From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932138Ab1JRImx (ORCPT ); Tue, 18 Oct 2011 04:42:53 -0400 Received: from casper.infradead.org ([85.118.1.10]:40030 "EHLO casper.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751062Ab1JRImw convert rfc822-to-8bit (ORCPT ); Tue, 18 Oct 2011 04:42:52 -0400 Subject: Re: patch] cpusets, cgroups: disallow attaching kthreadd From: Peter Zijlstra To: Mike Galbraith Cc: LKML , Tejun Heo , Li Zefan , Paul Menage , David Rientjes Date: Tue, 18 Oct 2011 10:42:35 +0200 In-Reply-To: <1318925436.9641.23.camel@marge.simson.net> 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> Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 8BIT X-Mailer: Evolution 3.0.3- Message-ID: <1318927355.21167.3.camel@twins> Mime-Version: 1.0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue, 2011-10-18 at 10:10 +0200, Mike Galbraith wrote: > --- > 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; > > Why special case these two, why not simply disallow moving kthreadd into _any_ cgroup what so ever and be done with it? --- diff --git a/kernel/cgroup.c b/kernel/cgroup.c index 453100a..18eed58 100644 --- a/kernel/cgroup.c +++ b/kernel/cgroup.c @@ -1824,6 +1824,9 @@ int cgroup_attach_task(struct cgroup *cgrp, struct task_struct *tsk) struct cgroup *oldcgrp; struct cgroupfs_root *root = cgrp->root; + if (tsk == kthreadd_task) + return -EINVAL; + /* Nothing to do if the task is already in that cgroup */ oldcgrp = task_cgroup_from_root(tsk, root); if (cgrp == oldcgrp)