locking/mutex: Introduce devm_mutex_init()

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 wrapping.
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() will be
extended so introduce devm_mutex_init().

Suggested-by: Christophe Leroy <[email protected]>
Signed-off-by: George Stark <[email protected]>
Reviewed-by: Christophe Leroy <[email protected]>
Reviewed-by: Andy Shevchenko <[email protected]>
Reviewed-by: Marek Behún <[email protected]>
Acked-by: Waiman Long <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Lee Jones <[email protected]>

1 files changed, 27 insertions, 0 deletions

diff --git a/include/linux/mutex.h b/include/linux/mutex.h
index 67edc4ca2bee..a561c629d89f 100644
--- a/include/linux/mutex.h
+++ b/include/linux/mutex.h
@@ -22,6 +22,8 @@
 #include <linux/cleanup.h>
 #include <linux/mutex_types.h>
 
+struct device;
+
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)			\
 		, .dep_map = {					\
@@ -117,6 +119,31 @@ do {							\
 } while (0)
 #endif /* CONFIG_PREEMPT_RT */
 
+#ifdef CONFIG_DEBUG_MUTEXES
+
+int __devm_mutex_init(struct device *dev, struct mutex *lock);
+
+#else
+
+static inline int __devm_mutex_init(struct device *dev, struct mutex *lock)
+{
+	/*
+	 * When CONFIG_DEBUG_MUTEXES is off mutex_destroy() is just a nop so
+	 * no really need to register it in the devm subsystem.
+	 */
+	return 0;
+}
+
+#endif
+
+#define devm_mutex_init(dev, mutex)			\
+({							\
+	typeof(mutex) mutex_ = (mutex);			\
+							\
+	mutex_init(mutex_);				\
+	__devm_mutex_init(dev, mutex_);			\
+})
+
 /*
  * See kernel/locking/mutex.c for detailed documentation of these APIs.
  * Also see Documentation/locking/mutex-design.rst.