Re: [RFC][PATCH -mm 3/3] freezer: Fix problem with kthread_stop

Rafael J. Wysocki
2007-04-23T21:26:42Z

On Monday, 23 April 2007 23:16, Gautham R Shenoy wrote:
> On Tue, Apr 24, 2007 at 12:46:37AM +0400, Oleg Nesterov wrote:
> > On 04/23, Rafael J. Wysocki wrote:
> > >
> > > On Monday, 23 April 2007 14:35, Gautham R Shenoy wrote:
> > > > > + if (!freezer_should_exempt(current)) {
> > > > task_lock(k);
> > > > > + /* We are freezable, so we must make sure that the thread being
> > > > > + * stopped is not frozen and will not be frozen until it dies
> > > > > + */
> > > > > + freezer_exempt(k);
> > > > > + if (frozen(k))
> > > > > + clear_frozen_flag(k);
> > > > task_unlock(k);
> > > > > + }
> > >
> > > Yes, that's correct. We need to take task_lock() to avoid the race with
> > > refrigerator().
> >
> > Even if we use thaw_task() ?
>
> I don't think so. As you correctly pointed out, thaw_task() is race free
> w.r.t the refrigerator().

Agreed.

Rafael