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[PATCH 2/6] regulator: core: introduce function to lock regulators and its supplies

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  [PATCH 2/6] regulator: core: introduce function to lock regulators and its supplies Sascha Hauer <s.hauer@pengutronix.de> - 2015-09-30 16:10 +0200
    Re: [PATCH 2/6] regulator: core: introduce function to lock  regulators and its supplies kbuild test robot <lkp@intel.com> - 2015-09-30 16:30 +0200

#1236325 — [PATCH 2/6] regulator: core: introduce function to lock regulators and its supplies

Each regulator_dev is locked with its own mutex. This is fine as long
as only one regulator_dev is locked, but makes lockdep unhappy when we
have to walk up the supply chain like it can happen in
regulator_get_voltage:

regulator_get_voltage ->
 mutex_lock(&regulator->rdev->mutex) ->
_regulator_get_voltage(regulator->rdev) ->
regulator_get_voltage(rdev->supply) ->
mutex_lock(&regulator->rdev->mutex);

This causes lockdep to issue a possible deadlock warning.

There are at least two ways to work around this:

- We can always lock the whole supply chain using the functions
  introduced with this patch.
- We could store the current voltage in struct regulator_rdev so
  that we do not have to walk up the supply chain for the
  _regulator_get_voltage case.

Anyway, regulator_lock_supply/regulator_unlock_supply will be needed
once we allow regulator_set_voltage to optimize the supply voltages.

Signed-off-by: Sascha Hauer <s.hauer@pengutronix.de>
---
 drivers/regulator/core.c | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index bd9db70..e5de3d9 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -132,6 +132,45 @@ static bool have_full_constraints(void)
 }
 
 /**
+ * regulator_lock_supply - lock a regulator and its supplies
+ * @rdev:         regulator source
+ */
+static void regulator_lock_supply(struct regulator_dev *rdev)
+{
+	struct regulator *supply;
+	int i = 0;
+
+	while (1) {
+		mutex_lock_nested(&rdev->mutex, i++);
+		supply = rdev->supply;
+
+		if (!rdev->supply)
+			return;
+
+		rdev = supply->rdev;
+	}
+}
+
+/**
+ * regulator_unlock_supply - unlock a regulator and its supplies
+ * @rdev:         regulator source
+ */
+static void regulator_unlock_supply(struct regulator_dev *rdev)
+{
+	struct regulator *supply;
+
+	while (1) {
+		mutex_unlock(&rdev->mutex);
+		supply = rdev->supply;
+
+		if (!rdev->supply)
+			return;
+
+		rdev = supply->rdev;
+	}
+}
+
+/**
  * of_get_regulator - get a regulator device node based on supply name
  * @dev: Device pointer for the consumer (of regulator) device
  * @supply: regulator supply name
-- 
2.5.3

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#1236401 — Re: [PATCH 2/6] regulator: core: introduce function to lock regulators and its supplies

[Multipart message — attachments visible in raw view] — view raw

Hi Sascha,

[auto build test results on v4.3-rc3 -- if it's inappropriate base, please ignore]

config: x86_64-randconfig-i0-201539 (attached as .config)
reproduce:
  git checkout 70f6f03239f72ac3a34fad792af5200c613f4dbc
  # save the attached .config to linux build tree
  make ARCH=x86_64 

All warnings (new ones prefixed by >>):

   drivers/regulator/core.c: In function 'regulator_lock_supply':
>> drivers/regulator/core.c:141:6: warning: unused variable 'i' [-Wunused-variable]
     int i = 0;
         ^
   drivers/regulator/core.c: At top level:
   drivers/regulator/core.c:138:13: warning: 'regulator_lock_supply' defined but not used [-Wunused-function]
    static void regulator_lock_supply(struct regulator_dev *rdev)
                ^
   drivers/regulator/core.c:158:13: warning: 'regulator_unlock_supply' defined but not used [-Wunused-function]
    static void regulator_unlock_supply(struct regulator_dev *rdev)
                ^

vim +/i +141 drivers/regulator/core.c

   125		else
   126			return "";
   127	}
   128	
   129	static bool have_full_constraints(void)
   130	{
   131		return has_full_constraints || of_have_populated_dt();
   132	}
   133	
   134	/**
   135	 * regulator_lock_supply - lock a regulator and its supplies
   136	 * @rdev:         regulator source
   137	 */
   138	static void regulator_lock_supply(struct regulator_dev *rdev)
   139	{
   140		struct regulator *supply;
 > 141		int i = 0;
   142	
   143		while (1) {
   144			mutex_lock_nested(&rdev->mutex, i++);
   145			supply = rdev->supply;
   146	
   147			if (!rdev->supply)
   148				return;
   149	

---
0-DAY kernel test infrastructure                Open Source Technology Center
https://lists.01.org/pipermail/kbuild-all                   Intel Corporation

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