From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <linux-kernel-owner@vger.kernel.org>
Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand
	id S1752567Ab1JJRbJ (ORCPT <rfc822;w@1wt.eu>);
	Mon, 10 Oct 2011 13:31:09 -0400
Received: from mail-iy0-f174.google.com ([209.85.210.174]:45181 "EHLO
	mail-iy0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org
	with ESMTP id S1751284Ab1JJRbI (ORCPT
	<rfc822;linux-kernel@vger.kernel.org>);
	Mon, 10 Oct 2011 13:31:08 -0400
Date: Mon, 10 Oct 2011 10:31:02 -0700
From: Tejun Heo <htejun@gmail.com>
To: Oleg Nesterov <oleg@redhat.com>
Cc: rjw@sisk.pl, paul@paulmenage.org, lizf@cn.fujitsu.com,
        linux-pm@lists.linux-foundation.org, linux-kernel@vger.kernel.org,
        containers@lists.linux-foundation.org, fweisbec@gmail.com,
        matthltc@us.ibm.com, akpm@linux-foundation.org,
        Paul Menage <menage@google.com>
Subject: Re: [PATCH 4/4] cgroup: always lock threadgroup during migration
Message-ID: <20111010173102.GF8100@google.com>
References: <1315159280-25032-1-git-send-email-htejun@gmail.com>
 <1315159280-25032-5-git-send-email-htejun@gmail.com>
 <20110918174117.GB2384@redhat.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <20110918174117.GB2384@redhat.com>
User-Agent: Mutt/1.5.20 (2009-06-14)
Sender: linux-kernel-owner@vger.kernel.org
List-ID: <linux-kernel.vger.kernel.org>
X-Mailing-List: linux-kernel@vger.kernel.org

On Sun, Sep 18, 2011 at 07:41:17PM +0200, Oleg Nesterov wrote:
> On 09/05, Tejun Heo wrote:
> >
> > * Remove -ESRCH failure path from cgroup_task_migrate().  With the
> >   above changes, it's guaranteed to be called only for live tasks.
> 
> I think you can remove another similar check,
> 
> > @@ -2044,6 +2044,10 @@ int cgroup_attach_proc(struct cgroup *cgrp, struct task_struct *leader)
> >  	tsk = leader;
> >  	i = 0;
> >  	do {
> > +		/* @tsk either already exited or can't exit until the end */
> > +		if (tsk->flags & PF_EXITING)
> > +			continue;
> > +
> >  		/* as per above, nr_threads may decrease, but not increase. */
> >  		BUG_ON(i >= group_size);
> >  		get_task_struct(tsk);
> 
> And then cgroup_attach_proc() does
> 
> 	for (i = 0; i < group_size; i++) {
> 		...
> 		task_lock(tsk);
> 		if (tsk->flags & PF_EXITING) {
> 			task_unlock(tsk);
> 			continue;
> 
> Afaics, this is no longer needed.

Indeed, removed.

Thank you.

-- 
tejun