linux-kernel - [PATCH] regulator: recursive locking detected

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Message-ID: <1301650411-17762-1-git-send-email-robert.rosengren@stericsson.com>
Date:	Fri, 1 Apr 2011 11:33:31 +0200
From:	Robert Rosengren <robert.rosengren@...ricsson.com>
To:	Liam Girdwood <lrg@...mlogic.co.uk>,
	Mark Brown <broonie@...nsource.wolfsonmicro.com>,
	<linux-kernel@...r.kernel.org>
Cc:	Bengt Jonsson <bengt.g.jonsson@...ricsson.com>,
	Linus Walleij <linus.walleij@...aro.org>,
	Robert Rosengren <robert.rosengren@...ricsson.com>
Subject: [PATCH] regulator: recursive locking detected

"possible recursive locking detected"-warnings are issued when a
regulator has specified supply regulator. Both when enabling and
disabling regulators uses recursive call chains for notify the supply
regulators. 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.

Signed-off-by: Robert Rosengren <robert.rosengren@...ricsson.com>
Acked-by: Linus Walleij <linus.walleij@...aro.org>
---
 drivers/regulator/core.c |   20 ++++++++++++--------
 1 files changed, 12 insertions(+), 8 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 3ffc697..2a66c6b 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -87,7 +87,7 @@ 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 int _regulator_do_set_voltage(struct regulator_dev *rdev,
 				     int min_uV, int max_uV);
 
@@ -1407,7 +1407,7 @@ static int _regulator_disable(struct regulator_dev *rdev,
 			trace_regulator_disable_complete(rdev_get_name(rdev));
 
 			_notifier_call_chain(rdev, REGULATOR_EVENT_DISABLE,
-					     NULL);
+					     NULL, 0);
 		}
 
 		/* decrease our supplies ref count and disable if required */
@@ -1477,7 +1477,7 @@ 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 */
@@ -1699,7 +1699,7 @@ static int _regulator_do_set_voltage(struct regulator_dev *rdev,
 
 	if (ret == 0)
 		_notifier_call_chain(rdev, REGULATOR_EVENT_VOLTAGE_CHANGE,
-				     NULL);
+				     NULL, 0);
 
 	trace_regulator_set_voltage_complete(rdev_get_name(rdev), selector);
 
@@ -2167,19 +2167,23 @@ 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);
 	}
 }
@@ -2333,7 +2337,7 @@ 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;
 
 }
-- 
1.7.4.1

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