Re: [PATCH 5/7] cgroup_freezer: allow moving tasks in and out of afrozen cgroup
From: Oleg Nesterov
Date: Tue Oct 23 2012 - 12:12:58 EST
On 10/22, Tejun Heo wrote:
> On Mon, Oct 22, 2012 at 09:25:06PM +0200, Oleg Nesterov wrote:
> > > @@ -190,12 +201,12 @@ static void freezer_fork(struct task_struct *task)
> > > goto out;
> > >
> > > spin_lock_irq(&freezer->lock);
> > > - BUG_ON(freezer->state == CGROUP_FROZEN);
> > > -
> > > - /* Locking avoids race with FREEZING -> THAWED transitions. */
> > > - if (freezer->state == CGROUP_FREEZING)
> > > + /*
> > > + * @task might have been just migrated into a FROZEN cgroup.
> > Confused. If it was migrated, then freezer_attach() should take care
> > do freeze_task?
> Hmmm... there's a window where a task is migrated but ->attach()
> hasn't completed yet, so freezer_attach() might not have kicked in
Yes, I see.
Indeed, cgroup_task_migrate() is called before ->attach().
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