linux-kernel - Re: [PATCH 4/4] forget_original

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Message-Id: <20090210232324.399ADFC3DB@magilla.sf.frob.com>
Date:	Tue, 10 Feb 2009 15:23:24 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...hat.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	"Eric W. Biederman" <ebiederm@...ssion.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 4/4] forget_original_parent: cleanup ptrace pathes

> It doesn't really hurt, but a bit ugly. Imho.

Agreed.

> How about below? Modulo comments and some other cleanups. For example,
> I think it is better to move the changing of ->real_parent into
> reparent_thread().

The exact split between reparent_thread and forget_original_parent (and
their names) never made much sense to me.

If ptrace_exit does its own lock/unlock, then it could move much earlier.
I'd be inclined to do it right before exit_signals().  But it should at
least short-circuit and not lock for list_empty(->ptraced), so we're not
adding a whole lock_irq/unlock_irq to the common case of no ptrace use.

> 			xxx = &p->real_parent->children;
> 			if (reparent_thread(father, p))
> 				xxx = &child_dead;
> 			list_move_tail(&p->sibling, xxx);;

I'd thought of this before.  But I didn't mention it because I was afraid
to wonder what might care about the use of ->sibling.  It really looks like
nothing does.  This is clearly the clean and nice way to go if there is no
problem with it.  

This change and moving ptrace_exit around should probably be separate patches.

Thanks,
Roland
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