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

[Ming Lei <ming.lei@redhat.com>]

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@oss.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