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cpufreq : Fix crash input event handler on governor switch

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When an input event and CPU1 hotplug occurs at the same
time, a race condition can happen between cpufreq and
cpu hotplug resulting in a kernel panic.
When a hotplug operation is underway on CPU1,
__cpufreq_remove_dev is called. __cpufreq_remove_dev gets
the lock, proceeds to free the policy info of the current
governor and calls the ondemand governor with a STOP event.
If an input event occurs around the same time, it waits
for __cpufreq_remove_dev to release the lock. Meanwhile,
the ondemand governor clears some of its settings, but
fails to clear its local current policy. As soon as the
input event handler acquires the lock, it now uses the
invalid ondemand current policy handle to make frequency
changes. This results in a kernel panic.

Skip making frequency changes if this condition happens.

CRs-fixed: 327622,319348
Change-Id: I78227352fc66cc3ec5ab095c45eda76a92d1ba46
Signed-off-by: Anitha Anand <anithas@codeaurora.org>
This commit is contained in:
Anitha Anand 2012-01-18 17:17:40 -08:00 committed by Stephen Boyd
parent 64ea8edaa8
commit 988f1224aa
1 changed files with 3 additions and 0 deletions
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3
drivers/cpufreq/cpufreq_ondemand.c
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@ -872,6 +872,9 @@ static int cpufreq_governor_dbs(struct cpufreq_policy *policy,
mutex_lock(&dbs_mutex); mutex_lock(&dbs_mutex);
mutex_destroy(&this_dbs_info->timer_mutex); mutex_destroy(&this_dbs_info->timer_mutex);
dbs_enable--; dbs_enable--;
/* If device is being removed, policy is no longer
* valid. */
this_dbs_info->cur_policy = NULL;
if (!cpu) if (!cpu)
input_unregister_handler(&dbs_input_handler); input_unregister_handler(&dbs_input_handler);
mutex_unlock(&dbs_mutex); mutex_unlock(&dbs_mutex);