kernel/futex: Move hb unlock out of unqueue_me_pi()

This improves the code readability, and the locking more obvious
as it becomes symmetric for the caller.
Signed-off-by: Davidlohr Bueso <dbueso@suse.de>
Signed-off-by: Thomas Gleixner <tglx@linutronix.de>
Acked-by: Peter Zijlstra (Intel) <peterz@infradead.org>
Link: https://lore.kernel.org/r/20210226175029.50335-3-dave@stgolabs.net

kernel/futex.c

@@ -2318,19 +2318,15 @@ static int unqueue_me(struct futex_q *q)
 
 /*
  * PI futexes can not be requeued and must remove themself from the
- * hash bucket. The hash bucket lock (i.e. lock_ptr) is held on entry
- * and dropped here.
+ * hash bucket. The hash bucket lock (i.e. lock_ptr) is held.
  */
 static void unqueue_me_pi(struct futex_q *q)
-	__releases(q->lock_ptr)
 {
 	__unqueue_futex(q);
 
 	BUG_ON(!q->pi_state);
 	put_pi_state(q->pi_state);
 	q->pi_state = NULL;
-
-	spin_unlock(q->lock_ptr);
 }
 
 static int __fixup_pi_state_owner(u32 __user *uaddr, struct futex_q *q,
@@ -2913,8 +2909,8 @@ static int futex_lock_pi(u32 __user *uaddr, unsigned int flags,
 	if (res)
 		ret = (res < 0) ? res : 0;
 
-	/* Unqueue and drop the lock */
 	unqueue_me_pi(&q);
+	spin_unlock(q.lock_ptr);
 	goto out;
 
 out_unlock_put_key:
@@ -3290,8 +3286,8 @@ static int futex_wait_requeue_pi(u32 __user *uaddr, unsigned int flags,
 		if (res)
 			ret = (res < 0) ? res : 0;
 
-		/* Unqueue and drop the lock. */
 		unqueue_me_pi(&q);
+		spin_unlock(q.lock_ptr);
 	}
 
 	if (ret == -EINTR) {