linux-kernel - Re: 2.6.27-rc1 and 2.6.26.1: critical thermal shutdown on thinkpad x60 (bisected)

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Date:	Tue, 12 Aug 2008 18:01:18 +0200
From:	Thomas Renninger <trenn@...e.de>
To:	Milan Broz <mbroz@...hat.com>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>, Pavel Machek <pavel@...e.cz>,
	Andi Kleen <andi@...stfloor.org>,
	kernel list <linux-kernel@...r.kernel.org>,
	ACPI mailing list <linux-acpi@...r.kernel.org>,
	Alexey Starikovskiy <astarikovskiy@...e.de>,
	"Greg Kroah-Hartman" <gregkh@...ell.com>, stable@...nel.org
Subject: Re: 2.6.27-rc1 and 2.6.26.1: critical thermal shutdown on thinkpad x60 (bisected)

On Tuesday 12 August 2008 17:48:27 Milan Broz wrote:
> >>>> yes. maybe some userspace tool controlling frequency is involved, no
> >>>> idea yet. But it is 2.6.26 tree for sure.
> >>>
> >>> So it definitely is in 2.6.26.2, and it definitely is in 2.6.26?
> >
> > The bug is _not_ in 2.6.26, it was introduced in 2.6.26.1.
> >
> > The problem is, that now the CPU frequency doesn't decrease at some
> > temperature level and fan is unable to cool it properly.
Hmm, the machine should still not shut down. We need the virtual
passive trip point...
> >
> > bisect on 2.6.26.y tree finished in this patch:
> > (I expect similar patch in 2.6.27-rc)
> >
> > commit 04f496871e8af87a1e40c504371a206fd7389193
> > Author: Thomas Renninger <trenn@...e.de>
> > Date:   Wed Jul 30 18:20:10 2008 +0000
>
> and this seems to fix it for me:
> --
>
> Do not use unsigned int if there is test for negative number...
>
> See drivers/acpi/processor_perflib.c
>   static unsigned int ignore_ppc = -1;
> ...
>   if (event == CPUFREQ_START && ignore_ppc <= 0) {
>        ignore_ppc = 0;
> ...
>
> Signed-off-by: Milan Broz <mbroz@...hat.com>
> ---
>  drivers/acpi/processor_perflib.c |    2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> Index: linux-2.6.26.y/drivers/acpi/processor_perflib.c
> ===================================================================
> --- linux-2.6.26.y.orig/drivers/acpi/processor_perflib.c	2008-08-12
> 17:20:07.000000000 +0200 +++
> linux-2.6.26.y/drivers/acpi/processor_perflib.c	2008-08-12
> 17:35:53.000000000 +0200 @@ -70,7 +70,7 @@ static
> DEFINE_MUTEX(performance_mutex);
>   *  0 -> cpufreq low level drivers initialized -> consider _PPC values
>   *  1 -> ignore _PPC totally -> forced by user through boot param
>   */
> -static unsigned int ignore_ppc = -1;
> +static int ignore_ppc = -1;
Ohh dear..., what kind of obvious bug have I introduced.

Thanks a lot!

         Thomas
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