ixgbe: 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.

ixgbe uses NAPI for TX completions, so we better let core
networking stack call the napi->poll() to avoid the capture.
Reported-by: Song Liu <songliubraving@fb.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
Tested-by: Song Liu <songliubraving@fb.com>
Cc: Jeff Kirsher <jeffrey.t.kirsher@intel.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/intel/ixgbe/ixgbe_main.c

@@ -8768,28 +8768,6 @@ static int ixgbe_del_sanmac_netdev(struct net_device *dev)
 	return err;
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-/*
- * Polling 'interrupt' - used by things like netconsole to send skbs
- * without having to re-enable interrupts. It's not called while
- * the interrupt routine is executing.
- */
-static void ixgbe_netpoll(struct net_device *netdev)
-{
-	struct ixgbe_adapter *adapter = netdev_priv(netdev);
-	int i;
-
-	/* if interface is down do nothing */
-	if (test_bit(__IXGBE_DOWN, &adapter->state))
-		return;
-
-	/* loop through and schedule all active queues */
-	for (i = 0; i < adapter->num_q_vectors; i++)
-		ixgbe_msix_clean_rings(0, adapter->q_vector[i]);
-}
-
-#endif
-
 static void ixgbe_get_ring_stats64(struct rtnl_link_stats64 *stats,
 				   struct ixgbe_ring *ring)
 {
@@ -10251,9 +10229,6 @@ static const struct net_device_ops ixgbe_netdev_ops = {
 	.ndo_get_vf_config	= ixgbe_ndo_get_vf_config,
 	.ndo_get_stats64	= ixgbe_get_stats64,
 	.ndo_setup_tc		= __ixgbe_setup_tc,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= ixgbe_netpoll,
-#endif
 #ifdef IXGBE_FCOE
 	.ndo_select_queue	= ixgbe_select_queue,
 	.ndo_fcoe_ddp_setup = ixgbe_fcoe_ddp_get,