From: Tejun Heo <tj@kernel.org>
To: Frederic Weisbecker <fweisbec@gmail.com>
Cc: paul@paulmenage.org, rjw@sisk.pl, lizf@cn.fujitsu.com,
Linus Torvalds <torvalds@linux-foundation.org>,
linux-pm@lists.linux-foundation.org,
linux-kernel@vger.kernel.org,
containers@lists.linux-foundation.org, matthltc@us.ibm.com,
akpm@linux-foundation.org, oleg@redhat.com,
kamezawa.hiroyu@Jp.fujitsu.com
Subject: Re: [PATCH UPDATED 03/10] threadgroup: extend threadgroup_lock() to cover exit and exec
Date: Sun, 27 Nov 2011 11:30:01 -0800 [thread overview]
Message-ID: <20111127193001.GC4266@google.com> (raw)
In-Reply-To: <20111125140136.GC23307@somewhere.redhat.com>
Hello, Frederic.
On Fri, Nov 25, 2011 at 03:01:39PM +0100, Frederic Weisbecker wrote:
> > + /*
> > + * @tsk's threadgroup is going through changes - lock out users
> > + * which expect stable threadgroup. Do this before actually
> > + * starting tearing down @tsk so that locked threadgroup has either
> > + * alive or dead tasks, not something inbetween.
> > + */
> > + threadgroup_change_begin(tsk);
> > +
>
> I still wonder why there is a so big coverage of this lock. I mean
> why is it called right before exit_irq_thread() and released so late.
> All we want is to lock cgroup_exit() I think, after which tasks can't be
> migrated.
That way, cgroup plugins never see tasks in the process of
deconstruction. Its ->mm, ->sighand, ->signal and so on either don't
exist or continue to exist across all cgroup callbacks. It's simpler
and safer (especially as bugs in this area would only be visible when
migration and exit race), and if we're gonna synchronize exit path at
all, there isn't anything to lose by excluding the whole thing.
Thanks.
--
tejun
next prev parent reply other threads:[~2011-11-27 19:30 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-11-01 23:46 [PATCHSET] cgroup: stable threadgroup during attach & subsys methods consolidation Tejun Heo
2011-11-01 23:46 ` [PATCH 01/10] cgroup: add cgroup_root_mutex Tejun Heo
2011-11-04 8:38 ` KAMEZAWA Hiroyuki
2011-11-01 23:46 ` [PATCH 02/10] threadgroup: rename signal->threadgroup_fork_lock to ->group_rwsem Tejun Heo
2011-11-04 8:40 ` KAMEZAWA Hiroyuki
2011-11-04 15:16 ` Tejun Heo
2011-11-01 23:46 ` [PATCH 03/10] threadgroup: extend threadgroup_lock() to cover exit and exec Tejun Heo
2011-11-04 8:45 ` KAMEZAWA Hiroyuki
2011-11-13 16:44 ` Frederic Weisbecker
2011-11-14 13:54 ` Frederic Weisbecker
2011-11-21 22:03 ` Tejun Heo
2011-11-23 14:34 ` Frederic Weisbecker
2011-11-21 21:58 ` Tejun Heo
2011-11-23 14:02 ` Frederic Weisbecker
2011-11-24 21:22 ` Tejun Heo
2011-11-13 18:20 ` Frederic Weisbecker
2011-11-24 22:50 ` [PATCH UPDATED " Tejun Heo
2011-11-25 4:02 ` Linus Torvalds
2011-11-27 19:21 ` Tejun Heo
2011-11-27 21:25 ` Tejun Heo
2011-12-01 19:29 ` Tejun Heo
2011-11-25 14:01 ` Frederic Weisbecker
2011-11-27 19:30 ` Tejun Heo [this message]
2011-12-02 16:28 ` Frederic Weisbecker
2011-12-05 18:43 ` Tejun Heo
2011-12-07 15:30 ` Frederic Weisbecker
2011-12-07 18:22 ` Tejun Heo
2011-12-08 20:50 ` [PATCH UPDATED AGAIN " Tejun Heo
2011-12-09 23:42 ` Frederic Weisbecker
2011-12-13 1:33 ` Tejun Heo
2011-12-13 2:17 ` Tejun Heo
2011-11-01 23:46 ` [PATCH 04/10] cgroup: always lock threadgroup during migration Tejun Heo
2011-11-04 8:54 ` KAMEZAWA Hiroyuki
2011-11-04 15:21 ` Tejun Heo
2011-11-14 18:46 ` Frederic Weisbecker
2011-11-14 18:52 ` Frederic Weisbecker
2011-11-21 22:05 ` Tejun Heo
2011-11-01 23:46 ` [PATCH 05/10] cgroup: subsys->attach_task() should be called after migration Tejun Heo
2011-11-14 20:06 ` Frederic Weisbecker
2011-11-21 22:04 ` Tejun Heo
2011-11-01 23:46 ` [PATCH 06/10] cgroup: improve old cgroup handling in cgroup_attach_proc() Tejun Heo
2011-11-14 20:37 ` Frederic Weisbecker
2011-11-01 23:46 ` [PATCH 07/10] cgroup: introduce cgroup_taskset and use it in subsys->can_attach(), cancel_attach() and attach() Tejun Heo
2011-11-14 21:16 ` Frederic Weisbecker
2011-11-01 23:46 ` [PATCH 08/10] cgroup: don't use subsys->can_attach_task() or ->attach_task() Tejun Heo
2011-11-04 9:08 ` KAMEZAWA Hiroyuki
2011-11-14 23:54 ` Frederic Weisbecker
2011-11-01 23:46 ` [PATCH 09/10] cgroup, cpuset: don't use ss->pre_attach() Tejun Heo
2011-11-15 0:51 ` Frederic Weisbecker
2011-11-01 23:46 ` [PATCH 10/10] cgroup: kill subsys->can_attach_task(), pre_attach() and attach_task() Tejun Heo
2011-11-04 9:10 ` KAMEZAWA Hiroyuki
2011-11-15 0:54 ` Frederic Weisbecker
2011-11-21 22:07 ` [PATCHSET] cgroup: stable threadgroup during attach & subsys methods consolidation Tejun Heo
2011-11-22 2:27 ` Li Zefan
2011-11-22 16:20 ` Tejun Heo
2011-11-24 22:51 ` Tejun Heo
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