From mboxrd@z Thu Jan 1 00:00:00 1970 Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.remote-ip=100.103.45.18 ARC-Seal: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; cv=none; t=1794047523; b=od4zMqGG7GuXMKO2JYrYthzvyu2DbizwWFnWdtPatsA8hNOtetSCyauYXdDv7Rg4Pw+O rCmUj33LdQGK+V7kIrZlDsm+q52GXc0veyNLm5Rqud+DSDXYbntIrgBXKxKBkISdHJ2WO JFFrxRfK32jBPQq6b3pl0Tciukdm7xRCoMx+GlxZEH3eHUBrXu2BSUt0x//sP+Iqb0Dzt th8zi2ZYb+8s9aBtfcgpVWm8P8yd/voLm9xVW7t0vithEZJ9rflQPKB7Ee/6U5gQQ85jK 3aaFWFdKy3j1MhEt087Lm/DaDnB4asP3FKxJQWfd/wOZ9nZiAJWeJExI7Hf/6LuhLNA== ARC-Message-Signature: i=1; d=subspace.kernel.org; s=arc20261015; a=rsa-sha256; c=relaxed/relaxed; t=1794047523; h=Received:DKIM-Signature:From:To:Cc:Subject:Date:Message-ID:X-Mailer: MIME-Version:Content-Type:Content-Transfer-Encoding; bh=xTHT0Y3Sboj2VwsYRr0cONYKvrU3bPUSJLar5v1U++o=; b=SLsy0nyENgmI8k62YiEmRkqOh19JUziZyEVNdmfcGB9CW68eBAlyJ7NNF79hYP2HCcyQ MfpuGa5dKIcnC82ZANVUhBEWv7DQQ11hOTj763r/A1VHsPC3/aqf1sj8JcrawFan4/dZ1 wS/yAZvj9hxVcu1wrU2LaGNECMBvoHWkDAYG381/GkijNe1nuUbFOLYJxn0GKP9Kvg4Vx pzLWWb2pXNfnUcS7S6rzzscdRTghjgxd7AwYqyCZjZjCOGCVeojWGJuwQoZqMycRcAQXs AcBSfZinxVJi8LF2L8y7GwNtiv3ko0cnVcmsPmupeB+QUwyqOgy5T5zDDTsr8U7CVog== ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dkim=pass header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Uuee91z1; arc=none smtp.remote-ip=100.103.45.18 Received: from smtp.kernel.org (quasi.space.kernel.org [100.103.45.18]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (prime256v1)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 583CC606A32D for ; Sat, 7 Nov 2026 10:32:03 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.a=rsa-sha256 header.s=k20260515 header.b=Uuee91z1 Received: by smtp.kernel.org (Postfix) with ESMTPSA id EC9EE1F0089F; Sat, 7 Nov 2026 10:32:01 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel.org; s=k20260515; t=1794047523; bh=xTHT0Y3Sboj2VwsYRr0cONYKvrU3bPUSJLar5v1U++o=; h=From:To:Cc:Subject:Date; b=Uuee91z1ZBo/GRpxgQD4VSlMEulSVqNEww8O6Q/TIeD8VfMXz/kblmUNwPacFqEGb bv0umoyyzhtKjoliZAGBTNubfiftmLnNuy/L9PBdjnT7lDPIp08X+dC7n0gG5C8Lun Dv1Y4DUJNJGVd9upbFt1PgkDc3IRJlT/9AA/zIidmNscg+St8KU7NXEujk338dcQ7/ PmgmdyLWyKkYUHA1YUy+yqE/txK++AftzrwxEl9al7L3qLEMPlB4vkgFuXHR5ietH5 25ZXQ47/a4+p9MTlVicGFQvoiHUHQj+8wsyq350KMkoQFOlUBdrXB/HCTwgDUFDgFg Wr2cGPVKji7gg== From: Sasha Levin To: jiayuan.chen@linux.dev, akpm@linux-foundation.org, muchun.song@linux.dev, hannes@cmpxchg.org, mhocko@suse.com, chrisl@kernel.org, jack@suse.cz, axboe@kernel.dk, roman.gushchin@linux.dev, shakeel.butt@linux.dev, tj@kernel.org Cc: stable@vger.kernel.org Subject: FAILED: patch "[PATCH] mm/memcontrol: fix data-race on reading jiffies_64" failed to apply to 6.6-stable tree Date: Sat, 7 Nov 2026 05:32:00 -0500 Message-ID: <20261107053200-failed-6.6-c20cf1c3c8cd@kernel.org> X-Mailer: git-send-email 2.53.0 X-Mailing-List: stable@vger.kernel.org List-Id: List-Post: List-Help: List-Subscribe: List-Unsubscribe: List-Owner: Precedence: list MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The patch below does not apply to the 6.6-stable tree. If someone wants it applied there, or to any other stable or longterm tree, then please email the backport, including the original git commit id to . To reproduce the conflict and resubmit, you may use the following commands: git fetch https://git.kernel.org/pub/scm/linux/kernel/git/stable/linux.git/ linux-6.6.y git checkout FETCH_HEAD git cherry-pick -x c20cf1c3c8cdd98618d6fcc794003a0e003ae858 # git commit -s git send-email --to '' --in-reply-to '20261107053200-failed-6.6-c20cf1c3c8cd@kernel.org' --subject-prefix 'PATCH 6.6.y' 'HEAD^..' Thanks, Sasha ------------------ original commit in Linus's tree ------------------ >From c20cf1c3c8cdd98618d6fcc794003a0e003ae858 Mon Sep 17 00:00:00 2001 From: Jiayuan Chen Date: Thu, 27 Aug 2026 10:54:56 +0800 Subject: [PATCH] mm/memcontrol: fix data-race on reading jiffies_64 KCSAN reported a data-race between tick_do_update_jiffies64() updating jiffies_64 and mem_cgroup_flush_stats_ratelimited() reading it directly. Unlike jiffies, jiffies_64 is not volatile, so raw reads are plain accesses and can even be torn on 32-bit. Use get_jiffies_64() instead, and fix the same pattern in mem_cgroup_flush_foreign(). Link: https://lore.kernel.org/20260827025457.116191-1-jiayuan.chen@linux.dev Fixes: 508bed884767 ("mm: memcg: change flush_next_time to flush_last_time") Fixes: 97b27821b485 ("writeback, memcg: Implement foreign dirty flushing") Signed-off-by: Jiayuan Chen Signed-off-by: Andrew Morton Reported-by: syzbot+ced4d9a8cadb5ef3adae@syzkaller.appspotmail.com Acked-by: Muchun Song Acked-by: Johannes Weiner Acked-by: Michal Hocko Cc: Chris Li Cc: Jan Kara Cc: Jens Axboe Cc: Roman Gushchin Cc: Shakeel Butt Cc: Tejun Heo Cc: --- mm/memcontrol.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/mm/memcontrol.c b/mm/memcontrol.c index 856a7d07586cc..d399710e9799a 100644 --- a/mm/memcontrol.c +++ b/mm/memcontrol.c @@ -757,7 +757,7 @@ static void __mem_cgroup_flush_stats(struct mem_cgroup *memcg, bool force) return; if (mem_cgroup_is_root(memcg)) - WRITE_ONCE(flush_last_time, jiffies_64); + WRITE_ONCE(flush_last_time, get_jiffies_64()); css_rstat_flush(&memcg->css); } @@ -785,7 +785,7 @@ void mem_cgroup_flush_stats(struct mem_cgroup *memcg) void mem_cgroup_flush_stats_ratelimited(struct mem_cgroup *memcg) { /* Only flush if the periodic flusher is one full cycle late */ - if (time_after64(jiffies_64, READ_ONCE(flush_last_time) + 2*FLUSH_TIME)) + if (time_after64(get_jiffies_64(), READ_ONCE(flush_last_time) + 2 * FLUSH_TIME)) mem_cgroup_flush_stats(memcg); } @@ -3946,7 +3946,7 @@ void mem_cgroup_flush_foreign(struct bdi_writeback *wb) { struct mem_cgroup *memcg = mem_cgroup_from_css(wb->memcg_css); unsigned long intv = msecs_to_jiffies(dirty_expire_interval * 10); - u64 now = jiffies_64; + u64 now = get_jiffies_64(); int i; for (i = 0; i < MEMCG_CGWB_FRN_CNT; i++) { -- 2.53.0