On Saturday 14 June 2008 00:14:00 Mark McLoughlin wrote:

On Thu, 2008-05-29 at 16:34 +1000, Rusty Russell wrote:

quoted

On Tuesday 27 May 2008 21:06:26 Mark McLoughlin wrote:

quoted

On Mon, 2008-05-26 at 17:42 +1000, Rusty Russell wrote:

quoted

If we fail to transmit a packet, we assume the queue is full and put
the skb into last_xmit_skb.  However, if more space frees up before
we xmit it, we loop, and the result can be transmitting the same skb
twice.

Fix is simple: set skb to NULL if we've used it in some way, and
check before sending.

Great! It's a corner case, but it's no more complicated to do it your
way.

Minor mod, I find it clearer to have the vi->last_xmit_skb = NULL; under
the branch:

Subject: [PATCH] virtio_net: Delay dropping tx skbs
Date: Tue, 27 May 2008 12:06:26 +0100
From: Mark McLoughlin <redacted>

Currently we drop the skb in start_xmit() if we have a
queued buffer and fail to transmit it.

However, if we delay dropping it until we've stopped the
queue and enabled the tx notification callback, then there
is a chance space might become available for it.

Hmm, we lost this one somewhere along the way ...

Good catch.  Looks like it got folded, but pre-folded version got merged.  
Sorry, I've restored it to my series.

Thanks,
Rusty.