Re: [PATCH v2 2/7] vdpa/mlx5: fix dead loop when process interrupted

[Maxime Coquelin <maxime.coquelin@redhat.com>]

On 2/24/22 16:50, Xueming Li wrote:
> In Ctrl+C handling, sometimes kick handling thread gets endless EGAIN
> error and fall into dead lock.
> 
> Kick happens frequently in real system due to busy traffic or retry
> mechanism. This patch simplifies kick firmware anyway and skip setting
> hardware notifier due to potential device error, notifier could be set
> in next successful kick request.
> 
> Fixes: 62c813706e41 ("vdpa/mlx5: map doorbell")
> Cc: stable@dpdk.org
> 
> Signed-off-by: Xueming Li <xuemingl@nvidia.com>
> ---
>   drivers/vdpa/mlx5/mlx5_vdpa_virtq.c | 8 +++++---
>   1 file changed, 5 insertions(+), 3 deletions(-)
> 
> diff --git a/drivers/vdpa/mlx5/mlx5_vdpa_virtq.c b/drivers/vdpa/mlx5/mlx5_vdpa_virtq.c
> index de324506cb9..e1e05924a40 100644
> --- a/drivers/vdpa/mlx5/mlx5_vdpa_virtq.c
> +++ b/drivers/vdpa/mlx5/mlx5_vdpa_virtq.c
> @@ -23,11 +23,11 @@ mlx5_vdpa_virtq_kick_handler(void *cb_arg)
>   	struct mlx5_vdpa_priv *priv = virtq->priv;
>   	uint64_t buf;
>   	int nbytes;
> +	int retry;
>   
>   	if (rte_intr_fd_get(virtq->intr_handle) < 0)
>   		return;
> -
> -	do {
> +	for (retry = 0; retry < 3; ++retry) {
>   		nbytes = read(rte_intr_fd_get(virtq->intr_handle), &buf,
>   			      8);
>   		if (nbytes < 0) {
> @@ -39,7 +39,9 @@ mlx5_vdpa_virtq_kick_handler(void *cb_arg)
>   				virtq->index, strerror(errno));
>   		}
>   		break;
> -	} while (1);
> +	}
> +	if (nbytes < 0)
> +		return;
>   	rte_write32(virtq->index, priv->virtq_db_addr);
>   	if (virtq->notifier_state == MLX5_VDPA_NOTIFIER_STATE_DISABLED) {
>   		if (rte_vhost_host_notifier_ctrl(priv->vid, virtq->index, true))

Reviewed-by: Maxime Coquelin <maxime.coquelin@redhat.com>

Thanks,
Maxime