Should this freezable kthread return now?
bool kthread_freezable_should_stop(bool * was_frozen);
was_frozen
optional out parameter, indicates whether current 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.