From: Mike Galbraith <efault@gmx.de>
To: Peter Zijlstra <a.p.zijlstra@chello.nl>
Cc: LKML <linux-kernel@vger.kernel.org>, Tejun Heo <htejun@gmail.com>,
Li Zefan <lizf@cn.fujitsu.com>, Paul Menage <paul@paulmenage.org>,
David Rientjes <rientjes@google.com>
Subject: Re: patch] cpusets, cgroups: disallow attaching kthreadd
Date: Tue, 18 Oct 2011 12:11:33 +0200 [thread overview]
Message-ID: <1318932693.6748.5.camel@marge.simson.net> (raw)
In-Reply-To: <1318929825.9641.32.camel@marge.simson.net>
On Tue, 2011-10-18 at 11:23 +0200, Mike Galbraith wrote:
> On Tue, 2011-10-18 at 11:06 +0200, Peter Zijlstra wrote:
> > On Tue, 2011-10-18 at 10:47 +0200, Mike Galbraith wrote:
> > > On Tue, 2011-10-18 at 10:42 +0200, Peter Zijlstra wrote:
> > >
> > > > Why special case these two, why not simply disallow moving kthreadd into
> > > > _any_ cgroup what so ever and be done with it?
> > >
> > > These were the cases where it hurt, and cpusets don't have to be a
> > > component of a cgroup. So we'd still need the cpuset bit.
> >
> > but but but,, cpusetes are a cgroup thingy?!
>
> By golly, mount -t cpuset and the thing does say type cgroup. How 'bout
> that, learn something new every day. Dinkier is better.
From: Peter Zijlstra <a.p.zijlstra@chello.nl>
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 <efault@gmx.de>
---
kernel/cgroup.c | 9 +++++++++
1 file changed, 9 insertions(+)
Index: linux-3.0-tip/kernel/cgroup.c
===================================================================
--- linux-3.0-tip.orig/kernel/cgroup.c
+++ linux-3.0-tip/kernel/cgroup.c
@@ -60,6 +60,7 @@
#include <linux/eventfd.h>
#include <linux/poll.h>
#include <linux/flex_array.h> /* used in cgroup_attach_proc */
+#include <linux/kthread.h>
#include <linux/atomic.h>
@@ -1824,6 +1825,14 @@ int cgroup_attach_task(struct cgroup *cg
struct cgroup *oldcgrp;
struct cgroupfs_root *root = cgrp->root;
+ /*
+ * Workqueue threads may acquire PF_THREAD_BOUND and become
+ * trapped in a cpuset, or RT worker may be born in a cgroup
+ * with no rt_runtime allocated. Just say no.
+ */
+ 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)
next prev parent reply other threads:[~2011-10-18 10:11 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-09-23 6:21 [patch] cpusets: allow PF_THREAD_BOUND kworkers to escape from a cpuset Mike Galbraith
2011-09-23 7:00 ` Li Zefan
2011-09-23 7:19 ` Mike Galbraith
2011-09-23 9:12 ` David Rientjes
2011-09-23 9:42 ` Mike Galbraith
2011-09-23 10:53 ` Mike Galbraith
2011-09-23 13:27 ` David Rientjes
2011-09-23 14:33 ` Mike Galbraith
2011-09-23 18:16 ` Mike Galbraith
2011-09-23 20:20 ` David Rientjes
2011-09-24 3:21 ` Tejun Heo
2011-10-10 5:34 ` Mike Galbraith
2011-10-10 8:03 ` [patch] cpusets, cgroups: disallow attaching kthreadd Mike Galbraith
2011-10-10 16:43 ` Tejun Heo
2011-10-11 2:31 ` Mike Galbraith
2011-10-11 14:08 ` Peter Zijlstra
2011-10-11 16:57 ` Mike Galbraith
2011-10-12 1:22 ` David Rientjes
2011-10-12 1:45 ` Mike Galbraith
2011-10-12 1:20 ` David Rientjes
2011-10-18 8:10 ` patch] " Mike Galbraith
2011-10-18 8:16 ` David Rientjes
2011-10-18 8:42 ` Peter Zijlstra
2011-10-18 8:47 ` Mike Galbraith
2011-10-18 9:06 ` Peter Zijlstra
2011-10-18 9:23 ` Mike Galbraith
2011-10-18 10:11 ` Mike Galbraith [this message]
2011-10-18 20:38 ` David Rientjes
2011-10-19 4:00 ` Mike Galbraith
2011-10-19 4:53 ` Paul Menage
2011-10-19 4:56 ` Paul Menage
2011-10-19 5:28 ` Mike Galbraith
2011-10-19 7:50 ` Peter Zijlstra
2011-10-19 19:47 ` David Rientjes
2011-10-20 10:32 ` Peter Zijlstra
2011-10-20 21:24 ` David Rientjes
2011-10-19 4:57 ` Paul Menage
2011-10-19 5:24 ` [patch-final] " Mike Galbraith
2011-10-19 7:54 ` Peter Zijlstra
2011-10-19 8:00 ` Paul Menage
2011-10-19 8:21 ` Mike Galbraith
2011-10-26 20:27 ` David Rientjes
2011-11-10 20:51 ` David Rientjes
2011-12-06 20:13 ` David Rientjes
2011-12-06 22:47 ` Andrew Morton
2011-12-06 23:53 ` David Rientjes
2011-12-07 0:05 ` Andrew Morton
2011-12-07 3:18 ` [resubmit] " Mike Galbraith
2011-12-07 4:36 ` Mike Galbraith
2011-12-07 22:03 ` David Rientjes
2011-12-14 20:16 ` Andrew Morton
2011-12-15 2:50 ` David Rientjes
2012-01-06 22:06 ` Andrew Morton
2012-01-07 6:34 ` Mike Galbraith
2012-01-07 7:59 ` Andrew Morton
2011-12-07 22:01 ` David Rientjes
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