linux-kernel - Re: [PATCH] x86: Extend test_and_set_bit() test_and_clean_bit() to 64 bits in X86

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Message-ID: <4A0C27AA.4010006@zytor.com>
Date:	Thu, 14 May 2009 07:16:10 -0700
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Andi Kleen <andi@...stfloor.org>
CC:	Sheng Yang <sheng@...ux.intel.com>, linux-kernel@...r.kernel.org,
	linux-mm <linux-mm@...ck.org>, Ingo Molnar <mingo@...e.hu>
Subject: Re: [PATCH] x86: Extend test_and_set_bit() test_and_clean_bit() to
 64 bits in X86_64

Andi Kleen wrote:
>>>
>> The right way to do it is to pass the proper type of register.
> 
> For the input index register you don't actually need 64bit and for the
> value it's typically memory anyways.
> 

If you have a 64-bit operation you have a 64-bit index register.  And
you need a 64-bit index for it to handle over 2^31 (since it is signed.)

	-hpa

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

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