From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752276AbaJ0KSc (ORCPT ); Mon, 27 Oct 2014 06:18:32 -0400 Received: from relay.parallels.com ([195.214.232.42]:53153 "EHLO relay.parallels.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751667AbaJ0KSb (ORCPT ); Mon, 27 Oct 2014 06:18:31 -0400 Message-ID: <1414405105.19914.169.camel@tkhai> Subject: [PATCH] sched: Fix race between task_group and sched_task_group From: Kirill Tkhai To: CC: Peter Zijlstra , Oleg Nesterov , Ingo Molnar , Burke Libbey , Vladimir Davydov , Kirill Tkhai Date: Mon, 27 Oct 2014 14:18:25 +0400 Organization: Parallels Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.8.5-2+b3 MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Originating-IP: [10.30.26.172] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org The race may happen when somebody is changing task_group of a forking task. Child's cgroup is the same as parent's after dup_task_struct() (there just memory copying). Also, cfs_rq and rt_rq are the same as parent's. But if parent changes its task_group before it's called cgroup_post_fork(), we do not reflect this situation on child. Child's cfs_rq and rt_rq remain the same, while child's task_group changes in cgroup_post_fork(). To fix this we introduce fork() method, which calls sched_move_task() directly. This function changes sched_task_group on appropriate (also its logic has no problem with freshly created tasks, so we shouldn't introduce something special; we are able just to use it). Possibly, this decides the Burke Libbey's problem: https://lkml.org/lkml/2014/10/24/456 Signed-off-by: Kirill Tkhai --- kernel/sched/core.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 4499950..dde8adb 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7833,6 +7833,11 @@ static void cpu_cgroup_css_offline(struct cgroup_subsys_state *css) sched_offline_group(tg); } +static void cpu_cgroup_fork(struct task_struct *task) +{ + sched_move_task(task); +} + static int cpu_cgroup_can_attach(struct cgroup_subsys_state *css, struct cgroup_taskset *tset) { @@ -8205,6 +8210,7 @@ struct cgroup_subsys cpu_cgrp_subsys = { .css_free = cpu_cgroup_css_free, .css_online = cpu_cgroup_css_online, .css_offline = cpu_cgroup_css_offline, + .fork = cpu_cgroup_fork, .can_attach = cpu_cgroup_can_attach, .attach = cpu_cgroup_attach, .exit = cpu_cgroup_exit,