SAFE public projects git trees. - safe/jmp/linux-2.6/blob - 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 /*
 234  * Sample a process (thread group) clock for the given group_leader task.
 235  * Must be called with tasklist_lock held for reading.
 236  */
 237 static int cpu_clock_sample_group(const clockid_t which_clock,
 238                                   struct task_struct *p,
 239                                   union cpu_time_count *cpu)
 240 {
 241         struct task_cputime cputime;
 242
 243         thread_group_cputime(p, &cputime);
 244         switch (CPUCLOCK_WHICH(which_clock)) {
 245         default:
 246                 return -EINVAL;
 247         case CPUCLOCK_PROF:
 248                 cpu->cpu = cputime_add(cputime.utime, cputime.stime);
 249                 break;
 250         case CPUCLOCK_VIRT:
 251                 cpu->cpu = cputime.utime;
 252                 break;
 253         case CPUCLOCK_SCHED:
 254                 cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
 255                 break;
 256         }
 257         return 0;
 258 }
 259
 260
 261 int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 262 {
 263         const pid_t pid = CPUCLOCK_PID(which_clock);
 264         int error = -EINVAL;
 265         union cpu_time_count rtn;
 266
 267         if (pid == 0) {
 268                 /*
 269                  * Special case constant value for our own clocks.
 270                  * We don't have to do any lookup to find ourselves.
 271                  */
 272                 if (CPUCLOCK_PERTHREAD(which_clock)) {
 273                         /*
 274                          * Sampling just ourselves we can do with no locking.
 275                          */
 276                         error = cpu_clock_sample(which_clock,
 277                                                  current, &rtn);
 278                 } else {
 279                         read_lock(&tasklist_lock);
 280                         error = cpu_clock_sample_group(which_clock,
 281                                                        current, &rtn);
 282                         read_unlock(&tasklist_lock);
 283                 }
 284         } else {
 285                 /*
 286                  * Find the given PID, and validate that the caller
 287                  * should be able to see it.
 288                  */
 289                 struct task_struct *p;
 290                 rcu_read_lock();
 291                 p = find_task_by_vpid(pid);
 292                 if (p) {
 293                         if (CPUCLOCK_PERTHREAD(which_clock)) {
 294                                 if (same_thread_group(p, current)) {
 295                                         error = cpu_clock_sample(which_clock,
 296                                                                  p, &rtn);
 297                                 }
 298                         } else {
 299                                 read_lock(&tasklist_lock);
 300                                 if (thread_group_leader(p) && p->signal) {
 301                                         error =
 302                                             cpu_clock_sample_group(which_clock,
 303                                                                    p, &rtn);
 304                                 }
 305                                 read_unlock(&tasklist_lock);
 306                         }
 307                 }
 308                 rcu_read_unlock();
 309         }
 310
 311         if (error)
 312                 return error;
 313         sample_to_timespec(which_clock, rtn, tp);
 314         return 0;
 315 }
 316
 317
 318 /*
 319  * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 320  * This is called from sys_timer_create with the new timer already locked.
 321  */
 322 int posix_cpu_timer_create(struct k_itimer *new_timer)
 323 {
 324         int ret = 0;
 325         const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
 326         struct task_struct *p;
 327
 328         if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 329                 return -EINVAL;
 330
 331         INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 332         new_timer->it.cpu.incr.sched = 0;
 333         new_timer->it.cpu.expires.sched = 0;
 334
 335         read_lock(&tasklist_lock);
 336         if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
 337                 if (pid == 0) {
 338                         p = current;
 339                 } else {
 340                         p = find_task_by_vpid(pid);
 341                         if (p && !same_thread_group(p, current))
 342                                 p = NULL;
 343                 }
 344         } else {
 345                 if (pid == 0) {
 346                         p = current->group_leader;
 347                 } else {
 348                         p = find_task_by_vpid(pid);
 349                         if (p && !thread_group_leader(p))
 350                                 p = NULL;
 351                 }
 352         }
 353         new_timer->it.cpu.task = p;
 354         if (p) {
 355                 get_task_struct(p);
 356         } else {
 357                 ret = -EINVAL;
 358         }
 359         read_unlock(&tasklist_lock);
 360
 361         return ret;
 362 }
 363
 364 /*
 365  * Clean up a CPU-clock timer that is about to be destroyed.
 366  * This is called from timer deletion with the timer already locked.
 367  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 368  * and try again.  (This happens when the timer is in the middle of firing.)
 369  */
 370 int posix_cpu_timer_del(struct k_itimer *timer)
 371 {
 372         struct task_struct *p = timer->it.cpu.task;
 373         int ret = 0;
 374
 375         if (likely(p != NULL)) {
 376                 read_lock(&tasklist_lock);
 377                 if (unlikely(p->signal == NULL)) {
 378                         /*
 379                          * We raced with the reaping of the task.
 380                          * The deletion should have cleared us off the list.
 381                          */
 382                         BUG_ON(!list_empty(&timer->it.cpu.entry));
 383                 } else {
 384                         spin_lock(&p->sighand->siglock);
 385                         if (timer->it.cpu.firing)
 386                                 ret = TIMER_RETRY;
 387                         else
 388                                 list_del(&timer->it.cpu.entry);
 389                         spin_unlock(&p->sighand->siglock);
 390                 }
 391                 read_unlock(&tasklist_lock);
 392
 393                 if (!ret)
 394                         put_task_struct(p);
 395         }
 396
 397         return ret;
 398 }
 399
 400 /*
 401  * Clean out CPU timers still ticking when a thread exited.  The task
 402  * pointer is cleared, and the expiry time is replaced with the residual
 403  * time for later timer_gettime calls to return.
 404  * This must be called with the siglock held.
 405  */
 406 static void cleanup_timers(struct list_head *head,
 407                            cputime_t utime, cputime_t stime,
 408                            unsigned long long sum_exec_runtime)
 409 {
 410         struct cpu_timer_list *timer, *next;
 411         cputime_t ptime = cputime_add(utime, stime);
 412
 413         list_for_each_entry_safe(timer, next, head, entry) {
 414                 list_del_init(&timer->entry);
 415                 if (cputime_lt(timer->expires.cpu, ptime)) {
 416                         timer->expires.cpu = cputime_zero;
 417                 } else {
 418                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
 419                                                          ptime);
 420                 }
 421         }
 422
 423         ++head;
 424         list_for_each_entry_safe(timer, next, head, entry) {
 425                 list_del_init(&timer->entry);
 426                 if (cputime_lt(timer->expires.cpu, utime)) {
 427                         timer->expires.cpu = cputime_zero;
 428                 } else {
 429                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
 430                                                          utime);
 431                 }
 432         }
 433
 434         ++head;
 435         list_for_each_entry_safe(timer, next, head, entry) {
 436                 list_del_init(&timer->entry);
 437                 if (timer->expires.sched < sum_exec_runtime) {
 438                         timer->expires.sched = 0;
 439                 } else {
 440                         timer->expires.sched -= sum_exec_runtime;
 441                 }
 442         }
 443 }
 444
 445 /*
 446  * These are both called with the siglock held, when the current thread
 447  * is being reaped.  When the final (leader) thread in the group is reaped,
 448  * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 449  */
 450 void posix_cpu_timers_exit(struct task_struct *tsk)
 451 {
 452         cleanup_timers(tsk->cpu_timers,
 453                        tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
 454
 455 }
 456 void posix_cpu_timers_exit_group(struct task_struct *tsk)
 457 {
 458         struct task_cputime cputime;
 459
 460         thread_group_cputime(tsk, &cputime);
 461         cleanup_timers(tsk->signal->cpu_timers,
 462                        cputime.utime, cputime.stime, cputime.sum_exec_runtime);
 463 }
 464
 465 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 466 {
 467         /*
 468          * That's all for this thread or process.
 469          * We leave our residual in expires to be reported.
 470          */
 471         put_task_struct(timer->it.cpu.task);
 472         timer->it.cpu.task = NULL;
 473         timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
 474                                              timer->it.cpu.expires,
 475                                              now);
 476 }
 477
 478 /*
 479  * Insert the timer on the appropriate list before any timers that
 480  * expire later.  This must be called with the tasklist_lock held
 481  * for reading, and interrupts disabled.
 482  */
 483 static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 484 {
 485         struct task_struct *p = timer->it.cpu.task;
 486         struct list_head *head, *listpos;
 487         struct cpu_timer_list *const nt = &timer->it.cpu;
 488         struct cpu_timer_list *next;
 489         unsigned long i;
 490
 491         head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
 492                 p->cpu_timers : p->signal->cpu_timers);
 493         head += CPUCLOCK_WHICH(timer->it_clock);
 494
 495         BUG_ON(!irqs_disabled());
 496         spin_lock(&p->sighand->siglock);
 497
 498         listpos = head;
 499         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 500                 list_for_each_entry(next, head, entry) {
 501                         if (next->expires.sched > nt->expires.sched)
 502                                 break;
 503                         listpos = &next->entry;
 504                 }
 505         } else {
 506                 list_for_each_entry(next, head, entry) {
 507                         if (cputime_gt(next->expires.cpu, nt->expires.cpu))
 508                                 break;
 509                         listpos = &next->entry;
 510                 }
 511         }
 512         list_add(&nt->entry, listpos);
 513
 514         if (listpos == head) {
 515                 /*
 516                  * We are the new earliest-expiring timer.
 517                  * If we are a thread timer, there can always
 518                  * be a process timer telling us to stop earlier.
 519                  */
 520
 521                 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 522                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
 523                         default:
 524                                 BUG();
 525                         case CPUCLOCK_PROF:
 526                                 if (cputime_eq(p->cputime_expires.prof_exp,
 527                                                cputime_zero) ||
 528                                     cputime_gt(p->cputime_expires.prof_exp,
 529                                                nt->expires.cpu))
 530                                         p->cputime_expires.prof_exp =
 531                                                 nt->expires.cpu;
 532                                 break;
 533                         case CPUCLOCK_VIRT:
 534                                 if (cputime_eq(p->cputime_expires.virt_exp,
 535                                                cputime_zero) ||
 536                                     cputime_gt(p->cputime_expires.virt_exp,
 537                                                nt->expires.cpu))
 538                                         p->cputime_expires.virt_exp =
 539                                                 nt->expires.cpu;
 540                                 break;
 541                         case CPUCLOCK_SCHED:
 542                                 if (p->cputime_expires.sched_exp == 0 ||
 543                                     p->cputime_expires.sched_exp >
 544                                                         nt->expires.sched)
 545                                         p->cputime_expires.sched_exp =
 546                                                 nt->expires.sched;
 547                                 break;
 548                         }
 549                 } else {
 550                         /*
 551                          * For a process timer, set the cached expiration time.
 552                          */
 553                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
 554                         default:
 555                                 BUG();
 556                         case CPUCLOCK_VIRT:
 557                                 if (!cputime_eq(p->signal->it_virt_expires,
 558                                                 cputime_zero) &&
 559                                     cputime_lt(p->signal->it_virt_expires,
 560                                                timer->it.cpu.expires.cpu))
 561                                         break;
 562                                 p->signal->cputime_expires.virt_exp =
 563                                         timer->it.cpu.expires.cpu;
 564                                 break;
 565                         case CPUCLOCK_PROF:
 566                                 if (!cputime_eq(p->signal->it_prof_expires,
 567                                                 cputime_zero) &&
 568                                     cputime_lt(p->signal->it_prof_expires,
 569                                                timer->it.cpu.expires.cpu))
 570                                         break;
 571                                 i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
 572                                 if (i != RLIM_INFINITY &&
 573                                     i <= cputime_to_secs(timer->it.cpu.expires.cpu))
 574                                         break;
 575                                 p->signal->cputime_expires.prof_exp =
 576                                         timer->it.cpu.expires.cpu;
 577                                 break;
 578                         case CPUCLOCK_SCHED:
 579                                 p->signal->cputime_expires.sched_exp =
 580                                         timer->it.cpu.expires.sched;
 581                                 break;
 582                         }
 583                 }
 584         }
 585
 586         spin_unlock(&p->sighand->siglock);
 587 }
 588
 589 /*
 590  * The timer is locked, fire it and arrange for its reload.
 591  */
 592 static void cpu_timer_fire(struct k_itimer *timer)
 593 {
 594         if (unlikely(timer->sigq == NULL)) {
 595                 /*
 596                  * This a special case for clock_nanosleep,
 597                  * not a normal timer from sys_timer_create.
 598                  */
 599                 wake_up_process(timer->it_process);
 600                 timer->it.cpu.expires.sched = 0;
 601         } else if (timer->it.cpu.incr.sched == 0) {
 602                 /*
 603                  * One-shot timer.  Clear it as soon as it's fired.
 604                  */
 605                 posix_timer_event(timer, 0);
 606                 timer->it.cpu.expires.sched = 0;
 607         } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 608                 /*
 609                  * The signal did not get queued because the signal
 610                  * was ignored, so we won't get any callback to
 611                  * reload the timer.  But we need to keep it
 612                  * ticking in case the signal is deliverable next time.
 613                  */
 614                 posix_cpu_timer_schedule(timer);
 615         }
 616 }
 617
 618 /*
 619  * Guts of sys_timer_settime for CPU timers.
 620  * This is called with the timer locked and interrupts disabled.
 621  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 622  * and try again.  (This happens when the timer is in the middle of firing.)
 623  */
 624 int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 625                         struct itimerspec *new, struct itimerspec *old)
 626 {
 627         struct task_struct *p = timer->it.cpu.task;
 628         union cpu_time_count old_expires, new_expires, val;
 629         int ret;
 630
 631         if (unlikely(p == NULL)) {
 632                 /*
 633                  * Timer refers to a dead task's clock.
 634                  */
 635                 return -ESRCH;
 636         }
 637
 638         new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
 639
 640         read_lock(&tasklist_lock);
 641         /*
 642          * We need the tasklist_lock to protect against reaping that
 643          * clears p->signal.  If p has just been reaped, we can no
 644          * longer get any information about it at all.
 645          */
 646         if (unlikely(p->signal == NULL)) {
 647                 read_unlock(&tasklist_lock);
 648                 put_task_struct(p);
 649                 timer->it.cpu.task = NULL;
 650                 return -ESRCH;
 651         }
 652
 653         /*
 654          * Disarm any old timer after extracting its expiry time.
 655          */
 656         BUG_ON(!irqs_disabled());
 657
 658         ret = 0;
 659         spin_lock(&p->sighand->siglock);
 660         old_expires = timer->it.cpu.expires;
 661         if (unlikely(timer->it.cpu.firing)) {
 662                 timer->it.cpu.firing = -1;
 663                 ret = TIMER_RETRY;
 664         } else
 665                 list_del_init(&timer->it.cpu.entry);
 666         spin_unlock(&p->sighand->siglock);
 667
 668         /*
 669          * We need to sample the current value to convert the new
 670          * value from to relative and absolute, and to convert the
 671          * old value from absolute to relative.  To set a process
 672          * timer, we need a sample to balance the thread expiry
 673          * times (in arm_timer).  With an absolute time, we must
 674          * check if it's already passed.  In short, we need a sample.
 675          */
 676         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 677                 cpu_clock_sample(timer->it_clock, p, &val);
 678         } else {
 679                 cpu_clock_sample_group(timer->it_clock, p, &val);
 680         }
 681
 682         if (old) {
 683                 if (old_expires.sched == 0) {
 684                         old->it_value.tv_sec = 0;
 685                         old->it_value.tv_nsec = 0;
 686                 } else {
 687                         /*
 688                          * Update the timer in case it has
 689                          * overrun already.  If it has,
 690                          * we'll report it as having overrun
 691                          * and with the next reloaded timer
 692                          * already ticking, though we are
 693                          * swallowing that pending
 694                          * notification here to install the
 695                          * new setting.
 696                          */
 697                         bump_cpu_timer(timer, val);
 698                         if (cpu_time_before(timer->it_clock, val,
 699                                             timer->it.cpu.expires)) {
 700                                 old_expires = cpu_time_sub(
 701                                         timer->it_clock,
 702                                         timer->it.cpu.expires, val);
 703                                 sample_to_timespec(timer->it_clock,
 704                                                    old_expires,
 705                                                    &old->it_value);
 706                         } else {
 707                                 old->it_value.tv_nsec = 1;
 708                                 old->it_value.tv_sec = 0;
 709                         }
 710                 }
 711         }
 712
 713         if (unlikely(ret)) {
 714                 /*
 715                  * We are colliding with the timer actually firing.
 716                  * Punt after filling in the timer's old value, and
 717                  * disable this firing since we are already reporting
 718                  * it as an overrun (thanks to bump_cpu_timer above).
 719                  */
 720                 read_unlock(&tasklist_lock);
 721                 goto out;
 722         }
 723
 724         if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
 725                 cpu_time_add(timer->it_clock, &new_expires, val);
 726         }
 727
 728         /*
 729          * Install the new expiry time (or zero).
 730          * For a timer with no notification action, we don't actually
 731          * arm the timer (we'll just fake it for timer_gettime).
 732          */
 733         timer->it.cpu.expires = new_expires;
 734         if (new_expires.sched != 0 &&
 735             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 736             cpu_time_before(timer->it_clock, val, new_expires)) {
 737                 arm_timer(timer, val);
 738         }
 739
 740         read_unlock(&tasklist_lock);
 741
 742         /*
 743          * Install the new reload setting, and
 744          * set up the signal and overrun bookkeeping.
 745          */
 746         timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
 747                                                 &new->it_interval);
 748
 749         /*
 750          * This acts as a modification timestamp for the timer,
 751          * so any automatic reload attempt will punt on seeing
 752          * that we have reset the timer manually.
 753          */
 754         timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 755                 ~REQUEUE_PENDING;
 756         timer->it_overrun_last = 0;
 757         timer->it_overrun = -1;
 758
 759         if (new_expires.sched != 0 &&
 760             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 761             !cpu_time_before(timer->it_clock, val, new_expires)) {
 762                 /*
 763                  * The designated time already passed, so we notify
 764                  * immediately, even if the thread never runs to
 765                  * accumulate more time on this clock.
 766                  */
 767                 cpu_timer_fire(timer);
 768         }
 769
 770         ret = 0;
 771  out:
 772         if (old) {
 773                 sample_to_timespec(timer->it_clock,
 774                                    timer->it.cpu.incr, &old->it_interval);
 775         }
 776         return ret;
 777 }
 778
 779 void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 780 {
 781         union cpu_time_count now;
 782         struct task_struct *p = timer->it.cpu.task;
 783         int clear_dead;
 784
 785         /*
 786          * Easy part: convert the reload time.
 787          */
 788         sample_to_timespec(timer->it_clock,
 789                            timer->it.cpu.incr, &itp->it_interval);
 790
 791         if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
 792                 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 793                 return;
 794         }
 795
 796         if (unlikely(p == NULL)) {
 797                 /*
 798                  * This task already died and the timer will never fire.
 799                  * In this case, expires is actually the dead value.
 800                  */
 801         dead:
 802                 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
 803                                    &itp->it_value);
 804                 return;
 805         }
 806
 807         /*
 808          * Sample the clock to take the difference with the expiry time.
 809          */
 810         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 811                 cpu_clock_sample(timer->it_clock, p, &now);
 812                 clear_dead = p->exit_state;
 813         } else {
 814                 read_lock(&tasklist_lock);
 815                 if (unlikely(p->signal == NULL)) {
 816                         /*
 817                          * The process has been reaped.
 818                          * We can't even collect a sample any more.
 819                          * Call the timer disarmed, nothing else to do.
 820                          */
 821                         put_task_struct(p);
 822                         timer->it.cpu.task = NULL;
 823                         timer->it.cpu.expires.sched = 0;
 824                         read_unlock(&tasklist_lock);
 825                         goto dead;
 826                 } else {
 827                         cpu_clock_sample_group(timer->it_clock, p, &now);
 828                         clear_dead = (unlikely(p->exit_state) &&
 829                                       thread_group_empty(p));
 830                 }
 831                 read_unlock(&tasklist_lock);
 832         }
 833
 834         if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 835                 if (timer->it.cpu.incr.sched == 0 &&
 836                     cpu_time_before(timer->it_clock,
 837                                     timer->it.cpu.expires, now)) {
 838                         /*
 839                          * Do-nothing timer expired and has no reload,
 840                          * so it's as if it was never set.
 841                          */
 842                         timer->it.cpu.expires.sched = 0;
 843                         itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 844                         return;
 845                 }
 846                 /*
 847                  * Account for any expirations and reloads that should
 848                  * have happened.
 849                  */
 850                 bump_cpu_timer(timer, now);
 851         }
 852
 853         if (unlikely(clear_dead)) {
 854                 /*
 855                  * We've noticed that the thread is dead, but
 856                  * not yet reaped.  Take this opportunity to
 857                  * drop our task ref.
 858                  */
 859                 clear_dead_task(timer, now);
 860                 goto dead;
 861         }
 862
 863         if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
 864                 sample_to_timespec(timer->it_clock,
 865                                    cpu_time_sub(timer->it_clock,
 866                                                 timer->it.cpu.expires, now),
 867                                    &itp->it_value);
 868         } else {
 869                 /*
 870                  * The timer should have expired already, but the firing
 871                  * hasn't taken place yet.  Say it's just about to expire.
 872                  */
 873                 itp->it_value.tv_nsec = 1;
 874                 itp->it_value.tv_sec = 0;
 875         }
 876 }
 877
 878 /*
 879  * Check for any per-thread CPU timers that have fired and move them off
 880  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 881  * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 882  */
 883 static void check_thread_timers(struct task_struct *tsk,
 884                                 struct list_head *firing)
 885 {
 886         int maxfire;
 887         struct list_head *timers = tsk->cpu_timers;
 888         struct signal_struct *const sig = tsk->signal;
 889
 890         maxfire = 20;
 891         tsk->cputime_expires.prof_exp = cputime_zero;
 892         while (!list_empty(timers)) {
 893                 struct cpu_timer_list *t = list_first_entry(timers,
 894                                                       struct cpu_timer_list,
 895                                                       entry);
 896                 if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
 897                         tsk->cputime_expires.prof_exp = t->expires.cpu;
 898                         break;
 899                 }
 900                 t->firing = 1;
 901                 list_move_tail(&t->entry, firing);
 902         }
 903
 904         ++timers;
 905         maxfire = 20;
 906         tsk->cputime_expires.virt_exp = cputime_zero;
 907         while (!list_empty(timers)) {
 908                 struct cpu_timer_list *t = list_first_entry(timers,
 909                                                       struct cpu_timer_list,
 910                                                       entry);
 911                 if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
 912                         tsk->cputime_expires.virt_exp = t->expires.cpu;
 913                         break;
 914                 }
 915                 t->firing = 1;
 916                 list_move_tail(&t->entry, firing);
 917         }
 918
 919         ++timers;
 920         maxfire = 20;
 921         tsk->cputime_expires.sched_exp = 0;
 922         while (!list_empty(timers)) {
 923                 struct cpu_timer_list *t = list_first_entry(timers,
 924                                                       struct cpu_timer_list,
 925                                                       entry);
 926                 if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
 927                         tsk->cputime_expires.sched_exp = t->expires.sched;
 928                         break;
 929                 }
 930                 t->firing = 1;
 931                 list_move_tail(&t->entry, firing);
 932         }
 933
 934         /*
 935          * Check for the special case thread timers.
 936          */
 937         if (sig->rlim[RLIMIT_RTTIME].rlim_cur != RLIM_INFINITY) {
 938                 unsigned long hard = sig->rlim[RLIMIT_RTTIME].rlim_max;
 939                 unsigned long *soft = &sig->rlim[RLIMIT_RTTIME].rlim_cur;
 940
 941                 if (hard != RLIM_INFINITY &&
 942                     tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
 943                         /*
 944                          * At the hard limit, we just die.
 945                          * No need to calculate anything else now.
 946                          */
 947                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
 948                         return;
 949                 }
 950                 if (tsk->rt.timeout > DIV_ROUND_UP(*soft, USEC_PER_SEC/HZ)) {
 951                         /*
 952                          * At the soft limit, send a SIGXCPU every second.
 953                          */
 954                         if (sig->rlim[RLIMIT_RTTIME].rlim_cur
 955                             < sig->rlim[RLIMIT_RTTIME].rlim_max) {
 956                                 sig->rlim[RLIMIT_RTTIME].rlim_cur +=
 957                                                                 USEC_PER_SEC;
 958                         }
 959                         printk(KERN_INFO
 960                                 "RT Watchdog Timeout: %s[%d]\n",
 961                                 tsk->comm, task_pid_nr(tsk));
 962                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
 963                 }
 964         }
 965 }
 966
 967 /*
 968  * Check for any per-thread CPU timers that have fired and move them
 969  * off the tsk->*_timers list onto the firing list.  Per-thread timers
 970  * have already been taken off.
 971  */
 972 static void check_process_timers(struct task_struct *tsk,
 973                                  struct list_head *firing)
 974 {
 975         int maxfire;
 976         struct signal_struct *const sig = tsk->signal;
 977         cputime_t utime, ptime, virt_expires, prof_expires;
 978         unsigned long long sum_sched_runtime, sched_expires;
 979         struct list_head *timers = sig->cpu_timers;
 980         struct task_cputime cputime;
 981
 982         /*
 983          * Don't sample the current process CPU clocks if there are no timers.
 984          */
 985         if (list_empty(&timers[CPUCLOCK_PROF]) &&
 986             cputime_eq(sig->it_prof_expires, cputime_zero) &&
 987             sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
 988             list_empty(&timers[CPUCLOCK_VIRT]) &&
 989             cputime_eq(sig->it_virt_expires, cputime_zero) &&
 990             list_empty(&timers[CPUCLOCK_SCHED]))
 991                 return;
 992
 993         /*
 994          * Collect the current process totals.
 995          */
 996         thread_group_cputime(tsk, &cputime);
 997         utime = cputime.utime;
 998         ptime = cputime_add(utime, cputime.stime);
 999         sum_sched_runtime = cputime.sum_exec_runtime;
1000         maxfire = 20;
1001         prof_expires = cputime_zero;
1002         while (!list_empty(timers)) {
1003                 struct cpu_timer_list *tl = list_first_entry(timers,
1004                                                       struct cpu_timer_list,
1005                                                       entry);
1006                 if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
1007                         prof_expires = tl->expires.cpu;
1008                         break;
1009                 }
1010                 tl->firing = 1;
1011                 list_move_tail(&tl->entry, firing);
1012         }
1013
1014         ++timers;
1015         maxfire = 20;
1016         virt_expires = cputime_zero;
1017         while (!list_empty(timers)) {
1018                 struct cpu_timer_list *tl = list_first_entry(timers,
1019                                                       struct cpu_timer_list,
1020                                                       entry);
1021                 if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
1022                         virt_expires = tl->expires.cpu;
1023                         break;
1024                 }
1025                 tl->firing = 1;
1026                 list_move_tail(&tl->entry, firing);
1027         }
1028
1029         ++timers;
1030         maxfire = 20;
1031         sched_expires = 0;
1032         while (!list_empty(timers)) {
1033                 struct cpu_timer_list *tl = list_first_entry(timers,
1034                                                       struct cpu_timer_list,
1035                                                       entry);
1036                 if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
1037                         sched_expires = tl->expires.sched;
1038                         break;
1039                 }
1040                 tl->firing = 1;
1041                 list_move_tail(&tl->entry, firing);
1042         }
1043
1044         /*
1045          * Check for the special case process timers.
1046          */
1047         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1048                 if (cputime_ge(ptime, sig->it_prof_expires)) {
1049                         /* ITIMER_PROF fires and reloads.  */
1050                         sig->it_prof_expires = sig->it_prof_incr;
1051                         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1052                                 sig->it_prof_expires = cputime_add(
1053                                         sig->it_prof_expires, ptime);
1054                         }
1055                         __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
1056                 }
1057                 if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
1058                     (cputime_eq(prof_expires, cputime_zero) ||
1059                      cputime_lt(sig->it_prof_expires, prof_expires))) {
1060                         prof_expires = sig->it_prof_expires;
1061                 }
1062         }
1063         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1064                 if (cputime_ge(utime, sig->it_virt_expires)) {
1065                         /* ITIMER_VIRTUAL fires and reloads.  */
1066                         sig->it_virt_expires = sig->it_virt_incr;
1067                         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1068                                 sig->it_virt_expires = cputime_add(
1069                                         sig->it_virt_expires, utime);
1070                         }
1071                         __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
1072                 }
1073                 if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
1074                     (cputime_eq(virt_expires, cputime_zero) ||
1075                      cputime_lt(sig->it_virt_expires, virt_expires))) {
1076                         virt_expires = sig->it_virt_expires;
1077                 }
1078         }
1079         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
1080                 unsigned long psecs = cputime_to_secs(ptime);
1081                 cputime_t x;
1082                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
1083                         /*
1084                          * At the hard limit, we just die.
1085                          * No need to calculate anything else now.
1086                          */
1087                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1088                         return;
1089                 }
1090                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
1091                         /*
1092                          * At the soft limit, send a SIGXCPU every second.
1093                          */
1094                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1095                         if (sig->rlim[RLIMIT_CPU].rlim_cur
1096                             < sig->rlim[RLIMIT_CPU].rlim_max) {
1097                                 sig->rlim[RLIMIT_CPU].rlim_cur++;
1098                         }
1099                 }
1100                 x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
1101                 if (cputime_eq(prof_expires, cputime_zero) ||
1102                     cputime_lt(x, prof_expires)) {
1103                         prof_expires = x;
1104                 }
1105         }
1106
1107         if (!cputime_eq(prof_expires, cputime_zero) &&
1108             (cputime_eq(sig->cputime_expires.prof_exp, cputime_zero) ||
1109              cputime_gt(sig->cputime_expires.prof_exp, prof_expires)))
1110                 sig->cputime_expires.prof_exp = prof_expires;
1111         if (!cputime_eq(virt_expires, cputime_zero) &&
1112             (cputime_eq(sig->cputime_expires.virt_exp, cputime_zero) ||
1113              cputime_gt(sig->cputime_expires.virt_exp, virt_expires)))
1114                 sig->cputime_expires.virt_exp = virt_expires;
1115         if (sched_expires != 0 &&
1116             (sig->cputime_expires.sched_exp == 0 ||
1117              sig->cputime_expires.sched_exp > sched_expires))
1118                 sig->cputime_expires.sched_exp = sched_expires;
1119 }
1120
1121 /*
1122  * This is called from the signal code (via do_schedule_next_timer)
1123  * when the last timer signal was delivered and we have to reload the timer.
1124  */
1125 void posix_cpu_timer_schedule(struct k_itimer *timer)
1126 {
1127         struct task_struct *p = timer->it.cpu.task;
1128         union cpu_time_count now;
1129
1130         if (unlikely(p == NULL))
1131                 /*
1132                  * The task was cleaned up already, no future firings.
1133                  */
1134                 goto out;
1135
1136         /*
1137          * Fetch the current sample and update the timer's expiry time.
1138          */
1139         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1140                 cpu_clock_sample(timer->it_clock, p, &now);
1141                 bump_cpu_timer(timer, now);
1142                 if (unlikely(p->exit_state)) {
1143                         clear_dead_task(timer, now);
1144                         goto out;
1145                 }
1146                 read_lock(&tasklist_lock); /* arm_timer needs it.  */
1147         } else {
1148                 read_lock(&tasklist_lock);
1149                 if (unlikely(p->signal == NULL)) {
1150                         /*
1151                          * The process has been reaped.
1152                          * We can't even collect a sample any more.
1153                          */
1154                         put_task_struct(p);
1155                         timer->it.cpu.task = p = NULL;
1156                         timer->it.cpu.expires.sched = 0;
1157                         goto out_unlock;
1158                 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1159                         /*
1160                          * We've noticed that the thread is dead, but
1161                          * not yet reaped.  Take this opportunity to
1162                          * drop our task ref.
1163                          */
1164                         clear_dead_task(timer, now);
1165                         goto out_unlock;
1166                 }
1167                 cpu_clock_sample_group(timer->it_clock, p, &now);
1168                 bump_cpu_timer(timer, now);
1169                 /* Leave the tasklist_lock locked for the call below.  */
1170         }
1171
1172         /*
1173          * Now re-arm for the new expiry time.
1174          */
1175         arm_timer(timer, now);
1176
1177 out_unlock:
1178         read_unlock(&tasklist_lock);
1179
1180 out:
1181         timer->it_overrun_last = timer->it_overrun;
1182         timer->it_overrun = -1;
1183         ++timer->it_requeue_pending;
1184 }
1185
1186 /**
1187  * task_cputime_zero - Check a task_cputime struct for all zero fields.
1188  *
1189  * @cputime:    The struct to compare.
1190  *
1191  * Checks @cputime to see if all fields are zero.  Returns true if all fields
1192  * are zero, false if any field is nonzero.
1193  */
1194 static inline int task_cputime_zero(const struct task_cputime *cputime)
1195 {
1196         if (cputime_eq(cputime->utime, cputime_zero) &&
1197             cputime_eq(cputime->stime, cputime_zero) &&
1198             cputime->sum_exec_runtime == 0)
1199                 return 1;
1200         return 0;
1201 }
1202
1203 /**
1204  * task_cputime_expired - Compare two task_cputime entities.
1205  *
1206  * @sample:     The task_cputime structure to be checked for expiration.
1207  * @expires:    Expiration times, against which @sample will be checked.
1208  *
1209  * Checks @sample against @expires to see if any field of @sample has expired.
1210  * Returns true if any field of the former is greater than the corresponding
1211  * field of the latter if the latter field is set.  Otherwise returns false.
1212  */
1213 static inline int task_cputime_expired(const struct task_cputime *sample,
1214                                         const struct task_cputime *expires)
1215 {
1216         if (!cputime_eq(expires->utime, cputime_zero) &&
1217             cputime_ge(sample->utime, expires->utime))
1218                 return 1;
1219         if (!cputime_eq(expires->stime, cputime_zero) &&
1220             cputime_ge(cputime_add(sample->utime, sample->stime),
1221                        expires->stime))
1222                 return 1;
1223         if (expires->sum_exec_runtime != 0 &&
1224             sample->sum_exec_runtime >= expires->sum_exec_runtime)
1225                 return 1;
1226         return 0;
1227 }
1228
1229 /**
1230  * fastpath_timer_check - POSIX CPU timers fast path.
1231  *
1232  * @tsk:        The task (thread) being checked.
1233  *
1234  * Check the task and thread group timers.  If both are zero (there are no
1235  * timers set) return false.  Otherwise snapshot the task and thread group
1236  * timers and compare them with the corresponding expiration times.  Return
1237  * true if a timer has expired, else return false.
1238  */
1239 static inline int fastpath_timer_check(struct task_struct *tsk)
1240 {
1241         struct signal_struct *sig;
1242
1243         /* tsk == current, ensure it is safe to use ->signal/sighand */
1244         if (unlikely(tsk->exit_state))
1245                 return 0;
1246
1247         if (!task_cputime_zero(&tsk->cputime_expires)) {
1248                 struct task_cputime task_sample = {
1249                         .utime = tsk->utime,
1250                         .stime = tsk->stime,
1251                         .sum_exec_runtime = tsk->se.sum_exec_runtime
1252                 };
1253
1254                 if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1255                         return 1;
1256         }
1257
1258         sig = tsk->signal;
1259         if (!task_cputime_zero(&sig->cputime_expires)) {
1260                 struct task_cputime group_sample;
1261
1262                 thread_group_cputime(tsk, &group_sample);
1263                 if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1264                         return 1;
1265         }
1266         return 0;
1267 }
1268
1269 /*
1270  * This is called from the timer interrupt handler.  The irq handler has
1271  * already updated our counts.  We need to check if any timers fire now.
1272  * Interrupts are disabled.
1273  */
1274 void run_posix_cpu_timers(struct task_struct *tsk)
1275 {
1276         LIST_HEAD(firing);
1277         struct k_itimer *timer, *next;
1278
1279         BUG_ON(!irqs_disabled());
1280
1281         /*
1282          * The fast path checks that there are no expired thread or thread
1283          * group timers.  If that's so, just return.
1284          */
1285         if (!fastpath_timer_check(tsk))
1286                 return;
1287
1288         spin_lock(&tsk->sighand->siglock);
1289         /*
1290          * Here we take off tsk->signal->cpu_timers[N] and
1291          * tsk->cpu_timers[N] all the timers that are firing, and
1292          * put them on the firing list.
1293          */
1294         check_thread_timers(tsk, &firing);
1295         check_process_timers(tsk, &firing);
1296
1297         /*
1298          * We must release these locks before taking any timer's lock.
1299          * There is a potential race with timer deletion here, as the
1300          * siglock now protects our private firing list.  We have set
1301          * the firing flag in each timer, so that a deletion attempt
1302          * that gets the timer lock before we do will give it up and
1303          * spin until we've taken care of that timer below.
1304          */
1305         spin_unlock(&tsk->sighand->siglock);
1306
1307         /*
1308          * Now that all the timers on our list have the firing flag,
1309          * noone will touch their list entries but us.  We'll take
1310          * each timer's lock before clearing its firing flag, so no
1311          * timer call will interfere.
1312          */
1313         list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1314                 int firing;
1315                 spin_lock(&timer->it_lock);
1316                 list_del_init(&timer->it.cpu.entry);
1317                 firing = timer->it.cpu.firing;
1318                 timer->it.cpu.firing = 0;
1319                 /*
1320                  * The firing flag is -1 if we collided with a reset
1321                  * of the timer, which already reported this
1322                  * almost-firing as an overrun.  So don't generate an event.
1323                  */
1324                 if (likely(firing >= 0)) {
1325                         cpu_timer_fire(timer);
1326                 }
1327                 spin_unlock(&timer->it_lock);
1328         }
1329 }
1330
1331 /*
1332  * Set one of the process-wide special case CPU timers.
1333  * The tsk->sighand->siglock must be held by the caller.
1334  * The *newval argument is relative and we update it to be absolute, *oldval
1335  * is absolute and we update it to be relative.
1336  */
1337 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1338                            cputime_t *newval, cputime_t *oldval)
1339 {
1340         union cpu_time_count now;
1341         struct list_head *head;
1342
1343         BUG_ON(clock_idx == CPUCLOCK_SCHED);
1344         cpu_clock_sample_group(clock_idx, tsk, &now);
1345
1346         if (oldval) {
1347                 if (!cputime_eq(*oldval, cputime_zero)) {
1348                         if (cputime_le(*oldval, now.cpu)) {
1349                                 /* Just about to fire. */
1350                                 *oldval = jiffies_to_cputime(1);
1351                         } else {
1352                                 *oldval = cputime_sub(*oldval, now.cpu);
1353                         }
1354                 }
1355
1356                 if (cputime_eq(*newval, cputime_zero))
1357                         return;
1358                 *newval = cputime_add(*newval, now.cpu);
1359
1360                 /*
1361                  * If the RLIMIT_CPU timer will expire before the
1362                  * ITIMER_PROF timer, we have nothing else to do.
1363                  */
1364                 if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
1365                     < cputime_to_secs(*newval))
1366                         return;
1367         }
1368
1369         /*
1370          * Check whether there are any process timers already set to fire
1371          * before this one.  If so, we don't have anything more to do.
1372          */
1373         head = &tsk->signal->cpu_timers[clock_idx];
1374         if (list_empty(head) ||
1375             cputime_ge(list_first_entry(head,
1376                                   struct cpu_timer_list, entry)->expires.cpu,
1377                        *newval)) {
1378                 switch (clock_idx) {
1379                 case CPUCLOCK_PROF:
1380                         tsk->signal->cputime_expires.prof_exp = *newval;
1381                         break;
1382                 case CPUCLOCK_VIRT:
1383                         tsk->signal->cputime_expires.virt_exp = *newval;
1384                         break;
1385                 }
1386         }
1387 }
1388
1389 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1390                             struct timespec *rqtp, struct itimerspec *it)
1391 {
1392         struct k_itimer timer;
1393         int error;
1394
1395         /*
1396          * Set up a temporary timer and then wait for it to go off.
1397          */
1398         memset(&timer, 0, sizeof timer);
1399         spin_lock_init(&timer.it_lock);
1400         timer.it_clock = which_clock;
1401         timer.it_overrun = -1;
1402         error = posix_cpu_timer_create(&timer);
1403         timer.it_process = current;
1404         if (!error) {
1405                 static struct itimerspec zero_it;
1406
1407                 memset(it, 0, sizeof *it);
1408                 it->it_value = *rqtp;
1409
1410                 spin_lock_irq(&timer.it_lock);
1411                 error = posix_cpu_timer_set(&timer, flags, it, NULL);
1412                 if (error) {
1413                         spin_unlock_irq(&timer.it_lock);
1414                         return error;
1415                 }
1416
1417                 while (!signal_pending(current)) {
1418                         if (timer.it.cpu.expires.sched == 0) {
1419                                 /*
1420                                  * Our timer fired and was reset.
1421                                  */
1422                                 spin_unlock_irq(&timer.it_lock);
1423                                 return 0;
1424                         }
1425
1426                         /*
1427                          * Block until cpu_timer_fire (or a signal) wakes us.
1428                          */
1429                         __set_current_state(TASK_INTERRUPTIBLE);
1430                         spin_unlock_irq(&timer.it_lock);
1431                         schedule();
1432                         spin_lock_irq(&timer.it_lock);
1433                 }
1434
1435                 /*
1436                  * We were interrupted by a signal.
1437                  */
1438                 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1439                 posix_cpu_timer_set(&timer, 0, &zero_it, it);
1440                 spin_unlock_irq(&timer.it_lock);
1441
1442                 if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1443                         /*
1444                          * It actually did fire already.
1445                          */
1446                         return 0;
1447                 }
1448
1449                 error = -ERESTART_RESTARTBLOCK;
1450         }
1451
1452         return error;
1453 }
1454
1455 int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1456                      struct timespec *rqtp, struct timespec __user *rmtp)
1457 {
1458         struct restart_block *restart_block =
1459             &current_thread_info()->restart_block;
1460         struct itimerspec it;
1461         int error;
1462
1463         /*
1464          * Diagnose required errors first.
1465          */
1466         if (CPUCLOCK_PERTHREAD(which_clock) &&
1467             (CPUCLOCK_PID(which_clock) == 0 ||
1468              CPUCLOCK_PID(which_clock) == current->pid))
1469                 return -EINVAL;
1470
1471         error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1472
1473         if (error == -ERESTART_RESTARTBLOCK) {
1474
1475                 if (flags & TIMER_ABSTIME)
1476                         return -ERESTARTNOHAND;
1477                 /*
1478                  * Report back to the user the time still remaining.
1479                  */
1480                 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1481                         return -EFAULT;
1482
1483                 restart_block->fn = posix_cpu_nsleep_restart;
1484                 restart_block->arg0 = which_clock;
1485                 restart_block->arg1 = (unsigned long) rmtp;
1486                 restart_block->arg2 = rqtp->tv_sec;
1487                 restart_block->arg3 = rqtp->tv_nsec;
1488         }
1489         return error;
1490 }
1491
1492 long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1493 {
1494         clockid_t which_clock = restart_block->arg0;
1495         struct timespec __user *rmtp;
1496         struct timespec t;
1497         struct itimerspec it;
1498         int error;
1499
1500         rmtp = (struct timespec __user *) restart_block->arg1;
1501         t.tv_sec = restart_block->arg2;
1502         t.tv_nsec = restart_block->arg3;
1503
1504         restart_block->fn = do_no_restart_syscall;
1505         error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1506
1507         if (error == -ERESTART_RESTARTBLOCK) {
1508                 /*
1509                  * Report back to the user the time still remaining.
1510                  */
1511                 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1512                         return -EFAULT;
1513
1514                 restart_block->fn = posix_cpu_nsleep_restart;
1515                 restart_block->arg0 = which_clock;
1516                 restart_block->arg1 = (unsigned long) rmtp;
1517                 restart_block->arg2 = t.tv_sec;
1518                 restart_block->arg3 = t.tv_nsec;
1519         }
1520         return error;
1521
1522 }
1523
1524
1525 #define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1526 #define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1527
1528 static int process_cpu_clock_getres(const clockid_t which_clock,
1529                                     struct timespec *tp)
1530 {
1531         return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1532 }
1533 static int process_cpu_clock_get(const clockid_t which_clock,
1534                                  struct timespec *tp)
1535 {
1536         return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1537 }
1538 static int process_cpu_timer_create(struct k_itimer *timer)
1539 {
1540         timer->it_clock = PROCESS_CLOCK;
1541         return posix_cpu_timer_create(timer);
1542 }
1543 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1544                               struct timespec *rqtp,
1545                               struct timespec __user *rmtp)
1546 {
1547         return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1548 }
1549 static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1550 {
1551         return -EINVAL;
1552 }
1553 static int thread_cpu_clock_getres(const clockid_t which_clock,
1554                                    struct timespec *tp)
1555 {
1556         return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1557 }
1558 static int thread_cpu_clock_get(const clockid_t which_clock,
1559                                 struct timespec *tp)
1560 {
1561         return posix_cpu_clock_get(THREAD_CLOCK, tp);
1562 }
1563 static int thread_cpu_timer_create(struct k_itimer *timer)
1564 {
1565         timer->it_clock = THREAD_CLOCK;
1566         return posix_cpu_timer_create(timer);
1567 }
1568 static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
1569                               struct timespec *rqtp, struct timespec __user *rmtp)
1570 {
1571         return -EINVAL;
1572 }
1573 static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
1574 {
1575         return -EINVAL;
1576 }
1577
1578 static __init int init_posix_cpu_timers(void)
1579 {
1580         struct k_clock process = {
1581                 .clock_getres = process_cpu_clock_getres,
1582                 .clock_get = process_cpu_clock_get,
1583                 .clock_set = do_posix_clock_nosettime,
1584                 .timer_create = process_cpu_timer_create,
1585                 .nsleep = process_cpu_nsleep,
1586                 .nsleep_restart = process_cpu_nsleep_restart,
1587         };
1588         struct k_clock thread = {
1589                 .clock_getres = thread_cpu_clock_getres,
1590                 .clock_get = thread_cpu_clock_get,
1591                 .clock_set = do_posix_clock_nosettime,
1592                 .timer_create = thread_cpu_timer_create,
1593                 .nsleep = thread_cpu_nsleep,
1594                 .nsleep_restart = thread_cpu_nsleep_restart,
1595         };
1596
1597         register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1598         register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1599
1600         return 0;
1601 }
1602 __initcall(init_posix_cpu_timers);