linux-kernel - Re: [PATCH 08/10] x86-32: support atomic64

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Message-ID: <4B7D5AC6.9070103@zytor.com>
Date:	Thu, 18 Feb 2010 07:20:38 -0800
From:	"H. Peter Anvin" <hpa@...or.com>
To:	Peter Zijlstra <peterz@...radead.org>
CC:	Luca Barbieri <luca@...a-barbieri.com>, mingo@...e.hu,
	akpm@...ux-foundation.org, linux-kernel@...r.kernel.org
Subject: Re: [PATCH 08/10] x86-32: support atomic64_t on 386/486 UP/SMP

On 02/18/2010 02:25 AM, Peter Zijlstra wrote:
> On Wed, 2010-02-17 at 12:42 +0100, Luca Barbieri wrote:
>> This patch makes atomic64 use either the generic implementation or
>> the rewritten cmpxchg8b one just introduced by inserting a "call" to
>> either, using the alternatives system to dynamically switch the calls.
>>
>> This allows to use atomic64_t on 386/486 which lack cmpxchg8b
> 
> IIRC we dropped <i586 SMP support, and since we don't have a PMU on
> those chips atomic64_t doesn't need to be NMI safe, so a simple
> UP-IRQ-disable implementation should suffice.

... which is what we have now, with the cmpxchg8b alternates emulation.

	-hpa

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

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