linux-kernel - Re: [PATCH 7/8] job control: Notify the real parent of job control events regardless of ptrace

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Date:	Tue, 22 Mar 2011 20:44:16 +0100
From:	Oleg Nesterov <oleg@...hat.com>
To:	Tejun Heo <tj@...nel.org>
Cc:	roland@...hat.com, jan.kratochvil@...hat.com,
	vda.linux@...glemail.com, linux-kernel@...r.kernel.org,
	torvalds@...ux-foundation.org, akpm@...ux-foundation.org,
	indan@....nu
Subject: Re: [PATCH 7/8] job control: Notify the real parent of job control
	events regardless of ptrace

On 03/22, Tejun Heo wrote:
>
> On Mon, Mar 21, 2011 at 06:43:06PM +0100, Oleg Nesterov wrote:
> > Hmm... in fact I can't convince myself we really need to look at
> > child->group_leader, will recheck... Anyway, this is minor too.
>
> Care to elaborate?

child->real_parent must be equal to child->group_leader->real_parent.

What we need is ptrace_reparented(). But as I said, it should be
fixed first (I think) and this needs a separate patch/discussion.

So yes, we need a new helper.

Well, and look at get_signal_to_deliver(),

		leader = current->group_leader;
		if (task_ptrace(leader) && !real_parent_is_ptracer(leader))
			do_notify_parent_cldstop(leader, true, why);

Indeed. But in fact task_ptrace(leader) is not needed. If
real_parent_is_ptracer(tsk) returns false, then tsk must be ptraced.

So we could write

		if (!real_parent_is_ptracer(leader))
			do_notify_parent_cldstop(leader, true, why);

but now this looks confusing because of the naming. Compare with

		if (ptrace_reparented(leader))
			do_notify_parent_cldstop(leader);

Oleg.

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