On 1/8/25 6:25 PM, Christoph Hellwig wrote:
> queue_attr_store() always freezes a device queue before calling the
> attribute store operation. For attributes that control queue limits, the
> store operation will also lock the queue limits with a call to
> queue_limits_start_update(). However, some drivers (e.g. SCSI sd) may
> need to issue commands to a device to obtain limit values from the
> hardware with the queue limits locked. This creates a potential ABBA
> deadlock situation if a user attempts to modify a limit (thus freezing
> the device queue) while the device driver starts a revalidation of the
> device queue limits.
>
> Avoid such deadlock by not freezing the queue before calling the
> ->store_limit() method in struct queue_sysfs_entry and instead use the
> queue_limits_commit_update_frozen helper to freeze the queue after taking
> the limits lock.
>
> (commit log adapted from a similar patch from Damien Le Moal)
>
> Fixes: ff956a3be95b ("block: use queue_limits_commit_update in queue_discard_max_store")
> Fixes: 0327ca9d53bf ("block: use queue_limits_commit_update in queue_max_sectors_store")
> Signed-off-by: Christoph Hellwig <hch@xxxxxx>
> Reviewed-by: Nilay Shroff <nilay@xxxxxxxxxxxxx>
Reviewed-by: Damien Le Moal <dlemoal@xxxxxxxxxx>
--
Damien Le Moal
Western Digital Research
