netdev - Re: [PATCH] net: orphan queued skbs if device tx can stall

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Message-ID: <20120408234951.GA15993@gondor.apana.org.au>
Date:	Mon, 9 Apr 2012 07:49:51 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	"Michael S. Tsirkin" <mst@...hat.com>
Cc:	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	"David S. Miller" <davem@...emloft.net>,
	Jamal Hadi Salim <hadi@...erus.ca>,
	Stephen Hemminger <shemminger@...tta.com>,
	Jason Wang <jasowang@...hat.com>,
	Neil Horman <nhorman@...driver.com>,
	Jiri Pirko <jpirko@...hat.com>,
	Jeff Kirsher <jeffrey.t.kirsher@...el.com>,
	Eric Dumazet <eric.dumazet@...il.com>,
	Michał Mirosław <mirq-linux@...e.qmqm.pl>,
	Ben Hutchings <bhutchings@...arflare.com>
Subject: Re: [PATCH] net: orphan queued skbs if device tx can stall

On Sun, Apr 08, 2012 at 08:13:25PM +0300, Michael S. Tsirkin wrote:
> commit 0110d6f22f392f976e84ab49da1b42f85b64a3c5
> tun: orphan an skb on tx
> Fixed a configuration where skbs get queued
> at the tun device forever, blocking senders.
> 
> However this fix isn't waterproof:
> userspace can control whether the interface
> is stopped, and if it is, packets
> get queued in the qdisc, again potentially forever.
> 
> Complete the fix by setting a private flag and orphaning
> at the qdisc level.
> 
> Signed-off-by: Michael S. Tsirkin <mst@...hat.com>

1) Doesn't this break local UDP push-back?
2) Isn't the stall a bug in the backend and isn't this just
papering over that?

Cheers,
-- 
Email: Herbert Xu <herbert@...dor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
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