i40evf: 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.

i40evf 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: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: NDavid S. Miller <davem@davemloft.net>

drivers/net/ethernet/intel/i40evf/i40evf_main.c

@@ -396,29 +396,6 @@ static void i40evf_map_rings_to_vectors(struct i40evf_adapter *adapter)
 	adapter->aq_required |= I40EVF_FLAG_AQ_MAP_VECTORS;
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-/**
- * i40evf_netpoll - A Polling 'interrupt' handler
- * @netdev: network interface device structure
- *
- * This is used by netconsole to send skbs without having to re-enable
- * interrupts.  It's not called while the normal interrupt routine is executing.
- **/
-static void i40evf_netpoll(struct net_device *netdev)
-{
-	struct i40evf_adapter *adapter = netdev_priv(netdev);
-	int q_vectors = adapter->num_msix_vectors - NONQ_VECS;
-	int i;
-
-	/* if interface is down do nothing */
-	if (test_bit(__I40E_VSI_DOWN, adapter->vsi.state))
-		return;
-
-	for (i = 0; i < q_vectors; i++)
-		i40evf_msix_clean_rings(0, &adapter->q_vectors[i]);
-}
-
-#endif
 /**
  * i40evf_irq_affinity_notify - Callback for affinity changes
  * @notify: context as to what irq was changed
@@ -3229,9 +3206,6 @@ static const struct net_device_ops i40evf_netdev_ops = {
 	.ndo_features_check	= i40evf_features_check,
 	.ndo_fix_features	= i40evf_fix_features,
 	.ndo_set_features	= i40evf_set_features,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= i40evf_netpoll,
-#endif
 	.ndo_setup_tc		= i40evf_setup_tc,
 };