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posix-cpu-timers.c

/*
 * Implement CPU time clocks for the POSIX clock interface.
 */

#include <linux/sched.h>
#include <linux/posix-timers.h>
#include <asm/uaccess.h>
#include <linux/errno.h>

static int check_clock(const clockid_t which_clock)
{
      int error = 0;
      struct task_struct *p;
      const pid_t pid = CPUCLOCK_PID(which_clock);

      if (CPUCLOCK_WHICH(which_clock) >= CPUCLOCK_MAX)
            return -EINVAL;

      if (pid == 0)
            return 0;

      read_lock(&tasklist_lock);
      p = find_task_by_pid(pid);
      if (!p || !(CPUCLOCK_PERTHREAD(which_clock) ?
               same_thread_group(p, current) : thread_group_leader(p))) {
            error = -EINVAL;
      }
      read_unlock(&tasklist_lock);

      return error;
}

static inline union cpu_time_count
timespec_to_sample(const clockid_t which_clock, const struct timespec *tp)
{
      union cpu_time_count ret;
      ret.sched = 0;          /* high half always zero when .cpu used */
      if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
            ret.sched = (unsigned long long)tp->tv_sec * NSEC_PER_SEC + tp->tv_nsec;
      } else {
            ret.cpu = timespec_to_cputime(tp);
      }
      return ret;
}

static void sample_to_timespec(const clockid_t which_clock,
                         union cpu_time_count cpu,
                         struct timespec *tp)
{
      if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
            tp->tv_sec = div_long_long_rem(cpu.sched,
                                     NSEC_PER_SEC, &tp->tv_nsec);
      } else {
            cputime_to_timespec(cpu.cpu, tp);
      }
}

static inline int cpu_time_before(const clockid_t which_clock,
                          union cpu_time_count now,
                          union cpu_time_count then)
{
      if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
            return now.sched < then.sched;
      }  else {
            return cputime_lt(now.cpu, then.cpu);
      }
}
static inline void cpu_time_add(const clockid_t which_clock,
                        union cpu_time_count *acc,
                          union cpu_time_count val)
{
      if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
            acc->sched += val.sched;
      }  else {
            acc->cpu = cputime_add(acc->cpu, val.cpu);
      }
}
static inline union cpu_time_count cpu_time_sub(const clockid_t which_clock,
                                    union cpu_time_count a,
                                    union cpu_time_count b)
{
      if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
            a.sched -= b.sched;
      }  else {
            a.cpu = cputime_sub(a.cpu, b.cpu);
      }
      return a;
}

/*
 * Divide and limit the result to res >= 1
 *
 * This is necessary to prevent signal delivery starvation, when the result of
 * the division would be rounded down to 0.
 */
static inline cputime_t cputime_div_non_zero(cputime_t time, unsigned long div)
{
      cputime_t res = cputime_div(time, div);

      return max_t(cputime_t, res, 1);
}

/*
 * Update expiry time from increment, and increase overrun count,
 * given the current clock sample.
 */
static void bump_cpu_timer(struct k_itimer *timer,
                          union cpu_time_count now)
{
      int i;

      if (timer->it.cpu.incr.sched == 0)
            return;

      if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
            unsigned long long delta, incr;

            if (now.sched < timer->it.cpu.expires.sched)
                  return;
            incr = timer->it.cpu.incr.sched;
            delta = now.sched + incr - timer->it.cpu.expires.sched;
            /* Don't use (incr*2 < delta), incr*2 might overflow. */
            for (i = 0; incr < delta - incr; i++)
                  incr = incr << 1;
            for (; i >= 0; incr >>= 1, i--) {
                  if (delta < incr)
                        continue;
                  timer->it.cpu.expires.sched += incr;
                  timer->it_overrun += 1 << i;
                  delta -= incr;
            }
      } else {
            cputime_t delta, incr;

            if (cputime_lt(now.cpu, timer->it.cpu.expires.cpu))
                  return;
            incr = timer->it.cpu.incr.cpu;
            delta = cputime_sub(cputime_add(now.cpu, incr),
                            timer->it.cpu.expires.cpu);
            /* Don't use (incr*2 < delta), incr*2 might overflow. */
            for (i = 0; cputime_lt(incr, cputime_sub(delta, incr)); i++)
                       incr = cputime_add(incr, incr);
            for (; i >= 0; incr = cputime_halve(incr), i--) {
                  if (cputime_lt(delta, incr))
                        continue;
                  timer->it.cpu.expires.cpu =
                        cputime_add(timer->it.cpu.expires.cpu, incr);
                  timer->it_overrun += 1 << i;
                  delta = cputime_sub(delta, incr);
            }
      }
}

static inline cputime_t prof_ticks(struct task_struct *p)
{
      return cputime_add(p->utime, p->stime);
}
static inline cputime_t virt_ticks(struct task_struct *p)
{
      return p->utime;
}
static inline unsigned long long sched_ns(struct task_struct *p)
{
      return task_sched_runtime(p);
}

int posix_cpu_clock_getres(const clockid_t which_clock, struct timespec *tp)
{
      int error = check_clock(which_clock);
      if (!error) {
            tp->tv_sec = 0;
            tp->tv_nsec = ((NSEC_PER_SEC + HZ - 1) / HZ);
            if (CPUCLOCK_WHICH(which_clock) == CPUCLOCK_SCHED) {
                  /*
                   * If sched_clock is using a cycle counter, we
                   * don't have any idea of its true resolution
                   * exported, but it is much more than 1s/HZ.
                   */
                  tp->tv_nsec = 1;
            }
      }
      return error;
}

int posix_cpu_clock_set(const clockid_t which_clock, const struct timespec *tp)
{
      /*
       * You can never reset a CPU clock, but we check for other errors
       * in the call before failing with EPERM.
       */
      int error = check_clock(which_clock);
      if (error == 0) {
            error = -EPERM;
      }
      return error;
}


/*
 * Sample a per-thread clock for the given task.
 */
static int cpu_clock_sample(const clockid_t which_clock, struct task_struct *p,
                      union cpu_time_count *cpu)
{
      switch (CPUCLOCK_WHICH(which_clock)) {
      default:
            return -EINVAL;
      case CPUCLOCK_PROF:
            cpu->cpu = prof_ticks(p);
            break;
      case CPUCLOCK_VIRT:
            cpu->cpu = virt_ticks(p);
            break;
      case CPUCLOCK_SCHED:
            cpu->sched = sched_ns(p);
            break;
      }
      return 0;
}

/*
 * Sample a process (thread group) clock for the given group_leader task.
 * Must be called with tasklist_lock held for reading.
 * Must be called with tasklist_lock held for reading, and p->sighand->siglock.
 */
static int cpu_clock_sample_group_locked(unsigned int clock_idx,
                               struct task_struct *p,
                               union cpu_time_count *cpu)
{
      struct task_struct *t = p;
      switch (clock_idx) {
      default:
            return -EINVAL;
      case CPUCLOCK_PROF:
            cpu->cpu = cputime_add(p->signal->utime, p->signal->stime);
            do {
                  cpu->cpu = cputime_add(cpu->cpu, prof_ticks(t));
                  t = next_thread(t);
            } while (t != p);
            break;
      case CPUCLOCK_VIRT:
            cpu->cpu = p->signal->utime;
            do {
                  cpu->cpu = cputime_add(cpu->cpu, virt_ticks(t));
                  t = next_thread(t);
            } while (t != p);
            break;
      case CPUCLOCK_SCHED:
            cpu->sched = p->signal->sum_sched_runtime;
            /* Add in each other live thread.  */
            while ((t = next_thread(t)) != p) {
                  cpu->sched += t->se.sum_exec_runtime;
            }
            cpu->sched += sched_ns(p);
            break;
      }
      return 0;
}

/*
 * Sample a process (thread group) clock for the given group_leader task.
 * Must be called with tasklist_lock held for reading.
 */
static int cpu_clock_sample_group(const clockid_t which_clock,
                          struct task_struct *p,
                          union cpu_time_count *cpu)
{
      int ret;
      unsigned long flags;
      spin_lock_irqsave(&p->sighand->siglock, flags);
      ret = cpu_clock_sample_group_locked(CPUCLOCK_WHICH(which_clock), p,
                                  cpu);
      spin_unlock_irqrestore(&p->sighand->siglock, flags);
      return ret;
}


int posix_cpu_clock_get(const clockid_t which_clock, struct timespec *tp)
{
      const pid_t pid = CPUCLOCK_PID(which_clock);
      int error = -EINVAL;
      union cpu_time_count rtn;

      if (pid == 0) {
            /*
             * Special case constant value for our own clocks.
             * We don't have to do any lookup to find ourselves.
             */
            if (CPUCLOCK_PERTHREAD(which_clock)) {
                  /*
                   * Sampling just ourselves we can do with no locking.
                   */
                  error = cpu_clock_sample(which_clock,
                                     current, &rtn);
            } else {
                  read_lock(&tasklist_lock);
                  error = cpu_clock_sample_group(which_clock,
                                           current, &rtn);
                  read_unlock(&tasklist_lock);
            }
      } else {
            /*
             * Find the given PID, and validate that the caller
             * should be able to see it.
             */
            struct task_struct *p;
            rcu_read_lock();
            p = find_task_by_pid(pid);
            if (p) {
                  if (CPUCLOCK_PERTHREAD(which_clock)) {
                        if (same_thread_group(p, current)) {
                              error = cpu_clock_sample(which_clock,
                                                 p, &rtn);
                        }
                  } else {
                        read_lock(&tasklist_lock);
                        if (thread_group_leader(p) && p->signal) {
                              error =
                                  cpu_clock_sample_group(which_clock,
                                                     p, &rtn);
                        }
                        read_unlock(&tasklist_lock);
                  }
            }
            rcu_read_unlock();
      }

      if (error)
            return error;
      sample_to_timespec(which_clock, rtn, tp);
      return 0;
}


/*
 * Validate the clockid_t for a new CPU-clock timer, and initialize the timer.
 * This is called from sys_timer_create with the new timer already locked.
 */
int posix_cpu_timer_create(struct k_itimer *new_timer)
{
      int ret = 0;
      const pid_t pid = CPUCLOCK_PID(new_timer->it_clock);
      struct task_struct *p;

      if (CPUCLOCK_WHICH(new_timer->it_clock) >= CPUCLOCK_MAX)
            return -EINVAL;

      INIT_LIST_HEAD(&new_timer->it.cpu.entry);
      new_timer->it.cpu.incr.sched = 0;
      new_timer->it.cpu.expires.sched = 0;

      read_lock(&tasklist_lock);
      if (CPUCLOCK_PERTHREAD(new_timer->it_clock)) {
            if (pid == 0) {
                  p = current;
            } else {
                  p = find_task_by_pid(pid);
                  if (p && !same_thread_group(p, current))
                        p = NULL;
            }
      } else {
            if (pid == 0) {
                  p = current->group_leader;
            } else {
                  p = find_task_by_pid(pid);
                  if (p && !thread_group_leader(p))
                        p = NULL;
            }
      }
      new_timer->it.cpu.task = p;
      if (p) {
            get_task_struct(p);
      } else {
            ret = -EINVAL;
      }
      read_unlock(&tasklist_lock);

      return ret;
}

/*
 * Clean up a CPU-clock timer that is about to be destroyed.
 * This is called from timer deletion with the timer already locked.
 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 * and try again.  (This happens when the timer is in the middle of firing.)
 */
int posix_cpu_timer_del(struct k_itimer *timer)
{
      struct task_struct *p = timer->it.cpu.task;
      int ret = 0;

      if (likely(p != NULL)) {
            read_lock(&tasklist_lock);
            if (unlikely(p->signal == NULL)) {
                  /*
                   * We raced with the reaping of the task.
                   * The deletion should have cleared us off the list.
                   */
                  BUG_ON(!list_empty(&timer->it.cpu.entry));
            } else {
                  spin_lock(&p->sighand->siglock);
                  if (timer->it.cpu.firing)
                        ret = TIMER_RETRY;
                  else
                        list_del(&timer->it.cpu.entry);
                  spin_unlock(&p->sighand->siglock);
            }
            read_unlock(&tasklist_lock);

            if (!ret)
                  put_task_struct(p);
      }

      return ret;
}

/*
 * Clean out CPU timers still ticking when a thread exited.  The task
 * pointer is cleared, and the expiry time is replaced with the residual
 * time for later timer_gettime calls to return.
 * This must be called with the siglock held.
 */
static void cleanup_timers(struct list_head *head,
                     cputime_t utime, cputime_t stime,
                     unsigned long long sum_exec_runtime)
{
      struct cpu_timer_list *timer, *next;
      cputime_t ptime = cputime_add(utime, stime);

      list_for_each_entry_safe(timer, next, head, entry) {
            list_del_init(&timer->entry);
            if (cputime_lt(timer->expires.cpu, ptime)) {
                  timer->expires.cpu = cputime_zero;
            } else {
                  timer->expires.cpu = cputime_sub(timer->expires.cpu,
                                           ptime);
            }
      }

      ++head;
      list_for_each_entry_safe(timer, next, head, entry) {
            list_del_init(&timer->entry);
            if (cputime_lt(timer->expires.cpu, utime)) {
                  timer->expires.cpu = cputime_zero;
            } else {
                  timer->expires.cpu = cputime_sub(timer->expires.cpu,
                                           utime);
            }
      }

      ++head;
      list_for_each_entry_safe(timer, next, head, entry) {
            list_del_init(&timer->entry);
            if (timer->expires.sched < sum_exec_runtime) {
                  timer->expires.sched = 0;
            } else {
                  timer->expires.sched -= sum_exec_runtime;
            }
      }
}

/*
 * These are both called with the siglock held, when the current thread
 * is being reaped.  When the final (leader) thread in the group is reaped,
 * posix_cpu_timers_exit_group will be called after posix_cpu_timers_exit.
 */
void posix_cpu_timers_exit(struct task_struct *tsk)
{
      cleanup_timers(tsk->cpu_timers,
                   tsk->utime, tsk->stime, tsk->se.sum_exec_runtime);

}
void posix_cpu_timers_exit_group(struct task_struct *tsk)
{
      cleanup_timers(tsk->signal->cpu_timers,
                   cputime_add(tsk->utime, tsk->signal->utime),
                   cputime_add(tsk->stime, tsk->signal->stime),
                 tsk->se.sum_exec_runtime + tsk->signal->sum_sched_runtime);
}


/*
 * Set the expiry times of all the threads in the process so one of them
 * will go off before the process cumulative expiry total is reached.
 */
static void process_timer_rebalance(struct task_struct *p,
                            unsigned int clock_idx,
                            union cpu_time_count expires,
                            union cpu_time_count val)
{
      cputime_t ticks, left;
      unsigned long long ns, nsleft;
      struct task_struct *t = p;
      unsigned int nthreads = atomic_read(&p->signal->live);

      if (!nthreads)
            return;

      switch (clock_idx) {
      default:
            BUG();
            break;
      case CPUCLOCK_PROF:
            left = cputime_div_non_zero(cputime_sub(expires.cpu, val.cpu),
                               nthreads);
            do {
                  if (likely(!(t->flags & PF_EXITING))) {
                        ticks = cputime_add(prof_ticks(t), left);
                        if (cputime_eq(t->it_prof_expires,
                                     cputime_zero) ||
                            cputime_gt(t->it_prof_expires, ticks)) {
                              t->it_prof_expires = ticks;
                        }
                  }
                  t = next_thread(t);
            } while (t != p);
            break;
      case CPUCLOCK_VIRT:
            left = cputime_div_non_zero(cputime_sub(expires.cpu, val.cpu),
                               nthreads);
            do {
                  if (likely(!(t->flags & PF_EXITING))) {
                        ticks = cputime_add(virt_ticks(t), left);
                        if (cputime_eq(t->it_virt_expires,
                                     cputime_zero) ||
                            cputime_gt(t->it_virt_expires, ticks)) {
                              t->it_virt_expires = ticks;
                        }
                  }
                  t = next_thread(t);
            } while (t != p);
            break;
      case CPUCLOCK_SCHED:
            nsleft = expires.sched - val.sched;
            do_div(nsleft, nthreads);
            nsleft = max_t(unsigned long long, nsleft, 1);
            do {
                  if (likely(!(t->flags & PF_EXITING))) {
                        ns = t->se.sum_exec_runtime + nsleft;
                        if (t->it_sched_expires == 0 ||
                            t->it_sched_expires > ns) {
                              t->it_sched_expires = ns;
                        }
                  }
                  t = next_thread(t);
            } while (t != p);
            break;
      }
}

static void clear_dead_task(struct k_itimer *timer, union cpu_time_count now)
{
      /*
       * That's all for this thread or process.
       * We leave our residual in expires to be reported.
       */
      put_task_struct(timer->it.cpu.task);
      timer->it.cpu.task = NULL;
      timer->it.cpu.expires = cpu_time_sub(timer->it_clock,
                                   timer->it.cpu.expires,
                                   now);
}

/*
 * Insert the timer on the appropriate list before any timers that
 * expire later.  This must be called with the tasklist_lock held
 * for reading, and interrupts disabled.
 */
static void arm_timer(struct k_itimer *timer, union cpu_time_count now)
{
      struct task_struct *p = timer->it.cpu.task;
      struct list_head *head, *listpos;
      struct cpu_timer_list *const nt = &timer->it.cpu;
      struct cpu_timer_list *next;
      unsigned long i;

      head = (CPUCLOCK_PERTHREAD(timer->it_clock) ?
            p->cpu_timers : p->signal->cpu_timers);
      head += CPUCLOCK_WHICH(timer->it_clock);

      BUG_ON(!irqs_disabled());
      spin_lock(&p->sighand->siglock);

      listpos = head;
      if (CPUCLOCK_WHICH(timer->it_clock) == CPUCLOCK_SCHED) {
            list_for_each_entry(next, head, entry) {
                  if (next->expires.sched > nt->expires.sched)
                        break;
                  listpos = &next->entry;
            }
      } else {
            list_for_each_entry(next, head, entry) {
                  if (cputime_gt(next->expires.cpu, nt->expires.cpu))
                        break;
                  listpos = &next->entry;
            }
      }
      list_add(&nt->entry, listpos);

      if (listpos == head) {
            /*
             * We are the new earliest-expiring timer.
             * If we are a thread timer, there can always
             * be a process timer telling us to stop earlier.
             */

            if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
                  switch (CPUCLOCK_WHICH(timer->it_clock)) {
                  default:
                        BUG();
                  case CPUCLOCK_PROF:
                        if (cputime_eq(p->it_prof_expires,
                                     cputime_zero) ||
                            cputime_gt(p->it_prof_expires,
                                     nt->expires.cpu))
                              p->it_prof_expires = nt->expires.cpu;
                        break;
                  case CPUCLOCK_VIRT:
                        if (cputime_eq(p->it_virt_expires,
                                     cputime_zero) ||
                            cputime_gt(p->it_virt_expires,
                                     nt->expires.cpu))
                              p->it_virt_expires = nt->expires.cpu;
                        break;
                  case CPUCLOCK_SCHED:
                        if (p->it_sched_expires == 0 ||
                            p->it_sched_expires > nt->expires.sched)
                              p->it_sched_expires = nt->expires.sched;
                        break;
                  }
            } else {
                  /*
                   * For a process timer, we must balance
                   * all the live threads' expirations.
                   */
                  switch (CPUCLOCK_WHICH(timer->it_clock)) {
                  default:
                        BUG();
                  case CPUCLOCK_VIRT:
                        if (!cputime_eq(p->signal->it_virt_expires,
                                    cputime_zero) &&
                            cputime_lt(p->signal->it_virt_expires,
                                     timer->it.cpu.expires.cpu))
                              break;
                        goto rebalance;
                  case CPUCLOCK_PROF:
                        if (!cputime_eq(p->signal->it_prof_expires,
                                    cputime_zero) &&
                            cputime_lt(p->signal->it_prof_expires,
                                     timer->it.cpu.expires.cpu))
                              break;
                        i = p->signal->rlim[RLIMIT_CPU].rlim_cur;
                        if (i != RLIM_INFINITY &&
                            i <= cputime_to_secs(timer->it.cpu.expires.cpu))
                              break;
                        goto rebalance;
                  case CPUCLOCK_SCHED:
                  rebalance:
                        process_timer_rebalance(
                              timer->it.cpu.task,
                              CPUCLOCK_WHICH(timer->it_clock),
                              timer->it.cpu.expires, now);
                        break;
                  }
            }
      }

      spin_unlock(&p->sighand->siglock);
}

/*
 * The timer is locked, fire it and arrange for its reload.
 */
static void cpu_timer_fire(struct k_itimer *timer)
{
      if (unlikely(timer->sigq == NULL)) {
            /*
             * This a special case for clock_nanosleep,
             * not a normal timer from sys_timer_create.
             */
            wake_up_process(timer->it_process);
            timer->it.cpu.expires.sched = 0;
      } else if (timer->it.cpu.incr.sched == 0) {
            /*
             * One-shot timer.  Clear it as soon as it's fired.
             */
            posix_timer_event(timer, 0);
            timer->it.cpu.expires.sched = 0;
      } else if (posix_timer_event(timer, ++timer->it_requeue_pending)) {
            /*
             * The signal did not get queued because the signal
             * was ignored, so we won't get any callback to
             * reload the timer.  But we need to keep it
             * ticking in case the signal is deliverable next time.
             */
            posix_cpu_timer_schedule(timer);
      }
}

/*
 * Guts of sys_timer_settime for CPU timers.
 * This is called with the timer locked and interrupts disabled.
 * If we return TIMER_RETRY, it's necessary to release the timer's lock
 * and try again.  (This happens when the timer is in the middle of firing.)
 */
int posix_cpu_timer_set(struct k_itimer *timer, int flags,
                  struct itimerspec *new, struct itimerspec *old)
{
      struct task_struct *p = timer->it.cpu.task;
      union cpu_time_count old_expires, new_expires, val;
      int ret;

      if (unlikely(p == NULL)) {
            /*
             * Timer refers to a dead task's clock.
             */
            return -ESRCH;
      }

      new_expires = timespec_to_sample(timer->it_clock, &new->it_value);

      read_lock(&tasklist_lock);
      /*
       * We need the tasklist_lock to protect against reaping that
       * clears p->signal.  If p has just been reaped, we can no
       * longer get any information about it at all.
       */
      if (unlikely(p->signal == NULL)) {
            read_unlock(&tasklist_lock);
            put_task_struct(p);
            timer->it.cpu.task = NULL;
            return -ESRCH;
      }

      /*
       * Disarm any old timer after extracting its expiry time.
       */
      BUG_ON(!irqs_disabled());

      ret = 0;
      spin_lock(&p->sighand->siglock);
      old_expires = timer->it.cpu.expires;
      if (unlikely(timer->it.cpu.firing)) {
            timer->it.cpu.firing = -1;
            ret = TIMER_RETRY;
      } else
            list_del_init(&timer->it.cpu.entry);
      spin_unlock(&p->sighand->siglock);

      /*
       * We need to sample the current value to convert the new
       * value from to relative and absolute, and to convert the
       * old value from absolute to relative.  To set a process
       * timer, we need a sample to balance the thread expiry
       * times (in arm_timer).  With an absolute time, we must
       * check if it's already passed.  In short, we need a sample.
       */
      if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
            cpu_clock_sample(timer->it_clock, p, &val);
      } else {
            cpu_clock_sample_group(timer->it_clock, p, &val);
      }

      if (old) {
            if (old_expires.sched == 0) {
                  old->it_value.tv_sec = 0;
                  old->it_value.tv_nsec = 0;
            } else {
                  /*
                   * Update the timer in case it has
                   * overrun already.  If it has,
                   * we'll report it as having overrun
                   * and with the next reloaded timer
                   * already ticking, though we are
                   * swallowing that pending
                   * notification here to install the
                   * new setting.
                   */
                  bump_cpu_timer(timer, val);
                  if (cpu_time_before(timer->it_clock, val,
                                  timer->it.cpu.expires)) {
                        old_expires = cpu_time_sub(
                              timer->it_clock,
                              timer->it.cpu.expires, val);
                        sample_to_timespec(timer->it_clock,
                                       old_expires,
                                       &old->it_value);
                  } else {
                        old->it_value.tv_nsec = 1;
                        old->it_value.tv_sec = 0;
                  }
            }
      }

      if (unlikely(ret)) {
            /*
             * We are colliding with the timer actually firing.
             * Punt after filling in the timer's old value, and
             * disable this firing since we are already reporting
             * it as an overrun (thanks to bump_cpu_timer above).
             */
            read_unlock(&tasklist_lock);
            goto out;
      }

      if (new_expires.sched != 0 && !(flags & TIMER_ABSTIME)) {
            cpu_time_add(timer->it_clock, &new_expires, val);
      }

      /*
       * Install the new expiry time (or zero).
       * For a timer with no notification action, we don't actually
       * arm the timer (we'll just fake it for timer_gettime).
       */
      timer->it.cpu.expires = new_expires;
      if (new_expires.sched != 0 &&
          (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
          cpu_time_before(timer->it_clock, val, new_expires)) {
            arm_timer(timer, val);
      }

      read_unlock(&tasklist_lock);

      /*
       * Install the new reload setting, and
       * set up the signal and overrun bookkeeping.
       */
      timer->it.cpu.incr = timespec_to_sample(timer->it_clock,
                                    &new->it_interval);

      /*
       * This acts as a modification timestamp for the timer,
       * so any automatic reload attempt will punt on seeing
       * that we have reset the timer manually.
       */
      timer->it_requeue_pending = (timer->it_requeue_pending + 2) &
            ~REQUEUE_PENDING;
      timer->it_overrun_last = 0;
      timer->it_overrun = -1;

      if (new_expires.sched != 0 &&
          (timer->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE &&
          !cpu_time_before(timer->it_clock, val, new_expires)) {
            /*
             * The designated time already passed, so we notify
             * immediately, even if the thread never runs to
             * accumulate more time on this clock.
             */
            cpu_timer_fire(timer);
      }

      ret = 0;
 out:
      if (old) {
            sample_to_timespec(timer->it_clock,
                           timer->it.cpu.incr, &old->it_interval);
      }
      return ret;
}

void posix_cpu_timer_get(struct k_itimer *timer, struct itimerspec *itp)
{
      union cpu_time_count now;
      struct task_struct *p = timer->it.cpu.task;
      int clear_dead;

      /*
       * Easy part: convert the reload time.
       */
      sample_to_timespec(timer->it_clock,
                     timer->it.cpu.incr, &itp->it_interval);

      if (timer->it.cpu.expires.sched == 0) {   /* Timer not armed at all.  */
            itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
            return;
      }

      if (unlikely(p == NULL)) {
            /*
             * This task already died and the timer will never fire.
             * In this case, expires is actually the dead value.
             */
      dead:
            sample_to_timespec(timer->it_clock, timer->it.cpu.expires,
                           &itp->it_value);
            return;
      }

      /*
       * Sample the clock to take the difference with the expiry time.
       */
      if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
            cpu_clock_sample(timer->it_clock, p, &now);
            clear_dead = p->exit_state;
      } else {
            read_lock(&tasklist_lock);
            if (unlikely(p->signal == NULL)) {
                  /*
                   * The process has been reaped.
                   * We can't even collect a sample any more.
                   * Call the timer disarmed, nothing else to do.
                   */
                  put_task_struct(p);
                  timer->it.cpu.task = NULL;
                  timer->it.cpu.expires.sched = 0;
                  read_unlock(&tasklist_lock);
                  goto dead;
            } else {
                  cpu_clock_sample_group(timer->it_clock, p, &now);
                  clear_dead = (unlikely(p->exit_state) &&
                              thread_group_empty(p));
            }
            read_unlock(&tasklist_lock);
      }

      if ((timer->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE) {
            if (timer->it.cpu.incr.sched == 0 &&
                cpu_time_before(timer->it_clock,
                            timer->it.cpu.expires, now)) {
                  /*
                   * Do-nothing timer expired and has no reload,
                   * so it's as if it was never set.
                   */
                  timer->it.cpu.expires.sched = 0;
                  itp->it_value.tv_sec = itp->it_value.tv_nsec = 0;
                  return;
            }
            /*
             * Account for any expirations and reloads that should
             * have happened.
             */
            bump_cpu_timer(timer, now);
      }

      if (unlikely(clear_dead)) {
            /*
             * We've noticed that the thread is dead, but
             * not yet reaped.  Take this opportunity to
             * drop our task ref.
             */
            clear_dead_task(timer, now);
            goto dead;
      }

      if (cpu_time_before(timer->it_clock, now, timer->it.cpu.expires)) {
            sample_to_timespec(timer->it_clock,
                           cpu_time_sub(timer->it_clock,
                                    timer->it.cpu.expires, now),
                           &itp->it_value);
      } else {
            /*
             * The timer should have expired already, but the firing
             * hasn't taken place yet.  Say it's just about to expire.
             */
            itp->it_value.tv_nsec = 1;
            itp->it_value.tv_sec = 0;
      }
}

/*
 * Check for any per-thread CPU timers that have fired and move them off
 * the tsk->cpu_timers[N] list onto the firing list.  Here we update the
 * tsk->it_*_expires values to reflect the remaining thread CPU timers.
 */
static void check_thread_timers(struct task_struct *tsk,
                        struct list_head *firing)
{
      int maxfire;
      struct list_head *timers = tsk->cpu_timers;

      maxfire = 20;
      tsk->it_prof_expires = cputime_zero;
      while (!list_empty(timers)) {
            struct cpu_timer_list *t = list_first_entry(timers,
                                          struct cpu_timer_list,
                                          entry);
            if (!--maxfire || cputime_lt(prof_ticks(tsk), t->expires.cpu)) {
                  tsk->it_prof_expires = t->expires.cpu;
                  break;
            }
            t->firing = 1;
            list_move_tail(&t->entry, firing);
      }

      ++timers;
      maxfire = 20;
      tsk->it_virt_expires = cputime_zero;
      while (!list_empty(timers)) {
            struct cpu_timer_list *t = list_first_entry(timers,
                                          struct cpu_timer_list,
                                          entry);
            if (!--maxfire || cputime_lt(virt_ticks(tsk), t->expires.cpu)) {
                  tsk->it_virt_expires = t->expires.cpu;
                  break;
            }
            t->firing = 1;
            list_move_tail(&t->entry, firing);
      }

      ++timers;
      maxfire = 20;
      tsk->it_sched_expires = 0;
      while (!list_empty(timers)) {
            struct cpu_timer_list *t = list_first_entry(timers,
                                          struct cpu_timer_list,
                                          entry);
            if (!--maxfire || tsk->se.sum_exec_runtime < t->expires.sched) {
                  tsk->it_sched_expires = t->expires.sched;
                  break;
            }
            t->firing = 1;
            list_move_tail(&t->entry, firing);
      }
}

/*
 * Check for any per-thread CPU timers that have fired and move them
 * off the tsk->*_timers list onto the firing list.  Per-thread timers
 * have already been taken off.
 */
static void check_process_timers(struct task_struct *tsk,
                         struct list_head *firing)
{
      int maxfire;
      struct signal_struct *const sig = tsk->signal;
      cputime_t utime, stime, ptime, virt_expires, prof_expires;
      unsigned long long sum_sched_runtime, sched_expires;
      struct task_struct *t;
      struct list_head *timers = sig->cpu_timers;

      /*
       * Don't sample the current process CPU clocks if there are no timers.
       */
      if (list_empty(&timers[CPUCLOCK_PROF]) &&
          cputime_eq(sig->it_prof_expires, cputime_zero) &&
          sig->rlim[RLIMIT_CPU].rlim_cur == RLIM_INFINITY &&
          list_empty(&timers[CPUCLOCK_VIRT]) &&
          cputime_eq(sig->it_virt_expires, cputime_zero) &&
          list_empty(&timers[CPUCLOCK_SCHED]))
            return;

      /*
       * Collect the current process totals.
       */
      utime = sig->utime;
      stime = sig->stime;
      sum_sched_runtime = sig->sum_sched_runtime;
      t = tsk;
      do {
            utime = cputime_add(utime, t->utime);
            stime = cputime_add(stime, t->stime);
            sum_sched_runtime += t->se.sum_exec_runtime;
            t = next_thread(t);
      } while (t != tsk);
      ptime = cputime_add(utime, stime);

      maxfire = 20;
      prof_expires = cputime_zero;
      while (!list_empty(timers)) {
            struct cpu_timer_list *t = list_first_entry(timers,
                                          struct cpu_timer_list,
                                          entry);
            if (!--maxfire || cputime_lt(ptime, t->expires.cpu)) {
                  prof_expires = t->expires.cpu;
                  break;
            }
            t->firing = 1;
            list_move_tail(&t->entry, firing);
      }

      ++timers;
      maxfire = 20;
      virt_expires = cputime_zero;
      while (!list_empty(timers)) {
            struct cpu_timer_list *t = list_first_entry(timers,
                                          struct cpu_timer_list,
                                          entry);
            if (!--maxfire || cputime_lt(utime, t->expires.cpu)) {
                  virt_expires = t->expires.cpu;
                  break;
            }
            t->firing = 1;
            list_move_tail(&t->entry, firing);
      }

      ++timers;
      maxfire = 20;
      sched_expires = 0;
      while (!list_empty(timers)) {
            struct cpu_timer_list *t = list_first_entry(timers,
                                          struct cpu_timer_list,
                                          entry);
            if (!--maxfire || sum_sched_runtime < t->expires.sched) {
                  sched_expires = t->expires.sched;
                  break;
            }
            t->firing = 1;
            list_move_tail(&t->entry, firing);
      }

      /*
       * Check for the special case process timers.
       */
      if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
            if (cputime_ge(ptime, sig->it_prof_expires)) {
                  /* ITIMER_PROF fires and reloads.  */
                  sig->it_prof_expires = sig->it_prof_incr;
                  if (!cputime_eq(sig->it_prof_expires, cputime_zero)) {
                        sig->it_prof_expires = cputime_add(
                              sig->it_prof_expires, ptime);
                  }
                  __group_send_sig_info(SIGPROF, SEND_SIG_PRIV, tsk);
            }
            if (!cputime_eq(sig->it_prof_expires, cputime_zero) &&
                (cputime_eq(prof_expires, cputime_zero) ||
                 cputime_lt(sig->it_prof_expires, prof_expires))) {
                  prof_expires = sig->it_prof_expires;
            }
      }
      if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
            if (cputime_ge(utime, sig->it_virt_expires)) {
                  /* ITIMER_VIRTUAL fires and reloads.  */
                  sig->it_virt_expires = sig->it_virt_incr;
                  if (!cputime_eq(sig->it_virt_expires, cputime_zero)) {
                        sig->it_virt_expires = cputime_add(
                              sig->it_virt_expires, utime);
                  }
                  __group_send_sig_info(SIGVTALRM, SEND_SIG_PRIV, tsk);
            }
            if (!cputime_eq(sig->it_virt_expires, cputime_zero) &&
                (cputime_eq(virt_expires, cputime_zero) ||
                 cputime_lt(sig->it_virt_expires, virt_expires))) {
                  virt_expires = sig->it_virt_expires;
            }
      }
      if (sig->rlim[RLIMIT_CPU].rlim_cur != RLIM_INFINITY) {
            unsigned long psecs = cputime_to_secs(ptime);
            cputime_t x;
            if (psecs >= sig->rlim[RLIMIT_CPU].rlim_max) {
                  /*
                   * At the hard limit, we just die.
                   * No need to calculate anything else now.
                   */
                  __group_send_sig_info(SIGKILL, SEND_SIG_PRIV, tsk);
                  return;
            }
            if (psecs >= sig->rlim[RLIMIT_CPU].rlim_cur) {
                  /*
                   * At the soft limit, send a SIGXCPU every second.
                   */
                  __group_send_sig_info(SIGXCPU, SEND_SIG_PRIV, tsk);
                  if (sig->rlim[RLIMIT_CPU].rlim_cur
                      < sig->rlim[RLIMIT_CPU].rlim_max) {
                        sig->rlim[RLIMIT_CPU].rlim_cur++;
                  }
            }
            x = secs_to_cputime(sig->rlim[RLIMIT_CPU].rlim_cur);
            if (cputime_eq(prof_expires, cputime_zero) ||
                cputime_lt(x, prof_expires)) {
                  prof_expires = x;
            }
      }

      if (!cputime_eq(prof_expires, cputime_zero) ||
          !cputime_eq(virt_expires, cputime_zero) ||
          sched_expires != 0) {
            /*
             * Rebalance the threads' expiry times for the remaining
             * process CPU timers.
             */

            cputime_t prof_left, virt_left, ticks;
            unsigned long long sched_left, sched;
            const unsigned int nthreads = atomic_read(&sig->live);

            if (!nthreads)
                  return;

            prof_left = cputime_sub(prof_expires, utime);
            prof_left = cputime_sub(prof_left, stime);
            prof_left = cputime_div_non_zero(prof_left, nthreads);
            virt_left = cputime_sub(virt_expires, utime);
            virt_left = cputime_div_non_zero(virt_left, nthreads);
            if (sched_expires) {
                  sched_left = sched_expires - sum_sched_runtime;
                  do_div(sched_left, nthreads);
                  sched_left = max_t(unsigned long long, sched_left, 1);
            } else {
                  sched_left = 0;
            }
            t = tsk;
            do {
                  if (unlikely(t->flags & PF_EXITING))
                        continue;

                  ticks = cputime_add(cputime_add(t->utime, t->stime),
                                  prof_left);
                  if (!cputime_eq(prof_expires, cputime_zero) &&
                      (cputime_eq(t->it_prof_expires, cputime_zero) ||
                       cputime_gt(t->it_prof_expires, ticks))) {
                        t->it_prof_expires = ticks;
                  }

                  ticks = cputime_add(t->utime, virt_left);
                  if (!cputime_eq(virt_expires, cputime_zero) &&
                      (cputime_eq(t->it_virt_expires, cputime_zero) ||
                       cputime_gt(t->it_virt_expires, ticks))) {
                        t->it_virt_expires = ticks;
                  }

                  sched = t->se.sum_exec_runtime + sched_left;
                  if (sched_expires && (t->it_sched_expires == 0 ||
                                    t->it_sched_expires > sched)) {
                        t->it_sched_expires = sched;
                  }
            } while ((t = next_thread(t)) != tsk);
      }
}

/*
 * This is called from the signal code (via do_schedule_next_timer)
 * when the last timer signal was delivered and we have to reload the timer.
 */
void posix_cpu_timer_schedule(struct k_itimer *timer)
{
      struct task_struct *p = timer->it.cpu.task;
      union cpu_time_count now;

      if (unlikely(p == NULL))
            /*
             * The task was cleaned up already, no future firings.
             */
            goto out;

      /*
       * Fetch the current sample and update the timer's expiry time.
       */
      if (CPUCLOCK_PERTHREAD(timer->it_clock)) {
            cpu_clock_sample(timer->it_clock, p, &now);
            bump_cpu_timer(timer, now);
            if (unlikely(p->exit_state)) {
                  clear_dead_task(timer, now);
                  goto out;
            }
            read_lock(&tasklist_lock); /* arm_timer needs it.  */
      } else {
            read_lock(&tasklist_lock);
            if (unlikely(p->signal == NULL)) {
                  /*
                   * The process has been reaped.
                   * We can't even collect a sample any more.
                   */
                  put_task_struct(p);
                  timer->it.cpu.task = p = NULL;
                  timer->it.cpu.expires.sched = 0;
                  goto out_unlock;
            } else if (unlikely(p->exit_state) && thread_group_empty(p)) {
                  /*
                   * We've noticed that the thread is dead, but
                   * not yet reaped.  Take this opportunity to
                   * drop our task ref.
                   */
                  clear_dead_task(timer, now);
                  goto out_unlock;
            }
            cpu_clock_sample_group(timer->it_clock, p, &now);
            bump_cpu_timer(timer, now);
            /* Leave the tasklist_lock locked for the call below.  */
      }

      /*
       * Now re-arm for the new expiry time.
       */
      arm_timer(timer, now);

out_unlock:
      read_unlock(&tasklist_lock);

out:
      timer->it_overrun_last = timer->it_overrun;
      timer->it_overrun = -1;
      ++timer->it_requeue_pending;
}

/*
 * This is called from the timer interrupt handler.  The irq handler has
 * already updated our counts.  We need to check if any timers fire now.
 * Interrupts are disabled.
 */
void run_posix_cpu_timers(struct task_struct *tsk)
{
      LIST_HEAD(firing);
      struct k_itimer *timer, *next;

      BUG_ON(!irqs_disabled());

#define UNEXPIRED(clock) \
            (cputime_eq(tsk->it_##clock##_expires, cputime_zero) || \
             cputime_lt(clock##_ticks(tsk), tsk->it_##clock##_expires))

      if (UNEXPIRED(prof) && UNEXPIRED(virt) &&
          (tsk->it_sched_expires == 0 ||
           tsk->se.sum_exec_runtime < tsk->it_sched_expires))
            return;

#undef      UNEXPIRED

      /*
       * Double-check with locks held.
       */
      read_lock(&tasklist_lock);
      if (likely(tsk->signal != NULL)) {
            spin_lock(&tsk->sighand->siglock);

            /*
             * Here we take off tsk->cpu_timers[N] and tsk->signal->cpu_timers[N]
             * all the timers that are firing, and put them on the firing list.
             */
            check_thread_timers(tsk, &firing);
            check_process_timers(tsk, &firing);

            /*
             * We must release these locks before taking any timer's lock.
             * There is a potential race with timer deletion here, as the
             * siglock now protects our private firing list.  We have set
             * the firing flag in each timer, so that a deletion attempt
             * that gets the timer lock before we do will give it up and
             * spin until we've taken care of that timer below.
             */
            spin_unlock(&tsk->sighand->siglock);
      }
      read_unlock(&tasklist_lock);

      /*
       * Now that all the timers on our list have the firing flag,
       * noone will touch their list entries but us.  We'll take
       * each timer's lock before clearing its firing flag, so no
       * timer call will interfere.
       */
      list_for_each_entry_safe(timer, next, &firing, it.cpu.entry) {
            int firing;
            spin_lock(&timer->it_lock);
            list_del_init(&timer->it.cpu.entry);
            firing = timer->it.cpu.firing;
            timer->it.cpu.firing = 0;
            /*
             * The firing flag is -1 if we collided with a reset
             * of the timer, which already reported this
             * almost-firing as an overrun.  So don't generate an event.
             */
            if (likely(firing >= 0)) {
                  cpu_timer_fire(timer);
            }
            spin_unlock(&timer->it_lock);
      }
}

/*
 * Set one of the process-wide special case CPU timers.
 * The tasklist_lock and tsk->sighand->siglock must be held by the caller.
 * The oldval argument is null for the RLIMIT_CPU timer, where *newval is
 * absolute; non-null for ITIMER_*, where *newval is relative and we update
 * it to be absolute, *oldval is absolute and we update it to be relative.
 */
void set_process_cpu_timer(struct task_struct *tsk, unsigned int clock_idx,
                     cputime_t *newval, cputime_t *oldval)
{
      union cpu_time_count now;
      struct list_head *head;

      BUG_ON(clock_idx == CPUCLOCK_SCHED);
      cpu_clock_sample_group_locked(clock_idx, tsk, &now);

      if (oldval) {
            if (!cputime_eq(*oldval, cputime_zero)) {
                  if (cputime_le(*oldval, now.cpu)) {
                        /* Just about to fire. */
                        *oldval = jiffies_to_cputime(1);
                  } else {
                        *oldval = cputime_sub(*oldval, now.cpu);
                  }
            }

            if (cputime_eq(*newval, cputime_zero))
                  return;
            *newval = cputime_add(*newval, now.cpu);

            /*
             * If the RLIMIT_CPU timer will expire before the
             * ITIMER_PROF timer, we have nothing else to do.
             */
            if (tsk->signal->rlim[RLIMIT_CPU].rlim_cur
                < cputime_to_secs(*newval))
                  return;
      }

      /*
       * Check whether there are any process timers already set to fire
       * before this one.  If so, we don't have anything more to do.
       */
      head = &tsk->signal->cpu_timers[clock_idx];
      if (list_empty(head) ||
          cputime_ge(list_first_entry(head,
                          struct cpu_timer_list, entry)->expires.cpu,
                   *newval)) {
            /*
             * Rejigger each thread's expiry time so that one will
             * notice before we hit the process-cumulative expiry time.
             */
            union cpu_time_count expires = { .sched = 0 };
            expires.cpu = *newval;
            process_timer_rebalance(tsk, clock_idx, expires, now);
      }
}

static int do_cpu_nanosleep(const clockid_t which_clock, int flags,
                      struct timespec *rqtp, struct itimerspec *it)
{
      struct k_itimer timer;
      int error;

      /*
       * Set up a temporary timer and then wait for it to go off.
       */
      memset(&timer, 0, sizeof timer);
      spin_lock_init(&timer.it_lock);
      timer.it_clock = which_clock;
      timer.it_overrun = -1;
      error = posix_cpu_timer_create(&timer);
      timer.it_process = current;
      if (!error) {
            static struct itimerspec zero_it;

            memset(it, 0, sizeof *it);
            it->it_value = *rqtp;

            spin_lock_irq(&timer.it_lock);
            error = posix_cpu_timer_set(&timer, flags, it, NULL);
            if (error) {
                  spin_unlock_irq(&timer.it_lock);
                  return error;
            }

            while (!signal_pending(current)) {
                  if (timer.it.cpu.expires.sched == 0) {
                        /*
                         * Our timer fired and was reset.
                         */
                        spin_unlock_irq(&timer.it_lock);
                        return 0;
                  }

                  /*
                   * Block until cpu_timer_fire (or a signal) wakes us.
                   */
                  __set_current_state(TASK_INTERRUPTIBLE);
                  spin_unlock_irq(&timer.it_lock);
                  schedule();
                  spin_lock_irq(&timer.it_lock);
            }

            /*
             * We were interrupted by a signal.
             */
            sample_to_timespec(which_clock, timer.it.cpu.expires, rqtp);
            posix_cpu_timer_set(&timer, 0, &zero_it, it);
            spin_unlock_irq(&timer.it_lock);

            if ((it->it_value.tv_sec | it->it_value.tv_nsec) == 0) {
                  /*
                   * It actually did fire already.
                   */
                  return 0;
            }

            error = -ERESTART_RESTARTBLOCK;
      }

      return error;
}

int posix_cpu_nsleep(const clockid_t which_clock, int flags,
                 struct timespec *rqtp, struct timespec __user *rmtp)
{
      struct restart_block *restart_block =
          &current_thread_info()->restart_block;
      struct itimerspec it;
      int error;

      /*
       * Diagnose required errors first.
       */
      if (CPUCLOCK_PERTHREAD(which_clock) &&
          (CPUCLOCK_PID(which_clock) == 0 ||
           CPUCLOCK_PID(which_clock) == current->pid))
            return -EINVAL;

      error = do_cpu_nanosleep(which_clock, flags, rqtp, &it);

      if (error == -ERESTART_RESTARTBLOCK) {

                  if (flags & TIMER_ABSTIME)
                  return -ERESTARTNOHAND;
            /*
             * Report back to the user the time still remaining.
             */
            if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
                  return -EFAULT;

            restart_block->fn = posix_cpu_nsleep_restart;
            restart_block->arg0 = which_clock;
            restart_block->arg1 = (unsigned long) rmtp;
            restart_block->arg2 = rqtp->tv_sec;
            restart_block->arg3 = rqtp->tv_nsec;
      }
      return error;
}

long posix_cpu_nsleep_restart(struct restart_block *restart_block)
{
      clockid_t which_clock = restart_block->arg0;
      struct timespec __user *rmtp;
      struct timespec t;
      struct itimerspec it;
      int error;

      rmtp = (struct timespec __user *) restart_block->arg1;
      t.tv_sec = restart_block->arg2;
      t.tv_nsec = restart_block->arg3;

      restart_block->fn = do_no_restart_syscall;
      error = do_cpu_nanosleep(which_clock, TIMER_ABSTIME, &t, &it);

      if (error == -ERESTART_RESTARTBLOCK) {
            /*
             * Report back to the user the time still remaining.
             */
            if (rmtp != NULL && copy_to_user(rmtp, &it.it_value, sizeof *rmtp))
                  return -EFAULT;

            restart_block->fn = posix_cpu_nsleep_restart;
            restart_block->arg0 = which_clock;
            restart_block->arg1 = (unsigned long) rmtp;
            restart_block->arg2 = t.tv_sec;
            restart_block->arg3 = t.tv_nsec;
      }
      return error;

}


#define PROCESS_CLOCK   MAKE_PROCESS_CPUCLOCK(0, CPUCLOCK_SCHED)
#define THREAD_CLOCK    MAKE_THREAD_CPUCLOCK(0, CPUCLOCK_SCHED)

static int process_cpu_clock_getres(const clockid_t which_clock,
                            struct timespec *tp)
{
      return posix_cpu_clock_getres(PROCESS_CLOCK, tp);
}
static int process_cpu_clock_get(const clockid_t which_clock,
                         struct timespec *tp)
{
      return posix_cpu_clock_get(PROCESS_CLOCK, tp);
}
static int process_cpu_timer_create(struct k_itimer *timer)
{
      timer->it_clock = PROCESS_CLOCK;
      return posix_cpu_timer_create(timer);
}
static int process_cpu_nsleep(const clockid_t which_clock, int flags,
                        struct timespec *rqtp,
                        struct timespec __user *rmtp)
{
      return posix_cpu_nsleep(PROCESS_CLOCK, flags, rqtp, rmtp);
}
static long process_cpu_nsleep_restart(struct restart_block *restart_block)
{
      return -EINVAL;
}
static int thread_cpu_clock_getres(const clockid_t which_clock,
                           struct timespec *tp)
{
      return posix_cpu_clock_getres(THREAD_CLOCK, tp);
}
static int thread_cpu_clock_get(const clockid_t which_clock,
                        struct timespec *tp)
{
      return posix_cpu_clock_get(THREAD_CLOCK, tp);
}
static int thread_cpu_timer_create(struct k_itimer *timer)
{
      timer->it_clock = THREAD_CLOCK;
      return posix_cpu_timer_create(timer);
}
static int thread_cpu_nsleep(const clockid_t which_clock, int flags,
                        struct timespec *rqtp, struct timespec __user *rmtp)
{
      return -EINVAL;
}
static long thread_cpu_nsleep_restart(struct restart_block *restart_block)
{
      return -EINVAL;
}

static __init int init_posix_cpu_timers(void)
{
      struct k_clock process = {
            .clock_getres = process_cpu_clock_getres,
            .clock_get = process_cpu_clock_get,
            .clock_set = do_posix_clock_nosettime,
            .timer_create = process_cpu_timer_create,
            .nsleep = process_cpu_nsleep,
            .nsleep_restart = process_cpu_nsleep_restart,
      };
      struct k_clock thread = {
            .clock_getres = thread_cpu_clock_getres,
            .clock_get = thread_cpu_clock_get,
            .clock_set = do_posix_clock_nosettime,
            .timer_create = thread_cpu_timer_create,
            .nsleep = thread_cpu_nsleep,
            .nsleep_restart = thread_cpu_nsleep_restart,
      };

      register_posix_clock(CLOCK_PROCESS_CPUTIME_ID, &process);
      register_posix_clock(CLOCK_THREAD_CPUTIME_ID, &thread);

      return 0;
}
__initcall(init_posix_cpu_timers);

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