linux-kernel - Re: [PATCH] x86: remove unneeded endless loop in BUG()

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Message-ID: <499DC5A6.1080305@zytor.com>
Date:	Thu, 19 Feb 2009 12:48:38 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Jeremy Fitzhardinge <jeremy@...p.org>
CC:	Ingo Molnar <mingo@...e.hu>, Petr Tesarik <ptesarik@...e.cz>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] x86: remove unneeded endless loop in BUG()

Jeremy Fitzhardinge wrote:
> 
> There's no reason to expect an "asm volatile" to stay put; the 
> "volatile" has nothing to do with preventing code motion.  The only way 
> to make an asm stick in one place is with data dependencies, and I'm not 
> sure what the dependency for __builtin_trap might be.  I'm guessing its 
> a "memory" clobber, but that's pure guesswork.
> 

I looked through this with HJL; the bottom line is that although it 
probably would work, it's not worth it.

I submitted GCC bug 39252 to get __builtin_not_reached(); instead.

	-hpa
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