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

include/linux/mutex.h

···
 #include <linux/cleanup.h>
 #include <linux/mutex_types.h>
 
+struct device;
+
 #ifdef CONFIG_DEBUG_LOCK_ALLOC
 # define __DEP_MAP_MUTEX_INITIALIZER(lockname)			\
 		, .dep_map = {					\
···
 	__mutex_init((mutex), #mutex, &__key);		\
 } 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.

kernel/locking/mutex-debug.c

···
  */
 #include <linux/mutex.h>
 #include <linux/delay.h>
+#include <linux/device.h>
 #include <linux/export.h>
 #include <linux/poison.h>
 #include <linux/sched.h>
···
 #endif
 	lock->magic = lock;
 }
+
+static void devm_mutex_release(void *res)
+{
+	mutex_destroy(res);
+}
+
+int __devm_mutex_init(struct device *dev, struct mutex *lock)
+{
+	return devm_add_action_or_reset(dev, devm_mutex_release, lock);
+}
+EXPORT_SYMBOL_GPL(__devm_mutex_init);
 
 /***
  * mutex_destroy - mark a mutex unusable