locking/rwsem: Add missing __init_rwsem() for PREEMPT_RT

730633f became the first direct caller of __init_rwsem() vs the
usual init_rwsem(), exposing PREEMPT_RT's lack thereof.  Add it.

[ tglx: Move it out of line ]

Signed-off-by: Mike Galbraith <efault@gmx.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Link: https://lore.kernel.org/r/50a936b7d8f12277d6ec7ed2ef0421a381056909.camel@gmx.de

Author: Mike Galbraith

include/linux/rwsem.h

@@ -142,22 +142,14 @@ struct rw_semaphore {
 #define DECLARE_RWSEM(lockname) \
 	struct rw_semaphore lockname = __RWSEM_INITIALIZER(lockname)
 
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-extern void  __rwsem_init(struct rw_semaphore *rwsem, const char *name,
+extern void  __init_rwsem(struct rw_semaphore *rwsem, const char *name,
 			  struct lock_class_key *key);
-#else
-static inline void  __rwsem_init(struct rw_semaphore *rwsem, const char *name,
-				 struct lock_class_key *key)
-{
-}
-#endif
 
 #define init_rwsem(sem)						\
 do {								\
 	static struct lock_class_key __key;			\
 								\
-	init_rwbase_rt(&(sem)->rwbase);			\
-	__rwsem_init((sem), #sem, &__key);			\
+	__init_rwsem((sem), #sem, &__key);			\
 } while (0)
 
 static __always_inline int rwsem_is_locked(struct rw_semaphore *sem)

kernel/locking/rwsem.c

@@ -1376,15 +1376,17 @@ static inline void __downgrade_write(struct rw_semaphore *sem)
 
 #include "rwbase_rt.c"
 
-#ifdef CONFIG_DEBUG_LOCK_ALLOC
-void __rwsem_init(struct rw_semaphore *sem, const char *name,
+void __init_rwsem(struct rw_semaphore *sem, const char *name,
 		  struct lock_class_key *key)
 {
+	init_rwbase_rt(&(sem)->rwbase);
+
+#ifdef CONFIG_DEBUG_LOCK_ALLOC
 	debug_check_no_locks_freed((void *)sem, sizeof(*sem));
 	lockdep_init_map_wait(&sem->dep_map, name, key, 0, LD_WAIT_SLEEP);
-}
-EXPORT_SYMBOL(__rwsem_init);
 #endif
+}
+EXPORT_SYMBOL(__init_rwsem);
 
 static inline void __down_read(struct rw_semaphore *sem)
 {