Java死锁 Thread Dump分析详解编程语言

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 } 

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 } 

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：

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): 

 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) 

 20 Locked ownable synchronizers: 

 21 - 0x090afed0 (a java.util.concurrent.ThreadPoolExecutor$Worker) 

 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) 

 31 Locked ownable synchronizers: 

 32 - None 

 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) 

 47 Locked ownable synchronizers: 

 48 - None 

 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) 

 64 Locked ownable synchronizers: 

 65 - None 

 67 "DestroyJavaVM" prio=6 tid=0x005fb000 nid=0x19f4 waiting on condition [0x00000000] 

 68 java.lang.Thread.State: RUNNABLE 

 70 Locked ownable synchronizers: 

 71 - None 

 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) 

 81 Locked ownable synchronizers: 

 82 - None 

 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) 

 92 Locked ownable synchronizers: 

 93 - None 

 95 "Service Thread" daemon prio=6 tid=0x00c65000 nid=0x7c8 runnable [0x00000000] 

 96 java.lang.Thread.State: RUNNABLE 

 98 Locked ownable synchronizers: 

 99 - None 

101 "C1 CompilerThread0" daemon prio=10 tid=0x00c58400 nid=0x193c waiting on condition [0x00000000] 

102 java.lang.Thread.State: RUNNABLE 

104 Locked ownable synchronizers: 

105 - None 

107 "Attach Listener" daemon prio=10 tid=0x00c53000 nid=0x110c waiting on condition [0x00000000] 

108 java.lang.Thread.State: RUNNABLE 

110 Locked ownable synchronizers: 

111 - None 

113 "Signal Dispatcher" daemon prio=10 tid=0x00c50000 nid=0x1900 runnable [0x00000000] 

114 java.lang.Thread.State: RUNNABLE 

116 Locked ownable synchronizers: 

117 - None 

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) 

128 Locked ownable synchronizers: 

129 - None 

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) 

139 Locked ownable synchronizers: 

140 - None 

142 "VM Thread" prio=10 tid=0x00bd5400 nid=0x140c runnable 

144 "VM Periodic Task Thread" prio=10 tid=0x00c76400 nid=0x1978 waiting on condition 

146 JNI global references: 192 

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" 

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) 

173 Found 1 deadlock.

看最后的红色字体，已经很清晰的说明了一切。

原创文章，作者：ItWorker，如若转载，请注明出处：https://blog.ytso.com/19412.html