locking/osq_lock: Clarify osq_wait_next()

JIRA: https://issues.redhat.com/browse/RHEL-35759

commit b106bcf
Author: David Laight <David.Laight@ACULAB.COM>
Date:   Fri, 29 Dec 2023 20:56:03 +0000

    locking/osq_lock: Clarify osq_wait_next()

    Directly return NULL or 'next' instead of breaking out of the loop.

    Signed-off-by: David Laight <david.laight@aculab.com>
    [ Split original patch into two independent parts  - Linus ]
    Link: https://lore.kernel.org/lkml/7c8828aec72e42eeb841ca0ee3397e9a@AcuMS.aculab.com/
    Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

Signed-off-by: Waiman Long <longman@redhat.com>

Author: Waiman-Long

kernel/locking/osq_lock.c

@@ -55,7 +55,6 @@ osq_wait_next(struct optimistic_spin_queue *lock,
 	      struct optimistic_spin_node *node,
 	      int old_cpu)
 {
-	struct optimistic_spin_node *next = NULL;
 	int curr = encode_cpu(smp_processor_id());
 
 	for (;;) {
@@ -66,7 +65,7 @@ osq_wait_next(struct optimistic_spin_queue *lock,
 			 * will now observe @lock and will complete its
 			 * unlock()/unqueue().
 			 */
-			break;
+			return NULL;
 		}
 
 		/*
@@ -80,15 +79,15 @@ osq_wait_next(struct optimistic_spin_queue *lock,
 		 * wait for a new @node->next from its Step-C.
 		 */
 		if (node->next) {
+			struct optimistic_spin_node *next;
+
 			next = xchg(&node->next, NULL);
 			if (next)
-				break;
+				return next;
 		}
 
 		cpu_relax();
 	}
-
-	return next;
 }
 
 bool osq_lock(struct optimistic_spin_queue *lock)