linux-kernel - Re: regression in 2.6.23-rc8

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Message-Id: <200709292308.13593.rjw@sisk.pl>
Date:	Sat, 29 Sep 2007 23:08:12 +0200
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Bill Davidsen <davidsen@....com>
Cc:	Alexey Starikovskiy <astarikovskiy@...e.de>,
	Mark Lord <lkml@....ca>, "H. Peter Anvin" <hpa@...or.com>,
	linux-kernel@...r.kernel.org
Subject: Re: regression in 2.6.23-rc8 - power off failed

On Saturday, 29 September 2007 22:47, Bill Davidsen wrote:
> Alexey Starikovskiy wrote:
> 
> > -static void
> > -acpi_power_off (void)
> > -{
> > -       printk("%s called\n",__FUNCTION__);
> > -       /* Some SMP machines only can poweroff in boot CPU */
> > -       set_cpus_allowed(current, cpumask_of_cpu(0));
> > ACPI in kernel 2.6.12 did disable non-boot cpus too in powe_off.
> > Later only comment was left for some reason...
> > 
> Am I midreading that code, or does it really assume that the boot cpu is 
> always zero? Or just that zero will be able to do the power off?
> 
> In any case I have had an SMP machine which did not have a CPU zero, and 
> it was discussed here, I believe. Wonder what happens if you set 
> affinity to a CPU you don't have...

Good question, but it also caused other problems to appear, IIRC.

IMHO, it's better to call disable_nonboot_cpus() in an appropriate place
anyway.

Greetings,
Rafael
-
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