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Subject[PATCH 26/38] tick-sched: don't call update_wall_time() when delta is lesser than tick_period
Date
In tick_do_update_jiffies64() we are processing ticks only if delta is greater
than tick_period. This is what we are supposed to do here and it broke a bit
with this patch:

commit 47a1b796306356f358e515149d86baf0cc6bf007
Author: John Stultz <john.stultz@linaro.org>
Date: Thu Dec 12 13:10:55 2013 -0800

tick/timekeeping: Call update_wall_time outside the jiffies lock

With above patch, we might end up calling update_wall_time() even if delta is
found to be smaller that tick_period. Fix this by reversing the check and
returning early.

Cc: John Stultz <john.stultz@linaro.org>
Signed-off-by: Viresh Kumar <viresh.kumar@linaro.org>
---
kernel/time/tick-sched.c | 32 +++++++++++++++++---------------
1 file changed, 17 insertions(+), 15 deletions(-)

diff --git a/kernel/time/tick-sched.c b/kernel/time/tick-sched.c
index b7b09b9..bff7f97 100644
--- a/kernel/time/tick-sched.c
+++ b/kernel/time/tick-sched.c
@@ -65,26 +65,28 @@ static void tick_do_update_jiffies64(ktime_t now)
write_seqlock(&jiffies_lock);

delta = ktime_sub(now, last_jiffies_update);
- if (delta.tv64 >= tick_period.tv64) {
-
- delta = ktime_sub(delta, tick_period);
- last_jiffies_update = ktime_add(last_jiffies_update,
- tick_period);
+ if (delta.tv64 < tick_period.tv64) {
+ write_sequnlock(&jiffies_lock);
+ return;
+ }

- /* Slow path for long timeouts */
- if (unlikely(delta.tv64 >= tick_period.tv64)) {
- s64 incr = ktime_to_ns(tick_period);
+ delta = ktime_sub(delta, tick_period);
+ last_jiffies_update = ktime_add(last_jiffies_update, tick_period);

- ticks = ktime_divns(delta, incr);
+ /* Slow path for long timeouts */
+ if (unlikely(delta.tv64 >= tick_period.tv64)) {
+ s64 incr = ktime_to_ns(tick_period);

- last_jiffies_update = ktime_add_ns(last_jiffies_update,
- incr * ticks);
- }
- do_timer(++ticks);
+ ticks = ktime_divns(delta, incr);

- /* Keep the tick_next_period variable up to date */
- tick_next_period = ktime_add(last_jiffies_update, tick_period);
+ last_jiffies_update = ktime_add_ns(last_jiffies_update,
+ incr * ticks);
}
+ do_timer(++ticks);
+
+ /* Keep the tick_next_period variable up to date */
+ tick_next_period = ktime_add(last_jiffies_update, tick_period);
+
write_sequnlock(&jiffies_lock);
update_wall_time();
}
--
1.7.12.rc2.18.g61b472e


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