linux-kernel - Re: [PATCH] pidfd: exit: kill the no longer used thread_group

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Date: Wed, 7 Feb 2024 09:45:15 +0100
From: Christian Brauner <brauner@...nel.org>
To: Tycho Andersen <tycho@...ho.pizza>
Cc: Oleg Nesterov <oleg@...hat.com>, Andy Lutomirski <luto@...capital.net>, 
	"Eric W. Biederman" <ebiederm@...ssion.com>, linux-kernel@...r.kernel.org
Subject: Re: [PATCH] pidfd: exit: kill the no longer used
 thread_group_exited()

On Tue, Feb 06, 2024 at 10:04:08AM -0700, Tycho Andersen wrote:
> On Mon, Feb 05, 2024 at 06:43:47PM +0100, Oleg Nesterov wrote:
> > It was used by pidfd_poll() but now it has no callers.
> > 
> > If it finally finds a modular user we can revert this change, but note
> > that the comment above this helper and the changelog in 38fd525a4c61
> > ("exit: Factor thread_group_exited out of pidfd_poll") are not accurate,
> > thread_group_exited() won't return true if all other threads have passed
> > exit_notify() and are zombies, it returns true only when all other threads
> > are completely gone. Not to mention that it can only work if the task
> > identified by @pid is a thread-group leader.
> > 
> > Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> 
> Reviewed-by: Tycho Andersen <tandersen@...flix.com>

On Tue, Feb 06, 2024 at 10:03:41AM -0700, Tycho Andersen wrote:
> On Mon, Feb 05, 2024 at 03:13:48PM +0100, Oleg Nesterov wrote:
> > rather than wake_up_all(). This way do_notify_pidfd() won't wakeup the
> > POLLHUP-only waiters which wait for pid_task() == NULL.
> > 
> > TODO:
> >     - as Christian pointed out, this asks for the new wake_up_all_poll()
> >       helper, it can already have other users.
> > 
> >     - we can probably discriminate the PIDFD_THREAD and non-PIDFD_THREAD
> >       waiters, but this needs more work. See
> >       https://lore.kernel.org/all/20240205140848.GA15853@redhat.com/
> > 
> > Signed-off-by: Oleg Nesterov <oleg@...hat.com>
> 
> Reviewed-by: Tycho Andersen <tandersen@...flix.com>

I updated the trailers with your RVBs.