Merge branch 'timers.2014.02.25a' of git://git.kernel.org/pub/scm/linux/kernel/git/paulmck/linux-rcu into timers/core

Signed-off-by: Thomas Gleixner <tglx@linutronix.de>

1 files changed, 28 insertions, 2 deletions

diff --git a/kernel/timer.c b/kernel/timer.c
index b75e7893be14..a71bdfdb51e7 100644
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -81,6 +81,7 @@ struct tvec_base {
         unsigned long timer_jiffies;
         unsigned long next_timer;
         unsigned long active_timers;
+        unsigned long all_timers;
         struct tvec_root tv1;
         struct tvec tv2;
         struct tvec tv3;
@@ -337,6 +338,20 @@ void set_timer_slack(struct timer_list *timer, int slack_hz)
 }
 EXPORT_SYMBOL_GPL(set_timer_slack);
 
+/*
+ * If the list is empty, catch up ->timer_jiffies to the current time.
+ * The caller must hold the tvec_base lock.  Returns true if the list
+ * was empty and therefore ->timer_jiffies was updated.
+ */
+static bool catchup_timer_jiffies(struct tvec_base *base)
+{
+        if (!base->all_timers) {
+                base->timer_jiffies = jiffies;
+                return true;
+        }
+        return false;
+}
+
 static void
 __internal_add_timer(struct tvec_base *base, struct timer_list *timer)
 {
@@ -383,15 +398,17 @@ __internal_add_timer(struct tvec_base *base, struct timer_list *timer)
 
 static void internal_add_timer(struct tvec_base *base, struct timer_list *timer)
 {
+        (void)catchup_timer_jiffies(base);
         __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))
+                if (!base->active_timers++ ||
+                    time_before(timer->expires, base->next_timer))
                         base->next_timer = timer->expires;
-                base->active_timers++;
         }
+        base->all_timers++;
 }
 
 #ifdef CONFIG_TIMER_STATS
@@ -671,6 +688,8 @@ detach_expired_timer(struct timer_list *timer, struct tvec_base *base)
         detach_timer(timer, true);
         if (!tbase_get_deferrable(timer->base))
                 base->active_timers--;
+        base->all_timers--;
+        (void)catchup_timer_jiffies(base);
 }
 
 static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
@@ -685,6 +704,8 @@ static int detach_if_pending(struct timer_list *timer, struct tvec_base *base,
                 if (timer->expires == base->next_timer)
                         base->next_timer = base->timer_jiffies;
         }
+        base->all_timers--;
+        (void)catchup_timer_jiffies(base);
         return 1;
 }
 
@@ -1153,6 +1174,10 @@ static inline void __run_timers(struct tvec_base *base)
         struct timer_list *timer;
 
         spin_lock_irq(&base->lock);
+        if (catchup_timer_jiffies(base)) {
+                spin_unlock_irq(&base->lock);
+                return;
+        }
         while (time_after_eq(jiffies, base->timer_jiffies)) {
                 struct list_head work_list;
                 struct list_head *head = &work_list;
@@ -1566,6 +1591,7 @@ static int init_timers_cpu(int cpu)
         base->timer_jiffies = jiffies;
         base->next_timer = base->timer_jiffies;
         base->active_timers = 0;
+        base->all_timers = 0;
         return 0;
 }