Messages in this thread Patch in this message | | | From | Sascha Hauer <> | Subject | [PATCH 2/6] regulator: core: introduce function to lock regulators and its supplies | Date | Wed, 30 Sep 2015 16:05:42 +0200 |
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Each regulator_dev is locked with its own mutex. This is fine as long as only one regulator_dev is locked, but makes lockdep unhappy when we have to walk up the supply chain like it can happen in regulator_get_voltage:
regulator_get_voltage -> mutex_lock(®ulator->rdev->mutex) -> _regulator_get_voltage(regulator->rdev) -> regulator_get_voltage(rdev->supply) -> mutex_lock(®ulator->rdev->mutex);
This causes lockdep to issue a possible deadlock warning.
There are at least two ways to work around this:
- We can always lock the whole supply chain using the functions introduced with this patch. - We could store the current voltage in struct regulator_rdev so that we do not have to walk up the supply chain for the _regulator_get_voltage case.
Anyway, regulator_lock_supply/regulator_unlock_supply will be needed once we allow regulator_set_voltage to optimize the supply voltages.
Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de> --- drivers/regulator/core.c | 39 +++++++++++++++++++++++++++++++++++++++ 1 file changed, 39 insertions(+)
diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c index bd9db70..e5de3d9 100644 --- a/drivers/regulator/core.c +++ b/drivers/regulator/core.c @@ -132,6 +132,45 @@ static bool have_full_constraints(void) } /** + * regulator_lock_supply - lock a regulator and its supplies + * @rdev: regulator source + */ +static void regulator_lock_supply(struct regulator_dev *rdev) +{ + struct regulator *supply; + int i = 0; + + while (1) { + mutex_lock_nested(&rdev->mutex, i++); + supply = rdev->supply; + + if (!rdev->supply) + return; + + rdev = supply->rdev; + } +} + +/** + * regulator_unlock_supply - unlock a regulator and its supplies + * @rdev: regulator source + */ +static void regulator_unlock_supply(struct regulator_dev *rdev) +{ + struct regulator *supply; + + while (1) { + mutex_unlock(&rdev->mutex); + supply = rdev->supply; + + if (!rdev->supply) + return; + + rdev = supply->rdev; + } +} + +/** * of_get_regulator - get a regulator device node based on supply name * @dev: Device pointer for the consumer (of regulator) device * @supply: regulator supply name -- 2.5.3
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