kthread_freezable_should_stop — should this freezable kthread return now?
| bool kthread_freezable_should_stop ( | bool * was_frozen ); | 
   kthread_should_stop for freezable kthreads, which will enter
   refrigerator if necessary.  This function is safe from kthread_stop /
   freezer deadlock and freezable kthreads should use this function instead
   of calling try_to_freeze directly.