[PATCH v2 02/37] baseband/acc100: update ring availability calculation

[Maxime Coquelin]

Hi,

On 8/20/22 04:31, Hernan Vargas wrote:
> Refactor of the queue availability computation to prevent the
> application to dequeue more than what may have been enqueued.
> 

That sounds like a fix, is it?

If so, it should have the Fixes tag, so that existing application can
get the fix without having to upgrade to a newer DPDK version that may
have introduced API/ABI changes.

> Signed-off-by: Hernan Vargas <hernan.vargas at intel.com>
> ---
>   drivers/baseband/acc100/rte_acc100_pmd.c | 39 ++++++++++++++++--------
>   1 file changed, 27 insertions(+), 12 deletions(-)
> 
> diff --git a/drivers/baseband/acc100/rte_acc100_pmd.c b/drivers/baseband/acc100/rte_acc100_pmd.c
> index 7f698ec3d2..0598d33582 100644
> --- a/drivers/baseband/acc100/rte_acc100_pmd.c
> +++ b/drivers/baseband/acc100/rte_acc100_pmd.c
> @@ -3465,13 +3465,27 @@ acc100_enqueue_queue_full(struct rte_bbdev_queue_data *q_data)
>   	acc100_enqueue_status(q_data, RTE_BBDEV_ENQ_STATUS_QUEUE_FULL);
>   }
>   
> +/* Number of available descriptor in ring to enqueue */

s/descriptor/descriptors/

> +static uint32_t
> +acc100_ring_avail_enq(struct acc100_queue *q)
> +{
> +	return (q->sw_ring_depth - 1 + q->sw_ring_tail - q->sw_ring_head) % q->sw_ring_depth;
> +}
> +
> +/* Number of available descriptor in ring to dequeue */

s/descriptor/descriptors/

> +static uint32_t
> +acc100_ring_avail_deq(struct acc100_queue *q)
> +{
> +	return (q->sw_ring_depth + q->sw_ring_head - q->sw_ring_tail) % q->sw_ring_depth;
> +}
> +
>   /* Enqueue encode operations for ACC100 device in CB mode. */
>   static uint16_t
>   acc100_enqueue_enc_cb(struct rte_bbdev_queue_data *q_data,
>   		struct rte_bbdev_enc_op **ops, uint16_t num)
>   {
>   	struct acc100_queue *q = q_data->queue_private;
> -	int32_t avail = q->sw_ring_depth + q->sw_ring_tail - q->sw_ring_head;
> +	int32_t avail = acc100_ring_avail_enq(q);

acc100_ring_avail_enq returns an uint32_t, but avail is an int32_t.

I think avail should be a uint32_t and underflow check should be changed to:

	if (unlikely(avail == 0)) {

Same comment applies in other places.

Maxime