多线程【死锁案例及死锁的排查】
作者:互联网
一、死锁案例
class HoldLockThread extends Thread{
private String lockA;
private String lockB;
public HoldLockThread(String lockA, String lockB){
this.lockA = lockA;
this.lockB = lockB;
}
@Override
public void run() {
synchronized (lockA){
System.out.println(Thread.currentThread().getName() + "持有:" + lockA + "锁");
try {
Thread.sleep(2000);
} catch (InterruptedException e) {
e.printStackTrace();
}
synchronized (lockB){
System.out.println(Thread.currentThread().getName() + "持有:" + lockA + "锁");
}
}
}
}
public class DeadLockDemo {
public static void main(String[] args) {
String lockA = "lockA";
String lockB = "lockB";
new Thread(new HoldLockThread(lockA, lockB), "线程1").start();
new Thread(new HoldLockThread(lockB, lockA), "线程2").start();
}
}
二、问题的排查
当程序运行到一半卡不不继续运行时,如何排查是不是死锁导致的呢?
主要通过两个命令来排查,分别为:jps 和 jstack。
(一)jps
可以在 IDEA 的 Terminal 工具输入:jps -l 命令来查看当前发生死锁的线程id
(二)jstack
针对获取到的线程 id,使用 jstack 命令查看栈相关信息。
如果出现如下信息,则说明确实是程序中出现死锁了,那么只需做相关调整即可解决。
Found one Java-level deadlock: ============================= "线程2": waiting to lock monitor 0x000002937e722398 (object 0x00000000d613fa60, a java.lang.String), which is held by "线程1" "线程1": waiting to lock monitor 0x000002937d8ef548 (object 0x00000000d613fa98, a java.lang.String), which is held by "线程2" Java stack information for the threads listed above: =================================================== "线程2": at com.zuobiao.thread.HoldLockThread.run(DeadLockDemo.java:23) - waiting to lock <0x00000000d613fa60> (a java.lang.String) - locked <0x00000000d613fa98> (a java.lang.String) at java.lang.Thread.run(Thread.java:748) "线程1": at com.zuobiao.thread.HoldLockThread.run(DeadLockDemo.java:23) - waiting to lock <0x00000000d613fa98> (a java.lang.String) - locked <0x00000000d613fa60> (a java.lang.String) at java.lang.Thread.run(Thread.java:748) Found 1 deadlock.java
Java新手,若有错误,欢迎指正!
标签:lockB,lockA,java,String,Thread,排查,死锁,线程,多线程 来源: https://www.cnblogs.com/Java-biao/p/14423261.html