read_lock(&tasklist_lock);
 366                                 if (thread_group_leader(p) && p->signal) {
 367                                         error =
 368                                             cpu_clock_sample_group(which_clock,
 369                                                                    p, &rtn);
 370                                 }
 371                                 read_unlock(&tasklist_lock);
 372                         }
 373                 }
 374                 rcu_read_unlock();
 375         }
 376
 377         if (error)
 378                 return error;
 379         sample_to_timespec(which_clock, rtn, tp);
 380         return 0;
 381 }
 382
 383
 384 /*
 385  * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 386  * This is called from sys_timer_create() and do_cpu_nanosleep() with the
 387  * new timer already all-zeros initialized.
 388  */
 389 int posix_cpu_timer_create(struct k_itimer *new_timer)
 390 {
 391         int ret = 0;
 392         const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
 393         struct task_struct *p;
 394
 395         if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 396                 return -EINVAL;
 397
 398         INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 399
 400         read_lock(&tasklist_lock);
 401         if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
 402                 if (pid == 0) {
 403                         p = current;
 404                 } else {
 405                         p = find_task_by_vpid(pid);
 406                         if (p && !same_thread_group(p, current))
 407                                 p = NULL;
 408                 }
 409         } else {
 410                 if (pid == 0) {
 411                         p = current->group_leader;
 412                 } else {
 413                         p = find_task_by_vpid(pid);
 414                         if (p && !thread_group_leader(p))
 415                                 p = NULL;
 416                 }
 417         }
 418         new_timer->it.cpu.task = p;
 419         if (p) {
 420                 get_task_struct(p);
 421         } else {
 422                 ret = -EINVAL;
 423         }
 424         read_unlock(&tasklist_lock);
 425
 426         return ret;
 427 }
 428
 429 /*
 430  * Clean up a CPU-clock timer that is about to be destroyed.
 431  * This is called from timer deletion with the timer already locked.
 432  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 433  * and try again.  (This happens when the timer is in the middle of firing.)
 434  */
 435 int posix_cpu_timer_del(struct k_itimer *timer)
 436 {
 437         struct task_struct *p = timer->it.cpu.task;
 438         int ret = 0;
 439
 440         if (likely(p != NULL)) {
 441                 read_lock(&tasklist_lock);
 442                 if (unlikely(p->signal == NULL)) {
 443                         /*
 444                          * We raced with the reaping of the task.
 445                          * The deletion should have cleared us off the list.
 446                          */
 447                         BUG_ON(!list_empty(&timer->it.cpu.entry));
 448                 } else {
 449                         spin_lock(&p->sighand->siglock);
 450                         if (timer->it.cpu.firing)
 451                                 ret = TIMER_RETRY;
 452                         else
 453                                 list_del(&timer->it.cpu.entry);
 454                         spin_unlock(&p->sighand->siglock);
 455                 }
 456                 read_unlock(&tasklist_lock);
 457
 458                 if (!ret)
 459                         put_task_struct(p);
 460         }
 461
 462         return ret;
 463 }
 464
 465 /*
 466  * Clean out CPU timers still ticking when a thread exited.  The task
 467  * pointer is cleared, and the expiry time is replaced with the residual
 468  * time for later timer_gettime calls to return.
 469  * This must be called with the siglock held.
 470  */
 471 static void cleanup_timers(struct list_head *head,
 472                            cputime_t utime, cputime_t stime,
 473                            unsigned long long sum_exec_runtime)
 474 {
 475         struct cpu_timer_list *timer, *next;
 476         cputime_t ptime = cputime_add(utime, stime);
 477
 478         list_for_each_entry_safe(timer, next, head, entry) {
 479                 list_del_init(&timer->entry);
 480                 if (cputime_lt(timer->expires.cpu, ptime)) {
 481                         timer->expires.cpu = cputime_zero;
 482                 } else {
 483                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
 484                                                          ptime);
 485                 }
 486         }
 487
 488         ++head;
 489         list_for_each_entry_safe(timer, next, head, entry) {
 490                 list_del_init(&timer->entry);
 491                 if (cputime_lt(timer->expires.cpu, utime)) {
 492                         timer->expires.cpu = cputime_zero;
 493                 } else {
 494                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
 495                                                          utime);
 496                 }
 497         }
 498
 499         ++head;
 500         list_for_each_entry_safe(timer, next, head, entry) {
 501                 list_del_init(&timer->entry);
 502                 if (timer->expires.sched < sum_exec_runtime) {
 503                         timer->expires.sched = 0;
 504                 } else {
 505                         timer->expires.sched -= sum_exec_runtime;
 506                 }
 507         }
 508 }
 509
 510 /*
 511  * These are both called with the siglock held, when the current thread
 512  * is being reaped.  When the final (leader) thread in the group is reaped,
 513  * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 514  */
 515 void posix_cpu_timers_exit(struct task_struct *tsk)
 516 {
 517         cleanup_timers(tsk->cpu_timers,
 518                        tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
 519
 520 }
 521 void posix_cpu_timers_exit_group(struct task_struct *tsk)
 522 {
 523         struct signal_struct *const sig = tsk->signal;
 524
 525         cleanup_timers(tsk->signal->cpu_timers,
 526                        cputime_add(tsk->utime, sig->utime),
 527                        cputime_add(tsk->stime, sig->stime),
 528                        tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
 529 }
 530
 531 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 532 {
 533         /*
 534          * That's all for this thread or process.
 535          * We leave our residual in expires to be reported.
 536          */
 537         put_task_struct(timer->it.cpu.task);
 538         timer->it.cpu.task = NULL;
 539         timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
 540                                              timer->it.cpu.expires,
 541                                              now);
 542 }
 543
 544 static inline int expires_gt(cputime_t expires, cputime_t new_exp)
 545 {
 546         return cputime_eq(expires, cputime_zero) ||
 547                cputime_gt(expires, new_exp);
 548 }
 549
 550 /*
 551  * Insert the timer on the appropriate list before any timers that
 552  * expire later.  This must be called with the tasklist_lock held
 553  * for reading, interrupts disabled and p->sighand->siglock taken.
 554  */
 555 static void arm_timer(struct k_itimer *timer)
 556 {
 557         struct task_struct *p = timer->it.cpu.task;
 558         struct list_head *head, *listpos;
 559         struct task_cputime *cputime_expires;
 560         struct cpu_timer_list *const nt = &timer->it.cpu;
 561         struct cpu_timer_list *next;
 562
 563         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 564                 head = p->cpu_timers;
 565                 cputime_expires = &p->cputime_expires;
 566         } else {
 567                 head = p->signal->cpu_timers;
 568                 cputime_expires = &p->signal->cputime_expires;
 569         }
 570         head += CPUCLOCK_WHICH(timer->it_clock);
 571
 572         listpos = head;
 573         list_for_each_entry(next, head, entry) {
 574                 if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
 575                         break;
 576                 listpos = &next->entry;
 577         }
 578         list_add(&nt->entry, listpos);
 579
 580         if (listpos == head) {
 581                 union cpu_time_count *exp = &nt->expires;
 582
 583                 /*
 584                  * We are the new earliest-expiring POSIX 1.b timer, hence
 585                  * need to update expiration cache. Take into account that
 586                  * for process timers we share expiration cache with itimers
 587                  * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
 588                  */
 589
 590                 switch (CPUCLOCK_WHICH(timer->it_clock)) {
 591                 case CPUCLOCK_PROF:
 592                         if (expires_gt(cputime_expires->prof_exp, exp->cpu))
 593                                 cputime_expires->prof_exp = exp->cpu;
 594                         break;
 595                 case CPUCLOCK_VIRT:
 596                         if (expires_gt(cputime_expires->virt_exp, exp->cpu))
 597                                 cputime_expires->virt_exp = exp->cpu;
 598                         break;
 599                 case CPUCLOCK_SCHED:
 600                         if (cputime_expires->sched_exp == 0 ||
 601                             cputime_expires->sched_exp > exp->sched)
 602                                 cputime_expires->sched_exp = exp->sched;
 603                         break;
 604                 }
 605         }
 606 }
 607
 608 /*
 609  * The timer is locked, fire it and arrange for its reload.
 610  */
 611 static void cpu_timer_fire(struct k_itimer *timer)
 612 {
 613         if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 614                 /*
 615                  * User don't want any signal.
 616                  */
 617                 timer->it.cpu.expires.sched = 0;
 618         } else if (unlikely(timer->sigq == NULL)) {
 619                 /*
 620                  * This a special case for clock_nanosleep,
 621                  * not a normal timer from sys_timer_create.
 622                  */
 623                 wake_up_process(timer->it_process);
 624                 timer->it.cpu.expires.sched = 0;
 625         } else if (timer->it.cpu.incr.sched == 0) {
 626                 /*
 627                  * One-shot timer.  Clear it as soon as it's fired.
 628                  */
 629                 posix_timer_event(timer, 0);
 630                 timer->it.cpu.expires.sched = 0;
 631         } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 632                 /*
 633                  * The signal did not get queued because the signal
 634                  * was ignored, so we won't get any callback to
 635                  * reload the timer.  But we need to keep it
 636                  * ticking in case the signal is deliverable next time.
 637                  */
 638                 posix_cpu_timer_schedule(timer);
 639         }
 640 }
 641
 642 /*
 643  * Sample a process (thread group) timer for the given group_leader task.
 644  * Must be called with tasklist_lock held for reading.
 645  */
 646 static int cpu_timer_sample_group(const clockid_t which_clock,
 647                                   struct task_struct *p,
 648                                   union cpu_time_count *cpu)
 649 {
 650         struct task_cputime cputime;
 651
 652         thread_group_cputimer(p, &cputime);
 653         switch (CPUCLOCK_WHICH(which_clock)) {
 654         default:
 655                 return -EINVAL;
 656         case CPUCLOCK_PROF:
 657                 cpu->cpu = cputime_add(cputime.utime, cputime.stime);
 658                 break;
 659         case CPUCLOCK_VIRT:
 660                 cpu->cpu = cputime.utime;
 661                 break;
 662         case CPUCLOCK_SCHED:
 663                 cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
 664                 break;
 665         }
 666         return 0;
 667 }
 668
 669 /*
 670  * Guts of sys_timer_settime for CPU timers.
 671  * This is called with the timer locked and interrupts disabled.
 672  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 673  * and try again.  (This happens when the timer is in the middle of firing.)
 674  */
 675 int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 676                         struct itimerspec *new, struct itimerspec *old)
 677 {
 678         struct task_struct *p = timer->it.cpu.task;
 679         union cpu_time_count old_expires, new_expires, old_incr, val;
 680         int ret;
 681
 682         if (unlikely(p == NULL)) {
 683                 /*
 684                  * Timer refers to a dead task's clock.
 685                  */
 686                 return -ESRCH;
 687         }
 688
 689         new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
 690
 691         read_lock(&tasklist_lock);
 692         /*
 693          * We need the tasklist_lock to protect against reaping that
 694          * clears p->signal.  If p has just been reaped, we can no
 695          * longer get any information about it at all.
 696          */
 697         if (unlikely(p->signal == NULL)) {
 698                 read_unlock(&tasklist_lock);
 699                 put_task_struct(p);
 700                 timer->it.cpu.task = NULL;
 701                 return -ESRCH;
 702         }
 703
 704         /*
 705          * Disarm any old timer after extracting its expiry time.
 706          */
 707         BUG_ON(!irqs_disabled());
 708
 709         ret = 0;
 710         old_incr = timer->it.cpu.incr;
 711         spin_lock(&p->sighand->siglock);
 712         old_expires = timer->it.cpu.expires;
 713         if (unlikely(timer->it.cpu.firing)) {
 714                 timer->it.cpu.firing = -1;
 715                 ret = TIMER_RETRY;
 716         } else
 717                 list_del_init(&timer->it.cpu.entry);
 718
 719         /*
 720          * We need to sample the current value to convert the new
 721          * value from to relative and absolute, and to convert the
 722          * old value from absolute to relative.  To set a process
 723          * timer, we need a sample to balance the thread expiry
 724          * times (in arm_timer).  With an absolute time, we must
 725          * check if it's already passed.  In short, we need a sample.
 726          */
 727         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 728                 cpu_clock_sample(timer->it_clock, p, &val);
 729         } else {
 730                 cpu_timer_sample_group(timer->it_clock, p, &val);
 731         }
 732
 733         if (old) {
 734                 if (old_expires.sched == 0) {
 735                         old->it_value.tv_sec = 0;
 736                         old->it_value.tv_nsec = 0;
 737                 } else {
 738                         /*
 739                          * Update the timer in case it has
 740                          * overrun already.  If it has,
 741                          * we'll report it as having overrun
 742                          * and with the next reloaded timer
 743                          * already ticking, though we are
 744                          * swallowing that pending
 745                          * notification here to install the
 746                          * new setting.
 747                          */
 748                         bump_cpu_timer(timer, val);
 749                         if (cpu_time_before(timer->it_clock, val,
 750                                             timer->it.cpu.expires)) {
 751                                 old_expires = cpu_time_sub(
 752                                         timer->it_clock,
 753                                         timer->it.cpu.expires, val);
 754                                 sample_to_timespec(timer->it_clock,
 755                                                    old_expires,
 756                                                    &old->it_value);
 757                         } else {
 758                                 old->it_value.tv_nsec = 1;
 759                                 old->it_value.tv_sec = 0;
 760                         }
 761                 }
 762         }
 763
 764         if (unlikely(ret)) {
 765                 /*
 766                  * We are colliding with the timer actually firing.
 767                  * Punt after filling in the timer's old value, and
 768                  * disable this firing since we are already reporting
 769                  * it as an overrun (thanks to bump_cpu_timer above).
 770                  */
 771                 spin_unlock(&p->sighand->siglock);
 772                 read_unlock(&tasklist_lock);
 773                 goto out;
 774         }
 775
 776         if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
 777                 cpu_time_add(timer->it_clock, &new_expires, val);
 778         }
 779
 780         /*
 781          * Install the new expiry time (or zero).
 782          * For a timer with no notification action, we don't actually
 783          * arm the timer (we'll just fake it for timer_gettime).
 784          */
 785         timer->it.cpu.expires = new_expires;
 786         if (new_expires.sched != 0 &&
 787             cpu_time_before(timer->it_clock, val, new_expires)) {
 788                 arm_timer(timer);
 789         }
 790
 791         spin_unlock(&p->sighand->siglock);
 792         read_unlock(&tasklist_lock);
 793
 794         /*
 795          * Install the new reload setting, and
 796          * set up the signal and overrun bookkeeping.
 797          */
 798         timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
 799                                                 &new->it_interval);
 800
 801         /*
 802          * This acts as a modification timestamp for the timer,
 803          * so any automatic reload attempt will punt on seeing
 804          * that we have reset the timer manually.
 805          */
 806         timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 807                 ~REQUEUE_PENDING;
 808         timer->it_overrun_last = 0;
 809         timer->it_overrun = -1;
 810
 811         if (new_expires.sched != 0 &&
 812             !cpu_time_before(timer->it_clock, val, new_expires)) {
 813                 /*
 814                  * The designated time already passed, so we notify
 815                  * immediately, even if the thread never runs to
 816                  * accumulate more time on this clock.
 817                  */
 818                 cpu_timer_fire(timer);
 819         }
 820
 821         ret = 0;
 822  out:
 823         if (old) {
 824                 sample_to_timespec(timer->it_clock,
 825                                    old_incr, &old->it_interval);
 826         }
 827         return ret;
 828 }
 829
 830 void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 831 {
 832         union cpu_time_count now;
 833         struct task_struct *p = timer->it.cpu.task;
 834         int clear_dead;
 835
 836         /*
 837          * Easy part: convert the reload time.
 838          */
 839         sample_to_timespec(timer->it_clock,
 840                            timer->it.cpu.incr, &itp->it_interval);
 841
 842         if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
 843                 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 844                 return;
 845         }
 846
 847         if (unlikely(p == NULL)) {
 848                 /*
 849                  * This task already died and the timer will never fire.
 850                  * In this case, expires is actually the dead value.
 851                  */
 852         dead:
 853                 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
 854                                    &itp->it_value);
 855                 return;
 856         }
 857
 858         /*
 859          * Sample the clock to take the difference with the expiry time.
 860          */
 861         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 862                 cpu_clock_sample(timer->it_clock, p, &now);
 863                 clear_dead = p->exit_state;
 864         } else {
 865                 read_lock(&tasklist_lock);
 866                 if (unlikely(p->signal == NULL)) {
 867                         /*
 868                          * The process has been reaped.
 869                          * We can't even collect a sample any more.
 870                          * Call the timer disarmed, nothing else to do.
 871                          */
 872                         put_task_struct(p);
 873                         timer->it.cpu.task = NULL;
 874                         timer->it.cpu.expires.sched = 0;
 875                         read_unlock(&tasklist_lock);
 876                         goto dead;
 877                 } else {
 878                         cpu_timer_sample_group(timer->it_clock, p, &now);
 879                         clear_dead = (unlikely(p->exit_state) &&
 880                                       thread_group_empty(p));
 881                 }
 882                 read_unlock(&tasklist_lock);
 883         }
 884
 885         if (unlikely(clear_dead)) {
 886                 /*
 887                  * We've noticed that the thread is dead, but
 888                  * not yet reaped.  Take this opportunity to
 889                  * drop our task ref.
 890                  */
 891                 clear_dead_task(timer, now);
 892                 goto dead;
 893         }
 894
 895         if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
 896                 sample_to_timespec(timer->it_clock,
 897                                    cpu_time_sub(timer->it_clock,
 898                                                 timer->it.cpu.expires, now),
 899                                    &itp->it_value);
 900         } else {
 901                 /*
 902                  * The timer should have expired already, but the firing
 903                  * hasn't taken place yet.  Say it's just about to expire.
 904                  */
 905                 itp->it_value.tv_nsec = 1;
 906                 itp->it_value.tv_sec = 0;
 907         }
 908 }
 909
 910 /*
 911  * Check for any per-thread CPU timers that have fired and move them off
 912  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 913  * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 914  */
 915 static void check_thread_timers(struct task_struct *tsk,
 916                                 struct list_head *firing)
 917 {
 918         int maxfire;
 919         struct list_head *timers = tsk->cpu_timers;
 920         struct signal_struct *const sig = tsk->signal;
 921         unsigned long soft;
 922
 923         maxfire = 20;
 924         tsk->cputime_expires.prof_exp = cputime_zero;
 925         while (!list_empty(timers)) {
 926                 struct cpu_timer_list *t = list_first_entry(timers,
 927                                                       struct cpu_timer_list,
 928                                                       entry);
 929                 if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
 930                         tsk->cputime_expires.prof_exp = t->expires.cpu;
 931                         break;
 932                 }
 933                 t->firing = 1;
 934                 list_move_tail(&t->entry, firing);
 935         }
 936
 937         ++timers;
 938         maxfire = 20;
 939         tsk->cputime_expires.virt_exp = cputime_zero;
 940         while (!list_empty(timers)) {
 941                 struct cpu_timer_list *t = list_first_entry(timers,
 942                                                       struct cpu_timer_list,
 943                                                       entry);
 944                 if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
 945                         tsk->cputime_expires.virt_exp = t->expires.cpu;
 946                         break;
 947                 }
 948                 t->firing = 1;
 949                 list_move_tail(&t->entry, firing);
 950         }
 951
 952         ++timers;
 953         maxfire = 20;
 954         tsk->cputime_expires.sched_exp = 0;
 955         while (!list_empty(timers)) {
 956                 struct cpu_timer_list *t = list_first_entry(timers,
 957                                                       struct cpu_timer_list,
 958                                                       entry);
 959                 if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
 960                         tsk->cputime_expires.sched_exp = t->expires.sched;
 961                         break;
 962                 }
 963                 t->firing = 1;
 964                 list_move_tail(&t->entry, firing);
 965         }
 966
 967         /*
 968          * Check for the special case thread timers.
 969          */
 970         soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
 971         if (soft != RLIM_INFINITY) {
 972                 unsigned long hard =
 973                         ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
 974
 975                 if (hard != RLIM_INFINITY &&
 976                     tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
 977                         /*
 978                          * At the hard limit, we just die.
 979                          * No need to calculate anything else now.
 980                          */
 981                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
 982                         return;
 983                 }
 984                 if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
 985                         /*
 986                          * At the soft limit, send a SIGXCPU every second.
 987                          */
 988                         if (soft < hard) {
 989                                 soft += USEC_PER_SEC;
 990                                 sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
 991                         }
 992                         printk(KERN_INFO
 993                                 "RT Watchdog Timeout: %s[%d]\n",
 994                                 tsk->comm, task_pid_nr(tsk));
 995                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
 996                 }
 997         }
 998 }
 999
1000 static void stop_process_timers(struct signal_struct *sig)
1001 {
1002         struct thread_group_cputimer *cputimer = &sig->cputimer;
1003         unsigned long flags;
1004
1005         spin_lock_irqsave(&cputimer->lock, flags);
1006         cputimer->running = 0;
1007         spin_unlock_irqrestore(&cputimer->lock, flags);
1008 }
1009
1010 static u32 onecputick;
1011
1012 static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
1013                              cputime_t *expires, cputime_t cur_time, int signo)
1014 {
1015         if (cputime_eq(it->expires, cputime_zero))
1016                 return;
1017
1018         if (cputime_ge(cur_time, it->expires)) {
1019                 if (!cputime_eq(it->incr, cputime_zero)) {
1020                         it->expires = cputime_add(it->expires, it->incr);
1021                         it->error += it->incr_error;
1022                         if (it->error >= onecputick) {
1023                                 it->expires = cputime_sub(it->expires,
1024                                                           cputime_one_jiffy);
1025                                 it->error -= onecputick;
1026                         }
1027                 } else {
1028                         it->expires = cputime_zero;
1029                 }
1030
1031                 trace_itimer_expire(signo == SIGPROF ?
1032                                     ITIMER_PROF : ITIMER_VIRTUAL,
1033                                     tsk->signal->leader_pid, cur_time);
1034                 __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
1035         }
1036
1037         if (!cputime_eq(it->expires, cputime_zero) &&
1038             (cputime_eq(*expires, cputime_zero) ||
1039              cputime_lt(it->expires, *expires))) {
1040                 *expires = it->expires;
1041         }
1042 }
1043
1044 /**
1045  * task_cputime_zero - Check a task_cputime struct for all zero fields.
1046  *
1047  * @cputime:    The struct to compare.
1048  *
1049  * Checks @cputime to see if all fields are zero.  Returns true if all fields
1050  * are zero, false if any field is nonzero.
1051  */
1052 static inline int task_cputime_zero(const struct task_cputime *cputime)
1053 {
1054         if (cputime_eq(cputime->utime, cputime_zero) &&
1055             cputime_eq(cputime->stime, cputime_zero) &&
1056             cputime->sum_exec_runtime == 0)
1057                 return 1;
1058         return 0;
1059 }
1060
1061 /*
1062  * Check for any per-thread CPU timers that have fired and move them
1063  * off the tsk->*_timers list onto the firing list.  Per-thread timers
1064  * have already been taken off.
1065  */
1066 static void check_process_timers(struct task_struct *tsk,
1067                                  struct list_head *firing)
1068 {
1069         int maxfire;
1070         struct signal_struct *const sig = tsk->signal;
1071         cputime_t utime, ptime, virt_expires, prof_expires;
1072         unsigned long long sum_sched_runtime, sched_expires;
1073         struct list_head *timers = sig->cpu_timers;
1074         struct task_cputime cputime;
1075         unsigned long soft;
1076
1077         /*
1078          * Collect the current process totals.
1079          */
1080         thread_group_cputimer(tsk, &cputime);
1081         utime = cputime.utime;
1082         ptime = cputime_add(utime, cputime.stime);
1083         sum_sched_runtime = cputime.sum_exec_runtime;
1084         maxfire = 20;
1085         prof_expires = cputime_zero;
1086         while (!list_empty(timers)) {
1087                 struct cpu_timer_list *tl = list_first_entry(timers,
1088                                                       struct cpu_timer_list,
1089                                                       entry);
1090                 if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
1091                         prof_expires = tl->expires.cpu;
1092                         break;
1093                 }
1094                 tl->firing = 1;
1095                 list_move_tail(&tl->entry, firing);
1096         }
1097
1098         ++timers;
1099         maxfire = 20;
1100         virt_expires = cputime_zero;
1101         while (!list_empty(timers)) {
1102                 struct cpu_timer_list *tl = list_first_entry(timers,
1103                                                       struct cpu_timer_list,
1104                                                       entry);
1105                 if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
1106                         virt_expires = tl->expires.cpu;
1107                         break;
1108                 }
1109                 tl->firing = 1;
1110                 list_move_tail(&tl->entry, firing);
1111         }
1112
1113         ++timers;
1114         maxfire = 20;
1115         sched_expires = 0;
1116         while (!list_empty(timers)) {
1117                 struct cpu_timer_list *tl = list_first_entry(timers,
1118                                                       struct cpu_timer_list,
1119                                                       entry);
1120                 if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
1121                         sched_expires = tl->expires.sched;
1122                         break;
1123                 }
1124                 tl->firing = 1;
1125                 list_move_tail(&tl->entry, firing);
1126         }
1127
1128         /*
1129          * Check for the special case process timers.
1130          */
1131         check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
1132                          SIGPROF);
1133         check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
1134                          SIGVTALRM);
1135         soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1136         if (soft != RLIM_INFINITY) {
1137                 unsigned long psecs = cputime_to_secs(ptime);
1138                 unsigned long hard =
1139                         ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
1140                 cputime_t x;
1141                 if (psecs >= hard) {
1142                         /*
1143                          * At the hard limit, we just die.
1144                          * No need to calculate anything else now.
1145                          */
1146                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1147                         return;
1148                 }
1149                 if (psecs >= soft) {
1150                         /*
1151                          * At the soft limit, send a SIGXCPU every second.
1152                          */
1153                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1154                         if (soft < hard) {
1155                                 soft++;
1156                                 sig->rlim[RLIMIT_CPU].rlim_cur = soft;
1157                         }
1158                 }
1159                 x = secs_to_cputime(soft);
1160                 if (cputime_eq(prof_expires, cputime_zero) ||
1161                     cputime_lt(x, prof_expires)) {
1162                         prof_expires = x;
1163                 }
1164         }
1165
1166         sig->cputime_expires.prof_exp = prof_expires;
1167         sig->cputime_expires.virt_exp = virt_expires;
1168         sig->cputime_expires.sched_exp = sched_expires;
1169         if (task_cputime_zero(&sig->cputime_expires))
1170                 stop_process_timers(sig);
1171 }
1172
1173 /*
1174  * This is called from the signal code (via do_schedule_next_timer)
1175  * when the last timer signal was delivered and we have to reload the timer.
1176  */
1177 void posix_cpu_timer_schedule(struct k_itimer *timer)
1178 {
1179         struct task_struct *p = timer->it.cpu.task;
1180         union cpu_time_count now;
1181
1182         if (unlikely(p == NULL))
1183                 /*
1184                  * The task was cleaned up already, no future firings.
1185                  */
1186                 goto out;
1187
1188         /*
1189          * Fetch the current sample and update the timer's expiry time.
1190          */
1191         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1192                 cpu_clock_sample(timer->it_clock, p, &now);
1193                 bump_cpu_timer(timer, now);
1194                 if (unlikely(p->exit_state)) {
1195                         clear_dead_task(timer, now);
1196                         goto out;
1197                 }
1198                 read_lock(&tasklist_lock); /* arm_timer needs it.  */
1199                 spin_lock(&p->sighand->siglock);
1200         } else {
1201                 read_lock(&tasklist_lock);
1202                 if (unlikely(p->signal == NULL)) {
1203                         /*
1204                          * The process has been reaped.
1205                          * We can't even collect a sample any more.
1206                          */
1207                         put_task_struct(p);
1208                         timer->it.cpu.task = p = NULL;
1209                         timer->it.cpu.expires.sched = 0;
1210                         goto out_unlock;
1211                 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1212                         /*
1213                          * We've noticed that the thread is dead, but
1214                          * not yet reaped.  Take this opportunity to
1215                          * drop our task ref.
1216                          */
1217                         clear_dead_task(timer, now);
1218                         goto out_unlock;
1219                 }
1220                 spin_lock(&p->sighand->siglock);
1221                 cpu_timer_sample_group(timer->it_clock, p, &now);
1222                 bump_cpu_timer(timer, now);
1223                 /* Leave the tasklist_lock locked for the call below.  */
1224         }
1225
1226         /*
1227          * Now re-arm for the new expiry time.
1228          */
1229         BUG_ON(!irqs_disabled());
1230         arm_timer(timer);
1231         spin_unlock(&p->sighand->siglock);
1232
1233 out_unlock:
1234         read_unlock(&tasklist_lock);
1235
1236 out:
1237         timer->it_overrun_last = timer->it_overrun;
1238         timer->it_overrun = -1;
1239         ++timer->it_requeue_pending;
1240 }
1241
1242 /**
1243  * task_cputime_expired - Compare two task_cputime entities.
1244  *
1245  * @sample:     The task_cputime structure to be checked for expiration.
1246  * @expires:    Expiration times, against which @sample will be checked.
1247  *
1248  * Checks @sample against @expires to see if any field of @sample has expired.
1249  * Returns true if any field of the former is greater than the corresponding
1250  * field of the latter if the latter field is set.  Otherwise returns false.
1251  */
1252 static inline int task_cputime_expired(const struct task_cputime *sample,
1253                                         const struct task_cputime *expires)
1254 {
1255         if (!cputime_eq(expires->utime, cputime_zero) &&
1256             cputime_ge(sample->utime, expires->utime))
1257                 return 1;
1258         if (!cputime_eq(expires->stime, cputime_zero) &&
1259             cputime_ge(cputime_add(sample->utime, sample->stime),
1260                        expires->stime))
1261                 return 1;
1262         if (expires->sum_exec_runtime != 0 &&
1263             sample->sum_exec_runtime >= expires->sum_exec_runtime)
1264                 return 1;
1265         return 0;
1266 }
1267
1268 /**
1269  * fastpath_timer_check - POSIX CPU timers fast path.
1270  *
1271  * @tsk:        The task (thread) being checked.
1272  *
1273  * Check the task and thread group timers.  If both are zero (there are no
1274  * timers set) return false.  Otherwise snapshot the task and thread group
1275  * timers and compare them with the corresponding expiration times.  Return
1276  * true if a timer has expired, else return false.
1277  */
1278 static inline int fastpath_timer_check(struct task_struct *tsk)
1279 {
1280         struct signal_struct *sig;
1281
1282         /* tsk == current, ensure it is safe to use ->signal/sighand */
1283         if (unlikely(tsk->exit_state))
1284                 return 0;
1285
1286         if (!task_cputime_zero(&tsk->cputime_expires)) {
1287                 struct task_cputime task_sample = {
1288                         .utime = tsk->utime,
1289                         .stime = tsk->stime,
1290                         .sum_exec_runtime = tsk->se.sum_exec_runtime
1291                 };
1292
1293                 if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1294                         return 1;
1295         }
1296
1297         sig = tsk->signal;
1298         if (sig->cputimer.running) {
1299                 struct task_cputime group_sample;
1300
1301                 thread_group_cputimer(tsk, &group_sample);
1302                 if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1303                         return 1;
1304         }
1305
1306         return 0;
1307 }
1308
1309 /*
1310  * This is called from the timer interrupt handler.  The irq handler has
1311  * already updated our counts.  We need to check if any timers fire now.
1312  * Interrupts are disabled.
1313  */
1314 void run_posix_cpu_timers(struct task_struct *tsk)
1315 {
1316         LIST_HEAD(firing);
1317         struct k_itimer *timer, *next;
1318
1319         BUG_ON(!irqs_disabled());
1320
1321         /*
1322          * The fast path checks that there are no expired thread or thread
1323          * group timers.  If that's so, just return.
1324          */
1325         if (!fastpath_timer_check(tsk))
1326                 return;
1327
1328         spin_lock(&tsk->sighand->siglock);
1329         /*
1330          * Here we take off tsk->signal->cpu_timers[N] and
1331          * tsk->cpu_timers[N] all the timers that are firing, and
1332          * put them on the firing list.
1333          */
1334         check_thread_timers(tsk, &firing);
1335         /*
1336          * If there are any active process wide timers (POSIX 1.b, itimers,
1337          * RLIMIT_CPU) cputimer must be running.
1338          */
1339         if (tsk->signal->cputimer.running)
1340                 check_process_timers(tsk, &firing);
1341
1342         /*
1343          * We must release these locks before taking any timer's lock.
1344          * There is a potential race with timer deletion here, as the
1345          * siglock now protects our private firing list.  We have set
1346          * the firing flag in each timer, so that a deletion attempt
1347          * that gets the timer lock before we do will give it up and
1348          * spin until we've taken care of that timer below.
1349          */
1350         spin_unlock(&tsk->sighand->siglock);
1351
1352         /*
1353          * Now that all the timers on our list have the firing flag,
1354          * noone will touch their list entries but us.  We'll take
1355          * each timer's lock before clearing its firing flag, so no
1356          * timer call will interfere.
1357          */
1358         list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1359                 int cpu_firing;
1360
1361                 spin_lock(&timer->it_lock);
1362                 list_del_init(&timer->it.cpu.entry);
1363                 cpu_firing = timer->it.cpu.firing;
1364                 timer->it.cpu.firing = 0;
1365                 /*
1366                  * The firing flag is -1 if we collided with a reset
1367                  * of the timer, which already reported this
1368                  * almost-firing as an overrun.  So don't generate an event.
1369                  */
1370                 if (likely(cpu_firing >= 0))
1371                         cpu_timer_fire(timer);
1372                 spin_unlock(&timer->it_lock);
1373         }
1374 }
1375
1376 /*
1377  * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1378  * The tsk->sighand->siglock must be held by the caller.
1379  */
1380 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1381                            cputime_t *newval, cputime_t *oldval)
1382 {
1383         union cpu_time_count now;
1384
1385         BUG_ON(clock_idx == CPUCLOCK_SCHED);
1386         cpu_timer_sample_group(clock_idx, tsk, &now);
1387
1388         if (oldval) {
1389                 /*
1390                  * We are setting itimer. The *oldval is absolute and we update
1391                  * it to be relative, *newval argument is relative and we update
1392                  * it to be absolute.
1393                  */
1394                 if (!cputime_eq(*oldval, cputime_zero)) {
1395                         if (cputime_le(*oldval, now.cpu)) {
1396                                 /* Just about to fire. */
1397                                 *oldval = cputime_one_jiffy;
1398                         } else {
1399                                 *oldval = cputime_sub(*oldval, now.cpu);
1400                         }
1401                 }
1402
1403                 if (cputime_eq(*newval, cputime_zero))
1404                         return;
1405                 *newval = cputime_add(*newval, now.cpu);
1406         }
1407
1408         /*
1409          * Update expiration cache if we are the earliest timer, or eventually
1410          * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
1411          */
1412         switch (clock_idx) {
1413         case CPUCLOCK_PROF:
1414                 if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
1415                         tsk->signal->cputime_expires.prof_exp = *newval;
1416                 break;
1417         case CPUCLOCK_VIRT:
1418                 if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
1419                         tsk->signal->cputime_expires.virt_exp = *newval;
1420                 break;
1421         }
1422 }
1423
1424 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1425                             struct timespec *rqtp, struct itimerspec *it)
1426 {
1427         struct k_itimer timer;
1428         int error;
1429
1430         /*
1431          * Set up a temporary timer and then wait for it to go off.
1432          */
1433         memset(&timer, 0, sizeof timer);
1434         spin_lock_init(&timer.it_lock);
1435         timer.it_clock = which_clock;
1436         timer.it_overrun = -1;
1437         error = posix_cpu_timer_create(&timer);
1438         timer.it_process = current;
1439         if (!error) {
1440                 static struct itimerspec zero_it;
1441
1442                 memset(it, 0, sizeof *it);
1443                 it->it_value = *rqtp;
1444
1445                 spin_lock_irq(&timer.it_lock);
1446                 error = posix_cpu_timer_set(&timer, flags, it, NULL);
1447                 if (error) {
1448                         spin_unlock_irq(&timer.it_lock);
1449                         return error;
1450                 }
1451
1452                 while (!signal_pending(current)) {
1453                         if (timer.it.cpu.expires.sched == 0) {
1454                                 /*
1455                                  * Our timer fired and was reset.
1456                                  */
1457                                 spin_unlock_irq(&timer.it_lock);
1458                                 return 0;
1459                         }
1460
1461                         /*
1462                          * Block until cpu_timer_fire (or a signal) wakes us.
1463                          */
1464                         __set_current_state(TASK_INTERRUPTIBLE);
1465                         spin_unlock_irq(&timer.it_lock);
1466                         schedule();
1467                         spin_lock_irq(&timer.it_lock);
1468                 }
1469
1470                 /*
1471                  * We were interrupted by a signal.
1472                  */
1473                 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1474                 posix_cpu_timer_set(&timer, 0, &zero_it, it);
1475                 spin_unlock_irq(&timer.it_lock);
1476
1477                 if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1478                         /*
1479                          * It actually did fire already.
1480                          */
1481                         return 0;
1482                 }
1483
1484                 error = -ERESTART_RESTARTBLOCK;
1485         }
1486
1487         return error;
1488 }
1489
1490 int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1491                      struct timespec *rqtp, struct timespec __user *rmtp)
1492 {
1493         struct restart_block *restart_block =
1494             &current_thread_info()->restart_block;
1495         struct itimerspec it;
1496         int error;
1497
1498         /*
1499          * Diagnose required errors first.
1500          */
1501         if (CPUCLOCK_PERTHREAD(which_clock) &&
1502             (CPUCLOCK_PID(which_clock) == 0 ||
1503              CPUCLOCK_PID(which_clock) == current->pid))
1504                 return -EINVAL;
1505
1506         error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1507
1508         if (error == -ERESTART_RESTARTBLOCK) {
1509
1510                 if (flags & TIMER_ABSTIME)
1511                         return -ERESTARTNOHAND;
1512                 /*
1513                  * Report back to the user the time still remaining.
1514                  */
1515                 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1516                         return -EFAULT;
1517
1518                 restart_block->fn = posix_cpu_nsleep_restart;
1519                 restart_block->arg0 = which_clock;
1520                 restart_block->arg1 = (unsigned long) rmtp;
1521                 restart_block->arg2 = rqtp->tv_sec;
1522                 restart_block->arg3 = rqtp->tv_nsec;
1523         }
1524         return error;
1525 }
1526
1527 long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1528 {
1529         clockid_t which_clock = restart_block->arg0;
1530         struct timespec __user *rmtp;
1531         struct timespec t;
1532         struct itimerspec it;
1533         int error;
1534
1535         rmtp = (struct timespec __user *) restart_block->arg1;
1536         t.tv_sec = restart_block->arg2;
1537         t.tv_nsec = restart_block->arg3;
1538
1539         restart_block->fn = do_no_restart_syscall;
1540         error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1541
1542         if (error == -ERESTART_RESTARTBLOCK) {
1543                 /*
1544                  * Report back to the user the time still remaining.
1545                  */
1546                 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1547                         return -EFAULT;
1548
1549                 restart_block->fn = posix_cpu_nsleep_restart;
1550                 restart_block->arg0 = which_clock;
1551                 restart_block->arg1 = (unsigned long) rmtp;
1552                 restart_block->arg2 = t.tv_sec;
1553                 restart_block->arg3 = t.tv_nsec;
1554         }
1555         return error;
1556
1557 }
1558
1559
1560 #define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1561 #define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1562
1563 static int process_cpu_clock_getres(const clockid_t which_clock,
1564                                     struct timespec *tp)
1565 {
1566         return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1567 }
1568 static int process_cpu_clock_get(const clockid_t which_clock,
1569                                  struct timespec *tp)
1570 {
1571         return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1572 }
1573 static int process_cpu_timer_create(struct k_itimer *timer)
1574 {
1575         timer->it_clock = PROCESS_CLOCK;
1576         return posix_cpu_timer_create(timer);
1577 }
1578 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1579                               struct timespec *rqtp,
1580                               struct timespec __user *rmtp)
1581 {
1582         return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1583 }
1584 static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1585 {
1586         return -EINVAL;
1587 }
1588 static int thread_cpu_clock_getres(const clockid_t which_clock,
1589                                    struct timespec *tp)
1590 {
1591         return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1592 }
1593 static int thread_cpu_clock_get(const clockid_t which_clock,
1594                                 struct timespec *tp)
1595 {
1596         return posix_cpu_clock_get(THREAD_CLOCK, tp);
1597 }
1598 static int thread_cpu_timer_create(struct k_itimer *timer)
1599 {
1600         timer->it_clock = THREAD_CLOCK;
1601         return posix_cpu_timer_create(timer);
1602 }
1603 static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
1604                               struct timespec *rqtp, struct timespec __user *rmtp)
1605 {
1606         return -EINVAL;
1607 }
1608 static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
1609 {
1610         return -EINVAL;
1611 }
1612
1613 static __init int init_posix_cpu_timers(void)
1614 {
1615         struct k_clock process = {
1616                 .clock_getres = process_cpu_clock_getres,
1617                 .clock_get = process_cpu_clock_get,
1618                 .clock_set = do_posix_clock_nosettime,
1619                 .timer_create = process_cpu_timer_create,
1620                 .nsleep = process_cpu_nsleep,
1621                 .nsleep_restart = process_cpu_nsleep_restart,
1622         };
1623         struct k_clock thread = {
1624                 .clock_getres = thread_cpu_clock_getres,
1625                 .clock_get = thread_cpu_clock_get,
1626                 .clock_set = do_posix_clock_nosettime,
1627                 .timer_create = thread_cpu_timer_create,
1628                 .nsleep = thread_cpu_nsleep,
1629                 .nsleep_restart = thread_cpu_nsleep_restart,
1630         };
1631         struct timespec ts;
1632
1633         register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1634         register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1635
1636         cputime_to_timespec(cputime_one_jiffy, &ts);
1637         onecputick = ts.tv_nsec;
1638         WARN_ON(ts.tv_sec != 0);
1639
1640         return 0;
1641 }
1642 __initcall(init_posix_cpu_timers);