linux/kernel/time/posix-cpu-timers.c
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   1// SPDX-License-Identifier: GPL-2.0
   2/*
   3 * Implement CPU time clocks for the POSIX clock interface.
   4 */
   5
   6#include <linux/sched/signal.h>
   7#include <linux/sched/cputime.h>
   8#include <linux/posix-timers.h>
   9#include <linux/errno.h>
  10#include <linux/math64.h>
  11#include <linux/uaccess.h>
  12#include <linux/kernel_stat.h>
  13#include <trace/events/timer.h>
  14#include <linux/tick.h>
  15#include <linux/workqueue.h>
  16#include <linux/compat.h>
  17#include <linux/sched/deadline.h>
  18
  19#include "posix-timers.h"
  20
  21static void posix_cpu_timer_rearm(struct k_itimer *timer);
  22
  23void posix_cputimers_group_init(struct posix_cputimers *pct, u64 cpu_limit)
  24{
  25        posix_cputimers_init(pct);
  26        if (cpu_limit != RLIM_INFINITY) {
  27                pct->bases[CPUCLOCK_PROF].nextevt = cpu_limit * NSEC_PER_SEC;
  28                pct->timers_active = true;
  29        }
  30}
  31
  32/*
  33 * Called after updating RLIMIT_CPU to run cpu timer and update
  34 * tsk->signal->posix_cputimers.bases[clock].nextevt expiration cache if
  35 * necessary. Needs siglock protection since other code may update the
  36 * expiration cache as well.
  37 */
  38void update_rlimit_cpu(struct task_struct *task, unsigned long rlim_new)
  39{
  40        u64 nsecs = rlim_new * NSEC_PER_SEC;
  41
  42        spin_lock_irq(&task->sighand->siglock);
  43        set_process_cpu_timer(task, CPUCLOCK_PROF, &nsecs, NULL);
  44        spin_unlock_irq(&task->sighand->siglock);
  45}
  46
  47/*
  48 * Functions for validating access to tasks.
  49 */
  50static struct pid *pid_for_clock(const clockid_t clock, bool gettime)
  51{
  52        const bool thread = !!CPUCLOCK_PERTHREAD(clock);
  53        const pid_t upid = CPUCLOCK_PID(clock);
  54        struct pid *pid;
  55
  56        if (CPUCLOCK_WHICH(clock) >= CPUCLOCK_MAX)
  57                return NULL;
  58
  59        /*
  60         * If the encoded PID is 0, then the timer is targeted at current
  61         * or the process to which current belongs.
  62         */
  63        if (upid == 0)
  64                return thread ? task_pid(current) : task_tgid(current);
  65
  66        pid = find_vpid(upid);
  67        if (!pid)
  68                return NULL;
  69
  70        if (thread) {
  71                struct task_struct *tsk = pid_task(pid, PIDTYPE_PID);
  72                return (tsk && same_thread_group(tsk, current)) ? pid : NULL;
  73        }
  74
  75        /*
  76         * For clock_gettime(PROCESS) allow finding the process by
  77         * with the pid of the current task.  The code needs the tgid
  78         * of the process so that pid_task(pid, PIDTYPE_TGID) can be
  79         * used to find the process.
  80         */
  81        if (gettime && (pid == task_pid(current)))
  82                return task_tgid(current);
  83
  84        /*
  85         * For processes require that pid identifies a process.
  86         */
  87        return pid_has_task(pid, PIDTYPE_TGID) ? pid : NULL;
  88}
  89
  90static inline int validate_clock_permissions(const clockid_t clock)
  91{
  92        int ret;
  93
  94        rcu_read_lock();
  95        ret = pid_for_clock(clock, false) ? 0 : -EINVAL;
  96        rcu_read_unlock();
  97
  98        return ret;
  99}
 100
 101static inline enum pid_type clock_pid_type(const clockid_t clock)
 102{
 103        return CPUCLOCK_PERTHREAD(clock) ? PIDTYPE_PID : PIDTYPE_TGID;
 104}
 105
 106static inline struct task_struct *cpu_timer_task_rcu(struct k_itimer *timer)
 107{
 108        return pid_task(timer->it.cpu.pid, clock_pid_type(timer->it_clock));
 109}
 110
 111/*
 112 * Update expiry time from increment, and increase overrun count,
 113 * given the current clock sample.
 114 */
 115static u64 bump_cpu_timer(struct k_itimer *timer, u64 now)
 116{
 117        u64 delta, incr, expires = timer->it.cpu.node.expires;
 118        int i;
 119
 120        if (!timer->it_interval)
 121                return expires;
 122
 123        if (now < expires)
 124                return expires;
 125
 126        incr = timer->it_interval;
 127        delta = now + incr - expires;
 128
 129        /* Don't use (incr*2 < delta), incr*2 might overflow. */
 130        for (i = 0; incr < delta - incr; i++)
 131                incr = incr << 1;
 132
 133        for (; i >= 0; incr >>= 1, i--) {
 134                if (delta < incr)
 135                        continue;
 136
 137                timer->it.cpu.node.expires += incr;
 138                timer->it_overrun += 1LL << i;
 139                delta -= incr;
 140        }
 141        return timer->it.cpu.node.expires;
 142}
 143
 144/* Check whether all cache entries contain U64_MAX, i.e. eternal expiry time */
 145static inline bool expiry_cache_is_inactive(const struct posix_cputimers *pct)
 146{
 147        return !(~pct->bases[CPUCLOCK_PROF].nextevt |
 148                 ~pct->bases[CPUCLOCK_VIRT].nextevt |
 149                 ~pct->bases[CPUCLOCK_SCHED].nextevt);
 150}
 151
 152static int
 153posix_cpu_clock_getres(const clockid_t which_clock, struct timespec64 *tp)
 154{
 155        int error = validate_clock_permissions(which_clock);
 156
 157        if (!error) {
 158                tp->tv_sec = 0;
 159                tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
 160                if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
 161                        /*
 162                         * If sched_clock is using a cycle counter, we
 163                         * don't have any idea of its true resolution
 164                         * exported, but it is much more than 1s/HZ.
 165                         */
 166                        tp->tv_nsec = 1;
 167                }
 168        }
 169        return error;
 170}
 171
 172static int
 173posix_cpu_clock_set(const clockid_t clock, const struct timespec64 *tp)
 174{
 175        int error = validate_clock_permissions(clock);
 176
 177        /*
 178         * You can never reset a CPU clock, but we check for other errors
 179         * in the call before failing with EPERM.
 180         */
 181        return error ? : -EPERM;
 182}
 183
 184/*
 185 * Sample a per-thread clock for the given task. clkid is validated.
 186 */
 187static u64 cpu_clock_sample(const clockid_t clkid, struct task_struct *p)
 188{
 189        u64 utime, stime;
 190
 191        if (clkid == CPUCLOCK_SCHED)
 192                return task_sched_runtime(p);
 193
 194        task_cputime(p, &utime, &stime);
 195
 196        switch (clkid) {
 197        case CPUCLOCK_PROF:
 198                return utime + stime;
 199        case CPUCLOCK_VIRT:
 200                return utime;
 201        default:
 202                WARN_ON_ONCE(1);
 203        }
 204        return 0;
 205}
 206
 207static inline void store_samples(u64 *samples, u64 stime, u64 utime, u64 rtime)
 208{
 209        samples[CPUCLOCK_PROF] = stime + utime;
 210        samples[CPUCLOCK_VIRT] = utime;
 211        samples[CPUCLOCK_SCHED] = rtime;
 212}
 213
 214static void task_sample_cputime(struct task_struct *p, u64 *samples)
 215{
 216        u64 stime, utime;
 217
 218        task_cputime(p, &utime, &stime);
 219        store_samples(samples, stime, utime, p->se.sum_exec_runtime);
 220}
 221
 222static void proc_sample_cputime_atomic(struct task_cputime_atomic *at,
 223                                       u64 *samples)
 224{
 225        u64 stime, utime, rtime;
 226
 227        utime = atomic64_read(&at->utime);
 228        stime = atomic64_read(&at->stime);
 229        rtime = atomic64_read(&at->sum_exec_runtime);
 230        store_samples(samples, stime, utime, rtime);
 231}
 232
 233/*
 234 * Set cputime to sum_cputime if sum_cputime > cputime. Use cmpxchg
 235 * to avoid race conditions with concurrent updates to cputime.
 236 */
 237static inline void __update_gt_cputime(atomic64_t *cputime, u64 sum_cputime)
 238{
 239        u64 curr_cputime;
 240retry:
 241        curr_cputime = atomic64_read(cputime);
 242        if (sum_cputime > curr_cputime) {
 243                if (atomic64_cmpxchg(cputime, curr_cputime, sum_cputime) != curr_cputime)
 244                        goto retry;
 245        }
 246}
 247
 248static void update_gt_cputime(struct task_cputime_atomic *cputime_atomic,
 249                              struct task_cputime *sum)
 250{
 251        __update_gt_cputime(&cputime_atomic->utime, sum->utime);
 252        __update_gt_cputime(&cputime_atomic->stime, sum->stime);
 253        __update_gt_cputime(&cputime_atomic->sum_exec_runtime, sum->sum_exec_runtime);
 254}
 255
 256/**
 257 * thread_group_sample_cputime - Sample cputime for a given task
 258 * @tsk:        Task for which cputime needs to be started
 259 * @samples:    Storage for time samples
 260 *
 261 * Called from sys_getitimer() to calculate the expiry time of an active
 262 * timer. That means group cputime accounting is already active. Called
 263 * with task sighand lock held.
 264 *
 265 * Updates @times with an uptodate sample of the thread group cputimes.
 266 */
 267void thread_group_sample_cputime(struct task_struct *tsk, u64 *samples)
 268{
 269        struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 270        struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
 271
 272        WARN_ON_ONCE(!pct->timers_active);
 273
 274        proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
 275}
 276
 277/**
 278 * thread_group_start_cputime - Start cputime and return a sample
 279 * @tsk:        Task for which cputime needs to be started
 280 * @samples:    Storage for time samples
 281 *
 282 * The thread group cputime accounting is avoided when there are no posix
 283 * CPU timers armed. Before starting a timer it's required to check whether
 284 * the time accounting is active. If not, a full update of the atomic
 285 * accounting store needs to be done and the accounting enabled.
 286 *
 287 * Updates @times with an uptodate sample of the thread group cputimes.
 288 */
 289static void thread_group_start_cputime(struct task_struct *tsk, u64 *samples)
 290{
 291        struct thread_group_cputimer *cputimer = &tsk->signal->cputimer;
 292        struct posix_cputimers *pct = &tsk->signal->posix_cputimers;
 293
 294        /* Check if cputimer isn't running. This is accessed without locking. */
 295        if (!READ_ONCE(pct->timers_active)) {
 296                struct task_cputime sum;
 297
 298                /*
 299                 * The POSIX timer interface allows for absolute time expiry
 300                 * values through the TIMER_ABSTIME flag, therefore we have
 301                 * to synchronize the timer to the clock every time we start it.
 302                 */
 303                thread_group_cputime(tsk, &sum);
 304                update_gt_cputime(&cputimer->cputime_atomic, &sum);
 305
 306                /*
 307                 * We're setting timers_active without a lock. Ensure this
 308                 * only gets written to in one operation. We set it after
 309                 * update_gt_cputime() as a small optimization, but
 310                 * barriers are not required because update_gt_cputime()
 311                 * can handle concurrent updates.
 312                 */
 313                WRITE_ONCE(pct->timers_active, true);
 314        }
 315        proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
 316}
 317
 318static void __thread_group_cputime(struct task_struct *tsk, u64 *samples)
 319{
 320        struct task_cputime ct;
 321
 322        thread_group_cputime(tsk, &ct);
 323        store_samples(samples, ct.stime, ct.utime, ct.sum_exec_runtime);
 324}
 325
 326/*
 327 * Sample a process (thread group) clock for the given task clkid. If the
 328 * group's cputime accounting is already enabled, read the atomic
 329 * store. Otherwise a full update is required.  clkid is already validated.
 330 */
 331static u64 cpu_clock_sample_group(const clockid_t clkid, struct task_struct *p,
 332                                  bool start)
 333{
 334        struct thread_group_cputimer *cputimer = &p->signal->cputimer;
 335        struct posix_cputimers *pct = &p->signal->posix_cputimers;
 336        u64 samples[CPUCLOCK_MAX];
 337
 338        if (!READ_ONCE(pct->timers_active)) {
 339                if (start)
 340                        thread_group_start_cputime(p, samples);
 341                else
 342                        __thread_group_cputime(p, samples);
 343        } else {
 344                proc_sample_cputime_atomic(&cputimer->cputime_atomic, samples);
 345        }
 346
 347        return samples[clkid];
 348}
 349
 350static int posix_cpu_clock_get(const clockid_t clock, struct timespec64 *tp)
 351{
 352        const clockid_t clkid = CPUCLOCK_WHICH(clock);
 353        struct task_struct *tsk;
 354        u64 t;
 355
 356        rcu_read_lock();
 357        tsk = pid_task(pid_for_clock(clock, true), clock_pid_type(clock));
 358        if (!tsk) {
 359                rcu_read_unlock();
 360                return -EINVAL;
 361        }
 362
 363        if (CPUCLOCK_PERTHREAD(clock))
 364                t = cpu_clock_sample(clkid, tsk);
 365        else
 366                t = cpu_clock_sample_group(clkid, tsk, false);
 367        rcu_read_unlock();
 368
 369        *tp = ns_to_timespec64(t);
 370        return 0;
 371}
 372
 373/*
 374 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 375 * This is called from sys_timer_create() and do_cpu_nanosleep() with the
 376 * new timer already all-zeros initialized.
 377 */
 378static int posix_cpu_timer_create(struct k_itimer *new_timer)
 379{
 380        static struct lock_class_key posix_cpu_timers_key;
 381        struct pid *pid;
 382
 383        rcu_read_lock();
 384        pid = pid_for_clock(new_timer->it_clock, false);
 385        if (!pid) {
 386                rcu_read_unlock();
 387                return -EINVAL;
 388        }
 389
 390        /*
 391         * If posix timer expiry is handled in task work context then
 392         * timer::it_lock can be taken without disabling interrupts as all
 393         * other locking happens in task context. This requires a separate
 394         * lock class key otherwise regular posix timer expiry would record
 395         * the lock class being taken in interrupt context and generate a
 396         * false positive warning.
 397         */
 398        if (IS_ENABLED(CONFIG_POSIX_CPU_TIMERS_TASK_WORK))
 399                lockdep_set_class(&new_timer->it_lock, &posix_cpu_timers_key);
 400
 401        new_timer->kclock = &clock_posix_cpu;
 402        timerqueue_init(&new_timer->it.cpu.node);
 403        new_timer->it.cpu.pid = get_pid(pid);
 404        rcu_read_unlock();
 405        return 0;
 406}
 407
 408/*
 409 * Clean up a CPU-clock timer that is about to be destroyed.
 410 * This is called from timer deletion with the timer already locked.
 411 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 412 * and try again.  (This happens when the timer is in the middle of firing.)
 413 */
 414static int posix_cpu_timer_del(struct k_itimer *timer)
 415{
 416        struct cpu_timer *ctmr = &timer->it.cpu;
 417        struct sighand_struct *sighand;
 418        struct task_struct *p;
 419        unsigned long flags;
 420        int ret = 0;
 421
 422        rcu_read_lock();
 423        p = cpu_timer_task_rcu(timer);
 424        if (!p)
 425                goto out;
 426
 427        /*
 428         * Protect against sighand release/switch in exit/exec and process/
 429         * thread timer list entry concurrent read/writes.
 430         */
 431        sighand = lock_task_sighand(p, &flags);
 432        if (unlikely(sighand == NULL)) {
 433                /*
 434                 * This raced with the reaping of the task. The exit cleanup
 435                 * should have removed this timer from the timer queue.
 436                 */
 437                WARN_ON_ONCE(ctmr->head || timerqueue_node_queued(&ctmr->node));
 438        } else {
 439                if (timer->it.cpu.firing)
 440                        ret = TIMER_RETRY;
 441                else
 442                        cpu_timer_dequeue(ctmr);
 443
 444                unlock_task_sighand(p, &flags);
 445        }
 446
 447out:
 448        rcu_read_unlock();
 449        if (!ret)
 450                put_pid(ctmr->pid);
 451
 452        return ret;
 453}
 454
 455static void cleanup_timerqueue(struct timerqueue_head *head)
 456{
 457        struct timerqueue_node *node;
 458        struct cpu_timer *ctmr;
 459
 460        while ((node = timerqueue_getnext(head))) {
 461                timerqueue_del(head, node);
 462                ctmr = container_of(node, struct cpu_timer, node);
 463                ctmr->head = NULL;
 464        }
 465}
 466
 467/*
 468 * Clean out CPU timers which are still armed when a thread exits. The
 469 * timers are only removed from the list. No other updates are done. The
 470 * corresponding posix timers are still accessible, but cannot be rearmed.
 471 *
 472 * This must be called with the siglock held.
 473 */
 474static void cleanup_timers(struct posix_cputimers *pct)
 475{
 476        cleanup_timerqueue(&pct->bases[CPUCLOCK_PROF].tqhead);
 477        cleanup_timerqueue(&pct->bases[CPUCLOCK_VIRT].tqhead);
 478        cleanup_timerqueue(&pct->bases[CPUCLOCK_SCHED].tqhead);
 479}
 480
 481/*
 482 * These are both called with the siglock held, when the current thread
 483 * is being reaped.  When the final (leader) thread in the group is reaped,
 484 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 485 */
 486void posix_cpu_timers_exit(struct task_struct *tsk)
 487{
 488        cleanup_timers(&tsk->posix_cputimers);
 489}
 490void posix_cpu_timers_exit_group(struct task_struct *tsk)
 491{
 492        cleanup_timers(&tsk->signal->posix_cputimers);
 493}
 494
 495/*
 496 * Insert the timer on the appropriate list before any timers that
 497 * expire later.  This must be called with the sighand lock held.
 498 */
 499static void arm_timer(struct k_itimer *timer, struct task_struct *p)
 500{
 501        int clkidx = CPUCLOCK_WHICH(timer->it_clock);
 502        struct cpu_timer *ctmr = &timer->it.cpu;
 503        u64 newexp = cpu_timer_getexpires(ctmr);
 504        struct posix_cputimer_base *base;
 505
 506        if (CPUCLOCK_PERTHREAD(timer->it_clock))
 507                base = p->posix_cputimers.bases + clkidx;
 508        else
 509                base = p->signal->posix_cputimers.bases + clkidx;
 510
 511        if (!cpu_timer_enqueue(&base->tqhead, ctmr))
 512                return;
 513
 514        /*
 515         * We are the new earliest-expiring POSIX 1.b timer, hence
 516         * need to update expiration cache. Take into account that
 517         * for process timers we share expiration cache with itimers
 518         * and RLIMIT_CPU and for thread timers with RLIMIT_RTTIME.
 519         */
 520        if (newexp < base->nextevt)
 521                base->nextevt = newexp;
 522
 523        if (CPUCLOCK_PERTHREAD(timer->it_clock))
 524                tick_dep_set_task(p, TICK_DEP_BIT_POSIX_TIMER);
 525        else
 526                tick_dep_set_signal(p, TICK_DEP_BIT_POSIX_TIMER);
 527}
 528
 529/*
 530 * The timer is locked, fire it and arrange for its reload.
 531 */
 532static void cpu_timer_fire(struct k_itimer *timer)
 533{
 534        struct cpu_timer *ctmr = &timer->it.cpu;
 535
 536        if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
 537                /*
 538                 * User don't want any signal.
 539                 */
 540                cpu_timer_setexpires(ctmr, 0);
 541        } else if (unlikely(timer->sigq == NULL)) {
 542                /*
 543                 * This a special case for clock_nanosleep,
 544                 * not a normal timer from sys_timer_create.
 545                 */
 546                wake_up_process(timer->it_process);
 547                cpu_timer_setexpires(ctmr, 0);
 548        } else if (!timer->it_interval) {
 549                /*
 550                 * One-shot timer.  Clear it as soon as it's fired.
 551                 */
 552                posix_timer_event(timer, 0);
 553                cpu_timer_setexpires(ctmr, 0);
 554        } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
 555                /*
 556                 * The signal did not get queued because the signal
 557                 * was ignored, so we won't get any callback to
 558                 * reload the timer.  But we need to keep it
 559                 * ticking in case the signal is deliverable next time.
 560                 */
 561                posix_cpu_timer_rearm(timer);
 562                ++timer->it_requeue_pending;
 563        }
 564}
 565
 566/*
 567 * Guts of sys_timer_settime for CPU timers.
 568 * This is called with the timer locked and interrupts disabled.
 569 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 570 * and try again.  (This happens when the timer is in the middle of firing.)
 571 */
 572static int posix_cpu_timer_set(struct k_itimer *timer, int timer_flags,
 573                               struct itimerspec64 *new, struct itimerspec64 *old)
 574{
 575        clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
 576        u64 old_expires, new_expires, old_incr, val;
 577        struct cpu_timer *ctmr = &timer->it.cpu;
 578        struct sighand_struct *sighand;
 579        struct task_struct *p;
 580        unsigned long flags;
 581        int ret = 0;
 582
 583        rcu_read_lock();
 584        p = cpu_timer_task_rcu(timer);
 585        if (!p) {
 586                /*
 587                 * If p has just been reaped, we can no
 588                 * longer get any information about it at all.
 589                 */
 590                rcu_read_unlock();
 591                return -ESRCH;
 592        }
 593
 594        /*
 595         * Use the to_ktime conversion because that clamps the maximum
 596         * value to KTIME_MAX and avoid multiplication overflows.
 597         */
 598        new_expires = ktime_to_ns(timespec64_to_ktime(new->it_value));
 599
 600        /*
 601         * Protect against sighand release/switch in exit/exec and p->cpu_timers
 602         * and p->signal->cpu_timers read/write in arm_timer()
 603         */
 604        sighand = lock_task_sighand(p, &flags);
 605        /*
 606         * If p has just been reaped, we can no
 607         * longer get any information about it at all.
 608         */
 609        if (unlikely(sighand == NULL)) {
 610                rcu_read_unlock();
 611                return -ESRCH;
 612        }
 613
 614        /*
 615         * Disarm any old timer after extracting its expiry time.
 616         */
 617        old_incr = timer->it_interval;
 618        old_expires = cpu_timer_getexpires(ctmr);
 619
 620        if (unlikely(timer->it.cpu.firing)) {
 621                timer->it.cpu.firing = -1;
 622                ret = TIMER_RETRY;
 623        } else {
 624                cpu_timer_dequeue(ctmr);
 625        }
 626
 627        /*
 628         * We need to sample the current value to convert the new
 629         * value from to relative and absolute, and to convert the
 630         * old value from absolute to relative.  To set a process
 631         * timer, we need a sample to balance the thread expiry
 632         * times (in arm_timer).  With an absolute time, we must
 633         * check if it's already passed.  In short, we need a sample.
 634         */
 635        if (CPUCLOCK_PERTHREAD(timer->it_clock))
 636                val = cpu_clock_sample(clkid, p);
 637        else
 638                val = cpu_clock_sample_group(clkid, p, true);
 639
 640        if (old) {
 641                if (old_expires == 0) {
 642                        old->it_value.tv_sec = 0;
 643                        old->it_value.tv_nsec = 0;
 644                } else {
 645                        /*
 646                         * Update the timer in case it has overrun already.
 647                         * If it has, we'll report it as having overrun and
 648                         * with the next reloaded timer already ticking,
 649                         * though we are swallowing that pending
 650                         * notification here to install the new setting.
 651                         */
 652                        u64 exp = bump_cpu_timer(timer, val);
 653
 654                        if (val < exp) {
 655                                old_expires = exp - val;
 656                                old->it_value = ns_to_timespec64(old_expires);
 657                        } else {
 658                                old->it_value.tv_nsec = 1;
 659                                old->it_value.tv_sec = 0;
 660                        }
 661                }
 662        }
 663
 664        if (unlikely(ret)) {
 665                /*
 666                 * We are colliding with the timer actually firing.
 667                 * Punt after filling in the timer's old value, and
 668                 * disable this firing since we are already reporting
 669                 * it as an overrun (thanks to bump_cpu_timer above).
 670                 */
 671                unlock_task_sighand(p, &flags);
 672                goto out;
 673        }
 674
 675        if (new_expires != 0 && !(timer_flags & TIMER_ABSTIME)) {
 676                new_expires += val;
 677        }
 678
 679        /*
 680         * Install the new expiry time (or zero).
 681         * For a timer with no notification action, we don't actually
 682         * arm the timer (we'll just fake it for timer_gettime).
 683         */
 684        cpu_timer_setexpires(ctmr, new_expires);
 685        if (new_expires != 0 && val < new_expires) {
 686                arm_timer(timer, p);
 687        }
 688
 689        unlock_task_sighand(p, &flags);
 690        /*
 691         * Install the new reload setting, and
 692         * set up the signal and overrun bookkeeping.
 693         */
 694        timer->it_interval = timespec64_to_ktime(new->it_interval);
 695
 696        /*
 697         * This acts as a modification timestamp for the timer,
 698         * so any automatic reload attempt will punt on seeing
 699         * that we have reset the timer manually.
 700         */
 701        timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
 702                ~REQUEUE_PENDING;
 703        timer->it_overrun_last = 0;
 704        timer->it_overrun = -1;
 705
 706        if (new_expires != 0 && !(val < new_expires)) {
 707                /*
 708                 * The designated time already passed, so we notify
 709                 * immediately, even if the thread never runs to
 710                 * accumulate more time on this clock.
 711                 */
 712                cpu_timer_fire(timer);
 713        }
 714
 715        ret = 0;
 716 out:
 717        rcu_read_unlock();
 718        if (old)
 719                old->it_interval = ns_to_timespec64(old_incr);
 720
 721        return ret;
 722}
 723
 724static void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec64 *itp)
 725{
 726        clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
 727        struct cpu_timer *ctmr = &timer->it.cpu;
 728        u64 now, expires = cpu_timer_getexpires(ctmr);
 729        struct task_struct *p;
 730
 731        rcu_read_lock();
 732        p = cpu_timer_task_rcu(timer);
 733        if (!p)
 734                goto out;
 735
 736        /*
 737         * Easy part: convert the reload time.
 738         */
 739        itp->it_interval = ktime_to_timespec64(timer->it_interval);
 740
 741        if (!expires)
 742                goto out;
 743
 744        /*
 745         * Sample the clock to take the difference with the expiry time.
 746         */
 747        if (CPUCLOCK_PERTHREAD(timer->it_clock))
 748                now = cpu_clock_sample(clkid, p);
 749        else
 750                now = cpu_clock_sample_group(clkid, p, false);
 751
 752        if (now < expires) {
 753                itp->it_value = ns_to_timespec64(expires - now);
 754        } else {
 755                /*
 756                 * The timer should have expired already, but the firing
 757                 * hasn't taken place yet.  Say it's just about to expire.
 758                 */
 759                itp->it_value.tv_nsec = 1;
 760                itp->it_value.tv_sec = 0;
 761        }
 762out:
 763        rcu_read_unlock();
 764}
 765
 766#define MAX_COLLECTED   20
 767
 768static u64 collect_timerqueue(struct timerqueue_head *head,
 769                              struct list_head *firing, u64 now)
 770{
 771        struct timerqueue_node *next;
 772        int i = 0;
 773
 774        while ((next = timerqueue_getnext(head))) {
 775                struct cpu_timer *ctmr;
 776                u64 expires;
 777
 778                ctmr = container_of(next, struct cpu_timer, node);
 779                expires = cpu_timer_getexpires(ctmr);
 780                /* Limit the number of timers to expire at once */
 781                if (++i == MAX_COLLECTED || now < expires)
 782                        return expires;
 783
 784                ctmr->firing = 1;
 785                cpu_timer_dequeue(ctmr);
 786                list_add_tail(&ctmr->elist, firing);
 787        }
 788
 789        return U64_MAX;
 790}
 791
 792static void collect_posix_cputimers(struct posix_cputimers *pct, u64 *samples,
 793                                    struct list_head *firing)
 794{
 795        struct posix_cputimer_base *base = pct->bases;
 796        int i;
 797
 798        for (i = 0; i < CPUCLOCK_MAX; i++, base++) {
 799                base->nextevt = collect_timerqueue(&base->tqhead, firing,
 800                                                    samples[i]);
 801        }
 802}
 803
 804static inline void check_dl_overrun(struct task_struct *tsk)
 805{
 806        if (tsk->dl.dl_overrun) {
 807                tsk->dl.dl_overrun = 0;
 808                __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
 809        }
 810}
 811
 812static bool check_rlimit(u64 time, u64 limit, int signo, bool rt, bool hard)
 813{
 814        if (time < limit)
 815                return false;
 816
 817        if (print_fatal_signals) {
 818                pr_info("%s Watchdog Timeout (%s): %s[%d]\n",
 819                        rt ? "RT" : "CPU", hard ? "hard" : "soft",
 820                        current->comm, task_pid_nr(current));
 821        }
 822        __group_send_sig_info(signo, SEND_SIG_PRIV, current);
 823        return true;
 824}
 825
 826/*
 827 * Check for any per-thread CPU timers that have fired and move them off
 828 * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 829 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 830 */
 831static void check_thread_timers(struct task_struct *tsk,
 832                                struct list_head *firing)
 833{
 834        struct posix_cputimers *pct = &tsk->posix_cputimers;
 835        u64 samples[CPUCLOCK_MAX];
 836        unsigned long soft;
 837
 838        if (dl_task(tsk))
 839                check_dl_overrun(tsk);
 840
 841        if (expiry_cache_is_inactive(pct))
 842                return;
 843
 844        task_sample_cputime(tsk, samples);
 845        collect_posix_cputimers(pct, samples, firing);
 846
 847        /*
 848         * Check for the special case thread timers.
 849         */
 850        soft = task_rlimit(tsk, RLIMIT_RTTIME);
 851        if (soft != RLIM_INFINITY) {
 852                /* Task RT timeout is accounted in jiffies. RTTIME is usec */
 853                unsigned long rttime = tsk->rt.timeout * (USEC_PER_SEC / HZ);
 854                unsigned long hard = task_rlimit_max(tsk, RLIMIT_RTTIME);
 855
 856                /* At the hard limit, send SIGKILL. No further action. */
 857                if (hard != RLIM_INFINITY &&
 858                    check_rlimit(rttime, hard, SIGKILL, true, true))
 859                        return;
 860
 861                /* At the soft limit, send a SIGXCPU every second */
 862                if (check_rlimit(rttime, soft, SIGXCPU, true, false)) {
 863                        soft += USEC_PER_SEC;
 864                        tsk->signal->rlim[RLIMIT_RTTIME].rlim_cur = soft;
 865                }
 866        }
 867
 868        if (expiry_cache_is_inactive(pct))
 869                tick_dep_clear_task(tsk, TICK_DEP_BIT_POSIX_TIMER);
 870}
 871
 872static inline void stop_process_timers(struct signal_struct *sig)
 873{
 874        struct posix_cputimers *pct = &sig->posix_cputimers;
 875
 876        /* Turn off the active flag. This is done without locking. */
 877        WRITE_ONCE(pct->timers_active, false);
 878        tick_dep_clear_signal(sig, TICK_DEP_BIT_POSIX_TIMER);
 879}
 880
 881static void check_cpu_itimer(struct task_struct *tsk, struct cpu_itimer *it,
 882                             u64 *expires, u64 cur_time, int signo)
 883{
 884        if (!it->expires)
 885                return;
 886
 887        if (cur_time >= it->expires) {
 888                if (it->incr)
 889                        it->expires += it->incr;
 890                else
 891                        it->expires = 0;
 892
 893                trace_itimer_expire(signo == SIGPROF ?
 894                                    ITIMER_PROF : ITIMER_VIRTUAL,
 895                                    task_tgid(tsk), cur_time);
 896                __group_send_sig_info(signo, SEND_SIG_PRIV, tsk);
 897        }
 898
 899        if (it->expires && it->expires < *expires)
 900                *expires = it->expires;
 901}
 902
 903/*
 904 * Check for any per-thread CPU timers that have fired and move them
 905 * off the tsk->*_timers list onto the firing list.  Per-thread timers
 906 * have already been taken off.
 907 */
 908static void check_process_timers(struct task_struct *tsk,
 909                                 struct list_head *firing)
 910{
 911        struct signal_struct *const sig = tsk->signal;
 912        struct posix_cputimers *pct = &sig->posix_cputimers;
 913        u64 samples[CPUCLOCK_MAX];
 914        unsigned long soft;
 915
 916        /*
 917         * If there are no active process wide timers (POSIX 1.b, itimers,
 918         * RLIMIT_CPU) nothing to check. Also skip the process wide timer
 919         * processing when there is already another task handling them.
 920         */
 921        if (!READ_ONCE(pct->timers_active) || pct->expiry_active)
 922                return;
 923
 924        /*
 925         * Signify that a thread is checking for process timers.
 926         * Write access to this field is protected by the sighand lock.
 927         */
 928        pct->expiry_active = true;
 929
 930        /*
 931         * Collect the current process totals. Group accounting is active
 932         * so the sample can be taken directly.
 933         */
 934        proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic, samples);
 935        collect_posix_cputimers(pct, samples, firing);
 936
 937        /*
 938         * Check for the special case process timers.
 939         */
 940        check_cpu_itimer(tsk, &sig->it[CPUCLOCK_PROF],
 941                         &pct->bases[CPUCLOCK_PROF].nextevt,
 942                         samples[CPUCLOCK_PROF], SIGPROF);
 943        check_cpu_itimer(tsk, &sig->it[CPUCLOCK_VIRT],
 944                         &pct->bases[CPUCLOCK_VIRT].nextevt,
 945                         samples[CPUCLOCK_VIRT], SIGVTALRM);
 946
 947        soft = task_rlimit(tsk, RLIMIT_CPU);
 948        if (soft != RLIM_INFINITY) {
 949                /* RLIMIT_CPU is in seconds. Samples are nanoseconds */
 950                unsigned long hard = task_rlimit_max(tsk, RLIMIT_CPU);
 951                u64 ptime = samples[CPUCLOCK_PROF];
 952                u64 softns = (u64)soft * NSEC_PER_SEC;
 953                u64 hardns = (u64)hard * NSEC_PER_SEC;
 954
 955                /* At the hard limit, send SIGKILL. No further action. */
 956                if (hard != RLIM_INFINITY &&
 957                    check_rlimit(ptime, hardns, SIGKILL, false, true))
 958                        return;
 959
 960                /* At the soft limit, send a SIGXCPU every second */
 961                if (check_rlimit(ptime, softns, SIGXCPU, false, false)) {
 962                        sig->rlim[RLIMIT_CPU].rlim_cur = soft + 1;
 963                        softns += NSEC_PER_SEC;
 964                }
 965
 966                /* Update the expiry cache */
 967                if (softns < pct->bases[CPUCLOCK_PROF].nextevt)
 968                        pct->bases[CPUCLOCK_PROF].nextevt = softns;
 969        }
 970
 971        if (expiry_cache_is_inactive(pct))
 972                stop_process_timers(sig);
 973
 974        pct->expiry_active = false;
 975}
 976
 977/*
 978 * This is called from the signal code (via posixtimer_rearm)
 979 * when the last timer signal was delivered and we have to reload the timer.
 980 */
 981static void posix_cpu_timer_rearm(struct k_itimer *timer)
 982{
 983        clockid_t clkid = CPUCLOCK_WHICH(timer->it_clock);
 984        struct task_struct *p;
 985        struct sighand_struct *sighand;
 986        unsigned long flags;
 987        u64 now;
 988
 989        rcu_read_lock();
 990        p = cpu_timer_task_rcu(timer);
 991        if (!p)
 992                goto out;
 993
 994        /* Protect timer list r/w in arm_timer() */
 995        sighand = lock_task_sighand(p, &flags);
 996        if (unlikely(sighand == NULL))
 997                goto out;
 998
 999        /*
1000         * Fetch the current sample and update the timer's expiry time.
1001         */
1002        if (CPUCLOCK_PERTHREAD(timer->it_clock))
1003                now = cpu_clock_sample(clkid, p);
1004        else
1005                now = cpu_clock_sample_group(clkid, p, true);
1006
1007        bump_cpu_timer(timer, now);
1008
1009        /*
1010         * Now re-arm for the new expiry time.
1011         */
1012        arm_timer(timer, p);
1013        unlock_task_sighand(p, &flags);
1014out:
1015        rcu_read_unlock();
1016}
1017
1018/**
1019 * task_cputimers_expired - Check whether posix CPU timers are expired
1020 *
1021 * @samples:    Array of current samples for the CPUCLOCK clocks
1022 * @pct:        Pointer to a posix_cputimers container
1023 *
1024 * Returns true if any member of @samples is greater than the corresponding
1025 * member of @pct->bases[CLK].nextevt. False otherwise
1026 */
1027static inline bool
1028task_cputimers_expired(const u64 *samples, struct posix_cputimers *pct)
1029{
1030        int i;
1031
1032        for (i = 0; i < CPUCLOCK_MAX; i++) {
1033                if (samples[i] >= pct->bases[i].nextevt)
1034                        return true;
1035        }
1036        return false;
1037}
1038
1039/**
1040 * fastpath_timer_check - POSIX CPU timers fast path.
1041 *
1042 * @tsk:        The task (thread) being checked.
1043 *
1044 * Check the task and thread group timers.  If both are zero (there are no
1045 * timers set) return false.  Otherwise snapshot the task and thread group
1046 * timers and compare them with the corresponding expiration times.  Return
1047 * true if a timer has expired, else return false.
1048 */
1049static inline bool fastpath_timer_check(struct task_struct *tsk)
1050{
1051        struct posix_cputimers *pct = &tsk->posix_cputimers;
1052        struct signal_struct *sig;
1053
1054        if (!expiry_cache_is_inactive(pct)) {
1055                u64 samples[CPUCLOCK_MAX];
1056
1057                task_sample_cputime(tsk, samples);
1058                if (task_cputimers_expired(samples, pct))
1059                        return true;
1060        }
1061
1062        sig = tsk->signal;
1063        pct = &sig->posix_cputimers;
1064        /*
1065         * Check if thread group timers expired when timers are active and
1066         * no other thread in the group is already handling expiry for
1067         * thread group cputimers. These fields are read without the
1068         * sighand lock. However, this is fine because this is meant to be
1069         * a fastpath heuristic to determine whether we should try to
1070         * acquire the sighand lock to handle timer expiry.
1071         *
1072         * In the worst case scenario, if concurrently timers_active is set
1073         * or expiry_active is cleared, but the current thread doesn't see
1074         * the change yet, the timer checks are delayed until the next
1075         * thread in the group gets a scheduler interrupt to handle the
1076         * timer. This isn't an issue in practice because these types of
1077         * delays with signals actually getting sent are expected.
1078         */
1079        if (READ_ONCE(pct->timers_active) && !READ_ONCE(pct->expiry_active)) {
1080                u64 samples[CPUCLOCK_MAX];
1081
1082                proc_sample_cputime_atomic(&sig->cputimer.cputime_atomic,
1083                                           samples);
1084
1085                if (task_cputimers_expired(samples, pct))
1086                        return true;
1087        }
1088
1089        if (dl_task(tsk) && tsk->dl.dl_overrun)
1090                return true;
1091
1092        return false;
1093}
1094
1095static void handle_posix_cpu_timers(struct task_struct *tsk);
1096
1097#ifdef CONFIG_POSIX_CPU_TIMERS_TASK_WORK
1098static void posix_cpu_timers_work(struct callback_head *work)
1099{
1100        handle_posix_cpu_timers(current);
1101}
1102
1103/*
1104 * Initialize posix CPU timers task work in init task. Out of line to
1105 * keep the callback static and to avoid header recursion hell.
1106 */
1107void __init posix_cputimers_init_work(void)
1108{
1109        init_task_work(&current->posix_cputimers_work.work,
1110                       posix_cpu_timers_work);
1111}
1112
1113/*
1114 * Note: All operations on tsk->posix_cputimer_work.scheduled happen either
1115 * in hard interrupt context or in task context with interrupts
1116 * disabled. Aside of that the writer/reader interaction is always in the
1117 * context of the current task, which means they are strict per CPU.
1118 */
1119static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1120{
1121        return tsk->posix_cputimers_work.scheduled;
1122}
1123
1124static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1125{
1126        if (WARN_ON_ONCE(tsk->posix_cputimers_work.scheduled))
1127                return;
1128
1129        /* Schedule task work to actually expire the timers */
1130        tsk->posix_cputimers_work.scheduled = true;
1131        task_work_add(tsk, &tsk->posix_cputimers_work.work, TWA_RESUME);
1132}
1133
1134static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1135                                                unsigned long start)
1136{
1137        bool ret = true;
1138
1139        /*
1140         * On !RT kernels interrupts are disabled while collecting expired
1141         * timers, so no tick can happen and the fast path check can be
1142         * reenabled without further checks.
1143         */
1144        if (!IS_ENABLED(CONFIG_PREEMPT_RT)) {
1145                tsk->posix_cputimers_work.scheduled = false;
1146                return true;
1147        }
1148
1149        /*
1150         * On RT enabled kernels ticks can happen while the expired timers
1151         * are collected under sighand lock. But any tick which observes
1152         * the CPUTIMERS_WORK_SCHEDULED bit set, does not run the fastpath
1153         * checks. So reenabling the tick work has do be done carefully:
1154         *
1155         * Disable interrupts and run the fast path check if jiffies have
1156         * advanced since the collecting of expired timers started. If
1157         * jiffies have not advanced or the fast path check did not find
1158         * newly expired timers, reenable the fast path check in the timer
1159         * interrupt. If there are newly expired timers, return false and
1160         * let the collection loop repeat.
1161         */
1162        local_irq_disable();
1163        if (start != jiffies && fastpath_timer_check(tsk))
1164                ret = false;
1165        else
1166                tsk->posix_cputimers_work.scheduled = false;
1167        local_irq_enable();
1168
1169        return ret;
1170}
1171#else /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1172static inline void __run_posix_cpu_timers(struct task_struct *tsk)
1173{
1174        lockdep_posixtimer_enter();
1175        handle_posix_cpu_timers(tsk);
1176        lockdep_posixtimer_exit();
1177}
1178
1179static inline bool posix_cpu_timers_work_scheduled(struct task_struct *tsk)
1180{
1181        return false;
1182}
1183
1184static inline bool posix_cpu_timers_enable_work(struct task_struct *tsk,
1185                                                unsigned long start)
1186{
1187        return true;
1188}
1189#endif /* CONFIG_POSIX_CPU_TIMERS_TASK_WORK */
1190
1191static void handle_posix_cpu_timers(struct task_struct *tsk)
1192{
1193        struct k_itimer *timer, *next;
1194        unsigned long flags, start;
1195        LIST_HEAD(firing);
1196
1197        if (!lock_task_sighand(tsk, &flags))
1198                return;
1199
1200        do {
1201                /*
1202                 * On RT locking sighand lock does not disable interrupts,
1203                 * so this needs to be careful vs. ticks. Store the current
1204                 * jiffies value.
1205                 */
1206                start = READ_ONCE(jiffies);
1207                barrier();
1208
1209                /*
1210                 * Here we take off tsk->signal->cpu_timers[N] and
1211                 * tsk->cpu_timers[N] all the timers that are firing, and
1212                 * put them on the firing list.
1213                 */
1214                check_thread_timers(tsk, &firing);
1215
1216                check_process_timers(tsk, &firing);
1217
1218                /*
1219                 * The above timer checks have updated the expiry cache and
1220                 * because nothing can have queued or modified timers after
1221                 * sighand lock was taken above it is guaranteed to be
1222                 * consistent. So the next timer interrupt fastpath check
1223                 * will find valid data.
1224                 *
1225                 * If timer expiry runs in the timer interrupt context then
1226                 * the loop is not relevant as timers will be directly
1227                 * expired in interrupt context. The stub function below
1228                 * returns always true which allows the compiler to
1229                 * optimize the loop out.
1230                 *
1231                 * If timer expiry is deferred to task work context then
1232                 * the following rules apply:
1233                 *
1234                 * - On !RT kernels no tick can have happened on this CPU
1235                 *   after sighand lock was acquired because interrupts are
1236                 *   disabled. So reenabling task work before dropping
1237                 *   sighand lock and reenabling interrupts is race free.
1238                 *
1239                 * - On RT kernels ticks might have happened but the tick
1240                 *   work ignored posix CPU timer handling because the
1241                 *   CPUTIMERS_WORK_SCHEDULED bit is set. Reenabling work
1242                 *   must be done very carefully including a check whether
1243                 *   ticks have happened since the start of the timer
1244                 *   expiry checks. posix_cpu_timers_enable_work() takes
1245                 *   care of that and eventually lets the expiry checks
1246                 *   run again.
1247                 */
1248        } while (!posix_cpu_timers_enable_work(tsk, start));
1249
1250        /*
1251         * We must release sighand lock before taking any timer's lock.
1252         * There is a potential race with timer deletion here, as the
1253         * siglock now protects our private firing list.  We have set
1254         * the firing flag in each timer, so that a deletion attempt
1255         * that gets the timer lock before we do will give it up and
1256         * spin until we've taken care of that timer below.
1257         */
1258        unlock_task_sighand(tsk, &flags);
1259
1260        /*
1261         * Now that all the timers on our list have the firing flag,
1262         * no one will touch their list entries but us.  We'll take
1263         * each timer's lock before clearing its firing flag, so no
1264         * timer call will interfere.
1265         */
1266        list_for_each_entry_safe(timer, next, &firing, it.cpu.elist) {
1267                int cpu_firing;
1268
1269                /*
1270                 * spin_lock() is sufficient here even independent of the
1271                 * expiry context. If expiry happens in hard interrupt
1272                 * context it's obvious. For task work context it's safe
1273                 * because all other operations on timer::it_lock happen in
1274                 * task context (syscall or exit).
1275                 */
1276                spin_lock(&timer->it_lock);
1277                list_del_init(&timer->it.cpu.elist);
1278                cpu_firing = timer->it.cpu.firing;
1279                timer->it.cpu.firing = 0;
1280                /*
1281                 * The firing flag is -1 if we collided with a reset
1282                 * of the timer, which already reported this
1283                 * almost-firing as an overrun.  So don't generate an event.
1284                 */
1285                if (likely(cpu_firing >= 0))
1286                        cpu_timer_fire(timer);
1287                spin_unlock(&timer->it_lock);
1288        }
1289}
1290
1291/*
1292 * This is called from the timer interrupt handler.  The irq handler has
1293 * already updated our counts.  We need to check if any timers fire now.
1294 * Interrupts are disabled.
1295 */
1296void run_posix_cpu_timers(void)
1297{
1298        struct task_struct *tsk = current;
1299
1300        lockdep_assert_irqs_disabled();
1301
1302        /*
1303         * If the actual expiry is deferred to task work context and the
1304         * work is already scheduled there is no point to do anything here.
1305         */
1306        if (posix_cpu_timers_work_scheduled(tsk))
1307                return;
1308
1309        /*
1310         * The fast path checks that there are no expired thread or thread
1311         * group timers.  If that's so, just return.
1312         */
1313        if (!fastpath_timer_check(tsk))
1314                return;
1315
1316        __run_posix_cpu_timers(tsk);
1317}
1318
1319/*
1320 * Set one of the process-wide special case CPU timers or RLIMIT_CPU.
1321 * The tsk->sighand->siglock must be held by the caller.
1322 */
1323void set_process_cpu_timer(struct task_struct *tsk, unsigned int clkid,
1324                           u64 *newval, u64 *oldval)
1325{
1326        u64 now, *nextevt;
1327
1328        if (WARN_ON_ONCE(clkid >= CPUCLOCK_SCHED))
1329                return;
1330
1331        nextevt = &tsk->signal->posix_cputimers.bases[clkid].nextevt;
1332        now = cpu_clock_sample_group(clkid, tsk, true);
1333
1334        if (oldval) {
1335                /*
1336                 * We are setting itimer. The *oldval is absolute and we update
1337                 * it to be relative, *newval argument is relative and we update
1338                 * it to be absolute.
1339                 */
1340                if (*oldval) {
1341                        if (*oldval <= now) {
1342                                /* Just about to fire. */
1343                                *oldval = TICK_NSEC;
1344                        } else {
1345                                *oldval -= now;
1346                        }
1347                }
1348
1349                if (!*newval)
1350                        return;
1351                *newval += now;
1352        }
1353
1354        /*
1355         * Update expiration cache if this is the earliest timer. CPUCLOCK_PROF
1356         * expiry cache is also used by RLIMIT_CPU!.
1357         */
1358        if (*newval < *nextevt)
1359                *nextevt = *newval;
1360
1361        tick_dep_set_signal(tsk, TICK_DEP_BIT_POSIX_TIMER);
1362}
1363
1364static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
1365                            const struct timespec64 *rqtp)
1366{
1367        struct itimerspec64 it;
1368        struct k_itimer timer;
1369        u64 expires;
1370        int error;
1371
1372        /*
1373         * Set up a temporary timer and then wait for it to go off.
1374         */
1375        memset(&timer, 0, sizeof timer);
1376        spin_lock_init(&timer.it_lock);
1377        timer.it_clock = which_clock;
1378        timer.it_overrun = -1;
1379        error = posix_cpu_timer_create(&timer);
1380        timer.it_process = current;
1381
1382        if (!error) {
1383                static struct itimerspec64 zero_it;
1384                struct restart_block *restart;
1385
1386                memset(&it, 0, sizeof(it));
1387                it.it_value = *rqtp;
1388
1389                spin_lock_irq(&timer.it_lock);
1390                error = posix_cpu_timer_set(&timer, flags, &it, NULL);
1391                if (error) {
1392                        spin_unlock_irq(&timer.it_lock);
1393                        return error;
1394                }
1395
1396                while (!signal_pending(current)) {
1397                        if (!cpu_timer_getexpires(&timer.it.cpu)) {
1398                                /*
1399                                 * Our timer fired and was reset, below
1400                                 * deletion can not fail.
1401                                 */
1402                                posix_cpu_timer_del(&timer);
1403                                spin_unlock_irq(&timer.it_lock);
1404                                return 0;
1405                        }
1406
1407                        /*
1408                         * Block until cpu_timer_fire (or a signal) wakes us.
1409                         */
1410                        __set_current_state(TASK_INTERRUPTIBLE);
1411                        spin_unlock_irq(&timer.it_lock);
1412                        schedule();
1413                        spin_lock_irq(&timer.it_lock);
1414                }
1415
1416                /*
1417                 * We were interrupted by a signal.
1418                 */
1419                expires = cpu_timer_getexpires(&timer.it.cpu);
1420                error = posix_cpu_timer_set(&timer, 0, &zero_it, &it);
1421                if (!error) {
1422                        /*
1423                         * Timer is now unarmed, deletion can not fail.
1424                         */
1425                        posix_cpu_timer_del(&timer);
1426                }
1427                spin_unlock_irq(&timer.it_lock);
1428
1429                while (error == TIMER_RETRY) {
1430                        /*
1431                         * We need to handle case when timer was or is in the
1432                         * middle of firing. In other cases we already freed
1433                         * resources.
1434                         */
1435                        spin_lock_irq(&timer.it_lock);
1436                        error = posix_cpu_timer_del(&timer);
1437                        spin_unlock_irq(&timer.it_lock);
1438                }
1439
1440                if ((it.it_value.tv_sec | it.it_value.tv_nsec) == 0) {
1441                        /*
1442                         * It actually did fire already.
1443                         */
1444                        return 0;
1445                }
1446
1447                error = -ERESTART_RESTARTBLOCK;
1448                /*
1449                 * Report back to the user the time still remaining.
1450                 */
1451                restart = &current->restart_block;
1452                restart->nanosleep.expires = expires;
1453                if (restart->nanosleep.type != TT_NONE)
1454                        error = nanosleep_copyout(restart, &it.it_value);
1455        }
1456
1457        return error;
1458}
1459
1460static long posix_cpu_nsleep_restart(struct restart_block *restart_block);
1461
1462static int posix_cpu_nsleep(const clockid_t which_clock, int flags,
1463                            const struct timespec64 *rqtp)
1464{
1465        struct restart_block *restart_block = &current->restart_block;
1466        int error;
1467
1468        /*
1469         * Diagnose required errors first.
1470         */
1471        if (CPUCLOCK_PERTHREAD(which_clock) &&
1472            (CPUCLOCK_PID(which_clock) == 0 ||
1473             CPUCLOCK_PID(which_clock) == task_pid_vnr(current)))
1474                return -EINVAL;
1475
1476        error = do_cpu_nanosleep(which_clock, flags, rqtp);
1477
1478        if (error == -ERESTART_RESTARTBLOCK) {
1479
1480                if (flags & TIMER_ABSTIME)
1481                        return -ERESTARTNOHAND;
1482
1483                restart_block->nanosleep.clockid = which_clock;
1484                set_restart_fn(restart_block, posix_cpu_nsleep_restart);
1485        }
1486        return error;
1487}
1488
1489static long posix_cpu_nsleep_restart(struct restart_block *restart_block)
1490{
1491        clockid_t which_clock = restart_block->nanosleep.clockid;
1492        struct timespec64 t;
1493
1494        t = ns_to_timespec64(restart_block->nanosleep.expires);
1495
1496        return do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t);
1497}
1498
1499#define PROCESS_CLOCK   make_process_cpuclock(0, CPUCLOCK_SCHED)
1500#define THREAD_CLOCK    make_thread_cpuclock(0, CPUCLOCK_SCHED)
1501
1502static int process_cpu_clock_getres(const clockid_t which_clock,
1503                                    struct timespec64 *tp)
1504{
1505        return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
1506}
1507static int process_cpu_clock_get(const clockid_t which_clock,
1508                                 struct timespec64 *tp)
1509{
1510        return posix_cpu_clock_get(PROCESS_CLOCK, tp);
1511}
1512static int process_cpu_timer_create(struct k_itimer *timer)
1513{
1514        timer->it_clock = PROCESS_CLOCK;
1515        return posix_cpu_timer_create(timer);
1516}
1517static int process_cpu_nsleep(const clockid_t which_clock, int flags,
1518                              const struct timespec64 *rqtp)
1519{
1520        return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp);
1521}
1522static int thread_cpu_clock_getres(const clockid_t which_clock,
1523                                   struct timespec64 *tp)
1524{
1525        return posix_cpu_clock_getres(THREAD_CLOCK, tp);
1526}
1527static int thread_cpu_clock_get(const clockid_t which_clock,
1528                                struct timespec64 *tp)
1529{
1530        return posix_cpu_clock_get(THREAD_CLOCK, tp);
1531}
1532static int thread_cpu_timer_create(struct k_itimer *timer)
1533{
1534        timer->it_clock = THREAD_CLOCK;
1535        return posix_cpu_timer_create(timer);
1536}
1537
1538const struct k_clock clock_posix_cpu = {
1539        .clock_getres           = posix_cpu_clock_getres,
1540        .clock_set              = posix_cpu_clock_set,
1541        .clock_get_timespec     = posix_cpu_clock_get,
1542        .timer_create           = posix_cpu_timer_create,
1543        .nsleep                 = posix_cpu_nsleep,
1544        .timer_set              = posix_cpu_timer_set,
1545        .timer_del              = posix_cpu_timer_del,
1546        .timer_get              = posix_cpu_timer_get,
1547        .timer_rearm            = posix_cpu_timer_rearm,
1548};
1549
1550const struct k_clock clock_process = {
1551        .clock_getres           = process_cpu_clock_getres,
1552        .clock_get_timespec     = process_cpu_clock_get,
1553        .timer_create           = process_cpu_timer_create,
1554        .nsleep                 = process_cpu_nsleep,
1555};
1556
1557const struct k_clock clock_thread = {
1558        .clock_getres           = thread_cpu_clock_getres,
1559        .clock_get_timespec     = thread_cpu_clock_get,
1560        .timer_create           = thread_cpu_timer_create,
1561};
1562
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