linux-kernel - Re: [PATCH] net: fix race in the receive/select

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Message-ID: <20090629172938.GE6760@one.firstfloor.org>
Date:	Mon, 29 Jun 2009 19:29:38 +0200
From:	Andi Kleen <andi@...stfloor.org>
To:	Zan Lynx <zlynx@....org>
Cc:	Andi Kleen <andi@...stfloor.org>, Jiri Olsa <jolsa@...hat.com>,
	netdev@...r.kernel.org, linux-kernel@...r.kernel.org,
	fbl@...hat.com, nhorman@...hat.com, davem@...hat.com,
	oleg@...hat.com, eric.dumazet@...il.com
Subject: Re: [PATCH] net: fix race in the receive/select

On Mon, Jun 29, 2009 at 10:59:57AM -0600, Zan Lynx wrote:
> Andi Kleen wrote:
> >At least on x86 I can't see how it happens. mb() is only a compile
> >time barrier and the compiler doesn't optimize over indirect callbacks
> >like __pollwait() anyways.
> 
> Just a note about this. That used to be true, that GCC didn't optimize 
> indirect calls. However, see -findirect-inlining in GCC 4.4.

I am aware of that, but ...

> 
> I am not saying that it applies here, but it is something to remember.

... it doesn't apply here because it works only for a few very simple
cases that don't apply for this code. Besides the kernel builds with -O2,
which only inlines functions called once or very small functions, which
also rules this out.

-Andi

-- 
ak@...ux.intel.com -- Speaking for myself only.
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