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    Subject[PATCH 4.4 115/163] regulator: core: Fix nested locking of supplies
    Date
    4.4-stable review patch.  If anyone has any objections, please let me know.

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

    From: Thierry Reding <treding@nvidia.com>

    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.

    Cc: Mark Brown <broonie@kernel.org>
    Cc: Arnd Bergmann <arnd@arndb.de>
    Fixes: fa731ac7ea04 ("regulator: core: avoid unused variable warning")
    Signed-off-by: Thierry Reding <treding@nvidia.com>
    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 | 11 +++++++++--
    1 file changed, 9 insertions(+), 2 deletions(-)

    --- a/drivers/regulator/core.c
    +++ b/drivers/regulator/core.c
    @@ -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);
    }


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