From: Todd Poynor Date: Thu, 20 Dec 2012 23:51:00 +0000 (-0800) Subject: cpufreq: interactive: fix race on timer restart on governor start X-Git-Tag: firefly_0821_release~2958^2~278 X-Git-Url: http://demsky.eecs.uci.edu/git/?a=commitdiff_plain;h=1dc7486fd81019314463d5077d8b4d13c41f3b34;p=firefly-linux-kernel-4.4.55.git cpufreq: interactive: fix race on timer restart on governor start 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 Signed-off-by: Todd Poynor --- diff --git a/drivers/cpufreq/cpufreq_interactive.c b/drivers/cpufreq/cpufreq_interactive.c index 74f56093d2f3..d22d162c9f27 100644 --- a/drivers/cpufreq/cpufreq_interactive.c +++ b/drivers/cpufreq/cpufreq_interactive.c @@ -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); } /*