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Date:	Tue, 10 Oct 2006 08:41:46 -0700
From:	Tim Chen <tim.c.chen@...ux.intel.com>
To:	Steven Rostedt <rostedt@...dmis.org>
Cc:	Andrew Morton <akpm@...l.org>,
	Jeremy Fitzhardinge <jeremy@...p.org>,
	herbert@...dor.apana.org.au, linux-kernel@...r.kernel.org,
	leonid.i.ananiev@...el.com
Subject: Re: [PATCH] Fix WARN_ON / WARN_ON_ONCE regression

On Tue, 2006-10-10 at 09:04 -0400, Steven Rostedt wrote:

> 
> Holy crap!  I wonder where else in the kernel gcc is doing this. (of
> course I'm using gcc4 so I don't know).  Is there another gcc attribute
> to actually tell gcc that a variable is really mostly read only (besides
> placing it in a mostly read only elf section)?
> 
> What was wrong with the original WARN_ON_ONCE with
> 
>   if (unlikely(condition) && __warn_once)
> 
> This didn't have the cache crash problem too, did it?
> I don't have a gcc3 around to test.

In the original WARN_ON_ONCE, gcc3 only writes to __warn_once when
(condition) is true.  So it does not cause cache bouncing by always
writing to __warn_once.

Tim
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