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

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Message-ID: <20090528203022.GB1290@ucw.cz>
Date:	Thu, 28 May 2009 22:30:22 +0200
From:	Pavel Machek <pavel@....cz>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	lkml@...ethan.org, 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

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.

hp2133 did _not_ have that problem.

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
-- 
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
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