Re: [PATCH 07/16] signal: Wake up the designated parent

Oleg Nesterov
2022-06-07T15:26:54Z

On 06/06, Eric W. Biederman wrote:
>
> Which if I have had enough sleep reduces this patch to just:
>
> diff --git a/kernel/exit.c b/kernel/exit.c
> index f072959fcab7..c8156366b722 100644
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -1431,8 +1431,10 @@ static int child_wait_callback(wait_queue_entry_t *wait, unsigned mode,
> if (!eligible_pid(wo, p))
> return 0;
>
> - if ((wo->wo_flags & __WNOTHREAD) && wait->private != p->parent)
> - return 0;
> + if ((wo->wo_flags & __WNOTHREAD) &&
> + (wait->private != p->parent) &&
> + (wait->private != p->real_parent))
> + return 0;
>
> return default_wake_function(wait, mode, sync, key);
> }
>
>
> I think that solves the issue without missing wake-ups without adding
> any more.

Agreed, and looks much simpler.

> For the same set of reasons it looks like the __wake_up_parent in
> __ptrace_detach is just simply dead code. I don't think there is a case
> where when !ptrace_reparented the thread that is the real_parent can
> sleep in do_wait when the thread that was calling ptrace could not.

Yes... this doesn't really differ from the case when one thread reaps
a natural child and another thread sleep in do_wait().

> That needs a very close look to confirm.

Yes.

Oleg.