Re: [PATCH v2] xen-blkfront: Fix IO race during unplug

[Roger Pau Monné <roger@xxxxxxxxxxxxxx>]

On Tue, Oct 06, 2026 at 05:34:07PM +0100, Ross Lagerwall wrote:
> During unplug, blkfront stops the hw queues and marks the disk as dead,
> then later during removal calls del_gendisk(). However, IO issued after
> the hw queues are stopped but before the call to del_gendisk() will be
> queued but never handled. This causes del_gendisk() to hang forever
> waiting for the queue refcount to drop to zero.
> 
> This can be reproduced by issuing IO during an artificial delay after
> stopping the hw queues.
> 
> Fix this by simply not stopping the hw queues directly. Marking the disk
> as dead already freezes the queue which prevents new requests being
> added and it synchronously runs the hw queues to clear anything pending.
> If the hw queues are stopped when calling blk_mark_disk_dead(), running
> the hw queues is a no-op and can leave queued requests unprocessed.
> 
> Cc: stable@xxxxxxxxxxxxxxx
> Assisted-by: LLM
> Signed-off-by: Ross Lagerwall <ross.lagerwall@xxxxxxxxxx>

Acked-by: Roger Pau Monné <roger@xxxxxxxxxxxxxx>

Thanks, Roger.