mlx5: 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.

mlx5 uses NAPI for TX completions, so we better let core
networking stack call the napi->poll() to avoid the capture.

Signed-off-by: Eric Dumazet <[email protected]>
Cc: Saeed Mahameed <[email protected]>
Signed-off-by: David S. Miller <[email protected]>

Author: edumazet

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

@@ -4315,22 +4315,6 @@ static int mlx5e_xdp(struct net_device *dev, struct netdev_bpf *xdp)
 	}
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-/* Fake "interrupt" called by netpoll (eg netconsole) to send skbs without
- * reenabling interrupts.
- */
-static void mlx5e_netpoll(struct net_device *dev)
-{
-	struct mlx5e_priv *priv = netdev_priv(dev);
-	struct mlx5e_channels *chs = &priv->channels;
-
-	int i;
-
-	for (i = 0; i < chs->num; i++)
-		napi_schedule(&chs->c[i]->napi);
-}
-#endif
-
 static const struct net_device_ops mlx5e_netdev_ops = {
 	.ndo_open                = mlx5e_open,
 	.ndo_stop                = mlx5e_close,
@@ -4356,9 +4340,6 @@ static const struct net_device_ops mlx5e_netdev_ops = {
 #ifdef CONFIG_MLX5_EN_ARFS
 	.ndo_rx_flow_steer	 = mlx5e_rx_flow_steer,
 #endif
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller     = mlx5e_netpoll,
-#endif
 #ifdef CONFIG_MLX5_ESWITCH
 	/* SRIOV E-Switch NDOs */
 	.ndo_set_vf_mac          = mlx5e_set_vf_mac,