From: Oleg Nesterov <oleg@redhat.com>
To: Tejun Heo <tj@kernel.org>
Cc: rjw@sisk.pl, linux-kernel@vger.kernel.org, lizefan@huawei.com,
containers@lists.linux-foundation.org, cgroups@vger.kernel.org,
stable@vger.kernel.org
Subject: Re: [PATCH 2/7] freezer: add missing mb's to freezer_count() and freezer_should_skip()
Date: Tue, 23 Oct 2012 17:39:19 +0200 [thread overview]
Message-ID: <20121023153919.GA16201@redhat.com> (raw)
In-Reply-To: <20121022211317.GD5951@atj.dyndns.org>
Hi Tejun,
On 10/22, Tejun Heo wrote:
>
> On Mon, Oct 22, 2012 at 07:44:04PM +0200, Oleg Nesterov wrote:
>
> > We probably have another similar race. If ptrace_stop()->may_ptrace_stop()
> > returns false, the task does
> >
> > __set_current_state(TASK_RUNNING);
> > // no mb in between
> > try_to_freeze();
> >
> > And this can race with task_is_stopped_or_traced() check in the same way.
> > (of course this is only theoretical).
> >
> > do_signal_stop() is probably fine, we can rely on ->siglock.
>
> Hmm.... Guess we should drop __ from set_current_state.
Yes.
Or we can change ptrace_stop() and do_signal_stop() to use freezer_do_not_count/
freezer_count and remove task_is_stopped_or_traced() from update_if_frozen()
and try_to_freeze_tasks(). But this means that do_signal_stop() will call
try_to_freeze() twice, unless we add __freezer_count() which only clears
PF_FREEZER_SKIP.
> I wonder
> whether we should just add mb to freezing()? What do you think?
Yes, I thought about this too. I just do not know what would be better.
Oleg.
next prev parent reply other threads:[~2012-10-23 15:38 UTC|newest]
Thread overview: 63+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-10-16 22:28 [PATCHSET cgroup/for-3.8] cgroup_freezer: allow migration regardless of freezer state and update locking Tejun Heo
2012-10-16 22:28 ` [PATCH 1/7] cgroup: cgroup_subsys->fork() should be called after the task is added to css_set Tejun Heo
2012-10-17 8:28 ` Li Zefan
2012-10-18 1:25 ` Li Zefan
2012-10-21 19:11 ` Oleg Nesterov
2012-10-21 19:22 ` Tejun Heo
2012-10-22 18:04 ` Oleg Nesterov
2012-10-22 21:16 ` Tejun Heo
2012-10-23 15:51 ` Oleg Nesterov
2012-10-24 19:04 ` Tejun Heo
2012-10-25 17:42 ` Oleg Nesterov
2012-12-20 5:25 ` Herton Ronaldo Krzesinski
2012-12-28 21:22 ` [PATCH] cgroup: remove unused dummy cgroup_fork_callbacks() Tejun Heo
2012-10-16 22:28 ` [PATCH 2/7] freezer: add missing mb's to freezer_count() and freezer_should_skip() Tejun Heo
2012-10-22 17:44 ` Oleg Nesterov
2012-10-22 21:13 ` Tejun Heo
2012-10-23 15:39 ` Oleg Nesterov [this message]
2012-10-24 18:57 ` Tejun Heo
2012-10-25 16:39 ` [PATCH 0/1] (Was: freezer: add missing mb's to freezer_count() and freezer_should_skip()) Oleg Nesterov
2012-10-25 16:39 ` [PATCH 1/1] freezer: change ptrace_stop/do_signal_stop to use freezable_schedule() Oleg Nesterov
2012-10-25 17:18 ` Tejun Heo
2012-10-25 17:34 ` Oleg Nesterov
2012-10-25 17:36 ` Tejun Heo
2012-10-26 17:45 ` [PATCH v2 0/1] " Oleg Nesterov
2012-10-26 17:46 ` [PATCH v2 1/1] " Oleg Nesterov
2012-10-26 17:52 ` Tejun Heo
2012-10-26 18:01 ` Oleg Nesterov
2012-10-26 21:14 ` Rafael J. Wysocki
2012-10-26 21:29 ` Rafael J. Wysocki
2012-10-26 21:29 ` Tejun Heo
2012-10-28 0:16 ` Rafael J. Wysocki
2012-10-27 22:22 ` Ben Hutchings
2012-10-28 13:45 ` Oleg Nesterov
2012-10-16 22:28 ` [PATCH 3/7] cgroup_freezer: make it official that writes to freezer.state don't fail Tejun Heo
2012-10-16 22:28 ` [PATCH 4/7] cgroup_freezer: don't stall transition to FROZEN for PF_NOFREEZE or PF_FREEZER_SKIP tasks Tejun Heo
2012-10-22 18:34 ` Oleg Nesterov
2012-10-22 21:18 ` Tejun Heo
2012-10-23 15:55 ` Oleg Nesterov
2012-10-24 19:06 ` Tejun Heo
2012-10-25 17:12 ` [PATCH 0/1] (Was: cgroup_freezer: don't stall transition to FROZEN for PF_NOFREEZE or PF_FREEZER_SKIP tasks) Oleg Nesterov
2012-10-25 17:12 ` [PATCH 1/1] freezer: exec should clear PF_NOFREEZE along with PF_KTHREAD Oleg Nesterov
2012-10-25 17:20 ` Tejun Heo
2012-10-25 17:37 ` Oleg Nesterov
2012-10-25 17:37 ` Tejun Heo
2012-10-25 20:13 ` Rafael J. Wysocki
2012-10-16 22:28 ` [PATCH 5/7] cgroup_freezer: allow moving tasks in and out of a frozen cgroup Tejun Heo
2012-10-22 19:25 ` Oleg Nesterov
2012-10-22 21:25 ` Tejun Heo
2012-10-23 16:14 ` Oleg Nesterov
2012-10-16 22:28 ` [PATCH 6/7] cgroup_freezer: prepare update_if_frozen() for locking change Tejun Heo
2012-10-16 22:28 ` [PATCH 7/7] cgroup_freezer: don't use cgroup_lock_live_group() Tejun Heo
2012-10-17 19:16 ` [PATCHSET cgroup/for-3.8] cgroup_freezer: allow migration regardless of freezer state and update locking Matt Helsley
2012-10-18 21:14 ` Tejun Heo
2012-10-18 22:21 ` Matt Helsley
2012-10-18 22:35 ` Tejun Heo
2012-10-18 23:47 ` Matt Helsley
2012-10-19 0:01 ` Tejun Heo
2012-10-19 1:29 ` Matt Helsley
2012-10-19 20:02 ` Tejun Heo
2012-10-19 16:54 ` Rafael J. Wysocki
2012-10-19 20:04 ` Tejun Heo
2012-10-21 19:18 ` Oleg Nesterov
2012-10-21 19:24 ` Tejun Heo
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