Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753373AbdDKGFL (ORCPT ); Tue, 11 Apr 2017 02:05:11 -0400 Received: from mail-wm0-f67.google.com ([74.125.82.67]:35918 "EHLO mail-wm0-f67.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751273AbdDKGFJ (ORCPT ); Tue, 11 Apr 2017 02:05:09 -0400 Subject: Re: [PATCH 3.12 127/142] cgroup: use an ordered workqueue for cgroup destruction To: Hugh Dickins References: <44fd2c917b3231817b683877f606670fc734c932.1491838390.git.jslaby@suse.cz> Cc: stable@vger.kernel.org, linux-kernel@vger.kernel.org, Tejun Heo From: Jiri Slaby Message-ID: Date: Tue, 11 Apr 2017 08:05:05 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:45.0) Gecko/20100101 Thunderbird/45.8.0 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: 1833 Lines: 45 On 04/10/2017, 09:30 PM, Hugh Dickins wrote: > On Mon, 10 Apr 2017, 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 > > Deja vu, it won't lie down! See your mailbox of 2016-11-25..28: > > No, please drop this one. It was indeed marked for stable at the time, > but then reverted by 1a11533fbd71792e8c5d36f6763fbce8df0d231d; and you > already have in 3.12-stable the commit which in the end we used to fix > the issue, 4fb1a86fb5e4209a7d4426d4e586c58e9edc74ac > "memcg: reparent charges of children before processing parent". Hmm, right. If only people stopped asking me to pick it. Dropped and blacklisted. Thanks! -- js suse labs