Re: 2.6.33-rc4 i686 clone function looping (seems real!)

["Serge E. Hallyn" <serue-r/Jw6+rmf7HQT0dZR+AlfA@public.gmane.org>]

Quoting Peter Zijlstra (peterz-wEGCiKHe2LqWVfeAwA7xHQ@public.gmane.org):
> On Thu, 2010-01-21 at 11:13 -0600, Serge E. Hallyn wrote:
> > The culprit is e2912009fb7b715728311b0d8fe327a1432b3f79
> >     sched: Ensure set_task_cpu() is never called on blocked tasks
> > 
> > If you mount both the ns and cpuset cgroups with this patch applied,
> > then doing clone with CLONE_NEWPID, CLONE_NEWNET, etc, you get the
> > hang.  The hang is actually hard enough that alt-sysrq isn't helpful :)
> > Still trying to figure out what is going on - Peter, any ideas offhand?
> 
> 
> Does it replicate on x86_64 ?

Hmm, doesn't seem to, no.

> /me looks at the NEWPID and NEWNET code
> 
> 
> Hmm, I have an idea.. does it really need the ns cgroup stuff?

To reproduce it?  Well, there might be some other way to
trigger it, but mounting just cpusets and moving a task into
a different cpuset doesn't trigger it...  So really it must
be something to do with kernel/cgroup.c:cgroup_clone()

> Let me try and come up with a debug patch...

thanks,
-serge