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posix-timers.c

/*
 * linux/kernel/posix-timers.c
 *
 *
 * 2002-10-15  Posix Clocks & timers
 *                           by George Anzinger george@mvista.com
 *
 *                     Copyright (C) 2002 2003 by MontaVista Software.
 *
 * 2004-06-01  Fix CLOCK_REALTIME clock/timer TIMER_ABSTIME bug.
 *                     Copyright (C) 2004 Boris Hu
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or (at
 * your option) any later version.
 *
 * This program is distributed in the hope that it will be useful, but
 * WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
 * General Public License for more details.

 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 675 Mass Ave, Cambridge, MA 02139, USA.
 *
 * MontaVista Software | 1237 East Arques Avenue | Sunnyvale | CA 94085 | USA
 */

/* These are all the functions necessary to implement
 * POSIX clocks & timers
 */
#include <linux/mm.h>
#include <linux/interrupt.h>
#include <linux/slab.h>
#include <linux/time.h>
#include <linux/mutex.h>

#include <asm/uaccess.h>
#include <asm/semaphore.h>
#include <linux/list.h>
#include <linux/init.h>
#include <linux/compiler.h>
#include <linux/idr.h>
#include <linux/posix-timers.h>
#include <linux/syscalls.h>
#include <linux/wait.h>
#include <linux/workqueue.h>
#include <linux/module.h>

/*
 * Management arrays for POSIX timers.     Timers are kept in slab memory
 * Timer ids are allocated by an external routine that keeps track of the
 * id and the timer.  The external interface is:
 *
 * void *idr_find(struct idr *idp, int id);           to find timer_id <id>
 * int idr_get_new(struct idr *idp, void *ptr);       to get a new id and
 *                                                    related it to <ptr>
 * void idr_remove(struct idr *idp, int id);          to release <id>
 * void idr_init(struct idr *idp);                    to initialize <idp>
 *                                                    which we supply.
 * The idr_get_new *may* call slab for more memory so it must not be
 * called under a spin lock.  Likewise idr_remore may release memory
 * (but it may be ok to do this under a lock...).
 * idr_find is just a memory look up and is quite fast.  A -1 return
 * indicates that the requested id does not exist.
 */

/*
 * Lets keep our timers in a slab cache :-)
 */
static struct kmem_cache *posix_timers_cache;
static struct idr posix_timers_id;
static DEFINE_SPINLOCK(idr_lock);

/*
 * we assume that the new SIGEV_THREAD_ID shares no bits with the other
 * SIGEV values.  Here we put out an error if this assumption fails.
 */
#if SIGEV_THREAD_ID != (SIGEV_THREAD_ID & \
                       ~(SIGEV_SIGNAL | SIGEV_NONE | SIGEV_THREAD))
#error "SIGEV_THREAD_ID must not share bit with other SIGEV values!"
#endif


/*
 * The timer ID is turned into a timer address by idr_find().
 * Verifying a valid ID consists of:
 *
 * a) checking that idr_find() returns other than -1.
 * b) checking that the timer id matches the one in the timer itself.
 * c) that the timer owner is in the callers thread group.
 */

/*
 * CLOCKs: The POSIX standard calls for a couple of clocks and allows us
 *        to implement others.  This structure defines the various
 *        clocks and allows the possibility of adding others.      We
 *        provide an interface to add clocks to the table and expect
 *        the "arch" code to add at least one clock that is high
 *        resolution.    Here we define the standard CLOCK_REALTIME as a
 *        1/HZ resolution clock.
 *
 * RESOLUTION: Clock resolution is used to round up timer and interval
 *        times, NOT to report clock times, which are reported with as
 *        much resolution as the system can muster.  In some cases this
 *        resolution may depend on the underlying clock hardware and
 *        may not be quantifiable until run time, and only then is the
 *        necessary code is written.      The standard says we should say
 *        something about this issue in the documentation...
 *
 * FUNCTIONS: The CLOCKs structure defines possible functions to handle
 *        various clock functions.  For clocks that use the standard
 *        system timer code these entries should be NULL.  This will
 *        allow dispatch without the overhead of indirect function
 *        calls.  CLOCKS that depend on other sources (e.g. WWV or GPS)
 *        must supply functions here, even if the function just returns
 *        ENOSYS.  The standard POSIX timer management code assumes the
 *        following: 1.) The k_itimer struct (sched.h) is used for the
 *        timer.  2.) The list, it_lock, it_clock, it_id and it_process
 *        fields are not modified by timer code.
 *
 *          At this time all functions EXCEPT clock_nanosleep can be
 *          redirected by the CLOCKS structure.  Clock_nanosleep is in
 *          there, but the code ignores it.
 *
 * Permissions: It is assumed that the clock_settime() function defined
 *        for each clock will take care of permission checks.      Some
 *        clocks may be set able by any user (i.e. local process
 *        clocks) others not.  Currently the only set able clock we
 *        have is CLOCK_REALTIME and its high res counter part, both of
 *        which we beg off on and pass to do_sys_settimeofday().
 */

static struct k_clock posix_clocks[MAX_CLOCKS];

/*
 * These ones are defined below.
 */
static int common_nsleep(const clockid_t, int flags, struct timespec *t,
                   struct timespec __user *rmtp);
static void common_timer_get(struct k_itimer *, struct itimerspec *);
static int common_timer_set(struct k_itimer *, int,
                      struct itimerspec *, struct itimerspec *);
static int common_timer_del(struct k_itimer *timer);

static enum hrtimer_restart posix_timer_fn(struct hrtimer *data);

static struct k_itimer *lock_timer(timer_t timer_id, unsigned long *flags);

static inline void unlock_timer(struct k_itimer *timr, unsigned long flags)
{
      spin_unlock_irqrestore(&timr->it_lock, flags);
}

/*
 * Call the k_clock hook function if non-null, or the default function.
 */
#define CLOCK_DISPATCH(clock, call, arglist) \
      ((clock) < 0 ? posix_cpu_##call arglist : \
       (posix_clocks[clock].call != NULL \
        ? (*posix_clocks[clock].call) arglist : common_##call arglist))

/*
 * Default clock hook functions when the struct k_clock passed
 * to register_posix_clock leaves a function pointer null.
 *
 * The function common_CALL is the default implementation for
 * the function pointer CALL in struct k_clock.
 */

static inline int common_clock_getres(const clockid_t which_clock,
                              struct timespec *tp)
{
      tp->tv_sec = 0;
      tp->tv_nsec = posix_clocks[which_clock].res;
      return 0;
}

/*
 * Get real time for posix timers
 */
static int common_clock_get(clockid_t which_clock, struct timespec *tp)
{
      ktime_get_real_ts(tp);
      return 0;
}

static inline int common_clock_set(const clockid_t which_clock,
                           struct timespec *tp)
{
      return do_sys_settimeofday(tp, NULL);
}

static int common_timer_create(struct k_itimer *new_timer)
{
      hrtimer_init(&new_timer->it.real.timer, new_timer->it_clock, 0);
      return 0;
}

/*
 * Return nonzero if we know a priori this clockid_t value is bogus.
 */
static inline int invalid_clockid(const clockid_t which_clock)
{
      if (which_clock < 0)    /* CPU clock, posix_cpu_* will check it */
            return 0;
      if ((unsigned) which_clock >= MAX_CLOCKS)
            return 1;
      if (posix_clocks[which_clock].clock_getres != NULL)
            return 0;
      if (posix_clocks[which_clock].res != 0)
            return 0;
      return 1;
}

/*
 * Get monotonic time for posix timers
 */
static int posix_ktime_get_ts(clockid_t which_clock, struct timespec *tp)
{
      ktime_get_ts(tp);
      return 0;
}

/*
 * Initialize everything, well, just everything in Posix clocks/timers ;)
 */
static __init int init_posix_timers(void)
{
      struct k_clock clock_realtime = {
            .clock_getres = hrtimer_get_res,
      };
      struct k_clock clock_monotonic = {
            .clock_getres = hrtimer_get_res,
            .clock_get = posix_ktime_get_ts,
            .clock_set = do_posix_clock_nosettime,
      };

      register_posix_clock(CLOCK_REALTIME, &clock_realtime);
      register_posix_clock(CLOCK_MONOTONIC, &clock_monotonic);

      posix_timers_cache = kmem_cache_create("posix_timers_cache",
                              sizeof (struct k_itimer), 0, SLAB_PANIC,
                              NULL);
      idr_init(&posix_timers_id);
      return 0;
}

__initcall(init_posix_timers);

static void schedule_next_timer(struct k_itimer *timr)
{
      struct hrtimer *timer = &timr->it.real.timer;

      if (timr->it.real.interval.tv64 == 0)
            return;

      timr->it_overrun += hrtimer_forward(timer, timer->base->get_time(),
                                  timr->it.real.interval);

      timr->it_overrun_last = timr->it_overrun;
      timr->it_overrun = -1;
      ++timr->it_requeue_pending;
      hrtimer_restart(timer);
}

/*
 * This function is exported for use by the signal deliver code.  It is
 * called just prior to the info block being released and passes that
 * block to us.  It's function is to update the overrun entry AND to
 * restart the timer.  It should only be called if the timer is to be
 * restarted (i.e. we have flagged this in the sys_private entry of the
 * info block).
 *
 * To protect aginst the timer going away while the interrupt is queued,
 * we require that the it_requeue_pending flag be set.
 */
void do_schedule_next_timer(struct siginfo *info)
{
      struct k_itimer *timr;
      unsigned long flags;

      timr = lock_timer(info->si_tid, &flags);

      if (timr && timr->it_requeue_pending == info->si_sys_private) {
            if (timr->it_clock < 0)
                  posix_cpu_timer_schedule(timr);
            else
                  schedule_next_timer(timr);

            info->si_overrun = timr->it_overrun_last;
      }

      if (timr)
            unlock_timer(timr, flags);
}

int posix_timer_event(struct k_itimer *timr,int si_private)
{
      memset(&timr->sigq->info, 0, sizeof(siginfo_t));
      timr->sigq->info.si_sys_private = si_private;
      /* Send signal to the process that owns this timer.*/

      timr->sigq->info.si_signo = timr->it_sigev_signo;
      timr->sigq->info.si_errno = 0;
      timr->sigq->info.si_code = SI_TIMER;
      timr->sigq->info.si_tid = timr->it_id;
      timr->sigq->info.si_value = timr->it_sigev_value;

      if (timr->it_sigev_notify & SIGEV_THREAD_ID) {
            struct task_struct *leader;
            int ret = send_sigqueue(timr->it_sigev_signo, timr->sigq,
                              timr->it_process);

            if (likely(ret >= 0))
                  return ret;

            timr->it_sigev_notify = SIGEV_SIGNAL;
            leader = timr->it_process->group_leader;
            put_task_struct(timr->it_process);
            timr->it_process = leader;
      }

      return send_group_sigqueue(timr->it_sigev_signo, timr->sigq,
                           timr->it_process);
}
EXPORT_SYMBOL_GPL(posix_timer_event);

/*
 * This function gets called when a POSIX.1b interval timer expires.  It
 * is used as a callback from the kernel internal timer.  The
 * run_timer_list code ALWAYS calls with interrupts on.

 * This code is for CLOCK_REALTIME* and CLOCK_MONOTONIC* timers.
 */
static enum hrtimer_restart posix_timer_fn(struct hrtimer *timer)
{
      struct k_itimer *timr;
      unsigned long flags;
      int si_private = 0;
      enum hrtimer_restart ret = HRTIMER_NORESTART;

      timr = container_of(timer, struct k_itimer, it.real.timer);
      spin_lock_irqsave(&timr->it_lock, flags);

      if (timr->it.real.interval.tv64 != 0)
            si_private = ++timr->it_requeue_pending;

      if (posix_timer_event(timr, si_private)) {
            /*
             * signal was not sent because of sig_ignor
             * we will not get a call back to restart it AND
             * it should be restarted.
             */
            if (timr->it.real.interval.tv64 != 0) {
                  ktime_t now = hrtimer_cb_get_time(timer);

                  /*
                   * FIXME: What we really want, is to stop this
                   * timer completely and restart it in case the
                   * SIG_IGN is removed. This is a non trivial
                   * change which involves sighand locking
                   * (sigh !), which we don't want to do late in
                   * the release cycle.
                   *
                   * For now we just let timers with an interval
                   * less than a jiffie expire every jiffie to
                   * avoid softirq starvation in case of SIG_IGN
                   * and a very small interval, which would put
                   * the timer right back on the softirq pending
                   * list. By moving now ahead of time we trick
                   * hrtimer_forward() to expire the timer
                   * later, while we still maintain the overrun
                   * accuracy, but have some inconsistency in
                   * the timer_gettime() case. This is at least
                   * better than a starved softirq. A more
                   * complex fix which solves also another related
                   * inconsistency is already in the pipeline.
                   */
#ifdef CONFIG_HIGH_RES_TIMERS
                  {
                        ktime_t kj = ktime_set(0, NSEC_PER_SEC / HZ);

                        if (timr->it.real.interval.tv64 < kj.tv64)
                              now = ktime_add(now, kj);
                  }
#endif
                  timr->it_overrun +=
                        hrtimer_forward(timer, now,
                                    timr->it.real.interval);
                  ret = HRTIMER_RESTART;
                  ++timr->it_requeue_pending;
            }
      }

      unlock_timer(timr, flags);
      return ret;
}

static struct task_struct * good_sigevent(sigevent_t * event)
{
      struct task_struct *rtn = current->group_leader;

      if ((event->sigev_notify & SIGEV_THREAD_ID ) &&
            (!(rtn = find_task_by_pid(event->sigev_notify_thread_id)) ||
             !same_thread_group(rtn, current) ||
             (event->sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_SIGNAL))
            return NULL;

      if (((event->sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE) &&
          ((event->sigev_signo <= 0) || (event->sigev_signo > SIGRTMAX)))
            return NULL;

      return rtn;
}

void register_posix_clock(const clockid_t clock_id, struct k_clock *new_clock)
{
      if ((unsigned) clock_id >= MAX_CLOCKS) {
            printk("POSIX clock register failed for clock_id %d\n",
                   clock_id);
            return;
      }

      posix_clocks[clock_id] = *new_clock;
}
EXPORT_SYMBOL_GPL(register_posix_clock);

static struct k_itimer * alloc_posix_timer(void)
{
      struct k_itimer *tmr;
      tmr = kmem_cache_zalloc(posix_timers_cache, GFP_KERNEL);
      if (!tmr)
            return tmr;
      if (unlikely(!(tmr->sigq = sigqueue_alloc()))) {
            kmem_cache_free(posix_timers_cache, tmr);
            tmr = NULL;
      }
      return tmr;
}

#define IT_ID_SET 1
#define IT_ID_NOT_SET   0
static void release_posix_timer(struct k_itimer *tmr, int it_id_set)
{
      if (it_id_set) {
            unsigned long flags;
            spin_lock_irqsave(&idr_lock, flags);
            idr_remove(&posix_timers_id, tmr->it_id);
            spin_unlock_irqrestore(&idr_lock, flags);
      }
      sigqueue_free(tmr->sigq);
      if (unlikely(tmr->it_process) &&
          tmr->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
            put_task_struct(tmr->it_process);
      kmem_cache_free(posix_timers_cache, tmr);
}

/* Create a POSIX.1b interval timer. */

asmlinkage long
sys_timer_create(const clockid_t which_clock,
             struct sigevent __user *timer_event_spec,
             timer_t __user * created_timer_id)
{
      int error = 0;
      struct k_itimer *new_timer = NULL;
      int new_timer_id;
      struct task_struct *process = NULL;
      unsigned long flags;
      sigevent_t event;
      int it_id_set = IT_ID_NOT_SET;

      if (invalid_clockid(which_clock))
            return -EINVAL;

      new_timer = alloc_posix_timer();
      if (unlikely(!new_timer))
            return -EAGAIN;

      spin_lock_init(&new_timer->it_lock);
 retry:
      if (unlikely(!idr_pre_get(&posix_timers_id, GFP_KERNEL))) {
            error = -EAGAIN;
            goto out;
      }
      spin_lock_irq(&idr_lock);
      error = idr_get_new(&posix_timers_id, (void *) new_timer,
                      &new_timer_id);
      spin_unlock_irq(&idr_lock);
      if (error == -EAGAIN)
            goto retry;
      else if (error) {
            /*
             * Wierd looking, but we return EAGAIN if the IDR is
             * full (proper POSIX return value for this)
             */
            error = -EAGAIN;
            goto out;
      }

      it_id_set = IT_ID_SET;
      new_timer->it_id = (timer_t) new_timer_id;
      new_timer->it_clock = which_clock;
      new_timer->it_overrun = -1;
      error = CLOCK_DISPATCH(which_clock, timer_create, (new_timer));
      if (error)
            goto out;

      /*
       * return the timer_id now.  The next step is hard to
       * back out if there is an error.
       */
      if (copy_to_user(created_timer_id,
                   &new_timer_id, sizeof (new_timer_id))) {
            error = -EFAULT;
            goto out;
      }
      if (timer_event_spec) {
            if (copy_from_user(&event, timer_event_spec, sizeof (event))) {
                  error = -EFAULT;
                  goto out;
            }
            new_timer->it_sigev_notify = event.sigev_notify;
            new_timer->it_sigev_signo = event.sigev_signo;
            new_timer->it_sigev_value = event.sigev_value;

            read_lock(&tasklist_lock);
            if ((process = good_sigevent(&event))) {
                  /*
                   * We may be setting up this process for another
                   * thread.  It may be exiting.  To catch this
                   * case the we check the PF_EXITING flag.  If
                   * the flag is not set, the siglock will catch
                   * him before it is too late (in exit_itimers).
                   *
                   * The exec case is a bit more invloved but easy
                   * to code.  If the process is in our thread
                   * group (and it must be or we would not allow
                   * it here) and is doing an exec, it will cause
                   * us to be killed.  In this case it will wait
                   * for us to die which means we can finish this
                   * linkage with our last gasp. I.e. no code :)
                   */
                  spin_lock_irqsave(&process->sighand->siglock, flags);
                  if (!(process->flags & PF_EXITING)) {
                        new_timer->it_process = process;
                        list_add(&new_timer->list,
                               &process->signal->posix_timers);
                        if (new_timer->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
                              get_task_struct(process);
                        spin_unlock_irqrestore(&process->sighand->siglock, flags);
                  } else {
                        spin_unlock_irqrestore(&process->sighand->siglock, flags);
                        process = NULL;
                  }
            }
            read_unlock(&tasklist_lock);
            if (!process) {
                  error = -EINVAL;
                  goto out;
            }
      } else {
            new_timer->it_sigev_notify = SIGEV_SIGNAL;
            new_timer->it_sigev_signo = SIGALRM;
            new_timer->it_sigev_value.sival_int = new_timer->it_id;
            process = current->group_leader;
            spin_lock_irqsave(&process->sighand->siglock, flags);
            new_timer->it_process = process;
            list_add(&new_timer->list, &process->signal->posix_timers);
            spin_unlock_irqrestore(&process->sighand->siglock, flags);
      }

      /*
       * In the case of the timer belonging to another task, after
       * the task is unlocked, the timer is owned by the other task
       * and may cease to exist at any time.  Don't use or modify
       * new_timer after the unlock call.
       */

out:
      if (error)
            release_posix_timer(new_timer, it_id_set);

      return error;
}

/*
 * Locking issues: We need to protect the result of the id look up until
 * we get the timer locked down so it is not deleted under us.  The
 * removal is done under the idr spinlock so we use that here to bridge
 * the find to the timer lock.  To avoid a dead lock, the timer id MUST
 * be release with out holding the timer lock.
 */
static struct k_itimer * lock_timer(timer_t timer_id, unsigned long *flags)
{
      struct k_itimer *timr;
      /*
       * Watch out here.  We do a irqsave on the idr_lock and pass the
       * flags part over to the timer lock.  Must not let interrupts in
       * while we are moving the lock.
       */

      spin_lock_irqsave(&idr_lock, *flags);
      timr = (struct k_itimer *) idr_find(&posix_timers_id, (int) timer_id);
      if (timr) {
            spin_lock(&timr->it_lock);

            if ((timr->it_id != timer_id) || !(timr->it_process) ||
                        !same_thread_group(timr->it_process, current)) {
                  spin_unlock(&timr->it_lock);
                  spin_unlock_irqrestore(&idr_lock, *flags);
                  timr = NULL;
            } else
                  spin_unlock(&idr_lock);
      } else
            spin_unlock_irqrestore(&idr_lock, *flags);

      return timr;
}

/*
 * Get the time remaining on a POSIX.1b interval timer.  This function
 * is ALWAYS called with spin_lock_irq on the timer, thus it must not
 * mess with irq.
 *
 * We have a couple of messes to clean up here.  First there is the case
 * of a timer that has a requeue pending.  These timers should appear to
 * be in the timer list with an expiry as if we were to requeue them
 * now.
 *
 * The second issue is the SIGEV_NONE timer which may be active but is
 * not really ever put in the timer list (to save system resources).
 * This timer may be expired, and if so, we will do it here.  Otherwise
 * it is the same as a requeue pending timer WRT to what we should
 * report.
 */
static void
common_timer_get(struct k_itimer *timr, struct itimerspec *cur_setting)
{
      ktime_t now, remaining, iv;
      struct hrtimer *timer = &timr->it.real.timer;

      memset(cur_setting, 0, sizeof(struct itimerspec));

      iv = timr->it.real.interval;

      /* interval timer ? */
      if (iv.tv64)
            cur_setting->it_interval = ktime_to_timespec(iv);
      else if (!hrtimer_active(timer) &&
             (timr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE)
            return;

      now = timer->base->get_time();

      /*
       * When a requeue is pending or this is a SIGEV_NONE
       * timer move the expiry time forward by intervals, so
       * expiry is > now.
       */
      if (iv.tv64 && (timr->it_requeue_pending & REQUEUE_PENDING ||
          (timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE))
            timr->it_overrun += hrtimer_forward(timer, now, iv);

      remaining = ktime_sub(timer->expires, now);
      /* Return 0 only, when the timer is expired and not pending */
      if (remaining.tv64 <= 0) {
            /*
             * A single shot SIGEV_NONE timer must return 0, when
             * it is expired !
             */
            if ((timr->it_sigev_notify & ~SIGEV_THREAD_ID) != SIGEV_NONE)
                  cur_setting->it_value.tv_nsec = 1;
      } else
            cur_setting->it_value = ktime_to_timespec(remaining);
}

/* Get the time remaining on a POSIX.1b interval timer. */
asmlinkage long
sys_timer_gettime(timer_t timer_id, struct itimerspec __user *setting)
{
      struct k_itimer *timr;
      struct itimerspec cur_setting;
      unsigned long flags;

      timr = lock_timer(timer_id, &flags);
      if (!timr)
            return -EINVAL;

      CLOCK_DISPATCH(timr->it_clock, timer_get, (timr, &cur_setting));

      unlock_timer(timr, flags);

      if (copy_to_user(setting, &cur_setting, sizeof (cur_setting)))
            return -EFAULT;

      return 0;
}

/*
 * Get the number of overruns of a POSIX.1b interval timer.  This is to
 * be the overrun of the timer last delivered.  At the same time we are
 * accumulating overruns on the next timer.  The overrun is frozen when
 * the signal is delivered, either at the notify time (if the info block
 * is not queued) or at the actual delivery time (as we are informed by
 * the call back to do_schedule_next_timer().  So all we need to do is
 * to pick up the frozen overrun.
 */
asmlinkage long
sys_timer_getoverrun(timer_t timer_id)
{
      struct k_itimer *timr;
      int overrun;
      unsigned long flags;

      timr = lock_timer(timer_id, &flags);
      if (!timr)
            return -EINVAL;

      overrun = timr->it_overrun_last;
      unlock_timer(timr, flags);

      return overrun;
}

/* Set a POSIX.1b interval timer. */
/* timr->it_lock is taken. */
static int
common_timer_set(struct k_itimer *timr, int flags,
             struct itimerspec *new_setting, struct itimerspec *old_setting)
{
      struct hrtimer *timer = &timr->it.real.timer;
      enum hrtimer_mode mode;

      if (old_setting)
            common_timer_get(timr, old_setting);

      /* disable the timer */
      timr->it.real.interval.tv64 = 0;
      /*
       * careful here.  If smp we could be in the "fire" routine which will
       * be spinning as we hold the lock.  But this is ONLY an SMP issue.
       */
      if (hrtimer_try_to_cancel(timer) < 0)
            return TIMER_RETRY;

      timr->it_requeue_pending = (timr->it_requeue_pending + 2) & 
            ~REQUEUE_PENDING;
      timr->it_overrun_last = 0;

      /* switch off the timer when it_value is zero */
      if (!new_setting->it_value.tv_sec && !new_setting->it_value.tv_nsec)
            return 0;

      mode = flags & TIMER_ABSTIME ? HRTIMER_MODE_ABS : HRTIMER_MODE_REL;
      hrtimer_init(&timr->it.real.timer, timr->it_clock, mode);
      timr->it.real.timer.function = posix_timer_fn;

      timer->expires = timespec_to_ktime(new_setting->it_value);

      /* Convert interval */
      timr->it.real.interval = timespec_to_ktime(new_setting->it_interval);

      /* SIGEV_NONE timers are not queued ! See common_timer_get */
      if (((timr->it_sigev_notify & ~SIGEV_THREAD_ID) == SIGEV_NONE)) {
            /* Setup correct expiry time for relative timers */
            if (mode == HRTIMER_MODE_REL)
                  timer->expires = ktime_add(timer->expires,
                                       timer->base->get_time());
            return 0;
      }

      hrtimer_start(timer, timer->expires, mode);
      return 0;
}

/* Set a POSIX.1b interval timer */
asmlinkage long
sys_timer_settime(timer_t timer_id, int flags,
              const struct itimerspec __user *new_setting,
              struct itimerspec __user *old_setting)
{
      struct k_itimer *timr;
      struct itimerspec new_spec, old_spec;
      int error = 0;
      unsigned long flag;
      struct itimerspec *rtn = old_setting ? &old_spec : NULL;

      if (!new_setting)
            return -EINVAL;

      if (copy_from_user(&new_spec, new_setting, sizeof (new_spec)))
            return -EFAULT;

      if (!timespec_valid(&new_spec.it_interval) ||
          !timespec_valid(&new_spec.it_value))
            return -EINVAL;
retry:
      timr = lock_timer(timer_id, &flag);
      if (!timr)
            return -EINVAL;

      error = CLOCK_DISPATCH(timr->it_clock, timer_set,
                         (timr, flags, &new_spec, rtn));

      unlock_timer(timr, flag);
      if (error == TIMER_RETRY) {
            rtn = NULL; // We already got the old time...
            goto retry;
      }

      if (old_setting && !error &&
          copy_to_user(old_setting, &old_spec, sizeof (old_spec)))
            error = -EFAULT;

      return error;
}

static inline int common_timer_del(struct k_itimer *timer)
{
      timer->it.real.interval.tv64 = 0;

      if (hrtimer_try_to_cancel(&timer->it.real.timer) < 0)
            return TIMER_RETRY;
      return 0;
}

static inline int timer_delete_hook(struct k_itimer *timer)
{
      return CLOCK_DISPATCH(timer->it_clock, timer_del, (timer));
}

/* Delete a POSIX.1b interval timer. */
asmlinkage long
sys_timer_delete(timer_t timer_id)
{
      struct k_itimer *timer;
      unsigned long flags;

retry_delete:
      timer = lock_timer(timer_id, &flags);
      if (!timer)
            return -EINVAL;

      if (timer_delete_hook(timer) == TIMER_RETRY) {
            unlock_timer(timer, flags);
            goto retry_delete;
      }

      spin_lock(&current->sighand->siglock);
      list_del(&timer->list);
      spin_unlock(&current->sighand->siglock);
      /*
       * This keeps any tasks waiting on the spin lock from thinking
       * they got something (see the lock code above).
       */
      if (timer->it_process) {
            if (timer->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
                  put_task_struct(timer->it_process);
            timer->it_process = NULL;
      }
      unlock_timer(timer, flags);
      release_posix_timer(timer, IT_ID_SET);
      return 0;
}

/*
 * return timer owned by the process, used by exit_itimers
 */
static void itimer_delete(struct k_itimer *timer)
{
      unsigned long flags;

retry_delete:
      spin_lock_irqsave(&timer->it_lock, flags);

      if (timer_delete_hook(timer) == TIMER_RETRY) {
            unlock_timer(timer, flags);
            goto retry_delete;
      }
      list_del(&timer->list);
      /*
       * This keeps any tasks waiting on the spin lock from thinking
       * they got something (see the lock code above).
       */
      if (timer->it_process) {
            if (timer->it_sigev_notify == (SIGEV_SIGNAL|SIGEV_THREAD_ID))
                  put_task_struct(timer->it_process);
            timer->it_process = NULL;
      }
      unlock_timer(timer, flags);
      release_posix_timer(timer, IT_ID_SET);
}

/*
 * This is called by do_exit or de_thread, only when there are no more
 * references to the shared signal_struct.
 */
void exit_itimers(struct signal_struct *sig)
{
      struct k_itimer *tmr;

      while (!list_empty(&sig->posix_timers)) {
            tmr = list_entry(sig->posix_timers.next, struct k_itimer, list);
            itimer_delete(tmr);
      }
}

/* Not available / possible... functions */
int do_posix_clock_nosettime(const clockid_t clockid, struct timespec *tp)
{
      return -EINVAL;
}
EXPORT_SYMBOL_GPL(do_posix_clock_nosettime);

int do_posix_clock_nonanosleep(const clockid_t clock, int flags,
                         struct timespec *t, struct timespec __user *r)
{
#ifndef ENOTSUP
      return -EOPNOTSUPP;     /* aka ENOTSUP in userland for POSIX */
#else  /*  parisc does define it separately.  */
      return -ENOTSUP;
#endif
}
EXPORT_SYMBOL_GPL(do_posix_clock_nonanosleep);

asmlinkage long sys_clock_settime(const clockid_t which_clock,
                          const struct timespec __user *tp)
{
      struct timespec new_tp;

      if (invalid_clockid(which_clock))
            return -EINVAL;
      if (copy_from_user(&new_tp, tp, sizeof (*tp)))
            return -EFAULT;

      return CLOCK_DISPATCH(which_clock, clock_set, (which_clock, &new_tp));
}

asmlinkage long
sys_clock_gettime(const clockid_t which_clock, struct timespec __user *tp)
{
      struct timespec kernel_tp;
      int error;

      if (invalid_clockid(which_clock))
            return -EINVAL;
      error = CLOCK_DISPATCH(which_clock, clock_get,
                         (which_clock, &kernel_tp));
      if (!error && copy_to_user(tp, &kernel_tp, sizeof (kernel_tp)))
            error = -EFAULT;

      return error;

}

asmlinkage long
sys_clock_getres(const clockid_t which_clock, struct timespec __user *tp)
{
      struct timespec rtn_tp;
      int error;

      if (invalid_clockid(which_clock))
            return -EINVAL;

      error = CLOCK_DISPATCH(which_clock, clock_getres,
                         (which_clock, &rtn_tp));

      if (!error && tp && copy_to_user(tp, &rtn_tp, sizeof (rtn_tp))) {
            error = -EFAULT;
      }

      return error;
}

/*
 * nanosleep for monotonic and realtime clocks
 */
static int common_nsleep(const clockid_t which_clock, int flags,
                   struct timespec *tsave, struct timespec __user *rmtp)
{
      struct timespec rmt;
      int ret;

      ret = hrtimer_nanosleep(tsave, rmtp ? &rmt : NULL,
                        flags & TIMER_ABSTIME ?
                        HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
                        which_clock);

      if (ret && rmtp) {
            if (copy_to_user(rmtp, &rmt, sizeof(*rmtp)))
                  return -EFAULT;
      }

      return ret;
}

asmlinkage long
sys_clock_nanosleep(const clockid_t which_clock, int flags,
                const struct timespec __user *rqtp,
                struct timespec __user *rmtp)
{
      struct timespec t;

      if (invalid_clockid(which_clock))
            return -EINVAL;

      if (copy_from_user(&t, rqtp, sizeof (struct timespec)))
            return -EFAULT;

      if (!timespec_valid(&t))
            return -EINVAL;

      return CLOCK_DISPATCH(which_clock, nsleep,
                        (which_clock, flags, &t, rmtp));
}

/*
 * nanosleep_restart for monotonic and realtime clocks
 */
static int common_nsleep_restart(struct restart_block *restart_block)
{
      return hrtimer_nanosleep_restart(restart_block);
}

/*
 * This will restart clock_nanosleep. This is required only by
 * compat_clock_nanosleep_restart for now.
 */
long
clock_nanosleep_restart(struct restart_block *restart_block)
{
      clockid_t which_clock = restart_block->arg0;

      return CLOCK_DISPATCH(which_clock, nsleep_restart,
                        (restart_block));
}

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