Java死锁 Thread Dump分析

Java中的死锁是指两个线程在互相等待对方释放锁的无限期阻塞现象。

举个例子:

 1 public class TestDeadLock {
 2     public static void main(String[] args) {
 3         Dead1 d1 = new Dead1("Thread1");
 4         Dead2 d2 = new Dead2("Thread2");
 5         d1.setDead2(d2);
 6         d2.setDead1(d1);
 7         d1.start();
 8         d2.start();
 9     }
10 }
11 
12 class Dead1 extends Thread {
13     public Dead2 d2;
14     public Dead1(String name) {
15         super(name);
16     }
17     public void setDead2(Dead2 d2) {
18         this.d2 = d2;
19     }
20     public void run() {
21         test();
22     }
23     public synchronized void test() {
24         try {
25             Thread.sleep(500);
26         } catch (InterruptedException e) {
27             e.printStackTrace();
28         }
29         // 需要获取d2的锁,但是d2此时被另一个线程所拥有。
30         d2.test();
31     }
32 }
33 
34 class Dead2 extends Thread {
35     public Dead1 d1;
36     public Dead2(String name) {
37         super(name);
38     }
39     public void setDead1(Dead1 d1) {
40         this.d1 = d1;
41     }
42     public void run() {
43         test();
44     }
45     public synchronized void test() {
46         try {
47             Thread.sleep(500);
48         } catch (InterruptedException e) {
49             e.printStackTrace();
50         }
51         // 需要获取d1的锁,但是d1此时被另一个线程所拥有。
52         d1.test();
53     }
54 }

 

例子中,类Dead1和类Dead2分别继承Thread类,同时Dead1类里面定义了Dead2类型的变量,Dead2类里面定义了Dead1类型的变量,当在主线程里面分别创建它们的线程实例并分别调用set方法赋值。

1。当线程Thread1(d1)启动时,它需要调用自己的test方法,而test方法里面需要调用Thread2(d2)的test方法,所以Thread1需要获得d2的锁,

2。但是此时Thread2很可能已经进入了Dead2类的test方法,它已经获得了d2的锁,它正在等待线程1释放d1锁,而线程1又在等待线程2释放锁,

3。于是,死锁产生了。程序永远不会结束。

  为了更好的证明死锁产生了,我们可以使用Java自带的VisualVM工具来查看Java Dump:

《Java死锁 Thread Dump分析》

由于我的系统是日文的,所以显示的是日语。

再看详细的Thread Dump信息:

  1 2014-05-28 17:03:38
  2 Full thread dump Java HotSpot(TM) Client VM (23.7-b01 mixed mode):
  3 
  4 "RMI TCP Connection(4)-133.197.178.192" daemon prio=6 tid=0x00d6f800 nid=0x1060 runnable [0x18b6f000]
  5    java.lang.Thread.State: RUNNABLE
  6     at java.net.SocketInputStream.socketRead0(Native Method)
  7     at java.net.SocketInputStream.read(SocketInputStream.java:150)
  8     at java.net.SocketInputStream.read(SocketInputStream.java:121)
  9     at java.io.BufferedInputStream.fill(BufferedInputStream.java:235)
 10     at java.io.BufferedInputStream.read(BufferedInputStream.java:254)
 11     - locked <0x090afdd0> (a java.io.BufferedInputStream)
 12     at java.io.FilterInputStream.read(FilterInputStream.java:83)
 13     at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:535)
 14     at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:808)
 15     at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:667)
 16     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145)
 17     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
 18     at java.lang.Thread.run(Thread.java:722)
 19 
 20    Locked ownable synchronizers:
 21     - <0x090afed0> (a java.util.concurrent.ThreadPoolExecutor$Worker)
 22 
 23 "JMX server connection timeout 15" daemon prio=6 tid=0x185b9400 nid=0x18b4 in Object.wait() [0x18a0f000]
 24    java.lang.Thread.State: TIMED_WAITING (on object monitor)
 25     at java.lang.Object.wait(Native Method)
 26     - waiting on <0x09040bd0> (a [I)
 27     at com.sun.jmx.remote.internal.ServerCommunicatorAdmin$Timeout.run(ServerCommunicatorAdmin.java:168)
 28     - locked <0x09040bd0> (a [I)
 29     at java.lang.Thread.run(Thread.java:722)
 30 
 31    Locked ownable synchronizers:
 32     - None
 33 
 34 "RMI Scheduler(0)" daemon prio=6 tid=0x185a8000 nid=0x1df8 waiting on condition [0x17e2f000]
 35    java.lang.Thread.State: TIMED_WAITING (parking)
 36     at sun.misc.Unsafe.park(Native Method)
 37     - parking to wait for  <0x08f71080> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)
 38     at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:226)
 39     at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2082)
 40     at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1090)
 41     at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:807)
 42     at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068)
 43     at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130)
 44     at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615)
 45     at java.lang.Thread.run(Thread.java:722)
 46 
 47    Locked ownable synchronizers:
 48     - None
 49 
 50 "RMI TCP Accept-0" daemon prio=6 tid=0x00daf800 nid=0x5b8 runnable [0x1817f000]
 51    java.lang.Thread.State: RUNNABLE
 52     at java.net.DualStackPlainSocketImpl.accept0(Native Method)
 53     at java.net.DualStackPlainSocketImpl.socketAccept(DualStackPlainSocketImpl.java:121)
 54     at java.net.AbstractPlainSocketImpl.accept(AbstractPlainSocketImpl.java:398)
 55     at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:183)
 56     - locked <0x08fc4a18> (a java.net.SocksSocketImpl)
 57     at java.net.ServerSocket.implAccept(ServerSocket.java:522)
 58     at java.net.ServerSocket.accept(ServerSocket.java:490)
 59     at sun.management.jmxremote.LocalRMIServerSocketFactory$1.accept(LocalRMIServerSocketFactory.java:52)
 60     at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(TCPTransport.java:387)
 61     at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(TCPTransport.java:359)
 62     at java.lang.Thread.run(Thread.java:722)
 63 
 64    Locked ownable synchronizers:
 65     - None
 66 
 67 "DestroyJavaVM" prio=6 tid=0x005fb000 nid=0x19f4 waiting on condition [0x00000000]
 68    java.lang.Thread.State: RUNNABLE
 69 
 70    Locked ownable synchronizers:
 71     - None
 72 
 73 "Thread2" prio=6 tid=0x00c96c00 nid=0xdac waiting for monitor entry [0x17fbf000]
 74    java.lang.Thread.State: BLOCKED (on object monitor)
 75     at Dead1.test(TestDeadLock.java:25)
 76     - waiting to lock <0x08fc4b90> (a Dead1)
 77     at Dead2.test(TestDeadLock.java:52)
 78     - locked <0x08fc4b28> (a Dead2)
 79     at Dead2.run(TestDeadLock.java:43)
 80 
 81    Locked ownable synchronizers:
 82     - None
 83 
 84 "Thread1" prio=6 tid=0x00c94800 nid=0xb54 waiting for monitor entry [0x17ddf000]
 85    java.lang.Thread.State: BLOCKED (on object monitor)
 86     at Dead2.test(TestDeadLock.java:47)
 87     - waiting to lock <0x08fc4b28> (a Dead2)
 88     at Dead1.test(TestDeadLock.java:30)
 89     - locked <0x08fc4b90> (a Dead1)
 90     at Dead1.run(TestDeadLock.java:21)
 91 
 92    Locked ownable synchronizers:
 93     - None
 94 
 95 "Service Thread" daemon prio=6 tid=0x00c65000 nid=0x7c8 runnable [0x00000000]
 96    java.lang.Thread.State: RUNNABLE
 97 
 98    Locked ownable synchronizers:
 99     - None
100 
101 "C1 CompilerThread0" daemon prio=10 tid=0x00c58400 nid=0x193c waiting on condition [0x00000000]
102    java.lang.Thread.State: RUNNABLE
103 
104    Locked ownable synchronizers:
105     - None
106 
107 "Attach Listener" daemon prio=10 tid=0x00c53000 nid=0x110c waiting on condition [0x00000000]
108    java.lang.Thread.State: RUNNABLE
109 
110    Locked ownable synchronizers:
111     - None
112 
113 "Signal Dispatcher" daemon prio=10 tid=0x00c50000 nid=0x1900 runnable [0x00000000]
114    java.lang.Thread.State: RUNNABLE
115 
116    Locked ownable synchronizers:
117     - None
118 
119 "Finalizer" daemon prio=8 tid=0x00bdf400 nid=0x1c0c in Object.wait() [0x17ccf000]
120    java.lang.Thread.State: WAITING (on object monitor)
121     at java.lang.Object.wait(Native Method)
122     - waiting on <0x08fc4e00> (a java.lang.ref.ReferenceQueue$Lock)
123     at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135)
124     - locked <0x08fc4e00> (a java.lang.ref.ReferenceQueue$Lock)
125     at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151)
126     at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:177)
127 
128    Locked ownable synchronizers:
129     - None
130 
131 "Reference Handler" daemon prio=10 tid=0x00bda800 nid=0x1718 in Object.wait() [0x17c2f000]
132    java.lang.Thread.State: WAITING (on object monitor)
133     at java.lang.Object.wait(Native Method)
134     - waiting on <0x08fc45d8> (a java.lang.ref.Reference$Lock)
135     at java.lang.Object.wait(Object.java:503)
136     at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:133)
137     - locked <0x08fc45d8> (a java.lang.ref.Reference$Lock)
138 
139    Locked ownable synchronizers:
140     - None
141 
142 "VM Thread" prio=10 tid=0x00bd5400 nid=0x140c runnable 
143 
144 "VM Periodic Task Thread" prio=10 tid=0x00c76400 nid=0x1978 waiting on condition 
145 
146 JNI global references: 192
147 
148 
149 Found one Java-level deadlock:
150 =============================
151 "Thread2":
152   waiting to lock monitor 0x00bdf354 (object 0x08fc4b90, a Dead1),
153   which is held by "Thread1"
154 "Thread1":
155   waiting to lock monitor 0x00bde724 (object 0x08fc4b28, a Dead2),
156   which is held by "Thread2"
157 
158 Java stack information for the threads listed above:
159 ===================================================
160 "Thread2":
161     at Dead1.test(TestDeadLock.java:25)
162     - waiting to lock <0x08fc4b90> (a Dead1)
163     at Dead2.test(TestDeadLock.java:52)
164     - locked <0x08fc4b28> (a Dead2)
165     at Dead2.run(TestDeadLock.java:43)
166 "Thread1":
167     at Dead2.test(TestDeadLock.java:47)
168     - waiting to lock <0x08fc4b28> (a Dead2) 169     at Dead1.test(TestDeadLock.java:30)
170     - locked <0x08fc4b90> (a Dead1)
171     at Dead1.run(TestDeadLock.java:21)
172 
173 Found 1 deadlock.

看最后的红色字体,已经很清晰的说明了一切。

    原文作者:画水
    原文地址: https://www.cnblogs.com/huashui/p/3757284.html
    本文转自网络文章,转载此文章仅为分享知识,如有侵权,请联系博主进行删除。
点赞