java 线程死锁的检测

例子程序：

import java.util.concurrent.CountDownLatch;
import java.util.concurrent.ExecutorService;
import java.util.concurrent.Executors;

/**
 * Hello world!
 */
public class App {
    public static void main(String[] args) throws InterruptedException {
        System.out.println("Hello World!");
        ExecutorService executorService = Executors.newFixedThreadPool(2);
        byte[] i = new byte[0];
        byte[] j = new byte[0];
        final CountDownLatch countDownLatch = new CountDownLatch(2);
        executorService.execute(new DeadThread1(i, j,countDownLatch));
        executorService.execute(new DeadThread2(i, j,countDownLatch));
        countDownLatch.await();
        System.out.println("done !!!");
    }

    public static class DeadThread1 implements Runnable {

        private byte[] i;
        private byte[] j;
        private CountDownLatch countDownLatch;

        public DeadThread1(byte[] i, byte[] j, CountDownLatch countDownLatch) {
            this.i = i;
            this.j = j;
            this.countDownLatch = countDownLatch;
        }


        @Override
        public void run() {
            synchronized (i) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();  
                }
                synchronized (j) {
                    System.out.println(Thread.currentThread().getName() + "is running!!");
                    countDownLatch.countDown();
                }
            }
        }
    }

    public static class DeadThread2 implements Runnable {

        private byte[] i;
        private byte[] j;
        private CountDownLatch countDownLatch;

        public DeadThread2(byte[] i, byte[] j, CountDownLatch countDownLatch) {
            this.i = i;
            this.j = j;
            this.countDownLatch = countDownLatch;
        }


        @Override
        public void run() {
            synchronized (j) {
                try {
                    Thread.sleep(1000);
                } catch (InterruptedException e) {
                    e.printStackTrace();  
                }
                synchronized (i) {
                    System.out.println(Thread.currentThread().getName() + "is running!!");
                    countDownLatch.countDown();
                }
            }
        }
    }
}

通过jps找到当前进程号：

guohaozhao116008@GUOHAOZHAO11600 /d
$ jps
7448 RemoteMavenServer
6600 JConsole
6340 Jps
6272
7268 AppMain

通过jstack查看堆栈信息：

guohaozhao116008@GUOHAOZHAO11600 /d
$ jstack
Usage:
    jstack [-l] 
        (to connect to running process)
    jstack -F [-m] [-l] 
        (to connect to a hung process)
    jstack [-m] [-l]  
        (to connect to a core file)
    jstack [-m] [-l] [server_id@]
        (to connect to a remote debug server)

Options:
    -F  to force a thread dump. Use when jstack  does not respond (process is hung)
    -m  to print both java and native frames (mixed mode)
    -l  long listing. Prints additional information about locks
    -h or -help to print this help message

guohaozhao116008@GUOHAOZHAO11600 /d
$ jps
7448 RemoteMavenServer
6600 JConsole
6340 Jps
6272
7268 AppMain

guohaozhao116008@GUOHAOZHAO11600 /d
$ jstack -l 7268
2013-05-30 18:36:41
Full thread dump Java HotSpot(TM) 64-Bit Server VM (20.14-b01 mixed mode):

Found one Java-level deadlock:
=============================
"pool-1-thread-2":
  waiting to lock monitor 0x000000000677c208 (object 0x00000000eafc3e18, a [B),
  which is held by "pool-1-thread-1"
"pool-1-thread-1":
  waiting to lock monitor 0x0000000006771be8 (object 0x00000000eafc3e28, a [B),
  which is held by "pool-1-thread-2"

Java stack information for the threads listed above:
===================================================
"pool-1-thread-2":
        at com.sohu.suc.App$DeadThread2.run(App.java:74)
        - waiting to lock <0x00000000eafc3e18> (a [B)
        - locked <0x00000000eafc3e28> (a [B)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
        at java.lang.Thread.run(Thread.java:662)
"pool-1-thread-1":
        at com.sohu.suc.App$DeadThread1.run(App.java:45)
        - waiting to lock <0x00000000eafc3e28> (a [B)
        - locked <0x00000000eafc3e18> (a [B)
        at java.util.concurrent.ThreadPoolExecutor$Worker.runTask(ThreadPoolExecutor.java:895)
        at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:918)
        at java.lang.Thread.run(Thread.java:662)

Found 1 deadlock.

可以看到：

这里发生了死锁。

使用图形工具 jconsole 同样可以检测到：

[img]http://dl2.iteye.com/upload/attachment/0085/2222/37bc8d9c-0c92-37b4-8172-72aa7bbcdfbd.png[/img]