linux-kernel - Re: [PATCH 1/2] ACPI processor: force throttling state when BIOS returns incorrect value

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Message-Id: <20090819115855.193ea8bb.akpm@linux-foundation.org>
Date:	Wed, 19 Aug 2009 11:58:55 -0700
From:	Andrew Morton <akpm@...ux-foundation.org>
To:	Frans Pop <elendil@...net.nl>
Cc:	linux-acpi@...r.kernel.org, linux-kernel@...r.kernel.org,
	lenb@...el.com, rui.zhang@...el.com, stable@...nel.org
Subject: Re: [PATCH 1/2] ACPI processor: force throttling state when BIOS
 returns incorrect value

(cc stable)

On Mon, 17 Aug 2009 14:43:34 +0200 Frans Pop <elendil@...net.nl> wrote:

> If the BIOS reports an invalid throttling state (which seems to be
> fairly common after system boot), a reset is done to state T0.
> Because of a check in acpi_processor_get_throttling_ptc(), the reset
> never actually gets executed, which results in the error reoccurring
> on every access of for example /proc/acpi/processor/CPU0/throttling.
> 
> Add a 'force' option to acpi_processor_set_throttling() to ensure
> the reset really takes effect.
> 
> http://bugzilla.kernel.org/show_bug.cgi?id=13389
> 
> Signed-off-by: Frans Pop <elendil@...net.nl>
> Acked-by: Zhang Rui <rui.zhang@...el.com>

Unfortunately there are changes in linux-next which make this patch
inapplicable in non-trivial ways.

So we'll be needing one flavour of the patch for 2.6.30.x and 2.6.31.x
(the patch you just sent) and a different flavour for 2.6.32.

Or we preempt the pending linux-next changes and jam these patches into the
tree first.

>
> This patch, together with the next one, fixes a regression introduced in
> 2.6.30, listed on the regression list. They have been available for 2.5
> months now in bugzilla, but have not been picked up, despite various
> reminders and without any reason given.
> 
> Google shows that numerous people are hitting this issue. The issue is in
> itself relatively minor, but the bug in the code is clear.
> 
> The patches have been in all mu kernels and today testing has shown that
> throttling works correctly with the patches applied when the system
> overheats (http://bugzilla.kernel.org/show_bug.cgi?id=13918#c14).

OK, that sucks.

Guys, what happened here?  Fixing regressions surely is our number one
hair-on-fire priority, yet the ACPI developers have found other things
to be doing for two and a half months and now we have a mess on our
hands.

Did this just fall through the cracks or is there some problem?
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