- do a manual preemption-check in task_rq_unlock().

kernel/sched.c

@@ -181,6 +181,7 @@ static inline runqueue_t *task_rq_lock(task_t *p, unsigned long *flags)
 static inline void task_rq_unlock(runqueue_t *rq, unsigned long *flags)
 {
 	_raw_spin_unlock_irqrestore(&rq->lock, *flags);
+	preempt_check_resched();
 }
 
 /*