Commit cd7e9034 authored Mar 13, 2008 by Divy Le Ray Committed by Jeff Garzik Mar 17, 2008

cxgb3: Fix transmit queue stop mechanism



The last change in the Tx queue stop mechanism opens a window
where the Tx queue might be stopped after pending credits
returned.

Tx credits are returned via a control message generated by the HW.
It returns tx credits on demand, triggered by a completion bit
set in selective transmit packet headers.

The current code can lead to the Tx queue stopped
with all pending credits returned, and the current frame
not triggering a credit return. The Tx queue will then never be
awaken.

The driver could alternatively request a completion for packets
that stop the queue. It's however safer at this point to go back
to the pre-existing behaviour.

Signed-off-by: Divy Le Ray <divy@chelsio.com>
Signed-off-by: Jeff Garzik <jeff@garzik.org>

parent cdb34697

drivers/net/cxgb3/sge.c

+9 −3

Original line number	Diff line number	Diff line
		@@ -1107,10 +1107,16 @@ int t3_eth_xmit(struct sk_buff skb, struct net_device dev)
		}

		q->in_use += ndesc;
		if (unlikely(credits - ndesc < q->stop_thres))
		if (USE_GTS \|\| !should_restart_tx(q))
		if (unlikely(credits - ndesc < q->stop_thres)) {
		t3_stop_queue(dev, qs, q);

		if (should_restart_tx(q) &&
		test_and_clear_bit(TXQ_ETH, &qs->txq_stopped)) {
		q->restarts++;
		netif_wake_queue(dev);
		}
		}

		gen = q->gen;
		q->unacked += ndesc;
		compl = (q->unacked & 8) << (S_WR_COMPL - 3);

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