java死锁和死锁定位分析

超、凢脫俗 2023-05-22 22:18 60阅读 0赞

1.死锁：死锁是指两个或者两个以上的进程在执行的过程中，因为争夺资源而造成的一种互相等待的现象，若无外力干涉，那他们将无法推进下去

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29sZHNoYXVp_size_16_color_FFFFFF_t_70][]

2.死锁的代码

package con.carry.并发.死锁;
    
    
    /**
     * 死锁是指两个以上的线程
     */
    public class DeadThreadDemo {
    
    
        public static void main(String[] args) {
            ShareData shareData = new ShareData();
            String lockA = "LockA";
            String lockB = "LockB";
            new Thread(() -> {
                shareData.say(lockA, lockB);
            },"A").start();
    
            new Thread(() -> {
                shareData.say(lockB, lockA);
            },"B").start();
        }
    
    }
    
    
    class ShareData {
        public void say(String lockA, String lockB) {
            synchronized (lockA) {
                System.out.println("lockA 上锁了,尝试获取lockB" + lockB);
                try {
                    Thread.sleep(2000);
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                synchronized (lockB) {
                    System.out.println("lockB 上锁了,尝试获取lockA" + lockA);
                }
            }
        }
    }

这个代码的运行结果如下：

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29sZHNoYXVp_size_16_color_FFFFFF_t_70 1][]

3.线上如何检查死锁

1.利用jps查看哪个类有问题

![20200418161114933.png][]

2.利用jstack 进程id查看

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29sZHNoYXVp_size_16_color_FFFFFF_t_70 2][]

[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29sZHNoYXVp_size_16_color_FFFFFF_t_70]: /images/20230521/8bffb9a7143a459c8e8c44ded7f860a5.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29sZHNoYXVp_size_16_color_FFFFFF_t_70 1]: /images/20230521/91bf74c977b24ef2b7a416b8e393383f.png
[20200418161114933.png]: /images/20230521/3f4cf3a538054424a36e073db4535be5.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L29sZHNoYXVp_size_16_color_FFFFFF_t_70 2]: /images/20230521/0a2b55dacb1a400496e9393a2d149db8.png