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sched_clock: Avoid corrupting hrtimer tree during suspend 

During suspend we call sched_clock_poll() to update the epoch and
accumulated time and reprogram the sched_clock_timer to fire
before the next wrap-around time. Unfortunately,
sched_clock_poll() doesn't restart the timer, instead it relies
on the hrtimer layer to do that and during suspend we aren't
calling that function from the hrtimer layer. Instead, we're
reprogramming the expires time while the hrtimer is enqueued,
which can cause the hrtimer tree to be corrupted. Furthermore, we
restart the timer during suspend but we update the epoch during
resume which seems counter-intuitive.

Let's fix this by saving the accumulated state and canceling the
timer during suspend. On resume we can update the epoch and
restart the timer similar to what we would do if we were starting
the clock for the first time.

Change-Id: Iee2a1cca42e5b681347ea0607e9af420a63892d7
CRs-Fixed: 696826
Fixes: a08ca5d1089d "sched_clock: Use an hrtimer instead of timer"
Signed-off-by: Stephen Boyd <sboyd@codeaurora.org>
This commit is contained in:
Stephen Boyd 2014-07-17 10:40:15 -07:00
parent 548e7c2846
commit 1dc620b1a7
1 changed files with 3 additions and 1 deletions
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4
kernel/time/sched_clock.c
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@ -200,7 +200,8 @@ void __init sched_clock_postinit(void)
static int sched_clock_suspend(void)
{
sched_clock_poll(&sched_clock_timer);
update_sched_clock();
hrtimer_cancel(&sched_clock_timer);
cd.suspended = true;
return 0;
}
@ -208,6 +209,7 @@ static int sched_clock_suspend(void)
static void sched_clock_resume(void)
{
cd.epoch_cyc = read_sched_clock();
hrtimer_start(&sched_clock_timer, cd.wrap_kt, HRTIMER_MODE_REL);
cd.suspended = false;
}