netpoll deferred transmit path

When the netpoll beast got busy, he tended to babble.
Instead of talking out of his large mouth as normal,
he tended to try to snort out other orifices. This lead
to words (skbs) ending up in odd places (like NIT) that
he did not intend.

The normal way of talking wouldn't work, but he could
at least change to using the same tone all the time.
Signed-off-by: NStephen Hemminger <shemminger@osdl.org>

net/core/netpoll.c

@@ -55,9 +55,25 @@ static void queue_process(void *p)
 	struct netpoll_info *npinfo = p;
 	struct sk_buff *skb;
 
-	while ((skb = skb_dequeue(&npinfo->txq)))
-		dev_queue_xmit(skb);
+	while ((skb = skb_dequeue(&npinfo->txq))) {
+		struct net_device *dev = skb->dev;
 
+		if (!netif_device_present(dev) || !netif_running(dev)) {
+			__kfree_skb(skb);
+			continue;
+		}
+
+		netif_tx_lock_bh(dev);
+		if (netif_queue_stopped(dev) ||
+		    dev->hard_start_xmit(skb, dev) != NETDEV_TX_OK) {
+			skb_queue_head(&npinfo->txq, skb);
+			netif_tx_unlock_bh(dev);
+
+			schedule_delayed_work(&npinfo->tx_work, HZ/10);
+			return;
+		}
+		netif_tx_unlock_bh(dev);
+	}
 }
 
 void netpoll_queue(struct sk_buff *skb)
@@ -765,6 +781,7 @@ void netpoll_cleanup(struct netpoll *np)
 			if (atomic_dec_and_test(&npinfo->refcnt)) {
 				skb_queue_purge(&npinfo->arp_tx);
  				skb_queue_purge(&npinfo->txq);
+				cancel_rearming_delayed_work(&npinfo->tx_work);
  				flush_scheduled_work();
 
 				kfree(npinfo);