lkml.org 
[lkml]   [2008]   [Aug]   [5]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
Date
From
SubjectRe: + pm-introduce-new-interfaces-schedule_work_on-and-queue_work_on.patch added to -mm tree
Hi!

> > > This means that
> > >
> > > pm-schedule-sysrq-poweroff-on-boot-cpu.patch
> > >
> > > is not 100% right. It is still possible to hang/deadlock if we race
> > > with cpu_down(first_cpu(cpu_online_map)).
> >
> > Yes, you're right.
> > But then should we fix disable_nonboot_cpus as well?
> >
> > int disable_nonboot_cpus(void)
> > {
> > first_cpu = first_cpu(cpu_online_map);
> > ...
> >
> > for_each_online_cpu(cpu) {
> > if (cpu == first_cpu)
> > continue;
> > error = _cpu_down(cpu, 1);
> > ...
> > }
> > ...
> > }
>
> Note that disable_nonboot_cpus() does first_cpu = first_cpu() under
> cpu_maps_update_begin(), so we can't race with cpu-hotplug.
>
> However, this afaics means that its name is wrong, and
> printk("Disabling non-boot CPUs ...\n") is not right too.
> What it does is disable_all_but_one_cpus().

I thought that first cpu is defined to be boot cpu?

> And, it is not clear why disable_nonboot_cpus() assumes that
> all but first_cpu(cpu_online_map) must have .hotpluggable == 1.

Where does it assume that?

It will fail if some CPUs can't be unplugged, and I'm afraid suspend
can't work in such case...

> And, if one of the callers really need to preserve the boot CPU,
> I don't understand how it is guaranteed it must be first_cpu().

Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html


\
 
 \ /
  Last update: 2008-08-05 22:07    [W:0.050 / U:0.220 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site