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   /*
    * 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 <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;
 }
 
 static int no_timer_create(struct k_itimer *new_timer)
 {
         return -EOPNOTSUPP;
 }
 
 /*
  * 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;
 }
 
 /*
  * Get monotonic time for posix timers
  */
 static int posix_get_monotonic_raw(clockid_t which_clock, struct timespec *tp)
 {
         getrawmonotonic(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,
         };
         struct k_clock clock_monotonic_raw = {
                 .clock_getres = hrtimer_get_res,
                 .clock_get = posix_get_monotonic_raw,
                 .clock_set = do_posix_clock_nosettime,
                 .timer_create = no_timer_create,
         };
 
         register_posix_clock(CLOCK_REALTIME, &clock_realtime);
         register_posix_clock(CLOCK_MONOTONIC, &clock_monotonic);
         register_posix_clock(CLOCK_MONOTONIC_RAW, &clock_monotonic_raw);
 
         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 += (unsigned int) 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)
 {
         int shared, ret;
         /*
          * FIXME: if ->sigq is queued we can race with
          * dequeue_signal()->do_schedule_next_timer().
          *
          * If dequeue_signal() sees the "right" value of
          * si_sys_private it calls do_schedule_next_timer().
          * We re-queue ->sigq and drop ->it_lock().
          * do_schedule_next_timer() locks the timer
          * and re-schedules it while ->sigq is pending.
          * Not really bad, but not that we want.
          */
         timr->sigq->info.si_sys_private = si_private;
 
         shared = !(timr->it_sigev_notify & SIGEV_THREAD_ID);
         ret = send_sigqueue(timr->sigq, timr->it_process, shared);
         /* If we failed to send the signal the timer stops. */
         return ret > 0;
 }
 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 += (unsigned int)
                                 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_vpid(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);
                 return NULL;
         }
         memset(&tmr->sigq->info, 0, sizeof(siginfo_t));
         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);
         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)
 {
         struct k_itimer *new_timer;
         int error, new_timer_id;
         struct task_struct *process;
         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, new_timer, &new_timer_id);
         spin_unlock_irq(&idr_lock);
         if (error) {
                 if (error == -EAGAIN)
                         goto retry;
                 /*
                  * Weird 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;
                 }
                 rcu_read_lock();
                 process = good_sigevent(&event);
                 if (process)
                         get_task_struct(process);
                 rcu_read_unlock();
                 if (!process) {
                         error = -EINVAL;
                         goto out;
                 }
         } else {
                 event.sigev_notify = SIGEV_SIGNAL;
                 event.sigev_signo = SIGALRM;
                 event.sigev_value.sival_int = new_timer->it_id;
                 process = current->group_leader;
                 get_task_struct(process);
         }
 
         new_timer->it_sigev_notify     = event.sigev_notify;
         new_timer->sigq->info.si_signo = event.sigev_signo;
         new_timer->sigq->info.si_value = event.sigev_value;
         new_timer->sigq->info.si_tid   = new_timer->it_id;
         new_timer->sigq->info.si_code  = SI_TIMER;
 
         spin_lock_irq(&current->sighand->siglock);
         new_timer->it_process = process;
         list_add(&new_timer->list, &current->signal->posix_timers);
         spin_unlock_irq(&current->sighand->siglock);
 
         return 0;
          /*
          * 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:
         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 = idr_find(&posix_timers_id, (int)timer_id);
         if (timr) {
                 spin_lock(&timr->it_lock);
                 if (timr->it_process &&
                     same_thread_group(timr->it_process, current)) {
                         spin_unlock(&idr_lock);
                         return timr;
                 }
                 spin_unlock(&timr->it_lock);
         }
         spin_unlock_irqrestore(&idr_lock, *flags);
 
         return NULL;
 }
 
 /*
  * 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 += (unsigned int) hrtimer_forward(timer, now, iv);
 
         remaining = ktime_sub(hrtimer_get_expires(timer), 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;
 
         hrtimer_set_expires(timer, 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) {
                         hrtimer_add_expires(timer, timer->base->get_time());
                 }
                 return 0;
         }
 
         hrtimer_start_expires(timer, 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).
          */
         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).
          */
         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)
 {
         return hrtimer_nanosleep(tsave, rmtp, flags & TIMER_ABSTIME ?
                                  HRTIMER_MODE_ABS : HRTIMER_MODE_REL,
                                  which_clock);
 }
 
 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));
}