linux-kernel - Re: New conflict message in latest GIT

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Message-Id: <200807231256.42743.bjorn.helgaas@hp.com>
Date:	Wed, 23 Jul 2008 12:56:42 -0600
From:	Bjorn Helgaas <bjorn.helgaas@...com>
To:	"Fabio Comolli" <fabio.comolli@...il.com>
Cc:	"Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
	Rene Herman <rene.herman@...access.nl>,
	Andrew Morton <akpm@...l.org>,
	Thomas Renninger <trenn@...e.de>,
	Jean Delvare <khali@...ux-fr.org>
Subject: Re: New conflict message in latest GIT

On Tuesday 22 July 2008 12:56:36 pm Fabio Comolli wrote:
> Linus' GIT tree 2.6.26-05752-g93ded9b shows this message:
> 
> i801_smbus 0000:00:1f.3: PCI INT B -> GSI 19 (level, low) -> IRQ 19
> ACPI: I/O resource 0000:00:1f.3 [0x18e0-0x18ff] conflicts with ACPI
> region SMBI [0x18e0-0x18ef]
> ACPI: Device needs an ACPI driver
> 
> There is no equivalent in 2.6.26 or previous kernels.

The "ACPI: I/O resource ... conflicts with ..." message was added by
Thomas:
  http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=df92e695998e1bc6e426a840eb86d6d1ee87e2a5

That conflict checking infrastructure was in 2.6.26, but Jean's
change to make the i801_smbus driver use it didn't happen until
about a week ago:
  http://git.kernel.org/?p=linux/kernel/git/torvalds/linux-2.6.git;a=commitdiff;h=54fb4a05af0a4b814e6716cfdf3fa97fc6be7a32

The message is telling us that the i801_smbus driver thinks it owns
the 0x18e0-0x18ff region, but there's also an ACPI opregion that
references that region.  There's no coordination between ACPI and
the i801_smbus driver, so there may be issues where nearly
simultaneous accesses cause incorrect behavior, e.g,. one may
read the wrong value from a temperature sensor.  That, of course,
can lead to more serious things like unintended machine shutdowns.

I don't have any ideas about how to address this.  I think Thomas's
intent was to collect better information for unreproducible bugs.
(Maybe this sort of conflict should even set a taint flag?)

Bjorn

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