From: Christoph Hellwig <hch@lst.de>
To: Damien Le Moal <dlemoal@kernel.org>
Cc: Jens Axboe <axboe@kernel.dk>,
linux-block@vger.kernel.org, linux-nvme@lists.infradead.org,
Christoph Hellwig <hch@lst.de>, Keith Busch <kbusch@kernel.org>,
Sagi Grimberg <sagi@grimberg.me>, Ming Lei <ming.lei@redhat.com>,
Nilay Shroff <nilay@linux.ibm.com>
Subject: Re: [PATCH 2/3] block: Fix __blk_mq_update_nr_hw_queues() queue freeze and limits lock order
Date: Mon, 6 Jan 2025 09:30:14 +0100 [thread overview]
Message-ID: <20250106083014.GD18408@lst.de> (raw)
In-Reply-To: <20250104132522.247376-3-dlemoal@kernel.org>
On Sat, Jan 04, 2025 at 10:25:21PM +0900, Damien Le Moal wrote:
> __blk_mq_update_nr_hw_queues() freezes a device queues during operation,
> which also includes updating the BLK_FEAT_POLL feature flag for the
> device queues using queue_limits_start_update() and
> queue_limits_commit_update(). This call order thus creates an invalid
> ordering of a queue freeze and queue limit locking which can lead to a
> deadlock when the device driver must issue commands to probe the device
> when revalidating its limits.
>
> Avoid this issue by moving the update of the BLK_FEAT_POLL feature flag
> out of the main queue remapping loop to the end of
> __blk_mq_update_nr_hw_queues(), after the device queues have been
> unfrozen.
What happens if I/O is queued after the unfreeze, but before clearing
the poll flag?
next prev parent reply other threads:[~2025-01-06 8:30 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-01-04 13:25 [PATCH 0/3] Fix queue freeze and limit locking order Damien Le Moal
2025-01-04 13:25 ` [PATCH 1/3] block: Fix sysfs queue freeze and limits lock order Damien Le Moal
2025-01-04 16:26 ` Nilay Shroff
2025-01-06 8:27 ` Christoph Hellwig
2025-01-06 3:31 ` Ming Lei
2025-01-06 3:35 ` Damien Le Moal
2025-01-06 3:40 ` Ming Lei
2025-01-06 8:29 ` Christoph Hellwig
2025-01-06 11:15 ` Ming Lei
2025-01-06 15:29 ` Christoph Hellwig
2025-01-07 0:45 ` Ming Lei
2025-01-07 6:18 ` Christoph Hellwig
2025-01-06 8:25 ` Christoph Hellwig
2025-01-04 13:25 ` [PATCH 2/3] block: Fix __blk_mq_update_nr_hw_queues() " Damien Le Moal
2025-01-06 8:30 ` Christoph Hellwig [this message]
2025-01-06 9:58 ` Damien Le Moal
2025-01-06 10:00 ` Christoph Hellwig
2025-01-04 13:25 ` [PATCH 3/3] nvme: Fix " Damien Le Moal
2025-01-06 8:31 ` Christoph Hellwig
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