[3.16.y-ckt stable] Patch "ASoC: Use nested lock for snd_soc_dapm_mutex_lock" has been added to the 3.16.y-ckt tree

[Luis Henriques]

This is a note to let you know that I have just added a patch titled

    ASoC: Use nested lock for snd_soc_dapm_mutex_lock

to the linux-3.16.y-queue branch of the 3.16.y-ckt extended stable tree 
which can be found at:

    http://kernel.ubuntu.com/git/ubuntu/linux.git/log/?h=linux-3.16.y-queue

This patch is scheduled to be released in version 3.16.7-ckt23.

If you, or anyone else, feels it should not be added to this tree, please 
reply to this email.

For more information about the 3.16.y-ckt tree, see
https://wiki.ubuntu.com/Kernel/Dev/ExtendedStable

Thanks.
-Luis

---8<------------------------------------------------------------

>From c51d615074406a406c4f6e97dd8afb3fe1bc7733 Mon Sep 17 00:00:00 2001
From: Charles Keepax <ckeepax at opensource.wolfsonmicro.com>
Date: Tue, 29 Dec 2015 16:25:13 +0000
Subject: ASoC: Use nested lock for snd_soc_dapm_mutex_lock

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 at opensource.wolfsonmicro.com>
Signed-off-by: Mark Brown <broonie at kernel.org>
Signed-off-by: Luis Henriques <luis.henriques at canonical.com>
---
 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 a34d34649195..4dc6904ebbf9 100644
--- a/include/sound/soc.h
+++ b/include/sound/soc.h
@@ -1390,7 +1390,7 @@ 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)