linux-kernel - Re: Problems with SMP & ACPI powering off

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Date:	Fri, 28 Sep 2007 09:46:32 -0400
From:	Mark Lord <lkml@....ca>
To:	"Rafael J. Wysocki" <rjw@...k.pl>
Cc:	Len Brown <lenb@...nel.org>,
	Linux Kernel <linux-kernel@...r.kernel.org>,
	simon.derr@...l.net
Subject: Re: Problems with SMP & ACPI powering off

Rafael J. Wysocki wrote:
> On Friday, 28 September 2007 15:22, Mark Lord wrote:
>> Rafael J. Wysocki wrote:
>>> On Friday, 28 September 2007 06:57, Len Brown wrote:
>>>> On Thursday 27 September 2007 18:00, Rafael J. Wysocki wrote:
>>>>> On Thursday, 27 September 2007 23:29, Mark Lord wrote:
>>>>>> Question:  do we disable all CPUs except 0 when doing ACPI power off?
>>>>> No, but we should.
>>>> We used to.
>>>> It is absolutely mandatory -- else it confuses the BIOS on some boards
>>>> b/c it isn't expecting SMM to get entered from other than cpu0.
>>> Can we use the CPU hotplug for that, like in the suspend/hibernation case?
>> Well, so far it's working:  about ten poweroffs since I patched it,
>> and no issues with any of them.  Prior to that, it seemed like about
>> one in five poweroffs wouldn't (power off).
>>
>> It'll take a lot more testing to confirm, though.
>>
>> What can I call to determine if more than one CPU is enabled, anyway?
>>
>> Here's the hack I'm using here, very situation (2 cores) specific,
>> and it still has some printk's leftover with a sleep so I have time
>> to read them before the lights go out.  :)
> 
> Well, we have disable_nonboot_cpus() that we use for suspend and that is
> supposed to be general.
> 
> The question is when to call it.

How about from the obvious candidate: kernel/sys.c::kernel_power_off() ?

I'll rework my hack into a proper patch there,
repost it here, and test with it for another day or two.

-ml
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