regulator: core: fix regulator_lock_supply regression

commit bb41897e38c53458a88b271f2fbcd905ee1f9584 upstream.

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>
Cc: Guenter Roeck <linux@roeck-us.net>
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index c70017d5f74bb2d1305eb5d3f35a2885fbf9b51f..daffff83ced2a6177db324c82d38803c9a411da1 100644 (file)
--- 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);
 }