locking/mutex: Define mutex_init() once

With CONFIG_PREEMPT_RT disabled __mutex_init() is a function. With
CONFIG_PREEMPT_RT enabled, __mutex_init() is a macro. I assume this is why
mutex_init() is defined twice as exactly the same macro.

Prepare for introducing a new macro for mutex initialization by combining
the two identical mutex_init() definitions into a single definition. This
patch does not change any functionality because the C preprocessor expands
macros when it encounters the macro name and not when a macro definition
is encountered. See also commit bb630f9 ("locking/rtmutex: Add mutex
variant for RT").

Acked-by: Peter Zijlstra (Intel) <[email protected]>
Cc: Thomas Gleixner <[email protected]>
Cc: Ingo Molnar <[email protected]>
Signed-off-by: Bart Van Assche <[email protected]>
Link: https://lore.kernel.org/r/[email protected]
Signed-off-by: Greg Kroah-Hartman <[email protected]>

Author: bvanassche

include/linux/mutex.h

@@ -49,7 +49,6 @@ static inline void mutex_destroy(struct mutex *lock) {}
 
 #endif
 
-#ifndef CONFIG_PREEMPT_RT
 /**
  * mutex_init - initialize the mutex
  * @mutex: the mutex to be initialized
@@ -65,6 +64,7 @@ do {									\
 	__mutex_init((mutex), #mutex, &__key);				\
 } while (0)
 
+#ifndef CONFIG_PREEMPT_RT
 #define __MUTEX_INITIALIZER(lockname) \
 		{ .owner = ATOMIC_LONG_INIT(0) \
 		, .wait_lock = __RAW_SPIN_LOCK_UNLOCKED(lockname.wait_lock) \
@@ -111,12 +111,6 @@ do {							\
 	__mutex_rt_init((mutex), name, key);		\
 } while (0)
 
-#define mutex_init(mutex)				\
-do {							\
-	static struct lock_class_key __key;		\
-							\
-	__mutex_init((mutex), #mutex, &__key);		\
-} while (0)
 #endif /* CONFIG_PREEMPT_RT */
 
 #ifdef CONFIG_DEBUG_MUTEXES