1 files changed, 61 insertions, 49 deletions

diff --git a/kernel/timer.c b/kernel/timer.c
index 6ec7e7e0db4..a61c09374eb 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -77,6 +77,7 @@ struct tvec_base {
         struct timer_list *running_timer;
         unsigned long timer_jiffies;
         unsigned long next_timer;
+        unsigned long active_timers;
         struct tvec_root tv1;
         struct tvec tv2;
         struct tvec tv3;
@@ -330,7 +331,8 @@ void set_timer_slack(struct timer_list *timer, int slack_hz)
 }
 EXPORT_SYMBOL_GPL(set_timer_slack);
 
-static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
+static void
+__internal_add_timer(struct tvec_base *base, struct timer_list *timer)
 {
         unsigned long expires = timer->expires;
         unsigned long idx = expires - base->timer_jiffies;
@@ -372,6 +374,19 @@ static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
         list_add_tail(&timer->entry, vec);
 }
 
+static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
+{
+        __internal_add_timer(base, timer);
+        /*
+         * Update base->active_timers and base->next_timer
+         */
+        if (!tbase_get_deferrable(timer->base)) {
+                if (time_before(timer->expires, base->next_timer))
+                        base->next_timer = timer->expires;
+                base->active_timers++;
+        }
+}
+
 #ifdef CONFIG_TIMER_STATS
 void __timer_stats_timer_set_start_info(struct timer_list *timer, void *addr)
 {
@@ -654,8 +669,7 @@ void init_timer_deferrable_key(struct timer_list *timer,
 }
 EXPORT_SYMBOL(init_timer_deferrable_key);
 
-static inline void detach_timer(struct timer_list *timer,
-                                int clear_pending)
+static inline void detach_timer(struct timer_list *timer, bool clear_pending)
 {
         struct list_head *entry = &timer->entry;
 
@@ -667,6 +681,29 @@ static inline void detach_timer(struct timer_list *timer,
         entry->prev = LIST_POISON2;
 }
 
+static inline void
+detach_expired_timer(struct timer_list *timer, struct tvec_base *base)
+{
+        detach_timer(timer, true);
+        if (!tbase_get_deferrable(timer->base))
+                timer->base->active_timers--;
+}
+
+static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
+                             bool clear_pending)
+{
+        if (!timer_pending(timer))
+                return 0;
+
+        detach_timer(timer, clear_pending);
+        if (!tbase_get_deferrable(timer->base)) {
+                timer->base->active_timers--;
+                if (timer->expires == base->next_timer)
+                        base->next_timer = base->timer_jiffies;
+        }
+        return 1;
+}
+
 /*
  * We are using hashed locking: holding per_cpu(tvec_bases).lock
  * means that all timers which are tied to this base via timer->base are
@@ -712,16 +749,9 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
 
         base = lock_timer_base(timer, &flags);
 
-        if (timer_pending(timer)) {
-                detach_timer(timer, 0);
-                if (timer->expires == base->next_timer &&
-                    !tbase_get_deferrable(timer->base))
-                        base->next_timer = base->timer_jiffies;
-                ret = 1;
-        } else {
-                if (pending_only)
-                        goto out_unlock;
-        }
+        ret = detach_if_pending(timer, base, false);
+        if (!ret && pending_only)
+                goto out_unlock;
 
         debug_activate(timer, expires);
 
@@ -752,9 +782,6 @@ __mod_timer(struct timer_list *timer, unsigned long expires,
         }
 
         timer->expires = expires;
-        if (time_before(timer->expires, base->next_timer) &&
-            !tbase_get_deferrable(timer->base))
-                base->next_timer = timer->expires;
         internal_add_timer(base, timer);
 
 out_unlock:
@@ -920,9 +947,6 @@ void add_timer_on(struct timer_list *timer, int cpu)
         spin_lock_irqsave(&base->lock, flags);
         timer_set_base(timer, base);
         debug_activate(timer, timer->expires);
-        if (time_before(timer->expires, base->next_timer) &&
-            !tbase_get_deferrable(timer->base))
-                base->next_timer = timer->expires;
         internal_add_timer(base, timer);
         /*
          * Check whether the other CPU is idle and needs to be
@@ -959,13 +983,7 @@ int del_timer(struct timer_list *timer)
         timer_stats_timer_clear_start_info(timer);
         if (timer_pending(timer)) {
                 base = lock_timer_base(timer, &flags);
-                if (timer_pending(timer)) {
-                        detach_timer(timer, 1);
-                        if (timer->expires == base->next_timer &&
-                            !tbase_get_deferrable(timer->base))
-                                base->next_timer = base->timer_jiffies;
-                        ret = 1;
-                }
+                ret = detach_if_pending(timer, base, true);
                 spin_unlock_irqrestore(&base->lock, flags);
         }
 
@@ -990,19 +1008,10 @@ int try_to_del_timer_sync(struct timer_list *timer)
 
         base = lock_timer_base(timer, &flags);
 
-        if (base->running_timer == timer)
-                goto out;
-
-        timer_stats_timer_clear_start_info(timer);
-        ret = 0;
-        if (timer_pending(timer)) {
-                detach_timer(timer, 1);
-                if (timer->expires == base->next_timer &&
-                    !tbase_get_deferrable(timer->base))
-                        base->next_timer = base->timer_jiffies;
-                ret = 1;
+        if (base->running_timer != timer) {
+                timer_stats_timer_clear_start_info(timer);
+                ret = detach_if_pending(timer, base, true);
         }
-out:
         spin_unlock_irqrestore(&base->lock, flags);
 
         return ret;
@@ -1089,7 +1098,8 @@ static int cascade(struct tvec_base *base, struct tvec *tv, int index)
          */
         list_for_each_entry_safe(timer, tmp, &tv_list, entry) {
                 BUG_ON(tbase_get_base(timer->base) != base);
-                internal_add_timer(base, timer);
+                /* No accounting, while moving them */
+                __internal_add_timer(base, timer);
         }
 
         return index;
@@ -1178,7 +1188,7 @@ static inline void __run_timers(struct tvec_base *base)
                         timer_stats_account_timer(timer);
 
                         base->running_timer = timer;
-                        detach_timer(timer, 1);
+                        detach_expired_timer(timer, base);
 
                         spin_unlock_irq(&base->lock);
                         call_timer_fn(timer, fn, data);
@@ -1316,18 +1326,21 @@ static unsigned long cmp_next_hrtimer_event(unsigned long now,
 unsigned long get_next_timer_interrupt(unsigned long now)
 {
         struct tvec_base *base = __this_cpu_read(tvec_bases);
-        unsigned long expires;
+        unsigned long expires = now + NEXT_TIMER_MAX_DELTA;
 
         /*
          * Pretend that there is no timer pending if the cpu is offline.
          * Possible pending timers will be migrated later to an active cpu.
          */
         if (cpu_is_offline(smp_processor_id()))
-                return now + NEXT_TIMER_MAX_DELTA;
+                return expires;
+
         spin_lock(&base->lock);
-        if (time_before_eq(base->next_timer, base->timer_jiffies))
-                base->next_timer = __next_timer_interrupt(base);
-        expires = base->next_timer;
+        if (base->active_timers) {
+                if (time_before_eq(base->next_timer, base->timer_jiffies))
+                        base->next_timer = __next_timer_interrupt(base);
+                expires = base->next_timer;
+        }
         spin_unlock(&base->lock);
 
         if (time_before_eq(expires, now))
@@ -1704,6 +1717,7 @@ static int __cpuinit init_timers_cpu(int cpu)
 
         base->timer_jiffies = jiffies;
         base->next_timer = base->timer_jiffies;
+        base->active_timers = 0;
         return 0;
 }
 
@@ -1714,11 +1728,9 @@ static void migrate_timer_list(struct tvec_base *new_base, struct list_head *hea
 
         while (!list_empty(head)) {
                 timer = list_first_entry(head, struct timer_list, entry);
-                detach_timer(timer, 0);
+                /* We ignore the accounting on the dying cpu */
+                detach_timer(timer, false);
                 timer_set_base(timer, new_base);
-                if (time_before(timer->expires, new_base->next_timer) &&
-                    !tbase_get_deferrable(timer->base))
-                        new_base->next_timer = timer->expires;
                 internal_add_timer(new_base, timer);
         }
 }