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

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Date:	Fri, 28 Sep 2007 15:44:29 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Mark Lord <lkml@....ca>
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

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.

Greetings,
Rafael
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