linux-kernel - [PATCH] regulator: Add lockdep asserts to help detecting locking misuse

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Date:	Wed, 10 Jun 2015 15:23:12 +0900
From:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
To:	Liam Girdwood <lgirdwood@...il.com>,
	Mark Brown <broonie@...nel.org>, linux-kernel@...r.kernel.org
Cc:	Krzysztof Kozlowski <k.kozlowski@...sung.com>
Subject: [PATCH] regulator: Add lockdep asserts to help detecting locking misuse

Add lockdep_assert_held_once() to functions explicitly mentioning that
rdev or regulator_list mutex must be held. Using WARN_ONCE shouldn't
pollute the dmesg to much.

The patch (if CONFIG_LOCKDEP enabled) will show warnings in certain
regulators calling regulator_notifier_call_chain() without rdev->mutex
held.

Signed-off-by: Krzysztof Kozlowski <k.kozlowski@...sung.com>

---

Warnings for missing locks when calling regulator_notifier_call_chain()
should appear on many regulators except wm8350-regulator.c, e.g.:
da9055-regulator.c, da9062-regulator.c, da9063-regulator.c,
da9211-regulator.c, wm831x-dcdc.c and few more.

The question is whether the lock during that call should be held?
---
 drivers/regulator/core.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 443eaab933fc..2d11731db7cb 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -640,6 +640,8 @@ static int drms_uA_update(struct regulator_dev *rdev)
 	int current_uA = 0, output_uV, input_uV, err;
 	unsigned int mode;
 
+	lockdep_assert_held_once(&rdev->mutex);
+
 	/*
 	 * first check to see if we can set modes at all, otherwise just
 	 * tell the consumer everything is OK.
@@ -758,6 +760,8 @@ static int suspend_set_state(struct regulator_dev *rdev,
 /* locks held by caller */
 static int suspend_prepare(struct regulator_dev *rdev, suspend_state_t state)
 {
+	lockdep_assert_held_once(&rdev->mutex);
+
 	if (!rdev->constraints)
 		return -EINVAL;
 
@@ -1555,6 +1559,8 @@ static void _regulator_put(struct regulator *regulator)
 	if (regulator == NULL || IS_ERR(regulator))
 		return;
 
+	lockdep_assert_held_once(&regulator_list_mutex);
+
 	rdev = regulator->rdev;
 
 	debugfs_remove_recursive(regulator->debugfs);
@@ -1933,6 +1939,8 @@ static int _regulator_enable(struct regulator_dev *rdev)
 {
 	int ret;
 
+	lockdep_assert_held_once(&rdev->mutex);
+
 	/* check voltage and requested load before enabling */
 	if (rdev->constraints &&
 	    (rdev->constraints->valid_ops_mask & REGULATOR_CHANGE_DRMS))
@@ -2033,6 +2041,8 @@ static int _regulator_disable(struct regulator_dev *rdev)
 {
 	int ret = 0;
 
+	lockdep_assert_held_once(&rdev->mutex);
+
 	if (WARN(rdev->use_count <= 0,
 		 "unbalanced disables for %s\n", rdev_get_name(rdev)))
 		return -EIO;
@@ -2111,6 +2121,8 @@ static int _regulator_force_disable(struct regulator_dev *rdev)
 {
 	int ret = 0;
 
+	lockdep_assert_held_once(&rdev->mutex);
+
 	ret = _notifier_call_chain(rdev, REGULATOR_EVENT_FORCE_DISABLE |
 			REGULATOR_EVENT_PRE_DISABLE, NULL);
 	if (ret & NOTIFY_STOP_MASK)
@@ -3407,6 +3419,8 @@ EXPORT_SYMBOL_GPL(regulator_bulk_free);
 int regulator_notifier_call_chain(struct regulator_dev *rdev,
 				  unsigned long event, void *data)
 {
+	lockdep_assert_held_once(&rdev->mutex);
+
 	_notifier_call_chain(rdev, event, data);
 	return NOTIFY_DONE;
 
-- 
1.9.1

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