Method add

os/src/task/manager.rs:18–20

(&mut self, task: Arc<TaskControlBlock>)

        }
    }
    pub fn add(&mut self, task: Arc<TaskControlBlock>) {
        self.ready_queue.push_back(task);
    }
    pub fn fetch(&mut self) -> Option<Arc<TaskControlBlock>> {
        self.ready_queue.pop_front()
    }