timers: Reduce __run_timers() latency for empty list

[firefly-linux-kernel-4.4.55.git] / kernel / timer.c

diff --git a/kernel/timer.c b/kernel/timer.c
index fdc43834f3afc5deb6e83e8c674baf74c31ad585..c8bc7091d8f37c1e817baba6b618f350103d4d52 100644 (file)
--- a/kernel/timer.c
+++ b/kernel/timer.c
@@ -338,6 +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)
 {
@@ -1150,6 +1164,10 @@ 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;