linux-kernel - Re: [PATCH] block: Fix blk_sync_queue() to properly stop timeout timer

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Message-ID: <aDjcA_H7Ec9VICps@kbusch-mbp>
Date: Thu, 29 May 2025 16:13:23 -0600
From: Keith Busch <kbusch@...nel.org>
To: Mohamed Khalfella <mkhalfella@...estorage.com>
Cc: James Smart <james.smart@...adcom.com>, Jens Axboe <axboe@...nel.dk>,
	Christoph Hellwig <hch@....de>, Sagi Grimberg <sagi@...mberg.me>,
	linux-nvme@...ts.infradead.org, linux-kernel@...r.kernel.org,
	linux-block@...r.kernel.org,
	Yuanyuan Zhong <yzhong@...estorage.com>,
	Michael Liang <mliang@...estorage.com>,
	Randy Jennings <randyj@...estorage.com>
Subject: Re: [PATCH] block: Fix blk_sync_queue() to properly stop timeout
 timer

On Thu, May 29, 2025 at 03:49:28PM -0600, Mohamed Khalfella wrote:
> nvme-fc initiator hit hung_task with stacktrace above while handling
> request timeout call. The work thread is waiting for itself to finish
> which is never going to happen. From the stacktrace the nvme controller
> was in NVME_CTRL_CONNECTING state when nvme_fc_timeout() was called.
> We do not expect to get IO timeout call in NVME_CTRL_CONNECTING state
> because blk_sync_queue() must have been called on this queue before
> switching from NVME_CTRL_RESETTING to NVME_CTRL_CONNECTING.
> 
> It turned out that blk_sync_queue() did not stop q->timeout_work from
> running as expected. nvme_fc_timeout() returned BLK_EH_RESET_TIMER
> causing q->timeout to be rearmed after it was canceled earlier.
> q->timeout queued q->timeout_work after the controller switched to
> NVME_CTRL_CONNECTING state causing deadlock above.
> 
> Add QUEUE_FLAG_NOTIMEOUT queue flag to tell q->timeout not to queue
> q->timeout_work while queue is being synced. Update blk_sync_queue() to
> cancel q->timeout_work first and then cancel q->timeout.

I feel like this is a nvme-fc problem that doesn't need the block layer
to handle. Just don't sync the queues within the timeout workqueue
context.