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 5AEDE46B9B; Wed, 21 Feb 2024 13:18:08 +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=1708521488; cv=none; b=G3XmBNAow+oi5i/0IJmbrIVOJKeqQx4gG/fcD6FlYXt75BR0Lc9HdDbMr9H6iS8VzKFINqNsXChqonAAkminAJtBb2QKa0CYIP+CefdZno+PeOFuBeWEvo1jZ5pBtYnLt8Yr6UfbojSBZsqxcEszrivAe49PwaZv0RZPwHD2tlk= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1708521488; c=relaxed/simple; bh=pcVRx/ZNJ+WGfIZPTrCTS2RwNZUzVLVYpjCx/L4qJr0=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=fZ8PCJ5cPt2PX68Ob6ITxrQpBzYalpqnAAesg4T2szfQ8VnQ8Oc6NkSGyFFdfoTp2d6TczliGjfDr1H3nEt6UUxO3SBF1HzWQULvcSA9H213w/71uXg+UXnDLv3WdAF0kN4zzkap+Bv6A7MNtSKp6P+x2DX1mabpmWrDo4PPFBY= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b=Ayu2N0Lv; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linuxfoundation.org header.i=@linuxfoundation.org header.b="Ayu2N0Lv" Received: by smtp.kernel.org (Postfix) with ESMTPSA id BF59DC433F1; Wed, 21 Feb 2024 13:18:07 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linuxfoundation.org; s=korg; t=1708521488; bh=pcVRx/ZNJ+WGfIZPTrCTS2RwNZUzVLVYpjCx/L4qJr0=; h=From:To:Cc:Subject:Date:In-Reply-To:References:From; b=Ayu2N0LvICxjJteT5SCyShfi424POaMSyojSHbHamGdj316EIKIQ8krc8RwxwSVnV h9MPmrJQgaMsRb2TLlseO3qkXvM+QaVEK9LvSqvBNAX8Xg44Rqwz3zqMxYGZExi75y AAQqPkPbK/12zvYEE4RIo0GTaMx9mG9ZDYk8ueow= From: Greg Kroah-Hartman To: stable@vger.kernel.org Cc: Greg Kroah-Hartman , patches@lists.linux.dev, Jan Kara , Kemeng Shi , Changhui Zhong , Ming Lei , Jens Axboe , Sasha Levin Subject: [PATCH 4.19 126/202] blk-mq: fix IO hang from sbitmap wakeup race Date: Wed, 21 Feb 2024 14:07:07 +0100 Message-ID: <20240221125935.778038382@linuxfoundation.org> X-Mailer: git-send-email 2.43.2 In-Reply-To: <20240221125931.742034354@linuxfoundation.org> References: <20240221125931.742034354@linuxfoundation.org> User-Agent: quilt/0.67 X-stable: review X-Patchwork-Hint: ignore Precedence: bulk X-Mailing-List: patches@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: 8bit 4.19-stable review patch. If anyone has any objections, please let me know. ------------------ 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