netdev - Re: [PATCH 2/4] virtio_net: return NETDEV_TX_BUSY instead of queueing an extra skb.

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Message-ID: <20090614064528.GA29130@gondor.apana.org.au>
Date:	Sun, 14 Jun 2009 16:45:28 +1000
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	Rusty Russell <rusty@...tcorp.com.au>
Cc:	netdev@...r.kernel.org, virtualization@...ts.linux-foundation.org,
	David Miller <davem@...emloft.net>
Subject: Re: [PATCH 2/4] virtio_net: return NETDEV_TX_BUSY instead of
	queueing an extra skb.

On Sat, Jun 13, 2009 at 10:00:37PM +0930, Rusty Russell wrote:
> 
> But re your comment that the 67 drivers using TX_BUSY are doing it because of 
> driver bugs, that's hard to believe.  It either hardly ever happens (in which 
> case just drop the packet), or it happens (in which case we should handle it 
> correctly).

Most of them just do this:

start_xmit:

if (unlikely(queue is full)) {
	/* This should never happen. */
	return TX_BUSY;
}

transmit

if (queue is full)
	stop queue

Cheers,
-- 
Visit Openswan at http://www.openswan.org/
Email: Herbert Xu ~{PmV>HI~} <herbert@...dor.apana.org.au>
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