linux-kernel - Re: [PATCH] blk-mq: Abort suspend when wakeup events are pending

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Message-ID: <aS6vYCg2Gks2BGHn@fedora>
Date: Tue, 2 Dec 2025 17:20:32 +0800
From: Ming Lei <ming.lei@...hat.com>
To: Cong Zhang <cong.zhang@....qualcomm.com>
Cc: Jens Axboe <axboe@...nel.dk>, Daniel Wagner <dwagner@...e.de>,
	Hannes Reinecke <hare@...e.de>, linux-arm-msm@...r.kernel.org,
	linux-block@...r.kernel.org, linux-kernel@...r.kernel.org,
	pavan.kondeti@....qualcomm.com
Subject: Re: [PATCH] blk-mq: Abort suspend when wakeup events are pending

On Tue, Dec 02, 2025 at 11:56:12AM +0800, Cong Zhang wrote:
> During system suspend, wakeup capable IRQs for block device can be
> delayed, which can cause blk_mq_hctx_notify_offline() to hang
> indefinitely while waiting for pending request to complete.
> Skip the request waiting loop and abort suspend when wakeup events are
> pending to prevent the deadlock.
> 
> Fixes: bf0beec0607d ("blk-mq: drain I/O when all CPUs in a hctx are offline")
> Signed-off-by: Cong Zhang <cong.zhang@....qualcomm.com>
> ---
> The issue was found during system suspend with a no_soft_reset
> virtio-blk device. Here is the detailed analysis:
> - When system suspend starts and no_soft_reset is enabled, virtio-blk
>   does not call its suspend callback.
> - Some requests are dispatched and queued. After sending the virtqueue
>   notifier, the kernel waits for an IRQ to complete the request.
> - The virtio-blk IRQ is wakeup-capable. When the IRQ is triggered, it
>   remains pending because the device is in the suspend process.

Can you explain a bit for above point? Why does the IRQ remains pending
and not get handled?


Thanks, 
Ming