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

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Message-ID: <20090524064905.GH20452@prithivi.gnumonks.org>
Date:	Sun, 24 May 2009 14:49:05 +0800
From:	Harald Welte <HaraldWelte@...tech.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	lkml@...ethan.org, 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

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.

> I'm wondering if we have to revive the OOSTORE hack, or some other
> workaround.  It is of course hard for me to track this down since (a) I
> don't have access to the CPU documentation, 

As far as I know, there really is no such documentation.. all documentation
that I've ever seen internally is electrical data sheets and high-level feature
set descriptiosn, CPUID, MSR and padlock.  There are no  actual x86 instruction
set documents... Centaur is < 100 people, they don't have the resources to work
on documents along the lines of what Intel has...

> and (b) I work for Intel now, which limits the amount of time I can
> realistically spend on this.

Sure, thanks for letting me know.
-- 
- Harald Welte <HaraldWelte@...tech.com>	    http://linux.via.com.tw/
============================================================================
VIA Open Source Liaison
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