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
  12 /*
  13  * Called after updating RLIMIT_CPU to set timer expiration if necessary.
  14  */
  15 void update_rlimit_cpu(unsigned long rlim_new)
  16 {
  17         cputime_t cputime;
  18
  19         cputime = secs_to_cputime(rlim_new);
  20         if (cputime_eq(current->signal->it_prof_expires, cputime_zero) ||
  21             cputime_lt(current->signal->it_prof_expires, cputime)) {
  22                 spin_lock_irq(&current->sighand->siglock);
  23                 set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
  24                 spin_unlock_irq(&current->sighand->siglock);
  25         }
  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 = p->se.sum_exec_runtime + task_delta_exec(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         thread_group_cputime(p, &cputime);
 309         switch (CPUCLOCK_WHICH(which_clock)) {
 310         default:
 311                 return -EINVAL;
 312         case CPUCLOCK_PROF:
 313                 cpu->cpu = cputime_add(cputime.utime, cputime.stime);
 314                 break;
 315         case CPUCLOCK_VIRT:
 316                 cpu->cpu = cputime.utime;
 317                 break;
 318         case CPUCLOCK_SCHED:
 319                 cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
 320                 break;
 321         }
 322         return 0;
 323 }
 324
 325
 326 int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 327 {
 328         const pid_t pid = CPUCLOCK_PID(which_clock);
 329         int error = -EINVAL;
 330         union cpu_time_count rtn;
 331
 332         if (pid == 0) {
 333                 /*
 334                  * Special case constant value for our own clocks.
 335                  * We don't have to do any lookup to find ourselves.
 336                  */
 337                 if (CPUCLOCK_PERTHREAD(which_clock)) {
 338                         /*
 339                          * Sampling just ourselves we can do with no locking.
 340                          */
 341                         error = cpu_clock_sample(which_clock,
 342                                                  current, &rtn);
 343                 } else {
 344                         read_lock(&tasklist_lock);
 345                         error = cpu_clock_sample_group(which_clock,
 346                                                        current, &rtn);
 347                         read_unlock(&tasklist_lock);
 348                 }
 349         } else {
 350                 /*
 351                  * Find the given PID, and validate that the caller
 352                  * should be able to see it.
 353                  */
 354                 struct task_struct *p;
 355                 rcu_read_lock();
 356                 p = find_task_by_vpid(pid);
 357                 if (p) {
 358                         if (CPUCLOCK_PERTHREAD(which_clock)) {
 359                                 if (same_thread_group(p, current)) {
 360                                         error = cpu_clock_sample(which_clock,
 361                                                                  p, &rtn);
 362                                 }
 363                         } else {
 364                                 read_lock(&tasklist_lock);
 365                                 if (thread_group_leader(p) && p->signal) {
 366                                         error =
 367                                             cpu_clock_sample_group(which_clock,
 368                                                                    p, &rtn);
 369                                 }
 370                                 read_unlock(&tasklist_lock);
 371                         }
 372                 }
 373                 rcu_read_unlock();
 374         }
 375
 376         if (error)
 377                 return error;
 378         sample_to_timespec(which_clock, rtn, tp);
 379         return 0;
 380 }
 381
 382
 383 /*
 384  * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 385  * This is called from sys_timer_create with the new timer already locked.
 386  */
 387 int posix_cpu_timer_create(struct k_itimer *new_timer)
 388 {
 389         int ret = 0;
 390         const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
 391         struct task_struct *p;
 392
 393         if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 394                 return -EINVAL;
 395
 396         INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 397         new_timer->it.cpu.incr.sched = 0;
 398         new_timer->it.cpu.expires.sched = 0;
 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 task_cputime cputime;
 524
 525         thread_group_cputimer(tsk, &cputime);
 526         cleanup_timers(tsk->signal->cpu_timers,
 527                        cputime.utime, cputime.stime, cputime.sum_exec_runtime);
 528 }
 529
 530 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 531 {
 532         /*
 533          * That's all for this thread or process.
 534          * We leave our residual in expires to be reported.
 535          */
 536         put_task_struct(timer->it.cpu.task);
 537         timer->it.cpu.task = NULL;
 538         timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
 539                                              timer->it.cpu.expires,
 540                                              now);
 541 }
 542
 543 /*
 544  * Insert the timer on the appropriate list before any timers that
 545  * expire later.  This must be called with the tasklist_lock held
 546  * for reading, and interrupts disabled.
 547  */
 548 static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 549 {
 550         struct task_struct *p = timer->it.cpu.task;
 551         struct list_head *head, *listpos;
 552         struct cpu_timer_list *const nt = &timer->it.cpu;
 553         struct cpu_timer_list *next;
 554         unsigned long i;
 555
 556         head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
 557                 p->cpu_timers : p->signal->cpu_timers);
 558         head += CPUCLOCK_WHICH(timer->it_clock);
 559
 560         BUG_ON(!irqs_disabled());
 561         spin_lock(&p->sighand->siglock);
 562
 563         listpos = head;
 564         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 565                 list_for_each_entry(next, head, entry) {
 566                         if (next->expires.sched > nt->expires.sched)
 567                                 break;
 568                         listpos = &next->entry;
 569                 }
 570         } else {
 571                 list_for_each_entry(next, head, entry) {
 572                         if (cputime_gt(next->expires.cpu, nt->expires.cpu))
 573                                 break;
 574                         listpos = &next->entry;
 575                 }
 576         }
 577         list_add(&nt->entry, listpos);
 578
 579         if (listpos == head) {
 580                 /*
 581                  * We are the new earliest-expiring timer.
 582                  * If we are a thread timer, there can always
 583                  * be a process timer telling us to stop earlier.
 584                  */
 585
 586                 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 587                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
 588                         default:
 589                                 BUG();
 590                         case CPUCLOCK_PROF:
 591                                 if (cputime_eq(p->cputime_expires.prof_exp,
 592                                                cputime_zero) ||
 593                                     cputime_gt(p->cputime_expires.prof_exp,
 594                                                nt->expires.cpu))
 595                                         p->cputime_expires.prof_exp =
 596                                                 nt->expires.cpu;
 597                                 break;
 598                         case CPUCLOCK_VIRT:
 599                                 if (cputime_eq(p->cputime_expires.virt_exp,
 600                                                cputime_zero) ||
 601                                     cputime_gt(p->cputime_expires.virt_exp,
 602                                                nt->expires.cpu))
 603                                         p->cputime_expires.virt_exp =
 604                                                 nt->expires.cpu;
 605                                 break;
 606                         case CPUCLOCK_SCHED:
 607                                 if (p->cputime_expires.sched_exp == 0 ||
 608                                     p->cputime_expires.sched_exp >
 609                                                         nt->expires.sched)
 610                                         p->cputime_expires.sched_exp =
 611                                                 nt->expires.sched;
 612                                 break;
 613                         }
 614                 } else {
 615                         /*
 616                          * For a process timer, set the cached expiration time.
 617                          */
 618                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
 619                         default:
 620                                 BUG();
 621                         case CPUCLOCK_VIRT:
 622                                 if (!cputime_eq(p->signal->it_virt_expires,
 623                                                 cputime_zero) &&
 624                                     cputime_lt(p->signal->it_virt_expires,
 625                                                timer->it.cpu.expires.cpu))
 626                                         break;
 627                                 p->signal->cputime_expires.virt_exp =
 628                                         timer->it.cpu.expires.cpu;
 629                                 break;
 630                         case CPUCLOCK_PROF:
 631                                 if (!cputime_eq(p->signal->it_prof_expires,
 632                                                 cputime_zero) &&
 633                                     cputime_lt(p->signal->it_prof_expires,
 634                                                timer->it.cpu.expires.cpu))
 635                                         break;
 636                                 i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
 637                                 if (i != RLIM_INFINITY &&
 638                                     i <= cputime_to_secs(timer->it.cpu.expires.cpu))
 639                                         break;
 640                                 p->signal->cputime_expires.prof_exp =
 641                                         timer->it.cpu.expires.cpu;
 642                                 break;
 643                         case CPUCLOCK_SCHED:
 644                                 p->signal->cputime_expires.sched_exp =
 645                                         timer->it.cpu.expires.sched;
 646                                 break;
 647                         }
 648                 }
 649         }
 650
 651         spin_unlock(&p->sighand->siglock);
 652 }
 653
 654 /*
 655  * The timer is locked, fire it and arrange for its reload.
 656  */
 657 static void cpu_timer_fire(struct k_itimer *timer)
 658 {
 659         if (unlikely(timer->sigq == NULL)) {
 660                 /*
 661                  * This a special case for clock_nanosleep,
 662                  * not a normal timer from sys_timer_create.
 663                  */
 664                 wake_up_process(timer->it_process);
 665                 timer->it.cpu.expires.sched = 0;
 666         } else if (timer->it.cpu.incr.sched == 0) {
 667                 /*
 668                  * One-shot timer.  Clear it as soon as it's fired.
 669                  */
 670                 posix_timer_event(timer, 0);
 671                 timer->it.cpu.expires.sched = 0;
 672         } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 673                 /*
 674                  * The signal did not get queued because the signal
 675                  * was ignored, so we won't get any callback to
 676                  * reload the timer.  But we need to keep it
 677                  * ticking in case the signal is deliverable next time.
 678                  */
 679                 posix_cpu_timer_schedule(timer);
 680         }
 681 }
 682
 683 /*
 684  * Sample a process (thread group) timer for the given group_leader task.
 685  * Must be called with tasklist_lock held for reading.
 686  */
 687 static int cpu_timer_sample_group(const clockid_t which_clock,
 688                                   struct task_struct *p,
 689                                   union cpu_time_count *cpu)
 690 {
 691         struct task_cputime cputime;
 692
 693         thread_group_cputimer(p, &cputime);
 694         switch (CPUCLOCK_WHICH(which_clock)) {
 695         default:
 696                 return -EINVAL;
 697         case CPUCLOCK_PROF:
 698                 cpu->cpu = cputime_add(cputime.utime, cputime.stime);
 699                 break;
 700         case CPUCLOCK_VIRT:
 701                 cpu->cpu = cputime.utime;
 702                 break;
 703         case CPUCLOCK_SCHED:
 704                 cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
 705                 break;
 706         }
 707         return 0;
 708 }
 709
 710 /*
 711  * Guts of sys_timer_settime for CPU timers.
 712  * This is called with the timer locked and interrupts disabled.
 713  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 714  * and try again.  (This happens when the timer is in the middle of firing.)
 715  */
 716 int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 717                         struct itimerspec *new, struct itimerspec *old)
 718 {
 719         struct task_struct *p = timer->it.cpu.task;
 720         union cpu_time_count old_expires, new_expires, val;
 721         int ret;
 722
 723         if (unlikely(p == NULL)) {
 724                 /*
 725                  * Timer refers to a dead task's clock.
 726                  */
 727                 return -ESRCH;
 728         }
 729
 730         new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
 731
 732         read_lock(&tasklist_lock);
 733         /*
 734          * We need the tasklist_lock to protect against reaping that
 735          * clears p->signal.  If p has just been reaped, we can no
 736          * longer get any information about it at all.
 737          */
 738         if (unlikely(p->signal == NULL)) {
 739                 read_unlock(&tasklist_lock);
 740                 put_task_struct(p);
 741                 timer->it.cpu.task = NULL;
 742                 return -ESRCH;
 743         }
 744
 745         /*
 746          * Disarm any old timer after extracting its expiry time.
 747          */
 748         BUG_ON(!irqs_disabled());
 749
 750         ret = 0;
 751         spin_lock(&p->sighand->siglock);
 752         old_expires = timer->it.cpu.expires;
 753         if (unlikely(timer->it.cpu.firing)) {
 754                 timer->it.cpu.firing = -1;
 755                 ret = TIMER_RETRY;
 756         } else
 757                 list_del_init(&timer->it.cpu.entry);
 758         spin_unlock(&p->sighand->siglock);
 759
 760         /*
 761          * We need to sample the current value to convert the new
 762          * value from to relative and absolute, and to convert the
 763          * old value from absolute to relative.  To set a process
 764          * timer, we need a sample to balance the thread expiry
 765          * times (in arm_timer).  With an absolute time, we must
 766          * check if it's already passed.  In short, we need a sample.
 767          */
 768         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 769                 cpu_clock_sample(timer->it_clock, p, &val);
 770         } else {
 771                 cpu_timer_sample_group(timer->it_clock, p, &val);
 772         }
 773
 774         if (old) {
 775                 if (old_expires.sched == 0) {
 776                         old->it_value.tv_sec = 0;
 777                         old->it_value.tv_nsec = 0;
 778                 } else {
 779                         /*
 780                          * Update the timer in case it has
 781                          * overrun already.  If it has,
 782                          * we'll report it as having overrun
 783                          * and with the next reloaded timer
 784                          * already ticking, though we are
 785                          * swallowing that pending
 786                          * notification here to install the
 787                          * new setting.
 788                          */
 789                         bump_cpu_timer(timer, val);
 790                         if (cpu_time_before(timer->it_clock, val,
 791                                             timer->it.cpu.expires)) {
 792                                 old_expires = cpu_time_sub(
 793                                         timer->it_clock,
 794                                         timer->it.cpu.expires, val);
 795                                 sample_to_timespec(timer->it_clock,
 796                                                    old_expires,
 797                                                    &old->it_value);
 798                         } else {
 799                                 old->it_value.tv_nsec = 1;
 800                                 old->it_value.tv_sec = 0;
 801                         }
 802                 }
 803         }
 804
 805         if (unlikely(ret)) {
 806                 /*
 807                  * We are colliding with the timer actually firing.
 808                  * Punt after filling in the timer's old value, and
 809                  * disable this firing since we are already reporting
 810                  * it as an overrun (thanks to bump_cpu_timer above).
 811                  */
 812                 read_unlock(&tasklist_lock);
 813                 goto out;
 814         }
 815
 816         if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
 817                 cpu_time_add(timer->it_clock, &new_expires, val);
 818         }
 819
 820         /*
 821          * Install the new expiry time (or zero).
 822          * For a timer with no notification action, we don't actually
 823          * arm the timer (we'll just fake it for timer_gettime).
 824          */
 825         timer->it.cpu.expires = new_expires;
 826         if (new_expires.sched != 0 &&
 827             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 828             cpu_time_before(timer->it_clock, val, new_expires)) {
 829                 arm_timer(timer, val);
 830         }
 831
 832         read_unlock(&tasklist_lock);
 833
 834         /*
 835          * Install the new reload setting, and
 836          * set up the signal and overrun bookkeeping.
 837          */
 838         timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
 839                                                 &new->it_interval);
 840
 841         /*
 842          * This acts as a modification timestamp for the timer,
 843          * so any automatic reload attempt will punt on seeing
 844          * that we have reset the timer manually.
 845          */
 846         timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 847                 ~REQUEUE_PENDING;
 848         timer->it_overrun_last = 0;
 849         timer->it_overrun = -1;
 850
 851         if (new_expires.sched != 0 &&
 852             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 853             !cpu_time_before(timer->it_clock, val, new_expires)) {
 854                 /*
 855                  * The designated time already passed, so we notify
 856                  * immediately, even if the thread never runs to
 857                  * accumulate more time on this clock.
 858                  */
 859                 cpu_timer_fire(timer);
 860         }
 861
 862         ret = 0;
 863  out:
 864         if (old) {
 865                 sample_to_timespec(timer->it_clock,
 866                                    timer->it.cpu.incr, &old->it_interval);
 867         }
 868         return ret;
 869 }
 870
 871 void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 872 {
 873         union cpu_time_count now;
 874         struct task_struct *p = timer->it.cpu.task;
 875         int clear_dead;
 876
 877         /*
 878          * Easy part: convert the reload time.
 879          */
 880         sample_to_timespec(timer->it_clock,
 881                            timer->it.cpu.incr, &itp->it_interval);
 882
 883         if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
 884                 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 885                 return;
 886         }
 887
 888         if (unlikely(p == NULL)) {
 889                 /*
 890                  * This task already died and the timer will never fire.
 891                  * In this case, expires is actually the dead value.
 892                  */
 893         dead:
 894                 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
 895                                    &itp->it_value);
 896                 return;
 897         }
 898
 899         /*
 900          * Sample the clock to take the difference with the expiry time.
 901          */
 902         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 903                 cpu_clock_sample(timer->it_clock, p, &now);
 904                 clear_dead = p->exit_state;
 905         } else {
 906                 read_lock(&tasklist_lock);
 907                 if (unlikely(p->signal == NULL)) {
 908                         /*
 909                          * The process has been reaped.
 910                          * We can't even collect a sample any more.
 911                          * Call the timer disarmed, nothing else to do.
 912                          */
 913                         put_task_struct(p);
 914                         timer->it.cpu.task = NULL;
 915                         timer->it.cpu.expires.sched = 0;
 916                         read_unlock(&tasklist_lock);
 917                         goto dead;
 918                 } else {
 919                         cpu_timer_sample_group(timer->it_clock, p, &now);
 920                         clear_dead = (unlikely(p->exit_state) &&
 921                                       thread_group_empty(p));
 922                 }
 923                 read_unlock(&tasklist_lock);
 924         }
 925
 926         if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 927                 if (timer->it.cpu.incr.sched == 0 &&
 928                     cpu_time_before(timer->it_clock,
 929                                     timer->it.cpu.expires, now)) {
 930                         /*
 931                          * Do-nothing timer expired and has no reload,
 932                          * so it's as if it was never set.
 933                          */
 934                         timer->it.cpu.expires.sched = 0;
 935                         itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 936                         return;
 937                 }
 938                 /*
 939                  * Account for any expirations and reloads that should
 940                  * have happened.
 941                  */
 942                 bump_cpu_timer(timer, now);
 943         }
 944
 945         if (unlikely(clear_dead)) {
 946                 /*
 947                  * We've noticed that the thread is dead, but
 948                  * not yet reaped.  Take this opportunity to
 949                  * drop our task ref.
 950                  */
 951                 clear_dead_task(timer, now);
 952                 goto dead;
 953         }
 954
 955         if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
 956                 sample_to_timespec(timer->it_clock,
 957                                    cpu_time_sub(timer->it_clock,
 958                                                 timer->it.cpu.expires, now),
 959                                    &itp->it_value);
 960         } else {
 961                 /*
 962                  * The timer should have expired already, but the firing
 963                  * hasn't taken place yet.  Say it's just about to expire.
 964                  */
 965                 itp->it_value.tv_nsec = 1;
 966                 itp->it_value.tv_sec = 0;
 967         }
 968 }
 969
 970 /*
 971  * Check for any per-thread CPU timers that have fired and move them off
 972  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 973  * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 974  */
 975 static void check_thread_timers(struct task_struct *tsk,
 976                                 struct list_head *firing)
 977 {
 978         int maxfire;
 979         struct list_head *timers = tsk->cpu_timers;
 980         struct signal_struct *const sig = tsk->signal;
 981
 982         maxfire = 20;
 983         tsk->cputime_expires.prof_exp = cputime_zero;
 984         while (!list_empty(timers)) {
 985                 struct cpu_timer_list *t = list_first_entry(timers,
 986                                                       struct cpu_timer_list,
 987                                                       entry);
 988                 if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
 989                         tsk->cputime_expires.prof_exp = t->expires.cpu;
 990                         break;
 991                 }
 992                 t->firing = 1;
 993                 list_move_tail(&t->entry, firing);
 994         }
 995
 996         ++timers;
 997         maxfire = 20;
 998         tsk->cputime_expires.virt_exp = cputime_zero;
 999         while (!list_empty(timers)) {
1000                 struct cpu_timer_list *t = list_first_entry(timers,
1001                                                       struct cpu_timer_list,
1002                                                       entry);
1003                 if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
1004                         tsk->cputime_expires.virt_exp = t->expires.cpu;
1005                         break;
1006                 }
1007                 t->firing = 1;
1008                 list_move_tail(&t->entry, firing);
1009         }
1010
1011         ++timers;
1012         maxfire = 20;
1013         tsk->cputime_expires.sched_exp = 0;
1014         while (!list_empty(timers)) {
1015                 struct cpu_timer_list *t = list_first_entry(timers,
1016                                                       struct cpu_timer_list,
1017                                                       entry);
1018                 if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
1019                         tsk->cputime_expires.sched_exp = t->expires.sched;
1020                         break;
1021                 }
1022                 t->firing = 1;
1023                 list_move_tail(&t->entry, firing);
1024         }
1025
1026         /*
1027          * Check for the special case thread timers.
1028          */
1029         if (sig->rlim[RLIMIT_RTTIME].rlim_cur != RLIM_INFINITY) {
1030                 unsigned long hard = sig->rlim[RLIMIT_RTTIME].rlim_max;
1031                 unsigned long *soft = &sig->rlim[RLIMIT_RTTIME].rlim_cur;
1032
1033                 if (hard != RLIM_INFINITY &&
1034                     tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
1035                         /*
1036                          * At the hard limit, we just die.
1037                          * No need to calculate anything else now.
1038                          */
1039                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1040                         return;
1041                 }
1042                 if (tsk->rt.timeout > DIV_ROUND_UP(*soft, USEC_PER_SEC/HZ)) {
1043                         /*
1044                          * At the soft limit, send a SIGXCPU every second.
1045                          */
1046                         if (sig->rlim[RLIMIT_RTTIME].rlim_cur
1047                             < sig->rlim[RLIMIT_RTTIME].rlim_max) {
1048                                 sig->rlim[RLIMIT_RTTIME].rlim_cur +=
1049                                                                 USEC_PER_SEC;
1050                         }
1051                         printk(KERN_INFO
1052                                 "RT Watchdog Timeout: %s[%d]\n",
1053                                 tsk->comm, task_pid_nr(tsk));
1054                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1055                 }
1056         }
1057 }
1058
1059 static void stop_process_timers(struct task_struct *tsk)
1060 {
1061         struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
1062         unsigned long flags;
1063
1064         if (!cputimer->running)
1065                 return;
1066
1067         spin_lock_irqsave(&cputimer->lock, flags);
1068         cputimer->running = 0;
1069         spin_unlock_irqrestore(&cputimer->lock, flags);
1070 }
1071
1072 /*
1073  * Check for any per-thread CPU timers that have fired and move them
1074  * off the tsk->*_timers list onto the firing list.  Per-thread timers
1075  * have already been taken off.
1076  */
1077 static void check_process_timers(struct task_struct *tsk,
1078                                  struct list_head *firing)
1079 {
1080         int maxfire;
1081         struct signal_struct *const sig = tsk->signal;
1082         cputime_t utime, ptime, virt_expires, prof_expires;
1083         unsigned long long sum_sched_runtime, sched_expires;
1084         struct list_head *timers = sig->cpu_timers;
1085         struct task_cputime cputime;
1086
1087         /*
1088          * Don't sample the current process CPU clocks if there are no timers.
1089          */
1090         if (list_empty(&timers[CPUCLOCK_PROF]) &&
1091             cputime_eq(sig->it_prof_expires, cputime_zero) &&
1092             sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
1093             list_empty(&timers[CPUCLOCK_VIRT]) &&
1094             cputime_eq(sig->it_virt_expires, cputime_zero) &&
1095             list_empty(&timers[CPUCLOCK_SCHED])) {
1096                 stop_process_timers(tsk);
1097                 return;
1098         }
1099
1100         /*
1101          * Collect the current process totals.
1102          */
1103         thread_group_cputimer(tsk, &cputime);
1104         utime = cputime.utime;
1105         ptime = cputime_add(utime, cputime.stime);
1106         sum_sched_runtime = cputime.sum_exec_runtime;
1107         maxfire = 20;
1108         prof_expires = cputime_zero;
1109         while (!list_empty(timers)) {
1110                 struct cpu_timer_list *tl = list_first_entry(timers,
1111                                                       struct cpu_timer_list,
1112                                                       entry);
1113                 if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
1114                         prof_expires = tl->expires.cpu;
1115                         break;
1116                 }
1117                 tl->firing = 1;
1118                 list_move_tail(&tl->entry, firing);
1119         }
1120
1121         ++timers;
1122         maxfire = 20;
1123         virt_expires = cputime_zero;
1124         while (!list_empty(timers)) {
1125                 struct cpu_timer_list *tl = list_first_entry(timers,
1126                                                       struct cpu_timer_list,
1127                                                       entry);
1128                 if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
1129                         virt_expires = tl->expires.cpu;
1130                         break;
1131                 }
1132                 tl->firing = 1;
1133                 list_move_tail(&tl->entry, firing);
1134         }
1135
1136         ++timers;
1137         maxfire = 20;
1138         sched_expires = 0;
1139         while (!list_empty(timers)) {
1140                 struct cpu_timer_list *tl = list_first_entry(timers,
1141                                                       struct cpu_timer_list,
1142                                                       entry);
1143                 if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
1144                         sched_expires = tl->expires.sched;
1145                         break;
1146                 }
1147                 tl->firing = 1;
1148                 list_move_tail(&tl->entry, firing);
1149         }
1150
1151         /*
1152          * Check for the special case process timers.
1153          */
1154         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1155                 if (cputime_ge(ptime, sig->it_prof_expires)) {
1156                         /* ITIMER_PROF fires and reloads.  */
1157                         sig->it_prof_expires = sig->it_prof_incr;
1158                         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1159                                 sig->it_prof_expires = cputime_add(
1160                                         sig->it_prof_expires, ptime);
1161                         }
1162                         __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
1163                 }
1164                 if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
1165                     (cputime_eq(prof_expires, cputime_zero) ||
1166                      cputime_lt(sig->it_prof_expires, prof_expires))) {
1167                         prof_expires = sig->it_prof_expires;
1168                 }
1169         }
1170         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1171                 if (cputime_ge(utime, sig->it_virt_expires)) {
1172                         /* ITIMER_VIRTUAL fires and reloads.  */
1173                         sig->it_virt_expires = sig->it_virt_incr;
1174                         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1175                                 sig->it_virt_expires = cputime_add(
1176                                         sig->it_virt_expires, utime);
1177                         }
1178                         __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
1179                 }
1180                 if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
1181                     (cputime_eq(virt_expires, cputime_zero) ||
1182                      cputime_lt(sig->it_virt_expires, virt_expires))) {
1183                         virt_expires = sig->it_virt_expires;
1184                 }
1185         }
1186         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
1187                 unsigned long psecs = cputime_to_secs(ptime);
1188                 cputime_t x;
1189                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
1190                         /*
1191                          * At the hard limit, we just die.
1192                          * No need to calculate anything else now.
1193                          */
1194                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1195                         return;
1196                 }
1197                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
1198                         /*
1199                          * At the soft limit, send a SIGXCPU every second.
1200                          */
1201                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1202                         if (sig->rlim[RLIMIT_CPU].rlim_cur
1203                             < sig->rlim[RLIMIT_CPU].rlim_max) {
1204                                 sig->rlim[RLIMIT_CPU].rlim_cur++;
1205                         }
1206                 }
1207                 x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
1208                 if (cputime_eq(prof_expires, cputime_zero) ||
1209                     cputime_lt(x, prof_expires)) {
1210                         prof_expires = x;
1211                 }
1212         }
1213
1214         if (!cputime_eq(prof_expires, cputime_zero) &&
1215             (cputime_eq(sig->cputime_expires.prof_exp, cputime_zero) ||
1216              cputime_gt(sig->cputime_expires.prof_exp, prof_expires)))
1217                 sig->cputime_expires.prof_exp = prof_expires;
1218         if (!cputime_eq(virt_expires, cputime_zero) &&
1219             (cputime_eq(sig->cputime_expires.virt_exp, cputime_zero) ||
1220              cputime_gt(sig->cputime_expires.virt_exp, virt_expires)))
1221                 sig->cputime_expires.virt_exp = virt_expires;
1222         if (sched_expires != 0 &&
1223             (sig->cputime_expires.sched_exp == 0 ||
1224              sig->cputime_expires.sched_exp > sched_expires))
1225                 sig->cputime_expires.sched_exp = sched_expires;
1226 }
1227
1228 /*
1229  * This is called from the signal code (via do_schedule_next_timer)
1230  * when the last timer signal was delivered and we have to reload the timer.
1231  */
1232 void posix_cpu_timer_schedule(struct k_itimer *timer)
1233 {
1234         struct task_struct *p = timer->it.cpu.task;
1235         union cpu_time_count now;
1236
1237         if (unlikely(p == NULL))
1238                 /*
1239                  * The task was cleaned up already, no future firings.
1240                  */
1241                 goto out;
1242
1243         /*
1244          * Fetch the current sample and update the timer's expiry time.
1245          */
1246         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1247                 cpu_clock_sample(timer->it_clock, p, &now);
1248                 bump_cpu_timer(timer, now);
1249                 if (unlikely(p->exit_state)) {
1250                         clear_dead_task(timer, now);
1251                         goto out;
1252                 }
1253                 read_lock(&tasklist_lock); /* arm_timer needs it.  */
1254         } else {
1255                 read_lock(&tasklist_lock);
1256                 if (unlikely(p->signal == NULL)) {
1257                         /*
1258                          * The process has been reaped.
1259                          * We can't even collect a sample any more.
1260                          */
1261                         put_task_struct(p);
1262                         timer->it.cpu.task = p = NULL;
1263                         timer->it.cpu.expires.sched = 0;
1264                         goto out_unlock;
1265                 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1266                         /*
1267                          * We've noticed that the thread is dead, but
1268                          * not yet reaped.  Take this opportunity to
1269                          * drop our task ref.
1270                          */
1271                         clear_dead_task(timer, now);
1272                         goto out_unlock;
1273                 }
1274                 cpu_timer_sample_group(timer->it_clock, p, &now);
1275                 bump_cpu_timer(timer, now);
1276                 /* Leave the tasklist_lock locked for the call below.  */
1277         }
1278
1279         /*
1280          * Now re-arm for the new expiry time.
1281          */
1282         arm_timer(timer, now);
1283
1284 out_unlock:
1285         read_unlock(&tasklist_lock);
1286
1287 out:
1288         timer->it_overrun_last = timer->it_overrun;
1289         timer->it_overrun = -1;
1290         ++timer->it_requeue_pending;
1291 }
1292
1293 /**
1294  * task_cputime_zero - Check a task_cputime struct for all zero fields.
1295  *
1296  * @cputime:    The struct to compare.
1297  *
1298  * Checks @cputime to see if all fields are zero.  Returns true if all fields
1299  * are zero, false if any field is nonzero.
1300  */
1301 static inline int task_cputime_zero(const struct task_cputime *cputime)
1302 {
1303         if (cputime_eq(cputime->utime, cputime_zero) &&
1304             cputime_eq(cputime->stime, cputime_zero) &&
1305             cputime->sum_exec_runtime == 0)
1306                 return 1;
1307         return 0;
1308 }
1309
1310 /**
1311  * task_cputime_expired - Compare two task_cputime entities.
1312  *
1313  * @sample:     The task_cputime structure to be checked for expiration.
1314  * @expires:    Expiration times, against which @sample will be checked.
1315  *
1316  * Checks @sample against @expires to see if any field of @sample has expired.
1317  * Returns true if any field of the former is greater than the corresponding
1318  * field of the latter if the latter field is set.  Otherwise returns false.
1319  */
1320 static inline int task_cputime_expired(const struct task_cputime *sample,
1321                                         const struct task_cputime *expires)
1322 {
1323         if (!cputime_eq(expires->utime, cputime_zero) &&
1324             cputime_ge(sample->utime, expires->utime))
1325                 return 1;
1326         if (!cputime_eq(expires->stime, cputime_zero) &&
1327             cputime_ge(cputime_add(sample->utime, sample->stime),
1328                        expires->stime))
1329                 return 1;
1330         if (expires->sum_exec_runtime != 0 &&
1331             sample->sum_exec_runtime >= expires->sum_exec_runtime)
1332                 return 1;
1333         return 0;
1334 }
1335
1336 /**
1337  * fastpath_timer_check - POSIX CPU timers fast path.
1338  *
1339  * @tsk:        The task (thread) being checked.
1340  *
1341  * Check the task and thread group timers.  If both are zero (there are no
1342  * timers set) return false.  Otherwise snapshot the task and thread group
1343  * timers and compare them with the corresponding expiration times.  Return
1344  * true if a timer has expired, else return false.
1345  */
1346 static inline int fastpath_timer_check(struct task_struct *tsk)
1347 {
1348         struct signal_struct *sig;
1349
1350         /* tsk == current, ensure it is safe to use ->signal/sighand */
1351         if (unlikely(tsk->exit_state))
1352                 return 0;
1353
1354         if (!task_cputime_zero(&tsk->cputime_expires)) {
1355                 struct task_cputime task_sample = {
1356                         .utime = tsk->utime,
1357                         .stime = tsk->stime,
1358                         .sum_exec_runtime = tsk->se.sum_exec_runtime
1359                 };
1360
1361                 if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1362                         return 1;
1363         }
1364
1365         sig = tsk->signal;
1366         if (!task_cputime_zero(&sig->cputime_expires)) {
1367                 struct task_cputime group_sample;
1368
1369                 thread_group_cputimer(tsk, &group_sample);
1370                 if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1371                         return 1;
1372         }
1373
1374         return sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY;
1375 }
1376
1377 /*
1378  * This is called from the timer interrupt handler.  The irq handler has
1379  * already updated our counts.  We need to check if any timers fire now.
1380  * Interrupts are disabled.
1381  */
1382 void run_posix_cpu_timers(struct task_struct *tsk)
1383 {
1384         LIST_HEAD(firing);
1385         struct k_itimer *timer, *next;
1386
1387         BUG_ON(!irqs_disabled());
1388
1389         /*
1390          * The fast path checks that there are no expired thread or thread
1391          * group timers.  If that's so, just return.
1392          */
1393         if (!fastpath_timer_check(tsk))
1394                 return;
1395
1396         spin_lock(&tsk->sighand->siglock);
1397         /*
1398          * Here we take off tsk->signal->cpu_timers[N] and
1399          * tsk->cpu_timers[N] all the timers that are firing, and
1400          * put them on the firing list.
1401          */
1402         check_thread_timers(tsk, &firing);
1403         check_process_timers(tsk, &firing);
1404
1405         /*
1406          * We must release these locks before taking any timer's lock.
1407          * There is a potential race with timer deletion here, as the
1408          * siglock now protects our private firing list.  We have set
1409          * the firing flag in each timer, so that a deletion attempt
1410          * that gets the timer lock before we do will give it up and
1411          * spin until we've taken care of that timer below.
1412          */
1413         spin_unlock(&tsk->sighand->siglock);
1414
1415         /*
1416          * Now that all the timers on our list have the firing flag,
1417          * noone will touch their list entries but us.  We'll take
1418          * each timer's lock before clearing its firing flag, so no
1419          * timer call will interfere.
1420          */
1421         list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1422                 int firing;
1423                 spin_lock(&timer->it_lock);
1424                 list_del_init(&timer->it.cpu.entry);
1425                 firing = timer->it.cpu.firing;
1426                 timer->it.cpu.firing = 0;
1427                 /*
1428                  * The firing flag is -1 if we collided with a reset
1429                  * of the timer, which already reported this
1430                  * almost-firing as an overrun.  So don't generate an event.
1431                  */
1432                 if (likely(firing >= 0)) {
1433                         cpu_timer_fire(timer);
1434                 }
1435                 spin_unlock(&timer->it_lock);
1436         }
1437 }
1438
1439 /*
1440  * Set one of the process-wide special case CPU timers.
1441  * The tsk->sighand->siglock must be held by the caller.
1442  * The *newval argument is relative and we update it to be absolute, *oldval
1443  * is absolute and we update it to be relative.
1444  */
1445 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1446                            cputime_t *newval, cputime_t *oldval)
1447 {
1448         union cpu_time_count now;
1449         struct list_head *head;
1450
1451         BUG_ON(clock_idx == CPUCLOCK_SCHED);
1452         cpu_timer_sample_group(clock_idx, tsk, &now);
1453
1454         if (oldval) {
1455                 if (!cputime_eq(*oldval, cputime_zero)) {
1456                         if (cputime_le(*oldval, now.cpu)) {
1457                                 /* Just about to fire. */
1458                                 *oldval = jiffies_to_cputime(1);
1459                         } else {
1460                                 *oldval = cputime_sub(*oldval, now.cpu);
1461                         }
1462                 }
1463
1464                 if (cputime_eq(*newval, cputime_zero))
1465                         return;
1466                 *newval = cputime_add(*newval, now.cpu);
1467
1468                 /*
1469                  * If the RLIMIT_CPU timer will expire before the
1470                  * ITIMER_PROF timer, we have nothing else to do.
1471                  */
1472                 if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
1473                     < cputime_to_secs(*newval))
1474                         return;
1475         }
1476
1477         /*
1478          * Check whether there are any process timers already set to fire
1479          * before this one.  If so, we don't have anything more to do.
1480          */
1481         head = &tsk->signal->cpu_timers[clock_idx];
1482         if (list_empty(head) ||
1483             cputime_ge(list_first_entry(head,
1484                                   struct cpu_timer_list, entry)->expires.cpu,
1485                        *newval)) {
1486                 switch (clock_idx) {
1487                 case CPUCLOCK_PROF:
1488                         tsk->signal->cputime_expires.prof_exp = *newval;
1489                         break;
1490                 case CPUCLOCK_VIRT:
1491                         tsk->signal->cputime_expires.virt_exp = *newval;
1492                         break;
1493                 }
1494         }
1495 }
1496
1497 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1498                             struct timespec *rqtp, struct itimerspec *it)
1499 {
1500         struct k_itimer timer;
1501         int error;
1502
1503         /*
1504          * Set up a temporary timer and then wait for it to go off.
1505          */
1506         memset(&timer, 0, sizeof timer);
1507         spin_lock_init(&timer.it_lock);
1508         timer.it_clock = which_clock;
1509         timer.it_overrun = -1;
1510         error = posix_cpu_timer_create(&timer);
1511         timer.it_process = current;
1512         if (!error) {
1513                 static struct itimerspec zero_it;
1514
1515                 memset(it, 0, sizeof *it);
1516                 it->it_value = *rqtp;
1517
1518                 spin_lock_irq(&timer.it_lock);
1519                 error = posix_cpu_timer_set(&timer, flags, it, NULL);
1520                 if (error) {
1521                         spin_unlock_irq(&timer.it_lock);
1522                         return error;
1523                 }
1524
1525                 while (!signal_pending(current)) {
1526                         if (timer.it.cpu.expires.sched == 0) {
1527                                 /*
1528                                  * Our timer fired and was reset.
1529                                  */
1530                                 spin_unlock_irq(&timer.it_lock);
1531                                 return 0;
1532                         }
1533
1534                         /*
1535                          * Block until cpu_timer_fire (or a signal) wakes us.
1536                          */
1537                         __set_current_state(TASK_INTERRUPTIBLE);
1538                         spin_unlock_irq(&timer.it_lock);
1539                         schedule();
1540                         spin_lock_irq(&timer.it_lock);
1541                 }
1542
1543                 /*
1544                  * We were interrupted by a signal.
1545                  */
1546                 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1547                 posix_cpu_timer_set(&timer, 0, &zero_it, it);
1548                 spin_unlock_irq(&timer.it_lock);
1549
1550                 if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1551                         /*
1552                          * It actually did fire already.
1553                          */
1554                         return 0;
1555                 }
1556
1557                 error = -ERESTART_RESTARTBLOCK;
1558         }
1559
1560         return error;
1561 }
1562
1563 int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1564                      struct timespec *rqtp, struct timespec __user *rmtp)
1565 {
1566         struct restart_block *restart_block =
1567             &current_thread_info()->restart_block;
1568         struct itimerspec it;
1569         int error;
1570
1571         /*
1572          * Diagnose required errors first.
1573          */
1574         if (CPUCLOCK_PERTHREAD(which_clock) &&
1575             (CPUCLOCK_PID(which_clock) == 0 ||
1576              CPUCLOCK_PID(which_clock) == current->pid))
1577                 return -EINVAL;
1578
1579         error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1580
1581         if (error == -ERESTART_RESTARTBLOCK) {
1582
1583                 if (flags & TIMER_ABSTIME)
1584                         return -ERESTARTNOHAND;
1585                 /*
1586                  * Report back to the user the time still remaining.
1587                  */
1588                 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1589                         return -EFAULT;
1590
1591                 restart_block->fn = posix_cpu_nsleep_restart;
1592                 restart_block->arg0 = which_clock;
1593                 restart_block->arg1 = (unsigned long) rmtp;
1594                 restart_block->arg2 = rqtp->tv_sec;
1595                 restart_block->arg3 = rqtp->tv_nsec;
1596         }
1597         return error;
1598 }
1599
1600 long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1601 {
1602         clockid_t which_clock = restart_block->arg0;
1603         struct timespec __user *rmtp;
1604         struct timespec t;
1605         struct itimerspec it;
1606         int error;
1607
1608         rmtp = (struct timespec __user *) restart_block->arg1;
1609         t.tv_sec = restart_block->arg2;
1610         t.tv_nsec = restart_block->arg3;
1611
1612         restart_block->fn = do_no_restart_syscall;
1613         error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1614
1615         if (error == -ERESTART_RESTARTBLOCK) {
1616                 /*
1617                  * Report back to the user the time still remaining.
1618                  */
1619                 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1620                         return -EFAULT;
1621
1622                 restart_block->fn = posix_cpu_nsleep_restart;
1623                 restart_block->arg0 = which_clock;
1624                 restart_block->arg1 = (unsigned long) rmtp;
1625                 restart_block->arg2 = t.tv_sec;
1626                 restart_block->arg3 = t.tv_nsec;
1627         }
1628         return error;
1629
1630 }
1631
1632
1633 #define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1634 #define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1635
1636 static int process_cpu_clock_getres(const clockid_t which_clock,
1637                                     struct timespec *tp)
1638 {
1639         return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1640 }
1641 static int process_cpu_clock_get(const clockid_t which_clock,
1642                                  struct timespec *tp)
1643 {
1644         return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1645 }
1646 static int process_cpu_timer_create(struct k_itimer *timer)
1647 {
1648         timer->it_clock = PROCESS_CLOCK;
1649         return posix_cpu_timer_create(timer);
1650 }
1651 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1652                               struct timespec *rqtp,
1653                               struct timespec __user *rmtp)
1654 {
1655         return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1656 }
1657 static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1658 {
1659         return -EINVAL;
1660 }
1661 static int thread_cpu_clock_getres(const clockid_t which_clock,
1662                                    struct timespec *tp)
1663 {
1664         return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1665 }
1666 static int thread_cpu_clock_get(const clockid_t which_clock,
1667                                 struct timespec *tp)
1668 {
1669         return posix_cpu_clock_get(THREAD_CLOCK, tp);
1670 }
1671 static int thread_cpu_timer_create(struct k_itimer *timer)
1672 {
1673         timer->it_clock = THREAD_CLOCK;
1674         return posix_cpu_timer_create(timer);
1675 }
1676 static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
1677                               struct timespec *rqtp, struct timespec __user *rmtp)
1678 {
1679         return -EINVAL;
1680 }
1681 static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
1682 {
1683         return -EINVAL;
1684 }
1685
1686 static __init int init_posix_cpu_timers(void)
1687 {
1688         struct k_clock process = {
1689                 .clock_getres = process_cpu_clock_getres,
1690                 .clock_get = process_cpu_clock_get,
1691                 .clock_set = do_posix_clock_nosettime,
1692                 .timer_create = process_cpu_timer_create,
1693                 .nsleep = process_cpu_nsleep,
1694                 .nsleep_restart = process_cpu_nsleep_restart,
1695         };
1696         struct k_clock thread = {
1697                 .clock_getres = thread_cpu_clock_getres,
1698                 .clock_get = thread_cpu_clock_get,
1699                 .clock_set = do_posix_clock_nosettime,
1700                 .timer_create = thread_cpu_timer_create,
1701                 .nsleep = thread_cpu_nsleep,
1702                 .nsleep_restart = thread_cpu_nsleep_restart,
1703         };
1704
1705         register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1706         register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1707
1708         return 0;
1709 }
1710 __initcall(init_posix_cpu_timers);