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From: Ming Lei <ming.lei@redhat.com>
To: Yu Kuai <yukuai@fnnas.com>
Cc: Jens Axboe <axboe@kernel.dk>,
	nilay@linux.ibm.com, hch@lst.de,
	Steven Rostedt <rostedt@goodmis.org>,
	Masami Hiramatsu <mhiramat@kernel.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Yi Zhang <yi.zhang@redhat.com>,
	Shinichiro Kawasaki <shinichiro.kawasaki@wdc.com>,
	Keith Busch <kbusch@kernel.org>, Sagi Grimberg <sagi@grimberg.me>,
	linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
	linux-trace-kernel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] blk-mq: use NOIO context to prevent deadlock during debugfs creation
Date: Fri, 13 Feb 2026 12:43:58 +0800	[thread overview]
Message-ID: <aY6sDstii_R_zOfs@fedora> (raw)
In-Reply-To: <20260212080135.1673063-1-yukuai@fnnas.com>

On Thu, Feb 12, 2026 at 04:01:35PM +0800, Yu Kuai wrote:
> Creating debugfs entries can trigger fs reclaim, which can enter back
> into the block layer request_queue. This can cause deadlock if the
> queue is frozen.
> 
> Previously, a WARN_ON_ONCE check was used in debugfs_create_files()
> to detect this condition, but it was racy since the queue can be frozen
> from another context at any time.

debugfs lock doesn't depend on queue freeze, so the implied deadlock isn't
obvious.

Can you explain a bit why freeze from another context may cause dead lock?


Thanks, 
Ming


  parent reply	other threads:[~2026-02-13  4:44 UTC|newest]

Thread overview: 5+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2026-02-12  8:01 [PATCH] blk-mq: use NOIO context to prevent deadlock during debugfs creation Yu Kuai
2026-02-12  8:46 ` Nilay Shroff
2026-02-13  4:08   ` Yu Kuai
2026-02-13  4:43 ` Ming Lei [this message]
2026-02-13  5:39   ` Yu Kuai

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