Re: CPU hotplug on i386

[Pavel Machek <pavel@ucw.cz>]

Hi!

> On Wed, Mar 16, 2005 at 02:21:52PM +0100, Pavel Machek wrote:
> > +	int cpu, error;
> > +	cpus_clear(frozen_cpus);
> > +	printk("Freezing cpus...\n");
> > +	for_each_online_cpu(cpu) {
> > +		if (!cpu)
> > +			continue;
> > +		cpu_set(cpu, frozen_cpus);
> > +		error = cpu_down(cpu);
> > +		if (!error)
> > +			continue;
> > +		printk("Error taking cpu %d down: %d\n", cpu, error);
> > +		panic("Too many cpus");
> >  	}
> > -	printk("ok\n");
> > +	BUG_ON(smp_processor_id() != 0);
> >  }
> >  
> >  void enable_nonboot_cpus(void)
> >  {
> > -	printk("Restarting CPUs");
> > -	atomic_set(&freeze, 0);
> > -	while (atomic_read(&cpu_counter)) {
> > -		cpu_relax();
> > -		barrier();
> > +	int cpu, error;
> > +	printk("Thawing cpus...\n");
> > +	for_each_cpu_mask(cpu, frozen_cpus) {
> > +		if (!cpu)
> > +			continue;
> > +		error = cpu_up(cpu);
> > +		if (!error)
> > +			continue;
> > +		printk("Error taking cpu %d up: %d\n", cpu, error);
> > +		panic("Not enough cpus");
> >  	}
> 
> If you're going to depend on CONFIG_HOTPLUG_CPU for swsusp on smp, why
> not offline the non-boot cpus from userspace?  Same goes for onlining
> additional cpus during resume.

I'd like to stay in control. I may want to stop drivers first,
or something like that. Plus I need to do that during resume, too, when
userspace is not available, yet.
								Pavel
-- 
People were complaining that M$ turns users into beta-testers...
...jr ghea gurz vagb qrirybcref, naq gurl frrz gb yvxr vg gung jnl!