[NET_SCHED]: Reread dev->qdisc for NETDEV_TX_OK

Now that we return the queue length after NETDEV_TX_OK we better
make sure that we have the right queue.  Otherwise we can cause a
stall after a really quick dev_deactive/dev_activate.

Signed-off-by: Herbert Xu <herbert@gondor.apana.org.au>
Signed-off-by: David S. Miller <davem@davemloft.net>

net/sched/sch_generic.c

@@ -132,6 +132,7 @@ static inline int qdisc_restart(struct net_device *dev)
 						netif_tx_unlock(dev);
 					}
 					spin_lock(&dev->queue_lock);
+					q = dev->qdisc;
 					goto out;
 				}
 				if (ret == NETDEV_TX_LOCKED && nolock) {