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Commit 8cbf811d authored by Jeffrey Carlyle's avatar Jeffrey Carlyle Committed by Liam Girdwood
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regulator: avoid deadlock when disabling regulator with supply 



I have a regulator A that sets regulator B as its supply. When I call
set_supply to add B as the supply for A, regulator A gets added to the
supply_list for regulator B.

When I call regulator_disable(A), I end up with a call chain like this:

regulator_disable(A)
> mutex_lock(A)
> _regulator_disable(A)
>> _regulator_disable(B)
>>> _notifier_call_chain(B)
>>>> mutex_lock(A)

Which results in dead lock since we are trying to acquire the mutex lock
for regulator A which we already hold.

This patch addresses this issue by moving the call to disable regulator
B outside of the lock aquired inside the initial call to
regulator_disable.

This change also addresses the issue of not acquiring the mutex for
regulator B before calling _regulator_disable(B).

Signed-off-by: default avatarJeffrey Carlyle <jeff.carlyle@motorola.com>
Acked-by: default avatarMark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: default avatarLiam Girdwood <lrg@slimlogic.co.uk>
parent 688fe99a

drivers/regulator/core.c

+26 −9
Original line number Diff line number Diff line
@@ -64,7 +64,8 @@ struct regulator { 
};



static int _regulator_is_enabled(struct regulator_dev *rdev);

static int _regulator_disable(struct regulator_dev *rdev);

static int _regulator_disable(struct regulator_dev *rdev,

		struct regulator_dev **supply_rdev_ptr);

static int _regulator_get_voltage(struct regulator_dev *rdev);

static int _regulator_get_current_limit(struct regulator_dev *rdev);

static unsigned int _regulator_get_mode(struct regulator_dev *rdev);
@@ -1354,7 +1355,8 @@ int regulator_enable(struct regulator *regulator) 
EXPORT_SYMBOL_GPL(regulator_enable);



/* locks held by regulator_disable() */

static int _regulator_disable(struct regulator_dev *rdev)

static int _regulator_disable(struct regulator_dev *rdev,

		struct regulator_dev **supply_rdev_ptr)

{

	int ret = 0;
@@ -1382,8 +1384,7 @@ static int _regulator_disable(struct regulator_dev *rdev) 
		}



		/* decrease our supplies ref count and disable if required */

		if (rdev->supply)

			_regulator_disable(rdev->supply);

		*supply_rdev_ptr = rdev->supply;



		rdev->use_count = 0;

	} else if (rdev->use_count > 1) {
@@ -1413,17 +1414,29 @@ static int _regulator_disable(struct regulator_dev *rdev) 
int regulator_disable(struct regulator *regulator)

{

	struct regulator_dev *rdev = regulator->rdev;

	struct regulator_dev *supply_rdev = NULL;

	int ret = 0;



	mutex_lock(&rdev->mutex);

	ret = _regulator_disable(rdev);

	ret = _regulator_disable(rdev, &supply_rdev);

	mutex_unlock(&rdev->mutex);



	/* decrease our supplies ref count and disable if required */

	while (supply_rdev != NULL) {

		rdev = supply_rdev;



		mutex_lock(&rdev->mutex);

		_regulator_disable(rdev, &supply_rdev);

		mutex_unlock(&rdev->mutex);

	}



	return ret;

}

EXPORT_SYMBOL_GPL(regulator_disable);



/* locks held by regulator_force_disable() */

static int _regulator_force_disable(struct regulator_dev *rdev)

static int _regulator_force_disable(struct regulator_dev *rdev,

		struct regulator_dev **supply_rdev_ptr)

{

	int ret = 0;
@@ -1442,8 +1455,7 @@ static int _regulator_force_disable(struct regulator_dev *rdev) 
	}



	/* decrease our supplies ref count and disable if required */

	if (rdev->supply)

		_regulator_disable(rdev->supply);

	*supply_rdev_ptr = rdev->supply;



	rdev->use_count = 0;

	return ret;
@@ -1460,12 +1472,17 @@ static int _regulator_force_disable(struct regulator_dev *rdev) 
 */

int regulator_force_disable(struct regulator *regulator)

{

	struct regulator_dev *supply_rdev = NULL;

	int ret;



	mutex_lock(&regulator->rdev->mutex);

	regulator->uA_load = 0;

	ret = _regulator_force_disable(regulator->rdev);

	ret = _regulator_force_disable(regulator->rdev, &supply_rdev);

	mutex_unlock(&regulator->rdev->mutex);



	if (supply_rdev)

		regulator_disable(get_device_regulator(rdev_get_dev(supply_rdev)));



	return ret;

}

EXPORT_SYMBOL_GPL(regulator_force_disable);