linux-kernel - Re: [PATCH 1/1] prctl: pdeath_signal sent when parent thread (instead of parent process) dies

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Date:	Fri, 1 Jun 2012 21:02:30 +0200
From:	Oleg Nesterov <oleg@...hat.com>
To:	Filipe Brandenburger <filbranden@...il.com>
Cc:	Tejun Heo <tj@...nel.org>,
	Andrew Morton <akpm@...ux-foundation.org>,
	David Rientjes <rientjes@...gle.com>,
	Peter Zijlstra <a.p.zijlstra@...llo.nl>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 1/1] prctl: pdeath_signal sent when parent thread
	(instead of parent process) dies

On 05/29, Filipe Brandenburger wrote:
>
> --- a/kernel/exit.c
> +++ b/kernel/exit.c
> @@ -806,7 +806,8 @@ static void forget_original_parent(struct task_struct *father)
>  				BUG_ON(t->ptrace);
>  				t->parent = t->real_parent;
>  			}
> -			if (t->pdeath_signal)
> +			if (t->pdeath_signal &&
> +			    !same_thread_group(father, reaper))
>  				group_send_sig_info(t->pdeath_signal,
>  						    SEND_SIG_NOINFO, t);
>  		} while_each_thread(p, t);

Filipe, you can't even imagine how much do I like this change
personally ;) Although I think that pdeath_signal code should
be moved into reparent_leader(). I suggested this many times.

But I was told there are users which depend on current behaviour,
they really want to know when the parent _thread_ exits.

Why? I have no idea. And I agree this is ugly, but we can't
break user-space.

Oleg.

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