From 693fc06e98514c2d5951ead4aca40cf8b21100b1 Mon Sep 17 00:00:00 2001 From: Uros Bizjak Date: Thu, 14 Jul 2022 19:32:55 +0200 Subject: [PATCH] epoll: use try_cmpxchg in list_add_tail_lockless Use try_cmpxchg instead of cmpxchg (*ptr, old, new) == old in list_add_tail_lockless. x86 CMPXCHG instruction returns success in ZF flag, so this change saves a compare after cmpxchg (and related move instruction in front of cmpxchg). No functional change intended. Link: https://lkml.kernel.org/r/20220714173255.12987-1-ubizjak@gmail.com Signed-off-by: Uros Bizjak Cc: Alexander Viro Signed-off-by: Andrew Morton --- fs/eventpoll.c | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/fs/eventpoll.c b/fs/eventpoll.c index 8b56b94e2f56..52954d4637b5 100644 --- a/fs/eventpoll.c +++ b/fs/eventpoll.c @@ -1065,7 +1065,7 @@ static inline bool list_add_tail_lockless(struct list_head *new, * added to the list from another CPU: the winner observes * new->next == new. */ - if (cmpxchg(&new->next, new, head) != new) + if (!try_cmpxchg(&new->next, &new, head)) return false; /*