mlx4: remove ndo_poll_controller

As diagnosed by Song Liu, ndo_poll_controller() can
be very dangerous on loaded hosts, since the cpu
calling ndo_poll_controller() might steal all NAPI
contexts (for all RX/TX queues of the NIC). This capture
can last for unlimited amount of time, since one
cpu is generally not able to drain all the queues under load.

mlx4 uses NAPI for TX completions, so we better let core
networking stack call the napi->poll() to avoid the capture.
Signed-off-by: NEric Dumazet <edumazet@google.com>
Cc: Tariq Toukan <tariqt@mellanox.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/mellanox/mlx4/en_netdev.c

@@ -1286,20 +1286,6 @@ static void mlx4_en_do_set_rx_mode(struct work_struct *work)
 	mutex_unlock(&mdev->state_lock);
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-static void mlx4_en_netpoll(struct net_device *dev)
-{
-	struct mlx4_en_priv *priv = netdev_priv(dev);
-	struct mlx4_en_cq *cq;
-	int i;
-
-	for (i = 0; i < priv->tx_ring_num[TX]; i++) {
-		cq = priv->tx_cq[TX][i];
-		napi_schedule(&cq->napi);
-	}
-}
-#endif
-
 static int mlx4_en_set_rss_steer_rules(struct mlx4_en_priv *priv)
 {
 	u64 reg_id;
@@ -2946,9 +2932,6 @@ static const struct net_device_ops mlx4_netdev_ops = {
 	.ndo_tx_timeout		= mlx4_en_tx_timeout,
 	.ndo_vlan_rx_add_vid	= mlx4_en_vlan_rx_add_vid,
 	.ndo_vlan_rx_kill_vid	= mlx4_en_vlan_rx_kill_vid,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= mlx4_en_netpoll,
-#endif
 	.ndo_set_features	= mlx4_en_set_features,
 	.ndo_fix_features	= mlx4_en_fix_features,
 	.ndo_setup_tc		= __mlx4_en_setup_tc,
@@ -2983,9 +2966,6 @@ static const struct net_device_ops mlx4_netdev_ops_master = {
 	.ndo_set_vf_link_state	= mlx4_en_set_vf_link_state,
 	.ndo_get_vf_stats       = mlx4_en_get_vf_stats,
 	.ndo_get_vf_config	= mlx4_en_get_vf_config,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= mlx4_en_netpoll,
-#endif
 	.ndo_set_features	= mlx4_en_set_features,
 	.ndo_fix_features	= mlx4_en_fix_features,
 	.ndo_setup_tc		= __mlx4_en_setup_tc,