[PATCH] iseries_veth: Supress spurious WARN_ON() at module unload

My patch from a few weeks back (now in mainline), called "Cleanup skbs to
prevent unregister_netdevice() hanging", can cause our TX timeout code to
fire on machines with lots of VLANs (because it takes > 2 seconds between
when we stop the queues and when we're finished stopping the connections).

When that happens the TX timeout code freaks out and does a WARN_ON()
because as far as it's concerned there shouldn't be a TX timeout happening,
which is fair enough.

I have a "proper" fix for this, which is to a) do refcounting on
connections and b) implement a proper ack timer so we don't keep unacked
skbs lying around for ever.  But for 2.6.12 I propose just supressing the
WARN_ON().  Users will still see the "NETDEV WATCHDOG" warning, but that's
not nearly as bad as a WARN_ON() which users interpret as an Oops.
Signed-off-by: NMichael Ellerman <michael@ellerman.id.au>
Signed-off-by: NAndrew Morton <akpm@osdl.org>
Signed-off-by: NLinus Torvalds <torvalds@osdl.org>

drivers/net/iseries_veth.c

@@ -802,13 +802,14 @@ static void veth_tx_timeout(struct net_device *dev)
 
 	spin_lock_irqsave(&port->pending_gate, flags);
 
+	if (!port->pending_lpmask) {
+		spin_unlock_irqrestore(&port->pending_gate, flags);
+		return;
+	}
+
 	printk(KERN_WARNING "%s: Tx timeout!  Resetting lp connections: %08x\n",
 	       dev->name, port->pending_lpmask);
 
-	/* If we've timed out the queue must be stopped, which should
-	 * only ever happen when there is a pending packet. */
-	WARN_ON(! port->pending_lpmask);
-
 	for (i = 0; i < HVMAXARCHITECTEDLPS; i++) {
 		struct veth_lpar_connection *cnx = veth_cnx[i];