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

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Date:	Thu, 28 May 2009 15:54:57 -0500
From:	"Michael S. Zick" <lkml@...ethan.org>
To:	Pavel Machek <pavel@....cz>
Cc:	"H. Peter Anvin" <hpa@...or.com>,
	Harald Welte <HaraldWelte@...tech.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 Thu May 28 2009, Pavel Machek wrote:
> Hi!
> 
> > > @hpa - I still like your suggestion that it is only one (or a few)
> > > uses of atomic ops that is incorrect and in general atomic ops
> > > should compile away on uni-processor.
> > > 
> > 
> > Actually, the more I think about it the more I suspect there is a race
> > condition either in the chip set or in any VIA-specific drivers (if
> > there are any.)  Putting LOCKs in random places will slow the CPU down
> > significantly, so it might resolve the race condition without actually
> > solving the problem.
> 
> Which you can verify; replace lock with something slow (pushad,
> popad)? And see what happens.
> 
> (And if it never ever triggers on hp2133, you have strong clue that it
> may not be cpu-related, but bios-related or chipset related or something).
> 
> Some time ago I was trying to debug misterious hangs on some
> via/fic machines. 
> 
> We never figured out what was wrong, but we discovered many other bios
> bugs, and those were not being fixed; so debugging was
> hard/impossible. Unfortunately I no longer have access to that hw.
> 

Then I am not losing my mind here - *it is* a difficult problem.  ;)

> hp2133 did _not_ have that problem.
>

Today's build has been playing me music for over 8 hours on the
HP-2133 (C7M-CN896) but can't get past a couple of hours on the
(fic) Everex Cloudbook (C7M-CX700).

Also, the distro on the Cloudbook is using pulse-audio - the
distro on the HP is not.  So I am reviewing the recent bug
fixes to kernel/futex for something over-looked.  ;)
May be a wild goose chase, but I think pulse-audio uses futexes.

Thanks for the other hints.

Mike 
> Try forcing maximum throttling, then move mouse for like five
> seconds. If kbc dies, you have same buggy bios, and probably are
> debugging same problem....
> 								Pavel


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