+ if (unlikely(dev->xmit_lock_owner == smp_processor_id())) {
+ /*
+ * Same CPU holding the lock. It may be a transient
+ * configuration error, when hard_start_xmit() recurses. We
+ * detect it by checking xmit owner and drop the packet when
+ * deadloop is detected. Return OK to try the next skb.
+ */
+ kfree_skb(skb);
+ if (net_ratelimit())
+ printk(KERN_WARNING "Dead loop on netdevice %s, "
+ "fix it urgently!\n", dev->name);
+ ret = qdisc_qlen(q);
+ } else {
+ /*
+ * Another cpu is holding lock, requeue & delay xmits for
+ * some time.
+ */
+ __get_cpu_var(netdev_rx_stat).cpu_collision++;
+ ret = dev_requeue_skb(skb, dev, q);
+ }
+
+ return ret;
+}
+
+/*
+ * NOTE: Called under dev->queue_lock with locally disabled BH.
+ *
+ * __LINK_STATE_QDISC_RUNNING guarantees only one CPU can process this
+ * device at a time. dev->queue_lock serializes queue accesses for
+ * this device AND dev->qdisc pointer itself.
+ *
+ * netif_tx_lock serializes accesses to device driver.
+ *
+ * dev->queue_lock and netif_tx_lock are mutually exclusive,
+ * if one is grabbed, another must be free.
+ *
+ * Note, that this procedure can be called by a watchdog timer
+ *
+ * Returns to the caller:
+ * 0 - queue is empty or throttled.
+ * >0 - queue is not empty.
+ *
+ */