SAFE public projects git trees. - safe/jmp/linux-2.6/blob - kernel/posix-cpu-timers.c

   1 /*
   2  * Implement CPU time clocks for the POSIX clock interface.
   3  */
   4
   5 #include <linux/sched.h>
   6 #include <linux/posix-timers.h>
   7 #include <linux/errno.h>
   8 #include <linux/math64.h>
   9 #include <asm/uaccess.h>
  10 #include <linux/kernel_stat.h>
  11
  12 /*
  13  * Called after updating RLIMIT_CPU to set timer expiration if necessary.
  14  */
  15 void update_rlimit_cpu(unsigned long rlim_new)
  16 {
  17         cputime_t cputime;
  18
  19         cputime = secs_to_cputime(rlim_new);
  20         if (cputime_eq(current->signal->it_prof_expires, cputime_zero) ||
  21             cputime_lt(current->signal->it_prof_expires, cputime)) {
  22                 spin_lock_irq(&current->sighand->siglock);
  23                 set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
  24                 spin_unlock_irq(&current->sighand->siglock);
  25         }
  26 }
  27
  28 static int check_clock(const clockid_t which_clock)
  29 {
  30         int error = 0;
  31         struct task_struct *p;
  32         const pid_t pid = CPUCLOCK_PID(which_clock);
  33
  34         if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
  35                 return -EINVAL;
  36
  37         if (pid == 0)
  38                 return 0;
  39
  40         read_lock(&tasklist_lock);
  41         p = find_task_by_vpid(pid);
  42         if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
  43                    same_thread_group(p, current) : thread_group_leader(p))) {
  44                 error = -EINVAL;
  45         }
  46         read_unlock(&tasklist_lock);
  47
  48         return error;
  49 }
  50
  51 static inline union cpu_time_count
  52 timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
  53 {
  54         union cpu_time_count ret;
  55         ret.sched = 0;          /* high half always zero when .cpu used */
  56         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  57                 ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
  58         } else {
  59                 ret.cpu = timespec_to_cputime(tp);
  60         }
  61         return ret;
  62 }
  63
  64 static void sample_to_timespec(const clockid_t which_clock,
  65                                union cpu_time_count cpu,
  66                                struct timespec *tp)
  67 {
  68         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
  69                 *tp = ns_to_timespec(cpu.sched);
  70         else
  71                 cputime_to_timespec(cpu.cpu, tp);
  72 }
  73
  74 static inline int cpu_time_before(const clockid_t which_clock,
  75                                   union cpu_time_count now,
  76                                   union cpu_time_count then)
  77 {
  78         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  79                 return now.sched < then.sched;
  80         }  else {
  81                 return cputime_lt(now.cpu, then.cpu);
  82         }
  83 }
  84 static inline void cpu_time_add(const clockid_t which_clock,
  85                                 union cpu_time_count *acc,
  86                                 union cpu_time_count val)
  87 {
  88         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  89                 acc->sched += val.sched;
  90         }  else {
  91                 acc->cpu = cputime_add(acc->cpu, val.cpu);
  92         }
  93 }
  94 static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
  95                                                 union cpu_time_count a,
  96                                                 union cpu_time_count b)
  97 {
  98         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  99                 a.sched -= b.sched;
 100         }  else {
 101                 a.cpu = cputime_sub(a.cpu, b.cpu);
 102         }
 103         return a;
 104 }
 105
 106 /*
 107  * Divide and limit the result to res >= 1
 108  *
 109  * This is necessary to prevent signal delivery starvation, when the result of
 110  * the division would be rounded down to 0.
 111  */
 112 static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
 113 {
 114         cputime_t res = cputime_div(time, div);
 115
 116         return max_t(cputime_t, res, 1);
 117 }
 118
 119 /*
 120  * Update expiry time from increment, and increase overrun count,
 121  * given the current clock sample.
 122  */
 123 static void bump_cpu_timer(struct k_itimer *timer,
 124                                   union cpu_time_count now)
 125 {
 126         int i;
 127
 128         if (timer->it.cpu.incr.sched == 0)
 129                 return;
 130
 131         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 132                 unsigned long long delta, incr;
 133
 134                 if (now.sched < timer->it.cpu.expires.sched)
 135                         return;
 136                 incr = timer->it.cpu.incr.sched;
 137                 delta = now.sched + incr - timer->it.cpu.expires.sched;
 138                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 139                 for (i = 0; incr < delta - incr; i++)
 140                         incr = incr << 1;
 141                 for (; i >= 0; incr >>= 1, i--) {
 142                         if (delta < incr)
 143                                 continue;
 144                         timer->it.cpu.expires.sched += incr;
 145                         timer->it_overrun += 1 << i;
 146                         delta -= incr;
 147                 }
 148         } else {
 149                 cputime_t delta, incr;
 150
 151                 if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
 152                         return;
 153                 incr = timer->it.cpu.incr.cpu;
 154                 delta = cputime_sub(cputime_add(now.cpu, incr),
 155                                     timer->it.cpu.expires.cpu);
 156                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 157                 for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
 158                              incr = cputime_add(incr, incr);
 159                 for (; i >= 0; incr = cputime_halve(incr), i--) {
 160                         if (cputime_lt(delta, incr))
 161                                 continue;
 162                         timer->it.cpu.expires.cpu =
 163                                 cputime_add(timer->it.cpu.expires.cpu, incr);
 164                         timer->it_overrun += 1 << i;
 165                         delta = cputime_sub(delta, incr);
 166                 }
 167         }
 168 }
 169
 170 static inline cputime_t prof_ticks(struct task_struct *p)
 171 {
 172         return cputime_add(p->utime, p->stime);
 173 }
 174 static inline cputime_t virt_ticks(struct task_struct *p)
 175 {
 176         return p->utime;
 177 }
 178
 179 int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
 180 {
 181         int error = check_clock(which_clock);
 182         if (!error) {
 183                 tp->tv_sec = 0;
 184                 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
 185                 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 186                         /*
 187                          * If sched_clock is using a cycle counter, we
 188                          * don't have any idea of its true resolution
 189                          * exported, but it is much more than 1s/HZ.
 190                          */
 191                         tp->tv_nsec = 1;
 192                 }
 193         }
 194         return error;
 195 }
 196
 197 int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
 198 {
 199         /*
 200          * You can never reset a CPU clock, but we check for other errors
 201          * in the call before failing with EPERM.
 202          */
 203         int error = check_clock(which_clock);
 204         if (error == 0) {
 205                 error = -EPERM;
 206         }
 207         return error;
 208 }
 209
 210
 211 /*
 212  * Sample a per-thread clock for the given task.
 213  */
 214 static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
 215                             union cpu_time_count *cpu)
 216 {
 217         switch (CPUCLOCK_WHICH(which_clock)) {
 218         default:
 219                 return -EINVAL;
 220         case CPUCLOCK_PROF:
 221                 cpu->cpu = prof_ticks(p);
 222                 break;
 223         case CPUCLOCK_VIRT:
 224                 cpu->cpu = virt_ticks(p);
 225                 break;
 226         case CPUCLOCK_SCHED:
 227                 cpu->sched = p->se.sum_exec_runtime + task_delta_exec(p);
 228                 break;
 229         }
 230         return 0;
 231 }
 232
 233 void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
 234 {
 235         struct sighand_struct *sighand;
 236         struct signal_struct *sig;
 237         struct task_struct *t;
 238
 239         *times = INIT_CPUTIME;
 240
 241         rcu_read_lock();
 242         sighand = rcu_dereference(tsk->sighand);
 243         if (!sighand)
 244                 goto out;
 245
 246         sig = tsk->signal;
 247
 248         t = tsk;
 249         do {
 250                 times->utime = cputime_add(times->utime, t->utime);
 251                 times->stime = cputime_add(times->stime, t->stime);
 252                 times->sum_exec_runtime += t->se.sum_exec_runtime;
 253
 254                 t = next_thread(t);
 255         } while (t != tsk);
 256
 257         times->utime = cputime_add(times->utime, sig->utime);
 258         times->stime = cputime_add(times->stime, sig->stime);
 259         times->sum_exec_runtime += sig->sum_sched_runtime;
 260 out:
 261         rcu_read_unlock();
 262 }
 263
 264 /*
 265  * Sample a process (thread group) clock for the given group_leader task.
 266  * Must be called with tasklist_lock held for reading.
 267  */
 268 static int cpu_clock_sample_group(const clockid_t which_clock,
 269                                   struct task_struct *p,
 270                                   union cpu_time_count *cpu)
 271 {
 272         struct task_cputime cputime;
 273
 274         thread_group_cputime(p, &cputime);
 275         switch (CPUCLOCK_WHICH(which_clock)) {
 276         default:
 277                 return -EINVAL;
 278         case CPUCLOCK_PROF:
 279                 cpu->cpu = cputime_add(cputime.utime, cputime.stime);
 280                 break;
 281         case CPUCLOCK_VIRT:
 282                 cpu->cpu = cputime.utime;
 283                 break;
 284         case CPUCLOCK_SCHED:
 285                 cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
 286                 break;
 287         }
 288         return 0;
 289 }
 290
 291
 292 int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 293 {
 294         const pid_t pid = CPUCLOCK_PID(which_clock);
 295         int error = -EINVAL;
 296         union cpu_time_count rtn;
 297
 298         if (pid == 0) {
 299                 /*
 300                  * Special case constant value for our own clocks.
 301                  * We don't have to do any lookup to find ourselves.
 302                  */
 303                 if (CPUCLOCK_PERTHREAD(which_clock)) {
 304                         /*
 305                          * Sampling just ourselves we can do with no locking.
 306                          */
 307                         error = cpu_clock_sample(which_clock,
 308                                                  current, &rtn);
 309                 } else {
 310                         read_lock(&tasklist_lock);
 311                         error = cpu_clock_sample_group(which_clock,
 312                                                        current, &rtn);
 313                         read_unlock(&tasklist_lock);
 314                 }
 315         } else {
 316                 /*
 317                  * Find the given PID, and validate that the caller
 318                  * should be able to see it.
 319                  */
 320                 struct task_struct *p;
 321                 rcu_read_lock();
 322                 p = find_task_by_vpid(pid);
 323                 if (p) {
 324                         if (CPUCLOCK_PERTHREAD(which_clock)) {
 325                                 if (same_thread_group(p, current)) {
 326                                         error = cpu_clock_sample(which_clock,
 327                                                                  p, &rtn);
 328                                 }
 329                         } else {
 330                                 read_lock(&tasklist_lock);
 331                                 if (thread_group_leader(p) && p->signal) {
 332                                         error =
 333                                             cpu_clock_sample_group(which_clock,
 334                                                                    p, &rtn);
 335                                 }
 336                                 read_unlock(&tasklist_lock);
 337                         }
 338                 }
 339                 rcu_read_unlock();
 340         }
 341
 342         if (error)
 343                 return error;
 344         sample_to_timespec(which_clock, rtn, tp);
 345         return 0;
 346 }
 347
 348
 349 /*
 350  * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 351  * This is called from sys_timer_create with the new timer already locked.
 352  */
 353 int posix_cpu_timer_create(struct k_itimer *new_timer)
 354 {
 355         int ret = 0;
 356         const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
 357         struct task_struct *p;
 358
 359         if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 360                 return -EINVAL;
 361
 362         INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 363         new_timer->it.cpu.incr.sched = 0;
 364         new_timer->it.cpu.expires.sched = 0;
 365
 366         read_lock(&tasklist_lock);
 367         if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
 368                 if (pid == 0) {
 369                         p = current;
 370                 } else {
 371                         p = find_task_by_vpid(pid);
 372                         if (p && !same_thread_group(p, current))
 373                                 p = NULL;
 374                 }
 375         } else {
 376                 if (pid == 0) {
 377                         p = current->group_leader;
 378                 } else {
 379                         p = find_task_by_vpid(pid);
 380                         if (p && !thread_group_leader(p))
 381                                 p = NULL;
 382                 }
 383         }
 384         new_timer->it.cpu.task = p;
 385         if (p) {
 386                 get_task_struct(p);
 387         } else {
 388                 ret = -EINVAL;
 389         }
 390         read_unlock(&tasklist_lock);
 391
 392         return ret;
 393 }
 394
 395 /*
 396  * Clean up a CPU-clock timer that is about to be destroyed.
 397  * This is called from timer deletion with the timer already locked.
 398  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 399  * and try again.  (This happens when the timer is in the middle of firing.)
 400  */
 401 int posix_cpu_timer_del(struct k_itimer *timer)
 402 {
 403         struct task_struct *p = timer->it.cpu.task;
 404         int ret = 0;
 405
 406         if (likely(p != NULL)) {
 407                 read_lock(&tasklist_lock);
 408                 if (unlikely(p->signal == NULL)) {
 409                         /*
 410                          * We raced with the reaping of the task.
 411                          * The deletion should have cleared us off the list.
 412                          */
 413                         BUG_ON(!list_empty(&timer->it.cpu.entry));
 414                 } else {
 415                         spin_lock(&p->sighand->siglock);
 416                         if (timer->it.cpu.firing)
 417                                 ret = TIMER_RETRY;
 418                         else
 419                                 list_del(&timer->it.cpu.entry);
 420                         spin_unlock(&p->sighand->siglock);
 421                 }
 422                 read_unlock(&tasklist_lock);
 423
 424                 if (!ret)
 425                         put_task_struct(p);
 426         }
 427
 428         return ret;
 429 }
 430
 431 /*
 432  * Clean out CPU timers still ticking when a thread exited.  The task
 433  * pointer is cleared, and the expiry time is replaced with the residual
 434  * time for later timer_gettime calls to return.
 435  * This must be called with the siglock held.
 436  */
 437 static void cleanup_timers(struct list_head *head,
 438                            cputime_t utime, cputime_t stime,
 439                            unsigned long long sum_exec_runtime)
 440 {
 441         struct cpu_timer_list *timer, *next;
 442         cputime_t ptime = cputime_add(utime, stime);
 443
 444         list_for_each_entry_safe(timer, next, head, entry) {
 445                 list_del_init(&timer->entry);
 446                 if (cputime_lt(timer->expires.cpu, ptime)) {
 447                         timer->expires.cpu = cputime_zero;
 448                 } else {
 449                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
 450                                                          ptime);
 451                 }
 452         }
 453
 454         ++head;
 455         list_for_each_entry_safe(timer, next, head, entry) {
 456                 list_del_init(&timer->entry);
 457                 if (cputime_lt(timer->expires.cpu, utime)) {
 458                         timer->expires.cpu = cputime_zero;
 459                 } else {
 460                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
 461                                                          utime);
 462                 }
 463         }
 464
 465         ++head;
 466         list_for_each_entry_safe(timer, next, head, entry) {
 467                 list_del_init(&timer->entry);
 468                 if (timer->expires.sched < sum_exec_runtime) {
 469                         timer->expires.sched = 0;
 470                 } else {
 471                         timer->expires.sched -= sum_exec_runtime;
 472                 }
 473         }
 474 }
 475
 476 /*
 477  * These are both called with the siglock held, when the current thread
 478  * is being reaped.  When the final (leader) thread in the group is reaped,
 479  * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 480  */
 481 void posix_cpu_timers_exit(struct task_struct *tsk)
 482 {
 483         cleanup_timers(tsk->cpu_timers,
 484                        tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
 485
 486 }
 487 void posix_cpu_timers_exit_group(struct task_struct *tsk)
 488 {
 489         struct task_cputime cputime;
 490
 491         thread_group_cputimer(tsk, &cputime);
 492         cleanup_timers(tsk->signal->cpu_timers,
 493                        cputime.utime, cputime.stime, cputime.sum_exec_runtime);
 494 }
 495
 496 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 497 {
 498         /*
 499          * That's all for this thread or process.
 500          * We leave our residual in expires to be reported.
 501          */
 502         put_task_struct(timer->it.cpu.task);
 503         timer->it.cpu.task = NULL;
 504         timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
 505                                              timer->it.cpu.expires,
 506                                              now);
 507 }
 508
 509 /*
 510  * Insert the timer on the appropriate list before any timers that
 511  * expire later.  This must be called with the tasklist_lock held
 512  * for reading, and interrupts disabled.
 513  */
 514 static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 515 {
 516         struct task_struct *p = timer->it.cpu.task;
 517         struct list_head *head, *listpos;
 518         struct cpu_timer_list *const nt = &timer->it.cpu;
 519         struct cpu_timer_list *next;
 520         unsigned long i;
 521
 522         head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
 523                 p->cpu_timers : p->signal->cpu_timers);
 524         head += CPUCLOCK_WHICH(timer->it_clock);
 525
 526         BUG_ON(!irqs_disabled());
 527         spin_lock(&p->sighand->siglock);
 528
 529         listpos = head;
 530         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 531                 list_for_each_entry(next, head, entry) {
 532                         if (next->expires.sched > nt->expires.sched)
 533                                 break;
 534                         listpos = &next->entry;
 535                 }
 536         } else {
 537                 list_for_each_entry(next, head, entry) {
 538                         if (cputime_gt(next->expires.cpu, nt->expires.cpu))
 539                                 break;
 540                         listpos = &next->entry;
 541                 }
 542         }
 543         list_add(&nt->entry, listpos);
 544
 545         if (listpos == head) {
 546                 /*
 547                  * We are the new earliest-expiring timer.
 548                  * If we are a thread timer, there can always
 549                  * be a process timer telling us to stop earlier.
 550                  */
 551
 552                 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 553                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
 554                         default:
 555                                 BUG();
 556                         case CPUCLOCK_PROF:
 557                                 if (cputime_eq(p->cputime_expires.prof_exp,
 558                                                cputime_zero) ||
 559                                     cputime_gt(p->cputime_expires.prof_exp,
 560                                                nt->expires.cpu))
 561                                         p->cputime_expires.prof_exp =
 562                                                 nt->expires.cpu;
 563                                 break;
 564                         case CPUCLOCK_VIRT:
 565                                 if (cputime_eq(p->cputime_expires.virt_exp,
 566                                                cputime_zero) ||
 567                                     cputime_gt(p->cputime_expires.virt_exp,
 568                                                nt->expires.cpu))
 569                                         p->cputime_expires.virt_exp =
 570                                                 nt->expires.cpu;
 571                                 break;
 572                         case CPUCLOCK_SCHED:
 573                                 if (p->cputime_expires.sched_exp == 0 ||
 574                                     p->cputime_expires.sched_exp >
 575                                                         nt->expires.sched)
 576                                         p->cputime_expires.sched_exp =
 577                                                 nt->expires.sched;
 578                                 break;
 579                         }
 580                 } else {
 581                         /*
 582                          * For a process timer, set the cached expiration time.
 583                          */
 584                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
 585                         default:
 586                                 BUG();
 587                         case CPUCLOCK_VIRT:
 588                                 if (!cputime_eq(p->signal->it_virt_expires,
 589                                                 cputime_zero) &&
 590                                     cputime_lt(p->signal->it_virt_expires,
 591                                                timer->it.cpu.expires.cpu))
 592                                         break;
 593                                 p->signal->cputime_expires.virt_exp =
 594                                         timer->it.cpu.expires.cpu;
 595                                 break;
 596                         case CPUCLOCK_PROF:
 597                                 if (!cputime_eq(p->signal->it_prof_expires,
 598                                                 cputime_zero) &&
 599                                     cputime_lt(p->signal->it_prof_expires,
 600                                                timer->it.cpu.expires.cpu))
 601                                         break;
 602                                 i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
 603                                 if (i != RLIM_INFINITY &&
 604                                     i <= cputime_to_secs(timer->it.cpu.expires.cpu))
 605                                         break;
 606                                 p->signal->cputime_expires.prof_exp =
 607                                         timer->it.cpu.expires.cpu;
 608                                 break;
 609                         case CPUCLOCK_SCHED:
 610                                 p->signal->cputime_expires.sched_exp =
 611                                         timer->it.cpu.expires.sched;
 612                                 break;
 613                         }
 614                 }
 615         }
 616
 617         spin_unlock(&p->sighand->siglock);
 618 }
 619
 620 /*
 621  * The timer is locked, fire it and arrange for its reload.
 622  */
 623 static void cpu_timer_fire(struct k_itimer *timer)
 624 {
 625         if (unlikely(timer->sigq == NULL)) {
 626                 /*
 627                  * This a special case for clock_nanosleep,
 628                  * not a normal timer from sys_timer_create.
 629                  */
 630                 wake_up_process(timer->it_process);
 631                 timer->it.cpu.expires.sched = 0;
 632         } else if (timer->it.cpu.incr.sched == 0) {
 633                 /*
 634                  * One-shot timer.  Clear it as soon as it's fired.
 635                  */
 636                 posix_timer_event(timer, 0);
 637                 timer->it.cpu.expires.sched = 0;
 638         } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 639                 /*
 640                  * The signal did not get queued because the signal
 641                  * was ignored, so we won't get any callback to
 642                  * reload the timer.  But we need to keep it
 643                  * ticking in case the signal is deliverable next time.
 644                  */
 645                 posix_cpu_timer_schedule(timer);
 646         }
 647 }
 648
 649 /*
 650  * Guts of sys_timer_settime for CPU timers.
 651  * This is called with the timer locked and interrupts disabled.
 652  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 653  * and try again.  (This happens when the timer is in the middle of firing.)
 654  */
 655 int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 656                         struct itimerspec *new, struct itimerspec *old)
 657 {
 658         struct task_struct *p = timer->it.cpu.task;
 659         union cpu_time_count old_expires, new_expires, val;
 660         int ret;
 661
 662         if (unlikely(p == NULL)) {
 663                 /*
 664                  * Timer refers to a dead task's clock.
 665                  */
 666                 return -ESRCH;
 667         }
 668
 669         new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
 670
 671         read_lock(&tasklist_lock);
 672         /*
 673          * We need the tasklist_lock to protect against reaping that
 674          * clears p->signal.  If p has just been reaped, we can no
 675          * longer get any information about it at all.
 676          */
 677         if (unlikely(p->signal == NULL)) {
 678                 read_unlock(&tasklist_lock);
 679                 put_task_struct(p);
 680                 timer->it.cpu.task = NULL;
 681                 return -ESRCH;
 682         }
 683
 684         /*
 685          * Disarm any old timer after extracting its expiry time.
 686          */
 687         BUG_ON(!irqs_disabled());
 688
 689         ret = 0;
 690         spin_lock(&p->sighand->siglock);
 691         old_expires = timer->it.cpu.expires;
 692         if (unlikely(timer->it.cpu.firing)) {
 693                 timer->it.cpu.firing = -1;
 694                 ret = TIMER_RETRY;
 695         } else
 696                 list_del_init(&timer->it.cpu.entry);
 697         spin_unlock(&p->sighand->siglock);
 698
 699         /*
 700          * We need to sample the current value to convert the new
 701          * value from to relative and absolute, and to convert the
 702          * old value from absolute to relative.  To set a process
 703          * timer, we need a sample to balance the thread expiry
 704          * times (in arm_timer).  With an absolute time, we must
 705          * check if it's already passed.  In short, we need a sample.
 706          */
 707         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 708                 cpu_clock_sample(timer->it_clock, p, &val);
 709         } else {
 710                 cpu_clock_sample_group(timer->it_clock, p, &val);
 711         }
 712
 713         if (old) {
 714                 if (old_expires.sched == 0) {
 715                         old->it_value.tv_sec = 0;
 716                         old->it_value.tv_nsec = 0;
 717                 } else {
 718                         /*
 719                          * Update the timer in case it has
 720                          * overrun already.  If it has,
 721                          * we'll report it as having overrun
 722                          * and with the next reloaded timer
 723                          * already ticking, though we are
 724                          * swallowing that pending
 725                          * notification here to install the
 726                          * new setting.
 727                          */
 728                         bump_cpu_timer(timer, val);
 729                         if (cpu_time_before(timer->it_clock, val,
 730                                             timer->it.cpu.expires)) {
 731                                 old_expires = cpu_time_sub(
 732                                         timer->it_clock,
 733                                         timer->it.cpu.expires, val);
 734                                 sample_to_timespec(timer->it_clock,
 735                                                    old_expires,
 736                                                    &old->it_value);
 737                         } else {
 738                                 old->it_value.tv_nsec = 1;
 739                                 old->it_value.tv_sec = 0;
 740                         }
 741                 }
 742         }
 743
 744         if (unlikely(ret)) {
 745                 /*
 746                  * We are colliding with the timer actually firing.
 747                  * Punt after filling in the timer's old value, and
 748                  * disable this firing since we are already reporting
 749                  * it as an overrun (thanks to bump_cpu_timer above).
 750                  */
 751                 read_unlock(&tasklist_lock);
 752                 goto out;
 753         }
 754
 755         if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
 756                 cpu_time_add(timer->it_clock, &new_expires, val);
 757         }
 758
 759         /*
 760          * Install the new expiry time (or zero).
 761          * For a timer with no notification action, we don't actually
 762          * arm the timer (we'll just fake it for timer_gettime).
 763          */
 764         timer->it.cpu.expires = new_expires;
 765         if (new_expires.sched != 0 &&
 766             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 767             cpu_time_before(timer->it_clock, val, new_expires)) {
 768                 arm_timer(timer, val);
 769         }
 770
 771         read_unlock(&tasklist_lock);
 772
 773         /*
 774          * Install the new reload setting, and
 775          * set up the signal and overrun bookkeeping.
 776          */
 777         timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
 778                                                 &new->it_interval);
 779
 780         /*
 781          * This acts as a modification timestamp for the timer,
 782          * so any automatic reload attempt will punt on seeing
 783          * that we have reset the timer manually.
 784          */
 785         timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 786                 ~REQUEUE_PENDING;
 787         timer->it_overrun_last = 0;
 788         timer->it_overrun = -1;
 789
 790         if (new_expires.sched != 0 &&
 791             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 792             !cpu_time_before(timer->it_clock, val, new_expires)) {
 793                 /*
 794                  * The designated time already passed, so we notify
 795                  * immediately, even if the thread never runs to
 796                  * accumulate more time on this clock.
 797                  */
 798                 cpu_timer_fire(timer);
 799         }
 800
 801         ret = 0;
 802  out:
 803         if (old) {
 804                 sample_to_timespec(timer->it_clock,
 805                                    timer->it.cpu.incr, &old->it_interval);
 806         }
 807         return ret;
 808 }
 809
 810 void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 811 {
 812         union cpu_time_count now;
 813         struct task_struct *p = timer->it.cpu.task;
 814         int clear_dead;
 815
 816         /*
 817          * Easy part: convert the reload time.
 818          */
 819         sample_to_timespec(timer->it_clock,
 820                            timer->it.cpu.incr, &itp->it_interval);
 821
 822         if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
 823                 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 824                 return;
 825         }
 826
 827         if (unlikely(p == NULL)) {
 828                 /*
 829                  * This task already died and the timer will never fire.
 830                  * In this case, expires is actually the dead value.
 831                  */
 832         dead:
 833                 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
 834                                    &itp->it_value);
 835                 return;
 836         }
 837
 838         /*
 839          * Sample the clock to take the difference with the expiry time.
 840          */
 841         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 842                 cpu_clock_sample(timer->it_clock, p, &now);
 843                 clear_dead = p->exit_state;
 844         } else {
 845                 read_lock(&tasklist_lock);
 846                 if (unlikely(p->signal == NULL)) {
 847                         /*
 848                          * The process has been reaped.
 849                          * We can't even collect a sample any more.
 850                          * Call the timer disarmed, nothing else to do.
 851                          */
 852                         put_task_struct(p);
 853                         timer->it.cpu.task = NULL;
 854                         timer->it.cpu.expires.sched = 0;
 855                         read_unlock(&tasklist_lock);
 856                         goto dead;
 857                 } else {
 858                         cpu_clock_sample_group(timer->it_clock, p, &now);
 859                         clear_dead = (unlikely(p->exit_state) &&
 860                                       thread_group_empty(p));
 861                 }
 862                 read_unlock(&tasklist_lock);
 863         }
 864
 865         if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 866                 if (timer->it.cpu.incr.sched == 0 &&
 867                     cpu_time_before(timer->it_clock,
 868                                     timer->it.cpu.expires, now)) {
 869                         /*
 870                          * Do-nothing timer expired and has no reload,
 871                          * so it's as if it was never set.
 872                          */
 873                         timer->it.cpu.expires.sched = 0;
 874                         itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 875                         return;
 876                 }
 877                 /*
 878                  * Account for any expirations and reloads that should
 879                  * have happened.
 880                  */
 881                 bump_cpu_timer(timer, now);
 882         }
 883
 884         if (unlikely(clear_dead)) {
 885                 /*
 886                  * We've noticed that the thread is dead, but
 887                  * not yet reaped.  Take this opportunity to
 888                  * drop our task ref.
 889                  */
 890                 clear_dead_task(timer, now);
 891                 goto dead;
 892         }
 893
 894         if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
 895                 sample_to_timespec(timer->it_clock,
 896                                    cpu_time_sub(timer->it_clock,
 897                                                 timer->it.cpu.expires, now),
 898                                    &itp->it_value);
 899         } else {
 900                 /*
 901                  * The timer should have expired already, but the firing
 902                  * hasn't taken place yet.  Say it's just about to expire.
 903                  */
 904                 itp->it_value.tv_nsec = 1;
 905                 itp->it_value.tv_sec = 0;
 906         }
 907 }
 908
 909 /*
 910  * Check for any per-thread CPU timers that have fired and move them off
 911  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 912  * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 913  */
 914 static void check_thread_timers(struct task_struct *tsk,
 915                                 struct list_head *firing)
 916 {
 917         int maxfire;
 918         struct list_head *timers = tsk->cpu_timers;
 919         struct signal_struct *const sig = tsk->signal;
 920
 921         maxfire = 20;
 922         tsk->cputime_expires.prof_exp = cputime_zero;
 923         while (!list_empty(timers)) {
 924                 struct cpu_timer_list *t = list_first_entry(timers,
 925                                                       struct cpu_timer_list,
 926                                                       entry);
 927                 if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
 928                         tsk->cputime_expires.prof_exp = t->expires.cpu;
 929                         break;
 930                 }
 931                 t->firing = 1;
 932                 list_move_tail(&t->entry, firing);
 933         }
 934
 935         ++timers;
 936         maxfire = 20;
 937         tsk->cputime_expires.virt_exp = cputime_zero;
 938         while (!list_empty(timers)) {
 939                 struct cpu_timer_list *t = list_first_entry(timers,
 940                                                       struct cpu_timer_list,
 941                                                       entry);
 942                 if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
 943                         tsk->cputime_expires.virt_exp = t->expires.cpu;
 944                         break;
 945                 }
 946                 t->firing = 1;
 947                 list_move_tail(&t->entry, firing);
 948         }
 949
 950         ++timers;
 951         maxfire = 20;
 952         tsk->cputime_expires.sched_exp = 0;
 953         while (!list_empty(timers)) {
 954                 struct cpu_timer_list *t = list_first_entry(timers,
 955                                                       struct cpu_timer_list,
 956                                                       entry);
 957                 if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
 958                         tsk->cputime_expires.sched_exp = t->expires.sched;
 959                         break;
 960                 }
 961                 t->firing = 1;
 962                 list_move_tail(&t->entry, firing);
 963         }
 964
 965         /*
 966          * Check for the special case thread timers.
 967          */
 968         if (sig->rlim[RLIMIT_RTTIME].rlim_cur != RLIM_INFINITY) {
 969                 unsigned long hard = sig->rlim[RLIMIT_RTTIME].rlim_max;
 970                 unsigned long *soft = &sig->rlim[RLIMIT_RTTIME].rlim_cur;
 971
 972                 if (hard != RLIM_INFINITY &&
 973                     tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
 974                         /*
 975                          * At the hard limit, we just die.
 976                          * No need to calculate anything else now.
 977                          */
 978                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
 979                         return;
 980                 }
 981                 if (tsk->rt.timeout > DIV_ROUND_UP(*soft, USEC_PER_SEC/HZ)) {
 982                         /*
 983                          * At the soft limit, send a SIGXCPU every second.
 984                          */
 985                         if (sig->rlim[RLIMIT_RTTIME].rlim_cur
 986                             < sig->rlim[RLIMIT_RTTIME].rlim_max) {
 987                                 sig->rlim[RLIMIT_RTTIME].rlim_cur +=
 988                                                                 USEC_PER_SEC;
 989                         }
 990                         printk(KERN_INFO
 991                                 "RT Watchdog Timeout: %s[%d]\n",
 992                                 tsk->comm, task_pid_nr(tsk));
 993                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
 994                 }
 995         }
 996 }
 997
 998 static void stop_process_timers(struct task_struct *tsk)
 999 {
1000         struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
1001         unsigned long flags;
1002
1003         if (!cputimer->running)
1004                 return;
1005
1006         spin_lock_irqsave(&cputimer->lock, flags);
1007         cputimer->running = 0;
1008         spin_unlock_irqrestore(&cputimer->lock, flags);
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, ptime, virt_expires, prof_expires;
1022         unsigned long long sum_sched_runtime, sched_expires;
1023         struct list_head *timers = sig->cpu_timers;
1024         struct task_cputime cputime;
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                 stop_process_timers(tsk);
1036                 return;
1037         }
1038
1039         /*
1040          * Collect the current process totals.
1041          */
1042         thread_group_cputimer(tsk, &cputime);
1043         utime = cputime.utime;
1044         ptime = cputime_add(utime, cputime.stime);
1045         sum_sched_runtime = cputime.sum_exec_runtime;
1046         maxfire = 20;
1047         prof_expires = cputime_zero;
1048         while (!list_empty(timers)) {
1049                 struct cpu_timer_list *tl = list_first_entry(timers,
1050                                                       struct cpu_timer_list,
1051                                                       entry);
1052                 if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
1053                         prof_expires = tl->expires.cpu;
1054                         break;
1055                 }
1056                 tl->firing = 1;
1057                 list_move_tail(&tl->entry, firing);
1058         }
1059
1060         ++timers;
1061         maxfire = 20;
1062         virt_expires = cputime_zero;
1063         while (!list_empty(timers)) {
1064                 struct cpu_timer_list *tl = list_first_entry(timers,
1065                                                       struct cpu_timer_list,
1066                                                       entry);
1067                 if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
1068                         virt_expires = tl->expires.cpu;
1069                         break;
1070                 }
1071                 tl->firing = 1;
1072                 list_move_tail(&tl->entry, firing);
1073         }
1074
1075         ++timers;
1076         maxfire = 20;
1077         sched_expires = 0;
1078         while (!list_empty(timers)) {
1079                 struct cpu_timer_list *tl = list_first_entry(timers,
1080                                                       struct cpu_timer_list,
1081                                                       entry);
1082                 if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
1083                         sched_expires = tl->expires.sched;
1084                         break;
1085                 }
1086                 tl->firing = 1;
1087                 list_move_tail(&tl->entry, firing);
1088         }
1089
1090         /*
1091          * Check for the special case process timers.
1092          */
1093         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1094                 if (cputime_ge(ptime, sig->it_prof_expires)) {
1095                         /* ITIMER_PROF fires and reloads.  */
1096                         sig->it_prof_expires = sig->it_prof_incr;
1097                         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1098                                 sig->it_prof_expires = cputime_add(
1099                                         sig->it_prof_expires, ptime);
1100                         }
1101                         __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
1102                 }
1103                 if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
1104                     (cputime_eq(prof_expires, cputime_zero) ||
1105                      cputime_lt(sig->it_prof_expires, prof_expires))) {
1106                         prof_expires = sig->it_prof_expires;
1107                 }
1108         }
1109         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1110                 if (cputime_ge(utime, sig->it_virt_expires)) {
1111                         /* ITIMER_VIRTUAL fires and reloads.  */
1112                         sig->it_virt_expires = sig->it_virt_incr;
1113                         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1114                                 sig->it_virt_expires = cputime_add(
1115                                         sig->it_virt_expires, utime);
1116                         }
1117                         __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
1118                 }
1119                 if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
1120                     (cputime_eq(virt_expires, cputime_zero) ||
1121                      cputime_lt(sig->it_virt_expires, virt_expires))) {
1122                         virt_expires = sig->it_virt_expires;
1123                 }
1124         }
1125         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
1126                 unsigned long psecs = cputime_to_secs(ptime);
1127                 cputime_t x;
1128                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
1129                         /*
1130                          * At the hard limit, we just die.
1131                          * No need to calculate anything else now.
1132                          */
1133                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1134                         return;
1135                 }
1136                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
1137                         /*
1138                          * At the soft limit, send a SIGXCPU every second.
1139                          */
1140                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1141                         if (sig->rlim[RLIMIT_CPU].rlim_cur
1142                             < sig->rlim[RLIMIT_CPU].rlim_max) {
1143                                 sig->rlim[RLIMIT_CPU].rlim_cur++;
1144                         }
1145                 }
1146                 x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
1147                 if (cputime_eq(prof_expires, cputime_zero) ||
1148                     cputime_lt(x, prof_expires)) {
1149                         prof_expires = x;
1150                 }
1151         }
1152
1153         if (!cputime_eq(prof_expires, cputime_zero) &&
1154             (cputime_eq(sig->cputime_expires.prof_exp, cputime_zero) ||
1155              cputime_gt(sig->cputime_expires.prof_exp, prof_expires)))
1156                 sig->cputime_expires.prof_exp = prof_expires;
1157         if (!cputime_eq(virt_expires, cputime_zero) &&
1158             (cputime_eq(sig->cputime_expires.virt_exp, cputime_zero) ||
1159              cputime_gt(sig->cputime_expires.virt_exp, virt_expires)))
1160                 sig->cputime_expires.virt_exp = virt_expires;
1161         if (sched_expires != 0 &&
1162             (sig->cputime_expires.sched_exp == 0 ||
1163              sig->cputime_expires.sched_exp > sched_expires))
1164                 sig->cputime_expires.sched_exp = sched_expires;
1165 }
1166
1167 /*
1168  * This is called from the signal code (via do_schedule_next_timer)
1169  * when the last timer signal was delivered and we have to reload the timer.
1170  */
1171 void posix_cpu_timer_schedule(struct k_itimer *timer)
1172 {
1173         struct task_struct *p = timer->it.cpu.task;
1174         union cpu_time_count now;
1175
1176         if (unlikely(p == NULL))
1177                 /*
1178                  * The task was cleaned up already, no future firings.
1179                  */
1180                 goto out;
1181
1182         /*
1183          * Fetch the current sample and update the timer's expiry time.
1184          */
1185         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1186                 cpu_clock_sample(timer->it_clock, p, &now);
1187                 bump_cpu_timer(timer, now);
1188                 if (unlikely(p->exit_state)) {
1189                         clear_dead_task(timer, now);
1190                         goto out;
1191                 }
1192                 read_lock(&tasklist_lock); /* arm_timer needs it.  */
1193         } else {
1194                 read_lock(&tasklist_lock);
1195                 if (unlikely(p->signal == NULL)) {
1196                         /*
1197                          * The process has been reaped.
1198                          * We can't even collect a sample any more.
1199                          */
1200                         put_task_struct(p);
1201                         timer->it.cpu.task = p = NULL;
1202                         timer->it.cpu.expires.sched = 0;
1203                         goto out_unlock;
1204                 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1205                         /*
1206                          * We've noticed that the thread is dead, but
1207                          * not yet reaped.  Take this opportunity to
1208                          * drop our task ref.
1209                          */
1210                         clear_dead_task(timer, now);
1211                         goto out_unlock;
1212                 }
1213                 cpu_clock_sample_group(timer->it_clock, p, &now);
1214                 bump_cpu_timer(timer, now);
1215                 /* Leave the tasklist_lock locked for the call below.  */
1216         }
1217
1218         /*
1219          * Now re-arm for the new expiry time.
1220          */
1221         arm_timer(timer, now);
1222
1223 out_unlock:
1224         read_unlock(&tasklist_lock);
1225
1226 out:
1227         timer->it_overrun_last = timer->it_overrun;
1228         timer->it_overrun = -1;
1229         ++timer->it_requeue_pending;
1230 }
1231
1232 /**
1233  * task_cputime_zero - Check a task_cputime struct for all zero fields.
1234  *
1235  * @cputime:    The struct to compare.
1236  *
1237  * Checks @cputime to see if all fields are zero.  Returns true if all fields
1238  * are zero, false if any field is nonzero.
1239  */
1240 static inline int task_cputime_zero(const struct task_cputime *cputime)
1241 {
1242         if (cputime_eq(cputime->utime, cputime_zero) &&
1243             cputime_eq(cputime->stime, cputime_zero) &&
1244             cputime->sum_exec_runtime == 0)
1245                 return 1;
1246         return 0;
1247 }
1248
1249 /**
1250  * task_cputime_expired - Compare two task_cputime entities.
1251  *
1252  * @sample:     The task_cputime structure to be checked for expiration.
1253  * @expires:    Expiration times, against which @sample will be checked.
1254  *
1255  * Checks @sample against @expires to see if any field of @sample has expired.
1256  * Returns true if any field of the former is greater than the corresponding
1257  * field of the latter if the latter field is set.  Otherwise returns false.
1258  */
1259 static inline int task_cputime_expired(const struct task_cputime *sample,
1260                                         const struct task_cputime *expires)
1261 {
1262         if (!cputime_eq(expires->utime, cputime_zero) &&
1263             cputime_ge(sample->utime, expires->utime))
1264                 return 1;
1265         if (!cputime_eq(expires->stime, cputime_zero) &&
1266             cputime_ge(cputime_add(sample->utime, sample->stime),
1267                        expires->stime))
1268                 return 1;
1269         if (expires->sum_exec_runtime != 0 &&
1270             sample->sum_exec_runtime >= expires->sum_exec_runtime)
1271                 return 1;
1272         return 0;
1273 }
1274
1275 /**
1276  * fastpath_timer_check - POSIX CPU timers fast path.
1277  *
1278  * @tsk:        The task (thread) being checked.
1279  *
1280  * Check the task and thread group timers.  If both are zero (there are no
1281  * timers set) return false.  Otherwise snapshot the task and thread group
1282  * timers and compare them with the corresponding expiration times.  Return
1283  * true if a timer has expired, else return false.
1284  */
1285 static inline int fastpath_timer_check(struct task_struct *tsk)
1286 {
1287         struct signal_struct *sig;
1288
1289         /* tsk == current, ensure it is safe to use ->signal/sighand */
1290         if (unlikely(tsk->exit_state))
1291                 return 0;
1292
1293         if (!task_cputime_zero(&tsk->cputime_expires)) {
1294                 struct task_cputime task_sample = {
1295                         .utime = tsk->utime,
1296                         .stime = tsk->stime,
1297                         .sum_exec_runtime = tsk->se.sum_exec_runtime
1298                 };
1299
1300                 if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1301                         return 1;
1302         }
1303
1304         sig = tsk->signal;
1305         if (!task_cputime_zero(&sig->cputime_expires)) {
1306                 struct task_cputime group_sample;
1307
1308                 thread_group_cputimer(tsk, &group_sample);
1309                 if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1310                         return 1;
1311         }
1312         return 0;
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         /*
1328          * The fast path checks that there are no expired thread or thread
1329          * group timers.  If that's so, just return.
1330          */
1331         if (!fastpath_timer_check(tsk))
1332                 return;
1333
1334         spin_lock(&tsk->sighand->siglock);
1335         /*
1336          * Here we take off tsk->signal->cpu_timers[N] and
1337          * tsk->cpu_timers[N] all the timers that are firing, and
1338          * put them on the firing list.
1339          */
1340         check_thread_timers(tsk, &firing);
1341         check_process_timers(tsk, &firing);
1342
1343         /*
1344          * We must release these locks before taking any timer's lock.
1345          * There is a potential race with timer deletion here, as the
1346          * siglock now protects our private firing list.  We have set
1347          * the firing flag in each timer, so that a deletion attempt
1348          * that gets the timer lock before we do will give it up and
1349          * spin until we've taken care of that timer below.
1350          */
1351         spin_unlock(&tsk->sighand->siglock);
1352
1353         /*
1354          * Now that all the timers on our list have the firing flag,
1355          * noone will touch their list entries but us.  We'll take
1356          * each timer's lock before clearing its firing flag, so no
1357          * timer call will interfere.
1358          */
1359         list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1360                 int firing;
1361                 spin_lock(&timer->it_lock);
1362                 list_del_init(&timer->it.cpu.entry);
1363                 firing = timer->it.cpu.firing;
1364                 timer->it.cpu.firing = 0;
1365                 /*
1366                  * The firing flag is -1 if we collided with a reset
1367                  * of the timer, which already reported this
1368                  * almost-firing as an overrun.  So don't generate an event.
1369                  */
1370                 if (likely(firing >= 0)) {
1371                         cpu_timer_fire(timer);
1372                 }
1373                 spin_unlock(&timer->it_lock);
1374         }
1375 }
1376
1377 /*
1378  * Sample a process (thread group) timer for the given group_leader task.
1379  * Must be called with tasklist_lock held for reading.
1380  */
1381 static int cpu_timer_sample_group(const clockid_t which_clock,
1382                                   struct task_struct *p,
1383                                   union cpu_time_count *cpu)
1384 {
1385         struct task_cputime cputime;
1386
1387         thread_group_cputimer(p, &cputime);
1388         switch (CPUCLOCK_WHICH(which_clock)) {
1389         default:
1390                 return -EINVAL;
1391         case CPUCLOCK_PROF:
1392                 cpu->cpu = cputime_add(cputime.utime, cputime.stime);
1393                 break;
1394         case CPUCLOCK_VIRT:
1395                 cpu->cpu = cputime.utime;
1396                 break;
1397         case CPUCLOCK_SCHED:
1398                 cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
1399                 break;
1400         }
1401         return 0;
1402 }
1403
1404 /*
1405  * Set one of the process-wide special case CPU timers.
1406  * The tsk->sighand->siglock must be held by the caller.
1407  * The *newval argument is relative and we update it to be absolute, *oldval
1408  * is absolute and we update it to be relative.
1409  */
1410 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1411                            cputime_t *newval, cputime_t *oldval)
1412 {
1413         union cpu_time_count now;
1414         struct list_head *head;
1415
1416         BUG_ON(clock_idx == CPUCLOCK_SCHED);
1417         cpu_timer_sample_group(clock_idx, tsk, &now);
1418
1419         if (oldval) {
1420                 if (!cputime_eq(*oldval, cputime_zero)) {
1421                         if (cputime_le(*oldval, now.cpu)) {
1422                                 /* Just about to fire. */
1423                                 *oldval = jiffies_to_cputime(1);
1424                         } else {
1425                                 *oldval = cputime_sub(*oldval, now.cpu);
1426                         }
1427                 }
1428
1429                 if (cputime_eq(*newval, cputime_zero))
1430                         return;
1431                 *newval = cputime_add(*newval, now.cpu);
1432
1433                 /*
1434                  * If the RLIMIT_CPU timer will expire before the
1435                  * ITIMER_PROF timer, we have nothing else to do.
1436                  */
1437                 if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
1438                     < cputime_to_secs(*newval))
1439                         return;
1440         }
1441
1442         /*
1443          * Check whether there are any process timers already set to fire
1444          * before this one.  If so, we don't have anything more to do.
1445          */
1446         head = &tsk->signal->cpu_timers[clock_idx];
1447         if (list_empty(head) ||
1448             cputime_ge(list_first_entry(head,
1449                                   struct cpu_timer_list, entry)->expires.cpu,
1450                        *newval)) {
1451                 switch (clock_idx) {
1452                 case CPUCLOCK_PROF:
1453                         tsk->signal->cputime_expires.prof_exp = *newval;
1454                         break;
1455                 case CPUCLOCK_VIRT:
1456                         tsk->signal->cputime_expires.virt_exp = *newval;
1457                         break;
1458                 }
1459         }
1460 }
1461
1462 static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1463                             struct timespec *rqtp, struct itimerspec *it)
1464 {
1465         struct k_itimer timer;
1466         int error;
1467
1468         /*
1469          * Set up a temporary timer and then wait for it to go off.
1470          */
1471         memset(&timer, 0, sizeof timer);
1472         spin_lock_init(&timer.it_lock);
1473         timer.it_clock = which_clock;
1474         timer.it_overrun = -1;
1475         error = posix_cpu_timer_create(&timer);
1476         timer.it_process = current;
1477         if (!error) {
1478                 static struct itimerspec zero_it;
1479
1480                 memset(it, 0, sizeof *it);
1481                 it->it_value = *rqtp;
1482
1483                 spin_lock_irq(&timer.it_lock);
1484                 error = posix_cpu_timer_set(&timer, flags, it, NULL);
1485                 if (error) {
1486                         spin_unlock_irq(&timer.it_lock);
1487                         return error;
1488                 }
1489
1490                 while (!signal_pending(current)) {
1491                         if (timer.it.cpu.expires.sched == 0) {
1492                                 /*
1493                                  * Our timer fired and was reset.
1494                                  */
1495                                 spin_unlock_irq(&timer.it_lock);
1496                                 return 0;
1497                         }
1498
1499                         /*
1500                          * Block until cpu_timer_fire (or a signal) wakes us.
1501                          */
1502                         __set_current_state(TASK_INTERRUPTIBLE);
1503                         spin_unlock_irq(&timer.it_lock);
1504                         schedule();
1505                         spin_lock_irq(&timer.it_lock);
1506                 }
1507
1508                 /*
1509                  * We were interrupted by a signal.
1510                  */
1511                 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1512                 posix_cpu_timer_set(&timer, 0, &zero_it, it);
1513                 spin_unlock_irq(&timer.it_lock);
1514
1515                 if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1516                         /*
1517                          * It actually did fire already.
1518                          */
1519                         return 0;
1520                 }
1521
1522                 error = -ERESTART_RESTARTBLOCK;
1523         }
1524
1525         return error;
1526 }
1527
1528 int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1529                      struct timespec *rqtp, struct timespec __user *rmtp)
1530 {
1531         struct restart_block *restart_block =
1532             &current_thread_info()->restart_block;
1533         struct itimerspec it;
1534         int error;
1535
1536         /*
1537          * Diagnose required errors first.
1538          */
1539         if (CPUCLOCK_PERTHREAD(which_clock) &&
1540             (CPUCLOCK_PID(which_clock) == 0 ||
1541              CPUCLOCK_PID(which_clock) == current->pid))
1542                 return -EINVAL;
1543
1544         error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1545
1546         if (error == -ERESTART_RESTARTBLOCK) {
1547
1548                 if (flags & TIMER_ABSTIME)
1549                         return -ERESTARTNOHAND;
1550                 /*
1551                  * Report back to the user the time still remaining.
1552                  */
1553                 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1554                         return -EFAULT;
1555
1556                 restart_block->fn = posix_cpu_nsleep_restart;
1557                 restart_block->arg0 = which_clock;
1558                 restart_block->arg1 = (unsigned long) rmtp;
1559                 restart_block->arg2 = rqtp->tv_sec;
1560                 restart_block->arg3 = rqtp->tv_nsec;
1561         }
1562         return error;
1563 }
1564
1565 long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1566 {
1567         clockid_t which_clock = restart_block->arg0;
1568         struct timespec __user *rmtp;
1569         struct timespec t;
1570         struct itimerspec it;
1571         int error;
1572
1573         rmtp = (struct timespec __user *) restart_block->arg1;
1574         t.tv_sec = restart_block->arg2;
1575         t.tv_nsec = restart_block->arg3;
1576
1577         restart_block->fn = do_no_restart_syscall;
1578         error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1579
1580         if (error == -ERESTART_RESTARTBLOCK) {
1581                 /*
1582                  * Report back to the user the time still remaining.
1583                  */
1584                 if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1585                         return -EFAULT;
1586
1587                 restart_block->fn = posix_cpu_nsleep_restart;
1588                 restart_block->arg0 = which_clock;
1589                 restart_block->arg1 = (unsigned long) rmtp;
1590                 restart_block->arg2 = t.tv_sec;
1591                 restart_block->arg3 = t.tv_nsec;
1592         }
1593         return error;
1594
1595 }
1596
1597
1598 #define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1599 #define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1600
1601 static int process_cpu_clock_getres(const clockid_t which_clock,
1602                                     struct timespec *tp)
1603 {
1604         return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1605 }
1606 static int process_cpu_clock_get(const clockid_t which_clock,
1607                                  struct timespec *tp)
1608 {
1609         return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1610 }
1611 static int process_cpu_timer_create(struct k_itimer *timer)
1612 {
1613         timer->it_clock = PROCESS_CLOCK;
1614         return posix_cpu_timer_create(timer);
1615 }
1616 static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1617                               struct timespec *rqtp,
1618                               struct timespec __user *rmtp)
1619 {
1620         return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1621 }
1622 static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1623 {
1624         return -EINVAL;
1625 }
1626 static int thread_cpu_clock_getres(const clockid_t which_clock,
1627                                    struct timespec *tp)
1628 {
1629         return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1630 }
1631 static int thread_cpu_clock_get(const clockid_t which_clock,
1632                                 struct timespec *tp)
1633 {
1634         return posix_cpu_clock_get(THREAD_CLOCK, tp);
1635 }
1636 static int thread_cpu_timer_create(struct k_itimer *timer)
1637 {
1638         timer->it_clock = THREAD_CLOCK;
1639         return posix_cpu_timer_create(timer);
1640 }
1641 static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
1642                               struct timespec *rqtp, struct timespec __user *rmtp)
1643 {
1644         return -EINVAL;
1645 }
1646 static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
1647 {
1648         return -EINVAL;
1649 }
1650
1651 static __init int init_posix_cpu_timers(void)
1652 {
1653         struct k_clock process = {
1654                 .clock_getres = process_cpu_clock_getres,
1655                 .clock_get = process_cpu_clock_get,
1656                 .clock_set = do_posix_clock_nosettime,
1657                 .timer_create = process_cpu_timer_create,
1658                 .nsleep = process_cpu_nsleep,
1659                 .nsleep_restart = process_cpu_nsleep_restart,
1660         };
1661         struct k_clock thread = {
1662                 .clock_getres = thread_cpu_clock_getres,
1663                 .clock_get = thread_cpu_clock_get,
1664                 .clock_set = do_posix_clock_nosettime,
1665                 .timer_create = thread_cpu_timer_create,
1666                 .nsleep = thread_cpu_nsleep,
1667                 .nsleep_restart = thread_cpu_nsleep_restart,
1668         };
1669
1670         register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1671         register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1672
1673         return 0;
1674 }
1675 __initcall(init_posix_cpu_timers);