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(const 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                    same_thread_group(p, current) : thread_group_leader(p))) {
  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(const 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 = (unsigned long long)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(const 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(const 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(const 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(const 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  * Divide and limit the result to res >= 1
  92  *
  93  * This is necessary to prevent signal delivery starvation, when the result of
  94  * the division would be rounded down to 0.
  95  */
  96 static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
  97 {
  98         cputime_t res = cputime_div(time, div);
  99
 100         return max_t(cputime_t, res, 1);
 101 }
 102
 103 /*
 104  * Update expiry time from increment, and increase overrun count,
 105  * given the current clock sample.
 106  */
 107 static void bump_cpu_timer(struct k_itimer *timer,
 108                                   union cpu_time_count now)
 109 {
 110         int i;
 111
 112         if (timer->it.cpu.incr.sched == 0)
 113                 return;
 114
 115         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 116                 unsigned long long delta, incr;
 117
 118                 if (now.sched < timer->it.cpu.expires.sched)
 119                         return;
 120                 incr = timer->it.cpu.incr.sched;
 121                 delta = now.sched + incr - timer->it.cpu.expires.sched;
 122                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 123                 for (i = 0; incr < delta - incr; i++)
 124                         incr = incr << 1;
 125                 for (; i >= 0; incr >>= 1, i--) {
 126                         if (delta < incr)
 127                                 continue;
 128                         timer->it.cpu.expires.sched += incr;
 129                         timer->it_overrun += 1 << i;
 130                         delta -= incr;
 131                 }
 132         } else {
 133                 cputime_t delta, incr;
 134
 135                 if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
 136                         return;
 137                 incr = timer->it.cpu.incr.cpu;
 138                 delta = cputime_sub(cputime_add(now.cpu, incr),
 139                                     timer->it.cpu.expires.cpu);
 140                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 141                 for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
 142                              incr = cputime_add(incr, incr);
 143                 for (; i >= 0; incr = cputime_halve(incr), i--) {
 144                         if (cputime_lt(delta, incr))
 145                                 continue;
 146                         timer->it.cpu.expires.cpu =
 147                                 cputime_add(timer->it.cpu.expires.cpu, incr);
 148                         timer->it_overrun += 1 << i;
 149                         delta = cputime_sub(delta, incr);
 150                 }
 151         }
 152 }
 153
 154 static inline cputime_t prof_ticks(struct task_struct *p)
 155 {
 156         return cputime_add(p->utime, p->stime);
 157 }
 158 static inline cputime_t virt_ticks(struct task_struct *p)
 159 {
 160         return p->utime;
 161 }
 162 static inline unsigned long long sched_ns(struct task_struct *p)
 163 {
 164         return task_sched_runtime(p);
 165 }
 166
 167 int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
 168 {
 169         int error = check_clock(which_clock);
 170         if (!error) {
 171                 tp->tv_sec = 0;
 172                 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
 173                 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 174                         /*
 175                          * If sched_clock is using a cycle counter, we
 176                          * don't have any idea of its true resolution
 177                          * exported, but it is much more than 1s/HZ.
 178                          */
 179                         tp->tv_nsec = 1;
 180                 }
 181         }
 182         return error;
 183 }
 184
 185 int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
 186 {
 187         /*
 188          * You can never reset a CPU clock, but we check for other errors
 189          * in the call before failing with EPERM.
 190          */
 191         int error = check_clock(which_clock);
 192         if (error == 0) {
 193                 error = -EPERM;
 194         }
 195         return error;
 196 }
 197
 198
 199 /*
 200  * Sample a per-thread clock for the given task.
 201  */
 202 static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
 203                             union cpu_time_count *cpu)
 204 {
 205         switch (CPUCLOCK_WHICH(which_clock)) {
 206         default:
 207                 return -EINVAL;
 208         case CPUCLOCK_PROF:
 209                 cpu->cpu = prof_ticks(p);
 210                 break;
 211         case CPUCLOCK_VIRT:
 212                 cpu->cpu = virt_ticks(p);
 213                 break;
 214         case CPUCLOCK_SCHED:
 215                 cpu->sched = sched_ns(p);
 216                 break;
 217         }
 218         return 0;
 219 }
 220
 221 /*
 222  * Sample a process (thread group) clock for the given group_leader task.
 223  * Must be called with tasklist_lock held for reading.
 224  * Must be called with tasklist_lock held for reading, and p->sighand->siglock.
 225  */
 226 static int cpu_clock_sample_group_locked(unsigned int clock_idx,
 227                                          struct task_struct *p,
 228                                          union cpu_time_count *cpu)
 229 {
 230         struct task_struct *t = p;
 231         switch (clock_idx) {
 232         default:
 233                 return -EINVAL;
 234         case CPUCLOCK_PROF:
 235                 cpu->cpu = cputime_add(p->signal->utime, p->signal->stime);
 236                 do {
 237                         cpu->cpu = cputime_add(cpu->cpu, prof_ticks(t));
 238                         t = next_thread(t);
 239                 } while (t != p);
 240                 break;
 241         case CPUCLOCK_VIRT:
 242                 cpu->cpu = p->signal->utime;
 243                 do {
 244                         cpu->cpu = cputime_add(cpu->cpu, virt_ticks(t));
 245                         t = next_thread(t);
 246                 } while (t != p);
 247                 break;
 248         case CPUCLOCK_SCHED:
 249                 cpu->sched = p->signal->sum_sched_runtime;
 250                 /* Add in each other live thread.  */
 251                 while ((t = next_thread(t)) != p) {
 252                         cpu->sched += t->se.sum_exec_runtime;
 253                 }
 254                 cpu->sched += sched_ns(p);
 255                 break;
 256         }
 257         return 0;
 258 }
 259
 260 /*
 261  * Sample a process (thread group) clock for the given group_leader task.
 262  * Must be called with tasklist_lock held for reading.
 263  */
 264 static int cpu_clock_sample_group(const clockid_t which_clock,
 265                                   struct task_struct *p,
 266                                   union cpu_time_count *cpu)
 267 {
 268         int ret;
 269         unsigned long flags;
 270         spin_lock_irqsave(&p->sighand->siglock, flags);
 271         ret = cpu_clock_sample_group_locked(CPUCLOCK_WHICH(which_clock), p,
 272                                             cpu);
 273         spin_unlock_irqrestore(&p->sighand->siglock, flags);
 274         return ret;
 275 }
 276
 277
 278 int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 279 {
 280         const pid_t pid = CPUCLOCK_PID(which_clock);
 281         int error = -EINVAL;
 282         union cpu_time_count rtn;
 283
 284         if (pid == 0) {
 285                 /*
 286                  * Special case constant value for our own clocks.
 287                  * We don't have to do any lookup to find ourselves.
 288                  */
 289                 if (CPUCLOCK_PERTHREAD(which_clock)) {
 290                         /*
 291                          * Sampling just ourselves we can do with no locking.
 292                          */
 293                         error = cpu_clock_sample(which_clock,
 294                                                  current, &rtn);
 295                 } else {
 296                         read_lock(&tasklist_lock);
 297                         error = cpu_clock_sample_group(which_clock,
 298                                                        current, &rtn);
 299                         read_unlock(&tasklist_lock);
 300                 }
 301         } else {
 302                 /*
 303                  * Find the given PID, and validate that the caller
 304                  * should be able to see it.
 305                  */
 306                 struct task_struct *p;
 307                 rcu_read_lock();
 308                 p = find_task_by_pid(pid);
 309                 if (p) {
 310                         if (CPUCLOCK_PERTHREAD(which_clock)) {
 311                                 if (same_thread_group(p, current)) {
 312                                         error = cpu_clock_sample(which_clock,
 313                                                                  p, &rtn);
 314                                 }
 315                         } else {
 316                                 read_lock(&tasklist_lock);
 317                                 if (thread_group_leader(p) && p->signal) {
 318                                         error =
 319                                             cpu_clock_sample_group(which_clock,
 320                                                                    p, &rtn);
 321                                 }
 322                                 read_unlock(&tasklist_lock);
 323                         }
 324                 }
 325                 rcu_read_unlock();
 326         }
 327
 328         if (error)
 329                 return error;
 330         sample_to_timespec(which_clock, rtn, tp);
 331         return 0;
 332 }
 333
 334
 335 /*
 336  * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 337  * This is called from sys_timer_create with the new timer already locked.
 338  */
 339 int posix_cpu_timer_create(struct k_itimer *new_timer)
 340 {
 341         int ret = 0;
 342         const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
 343         struct task_struct *p;
 344
 345         if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 346                 return -EINVAL;
 347
 348         INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 349         new_timer->it.cpu.incr.sched = 0;
 350         new_timer->it.cpu.expires.sched = 0;
 351
 352         read_lock(&tasklist_lock);
 353         if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
 354                 if (pid == 0) {
 355                         p = current;
 356                 } else {
 357                         p = find_task_by_pid(pid);
 358                         if (p && !same_thread_group(p, current))
 359                                 p = NULL;
 360                 }
 361         } else {
 362                 if (pid == 0) {
 363                         p = current->group_leader;
 364                 } else {
 365                         p = find_task_by_pid(pid);
 366                         if (p && !thread_group_leader(p))
 367                                 p = NULL;
 368                 }
 369         }
 370         new_timer->it.cpu.task = p;
 371         if (p) {
 372                 get_task_struct(p);
 373         } else {
 374                 ret = -EINVAL;
 375         }
 376         read_unlock(&tasklist_lock);
 377
 378         return ret;
 379 }
 380
 381 /*
 382  * Clean up a CPU-clock timer that is about to be destroyed.
 383  * This is called from timer deletion with the timer already locked.
 384  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 385  * and try again.  (This happens when the timer is in the middle of firing.)
 386  */
 387 int posix_cpu_timer_del(struct k_itimer *timer)
 388 {
 389         struct task_struct *p = timer->it.cpu.task;
 390         int ret = 0;
 391
 392         if (likely(p != NULL)) {
 393                 read_lock(&tasklist_lock);
 394                 if (unlikely(p->signal == NULL)) {
 395                         /*
 396                          * We raced with the reaping of the task.
 397                          * The deletion should have cleared us off the list.
 398                          */
 399                         BUG_ON(!list_empty(&timer->it.cpu.entry));
 400                 } else {
 401                         spin_lock(&p->sighand->siglock);
 402                         if (timer->it.cpu.firing)
 403                                 ret = TIMER_RETRY;
 404                         else
 405                                 list_del(&timer->it.cpu.entry);
 406                         spin_unlock(&p->sighand->siglock);
 407                 }
 408                 read_unlock(&tasklist_lock);
 409
 410                 if (!ret)
 411                         put_task_struct(p);
 412         }
 413
 414         return ret;
 415 }
 416
 417 /*
 418  * Clean out CPU timers still ticking when a thread exited.  The task
 419  * pointer is cleared, and the expiry time is replaced with the residual
 420  * time for later timer_gettime calls to return.
 421  * This must be called with the siglock held.
 422  */
 423 static void cleanup_timers(struct list_head *head,
 424                            cputime_t utime, cputime_t stime,
 425                            unsigned long long sum_exec_runtime)
 426 {
 427         struct cpu_timer_list *timer, *next;
 428         cputime_t ptime = cputime_add(utime, stime);
 429
 430         list_for_each_entry_safe(timer, next, head, entry) {
 431                 list_del_init(&timer->entry);
 432                 if (cputime_lt(timer->expires.cpu, ptime)) {
 433                         timer->expires.cpu = cputime_zero;
 434                 } else {
 435                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
 436                                                          ptime);
 437                 }
 438         }
 439
 440         ++head;
 441         list_for_each_entry_safe(timer, next, head, entry) {
 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                 list_del_init(&timer->entry);
 454                 if (timer->expires.sched < sum_exec_runtime) {
 455                         timer->expires.sched = 0;
 456                 } else {
 457                         timer->expires.sched -= sum_exec_runtime;
 458                 }
 459         }
 460 }
 461
 462 /*
 463  * These are both called with the siglock held, when the current thread
 464  * is being reaped.  When the final (leader) thread in the group is reaped,
 465  * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 466  */
 467 void posix_cpu_timers_exit(struct task_struct *tsk)
 468 {
 469         cleanup_timers(tsk->cpu_timers,
 470                        tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
 471
 472 }
 473 void posix_cpu_timers_exit_group(struct task_struct *tsk)
 474 {
 475         cleanup_timers(tsk->signal->cpu_timers,
 476                        cputime_add(tsk->utime, tsk->signal->utime),
 477                        cputime_add(tsk->stime, tsk->signal->stime),
 478                      tsk->se.sum_exec_runtime + tsk->signal->sum_sched_runtime);
 479 }
 480
 481
 482 /*
 483  * Set the expiry times of all the threads in the process so one of them
 484  * will go off before the process cumulative expiry total is reached.
 485  */
 486 static void process_timer_rebalance(struct task_struct *p,
 487                                     unsigned int clock_idx,
 488                                     union cpu_time_count expires,
 489                                     union cpu_time_count val)
 490 {
 491         cputime_t ticks, left;
 492         unsigned long long ns, nsleft;
 493         struct task_struct *t = p;
 494         unsigned int nthreads = atomic_read(&p->signal->live);
 495
 496         if (!nthreads)
 497                 return;
 498
 499         switch (clock_idx) {
 500         default:
 501                 BUG();
 502                 break;
 503         case CPUCLOCK_PROF:
 504                 left = cputime_div_non_zero(cputime_sub(expires.cpu, val.cpu),
 505                                        nthreads);
 506                 do {
 507                         if (likely(!(t->flags & PF_EXITING))) {
 508                                 ticks = cputime_add(prof_ticks(t), left);
 509                                 if (cputime_eq(t->it_prof_expires,
 510                                                cputime_zero) ||
 511                                     cputime_gt(t->it_prof_expires, ticks)) {
 512                                         t->it_prof_expires = ticks;
 513                                 }
 514                         }
 515                         t = next_thread(t);
 516                 } while (t != p);
 517                 break;
 518         case CPUCLOCK_VIRT:
 519                 left = cputime_div_non_zero(cputime_sub(expires.cpu, val.cpu),
 520                                        nthreads);
 521                 do {
 522                         if (likely(!(t->flags & PF_EXITING))) {
 523                                 ticks = cputime_add(virt_ticks(t), left);
 524                                 if (cputime_eq(t->it_virt_expires,
 525                                                cputime_zero) ||
 526                                     cputime_gt(t->it_virt_expires, ticks)) {
 527                                         t->it_virt_expires = ticks;
 528                                 }
 529                         }
 530                         t = next_thread(t);
 531                 } while (t != p);
 532                 break;
 533         case CPUCLOCK_SCHED:
 534                 nsleft = expires.sched - val.sched;
 535                 do_div(nsleft, nthreads);
 536                 nsleft = max_t(unsigned long long, nsleft, 1);
 537                 do {
 538                         if (likely(!(t->flags & PF_EXITING))) {
 539                                 ns = t->se.sum_exec_runtime + nsleft;
 540                                 if (t->it_sched_expires == 0 ||
 541                                     t->it_sched_expires > ns) {
 542                                         t->it_sched_expires = ns;
 543                                 }
 544                         }
 545                         t = next_thread(t);
 546                 } while (t != p);
 547                 break;
 548         }
 549 }
 550
 551 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 552 {
 553         /*
 554          * That's all for this thread or process.
 555          * We leave our residual in expires to be reported.
 556          */
 557         put_task_struct(timer->it.cpu.task);
 558         timer->it.cpu.task = NULL;
 559         timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
 560                                              timer->it.cpu.expires,
 561                                              now);
 562 }
 563
 564 /*
 565  * Insert the timer on the appropriate list before any timers that
 566  * expire later.  This must be called with the tasklist_lock held
 567  * for reading, and interrupts disabled.
 568  */
 569 static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 570 {
 571         struct task_struct *p = timer->it.cpu.task;
 572         struct list_head *head, *listpos;
 573         struct cpu_timer_list *const nt = &timer->it.cpu;
 574         struct cpu_timer_list *next;
 575         unsigned long i;
 576
 577         head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
 578                 p->cpu_timers : p->signal->cpu_timers);
 579         head += CPUCLOCK_WHICH(timer->it_clock);
 580
 581         BUG_ON(!irqs_disabled());
 582         spin_lock(&p->sighand->siglock);
 583
 584         listpos = head;
 585         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 586                 list_for_each_entry(next, head, entry) {
 587                         if (next->expires.sched > nt->expires.sched)
 588                                 break;
 589                         listpos = &next->entry;
 590                 }
 591         } else {
 592                 list_for_each_entry(next, head, entry) {
 593                         if (cputime_gt(next->expires.cpu, nt->expires.cpu))
 594                                 break;
 595                         listpos = &next->entry;
 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
 740         ret = 0;
 741         spin_lock(&p->sighand->siglock);
 742         old_expires = timer->it.cpu.expires;
 743         if (unlikely(timer->it.cpu.firing)) {
 744                 timer->it.cpu.firing = -1;
 745                 ret = TIMER_RETRY;
 746         } else
 747                 list_del_init(&timer->it.cpu.entry);
 748         spin_unlock(&p->sighand->siglock);
 749
 750         /*
 751          * We need to sample the current value to convert the new
 752          * value from to relative and absolute, and to convert the
 753          * old value from absolute to relative.  To set a process
 754          * timer, we need a sample to balance the thread expiry
 755          * times (in arm_timer).  With an absolute time, we must
 756          * check if it's already passed.  In short, we need a sample.
 757          */
 758         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 759                 cpu_clock_sample(timer->it_clock, p, &val);
 760         } else {
 761                 cpu_clock_sample_group(timer->it_clock, p, &val);
 762         }
 763
 764         if (old) {
 765                 if (old_expires.sched == 0) {
 766                         old->it_value.tv_sec = 0;
 767                         old->it_value.tv_nsec = 0;
 768                 } else {
 769                         /*
 770                          * Update the timer in case it has
 771                          * overrun already.  If it has,
 772                          * we'll report it as having overrun
 773                          * and with the next reloaded timer
 774                          * already ticking, though we are
 775                          * swallowing that pending
 776                          * notification here to install the
 777                          * new setting.
 778                          */
 779                         bump_cpu_timer(timer, val);
 780                         if (cpu_time_before(timer->it_clock, val,
 781                                             timer->it.cpu.expires)) {
 782                                 old_expires = cpu_time_sub(
 783                                         timer->it_clock,
 784                                         timer->it.cpu.expires, val);
 785                                 sample_to_timespec(timer->it_clock,
 786                                                    old_expires,
 787                                                    &old->it_value);
 788                         } else {
 789                                 old->it_value.tv_nsec = 1;
 790                                 old->it_value.tv_sec = 0;
 791                         }
 792                 }
 793         }
 794
 795         if (unlikely(ret)) {
 796                 /*
 797                  * We are colliding with the timer actually firing.
 798                  * Punt after filling in the timer's old value, and
 799                  * disable this firing since we are already reporting
 800                  * it as an overrun (thanks to bump_cpu_timer above).
 801                  */
 802                 read_unlock(&tasklist_lock);
 803                 goto out;
 804         }
 805
 806         if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
 807                 cpu_time_add(timer->it_clock, &new_expires, val);
 808         }
 809
 810         /*
 811          * Install the new expiry time (or zero).
 812          * For a timer with no notification action, we don't actually
 813          * arm the timer (we'll just fake it for timer_gettime).
 814          */
 815         timer->it.cpu.expires = new_expires;
 816         if (new_expires.sched != 0 &&
 817             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 818             cpu_time_before(timer->it_clock, val, new_expires)) {
 819                 arm_timer(timer, val);
 820         }
 821
 822         read_unlock(&tasklist_lock);
 823
 824         /*
 825          * Install the new reload setting, and
 826          * set up the signal and overrun bookkeeping.
 827          */
 828         timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
 829                                                 &new->it_interval);
 830
 831         /*
 832          * This acts as a modification timestamp for the timer,
 833          * so any automatic reload attempt will punt on seeing
 834          * that we have reset the timer manually.
 835          */
 836         timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 837                 ~REQUEUE_PENDING;
 838         timer->it_overrun_last = 0;
 839         timer->it_overrun = -1;
 840
 841         if (new_expires.sched != 0 &&
 842             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 843             !cpu_time_before(timer->it_clock, val, new_expires)) {
 844                 /*
 845                  * The designated time already passed, so we notify
 846                  * immediately, even if the thread never runs to
 847                  * accumulate more time on this clock.
 848                  */
 849                 cpu_timer_fire(timer);
 850         }
 851
 852         ret = 0;
 853  out:
 854         if (old) {
 855                 sample_to_timespec(timer->it_clock,
 856                                    timer->it.cpu.incr, &old->it_interval);
 857         }
 858         return ret;
 859 }
 860
 861 void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 862 {
 863         union cpu_time_count now;
 864         struct task_struct *p = timer->it.cpu.task;
 865         int clear_dead;
 866
 867         /*
 868          * Easy part: convert the reload time.
 869          */
 870         sample_to_timespec(timer->it_clock,
 871                            timer->it.cpu.incr, &itp->it_interval);
 872
 873         if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
 874                 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 875                 return;
 876         }
 877
 878         if (unlikely(p == NULL)) {
 879                 /*
 880                  * This task already died and the timer will never fire.
 881                  * In this case, expires is actually the dead value.
 882                  */
 883         dead:
 884                 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
 885                                    &itp->it_value);
 886                 return;
 887         }
 888
 889         /*
 890          * Sample the clock to take the difference with the expiry time.
 891          */
 892         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 893                 cpu_clock_sample(timer->it_clock, p, &now);
 894                 clear_dead = p->exit_state;
 895         } else {
 896                 read_lock(&tasklist_lock);
 897                 if (unlikely(p->signal == NULL)) {
 898                         /*
 899                          * The process has been reaped.
 900                          * We can't even collect a sample any more.
 901                          * Call the timer disarmed, nothing else to do.
 902                          */
 903                         put_task_struct(p);
 904                         timer->it.cpu.task = NULL;
 905                         timer->it.cpu.expires.sched = 0;
 906                         read_unlock(&tasklist_lock);
 907                         goto dead;
 908                 } else {
 909                         cpu_clock_sample_group(timer->it_clock, p, &now);
 910                         clear_dead = (unlikely(p->exit_state) &&
 911                                       thread_group_empty(p));
 912                 }
 913                 read_unlock(&tasklist_lock);
 914         }
 915
 916         if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 917                 if (timer->it.cpu.incr.sched == 0 &&
 918                     cpu_time_before(timer->it_clock,
 919                                     timer->it.cpu.expires, now)) {
 920                         /*
 921                          * Do-nothing timer expired and has no reload,
 922                          * so it's as if it was never set.
 923                          */
 924                         timer->it.cpu.expires.sched = 0;
 925                         itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 926                         return;
 927                 }
 928                 /*
 929                  * Account for any expirations and reloads that should
 930                  * have happened.
 931                  */
 932                 bump_cpu_timer(timer, now);
 933         }
 934
 935         if (unlikely(clear_dead)) {
 936                 /*
 937                  * We've noticed that the thread is dead, but
 938                  * not yet reaped.  Take this opportunity to
 939                  * drop our task ref.
 940                  */
 941                 clear_dead_task(timer, now);
 942                 goto dead;
 943         }
 944
 945         if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
 946                 sample_to_timespec(timer->it_clock,
 947                                    cpu_time_sub(timer->it_clock,
 948                                                 timer->it.cpu.expires, now),
 949                                    &itp->it_value);
 950         } else {
 951                 /*
 952                  * The timer should have expired already, but the firing
 953                  * hasn't taken place yet.  Say it's just about to expire.
 954                  */
 955                 itp->it_value.tv_nsec = 1;
 956                 itp->it_value.tv_sec = 0;
 957         }
 958 }
 959
 960 /*
 961  * Check for any per-thread CPU timers that have fired and move them off
 962  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 963  * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 964  */
 965 static void check_thread_timers(struct task_struct *tsk,
 966                                 struct list_head *firing)
 967 {
 968         int maxfire;
 969         struct list_head *timers = tsk->cpu_timers;
 970         struct signal_struct *const sig = tsk->signal;
 971
 972         maxfire = 20;
 973         tsk->it_prof_expires = cputime_zero;
 974         while (!list_empty(timers)) {
 975                 struct cpu_timer_list *t = list_first_entry(timers,
 976                                                       struct cpu_timer_list,
 977                                                       entry);
 978                 if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
 979                         tsk->it_prof_expires = t->expires.cpu;
 980                         break;
 981                 }
 982                 t->firing = 1;
 983                 list_move_tail(&t->entry, firing);
 984         }
 985
 986         ++timers;
 987         maxfire = 20;
 988         tsk->it_virt_expires = cputime_zero;
 989         while (!list_empty(timers)) {
 990                 struct cpu_timer_list *t = list_first_entry(timers,
 991                                                       struct cpu_timer_list,
 992                                                       entry);
 993                 if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
 994                         tsk->it_virt_expires = t->expires.cpu;
 995                         break;
 996                 }
 997                 t->firing = 1;
 998                 list_move_tail(&t->entry, firing);
 999         }
1000
1001         ++timers;
1002         maxfire = 20;
1003         tsk->it_sched_expires = 0;
1004         while (!list_empty(timers)) {
1005                 struct cpu_timer_list *t = list_first_entry(timers,
1006                                                       struct cpu_timer_list,
1007                                                       entry);
1008                 if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
1009                         tsk->it_sched_expires = t->expires.sched;
1010                         break;
1011                 }
1012                 t->firing = 1;
1013                 list_move_tail(&t->entry, firing);
1014         }
1015
1016         /*
1017          * Check for the special case thread timers.
1018          */
1019         if (sig->rlim[RLIMIT_RTTIME].rlim_cur != RLIM_INFINITY) {
1020                 unsigned long hard = sig->rlim[RLIMIT_RTTIME].rlim_max;
1021                 unsigned long *soft = &sig->rlim[RLIMIT_RTTIME].rlim_cur;
1022
1023                 if (hard != RLIM_INFINITY &&
1024                     tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
1025                         /*
1026                          * At the hard limit, we just die.
1027                          * No need to calculate anything else now.
1028                          */
1029                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1030                         return;
1031                 }
1032                 if (tsk->rt.timeout > DIV_ROUND_UP(*soft, USEC_PER_SEC/HZ)) {
1033                         /*
1034                          * At the soft limit, send a SIGXCPU every second.
1035                          */
1036                         if (sig->rlim[RLIMIT_RTTIME].rlim_cur
1037                             < sig->rlim[RLIMIT_RTTIME].rlim_max) {
1038                                 sig->rlim[RLIMIT_RTTIME].rlim_cur +=
1039                                                                 USEC_PER_SEC;
1040                         }
1041                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1042                 }
1043         }
1044 }
1045
1046 /*
1047  * Check for any per-thread CPU timers that have fired and move them
1048  * off the tsk->*_timers list onto the firing list.  Per-thread timers
1049  * have already been taken off.
1050  */
1051 static void check_process_timers(struct task_struct *tsk,
1052                                  struct list_head *firing)
1053 {
1054         int maxfire;
1055         struct signal_struct *const sig = tsk->signal;
1056         cputime_t utime, stime, ptime, virt_expires, prof_expires;
1057         unsigned long long sum_sched_runtime, sched_expires;
1058         struct task_struct *t;
1059         struct list_head *timers = sig->cpu_timers;
1060
1061         /*
1062          * Don't sample the current process CPU clocks if there are no timers.
1063          */
1064         if (list_empty(&timers[CPUCLOCK_PROF]) &&
1065             cputime_eq(sig->it_prof_expires, cputime_zero) &&
1066             sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
1067             list_empty(&timers[CPUCLOCK_VIRT]) &&
1068             cputime_eq(sig->it_virt_expires, cputime_zero) &&
1069             list_empty(&timers[CPUCLOCK_SCHED]))
1070                 return;
1071
1072         /*
1073          * Collect the current process totals.
1074          */
1075         utime = sig->utime;
1076         stime = sig->stime;
1077         sum_sched_runtime = sig->sum_sched_runtime;
1078         t = tsk;
1079         do {
1080                 utime = cputime_add(utime, t->utime);
1081                 stime = cputime_add(stime, t->stime);
1082                 sum_sched_runtime += t->se.sum_exec_runtime;
1083                 t = next_thread(t);
1084         } while (t != tsk);
1085         ptime = cputime_add(utime, stime);
1086
1087         maxfire = 20;
1088         prof_expires = cputime_zero;
1089         while (!list_empty(timers)) {
1090                 struct cpu_timer_list *t = list_first_entry(timers,
1091                                                       struct cpu_timer_list,
1092                                                       entry);
1093                 if (!--maxfire || cputime_lt(ptime, t->expires.cpu)) {
1094                         prof_expires = t->expires.cpu;
1095                         break;
1096                 }
1097                 t->firing = 1;
1098                 list_move_tail(&t->entry, firing);
1099         }
1100
1101         ++timers;
1102         maxfire = 20;
1103         virt_expires = cputime_zero;
1104         while (!list_empty(timers)) {
1105                 struct cpu_timer_list *t = list_first_entry(timers,
1106                                                       struct cpu_timer_list,
1107                                                       entry);
1108                 if (!--maxfire || cputime_lt(utime, t->expires.cpu)) {
1109                         virt_expires = t->expires.cpu;
1110                         break;
1111                 }
1112                 t->firing = 1;
1113                 list_move_tail(&t->entry, firing);
1114         }
1115
1116         ++timers;
1117         maxfire = 20;
1118         sched_expires = 0;
1119         while (!list_empty(timers)) {
1120                 struct cpu_timer_list *t = list_first_entry(timers,
1121                                                       struct cpu_timer_list,
1122                                                       entry);
1123                 if (!--maxfire || sum_sched_runtime < t->expires.sched) {
1124                         sched_expires = t->expires.sched;
1125                         break;
1126                 }
1127                 t->firing = 1;
1128                 list_move_tail(&t->entry, firing);
1129         }
1130
1131         /*
1132          * Check for the special case process timers.
1133          */
1134         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1135                 if (cputime_ge(ptime, sig->it_prof_expires)) {
1136                         /* ITIMER_PROF fires and reloads.  */
1137                         sig->it_prof_expires = sig->it_prof_incr;
1138                         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1139                                 sig->it_prof_expires = cputime_add(
1140                                         sig->it_prof_expires, ptime);
1141                         }
1142                         __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
1143                 }
1144                 if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
1145                     (cputime_eq(prof_expires, cputime_zero) ||
1146                      cputime_lt(sig->it_prof_expires, prof_expires))) {
1147                         prof_expires = sig->it_prof_expires;
1148                 }
1149         }
1150         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1151                 if (cputime_ge(utime, sig->it_virt_expires)) {
1152                         /* ITIMER_VIRTUAL fires and reloads.  */
1153                         sig->it_virt_expires = sig->it_virt_incr;
1154                         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1155                                 sig->it_virt_expires = cputime_add(
1156                                         sig->it_virt_expires, utime);
1157                         }
1158                         __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
1159                 }
1160                 if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
1161                     (cputime_eq(virt_expires, cputime_zero) ||
1162                      cputime_lt(sig->it_virt_expires, virt_expires))) {
1163                         virt_expires = sig->it_virt_expires;
1164                 }
1165         }
1166         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
1167                 unsigned long psecs = cputime_to_secs(ptime);
1168                 cputime_t x;
1169                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
1170                         /*
1171                          * At the hard limit, we just die.
1172                          * No need to calculate anything else now.
1173                          */
1174                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1175                         return;
1176                 }
1177                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
1178                         /*
1179                          * At the soft limit, send a SIGXCPU every second.
1180                          */
1181                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1182                         if (sig->rlim[RLIMIT_CPU].rlim_cur
1183                             < sig->rlim[RLIMIT_CPU].rlim_max) {
1184                                 sig->rlim[RLIMIT_CPU].rlim_cur++;
1185                         }
1186                 }
1187                 x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
1188                 if (cputime_eq(prof_expires, cputime_zero) ||
1189                     cputime_lt(x, prof_expires)) {
1190                         prof_expires = x;
1191                 }
1192         }
1193
1194         if (!cputime_eq(prof_expires, cputime_zero) ||
1195             !cputime_eq(virt_expires, cputime_zero) ||
1196             sched_expires != 0) {
1197                 /*
1198                  * Rebalance the threads' expiry times for the remaining
1199                  * process CPU timers.
1200                  */
1201
1202                 cputime_t prof_left, virt_left, ticks;
1203                 unsigned long long sched_left, sched;
1204                 const unsigned int nthreads = atomic_read(&sig->live);
1205
1206                 if (!nthreads)
1207                         return;
1208
1209                 prof_left = cputime_sub(prof_expires, utime);
1210                 prof_left = cputime_sub(prof_left, stime);
1211                 prof_left = cputime_div_non_zero(prof_left, nthreads);
1212                 virt_left = cputime_sub(virt_expires, utime);
1213                 virt_left = cputime_div_non_zero(virt_left, nthreads);
1214                 if (sched_expires) {
1215                         sched_left = sched_expires - sum_sched_runtime;
1216                         do_div(sched_left, nthreads);
1217                         sched_left = max_t(unsigned long long, sched_left, 1);
1218                 } else {
1219                         sched_left = 0;
1220                 }
1221                 t = tsk;
1222                 do {
1223                         if (unlikely(t->flags & PF_EXITING))
1224                                 continue;
1225
1226                         ticks = cputime_add(cputime_add(t->utime, t->stime),
1227                                             prof_left);
1228                         if (!cputime_eq(prof_expires, cputime_zero) &&
1229                             (cputime_eq(t->it_prof_expires, cputime_zero) ||
1230                              cputime_gt(t->it_prof_expires, ticks))) {
1231                                 t->it_prof_expires = ticks;
1232                         }
1233
1234                         ticks = cputime_add(t->utime, virt_left);
1235                         if (!cputime_eq(virt_expires, cputime_zero) &&
1236                             (cputime_eq(t->it_virt_expires, cputime_zero) ||
1237                              cputime_gt(t->it_virt_expires, ticks))) {
1238                                 t->it_virt_expires = ticks;
1239                         }
1240
1241                         sched = t->se.sum_exec_runtime + sched_left;
1242                         if (sched_expires && (t->it_sched_expires == 0 ||
1243                                               t->it_sched_expires > sched)) {
1244                                 t->it_sched_expires = sched;
1245                         }
1246                 } while ((t = next_thread(t)) != tsk);
1247         }
1248 }
1249
1250 /*
1251  * This is called from the signal code (via do_schedule_next_timer)
1252  * when the last timer signal was delivered and we have to reload the timer.
1253  */
1254 void posix_cpu_timer_schedule(struct k_itimer *timer)
1255 {
1256         struct task_struct *p = timer->it.cpu.task;
1257         union cpu_time_count now;
1258
1259         if (unlikely(p == NULL))
1260                 /*
1261                  * The task was cleaned up already, no future firings.
1262                  */
1263                 goto out;
1264
1265         /*
1266          * Fetch the current sample and update the timer's expiry time.
1267          */
1268         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1269                 cpu_clock_sample(timer->it_clock, p, &now);
1270                 bump_cpu_timer(timer, now);
1271                 if (unlikely(p->exit_state)) {
1272                         clear_dead_task(timer, now);
1273                         goto out;
1274                 }
1275                 read_lock(&tasklist_lock); /* arm_timer needs it.  */
1276         } else {
1277                 read_lock(&tasklist_lock);
1278                 if (unlikely(p->signal == NULL)) {
1279                         /*
1280                          * The process has been reaped.
1281                          * We can't even collect a sample any more.
1282                          */
1283                         put_task_struct(p);
1284                         timer->it.cpu.task = p = NULL;
1285                         timer->it.cpu.expires.sched = 0;
1286                         goto out_unlock;
1287                 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1288                         /*
1289                          * We've noticed that the thread is dead, but
1290                          * not yet reaped.  Take this opportunity to
1291                          * drop our task ref.
1292                          */
1293                         clear_dead_task(timer, now);
1294                         goto out_unlock;
1295                 }
1296                 cpu_clock_sample_group(timer->it_clock, p, &now);
1297                 bump_cpu_timer(timer, now);
1298                 /* Leave the tasklist_lock locked for the call below.  */
1299         }
1300
1301         /*
1302          * Now re-arm for the new expiry time.
1303          */
1304         arm_timer(timer, now);
1305
1306 out_unlock:
1307         read_unlock(&tasklist_lock);
1308
1309 out:
1310         timer->it_overrun_last = timer->it_overrun;
1311         timer->it_overrun = -1;
1312         ++timer->it_requeue_pending;
1313 }
1314
1315 /*
1316  * This is called from the timer interrupt handler.  The irq handler has
1317  * already updated our counts.  We need to check if any timers fire now.
1318  * Interrupts are disabled.
1319  */
1320 void run_posix_cpu_timers(struct task_struct *tsk)
1321 {
1322         LIST_HEAD(firing);
1323         struct k_itimer *timer, *next;
1324
1325         BUG_ON(!irqs_disabled());
1326
1327 #define UNEXPIRED(clock) \
1328                 (cputime_eq(tsk->it_##clock##_expires, cputime_zero) || \
1329                  cputime_lt(clock##_ticks(tsk), tsk->it_##clock##_expires))
1330
1331         if (UNEXPIRED(prof) && UNEXPIRED(virt) &&
1332             (tsk->it_sched_expires == 0 ||
1333              tsk->se.sum_exec_runtime < tsk->it_sched_expires))
1334                 return;
1335
1336 #undef  UNEXPIRED
1337
1338         /*
1339          * Double-check with locks held.
1340          */
1341         read_lock(&tasklist_lock);
1342         if (likely(tsk->signal != NULL)) {
1343                 spin_lock(&tsk->sighand->siglock);
1344
1345                 /*
1346                  * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
1347                  * all the timers that are firing, and put them on the firing list.
1348                  */
1349                 check_thread_timers(tsk, &firing);
1350                 check_process_timers(tsk, &firing);
1351
1352                 /*
1353                  * We must release these locks before taking any timer's lock.
1354                  * There is a potential race with timer deletion here, as the
1355                  * siglock now protects our private firing list.  We have set
1356                  * the firing flag in each timer, so that a deletion attempt
1357                  * that gets the timer lock before we do will give it up and
1358                  * spin until we've taken care of that timer below.
1359                  */
1360                 spin_unlock(&tsk->sighand->siglock);
1361         }
1362         read_unlock(&tasklist_lock);
1363
1364         /*
1365          * Now that all the timers on our list have the firing flag,
1366          * noone will touch their list entries but us.  We'll take
1367          * each timer's lock before clearing its firing flag, so no
1368          * timer call will interfere.
1369          */
1370         list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1371                 int firing;
1372                 spin_lock(&timer->it_lock);
1373                 list_del_init(&timer->it.cpu.entry);
1374                 firing = timer->it.cpu.firing;
1375                 timer->it.cpu.firing = 0;
1376                 /*
1377                  * The firing flag is -1 if we collided with a reset
1378                  * of the timer, which already reported this
1379                  * almost-firing as an overrun.  So don't generate an event.
1380                  */
1381                 if (likely(firing >= 0)) {
1382                         cpu_timer_fire(timer);
1383                 }
1384                 spin_unlock(&timer->it_lock);
1385         }
1386 }
1387
1388 /*
1389  * Set one of the process-wide special case CPU timers.
1390  * The tasklist_lock and tsk->sighand->siglock must be held by the caller.
1391  * The oldval argument is null for the RLIMIT_CPU timer, where *newval is
1392  * absolute; non-null for ITIMER_*, where *newval is relative and we update
1393  * it to be absolute, *oldval is absolute and we update it to be relative.
1394  */
1395 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1396                            cputime_t *newval, cputime_t *oldval)
1397 {
1398         union cpu_time_count now;
1399         struct list_head *head;
1400
1401         BUG_ON(clock_idx == CPUCLOCK_SCHED);
1402         cpu_clock_sample_group_locked(clock_idx, tsk, &now);
1403
1404         if (oldval) {
1405                 if (!cputime_eq(*oldval, cputime_zero)) {
1406                         if (cputime_le(*oldval, now.cpu)) {
1407                                 /* Just about to fire. */
1408                                 *oldval = jiffies_to_cputime(1);
1409                         } else {
1410                                 *oldval = cputime_sub(*oldval, now.cpu);
1411                         }
1412                 }
1413
1414                 if (cputime_eq(*newval, cputime_zero))
1415                         return;
1416                 *newval = cputime_add(*newval, now.cpu);
1417
1418                 /*
1419                  * If the RLIMIT_CPU timer will expire before the
1420                  * ITIMER_PROF timer, we have nothing else to do.
1421                  */
1422                 if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
1423                     < cputime_to_secs(*newval))
1424                         return;
1425         }
1426
1427         /*
1428          * Check whether there are any process timers already set to fire
1429          * before this one.  If so, we don't have anything more to do.
1430          */
1431         head = &tsk->signal->cpu_timers[clock_idx];
1432         if (list_empty(head) ||
1433             cputime_ge(list_first_entry(head,
1434                                   struct cpu_timer_list, entry)->expires.cpu,
1435                        *newval)) {
1436                 /*
1437                  * Rejigger each thread's expiry time so that one will
1438                  * notice before we hit the process-cumulative expiry time.
1439                  */
1440                 union cpu_time_count expires = { .sched = 0 };
1441                 expires.cpu = *newval;
1442                 process_timer_rebalance(tsk, clock_idx, expires, now);
1443         }
1444 }
1445
1446 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1447                             struct timespec *rqtp, struct itimerspec *it)
1448 {
1449         struct k_itimer timer;
1450         int error;
1451
1452         /*
1453          * Set up a temporary timer and then wait for it to go off.
1454          */
1455         memset(&timer, 0, sizeof timer);
1456         spin_lock_init(&timer.it_lock);
1457         timer.it_clock = which_clock;
1458         timer.it_overrun = -1;
1459         error = posix_cpu_timer_create(&timer);
1460         timer.it_process = current;
1461         if (!error) {
1462                 static struct itimerspec zero_it;
1463
1464                 memset(it, 0, sizeof *it);
1465                 it->it_value = *rqtp;
1466
1467                 spin_lock_irq(&timer.it_lock);
1468                 error = posix_cpu_timer_set(&timer, flags, it, NULL);
1469                 if (error) {
1470                         spin_unlock_irq(&timer.it_lock);
1471                         return error;
1472                 }
1473
1474                 while (!signal_pending(current)) {
1475                         if (timer.it.cpu.expires.sched == 0) {
1476                                 /*
1477                                  * Our timer fired and was reset.
1478                                  */
1479                                 spin_unlock_irq(&timer.it_lock);
1480                                 return 0;
1481                         }
1482
1483                         /*
1484                          * Block until cpu_timer_fire (or a signal) wakes us.
1485                          */
1486                         __set_current_state(TASK_INTERRUPTIBLE);
1487                         spin_unlock_irq(&timer.it_lock);
1488                         schedule();
1489                         spin_lock_irq(&timer.it_lock);
1490                 }
1491
1492                 /*
1493                  * We were interrupted by a signal.
1494                  */
1495                 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1496                 posix_cpu_timer_set(&timer, 0, &zero_it, it);
1497                 spin_unlock_irq(&timer.it_lock);
1498
1499                 if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1500                         /*
1501                          * It actually did fire already.
1502                          */
1503                         return 0;
1504                 }
1505
1506                 error = -ERESTART_RESTARTBLOCK;
1507         }
1508
1509         return error;
1510 }
1511
1512 int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1513                      struct timespec *rqtp, struct timespec __user *rmtp)
1514 {
1515         struct restart_block *restart_block =
1516             &current_thread_info()->restart_block;
1517         struct itimerspec it;
1518         int error;
1519
1520         /*
1521          * Diagnose required errors first.
1522          */
1523         if (CPUCLOCK_PERTHREAD(which_clock) &&
1524             (CPUCLOCK_PID(which_clock) == 0 ||
1525              CPUCLOCK_PID(which_clock) == current->pid))
1526                 return -EINVAL;
1527
1528         error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1529
1530         if (error == -ERESTART_RESTARTBLOCK) {
1531
1532                 if (flags & TIMER_ABSTIME)
1533                         return -ERESTARTNOHAND;
1534                 /*
1535                  * Report back to the user the time still remaining.
1536                  */
1537                 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1538                         return -EFAULT;
1539
1540                 restart_block->fn = posix_cpu_nsleep_restart;
1541                 restart_block->arg0 = which_clock;
1542                 restart_block->arg1 = (unsigned long) rmtp;
1543                 restart_block->arg2 = rqtp->tv_sec;
1544                 restart_block->arg3 = rqtp->tv_nsec;
1545         }
1546         return error;
1547 }
1548
1549 long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1550 {
1551         clockid_t which_clock = restart_block->arg0;
1552         struct timespec __user *rmtp;
1553         struct timespec t;
1554         struct itimerspec it;
1555         int error;
1556
1557         rmtp = (struct timespec __user *) restart_block->arg1;
1558         t.tv_sec = restart_block->arg2;
1559         t.tv_nsec = restart_block->arg3;
1560
1561         restart_block->fn = do_no_restart_syscall;
1562         error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1563
1564         if (error == -ERESTART_RESTARTBLOCK) {
1565                 /*
1566                  * Report back to the user the time still remaining.
1567                  */
1568                 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1569                         return -EFAULT;
1570
1571                 restart_block->fn = posix_cpu_nsleep_restart;
1572                 restart_block->arg0 = which_clock;
1573                 restart_block->arg1 = (unsigned long) rmtp;
1574                 restart_block->arg2 = t.tv_sec;
1575                 restart_block->arg3 = t.tv_nsec;
1576         }
1577         return error;
1578
1579 }
1580
1581
1582 #define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1583 #define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1584
1585 static int process_cpu_clock_getres(const clockid_t which_clock,
1586                                     struct timespec *tp)
1587 {
1588         return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1589 }
1590 static int process_cpu_clock_get(const clockid_t which_clock,
1591                                  struct timespec *tp)
1592 {
1593         return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1594 }
1595 static int process_cpu_timer_create(struct k_itimer *timer)
1596 {
1597         timer->it_clock = PROCESS_CLOCK;
1598         return posix_cpu_timer_create(timer);
1599 }
1600 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1601                               struct timespec *rqtp,
1602                               struct timespec __user *rmtp)
1603 {
1604         return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1605 }
1606 static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1607 {
1608         return -EINVAL;
1609 }
1610 static int thread_cpu_clock_getres(const clockid_t which_clock,
1611                                    struct timespec *tp)
1612 {
1613         return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1614 }
1615 static int thread_cpu_clock_get(const clockid_t which_clock,
1616                                 struct timespec *tp)
1617 {
1618         return posix_cpu_clock_get(THREAD_CLOCK, tp);
1619 }
1620 static int thread_cpu_timer_create(struct k_itimer *timer)
1621 {
1622         timer->it_clock = THREAD_CLOCK;
1623         return posix_cpu_timer_create(timer);
1624 }
1625 static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
1626                               struct timespec *rqtp, struct timespec __user *rmtp)
1627 {
1628         return -EINVAL;
1629 }
1630 static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
1631 {
1632         return -EINVAL;
1633 }
1634
1635 static __init int init_posix_cpu_timers(void)
1636 {
1637         struct k_clock process = {
1638                 .clock_getres = process_cpu_clock_getres,
1639                 .clock_get = process_cpu_clock_get,
1640                 .clock_set = do_posix_clock_nosettime,
1641                 .timer_create = process_cpu_timer_create,
1642                 .nsleep = process_cpu_nsleep,
1643                 .nsleep_restart = process_cpu_nsleep_restart,
1644         };
1645         struct k_clock thread = {
1646                 .clock_getres = thread_cpu_clock_getres,
1647                 .clock_get = thread_cpu_clock_get,
1648                 .clock_set = do_posix_clock_nosettime,
1649                 .timer_create = thread_cpu_timer_create,
1650                 .nsleep = thread_cpu_nsleep,
1651                 .nsleep_restart = thread_cpu_nsleep_restart,
1652         };
1653
1654         register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1655         register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1656
1657         return 0;
1658 }
1659 __initcall(init_posix_cpu_timers);