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
  12/*
  13 * Allocate the thread_group_cputime structure appropriately and fill in the
  14 * current values of the fields.  Called from copy_signal() via
  15 * thread_group_cputime_clone_thread() when adding a second or subsequent
  16 * thread to a thread group.  Assumes interrupts are enabled when called.
  17 */
  18int thread_group_cputime_alloc(struct task_struct *tsk)
  19{
  20        struct signal_struct *sig = tsk->signal;
  21        struct task_cputime *cputime;
  22
  23        /*
  24         * If we have multiple threads and we don't already have a
  25         * per-CPU task_cputime struct (checked in the caller), allocate
  26         * one and fill it in with the times accumulated so far.  We may
  27         * race with another thread so recheck after we pick up the sighand
  28         * lock.
  29         */
  30        cputime = alloc_percpu(struct task_cputime);
  31        if (cputime == NULL)
  32                return -ENOMEM;
  33        spin_lock_irq(&tsk->sighand->siglock);
  34        if (sig->cputime.totals) {
  35                spin_unlock_irq(&tsk->sighand->siglock);
  36                free_percpu(cputime);
  37                return 0;
  38        }
  39        sig->cputime.totals = cputime;
  40        cputime = per_cpu_ptr(sig->cputime.totals, smp_processor_id());
  41        cputime->utime = tsk->utime;
  42        cputime->stime = tsk->stime;
  43        cputime->sum_exec_runtime = tsk->se.sum_exec_runtime;
  44        spin_unlock_irq(&tsk->sighand->siglock);
  45        return 0;
  46}
  47
  48/**
  49 * thread_group_cputime - Sum the thread group time fields across all CPUs.
  50 *
  51 * @tsk:        The task we use to identify the thread group.
  52 * @times:      task_cputime structure in which we return the summed fields.
  53 *
  54 * Walk the list of CPUs to sum the per-CPU time fields in the thread group
  55 * time structure.
  56 */
  57void thread_group_cputime(
  58        struct task_struct *tsk,
  59        struct task_cputime *times)
  60{
  61        struct signal_struct *sig;
  62        int i;
  63        struct task_cputime *tot;
  64
  65        sig = tsk->signal;
  66        if (unlikely(!sig) || !sig->cputime.totals) {
  67                times->utime = tsk->utime;
  68                times->stime = tsk->stime;
  69                times->sum_exec_runtime = tsk->se.sum_exec_runtime;
  70                return;
  71        }
  72        times->stime = times->utime = cputime_zero;
  73        times->sum_exec_runtime = 0;
  74        for_each_possible_cpu(i) {
  75                tot = per_cpu_ptr(tsk->signal->cputime.totals, i);
  76                times->utime = cputime_add(times->utime, tot->utime);
  77                times->stime = cputime_add(times->stime, tot->stime);
  78                times->sum_exec_runtime += tot->sum_exec_runtime;
  79        }
  80}
  81
  82/*
  83 * Called after updating RLIMIT_CPU to set timer expiration if necessary.
  84 */
  85void update_rlimit_cpu(unsigned long rlim_new)
  86{
  87        cputime_t cputime;
  88
  89        cputime = secs_to_cputime(rlim_new);
  90        if (cputime_eq(current->signal->it_prof_expires, cputime_zero) ||
  91            cputime_lt(current->signal->it_prof_expires, cputime)) {
  92                spin_lock_irq(&current->sighand->siglock);
  93                set_process_cpu_timer(current, CPUCLOCK_PROF, &cputime, NULL);
  94                spin_unlock_irq(&current->sighand->siglock);
  95        }
  96}
  97
  98static int check_clock(const clockid_t which_clock)
  99{
 100        int error = 0;
 101        struct task_struct *p;
 102        const pid_t pid = CPUCLOCK_PID(which_clock);
 103
 104        if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
 105                return -EINVAL;
 106
 107        if (pid == 0)
 108                return 0;
 109
 110        read_lock(&tasklist_lock);
 111        p = find_task_by_vpid(pid);
 112        if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
 113                   same_thread_group(p, current) : thread_group_leader(p))) {
 114                error = -EINVAL;
 115        }
 116        read_unlock(&tasklist_lock);
 117
 118        return error;
 119}
 120
 121static inline union cpu_time_count
 122timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
 123{
 124        union cpu_time_count ret;
 125        ret.sched = 0;          /* high half always zero when .cpu used */
 126        if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 127                ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
 128        } else {
 129                ret.cpu = timespec_to_cputime(tp);
 130        }
 131        return ret;
 132}
 133
 134static void sample_to_timespec(const clockid_t which_clock,
 135                               union cpu_time_count cpu,
 136                               struct timespec *tp)
 137{
 138        if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED)
 139                *tp = ns_to_timespec(cpu.sched);
 140        else
 141                cputime_to_timespec(cpu.cpu, tp);
 142}
 143
 144static inline int cpu_time_before(const clockid_t which_clock,
 145                                  union cpu_time_count now,
 146                                  union cpu_time_count then)
 147{
 148        if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 149                return now.sched < then.sched;
 150        }  else {
 151                return cputime_lt(now.cpu, then.cpu);
 152        }
 153}
 154static inline void cpu_time_add(const clockid_t which_clock,
 155                                union cpu_time_count *acc,
 156                                union cpu_time_count val)
 157{
 158        if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 159                acc->sched += val.sched;
 160        }  else {
 161                acc->cpu = cputime_add(acc->cpu, val.cpu);
 162        }
 163}
 164static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
 165                                                union cpu_time_count a,
 166                                                union cpu_time_count b)
 167{
 168        if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 169                a.sched -= b.sched;
 170        }  else {
 171                a.cpu = cputime_sub(a.cpu, b.cpu);
 172        }
 173        return a;
 174}
 175
 176/*
 177 * Divide and limit the result to res >= 1
 178 *
 179 * This is necessary to prevent signal delivery starvation, when the result of
 180 * the division would be rounded down to 0.
 181 */
 182static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
 183{
 184        cputime_t res = cputime_div(time, div);
 185
 186        return max_t(cputime_t, res, 1);
 187}
 188
 189/*
 190 * Update expiry time from increment, and increase overrun count,
 191 * given the current clock sample.
 192 */
 193static void bump_cpu_timer(struct k_itimer *timer,
 194                                  union cpu_time_count now)
 195{
 196        int i;
 197
 198        if (timer->it.cpu.incr.sched == 0)
 199                return;
 200
 201        if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 202                unsigned long long delta, incr;
 203
 204                if (now.sched < timer->it.cpu.expires.sched)
 205                        return;
 206                incr = timer->it.cpu.incr.sched;
 207                delta = now.sched + incr - timer->it.cpu.expires.sched;
 208                /* Don't use (incr*2 < delta), incr*2 might overflow. */
 209                for (i = 0; incr < delta - incr; i++)
 210                        incr = incr << 1;
 211                for (; i >= 0; incr >>= 1, i--) {
 212                        if (delta < incr)
 213                                continue;
 214                        timer->it.cpu.expires.sched += incr;
 215                        timer->it_overrun += 1 << i;
 216                        delta -= incr;
 217                }
 218        } else {
 219                cputime_t delta, incr;
 220
 221                if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
 222                        return;
 223                incr = timer->it.cpu.incr.cpu;
 224                delta = cputime_sub(cputime_add(now.cpu, incr),
 225                                    timer->it.cpu.expires.cpu);
 226                /* Don't use (incr*2 < delta), incr*2 might overflow. */
 227                for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
 228                             incr = cputime_add(incr, incr);
 229                for (; i >= 0; incr = cputime_halve(incr), i--) {
 230                        if (cputime_lt(delta, incr))
 231                                continue;
 232                        timer->it.cpu.expires.cpu =
 233                                cputime_add(timer->it.cpu.expires.cpu, incr);
 234                        timer->it_overrun += 1 << i;
 235                        delta = cputime_sub(delta, incr);
 236                }
 237        }
 238}
 239
 240static inline cputime_t prof_ticks(struct task_struct *p)
 241{
 242        return cputime_add(p->utime, p->stime);
 243}
 244static inline cputime_t virt_ticks(struct task_struct *p)
 245{
 246        return p->utime;
 247}
 248
 249int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
 250{
 251        int error = check_clock(which_clock);
 252        if (!error) {
 253                tp->tv_sec = 0;
 254                tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
 255                if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 256                        /*
 257                         * If sched_clock is using a cycle counter, we
 258                         * don't have any idea of its true resolution
 259                         * exported, but it is much more than 1s/HZ.
 260                         */
 261                        tp->tv_nsec = 1;
 262                }
 263        }
 264        return error;
 265}
 266
 267int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
 268{
 269        /*
 270         * You can never reset a CPU clock, but we check for other errors
 271         * in the call before failing with EPERM.
 272         */
 273        int error = check_clock(which_clock);
 274        if (error == 0) {
 275                error = -EPERM;
 276        }
 277        return error;
 278}
 279
 280
 281/*
 282 * Sample a per-thread clock for the given task.
 283 */
 284static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
 285                            union cpu_time_count *cpu)
 286{
 287        switch (CPUCLOCK_WHICH(which_clock)) {
 288        default:
 289                return -EINVAL;
 290        case CPUCLOCK_PROF:
 291                cpu->cpu = prof_ticks(p);
 292                break;
 293        case CPUCLOCK_VIRT:
 294                cpu->cpu = virt_ticks(p);
 295                break;
 296        case CPUCLOCK_SCHED:
 297                cpu->sched = p->se.sum_exec_runtime + task_delta_exec(p);
 298                break;
 299        }
 300        return 0;
 301}
 302
 303/*
 304 * Sample a process (thread group) clock for the given group_leader task.
 305 * Must be called with tasklist_lock held for reading.
 306 */
 307static int cpu_clock_sample_group(const clockid_t which_clock,
 308                                  struct task_struct *p,
 309                                  union cpu_time_count *cpu)
 310{
 311        struct task_cputime cputime;
 312
 313        thread_group_cputime(p, &cputime);
 314        switch (CPUCLOCK_WHICH(which_clock)) {
 315        default:
 316                return -EINVAL;
 317        case CPUCLOCK_PROF:
 318                cpu->cpu = cputime_add(cputime.utime, cputime.stime);
 319                break;
 320        case CPUCLOCK_VIRT:
 321                cpu->cpu = cputime.utime;
 322                break;
 323        case CPUCLOCK_SCHED:
 324                cpu->sched = cputime.sum_exec_runtime + task_delta_exec(p);
 325                break;
 326        }
 327        return 0;
 328}
 329
 330
 331int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
 332{
 333        const pid_t pid = CPUCLOCK_PID(which_clock);
 334        int error = -EINVAL;
 335        union cpu_time_count rtn;
 336
 337        if (pid == 0) {
 338                /*
 339                 * Special case constant value for our own clocks.
 340                 * We don't have to do any lookup to find ourselves.
 341                 */
 342                if (CPUCLOCK_PERTHREAD(which_clock)) {
 343                        /*
 344                         * Sampling just ourselves we can do with no locking.
 345                         */
 346                        error = cpu_clock_sample(which_clock,
 347                                                 current, &rtn);
 348                } else {
 349                        read_lock(&tasklist_lock);
 350                        error = cpu_clock_sample_group(which_clock,
 351                                                       current, &rtn);
 352                        read_unlock(&tasklist_lock);
 353                }
 354        } else {
 355                /*
 356                 * Find the given PID, and validate that the caller
 357                 * should be able to see it.
 358                 */
 359                struct task_struct *p;
 360                rcu_read_lock();
 361                p = find_task_by_vpid(pid);
 362                if (p) {
 363                        if (CPUCLOCK_PERTHREAD(which_clock)) {
 364                                if (same_thread_group(p, current)) {
 365                                        error = cpu_clock_sample(which_clock,
 366                                                                 p, &rtn);
 367                                }
 368                        } else {
 369                                read_lock(&tasklist_lock);
 370                                if (thread_group_leader(p) && p->signal) {
 371                                        error =
 372                                            cpu_clock_sample_group(which_clock,
 373                                                                   p, &rtn);
 374                                }
 375                                read_unlock(&tasklist_lock);
 376                        }
 377                }
 378                rcu_read_unlock();
 379        }
 380
 381        if (error)
 382                return error;
 383        sample_to_timespec(which_clock, rtn, tp);
 384        return 0;
 385}
 386
 387
 388/*
 389 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 390 * This is called from sys_timer_create with the new timer already locked.
 391 */
 392int posix_cpu_timer_create(struct k_itimer *new_timer)
 393{
 394        int ret = 0;
 395        const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
 396        struct task_struct *p;
 397
 398        if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
 399                return -EINVAL;
 400
 401        INIT_LIST_HEAD(&new_timer->it.cpu.entry);
 402        new_timer->it.cpu.incr.sched = 0;
 403        new_timer->it.cpu.expires.sched = 0;
 404
 405        read_lock(&tasklist_lock);
 406        if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
 407                if (pid == 0) {
 408                        p = current;
 409                } else {
 410                        p = find_task_by_vpid(pid);
 411                        if (p && !same_thread_group(p, current))
 412                                p = NULL;
 413                }
 414        } else {
 415                if (pid == 0) {
 416                        p = current->group_leader;
 417                } else {
 418                        p = find_task_by_vpid(pid);
 419                        if (p && !thread_group_leader(p))
 420                                p = NULL;
 421                }
 422        }
 423        new_timer->it.cpu.task = p;
 424        if (p) {
 425                get_task_struct(p);
 426        } else {
 427                ret = -EINVAL;
 428        }
 429        read_unlock(&tasklist_lock);
 430
 431        return ret;
 432}
 433
 434/*
 435 * Clean up a CPU-clock timer that is about to be destroyed.
 436 * This is called from timer deletion with the timer already locked.
 437 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 438 * and try again.  (This happens when the timer is in the middle of firing.)
 439 */
 440int posix_cpu_timer_del(struct k_itimer *timer)
 441{
 442        struct task_struct *p = timer->it.cpu.task;
 443        int ret = 0;
 444
 445        if (likely(p != NULL)) {
 446                read_lock(&tasklist_lock);
 447                if (unlikely(p->signal == NULL)) {
 448                        /*
 449                         * We raced with the reaping of the task.
 450                         * The deletion should have cleared us off the list.
 451                         */
 452                        BUG_ON(!list_empty(&timer->it.cpu.entry));
 453                } else {
 454                        spin_lock(&p->sighand->siglock);
 455                        if (timer->it.cpu.firing)
 456                                ret = TIMER_RETRY;
 457                        else
 458                                list_del(&timer->it.cpu.entry);
 459                        spin_unlock(&p->sighand->siglock);
 460                }
 461                read_unlock(&tasklist_lock);
 462
 463                if (!ret)
 464                        put_task_struct(p);
 465        }
 466
 467        return ret;
 468}
 469
 470/*
 471 * Clean out CPU timers still ticking when a thread exited.  The task
 472 * pointer is cleared, and the expiry time is replaced with the residual
 473 * time for later timer_gettime calls to return.
 474 * This must be called with the siglock held.
 475 */
 476static void cleanup_timers(struct list_head *head,
 477                           cputime_t utime, cputime_t stime,
 478                           unsigned long long sum_exec_runtime)
 479{
 480        struct cpu_timer_list *timer, *next;
 481        cputime_t ptime = cputime_add(utime, stime);
 482
 483        list_for_each_entry_safe(timer, next, head, entry) {
 484                list_del_init(&timer->entry);
 485                if (cputime_lt(timer->expires.cpu, ptime)) {
 486                        timer->expires.cpu = cputime_zero;
 487                } else {
 488                        timer->expires.cpu = cputime_sub(timer->expires.cpu,
 489                                                         ptime);
 490                }
 491        }
 492
 493        ++head;
 494        list_for_each_entry_safe(timer, next, head, entry) {
 495                list_del_init(&timer->entry);
 496                if (cputime_lt(timer->expires.cpu, utime)) {
 497                        timer->expires.cpu = cputime_zero;
 498                } else {
 499                        timer->expires.cpu = cputime_sub(timer->expires.cpu,
 500                                                         utime);
 501                }
 502        }
 503
 504        ++head;
 505        list_for_each_entry_safe(timer, next, head, entry) {
 506                list_del_init(&timer->entry);
 507                if (timer->expires.sched < sum_exec_runtime) {
 508                        timer->expires.sched = 0;
 509                } else {
 510                        timer->expires.sched -= sum_exec_runtime;
 511                }
 512        }
 513}
 514
 515/*
 516 * These are both called with the siglock held, when the current thread
 517 * is being reaped.  When the final (leader) thread in the group is reaped,
 518 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 519 */
 520void posix_cpu_timers_exit(struct task_struct *tsk)
 521{
 522        cleanup_timers(tsk->cpu_timers,
 523                       tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);
 524
 525}
 526void posix_cpu_timers_exit_group(struct task_struct *tsk)
 527{
 528        struct task_cputime cputime;
 529
 530        thread_group_cputime(tsk, &cputime);
 531        cleanup_timers(tsk->signal->cpu_timers,
 532                       cputime.utime, cputime.stime, cputime.sum_exec_runtime);
 533}
 534
 535static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
 536{
 537        /*
 538         * That's all for this thread or process.
 539         * We leave our residual in expires to be reported.
 540         */
 541        put_task_struct(timer->it.cpu.task);
 542        timer->it.cpu.task = NULL;
 543        timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
 544                                             timer->it.cpu.expires,
 545                                             now);
 546}
 547
 548/*
 549 * Insert the timer on the appropriate list before any timers that
 550 * expire later.  This must be called with the tasklist_lock held
 551 * for reading, and interrupts disabled.
 552 */
 553static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
 554{
 555        struct task_struct *p = timer->it.cpu.task;
 556        struct list_head *head, *listpos;
 557        struct cpu_timer_list *const nt = &timer->it.cpu;
 558        struct cpu_timer_list *next;
 559        unsigned long i;
 560
 561        head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
 562                p->cpu_timers : p->signal->cpu_timers);
 563        head += CPUCLOCK_WHICH(timer->it_clock);
 564
 565        BUG_ON(!irqs_disabled());
 566        spin_lock(&p->sighand->siglock);
 567
 568        listpos = head;
 569        if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
 570                list_for_each_entry(next, head, entry) {
 571                        if (next->expires.sched > nt->expires.sched)
 572                                break;
 573                        listpos = &next->entry;
 574                }
 575        } else {
 576                list_for_each_entry(next, head, entry) {
 577                        if (cputime_gt(next->expires.cpu, nt->expires.cpu))
 578                                break;
 579                        listpos = &next->entry;
 580                }
 581        }
 582        list_add(&nt->entry, listpos);
 583
 584        if (listpos == head) {
 585                /*
 586                 * We are the new earliest-expiring timer.
 587                 * If we are a thread timer, there can always
 588                 * be a process timer telling us to stop earlier.
 589                 */
 590
 591                if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 592                        switch (CPUCLOCK_WHICH(timer->it_clock)) {
 593                        default:
 594                                BUG();
 595                        case CPUCLOCK_PROF:
 596                                if (cputime_eq(p->cputime_expires.prof_exp,
 597                                               cputime_zero) ||
 598                                    cputime_gt(p->cputime_expires.prof_exp,
 599                                               nt->expires.cpu))
 600                                        p->cputime_expires.prof_exp =
 601                                                nt->expires.cpu;
 602                                break;
 603                        case CPUCLOCK_VIRT:
 604                                if (cputime_eq(p->cputime_expires.virt_exp,
 605                                               cputime_zero) ||
 606                                    cputime_gt(p->cputime_expires.virt_exp,
 607                                               nt->expires.cpu))
 608                                        p->cputime_expires.virt_exp =
 609                                                nt->expires.cpu;
 610                                break;
 611                        case CPUCLOCK_SCHED:
 612                                if (p->cputime_expires.sched_exp == 0 ||
 613                                    p->cputime_expires.sched_exp >
 614                                                        nt->expires.sched)
 615                                        p->cputime_expires.sched_exp =
 616                                                nt->expires.sched;
 617                                break;
 618                        }
 619                } else {
 620                        /*
 621                         * For a process timer, set the cached expiration time.
 622                         */
 623                        switch (CPUCLOCK_WHICH(timer->it_clock)) {
 624                        default:
 625                                BUG();
 626                        case CPUCLOCK_VIRT:
 627                                if (!cputime_eq(p->signal->it_virt_expires,
 628                                                cputime_zero) &&
 629                                    cputime_lt(p->signal->it_virt_expires,
 630                                               timer->it.cpu.expires.cpu))
 631                                        break;
 632                                p->signal->cputime_expires.virt_exp =
 633                                        timer->it.cpu.expires.cpu;
 634                                break;
 635                        case CPUCLOCK_PROF:
 636                                if (!cputime_eq(p->signal->it_prof_expires,
 637                                                cputime_zero) &&
 638                                    cputime_lt(p->signal->it_prof_expires,
 639                                               timer->it.cpu.expires.cpu))
 640                                        break;
 641                                i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
 642                                if (i != RLIM_INFINITY &&
 643                                    i <= cputime_to_secs(timer->it.cpu.expires.cpu))
 644                                        break;
 645                                p->signal->cputime_expires.prof_exp =
 646                                        timer->it.cpu.expires.cpu;
 647                                break;
 648                        case CPUCLOCK_SCHED:
 649                                p->signal->cputime_expires.sched_exp =
 650                                        timer->it.cpu.expires.sched;
 651                                break;
 652                        }
 653                }
 654        }
 655
 656        spin_unlock(&p->sighand->siglock);
 657}
 658
 659/*
 660 * The timer is locked, fire it and arrange for its reload.
 661 */
 662static void cpu_timer_fire(struct k_itimer *timer)
 663{
 664        if (unlikely(timer->sigq == NULL)) {
 665                /*
 666                 * This a special case for clock_nanosleep,
 667                 * not a normal timer from sys_timer_create.
 668                 */
 669                wake_up_process(timer->it_process);
 670                timer->it.cpu.expires.sched = 0;
 671        } else if (timer->it.cpu.incr.sched == 0) {
 672                /*
 673                 * One-shot timer.  Clear it as soon as it's fired.
 674                 */
 675                posix_timer_event(timer, 0);
 676                timer->it.cpu.expires.sched = 0;
 677        } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 678                /*
 679                 * The signal did not get queued because the signal
 680                 * was ignored, so we won't get any callback to
 681                 * reload the timer.  But we need to keep it
 682                 * ticking in case the signal is deliverable next time.
 683                 */
 684                posix_cpu_timer_schedule(timer);
 685        }
 686}
 687
 688/*
 689 * Guts of sys_timer_settime for CPU timers.
 690 * This is called with the timer locked and interrupts disabled.
 691 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 692 * and try again.  (This happens when the timer is in the middle of firing.)
 693 */
 694int posix_cpu_timer_set(struct k_itimer *timer, int flags,
 695                        struct itimerspec *new, struct itimerspec *old)
 696{
 697        struct task_struct *p = timer->it.cpu.task;
 698        union cpu_time_count old_expires, new_expires, val;
 699        int ret;
 700
 701        if (unlikely(p == NULL)) {
 702                /*
 703                 * Timer refers to a dead task's clock.
 704                 */
 705                return -ESRCH;
 706        }
 707
 708        new_expires = timespec_to_sample(timer->it_clock, &new->it_value);
 709
 710        read_lock(&tasklist_lock);
 711        /*
 712         * We need the tasklist_lock to protect against reaping that
 713         * clears p->signal.  If p has just been reaped, we can no
 714         * longer get any information about it at all.
 715         */
 716        if (unlikely(p->signal == NULL)) {
 717                read_unlock(&tasklist_lock);
 718                put_task_struct(p);
 719                timer->it.cpu.task = NULL;
 720                return -ESRCH;
 721        }
 722
 723        /*
 724         * Disarm any old timer after extracting its expiry time.
 725         */
 726        BUG_ON(!irqs_disabled());
 727
 728        ret = 0;
 729        spin_lock(&p->sighand->siglock);
 730        old_expires = timer->it.cpu.expires;
 731        if (unlikely(timer->it.cpu.firing)) {
 732                timer->it.cpu.firing = -1;
 733                ret = TIMER_RETRY;
 734        } else
 735                list_del_init(&timer->it.cpu.entry);
 736        spin_unlock(&p->sighand->siglock);
 737
 738        /*
 739         * We need to sample the current value to convert the new
 740         * value from to relative and absolute, and to convert the
 741         * old value from absolute to relative.  To set a process
 742         * timer, we need a sample to balance the thread expiry
 743         * times (in arm_timer).  With an absolute time, we must
 744         * check if it's already passed.  In short, we need a sample.
 745         */
 746        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 747                cpu_clock_sample(timer->it_clock, p, &val);
 748        } else {
 749                cpu_clock_sample_group(timer->it_clock, p, &val);
 750        }
 751
 752        if (old) {
 753                if (old_expires.sched == 0) {
 754                        old->it_value.tv_sec = 0;
 755                        old->it_value.tv_nsec = 0;
 756                } else {
 757                        /*
 758                         * Update the timer in case it has
 759                         * overrun already.  If it has,
 760                         * we'll report it as having overrun
 761                         * and with the next reloaded timer
 762                         * already ticking, though we are
 763                         * swallowing that pending
 764                         * notification here to install the
 765                         * new setting.
 766                         */
 767                        bump_cpu_timer(timer, val);
 768                        if (cpu_time_before(timer->it_clock, val,
 769                                            timer->it.cpu.expires)) {
 770                                old_expires = cpu_time_sub(
 771                                        timer->it_clock,
 772                                        timer->it.cpu.expires, val);
 773                                sample_to_timespec(timer->it_clock,
 774                                                   old_expires,
 775                                                   &old->it_value);
 776                        } else {
 777                                old->it_value.tv_nsec = 1;
 778                                old->it_value.tv_sec = 0;
 779                        }
 780                }
 781        }
 782
 783        if (unlikely(ret)) {
 784                /*
 785                 * We are colliding with the timer actually firing.
 786                 * Punt after filling in the timer's old value, and
 787                 * disable this firing since we are already reporting
 788                 * it as an overrun (thanks to bump_cpu_timer above).
 789                 */
 790                read_unlock(&tasklist_lock);
 791                goto out;
 792        }
 793
 794        if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
 795                cpu_time_add(timer->it_clock, &new_expires, val);
 796        }
 797
 798        /*
 799         * Install the new expiry time (or zero).
 800         * For a timer with no notification action, we don't actually
 801         * arm the timer (we'll just fake it for timer_gettime).
 802         */
 803        timer->it.cpu.expires = new_expires;
 804        if (new_expires.sched != 0 &&
 805            (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 806            cpu_time_before(timer->it_clock, val, new_expires)) {
 807                arm_timer(timer, val);
 808        }
 809
 810        read_unlock(&tasklist_lock);
 811
 812        /*
 813         * Install the new reload setting, and
 814         * set up the signal and overrun bookkeeping.
 815         */
 816        timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
 817                                                &new->it_interval);
 818
 819        /*
 820         * This acts as a modification timestamp for the timer,
 821         * so any automatic reload attempt will punt on seeing
 822         * that we have reset the timer manually.
 823         */
 824        timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 825                ~REQUEUE_PENDING;
 826        timer->it_overrun_last = 0;
 827        timer->it_overrun = -1;
 828
 829        if (new_expires.sched != 0 &&
 830            (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
 831            !cpu_time_before(timer->it_clock, val, new_expires)) {
 832                /*
 833                 * The designated time already passed, so we notify
 834                 * immediately, even if the thread never runs to
 835                 * accumulate more time on this clock.
 836                 */
 837                cpu_timer_fire(timer);
 838        }
 839
 840        ret = 0;
 841 out:
 842        if (old) {
 843                sample_to_timespec(timer->it_clock,
 844                                   timer->it.cpu.incr, &old->it_interval);
 845        }
 846        return ret;
 847}
 848
 849void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
 850{
 851        union cpu_time_count now;
 852        struct task_struct *p = timer->it.cpu.task;
 853        int clear_dead;
 854
 855        /*
 856         * Easy part: convert the reload time.
 857         */
 858        sample_to_timespec(timer->it_clock,
 859                           timer->it.cpu.incr, &itp->it_interval);
 860
 861        if (timer->it.cpu.expires.sched == 0) { /* Timer not armed at all.  */
 862                itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 863                return;
 864        }
 865
 866        if (unlikely(p == NULL)) {
 867                /*
 868                 * This task already died and the timer will never fire.
 869                 * In this case, expires is actually the dead value.
 870                 */
 871        dead:
 872                sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
 873                                   &itp->it_value);
 874                return;
 875        }
 876
 877        /*
 878         * Sample the clock to take the difference with the expiry time.
 879         */
 880        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
 881                cpu_clock_sample(timer->it_clock, p, &now);
 882                clear_dead = p->exit_state;
 883        } else {
 884                read_lock(&tasklist_lock);
 885                if (unlikely(p->signal == NULL)) {
 886                        /*
 887                         * The process has been reaped.
 888                         * We can't even collect a sample any more.
 889                         * Call the timer disarmed, nothing else to do.
 890                         */
 891                        put_task_struct(p);
 892                        timer->it.cpu.task = NULL;
 893                        timer->it.cpu.expires.sched = 0;
 894                        read_unlock(&tasklist_lock);
 895                        goto dead;
 896                } else {
 897                        cpu_clock_sample_group(timer->it_clock, p, &now);
 898                        clear_dead = (unlikely(p->exit_state) &&
 899                                      thread_group_empty(p));
 900                }
 901                read_unlock(&tasklist_lock);
 902        }
 903
 904        if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 905                if (timer->it.cpu.incr.sched == 0 &&
 906                    cpu_time_before(timer->it_clock,
 907                                    timer->it.cpu.expires, now)) {
 908                        /*
 909                         * Do-nothing timer expired and has no reload,
 910                         * so it's as if it was never set.
 911                         */
 912                        timer->it.cpu.expires.sched = 0;
 913                        itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
 914                        return;
 915                }
 916                /*
 917                 * Account for any expirations and reloads that should
 918                 * have happened.
 919                 */
 920                bump_cpu_timer(timer, now);
 921        }
 922
 923        if (unlikely(clear_dead)) {
 924                /*
 925                 * We've noticed that the thread is dead, but
 926                 * not yet reaped.  Take this opportunity to
 927                 * drop our task ref.
 928                 */
 929                clear_dead_task(timer, now);
 930                goto dead;
 931        }
 932
 933        if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
 934                sample_to_timespec(timer->it_clock,
 935                                   cpu_time_sub(timer->it_clock,
 936                                                timer->it.cpu.expires, now),
 937                                   &itp->it_value);
 938        } else {
 939                /*
 940                 * The timer should have expired already, but the firing
 941                 * hasn't taken place yet.  Say it's just about to expire.
 942                 */
 943                itp->it_value.tv_nsec = 1;
 944                itp->it_value.tv_sec = 0;
 945        }
 946}
 947
 948/*
 949 * Check for any per-thread CPU timers that have fired and move them off
 950 * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 951 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 952 */
 953static void check_thread_timers(struct task_struct *tsk,
 954                                struct list_head *firing)
 955{
 956        int maxfire;
 957        struct list_head *timers = tsk->cpu_timers;
 958        struct signal_struct *const sig = tsk->signal;
 959
 960        maxfire = 20;
 961        tsk->cputime_expires.prof_exp = cputime_zero;
 962        while (!list_empty(timers)) {
 963                struct cpu_timer_list *t = list_first_entry(timers,
 964                                                      struct cpu_timer_list,
 965                                                      entry);
 966                if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
 967                        tsk->cputime_expires.prof_exp = t->expires.cpu;
 968                        break;
 969                }
 970                t->firing = 1;
 971                list_move_tail(&t->entry, firing);
 972        }
 973
 974        ++timers;
 975        maxfire = 20;
 976        tsk->cputime_expires.virt_exp = cputime_zero;
 977        while (!list_empty(timers)) {
 978                struct cpu_timer_list *t = list_first_entry(timers,
 979                                                      struct cpu_timer_list,
 980                                                      entry);
 981                if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
 982                        tsk->cputime_expires.virt_exp = t->expires.cpu;
 983                        break;
 984                }
 985                t->firing = 1;
 986                list_move_tail(&t->entry, firing);
 987        }
 988
 989        ++timers;
 990        maxfire = 20;
 991        tsk->cputime_expires.sched_exp = 0;
 992        while (!list_empty(timers)) {
 993                struct cpu_timer_list *t = list_first_entry(timers,
 994                                                      struct cpu_timer_list,
 995                                                      entry);
 996                if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
 997                        tsk->cputime_expires.sched_exp = t->expires.sched;
 998                        break;
 999                }
1000                t->firing = 1;
1001                list_move_tail(&t->entry, firing);
1002        }
1003
1004        /*
1005         * Check for the special case thread timers.
1006         */
1007        if (sig->rlim[RLIMIT_RTTIME].rlim_cur != RLIM_INFINITY) {
1008                unsigned long hard = sig->rlim[RLIMIT_RTTIME].rlim_max;
1009                unsigned long *soft = &sig->rlim[RLIMIT_RTTIME].rlim_cur;
1010
1011                if (hard != RLIM_INFINITY &&
1012                    tsk->rt.timeout > DIV_ROUND_UP(hard, USEC_PER_SEC/HZ)) {
1013                        /*
1014                         * At the hard limit, we just die.
1015                         * No need to calculate anything else now.
1016                         */
1017                        __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1018                        return;
1019                }
1020                if (tsk->rt.timeout > DIV_ROUND_UP(*soft, USEC_PER_SEC/HZ)) {
1021                        /*
1022                         * At the soft limit, send a SIGXCPU every second.
1023                         */
1024                        if (sig->rlim[RLIMIT_RTTIME].rlim_cur
1025                            < sig->rlim[RLIMIT_RTTIME].rlim_max) {
1026                                sig->rlim[RLIMIT_RTTIME].rlim_cur +=
1027                                                                USEC_PER_SEC;
1028                        }
1029                        printk(KERN_INFO
1030                                "RT Watchdog Timeout: %s[%d]\n",
1031                                tsk->comm, task_pid_nr(tsk));
1032                        __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1033                }
1034        }
1035}
1036
1037/*
1038 * Check for any per-thread CPU timers that have fired and move them
1039 * off the tsk->*_timers list onto the firing list.  Per-thread timers
1040 * have already been taken off.
1041 */
1042static void check_process_timers(struct task_struct *tsk,
1043                                 struct list_head *firing)
1044{
1045        int maxfire;
1046        struct signal_struct *const sig = tsk->signal;
1047        cputime_t utime, ptime, virt_expires, prof_expires;
1048        unsigned long long sum_sched_runtime, sched_expires;
1049        struct list_head *timers = sig->cpu_timers;
1050        struct task_cputime cputime;
1051
1052        /*
1053         * Don't sample the current process CPU clocks if there are no timers.
1054         */
1055        if (list_empty(&timers[CPUCLOCK_PROF]) &&
1056            cputime_eq(sig->it_prof_expires, cputime_zero) &&
1057            sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
1058            list_empty(&timers[CPUCLOCK_VIRT]) &&
1059            cputime_eq(sig->it_virt_expires, cputime_zero) &&
1060            list_empty(&timers[CPUCLOCK_SCHED]))
1061                return;
1062
1063        /*
1064         * Collect the current process totals.
1065         */
1066        thread_group_cputime(tsk, &cputime);
1067        utime = cputime.utime;
1068        ptime = cputime_add(utime, cputime.stime);
1069        sum_sched_runtime = cputime.sum_exec_runtime;
1070        maxfire = 20;
1071        prof_expires = cputime_zero;
1072        while (!list_empty(timers)) {
1073                struct cpu_timer_list *tl = list_first_entry(timers,
1074                                                      struct cpu_timer_list,
1075                                                      entry);
1076                if (!--maxfire || cputime_lt(ptime, tl->expires.cpu)) {
1077                        prof_expires = tl->expires.cpu;
1078                        break;
1079                }
1080                tl->firing = 1;
1081                list_move_tail(&tl->entry, firing);
1082        }
1083
1084        ++timers;
1085        maxfire = 20;
1086        virt_expires = cputime_zero;
1087        while (!list_empty(timers)) {
1088                struct cpu_timer_list *tl = list_first_entry(timers,
1089                                                      struct cpu_timer_list,
1090                                                      entry);
1091                if (!--maxfire || cputime_lt(utime, tl->expires.cpu)) {
1092                        virt_expires = tl->expires.cpu;
1093                        break;
1094                }
1095                tl->firing = 1;
1096                list_move_tail(&tl->entry, firing);
1097        }
1098
1099        ++timers;
1100        maxfire = 20;
1101        sched_expires = 0;
1102        while (!list_empty(timers)) {
1103                struct cpu_timer_list *tl = list_first_entry(timers,
1104                                                      struct cpu_timer_list,
1105                                                      entry);
1106                if (!--maxfire || sum_sched_runtime < tl->expires.sched) {
1107                        sched_expires = tl->expires.sched;
1108                        break;
1109                }
1110                tl->firing = 1;
1111                list_move_tail(&tl->entry, firing);
1112        }
1113
1114        /*
1115         * Check for the special case process timers.
1116         */
1117        if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1118                if (cputime_ge(ptime, sig->it_prof_expires)) {
1119                        /* ITIMER_PROF fires and reloads.  */
1120                        sig->it_prof_expires = sig->it_prof_incr;
1121                        if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
1122                                sig->it_prof_expires = cputime_add(
1123                                        sig->it_prof_expires, ptime);
1124                        }
1125                        __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
1126                }
1127                if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
1128                    (cputime_eq(prof_expires, cputime_zero) ||
1129                     cputime_lt(sig->it_prof_expires, prof_expires))) {
1130                        prof_expires = sig->it_prof_expires;
1131                }
1132        }
1133        if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1134                if (cputime_ge(utime, sig->it_virt_expires)) {
1135                        /* ITIMER_VIRTUAL fires and reloads.  */
1136                        sig->it_virt_expires = sig->it_virt_incr;
1137                        if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
1138                                sig->it_virt_expires = cputime_add(
1139                                        sig->it_virt_expires, utime);
1140                        }
1141                        __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
1142                }
1143                if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
1144                    (cputime_eq(virt_expires, cputime_zero) ||
1145                     cputime_lt(sig->it_virt_expires, virt_expires))) {
1146                        virt_expires = sig->it_virt_expires;
1147                }
1148        }
1149        if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
1150                unsigned long psecs = cputime_to_secs(ptime);
1151                cputime_t x;
1152                if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
1153                        /*
1154                         * At the hard limit, we just die.
1155                         * No need to calculate anything else now.
1156                         */
1157                        __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
1158                        return;
1159                }
1160                if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
1161                        /*
1162                         * At the soft limit, send a SIGXCPU every second.
1163                         */
1164                        __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
1165                        if (sig->rlim[RLIMIT_CPU].rlim_cur
1166                            < sig->rlim[RLIMIT_CPU].rlim_max) {
1167                                sig->rlim[RLIMIT_CPU].rlim_cur++;
1168                        }
1169                }
1170                x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
1171                if (cputime_eq(prof_expires, cputime_zero) ||
1172                    cputime_lt(x, prof_expires)) {
1173                        prof_expires = x;
1174                }
1175        }
1176
1177        if (!cputime_eq(prof_expires, cputime_zero) &&
1178            (cputime_eq(sig->cputime_expires.prof_exp, cputime_zero) ||
1179             cputime_gt(sig->cputime_expires.prof_exp, prof_expires)))
1180                sig->cputime_expires.prof_exp = prof_expires;
1181        if (!cputime_eq(virt_expires, cputime_zero) &&
1182            (cputime_eq(sig->cputime_expires.virt_exp, cputime_zero) ||
1183             cputime_gt(sig->cputime_expires.virt_exp, virt_expires)))
1184                sig->cputime_expires.virt_exp = virt_expires;
1185        if (sched_expires != 0 &&
1186            (sig->cputime_expires.sched_exp == 0 ||
1187             sig->cputime_expires.sched_exp > sched_expires))
1188                sig->cputime_expires.sched_exp = sched_expires;
1189}
1190
1191/*
1192 * This is called from the signal code (via do_schedule_next_timer)
1193 * when the last timer signal was delivered and we have to reload the timer.
1194 */
1195void posix_cpu_timer_schedule(struct k_itimer *timer)
1196{
1197        struct task_struct *p = timer->it.cpu.task;
1198        union cpu_time_count now;
1199
1200        if (unlikely(p == NULL))
1201                /*
1202                 * The task was cleaned up already, no future firings.
1203                 */
1204                goto out;
1205
1206        /*
1207         * Fetch the current sample and update the timer's expiry time.
1208         */
1209        if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
1210                cpu_clock_sample(timer->it_clock, p, &now);
1211                bump_cpu_timer(timer, now);
1212                if (unlikely(p->exit_state)) {
1213                        clear_dead_task(timer, now);
1214                        goto out;
1215                }
1216                read_lock(&tasklist_lock); /* arm_timer needs it.  */
1217        } else {
1218                read_lock(&tasklist_lock);
1219                if (unlikely(p->signal == NULL)) {
1220                        /*
1221                         * The process has been reaped.
1222                         * We can't even collect a sample any more.
1223                         */
1224                        put_task_struct(p);
1225                        timer->it.cpu.task = p = NULL;
1226                        timer->it.cpu.expires.sched = 0;
1227                        goto out_unlock;
1228                } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
1229                        /*
1230                         * We've noticed that the thread is dead, but
1231                         * not yet reaped.  Take this opportunity to
1232                         * drop our task ref.
1233                         */
1234                        clear_dead_task(timer, now);
1235                        goto out_unlock;
1236                }
1237                cpu_clock_sample_group(timer->it_clock, p, &now);
1238                bump_cpu_timer(timer, now);
1239                /* Leave the tasklist_lock locked for the call below.  */
1240        }
1241
1242        /*
1243         * Now re-arm for the new expiry time.
1244         */
1245        arm_timer(timer, now);
1246
1247out_unlock:
1248        read_unlock(&tasklist_lock);
1249
1250out:
1251        timer->it_overrun_last = timer->it_overrun;
1252        timer->it_overrun = -1;
1253        ++timer->it_requeue_pending;
1254}
1255
1256/**
1257 * task_cputime_zero - Check a task_cputime struct for all zero fields.
1258 *
1259 * @cputime:    The struct to compare.
1260 *
1261 * Checks @cputime to see if all fields are zero.  Returns true if all fields
1262 * are zero, false if any field is nonzero.
1263 */
1264static inline int task_cputime_zero(const struct task_cputime *cputime)
1265{
1266        if (cputime_eq(cputime->utime, cputime_zero) &&
1267            cputime_eq(cputime->stime, cputime_zero) &&
1268            cputime->sum_exec_runtime == 0)
1269                return 1;
1270        return 0;
1271}
1272
1273/**
1274 * task_cputime_expired - Compare two task_cputime entities.
1275 *
1276 * @sample:     The task_cputime structure to be checked for expiration.
1277 * @expires:    Expiration times, against which @sample will be checked.
1278 *
1279 * Checks @sample against @expires to see if any field of @sample has expired.
1280 * Returns true if any field of the former is greater than the corresponding
1281 * field of the latter if the latter field is set.  Otherwise returns false.
1282 */
1283static inline int task_cputime_expired(const struct task_cputime *sample,
1284                                        const struct task_cputime *expires)
1285{
1286        if (!cputime_eq(expires->utime, cputime_zero) &&
1287            cputime_ge(sample->utime, expires->utime))
1288                return 1;
1289        if (!cputime_eq(expires->stime, cputime_zero) &&
1290            cputime_ge(cputime_add(sample->utime, sample->stime),
1291                       expires->stime))
1292                return 1;
1293        if (expires->sum_exec_runtime != 0 &&
1294            sample->sum_exec_runtime >= expires->sum_exec_runtime)
1295                return 1;
1296        return 0;
1297}
1298
1299/**
1300 * fastpath_timer_check - POSIX CPU timers fast path.
1301 *
1302 * @tsk:        The task (thread) being checked.
1303 *
1304 * Check the task and thread group timers.  If both are zero (there are no
1305 * timers set) return false.  Otherwise snapshot the task and thread group
1306 * timers and compare them with the corresponding expiration times.  Return
1307 * true if a timer has expired, else return false.
1308 */
1309static inline int fastpath_timer_check(struct task_struct *tsk)
1310{
1311        struct signal_struct *sig;
1312
1313        /* tsk == current, ensure it is safe to use ->signal/sighand */
1314        if (unlikely(tsk->exit_state))
1315                return 0;
1316
1317        if (!task_cputime_zero(&tsk->cputime_expires)) {
1318                struct task_cputime task_sample = {
1319                        .utime = tsk->utime,
1320                        .stime = tsk->stime,
1321                        .sum_exec_runtime = tsk->se.sum_exec_runtime
1322                };
1323
1324                if (task_cputime_expired(&task_sample, &tsk->cputime_expires))
1325                        return 1;
1326        }
1327
1328        sig = tsk->signal;
1329        if (!task_cputime_zero(&sig->cputime_expires)) {
1330                struct task_cputime group_sample;
1331
1332                thread_group_cputime(tsk, &group_sample);
1333                if (task_cputime_expired(&group_sample, &sig->cputime_expires))
1334                        return 1;
1335        }
1336        return 0;
1337}
1338
1339/*
1340 * This is called from the timer interrupt handler.  The irq handler has
1341 * already updated our counts.  We need to check if any timers fire now.
1342 * Interrupts are disabled.
1343 */
1344void run_posix_cpu_timers(struct task_struct *tsk)
1345{
1346        LIST_HEAD(firing);
1347        struct k_itimer *timer, *next;
1348
1349        BUG_ON(!irqs_disabled());
1350
1351        /*
1352         * The fast path checks that there are no expired thread or thread
1353         * group timers.  If that's so, just return.
1354         */
1355        if (!fastpath_timer_check(tsk))
1356                return;
1357
1358        spin_lock(&tsk->sighand->siglock);
1359        /*
1360         * Here we take off tsk->signal->cpu_timers[N] and
1361         * tsk->cpu_timers[N] all the timers that are firing, and
1362         * put them on the firing list.
1363         */
1364        check_thread_timers(tsk, &firing);
1365        check_process_timers(tsk, &firing);
1366
1367        /*
1368         * We must release these locks before taking any timer's lock.
1369         * There is a potential race with timer deletion here, as the
1370         * siglock now protects our private firing list.  We have set
1371         * the firing flag in each timer, so that a deletion attempt
1372         * that gets the timer lock before we do will give it up and
1373         * spin until we've taken care of that timer below.
1374         */
1375        spin_unlock(&tsk->sighand->siglock);
1376
1377        /*
1378         * Now that all the timers on our list have the firing flag,
1379         * noone will touch their list entries but us.  We'll take
1380         * each timer's lock before clearing its firing flag, so no
1381         * timer call will interfere.
1382         */
1383        list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
1384                int firing;
1385                spin_lock(&timer->it_lock);
1386                list_del_init(&timer->it.cpu.entry);
1387                firing = timer->it.cpu.firing;
1388                timer->it.cpu.firing = 0;
1389                /*
1390                 * The firing flag is -1 if we collided with a reset
1391                 * of the timer, which already reported this
1392                 * almost-firing as an overrun.  So don't generate an event.
1393                 */
1394                if (likely(firing >= 0)) {
1395                        cpu_timer_fire(timer);
1396                }
1397                spin_unlock(&timer->it_lock);
1398        }
1399}
1400
1401/*
1402 * Set one of the process-wide special case CPU timers.
1403 * The tsk->sighand->siglock must be held by the caller.
1404 * The *newval argument is relative and we update it to be absolute, *oldval
1405 * is absolute and we update it to be relative.
1406 */
1407void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
1408                           cputime_t *newval, cputime_t *oldval)
1409{
1410        union cpu_time_count now;
1411        struct list_head *head;
1412
1413        BUG_ON(clock_idx == CPUCLOCK_SCHED);
1414        cpu_clock_sample_group(clock_idx, tsk, &now);
1415
1416        if (oldval) {
1417                if (!cputime_eq(*oldval, cputime_zero)) {
1418                        if (cputime_le(*oldval, now.cpu)) {
1419                                /* Just about to fire. */
1420                                *oldval = jiffies_to_cputime(1);
1421                        } else {
1422                                *oldval = cputime_sub(*oldval, now.cpu);
1423                        }
1424                }
1425
1426                if (cputime_eq(*newval, cputime_zero))
1427                        return;
1428                *newval = cputime_add(*newval, now.cpu);
1429
1430                /*
1431                 * If the RLIMIT_CPU timer will expire before the
1432                 * ITIMER_PROF timer, we have nothing else to do.
1433                 */
1434                if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
1435                    < cputime_to_secs(*newval))
1436                        return;
1437        }
1438
1439        /*
1440         * Check whether there are any process timers already set to fire
1441         * before this one.  If so, we don't have anything more to do.
1442         */
1443        head = &tsk->signal->cpu_timers[clock_idx];
1444        if (list_empty(head) ||
1445            cputime_ge(list_first_entry(head,
1446                                  struct cpu_timer_list, entry)->expires.cpu,
1447                       *newval)) {
1448                switch (clock_idx) {
1449                case CPUCLOCK_PROF:
1450                        tsk->signal->cputime_expires.prof_exp = *newval;
1451                        break;
1452                case CPUCLOCK_VIRT:
1453                        tsk->signal->cputime_expires.virt_exp = *newval;
1454                        break;
1455                }
1456        }
1457}
1458
1459static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1460                            struct timespec *rqtp, struct itimerspec *it)
1461{
1462        struct k_itimer timer;
1463        int error;
1464
1465        /*
1466         * Set up a temporary timer and then wait for it to go off.
1467         */
1468        memset(&timer, 0, sizeof timer);
1469        spin_lock_init(&timer.it_lock);
1470        timer.it_clock = which_clock;
1471        timer.it_overrun = -1;
1472        error = posix_cpu_timer_create(&timer);
1473        timer.it_process = current;
1474        if (!error) {
1475                static struct itimerspec zero_it;
1476
1477                memset(it, 0, sizeof *it);
1478                it->it_value = *rqtp;
1479
1480                spin_lock_irq(&timer.it_lock);
1481                error = posix_cpu_timer_set(&timer, flags, it, NULL);
1482                if (error) {
1483                        spin_unlock_irq(&timer.it_lock);
1484                        return error;
1485                }
1486
1487                while (!signal_pending(current)) {
1488                        if (timer.it.cpu.expires.sched == 0) {
1489                                /*
1490                                 * Our timer fired and was reset.
1491                                 */
1492                                spin_unlock_irq(&timer.it_lock);
1493                                return 0;
1494                        }
1495
1496                        /*
1497                         * Block until cpu_timer_fire (or a signal) wakes us.
1498                         */
1499                        __set_current_state(TASK_INTERRUPTIBLE);
1500                        spin_unlock_irq(&timer.it_lock);
1501                        schedule();
1502                        spin_lock_irq(&timer.it_lock);
1503                }
1504
1505                /*
1506                 * We were interrupted by a signal.
1507                 */
1508                sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
1509                posix_cpu_timer_set(&timer, 0, &zero_it, it);
1510                spin_unlock_irq(&timer.it_lock);
1511
1512                if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
1513                        /*
1514                         * It actually did fire already.
1515                         */
1516                        return 0;
1517                }
1518
1519                error = -ERESTART_RESTARTBLOCK;
1520        }
1521
1522        return error;
1523}
1524
1525int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1526                     struct timespec *rqtp, struct timespec __user *rmtp)
1527{
1528        struct restart_block *restart_block =
1529            &current_thread_info()->restart_block;
1530        struct itimerspec it;
1531        int error;
1532
1533        /*
1534         * Diagnose required errors first.
1535         */
1536        if (CPUCLOCK_PERTHREAD(which_clock) &&
1537            (CPUCLOCK_PID(which_clock) == 0 ||
1538             CPUCLOCK_PID(which_clock) == current->pid))
1539                return -EINVAL;
1540
1541        error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);
1542
1543        if (error == -ERESTART_RESTARTBLOCK) {
1544
1545                if (flags & TIMER_ABSTIME)
1546                        return -ERESTARTNOHAND;
1547                /*
1548                 * Report back to the user the time still remaining.
1549                 */
1550                if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1551                        return -EFAULT;
1552
1553                restart_block->fn = posix_cpu_nsleep_restart;
1554                restart_block->arg0 = which_clock;
1555                restart_block->arg1 = (unsigned long) rmtp;
1556                restart_block->arg2 = rqtp->tv_sec;
1557                restart_block->arg3 = rqtp->tv_nsec;
1558        }
1559        return error;
1560}
1561
1562long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1563{
1564        clockid_t which_clock = restart_block->arg0;
1565        struct timespec __user *rmtp;
1566        struct timespec t;
1567        struct itimerspec it;
1568        int error;
1569
1570        rmtp = (struct timespec __user *) restart_block->arg1;
1571        t.tv_sec = restart_block->arg2;
1572        t.tv_nsec = restart_block->arg3;
1573
1574        restart_block->fn = do_no_restart_syscall;
1575        error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);
1576
1577        if (error == -ERESTART_RESTARTBLOCK) {
1578                /*
1579                 * Report back to the user the time still remaining.
1580                 */
1581                if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
1582                        return -EFAULT;
1583
1584                restart_block->fn = posix_cpu_nsleep_restart;
1585                restart_block->arg0 = which_clock;
1586                restart_block->arg1 = (unsigned long) rmtp;
1587                restart_block->arg2 = t.tv_sec;
1588                restart_block->arg3 = t.tv_nsec;
1589        }
1590        return error;
1591
1592}
1593
1594
1595#define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
1596#define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)
1597
1598static int process_cpu_clock_getres(const clockid_t which_clock,
1599                                    struct timespec *tp)
1600{
1601        return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1602}
1603static int process_cpu_clock_get(const clockid_t which_clock,
1604                                 struct timespec *tp)
1605{
1606        return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1607}
1608static int process_cpu_timer_create(struct k_itimer *timer)
1609{
1610        timer->it_clock = PROCESS_CLOCK;
1611        return posix_cpu_timer_create(timer);
1612}
1613static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1614                              struct timespec *rqtp,
1615                              struct timespec __user *rmtp)
1616{
1617        return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
1618}
1619static long process_cpu_nsleep_restart(struct restart_block *restart_block)
1620{
1621        return -EINVAL;
1622}
1623static int thread_cpu_clock_getres(const clockid_t which_clock,
1624                                   struct timespec *tp)
1625{
1626        return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1627}
1628static int thread_cpu_clock_get(const clockid_t which_clock,
1629                                struct timespec *tp)
1630{
1631        return posix_cpu_clock_get(THREAD_CLOCK, tp);
1632}
1633static int thread_cpu_timer_create(struct k_itimer *timer)
1634{
1635        timer->it_clock = THREAD_CLOCK;
1636        return posix_cpu_timer_create(timer);
1637}
1638static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
1639                              struct timespec *rqtp, struct timespec __user *rmtp)
1640{
1641        return -EINVAL;
1642}
1643static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
1644{
1645        return -EINVAL;
1646}
1647
1648static __init int init_posix_cpu_timers(void)
1649{
1650        struct k_clock process = {
1651                .clock_getres = process_cpu_clock_getres,
1652                .clock_get = process_cpu_clock_get,
1653                .clock_set = do_posix_clock_nosettime,
1654                .timer_create = process_cpu_timer_create,
1655                .nsleep = process_cpu_nsleep,
1656                .nsleep_restart = process_cpu_nsleep_restart,
1657        };
1658        struct k_clock thread = {
1659                .clock_getres = thread_cpu_clock_getres,
1660                .clock_get = thread_cpu_clock_get,
1661                .clock_set = do_posix_clock_nosettime,
1662                .timer_create = thread_cpu_timer_create,
1663                .nsleep = thread_cpu_nsleep,
1664                .nsleep_restart = thread_cpu_nsleep_restart,
1665        };
1666
1667        register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
1668        register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);
1669
1670        return 0;
1671}
1672__initcall(init_posix_cpu_timers);
1673