Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754523AbcK1I0u (ORCPT ); Mon, 28 Nov 2016 03:26:50 -0500 Received: from mail-wj0-f195.google.com ([209.85.210.195]:33423 "EHLO mail-wj0-f195.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754142AbcK1I0k (ORCPT ); Mon, 28 Nov 2016 03:26:40 -0500 Subject: Re: [PATCH 3.12 118/127] cgroup: use an ordered workqueue for cgroup destruction To: Hugh Dickins References: <58563cf6ff3ad14d9f08cd7ccb0656e7fe3872ef.1480062521.git.jslaby@suse.cz> Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo From: Jiri Slaby Message-ID: <71007886-13a5-c68b-679f-d4cf005af7c2@suse.cz> Date: Mon, 28 Nov 2016 09:26:37 +0100 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.4.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1381 Lines: 38 On 11/26/2016, 09:55 PM, Hugh Dickins wrote: > On Fri, 25 Nov 2016, Jiri Slaby wrote: > >> From: Hugh Dickins >> >> 3.12-stable review patch. If anyone has any objections, please let me know. >> >> =============== >> >> commit ab3f5faa6255a0eb4f832675507d9e295ca7e9ba upstream. >> >> 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. >> >> tj: Committing as the temporary fix until the reverse dependency can >> be removed from memcg. Comment updated accordingly. >> >> Fixes: e5fca243abae ("cgroup: use a dedicated workqueue for cgroup destruction") >> Suggested-by: Filipe Brandenburger >> Signed-off-by: Hugh Dickins >> Signed-off-by: Tejun Heo >> Signed-off-by: Jiri Slaby > > No, please drop this one. Dropped, thank you! -- js suse labs