linux-kernel - Re: [PATCH] swsusp: Disable nonboot CPUs before entering platform suspend

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Date:	Fri, 9 Mar 2007 13:29:34 +0100
From:	Heiko Carstens <heiko.carstens@...ibm.com>
To:	Pavel Machek <pavel@....cz>
Cc:	"Rafael J. Wysocki" <rjw@...k.pl>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] swsusp: Disable nonboot CPUs before entering platform suspend

On Wed, Mar 07, 2007 at 09:07:17PM +0000, Pavel Machek wrote:
> Hi!
> 
> > Prevent the WARN_ON() in arch/x86_64/kernel/acpi/sleep.c:init_low_mapping()
> > from triggering by disabling nonboot CPUs before we finally enter the platform
> > suspend.
> > 
> > Signed-off-by: Rafael J. Wysocki <rjw@...k.pl>
> > ---
> >  kernel/power/disk.c |    1 +
> >  kernel/power/user.c |    2 +-
> >  2 files changed, 2 insertions(+), 1 deletion(-)
> > 
> > Index: linux-2.6.21-rc2-mm2/kernel/power/disk.c
> > ===================================================================
> > --- linux-2.6.21-rc2-mm2.orig/kernel/power/disk.c
> > +++ linux-2.6.21-rc2-mm2/kernel/power/disk.c
> > @@ -61,6 +61,7 @@ static void power_down(suspend_disk_meth
> >  	switch(mode) {
> >  	case PM_DISK_PLATFORM:
> >  		if (pm_ops && pm_ops->enter) {
> > +			disable_nonboot_cpus();
> >  			kernel_shutdown_prepare(SYSTEM_SUSPEND_DISK);
> >  			pm_ops->enter(PM_SUSPEND_DISK);
> >  			break;
> 
> ...so, if pm_ops is non-null, power_down does nonboot cpu disabling,
> otherwise we proceed with cpus enabled?
> 
> That looks ugly.
> 
> Is the warning bogus? Or maybe we should *always* disable nonboot cpus
> in powerdown path?

Is disable_nonboot_cpus() assuming that first_cpu(cpu_present_map) is
the boot cpu? Just wondering why disable_nonboot_cpus() isn't using just
any_online_cpu(cpu_online_map)...
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