linux-kernel - Re: Andi, you broke my laptop :-)

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Date:	Thu, 10 May 2007 15:35:56 +0200
From:	"Joerg Roedel" <joerg.roedel@....com>
To:	"Andi Kleen" <andi@...stfloor.org>
cc:	"Pete Zaitcev" <zaitcev@...hat.com>, ak@...e.de,
	linux-kernel@...r.kernel.org, "Benny Halevy" <bhalevy@...asas.com>,
	akpm@...ux-foundation.org
Subject: Re: Andi, you broke my laptop :-)

On Thu, May 10, 2007 at 03:01:44PM +0200, Andi Kleen wrote:
> On Wed, May 09, 2007 at 12:56:16PM -0700, Pete Zaitcev wrote:
> > Hi, Andi:
> > 
> > The attached patch (actually, git show output) makes my Dell 1501 to hang
> > on boot. Sorry, I have no clue why... The culprit is found with git bisect.
> > But yes, it's an AMD MK-36. I use an x86_64 kernel. It is 100% reproducible.
> 
> MK-36? Does it have SVM? 
> 
> Anyways we previously had issues with this being miscompiled, but 
> I thought the latest patch should have been ok. What compiler do you use?
> 
> Can you send me a disassembly listing of arch/x86_64/kernel/time.o?

I debugged this problem a bit and my compiler[1]interprets the =A
constraint as %rax instead of %edx:%eax on x86_64 which causes the
problem. The appended patch provides a workaround for this and fixed the
hang on my machine.

[1] gcc version 4.1.3 20070429 (prerelease) (Debian 4.1.2-5)

Cc: Andi Kleen <ak@...e.de>
Signed-off-by: Joerg Roedel <joerg.roedel@....com>

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View attachment "x86_64_get_cycles_sync_fix.patch" of type "text/plain" (1904 bytes)