Re: APIC support prevents power off

From: Mikael Pettersson (
Date: Tue Jul 22 2003 - 03:35:36 EST

On Mon, 21 Jul 2003 11:54:14 +0200, Roger Luethi wrote:
>On Mon, 21 Jul 2003 03:13:52 +0200, Mikael Pettersson wrote:
>> On Sun, 20 Jul 2003 16:36:13 +0200, Roger Luethi wrote:
>> >On some UP boards (e.g. ASUS A7A266) enabling support for local APICs keeps
>> >the machine from powering off on shutdown. It will just hang instead.
>> >
>> >This has been observed by others before [1]. A warning in the respective
>> >configuration note seems in order (or a proper fix if anybody has one).
>> Insufficient data to draw anti-local-APIC conclusions.
>> - ensure you have the latest BIOS
>I tend not to touch the BIOS unless I have reason to believe an update will
>fix an actual problem.

Powering off invokes the BIOS. BIOSen are known to have bugs.
You really should check if a BIOS update is available.

>> - if you're using APM, ensure that CPU_IDLE and DISPLAY_BLANK are
>> disabled, and that APM isn't built as a module
>> (these things are known to cause APM hangs in UP APIC systems)
>> - if you're using ACPI, try without ACPI, or at least with ACPI not
>> doing any power management
>Your suggestions match my current configuration:

Your APM/ACPI config seems Ok, but what does CONFIG_SMP look like?
Enabling SMP disables APM's power off code, unless one boots with

Did your kernel have to actually enable the local APIC, or did
the BIOS boot us with it already enabled? Please send me a dmesg
from a boot with local APIC support enabled.

I can't seem to find any place where we disable the local APIC
on shutdown; reboot seems Ok but not poweroff (as far as I can see).
I think this might explain why some BIOSen hang at poweroff.

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