Patch "regulator: core: Fix nested locking of supplies" has been added to the 4.4-stable tree

This is a note to let you know that I've just added the patch titled

regulator: core: Fix nested locking of supplies

to the 4.4-stable tree which can be found at:
http://www.kernel.org/git/?p=linux/kernel/git/stable/stable-queue.git;a=summary

The filename of the patch is:
regulator-core-fix-nested-locking-of-supplies.patch
and it can be found in the queue-4.4 subdirectory.

If you, or anyone else, feels it should not be added to the stable tree, please let <[email protected]> know about it.

From: Thierry Reding <[email protected]>
Date: Wed, 2 Dec 2015 16:54:50 +0100
Subject: regulator: core: Fix nested locking of supplies

From: Thierry Reding <[email protected]>

commit 70a7fb80e85ae7f78f8e90cec3fbd862ea6a4d4b upstream.

Commit fa731ac7ea04 ("regulator: core: avoid unused variable warning") introduced a subtle change in how supplies are locked. Where previously code was always locking the regulator of the current iteration, the new implementation only locks the regulator if it has a supply. For any given power tree that means that the root will never get locked.

On the other hand the regulator_unlock_supply() will still release all the locks, which in turn causes the lock debugging code to warn about a mutex being unlocked which wasn't locked.

---
 drivers/regulator/core.c |   11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

@@ -132,6 +132,14 @@ static bool have_full_constraints(void)
 	return has_full_constraints || of_have_populated_dt();
 }
 
+static inline struct regulator_dev *rdev_get_supply(struct regulator_dev *rdev)
+{
+	if (rdev && rdev->supply)
+		return rdev->supply->rdev;
+
+	return NULL;
+}
+
 /**
  * regulator_lock_supply - lock a regulator and its supplies
  * @rdev:         regulator source

@@ -140,8 +148,7 @@ static void regulator_lock_supply(struct
 {
 	int i;
 
-	mutex_lock(&rdev->mutex);
-	for (i = 1; rdev; rdev = rdev->supply->rdev, i++)
+	for (i = 0; rdev; rdev = rdev_get_supply(rdev), i++)
 		mutex_lock_nested(&rdev->mutex, i);
 }
 

Patches currently in stable-queue which might be from [email protected] are

queue-4.4/regulator-core-fix-nested-locking-of-supplies.patch queue-4.4/revert-regulator-core-fix-nested-locking-of-supplies.patch