jstack的使用
有些时候我们需要查看下jvm中的线程执行情况，比如，发现服务器的CPU的负载突然增 高了、出现了死锁、死循环等，我们该如何分析呢？
由于程序是正常运行的，没有任何的输出，从日志方面也看不出什么问题，所以就需要 看下jvm的内部线程的执行情况，然后再进行分析查找出原因。
这个时候，就需要借助于jstack命令了，jstack的作用是将正在运行的jvm的线程情况进 行快照，并且打印出来
E:accpY2JVM>jstack 17656 2020-03-03 16:54:24 Full thread dump Java HotSpot(TM) Client VM (25.73-b02 mixed mode): "http-bio-8080-exec-6" #34 daemon prio=5 os_prio=0 tid=0x15535c00 nid=0x33ac waiting on condition [0x16f2f000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x0a270340> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) "http-bio-8080-exec-5" #33 daemon prio=5 os_prio=0 tid=0x15535800 nid=0x27d0 waiting on condition [0x16e9f000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x0a270340> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) "http-bio-8080-exec-4" #32 daemon prio=5 os_prio=0 tid=0x15538400 nid=0xa2c waiting on condition [0x16e0f000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x0a270340> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) "http-bio-8080-exec-3" #31 daemon prio=5 os_prio=0 tid=0x15535000 nid=0x4bf4 waiting on condition [0x16d7f000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x0a270340> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) "http-bio-8080-exec-2" #30 daemon prio=5 os_prio=0 tid=0x15537400 nid=0x4010 waiting on condition [0x16cef000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x0a270340> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) "http-bio-8080-exec-1" #29 daemon prio=5 os_prio=0 tid=0x15537000 nid=0x2478 waiting on condition [0x1635f000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x0a270340> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at java.util.concurrent.LinkedBlockingQueue.take(LinkedBlockingQueue.java:442) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:104) at org.apache.tomcat.util.threads.TaskQueue.take(TaskQueue.java:32) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at org.apache.tomcat.util.threads.TaskThread$WrappingRunnable.run(TaskThread.java:61) at java.lang.Thread.run(Thread.java:745) "ajp-bio-8009-AsyncTimeout" #26 daemon prio=5 os_prio=0 tid=0x15537c00 nid=0x3ddc waiting on condition [0x162cf000] java.lang.Thread.State: TIMED_WAITING (sleeping) at java.lang.Thread.sleep(Native Method) at org.apache.tomcat.util.net.JIoEndpoint$AsyncTimeout.run(JIoEndpoint.java:152) at java.lang.Thread.run(Thread.java:745) "ajp-bio-8009-Acceptor-0" #25 daemon prio=5 os_prio=0 tid=0x15536800 nid=0x51a0 runnable [0x1623f000] java.lang.Thread.State: RUNNABLE at java.net.DualStackPlainSocketImpl.accept0(Native Method) at java.net.DualStackPlainSocketImpl.socketAccept(DualStackPlainSocketImpl.java:131) at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409) at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:199) - locked <0x0a1352a8> (a java.net.SocksSocketImpl) at java.net.ServerSocket.implAccept(ServerSocket.java:545) at java.net.ServerSocket.accept(ServerSocket.java:513) at org.apache.tomcat.util.net.DefaultServerSocketFactory.acceptSocket(DefaultServerSocketFactory.java:60) at org.apache.tomcat.util.net.JIoEndpoint$Acceptor.run(JIoEndpoint.java:222) at java.lang.Thread.run(Thread.java:745) "http-bio-8080-AsyncTimeout" #24 daemon prio=5 os_prio=0 tid=0x15538800 nid=0x2390 waiting on condition [0x161af000] java.lang.Thread.State: TIMED_WAITING (sleeping) at java.lang.Thread.sleep(Native Method) at org.apache.tomcat.util.net.JIoEndpoint$AsyncTimeout.run(JIoEndpoint.java:152) at java.lang.Thread.run(Thread.java:745) "http-bio-8080-Acceptor-0" #23 daemon prio=5 os_prio=0 tid=0x154e4000 nid=0x3d3c runnable [0x1611f000] java.lang.Thread.State: RUNNABLE at java.net.DualStackPlainSocketImpl.accept0(Native Method) at java.net.DualStackPlainSocketImpl.socketAccept(DualStackPlainSocketImpl.java:131) at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409) at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:199) - locked <0x0a135390> (a java.net.SocksSocketImpl) at java.net.ServerSocket.implAccept(ServerSocket.java:545) at java.net.ServerSocket.accept(ServerSocket.java:513) at org.apache.tomcat.util.net.DefaultServerSocketFactory.acceptSocket(DefaultServerSocketFactory.java:60) at org.apache.tomcat.util.net.JIoEndpoint$Acceptor.run(JIoEndpoint.java:222) at java.lang.Thread.run(Thread.java:745) "ContainerBackgroundProcessor[StandardEngine[Catalina]]" #22 daemon prio=5 os_prio=0 tid=0x154e3c00 nid=0x1774 waiting on condition [0x1608f000] java.lang.Thread.State: TIMED_WAITING (sleeping) at java.lang.Thread.sleep(Native Method) at org.apache.catalina.core.ContainerBase$ContainerBackgroundProcessor.run(ContainerBase.java:1512) at java.lang.Thread.run(Thread.java:745) "GC Daemon" #18 daemon prio=2 os_prio=-2 tid=0x15484800 nid=0x4e2c in Object.wait() [0x15e6f000] java.lang.Thread.State: TIMED_WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x0a0dd158> (a sun.misc.GC$LatencyLock) at sun.misc.GC$Daemon.run(GC.java:117) - locked <0x0a0dd158> (a sun.misc.GC$LatencyLock) "RMI Scheduler(0)" #14 daemon prio=5 os_prio=0 tid=0x152b4c00 nid=0x617c waiting on condition [0x15aef000] java.lang.Thread.State: WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x09dbc780> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.park(LockSupport.java:175) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.await(AbstractQueuedSynchronizer.java:2039) at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1081) at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:809) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1067) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1127) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:617) at java.lang.Thread.run(Thread.java:745) "RMI TCP Accept-0" #12 daemon prio=5 os_prio=0 tid=0x151ac400 nid=0x252c runnable [0x1583f000] java.lang.Thread.State: RUNNABLE at java.net.DualStackPlainSocketImpl.accept0(Native Method) at java.net.DualStackPlainSocketImpl.socketAccept(DualStackPlainSocketImpl.java:131) at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409) at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:199) - locked <0x09eb9b28> (a java.net.SocksSocketImpl) at java.net.ServerSocket.implAccept(ServerSocket.java:545) at java.net.ServerSocket.accept(ServerSocket.java:513) at sun.management.jmxremote.LocalRMIServerSocketFactory$1.accept(LocalRMIServerSocketFactory.java:52) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(TCPTransport.java:400) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(TCPTransport.java:372) at java.lang.Thread.run(Thread.java:745) "RMI TCP Accept-1099" #11 daemon prio=5 os_prio=0 tid=0x14e50000 nid=0x4c7c runnable [0x156af000] java.lang.Thread.State: RUNNABLE at java.net.DualStackPlainSocketImpl.accept0(Native Method) at java.net.DualStackPlainSocketImpl.socketAccept(DualStackPlainSocketImpl.java:131) at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409) at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:199) - locked <0x09eb9e90> (a java.net.SocksSocketImpl) at java.net.ServerSocket.implAccept(ServerSocket.java:545) at java.net.ServerSocket.accept(ServerSocket.java:513) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(TCPTransport.java:400) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(TCPTransport.java:372) at java.lang.Thread.run(Thread.java:745) "RMI TCP Accept-0" #10 daemon prio=5 os_prio=0 tid=0x15198400 nid=0x5d1c runnable [0x1561f000] java.lang.Thread.State: RUNNABLE at java.net.DualStackPlainSocketImpl.accept0(Native Method) at java.net.DualStackPlainSocketImpl.socketAccept(DualStackPlainSocketImpl.java:131) at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409) at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:199) - locked <0x09eba190> (a java.net.SocksSocketImpl) at java.net.ServerSocket.implAccept(ServerSocket.java:545) at java.net.ServerSocket.accept(ServerSocket.java:513) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(TCPTransport.java:400) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(TCPTransport.java:372) at java.lang.Thread.run(Thread.java:745) "Service Thread" #7 daemon prio=9 os_prio=0 tid=0x14c99c00 nid=0x26f0 runnable [0x00000000] java.lang.Thread.State: RUNNABLE "C1 CompilerThread0" #6 daemon prio=9 os_prio=2 tid=0x14c91c00 nid=0x950 waiting on condition [0x00000000] java.lang.Thread.State: RUNNABLE "Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x14c91000 nid=0x53e4 waiting on condition [0x00000000] java.lang.Thread.State: RUNNABLE "Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x14cc6400 nid=0x3710 runnable [0x00000000] java.lang.Thread.State: RUNNABLE "Finalizer" #3 daemon prio=8 os_prio=1 tid=0x14c64800 nid=0x4a8c in Object.wait() [0x14eef000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x09eba9d8> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143) - locked <0x09eba9d8> (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=2 tid=0x14c63400 nid=0x5984 in Object.wait() [0x047ef000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x09ebab78> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:502) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:157) - locked <0x09ebab78> (a java.lang.ref.Reference$Lock) "main" #1 prio=5 os_prio=0 tid=0x0028d400 nid=0x10c4 runnable [0x00d2f000] java.lang.Thread.State: RUNNABLE at java.net.DualStackPlainSocketImpl.accept0(Native Method) at java.net.DualStackPlainSocketImpl.socketAccept(DualStackPlainSocketImpl.java:131) at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:409) at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:199) - locked <0x0a2e50d8> (a java.net.SocksSocketImpl) at java.net.ServerSocket.implAccept(ServerSocket.java:545) at java.net.ServerSocket.accept(ServerSocket.java:513) at org.apache.catalina.core.StandardServer.await(StandardServer.java:453) at org.apache.catalina.startup.Catalina.await(Catalina.java:777) at org.apache.catalina.startup.Catalina.start(Catalina.java:723) at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method) at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62) at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43) at java.lang.reflect.Method.invoke(Method.java:497) at org.apache.catalina.startup.Bootstrap.start(Bootstrap.java:321) at org.apache.catalina.startup.Bootstrap.main(Bootstrap.java:455) "VM Thread" os_prio=2 tid=0x00eddc00 nid=0x3378 runnable "VM Periodic Task Thread" os_prio=2 tid=0x151ad800 nid=0x5988 waiting on condition JNI global references: 266
线程的状态
在Java中线程的状态一共被分成6种：
1、初始态（NEW）
创建一个Thread对象，但还未调用start()启动线程时，线程处于初始态。
2、运行态（RUNNABLE）
在Java中，运行态包括 就绪态 和 运行态。
①就绪态
该状态下的线程已经获得执行所需的所有资源，只要CPU分配执行权就能运行。
所有就绪态的线程存放在就绪队列中。
②运行态
获得CPU执行权，正在执行的线程。
由于一个CPU同一时刻只能执行一条线程，因此每个CPU每个时刻只有一条运行态的线程。
3、阻塞态（BLOCKED）
当一条正在执行的线程请求某一资源失败时，就会进入阻塞态。
而在Java中，阻塞态专指请求锁失败时进入的状态。
由一个阻塞队列存放所有阻塞态的线程。
处于阻塞态的线程会不断请求资源，一旦请求成功，就会进入就绪队列，等待执行。
4、等待态（WAITING）
当前线程中调用wait、join、park函数时，当前线程就会进入等待态。
也有一个等待队列存放所有等待态的线程。
线程处于等待态表示它需要等待其他线程的指示才能继续运行。
进入等待态的线程会释放CPU执行权，并释放资源（如：锁）
5、超时等待态（TIMED_WAITING）
当运行中的线程调用sleep(time)、wait、join、parkNanos、parkUntil时，就会进入该状态；
它和等待态一样，并不是因为请求不到资源，而是主动进入，并且进入后需要其他线程唤醒；
进入该状态后释放CPU执行权 和 占有的资源。
与等待态的区别：到了超时时间后自动进入阻塞队列，开始竞争锁。
6、终止态（TERMINATED）
线程执行结束后的状态。
死锁问题
如果在生产环境发生了死锁，我们将看到的是部署的程序没有任何反应了，这个时候我们可以借助jstack进行分析
1、构造死锁
编写代码，启动2个线程，Thread1拿到了obj1锁，准备去拿obj2锁时，obj2已经被Thread2锁定，所以发送了死锁。
public class LockTest { //定义资源 private static Object obj1=new Object(); private static Object obj2=new Object(); //线程A：先获取到资源1，然后休眠2s，再获取资源2 private static class ThreadA implements Runnable{ @Override public void run() { synchronized (obj1){ System.out.println("ThreadA获取到了OBJ1资源"); try { //休眠2s，因为我们要将CPU资源让渡出去，这样线程B就可以先抢占obj2资源 Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } synchronized (obj2){ System.out.println("ThreadA获取到了OBJ2资源"); } } } } private static class ThreadB implements Runnable{ @Override public void run() { synchronized (obj2){ System.out.println("ThreadB获取到了OBJ2资源"); try { //休眠2s，因为我们要将CPU资源让渡出去，这样线程B就可以先抢占obj2资源 Thread.sleep(2000); } catch (InterruptedException e) { e.printStackTrace(); } synchronized (obj1){ System.out.println("ThreadA获取到了OBJ1资源"); } } } } public static void main(String[] args) { new Thread(new ThreadA()).start(); new Thread(new ThreadB()).start(); } }
使用jstack进行分析
E:accpY2JVM>jstack>ps 1595624 16548 Main 22292 RemoteMavenServer 4452 17656 Bootstrap 2536 Jps 10524 Launcher 8828 TestDeadLock E:北大青鸟Y2JVM文件>jstack 8828 2020-03-03 17:50:16 Full thread dump Java HotSpot(TM) Client VM (25.73-b02 mixed mode): "DestroyJavaVM" #10 prio=5 os_prio=0 tid=0x031bc400 nid=0x2628 waiting on condition [0x00000000] java.lang.Thread.State: RUNNABLE "Thread-1" #9 prio=5 os_prio=0 tid=0x1588dc00 nid=0x35a4 waiting for monitor entry [0x15f0f000] java.lang.Thread.State: BLOCKED (on object monitor) at TestDeadLock$Thread2.run(TestDeadLock.java:37) - waiting to lock <0x052e39d8> (a java.lang.Object) - locked <0x052e39e0> (a java.lang.Object) at java.lang.Thread.run(Thread.java:745) "Thread-0" #8 prio=5 os_prio=0 tid=0x1588d400 nid=0x2e40 waiting for monitor entry [0x15e7f000] java.lang.Thread.State: BLOCKED (on object monitor) at TestDeadLock$Thread1.run(TestDeadLock.java:20) - waiting to lock <0x052e39e0> (a java.lang.Object) - locked <0x052e39d8> (a java.lang.Object) at java.lang.Thread.run(Thread.java:745) "Service Thread" #7 daemon prio=9 os_prio=0 tid=0x15825400 nid=0x4dec runnable [0x00000000] java.lang.Thread.State: RUNNABLE "C1 CompilerThread0" #6 daemon prio=9 os_prio=2 tid=0x157d3800 nid=0x1df0 waiting on condition [0x00000000] java.lang.Thread.State: RUNNABLE "Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x157d0000 nid=0x2680 waiting on condition [0x00000000] java.lang.Thread.State: RUNNABLE "Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x157cf400 nid=0x2170 runnable [0x00000000] java.lang.Thread.State: RUNNABLE "Finalizer" #3 daemon prio=8 os_prio=1 tid=0x157a6c00 nid=0x200c in Object.wait() [0x15abf000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x05206458> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:143) - locked <0x05206458> (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=2 tid=0x0310e800 nid=0x17bc in Object.wait() [0x15a2f000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x05205f50> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:502) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:157) - locked <0x05205f50> (a java.lang.ref.Reference$Lock) "VM Thread" os_prio=2 tid=0x0310bc00 nid=0x1c18 runnable "VM Periodic Task Thread" os_prio=2 tid=0x15887400 nid=0x2338 waiting on condition JNI global references: 6 Found one Java-level deadlock: ============================= "Thread-1": waiting to lock monitor 0x157a56a4 (object 0x052e39d8, a java.lang.Object), which is held by "Thread-0" "Thread-0": waiting to lock monitor 0x157a63c4 (object 0x052e39e0, a java.lang.Object), which is held by "Thread-1" Java stack information for the threads listed above: =================================================== "Thread-1": at TestDeadLock$Thread2.run(TestDeadLock.java:37) - waiting to lock <0x052e39d8> (a java.lang.Object) - locked <0x052e39e0> (a java.lang.Object) at java.lang.Thread.run(Thread.java:745) "Thread-0": at TestDeadLock$Thread1.run(TestDeadLock.java:20) - waiting to lock <0x052e39e0> (a java.lang.Object) - locked <0x052e39d8> (a java.lang.Object) at java.lang.Thread.run(Thread.java:745) Found 1 deadlock.
在输出的信息中，已经看到了，发送一个死锁，关键看这个：
"Thread-1": at TestDeadLock$Thread2.run(TestDeadLock.java:37) - waiting to lock <0x052e39d8> (a java.lang.Object) - locked <0x052e39e0> (a java.lang.Object) at java.lang.Thread.run(Thread.java:745) "Thread-0": at TestDeadLock$Thread1.run(TestDeadLock.java:20) - waiting to lock <0x052e39e0> (a java.lang.Object) - locked <0x052e39d8> (a java.lang.Object) at java.lang.Thread.run(Thread.java:745)
可以清晰的看到：
Thread2获取了<0x052e39e0>的锁，等待获取<0x052e39d8>这个锁
Thread1获取了<0x052e39d8>的锁，等待获取<0x052e39e0>这个锁
由此可见，发生了死锁；