git.oblomov.eu Git - 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 <asm/uaccess.h>
   8 #include <linux/errno.h>
   9
  10 static int check_clock(clockid_t which_clock)
  11 {
  12         int error = 0;
  13         struct task_struct *p;
  14         const pid_t pid = CPUCLOCK_PID(which_clock);
  15
  16         if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
  17                 return -EINVAL;
  18
  19         if (pid == 0)
  20                 return 0;
  21
  22         read_lock(&tasklist_lock);
  23         p = find_task_by_pid(pid);
  24         if (!p || (CPUCLOCK_PERTHREAD(which_clock) ?
  25                    p->tgid != current->tgid : p->tgid != pid)) {
  26                 error = -EINVAL;
  27         }
  28         read_unlock(&tasklist_lock);
  29
  30         return error;
  31 }
  32
  33 static inline union cpu_time_count
  34 timespec_to_sample(clockid_t which_clock, const struct timespec *tp)
  35 {
  36         union cpu_time_count ret;
  37         ret.sched = 0;          /* high half always zero when .cpu used */
  38         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  39                 ret.sched = tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
  40         } else {
  41                 ret.cpu = timespec_to_cputime(tp);
  42         }
  43         return ret;
  44 }
  45
  46 static void sample_to_timespec(clockid_t which_clock,
  47                                union cpu_time_count cpu,
  48                                struct timespec *tp)
  49 {
  50         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  51                 tp->tv_sec = div_long_long_rem(cpu.sched,
  52                                                NSEC_PER_SEC, &tp->tv_nsec);
  53         } else {
  54                 cputime_to_timespec(cpu.cpu, tp);
  55         }
  56 }
  57
  58 static inline int cpu_time_before(clockid_t which_clock,
  59                                   union cpu_time_count now,
  60                                   union cpu_time_count then)
  61 {
  62         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  63                 return now.sched < then.sched;
  64         }  else {
  65                 return cputime_lt(now.cpu, then.cpu);
  66         }
  67 }
  68 static inline void cpu_time_add(clockid_t which_clock,
  69                                 union cpu_time_count *acc,
  70                                 union cpu_time_count val)
  71 {
  72         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  73                 acc->sched += val.sched;
  74         }  else {
  75                 acc->cpu = cputime_add(acc->cpu, val.cpu);
  76         }
  77 }
  78 static inline union cpu_time_count cpu_time_sub(clockid_t which_clock,
  79                                                 union cpu_time_count a,
  80                                                 union cpu_time_count b)
  81 {
  82         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  83                 a.sched -= b.sched;
  84         }  else {
  85                 a.cpu = cputime_sub(a.cpu, b.cpu);
  86         }
  87         return a;
  88 }
  89
  90 /*
  91  * Update expiry time from increment, and increase overrun count,
  92  * given the current clock sample.
  93  */
  94 static inline void bump_cpu_timer(struct k_itimer *timer,
  95                                   union cpu_time_count now)
  96 {
  97         int i;
  98
  99         if (timer->it.cpu.incr.sched == 0)
 100                 return;
 101
 102         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 103                 unsigned long long delta, incr;
 104
 105                 if (now.sched < timer->it.cpu.expires.sched)
 106                         return;
 107                 incr = timer->it.cpu.incr.sched;
 108                 delta = now.sched + incr - timer->it.cpu.expires.sched;
 109                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 110                 for (i = 0; incr < delta - incr; i++)
 111                         incr = incr << 1;
 112                 for (; i >= 0; incr >>= 1, i--) {
 113                         if (delta <= incr)
 114                                 continue;
 115                         timer->it.cpu.expires.sched += incr;
 116                         timer->it_overrun += 1 << i;
 117                         delta -= incr;
 118                 }
 119         } else {
 120                 cputime_t delta, incr;
 121
 122                 if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
 123                         return;
 124                 incr = timer->it.cpu.incr.cpu;
 125                 delta = cputime_sub(cputime_add(now.cpu, incr),
 126                                     timer->it.cpu.expires.cpu);
 127                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 128                 for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
 129                              incr = cputime_add(incr, incr);
 130                 for (; i >= 0; incr = cputime_halve(incr), i--) {
 131                         if (cputime_le(delta, incr))
 132                                 continue;
 133                         timer->it.cpu.expires.cpu =
 134                                 cputime_add(timer->it.cpu.expires.cpu, incr);
 135                         timer->it_overrun += 1 << i;
 136                         delta = cputime_sub(delta, incr);
 137                 }
 138         }
 139 }
 140
 141 static inline cputime_t prof_ticks(struct task_struct *p)
 142 {
 143         return cputime_add(p->utime, p->stime);
 144 }
 145 static inline cputime_t virt_ticks(struct task_struct *p)
 146 {
 147         return p->utime;
 148 }
 149 static inline unsigned long long sched_ns(struct task_struct *p)
 150 {
 151         return (p == current) ? current_sched_time(p) : p->sched_time;
 152 }
 153
 154 int posix_cpu_clock_getres(clockid_t which_clock, struct timespec *tp)
 155 {
 156         int error = check_clock(which_clock);
 157         if (!error) {
 158                 tp->tv_sec = 0;
 159                 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
 160                 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 161                         /*
 162                          * If sched_clock is using a cycle counter, we
 163                          * don't have any idea of its true resolution
 164                          * exported, but it is much more than 1s/HZ.
 165                          */
 166                         tp->tv_nsec = 1;
 167                 }
 168         }
 169         return error;
 170 }
 171
 172 int posix_cpu_clock_set(clockid_t which_clock, const struct timespec *tp)
 173 {
 174         /*
 175          * You can never reset a CPU clock, but we check for other errors
 176          * in the call before failing with EPERM.
 177          */
 178         int error = check_clock(which_clock);
 179         if (error == 0) {
 180                 error = -EPERM;
 181         }
 182         return error;
 183 }
 184
 185
 186 /*
 187  * Sample a per-thread clock for the given task.
 188  */
 189 static int cpu_clock_sample(clockid_t which_clock, struct task_struct *p,
 190                             union cpu_time_count *cpu)
 191 {
 192         switch (CPUCLOCK_WHICH(which_clock)) {
 193         default:
 194                 return -EINVAL;
 195         case CPUCLOCK_PROF:
 196                 cpu->cpu = prof_ticks(p);
 197                 break;
 198         case CPUCLOCK_VIRT:
 199                 cpu->cpu = virt_ticks(p);
 200                 break;
 201         case CPUCLOCK_SCHED:
 202                 cpu->sched = sched_ns(p);
 203                 break;
 204         }
 205         return 0;
 206 }
 207
 208 /*
 209  * Sample a process (thread group) clock for the given group_leader task.
 210  * Must be called with tasklist_lock held for reading.
 211  * Must be called with tasklist_lock held for reading, and p->sighand->siglock.
 212  */
 213 static int cpu_clock_sample_group_locked(unsigned int clock_idx,
 214                                          struct task_struct *p,
 215                                          union cpu_time_count *cpu)
 216 {
 217         struct task_struct *t = p;
 218         switch (clock_idx) {
 219         default:
 220                 return -EINVAL;
 221         case CPUCLOCK_PROF:
 222                 cpu->cpu = cputime_add(p->signal->utime, p->signal->stime);
 223                 do {
 224                         cpu->cpu = cputime_add(cpu->cpu, prof_ticks(t));
 225                         t = next_thread(t);
 226                 } while (t != p);
 227                 break;
 228         case CPUCLOCK_VIRT:
 229                 cpu->cpu = p->signal->utime;
 230                 do {
 231                         cpu->cpu = cputime_add(cpu->cpu, virt_ticks(t));
 232                         t = next_thread(t);
 233                 } while (t != p);
 234                 break;
 235         case CPUCLOCK_SCHED:
 236                 cpu->sched = p->signal->sched_time;
 237                 /* Add in each other live thread.  */
 238                 while ((t = next_thread(t)) != p) {
 239                         cpu->sched += t->sched_time;
 240                 }
 241                 if (p->tgid == current->tgid) {
 242                         /*
 243                          * We're sampling ourselves, so include the
 244                          * cycles not yet banked.  We still omit
 245                          * other threads running on other CPUs,
 246                          * so the total can always be behind as
 247                          * much as max(nthreads-1,ncpus) * (NSEC_PER_SEC/HZ).
 248                          */
 249                         cpu->sched += current_sched_time(current);
 250                 } else {
 251                         cpu->sched += p->sched_time;
 252                 }
 253                 break;
 254         }
 255         return 0;
 256 }
 257
 258 /*
 259  * Sample a process (thread group) clock for the given group_leader task.
 260  * Must be called with tasklist_lock held for reading.
 261  */
 262 static int cpu_clock_sample_group(clockid_t which_clock,
 263                                   struct task_struct *p,
 264                                   union cpu_time_count *cpu)
 265 {
 266         int ret;
 267         unsigned long flags;
 268         spin_lock_irqsave(&p->sighand->siglock, flags);
 269         ret = cpu_clock_sample_group_locked(CPUCLOCK_WHICH(which_clock), p,
 270                                             cpu);
 271         spin_unlock_irqrestore(&p->sighand->siglock, flags);
 272         return ret;
 273 }
 274
 275
 276 int posix_cpu_clock_get(clockid_t which_clock, struct timespec *tp)
 277 {
 278         const pid_t pid = CPUCLOCK_PID(which_clock);
 279         int error = -EINVAL;
 280         union cpu_time_count rtn;
 281
 282         if (pid == 0) {
 283                 /*
 284                  * Special case constant value for our own clocks.
 285                  * We don't have to do any lookup to find ourselves.
 286                  */
 287                 if (CPUCLOCK_PERTHREAD(which_clock)) {
 288                         /*
 289                          * Sampling just ourselves we can do with no locking.
 290                          */
 291                         error = cpu_clock_sample(which_clock,
 292                                                  current, &rtn);
 293                 } else {
 294                         read_lock(&tasklist_lock);
 295                         error = cpu_clock_sample_group(which_clock,
 296                                                        current, &rtn);
 297                         read_unlock(&tasklist_lock);
 298                 }
 299         } else {
 300                 /*
 301                  * Find the given PID, and validate that the caller
 302                  * should be able to see it.
 303                  */
 304                 struct task_struct *p;
 305                 read_lock(&tasklist_lock);
 306                 p = find_task_by_pid(pid);
 307                 if (p) {
 308                         if (CPUCLOCK_PERTHREAD(which_clock)) {
 309                                 if (p->tgid == current->tgid) {
 310                                         error = cpu_clock_sample(which_clock,
 311                                                                  p, &rtn);
 312                                 }
 313                         } else if (p->tgid == pid && p->signal) {
 314                                 error = cpu_clock_sample_group(which_clock,
 315                                                                p, &rtn);
 316                         }
 317                 }
 318                 read_unlock(&tasklist_lock);
 319         }
 320
 321         if (error)
 322                 return error;
 323         sample_to_timespec(which_clock, rtn, tp);
 324         return 0;
 325 }
 326
 327
 328 /*
 329  * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 330  * This is called from sys_timer_create with the new timer already locked.
 331  */
 332 int posix_cpu_timer_create(struct k_itimer *new_timer)
 333 {
 334         int ret = 0;
 335         const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
 336         struct task_struct *p;
 337
 338         if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 339                 return -EINVAL;
 340
 341         INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 342         new_timer->it.cpu.incr.sched = 0;
 343         new_timer->it.cpu.expires.sched = 0;
 344
 345         read_lock(&tasklist_lock);
 346         if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
 347                 if (pid == 0) {
 348                         p = current;
 349                 } else {
 350                         p = find_task_by_pid(pid);
 351                         if (p && p->tgid != current->tgid)
 352                                 p = NULL;
 353                 }
 354         } else {
 355                 if (pid == 0) {
 356                         p = current->group_leader;
 357                 } else {
 358                         p = find_task_by_pid(pid);
 359                         if (p && p->tgid != pid)
 360                                 p = NULL;
 361                 }
 362         }
 363         new_timer->it.cpu.task = p;
 364         if (p) {
 365                 get_task_struct(p);
 366         } else {
 367                 ret = -EINVAL;
 368         }
 369         read_unlock(&tasklist_lock);
 370
 371         return ret;
 372 }
 373
 374 /*
 375  * Clean up a CPU-clock timer that is about to be destroyed.
 376  * This is called from timer deletion with the timer already locked.
 377  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 378  * and try again.  (This happens when the timer is in the middle of firing.)
 379  */
 380 int posix_cpu_timer_del(struct k_itimer *timer)
 381 {
 382         struct task_struct *p = timer->it.cpu.task;
 383
 384         if (timer->it.cpu.firing)
 385                 return TIMER_RETRY;
 386
 387         if (unlikely(p == NULL))
 388                 return 0;
 389
 390         if (!list_empty(&timer->it.cpu.entry)) {
 391                 read_lock(&tasklist_lock);
 392                 if (unlikely(p->signal == NULL)) {
 393                         /*
 394                          * We raced with the reaping of the task.
 395                          * The deletion should have cleared us off the list.
 396                          */
 397                         BUG_ON(!list_empty(&timer->it.cpu.entry));
 398                 } else {
 399                         /*
 400                          * Take us off the task's timer list.
 401                          */
 402                         spin_lock(&p->sighand->siglock);
 403                         list_del(&timer->it.cpu.entry);
 404                         spin_unlock(&p->sighand->siglock);
 405                 }
 406                 read_unlock(&tasklist_lock);
 407         }
 408         put_task_struct(p);
 409
 410         return 0;
 411 }
 412
 413 /*
 414  * Clean out CPU timers still ticking when a thread exited.  The task
 415  * pointer is cleared, and the expiry time is replaced with the residual
 416  * time for later timer_gettime calls to return.
 417  * This must be called with the siglock held.
 418  */
 419 static void cleanup_timers(struct list_head *head,
 420                            cputime_t utime, cputime_t stime,
 421                            unsigned long long sched_time)
 422 {
 423         struct cpu_timer_list *timer, *next;
 424         cputime_t ptime = cputime_add(utime, stime);
 425
 426         list_for_each_entry_safe(timer, next, head, entry) {
 427                 put_task_struct(timer->task);
 428                 timer->task = NULL;
 429                 list_del_init(&timer->entry);
 430                 if (cputime_lt(timer->expires.cpu, ptime)) {
 431                         timer->expires.cpu = cputime_zero;
 432                 } else {
 433                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
 434                                                          ptime);
 435                 }
 436         }
 437
 438         ++head;
 439         list_for_each_entry_safe(timer, next, head, entry) {
 440                 put_task_struct(timer->task);
 441                 timer->task = NULL;
 442                 list_del_init(&timer->entry);
 443                 if (cputime_lt(timer->expires.cpu, utime)) {
 444                         timer->expires.cpu = cputime_zero;
 445                 } else {
 446                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
 447                                                          utime);
 448                 }
 449         }
 450
 451         ++head;
 452         list_for_each_entry_safe(timer, next, head, entry) {
 453                 put_task_struct(timer->task);
 454                 timer->task = NULL;
 455                 list_del_init(&timer->entry);
 456                 if (timer->expires.sched < sched_time) {
 457                         timer->expires.sched = 0;
 458                 } else {
 459                         timer->expires.sched -= sched_time;
 460                 }
 461         }
 462 }
 463
 464 /*
 465  * These are both called with the siglock held, when the current thread
 466  * is being reaped.  When the final (leader) thread in the group is reaped,
 467  * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 468  */
 469 void posix_cpu_timers_exit(struct task_struct *tsk)
 470 {
 471         cleanup_timers(tsk->cpu_timers,
 472                        tsk->utime, tsk->stime, tsk->sched_time);
 473
 474 }
 475 void posix_cpu_timers_exit_group(struct task_struct *tsk)
 476 {
 477         cleanup_timers(tsk->signal->cpu_timers,
 478                        cputime_add(tsk->utime, tsk->signal->utime),
 479                        cputime_add(tsk->stime, tsk->signal->stime),
 480                        tsk->sched_time + tsk->signal->sched_time);
 481 }
 482
 483
 484 /*
 485  * Set the expiry times of all the threads in the process so one of them
 486  * will go off before the process cumulative expiry total is reached.
 487  */
 488 static void process_timer_rebalance(struct task_struct *p,
 489                                     unsigned int clock_idx,
 490                                     union cpu_time_count expires,
 491                                     union cpu_time_count val)
 492 {
 493         cputime_t ticks, left;
 494         unsigned long long ns, nsleft;
 495         struct task_struct *t = p;
 496         unsigned int nthreads = atomic_read(&p->signal->live);
 497
 498         switch (clock_idx) {
 499         default:
 500                 BUG();
 501                 break;
 502         case CPUCLOCK_PROF:
 503                 left = cputime_div(cputime_sub(expires.cpu, val.cpu),
 504                                    nthreads);
 505                 do {
 506                         if (!unlikely(t->exit_state)) {
 507                                 ticks = cputime_add(prof_ticks(t), left);
 508                                 if (cputime_eq(t->it_prof_expires,
 509                                                cputime_zero) ||
 510                                     cputime_gt(t->it_prof_expires, ticks)) {
 511                                         t->it_prof_expires = ticks;
 512                                 }
 513                         }
 514                         t = next_thread(t);
 515                 } while (t != p);
 516                 break;
 517         case CPUCLOCK_VIRT:
 518                 left = cputime_div(cputime_sub(expires.cpu, val.cpu),
 519                                    nthreads);
 520                 do {
 521                         if (!unlikely(t->exit_state)) {
 522                                 ticks = cputime_add(virt_ticks(t), left);
 523                                 if (cputime_eq(t->it_virt_expires,
 524                                                cputime_zero) ||
 525                                     cputime_gt(t->it_virt_expires, ticks)) {
 526                                         t->it_virt_expires = ticks;
 527                                 }
 528                         }
 529                         t = next_thread(t);
 530                 } while (t != p);
 531                 break;
 532         case CPUCLOCK_SCHED:
 533                 nsleft = expires.sched - val.sched;
 534                 do_div(nsleft, nthreads);
 535                 do {
 536                         if (!unlikely(t->exit_state)) {
 537                                 ns = t->sched_time + nsleft;
 538                                 if (t->it_sched_expires == 0 ||
 539                                     t->it_sched_expires > ns) {
 540                                         t->it_sched_expires = ns;
 541                                 }
 542                         }
 543                         t = next_thread(t);
 544                 } while (t != p);
 545                 break;
 546         }
 547 }
 548
 549 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 550 {
 551         /*
 552          * That's all for this thread or process.
 553          * We leave our residual in expires to be reported.
 554          */
 555         put_task_struct(timer->it.cpu.task);
 556         timer->it.cpu.task = NULL;
 557         timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
 558                                              timer->it.cpu.expires,
 559                                              now);
 560 }
 561
 562 /*
 563  * Insert the timer on the appropriate list before any timers that
 564  * expire later.  This must be called with the tasklist_lock held
 565  * for reading, and interrupts disabled.
 566  */
 567 static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 568 {
 569         struct task_struct *p = timer->it.cpu.task;
 570         struct list_head *head, *listpos;
 571         struct cpu_timer_list *const nt = &timer->it.cpu;
 572         struct cpu_timer_list *next;
 573         unsigned long i;
 574
 575         head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
 576                 p->cpu_timers : p->signal->cpu_timers);
 577         head += CPUCLOCK_WHICH(timer->it_clock);
 578
 579         BUG_ON(!irqs_disabled());
 580         spin_lock(&p->sighand->siglock);
 581
 582         listpos = head;
 583         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 584                 list_for_each_entry(next, head, entry) {
 585                         if (next->expires.sched > nt->expires.sched) {
 586                                 listpos = &next->entry;
 587                                 break;
 588                         }
 589                 }
 590         } else {
 591                 list_for_each_entry(next, head, entry) {
 592                         if (cputime_gt(next->expires.cpu, nt->expires.cpu)) {
 593                                 listpos = &next->entry;
 594                                 break;
 595                         }
 596                 }
 597         }
 598         list_add(&nt->entry, listpos);
 599
 600         if (listpos == head) {
 601                 /*
 602                  * We are the new earliest-expiring timer.
 603                  * If we are a thread timer, there can always
 604                  * be a process timer telling us to stop earlier.
 605                  */
 606
 607                 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 608                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
 609                         default:
 610                                 BUG();
 611                         case CPUCLOCK_PROF:
 612                                 if (cputime_eq(p->it_prof_expires,
 613                                                cputime_zero) ||
 614                                     cputime_gt(p->it_prof_expires,
 615                                                nt->expires.cpu))
 616                                         p->it_prof_expires = nt->expires.cpu;
 617                                 break;
 618                         case CPUCLOCK_VIRT:
 619                                 if (cputime_eq(p->it_virt_expires,
 620                                                cputime_zero) ||
 621                                     cputime_gt(p->it_virt_expires,
 622                                                nt->expires.cpu))
 623                                         p->it_virt_expires = nt->expires.cpu;
 624                                 break;
 625                         case CPUCLOCK_SCHED:
 626                                 if (p->it_sched_expires == 0 ||
 627                                     p->it_sched_expires > nt->expires.sched)
 628                                         p->it_sched_expires = nt->expires.sched;
 629                                 break;
 630                         }
 631                 } else {
 632                         /*
 633                          * For a process timer, we must balance
 634                          * all the live threads' expirations.
 635                          */
 636                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
 637                         default:
 638                                 BUG();
 639                         case CPUCLOCK_VIRT:
 640                                 if (!cputime_eq(p->signal->it_virt_expires,
 641                                                 cputime_zero) &&
 642                                     cputime_lt(p->signal->it_virt_expires,
 643                                                timer->it.cpu.expires.cpu))
 644                                         break;
 645                                 goto rebalance;
 646                         case CPUCLOCK_PROF:
 647                                 if (!cputime_eq(p->signal->it_prof_expires,
 648                                                 cputime_zero) &&
 649                                     cputime_lt(p->signal->it_prof_expires,
 650                                                timer->it.cpu.expires.cpu))
 651                                         break;
 652                                 i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
 653                                 if (i != RLIM_INFINITY &&
 654                                     i <= cputime_to_secs(timer->it.cpu.expires.cpu))
 655                                         break;
 656                                 goto rebalance;
 657                         case CPUCLOCK_SCHED:
 658                         rebalance:
 659                                 process_timer_rebalance(
 660                                         timer->it.cpu.task,
 661                                         CPUCLOCK_WHICH(timer->it_clock),
 662                                         timer->it.cpu.expires, now);
 663                                 break;
 664                         }
 665                 }
 666         }
 667
 668         spin_unlock(&p->sighand->siglock);
 669 }
 670
 671 /*
 672  * The timer is locked, fire it and arrange for its reload.
 673  */
 674 static void cpu_timer_fire(struct k_itimer *timer)
 675 {
 676         if (unlikely(timer->sigq == NULL)) {
 677                 /*
 678                  * This a special case for clock_nanosleep,
 679                  * not a normal timer from sys_timer_create.
 680                  */
 681                 wake_up_process(timer->it_process);
 682                 timer->it.cpu.expires.sched = 0;
 683         } else if (timer->it.cpu.incr.sched == 0) {
 684                 /*
 685                  * One-shot timer.  Clear it as soon as it's fired.
 686                  */
 687                 posix_timer_event(timer, 0);
 688                 timer->it.cpu.expires.sched = 0;
 689         } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 690                 /*
 691                  * The signal did not get queued because the signal
 692                  * was ignored, so we won't get any callback to
 693                  * reload the timer.  But we need to keep it
 694                  * ticking in case the signal is deliverable next time.
 695                  */
 696                 posix_cpu_timer_schedule(timer);
 697         }
 698 }
 699
 700 /*
 701  * Guts of sys_timer_settime for CPU timers.
 702  * This is called with the timer locked and interrupts disabled.
 703  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 704  * and try again.  (This happens when the timer is in the middle of firing.)
 705  */
 706 int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 707                         struct itimerspec *new, struct itimerspec *old)
 708 {
 709         struct task_struct *p = timer->it.cpu.task;
 710         union cpu_time_count old_expires, new_expires, val;
 711         int ret;
 712
 713         if (unlikely(p == NULL)) {
 714                 /*
 715                  * Timer refers to a dead task's clock.
 716                  */
 717                 return -ESRCH;
 718         }
 719
 720         new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
 721
 722         read_lock(&tasklist_lock);
 723         /*
 724          * We need the tasklist_lock to protect against reaping that
 725          * clears p->signal.  If p has just been reaped, we can no
 726          * longer get any information about it at all.
 727          */
 728         if (unlikely(p->signal == NULL)) {
 729                 read_unlock(&tasklist_lock);
 730                 put_task_struct(p);
 731                 timer->it.cpu.task = NULL;
 732                 return -ESRCH;
 733         }
 734
 735         /*
 736          * Disarm any old timer after extracting its expiry time.
 737          */
 738         BUG_ON(!irqs_disabled());
 739         spin_lock(&p->sighand->siglock);
 740         old_expires = timer->it.cpu.expires;
 741         list_del_init(&timer->it.cpu.entry);
 742         spin_unlock(&p->sighand->siglock);
 743
 744         /*
 745          * We need to sample the current value to convert the new
 746          * value from to relative and absolute, and to convert the
 747          * old value from absolute to relative.  To set a process
 748          * timer, we need a sample to balance the thread expiry
 749          * times (in arm_timer).  With an absolute time, we must
 750          * check if it's already passed.  In short, we need a sample.
 751          */
 752         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 753                 cpu_clock_sample(timer->it_clock, p, &val);
 754         } else {
 755                 cpu_clock_sample_group(timer->it_clock, p, &val);
 756         }
 757
 758         if (old) {
 759                 if (old_expires.sched == 0) {
 760                         old->it_value.tv_sec = 0;
 761                         old->it_value.tv_nsec = 0;
 762                 } else {
 763                         /*
 764                          * Update the timer in case it has
 765                          * overrun already.  If it has,
 766                          * we'll report it as having overrun
 767                          * and with the next reloaded timer
 768                          * already ticking, though we are
 769                          * swallowing that pending
 770                          * notification here to install the
 771                          * new setting.
 772                          */
 773                         bump_cpu_timer(timer, val);
 774                         if (cpu_time_before(timer->it_clock, val,
 775                                             timer->it.cpu.expires)) {
 776                                 old_expires = cpu_time_sub(
 777                                         timer->it_clock,
 778                                         timer->it.cpu.expires, val);
 779                                 sample_to_timespec(timer->it_clock,
 780                                                    old_expires,
 781                                                    &old->it_value);
 782                         } else {
 783                                 old->it_value.tv_nsec = 1;
 784                                 old->it_value.tv_sec = 0;
 785                         }
 786                 }
 787         }
 788
 789         if (unlikely(timer->it.cpu.firing)) {
 790                 /*
 791                  * We are colliding with the timer actually firing.
 792                  * Punt after filling in the timer's old value, and
 793                  * disable this firing since we are already reporting
 794                  * it as an overrun (thanks to bump_cpu_timer above).
 795                  */
 796                 read_unlock(&tasklist_lock);
 797                 timer->it.cpu.firing = -1;
 798                 ret = TIMER_RETRY;
 799                 goto out;
 800         }
 801
 802         if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
 803                 cpu_time_add(timer->it_clock, &new_expires, val);
 804         }
 805
 806         /*
 807          * Install the new expiry time (or zero).
 808          * For a timer with no notification action, we don't actually
 809          * arm the timer (we'll just fake it for timer_gettime).
 810          */
 811         timer->it.cpu.expires = new_expires;
 812         if (new_expires.sched != 0 &&
 813             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 814             cpu_time_before(timer->it_clock, val, new_expires)) {
 815                 arm_timer(timer, val);
 816         }
 817
 818         read_unlock(&tasklist_lock);
 819
 820         /*
 821          * Install the new reload setting, and
 822          * set up the signal and overrun bookkeeping.
 823          */
 824         timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
 825                                                 &new->it_interval);
 826
 827         /*
 828          * This acts as a modification timestamp for the timer,
 829          * so any automatic reload attempt will punt on seeing
 830          * that we have reset the timer manually.
 831          */
 832         timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 833                 ~REQUEUE_PENDING;
 834         timer->it_overrun_last = 0;
 835         timer->it_overrun = -1;
 836
 837         if (new_expires.sched != 0 &&
 838             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 839             !cpu_time_before(timer->it_clock, val, new_expires)) {
 840                 /*
 841                  * The designated time already passed, so we notify
 842                  * immediately, even if the thread never runs to
 843                  * accumulate more time on this clock.
 844                  */
 845                 cpu_timer_fire(timer);
 846         }
 847
 848         ret = 0;
 849  out:
 850         if (old) {
 851                 sample_to_timespec(timer->it_clock,
 852                                    timer->it.cpu.incr, &old->it_interval);
 853         }
 854         return ret;
 855 }
 856
 857 void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 858 {
 859         union cpu_time_count now;
 860         struct task_struct *p = timer->it.cpu.task;
 861         int clear_dead;
 862
 863         /*
 864          * Easy part: convert the reload time.
 865          */
 866         sample_to_timespec(timer->it_clock,
 867                            timer->it.cpu.incr, &itp->it_interval);
 868
 869         if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
 870                 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 871                 return;
 872         }
 873
 874         if (unlikely(p == NULL)) {
 875                 /*
 876                  * This task already died and the timer will never fire.
 877                  * In this case, expires is actually the dead value.
 878                  */
 879         dead:
 880                 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
 881                                    &itp->it_value);
 882                 return;
 883         }
 884
 885         /*
 886          * Sample the clock to take the difference with the expiry time.
 887          */
 888         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 889                 cpu_clock_sample(timer->it_clock, p, &now);
 890                 clear_dead = p->exit_state;
 891         } else {
 892                 read_lock(&tasklist_lock);
 893                 if (unlikely(p->signal == NULL)) {
 894                         /*
 895                          * The process has been reaped.
 896                          * We can't even collect a sample any more.
 897                          * Call the timer disarmed, nothing else to do.
 898                          */
 899                         put_task_struct(p);
 900                         timer->it.cpu.task = NULL;
 901                         timer->it.cpu.expires.sched = 0;
 902                         read_unlock(&tasklist_lock);
 903                         goto dead;
 904                 } else {
 905                         cpu_clock_sample_group(timer->it_clock, p, &now);
 906                         clear_dead = (unlikely(p->exit_state) &&
 907                                       thread_group_empty(p));
 908                 }
 909                 read_unlock(&tasklist_lock);
 910         }
 911
 912         if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 913                 if (timer->it.cpu.incr.sched == 0 &&
 914                     cpu_time_before(timer->it_clock,
 915                                     timer->it.cpu.expires, now)) {
 916                         /*
 917                          * Do-nothing timer expired and has no reload,
 918                          * so it's as if it was never set.
 919                          */
 920                         timer->it.cpu.expires.sched = 0;
 921                         itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 922                         return;
 923                 }
 924                 /*
 925                  * Account for any expirations and reloads that should
 926                  * have happened.
 927                  */
 928                 bump_cpu_timer(timer, now);
 929         }
 930
 931         if (unlikely(clear_dead)) {
 932                 /*
 933                  * We've noticed that the thread is dead, but
 934                  * not yet reaped.  Take this opportunity to
 935                  * drop our task ref.
 936                  */
 937                 clear_dead_task(timer, now);
 938                 goto dead;
 939         }
 940
 941         if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
 942                 sample_to_timespec(timer->it_clock,
 943                                    cpu_time_sub(timer->it_clock,
 944                                                 timer->it.cpu.expires, now),
 945                                    &itp->it_value);
 946         } else {
 947                 /*
 948                  * The timer should have expired already, but the firing
 949                  * hasn't taken place yet.  Say it's just about to expire.
 950                  */
 951                 itp->it_value.tv_nsec = 1;
 952                 itp->it_value.tv_sec = 0;
 953         }
 954 }
 955
 956 /*
 957  * Check for any per-thread CPU timers that have fired and move them off
 958  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 959  * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 960  */
 961 static void check_thread_timers(struct task_struct *tsk,
 962                                 struct list_head *firing)
 963 {
 964         struct list_head *timers = tsk->cpu_timers;
 965
 966         tsk->it_prof_expires = cputime_zero;
 967         while (!list_empty(timers)) {
 968                 struct cpu_timer_list *t = list_entry(timers->next,
 969                                                       struct cpu_timer_list,
 970                                                       entry);
 971                 if (cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
 972                         tsk->it_prof_expires = t->expires.cpu;
 973                         break;
 974                 }
 975                 t->firing = 1;
 976                 list_move_tail(&t->entry, firing);
 977         }
 978
 979         ++timers;
 980         tsk->it_virt_expires = cputime_zero;
 981         while (!list_empty(timers)) {
 982                 struct cpu_timer_list *t = list_entry(timers->next,
 983                                                       struct cpu_timer_list,
 984                                                       entry);
 985                 if (cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
 986                         tsk->it_virt_expires = t->expires.cpu;
 987                         break;
 988                 }
 989                 t->firing = 1;
 990                 list_move_tail(&t->entry, firing);
 991         }
 992
 993         ++timers;
 994         tsk->it_sched_expires = 0;
 995         while (!list_empty(timers)) {
 996                 struct cpu_timer_list *t = list_entry(timers->next,
 997                                                       struct cpu_timer_list,
 998                                                       entry);
 999                 if (tsk->sched_time < t->expires.sched) {
1000                         tsk->it_sched_expires = t->expires.sched;
1001                         break;
1002                 }
1003                 t->firing = 1;
1004                 list_move_tail(&t->entry, firing);
1005         }
1006 }
1007
1008 /*
1009  * Check for any per-thread CPU timers that have fired and move them
1010  * off the tsk->*_timers list onto the firing list.  Per-thread timers
1011  * have already been taken off.
1012  */
1013 static void check_process_timers(struct task_struct *tsk,
1014                                  struct list_head *firing)
1015 {
1016         struct signal_struct *const sig = tsk->signal;
1017         cputime_t utime, stime, ptime, virt_expires, prof_expires;
1018         unsigned long long sched_time, sched_expires;
1019         struct task_struct *t;
1020         struct list_head *timers = sig->cpu_timers;
1021
1022         /*
1023          * Don't sample the current process CPU clocks if there are no timers.
1024          */
1025         if (list_empty(&timers[CPUCLOCK_PROF]) &&
1026             cputime_eq(sig->it_prof_expires, cputime_zero) &&
1027             sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
1028             list_empty(&timers[CPUCLOCK_VIRT]) &&
1029             cputime_eq(sig->it_virt_expires, cputime_zero) &&
1030             list_empty(&timers[CPUCLOCK_SCHED]))
1031                 return;
1032
1033         /*
1034          * Collect the current process totals.
1035          */
1036         utime = sig->utime;
1037         stime = sig->stime;
1038         sched_time = sig->sched_time;
1039         t = tsk;
1040         do {
1041                 utime = cputime_add(utime, t->utime);
1042                 stime = cputime_add(stime, t->stime);
1043                 sched_time += t->sched_time;
1044                 t = next_thread(t);
1045         } while (t != tsk);
1046         ptime = cputime_add(utime, stime);
1047
1048         prof_expires = cputime_zero;
1049         while (!list_empty(timers)) {
1050                 struct cpu_timer_list *t = list_entry(timers->next,
1051                                                       struct cpu_timer_list,
1052                                                       entry);
1053                 if (cputime_lt(ptime, t->expires.cpu)) {
1054                         prof_expires = t->expires.cpu;
1055                         break;
1056                 }
1057                 t->firing = 1;
1058                 list_move_tail(&t->entry, firing);
1059         }
1060
1061         ++timers;
1062         virt_expires = cputime_zero;
1063         while (!list_empty(timers)) {
1064                 struct cpu_timer_list *t = list_entry(timers->next,
1065                                                       struct cpu_timer_list,
1066                                                       entry);
1067                 if (cputime_lt(utime, t->expires.cpu)) {
1068                         virt_expires = t->expires.cpu;
1069                         break;
1070                 }
1071                 t->firing = 1;
1072                 list_move_tail(&t->entry, firing);
1073         }
1074
1075         ++timers;
1076         sched_expires = 0;
1077         while (!list_empty(timers)) {
1078                 struct cpu_timer_list *t = list_entry(timers->next,
1079                                                       struct cpu_timer_list,
1080                                                       entry);
1081                 if (sched_time < t->expires.sched) {
1082                         sched_expires = t->expires.sched;
1083                         break;
1084                 }
1085                 t->firing = 1;
1086                 list_move_tail(&t->entry, firing);
1087         }
1088
1089         /*
1090          * Check for the special case process timers.
1091          */
1092         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1093                 if (cputime_ge(ptime, sig->it_prof_expires)) {
1094                         /* ITIMER_PROF fires and reloads.  */
1095                         sig->it_prof_expires = sig->it_prof_incr;
1096                         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1097                                 sig->it_prof_expires = cputime_add(
1098                                         sig->it_prof_expires, ptime);
1099                         }
1100                         __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
1101                 }
1102                 if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
1103                     (cputime_eq(prof_expires, cputime_zero) ||
1104                      cputime_lt(sig->it_prof_expires, prof_expires))) {
1105                         prof_expires = sig->it_prof_expires;
1106                 }
1107         }
1108         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1109                 if (cputime_ge(utime, sig->it_virt_expires)) {
1110                         /* ITIMER_VIRTUAL fires and reloads.  */
1111                         sig->it_virt_expires = sig->it_virt_incr;
1112                         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1113                                 sig->it_virt_expires = cputime_add(
1114                                         sig->it_virt_expires, utime);
1115                         }
1116                         __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
1117                 }
1118                 if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
1119                     (cputime_eq(virt_expires, cputime_zero) ||
1120                      cputime_lt(sig->it_virt_expires, virt_expires))) {
1121                         virt_expires = sig->it_virt_expires;
1122                 }
1123         }
1124         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
1125                 unsigned long psecs = cputime_to_secs(ptime);
1126                 cputime_t x;
1127                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
1128                         /*
1129                          * At the hard limit, we just die.
1130                          * No need to calculate anything else now.
1131                          */
1132                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1133                         return;
1134                 }
1135                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
1136                         /*
1137                          * At the soft limit, send a SIGXCPU every second.
1138                          */
1139                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1140                         if (sig->rlim[RLIMIT_CPU].rlim_cur
1141                             < sig->rlim[RLIMIT_CPU].rlim_max) {
1142                                 sig->rlim[RLIMIT_CPU].rlim_cur++;
1143                         }
1144                 }
1145                 x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
1146                 if (cputime_eq(prof_expires, cputime_zero) ||
1147                     cputime_lt(x, prof_expires)) {
1148                         prof_expires = x;
1149                 }
1150         }
1151
1152         if (!cputime_eq(prof_expires, cputime_zero) ||
1153             !cputime_eq(virt_expires, cputime_zero) ||
1154             sched_expires != 0) {
1155                 /*
1156                  * Rebalance the threads' expiry times for the remaining
1157                  * process CPU timers.
1158                  */
1159
1160                 cputime_t prof_left, virt_left, ticks;
1161                 unsigned long long sched_left, sched;
1162                 const unsigned int nthreads = atomic_read(&sig->live);
1163
1164                 prof_left = cputime_sub(prof_expires, utime);
1165                 prof_left = cputime_sub(prof_left, stime);
1166                 prof_left = cputime_div(prof_left, nthreads);
1167                 virt_left = cputime_sub(virt_expires, utime);
1168                 virt_left = cputime_div(virt_left, nthreads);
1169                 if (sched_expires) {
1170                         sched_left = sched_expires - sched_time;
1171                         do_div(sched_left, nthreads);
1172                 } else {
1173                         sched_left = 0;
1174                 }
1175                 t = tsk;
1176                 do {
1177                         ticks = cputime_add(cputime_add(t->utime, t->stime),
1178                                             prof_left);
1179                         if (!cputime_eq(prof_expires, cputime_zero) &&
1180                             (cputime_eq(t->it_prof_expires, cputime_zero) ||
1181                              cputime_gt(t->it_prof_expires, ticks))) {
1182                                 t->it_prof_expires = ticks;
1183                         }
1184
1185                         ticks = cputime_add(t->utime, virt_left);
1186                         if (!cputime_eq(virt_expires, cputime_zero) &&
1187                             (cputime_eq(t->it_virt_expires, cputime_zero) ||
1188                              cputime_gt(t->it_virt_expires, ticks))) {
1189                                 t->it_virt_expires = ticks;
1190                         }
1191
1192                         sched = t->sched_time + sched_left;
1193                         if (sched_expires && (t->it_sched_expires == 0 ||
1194                                               t->it_sched_expires > sched)) {
1195                                 t->it_sched_expires = sched;
1196                         }
1197
1198                         do {
1199                                 t = next_thread(t);
1200                         } while (unlikely(t->exit_state));
1201                 } while (t != tsk);
1202         }
1203 }
1204
1205 /*
1206  * This is called from the signal code (via do_schedule_next_timer)
1207  * when the last timer signal was delivered and we have to reload the timer.
1208  */
1209 void posix_cpu_timer_schedule(struct k_itimer *timer)
1210 {
1211         struct task_struct *p = timer->it.cpu.task;
1212         union cpu_time_count now;
1213
1214         if (unlikely(p == NULL))
1215                 /*
1216                  * The task was cleaned up already, no future firings.
1217                  */
1218                 return;
1219
1220         /*
1221          * Fetch the current sample and update the timer's expiry time.
1222          */
1223         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1224                 cpu_clock_sample(timer->it_clock, p, &now);
1225                 bump_cpu_timer(timer, now);
1226                 if (unlikely(p->exit_state)) {
1227                         clear_dead_task(timer, now);
1228                         return;
1229                 }
1230                 read_lock(&tasklist_lock); /* arm_timer needs it.  */
1231         } else {
1232                 read_lock(&tasklist_lock);
1233                 if (unlikely(p->signal == NULL)) {
1234                         /*
1235                          * The process has been reaped.
1236                          * We can't even collect a sample any more.
1237                          */
1238                         put_task_struct(p);
1239                         timer->it.cpu.task = p = NULL;
1240                         timer->it.cpu.expires.sched = 0;
1241                         read_unlock(&tasklist_lock);
1242                         return;
1243                 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1244                         /*
1245                          * We've noticed that the thread is dead, but
1246                          * not yet reaped.  Take this opportunity to
1247                          * drop our task ref.
1248                          */
1249                         clear_dead_task(timer, now);
1250                         read_unlock(&tasklist_lock);
1251                         return;
1252                 }
1253                 cpu_clock_sample_group(timer->it_clock, p, &now);
1254                 bump_cpu_timer(timer, now);
1255                 /* Leave the tasklist_lock locked for the call below.  */
1256         }
1257
1258         /*
1259          * Now re-arm for the new expiry time.
1260          */
1261         arm_timer(timer, now);
1262
1263         read_unlock(&tasklist_lock);
1264 }
1265
1266 /*
1267  * This is called from the timer interrupt handler.  The irq handler has
1268  * already updated our counts.  We need to check if any timers fire now.
1269  * Interrupts are disabled.
1270  */
1271 void run_posix_cpu_timers(struct task_struct *tsk)
1272 {
1273         LIST_HEAD(firing);
1274         struct k_itimer *timer, *next;
1275
1276         BUG_ON(!irqs_disabled());
1277
1278 #define UNEXPIRED(clock) \
1279                 (cputime_eq(tsk->it_##clock##_expires, cputime_zero) || \
1280                  cputime_lt(clock##_ticks(tsk), tsk->it_##clock##_expires))
1281
1282         if (UNEXPIRED(prof) && UNEXPIRED(virt) &&
1283             (tsk->it_sched_expires == 0 ||
1284              tsk->sched_time < tsk->it_sched_expires))
1285                 return;
1286
1287 #undef  UNEXPIRED
1288
1289         BUG_ON(tsk->exit_state);
1290
1291         /*
1292          * Double-check with locks held.
1293          */
1294         read_lock(&tasklist_lock);
1295         spin_lock(&tsk->sighand->siglock);
1296
1297         /*
1298          * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
1299          * all the timers that are firing, and put them on the firing list.
1300          */
1301         check_thread_timers(tsk, &firing);
1302         check_process_timers(tsk, &firing);
1303
1304         /*
1305          * We must release these locks before taking any timer's lock.
1306          * There is a potential race with timer deletion here, as the
1307          * siglock now protects our private firing list.  We have set
1308          * the firing flag in each timer, so that a deletion attempt
1309          * that gets the timer lock before we do will give it up and
1310          * spin until we've taken care of that timer below.
1311          */
1312         spin_unlock(&tsk->sighand->siglock);
1313         read_unlock(&tasklist_lock);
1314
1315         /*
1316          * Now that all the timers on our list have the firing flag,
1317          * noone will touch their list entries but us.  We'll take
1318          * each timer's lock before clearing its firing flag, so no
1319          * timer call will interfere.
1320          */
1321         list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1322                 int firing;
1323                 spin_lock(&timer->it_lock);
1324                 list_del_init(&timer->it.cpu.entry);
1325                 firing = timer->it.cpu.firing;
1326                 timer->it.cpu.firing = 0;
1327                 /*
1328                  * The firing flag is -1 if we collided with a reset
1329                  * of the timer, which already reported this
1330                  * almost-firing as an overrun.  So don't generate an event.
1331                  */
1332                 if (likely(firing >= 0)) {
1333                         cpu_timer_fire(timer);
1334                 }
1335                 spin_unlock(&timer->it_lock);
1336         }
1337 }
1338
1339 /*
1340  * Set one of the process-wide special case CPU timers.
1341  * The tasklist_lock and tsk->sighand->siglock must be held by the caller.
1342  * The oldval argument is null for the RLIMIT_CPU timer, where *newval is
1343  * absolute; non-null for ITIMER_*, where *newval is relative and we update
1344  * it to be absolute, *oldval is absolute and we update it to be relative.
1345  */
1346 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1347                            cputime_t *newval, cputime_t *oldval)
1348 {
1349         union cpu_time_count now;
1350         struct list_head *head;
1351
1352         BUG_ON(clock_idx == CPUCLOCK_SCHED);
1353         cpu_clock_sample_group_locked(clock_idx, tsk, &now);
1354
1355         if (oldval) {
1356                 if (!cputime_eq(*oldval, cputime_zero)) {
1357                         if (cputime_le(*oldval, now.cpu)) {
1358                                 /* Just about to fire. */
1359                                 *oldval = jiffies_to_cputime(1);
1360                         } else {
1361                                 *oldval = cputime_sub(*oldval, now.cpu);
1362                         }
1363                 }
1364
1365                 if (cputime_eq(*newval, cputime_zero))
1366                         return;
1367                 *newval = cputime_add(*newval, now.cpu);
1368
1369                 /*
1370                  * If the RLIMIT_CPU timer will expire before the
1371                  * ITIMER_PROF timer, we have nothing else to do.
1372                  */
1373                 if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
1374                     < cputime_to_secs(*newval))
1375                         return;
1376         }
1377
1378         /*
1379          * Check whether there are any process timers already set to fire
1380          * before this one.  If so, we don't have anything more to do.
1381          */
1382         head = &tsk->signal->cpu_timers[clock_idx];
1383         if (list_empty(head) ||
1384             cputime_ge(list_entry(head->next,
1385                                   struct cpu_timer_list, entry)->expires.cpu,
1386                        *newval)) {
1387                 /*
1388                  * Rejigger each thread's expiry time so that one will
1389                  * notice before we hit the process-cumulative expiry time.
1390                  */
1391                 union cpu_time_count expires = { .sched = 0 };
1392                 expires.cpu = *newval;
1393                 process_timer_rebalance(tsk, clock_idx, expires, now);
1394         }
1395 }
1396
1397 static long posix_cpu_clock_nanosleep_restart(struct restart_block *);
1398
1399 int posix_cpu_nsleep(clockid_t which_clock, int flags,
1400                      struct timespec *rqtp)
1401 {
1402         struct restart_block *restart_block =
1403             &current_thread_info()->restart_block;
1404         struct k_itimer timer;
1405         int error;
1406
1407         /*
1408          * Diagnose required errors first.
1409          */
1410         if (CPUCLOCK_PERTHREAD(which_clock) &&
1411             (CPUCLOCK_PID(which_clock) == 0 ||
1412              CPUCLOCK_PID(which_clock) == current->pid))
1413                 return -EINVAL;
1414
1415         /*
1416          * Set up a temporary timer and then wait for it to go off.
1417          */
1418         memset(&timer, 0, sizeof timer);
1419         spin_lock_init(&timer.it_lock);
1420         timer.it_clock = which_clock;
1421         timer.it_overrun = -1;
1422         error = posix_cpu_timer_create(&timer);
1423         timer.it_process = current;
1424         if (!error) {
1425                 struct timespec __user *rmtp;
1426                 static struct itimerspec zero_it;
1427                 struct itimerspec it = { .it_value = *rqtp,
1428                                          .it_interval = {} };
1429
1430                 spin_lock_irq(&timer.it_lock);
1431                 error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1432                 if (error) {
1433                         spin_unlock_irq(&timer.it_lock);
1434                         return error;
1435                 }
1436
1437                 while (!signal_pending(current)) {
1438                         if (timer.it.cpu.expires.sched == 0) {
1439                                 /*
1440                                  * Our timer fired and was reset.
1441                                  */
1442                                 spin_unlock_irq(&timer.it_lock);
1443                                 return 0;
1444                         }
1445
1446                         /*
1447                          * Block until cpu_timer_fire (or a signal) wakes us.
1448                          */
1449                         __set_current_state(TASK_INTERRUPTIBLE);
1450                         spin_unlock_irq(&timer.it_lock);
1451                         schedule();
1452                         spin_lock_irq(&timer.it_lock);
1453                 }
1454
1455                 /*
1456                  * We were interrupted by a signal.
1457                  */
1458                 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1459                 posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1460                 spin_unlock_irq(&timer.it_lock);
1461
1462                 if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1463                         /*
1464                          * It actually did fire already.
1465                          */
1466                         return 0;
1467                 }
1468
1469                 /*
1470                  * Report back to the user the time still remaining.
1471                  */
1472                 rmtp = (struct timespec __user *) restart_block->arg1;
1473                 if (rmtp != NULL && !(flags & TIMER_ABSTIME) &&
1474                     copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1475                         return -EFAULT;
1476
1477                 restart_block->fn = posix_cpu_clock_nanosleep_restart;
1478                 /* Caller already set restart_block->arg1 */
1479                 restart_block->arg0 = which_clock;
1480                 restart_block->arg2 = rqtp->tv_sec;
1481                 restart_block->arg3 = rqtp->tv_nsec;
1482
1483                 error = -ERESTART_RESTARTBLOCK;
1484         }
1485
1486         return error;
1487 }
1488
1489 static long
1490 posix_cpu_clock_nanosleep_restart(struct restart_block *restart_block)
1491 {
1492         clockid_t which_clock = restart_block->arg0;
1493         struct timespec t = { .tv_sec = restart_block->arg2,
1494                               .tv_nsec = restart_block->arg3 };
1495         restart_block->fn = do_no_restart_syscall;
1496         return posix_cpu_nsleep(which_clock, TIMER_ABSTIME, &t);
1497 }
1498
1499
1500 #define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1501 #define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1502
1503 static int process_cpu_clock_getres(clockid_t which_clock, struct timespec *tp)
1504 {
1505         return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1506 }
1507 static int process_cpu_clock_get(clockid_t which_clock, struct timespec *tp)
1508 {
1509         return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1510 }
1511 static int process_cpu_timer_create(struct k_itimer *timer)
1512 {
1513         timer->it_clock = PROCESS_CLOCK;
1514         return posix_cpu_timer_create(timer);
1515 }
1516 static int process_cpu_nsleep(clockid_t which_clock, int flags,
1517                               struct timespec *rqtp)
1518 {
1519         return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
1520 }
1521 static int thread_cpu_clock_getres(clockid_t which_clock, struct timespec *tp)
1522 {
1523         return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1524 }
1525 static int thread_cpu_clock_get(clockid_t which_clock, struct timespec *tp)
1526 {
1527         return posix_cpu_clock_get(THREAD_CLOCK, tp);
1528 }
1529 static int thread_cpu_timer_create(struct k_itimer *timer)
1530 {
1531         timer->it_clock = THREAD_CLOCK;
1532         return posix_cpu_timer_create(timer);
1533 }
1534 static int thread_cpu_nsleep(clockid_t which_clock, int flags,
1535                               struct timespec *rqtp)
1536 {
1537         return -EINVAL;
1538 }
1539
1540 static __init int init_posix_cpu_timers(void)
1541 {
1542         struct k_clock process = {
1543                 .clock_getres = process_cpu_clock_getres,
1544                 .clock_get = process_cpu_clock_get,
1545                 .clock_set = do_posix_clock_nosettime,
1546                 .timer_create = process_cpu_timer_create,
1547                 .nsleep = process_cpu_nsleep,
1548         };
1549         struct k_clock thread = {
1550                 .clock_getres = thread_cpu_clock_getres,
1551                 .clock_get = thread_cpu_clock_get,
1552                 .clock_set = do_posix_clock_nosettime,
1553                 .timer_create = thread_cpu_timer_create,
1554                 .nsleep = thread_cpu_nsleep,
1555         };
1556
1557         register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1558         register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1559
1560         return 0;
1561 }
1562 __initcall(init_posix_cpu_timers);