[Devel] Re: [PATCH 1/15] Move exit_task_namespaces()

[Oleg Nesterov]

On 08/06, Pavel Emelyanov wrote:
> Oleg Nesterov wrote:
> >On 07/26, Pavel Emelyanov wrote:
> >>The reason to release namespaces after reparenting is that when task
> >>exits it may send a signal to its parent (SIGCHLD), but if the parent
> >>has already exited its namespaces there will be no way to decide what
> >>pid to dever to him - parent can be from different namespace.
> >
> >I almost forgot about this one...
> >
> >After reading the whole series, I can't understand the above explanation
> >any longer. The parent can't be from different namespace, either we have
> >another sub-thread, or we reparent the child to /sbin/init which should
> >be from the same namespace.
> 
> If the child that is a new namespace's init is exiting its parent is from the
> different namespace.

In that case it doesn't have childs. The were SIGKILL'ed before exit_notify().

> Moreover, we will probably want to implement "entering"
> the pid namespace, so  having tasks with parents from another namespace will
> be OK.

Well. I saw this word "entering", but I don't know the meaning. Just curious,
could you explain?

And, if an exiting task has a child which is already from another namespace,
why can't we release our namespace before re-parenting? I guess I need to
know what "entering" means to understand this...

Oleg.