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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: Jeffrey Carlyle <jeff.carlyle@motorola.com>
Acked-by: Mark Brown <broonie@opensource.wolfsonmicro.com>
Signed-off-by: Liam Girdwood <lrg@slimlogic.co.uk>
This commit is contained in:
Jeffrey Carlyle 2010-10-08 14:49:19 -05:00 committed by Liam Girdwood
parent 688fe99a43
commit 8cbf811dfd
1 changed files with 26 additions and 9 deletions
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35
drivers/regulator/core.c
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@ -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);