[PATCH 3.19.y-ckt 155/160] ASoC: Use nested lock for snd_soc_dapm_mutex_lock

From: Kamal Mostafa
Date: Tue Jan 19 2016 - 20:28:47 EST

3.19.8-ckt13 -stable review patch. If anyone has any objections, please let me know.


From: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxxxxxxxx>

commit 783513eec3209542fcd6ac0cbcb030b3c17a4827 upstream.

snd_soc_dapm_mutex_lock currently uses the un-nested call which can
cause lockdep warnings when called from control handlers (a relatively
common usage) and using modules. As creating the control causes a
potential mutex inversion with the handler, creating the control will
take the controls_rwsem under the dapm_mutex and accessing the control
will take the dapm_mutex under controls_rwsem.

All the users look like they want to be using the runtime class of the
lock anyway, so this patch just changes snd_soc_dapm_mutex_lock to use
the nested call, with the SND_SOC_DAPM_CLASS_RUNTIME class.

Fixes: f6d5e586b416 ("ASoC: dapm: Add helpers to lock/unlock DAPM mutex")
Signed-off-by: Charles Keepax <ckeepax@xxxxxxxxxxxxxxxxxxxxxxxxxxx>
Signed-off-by: Mark Brown <broonie@xxxxxxxxxx>
Signed-off-by: Kamal Mostafa <kamal@xxxxxxxxxxxxx>
include/sound/soc.h | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/include/sound/soc.h b/include/sound/soc.h
index c62fcf8..5847d59 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -1514,7 +1514,7 @@ extern const struct dev_pm_ops snd_soc_pm_ops;
/* Helper functions */
static inline void snd_soc_dapm_mutex_lock(struct snd_soc_dapm_context *dapm)
- mutex_lock(&dapm->card->dapm_mutex);
+ mutex_lock_nested(&dapm->card->dapm_mutex, SND_SOC_DAPM_CLASS_RUNTIME);

static inline void snd_soc_dapm_mutex_unlock(struct snd_soc_dapm_context *dapm)