LLTX fix proposal

Ok, how about we do this for 2.6.11 before it goes out and
do something more sophisticated (if necessary) later.

The BUG() we're trying to catch in the ->hard_start_xmit()
routines is the illegal state:

	driver_tx_queue_empty() && !netif_queue_stopped(dev)

Therefore we could handle the race, and avoid the printk() in
the race case but not in the BUG() case above.  The test in
tg3.c is currently:

	/* This is a hard error, log it. */
	if (unlikely(TX_BUFFS_AVAIL(tp) <= (skb_shinfo(skb)->nr_frags + 1))) {
		netif_stop_queue(dev);
		spin_unlock_irqrestore(&tp->tx_lock, flags);
		printk(KERN_ERR PFX "%s: BUG! Tx Ring full when queue awake!\n",
		       dev->name);
		return NETDEV_TX_BUSY;
	}

and I'm proposing we change it to something like:

	if (unlikely(TX_BUFFS_AVAIL(tp) <= (skb_shinfo(skb)->nr_frags + 1))) {
		/* We can race with queue processing on another
		 * cpu due to LLTX.  If the queue is not stopped,
		 * that is a hard error, log it.
		 */
		if (!netif_queue_stopped(dev)) {
			netif_stop_queue(dev);
			printk(KERN_ERR PFX "%s: BUG! Tx Ring full when "
			       "queue awake!\n",
			       dev->name);
		}
		spin_unlock_irqrestore(&tp->tx_lock, flags);
		return NETDEV_TX_BUSY;
	}

Any objections?

Again, I'm not saying %100 this is what we should do long-term.
It's meant to be correct and eliminate the bogus log messages
when the LLTX race is hit.