* [PATCH] llist: Avoid extra memory read in llist_add_batch
@ 2022-10-17 14:52 Uros Bizjak
0 siblings, 0 replies; only message in thread
From: Uros Bizjak @ 2022-10-17 14:52 UTC (permalink / raw)
To: linux-kernel; +Cc: Uros Bizjak, Andrew Morton
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
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