[PATCH v3 03/11] devm-helpers: introduce devm_mutex_init

[George Stark]

Using of devm API leads to a certain order of releasing resources.
So all dependent resources which are not devm-wrapped should be deleted
with respect to devm-release order. Mutex is one of such objects that
often is bound to other resources and has no own devm wrapper.
Since mutex_destroy() actually does nothing in non-debug builds
frequently calling mutex_destroy() is just ignored which is safe for now
but wrong formally and can lead to a problem if mutex_destroy() is
extended so introduce devm_mutex_init().

Signed-off-by: George Stark <gnstark@xxxxxxxxxxxxxxxxx>
---
 include/linux/devm-helpers.h | 27 +++++++++++++++++++++++++++
 1 file changed, 27 insertions(+)

diff --git a/include/linux/devm-helpers.h b/include/linux/devm-helpers.h
index 74891802200d..4043c3481d2e 100644
--- a/include/linux/devm-helpers.h
+++ b/include/linux/devm-helpers.h
@@ -24,6 +24,7 @@
  */
 
 #include <linux/device.h>
+#include <linux/mutex.h>
 #include <linux/workqueue.h>
 
 static inline void devm_delayed_work_drop(void *res)
@@ -76,4 +77,30 @@ static inline int devm_work_autocancel(struct device *dev,
 	return devm_add_action(dev, devm_work_drop, w);
 }
 
+#ifdef mutex_destroy
+static inline void devm_mutex_release(void *res)
+{
+	mutex_destroy(res);
+}
+#endif
+
+/**
+ * devm_mutex_init - Resource-managed mutex initialization
+ * @dev:	Device which lifetime mutex is bound to
+ * @lock:	Pointer to a mutex
+ *
+ * Initialize mutex which is automatically destroyed when the driver is detached.
+ *
+ * Returns: 0 on success or a negative error code on failure.
+ */
+static inline int devm_mutex_init(struct device *dev, struct mutex *lock)
+{
+	mutex_init(lock);
+#ifdef mutex_destroy
+	return devm_add_action_or_reset(dev, devm_mutex_release, lock);
+#else
+	return 0;
+#endif
+}
+
 #endif
-- 
2.25.1