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

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Message-ID: <20110323091736.GY12003@htj.dyndns.org>
Date:	Wed, 23 Mar 2011 10:17:36 +0100
From:	Tejun Heo <tj@...nel.org>
To:	Oleg Nesterov <oleg@...hat.com>
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

Hey, Oleg.

On Tue, Mar 22, 2011 at 08:44:16PM +0100, Oleg Nesterov wrote:
> 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.

Okay.

> 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);

I see but I don't think ptrace_reparented() is a good name for
!same_thread_group(child->parent, child->real_parent).  It gets too
confusing with child->parent != child->real_parent test.

Anyways, I'll leave the renaming for later patch and just update the
->group_leader part.

Thanks.

-- 
tejun
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