kernel/posix-cpu-timers.c

   1 /*
   2  * Implement CPU time clocks for the POSIX clock interface.
   3  */
   4
   5 #include <linux/sched.h>
   6 #include <linux/posix-timers.h>
   7 #include <asm/uaccess.h>
   8 #include <linux/errno.h>
   9
  10 static int check_clock(clockid_t which_clock)
  11 {
  12         int error = 0;
  13         struct task_struct *p;
  14         const pid_t pid = CPUCLOCK_PID(which_clock);
  15
  16         if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
  17                 return -EINVAL;
  18
  19         if (pid == 0)
  20                 return 0;
  21
  22         read_lock(&tasklist_lock);
  23         p = find_task_by_pid(pid);
  24         if (!p || (CPUCLOCK_PERTHREAD(which_clock) ?
  25                    p->tgid != current->tgid : p->tgid != pid)) {
  26                 error = -EINVAL;
  27         }
  28         read_unlock(&tasklist_lock);
  29
  30         return error;
  31 }
  32
  33 static inline union cpu_time_count
  34 timespec_to_sample(clockid_t which_clock, const struct timespec *tp)
  35 {
  36         union cpu_time_count ret;
  37         ret.sched = 0;          /* high half always zero when .cpu used */
  38         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  39                 ret.sched = tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
  40         } else {
  41                 ret.cpu = timespec_to_cputime(tp);
  42         }
  43         return ret;
  44 }
  45
  46 static void sample_to_timespec(clockid_t which_clock,
  47                                union cpu_time_count cpu,
  48                                struct timespec *tp)
  49 {
  50         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  51                 tp->tv_sec = div_long_long_rem(cpu.sched,
  52                                                NSEC_PER_SEC, &tp->tv_nsec);
  53         } else {
  54                 cputime_to_timespec(cpu.cpu, tp);
  55         }
  56 }
  57
  58 static inline int cpu_time_before(clockid_t which_clock,
  59                                   union cpu_time_count now,
  60                                   union cpu_time_count then)
  61 {
  62         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  63                 return now.sched < then.sched;
  64         }  else {
  65                 return cputime_lt(now.cpu, then.cpu);
  66         }
  67 }
  68 static inline void cpu_time_add(clockid_t which_clock,
  69                                 union cpu_time_count *acc,
  70                                 union cpu_time_count val)
  71 {
  72         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  73                 acc->sched += val.sched;
  74         }  else {
  75                 acc->cpu = cputime_add(acc->cpu, val.cpu);
  76         }
  77 }
  78 static inline union cpu_time_count cpu_time_sub(clockid_t which_clock,
  79                                                 union cpu_time_count a,
  80                                                 union cpu_time_count b)
  81 {
  82         if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
  83                 a.sched -= b.sched;
  84         }  else {
  85                 a.cpu = cputime_sub(a.cpu, b.cpu);
  86         }
  87         return a;
  88 }
  89
  90 /*
  91  * Update expiry time from increment, and increase overrun count,
  92  * given the current clock sample.
  93  */
  94 static inline void bump_cpu_timer(struct k_itimer *timer,
  95                                   union cpu_time_count now)
  96 {
  97         int i;
  98
  99         if (timer->it.cpu.incr.sched == 0)
 100                 return;
 101
 102         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 103                 unsigned long long delta, incr;
 104
 105                 if (now.sched < timer->it.cpu.expires.sched)
 106                         return;
 107                 incr = timer->it.cpu.incr.sched;
 108                 delta = now.sched + incr - timer->it.cpu.expires.sched;
 109                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 110                 for (i = 0; incr < delta - incr; i++)
 111                         incr = incr << 1;
 112                 for (; i >= 0; incr >>= 1, i--) {
 113                         if (delta <= incr)
 114                                 continue;
 115                         timer->it.cpu.expires.sched += incr;
 116                         timer->it_overrun += 1 << i;
 117                         delta -= incr;
 118                 }
 119         } else {
 120                 cputime_t delta, incr;
 121
 122                 if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
 123                         return;
 124                 incr = timer->it.cpu.incr.cpu;
 125                 delta = cputime_sub(cputime_add(now.cpu, incr),
 126                                     timer->it.cpu.expires.cpu);
 127                 /* Don't use (incr*2 < delta), incr*2 might overflow. */
 128                 for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
 129                              incr = cputime_add(incr, incr);
 130                 for (; i >= 0; incr = cputime_halve(incr), i--) {
 131                         if (cputime_le(delta, incr))
 132                                 continue;
 133                         timer->it.cpu.expires.cpu =
 134                                 cputime_add(timer->it.cpu.expires.cpu, incr);
 135                         timer->it_overrun += 1 << i;
 136                         delta = cputime_sub(delta, incr);
 137                 }
 138         }
 139 }
 140
 141 static inline cputime_t prof_ticks(struct task_struct *p)
 142 {
 143         return cputime_add(p->utime, p->stime);
 144 }
 145 static inline cputime_t virt_ticks(struct task_struct *p)
 146 {
 147         return p->utime;
 148 }
 149 static inline unsigned long long sched_ns(struct task_struct *p)
 150 {
 151         return (p == current) ? current_sched_time(p) : p->sched_time;
 152 }
 153
 154 int posix_cpu_clock_getres(clockid_t which_clock, struct timespec *tp)
 155 {
 156         int error = check_clock(which_clock);
 157         if (!error) {
 158                 tp->tv_sec = 0;
 159                 tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
 160                 if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 161                         /*
 162                          * If sched_clock is using a cycle counter, we
 163                          * don't have any idea of its true resolution
 164                          * exported, but it is much more than 1s/HZ.
 165                          */
 166                         tp->tv_nsec = 1;
 167                 }
 168         }
 169         return error;
 170 }
 171
 172 int posix_cpu_clock_set(clockid_t which_clock, const struct timespec *tp)
 173 {
 174         /*
 175          * You can never reset a CPU clock, but we check for other errors
 176          * in the call before failing with EPERM.
 177          */
 178         int error = check_clock(which_clock);
 179         if (error == 0) {
 180                 error = -EPERM;
 181         }
 182         return error;
 183 }
 184
 185
 186 /*
 187  * Sample a per-thread clock for the given task.
 188  */
 189 static int cpu_clock_sample(clockid_t which_clock, struct task_struct *p,
 190                             union cpu_time_count *cpu)
 191 {
 192         switch (CPUCLOCK_WHICH(which_clock)) {
 193         default:
 194                 return -EINVAL;
 195         case CPUCLOCK_PROF:
 196                 cpu->cpu = prof_ticks(p);
 197                 break;
 198         case CPUCLOCK_VIRT:
 199                 cpu->cpu = virt_ticks(p);
 200                 break;
 201         case CPUCLOCK_SCHED:
 202                 cpu->sched = sched_ns(p);
 203                 break;
 204         }
 205         return 0;
 206 }
 207
 208 /*
 209  * Sample a process (thread group) clock for the given group_leader task.
 210  * Must be called with tasklist_lock held for reading.
 211  * Must be called with tasklist_lock held for reading, and p->sighand->siglock.
 212  */
 213 static int cpu_clock_sample_group_locked(unsigned int clock_idx,
 214                                          struct task_struct *p,
 215                                          union cpu_time_count *cpu)
 216 {
 217         struct task_struct *t = p;
 218         switch (clock_idx) {
 219         default:
 220                 return -EINVAL;
 221         case CPUCLOCK_PROF:
 222                 cpu->cpu = cputime_add(p->signal->utime, p->signal->stime);
 223                 do {
 224                         cpu->cpu = cputime_add(cpu->cpu, prof_ticks(t));
 225                         t = next_thread(t);
 226                 } while (t != p);
 227                 break;
 228         case CPUCLOCK_VIRT:
 229                 cpu->cpu = p->signal->utime;
 230                 do {
 231                         cpu->cpu = cputime_add(cpu->cpu, virt_ticks(t));
 232                         t = next_thread(t);
 233                 } while (t != p);
 234                 break;
 235         case CPUCLOCK_SCHED:
 236                 cpu->sched = p->signal->sched_time;
 237                 /* Add in each other live thread.  */
 238                 while ((t = next_thread(t)) != p) {
 239                         cpu->sched += t->sched_time;
 240                 }
 241                 if (p->tgid == current->tgid) {
 242                         /*
 243                          * We're sampling ourselves, so include the
 244                          * cycles not yet banked.  We still omit
 245                          * other threads running on other CPUs,
 246                          * so the total can always be behind as
 247                          * much as max(nthreads-1,ncpus) * (NSEC_PER_SEC/HZ).
 248                          */
 249                         cpu->sched += current_sched_time(current);
 250                 } else {
 251                         cpu->sched += p->sched_time;
 252                 }
 253                 break;
 254         }
 255         return 0;
 256 }
 257
 258 /*
 259  * Sample a process (thread group) clock for the given group_leader task.
 260  * Must be called with tasklist_lock held for reading.
 261  */
 262 static int cpu_clock_sample_group(clockid_t which_clock,
 263                                   struct task_struct *p,
 264                                   union cpu_time_count *cpu)
 265 {
 266         int ret;
 267         unsigned long flags;
 268         spin_lock_irqsave(&p->sighand->siglock, flags);
 269         ret = cpu_clock_sample_group_locked(CPUCLOCK_WHICH(which_clock), p,
 270                                             cpu);
 271         spin_unlock_irqrestore(&p->sighand->siglock, flags);
 272         return ret;
 273 }
 274
 275
 276 int posix_cpu_clock_get(clockid_t which_clock, struct timespec *tp)
 277 {
 278         const pid_t pid = CPUCLOCK_PID(which_clock);
 279         int error = -EINVAL;
 280         union cpu_time_count rtn;
 281
 282         if (pid == 0) {
 283                 /*
 284                  * Special case constant value for our own clocks.
 285                  * We don't have to do any lookup to find ourselves.
 286                  */
 287                 if (CPUCLOCK_PERTHREAD(which_clock)) {
 288                         /*
 289                          * Sampling just ourselves we can do with no locking.
 290                          */
 291                         error = cpu_clock_sample(which_clock,
 292                                                  current, &rtn);
 293                 } else {
 294                         read_lock(&tasklist_lock);
 295                         error = cpu_clock_sample_group(which_clock,
 296                                                        current, &rtn);
 297                         read_unlock(&tasklist_lock);
 298                 }
 299         } else {
 300                 /*
 301                  * Find the given PID, and validate that the caller
 302                  * should be able to see it.
 303                  */
 304                 struct task_struct *p;
 305                 read_lock(&tasklist_lock);
 306                 p = find_task_by_pid(pid);
 307                 if (p) {
 308                         if (CPUCLOCK_PERTHREAD(which_clock)) {
 309                                 if (p->tgid == current->tgid) {
 310                                         error = cpu_clock_sample(which_clock,
 311                                                                  p, &rtn);
 312                                 }
 313                         } else if (p->tgid == pid && p->signal) {
 314                                 error = cpu_clock_sample_group(which_clock,
 315                                                                p, &rtn);
 316                         }
 317                 }
 318                 read_unlock(&tasklist_lock);
 319         }
 320
 321         if (error)
 322                 return error;
 323         sample_to_timespec(which_clock, rtn, tp);
 324         return 0;
 325 }
 326
 327
 328 /*
 329  * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 330  * This is called from sys_timer_create with the new timer already locked.
 331  */
 332 int posix_cpu_timer_create(struct k_itimer *new_timer)
 333 {
 334         int ret = 0;
 335         const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
 336         struct task_struct *p;
 337
 338         if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 339                 return -EINVAL;
 340
 341         INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 342         new_timer->it.cpu.incr.sched = 0;
 343         new_timer->it.cpu.expires.sched = 0;
 344
 345         read_lock(&tasklist_lock);
 346         if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
 347                 if (pid == 0) {
 348                         p = current;
 349                 } else {
 350                         p = find_task_by_pid(pid);
 351                         if (p && p->tgid != current->tgid)
 352                                 p = NULL;
 353                 }
 354         } else {
 355                 if (pid == 0) {
 356                         p = current->group_leader;
 357                 } else {
 358                         p = find_task_by_pid(pid);
 359                         if (p && p->tgid != pid)
 360                                 p = NULL;
 361                 }
 362         }
 363         new_timer->it.cpu.task = p;
 364         if (p) {
 365                 get_task_struct(p);
 366         } else {
 367                 ret = -EINVAL;
 368         }
 369         read_unlock(&tasklist_lock);
 370
 371         return ret;
 372 }
 373
 374 /*
 375  * Clean up a CPU-clock timer that is about to be destroyed.
 376  * This is called from timer deletion with the timer already locked.
 377  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 378  * and try again.  (This happens when the timer is in the middle of firing.)
 379  */
 380 int posix_cpu_timer_del(struct k_itimer *timer)
 381 {
 382         struct task_struct *p = timer->it.cpu.task;
 383
 384         if (timer->it.cpu.firing)
 385                 return TIMER_RETRY;
 386
 387         if (unlikely(p == NULL))
 388                 return 0;
 389
 390         spin_lock(&p->sighand->siglock);
 391         if (!list_empty(&timer->it.cpu.entry)) {
 392                 /*
 393                  * Take us off the task's timer list.  We don't need to
 394                  * take tasklist_lock and check for the task being reaped.
 395                  * If it was reaped, it already called posix_cpu_timers_exit
 396                  * and posix_cpu_timers_exit_group to clear all the timers
 397                  * that pointed to it.
 398                  */
 399                 list_del(&timer->it.cpu.entry);
 400                 put_task_struct(p);
 401         }
 402         spin_unlock(&p->sighand->siglock);
 403
 404         return 0;
 405 }
 406
 407 /*
 408  * Clean out CPU timers still ticking when a thread exited.  The task
 409  * pointer is cleared, and the expiry time is replaced with the residual
 410  * time for later timer_gettime calls to return.
 411  * This must be called with the siglock held.
 412  */
 413 static void cleanup_timers(struct list_head *head,
 414                            cputime_t utime, cputime_t stime,
 415                            unsigned long long sched_time)
 416 {
 417         struct cpu_timer_list *timer, *next;
 418         cputime_t ptime = cputime_add(utime, stime);
 419
 420         list_for_each_entry_safe(timer, next, head, entry) {
 421                 put_task_struct(timer->task);
 422                 timer->task = NULL;
 423                 list_del_init(&timer->entry);
 424                 if (cputime_lt(timer->expires.cpu, ptime)) {
 425                         timer->expires.cpu = cputime_zero;
 426                 } else {
 427                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
 428                                                          ptime);
 429                 }
 430         }
 431
 432         ++head;
 433         list_for_each_entry_safe(timer, next, head, entry) {
 434                 put_task_struct(timer->task);
 435                 timer->task = NULL;
 436                 list_del_init(&timer->entry);
 437                 if (cputime_lt(timer->expires.cpu, utime)) {
 438                         timer->expires.cpu = cputime_zero;
 439                 } else {
 440                         timer->expires.cpu = cputime_sub(timer->expires.cpu,
 441                                                          utime);
 442                 }
 443         }
 444
 445         ++head;
 446         list_for_each_entry_safe(timer, next, head, entry) {
 447                 put_task_struct(timer->task);
 448                 timer->task = NULL;
 449                 list_del_init(&timer->entry);
 450                 if (timer->expires.sched < sched_time) {
 451                         timer->expires.sched = 0;
 452                 } else {
 453                         timer->expires.sched -= sched_time;
 454                 }
 455         }
 456 }
 457
 458 /*
 459  * These are both called with the siglock held, when the current thread
 460  * is being reaped.  When the final (leader) thread in the group is reaped,
 461  * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 462  */
 463 void posix_cpu_timers_exit(struct task_struct *tsk)
 464 {
 465         cleanup_timers(tsk->cpu_timers,
 466                        tsk->utime, tsk->stime, tsk->sched_time);
 467
 468 }
 469 void posix_cpu_timers_exit_group(struct task_struct *tsk)
 470 {
 471         cleanup_timers(tsk->signal->cpu_timers,
 472                        cputime_add(tsk->utime, tsk->signal->utime),
 473                        cputime_add(tsk->stime, tsk->signal->stime),
 474                        tsk->sched_time + tsk->signal->sched_time);
 475 }
 476
 477
 478 /*
 479  * Set the expiry times of all the threads in the process so one of them
 480  * will go off before the process cumulative expiry total is reached.
 481  */
 482 static void process_timer_rebalance(struct task_struct *p,
 483                                     unsigned int clock_idx,
 484                                     union cpu_time_count expires,
 485                                     union cpu_time_count val)
 486 {
 487         cputime_t ticks, left;
 488         unsigned long long ns, nsleft;
 489         struct task_struct *t = p;
 490         unsigned int nthreads = atomic_read(&p->signal->live);
 491
 492         switch (clock_idx) {
 493         default:
 494                 BUG();
 495                 break;
 496         case CPUCLOCK_PROF:
 497                 left = cputime_div(cputime_sub(expires.cpu, val.cpu),
 498                                    nthreads);
 499                 do {
 500                         if (!unlikely(t->exit_state)) {
 501                                 ticks = cputime_add(prof_ticks(t), left);
 502                                 if (cputime_eq(t->it_prof_expires,
 503                                                cputime_zero) ||
 504                                     cputime_gt(t->it_prof_expires, ticks)) {
 505                                         t->it_prof_expires = ticks;
 506                                 }
 507                         }
 508                         t = next_thread(t);
 509                 } while (t != p);
 510                 break;
 511         case CPUCLOCK_VIRT:
 512                 left = cputime_div(cputime_sub(expires.cpu, val.cpu),
 513                                    nthreads);
 514                 do {
 515                         if (!unlikely(t->exit_state)) {
 516                                 ticks = cputime_add(virt_ticks(t), left);
 517                                 if (cputime_eq(t->it_virt_expires,
 518                                                cputime_zero) ||
 519                                     cputime_gt(t->it_virt_expires, ticks)) {
 520                                         t->it_virt_expires = ticks;
 521                                 }
 522                         }
 523                         t = next_thread(t);
 524                 } while (t != p);
 525                 break;
 526         case CPUCLOCK_SCHED:
 527                 nsleft = expires.sched - val.sched;
 528                 do_div(nsleft, nthreads);
 529                 do {
 530                         if (!unlikely(t->exit_state)) {
 531                                 ns = t->sched_time + nsleft;
 532                                 if (t->it_sched_expires == 0 ||
 533                                     t->it_sched_expires > ns) {
 534                                         t->it_sched_expires = ns;
 535                                 }
 536                         }
 537                         t = next_thread(t);
 538                 } while (t != p);
 539                 break;
 540         }
 541 }
 542
 543 static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 544 {
 545         /*
 546          * That's all for this thread or process.
 547          * We leave our residual in expires to be reported.
 548          */
 549         put_task_struct(timer->it.cpu.task);
 550         timer->it.cpu.task = NULL;
 551         timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
 552                                              timer->it.cpu.expires,
 553                                              now);
 554 }
 555
 556 /*
 557  * Insert the timer on the appropriate list before any timers that
 558  * expire later.  This must be called with the tasklist_lock held
 559  * for reading, and interrupts disabled.
 560  */
 561 static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 562 {
 563         struct task_struct *p = timer->it.cpu.task;
 564         struct list_head *head, *listpos;
 565         struct cpu_timer_list *const nt = &timer->it.cpu;
 566         struct cpu_timer_list *next;
 567         unsigned long i;
 568
 569         head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
 570                 p->cpu_timers : p->signal->cpu_timers);
 571         head += CPUCLOCK_WHICH(timer->it_clock);
 572
 573         BUG_ON(!irqs_disabled());
 574         spin_lock(&p->sighand->siglock);
 575
 576         listpos = head;
 577         if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 578                 list_for_each_entry(next, head, entry) {
 579                         if (next->expires.sched > nt->expires.sched) {
 580                                 listpos = &next->entry;
 581                                 break;
 582                         }
 583                 }
 584         } else {
 585                 list_for_each_entry(next, head, entry) {
 586                         if (cputime_gt(next->expires.cpu, nt->expires.cpu)) {
 587                                 listpos = &next->entry;
 588                                 break;
 589                         }
 590                 }
 591         }
 592         list_add(&nt->entry, listpos);
 593
 594         if (listpos == head) {
 595                 /*
 596                  * We are the new earliest-expiring timer.
 597                  * If we are a thread timer, there can always
 598                  * be a process timer telling us to stop earlier.
 599                  */
 600
 601                 if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 602                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
 603                         default:
 604                                 BUG();
 605                         case CPUCLOCK_PROF:
 606                                 if (cputime_eq(p->it_prof_expires,
 607                                                cputime_zero) ||
 608                                     cputime_gt(p->it_prof_expires,
 609                                                nt->expires.cpu))
 610                                         p->it_prof_expires = nt->expires.cpu;
 611                                 break;
 612                         case CPUCLOCK_VIRT:
 613                                 if (cputime_eq(p->it_virt_expires,
 614                                                cputime_zero) ||
 615                                     cputime_gt(p->it_virt_expires,
 616                                                nt->expires.cpu))
 617                                         p->it_virt_expires = nt->expires.cpu;
 618                                 break;
 619                         case CPUCLOCK_SCHED:
 620                                 if (p->it_sched_expires == 0 ||
 621                                     p->it_sched_expires > nt->expires.sched)
 622                                         p->it_sched_expires = nt->expires.sched;
 623                                 break;
 624                         }
 625                 } else {
 626                         /*
 627                          * For a process timer, we must balance
 628                          * all the live threads' expirations.
 629                          */
 630                         switch (CPUCLOCK_WHICH(timer->it_clock)) {
 631                         default:
 632                                 BUG();
 633                         case CPUCLOCK_VIRT:
 634                                 if (!cputime_eq(p->signal->it_virt_expires,
 635                                                 cputime_zero) &&
 636                                     cputime_lt(p->signal->it_virt_expires,
 637                                                timer->it.cpu.expires.cpu))
 638                                         break;
 639                                 goto rebalance;
 640                         case CPUCLOCK_PROF:
 641                                 if (!cputime_eq(p->signal->it_prof_expires,
 642                                                 cputime_zero) &&
 643                                     cputime_lt(p->signal->it_prof_expires,
 644                                                timer->it.cpu.expires.cpu))
 645                                         break;
 646                                 i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
 647                                 if (i != RLIM_INFINITY &&
 648                                     i <= cputime_to_secs(timer->it.cpu.expires.cpu))
 649                                         break;
 650                                 goto rebalance;
 651                         case CPUCLOCK_SCHED:
 652                         rebalance:
 653                                 process_timer_rebalance(
 654                                         timer->it.cpu.task,
 655                                         CPUCLOCK_WHICH(timer->it_clock),
 656                                         timer->it.cpu.expires, now);
 657                                 break;
 658                         }
 659                 }
 660         }
 661
 662         spin_unlock(&p->sighand->siglock);
 663 }
 664
 665 /*
 666  * The timer is locked, fire it and arrange for its reload.
 667  */
 668 static void cpu_timer_fire(struct k_itimer *timer)
 669 {
 670         if (unlikely(timer->sigq == NULL)) {
 671                 /*
 672                  * This a special case for clock_nanosleep,
 673                  * not a normal timer from sys_timer_create.
 674                  */
 675                 wake_up_process(timer->it_process);
 676                 timer->it.cpu.expires.sched = 0;
 677         } else if (timer->it.cpu.incr.sched == 0) {
 678                 /*
 679                  * One-shot timer.  Clear it as soon as it's fired.
 680                  */
 681                 posix_timer_event(timer, 0);
 682                 timer->it.cpu.expires.sched = 0;
 683         } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 684                 /*
 685                  * The signal did not get queued because the signal
 686                  * was ignored, so we won't get any callback to
 687                  * reload the timer.  But we need to keep it
 688                  * ticking in case the signal is deliverable next time.
 689                  */
 690                 posix_cpu_timer_schedule(timer);
 691         }
 692 }
 693
 694 /*
 695  * Guts of sys_timer_settime for CPU timers.
 696  * This is called with the timer locked and interrupts disabled.
 697  * If we return TIMER_RETRY, it's necessary to release the timer's lock
 698  * and try again.  (This happens when the timer is in the middle of firing.)
 699  */
 700 int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 701                         struct itimerspec *new, struct itimerspec *old)
 702 {
 703         struct task_struct *p = timer->it.cpu.task;
 704         union cpu_time_count old_expires, new_expires, val;
 705         int ret;
 706
 707         if (unlikely(p == NULL)) {
 708                 /*
 709                  * Timer refers to a dead task's clock.
 710                  */
 711                 return -ESRCH;
 712         }
 713
 714         new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
 715
 716         read_lock(&tasklist_lock);
 717         /*
 718          * We need the tasklist_lock to protect against reaping that
 719          * clears p->signal.  If p has just been reaped, we can no
 720          * longer get any information about it at all.
 721          */
 722         if (unlikely(p->signal == NULL)) {
 723                 read_unlock(&tasklist_lock);
 724                 put_task_struct(p);
 725                 timer->it.cpu.task = NULL;
 726                 return -ESRCH;
 727         }
 728
 729         /*
 730          * Disarm any old timer after extracting its expiry time.
 731          */
 732         BUG_ON(!irqs_disabled());
 733         spin_lock(&p->sighand->siglock);
 734         old_expires = timer->it.cpu.expires;
 735         list_del_init(&timer->it.cpu.entry);
 736         spin_unlock(&p->sighand->siglock);
 737
 738         /*
 739          * We need to sample the current value to convert the new
 740          * value from to relative and absolute, and to convert the
 741          * old value from absolute to relative.  To set a process
 742          * timer, we need a sample to balance the thread expiry
 743          * times (in arm_timer).  With an absolute time, we must
 744          * check if it's already passed.  In short, we need a sample.
 745          */
 746         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 747                 cpu_clock_sample(timer->it_clock, p, &val);
 748         } else {
 749                 cpu_clock_sample_group(timer->it_clock, p, &val);
 750         }
 751
 752         if (old) {
 753                 if (old_expires.sched == 0) {
 754                         old->it_value.tv_sec = 0;
 755                         old->it_value.tv_nsec = 0;
 756                 } else {
 757                         /*
 758                          * Update the timer in case it has
 759                          * overrun already.  If it has,
 760                          * we'll report it as having overrun
 761                          * and with the next reloaded timer
 762                          * already ticking, though we are
 763                          * swallowing that pending
 764                          * notification here to install the
 765                          * new setting.
 766                          */
 767                         bump_cpu_timer(timer, val);
 768                         if (cpu_time_before(timer->it_clock, val,
 769                                             timer->it.cpu.expires)) {
 770                                 old_expires = cpu_time_sub(
 771                                         timer->it_clock,
 772                                         timer->it.cpu.expires, val);
 773                                 sample_to_timespec(timer->it_clock,
 774                                                    old_expires,
 775                                                    &old->it_value);
 776                         } else {
 777                                 old->it_value.tv_nsec = 1;
 778                                 old->it_value.tv_sec = 0;
 779                         }
 780                 }
 781         }
 782
 783         if (unlikely(timer->it.cpu.firing)) {
 784                 /*
 785                  * We are colliding with the timer actually firing.
 786                  * Punt after filling in the timer's old value, and
 787                  * disable this firing since we are already reporting
 788                  * it as an overrun (thanks to bump_cpu_timer above).
 789                  */
 790                 read_unlock(&tasklist_lock);
 791                 timer->it.cpu.firing = -1;
 792                 ret = TIMER_RETRY;
 793                 goto out;
 794         }
 795
 796         if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
 797                 cpu_time_add(timer->it_clock, &new_expires, val);
 798         }
 799
 800         /*
 801          * Install the new expiry time (or zero).
 802          * For a timer with no notification action, we don't actually
 803          * arm the timer (we'll just fake it for timer_gettime).
 804          */
 805         timer->it.cpu.expires = new_expires;
 806         if (new_expires.sched != 0 &&
 807             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 808             cpu_time_before(timer->it_clock, val, new_expires)) {
 809                 arm_timer(timer, val);
 810         }
 811
 812         read_unlock(&tasklist_lock);
 813
 814         /*
 815          * Install the new reload setting, and
 816          * set up the signal and overrun bookkeeping.
 817          */
 818         timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
 819                                                 &new->it_interval);
 820
 821         /*
 822          * This acts as a modification timestamp for the timer,
 823          * so any automatic reload attempt will punt on seeing
 824          * that we have reset the timer manually.
 825          */
 826         timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 827                 ~REQUEUE_PENDING;
 828         timer->it_overrun_last = 0;
 829         timer->it_overrun = -1;
 830
 831         if (new_expires.sched != 0 &&
 832             (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 833             !cpu_time_before(timer->it_clock, val, new_expires)) {
 834                 /*
 835                  * The designated time already passed, so we notify
 836                  * immediately, even if the thread never runs to
 837                  * accumulate more time on this clock.
 838                  */
 839                 cpu_timer_fire(timer);
 840         }
 841
 842         ret = 0;
 843  out:
 844         if (old) {
 845                 sample_to_timespec(timer->it_clock,
 846                                    timer->it.cpu.incr, &old->it_interval);
 847         }
 848         return ret;
 849 }
 850
 851 void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 852 {
 853         union cpu_time_count now;
 854         struct task_struct *p = timer->it.cpu.task;
 855         int clear_dead;
 856
 857         /*
 858          * Easy part: convert the reload time.
 859          */
 860         sample_to_timespec(timer->it_clock,
 861                            timer->it.cpu.incr, &itp->it_interval);
 862
 863         if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
 864                 itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 865                 return;
 866         }
 867
 868         if (unlikely(p == NULL)) {
 869                 /*
 870                  * This task already died and the timer will never fire.
 871                  * In this case, expires is actually the dead value.
 872                  */
 873         dead:
 874                 sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
 875                                    &itp->it_value);
 876                 return;
 877         }
 878
 879         /*
 880          * Sample the clock to take the difference with the expiry time.
 881          */
 882         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 883                 cpu_clock_sample(timer->it_clock, p, &now);
 884                 clear_dead = p->exit_state;
 885         } else {
 886                 read_lock(&tasklist_lock);
 887                 if (unlikely(p->signal == NULL)) {
 888                         /*
 889                          * The process has been reaped.
 890                          * We can't even collect a sample any more.
 891                          * Call the timer disarmed, nothing else to do.
 892                          */
 893                         put_task_struct(p);
 894                         timer->it.cpu.task = NULL;
 895                         timer->it.cpu.expires.sched = 0;
 896                         read_unlock(&tasklist_lock);
 897                         goto dead;
 898                 } else {
 899                         cpu_clock_sample_group(timer->it_clock, p, &now);
 900                         clear_dead = (unlikely(p->exit_state) &&
 901                                       thread_group_empty(p));
 902                 }
 903                 read_unlock(&tasklist_lock);
 904         }
 905
 906         if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 907                 if (timer->it.cpu.incr.sched == 0 &&
 908                     cpu_time_before(timer->it_clock,
 909                                     timer->it.cpu.expires, now)) {
 910                         /*
 911                          * Do-nothing timer expired and has no reload,
 912                          * so it's as if it was never set.
 913                          */
 914                         timer->it.cpu.expires.sched = 0;
 915                         itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 916                         return;
 917                 }
 918                 /*
 919                  * Account for any expirations and reloads that should
 920                  * have happened.
 921                  */
 922                 bump_cpu_timer(timer, now);
 923         }
 924
 925         if (unlikely(clear_dead)) {
 926                 /*
 927                  * We've noticed that the thread is dead, but
 928                  * not yet reaped.  Take this opportunity to
 929                  * drop our task ref.
 930                  */
 931                 clear_dead_task(timer, now);
 932                 goto dead;
 933         }
 934
 935         if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
 936                 sample_to_timespec(timer->it_clock,
 937                                    cpu_time_sub(timer->it_clock,
 938                                                 timer->it.cpu.expires, now),
 939                                    &itp->it_value);
 940         } else {
 941                 /*
 942                  * The timer should have expired already, but the firing
 943                  * hasn't taken place yet.  Say it's just about to expire.
 944                  */
 945                 itp->it_value.tv_nsec = 1;
 946                 itp->it_value.tv_sec = 0;
 947         }
 948 }
 949
 950 /*
 951  * Check for any per-thread CPU timers that have fired and move them off
 952  * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 953  * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 954  */
 955 static void check_thread_timers(struct task_struct *tsk,
 956                                 struct list_head *firing)
 957 {
 958         struct list_head *timers = tsk->cpu_timers;
 959
 960         tsk->it_prof_expires = cputime_zero;
 961         while (!list_empty(timers)) {
 962                 struct cpu_timer_list *t = list_entry(timers->next,
 963                                                       struct cpu_timer_list,
 964                                                       entry);
 965                 if (cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
 966                         tsk->it_prof_expires = t->expires.cpu;
 967                         break;
 968                 }
 969                 t->firing = 1;
 970                 list_move_tail(&t->entry, firing);
 971         }
 972
 973         ++timers;
 974         tsk->it_virt_expires = cputime_zero;
 975         while (!list_empty(timers)) {
 976                 struct cpu_timer_list *t = list_entry(timers->next,
 977                                                       struct cpu_timer_list,
 978                                                       entry);
 979                 if (cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
 980                         tsk->it_virt_expires = t->expires.cpu;
 981                         break;
 982                 }
 983                 t->firing = 1;
 984                 list_move_tail(&t->entry, firing);
 985         }
 986
 987         ++timers;
 988         tsk->it_sched_expires = 0;
 989         while (!list_empty(timers)) {
 990                 struct cpu_timer_list *t = list_entry(timers->next,
 991                                                       struct cpu_timer_list,
 992                                                       entry);
 993                 if (tsk->sched_time < t->expires.sched) {
 994                         tsk->it_sched_expires = t->expires.sched;
 995                         break;
 996                 }
 997                 t->firing = 1;
 998                 list_move_tail(&t->entry, firing);
 999         }
1000 }
1001
1002 /*
1003  * Check for any per-thread CPU timers that have fired and move them
1004  * off the tsk->*_timers list onto the firing list.  Per-thread timers
1005  * have already been taken off.
1006  */
1007 static void check_process_timers(struct task_struct *tsk,
1008                                  struct list_head *firing)
1009 {
1010         struct signal_struct *const sig = tsk->signal;
1011         cputime_t utime, stime, ptime, virt_expires, prof_expires;
1012         unsigned long long sched_time, sched_expires;
1013         struct task_struct *t;
1014         struct list_head *timers = sig->cpu_timers;
1015
1016         /*
1017          * Don't sample the current process CPU clocks if there are no timers.
1018          */
1019         if (list_empty(&timers[CPUCLOCK_PROF]) &&
1020             cputime_eq(sig->it_prof_expires, cputime_zero) &&
1021             sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
1022             list_empty(&timers[CPUCLOCK_VIRT]) &&
1023             cputime_eq(sig->it_virt_expires, cputime_zero) &&
1024             list_empty(&timers[CPUCLOCK_SCHED]))
1025                 return;
1026
1027         /*
1028          * Collect the current process totals.
1029          */
1030         utime = sig->utime;
1031         stime = sig->stime;
1032         sched_time = sig->sched_time;
1033         t = tsk;
1034         do {
1035                 utime = cputime_add(utime, t->utime);
1036                 stime = cputime_add(stime, t->stime);
1037                 sched_time += t->sched_time;
1038                 t = next_thread(t);
1039         } while (t != tsk);
1040         ptime = cputime_add(utime, stime);
1041
1042         prof_expires = cputime_zero;
1043         while (!list_empty(timers)) {
1044                 struct cpu_timer_list *t = list_entry(timers->next,
1045                                                       struct cpu_timer_list,
1046                                                       entry);
1047                 if (cputime_lt(ptime, t->expires.cpu)) {
1048                         prof_expires = t->expires.cpu;
1049                         break;
1050                 }
1051                 t->firing = 1;
1052                 list_move_tail(&t->entry, firing);
1053         }
1054
1055         ++timers;
1056         virt_expires = cputime_zero;
1057         while (!list_empty(timers)) {
1058                 struct cpu_timer_list *t = list_entry(timers->next,
1059                                                       struct cpu_timer_list,
1060                                                       entry);
1061                 if (cputime_lt(utime, t->expires.cpu)) {
1062                         virt_expires = t->expires.cpu;
1063                         break;
1064                 }
1065                 t->firing = 1;
1066                 list_move_tail(&t->entry, firing);
1067         }
1068
1069         ++timers;
1070         sched_expires = 0;
1071         while (!list_empty(timers)) {
1072                 struct cpu_timer_list *t = list_entry(timers->next,
1073                                                       struct cpu_timer_list,
1074                                                       entry);
1075                 if (sched_time < t->expires.sched) {
1076                         sched_expires = t->expires.sched;
1077                         break;
1078                 }
1079                 t->firing = 1;
1080                 list_move_tail(&t->entry, firing);
1081         }
1082
1083         /*
1084          * Check for the special case process timers.
1085          */
1086         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1087                 if (cputime_ge(ptime, sig->it_prof_expires)) {
1088                         /* ITIMER_PROF fires and reloads.  */
1089                         sig->it_prof_expires = sig->it_prof_incr;
1090                         if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1091                                 sig->it_prof_expires = cputime_add(
1092                                         sig->it_prof_expires, ptime);
1093                         }
1094                         __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
1095                 }
1096                 if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
1097                     (cputime_eq(prof_expires, cputime_zero) ||
1098                      cputime_lt(sig->it_prof_expires, prof_expires))) {
1099                         prof_expires = sig->it_prof_expires;
1100                 }
1101         }
1102         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1103                 if (cputime_ge(utime, sig->it_virt_expires)) {
1104                         /* ITIMER_VIRTUAL fires and reloads.  */
1105                         sig->it_virt_expires = sig->it_virt_incr;
1106                         if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1107                                 sig->it_virt_expires = cputime_add(
1108                                         sig->it_virt_expires, utime);
1109                         }
1110                         __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
1111                 }
1112                 if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
1113                     (cputime_eq(virt_expires, cputime_zero) ||
1114                      cputime_lt(sig->it_virt_expires, virt_expires))) {
1115                         virt_expires = sig->it_virt_expires;
1116                 }
1117         }
1118         if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
1119                 unsigned long psecs = cputime_to_secs(ptime);
1120                 cputime_t x;
1121                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
1122                         /*
1123                          * At the hard limit, we just die.
1124                          * No need to calculate anything else now.
1125                          */
1126                         __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1127                         return;
1128                 }
1129                 if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
1130                         /*
1131                          * At the soft limit, send a SIGXCPU every second.
1132                          */
1133                         __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1134                         if (sig->rlim[RLIMIT_CPU].rlim_cur
1135                             < sig->rlim[RLIMIT_CPU].rlim_max) {
1136                                 sig->rlim[RLIMIT_CPU].rlim_cur++;
1137                         }
1138                 }
1139                 x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
1140                 if (cputime_eq(prof_expires, cputime_zero) ||
1141                     cputime_lt(x, prof_expires)) {
1142                         prof_expires = x;
1143                 }
1144         }
1145
1146         if (!cputime_eq(prof_expires, cputime_zero) ||
1147             !cputime_eq(virt_expires, cputime_zero) ||
1148             sched_expires != 0) {
1149                 /*
1150                  * Rebalance the threads' expiry times for the remaining
1151                  * process CPU timers.
1152                  */
1153
1154                 cputime_t prof_left, virt_left, ticks;
1155                 unsigned long long sched_left, sched;
1156                 const unsigned int nthreads = atomic_read(&sig->live);
1157
1158                 prof_left = cputime_sub(prof_expires, utime);
1159                 prof_left = cputime_sub(prof_left, stime);
1160                 prof_left = cputime_div(prof_left, nthreads);
1161                 virt_left = cputime_sub(virt_expires, utime);
1162                 virt_left = cputime_div(virt_left, nthreads);
1163                 if (sched_expires) {
1164                         sched_left = sched_expires - sched_time;
1165                         do_div(sched_left, nthreads);
1166                 } else {
1167                         sched_left = 0;
1168                 }
1169                 t = tsk;
1170                 do {
1171                         ticks = cputime_add(cputime_add(t->utime, t->stime),
1172                                             prof_left);
1173                         if (!cputime_eq(prof_expires, cputime_zero) &&
1174                             (cputime_eq(t->it_prof_expires, cputime_zero) ||
1175                              cputime_gt(t->it_prof_expires, ticks))) {
1176                                 t->it_prof_expires = ticks;
1177                         }
1178
1179                         ticks = cputime_add(t->utime, virt_left);
1180                         if (!cputime_eq(virt_expires, cputime_zero) &&
1181                             (cputime_eq(t->it_virt_expires, cputime_zero) ||
1182                              cputime_gt(t->it_virt_expires, ticks))) {
1183                                 t->it_virt_expires = ticks;
1184                         }
1185
1186                         sched = t->sched_time + sched_left;
1187                         if (sched_expires && (t->it_sched_expires == 0 ||
1188                                               t->it_sched_expires > sched)) {
1189                                 t->it_sched_expires = sched;
1190                         }
1191
1192                         do {
1193                                 t = next_thread(t);
1194                         } while (unlikely(t->exit_state));
1195                 } while (t != tsk);
1196         }
1197 }
1198
1199 /*
1200  * This is called from the signal code (via do_schedule_next_timer)
1201  * when the last timer signal was delivered and we have to reload the timer.
1202  */
1203 void posix_cpu_timer_schedule(struct k_itimer *timer)
1204 {
1205         struct task_struct *p = timer->it.cpu.task;
1206         union cpu_time_count now;
1207
1208         if (unlikely(p == NULL))
1209                 /*
1210                  * The task was cleaned up already, no future firings.
1211                  */
1212                 return;
1213
1214         /*
1215          * Fetch the current sample and update the timer's expiry time.
1216          */
1217         if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1218                 cpu_clock_sample(timer->it_clock, p, &now);
1219                 bump_cpu_timer(timer, now);
1220                 if (unlikely(p->exit_state)) {
1221                         clear_dead_task(timer, now);
1222                         return;
1223                 }
1224                 read_lock(&tasklist_lock); /* arm_timer needs it.  */
1225         } else {
1226                 read_lock(&tasklist_lock);
1227                 if (unlikely(p->signal == NULL)) {
1228                         /*
1229                          * The process has been reaped.
1230                          * We can't even collect a sample any more.
1231                          */
1232                         put_task_struct(p);
1233                         timer->it.cpu.task = p = NULL;
1234                         timer->it.cpu.expires.sched = 0;
1235                         read_unlock(&tasklist_lock);
1236                         return;
1237                 } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1238                         /*
1239                          * We've noticed that the thread is dead, but
1240                          * not yet reaped.  Take this opportunity to
1241                          * drop our task ref.
1242                          */
1243                         clear_dead_task(timer, now);
1244                         read_unlock(&tasklist_lock);
1245                         return;
1246                 }
1247                 cpu_clock_sample_group(timer->it_clock, p, &now);
1248                 bump_cpu_timer(timer, now);
1249                 /* Leave the tasklist_lock locked for the call below.  */
1250         }
1251
1252         /*
1253          * Now re-arm for the new expiry time.
1254          */
1255         arm_timer(timer, now);
1256
1257         read_unlock(&tasklist_lock);
1258 }
1259
1260 /*
1261  * This is called from the timer interrupt handler.  The irq handler has
1262  * already updated our counts.  We need to check if any timers fire now.
1263  * Interrupts are disabled.
1264  */
1265 void run_posix_cpu_timers(struct task_struct *tsk)
1266 {
1267         LIST_HEAD(firing);
1268         struct k_itimer *timer, *next;
1269
1270         BUG_ON(!irqs_disabled());
1271
1272 #define UNEXPIRED(clock) \
1273                 (cputime_eq(tsk->it_##clock##_expires, cputime_zero) || \
1274                  cputime_lt(clock##_ticks(tsk), tsk->it_##clock##_expires))
1275
1276         if (UNEXPIRED(prof) && UNEXPIRED(virt) &&
1277             (tsk->it_sched_expires == 0 ||
1278              tsk->sched_time < tsk->it_sched_expires))
1279                 return;
1280
1281 #undef  UNEXPIRED
1282
1283         BUG_ON(tsk->exit_state);
1284
1285         /*
1286          * Double-check with locks held.
1287          */
1288         read_lock(&tasklist_lock);
1289         spin_lock(&tsk->sighand->siglock);
1290
1291         /*
1292          * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
1293          * all the timers that are firing, and put them on the firing list.
1294          */
1295         check_thread_timers(tsk, &firing);
1296         check_process_timers(tsk, &firing);
1297
1298         /*
1299          * We must release these locks before taking any timer's lock.
1300          * There is a potential race with timer deletion here, as the
1301          * siglock now protects our private firing list.  We have set
1302          * the firing flag in each timer, so that a deletion attempt
1303          * that gets the timer lock before we do will give it up and
1304          * spin until we've taken care of that timer below.
1305          */
1306         spin_unlock(&tsk->sighand->siglock);
1307         read_unlock(&tasklist_lock);
1308
1309         /*
1310          * Now that all the timers on our list have the firing flag,
1311          * noone will touch their list entries but us.  We'll take
1312          * each timer's lock before clearing its firing flag, so no
1313          * timer call will interfere.
1314          */
1315         list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1316                 int firing;
1317                 spin_lock(&timer->it_lock);
1318                 list_del_init(&timer->it.cpu.entry);
1319                 firing = timer->it.cpu.firing;
1320                 timer->it.cpu.firing = 0;
1321                 /*
1322                  * The firing flag is -1 if we collided with a reset
1323                  * of the timer, which already reported this
1324                  * almost-firing as an overrun.  So don't generate an event.
1325                  */
1326                 if (likely(firing >= 0)) {
1327                         cpu_timer_fire(timer);
1328                 }
1329                 spin_unlock(&timer->it_lock);
1330         }
1331 }
1332
1333 /*
1334  * Set one of the process-wide special case CPU timers.
1335  * The tasklist_lock and tsk->sighand->siglock must be held by the caller.
1336  * The oldval argument is null for the RLIMIT_CPU timer, where *newval is
1337  * absolute; non-null for ITIMER_*, where *newval is relative and we update
1338  * it to be absolute, *oldval is absolute and we update it to be relative.
1339  */
1340 void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1341                            cputime_t *newval, cputime_t *oldval)
1342 {
1343         union cpu_time_count now;
1344         struct list_head *head;
1345
1346         BUG_ON(clock_idx == CPUCLOCK_SCHED);
1347         cpu_clock_sample_group_locked(clock_idx, tsk, &now);
1348
1349         if (oldval) {
1350                 if (!cputime_eq(*oldval, cputime_zero)) {
1351                         if (cputime_le(*oldval, now.cpu)) {
1352                                 /* Just about to fire. */
1353                                 *oldval = jiffies_to_cputime(1);
1354                         } else {
1355                                 *oldval = cputime_sub(*oldval, now.cpu);
1356                         }
1357                 }
1358
1359                 if (cputime_eq(*newval, cputime_zero))
1360                         return;
1361                 *newval = cputime_add(*newval, now.cpu);
1362
1363                 /*
1364                  * If the RLIMIT_CPU timer will expire before the
1365                  * ITIMER_PROF timer, we have nothing else to do.
1366                  */
1367                 if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
1368                     < cputime_to_secs(*newval))
1369                         return;
1370         }
1371
1372         /*
1373          * Check whether there are any process timers already set to fire
1374          * before this one.  If so, we don't have anything more to do.
1375          */
1376         head = &tsk->signal->cpu_timers[clock_idx];
1377         if (list_empty(head) ||
1378             cputime_ge(list_entry(head->next,
1379                                   struct cpu_timer_list, entry)->expires.cpu,
1380                        *newval)) {
1381                 /*
1382                  * Rejigger each thread's expiry time so that one will
1383                  * notice before we hit the process-cumulative expiry time.
1384                  */
1385                 union cpu_time_count expires = { .sched = 0 };
1386                 expires.cpu = *newval;
1387                 process_timer_rebalance(tsk, clock_idx, expires, now);
1388         }
1389 }
1390
1391 static long posix_cpu_clock_nanosleep_restart(struct restart_block *);
1392
1393 int posix_cpu_nsleep(clockid_t which_clock, int flags,
1394                      struct timespec *rqtp)
1395 {
1396         struct restart_block *restart_block =
1397             &current_thread_info()->restart_block;
1398         struct k_itimer timer;
1399         int error;
1400
1401         /*
1402          * Diagnose required errors first.
1403          */
1404         if (CPUCLOCK_PERTHREAD(which_clock) &&
1405             (CPUCLOCK_PID(which_clock) == 0 ||
1406              CPUCLOCK_PID(which_clock) == current->pid))
1407                 return -EINVAL;
1408
1409         /*
1410          * Set up a temporary timer and then wait for it to go off.
1411          */
1412         memset(&timer, 0, sizeof timer);
1413         spin_lock_init(&timer.it_lock);
1414         timer.it_clock = which_clock;
1415         timer.it_overrun = -1;
1416         error = posix_cpu_timer_create(&timer);
1417         timer.it_process = current;
1418         if (!error) {
1419                 struct timespec __user *rmtp;
1420                 static struct itimerspec zero_it;
1421                 struct itimerspec it = { .it_value = *rqtp,
1422                                          .it_interval = {} };
1423
1424                 spin_lock_irq(&timer.it_lock);
1425                 error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1426                 if (error) {
1427                         spin_unlock_irq(&timer.it_lock);
1428                         return error;
1429                 }
1430
1431                 while (!signal_pending(current)) {
1432                         if (timer.it.cpu.expires.sched == 0) {
1433                                 /*
1434                                  * Our timer fired and was reset.
1435                                  */
1436                                 spin_unlock_irq(&timer.it_lock);
1437                                 return 0;
1438                         }
1439
1440                         /*
1441                          * Block until cpu_timer_fire (or a signal) wakes us.
1442                          */
1443                         __set_current_state(TASK_INTERRUPTIBLE);
1444                         spin_unlock_irq(&timer.it_lock);
1445                         schedule();
1446                         spin_lock_irq(&timer.it_lock);
1447                 }
1448
1449                 /*
1450                  * We were interrupted by a signal.
1451                  */
1452                 sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1453                 posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1454                 spin_unlock_irq(&timer.it_lock);
1455
1456                 if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1457                         /*
1458                          * It actually did fire already.
1459                          */
1460                         return 0;
1461                 }
1462
1463                 /*
1464                  * Report back to the user the time still remaining.
1465                  */
1466                 rmtp = (struct timespec __user *) restart_block->arg1;
1467                 if (rmtp != NULL && !(flags & TIMER_ABSTIME) &&
1468                     copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1469                         return -EFAULT;
1470
1471                 restart_block->fn = posix_cpu_clock_nanosleep_restart;
1472                 /* Caller already set restart_block->arg1 */
1473                 restart_block->arg0 = which_clock;
1474                 restart_block->arg2 = rqtp->tv_sec;
1475                 restart_block->arg3 = rqtp->tv_nsec;
1476
1477                 error = -ERESTART_RESTARTBLOCK;
1478         }
1479
1480         return error;
1481 }
1482
1483 static long
1484 posix_cpu_clock_nanosleep_restart(struct restart_block *restart_block)
1485 {
1486         clockid_t which_clock = restart_block->arg0;
1487         struct timespec t = { .tv_sec = restart_block->arg2,
1488                               .tv_nsec = restart_block->arg3 };
1489         restart_block->fn = do_no_restart_syscall;
1490         return posix_cpu_nsleep(which_clock, TIMER_ABSTIME, &t);
1491 }
1492
1493
1494 #define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1495 #define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1496
1497 static int process_cpu_clock_getres(clockid_t which_clock, struct timespec *tp)
1498 {
1499         return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1500 }
1501 static int process_cpu_clock_get(clockid_t which_clock, struct timespec *tp)
1502 {
1503         return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1504 }
1505 static int process_cpu_timer_create(struct k_itimer *timer)
1506 {
1507         timer->it_clock = PROCESS_CLOCK;
1508         return posix_cpu_timer_create(timer);
1509 }
1510 static int process_cpu_nsleep(clockid_t which_clock, int flags,
1511                               struct timespec *rqtp)
1512 {
1513         return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
1514 }
1515 static int thread_cpu_clock_getres(clockid_t which_clock, struct timespec *tp)
1516 {
1517         return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1518 }
1519 static int thread_cpu_clock_get(clockid_t which_clock, struct timespec *tp)
1520 {
1521         return posix_cpu_clock_get(THREAD_CLOCK, tp);
1522 }
1523 static int thread_cpu_timer_create(struct k_itimer *timer)
1524 {
1525         timer->it_clock = THREAD_CLOCK;
1526         return posix_cpu_timer_create(timer);
1527 }
1528 static int thread_cpu_nsleep(clockid_t which_clock, int flags,
1529                               struct timespec *rqtp)
1530 {
1531         return -EINVAL;
1532 }
1533
1534 static __init int init_posix_cpu_timers(void)
1535 {
1536         struct k_clock process = {
1537                 .clock_getres = process_cpu_clock_getres,
1538                 .clock_get = process_cpu_clock_get,
1539                 .clock_set = do_posix_clock_nosettime,
1540                 .timer_create = process_cpu_timer_create,
1541                 .nsleep = process_cpu_nsleep,
1542         };
1543         struct k_clock thread = {
1544                 .clock_getres = thread_cpu_clock_getres,
1545                 .clock_get = thread_cpu_clock_get,
1546                 .clock_set = do_posix_clock_nosettime,
1547                 .timer_create = thread_cpu_timer_create,
1548                 .nsleep = thread_cpu_nsleep,
1549         };
1550
1551         register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1552         register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1553
1554         return 0;
1555 }
1556 __initcall(init_posix_cpu_timers);