linux-kernel - Re: [PATCH 2/2] introduce ptrace

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Date:	Tue,  4 Mar 2008 20:18:58 -0800 (PST)
From:	Roland McGrath <roland@...hat.com>
To:	Oleg Nesterov <oleg@...sign.ru>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org
Subject: Re: [PATCH 2/2] introduce ptrace_reparented() helper

> Somehow the patch I sent misses the change in ptrace.c, it can use the
> new helper too.

Actually, my pedantic streak prefers that to be in a separate patch.

I think the ptrace_reparented cleanup is fine, it is purely cosmetic and
improves readability.  

> -	if (!list_empty(&child->ptrace_list)) {
> +	if (ptrace_reparented(child)) {

This is changing the test from list_empty(&child->ptrace_list)
to child->parent == child->real_parent.  It should indeed be
impossible for those tests not to match.  But, paranoia is its
own reward.  I don't object to the change, but it should be
separate so bisect distinguishes it should it ever turn out to
matter in some way we are now overlooking.  I'd even be a
little inclined towards:

	if (child->real_parent == child->parent) {
		BUG_ON(!list_empty(&child->ptrace_list));
		return 0;
	} else {
		BUG_ON(list_empty(&child->ptrace_list));
		return 1;
	}

except of course you couldn't use that in the reparent_thread case.

Thanks,
Roland
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