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

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Date:	Fri, 9 Mar 2007 20:39:19 +0100
From:	"Rafael J. Wysocki" <rjw@...k.pl>
To:	Heiko Carstens <heiko.carstens@...ibm.com>
Cc:	Pavel Machek <pavel@....cz>,
	Andrew Morton <akpm@...ux-foundation.org>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: [PATCH] swsusp: Disable nonboot CPUs before entering platform suspend

On Friday, 9 March 2007 13:29, Heiko Carstens wrote:
> 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)...

Is your question related to the code in kernel/cpu.c?

Rafael
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