java线程转储
java的线程转储可以被定义为JVM中在某一个给定的时刻运行的所有线程的快照。一个线程转储可能包含一个单独的线程或者多个线程。在多线程环境中，比如J2EE应用服务器，将会有许多线程和线程组。每一个线程都有它自己的调用堆栈，在一个给定时刻，表现为一个独立功能。线程转储将会提供JVM中所有线程的堆栈信息，对于特定的线程也会给出更多信息。
java虚拟机进程和java线程
java虚拟机，或者称为JVM，是一个操作系统级别的进程。java线程是JVM进程的子进程或者轻量级进程（Solar中的叫法）。
生成java线程转储
线程转储可以通过向JVM进程发送一个SIGQUIT信号来生成。有两种不同方式来向进程发送这个信号：
在Unix中，使用“kill -3<pid>”命令，pid表示JVM进程的ID。
在Windows中，在JVM运行时按下CTRL+BREAK键 ,或者使用 jstack 来生成。
[fox]:jstack jstack用于打印出给定的java进程ID或core file或远程调试服务的Java堆栈信息。
Java线程状态
每一个java线程总是处于其生命周期的四个状态之一。
Runnable-线程正在运行，或者准备好获取CPU时间后运行。JRockit线程转储中把这种状态当做Active。
Waiting on Monitor-线程休眠，或者在等待一个对象，或者等待被其他线程唤醒。在线程对象中调用sleep()方法，或者在一个对象中调用wait()方法时就会有这种情况发生。
举个例子，在WebLogc服务器中，空闲的执行线程处于这种状态，他们会一直等待直到一个Socket reader线程有新的任务才唤醒他们。堆栈信息就会如下所示：
“ExecuteThread: ‘2’ for queue: ‘weblogic.admin.RMI'” daemon prio=5 tid=0x1752F040 nid=0x180c in Object.wait() [1887f000..1887fd8c]
at java.lang.Object.wait(Native Method) waiting on <04134D98> (a weblogic.kernel.ExecuteThread)
at java.lang.Object.wait(Object.java:426)
at weblogic.kernel.ExecuteThread.waitForRequest(ExecuteThread.java:126)
locked <04134D98> (a weblogic.kernel.ExecuteThread)
at weblogic.kernel.ExecuteThread.run(ExecuteThread.java:145)
在某些别的版本的JVM中称这种状态是CW，Object.wait()（像上面那样）。JRockit称之为WAITING。
Waiting for Monitor Entry——线程在等待获取一个对象的锁（其他线程可能持有这个同步锁）。这种情况发生在当两个或者更多线程尝试执行一段同步代码时。注意“锁”总是针对于一个对象而不是针对一个单独的方法。
这种情况的线程的简单堆栈信息如下：
如:
/** * * * @author mjorcen * @email mjorcen@gmail.com * @dateTime Jan 27, 2015 10:51:24 AM * @version 1 */ public class DeadThread { private static Object obj1 = new Object(); private static Object obj2 = new Object(); public static void main(String[] args) { new Thread(new Runnable() { public void run() { synchronized (obj1) { try { Thread.sleep(200); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } synchronized (obj2) { System.out.println(1); } } } }, "t-0").start(); new Thread(new Runnable() { public void run() { synchronized (obj2) { try { Thread.sleep(200); } catch (InterruptedException e) { // TODO Auto-generated catch block e.printStackTrace(); } synchronized (obj1) { System.out.println(2); } } } }, "t-1").start(); } }
在 jstack 中.
结果:
2015-01-27 10:54:12 Full thread dump Java HotSpot(TM) 64-Bit Server VM (24.55-b03 mixed mode): "RMI TCP Connection(2)-192.168.1.7" daemon prio=6 tid=0x000000000c016000 nid=0x1030 runnable [0x000000000d73e000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:152) at java.net.SocketInputStream.read(SocketInputStream.java:122) at java.io.BufferedInputStream.fill(BufferedInputStream.java:235) at java.io.BufferedInputStream.read(BufferedInputStream.java:254) - locked <0x00000007d73f8200> (a java.io.BufferedInputStream) at java.io.FilterInputStream.read(FilterInputStream.java:83) at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:538) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:811) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:670) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - <0x00000007d6f99578> (a java.util.concurrent.ThreadPoolExecutor$Worker) "JMX server connection timeout 16" daemon prio=6 tid=0x000000000bedc800 nid=0x1bc8 in Object.wait() [0x000000000ce2f000] java.lang.Thread.State: TIMED_WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x00000007d712d470> (a [I) at com.sun.jmx.remote.internal.ServerCommunicatorAdmin$Timeout.run(ServerCommunicatorAdmin.java:168) - locked <0x00000007d712d470> (a [I) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - None "RMI Scheduler(0)" daemon prio=6 tid=0x000000000bedc000 nid=0xa08 waiting on condition [0x000000000cc2e000] java.lang.Thread.State: TIMED_WAITING (parking) at sun.misc.Unsafe.park(Native Method) - parking to wait for <0x00000007d6ef7798> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject) at java.util.concurrent.locks.LockSupport.parkNanos(LockSupport.java:226) at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(AbstractQueuedSynchronizer.java:2082) at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:1090) at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(ScheduledThreadPoolExecutor.java:807) at java.util.concurrent.ThreadPoolExecutor.getTask(ThreadPoolExecutor.java:1068) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1130) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - None "RMI TCP Connection(1)-192.168.1.7" daemon prio=6 tid=0x000000000bf09800 nid=0x16e0 runnable [0x000000000cb0f000] java.lang.Thread.State: RUNNABLE at java.net.SocketInputStream.socketRead0(Native Method) at java.net.SocketInputStream.read(SocketInputStream.java:152) at java.net.SocketInputStream.read(SocketInputStream.java:122) at java.io.BufferedInputStream.fill(BufferedInputStream.java:235) at java.io.BufferedInputStream.read(BufferedInputStream.java:254) - locked <0x00000007d70d2dd0> (a java.io.BufferedInputStream) at java.io.FilterInputStream.read(FilterInputStream.java:83) at sun.rmi.transport.tcp.TCPTransport.handleMessages(TCPTransport.java:538) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(TCPTransport.java:811) at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(TCPTransport.java:670) at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1145) at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:615) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - <0x00000007d6f971f0> (a java.util.concurrent.ThreadPoolExecutor$Worker) "RMI TCP Accept-0" daemon prio=6 tid=0x000000000bf81800 nid=0x15c runnable [0x000000000c93f000] 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:398) at java.net.PlainSocketImpl.accept(PlainSocketImpl.java:198) - locked <0x00000007d6f07c40> (a java.net.SocksSocketImpl) at java.net.ServerSocket.implAccept(ServerSocket.java:530) at java.net.ServerSocket.accept(ServerSocket.java:498) at sun.management.jmxremote.LocalRMIServerSocketFactory$1.accept(LocalRMIServerSocketFactory.java:52) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(TCPTransport.java:388) at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(TCPTransport.java:360) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - None "DestroyJavaVM" prio=6 tid=0x000000000027d800 nid=0x1b0c waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "Thread-1" prio=6 tid=0x000000000be08800 nid=0x1864 waiting for monitor entry [0x000000000c34f000] java.lang.Thread.State: BLOCKED (on object monitor) at mjorcen.nio.test.DeadThread$2.run(DeadThread.java:48) - waiting to lock <0x00000007d6b1d530> (a java.lang.Object) - locked <0x00000007d6b1d540> (a java.lang.Object) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - None "Thread-0" prio=6 tid=0x000000000a74d800 nid=0x196c waiting for monitor entry [0x000000000bdff000] java.lang.Thread.State: BLOCKED (on object monitor) at mjorcen.nio.test.DeadThread$1.run(DeadThread.java:32) - waiting to lock <0x00000007d6b1d540> (a java.lang.Object) - locked <0x00000007d6b1d530> (a java.lang.Object) at java.lang.Thread.run(Thread.java:745) Locked ownable synchronizers: - None "Service Thread" daemon prio=6 tid=0x000000000a741000 nid=0x1aec runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "C2 CompilerThread1" daemon prio=10 tid=0x000000000a73c800 nid=0x1bd8 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "C2 CompilerThread0" daemon prio=10 tid=0x000000000a72b800 nid=0xba0 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "Attach Listener" daemon prio=10 tid=0x000000000a72a800 nid=0x12d0 waiting on condition [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "Signal Dispatcher" daemon prio=10 tid=0x000000000a729800 nid=0x5d4 runnable [0x0000000000000000] java.lang.Thread.State: RUNNABLE Locked ownable synchronizers: - None "Finalizer" daemon prio=8 tid=0x00000000024cf800 nid=0x192c in Object.wait() [0x000000000b6ef000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x00000007d6a85568> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:135) - locked <0x00000007d6a85568> (a java.lang.ref.ReferenceQueue$Lock) at java.lang.ref.ReferenceQueue.remove(ReferenceQueue.java:151) at java.lang.ref.Finalizer$FinalizerThread.run(Finalizer.java:189) Locked ownable synchronizers: - None "Reference Handler" daemon prio=10 tid=0x00000000024cb800 nid=0xae4 in Object.wait() [0x000000000b57f000] java.lang.Thread.State: WAITING (on object monitor) at java.lang.Object.wait(Native Method) - waiting on <0x00000007d6a850f0> (a java.lang.ref.Reference$Lock) at java.lang.Object.wait(Object.java:503) at java.lang.ref.Reference$ReferenceHandler.run(Reference.java:133) - locked <0x00000007d6a850f0> (a java.lang.ref.Reference$Lock) Locked ownable synchronizers: - None "VM Thread" prio=10 tid=0x000000000a6b2000 nid=0x1194 runnable "GC task thread#0 (ParallelGC)" prio=6 tid=0x0000000002404800 nid=0x1a74 runnable "GC task thread#1 (ParallelGC)" prio=6 tid=0x0000000002406000 nid=0x1a7c runnable "VM Periodic Task Thread" prio=10 tid=0x000000000a74a000 nid=0x13fc waiting on condition JNI global references: 150 Found one Java-level deadlock: ============================= "Thread-1": waiting to lock monitor 0x000000000a6ba6d8 (object 0x00000007d6b1d530, a java.lang.Object), which is held by "Thread-0" "Thread-0": waiting to lock monitor 0x000000000a6b9238 (object 0x00000007d6b1d540, a java.lang.Object), which is held by "Thread-1" Java stack information for the threads listed above: =================================================== "Thread-1": at mjorcen.nio.test.DeadThread$2.run(DeadThread.java:48) - waiting to lock <0x00000007d6b1d530> (a java.lang.Object) - locked <0x00000007d6b1d540> (a java.lang.Object) at java.lang.Thread.run(Thread.java:745) "Thread-0": at mjorcen.nio.test.DeadThread$1.run(DeadThread.java:32) - waiting to lock <0x00000007d6b1d540> (a java.lang.Object) - locked <0x00000007d6b1d530> (a java.lang.Object) at java.lang.Thread.run(Thread.java:745) Found 1 deadlock.
