linux-kernel - Re: Revert "gro: Fix legacy path napi

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Date:	Thu, 26 Mar 2009 11:40:59 +0800
From:	Herbert Xu <herbert@...dor.apana.org.au>
To:	David Miller <davem@...emloft.net>
Cc:	jarkao2@...il.com, mingo@...e.hu, r.schwebel@...gutronix.de,
	torvalds@...ux-foundation.org, blaschka@...ux.vnet.ibm.com,
	tglx@...utronix.de, a.p.zijlstra@...llo.nl,
	linux-kernel@...r.kernel.org, kernel@...gutronix.de
Subject: Re: Revert "gro: Fix legacy path napi_complete crash",

On Wed, Mar 25, 2009 at 08:20:50PM -0700, David Miller wrote:
>
> There is still a difference compared to your fix Herbert.  Jarek's
> patch flushes GRO first before the unlink.
> 
> I still believe that's critical, although like you I can't pinpoint
> why.
> 
> I know that GRO ought to be disabled here, but what if for some reason
> it isn't? :-)

Sure, I can accept that somehow someone has enabled GRO :) But
I'd still like to know why flushing the GRO afterwards would
lead to a hang.

> Adam Richter has successfully tested Jarek's variant, and if Ingo's
> tests show that it makes his problem go away too then I'm definitely
> going with Jarek's patch.

I don't have a problem with that.

I've asked Adam to test my patch as well.  So far the only failure
case against it has been on Ingo's machine, where the process_backlog
path isn't involved.  Yes it's used for loopback, but he's seeing
the hang on eth0, which with that config uses netif_receive_skb
so it should continue to work even if process_backlog completely
seizes up.

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