net/mlx5e: Protect hairpin entry flows list with spinlock

To remove dependency on rtnl lock, extend hairpin entry with spinlock and
use it to protect list of flows attached to hairpin entry from concurrent
modifications.
Signed-off-by: Vlad Buslov <vladbu@mellanox.com>
Reviewed-by: Jianbo Liu <jianbol@mellanox.com>
Reviewed-by: Roi Dayan <roid@mellanox.com>
Signed-off-by: Saeed Mahameed <saeedm@mellanox.com>

drivers/net/ethernet/mellanox/mlx5/core/en_tc.c

@@ -162,6 +162,8 @@ struct mlx5e_hairpin_entry {
 	/* a node of a hash table which keeps all the  hairpin entries */
 	struct hlist_node hairpin_hlist;
 
+	/* protects flows list */
+	spinlock_t flows_lock;
 	/* flows sharing the same hairpin */
 	struct list_head flows;
 
@@ -735,6 +737,7 @@ static int mlx5e_hairpin_flow_add(struct mlx5e_priv *priv,
 	if (!hpe)
 		return -ENOMEM;
 
+	spin_lock_init(&hpe->flows_lock);
 	INIT_LIST_HEAD(&hpe->flows);
 	hpe->peer_vhca_id = peer_id;
 	hpe->prio = match_prio;
@@ -782,7 +785,9 @@ static int mlx5e_hairpin_flow_add(struct mlx5e_priv *priv,
 		flow->nic_attr->hairpin_tirn = hpe->hp->tirn;
 	}
 	flow->hpe = hpe;
+	spin_lock(&hpe->flows_lock);
 	list_add(&flow->hairpin, &hpe->flows);
+	spin_unlock(&hpe->flows_lock);
 
 	return 0;
 
@@ -798,7 +803,10 @@ static void mlx5e_hairpin_flow_del(struct mlx5e_priv *priv,
 	if (!flow->hpe)
 		return;
 
+	spin_lock(&flow->hpe->flows_lock);
 	list_del(&flow->hairpin);
+	spin_unlock(&flow->hpe->flows_lock);
+
 	mlx5e_hairpin_put(priv, flow->hpe);
 	flow->hpe = NULL;
 }