Java虚拟机工具之堆栈跟踪工具jstack检测死锁-白红宇

Java虚拟机工具之堆栈跟踪工具jstack检测死锁

阅读量：4097 次

发布时间：2019-05-25

本文共 8358 字，大约阅读时间需要 27 分钟。

jstack是一个很实用的工具，不仅能定位到死循环的位置，还能找到死锁的位置，这个工具对我们直接在生产机上定位错误带来了极大的方便，尤其是那些不容易复现的错误。

首先呢，先写一个能产生死锁的代码。代码逻辑很简单，咱就产生两个线程，两个线程分别执行加锁与放锁两个动作，啥时候产生死锁呢，就是在两个线程都释放锁以后，又同时加锁，于是互相僵持，互相等待，产生死锁。

import java.util.concurrent.ExecutorService;import java.util.concurrent.Executors;/** * Created by Kevin on 11/4/16. */class MultiThread implements Runnable{    private Object o1;    private Object o2;    private int flag;    public MultiThread(Object o1, Object o2, int flag) {        this.o1 = o1;        this.o2 = o2;        this.flag = flag;    }    public void task1() throws InterruptedException{        synchronized (o1){            synchronized (o2){                System.out.println(Thread.currentThread().getName());            }        }    }    public void task2() throws InterruptedException{        synchronized (o2){            Thread.yield();            synchronized (o1) {                System.out.println(Thread.currentThread().getName());            }        }    }    @Override    public void run() {        while (true) {            try {                if (this.flag == 1) {                    this.task1();                } else {                    this.task2();                }            } catch (InterruptedException e) {                e.printStackTrace();            }        }    }}public class DeadLock {
       public static void main(String[] args){        Object o1 = new Object();        Object o2 = new Object();        ExecutorService executorService = Executors.newFixedThreadPool(10);        for (int flag = 0; flag < 2; flag++) {            executorService.execute(new MultiThread(o1, o2, flag));        }    }}

运行代码，你会发现控制台过一会儿就不动了，但是程序运行没有终止，下面用jstack看看到底啥问题。

首先要找到该进程的pid

$ jps11523 Main27894 AppMain27912 Launcher27933 Jps12046 JConsole

然后可以看到pid=27894，辣么用jstack查看一下27894：

$ jstack 278942016-11-07 14:59:55Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.101-b13 mixed mode):"Attach Listener" #13 daemon prio=9 os_prio=0 tid=0x00007f5660001000 nid=0x6d3b runnable [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"DestroyJavaVM" #12 prio=5 os_prio=0 tid=0x00007f569800a800 nid=0x6cf7 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"pool-1-thread-2" #11 prio=5 os_prio=0 tid=0x00007f5698156800 nid=0x6d07 waiting for monitor entry [0x00007f5684175000]   java.lang.Thread.State: BLOCKED (on object monitor)    at MultiThread.task1(DeadLock.java:21)    - waiting to lock <0x00000000ec215b70> (a java.lang.Object)    - locked <0x00000000ec215b60> (a java.lang.Object)    at MultiThread.run(DeadLock.java:41)    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)    at java.lang.Thread.run(Thread.java:745)"pool-1-thread-1" #10 prio=5 os_prio=0 tid=0x00007f5698155000 nid=0x6d06 waiting for monitor entry [0x00007f5684276000]   java.lang.Thread.State: BLOCKED (on object monitor)    at MultiThread.task2(DeadLock.java:30)    - waiting to lock <0x00000000ec215b60> (a java.lang.Object)    - locked <0x00000000ec215b70> (a java.lang.Object)    at MultiThread.run(DeadLock.java:43)    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)    at java.lang.Thread.run(Thread.java:745)"Monitor Ctrl-Break" #9 daemon prio=5 os_prio=0 tid=0x00007f5698152800 nid=0x6d05 runnable [0x00007f5684377000]   java.lang.Thread.State: RUNNABLE    at java.net.PlainSocketImpl.socketAccept(Native Method)    at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409)    at java.net.ServerSocket.implAccept(ServerSocket.java:545)    at java.net.ServerSocket.accept(ServerSocket.java:513)    at com.intellij.rt.execution.application.AppMain$1.run(AppMain.java:90)    at java.lang.Thread.run(Thread.java:745)"Service Thread" #8 daemon prio=9 os_prio=0 tid=0x00007f56980da800 nid=0x6d03 runnable [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"C1 CompilerThread2" #7 daemon prio=9 os_prio=0 tid=0x00007f56980bd000 nid=0x6d02 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"C2 CompilerThread1" #6 daemon prio=9 os_prio=0 tid=0x00007f56980bb800 nid=0x6d01 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"C2 CompilerThread0" #5 daemon prio=9 os_prio=0 tid=0x00007f56980b8800 nid=0x6d00 waiting on condition [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"Signal Dispatcher" #4 daemon prio=9 os_prio=0 tid=0x00007f56980b7000 nid=0x6cff runnable [0x0000000000000000]   java.lang.Thread.State: RUNNABLE"Finalizer" #3 daemon prio=8 os_prio=0 tid=0x00007f5698084000 nid=0x6cfe in Object.wait() [0x00007f5685682000]   java.lang.Thread.State: WAITING (on object monitor)    at java.lang.Object.wait(Native Method)    - waiting on <0x00000000ec188ee0> (a java.lang.ref.ReferenceQueue$Lock)    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143)    - locked <0x00000000ec188ee0> (a java.lang.ref.ReferenceQueue$Lock)    at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:164)    at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:209)"Reference Handler" #2 daemon prio=10 os_prio=0 tid=0x00007f569807f800 nid=0x6cfd in Object.wait() [0x00007f5685783000]   java.lang.Thread.State: WAITING (on object monitor)    at java.lang.Object.wait(Native Method)    - waiting on <0x00000000ec186b50> (a java.lang.ref.Reference$Lock)    at java.lang.Object.wait(Object.java:502)    at java.lang.ref.Reference.tryHandlePending(Reference.java:191)    - locked <0x00000000ec186b50> (a java.lang.ref.Reference$Lock)    at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:153)"VM Thread" os_prio=0 tid=0x00007f5698078000 nid=0x6cfc runnable "GC task thread#0 (ParallelGC)" os_prio=0 tid=0x00007f569801f800 nid=0x6cf8 runnable "GC task thread#1 (ParallelGC)" os_prio=0 tid=0x00007f5698021000 nid=0x6cf9 runnable "GC task thread#2 (ParallelGC)" os_prio=0 tid=0x00007f5698023000 nid=0x6cfa runnable "GC task thread#3 (ParallelGC)" os_prio=0 tid=0x00007f5698024800 nid=0x6cfb runnable "VM Periodic Task Thread" os_prio=0 tid=0x00007f56980dd000 nid=0x6d04 waiting on condition JNI global references: 15Found one Java-level deadlock:============================="pool-1-thread-2":  waiting to lock monitor 0x00007f56680062c8 (object 0x00000000ec215b70, a java.lang.Object),  which is held by "pool-1-thread-1""pool-1-thread-1":  waiting to lock monitor 0x00007f5668004e28 (object 0x00000000ec215b60, a java.lang.Object),  which is held by "pool-1-thread-2"Java stack information for the threads listed above:==================================================="pool-1-thread-2":    at MultiThread.task1(DeadLock.java:21)    - waiting to lock <0x00000000ec215b70> (a java.lang.Object)    - locked <0x00000000ec215b60> (a java.lang.Object)    at MultiThread.run(DeadLock.java:41)    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)    at java.lang.Thread.run(Thread.java:745)"pool-1-thread-1":    at MultiThread.task2(DeadLock.java:30)    - waiting to lock <0x00000000ec215b60> (a java.lang.Object)    - locked <0x00000000ec215b70> (a java.lang.Object)    at MultiThread.run(DeadLock.java:43)    at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1142)    at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617)    at java.lang.Thread.run(Thread.java:745)Found 1 deadlock.

看到没，其中有一段长这个模样：

Found one Java-level deadlock:============================="pool-1-thread-2":  waiting to lock monitor 0x00007f56680062c8 (object 0x00000000ec215b70, a java.lang.Object),  which is held by "pool-1-thread-1""pool-1-thread-1":  waiting to lock monitor 0x00007f5668004e28 (object 0x00000000ec215b60, a java.lang.Object),  which is held by "pool-1-thread-2"Java stack information for the threads listed above:==================================================="pool-1-thread-2":    at MultiThread.task1(DeadLock.java:21)    ......    at MultiThread.run(DeadLock.java:41)    ......    at MultiThread.task2(DeadLock.java:30)    ......    at MultiThread.run(DeadLock.java:43)    ......Found 1 deadlock.

人家说了这里有死锁，哪个文件，第几行都告你了，剩下的就自己去改吧。

转载地址：http://izhii.baihongyu.com/

你可能感兴趣的文章