On Tue, Jan 31, 2017 at 03:13:38PM +0200, Shahaf Shuler wrote:
> Query the link status can end up in an inconsist state where the port is
> down but it is reporting speed. For that another query is scheduled for a
> later time.
> A race condition is possible between the scheduled call and other link
> status interrupt handlers. When the scheduled query by-pass those handlers,
> the link status will be stuck in an in-consist state.
> This patch addresses the race condition by not blocking link status
> queries in case delayed query is on the flight.
>
> Fixes: 198a3c339a8f ("mlx5: handle link status interrupts")
> CC: sta...@dpdk.org
>
> Signed-off-by: Shahaf Shuler <shah...@mellanox.com>
> ---
> on v3:
> * allow only single alarm on the flight.
>
> on v2:
> * change the commit log to better explain the race
> * instead of blocking other interrupt handlers allow everyone to query the
> link status
> ---
> drivers/net/mlx5/mlx5_ethdev.c | 26 +++++++++++---------------
> 1 file changed, 11 insertions(+), 15 deletions(-)
>
> diff --git a/drivers/net/mlx5/mlx5_ethdev.c b/drivers/net/mlx5/mlx5_ethdev.c
> index e77238f..fcbe273 100644
> --- a/drivers/net/mlx5/mlx5_ethdev.c
> +++ b/drivers/net/mlx5/mlx5_ethdev.c
> @@ -1128,7 +1128,7 @@ struct priv *
> priv_dev_link_status_handler(struct priv *priv, struct rte_eth_dev *dev)
> {
> struct ibv_async_event event;
> - int port_change = 0;
> + struct rte_eth_link *link = &dev->data->dev_link;
> int ret = 0;
>
> /* Read all message and acknowledge them. */
> @@ -1136,29 +1136,24 @@ struct priv *
> if (ibv_get_async_event(priv->ctx, &event))
> break;
>
> - if (event.event_type == IBV_EVENT_PORT_ACTIVE ||
> - event.event_type == IBV_EVENT_PORT_ERR)
> - port_change = 1;
> - else
> + if (event.event_type != IBV_EVENT_PORT_ACTIVE &&
> + event.event_type != IBV_EVENT_PORT_ERR)
> DEBUG("event type %d on port %d not handled",
> event.event_type, event.element.port_num);
> ibv_ack_async_event(&event);
> }
> -
> - if (port_change ^ priv->pending_alarm) {
> - struct rte_eth_link *link = &dev->data->dev_link;
> -
> - priv->pending_alarm = 0;
> - mlx5_link_update(dev, 0);
> - if (((link->link_speed == 0) && link->link_status) ||
> - ((link->link_speed != 0) && !link->link_status)) {
> + mlx5_link_update(dev, 0);
> + if (((link->link_speed == 0) && link->link_status) ||
> + ((link->link_speed != 0) && !link->link_status)) {
> + if (!priv->pending_alarm) {
> /* Inconsistent status, check again later. */
> priv->pending_alarm = 1;
> rte_eal_alarm_set(MLX5_ALARM_TIMEOUT_US,
> mlx5_dev_link_status_handler,
> dev);
> - } else
> - ret = 1;
> + }
> + } else {
> + ret = 1;
> }
> return ret;
> }
> @@ -1178,6 +1173,7 @@ struct priv *
>
> priv_lock(priv);
> assert(priv->pending_alarm == 1);
> + priv->pending_alarm = 0;
> ret = priv_dev_link_status_handler(priv, dev);
> priv_unlock(priv);
> if (ret)
> --
> 1.8.3.1
Acked-by: Nelio Laranjeiro <nelio.laranje...@6wind.com>
--
Nélio Laranjeiro
6WIND
