linux-kernel - Re: [PATCH, re-send] Always trap on BUG()

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Message-ID: <51E47924.9030005@zytor.com>
Date:	Mon, 15 Jul 2013 15:35:16 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Russell King - ARM Linux <linux@....linux.org.uk>
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Arnd Bergmann <arnd@...db.de>, linux-arch@...r.kernel.org,
	linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org,
	Chen Gang <gang.chen@...anux.com>,
	Ingo Molnar <mingo@...nel.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	Geert Uytterhoeven <geert@...ux-m68k.org>
Subject: Re: [PATCH, re-send] Always trap on BUG()

On 07/15/2013 03:27 PM, Russell King - ARM Linux wrote:
> On Mon, Jul 15, 2013 at 03:16:12PM -0700, Andrew Morton wrote:
>> I've been thinking for a while that CONFIG_BUG=n is a pretty dumb thing
>> to do, and that maintaining it (and trying to fix the warnings it
>> produces) aren't worth the effort and that we should remove the whole
>> thing.  Perhaps your patch changes that calculus, dunno.  Please discuss.
> 
> This isn't about introducing "CONFIG_BUG=n" - this is about making a
> kernel with CONFIG_BUG=n build without producing tonnes and tonnes of
> warnings, as it does today.  It makes building randconfig pretty
> useless to find what could be more important warnings.
> 

Well, there are three alternatives here, right:

1. We can use unreachable(), which means that the compiler can assume it
never happens.

2. We can trap without metadata.

3. We can trap with metadata (current CONFIG_BUG=y).

I am *guessing* this does 2, but it isn't clear.

	-hpa


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