Re: [PATCH 2/2] ata: libata-core: fix cancellation of a port deferred qc work

[Igor Pylypiv <ipylypiv@google.com>]

On Fri, Feb 20, 2026 at 02:00:53PM +0900, Damien Le Moal wrote:
> cancel_work_sync() is a sleeping function so it cannot be called with
> the spin lock of a port being held. Move the call to this function in
> ata_port_detach() before locking the port and add a call to
> ata_scsi_requeue_deferred_qc() to make sure there are no remaining
> deferred qc.
> 
> Fixes: 0ea84089dbf6 ("ata: libata-scsi: avoid Non-NCQ command starvation")
> Signed-off-by: Damien Le Moal <dlemoal@kernel.org>
> ---
>  drivers/ata/libata-core.c | 13 +++++++++----
>  1 file changed, 9 insertions(+), 4 deletions(-)
> 
> diff --git a/drivers/ata/libata-core.c b/drivers/ata/libata-core.c
> index beb6984b379a..54afa4df987e 100644
> --- a/drivers/ata/libata-core.c
> +++ b/drivers/ata/libata-core.c
> @@ -6254,9 +6254,18 @@ static void ata_port_detach(struct ata_port *ap)
>  	/* Wait for any ongoing EH */
>  	ata_port_wait_eh(ap);
>  
> +	/* Requeue any remaining deferred qc. */
> +	ata_scsi_requeue_deferred_qc(ap);
> +

ata_scsi_requeue_deferred_qc() requires the port lock to be held (function
has a lockdep assert).

>  	mutex_lock(&ap->scsi_scan_mutex);
> +
> +	/* Make sure the deferred qc work finished. */
> +	cancel_work_sync(&ap->deferred_qc_work);
> +
>  	spin_lock_irqsave(ap->lock, flags);
>  
> +	WARN_ON(ap->deferred_qc);
> +
>  	/* Remove scsi devices */
>  	ata_for_each_link(link, ap, HOST_FIRST) {
>  		ata_for_each_dev(dev, link, ALL) {
> @@ -6269,10 +6278,6 @@ static void ata_port_detach(struct ata_port *ap)
>  		}
>  	}
>  
> -	/* Make sure the deferred qc work finished. */
> -	cancel_work_sync(&ap->deferred_qc_work);
> -	WARN_ON(ap->deferred_qc);
> -
>  	/* Tell EH to disable all devices */
>  	ap->pflags |= ATA_PFLAG_UNLOADING;
>  	ata_port_schedule_eh(ap);
> -- 
> 2.53.0
> 
>