From: Uros Bizjak <ubizjak@gmail.com>
To: linux-kernel@vger.kernel.org
Cc: Uros Bizjak <ubizjak@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>
Subject: [PATCH] llist: Avoid extra memory read in llist_add_batch
Date: Mon, 17 Oct 2022 16:52:26 +0200 [thread overview]
Message-ID: <20221017145226.4044-1-ubizjak@gmail.com> (raw)
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.
Cc: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Uros Bizjak <ubizjak@gmail.com>
---
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;
--
2.37.3
reply other threads:[~2022-10-17 14:53 UTC|newest]
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