linux-kernel - Re: [PATCH 1/1] block: Use RCU in blk_mq_[un]quiesce_tagset() instead of set->tag_list

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Message-ID: <77c5c064-2539-4ad9-8657-8a1db487522f@acm.org>
Date: Thu, 4 Dec 2025 09:31:55 -1000
From: Bart Van Assche <bvanassche@....org>
To: Mohamed Khalfella <mkhalfella@...estorage.com>
Cc: Chaitanya Kulkarni <kch@...dia.com>, Christoph Hellwig <hch@....de>,
 Jens Axboe <axboe@...nel.dk>, Keith Busch <kbusch@...nel.org>,
 Sagi Grimberg <sagi@...mberg.me>, Casey Chen <cachen@...estorage.com>,
 Yuanyuan Zhong <yzhong@...estorage.com>, Hannes Reinecke <hare@...e.de>,
 Ming Lei <ming.lei@...hat.com>, Waiman Long <llong@...hat.com>,
 Hillf Danton <hdanton@...a.com>, linux-nvme@...ts.infradead.org,
 linux-block@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] block: Use RCU in blk_mq_[un]quiesce_tagset() instead
 of set->tag_list_lock

On 12/4/25 9:15 AM, Mohamed Khalfella wrote:
> The stacktraces are from old 6.6.9 kernel.

Please always include stack traces from a recent upstream kernel in
patch descriptions.

> However, the issue is still
> applicable to recent kernels. This is an example from 6.13 kernel.

Thanks, these stack traces make it clear what is causing the deadlock.

 From nvme_timeout():

	/*
	 * Reset immediately if the controller is failed
	 */
	if (nvme_should_reset(dev, csts)) {
		nvme_warn_reset(dev, csts);
		nvme_dev_disable(dev, false);
		nvme_reset_ctrl(&dev->ctrl);
		return BLK_EH_DONE;
	}

Is my understanding correct that the above code is involved in the
reported deadlock? If so, has it been considered to run the code inside
the if-statement asynchronously (queue_work()) instead of calling it
synchronously? Would this be sufficient to fix the deadlock?

Thanks,

Bart.