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Commit 755b7a41 authored by Todd Poynor's avatar Todd Poynor Committed by Amit Pundir
Browse files

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: default avatarFrancisco Franco <francisco.franco@cloudcar.com>
Signed-off-by: default avatarTodd Poynor <toddpoynor@google.com>
parent 4235053a

drivers/cpufreq/cpufreq_interactive.c

+3 −3
Original line number Diff line number Diff line
@@ -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);

		}



		/*