Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932307AbcDKNXv (ORCPT ); Mon, 11 Apr 2016 09:23:51 -0400 Received: from mx2.suse.de ([195.135.220.15]:37391 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S932269AbcDKNXs (ORCPT ); Mon, 11 Apr 2016 09:23:48 -0400 X-Amavis-Alert: BAD HEADER SECTION, Duplicate header field: "References" From: Jiri Slaby To: stable@vger.kernel.org Cc: linux-kernel@vger.kernel.org, Kirill Tkhai , Peter Zijlstra , Linus Torvalds , Ingo Molnar , Jiri Slaby Subject: [PATCH 3.12 14/98] sched: Fix race between task_group and sched_task_group Date: Mon, 11 Apr 2016 15:22:16 +0200 Message-Id: <5b4535fb8df8eba6bc1f2ae1701e07a7c588b5fa.1460380917.git.jslaby@suse.cz> X-Mailer: git-send-email 2.8.1 In-Reply-To: References: In-Reply-To: References: Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 2156 Lines: 59 From: Kirill Tkhai 3.12-stable review patch. If anyone has any objections, please let me know. =============== commit eeb61e53ea19be0c4015b00b2e8b3b2185436f2b upstream. 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 Signed-off-by: Peter Zijlstra (Intel) Cc: Linus Torvalds Link: http://lkml.kernel.org/r/1414405105.19914.169.camel@tkhai Signed-off-by: Ingo Molnar Signed-off-by: Jiri Slaby --- kernel/sched/core.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/kernel/sched/core.c b/kernel/sched/core.c index 3800316d7424..7381119ec1e9 100644 --- a/kernel/sched/core.c +++ b/kernel/sched/core.c @@ -7233,6 +7233,11 @@ 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) { @@ -7602,6 +7607,7 @@ struct cgroup_subsys cpu_cgroup_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, -- 2.8.1