ipc: sem_putref() does not need the semaphore lock any more

ipc_rcu_putref() uses atomics for the refcount, and the games to lock
and unlock the semaphore just to try to keep the reference counting
working are no longer useful.
Acked-by: Davidlohr Bueso <davidlohr.bueso@hp.com>
Cc: Rik van Riel <riel@redhat.com>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

ipc/sem.c

@@ -329,9 +329,7 @@ static inline void sem_lock_and_putref(struct sem_array *sma)
 
 static inline void sem_putref(struct sem_array *sma)
 {
-	sem_lock_and_putref(sma);
-	sem_unlock(sma, -1);
-	rcu_read_unlock();
+	ipc_rcu_putref(sma);
 }
 
 static inline void sem_rmid(struct ipc_namespace *ns, struct sem_array *s)