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

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Date:	Mon, 25 May 2009 11:05:03 -0500
From:	"Michael S. Zick" <lkml@...ethan.org>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	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 Sun May 24 2009, Michael S. Zick wrote:
> On Sun May 24 2009, H. Peter Anvin wrote:
> > Michael S. Zick wrote:
> > > 
> > > @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.
> >
> 
> They are mostly out of the -09143 and -09144 builds -
> No cpufreq (I.E: no e_powersaver).
> The padlock-* drivers are modules which must be manually loaded. 
> 
> The i2c-viapro driver (in spite of its comments) does not work
> on CX700 (written before manual was released) - it is reading
> the serial number rather than the second data port. ;)
> (No access to the chipset temperature/voltage data on SMBus).
> 
> The via-fb driver just "doesn't work" - Haven't looked at it yet.
> 
> There is a VIA-specific driver for the VIA USB controller, but it
> isn't in the x86 part of the tree - Haven't looked at it yet.
> 
> There isn't a driver for the hardware watchdog on CX700 - 
> There isn't a driver for the machine error reporting -
> 
> = = = =
> 
> Although there may be timing requirement differences on the
> CX700 and CN896 - I think more likely a human error (typo)
> in the "clobber" lines of the asm - Have not yet audited that,
> but it is high on my list.
> 
> Note: I have seem to recall that newer gcc's optimizer presume 
> that the flags register is preserved across asm - 
> It didn't use to do that - but there is now a "cc" to deal with
> that - Have not yet audited for that, but it is high on my list.
> 
> Busy, busy, busy - -
> The -09144lk on C7-M/CX700 now up for 3 3/4 hours close to a new
> record - but ehci-hcd has not yet gone into a re-try loop.
>

The -09145{,lk}-db pair is posted now.
Same code-base/config as the -09144{,lk} pair with the addition 
of lockdep checking.
Details:
http://forum.netbookuser.com/viewtopic.php?pid=6980#p6980

Mike
> Mike
> > 	-hpa
> > 
> 
> 
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