[dpdk-stable] [PATCH] net/mlx5: fix inconsistent link status

[shahafs]

From: Shahaf Shuler <shahafs at mellanox.com>

[ backported from upstream commit a9f2fbc42f0c58df614896a407fd694899315233 ]

Querying the link status can end up being in an inconsistent state,
like the port is reporting speed although it is down.

For this case another query is scheduled.

A race condition can occur between the scheduled query and link
status interrupt handlers.

When the scheduled query by-pass interrupt handlers, the link status
will be stuck in an inconsistent state.

This patch addresses the race condition by not blocking link status
queries in case delayed query is used.

Fixes: 198a3c339a8f ("mlx5: handle link status interrupts")
Cc: stable at dpdk.org

Signed-off-by: Shahaf Shuler <shahafs at mellanox.com>
Acked-by: Nelio Laranjeiro <nelio.laranjeiro at 6wind.com>
---
 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 a709a3a..06cfd01 100644
--- a/drivers/net/mlx5/mlx5_ethdev.c
+++ b/drivers/net/mlx5/mlx5_ethdev.c
@@ -1183,7 +1183,7 @@ 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. */
@@ -1191,29 +1191,24 @@ 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_unlocked(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;
 }
@@ -1233,6 +1228,7 @@ 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