死锁篇

Posted 2021-03-06 lovestart

死锁篇

死锁定义

死锁是指两个或两个以上的进程在执行过程中,因争夺资源而造成的一一种==互相等待的现象==,若无外力干涉那它们都将无法推进下去，如果系统资源充足，进程的资源请求都能够得到满足，死锁出现的可能性就很低，否则就会因争夺有限的资源而陷入死锁。

死锁代码

public class DeadLock {
    public static void main(String[] args) {
        Object o1 = new Object();
        Object o2 = new Object();

        new Thread(()->{
            synchronized (o1) {
                System.out.println(Thread.currentThread().getName()+"	 我抢到了o1");
                try {
                    TimeUnit.SECONDS.sleep(2);} catch (InterruptedException e) {e.printStackTrace();}
                synchronized (o2) {
                    System.out.println(Thread.currentThread().getName()+"	 我抢到了o2");
                }
            }

        },"A").start();
        new Thread(()->{
            synchronized (o2) {
                System.out.println(Thread.currentThread().getName()+"	 我抢到了o2");
                try {
                    TimeUnit.SECONDS.sleep(1);} catch (InterruptedException e) {e.printStackTrace();}
                synchronized (o1) {
                    System.out.println(Thread.currentThread().getName()+"	 我抢到了o1");
                }
            }

        },"B").start();
    }
}

找到死锁

jps

jps -l 查看当前java运行的线程

18704 sun.tools.jps.Jps
13044 org.jetbrains.kotlin.daemon.KotlinCompileDaemon
10616 尚硅谷.juc.锁篇.死锁.DeadLock
20712 org.jetbrains.jps.cmdline.Launcher
23036 org.jetbrains.idea.maven.server.RemoteMavenServer36
5804

jstack

jstack 进程号

Java stack information for the threads listed above:
===================================================
"B":
        at 尚硅谷.juc.锁篇.死锁.DeadLock.lambda$main$1(DeadLock.java:33)
        - waiting to lock <0x00000000d621ba58> (a java.lang.Object)
        - locked <0x00000000d621ba68> (a java.lang.Object)
        at 尚硅谷.juc.锁篇.死锁.DeadLock$$Lambda$2/2093631819.run(Unknown Source)
        at java.lang.Thread.run(Thread.java:748)
"A":
        at 尚硅谷.juc.锁篇.死锁.DeadLock.lambda$main$0(DeadLock.java:22)
        - waiting to lock <0x00000000d621ba68> (a java.lang.Object)
        - locked <0x00000000d621ba58> (a java.lang.Object)
        at 尚硅谷.juc.锁篇.死锁.DeadLock$$Lambda$1/558638686.run(Unknown Source)
        at java.lang.Thread.run(Thread.java:748)

Found 1 deadlock.