Commit b55a0de8 authored Nov 03, 2014 by Vikram Mulukutla Committed by Karthik Parsha Nov 06, 2014

PM / devfreq: Workaround cpufreq REMOVE_POLICY versus hotplug lock race



It is not possible to ensure the synchronization of REMOVE_POLICY
notifications with CPU hotplug lock; {get,put}_online_cpus ensures
that hotplug cannot happen, but it is still possible to receive
REMOVE_POLICY notifications asynchronously while checking for online
CPUs within a {get,put}_online_cpus critical section.

Account for this by detecting that we haven't yet setup a local state
when the REMOVE_POLICY notification comes in.

Change-Id: I3cb750f3984ebe078154734444660675e8d8b5bc
Signed-off-by: Vikram Mulukutla <markivx@codeaurora.org>

parent 53e6e12c

drivers/devfreq/governor_cpufreq.c

+4 −2

Original line number	Original line	Diff line number	Diff line
	@@ -189,8 +189,10 @@ static int cpufreq_policy_notifier(struct notifier_block *nb,

	case CPUFREQ_REMOVE_POLICY:		case CPUFREQ_REMOVE_POLICY:
	mutex_lock(&state_lock);		mutex_lock(&state_lock);
			if (state[policy->cpu]) {
	state[policy->cpu]->on = false;		state[policy->cpu]->on = false;
	update_all_devfreqs();		update_all_devfreqs();
			}
	mutex_unlock(&state_lock);		mutex_unlock(&state_lock);
	break;		break;
	}		}