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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 <ubizjak@gmail.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Uros Bizjak 2022-10-17 16:52:26 +02:00 committed by Andrew Morton
parent add891f68d
commit 6a6d7602ca
1 changed files with 2 additions and 2 deletions
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4
lib/llist.c
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@ -26,10 +26,10 @@
bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last, bool llist_add_batch(struct llist_node *new_first, struct llist_node *new_last,
struct llist_head *head) struct llist_head *head)
{ {
struct llist_node *first; struct llist_node *first = READ_ONCE(head->first);
do { do {
new_last->next = first = READ_ONCE(head->first); new_last->next = first;
} while (!try_cmpxchg(&head->first, &first, new_first)); } while (!try_cmpxchg(&head->first, &first, new_first));
return !first; return !first;