nfp: 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.

nfp 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 <edumazet@google.com>
Cc: Jakub Kicinski <jakub.kicinski@netronome.com>
Acked-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Tested-by: Jakub Kicinski <jakub.kicinski@netronome.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/netronome/nfp/nfp_net_common.c

@@ -3146,21 +3146,6 @@ nfp_net_vlan_rx_kill_vid(struct net_device *netdev, __be16 proto, u16 vid)
 	return nfp_net_reconfig_mbox(nn, NFP_NET_CFG_MBOX_CMD_CTAG_FILTER_KILL);
 }
 
-#ifdef CONFIG_NET_POLL_CONTROLLER
-static void nfp_net_netpoll(struct net_device *netdev)
-{
-	struct nfp_net *nn = netdev_priv(netdev);
-	int i;
-
-	/* nfp_net's NAPIs are statically allocated so even if there is a race
-	 * with reconfig path this will simply try to schedule some disabled
-	 * NAPI instances.
-	 */
-	for (i = 0; i < nn->dp.num_stack_tx_rings; i++)
-		napi_schedule_irqoff(&nn->r_vecs[i].napi);
-}
-#endif
-
 static void nfp_net_stat64(struct net_device *netdev,
 			   struct rtnl_link_stats64 *stats)
 {
@@ -3519,9 +3504,6 @@ const struct net_device_ops nfp_net_netdev_ops = {
 	.ndo_get_stats64	= nfp_net_stat64,
 	.ndo_vlan_rx_add_vid	= nfp_net_vlan_rx_add_vid,
 	.ndo_vlan_rx_kill_vid	= nfp_net_vlan_rx_kill_vid,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller	= nfp_net_netpoll,
-#endif
 	.ndo_set_vf_mac         = nfp_app_set_vf_mac,
 	.ndo_set_vf_vlan        = nfp_app_set_vf_vlan,
 	.ndo_set_vf_spoofchk    = nfp_app_set_vf_spoofchk,