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

[Oleg Nesterov <oleg@tv-sign.ru>]

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.