kernel/time/posix-cpu-timers.c

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

DEFINITIONS
