From: David Miller <davem@davemloft.net>
Date: Mon, 26 May 2008 12:33:38 -0700 (PDT)

From: Jesper Krogh <redacted>
Date: Mon, 26 May 2008 21:03:34 +0200

quoted

Ok. Now I also hit it in production with the NFS-server, so this
is definately a real bug somewhere in the driver. Should I register it
at bugzilla?

Please feel free to do that.

BTW, I did stare at some of the transmit code of the NIU driver
while flying from Tokyo to Seattle a few hours ago, and I
found one possible theory on the transmit timeouts.

Can you try the patch below and let us know if the symptoms
continue?

[ Note to Matheos: The IRQ marking scheme of the NIU doesn't mesh
  well with how things work under Linux.  We really needs a
  "TX queue empty" interrupt status in order to handle all cases
  properly.  Otherwise we really cannot decide not mark some TX
  descriptors without potentially entering a deadlock condition.  ]

diff --git a/drivers/net/niu.c b/drivers/net/niu.c
index 918f802..7ab7f8e 100644
--- a/drivers/net/niu.c
+++ b/drivers/net/niu.c

@@ -6165,7 +6165,7 @@ static int niu_start_xmit(struct sk_buff *skb, struct net_device *dev)
 	rp->tx_buffs[prod].mapping = mapping;
 
 	mrk = TX_DESC_SOP;
-	if (++rp->mark_counter == rp->mark_freq) {
+	if (1 /*++rp->mark_counter == rp->mark_freq*/) {
 		rp->mark_counter = 0;
 		mrk |= TX_DESC_MARK;
 		rp->mark_pending++;