regulator: recursive locking detected when notifying supply regulators

A "possible recursive locking detected"-warning is issued when a
regulator has supply regulators and it shall notify the call chain.
This is due to locking mutexes of the same lock class, i.e. the locks
reside in the regulator_dev struct.

Since this is valid behavior for the regulators, this patch changes the
mutex lock into nested, as suggested in lockdep-design.txt.

ST-Ericsson ID: 283165
ST-Ericsson FOSS-OUT ID: Trivial

Change-Id: I8e9eae92783414dc49a99c44b7970a246aa9c273
Signed-off-by: Robert Rosengren <robert.rosengren@stericsson.com>
Reviewed-on: http://gerrit.lud.stericsson.com/gerrit/18538
Reviewed-by: Daniel WILLERUD <daniel.willerud@stericsson.com>
Reviewed-by: Jonas ABERG <jonas.aberg@stericsson.com>

1 files changed, 12 insertions, 8 deletions

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 16ee76f9930..0d78dfa7476 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -70,7 +70,7 @@ 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);
 static void _notifier_call_chain(struct regulator_dev *rdev,
-				  unsigned long event, void *data);
+				  unsigned long event, void *data, int lock_sublevel);
 
 static const char *rdev_get_name(struct regulator_dev *rdev)
 {
@@ -1408,7 +1408,7 @@ static int _regulator_disable(struct regulator_dev *rdev,
 			}
 
 			_notifier_call_chain(rdev, REGULATOR_EVENT_DISABLE,
-					     NULL);
+					     NULL, 0);
 		}
 
 		/* decrease our supplies ref count and disable if required */
@@ -1482,7 +1482,7 @@ static int _regulator_force_disable(struct regulator_dev *rdev,
 		}
 		/* notify other consumers that power has been forced off */
 		_notifier_call_chain(rdev, REGULATOR_EVENT_FORCE_DISABLE |
-			REGULATOR_EVENT_DISABLE, NULL);
+			REGULATOR_EVENT_DISABLE, NULL, 0);
 	}
 
 	/* decrease our supplies ref count and disable if required */
@@ -1670,7 +1670,7 @@ int regulator_set_voltage(struct regulator *regulator, int min_uV, int max_uV)
 	ret = rdev->desc->ops->set_voltage(rdev, min_uV, max_uV);
 
 out:
-	_notifier_call_chain(rdev, REGULATOR_EVENT_VOLTAGE_CHANGE, NULL);
+	_notifier_call_chain(rdev, REGULATOR_EVENT_VOLTAGE_CHANGE, NULL, 0);
 	mutex_unlock(&rdev->mutex);
 	return ret;
 }
@@ -1983,19 +1983,23 @@ EXPORT_SYMBOL_GPL(regulator_unregister_notifier);
 
 /* notify regulator consumers and downstream regulator consumers.
  * Note mutex must be held by caller.
+ * lock_sublevel should always be 0, only used for recursive calls.
  */
 static void _notifier_call_chain(struct regulator_dev *rdev,
-				  unsigned long event, void *data)
+				  unsigned long event, void *data, int lock_sublevel)
 {
 	struct regulator_dev *_rdev;
 
 	/* call rdev chain first */
 	blocking_notifier_call_chain(&rdev->notifier, event, NULL);
 
+	/* increase sublevel before stepping into nested regulators */
+	lock_sublevel++;
+
 	/* now notify regulator we supply */
 	list_for_each_entry(_rdev, &rdev->supply_list, slist) {
-		mutex_lock(&_rdev->mutex);
-		_notifier_call_chain(_rdev, event, data);
+		mutex_lock_nested(&_rdev->mutex, lock_sublevel);
+		_notifier_call_chain(_rdev, event, data, lock_sublevel);
 		mutex_unlock(&_rdev->mutex);
 	}
 }
@@ -2150,7 +2154,7 @@ EXPORT_SYMBOL_GPL(regulator_bulk_free);
 int regulator_notifier_call_chain(struct regulator_dev *rdev,
 				  unsigned long event, void *data)
 {
-	_notifier_call_chain(rdev, event, data);
+	_notifier_call_chain(rdev, event, data, 0);
 	return NOTIFY_DONE;
 
 }