死锁定位及分析

秒速五厘米 2021-10-18 16:50 295阅读 0赞

*  ### 什么是死锁？ ###

> 死锁指两个或两个以上的线程在执行过程中，因争夺资源而造成的一种互相等待的现象
> 
> 如：
> 
> 线程A持有A锁试图获取B锁  
> 线程B持有B锁试图获取A锁

*  ###  编写一个简单的死锁程序 ###

/**
     * @author ck
     * @create 2019-08-12 20:26
     */
    public class Deadlock {
        private String lockA;
        private String lockB;
    
        public Deadlock(String lockA, String lockB) {
            this.lockA = lockA;
            this.lockB = lockB;
        }
    
        public void get(){
            synchronized (lockA){
                System.out.println(Thread.currentThread().getName() + "获得"+lockA+",尝试获取" + lockB);
                synchronized (lockB){
                }
            }
        }
    
    
        public static void main(String[] args) {
            String lockA = "lockA";
            String lockB = "lockB";
    
    
            new Thread(() -> {
                Deadlock deadlock = new Deadlock(lockA,lockB);
                deadlock.get();
            },"AA").start();
    
            new Thread(() -> {
                Deadlock deadlock = new Deadlock(lockB,lockA);
                deadlock.get();
            },"BB").start();
    
        }
    }

运行结果

![20190812203816145.png][]

*  ###  死锁定位及分析 ###

1.打开命令行终端，切换到程序目录，使用  jps 指令查看当前正在运行的java程序

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NjE4Nzk3_size_16_color_FFFFFF_t_70][]

2.我们对一些可疑的程序进行分析，使用 jstack 进程号  查看程序运行信息

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NjE4Nzk3_size_16_color_FFFFFF_t_70 1][]

[20190812203816145.png]: /images/20211018/0ec376a7e92449b38c69903f5063be33.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NjE4Nzk3_size_16_color_FFFFFF_t_70]: /images/20211018/5612207bff0c487a95df7d4f3c0a2a03.png
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3FxXzM3NjE4Nzk3_size_16_color_FFFFFF_t_70 1]: /images/20211018/1bb30427c0074734806f967879dc09b1.png