evie/android_kernel_oneplus_msm8998
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cpufreq: interactive: fix race on timer restart on governor start

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Starting the governor, or restarting on a hotplugged-in CPU, can race
with the timer start in idle, triggering a BUG on timer already pending.
Start the timer before setting the enable flag, and use enable_sem to
protect the sequence (and ensure correct order of the update to the
enable flag).  Delete any existing timer for safety.

Change-Id: Ife77cf9fe099e8fd8543224cbf148c6722c2ffb0
Reported-by: Francisco Franco <francisco.franco@cloudcar.com>
Signed-off-by: Todd Poynor <toddpoynor@google.com>
This commit is contained in:
Todd Poynor 2012-12-20 15:51:00 -08:00 • committed by John Stultz
parent 583695f13b
commit 1dc7486fd8
1 changed files with 3 additions and 3 deletions
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6
drivers/cpufreq/cpufreq_interactive.c
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@ -919,17 +919,17 @@ static int cpufreq_governor_interactive(struct cpufreq_policy *policy,
ktime_to_us(ktime_get());
pcpu->hispeed_validate_time =
pcpu->floor_validate_time;
pcpu->governor_enabled = 1;
smp_wmb();
down_write(&pcpu->enable_sem);
expires = jiffies + usecs_to_jiffies(timer_rate);
pcpu->cpu_timer.expires = expires;
add_timer_on(&pcpu->cpu_timer, j);
if (timer_slack_val >= 0) {
expires += usecs_to_jiffies(timer_slack_val);
pcpu->cpu_slack_timer.expires = expires;
add_timer_on(&pcpu->cpu_slack_timer, j);
}
pcpu->governor_enabled = 1;
up_write(&pcpu->enable_sem);
}
/*