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

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Message-Id: <200905241332.39946.lkml@morethan.org>
Date:	Sun, 24 May 2009 13:32:37 -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, 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.

Mike
> 	-hpa
> 

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