Re: Problems with SMP & ACPI powering off

From: Mark Lord
Date: Fri Sep 28 2007 - 09:46:45 EST

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.

To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at
Please read the FAQ at