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    Subject[PATCH 4.4 113/163] regulator: core: fix regulator_lock_supply regression
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

    ------------------

    From: Arnd Bergmann <arnd@arndb.de>

    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>

    ---
    drivers/regulator/core.c | 3 ++-
    1 file changed, 2 insertions(+), 1 deletion(-)

    --- a/drivers/regulator/core.c
    +++ b/drivers/regulator/core.c
    @@ -140,7 +140,8 @@ static void regulator_lock_supply(struct
    {
    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);
    }


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