Applied "regulator: core: fix regulator_lock_supply regression" to the regulator tree

[Mark Brown <broonie@kernel.org>]

The patch

   regulator: core: fix regulator_lock_supply regression

has been applied to the regulator tree at

   git://git.kernel.org/pub/scm/linux/kernel/git/broonie/regulator.git 

All being well this means that it will be integrated into the linux-next
tree (usually sometime in the next 24 hours) and sent to Linus during
the next merge window (or sooner if it is a bug fix), however if
problems are discovered then the patch may be dropped or reverted.  

You may get further e-mails resulting from automated or manual testing
and review of the tree, please engage with people reporting problems and
send followup patches addressing any issues that are reported if needed.

If any updates are required or you are submitting further changes they
should be sent as incremental updates against current git, existing
patches will not be replaced.

Please add any relevant lists and maintainers to the CCs when replying
to this mail.

Thanks,
Mark

>From bb41897e38c53458a88b271f2fbcd905ee1f9584 Mon Sep 17 00:00:00 2001
From: Arnd Bergmann <arnd@arndb.de>
Date: Fri, 27 Nov 2015 14:46:41 +0100
Subject: [PATCH] regulator: core: fix regulator_lock_supply regression

As noticed by Geert Uytterhoeven, my patch to avoid a harmless build warning
in regulator_lock_supply() was total crap and introduced a real bug:

> [ BUG: bad unlock balance detected! ]
> kworker/u4:0/6 is trying to release lock (&rdev->mutex) at:
> [<c0247b84>] regulator_set_voltage+0x38/0x50

we still lock the regulator supplies, but not the actual regulators,
so we are missing a lock, and the unlock is unbalanced.

This rectifies it by first locking the regulator device itself before
using the same loop as before to lock its supplies.

Reported-by: Geert Uytterhoeven <geert@linux-m68k.org>
Signed-off-by: Arnd Bergmann <arnd@arndb.de>
Fixes: 716fec9d1965 ("[SUBMITTED] regulator: core: avoid unused variable warning")
Signed-off-by: Mark Brown <broonie@kernel.org>
---
 drivers/regulator/core.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index c70017d5f74b..daffff83ced2 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -140,7 +140,8 @@ static void regulator_lock_supply(struct regulator_dev *rdev)
 {
 	int i;
 
-	for (i = 0; rdev->supply; rdev = rdev->supply->rdev, i++)
+	mutex_lock(&rdev->mutex);
+	for (i = 1; rdev->supply; rdev = rdev->supply->rdev, i++)
 		mutex_lock_nested(&rdev->mutex, i);
 }
 
-- 
2.6.2