From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932888AbaKRVaa (ORCPT ); Tue, 18 Nov 2014 16:30:30 -0500 Received: from mx1.redhat.com ([209.132.183.28]:42186 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932079AbaKRVaZ (ORCPT ); Tue, 18 Nov 2014 16:30:25 -0500 Date: Tue, 18 Nov 2014 22:30:23 +0100 From: Oleg Nesterov To: Andrew Morton Cc: Aaron Tomlin , "Eric W. Biederman" , Kay Sievers , Lennart Poettering , Sterling Alexander , linux-kernel@vger.kernel.org Subject: [PATCH 4/6] exit: reparent: document the ->has_child_subreaper checks Message-ID: <20141118213023.GA5027@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20141118212952.GA4754@redhat.com> User-Agent: Mutt/1.5.18 (2008-05-17) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Swap the "init_task" and same_thread_group() checks. This way it is more simple to document these checks and we can remove the link to the previous discussion on lkml. Signed-off-by: Oleg Nesterov --- kernel/exit.c | 14 ++++++-------- 1 files changed, 6 insertions(+), 8 deletions(-) diff --git a/kernel/exit.c b/kernel/exit.c index ac7ba9b..266e4f4 100644 --- a/kernel/exit.c +++ b/kernel/exit.c @@ -495,18 +495,16 @@ static struct task_struct *find_new_reaper(struct task_struct *father) if (father->signal->has_child_subreaper) { struct task_struct *reaper; - /* - * Find the first ancestor marked as child_subreaper. - * Note that the code below checks same_thread_group(reaper, - * pid_ns->child_reaper). This is what we need to DTRT in a - * PID namespace. However we still need the check above, see - * http://marc.info/?l=linux-kernel&m=131385460420380 + * Find the first ->is_child_subreaper ancestor in our pid_ns. + * We start from father to ensure we can not look into another + * namespace, this is safe because all its threads are dead. */ for (reaper = father; - reaper != &init_task; + !same_thread_group(reaper, pid_ns->child_reaper); reaper = reaper->real_parent) { - if (same_thread_group(reaper, pid_ns->child_reaper)) + /* call_usermodehelper() descendants need this check */ + if (reaper == &init_task) break; if (!reaper->signal->is_child_subreaper) continue; -- 1.5.5.1