From mboxrd@z Thu Jan  1 00:00:00 1970
From: Oleg Nesterov <oleg-6lXkIZvqkOAvJsYlp49lxw@public.gmane.org>
Subject: Re: [PATCH 4/9] pid: Generalize task_active_pid_ns
Date: Thu, 13 Dec 2007 20:07:27 +0300
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To: "Eric W. Biederman" <ebiederm-aS9lmoZGLiVWk0Htik3J/w@public.gmane.org>
Cc: Linux Containers <containers-qjLDD68F18O7TbgM5vRIOg@public.gmane.org>, Andrew Morton <akpm-de/tnXTf+JLsfHDXvbKv3WD2FQJk+8+b@public.gmane.org>, Pavel Emelyanov <xemul-GEFAQzZX7r8dnm+yROfE0A@public.gmane.org>
List-Id: containers.vger.kernel.org

On 12/13, Eric W. Biederman wrote:
>
> Oleg Nesterov <oleg-6lXkIZvqkOAvJsYlp49lxw@public.gmane.org> writes:
> 
> > On 12/12, Eric W. Biederman wrote:
> >>
> >> Currently task_active_pid_ns is not safe to call after a
> >> task becomes a zombie and exit_task_namespaces is called,
> >> as nsproxy becomes NULL.  By reading the pid namespace from
> >> the pid of the task we can trivially solve this problem
> >
> > Confused. If the task becomes a zombie, we can't assume it has a valid
> > ->pids[].pid. The parent can release us as soon as exit_notify() drops
> > tasklist.
> 
> 
> What this allows me to do (as seen later in the patchset) is to send
> to call pid_nr_ns and deliver a signal to a task group without caring
> if the element of the task group I am talking to is a zombie or not.

Yes I see, thanks Eric. I was confused by changelog, and I missed the
subsequent changes which need task_active_pid_ns() of the reciever.

Oleg.