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| author | Mathieu Desnoyers <mathieu.desnoyers@polymtl.ca> | 2009-06-08 13:17:31 -0400 |
|---|---|---|
| committer | Dave Jones <davej@redhat.com> | 2009-09-01 12:45:18 -0400 |
| commit | 395913d0b1db37092ea3d9d69b832183b1dd84c5 (patch) | |
| tree | 2b1aff8df27bfb02332ee4fe207a989244583c0a /drivers/cpufreq/cpufreq.c | |
| parent | 0e625ac153126a0a62b7635fa9dc91f87ff39e38 (diff) | |
| download | lwn-395913d0b1db37092ea3d9d69b832183b1dd84c5.tar.gz lwn-395913d0b1db37092ea3d9d69b832183b1dd84c5.zip | |
[CPUFREQ] remove rwsem lock from CPUFREQ_GOV_STOP call (second call site)
remove rwsem lock from CPUFREQ_GOV_STOP call (second call site)
commit 42a06f2166f2f6f7bf04f32b4e823eacdceafdc9
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>
Diffstat (limited to 'drivers/cpufreq/cpufreq.c')
| -rw-r--r-- | drivers/cpufreq/cpufreq.c | 13 |
1 files changed, 12 insertions, 1 deletions
diff --git a/drivers/cpufreq/cpufreq.c b/drivers/cpufreq/cpufreq.c index 4da28444b235..3938c7817095 100644 --- a/drivers/cpufreq/cpufreq.c +++ b/drivers/cpufreq/cpufreq.c @@ -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; |