From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752911AbaBGPWG (ORCPT ); Fri, 7 Feb 2014 10:22:06 -0500 Received: from mail-qc0-f171.google.com ([209.85.216.171]:58101 "EHLO mail-qc0-f171.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752691AbaBGPWD (ORCPT ); Fri, 7 Feb 2014 10:22:03 -0500 Date: Fri, 7 Feb 2014 10:21:58 -0500 From: Tejun Heo To: Hugh Dickins Cc: Filipe Brandenburger , Li Zefan , Andrew Morton , Michal Hocko , Johannes Weiner , Greg Thelen , Michel Lespinasse , Markus Blank-Burian , Shawn Bohrer , cgroups@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org Subject: Re: [PATCH] cgroup: use an ordered workqueue for cgroup destruction Message-ID: <20140207152158.GC3304@htj.dyndns.org> References: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.5.21 (2010-09-15) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Feb 06, 2014 at 03:56:01PM -0800, Hugh Dickins wrote: > Sometimes the cleanup after memcg hierarchy testing gets stuck in > mem_cgroup_reparent_charges(), unable to bring non-kmem usage down to 0. > > There may turn out to be several causes, but a major cause is this: the > workitem to offline parent can get run before workitem to offline child; > parent's mem_cgroup_reparent_charges() circles around waiting for the > child's pages to be reparented to its lrus, but it's holding cgroup_mutex > which prevents the child from reaching its mem_cgroup_reparent_charges(). > > Just use an ordered workqueue for cgroup_destroy_wq. > > Fixes: e5fca243abae ("cgroup: use a dedicated workqueue for cgroup destruction") > Suggested-by: Filipe Brandenburger > Signed-off-by: Hugh Dickins > Cc: stable@vger.kernel.org # 3.10+ Applied to cgroup/for-3.14-fixes with comment updated to indicate that this is temporary. Thanks. -- tejun