From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753359Ab1LFUNP (ORCPT ); Tue, 6 Dec 2011 15:13:15 -0500 Received: from mail-vx0-f174.google.com ([209.85.220.174]:61757 "EHLO mail-vx0-f174.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752021Ab1LFUNO (ORCPT ); Tue, 6 Dec 2011 15:13:14 -0500 Date: Tue, 6 Dec 2011 12:13:10 -0800 (PST) From: David Rientjes X-X-Sender: rientjes@chino.kir.corp.google.com To: Andrew Morton , Mike Galbraith cc: Paul Menage , LKML , Tejun Heo , Li Zefan , Peter Zijlstra Subject: Re: [patch-final] Re: patch] cpusets, cgroups: disallow attaching kthreadd In-Reply-To: Message-ID: References: <1316758874.7393.2.camel@marge.simson.net> <4E7C2E7F.40307@cn.fujitsu.com> <1316762345.8168.4.camel@marge.simson.net> <1316770936.6641.11.camel@marge.simson.net> <1316775204.7562.9.camel@marge.simson.net> <1316788392.6544.33.camel@marge.simson.net> <1318224892.6161.45.camel@marge.simson.net> <1318233815.6527.5.camel@marge.simson.net> <1318925436.9641.23.camel@marge.simson.net> <1319001860.6222.34.camel@marge.simson.net> User-Agent: Alpine 2.00 (DEB 1167 2008-08-23) MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, 10 Nov 2011, David Rientjes wrote: > On Wed, 26 Oct 2011, David Rientjes wrote: > > > On Wed, 19 Oct 2011, Mike Galbraith wrote: > > > > > cpusets, cgroups: disallow attaching kthreadd > > > > > > Allowing kthreadd to be moved to a non-root group makes no sense, it being > > > a global resource, and needlessly leads unsuspecting users toward trouble. > > > > > > 1. An RT workqueue worker thread spawned in a task group with no rt_runtime > > > allocated is not schedulable. Simple user error, but harmful to the box. > > > > > > 2. A worker thread which acquires PF_THREAD_BOUND can never leave a cpuset, > > > rendering the cpuset immortal. > > > > > > Save the user some unexpected trouble, just say no. > > > > > > Signed-off-by: Mike Galbraith > > > Acked-by: David Rientjes > > > Acked-by: Paul Menage > > > > > > > Let's add Andrew to the cc so we can get it in -mm, I haven't seen it hit > > linux-next yet. > > > > Ping? Still missing from -mm and linux-next. > Ping #2? > > > --- > > > kernel/cpuset.c | 6 ++++-- > > > kernel/sched.c | 10 ++++++++++ > > > 2 files changed, 14 insertions(+), 2 deletions(-) > > > > > > Index: linux-3.0-tip/kernel/cpuset.c > > > =================================================================== > > > --- linux-3.0-tip.orig/kernel/cpuset.c > > > +++ linux-3.0-tip/kernel/cpuset.c > > > @@ -59,6 +59,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > > > > /* > > > * Workqueue for cpuset related tasks. > > > @@ -1382,9 +1383,10 @@ static int cpuset_can_attach(struct cgro > > > * set of allowed nodes is unnecessary. Thus, cpusets are not > > > * applicable for such threads. This prevents checking for success of > > > * set_cpus_allowed_ptr() on all attached tasks before cpus_allowed may > > > - * be changed. > > > + * be changed. We also disallow attaching kthreadd, to prevent it's > > > + * child from becoming trapped should it then acquire PF_THREAD_BOUND. > > > */ > > > - if (tsk->flags & PF_THREAD_BOUND) > > > + if (tsk->flags & PF_THREAD_BOUND || tsk == kthreadd_task) > > > return -EINVAL; > > > > > > return 0; > > > Index: linux-3.0-tip/kernel/sched.c > > > =================================================================== > > > --- linux-3.0-tip.orig/kernel/sched.c > > > +++ linux-3.0-tip/kernel/sched.c > > > @@ -71,6 +71,7 @@ > > > #include > > > #include > > > #include > > > +#include > > > > > > #include > > > #include > > > @@ -9141,6 +9142,15 @@ cpu_cgroup_destroy(struct cgroup_subsys > > > static int > > > cpu_cgroup_can_attach_task(struct cgroup *cgrp, struct task_struct *tsk) > > > { > > > + /* > > > + * kthreadd can fork workers for an RT workqueue in a cgroup > > > + * which may or may not have rt_runtime allocated. Just say no, > > > + * as attaching a global resource to a non-root group doesn't > > > + * make any sense anyway. > > > + */ > > > + if (tsk == kthreadd_task) > > > + return -EINVAL; > > > + > > > #ifdef CONFIG_RT_GROUP_SCHED > > > if (!sched_rt_can_attach(cgroup_tg(cgrp), tsk)) > > > return -EINVAL; >