Re: (pspace,pid) vs true pid virtualization

["Serge E. Hallyn" <serue@us.ibm.com>]

Quoting Eric W. Biederman (ebiederm@xmission.com):
> > I think it should be acceptable if a pidspace is visible in all it's
> > ancestor pidspaces.  I.e. if I create pspace2 and pspace3 from pid 234
> > in pspace1, then pspace2 doesn't need to be able to address pspace3
> > and vice versa.
> 
> A good rule.  Now consider pspace 4 which is a child of pid 567
> in pspace 3.
> 
> What should pspace 3 see? 

Implementation dependent.

What I'd like to see is:

> What should pspace 3 see? 

The pid of the init process for pspace 4.

> What should pspace 1 see?

The pid of the init process for pspace 3.

> What happens when you migrate pspace 3 into a different pspace
> on a different machine?

Nothing special.  "Migrate" was just a checkpoint (from pspace 1)
and a resume (from pspace N on some machine).  So now pspace N on
the new machine has created a new pspace - which happens to be
immediately populated with the contents of the old pspace 3 - and
see the pid of the init process of this new pspace.

> Is there a sane implementation for this?

IMO, definately yes.

But I haven't tried it, so my opinion is just that.

-serge