Commit 6a6d7602 authored by Uros Bizjak's avatar Uros Bizjak Committed by Andrew Morton
Browse files

llist: avoid extra memory read in llist_add_batch 

try_cmpxchg implicitly assigns old head->first value to "first" when
cmpxchg fails. There is no need to re-read the value in the loop.

Link: https://lkml.kernel.org/r/20221017145226.4044-1-ubizjak@gmail.com


Signed-off-by: default avatarUros Bizjak <ubizjak@gmail.com>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
parent add891f6

lib/llist.c

+2 −2
Original line number Diff line number Diff line
@@ -26,10 +26,10 @@ 
bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,

		     struct llist_head *head)

{

	struct llist_node *first;

	struct llist_node *first = READ_ONCE(head->first);



	do {

		new_last->next = first = READ_ONCE(head->first);

		new_last->next = first;

	} while (!try_cmpxchg(&head->first, &first, new_first));



	return !first;