1 files changed, 61 insertions, 49 deletions

diff --git a/kernel/timer.c b/kernel/timer.c
index 6ec7e7e..a61c093 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);
 	}
 }