linux/kernel/posix-cpu-timers.c
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   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#include <trace/events/timer.h>
  12
  13/*
  14 * Called after updating RLIMIT_CPU to run cpu timer and update
  15 * tsk->signal->cputime_expires expiration cache if necessary. Needs
  16 * siglock protection since other code may update expiration cache as
  17 * well.
  18 */
  19void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
  20{
  21        cputime_t cputime = secs_to_cputime(rlim_new);
  22
  23        spin_lock_irq(&task->sighand->siglock);
  24        set_process_cpu_timer(task, CPUCLOCK_PROF, &cputime, NULL);
  25        spin_unlock_irq(&task->sighand->siglock);
  26}
  27
  28static 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        rcu_read_lock();
  41        p = find_task_by_vpid(pid);
  42        if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
  43                   same_thread_group(p, current) : has_group_leader_pid(p))) {
  44                error = -EINVAL;
  45        }
  46        rcu_read_unlock();
  47
  48        return error;
  49}
  50
  51static inline union cpu_time_count
  52timespec_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
  64static 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
  74static 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}
  84static 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}
  94static 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 */
 112static 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 */
 123static 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
 170static inline cputime_t prof_ticks(struct task_struct *p)
 171{
 172        return cputime_add(p->utime, p->stime);
 173}
 174static inline cputime_t virt_ticks(struct task_struct *p)
 175{
 176        return p->utime;
 177}
 178
 179static int
 180posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
 181{
 182        int error = check_clock(which_clock);
 183        if (!error) {
 184                tp->tv_sec = 0;
 185                tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
 186                if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 187                        /*
 188                         * If sched_clock is using a cycle counter, we
 189                         * don't have any idea of its true resolution
 190                         * exported, but it is much more than 1s/HZ.
 191                         */
 192                        tp->tv_nsec = 1;
 193                }
 194        }
 195        return error;
 196}
 197
 198static int
 199posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
 200{
 201        /*
 202         * You can never reset a CPU clock, but we check for other errors
 203         * in the call before failing with EPERM.
 204         */
 205        int error = check_clock(which_clock);
 206        if (error == 0) {
 207                error = -EPERM;
 208        }
 209        return error;
 210}
 211
 212
 213/*
 214 * Sample a per-thread clock for the given task.
 215 */
 216static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
 217                            union cpu_time_count *cpu)
 218{
 219        switch (CPUCLOCK_WHICH(which_clock)) {
 220        default:
 221                return -EINVAL;
 222        case CPUCLOCK_PROF:
 223                cpu->cpu = prof_ticks(p);
 224                break;
 225        case CPUCLOCK_VIRT:
 226                cpu->cpu = virt_ticks(p);
 227                break;
 228        case CPUCLOCK_SCHED:
 229                cpu->sched = task_sched_runtime(p);
 230                break;
 231        }
 232        return 0;
 233}
 234
 235void thread_group_cputime(struct task_struct *tsk, struct task_cputime *times)
 236{
 237        struct signal_struct *sig = tsk->signal;
 238        struct task_struct *t;
 239
 240        times->utime = sig->utime;
 241        times->stime = sig->stime;
 242        times->sum_exec_runtime = sig->sum_sched_runtime;
 243
 244        rcu_read_lock();
 245        /* make sure we can trust tsk->thread_group list */
 246        if (!likely(pid_alive(tsk)))
 247                goto out;
 248
 249        t = tsk;
 250        do {
 251                times->utime = cputime_add(times->utime, t->utime);
 252                times->stime = cputime_add(times->stime, t->stime);
 253                times->sum_exec_runtime += t->se.sum_exec_runtime;
 254        } while_each_thread(tsk, t);
 255out:
 256        rcu_read_unlock();
 257}
 258
 259static void update_gt_cputime(struct task_cputime *a, struct task_cputime *b)
 260{
 261        if (cputime_gt(b->utime, a->utime))
 262                a->utime = b->utime;
 263
 264        if (cputime_gt(b->stime, a->stime))
 265                a->stime = b->stime;
 266
 267        if (b->sum_exec_runtime > a->sum_exec_runtime)
 268                a->sum_exec_runtime = b->sum_exec_runtime;
 269}
 270
 271void thread_group_cputimer(struct task_struct *tsk, struct task_cputime *times)
 272{
 273        struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 274        struct task_cputime sum;
 275        unsigned long flags;
 276
 277        spin_lock_irqsave(&cputimer->lock, flags);
 278        if (!cputimer->running) {
 279                cputimer->running = 1;
 280                /*
 281                 * The POSIX timer interface allows for absolute time expiry
 282                 * values through the TIMER_ABSTIME flag, therefore we have
 283                 * to synchronize the timer to the clock every time we start
 284                 * it.
 285                 */
 286                thread_group_cputime(tsk, &sum);
 287                update_gt_cputime(&cputimer->cputime, &sum);
 288        }
 289        *times = cputimer->cputime;
 290        spin_unlock_irqrestore(&cputimer->lock, flags);
 291}
 292
 293/*
 294 * Sample a process (thread group) clock for the given group_leader task.
 295 * Must be called with tasklist_lock held for reading.
 296 */
 297static int cpu_clock_sample_group(const clockid_t which_clock,
 298                                  struct task_struct *p,
 299                                  union cpu_time_count *cpu)
 300{
 301        struct task_cputime cputime;
 302
 303        switch (CPUCLOCK_WHICH(which_clock)) {
 304        default:
 305                return -EINVAL;
 306        case CPUCLOCK_PROF:
 307                thread_group_cputime(p, &cputime);
 308                cpu->cpu = cputime_add(cputime.utime, cputime.stime);
 309                break;
 310        case CPUCLOCK_VIRT:
 311                thread_group_cputime(p, &cputime);
 312                cpu->cpu = cputime.utime;
 313                break;
 314        case CPUCLOCK_SCHED:
 315                cpu->sched = thread_group_sched_runtime(p);
 316                break;
 317        }
 318        return 0;
 319}
 320
 321
 322static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 323{
 324        const pid_t pid = CPUCLOCK_PID(which_clock);
 325        int error = -EINVAL;
 326        union cpu_time_count rtn;
 327
 328        if (pid == 0) {
 329                /*
 330                 * Special case constant value for our own clocks.
 331                 * We don't have to do any lookup to find ourselves.
 332                 */
 333                if (CPUCLOCK_PERTHREAD(which_clock)) {
 334                        /*
 335                         * Sampling just ourselves we can do with no locking.
 336                         */
 337                        error = cpu_clock_sample(which_clock,
 338                                                 current, &rtn);
 339                } else {
 340                        read_lock(&tasklist_lock);
 341                        error = cpu_clock_sample_group(which_clock,
 342                                                       current, &rtn);
 343                        read_unlock(&tasklist_lock);
 344                }
 345        } else {
 346                /*
 347                 * Find the given PID, and validate that the caller
 348                 * should be able to see it.
 349                 */
 350                struct task_struct *p;
 351                rcu_read_lock();
 352                p = find_task_by_vpid(pid);
 353                if (p) {
 354                        if (CPUCLOCK_PERTHREAD(which_clock)) {
 355                                if (same_thread_group(p, current)) {
 356                                        error = cpu_clock_sample(which_clock,
 357                                                                 p, &rtn);
 358                                }
 359                        } else {
 360                                read_lock(&tasklist_lock);
 361                                if (thread_group_leader(p) && p->sighand) {
 362                                        error =
 363                                            cpu_clock_sample_group(which_clock,
 364                                                                   p, &rtn);
 365                                }
 366                                read_unlock(&tasklist_lock);
 367                        }
 368                }
 369                rcu_read_unlock();
 370        }
 371
 372        if (error)
 373                return error;
 374        sample_to_timespec(which_clock, rtn, tp);
 375        return 0;
 376}
 377
 378
 379/*
 380 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 381 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
 382 * new timer already all-zeros initialized.
 383 */
 384static int posix_cpu_timer_create(struct k_itimer *new_timer)
 385{
 386        int ret = 0;
 387        const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
 388        struct task_struct *p;
 389
 390        if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 391                return -EINVAL;
 392
 393        INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 394
 395        rcu_read_lock();
 396        if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
 397                if (pid == 0) {
 398                        p = current;
 399                } else {
 400                        p = find_task_by_vpid(pid);
 401                        if (p && !same_thread_group(p, current))
 402                                p = NULL;
 403                }
 404        } else {
 405                if (pid == 0) {
 406                        p = current->group_leader;
 407                } else {
 408                        p = find_task_by_vpid(pid);
 409                        if (p && !has_group_leader_pid(p))
 410                                p = NULL;
 411                }
 412        }
 413        new_timer->it.cpu.task = p;
 414        if (p) {
 415                get_task_struct(p);
 416        } else {
 417                ret = -EINVAL;
 418        }
 419        rcu_read_unlock();
 420
 421        return ret;
 422}
 423
 424/*
 425 * Clean up a CPU-clock timer that is about to be destroyed.
 426 * This is called from timer deletion with the timer already locked.
 427 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 428 * and try again.  (This happens when the timer is in the middle of firing.)
 429 */
 430static int posix_cpu_timer_del(struct k_itimer *timer)
 431{
 432        struct task_struct *p = timer->it.cpu.task;
 433        int ret = 0;
 434
 435        if (likely(p != NULL)) {
 436                read_lock(&tasklist_lock);
 437                if (unlikely(p->sighand == NULL)) {
 438                        /*
 439                         * We raced with the reaping of the task.
 440                         * The deletion should have cleared us off the list.
 441                         */
 442                        BUG_ON(!list_empty(&timer->it.cpu.entry));
 443                } else {
 444                        spin_lock(&p->sighand->siglock);
 445                        if (timer->it.cpu.firing)
 446                                ret = TIMER_RETRY;
 447                        else
 448                                list_del(&timer->it.cpu.entry);
 449                        spin_unlock(&p->sighand->siglock);
 450                }
 451                read_unlock(&tasklist_lock);
 452
 453                if (!ret)
 454                        put_task_struct(p);
 455        }
 456
 457        return ret;
 458}
 459
 460/*
 461 * Clean out CPU timers still ticking when a thread exited.  The task
 462 * pointer is cleared, and the expiry time is replaced with the residual
 463 * time for later timer_gettime calls to return.
 464 * This must be called with the siglock held.
 465 */
 466static void cleanup_timers(struct list_head *head,
 467                           cputime_t utime, cputime_t stime,
 468                           unsigned long long sum_exec_runtime)
 469{
 470        struct cpu_timer_list *timer, *next;
 471        cputime_t ptime = cputime_add(utime, stime);
 472
 473        list_for_each_entry_safe(timer, next, head, entry) {
 474                list_del_init(&timer->entry);
 475                if (cputime_lt(timer->expires.cpu, ptime)) {
 476                        timer->expires.cpu = cputime_zero;
 477                } else {
 478                        timer->expires.cpu = cputime_sub(timer->expires.cpu,
 479                                                         ptime);
 480                }
 481        }
 482
 483        ++head;
 484        list_for_each_entry_safe(timer, next, head, entry) {
 485                list_del_init(&timer->entry);
 486                if (cputime_lt(timer->expires.cpu, utime)) {
 487                        timer->expires.cpu = cputime_zero;
 488                } else {
 489                        timer->expires.cpu = cputime_sub(timer->expires.cpu,
 490                                                         utime);
 491                }
 492        }
 493
 494        ++head;
 495        list_for_each_entry_safe(timer, next, head, entry) {
 496                list_del_init(&timer->entry);
 497                if (timer->expires.sched < sum_exec_runtime) {
 498                        timer->expires.sched = 0;
 499                } else {
 500                        timer->expires.sched -= sum_exec_runtime;
 501                }
 502        }
 503}
 504
 505/*
 506 * These are both called with the siglock held, when the current thread
 507 * is being reaped.  When the final (leader) thread in the group is reaped,
 508 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 509 */
 510void posix_cpu_timers_exit(struct task_struct *tsk)
 511{
 512        cleanup_timers(tsk->cpu_timers,
 513                       tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
 514
 515}
 516void posix_cpu_timers_exit_group(struct task_struct *tsk)
 517{
 518        struct signal_struct *const sig = tsk->signal;
 519
 520        cleanup_timers(tsk->signal->cpu_timers,
 521                       cputime_add(tsk->utime, sig->utime),
 522                       cputime_add(tsk->stime, sig->stime),
 523                       tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
 524}
 525
 526static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 527{
 528        /*
 529         * That's all for this thread or process.
 530         * We leave our residual in expires to be reported.
 531         */
 532        put_task_struct(timer->it.cpu.task);
 533        timer->it.cpu.task = NULL;
 534        timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
 535                                             timer->it.cpu.expires,
 536                                             now);
 537}
 538
 539static inline int expires_gt(cputime_t expires, cputime_t new_exp)
 540{
 541        return cputime_eq(expires, cputime_zero) ||
 542               cputime_gt(expires, new_exp);
 543}
 544
 545/*
 546 * Insert the timer on the appropriate list before any timers that
 547 * expire later.  This must be called with the tasklist_lock held
 548 * for reading, interrupts disabled and p->sighand->siglock taken.
 549 */
 550static void arm_timer(struct k_itimer *timer)
 551{
 552        struct task_struct *p = timer->it.cpu.task;
 553        struct list_head *head, *listpos;
 554        struct task_cputime *cputime_expires;
 555        struct cpu_timer_list *const nt = &timer->it.cpu;
 556        struct cpu_timer_list *next;
 557
 558        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 559                head = p->cpu_timers;
 560                cputime_expires = &p->cputime_expires;
 561        } else {
 562                head = p->signal->cpu_timers;
 563                cputime_expires = &p->signal->cputime_expires;
 564        }
 565        head += CPUCLOCK_WHICH(timer->it_clock);
 566
 567        listpos = head;
 568        list_for_each_entry(next, head, entry) {
 569                if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
 570                        break;
 571                listpos = &next->entry;
 572        }
 573        list_add(&nt->entry, listpos);
 574
 575        if (listpos == head) {
 576                union cpu_time_count *exp = &nt->expires;
 577
 578                /*
 579                 * We are the new earliest-expiring POSIX 1.b timer, hence
 580                 * need to update expiration cache. Take into account that
 581                 * for process timers we share expiration cache with itimers
 582                 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
 583                 */
 584
 585                switch (CPUCLOCK_WHICH(timer->it_clock)) {
 586                case CPUCLOCK_PROF:
 587                        if (expires_gt(cputime_expires->prof_exp, exp->cpu))
 588                                cputime_expires->prof_exp = exp->cpu;
 589                        break;
 590                case CPUCLOCK_VIRT:
 591                        if (expires_gt(cputime_expires->virt_exp, exp->cpu))
 592                                cputime_expires->virt_exp = exp->cpu;
 593                        break;
 594                case CPUCLOCK_SCHED:
 595                        if (cputime_expires->sched_exp == 0 ||
 596                            cputime_expires->sched_exp > exp->sched)
 597                                cputime_expires->sched_exp = exp->sched;
 598                        break;
 599                }
 600        }
 601}
 602
 603/*
 604 * The timer is locked, fire it and arrange for its reload.
 605 */
 606static void cpu_timer_fire(struct k_itimer *timer)
 607{
 608        if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 609                /*
 610                 * User don't want any signal.
 611                 */
 612                timer->it.cpu.expires.sched = 0;
 613        } else if (unlikely(timer->sigq == NULL)) {
 614                /*
 615                 * This a special case for clock_nanosleep,
 616                 * not a normal timer from sys_timer_create.
 617                 */
 618                wake_up_process(timer->it_process);
 619                timer->it.cpu.expires.sched = 0;
 620        } else if (timer->it.cpu.incr.sched == 0) {
 621                /*
 622                 * One-shot timer.  Clear it as soon as it's fired.
 623                 */
 624                posix_timer_event(timer, 0);
 625                timer->it.cpu.expires.sched = 0;
 626        } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 627                /*
 628                 * The signal did not get queued because the signal
 629                 * was ignored, so we won't get any callback to
 630                 * reload the timer.  But we need to keep it
 631                 * ticking in case the signal is deliverable next time.
 632                 */
 633                posix_cpu_timer_schedule(timer);
 634        }
 635}
 636
 637/*
 638 * Sample a process (thread group) timer for the given group_leader task.
 639 * Must be called with tasklist_lock held for reading.
 640 */
 641static int cpu_timer_sample_group(const clockid_t which_clock,
 642                                  struct task_struct *p,
 643                                  union cpu_time_count *cpu)
 644{
 645        struct task_cputime cputime;
 646
 647        thread_group_cputimer(p, &cputime);
 648        switch (CPUCLOCK_WHICH(which_clock)) {
 649        default:
 650                return -EINVAL;
 651        case CPUCLOCK_PROF:
 652                cpu->cpu = cputime_add(cputime.utime, cputime.stime);
 653                break;
 654        case CPUCLOCK_VIRT:
 655                cpu->cpu = cputime.utime;
 656                break;
 657        case CPUCLOCK_SCHED:
 658                cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
 659                break;
 660        }
 661        return 0;
 662}
 663
 664/*
 665 * Guts of sys_timer_settime for CPU timers.
 666 * This is called with the timer locked and interrupts disabled.
 667 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 668 * and try again.  (This happens when the timer is in the middle of firing.)
 669 */
 670static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 671                               struct itimerspec *new, struct itimerspec *old)
 672{
 673        struct task_struct *p = timer->it.cpu.task;
 674        union cpu_time_count old_expires, new_expires, old_incr, val;
 675        int ret;
 676
 677        if (unlikely(p == NULL)) {
 678                /*
 679                 * Timer refers to a dead task's clock.
 680                 */
 681                return -ESRCH;
 682        }
 683
 684        new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
 685
 686        read_lock(&tasklist_lock);
 687        /*
 688         * We need the tasklist_lock to protect against reaping that
 689         * clears p->sighand.  If p has just been reaped, we can no
 690         * longer get any information about it at all.
 691         */
 692        if (unlikely(p->sighand == NULL)) {
 693                read_unlock(&tasklist_lock);
 694                put_task_struct(p);
 695                timer->it.cpu.task = NULL;
 696                return -ESRCH;
 697        }
 698
 699        /*
 700         * Disarm any old timer after extracting its expiry time.
 701         */
 702        BUG_ON(!irqs_disabled());
 703
 704        ret = 0;
 705        old_incr = timer->it.cpu.incr;
 706        spin_lock(&p->sighand->siglock);
 707        old_expires = timer->it.cpu.expires;
 708        if (unlikely(timer->it.cpu.firing)) {
 709                timer->it.cpu.firing = -1;
 710                ret = TIMER_RETRY;
 711        } else
 712                list_del_init(&timer->it.cpu.entry);
 713
 714        /*
 715         * We need to sample the current value to convert the new
 716         * value from to relative and absolute, and to convert the
 717         * old value from absolute to relative.  To set a process
 718         * timer, we need a sample to balance the thread expiry
 719         * times (in arm_timer).  With an absolute time, we must
 720         * check if it's already passed.  In short, we need a sample.
 721         */
 722        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 723                cpu_clock_sample(timer->it_clock, p, &val);
 724        } else {
 725                cpu_timer_sample_group(timer->it_clock, p, &val);
 726        }
 727
 728        if (old) {
 729                if (old_expires.sched == 0) {
 730                        old->it_value.tv_sec = 0;
 731                        old->it_value.tv_nsec = 0;
 732                } else {
 733                        /*
 734                         * Update the timer in case it has
 735                         * overrun already.  If it has,
 736                         * we'll report it as having overrun
 737                         * and with the next reloaded timer
 738                         * already ticking, though we are
 739                         * swallowing that pending
 740                         * notification here to install the
 741                         * new setting.
 742                         */
 743                        bump_cpu_timer(timer, val);
 744                        if (cpu_time_before(timer->it_clock, val,
 745                                            timer->it.cpu.expires)) {
 746                                old_expires = cpu_time_sub(
 747                                        timer->it_clock,
 748                                        timer->it.cpu.expires, val);
 749                                sample_to_timespec(timer->it_clock,
 750                                                   old_expires,
 751                                                   &old->it_value);
 752                        } else {
 753                                old->it_value.tv_nsec = 1;
 754                                old->it_value.tv_sec = 0;
 755                        }
 756                }
 757        }
 758
 759        if (unlikely(ret)) {
 760                /*
 761                 * We are colliding with the timer actually firing.
 762                 * Punt after filling in the timer's old value, and
 763                 * disable this firing since we are already reporting
 764                 * it as an overrun (thanks to bump_cpu_timer above).
 765                 */
 766                spin_unlock(&p->sighand->siglock);
 767                read_unlock(&tasklist_lock);
 768                goto out;
 769        }
 770
 771        if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
 772                cpu_time_add(timer->it_clock, &new_expires, val);
 773        }
 774
 775        /*
 776         * Install the new expiry time (or zero).
 777         * For a timer with no notification action, we don't actually
 778         * arm the timer (we'll just fake it for timer_gettime).
 779         */
 780        timer->it.cpu.expires = new_expires;
 781        if (new_expires.sched != 0 &&
 782            cpu_time_before(timer->it_clock, val, new_expires)) {
 783                arm_timer(timer);
 784        }
 785
 786        spin_unlock(&p->sighand->siglock);
 787        read_unlock(&tasklist_lock);
 788
 789        /*
 790         * Install the new reload setting, and
 791         * set up the signal and overrun bookkeeping.
 792         */
 793        timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
 794                                                &new->it_interval);
 795
 796        /*
 797         * This acts as a modification timestamp for the timer,
 798         * so any automatic reload attempt will punt on seeing
 799         * that we have reset the timer manually.
 800         */
 801        timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 802                ~REQUEUE_PENDING;
 803        timer->it_overrun_last = 0;
 804        timer->it_overrun = -1;
 805
 806        if (new_expires.sched != 0 &&
 807            !cpu_time_before(timer->it_clock, val, new_expires)) {
 808                /*
 809                 * The designated time already passed, so we notify
 810                 * immediately, even if the thread never runs to
 811                 * accumulate more time on this clock.
 812                 */
 813                cpu_timer_fire(timer);
 814        }
 815
 816        ret = 0;
 817 out:
 818        if (old) {
 819                sample_to_timespec(timer->it_clock,
 820                                   old_incr, &old->it_interval);
 821        }
 822        return ret;
 823}
 824
 825static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 826{
 827        union cpu_time_count now;
 828        struct task_struct *p = timer->it.cpu.task;
 829        int clear_dead;
 830
 831        /*
 832         * Easy part: convert the reload time.
 833         */
 834        sample_to_timespec(timer->it_clock,
 835                           timer->it.cpu.incr, &itp->it_interval);
 836
 837        if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
 838                itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 839                return;
 840        }
 841
 842        if (unlikely(p == NULL)) {
 843                /*
 844                 * This task already died and the timer will never fire.
 845                 * In this case, expires is actually the dead value.
 846                 */
 847        dead:
 848                sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
 849                                   &itp->it_value);
 850                return;
 851        }
 852
 853        /*
 854         * Sample the clock to take the difference with the expiry time.
 855         */
 856        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 857                cpu_clock_sample(timer->it_clock, p, &now);
 858                clear_dead = p->exit_state;
 859        } else {
 860                read_lock(&tasklist_lock);
 861                if (unlikely(p->sighand == NULL)) {
 862                        /*
 863                         * The process has been reaped.
 864                         * We can't even collect a sample any more.
 865                         * Call the timer disarmed, nothing else to do.
 866                         */
 867                        put_task_struct(p);
 868                        timer->it.cpu.task = NULL;
 869                        timer->it.cpu.expires.sched = 0;
 870                        read_unlock(&tasklist_lock);
 871                        goto dead;
 872                } else {
 873                        cpu_timer_sample_group(timer->it_clock, p, &now);
 874                        clear_dead = (unlikely(p->exit_state) &&
 875                                      thread_group_empty(p));
 876                }
 877                read_unlock(&tasklist_lock);
 878        }
 879
 880        if (unlikely(clear_dead)) {
 881                /*
 882                 * We've noticed that the thread is dead, but
 883                 * not yet reaped.  Take this opportunity to
 884                 * drop our task ref.
 885                 */
 886                clear_dead_task(timer, now);
 887                goto dead;
 888        }
 889
 890        if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
 891                sample_to_timespec(timer->it_clock,
 892                                   cpu_time_sub(timer->it_clock,
 893                                                timer->it.cpu.expires, now),
 894                                   &itp->it_value);
 895        } else {
 896                /*
 897                 * The timer should have expired already, but the firing
 898                 * hasn't taken place yet.  Say it's just about to expire.
 899                 */
 900                itp->it_value.tv_nsec = 1;
 901                itp->it_value.tv_sec = 0;
 902        }
 903}
 904
 905/*
 906 * Check for any per-thread CPU timers that have fired and move them off
 907 * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 908 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 909 */
 910static void check_thread_timers(struct task_struct *tsk,
 911                                struct list_head *firing)
 912{
 913        int maxfire;
 914        struct list_head *timers = tsk->cpu_timers;
 915        struct signal_struct *const sig = tsk->signal;
 916        unsigned long soft;
 917
 918        maxfire = 20;
 919        tsk->cputime_expires.prof_exp = cputime_zero;
 920        while (!list_empty(timers)) {
 921                struct cpu_timer_list *t = list_first_entry(timers,
 922                                                      struct cpu_timer_list,
 923                                                      entry);
 924                if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
 925                        tsk->cputime_expires.prof_exp = t->expires.cpu;
 926                        break;
 927                }
 928                t->firing = 1;
 929                list_move_tail(&t->entry, firing);
 930        }
 931
 932        ++timers;
 933        maxfire = 20;
 934        tsk->cputime_expires.virt_exp = cputime_zero;
 935        while (!list_empty(timers)) {
 936                struct cpu_timer_list *t = list_first_entry(timers,
 937                                                      struct cpu_timer_list,
 938                                                      entry);
 939                if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
 940                        tsk->cputime_expires.virt_exp = t->expires.cpu;
 941                        break;
 942                }
 943                t->firing = 1;
 944                list_move_tail(&t->entry, firing);
 945        }
 946
 947        ++timers;
 948        maxfire = 20;
 949        tsk->cputime_expires.sched_exp = 0;
 950        while (!list_empty(timers)) {
 951                struct cpu_timer_list *t = list_first_entry(timers,
 952                                                      struct cpu_timer_list,
 953                                                      entry);
 954                if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
 955                        tsk->cputime_expires.sched_exp = t->expires.sched;
 956                        break;
 957                }
 958                t->firing = 1;
 959                list_move_tail(&t->entry, firing);
 960        }
 961
 962        /*
 963         * Check for the special case thread timers.
 964         */
 965        soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
 966        if (soft != RLIM_INFINITY) {
 967                unsigned long hard =
 968                        ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
 969
 970                if (hard != RLIM_INFINITY &&
 971                    tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
 972                        /*
 973                         * At the hard limit, we just die.
 974                         * No need to calculate anything else now.
 975                         */
 976                        __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
 977                        return;
 978                }
 979                if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
 980                        /*
 981                         * At the soft limit, send a SIGXCPU every second.
 982                         */
 983                        if (soft < hard) {
 984                                soft += USEC_PER_SEC;
 985                                sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
 986                        }
 987                        printk(KERN_INFO
 988                                "RT Watchdog Timeout: %s[%d]\n",
 989                                tsk->comm, task_pid_nr(tsk));
 990                        __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
 991                }
 992        }
 993}
 994
 995static void stop_process_timers(struct signal_struct *sig)
 996{
 997        struct thread_group_cputimer *cputimer = &sig->cputimer;
 998        unsigned long flags;
 999
1000        spin_lock_irqsave(&cputimer->lock, flags);
1001        cputimer->running = 0;
1002        spin_unlock_irqrestore(&cputimer->lock, flags);
1003}
1004
1005static u32 onecputick;
1006
1007static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
1008                             cputime_t *expires, cputime_t cur_time, int signo)
1009{
1010        if (cputime_eq(it->expires, cputime_zero))
1011                return;
1012
1013        if (cputime_ge(cur_time, it->expires)) {
1014                if (!cputime_eq(it->incr, cputime_zero)) {
1015                        it->expires = cputime_add(it->expires, it->incr);
1016                        it->error += it->incr_error;
1017                        if (it->error >= onecputick) {
1018                                it->expires = cputime_sub(it->expires,
1019                                                          cputime_one_jiffy);
1020                                it->error -= onecputick;
1021                        }
1022                } else {
1023                        it->expires = cputime_zero;
1024                }
1025
1026                trace_itimer_expire(signo == SIGPROF ?
1027                                    ITIMER_PROF : ITIMER_VIRTUAL,
1028                                    tsk->signal->leader_pid, cur_time);
1029                __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
1030        }
1031
1032        if (!cputime_eq(it->expires, cputime_zero) &&
1033            (cputime_eq(*expires, cputime_zero) ||
1034             cputime_lt(it->expires, *expires))) {
1035                *expires = it->expires;
1036        }
1037}
1038
1039/**
1040 * task_cputime_zero - Check a task_cputime struct for all zero fields.
1041 *
1042 * @cputime:    The struct to compare.
1043 *
1044 * Checks @cputime to see if all fields are zero.  Returns true if all fields
1045 * are zero, false if any field is nonzero.
1046 */
1047static inline int task_cputime_zero(const struct task_cputime *cputime)
1048{
1049        if (cputime_eq(cputime->utime, cputime_zero) &&
1050            cputime_eq(cputime->stime, cputime_zero) &&
1051            cputime->sum_exec_runtime == 0)
1052                return 1;
1053        return 0;
1054}
1055
1056/*
1057 * Check for any per-thread CPU timers that have fired and move them
1058 * off the tsk->*_timers list onto the firing list.  Per-thread timers
1059 * have already been taken off.
1060 */
1061static void check_process_timers(struct task_struct *tsk,
1062                                 struct list_head *firing)
1063{
1064        int maxfire;
1065        struct signal_struct *const sig = tsk->signal;
1066        cputime_t utime, ptime, virt_expires, prof_expires;
1067        unsigned long long sum_sched_runtime, sched_expires;
1068        struct list_head *timers = sig->cpu_timers;
1069        struct task_cputime cputime;
1070        unsigned long soft;
1071
1072        /*
1073         * Collect the current process totals.
1074         */
1075        thread_group_cputimer(tsk, &cputime);
1076        utime = cputime.utime;
1077        ptime = cputime_add(utime, cputime.stime);
1078        sum_sched_runtime = cputime.sum_exec_runtime;
1079        maxfire = 20;
1080        prof_expires = cputime_zero;
1081        while (!list_empty(timers)) {
1082                struct cpu_timer_list *tl = list_first_entry(timers,
1083                                                      struct cpu_timer_list,
1084                                                      entry);
1085                if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
1086                        prof_expires = tl->expires.cpu;
1087                        break;
1088                }
1089                tl->firing = 1;
1090                list_move_tail(&tl->entry, firing);
1091        }
1092
1093        ++timers;
1094        maxfire = 20;
1095        virt_expires = cputime_zero;
1096        while (!list_empty(timers)) {
1097                struct cpu_timer_list *tl = list_first_entry(timers,
1098                                                      struct cpu_timer_list,
1099                                                      entry);
1100                if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
1101                        virt_expires = tl->expires.cpu;
1102                        break;
1103                }
1104                tl->firing = 1;
1105                list_move_tail(&tl->entry, firing);
1106        }
1107
1108        ++timers;
1109        maxfire = 20;
1110        sched_expires = 0;
1111        while (!list_empty(timers)) {
1112                struct cpu_timer_list *tl = list_first_entry(timers,
1113                                                      struct cpu_timer_list,
1114                                                      entry);
1115                if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
1116                        sched_expires = tl->expires.sched;
1117                        break;
1118                }
1119                tl->firing = 1;
1120                list_move_tail(&tl->entry, firing);
1121        }
1122
1123        /*
1124         * Check for the special case process timers.
1125         */
1126        check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
1127                         SIGPROF);
1128        check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
1129                         SIGVTALRM);
1130        soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1131        if (soft != RLIM_INFINITY) {
1132                unsigned long psecs = cputime_to_secs(ptime);
1133                unsigned long hard =
1134                        ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
1135                cputime_t x;
1136                if (psecs >= hard) {
1137                        /*
1138                         * At the hard limit, we just die.
1139                         * No need to calculate anything else now.
1140                         */
1141                        __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1142                        return;
1143                }
1144                if (psecs >= soft) {
1145                        /*
1146                         * At the soft limit, send a SIGXCPU every second.
1147                         */
1148                        __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1149                        if (soft < hard) {
1150                                soft++;
1151                                sig->rlim[RLIMIT_CPU].rlim_cur = soft;
1152                        }
1153                }
1154                x = secs_to_cputime(soft);
1155                if (cputime_eq(prof_expires, cputime_zero) ||
1156                    cputime_lt(x, prof_expires)) {
1157                        prof_expires = x;
1158                }
1159        }
1160
1161        sig->cputime_expires.prof_exp = prof_expires;
1162        sig->cputime_expires.virt_exp = virt_expires;
1163        sig->cputime_expires.sched_exp = sched_expires;
1164        if (task_cputime_zero(&sig->cputime_expires))
1165                stop_process_timers(sig);
1166}
1167
1168/*
1169 * This is called from the signal code (via do_schedule_next_timer)
1170 * when the last timer signal was delivered and we have to reload the timer.
1171 */
1172void posix_cpu_timer_schedule(struct k_itimer *timer)
1173{
1174        struct task_struct *p = timer->it.cpu.task;
1175        union cpu_time_count now;
1176
1177        if (unlikely(p == NULL))
1178                /*
1179                 * The task was cleaned up already, no future firings.
1180                 */
1181                goto out;
1182
1183        /*
1184         * Fetch the current sample and update the timer's expiry time.
1185         */
1186        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1187                cpu_clock_sample(timer->it_clock, p, &now);
1188                bump_cpu_timer(timer, now);
1189                if (unlikely(p->exit_state)) {
1190                        clear_dead_task(timer, now);
1191                        goto out;
1192                }
1193                read_lock(&tasklist_lock); /* arm_timer needs it.  */
1194                spin_lock(&p->sighand->siglock);
1195        } else {
1196                read_lock(&tasklist_lock);
1197                if (unlikely(p->sighand == NULL)) {
1198                        /*
1199                         * The process has been reaped.
1200                         * We can't even collect a sample any more.
1201                         */
1202                        put_task_struct(p);
1203                        timer->it.cpu.task = p = NULL;
1204                        timer->it.cpu.expires.sched = 0;
1205                        goto out_unlock;
1206                } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1207                        /*
1208                         * We've noticed that the thread is dead, but
1209                         * not yet reaped.  Take this opportunity to
1210                         * drop our task ref.
1211                         */
1212                        clear_dead_task(timer, now);
1213                        goto out_unlock;
1214                }
1215                spin_lock(&p->sighand->siglock);
1216                cpu_timer_sample_group(timer->it_clock, p, &now);
1217                bump_cpu_timer(timer, now);
1218                /* Leave the tasklist_lock locked for the call below.  */
1219        }
1220
1221        /*
1222         * Now re-arm for the new expiry time.
1223         */
1224        BUG_ON(!irqs_disabled());
1225        arm_timer(timer);
1226        spin_unlock(&p->sighand->siglock);
1227
1228out_unlock:
1229        read_unlock(&tasklist_lock);
1230
1231out:
1232        timer->it_overrun_last = timer->it_overrun;
1233        timer->it_overrun = -1;
1234        ++timer->it_requeue_pending;
1235}
1236
1237/**
1238 * task_cputime_expired - Compare two task_cputime entities.
1239 *
1240 * @sample:     The task_cputime structure to be checked for expiration.
1241 * @expires:    Expiration times, against which @sample will be checked.
1242 *
1243 * Checks @sample against @expires to see if any field of @sample has expired.
1244 * Returns true if any field of the former is greater than the corresponding
1245 * field of the latter if the latter field is set.  Otherwise returns false.
1246 */
1247static inline int task_cputime_expired(const struct task_cputime *sample,
1248                                        const struct task_cputime *expires)
1249{
1250        if (!cputime_eq(expires->utime, cputime_zero) &&
1251            cputime_ge(sample->utime, expires->utime))
1252                return 1;
1253        if (!cputime_eq(expires->stime, cputime_zero) &&
1254            cputime_ge(cputime_add(sample->utime, sample->stime),
1255                       expires->stime))
1256                return 1;
1257        if (expires->sum_exec_runtime != 0 &&
1258            sample->sum_exec_runtime >= expires->sum_exec_runtime)
1259                return 1;
1260        return 0;
1261}
1262
1263/**
1264 * fastpath_timer_check - POSIX CPU timers fast path.
1265 *
1266 * @tsk:        The task (thread) being checked.
1267 *
1268 * Check the task and thread group timers.  If both are zero (there are no
1269 * timers set) return false.  Otherwise snapshot the task and thread group
1270 * timers and compare them with the corresponding expiration times.  Return
1271 * true if a timer has expired, else return false.
1272 */
1273static inline int fastpath_timer_check(struct task_struct *tsk)
1274{
1275        struct signal_struct *sig;
1276
1277        if (!task_cputime_zero(&tsk->cputime_expires)) {
1278                struct task_cputime task_sample = {
1279                        .utime = tsk->utime,
1280                        .stime = tsk->stime,
1281                        .sum_exec_runtime = tsk->se.sum_exec_runtime
1282                };
1283
1284                if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1285                        return 1;
1286        }
1287
1288        sig = tsk->signal;
1289        if (sig->cputimer.running) {
1290                struct task_cputime group_sample;
1291
1292                spin_lock(&sig->cputimer.lock);
1293                group_sample = sig->cputimer.cputime;
1294                spin_unlock(&sig->cputimer.lock);
1295
1296                if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1297                        return 1;
1298        }
1299
1300        return 0;
1301}
1302
1303/*
1304 * This is called from the timer interrupt handler.  The irq handler has
1305 * already updated our counts.  We need to check if any timers fire now.
1306 * Interrupts are disabled.
1307 */
1308void run_posix_cpu_timers(struct task_struct *tsk)
1309{
1310        LIST_HEAD(firing);
1311        struct k_itimer *timer, *next;
1312        unsigned long flags;
1313
1314        BUG_ON(!irqs_disabled());
1315
1316        /*
1317         * The fast path checks that there are no expired thread or thread
1318         * group timers.  If that's so, just return.
1319         */
1320        if (!fastpath_timer_check(tsk))
1321                return;
1322
1323        if (!lock_task_sighand(tsk, &flags))
1324                return;
1325        /*
1326         * Here we take off tsk->signal->cpu_timers[N] and
1327         * tsk->cpu_timers[N] all the timers that are firing, and
1328         * put them on the firing list.
1329         */
1330        check_thread_timers(tsk, &firing);
1331        /*
1332         * If there are any active process wide timers (POSIX 1.b, itimers,
1333         * RLIMIT_CPU) cputimer must be running.
1334         */
1335        if (tsk->signal->cputimer.running)
1336                check_process_timers(tsk, &firing);
1337
1338        /*
1339         * We must release these locks before taking any timer's lock.
1340         * There is a potential race with timer deletion here, as the
1341         * siglock now protects our private firing list.  We have set
1342         * the firing flag in each timer, so that a deletion attempt
1343         * that gets the timer lock before we do will give it up and
1344         * spin until we've taken care of that timer below.
1345         */
1346        unlock_task_sighand(tsk, &flags);
1347
1348        /*
1349         * Now that all the timers on our list have the firing flag,
1350         * no one will touch their list entries but us.  We'll take
1351         * each timer's lock before clearing its firing flag, so no
1352         * timer call will interfere.
1353         */
1354        list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1355                int cpu_firing;
1356
1357                spin_lock(&timer->it_lock);
1358                list_del_init(&timer->it.cpu.entry);
1359                cpu_firing = timer->it.cpu.firing;
1360                timer->it.cpu.firing = 0;
1361                /*
1362                 * The firing flag is -1 if we collided with a reset
1363                 * of the timer, which already reported this
1364                 * almost-firing as an overrun.  So don't generate an event.
1365                 */
1366                if (likely(cpu_firing >= 0))
1367                        cpu_timer_fire(timer);
1368                spin_unlock(&timer->it_lock);
1369        }
1370}
1371
1372/*
1373 * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1374 * The tsk->sighand->siglock must be held by the caller.
1375 */
1376void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1377                           cputime_t *newval, cputime_t *oldval)
1378{
1379        union cpu_time_count now;
1380
1381        BUG_ON(clock_idx == CPUCLOCK_SCHED);
1382        cpu_timer_sample_group(clock_idx, tsk, &now);
1383
1384        if (oldval) {
1385                /*
1386                 * We are setting itimer. The *oldval is absolute and we update
1387                 * it to be relative, *newval argument is relative and we update
1388                 * it to be absolute.
1389                 */
1390                if (!cputime_eq(*oldval, cputime_zero)) {
1391                        if (cputime_le(*oldval, now.cpu)) {
1392                                /* Just about to fire. */
1393                                *oldval = cputime_one_jiffy;
1394                        } else {
1395                                *oldval = cputime_sub(*oldval, now.cpu);
1396                        }
1397                }
1398
1399                if (cputime_eq(*newval, cputime_zero))
1400                        return;
1401                *newval = cputime_add(*newval, now.cpu);
1402        }
1403
1404        /*
1405         * Update expiration cache if we are the earliest timer, or eventually
1406         * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
1407         */
1408        switch (clock_idx) {
1409        case CPUCLOCK_PROF:
1410                if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
1411                        tsk->signal->cputime_expires.prof_exp = *newval;
1412                break;
1413        case CPUCLOCK_VIRT:
1414                if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
1415                        tsk->signal->cputime_expires.virt_exp = *newval;
1416                break;
1417        }
1418}
1419
1420static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1421                            struct timespec *rqtp, struct itimerspec *it)
1422{
1423        struct k_itimer timer;
1424        int error;
1425
1426        /*
1427         * Set up a temporary timer and then wait for it to go off.
1428         */
1429        memset(&timer, 0, sizeof timer);
1430        spin_lock_init(&timer.it_lock);
1431        timer.it_clock = which_clock;
1432        timer.it_overrun = -1;
1433        error = posix_cpu_timer_create(&timer);
1434        timer.it_process = current;
1435        if (!error) {
1436                static struct itimerspec zero_it;
1437
1438                memset(it, 0, sizeof *it);
1439                it->it_value = *rqtp;
1440
1441                spin_lock_irq(&timer.it_lock);
1442                error = posix_cpu_timer_set(&timer, flags, it, NULL);
1443                if (error) {
1444                        spin_unlock_irq(&timer.it_lock);
1445                        return error;
1446                }
1447
1448                while (!signal_pending(current)) {
1449                        if (timer.it.cpu.expires.sched == 0) {
1450                                /*
1451                                 * Our timer fired and was reset.
1452                                 */
1453                                spin_unlock_irq(&timer.it_lock);
1454                                return 0;
1455                        }
1456
1457                        /*
1458                         * Block until cpu_timer_fire (or a signal) wakes us.
1459                         */
1460                        __set_current_state(TASK_INTERRUPTIBLE);
1461                        spin_unlock_irq(&timer.it_lock);
1462                        schedule();
1463                        spin_lock_irq(&timer.it_lock);
1464                }
1465
1466                /*
1467                 * We were interrupted by a signal.
1468                 */
1469                sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1470                posix_cpu_timer_set(&timer, 0, &zero_it, it);
1471                spin_unlock_irq(&timer.it_lock);
1472
1473                if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1474                        /*
1475                         * It actually did fire already.
1476                         */
1477                        return 0;
1478                }
1479
1480                error = -ERESTART_RESTARTBLOCK;
1481        }
1482
1483        return error;
1484}
1485
1486static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1487
1488static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1489                            struct timespec *rqtp, struct timespec __user *rmtp)
1490{
1491        struct restart_block *restart_block =
1492                &current_thread_info()->restart_block;
1493        struct itimerspec it;
1494        int error;
1495
1496        /*
1497         * Diagnose required errors first.
1498         */
1499        if (CPUCLOCK_PERTHREAD(which_clock) &&
1500            (CPUCLOCK_PID(which_clock) == 0 ||
1501             CPUCLOCK_PID(which_clock) == current->pid))
1502                return -EINVAL;
1503
1504        error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1505
1506        if (error == -ERESTART_RESTARTBLOCK) {
1507
1508                if (flags & TIMER_ABSTIME)
1509                        return -ERESTARTNOHAND;
1510                /*
1511                 * Report back to the user the time still remaining.
1512                 */
1513                if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1514                        return -EFAULT;
1515
1516                restart_block->fn = posix_cpu_nsleep_restart;
1517                restart_block->nanosleep.index = which_clock;
1518                restart_block->nanosleep.rmtp = rmtp;
1519                restart_block->nanosleep.expires = timespec_to_ns(rqtp);
1520        }
1521        return error;
1522}
1523
1524static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1525{
1526        clockid_t which_clock = restart_block->nanosleep.index;
1527        struct timespec t;
1528        struct itimerspec it;
1529        int error;
1530
1531        t = ns_to_timespec(restart_block->nanosleep.expires);
1532
1533        error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1534
1535        if (error == -ERESTART_RESTARTBLOCK) {
1536                struct timespec __user *rmtp = restart_block->nanosleep.rmtp;
1537                /*
1538                 * Report back to the user the time still remaining.
1539                 */
1540                if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1541                        return -EFAULT;
1542
1543                restart_block->nanosleep.expires = timespec_to_ns(&t);
1544        }
1545        return error;
1546
1547}
1548
1549#define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1550#define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1551
1552static int process_cpu_clock_getres(const clockid_t which_clock,
1553                                    struct timespec *tp)
1554{
1555        return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1556}
1557static int process_cpu_clock_get(const clockid_t which_clock,
1558                                 struct timespec *tp)
1559{
1560        return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1561}
1562static int process_cpu_timer_create(struct k_itimer *timer)
1563{
1564        timer->it_clock = PROCESS_CLOCK;
1565        return posix_cpu_timer_create(timer);
1566}
1567static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1568                              struct timespec *rqtp,
1569                              struct timespec __user *rmtp)
1570{
1571        return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1572}
1573static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1574{
1575        return -EINVAL;
1576}
1577static int thread_cpu_clock_getres(const clockid_t which_clock,
1578                                   struct timespec *tp)
1579{
1580        return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1581}
1582static int thread_cpu_clock_get(const clockid_t which_clock,
1583                                struct timespec *tp)
1584{
1585        return posix_cpu_clock_get(THREAD_CLOCK, tp);
1586}
1587static int thread_cpu_timer_create(struct k_itimer *timer)
1588{
1589        timer->it_clock = THREAD_CLOCK;
1590        return posix_cpu_timer_create(timer);
1591}
1592
1593struct k_clock clock_posix_cpu = {
1594        .clock_getres   = posix_cpu_clock_getres,
1595        .clock_set      = posix_cpu_clock_set,
1596        .clock_get      = posix_cpu_clock_get,
1597        .timer_create   = posix_cpu_timer_create,
1598        .nsleep         = posix_cpu_nsleep,
1599        .nsleep_restart = posix_cpu_nsleep_restart,
1600        .timer_set      = posix_cpu_timer_set,
1601        .timer_del      = posix_cpu_timer_del,
1602        .timer_get      = posix_cpu_timer_get,
1603};
1604
1605static __init int init_posix_cpu_timers(void)
1606{
1607        struct k_clock process = {
1608                .clock_getres   = process_cpu_clock_getres,
1609                .clock_get      = process_cpu_clock_get,
1610                .timer_create   = process_cpu_timer_create,
1611                .nsleep         = process_cpu_nsleep,
1612                .nsleep_restart = process_cpu_nsleep_restart,
1613        };
1614        struct k_clock thread = {
1615                .clock_getres   = thread_cpu_clock_getres,
1616                .clock_get      = thread_cpu_clock_get,
1617                .timer_create   = thread_cpu_timer_create,
1618        };
1619        struct timespec ts;
1620
1621        posix_timers_register_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1622        posix_timers_register_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1623
1624        cputime_to_timespec(cputime_one_jiffy, &ts);
1625        onecputick = ts.tv_nsec;
1626        WARN_ON(ts.tv_sec != 0);
1627
1628        return 0;
1629}
1630__initcall(init_posix_cpu_timers);
1631