From 6a6d7602caec1b49dda423b0d15a8c4f72c9c73d Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Mon, 17 Oct 2022 16:52:26 +0200 Subject: [PATCH] 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: Uros Bizjak Signed-off-by: Andrew Morton --- lib/llist.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/lib/llist.c b/lib/llist.c index 7d78b736e8af..6e668fa5a2c6 100644 --- a/lib/llist.c +++ b/lib/llist.c @@ -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;