linux-kernel - Re: [tip:x86/mce] x86/bitops: Move BIT

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Message-ID: <4FBD167F.7080305@zytor.com>
Date:	Wed, 23 May 2012 09:55:27 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Linus Torvalds <torvalds@...ux-foundation.org>
CC:	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	Borislav Petkov <borislav.petkov@....com>, mingo@...nel.org,
	linux-kernel@...r.kernel.org, frank.arnold@....com,
	akpm@...ux-foundation.org, tglx@...utronix.de,
	linux-tip-commits@...r.kernel.org
Subject: Re: [tip:x86/mce] x86/bitops: Move BIT_64() for a wider use

On 05/23/2012 09:54 AM, Linus Torvalds wrote:
> On Wed, May 23, 2012 at 9:47 AM, H. Peter Anvin <hpa@...or.com> wrote:
>>
>> Any reason we can't just tell people to use BIT() for a native "unsigned
>> long" type (32/64 bits) and BIT_64() if they really want a 64-bit result?
> 
> Well, that's what we're doing now. And it seems to have resulted in
> repeated bugs for architectures where most of the developers run on
> 64-bit machines, but the same code is actually supposed to work on
> 32-bit too (ie x86).
> 

Yes, but I fear that this will result in more subtle bugs which will
therefore be even harder to detect and diagnose.

	-hpa

-- 
H. Peter Anvin, Intel Open Source Technology Center
I work for Intel.  I don't speak on their behalf.

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