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authorZhenzhong Duan <[email protected]>2017-10-08 20:55:59 -0700
committerThomas Gleixner <[email protected]>2017-10-18 15:29:33 +0200
commitc310ce4dcb9df9b2f1be82caff7dae609fe53f72 (patch)
tree8fa396c14f6322c0c1eec01b7abd28f4cf25d6fc
parentb93ab338f7f0e39321b282d694a52736fdab172b (diff)
timers: Avoid an unnecessary iteration in __run_timers()
If the base clock is behind jiffies in the soft irq expiry code then the next timer is retrieved by get_next_timer_interrupt() to avoid incrementing base clock one by one. If the next timer interrupt is past current jiffies then the base clock is set to jiffies - 1. At the call site this is incremented and another iteration through the expiry loop is executed which checks empty hash buckets. That's a pointless excercise because it's already known that the next timer is past jiffies. Set the base clock in that case to jiffies directly so it gets incremented to jiffies + 1 at the call site resulting in immediate termination of the expiry loop. [ tglx: Massaged changelog and added comment to the code ] Signed-off-by: Zhenzhong Duan <[email protected]> Signed-off-by: Thomas Gleixner <[email protected]> Acked-by: Anna-Maria Gleixner <[email protected]> Cc: Joe Jin <[email protected]> Cc: [email protected] Cc: Srinivas Reddy Eeda <[email protected]> Cc: [email protected] Link: https://lkml.kernel.org/r/7086a857-f90c-4616-bbe8-f7696f21626c@default
-rw-r--r--kernel/time/timer.c7
1 files changed, 5 insertions, 2 deletions
diff --git a/kernel/time/timer.c b/kernel/time/timer.c
index 38613ced2324..ee1a88d8afb2 100644
--- a/kernel/time/timer.c
+++ b/kernel/time/timer.c
@@ -1560,8 +1560,11 @@ static int collect_expired_timers(struct timer_base *base,
* jiffies, otherwise forward to the next expiry time:
*/
if (time_after(next, jiffies)) {
- /* The call site will increment clock! */
- base->clk = jiffies - 1;
+ /*
+ * The call site will increment base->clk and then
+ * terminate the expiry loop immediately.
+ */
+ base->clk = jiffies;
return 0;
}
base->clk = next;