From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 4BE5F524A2; Sun, 28 Jan 2024 16:17:16 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706458636; cv=none; b=HjLCPTpVkZTQmUGcsicA1xdGj7tpDhDQfzDRD5qAPFF0c2Hzfp2wPQ4JrVKrHeZwoM4oWUB1raY1tD7qXWPGLT7Sgps06xMl7ycmpD1JTfVsN/X2CRJrwYMpm3uAmYhybcnRhJ0N/dH6jXMrf3jzPKV6lyrX/vBt3R/M2IwYlCI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1706458636; c=relaxed/simple; bh=76J1OpPZEDhDhLfl2S4BMXsylw8T+SlH2hIp+v1g98c=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=iEJyFqeVDW8PAH9GvU+vXEhJkZTDRify+Mum5rXGbEp5f8i+Aw1rH0NN+0287Uvra4dVjDS4lwKJfrVj7ADVc3s1zJaty634oeVuP60dnRJ5dqIIKgOzed17Zl2cUI6JbH21Fnio1apFxyEIoa3JunmSN4PyHW27yVpQC3+kdJ4= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b=KFToCTJe; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel.org header.i=@kernel.org header.b="KFToCTJe" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 23DB4C43390; Sun, 28 Jan 2024 16:17:15 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1706458636; bh=76J1OpPZEDhDhLfl2S4BMXsylw8T+SlH2hIp+v1g98c=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=KFToCTJeuLVqmoH/C2p6JrS//BhyqliuGeobjfA6SdjsoGz4rvKz86ykX2cHg11vC PGB3cIpIZ0MqadPQ7h6Rpw4fTfTFvM9IL7HEYaDAbU2quFE9vNh86L9rUtZtSlFQFc bBAZUQxCOf+sEAGqx4B6HdEwo703O7uylKXm7fUmrR0X2CkfzMZXc1yD/Tow5LJB/q vpSCcrwKgYhE2DV9Ps/urozkizAJjh0gDVp0iF50K5iRT4RTQ1UotcxeuNrPbe7Pgu a6DC4L8yqz75NEpwrQT5iqoGTCkRlZedISpA+J6g54mm4GybOMn+Padfl2IiGf98yG EyTVn6Fw7zXrg== From: Sasha Levin To: linux-kernel@vger.kernel.org, stable@vger.kernel.org Cc: Ming Lei , Jan Kara , Kemeng Shi , Changhui Zhong , Jens Axboe , Sasha Levin , linux-block@vger.kernel.org Subject: [PATCH AUTOSEL 4.19 6/8] blk-mq: fix IO hang from sbitmap wakeup race Date: Sun, 28 Jan 2024 11:16:57 -0500 Message-ID: <20240128161704.205756-6-sashal@kernel.org> X-Mailer: git-send-email 2.43.0 In-Reply-To: <20240128161704.205756-1-sashal@kernel.org> References: <20240128161704.205756-1-sashal@kernel.org> Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 X-stable: review X-Patchwork-Hint: Ignore X-stable-base: Linux 4.19.306 Content-Transfer-Encoding: 8bit From: Ming Lei [ Upstream commit 5266caaf5660529e3da53004b8b7174cab6374ed ] In blk_mq_mark_tag_wait(), __add_wait_queue() may be re-ordered with the following blk_mq_get_driver_tag() in case of getting driver tag failure. Then in __sbitmap_queue_wake_up(), waitqueue_active() may not observe the added waiter in blk_mq_mark_tag_wait() and wake up nothing, meantime blk_mq_mark_tag_wait() can't get driver tag successfully. This issue can be reproduced by running the following test in loop, and fio hang can be observed in < 30min when running it on my test VM in laptop. modprobe -r scsi_debug modprobe scsi_debug delay=0 dev_size_mb=4096 max_queue=1 host_max_queue=1 submit_queues=4 dev=`ls -d /sys/bus/pseudo/drivers/scsi_debug/adapter*/host*/target*/*/block/* | head -1 | xargs basename` fio --filename=/dev/"$dev" --direct=1 --rw=randrw --bs=4k --iodepth=1 \ --runtime=100 --numjobs=40 --time_based --name=test \ --ioengine=libaio Fix the issue by adding one explicit barrier in blk_mq_mark_tag_wait(), which is just fine in case of running out of tag. Cc: Jan Kara Cc: Kemeng Shi Reported-by: Changhui Zhong Signed-off-by: Ming Lei Link: https://lore.kernel.org/r/20240112122626.4181044-1-ming.lei@redhat.com Signed-off-by: Jens Axboe Signed-off-by: Sasha Levin --- block/blk-mq.c | 16 ++++++++++++++++ 1 file changed, 16 insertions(+) diff --git a/block/blk-mq.c b/block/blk-mq.c index ae70b4809bec..0cb559d63998 100644 --- a/block/blk-mq.c +++ b/block/blk-mq.c @@ -1064,6 +1064,22 @@ static bool blk_mq_mark_tag_wait(struct blk_mq_hw_ctx *hctx, wait->flags &= ~WQ_FLAG_EXCLUSIVE; __add_wait_queue(wq, wait); + /* + * Add one explicit barrier since blk_mq_get_driver_tag() may + * not imply barrier in case of failure. + * + * Order adding us to wait queue and allocating driver tag. + * + * The pair is the one implied in sbitmap_queue_wake_up() which + * orders clearing sbitmap tag bits and waitqueue_active() in + * __sbitmap_queue_wake_up(), since waitqueue_active() is lockless + * + * Otherwise, re-order of adding wait queue and getting driver tag + * may cause __sbitmap_queue_wake_up() to wake up nothing because + * the waitqueue_active() may not observe us in wait queue. + */ + smp_mb(); + /* * It's possible that a tag was freed in the window between the * allocation failure and adding the hardware queue to the wait -- 2.43.0