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 += task_sched_runtime(t);
 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        if (!cputimer->running) {
 278                /*
 279                 * The POSIX timer interface allows for absolute time expiry
 280                 * values through the TIMER_ABSTIME flag, therefore we have
 281                 * to synchronize the timer to the clock every time we start
 282                 * it.
 283                 */
 284                thread_group_cputime(tsk, &sum);
 285                spin_lock_irqsave(&cputimer->lock, flags);
 286                cputimer->running = 1;
 287                update_gt_cputime(&cputimer->cputime, &sum);
 288        } else
 289                spin_lock_irqsave(&cputimer->lock, flags);
 290        *times = cputimer->cputime;
 291        spin_unlock_irqrestore(&cputimer->lock, flags);
 292}
 293
 294/*
 295 * Sample a process (thread group) clock for the given group_leader task.
 296 * Must be called with tasklist_lock held for reading.
 297 */
 298static int cpu_clock_sample_group(const clockid_t which_clock,
 299                                  struct task_struct *p,
 300                                  union cpu_time_count *cpu)
 301{
 302        struct task_cputime cputime;
 303
 304        switch (CPUCLOCK_WHICH(which_clock)) {
 305        default:
 306                return -EINVAL;
 307        case CPUCLOCK_PROF:
 308                thread_group_cputime(p, &cputime);
 309                cpu->cpu = cputime_add(cputime.utime, cputime.stime);
 310                break;
 311        case CPUCLOCK_VIRT:
 312                thread_group_cputime(p, &cputime);
 313                cpu->cpu = cputime.utime;
 314                break;
 315        case CPUCLOCK_SCHED:
 316                thread_group_cputime(p, &cputime);
 317                cpu->sched = cputime.sum_exec_runtime;
 318                break;
 319        }
 320        return 0;
 321}
 322
 323
 324static int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 325{
 326        const pid_t pid = CPUCLOCK_PID(which_clock);
 327        int error = -EINVAL;
 328        union cpu_time_count rtn;
 329
 330        if (pid == 0) {
 331                /*
 332                 * Special case constant value for our own clocks.
 333                 * We don't have to do any lookup to find ourselves.
 334                 */
 335                if (CPUCLOCK_PERTHREAD(which_clock)) {
 336                        /*
 337                         * Sampling just ourselves we can do with no locking.
 338                         */
 339                        error = cpu_clock_sample(which_clock,
 340                                                 current, &rtn);
 341                } else {
 342                        read_lock(&tasklist_lock);
 343                        error = cpu_clock_sample_group(which_clock,
 344                                                       current, &rtn);
 345                        read_unlock(&tasklist_lock);
 346                }
 347        } else {
 348                /*
 349                 * Find the given PID, and validate that the caller
 350                 * should be able to see it.
 351                 */
 352                struct task_struct *p;
 353                rcu_read_lock();
 354                p = find_task_by_vpid(pid);
 355                if (p) {
 356                        if (CPUCLOCK_PERTHREAD(which_clock)) {
 357                                if (same_thread_group(p, current)) {
 358                                        error = cpu_clock_sample(which_clock,
 359                                                                 p, &rtn);
 360                                }
 361                        } else {
 362                                read_lock(&tasklist_lock);
 363                                if (thread_group_leader(p) && p->sighand) {
 364                                        error =
 365                                            cpu_clock_sample_group(which_clock,
 366                                                                   p, &rtn);
 367                                }
 368                                read_unlock(&tasklist_lock);
 369                        }
 370                }
 371                rcu_read_unlock();
 372        }
 373
 374        if (error)
 375                return error;
 376        sample_to_timespec(which_clock, rtn, tp);
 377        return 0;
 378}
 379
 380
 381/*
 382 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 383 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
 384 * new timer already all-zeros initialized.
 385 */
 386static int posix_cpu_timer_create(struct k_itimer *new_timer)
 387{
 388        int ret = 0;
 389        const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
 390        struct task_struct *p;
 391
 392        if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 393                return -EINVAL;
 394
 395        INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 396
 397        rcu_read_lock();
 398        if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
 399                if (pid == 0) {
 400                        p = current;
 401                } else {
 402                        p = find_task_by_vpid(pid);
 403                        if (p && !same_thread_group(p, current))
 404                                p = NULL;
 405                }
 406        } else {
 407                if (pid == 0) {
 408                        p = current->group_leader;
 409                } else {
 410                        p = find_task_by_vpid(pid);
 411                        if (p && !has_group_leader_pid(p))
 412                                p = NULL;
 413                }
 414        }
 415        new_timer->it.cpu.task = p;
 416        if (p) {
 417                get_task_struct(p);
 418        } else {
 419                ret = -EINVAL;
 420        }
 421        rcu_read_unlock();
 422
 423        return ret;
 424}
 425
 426/*
 427 * Clean up a CPU-clock timer that is about to be destroyed.
 428 * This is called from timer deletion with the timer already locked.
 429 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 430 * and try again.  (This happens when the timer is in the middle of firing.)
 431 */
 432static int posix_cpu_timer_del(struct k_itimer *timer)
 433{
 434        struct task_struct *p = timer->it.cpu.task;
 435        int ret = 0;
 436
 437        if (likely(p != NULL)) {
 438                read_lock(&tasklist_lock);
 439                if (unlikely(p->sighand == NULL)) {
 440                        /*
 441                         * We raced with the reaping of the task.
 442                         * The deletion should have cleared us off the list.
 443                         */
 444                        BUG_ON(!list_empty(&timer->it.cpu.entry));
 445                } else {
 446                        spin_lock(&p->sighand->siglock);
 447                        if (timer->it.cpu.firing)
 448                                ret = TIMER_RETRY;
 449                        else
 450                                list_del(&timer->it.cpu.entry);
 451                        spin_unlock(&p->sighand->siglock);
 452                }
 453                read_unlock(&tasklist_lock);
 454
 455                if (!ret)
 456                        put_task_struct(p);
 457        }
 458
 459        return ret;
 460}
 461
 462/*
 463 * Clean out CPU timers still ticking when a thread exited.  The task
 464 * pointer is cleared, and the expiry time is replaced with the residual
 465 * time for later timer_gettime calls to return.
 466 * This must be called with the siglock held.
 467 */
 468static void cleanup_timers(struct list_head *head,
 469                           cputime_t utime, cputime_t stime,
 470                           unsigned long long sum_exec_runtime)
 471{
 472        struct cpu_timer_list *timer, *next;
 473        cputime_t ptime = cputime_add(utime, stime);
 474
 475        list_for_each_entry_safe(timer, next, head, entry) {
 476                list_del_init(&timer->entry);
 477                if (cputime_lt(timer->expires.cpu, ptime)) {
 478                        timer->expires.cpu = cputime_zero;
 479                } else {
 480                        timer->expires.cpu = cputime_sub(timer->expires.cpu,
 481                                                         ptime);
 482                }
 483        }
 484
 485        ++head;
 486        list_for_each_entry_safe(timer, next, head, entry) {
 487                list_del_init(&timer->entry);
 488                if (cputime_lt(timer->expires.cpu, utime)) {
 489                        timer->expires.cpu = cputime_zero;
 490                } else {
 491                        timer->expires.cpu = cputime_sub(timer->expires.cpu,
 492                                                         utime);
 493                }
 494        }
 495
 496        ++head;
 497        list_for_each_entry_safe(timer, next, head, entry) {
 498                list_del_init(&timer->entry);
 499                if (timer->expires.sched < sum_exec_runtime) {
 500                        timer->expires.sched = 0;
 501                } else {
 502                        timer->expires.sched -= sum_exec_runtime;
 503                }
 504        }
 505}
 506
 507/*
 508 * These are both called with the siglock held, when the current thread
 509 * is being reaped.  When the final (leader) thread in the group is reaped,
 510 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 511 */
 512void posix_cpu_timers_exit(struct task_struct *tsk)
 513{
 514        cleanup_timers(tsk->cpu_timers,
 515                       tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
 516
 517}
 518void posix_cpu_timers_exit_group(struct task_struct *tsk)
 519{
 520        struct signal_struct *const sig = tsk->signal;
 521
 522        cleanup_timers(tsk->signal->cpu_timers,
 523                       cputime_add(tsk->utime, sig->utime),
 524                       cputime_add(tsk->stime, sig->stime),
 525                       tsk->se.sum_exec_runtime + sig->sum_sched_runtime);
 526}
 527
 528static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 529{
 530        /*
 531         * That's all for this thread or process.
 532         * We leave our residual in expires to be reported.
 533         */
 534        put_task_struct(timer->it.cpu.task);
 535        timer->it.cpu.task = NULL;
 536        timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
 537                                             timer->it.cpu.expires,
 538                                             now);
 539}
 540
 541static inline int expires_gt(cputime_t expires, cputime_t new_exp)
 542{
 543        return cputime_eq(expires, cputime_zero) ||
 544               cputime_gt(expires, new_exp);
 545}
 546
 547/*
 548 * Insert the timer on the appropriate list before any timers that
 549 * expire later.  This must be called with the tasklist_lock held
 550 * for reading, interrupts disabled and p->sighand->siglock taken.
 551 */
 552static void arm_timer(struct k_itimer *timer)
 553{
 554        struct task_struct *p = timer->it.cpu.task;
 555        struct list_head *head, *listpos;
 556        struct task_cputime *cputime_expires;
 557        struct cpu_timer_list *const nt = &timer->it.cpu;
 558        struct cpu_timer_list *next;
 559
 560        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 561                head = p->cpu_timers;
 562                cputime_expires = &p->cputime_expires;
 563        } else {
 564                head = p->signal->cpu_timers;
 565                cputime_expires = &p->signal->cputime_expires;
 566        }
 567        head += CPUCLOCK_WHICH(timer->it_clock);
 568
 569        listpos = head;
 570        list_for_each_entry(next, head, entry) {
 571                if (cpu_time_before(timer->it_clock, nt->expires, next->expires))
 572                        break;
 573                listpos = &next->entry;
 574        }
 575        list_add(&nt->entry, listpos);
 576
 577        if (listpos == head) {
 578                union cpu_time_count *exp = &nt->expires;
 579
 580                /*
 581                 * We are the new earliest-expiring POSIX 1.b timer, hence
 582                 * need to update expiration cache. Take into account that
 583                 * for process timers we share expiration cache with itimers
 584                 * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
 585                 */
 586
 587                switch (CPUCLOCK_WHICH(timer->it_clock)) {
 588                case CPUCLOCK_PROF:
 589                        if (expires_gt(cputime_expires->prof_exp, exp->cpu))
 590                                cputime_expires->prof_exp = exp->cpu;
 591                        break;
 592                case CPUCLOCK_VIRT:
 593                        if (expires_gt(cputime_expires->virt_exp, exp->cpu))
 594                                cputime_expires->virt_exp = exp->cpu;
 595                        break;
 596                case CPUCLOCK_SCHED:
 597                        if (cputime_expires->sched_exp == 0 ||
 598                            cputime_expires->sched_exp > exp->sched)
 599                                cputime_expires->sched_exp = exp->sched;
 600                        break;
 601                }
 602        }
 603}
 604
 605/*
 606 * The timer is locked, fire it and arrange for its reload.
 607 */
 608static void cpu_timer_fire(struct k_itimer *timer)
 609{
 610        if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 611                /*
 612                 * User don't want any signal.
 613                 */
 614                timer->it.cpu.expires.sched = 0;
 615        } else if (unlikely(timer->sigq == NULL)) {
 616                /*
 617                 * This a special case for clock_nanosleep,
 618                 * not a normal timer from sys_timer_create.
 619                 */
 620                wake_up_process(timer->it_process);
 621                timer->it.cpu.expires.sched = 0;
 622        } else if (timer->it.cpu.incr.sched == 0) {
 623                /*
 624                 * One-shot timer.  Clear it as soon as it's fired.
 625                 */
 626                posix_timer_event(timer, 0);
 627                timer->it.cpu.expires.sched = 0;
 628        } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 629                /*
 630                 * The signal did not get queued because the signal
 631                 * was ignored, so we won't get any callback to
 632                 * reload the timer.  But we need to keep it
 633                 * ticking in case the signal is deliverable next time.
 634                 */
 635                posix_cpu_timer_schedule(timer);
 636        }
 637}
 638
 639/*
 640 * Sample a process (thread group) timer for the given group_leader task.
 641 * Must be called with tasklist_lock held for reading.
 642 */
 643static int cpu_timer_sample_group(const clockid_t which_clock,
 644                                  struct task_struct *p,
 645                                  union cpu_time_count *cpu)
 646{
 647        struct task_cputime cputime;
 648
 649        thread_group_cputimer(p, &cputime);
 650        switch (CPUCLOCK_WHICH(which_clock)) {
 651        default:
 652                return -EINVAL;
 653        case CPUCLOCK_PROF:
 654                cpu->cpu = cputime_add(cputime.utime, cputime.stime);
 655                break;
 656        case CPUCLOCK_VIRT:
 657                cpu->cpu = cputime.utime;
 658                break;
 659        case CPUCLOCK_SCHED:
 660                cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
 661                break;
 662        }
 663        return 0;
 664}
 665
 666/*
 667 * Guts of sys_timer_settime for CPU timers.
 668 * This is called with the timer locked and interrupts disabled.
 669 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 670 * and try again.  (This happens when the timer is in the middle of firing.)
 671 */
 672static int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 673                               struct itimerspec *new, struct itimerspec *old)
 674{
 675        struct task_struct *p = timer->it.cpu.task;
 676        union cpu_time_count old_expires, new_expires, old_incr, val;
 677        int ret;
 678
 679        if (unlikely(p == NULL)) {
 680                /*
 681                 * Timer refers to a dead task's clock.
 682                 */
 683                return -ESRCH;
 684        }
 685
 686        new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
 687
 688        read_lock(&tasklist_lock);
 689        /*
 690         * We need the tasklist_lock to protect against reaping that
 691         * clears p->sighand.  If p has just been reaped, we can no
 692         * longer get any information about it at all.
 693         */
 694        if (unlikely(p->sighand == NULL)) {
 695                read_unlock(&tasklist_lock);
 696                put_task_struct(p);
 697                timer->it.cpu.task = NULL;
 698                return -ESRCH;
 699        }
 700
 701        /*
 702         * Disarm any old timer after extracting its expiry time.
 703         */
 704        BUG_ON(!irqs_disabled());
 705
 706        ret = 0;
 707        old_incr = timer->it.cpu.incr;
 708        spin_lock(&p->sighand->siglock);
 709        old_expires = timer->it.cpu.expires;
 710        if (unlikely(timer->it.cpu.firing)) {
 711                timer->it.cpu.firing = -1;
 712                ret = TIMER_RETRY;
 713        } else
 714                list_del_init(&timer->it.cpu.entry);
 715
 716        /*
 717         * We need to sample the current value to convert the new
 718         * value from to relative and absolute, and to convert the
 719         * old value from absolute to relative.  To set a process
 720         * timer, we need a sample to balance the thread expiry
 721         * times (in arm_timer).  With an absolute time, we must
 722         * check if it's already passed.  In short, we need a sample.
 723         */
 724        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 725                cpu_clock_sample(timer->it_clock, p, &val);
 726        } else {
 727                cpu_timer_sample_group(timer->it_clock, p, &val);
 728        }
 729
 730        if (old) {
 731                if (old_expires.sched == 0) {
 732                        old->it_value.tv_sec = 0;
 733                        old->it_value.tv_nsec = 0;
 734                } else {
 735                        /*
 736                         * Update the timer in case it has
 737                         * overrun already.  If it has,
 738                         * we'll report it as having overrun
 739                         * and with the next reloaded timer
 740                         * already ticking, though we are
 741                         * swallowing that pending
 742                         * notification here to install the
 743                         * new setting.
 744                         */
 745                        bump_cpu_timer(timer, val);
 746                        if (cpu_time_before(timer->it_clock, val,
 747                                            timer->it.cpu.expires)) {
 748                                old_expires = cpu_time_sub(
 749                                        timer->it_clock,
 750                                        timer->it.cpu.expires, val);
 751                                sample_to_timespec(timer->it_clock,
 752                                                   old_expires,
 753                                                   &old->it_value);
 754                        } else {
 755                                old->it_value.tv_nsec = 1;
 756                                old->it_value.tv_sec = 0;
 757                        }
 758                }
 759        }
 760
 761        if (unlikely(ret)) {
 762                /*
 763                 * We are colliding with the timer actually firing.
 764                 * Punt after filling in the timer's old value, and
 765                 * disable this firing since we are already reporting
 766                 * it as an overrun (thanks to bump_cpu_timer above).
 767                 */
 768                spin_unlock(&p->sighand->siglock);
 769                read_unlock(&tasklist_lock);
 770                goto out;
 771        }
 772
 773        if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
 774                cpu_time_add(timer->it_clock, &new_expires, val);
 775        }
 776
 777        /*
 778         * Install the new expiry time (or zero).
 779         * For a timer with no notification action, we don't actually
 780         * arm the timer (we'll just fake it for timer_gettime).
 781         */
 782        timer->it.cpu.expires = new_expires;
 783        if (new_expires.sched != 0 &&
 784            cpu_time_before(timer->it_clock, val, new_expires)) {
 785                arm_timer(timer);
 786        }
 787
 788        spin_unlock(&p->sighand->siglock);
 789        read_unlock(&tasklist_lock);
 790
 791        /*
 792         * Install the new reload setting, and
 793         * set up the signal and overrun bookkeeping.
 794         */
 795        timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
 796                                                &new->it_interval);
 797
 798        /*
 799         * This acts as a modification timestamp for the timer,
 800         * so any automatic reload attempt will punt on seeing
 801         * that we have reset the timer manually.
 802         */
 803        timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 804                ~REQUEUE_PENDING;
 805        timer->it_overrun_last = 0;
 806        timer->it_overrun = -1;
 807
 808        if (new_expires.sched != 0 &&
 809            !cpu_time_before(timer->it_clock, val, new_expires)) {
 810                /*
 811                 * The designated time already passed, so we notify
 812                 * immediately, even if the thread never runs to
 813                 * accumulate more time on this clock.
 814                 */
 815                cpu_timer_fire(timer);
 816        }
 817
 818        ret = 0;
 819 out:
 820        if (old) {
 821                sample_to_timespec(timer->it_clock,
 822                                   old_incr, &old->it_interval);
 823        }
 824        return ret;
 825}
 826
 827static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 828{
 829        union cpu_time_count now;
 830        struct task_struct *p = timer->it.cpu.task;
 831        int clear_dead;
 832
 833        /*
 834         * Easy part: convert the reload time.
 835         */
 836        sample_to_timespec(timer->it_clock,
 837                           timer->it.cpu.incr, &itp->it_interval);
 838
 839        if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
 840                itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 841                return;
 842        }
 843
 844        if (unlikely(p == NULL)) {
 845                /*
 846                 * This task already died and the timer will never fire.
 847                 * In this case, expires is actually the dead value.
 848                 */
 849        dead:
 850                sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
 851                                   &itp->it_value);
 852                return;
 853        }
 854
 855        /*
 856         * Sample the clock to take the difference with the expiry time.
 857         */
 858        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 859                cpu_clock_sample(timer->it_clock, p, &now);
 860                clear_dead = p->exit_state;
 861        } else {
 862                read_lock(&tasklist_lock);
 863                if (unlikely(p->sighand == NULL)) {
 864                        /*
 865                         * The process has been reaped.
 866                         * We can't even collect a sample any more.
 867                         * Call the timer disarmed, nothing else to do.
 868                         */
 869                        put_task_struct(p);
 870                        timer->it.cpu.task = NULL;
 871                        timer->it.cpu.expires.sched = 0;
 872                        read_unlock(&tasklist_lock);
 873                        goto dead;
 874                } else {
 875                        cpu_timer_sample_group(timer->it_clock, p, &now);
 876                        clear_dead = (unlikely(p->exit_state) &&
 877                                      thread_group_empty(p));
 878                }
 879                read_unlock(&tasklist_lock);
 880        }
 881
 882        if (unlikely(clear_dead)) {
 883                /*
 884                 * We've noticed that the thread is dead, but
 885                 * not yet reaped.  Take this opportunity to
 886                 * drop our task ref.
 887                 */
 888                clear_dead_task(timer, now);
 889                goto dead;
 890        }
 891
 892        if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
 893                sample_to_timespec(timer->it_clock,
 894                                   cpu_time_sub(timer->it_clock,
 895                                                timer->it.cpu.expires, now),
 896                                   &itp->it_value);
 897        } else {
 898                /*
 899                 * The timer should have expired already, but the firing
 900                 * hasn't taken place yet.  Say it's just about to expire.
 901                 */
 902                itp->it_value.tv_nsec = 1;
 903                itp->it_value.tv_sec = 0;
 904        }
 905}
 906
 907/*
 908 * Check for any per-thread CPU timers that have fired and move them off
 909 * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 910 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 911 */
 912static void check_thread_timers(struct task_struct *tsk,
 913                                struct list_head *firing)
 914{
 915        int maxfire;
 916        struct list_head *timers = tsk->cpu_timers;
 917        struct signal_struct *const sig = tsk->signal;
 918        unsigned long soft;
 919
 920        maxfire = 20;
 921        tsk->cputime_expires.prof_exp = cputime_zero;
 922        while (!list_empty(timers)) {
 923                struct cpu_timer_list *t = list_first_entry(timers,
 924                                                      struct cpu_timer_list,
 925                                                      entry);
 926                if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
 927                        tsk->cputime_expires.prof_exp = t->expires.cpu;
 928                        break;
 929                }
 930                t->firing = 1;
 931                list_move_tail(&t->entry, firing);
 932        }
 933
 934        ++timers;
 935        maxfire = 20;
 936        tsk->cputime_expires.virt_exp = cputime_zero;
 937        while (!list_empty(timers)) {
 938                struct cpu_timer_list *t = list_first_entry(timers,
 939                                                      struct cpu_timer_list,
 940                                                      entry);
 941                if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
 942                        tsk->cputime_expires.virt_exp = t->expires.cpu;
 943                        break;
 944                }
 945                t->firing = 1;
 946                list_move_tail(&t->entry, firing);
 947        }
 948
 949        ++timers;
 950        maxfire = 20;
 951        tsk->cputime_expires.sched_exp = 0;
 952        while (!list_empty(timers)) {
 953                struct cpu_timer_list *t = list_first_entry(timers,
 954                                                      struct cpu_timer_list,
 955                                                      entry);
 956                if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
 957                        tsk->cputime_expires.sched_exp = t->expires.sched;
 958                        break;
 959                }
 960                t->firing = 1;
 961                list_move_tail(&t->entry, firing);
 962        }
 963
 964        /*
 965         * Check for the special case thread timers.
 966         */
 967        soft = ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_cur);
 968        if (soft != RLIM_INFINITY) {
 969                unsigned long hard =
 970                        ACCESS_ONCE(sig->rlim[RLIMIT_RTTIME].rlim_max);
 971
 972                if (hard != RLIM_INFINITY &&
 973                    tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
 974                        /*
 975                         * At the hard limit, we just die.
 976                         * No need to calculate anything else now.
 977                         */
 978                        __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
 979                        return;
 980                }
 981                if (tsk->rt.timeout > DIV_ROUND_UP(soft, USEC_PER_SEC/HZ)) {
 982                        /*
 983                         * At the soft limit, send a SIGXCPU every second.
 984                         */
 985                        if (soft < hard) {
 986                                soft += USEC_PER_SEC;
 987                                sig->rlim[RLIMIT_RTTIME].rlim_cur = soft;
 988                        }
 989                        printk(KERN_INFO
 990                                "RT Watchdog Timeout: %s[%d]\n",
 991                                tsk->comm, task_pid_nr(tsk));
 992                        __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
 993                }
 994        }
 995}
 996
 997static void stop_process_timers(struct signal_struct *sig)
 998{
 999        struct thread_group_cputimer *cputimer = &sig->cputimer;
1000        unsigned long flags;
1001
1002        spin_lock_irqsave(&cputimer->lock, flags);
1003        cputimer->running = 0;
1004        spin_unlock_irqrestore(&cputimer->lock, flags);
1005}
1006
1007static u32 onecputick;
1008
1009static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
1010                             cputime_t *expires, cputime_t cur_time, int signo)
1011{
1012        if (cputime_eq(it->expires, cputime_zero))
1013                return;
1014
1015        if (cputime_ge(cur_time, it->expires)) {
1016                if (!cputime_eq(it->incr, cputime_zero)) {
1017                        it->expires = cputime_add(it->expires, it->incr);
1018                        it->error += it->incr_error;
1019                        if (it->error >= onecputick) {
1020                                it->expires = cputime_sub(it->expires,
1021                                                          cputime_one_jiffy);
1022                                it->error -= onecputick;
1023                        }
1024                } else {
1025                        it->expires = cputime_zero;
1026                }
1027
1028                trace_itimer_expire(signo == SIGPROF ?
1029                                    ITIMER_PROF : ITIMER_VIRTUAL,
1030                                    tsk->signal->leader_pid, cur_time);
1031                __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
1032        }
1033
1034        if (!cputime_eq(it->expires, cputime_zero) &&
1035            (cputime_eq(*expires, cputime_zero) ||
1036             cputime_lt(it->expires, *expires))) {
1037                *expires = it->expires;
1038        }
1039}
1040
1041/**
1042 * task_cputime_zero - Check a task_cputime struct for all zero fields.
1043 *
1044 * @cputime:    The struct to compare.
1045 *
1046 * Checks @cputime to see if all fields are zero.  Returns true if all fields
1047 * are zero, false if any field is nonzero.
1048 */
1049static inline int task_cputime_zero(const struct task_cputime *cputime)
1050{
1051        if (cputime_eq(cputime->utime, cputime_zero) &&
1052            cputime_eq(cputime->stime, cputime_zero) &&
1053            cputime->sum_exec_runtime == 0)
1054                return 1;
1055        return 0;
1056}
1057
1058/*
1059 * Check for any per-thread CPU timers that have fired and move them
1060 * off the tsk->*_timers list onto the firing list.  Per-thread timers
1061 * have already been taken off.
1062 */
1063static void check_process_timers(struct task_struct *tsk,
1064                                 struct list_head *firing)
1065{
1066        int maxfire;
1067        struct signal_struct *const sig = tsk->signal;
1068        cputime_t utime, ptime, virt_expires, prof_expires;
1069        unsigned long long sum_sched_runtime, sched_expires;
1070        struct list_head *timers = sig->cpu_timers;
1071        struct task_cputime cputime;
1072        unsigned long soft;
1073
1074        /*
1075         * Collect the current process totals.
1076         */
1077        thread_group_cputimer(tsk, &cputime);
1078        utime = cputime.utime;
1079        ptime = cputime_add(utime, cputime.stime);
1080        sum_sched_runtime = cputime.sum_exec_runtime;
1081        maxfire = 20;
1082        prof_expires = cputime_zero;
1083        while (!list_empty(timers)) {
1084                struct cpu_timer_list *tl = list_first_entry(timers,
1085                                                      struct cpu_timer_list,
1086                                                      entry);
1087                if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
1088                        prof_expires = tl->expires.cpu;
1089                        break;
1090                }
1091                tl->firing = 1;
1092                list_move_tail(&tl->entry, firing);
1093        }
1094
1095        ++timers;
1096        maxfire = 20;
1097        virt_expires = cputime_zero;
1098        while (!list_empty(timers)) {
1099                struct cpu_timer_list *tl = list_first_entry(timers,
1100                                                      struct cpu_timer_list,
1101                                                      entry);
1102                if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
1103                        virt_expires = tl->expires.cpu;
1104                        break;
1105                }
1106                tl->firing = 1;
1107                list_move_tail(&tl->entry, firing);
1108        }
1109
1110        ++timers;
1111        maxfire = 20;
1112        sched_expires = 0;
1113        while (!list_empty(timers)) {
1114                struct cpu_timer_list *tl = list_first_entry(timers,
1115                                                      struct cpu_timer_list,
1116                                                      entry);
1117                if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
1118                        sched_expires = tl->expires.sched;
1119                        break;
1120                }
1121                tl->firing = 1;
1122                list_move_tail(&tl->entry, firing);
1123        }
1124
1125        /*
1126         * Check for the special case process timers.
1127         */
1128        check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF], &prof_expires, ptime,
1129                         SIGPROF);
1130        check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT], &virt_expires, utime,
1131                         SIGVTALRM);
1132        soft = ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_cur);
1133        if (soft != RLIM_INFINITY) {
1134                unsigned long psecs = cputime_to_secs(ptime);
1135                unsigned long hard =
1136                        ACCESS_ONCE(sig->rlim[RLIMIT_CPU].rlim_max);
1137                cputime_t x;
1138                if (psecs >= hard) {
1139                        /*
1140                         * At the hard limit, we just die.
1141                         * No need to calculate anything else now.
1142                         */
1143                        __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1144                        return;
1145                }
1146                if (psecs >= soft) {
1147                        /*
1148                         * At the soft limit, send a SIGXCPU every second.
1149                         */
1150                        __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1151                        if (soft < hard) {
1152                                soft++;
1153                                sig->rlim[RLIMIT_CPU].rlim_cur = soft;
1154                        }
1155                }
1156                x = secs_to_cputime(soft);
1157                if (cputime_eq(prof_expires, cputime_zero) ||
1158                    cputime_lt(x, prof_expires)) {
1159                        prof_expires = x;
1160                }
1161        }
1162
1163        sig->cputime_expires.prof_exp = prof_expires;
1164        sig->cputime_expires.virt_exp = virt_expires;
1165        sig->cputime_expires.sched_exp = sched_expires;
1166        if (task_cputime_zero(&sig->cputime_expires))
1167                stop_process_timers(sig);
1168}
1169
1170/*
1171 * This is called from the signal code (via do_schedule_next_timer)
1172 * when the last timer signal was delivered and we have to reload the timer.
1173 */
1174void posix_cpu_timer_schedule(struct k_itimer *timer)
1175{
1176        struct task_struct *p = timer->it.cpu.task;
1177        union cpu_time_count now;
1178
1179        if (unlikely(p == NULL))
1180                /*
1181                 * The task was cleaned up already, no future firings.
1182                 */
1183                goto out;
1184
1185        /*
1186         * Fetch the current sample and update the timer's expiry time.
1187         */
1188        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1189                cpu_clock_sample(timer->it_clock, p, &now);
1190                bump_cpu_timer(timer, now);
1191                if (unlikely(p->exit_state)) {
1192                        clear_dead_task(timer, now);
1193                        goto out;
1194                }
1195                read_lock(&tasklist_lock); /* arm_timer needs it.  */
1196                spin_lock(&p->sighand->siglock);
1197        } else {
1198                read_lock(&tasklist_lock);
1199                if (unlikely(p->sighand == NULL)) {
1200                        /*
1201                         * The process has been reaped.
1202                         * We can't even collect a sample any more.
1203                         */
1204                        put_task_struct(p);
1205                        timer->it.cpu.task = p = NULL;
1206                        timer->it.cpu.expires.sched = 0;
1207                        goto out_unlock;
1208                } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1209                        /*
1210                         * We've noticed that the thread is dead, but
1211                         * not yet reaped.  Take this opportunity to
1212                         * drop our task ref.
1213                         */
1214                        clear_dead_task(timer, now);
1215                        goto out_unlock;
1216                }
1217                spin_lock(&p->sighand->siglock);
1218                cpu_timer_sample_group(timer->it_clock, p, &now);
1219                bump_cpu_timer(timer, now);
1220                /* Leave the tasklist_lock locked for the call below.  */
1221        }
1222
1223        /*
1224         * Now re-arm for the new expiry time.
1225         */
1226        BUG_ON(!irqs_disabled());
1227        arm_timer(timer);
1228        spin_unlock(&p->sighand->siglock);
1229
1230out_unlock:
1231        read_unlock(&tasklist_lock);
1232
1233out:
1234        timer->it_overrun_last = timer->it_overrun;
1235        timer->it_overrun = -1;
1236        ++timer->it_requeue_pending;
1237}
1238
1239/**
1240 * task_cputime_expired - Compare two task_cputime entities.
1241 *
1242 * @sample:     The task_cputime structure to be checked for expiration.
1243 * @expires:    Expiration times, against which @sample will be checked.
1244 *
1245 * Checks @sample against @expires to see if any field of @sample has expired.
1246 * Returns true if any field of the former is greater than the corresponding
1247 * field of the latter if the latter field is set.  Otherwise returns false.
1248 */
1249static inline int task_cputime_expired(const struct task_cputime *sample,
1250                                        const struct task_cputime *expires)
1251{
1252        if (!cputime_eq(expires->utime, cputime_zero) &&
1253            cputime_ge(sample->utime, expires->utime))
1254                return 1;
1255        if (!cputime_eq(expires->stime, cputime_zero) &&
1256            cputime_ge(cputime_add(sample->utime, sample->stime),
1257                       expires->stime))
1258                return 1;
1259        if (expires->sum_exec_runtime != 0 &&
1260            sample->sum_exec_runtime >= expires->sum_exec_runtime)
1261                return 1;
1262        return 0;
1263}
1264
1265/**
1266 * fastpath_timer_check - POSIX CPU timers fast path.
1267 *
1268 * @tsk:        The task (thread) being checked.
1269 *
1270 * Check the task and thread group timers.  If both are zero (there are no
1271 * timers set) return false.  Otherwise snapshot the task and thread group
1272 * timers and compare them with the corresponding expiration times.  Return
1273 * true if a timer has expired, else return false.
1274 */
1275static inline int fastpath_timer_check(struct task_struct *tsk)
1276{
1277        struct signal_struct *sig;
1278
1279        if (!task_cputime_zero(&tsk->cputime_expires)) {
1280                struct task_cputime task_sample = {
1281                        .utime = tsk->utime,
1282                        .stime = tsk->stime,
1283                        .sum_exec_runtime = tsk->se.sum_exec_runtime
1284                };
1285
1286                if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1287                        return 1;
1288        }
1289
1290        sig = tsk->signal;
1291        if (sig->cputimer.running) {
1292                struct task_cputime group_sample;
1293
1294                spin_lock(&sig->cputimer.lock);
1295                group_sample = sig->cputimer.cputime;
1296                spin_unlock(&sig->cputimer.lock);
1297
1298                if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1299                        return 1;
1300        }
1301
1302        return 0;
1303}
1304
1305/*
1306 * This is called from the timer interrupt handler.  The irq handler has
1307 * already updated our counts.  We need to check if any timers fire now.
1308 * Interrupts are disabled.
1309 */
1310void run_posix_cpu_timers(struct task_struct *tsk)
1311{
1312        LIST_HEAD(firing);
1313        struct k_itimer *timer, *next;
1314        unsigned long flags;
1315
1316        BUG_ON(!irqs_disabled());
1317
1318        /*
1319         * The fast path checks that there are no expired thread or thread
1320         * group timers.  If that's so, just return.
1321         */
1322        if (!fastpath_timer_check(tsk))
1323                return;
1324
1325        if (!lock_task_sighand(tsk, &flags))
1326                return;
1327        /*
1328         * Here we take off tsk->signal->cpu_timers[N] and
1329         * tsk->cpu_timers[N] all the timers that are firing, and
1330         * put them on the firing list.
1331         */
1332        check_thread_timers(tsk, &firing);
1333        /*
1334         * If there are any active process wide timers (POSIX 1.b, itimers,
1335         * RLIMIT_CPU) cputimer must be running.
1336         */
1337        if (tsk->signal->cputimer.running)
1338                check_process_timers(tsk, &firing);
1339
1340        /*
1341         * We must release these locks before taking any timer's lock.
1342         * There is a potential race with timer deletion here, as the
1343         * siglock now protects our private firing list.  We have set
1344         * the firing flag in each timer, so that a deletion attempt
1345         * that gets the timer lock before we do will give it up and
1346         * spin until we've taken care of that timer below.
1347         */
1348        unlock_task_sighand(tsk, &flags);
1349
1350        /*
1351         * Now that all the timers on our list have the firing flag,
1352         * no one will touch their list entries but us.  We'll take
1353         * each timer's lock before clearing its firing flag, so no
1354         * timer call will interfere.
1355         */
1356        list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1357                int cpu_firing;
1358
1359                spin_lock(&timer->it_lock);
1360                list_del_init(&timer->it.cpu.entry);
1361                cpu_firing = timer->it.cpu.firing;
1362                timer->it.cpu.firing = 0;
1363                /*
1364                 * The firing flag is -1 if we collided with a reset
1365                 * of the timer, which already reported this
1366                 * almost-firing as an overrun.  So don't generate an event.
1367                 */
1368                if (likely(cpu_firing >= 0))
1369                        cpu_timer_fire(timer);
1370                spin_unlock(&timer->it_lock);
1371        }
1372}
1373
1374/*
1375 * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1376 * The tsk->sighand->siglock must be held by the caller.
1377 */
1378void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1379                           cputime_t *newval, cputime_t *oldval)
1380{
1381        union cpu_time_count now;
1382
1383        BUG_ON(clock_idx == CPUCLOCK_SCHED);
1384        cpu_timer_sample_group(clock_idx, tsk, &now);
1385
1386        if (oldval) {
1387                /*
1388                 * We are setting itimer. The *oldval is absolute and we update
1389                 * it to be relative, *newval argument is relative and we update
1390                 * it to be absolute.
1391                 */
1392                if (!cputime_eq(*oldval, cputime_zero)) {
1393                        if (cputime_le(*oldval, now.cpu)) {
1394                                /* Just about to fire. */
1395                                *oldval = cputime_one_jiffy;
1396                        } else {
1397                                *oldval = cputime_sub(*oldval, now.cpu);
1398                        }
1399                }
1400
1401                if (cputime_eq(*newval, cputime_zero))
1402                        return;
1403                *newval = cputime_add(*newval, now.cpu);
1404        }
1405
1406        /*
1407         * Update expiration cache if we are the earliest timer, or eventually
1408         * RLIMIT_CPU limit is earlier than prof_exp cpu timer expire.
1409         */
1410        switch (clock_idx) {
1411        case CPUCLOCK_PROF:
1412                if (expires_gt(tsk->signal->cputime_expires.prof_exp, *newval))
1413                        tsk->signal->cputime_expires.prof_exp = *newval;
1414                break;
1415        case CPUCLOCK_VIRT:
1416                if (expires_gt(tsk->signal->cputime_expires.virt_exp, *newval))
1417                        tsk->signal->cputime_expires.virt_exp = *newval;
1418                break;
1419        }
1420}
1421
1422static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1423                            struct timespec *rqtp, struct itimerspec *it)
1424{
1425        struct k_itimer timer;
1426        int error;
1427
1428        /*
1429         * Set up a temporary timer and then wait for it to go off.
1430         */
1431        memset(&timer, 0, sizeof timer);
1432        spin_lock_init(&timer.it_lock);
1433        timer.it_clock = which_clock;
1434        timer.it_overrun = -1;
1435        error = posix_cpu_timer_create(&timer);
1436        timer.it_process = current;
1437        if (!error) {
1438                static struct itimerspec zero_it;
1439
1440                memset(it, 0, sizeof *it);
1441                it->it_value = *rqtp;
1442
1443                spin_lock_irq(&timer.it_lock);
1444                error = posix_cpu_timer_set(&timer, flags, it, NULL);
1445                if (error) {
1446                        spin_unlock_irq(&timer.it_lock);
1447                        return error;
1448                }
1449
1450                while (!signal_pending(current)) {
1451                        if (timer.it.cpu.expires.sched == 0) {
1452                                /*
1453                                 * Our timer fired and was reset.
1454                                 */
1455                                spin_unlock_irq(&timer.it_lock);
1456                                return 0;
1457                        }
1458
1459                        /*
1460                         * Block until cpu_timer_fire (or a signal) wakes us.
1461                         */
1462                        __set_current_state(TASK_INTERRUPTIBLE);
1463                        spin_unlock_irq(&timer.it_lock);
1464                        schedule();
1465                        spin_lock_irq(&timer.it_lock);
1466                }
1467
1468                /*
1469                 * We were interrupted by a signal.
1470                 */
1471                sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1472                posix_cpu_timer_set(&timer, 0, &zero_it, it);
1473                spin_unlock_irq(&timer.it_lock);
1474
1475                if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1476                        /*
1477                         * It actually did fire already.
1478                         */
1479                        return 0;
1480                }
1481
1482                error = -ERESTART_RESTARTBLOCK;
1483        }
1484
1485        return error;
1486}
1487
1488static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1489
1490static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1491                            struct timespec *rqtp, struct timespec __user *rmtp)
1492{
1493        struct restart_block *restart_block =
1494                &current_thread_info()->restart_block;
1495        struct itimerspec it;
1496        int error;
1497
1498        /*
1499         * Diagnose required errors first.
1500         */
1501        if (CPUCLOCK_PERTHREAD(which_clock) &&
1502            (CPUCLOCK_PID(which_clock) == 0 ||
1503             CPUCLOCK_PID(which_clock) == current->pid))
1504                return -EINVAL;
1505
1506        error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1507
1508        if (error == -ERESTART_RESTARTBLOCK) {
1509
1510                if (flags & TIMER_ABSTIME)
1511                        return -ERESTARTNOHAND;
1512                /*
1513                 * Report back to the user the time still remaining.
1514                 */
1515                if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1516                        return -EFAULT;
1517
1518                restart_block->fn = posix_cpu_nsleep_restart;
1519                restart_block->nanosleep.clockid = which_clock;
1520                restart_block->nanosleep.rmtp = rmtp;
1521                restart_block->nanosleep.expires = timespec_to_ns(rqtp);
1522        }
1523        return error;
1524}
1525
1526static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1527{
1528        clockid_t which_clock = restart_block->nanosleep.clockid;
1529        struct timespec t;
1530        struct itimerspec it;
1531        int error;
1532
1533        t = ns_to_timespec(restart_block->nanosleep.expires);
1534
1535        error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1536
1537        if (error == -ERESTART_RESTARTBLOCK) {
1538                struct timespec __user *rmtp = restart_block->nanosleep.rmtp;
1539                /*
1540                 * Report back to the user the time still remaining.
1541                 */
1542                if (rmtp && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1543                        return -EFAULT;
1544
1545                restart_block->nanosleep.expires = timespec_to_ns(&t);
1546        }
1547        return error;
1548
1549}
1550
1551#define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1552#define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1553
1554static int process_cpu_clock_getres(const clockid_t which_clock,
1555                                    struct timespec *tp)
1556{
1557        return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1558}
1559static int process_cpu_clock_get(const clockid_t which_clock,
1560                                 struct timespec *tp)
1561{
1562        return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1563}
1564static int process_cpu_timer_create(struct k_itimer *timer)
1565{
1566        timer->it_clock = PROCESS_CLOCK;
1567        return posix_cpu_timer_create(timer);
1568}
1569static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1570                              struct timespec *rqtp,
1571                              struct timespec __user *rmtp)
1572{
1573        return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1574}
1575static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1576{
1577        return -EINVAL;
1578}
1579static int thread_cpu_clock_getres(const clockid_t which_clock,
1580                                   struct timespec *tp)
1581{
1582        return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1583}
1584static int thread_cpu_clock_get(const clockid_t which_clock,
1585                                struct timespec *tp)
1586{
1587        return posix_cpu_clock_get(THREAD_CLOCK, tp);
1588}
1589static int thread_cpu_timer_create(struct k_itimer *timer)
1590{
1591        timer->it_clock = THREAD_CLOCK;
1592        return posix_cpu_timer_create(timer);
1593}
1594
1595struct k_clock clock_posix_cpu = {
1596        .clock_getres   = posix_cpu_clock_getres,
1597        .clock_set      = posix_cpu_clock_set,
1598        .clock_get      = posix_cpu_clock_get,
1599        .timer_create   = posix_cpu_timer_create,
1600        .nsleep         = posix_cpu_nsleep,
1601        .nsleep_restart = posix_cpu_nsleep_restart,
1602        .timer_set      = posix_cpu_timer_set,
1603        .timer_del      = posix_cpu_timer_del,
1604        .timer_get      = posix_cpu_timer_get,
1605};
1606
1607static __init int init_posix_cpu_timers(void)
1608{
1609        struct k_clock process = {
1610                .clock_getres   = process_cpu_clock_getres,
1611                .clock_get      = process_cpu_clock_get,
1612                .timer_create   = process_cpu_timer_create,
1613                .nsleep         = process_cpu_nsleep,
1614                .nsleep_restart = process_cpu_nsleep_restart,
1615        };
1616        struct k_clock thread = {
1617                .clock_getres   = thread_cpu_clock_getres,
1618                .clock_get      = thread_cpu_clock_get,
1619                .timer_create   = thread_cpu_timer_create,
1620        };
1621        struct timespec ts;
1622
1623        posix_timers_register_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1624        posix_timers_register_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1625
1626        cputime_to_timespec(cputime_one_jiffy, &ts);
1627        onecputick = ts.tv_nsec;
1628        WARN_ON(ts.tv_sec != 0);
1629
1630        return 0;
1631}
1632__initcall(init_posix_cpu_timers);
1633
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