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

Oleg Nesterov
2007-04-23T20:46:51Z

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() ?

Even if I am wrong, I think we should not use task_lock() for the freezing
related code, except in freezer.[ch]

Note also that without CONFIG_FREEZER freezer_should_exempt() == 0, so we
will do unneeded task_lock/task_unlock.

Oleg.