在多线程中检测到不合理的死锁 Java

Question

我有一个代码，其中实现 Runnable 的两个线程 classes 是运行并且共享 class 缓冲区的公共对象。

虽然我在我的知识范围内正确地使用了同步块和 wait() 和 notify() 方法，但是当我在 try/catch 块中使用 Thread.sleep(0) 休眠线程时，在一些被接受的输出结果之后，它陷入僵局。

当我用 1000 毫秒 Thread.sleep(1000) 休眠线程 Cook 和用 3000 毫秒 Thread.sleep(3000)

休眠线程 Bheem 时未检测到问题

这是线程中常见的生产者-消费者场景，我故意将消费者置于生产者之上。

P.S。 - 我已经给出了从最后一个修剪的 output。实际产量相当大。

以下代码在 Bheem class

public void consume() {

        while (ob.buffer >= 1) {
            synchronized (ob) {
                System.out.println(Thread.currentThread().getName()
                        + "    started eating Ladoos with currently "
                        + (ob.buffer--) + " ladoos in plate");

                try {
                    Thread.sleep(0); // bheem takes 1.5 sec to eat

                    ob.notify();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }

        synchronized (ob) {

            try {
                System.out
                        .println("Plate is empty, bheem will wait for ladoos to serve ");
                ob.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }

    public void run() {

        while (true) {

            consume();
        }
    }

这个在库克class

public void produce() {

        while (ob.buffer < 5) {
            synchronized (ob) {

                System.out.println(Thread.currentThread().getName()
                        + "  started making Ladoos with currently "
                        + (ob.buffer++) + " ladoos in plate");

                try {
                    Thread.sleep(0); // 1 sec time taken to make a ladoo

                    ob.notify();
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
            }
        }
        synchronized (ob) {

            try {
                System.out.println("Plate is full, cook will wait ");
                ob.wait();
            } catch (InterruptedException e) {
                e.printStackTrace();
            }
        }

    }

    public void run() {

        while (true) {

            produce();
        }

    }

这是调用的主要方法，只是为了理解观众

public static void main(String[] args) {

        Buffer b = new Buffer(0);

        Producer p = new Producer(b);
        Consumer c = new Consumer(b);

        Thread producer = new Thread(p, "Cook");
        Thread consumer = new Thread(c, "Bheem");

        System.out.println("Main started");
        // buffer size is taken as 5 max.
        consumer.start(); // bheem takes 1.5 sec to finish a ladoo



        /*try {
            Thread.sleep(2000);
        } catch (InterruptedException e) {
            e.printStackTrace();
        }*/


        producer.start(); // cook takes 1 sec to prepare ladoo

输出

Plate is empty, bheem will wait for ladoos to serve 
Cook  started making Ladoos with currently 0 ladoos in plate
Bheem    started eating Ladoos with currently 1 ladoos in plate
Plate is empty, bheem will wait for ladoos to serve 
Cook  started making Ladoos with currently 0 ladoos in plate
Bheem    started eating Ladoos with currently 1 ladoos in plate
Plate is empty, bheem will wait for ladoos to serve 
Cook  started making Ladoos with currently 0 ladoos in plate
Bheem    started eating Ladoos with currently 1 ladoos in plate
Plate is empty, bheem will wait for ladoos to serve 
Cook  started making Ladoos with currently 0 ladoos in plate
Bheem    started eating Ladoos with currently 1 ladoos in plate
Cook  started making Ladoos with currently 0 ladoos in plate
Cook  started making Ladoos with currently 1 ladoos in plate
Cook  started making Ladoos with currently 2 ladoos in plate
Cook  started making Ladoos with currently 3 ladoos in plate
Cook  started making Ladoos with currently 4 ladoos in plate
Plate is full, cook will wait 
Plate is empty, bheem will wait for ladoos to serve

Answer 1

当消费者拿走最后一个 ladoo 时，是什么阻止了您的生产者完全填满盘子并调用最后一个 notify() 在消费者设法调用 wait()？同样，当盘子变满时，是什么阻止了消费者在生产者进入 wait() 之前拿走最后一个 ladoo 并调用最后一个 notify()？

如果其他线程没有等待接收通知，则对 o.notify() 的调用无任何作用。也就是说对象o不记得有通知过

在多线程中检测到不合理的死锁 Java

Unreasonable deadLock detected in multithreading Java

java

multithreading

synchronization

deadlock

thread-safety