From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from out-171.mta1.migadu.com (out-171.mta1.migadu.com [95.215.58.171]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id E31713BBFA7; Sun, 2 Aug 2026 15:04:44 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=95.215.58.171 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785683087; cv=none; b=QeQhJKpaZvsoi8aIXgs8z7/f7R8IGprfHme4PyW2FlMPWOTRSVe0Db+5E7qzuCft+vaECaTvM6H/zAJePu3VqfOJPNb+zeG4KrmU0PZQzvEZJF4DoIfzG1cILbmDRsL1n+UDDa2VsotK8gdVT9mOLVvq8Zf5ruLNH3VblXK16v4= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1785683087; c=relaxed/simple; bh=PNImhYUF+IBH1SnJQQV6VVaaSWz80MXr0dLREmGyW/M=; h=From:To:Cc:Subject:Date:Message-ID:MIME-Version; b=bNdttYLQ/UzYyqlGPAHmSdZ++OCDP6aPV07G1G/jnhshpZqRec9kfoyHPucHQdN5Q37xQpqy4HUbu6I8wgYp73wPtx6YssyokxJVQ/KyHXL1FkobBKVzWBj0kZ5ylY5ZCOBw4xVPEFkeXr1fB/gudSid9TA8tFqOL0mx0Bz5eJE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev; spf=pass smtp.mailfrom=linux.dev; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b=vvIFGNv/; arc=none smtp.client-ip=95.215.58.171 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=linux.dev Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=linux.dev Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux.dev header.i=@linux.dev header.b="vvIFGNv/" X-Report-Abuse: Please report any abuse attempt to abuse@migadu.com and include these headers. DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=linux.dev; s=key1; t=1785683072; h=from:from:reply-to:subject:subject:date:date:message-id:message-id: to:to:cc:cc:mime-version:mime-version: content-transfer-encoding:content-transfer-encoding; bh=fNqPIMi1h+CgUvqJUxjQG3eAhWqTrsnnu3OCxhWLRis=; b=vvIFGNv/cVAe+VIyTugn7OGAVxjLXg1HeQV6m3E03rHSnv1qTae4500/d+FI9SP3S0EUCM I2reLsHEfEMEPqMqqvIMH6VBM0ez1fRSvVJGzl5RA77SYCK5mavZivERKUqxCjg4YGqC51 RD4i8mlCPmlT7nOGIy8+TRcZayMkPzs= From: Tao Cui 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 Subject: [PATCH] block/blk-cgroup-rwstat: use data_race() for online test Date: Sun, 2 Aug 2026 23:04:13 +0800 Message-ID: <20260802150413.29789-1-cui.tao@linux.dev> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Migadu-Flow: FLOW_OUT From: Tao Cui 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 --- 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