win10本地 Java死锁检查,使用jstack工具

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wx5efd5423d18bb 2022-07-04 10:45:14 博主文章分类：Java ©著作权

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Java死锁检查,使用jstack工具

jstack是java虚拟机自带的一种堆栈跟踪工具。

死锁代码

直接运行就会出现死锁,原因是因为加锁顺序不一致会导致死锁

public class DeadLockSample extends Thread {
  private String frs;
  private String second;

  public DeadLockSample(String name, String frs, String second) {
    super(name);
    this.frs = frs;
    this.second = second;
  }

  @Override
  public void run() {
    synchronized (frs) {
      System.out.println(this.getName() + " obtained: " + frs);
      try {
        Thread.sleep(1000L);
        synchronized (second) {
          System.out.println(this.getName() + " obtained: " + second);
        }
      } catch (InterruptedException e) {
        // Do nothing
      }
    }
  }

  public static void main(String[] args) throws InterruptedException {
    String lockA = "lockA";
    String lockB = "lockB";
//    因为加锁顺序不一致会导致死锁
    DeadLockSample t1 = new DeadLockSample("Thread1", lockA, lockB);
    DeadLockSample t2 = new DeadLockSample("Thread2", lockB, lockA);
    t1.start();
    t2.start();
    t1.join();
    t2.join();
  }
}

开始排查

记录Java程序的PID

win10本地 Java死锁检查,使用jstack工具_死锁

把这些程序的pid记录下来.

使用jstack工具

在jdk的bin目录下面用cmd执行命令 jstack PID

20216 是pid

cmd窗口执行:

D:\jdk\jdk1.8.0_172\bin>jstack 20216

如果不是这个PID就尝试别的java.exe进程的pid试试.仔细观察输出日志

死锁日志

查找日志 ,找到处于BLOCKED状态的线程,这里处于BLOCKED状态线程的日志我没有粘贴到这里, 自己在操作的时候用工具在日志搜索 “BLOCKED” 关键字就能搜索到.

Found one Java-level deadlock:
=============================
"Thread2":
  waiting to lock monitor 0x00000000246f5088 (object 0x00000007412fd740, a java.lang.String),
  which is held by "Thread1"
"Thread1":
  waiting to lock monitor 0x00000000246f3d48 (object 0x00000007412fd778, a java.lang.String),
  which is held by "Thread2"

Java stack information for the threads listed above:
===================================================
"Thread2":
        at die.DeadLockSample.run(DeadLockSample.java:20)
        - waiting to lock <0x00000007412fd740> (a java.lang.String)
        - locked <0x00000007412fd778> (a java.lang.String)
"Thread1":
        at die.DeadLockSample.run(DeadLockSample.java:20)
        - waiting to lock <0x00000007412fd778> (a java.lang.String)
        - locked <0x00000007412fd740> (a java.lang.String)

Found 1 deadlock.