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stm class: Fix locking in unbinding policy path

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[ Upstream commit 4c127fd16e ]

Right now, if stm device removal has to unbind from a policy (that is,
an stm device that has STP policy, gets removed), it will trigger a
nested lock on the stm device's policy mutex.

This patch fixes the problem by moving the locking from the policy
unbinding to policy removal (configfs path), where it's actually needed;
the other caller of the policy unbinding function already takes the
mutex around the call.

Signed-off-by: Alexander Shishkin <alexander.shishkin@linux.intel.com>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
Signed-off-by: Sasha Levin <sashal@kernel.org>
This commit is contained in:
Alexander Shishkin
2015-12-22 17:25:18 +02:00
committed by Greg Kroah-Hartman
parent 03d7b4edf7
commit a556f0babe
1 changed files with 15 additions and 3 deletions
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18
drivers/hwtracing/stm/policy.c
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@@ -272,13 +272,17 @@ void stp_policy_unbind(struct stp_policy *policy)
{
struct stm_device *stm = policy->stm;
/*
* stp_policy_release() will not call here if the policy is already
* unbound; other users should not either, as no link exists between
* this policy and anything else in that case
*/
if (WARN_ON_ONCE(!policy->stm))
return;
mutex_lock(&stm->policy_mutex);
stm->policy = NULL;
mutex_unlock(&stm->policy_mutex);
lockdep_assert_held(&stm->policy_mutex);
stm->policy = NULL;
policy->stm = NULL;
stm_put_device(stm);
@@ -287,8 +291,16 @@ void stp_policy_unbind(struct stp_policy *policy)
static void stp_policy_release(struct config_item *item)
{
struct stp_policy *policy = to_stp_policy(item);
struct stm_device *stm = policy->stm;
/* a policy *can* be unbound and still exist in configfs tree */
if (!stm)
return;
mutex_lock(&stm->policy_mutex);
stp_policy_unbind(policy);
mutex_unlock(&stm->policy_mutex);
kfree(policy);
}