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hrtimer.c

/*
 *  linux/kernel/hrtimer.c
 *
 *  Copyright(C) 2005-2006, Thomas Gleixner <tglx@linutronix.de>
 *  Copyright(C) 2005-2007, Red Hat, Inc., Ingo Molnar
 *  Copyright(C) 2006-2007  Timesys Corp., Thomas Gleixner
 *
 *  High-resolution kernel timers
 *
 *  In contrast to the low-resolution timeout API implemented in
 *  kernel/timer.c, hrtimers provide finer resolution and accuracy
 *  depending on system configuration and capabilities.
 *
 *  These timers are currently used for:
 *   - itimers
 *   - POSIX timers
 *   - nanosleep
 *   - precise in-kernel timing
 *
 *  Started by: Thomas Gleixner and Ingo Molnar
 *
 *  Credits:
 *    based on kernel/timer.c
 *
 *    Help, testing, suggestions, bugfixes, improvements were
 *    provided by:
 *
 *    George Anzinger, Andrew Morton, Steven Rostedt, Roman Zippel
 *    et. al.
 *
 *  For licencing details see kernel-base/COPYING
 */

#include <linux/cpu.h>
#include <linux/irq.h>
#include <linux/module.h>
#include <linux/percpu.h>
#include <linux/hrtimer.h>
#include <linux/notifier.h>
#include <linux/syscalls.h>
#include <linux/kallsyms.h>
#include <linux/interrupt.h>
#include <linux/tick.h>
#include <linux/seq_file.h>
#include <linux/err.h>

#include <asm/uaccess.h>

/**
 * ktime_get - get the monotonic time in ktime_t format
 *
 * returns the time in ktime_t format
 */
ktime_t ktime_get(void)
{
      struct timespec now;

      ktime_get_ts(&now);

      return timespec_to_ktime(now);
}
EXPORT_SYMBOL_GPL(ktime_get);

/**
 * ktime_get_real - get the real (wall-) time in ktime_t format
 *
 * returns the time in ktime_t format
 */
ktime_t ktime_get_real(void)
{
      struct timespec now;

      getnstimeofday(&now);

      return timespec_to_ktime(now);
}

EXPORT_SYMBOL_GPL(ktime_get_real);

/*
 * The timer bases:
 *
 * Note: If we want to add new timer bases, we have to skip the two
 * clock ids captured by the cpu-timers. We do this by holding empty
 * entries rather than doing math adjustment of the clock ids.
 * This ensures that we capture erroneous accesses to these clock ids
 * rather than moving them into the range of valid clock id's.
 */
DEFINE_PER_CPU(struct hrtimer_cpu_base, hrtimer_bases) =
{

      .clock_base =
      {
            {
                  .index = CLOCK_REALTIME,
                  .get_time = &ktime_get_real,
                  .resolution = KTIME_LOW_RES,
            },
            {
                  .index = CLOCK_MONOTONIC,
                  .get_time = &ktime_get,
                  .resolution = KTIME_LOW_RES,
            },
      }
};

/**
 * ktime_get_ts - get the monotonic clock in timespec format
 * @ts:           pointer to timespec variable
 *
 * The function calculates the monotonic clock from the realtime
 * clock and the wall_to_monotonic offset and stores the result
 * in normalized timespec format in the variable pointed to by @ts.
 */
void ktime_get_ts(struct timespec *ts)
{
      struct timespec tomono;
      unsigned long seq;

      do {
            seq = read_seqbegin(&xtime_lock);
            getnstimeofday(ts);
            tomono = wall_to_monotonic;

      } while (read_seqretry(&xtime_lock, seq));

      set_normalized_timespec(ts, ts->tv_sec + tomono.tv_sec,
                        ts->tv_nsec + tomono.tv_nsec);
}
EXPORT_SYMBOL_GPL(ktime_get_ts);

/*
 * Get the coarse grained time at the softirq based on xtime and
 * wall_to_monotonic.
 */
static void hrtimer_get_softirq_time(struct hrtimer_cpu_base *base)
{
      ktime_t xtim, tomono;
      struct timespec xts, tom;
      unsigned long seq;

      do {
            seq = read_seqbegin(&xtime_lock);
            xts = current_kernel_time();
            tom = wall_to_monotonic;
      } while (read_seqretry(&xtime_lock, seq));

      xtim = timespec_to_ktime(xts);
      tomono = timespec_to_ktime(tom);
      base->clock_base[CLOCK_REALTIME].softirq_time = xtim;
      base->clock_base[CLOCK_MONOTONIC].softirq_time =
            ktime_add(xtim, tomono);
}

/*
 * Helper function to check, whether the timer is running the callback
 * function
 */
static inline int hrtimer_callback_running(struct hrtimer *timer)
{
      return timer->state & HRTIMER_STATE_CALLBACK;
}

/*
 * Functions and macros which are different for UP/SMP systems are kept in a
 * single place
 */
#ifdef CONFIG_SMP

/*
 * We are using hashed locking: holding per_cpu(hrtimer_bases)[n].lock
 * means that all timers which are tied to this base via timer->base are
 * locked, and the base itself is locked too.
 *
 * So __run_timers/migrate_timers can safely modify all timers which could
 * be found on the lists/queues.
 *
 * When the timer's base is locked, and the timer removed from list, it is
 * possible to set timer->base = NULL and drop the lock: the timer remains
 * locked.
 */
static
struct hrtimer_clock_base *lock_hrtimer_base(const struct hrtimer *timer,
                                   unsigned long *flags)
{
      struct hrtimer_clock_base *base;

      for (;;) {
            base = timer->base;
            if (likely(base != NULL)) {
                  spin_lock_irqsave(&base->cpu_base->lock, *flags);
                  if (likely(base == timer->base))
                        return base;
                  /* The timer has migrated to another CPU: */
                  spin_unlock_irqrestore(&base->cpu_base->lock, *flags);
            }
            cpu_relax();
      }
}

/*
 * Switch the timer base to the current CPU when possible.
 */
static inline struct hrtimer_clock_base *
switch_hrtimer_base(struct hrtimer *timer, struct hrtimer_clock_base *base)
{
      struct hrtimer_clock_base *new_base;
      struct hrtimer_cpu_base *new_cpu_base;

      new_cpu_base = &__get_cpu_var(hrtimer_bases);
      new_base = &new_cpu_base->clock_base[base->index];

      if (base != new_base) {
            /*
             * We are trying to schedule the timer on the local CPU.
             * However we can't change timer's base while it is running,
             * so we keep it on the same CPU. No hassle vs. reprogramming
             * the event source in the high resolution case. The softirq
             * code will take care of this when the timer function has
             * completed. There is no conflict as we hold the lock until
             * the timer is enqueued.
             */
            if (unlikely(hrtimer_callback_running(timer)))
                  return base;

            /* See the comment in lock_timer_base() */
            timer->base = NULL;
            spin_unlock(&base->cpu_base->lock);
            spin_lock(&new_base->cpu_base->lock);
            timer->base = new_base;
      }
      return new_base;
}

#else /* CONFIG_SMP */

static inline struct hrtimer_clock_base *
lock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
{
      struct hrtimer_clock_base *base = timer->base;

      spin_lock_irqsave(&base->cpu_base->lock, *flags);

      return base;
}

# define switch_hrtimer_base(t, b)  (b)

#endif      /* !CONFIG_SMP */

/*
 * Functions for the union type storage format of ktime_t which are
 * too large for inlining:
 */
#if BITS_PER_LONG < 64
# ifndef CONFIG_KTIME_SCALAR
/**
 * ktime_add_ns - Add a scalar nanoseconds value to a ktime_t variable
 * @kt:           addend
 * @nsec:   the scalar nsec value to add
 *
 * Returns the sum of kt and nsec in ktime_t format
 */
ktime_t ktime_add_ns(const ktime_t kt, u64 nsec)
{
      ktime_t tmp;

      if (likely(nsec < NSEC_PER_SEC)) {
            tmp.tv64 = nsec;
      } else {
            unsigned long rem = do_div(nsec, NSEC_PER_SEC);

            tmp = ktime_set((long)nsec, rem);
      }

      return ktime_add(kt, tmp);
}

EXPORT_SYMBOL_GPL(ktime_add_ns);

/**
 * ktime_sub_ns - Subtract a scalar nanoseconds value from a ktime_t variable
 * @kt:           minuend
 * @nsec:   the scalar nsec value to subtract
 *
 * Returns the subtraction of @nsec from @kt in ktime_t format
 */
ktime_t ktime_sub_ns(const ktime_t kt, u64 nsec)
{
      ktime_t tmp;

      if (likely(nsec < NSEC_PER_SEC)) {
            tmp.tv64 = nsec;
      } else {
            unsigned long rem = do_div(nsec, NSEC_PER_SEC);

            tmp = ktime_set((long)nsec, rem);
      }

      return ktime_sub(kt, tmp);
}

EXPORT_SYMBOL_GPL(ktime_sub_ns);
# endif /* !CONFIG_KTIME_SCALAR */

/*
 * Divide a ktime value by a nanosecond value
 */
unsigned long ktime_divns(const ktime_t kt, s64 div)
{
      u64 dclc, inc, dns;
      int sft = 0;

      dclc = dns = ktime_to_ns(kt);
      inc = div;
      /* Make sure the divisor is less than 2^32: */
      while (div >> 32) {
            sft++;
            div >>= 1;
      }
      dclc >>= sft;
      do_div(dclc, (unsigned long) div);

      return (unsigned long) dclc;
}
#endif /* BITS_PER_LONG >= 64 */

/* High resolution timer related functions */
#ifdef CONFIG_HIGH_RES_TIMERS

/*
 * High resolution timer enabled ?
 */
static int hrtimer_hres_enabled __read_mostly  = 1;

/*
 * Enable / Disable high resolution mode
 */
static int __init setup_hrtimer_hres(char *str)
{
      if (!strcmp(str, "off"))
            hrtimer_hres_enabled = 0;
      else if (!strcmp(str, "on"))
            hrtimer_hres_enabled = 1;
      else
            return 0;
      return 1;
}

__setup("highres=", setup_hrtimer_hres);

/*
 * hrtimer_high_res_enabled - query, if the highres mode is enabled
 */
static inline int hrtimer_is_hres_enabled(void)
{
      return hrtimer_hres_enabled;
}

/*
 * Is the high resolution mode active ?
 */
static inline int hrtimer_hres_active(void)
{
      return __get_cpu_var(hrtimer_bases).hres_active;
}

/*
 * Reprogram the event source with checking both queues for the
 * next event
 * Called with interrupts disabled and base->lock held
 */
static void hrtimer_force_reprogram(struct hrtimer_cpu_base *cpu_base)
{
      int i;
      struct hrtimer_clock_base *base = cpu_base->clock_base;
      ktime_t expires;

      cpu_base->expires_next.tv64 = KTIME_MAX;

      for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
            struct hrtimer *timer;

            if (!base->first)
                  continue;
            timer = rb_entry(base->first, struct hrtimer, node);
            expires = ktime_sub(timer->expires, base->offset);
            if (expires.tv64 < cpu_base->expires_next.tv64)
                  cpu_base->expires_next = expires;
      }

      if (cpu_base->expires_next.tv64 != KTIME_MAX)
            tick_program_event(cpu_base->expires_next, 1);
}

/*
 * Shared reprogramming for clock_realtime and clock_monotonic
 *
 * When a timer is enqueued and expires earlier than the already enqueued
 * timers, we have to check, whether it expires earlier than the timer for
 * which the clock event device was armed.
 *
 * Called with interrupts disabled and base->cpu_base.lock held
 */
static int hrtimer_reprogram(struct hrtimer *timer,
                       struct hrtimer_clock_base *base)
{
      ktime_t *expires_next = &__get_cpu_var(hrtimer_bases).expires_next;
      ktime_t expires = ktime_sub(timer->expires, base->offset);
      int res;

      /*
       * When the callback is running, we do not reprogram the clock event
       * device. The timer callback is either running on a different CPU or
       * the callback is executed in the hrtimer_interrupt context. The
       * reprogramming is handled either by the softirq, which called the
       * callback or at the end of the hrtimer_interrupt.
       */
      if (hrtimer_callback_running(timer))
            return 0;

      if (expires.tv64 >= expires_next->tv64)
            return 0;

      /*
       * Clockevents returns -ETIME, when the event was in the past.
       */
      res = tick_program_event(expires, 0);
      if (!IS_ERR_VALUE(res))
            *expires_next = expires;
      return res;
}


/*
 * Retrigger next event is called after clock was set
 *
 * Called with interrupts disabled via on_each_cpu()
 */
static void retrigger_next_event(void *arg)
{
      struct hrtimer_cpu_base *base;
      struct timespec realtime_offset;
      unsigned long seq;

      if (!hrtimer_hres_active())
            return;

      do {
            seq = read_seqbegin(&xtime_lock);
            set_normalized_timespec(&realtime_offset,
                              -wall_to_monotonic.tv_sec,
                              -wall_to_monotonic.tv_nsec);
      } while (read_seqretry(&xtime_lock, seq));

      base = &__get_cpu_var(hrtimer_bases);

      /* Adjust CLOCK_REALTIME offset */
      spin_lock(&base->lock);
      base->clock_base[CLOCK_REALTIME].offset =
            timespec_to_ktime(realtime_offset);

      hrtimer_force_reprogram(base);
      spin_unlock(&base->lock);
}

/*
 * Clock realtime was set
 *
 * Change the offset of the realtime clock vs. the monotonic
 * clock.
 *
 * We might have to reprogram the high resolution timer interrupt. On
 * SMP we call the architecture specific code to retrigger _all_ high
 * resolution timer interrupts. On UP we just disable interrupts and
 * call the high resolution interrupt code.
 */
void clock_was_set(void)
{
      /* Retrigger the CPU local events everywhere */
      on_each_cpu(retrigger_next_event, NULL, 0, 1);
}

/*
 * During resume we might have to reprogram the high resolution timer
 * interrupt (on the local CPU):
 */
void hres_timers_resume(void)
{
      WARN_ON_ONCE(num_online_cpus() > 1);

      /* Retrigger the CPU local events: */
      retrigger_next_event(NULL);
}

/*
 * Check, whether the timer is on the callback pending list
 */
static inline int hrtimer_cb_pending(const struct hrtimer *timer)
{
      return timer->state & HRTIMER_STATE_PENDING;
}

/*
 * Remove a timer from the callback pending list
 */
static inline void hrtimer_remove_cb_pending(struct hrtimer *timer)
{
      list_del_init(&timer->cb_entry);
}

/*
 * Initialize the high resolution related parts of cpu_base
 */
static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base)
{
      base->expires_next.tv64 = KTIME_MAX;
      base->hres_active = 0;
      INIT_LIST_HEAD(&base->cb_pending);
}

/*
 * Initialize the high resolution related parts of a hrtimer
 */
static inline void hrtimer_init_timer_hres(struct hrtimer *timer)
{
      INIT_LIST_HEAD(&timer->cb_entry);
}

/*
 * When High resolution timers are active, try to reprogram. Note, that in case
 * the state has HRTIMER_STATE_CALLBACK set, no reprogramming and no expiry
 * check happens. The timer gets enqueued into the rbtree. The reprogramming
 * and expiry check is done in the hrtimer_interrupt or in the softirq.
 */
static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
                                  struct hrtimer_clock_base *base)
{
      if (base->cpu_base->hres_active && hrtimer_reprogram(timer, base)) {

            /* Timer is expired, act upon the callback mode */
            switch(timer->cb_mode) {
            case HRTIMER_CB_IRQSAFE_NO_RESTART:
                  /*
                   * We can call the callback from here. No restart
                   * happens, so no danger of recursion
                   */
                  BUG_ON(timer->function(timer) != HRTIMER_NORESTART);
                  return 1;
            case HRTIMER_CB_IRQSAFE_NO_SOFTIRQ:
                  /*
                   * This is solely for the sched tick emulation with
                   * dynamic tick support to ensure that we do not
                   * restart the tick right on the edge and end up with
                   * the tick timer in the softirq ! The calling site
                   * takes care of this.
                   */
                  return 1;
            case HRTIMER_CB_IRQSAFE:
            case HRTIMER_CB_SOFTIRQ:
                  /*
                   * Move everything else into the softirq pending list !
                   */
                  list_add_tail(&timer->cb_entry,
                              &base->cpu_base->cb_pending);
                  timer->state = HRTIMER_STATE_PENDING;
                  raise_softirq(HRTIMER_SOFTIRQ);
                  return 1;
            default:
                  BUG();
            }
      }
      return 0;
}

/*
 * Switch to high resolution mode
 */
static int hrtimer_switch_to_hres(void)
{
      int cpu = smp_processor_id();
      struct hrtimer_cpu_base *base = &per_cpu(hrtimer_bases, cpu);
      unsigned long flags;

      if (base->hres_active)
            return 1;

      local_irq_save(flags);

      if (tick_init_highres()) {
            local_irq_restore(flags);
            printk(KERN_WARNING "Could not switch to high resolution "
                            "mode on CPU %d\n", cpu);
            return 0;
      }
      base->hres_active = 1;
      base->clock_base[CLOCK_REALTIME].resolution = KTIME_HIGH_RES;
      base->clock_base[CLOCK_MONOTONIC].resolution = KTIME_HIGH_RES;

      tick_setup_sched_timer();

      /* "Retrigger" the interrupt to get things going */
      retrigger_next_event(NULL);
      local_irq_restore(flags);
      printk(KERN_DEBUG "Switched to high resolution mode on CPU %d\n",
             smp_processor_id());
      return 1;
}

#else

static inline int hrtimer_hres_active(void) { return 0; }
static inline int hrtimer_is_hres_enabled(void) { return 0; }
static inline int hrtimer_switch_to_hres(void) { return 0; }
static inline void hrtimer_force_reprogram(struct hrtimer_cpu_base *base) { }
static inline int hrtimer_enqueue_reprogram(struct hrtimer *timer,
                                  struct hrtimer_clock_base *base)
{
      return 0;
}
static inline int hrtimer_cb_pending(struct hrtimer *timer) { return 0; }
static inline void hrtimer_remove_cb_pending(struct hrtimer *timer) { }
static inline void hrtimer_init_hres(struct hrtimer_cpu_base *base) { }
static inline void hrtimer_init_timer_hres(struct hrtimer *timer) { }

#endif /* CONFIG_HIGH_RES_TIMERS */

#ifdef CONFIG_TIMER_STATS
void __timer_stats_hrtimer_set_start_info(struct hrtimer *timer, void *addr)
{
      if (timer->start_site)
            return;

      timer->start_site = addr;
      memcpy(timer->start_comm, current->comm, TASK_COMM_LEN);
      timer->start_pid = current->pid;
}
#endif

/*
 * Counterpart to lock_hrtimer_base above:
 */
static inline
void unlock_hrtimer_base(const struct hrtimer *timer, unsigned long *flags)
{
      spin_unlock_irqrestore(&timer->base->cpu_base->lock, *flags);
}

/**
 * hrtimer_forward - forward the timer expiry
 * @timer:  hrtimer to forward
 * @now:    forward past this time
 * @interval:     the interval to forward
 *
 * Forward the timer expiry so it will expire in the future.
 * Returns the number of overruns.
 */
unsigned long
hrtimer_forward(struct hrtimer *timer, ktime_t now, ktime_t interval)
{
      unsigned long orun = 1;
      ktime_t delta;

      delta = ktime_sub(now, timer->expires);

      if (delta.tv64 < 0)
            return 0;

      if (interval.tv64 < timer->base->resolution.tv64)
            interval.tv64 = timer->base->resolution.tv64;

      if (unlikely(delta.tv64 >= interval.tv64)) {
            s64 incr = ktime_to_ns(interval);

            orun = ktime_divns(delta, incr);
            timer->expires = ktime_add_ns(timer->expires, incr * orun);
            if (timer->expires.tv64 > now.tv64)
                  return orun;
            /*
             * This (and the ktime_add() below) is the
             * correction for exact:
             */
            orun++;
      }
      timer->expires = ktime_add(timer->expires, interval);
      /*
       * Make sure, that the result did not wrap with a very large
       * interval.
       */
      if (timer->expires.tv64 < 0)
            timer->expires = ktime_set(KTIME_SEC_MAX, 0);

      return orun;
}
EXPORT_SYMBOL_GPL(hrtimer_forward);

/*
 * enqueue_hrtimer - internal function to (re)start a timer
 *
 * The timer is inserted in expiry order. Insertion into the
 * red black tree is O(log(n)). Must hold the base lock.
 */
static void enqueue_hrtimer(struct hrtimer *timer,
                      struct hrtimer_clock_base *base, int reprogram)
{
      struct rb_node **link = &base->active.rb_node;
      struct rb_node *parent = NULL;
      struct hrtimer *entry;
      int leftmost = 1;

      /*
       * Find the right place in the rbtree:
       */
      while (*link) {
            parent = *link;
            entry = rb_entry(parent, struct hrtimer, node);
            /*
             * We dont care about collisions. Nodes with
             * the same expiry time stay together.
             */
            if (timer->expires.tv64 < entry->expires.tv64) {
                  link = &(*link)->rb_left;
            } else {
                  link = &(*link)->rb_right;
                  leftmost = 0;
            }
      }

      /*
       * Insert the timer to the rbtree and check whether it
       * replaces the first pending timer
       */
      if (leftmost) {
            /*
             * Reprogram the clock event device. When the timer is already
             * expired hrtimer_enqueue_reprogram has either called the
             * callback or added it to the pending list and raised the
             * softirq.
             *
             * This is a NOP for !HIGHRES
             */
            if (reprogram && hrtimer_enqueue_reprogram(timer, base))
                  return;

            base->first = &timer->node;
      }

      rb_link_node(&timer->node, parent, link);
      rb_insert_color(&timer->node, &base->active);
      /*
       * HRTIMER_STATE_ENQUEUED is or'ed to the current state to preserve the
       * state of a possibly running callback.
       */
      timer->state |= HRTIMER_STATE_ENQUEUED;
}

/*
 * __remove_hrtimer - internal function to remove a timer
 *
 * Caller must hold the base lock.
 *
 * High resolution timer mode reprograms the clock event device when the
 * timer is the one which expires next. The caller can disable this by setting
 * reprogram to zero. This is useful, when the context does a reprogramming
 * anyway (e.g. timer interrupt)
 */
static void __remove_hrtimer(struct hrtimer *timer,
                       struct hrtimer_clock_base *base,
                       unsigned long newstate, int reprogram)
{
      /* High res. callback list. NOP for !HIGHRES */
      if (hrtimer_cb_pending(timer))
            hrtimer_remove_cb_pending(timer);
      else {
            /*
             * Remove the timer from the rbtree and replace the
             * first entry pointer if necessary.
             */
            if (base->first == &timer->node) {
                  base->first = rb_next(&timer->node);
                  /* Reprogram the clock event device. if enabled */
                  if (reprogram && hrtimer_hres_active())
                        hrtimer_force_reprogram(base->cpu_base);
            }
            rb_erase(&timer->node, &base->active);
      }
      timer->state = newstate;
}

/*
 * remove hrtimer, called with base lock held
 */
static inline int
remove_hrtimer(struct hrtimer *timer, struct hrtimer_clock_base *base)
{
      if (hrtimer_is_queued(timer)) {
            int reprogram;

            /*
             * Remove the timer and force reprogramming when high
             * resolution mode is active and the timer is on the current
             * CPU. If we remove a timer on another CPU, reprogramming is
             * skipped. The interrupt event on this CPU is fired and
             * reprogramming happens in the interrupt handler. This is a
             * rare case and less expensive than a smp call.
             */
            timer_stats_hrtimer_clear_start_info(timer);
            reprogram = base->cpu_base == &__get_cpu_var(hrtimer_bases);
            __remove_hrtimer(timer, base, HRTIMER_STATE_INACTIVE,
                         reprogram);
            return 1;
      }
      return 0;
}

/**
 * hrtimer_start - (re)start an relative timer on the current CPU
 * @timer:  the timer to be added
 * @tim:    expiry time
 * @mode:   expiry mode: absolute (HRTIMER_ABS) or relative (HRTIMER_REL)
 *
 * Returns:
 *  0 on success
 *  1 when the timer was active
 */
int
hrtimer_start(struct hrtimer *timer, ktime_t tim, const enum hrtimer_mode mode)
{
      struct hrtimer_clock_base *base, *new_base;
      unsigned long flags;
      int ret;

      base = lock_hrtimer_base(timer, &flags);

      /* Remove an active timer from the queue: */
      ret = remove_hrtimer(timer, base);

      /* Switch the timer base, if necessary: */
      new_base = switch_hrtimer_base(timer, base);

      if (mode == HRTIMER_MODE_REL) {
            tim = ktime_add(tim, new_base->get_time());
            /*
             * CONFIG_TIME_LOW_RES is a temporary way for architectures
             * to signal that they simply return xtime in
             * do_gettimeoffset(). In this case we want to round up by
             * resolution when starting a relative timer, to avoid short
             * timeouts. This will go away with the GTOD framework.
             */
#ifdef CONFIG_TIME_LOW_RES
            tim = ktime_add(tim, base->resolution);
#endif
            /*
             * Careful here: User space might have asked for a
             * very long sleep, so the add above might result in a
             * negative number, which enqueues the timer in front
             * of the queue.
             */
            if (tim.tv64 < 0)
                  tim.tv64 = KTIME_MAX;
      }
      timer->expires = tim;

      timer_stats_hrtimer_set_start_info(timer);

      /*
       * Only allow reprogramming if the new base is on this CPU.
       * (it might still be on another CPU if the timer was pending)
       */
      enqueue_hrtimer(timer, new_base,
                  new_base->cpu_base == &__get_cpu_var(hrtimer_bases));

      unlock_hrtimer_base(timer, &flags);

      return ret;
}
EXPORT_SYMBOL_GPL(hrtimer_start);

/**
 * hrtimer_try_to_cancel - try to deactivate a timer
 * @timer:  hrtimer to stop
 *
 * Returns:
 *  0 when the timer was not active
 *  1 when the timer was active
 * -1 when the timer is currently excuting the callback function and
 *    cannot be stopped
 */
int hrtimer_try_to_cancel(struct hrtimer *timer)
{
      struct hrtimer_clock_base *base;
      unsigned long flags;
      int ret = -1;

      base = lock_hrtimer_base(timer, &flags);

      if (!hrtimer_callback_running(timer))
            ret = remove_hrtimer(timer, base);

      unlock_hrtimer_base(timer, &flags);

      return ret;

}
EXPORT_SYMBOL_GPL(hrtimer_try_to_cancel);

/**
 * hrtimer_cancel - cancel a timer and wait for the handler to finish.
 * @timer:  the timer to be cancelled
 *
 * Returns:
 *  0 when the timer was not active
 *  1 when the timer was active
 */
int hrtimer_cancel(struct hrtimer *timer)
{
      for (;;) {
            int ret = hrtimer_try_to_cancel(timer);

            if (ret >= 0)
                  return ret;
            cpu_relax();
      }
}
EXPORT_SYMBOL_GPL(hrtimer_cancel);

/**
 * hrtimer_get_remaining - get remaining time for the timer
 * @timer:  the timer to read
 */
ktime_t hrtimer_get_remaining(const struct hrtimer *timer)
{
      struct hrtimer_clock_base *base;
      unsigned long flags;
      ktime_t rem;

      base = lock_hrtimer_base(timer, &flags);
      rem = ktime_sub(timer->expires, base->get_time());
      unlock_hrtimer_base(timer, &flags);

      return rem;
}
EXPORT_SYMBOL_GPL(hrtimer_get_remaining);

#if defined(CONFIG_NO_IDLE_HZ) || defined(CONFIG_NO_HZ)
/**
 * hrtimer_get_next_event - get the time until next expiry event
 *
 * Returns the delta to the next expiry event or KTIME_MAX if no timer
 * is pending.
 */
ktime_t hrtimer_get_next_event(void)
{
      struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
      struct hrtimer_clock_base *base = cpu_base->clock_base;
      ktime_t delta, mindelta = { .tv64 = KTIME_MAX };
      unsigned long flags;
      int i;

      spin_lock_irqsave(&cpu_base->lock, flags);

      if (!hrtimer_hres_active()) {
            for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++, base++) {
                  struct hrtimer *timer;

                  if (!base->first)
                        continue;

                  timer = rb_entry(base->first, struct hrtimer, node);
                  delta.tv64 = timer->expires.tv64;
                  delta = ktime_sub(delta, base->get_time());
                  if (delta.tv64 < mindelta.tv64)
                        mindelta.tv64 = delta.tv64;
            }
      }

      spin_unlock_irqrestore(&cpu_base->lock, flags);

      if (mindelta.tv64 < 0)
            mindelta.tv64 = 0;
      return mindelta;
}
#endif

/**
 * hrtimer_init - initialize a timer to the given clock
 * @timer:  the timer to be initialized
 * @clock_id:     the clock to be used
 * @mode:   timer mode abs/rel
 */
void hrtimer_init(struct hrtimer *timer, clockid_t clock_id,
              enum hrtimer_mode mode)
{
      struct hrtimer_cpu_base *cpu_base;

      memset(timer, 0, sizeof(struct hrtimer));

      cpu_base = &__raw_get_cpu_var(hrtimer_bases);

      if (clock_id == CLOCK_REALTIME && mode != HRTIMER_MODE_ABS)
            clock_id = CLOCK_MONOTONIC;

      timer->base = &cpu_base->clock_base[clock_id];
      hrtimer_init_timer_hres(timer);

#ifdef CONFIG_TIMER_STATS
      timer->start_site = NULL;
      timer->start_pid = -1;
      memset(timer->start_comm, 0, TASK_COMM_LEN);
#endif
}
EXPORT_SYMBOL_GPL(hrtimer_init);

/**
 * hrtimer_get_res - get the timer resolution for a clock
 * @which_clock: which clock to query
 * @tp:            pointer to timespec variable to store the resolution
 *
 * Store the resolution of the clock selected by @which_clock in the
 * variable pointed to by @tp.
 */
int hrtimer_get_res(const clockid_t which_clock, struct timespec *tp)
{
      struct hrtimer_cpu_base *cpu_base;

      cpu_base = &__raw_get_cpu_var(hrtimer_bases);
      *tp = ktime_to_timespec(cpu_base->clock_base[which_clock].resolution);

      return 0;
}
EXPORT_SYMBOL_GPL(hrtimer_get_res);

#ifdef CONFIG_HIGH_RES_TIMERS

/*
 * High resolution timer interrupt
 * Called with interrupts disabled
 */
void hrtimer_interrupt(struct clock_event_device *dev)
{
      struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
      struct hrtimer_clock_base *base;
      ktime_t expires_next, now;
      int i, raise = 0;

      BUG_ON(!cpu_base->hres_active);
      cpu_base->nr_events++;
      dev->next_event.tv64 = KTIME_MAX;

 retry:
      now = ktime_get();

      expires_next.tv64 = KTIME_MAX;

      base = cpu_base->clock_base;

      for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
            ktime_t basenow;
            struct rb_node *node;

            spin_lock(&cpu_base->lock);

            basenow = ktime_add(now, base->offset);

            while ((node = base->first)) {
                  struct hrtimer *timer;

                  timer = rb_entry(node, struct hrtimer, node);

                  if (basenow.tv64 < timer->expires.tv64) {
                        ktime_t expires;

                        expires = ktime_sub(timer->expires,
                                        base->offset);
                        if (expires.tv64 < expires_next.tv64)
                              expires_next = expires;
                        break;
                  }

                  /* Move softirq callbacks to the pending list */
                  if (timer->cb_mode == HRTIMER_CB_SOFTIRQ) {
                        __remove_hrtimer(timer, base,
                                     HRTIMER_STATE_PENDING, 0);
                        list_add_tail(&timer->cb_entry,
                                    &base->cpu_base->cb_pending);
                        raise = 1;
                        continue;
                  }

                  __remove_hrtimer(timer, base,
                               HRTIMER_STATE_CALLBACK, 0);
                  timer_stats_account_hrtimer(timer);

                  /*
                   * Note: We clear the CALLBACK bit after
                   * enqueue_hrtimer to avoid reprogramming of
                   * the event hardware. This happens at the end
                   * of this function anyway.
                   */
                  if (timer->function(timer) != HRTIMER_NORESTART) {
                        BUG_ON(timer->state != HRTIMER_STATE_CALLBACK);
                        enqueue_hrtimer(timer, base, 0);
                  }
                  timer->state &= ~HRTIMER_STATE_CALLBACK;
            }
            spin_unlock(&cpu_base->lock);
            base++;
      }

      cpu_base->expires_next = expires_next;

      /* Reprogramming necessary ? */
      if (expires_next.tv64 != KTIME_MAX) {
            if (tick_program_event(expires_next, 0))
                  goto retry;
      }

      /* Raise softirq ? */
      if (raise)
            raise_softirq(HRTIMER_SOFTIRQ);
}

static void run_hrtimer_softirq(struct softirq_action *h)
{
      struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);

      spin_lock_irq(&cpu_base->lock);

      while (!list_empty(&cpu_base->cb_pending)) {
            enum hrtimer_restart (*fn)(struct hrtimer *);
            struct hrtimer *timer;
            int restart;

            timer = list_entry(cpu_base->cb_pending.next,
                           struct hrtimer, cb_entry);

            timer_stats_account_hrtimer(timer);

            fn = timer->function;
            __remove_hrtimer(timer, timer->base, HRTIMER_STATE_CALLBACK, 0);
            spin_unlock_irq(&cpu_base->lock);

            restart = fn(timer);

            spin_lock_irq(&cpu_base->lock);

            timer->state &= ~HRTIMER_STATE_CALLBACK;
            if (restart == HRTIMER_RESTART) {
                  BUG_ON(hrtimer_active(timer));
                  /*
                   * Enqueue the timer, allow reprogramming of the event
                   * device
                   */
                  enqueue_hrtimer(timer, timer->base, 1);
            } else if (hrtimer_active(timer)) {
                  /*
                   * If the timer was rearmed on another CPU, reprogram
                   * the event device.
                   */
                  if (timer->base->first == &timer->node)
                        hrtimer_reprogram(timer, timer->base);
            }
      }
      spin_unlock_irq(&cpu_base->lock);
}

#endif      /* CONFIG_HIGH_RES_TIMERS */

/*
 * Expire the per base hrtimer-queue:
 */
static inline void run_hrtimer_queue(struct hrtimer_cpu_base *cpu_base,
                             int index)
{
      struct rb_node *node;
      struct hrtimer_clock_base *base = &cpu_base->clock_base[index];

      if (!base->first)
            return;

      if (base->get_softirq_time)
            base->softirq_time = base->get_softirq_time();

      spin_lock_irq(&cpu_base->lock);

      while ((node = base->first)) {
            struct hrtimer *timer;
            enum hrtimer_restart (*fn)(struct hrtimer *);
            int restart;

            timer = rb_entry(node, struct hrtimer, node);
            if (base->softirq_time.tv64 <= timer->expires.tv64)
                  break;

#ifdef CONFIG_HIGH_RES_TIMERS
            WARN_ON_ONCE(timer->cb_mode == HRTIMER_CB_IRQSAFE_NO_SOFTIRQ);
#endif
            timer_stats_account_hrtimer(timer);

            fn = timer->function;
            __remove_hrtimer(timer, base, HRTIMER_STATE_CALLBACK, 0);
            spin_unlock_irq(&cpu_base->lock);

            restart = fn(timer);

            spin_lock_irq(&cpu_base->lock);

            timer->state &= ~HRTIMER_STATE_CALLBACK;
            if (restart != HRTIMER_NORESTART) {
                  BUG_ON(hrtimer_active(timer));
                  enqueue_hrtimer(timer, base, 0);
            }
      }
      spin_unlock_irq(&cpu_base->lock);
}

/*
 * Called from timer softirq every jiffy, expire hrtimers:
 *
 * For HRT its the fall back code to run the softirq in the timer
 * softirq context in case the hrtimer initialization failed or has
 * not been done yet.
 */
void hrtimer_run_queues(void)
{
      struct hrtimer_cpu_base *cpu_base = &__get_cpu_var(hrtimer_bases);
      int i;

      if (hrtimer_hres_active())
            return;

      /*
       * This _is_ ugly: We have to check in the softirq context,
       * whether we can switch to highres and / or nohz mode. The
       * clocksource switch happens in the timer interrupt with
       * xtime_lock held. Notification from there only sets the
       * check bit in the tick_oneshot code, otherwise we might
       * deadlock vs. xtime_lock.
       */
      if (tick_check_oneshot_change(!hrtimer_is_hres_enabled()))
            if (hrtimer_switch_to_hres())
                  return;

      hrtimer_get_softirq_time(cpu_base);

      for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
            run_hrtimer_queue(cpu_base, i);
}

/*
 * Sleep related functions:
 */
static enum hrtimer_restart hrtimer_wakeup(struct hrtimer *timer)
{
      struct hrtimer_sleeper *t =
            container_of(timer, struct hrtimer_sleeper, timer);
      struct task_struct *task = t->task;

      t->task = NULL;
      if (task)
            wake_up_process(task);

      return HRTIMER_NORESTART;
}

void hrtimer_init_sleeper(struct hrtimer_sleeper *sl, struct task_struct *task)
{
      sl->timer.function = hrtimer_wakeup;
      sl->task = task;
#ifdef CONFIG_HIGH_RES_TIMERS
      sl->timer.cb_mode = HRTIMER_CB_IRQSAFE_NO_RESTART;
#endif
}

static int __sched do_nanosleep(struct hrtimer_sleeper *t, enum hrtimer_mode mode)
{
      hrtimer_init_sleeper(t, current);

      do {
            set_current_state(TASK_INTERRUPTIBLE);
            hrtimer_start(&t->timer, t->timer.expires, mode);

            if (likely(t->task))
                  schedule();

            hrtimer_cancel(&t->timer);
            mode = HRTIMER_MODE_ABS;

      } while (t->task && !signal_pending(current));

      return t->task == NULL;
}

long __sched hrtimer_nanosleep_restart(struct restart_block *restart)
{
      struct hrtimer_sleeper t;
      struct timespec *rmtp;
      ktime_t time;

      restart->fn = do_no_restart_syscall;

      hrtimer_init(&t.timer, restart->arg0, HRTIMER_MODE_ABS);
      t.timer.expires.tv64 = ((u64)restart->arg3 << 32) | (u64) restart->arg2;

      if (do_nanosleep(&t, HRTIMER_MODE_ABS))
            return 0;

      rmtp = (struct timespec *)restart->arg1;
      if (rmtp) {
            time = ktime_sub(t.timer.expires, t.timer.base->get_time());
            if (time.tv64 <= 0)
                  return 0;
            *rmtp = ktime_to_timespec(time);
      }

      restart->fn = hrtimer_nanosleep_restart;

      /* The other values in restart are already filled in */
      return -ERESTART_RESTARTBLOCK;
}

long hrtimer_nanosleep(struct timespec *rqtp, struct timespec *rmtp,
                   const enum hrtimer_mode mode, const clockid_t clockid)
{
      struct restart_block *restart;
      struct hrtimer_sleeper t;
      ktime_t rem;

      hrtimer_init(&t.timer, clockid, mode);
      t.timer.expires = timespec_to_ktime(*rqtp);
      if (do_nanosleep(&t, mode))
            return 0;

      /* Absolute timers do not update the rmtp value and restart: */
      if (mode == HRTIMER_MODE_ABS)
            return -ERESTARTNOHAND;

      if (rmtp) {
            rem = ktime_sub(t.timer.expires, t.timer.base->get_time());
            if (rem.tv64 <= 0)
                  return 0;
            *rmtp = ktime_to_timespec(rem);
      }

      restart = &current_thread_info()->restart_block;
      restart->fn = hrtimer_nanosleep_restart;
      restart->arg0 = (unsigned long) t.timer.base->index;
      restart->arg1 = (unsigned long) rmtp;
      restart->arg2 = t.timer.expires.tv64 & 0xFFFFFFFF;
      restart->arg3 = t.timer.expires.tv64 >> 32;

      return -ERESTART_RESTARTBLOCK;
}

asmlinkage long
sys_nanosleep(struct timespec __user *rqtp, struct timespec __user *rmtp)
{
      struct timespec tu, rmt;
      int ret;

      if (copy_from_user(&tu, rqtp, sizeof(tu)))
            return -EFAULT;

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

      ret = hrtimer_nanosleep(&tu, rmtp ? &rmt : NULL, HRTIMER_MODE_REL,
                        CLOCK_MONOTONIC);

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

      return ret;
}

/*
 * Functions related to boot-time initialization:
 */
static void __cpuinit init_hrtimers_cpu(int cpu)
{
      struct hrtimer_cpu_base *cpu_base = &per_cpu(hrtimer_bases, cpu);
      int i;

      spin_lock_init(&cpu_base->lock);
      lockdep_set_class(&cpu_base->lock, &cpu_base->lock_key);

      for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++)
            cpu_base->clock_base[i].cpu_base = cpu_base;

      hrtimer_init_hres(cpu_base);
}

#ifdef CONFIG_HOTPLUG_CPU

static void migrate_hrtimer_list(struct hrtimer_clock_base *old_base,
                        struct hrtimer_clock_base *new_base)
{
      struct hrtimer *timer;
      struct rb_node *node;

      while ((node = rb_first(&old_base->active))) {
            timer = rb_entry(node, struct hrtimer, node);
            BUG_ON(hrtimer_callback_running(timer));
            __remove_hrtimer(timer, old_base, HRTIMER_STATE_INACTIVE, 0);
            timer->base = new_base;
            /*
             * Enqueue the timer. Allow reprogramming of the event device
             */
            enqueue_hrtimer(timer, new_base, 1);
      }
}

static void migrate_hrtimers(int cpu)
{
      struct hrtimer_cpu_base *old_base, *new_base;
      int i;

      BUG_ON(cpu_online(cpu));
      old_base = &per_cpu(hrtimer_bases, cpu);
      new_base = &get_cpu_var(hrtimer_bases);

      tick_cancel_sched_timer(cpu);

      local_irq_disable();
      double_spin_lock(&new_base->lock, &old_base->lock,
                   smp_processor_id() < cpu);

      for (i = 0; i < HRTIMER_MAX_CLOCK_BASES; i++) {
            migrate_hrtimer_list(&old_base->clock_base[i],
                             &new_base->clock_base[i]);
      }

      double_spin_unlock(&new_base->lock, &old_base->lock,
                     smp_processor_id() < cpu);
      local_irq_enable();
      put_cpu_var(hrtimer_bases);
}
#endif /* CONFIG_HOTPLUG_CPU */

static int __cpuinit hrtimer_cpu_notify(struct notifier_block *self,
                              unsigned long action, void *hcpu)
{
      unsigned int cpu = (long)hcpu;

      switch (action) {

      case CPU_UP_PREPARE:
      case CPU_UP_PREPARE_FROZEN:
            init_hrtimers_cpu(cpu);
            break;

#ifdef CONFIG_HOTPLUG_CPU
      case CPU_DEAD:
      case CPU_DEAD_FROZEN:
            clockevents_notify(CLOCK_EVT_NOTIFY_CPU_DEAD, &cpu);
            migrate_hrtimers(cpu);
            break;
#endif

      default:
            break;
      }

      return NOTIFY_OK;
}

static struct notifier_block __cpuinitdata hrtimers_nb = {
      .notifier_call = hrtimer_cpu_notify,
};

void __init hrtimers_init(void)
{
      hrtimer_cpu_notify(&hrtimers_nb, (unsigned long)CPU_UP_PREPARE,
                    (void *)(long)smp_processor_id());
      register_cpu_notifier(&hrtimers_nb);
#ifdef CONFIG_HIGH_RES_TIMERS
      open_softirq(HRTIMER_SOFTIRQ, run_hrtimer_softirq, NULL);
#endif
}


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