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