Commit 395913d0 authored Jun 08, 2009 by Mathieu Desnoyers Committed by Dave Jones Sep 01, 2009

[CPUFREQ] remove rwsem lock from CPUFREQ_GOV_STOP call (second call site)



remove rwsem lock from CPUFREQ_GOV_STOP call (second call site)

commit	42a06f21

Missed a call site for CPUFREQ_GOV_STOP to remove the rwlock taken around the
teardown. To make a long story short, the rwlock write-lock causes a circular
dependency with cancel_delayed_work_sync(), because the timer handler takes the
read lock.

Note that all callers to __cpufreq_set_policy are taking the rwsem. All sysfs
callers (writers) hold the write rwsem at the earliest sysfs calling stage.

However, the rwlock write-lock is not needed upon governor stop.

Signed-off-by: Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca>
Acked-by: Venkatesh Pallipadi <venkatesh.pallipadi@intel.com>
CC: rjw@sisk.pl
CC: mingo@elte.hu
CC: Shaohua Li <shaohua.li@intel.com>
CC: Pekka Enberg <penberg@cs.helsinki.fi>
CC: Dave Young <hidave.darkstar@gmail.com>
CC: "Rafael J. Wysocki" <rjw@sisk.pl>
CC: Rusty Russell <rusty@rustcorp.com.au>
CC: trenn@suse.de
CC: sven.wegener@stealer.net
CC: cpufreq@vger.kernel.org
Signed-off-by: Dave Jones <davej@redhat.com>

parent 0e625ac1

drivers/cpufreq/cpufreq.c

+12 −1

Original line number	Diff line number	Diff line
		@@ -61,6 +61,8 @@ static DEFINE_SPINLOCK(cpufreq_driver_lock);
		* are concerned with are online after they get the lock.
		* - Governor routines that can be called in cpufreq hotplug path should not
		* take this sem as top level hotplug notifier handler takes this.
		* - Lock should not be held across
		* __cpufreq_governor(data, CPUFREQ_GOV_STOP);
		*/
		static DEFINE_PER_CPU(int, policy_cpu);
		static DEFINE_PER_CPU(struct rw_semaphore, cpu_policy_rwsem);
		@@ -1707,8 +1709,17 @@ static int __cpufreq_set_policy(struct cpufreq_policy *data,
		dprintk("governor switch\n");

		/* end old governor */
		if (data->governor)
		if (data->governor) {
		/*
		* Need to release the rwsem around governor
		* stop due to lock dependency between
		* cancel_delayed_work_sync and the read lock
		* taken in the delayed work handler.
		*/
		unlock_policy_rwsem_write(data->cpu);
		__cpufreq_governor(data, CPUFREQ_GOV_STOP);
		lock_policy_rwsem_write(data->cpu);
		}

		/* start new governor */
		data->governor = policy->governor;

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