net: hns: 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.

hns 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: Yisen Zhuang <yisen.zhuang@huawei.com>
Cc: Salil Mehta <salil.mehta@huawei.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

drivers/net/ethernet/hisilicon/hns/hns_enet.c

@@ -1503,21 +1503,6 @@ static int hns_nic_do_ioctl(struct net_device *netdev, struct ifreq *ifr,
 	return phy_mii_ioctl(phy_dev, ifr, cmd);
 }
 
-/* use only for netconsole to poll with the device without interrupt */
-#ifdef CONFIG_NET_POLL_CONTROLLER
-static void hns_nic_poll_controller(struct net_device *ndev)
-{
-	struct hns_nic_priv *priv = netdev_priv(ndev);
-	unsigned long flags;
-	int i;
-
-	local_irq_save(flags);
-	for (i = 0; i < priv->ae_handle->q_num * 2; i++)
-		napi_schedule(&priv->ring_data[i].napi);
-	local_irq_restore(flags);
-}
-#endif
-
 static netdev_tx_t hns_nic_net_xmit(struct sk_buff *skb,
 				    struct net_device *ndev)
 {
@@ -1970,9 +1955,6 @@ static const struct net_device_ops hns_nic_netdev_ops = {
 	.ndo_set_features = hns_nic_set_features,
 	.ndo_fix_features = hns_nic_fix_features,
 	.ndo_get_stats64 = hns_nic_get_stats64,
-#ifdef CONFIG_NET_POLL_CONTROLLER
-	.ndo_poll_controller = hns_nic_poll_controller,
-#endif
 	.ndo_set_rx_mode = hns_nic_set_rx_mode,
 	.ndo_select_queue = hns_nic_select_queue,
 };