Re: [PATCH rc1-mm] simplify exec from init's subthread

[ebiederm@xmission.com (Eric W. Biederman)]

Oleg Nesterov <oleg@tv-sign.ru> writes:

> [ On top of "exec: allow init to exec from any thread.",
>   filename exec-allow-init-to-exec-from-any-thread.patch ]
>
> I think it is enough to take tasklist_lock for reading while
> changing child_reaper:
>
> 	Reparenting needs write_lock(tasklist_lock)
>
> 	Only one thread in a thread group can do exec()
>
> 	sighand->siglock garantees that get_signal_to_deliver()
> 	will not see a stale value of child_reaper.
>
> This means that we can change child_reaper earlier, without
> calling zap_other_threads() twice.
>
> "child_reaper = current" is a NOOP when init does exec from
> main thread, we don't care.

Looks good.  I fat fingered my locking anyway, and this
looks like a good fix, as well as the more obvious place,
to do this.

Acked-by:  Eric Biederman <ebiederm@xmission.com>