Java死锁的排查

https://blog.csdn.net/sidihuo/article/details/52474227

先弄个死锁的代码例子：

[java] view plain copy

1. public class DeadLock implements Runnable {  
2.   
3.     private int flagCurrent = -1;  
4.   
5.     private static int flagThread1 = 0;  
6.   
7.     private static int flagThread2 = 1;  
8.   
9.     private static Object object1 = new Integer(1);  
10.   
11.     private static Object object2 = new Double(2);  
12.   
13.     @Override  
14.     public void run() {  
15.   
16.         System.out.println("CurrentThread" + flagCurrent);  
17.   
18.         if (flagCurrent == flagThread1) {// 线程1进  
19.             synchronized (object1) {// 线程1先锁定object1（期间要等500ms去锁定object2）  
20.                 try {  
21.                     Thread.sleep(500);  
22.                 } catch (final Exception e) {  
23.                     e.printStackTrace();  
24.                 }  
25.                 // 此时线程2已经锁定object2，需要【等待】线程2释放object2，然后线程1锁定object2释放object2，再释放object1  
26.                 // 死锁发生：线程1等待线程2释放object2，线程1才释放object1；线程2等待线程1释放object1，线程2才释放object2；  
27.                 synchronized (object2) {  
28.                     System.out.println("1");  
29.                 }  
30.             }  
31.         }  
32.         if (flagCurrent == flagThread2) {// 线程2进  
33.             synchronized (object2) {// 线程2先锁定object2（期间要等500ms去锁定object1）  
34.                 try {  
35.                     Thread.sleep(500);  
36.                 } catch (final Exception e) {  
37.                     e.printStackTrace();  
38.                 }  
39.                 // 此时线程1已经锁定object1，需要【等待】线程1释放object1，然后线程2锁定object1释放object1，再释放object2  
40.                 // 死锁发生：线程1等待线程2释放object2，线程1才释放object1；线程2等待线程1释放object1，线程2才释放object2；  
41.                 synchronized (object1) {  
42.                     System.out.println("0");  
43.                 }  
44.             }  
45.         }  
46.     }  
47.   
48.     public static void main(final String[] args) {  
49.         final DeadLock runnableThread1 = new DeadLock();  
50.         final DeadLock runnableThread2 = new DeadLock();  
51.   
52.         runnableThread1.flagCurrent = flagThread1;  
53.         runnableThread2.flagCurrent = flagThread2;  
54.   
55.         new Thread(runnableThread1, "runnableThread1").start();  
56.         new Thread(runnableThread2, "runnableThread2").start();  
57.   
58.     }  
59. }  

查找死锁的2个方法：

1.用Jconsole

切换到线程那个选项卡，左下角有个死锁检查：

2.用Jstack

先jps 找出对应的代号，再Jstack -l  代号，就可看见了