linux-kernel - Re: [BUG FIX] Make x86_32 uni-processor Atomic ops, Atomic

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Message-Id: <200905301048.10639.lkml@morethan.org>
Date:	Sat, 30 May 2009 10:48:07 -0500
From:	"Michael S. Zick" <lkml@...ethan.org>
To:	Harald Welte <HaraldWelte@...tech.com>
Cc:	"H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...e.hu>,
	Thomas Gleixner <tglx@...utronix.de>,
	linux-kernel@...r.kernel.org, Alan Cox <alan@...rguk.ukuu.org.uk>
Subject: Re: [BUG FIX] Make x86_32 uni-processor Atomic ops, Atomic

On Sun May 24 2009, Harald Welte wrote:
> Dear hpa, and others,
> 
> On Sat, May 23, 2009 at 04:44:08PM -0700, H. Peter Anvin wrote:
> > It looks like there might be a problem with the C7-M ... Michael reports
> > that if he sets LOCK_PREFIX to "lock;" it works, but that shouldn't be
> > necessary for a uniprocessor.
> > 
> 
> I will try my best to help, though I have to admit I'm far from being
> a x86 expert, and particularly not with regard to low-level bits such as atomic
> operations.
> 
> So please give me some time to research some background about that,
> and read up all the details on the currently reported/described problem.
> 
> Once I understand it in full detail, I can talk to the right people inside
> CentaurLabs (VIA's CPU division).  
> 
> If somebody (optionally) can phrase a precise technical question that I can
> directly forward to somebody with low-level x86 knowledge but no Linux background,
> it would definitely help speeding up the process.
> 

Does the C7-M instruction set define the 'pause' instruction (0xf3,0x90)?
*Defined* since the P-4, but backward compatible with earlier ia32 processors
even though it falls into the "don't use rep before non-string instructions".

Mike

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