Re: Linux v2.6.16

[Rafael J. Wysocki]

Hi,

On Wednesday 22 March 2006 18:54, Ashok Raj wrote:
> On Wed, Mar 22, 2006 at 06:39:41PM +0100, Rafael J. Wysocki wrote:
> > > 
> > > Please consider for inclusion... resending with changelog per Andrew.
> > 
> > Please don't apply this patch.
> > 
> > CPU hotplug is used by swsusp for disabling the nonboot CPUs.  Software
> > suspend won't work on SMP without CPU hotplugging.
> > 
> 
> Hi Rafael,
> 
> what part of this is not suitable for swsusp? All we do is just use flat physical mode
> for IPI processing. The only difference is moving from logical flat mode to using
> flat physical mode.
> 
> Have you tested swsusp with CONFIG_GENERICARCH and CONFIG_HOTPLUG_CPU=y ?
> 
> It might help to explain why this would break your swsusp with SMP work?

On SMP systems swsusp (suspend in general, AFAICT) uses the disable_nonboot_cpus()
function defined in kernel/power/smp.c, which calls cpu_down() that is only
defined if CONFIG_HOTPLUG_CPU is set.  We can't suspend and resume SMP systems
reliably without it.

Greetings,
Rafael
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