From: Tao Cui <cui.tao@linux.dev>
To: axboe@kernel.dk
Cc: tj@kernel.org, josef@toxicpanda.com, yukuai@fygo.io,
cgroups@vger.kernel.org, linux-block@vger.kernel.org,
linux-kernel@vger.kernel.org, cui.tao@linux.dev,
Tao Cui <cuitao@kylinos.cn>
Subject: [PATCH] block/blk-cgroup-rwstat: use data_race() for online test
Date: Sun, 2 Aug 2026 23:04:13 +0800 [thread overview]
Message-ID: <20260802150413.29789-1-cui.tao@linux.dev> (raw)
From: Tao Cui <cuitao@kylinos.cn>
blkg_rwstat_recursive_sum() reads pos_blkg->online without the queue
lock that its doc comment requires, since blkcg_print_blkgs() stopped
holding it in 56cc24f59c14. Concurrent blkg_create/destroy flips
->online, tripping KCSAN. The race is harmless (RCU-protected, stale
online only causes minor stat noise). Use data_race() to annotate
the intentional lockless read.
Signed-off-by: Tao Cui <cuitao@kylinos.cn>
---
block/blk-cgroup-rwstat.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
diff --git a/block/blk-cgroup-rwstat.c b/block/blk-cgroup-rwstat.c
index aae910713814..71f74052ae03 100644
--- a/block/blk-cgroup-rwstat.c
+++ b/block/blk-cgroup-rwstat.c
@@ -107,7 +107,7 @@ void blkg_rwstat_recursive_sum(struct blkcg_gq *blkg, struct blkcg_policy *pol,
blkg_for_each_descendant_pre(pos_blkg, pos_css, blkg) {
struct blkg_rwstat *rwstat;
- if (!pos_blkg->online)
+ if (!data_race(pos_blkg->online))
continue;
if (pol) {
--
2.43.0
next reply other threads:[~2026-08-02 15:04 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-08-02 15:04 Tao Cui [this message]
2026-08-03 5:29 ` [PATCH] block/blk-cgroup-rwstat: use data_race() for online test Yu Kuai
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