[PATCH] regulator: simplify locking

From: Michał Mirosław
Date: Sun Aug 09 2020 - 17:17:01 EST


Simplify regulator locking by removing locking around locking. rdev->ref
is now accessed only when the lock is taken. The code still smells fishy,
but now its obvious why.

Fixes: f8702f9e4aa7 ("regulator: core: Use ww_mutex for regulators locking")
Signed-off-by: Michał Mirosław <mirq-linux@xxxxxxxxxxxx>
---
drivers/regulator/core.c | 37 ++++++--------------------------
include/linux/regulator/driver.h | 1 -
2 files changed, 6 insertions(+), 32 deletions(-)

diff --git a/drivers/regulator/core.c b/drivers/regulator/core.c
index 9e18997777d3..b0662927487c 100644
--- a/drivers/regulator/core.c
+++ b/drivers/regulator/core.c
@@ -45,7 +45,6 @@
pr_debug("%s: " fmt, rdev_get_name(rdev), ##__VA_ARGS__)

static DEFINE_WW_CLASS(regulator_ww_class);
-static DEFINE_MUTEX(regulator_nesting_mutex);
static DEFINE_MUTEX(regulator_list_mutex);
static LIST_HEAD(regulator_map_list);
static LIST_HEAD(regulator_ena_gpio_list);
@@ -150,32 +149,13 @@ static bool regulator_ops_is_valid(struct regulator_dev *rdev, int ops)
static inline int regulator_lock_nested(struct regulator_dev *rdev,
struct ww_acquire_ctx *ww_ctx)
{
- bool lock = false;
int ret = 0;

- mutex_lock(&regulator_nesting_mutex);
+ if (ww_ctx || !mutex_trylock_recursive(&rdev->mutex.base))
+ ret = ww_mutex_lock(&rdev->mutex, ww_ctx);

- if (ww_ctx || !ww_mutex_trylock(&rdev->mutex)) {
- if (rdev->mutex_owner == current)
- rdev->ref_cnt++;
- else
- lock = true;
-
- if (lock) {
- mutex_unlock(&regulator_nesting_mutex);
- ret = ww_mutex_lock(&rdev->mutex, ww_ctx);
- mutex_lock(&regulator_nesting_mutex);
- }
- } else {
- lock = true;
- }
-
- if (lock && ret != -EDEADLK) {
+ if (ret != -EDEADLK)
rdev->ref_cnt++;
- rdev->mutex_owner = current;
- }
-
- mutex_unlock(&regulator_nesting_mutex);

return ret;
}
@@ -205,16 +185,11 @@ EXPORT_SYMBOL_GPL(regulator_lock);
*/
void regulator_unlock(struct regulator_dev *rdev)
{
- mutex_lock(&regulator_nesting_mutex);
+ if (WARN_ON_ONCE(rdev->ref_cnt <= 0))
+ return;

- if (--rdev->ref_cnt == 0) {
- rdev->mutex_owner = NULL;
+ if (--rdev->ref_cnt == 0)
ww_mutex_unlock(&rdev->mutex);
- }
-
- WARN_ON_ONCE(rdev->ref_cnt < 0);
-
- mutex_unlock(&regulator_nesting_mutex);
}
EXPORT_SYMBOL_GPL(regulator_unlock);

diff --git a/include/linux/regulator/driver.h b/include/linux/regulator/driver.h
index 8539f34ae42b..2fe5b1bcbe2f 100644
--- a/include/linux/regulator/driver.h
+++ b/include/linux/regulator/driver.h
@@ -448,7 +448,6 @@ struct regulator_dev {

struct blocking_notifier_head notifier;
struct ww_mutex mutex; /* consumer lock */
- struct task_struct *mutex_owner;
int ref_cnt;
struct module *owner;
struct device dev;
--
2.20.1