1.相关代码

public class TestAwaitMain {

private static ReentrantLock  lock;

public static void main(String[] args) {

// TODO Auto-generated method stub

//1.线程A先持有锁

//  然后await

//在B中查询是否能获取锁

//如果能则说明 await()方法可以释放锁

lock=new ReentrantLock();

Condition condition = lock.newCondition();

//开辟两个线程

new Thread(new RunnableA(lock,condition),"t_A").start();

try {

  Thread.sleep(1000L);

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

new Thread(new RunnableB(lock,condition),"t_B").start();

lock.lock();

System.out.println("线程"+Thread.currentThread().getName()+"Condition队列长度是  :"+lock.getWaitQueueLength(condition));

System.out.println("等待获取lock锁的"+"AQS队列长度是 :"+lock.getQueueLength());

}

}

RunnableA

public class RunnableA implements Runnable {

private ReentrantLock lock;

private Condition condition;

public RunnableA(ReentrantLock lock, Condition condition) {

super();

this.lock = lock;

this.condition = condition;

}

@Override

public void run() {

System.out.println("线程A运行");

    //先阻塞

lock.lock();

System.out.println("线程"+Thread.currentThread().getName()+"的lock方法已经执行");

try {

System.out.println("线程"+Thread.currentThread().getName()+"持有锁吗 ?:"+lock.isHeldByCurrentThread());

System.out.println("持有锁的线程数:"+ lock.getHoldCount());

try {

System.out.println("线程"+Thread.currentThread().getName()+"准备执行await()方法");

System.out.println("线程"+Thread.currentThread().getName()+"等待获取锁的队列长度"+lock.getQueueLength());

System.out.println("线程"+Thread.currentThread().getName()+"Condition队列长度"+lock.getWaitQueueLength(condition));

lock.hasWaiters(condition);

//condition.await();

//此时，如果不执行await操作

//看看AQS队列的长度

Thread.sleep(10000L);

} catch (Exception e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

} finally {

// TODO: handle finally clause

//lock.unlock();

}

}

}

RunnableB

public class RunnableB implements Runnable {

    private ReentrantLock lock;

private Condition condition;

public RunnableB(ReentrantLock lock, Condition condition) {

super();

this.lock = lock;

this.condition = condition;

}

@Override

public void run() {

System.out.println("线程B运行");

    //先阻塞

lock.lock();

System.out.println("线程"+Thread.currentThread().getName()+"的lock方法已经执行");

try {

System.out.println("线程"+Thread.currentThread().getName()+"持有锁吗 ?:"+lock.isHeldByCurrentThread());

System.out.println("持有锁的线程数:"+ lock.getHoldCount());

try {

System.out.println("线程"+Thread.currentThread().getName()+"准备执行await()方法");

System.out.println("线程"+Thread.currentThread().getName()+"等待获取锁的AQS队列长度是 :"+lock.getQueueLength());

System.out.println("线程"+Thread.currentThread().getName()+"Condition队列长度是  "+lock.getWaitQueueLength(condition));

//lock.hasWaiters(condition);

condition.await();

} catch (InterruptedException e) {

// TODO Auto-generated catch block

e.printStackTrace();

}

} finally {

// TODO: handle finally clause

lock.unlock();

}

}

}

2.打开jvisualVM生成thread dump

线程dump

全部文件内容

2018-09-18 14:18:43

Full thread dump Java HotSpot(TM) 64-Bit Server VM (25.171-b11 mixed mode):

"JMX server connection timeout 21" #21 daemon prio=5 os_prio=0 tid=0x000000001b5dd000 nid=0x13b0 in Object.wait() [0x000000001e77f000]

  java.lang.Thread.State: TIMED_WAITING (on object monitor)

at java.lang.Object.wait(Native Method)

at com.sun.jmx.remote.internal.ServerCommunicatorAdmin$Timeout.run(Unknown Source)

- locked <0x00000000d8180db0> (a [I)

at java.lang.Thread.run(Unknown Source)

  Locked ownable synchronizers:

- None

"RMI TCP Connection(idle)" #20 daemon prio=5 os_prio=0 tid=0x000000001c731000 nid=0x2348 waiting on condition [0x000000001e27e000]

  java.lang.Thread.State: TIMED_WAITING (parking)

at sun.misc.Unsafe.park(Native Method)

- parking to wait for  <0x00000000d8191040> (a java.util.concurrent.SynchronousQueue$TransferStack)

at java.util.concurrent.locks.LockSupport.parkNanos(Unknown Source)

at java.util.concurrent.SynchronousQueue$TransferStack.awaitFulfill(Unknown Source)

at java.util.concurrent.SynchronousQueue$TransferStack.transfer(Unknown Source)

at java.util.concurrent.SynchronousQueue.poll(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor.getTask(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)

at java.lang.Thread.run(Unknown Source)

  Locked ownable synchronizers:

- None

"RMI TCP Connection(7)-192.168.1.235" #19 daemon prio=5 os_prio=0 tid=0x000000001c4ed000 nid=0x153c runnable [0x000000001d1ae000]

  java.lang.Thread.State: RUNNABLE

at java.net.SocketInputStream.socketRead0(Native Method)

at java.net.SocketInputStream.socketRead(Unknown Source)

at java.net.SocketInputStream.read(Unknown Source)

at java.net.SocketInputStream.read(Unknown Source)

at java.io.BufferedInputStream.fill(Unknown Source)

at java.io.BufferedInputStream.read(Unknown Source)

- locked <0x00000000d8190e50> (a java.io.BufferedInputStream)

at java.io.FilterInputStream.read(Unknown Source)

at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)

at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source)

at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(Unknown Source)

at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$3/1038727162.run(Unknown Source)

at java.security.AccessController.doPrivileged(Native Method)

at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)

at java.lang.Thread.run(Unknown Source)

  Locked ownable synchronizers:

- <0x00000000d8190fe0> (a java.util.concurrent.ThreadPoolExecutor$Worker)

"RMI TCP Connection(6)-192.168.1.235" #17 daemon prio=5 os_prio=0 tid=0x000000001c4d2800 nid=0x1618 runnable [0x000000001cfad000]

  java.lang.Thread.State: RUNNABLE

at java.net.SocketInputStream.socketRead0(Native Method)

at java.net.SocketInputStream.socketRead(Unknown Source)

at java.net.SocketInputStream.read(Unknown Source)

at java.net.SocketInputStream.read(Unknown Source)

at java.io.BufferedInputStream.fill(Unknown Source)

at java.io.BufferedInputStream.read(Unknown Source)

- locked <0x00000000d81b0278> (a java.io.BufferedInputStream)

at java.io.FilterInputStream.read(Unknown Source)

at sun.rmi.transport.tcp.TCPTransport.handleMessages(Unknown Source)

at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run0(Unknown Source)

at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.lambda$run$0(Unknown Source)

at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler$$Lambda$3/1038727162.run(Unknown Source)

at java.security.AccessController.doPrivileged(Native Method)

at sun.rmi.transport.tcp.TCPTransport$ConnectionHandler.run(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)

at java.lang.Thread.run(Unknown Source)

  Locked ownable synchronizers:

- <0x00000000d8191170> (a java.util.concurrent.ThreadPoolExecutor$Worker)

"JMX server connection timeout 16" #16 daemon prio=5 os_prio=0 tid=0x000000001c4bf000 nid=0x2b8c in Object.wait() [0x000000001ceaf000]

  java.lang.Thread.State: TIMED_WAITING (on object monitor)

at java.lang.Object.wait(Native Method)

at com.sun.jmx.remote.internal.ServerCommunicatorAdmin$Timeout.run(Unknown Source)

- locked <0x00000000d81be188> (a [I)

at java.lang.Thread.run(Unknown Source)

  Locked ownable synchronizers:

- None

"RMI Scheduler(0)" #15 daemon prio=5 os_prio=0 tid=0x000000001c4be800 nid=0x1354 waiting on condition [0x000000001cdaf000]

  java.lang.Thread.State: TIMED_WAITING (parking)

at sun.misc.Unsafe.park(Native Method)

- parking to wait for  <0x00000000d81be320> (a java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject)

at java.util.concurrent.locks.LockSupport.parkNanos(Unknown Source)

at java.util.concurrent.locks.AbstractQueuedSynchronizer$ConditionObject.awaitNanos(Unknown Source)

at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(Unknown Source)

at java.util.concurrent.ScheduledThreadPoolExecutor$DelayedWorkQueue.take(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor.getTask(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor.runWorker(Unknown Source)

at java.util.concurrent.ThreadPoolExecutor$Worker.run(Unknown Source)

at java.lang.Thread.run(Unknown Source)

  Locked ownable synchronizers:

- None

"RMI TCP Accept-0" #13 daemon prio=5 os_prio=0 tid=0x000000001c422000 nid=0xdf4 runnable [0x000000001c98f000]

  java.lang.Thread.State: RUNNABLE

at java.net.DualStackPlainSocketImpl.accept0(Native Method)

at java.net.DualStackPlainSocketImpl.socketAccept(Unknown Source)

at java.net.AbstractPlainSocketImpl.accept(Unknown Source)

at java.net.PlainSocketImpl.accept(Unknown Source)

- locked <0x00000000d81958a0> (a java.net.SocksSocketImpl)

at java.net.ServerSocket.implAccept(Unknown Source)

at java.net.ServerSocket.accept(Unknown Source)

at sun.management.jmxremote.LocalRMIServerSocketFactory$1.accept(Unknown Source)

at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.executeAcceptLoop(Unknown Source)

at sun.rmi.transport.tcp.TCPTransport$AcceptLoop.run(Unknown Source)

at java.lang.Thread.run(Unknown Source)

  Locked ownable synchronizers:

- None

"t_B" #11 prio=5 os_prio=0 tid=0x000000001b4ad000 nid=0x1a3c waiting on condition [0x000000001c08e000]

  java.lang.Thread.State: WAITING (parking)

at sun.misc.Unsafe.park(Native Method)

- parking to wait for  <0x00000000d8198268> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

at java.util.concurrent.locks.LockSupport.park(Unknown Source)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(Unknown Source)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(Unknown Source)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(Unknown Source)

at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(Unknown Source)

at java.util.concurrent.locks.ReentrantLock.lock(Unknown Source)

at com.concurrent.testawait.RunnableB.run(RunnableB.java:29)

at java.lang.Thread.run(Unknown Source)

  Locked ownable synchronizers:

- None

"Service Thread" #9 daemon prio=9 os_prio=0 tid=0x000000001b458800 nid=0x126c runnable [0x0000000000000000]

  java.lang.Thread.State: RUNNABLE

  Locked ownable synchronizers:

- None

"C1 CompilerThread2" #8 daemon prio=9 os_prio=2 tid=0x000000001b3dd800 nid=0xdb0 waiting on condition [0x0000000000000000]

  java.lang.Thread.State: RUNNABLE

  Locked ownable synchronizers:

- None

"C2 CompilerThread1" #7 daemon prio=9 os_prio=2 tid=0x000000001b3dd000 nid=0x1028 waiting on condition [0x0000000000000000]

  java.lang.Thread.State: RUNNABLE

  Locked ownable synchronizers:

- None

"C2 CompilerThread0" #6 daemon prio=9 os_prio=2 tid=0x000000001b3da800 nid=0x1f4 waiting on condition [0x0000000000000000]

  java.lang.Thread.State: RUNNABLE

  Locked ownable synchronizers:

- None

"Attach Listener" #5 daemon prio=5 os_prio=2 tid=0x000000001b3d7000 nid=0xaac waiting on condition [0x0000000000000000]

  java.lang.Thread.State: RUNNABLE

  Locked ownable synchronizers:

- None

"Signal Dispatcher" #4 daemon prio=9 os_prio=2 tid=0x000000001b3d3800 nid=0x2d84 runnable [0x0000000000000000]

  java.lang.Thread.State: RUNNABLE

  Locked ownable synchronizers:

- None

"Finalizer" #3 daemon prio=8 os_prio=1 tid=0x00000000199b1800 nid=0x750 in Object.wait() [0x000000001b32f000]

  java.lang.Thread.State: WAITING (on object monitor)

at java.lang.Object.wait(Native Method)

- waiting on <0x00000000d81bee58> (a java.lang.ref.ReferenceQueue$Lock)

at java.lang.ref.ReferenceQueue.remove(Unknown Source)

- locked <0x00000000d81bee58> (a java.lang.ref.ReferenceQueue$Lock)

at java.lang.ref.ReferenceQueue.remove(Unknown Source)

at java.lang.ref.Finalizer$FinalizerThread.run(Unknown Source)

  Locked ownable synchronizers:

- None

"Reference Handler" #2 daemon prio=10 os_prio=2 tid=0x0000000004cb6000 nid=0x2dd4 in Object.wait() [0x000000001b22e000]

  java.lang.Thread.State: WAITING (on object monitor)

at java.lang.Object.wait(Native Method)

- waiting on <0x00000000d81b06e0> (a java.lang.ref.Reference$Lock)

at java.lang.Object.wait(Unknown Source)

at java.lang.ref.Reference.tryHandlePending(Unknown Source)

- locked <0x00000000d81b06e0> (a java.lang.ref.Reference$Lock)

at java.lang.ref.Reference$ReferenceHandler.run(Unknown Source)

  Locked ownable synchronizers:

- None

"main" #1 prio=5 os_prio=0 tid=0x0000000004bc4000 nid=0x2c94 waiting on condition [0x000000000480f000]

  java.lang.Thread.State: WAITING (parking)

at sun.misc.Unsafe.park(Native Method)

- parking to wait for  <0x00000000d8198268> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

at java.util.concurrent.locks.LockSupport.park(Unknown Source)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(Unknown Source)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(Unknown Source)

at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(Unknown Source)

at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(Unknown Source)

at java.util.concurrent.locks.ReentrantLock.lock(Unknown Source)

at com.concurrent.testawait.TestAwaitMain.main(TestAwaitMain.java:27)

  Locked ownable synchronizers:

- None

"VM Thread" os_prio=2 tid=0x0000000019987800 nid=0x1c8c runnable

"GC task thread#0 (ParallelGC)" os_prio=0 tid=0x0000000004bda800 nid=0x18c8 runnable

"GC task thread#1 (ParallelGC)" os_prio=0 tid=0x0000000004bdc800 nid=0x170c runnable

"GC task thread#2 (ParallelGC)" os_prio=0 tid=0x0000000004bde000 nid=0x484 runnable

"GC task thread#3 (ParallelGC)" os_prio=0 tid=0x0000000004be0800 nid=0x1e84 runnable

"GC task thread#4 (ParallelGC)" os_prio=0 tid=0x0000000004be2800 nid=0x1348 runnable

"GC task thread#5 (ParallelGC)" os_prio=0 tid=0x0000000004be3800 nid=0x10b0 runnable

"VM Periodic Task Thread" os_prio=2 tid=0x000000001b49c800 nid=0x2f80 waiting on condition

JNI global references: 228

3.核心内容

"t_B" #11 prio=5 os_prio=0 tid=0x000000001b4ad000 nid=0x1a3c waiting on condition [0x000000001c08e000]

  java.lang.Thread.State: WAITING (parking)

        at sun.misc.Unsafe.park(Native Method)

        - parking to wait for  <0x00000000d8198268> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

        at java.util.concurrent.locks.LockSupport.park(Unknown Source)

        at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(Unknown Source)

        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(Unknown Source)

        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(Unknown Source)

        at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(Unknown Source)

        at java.util.concurrent.locks.ReentrantLock.lock(Unknown Source)

        at com.concurrent.testawait.RunnableB.run(RunnableB.java:29)

        at java.lang.Thread.run(Unknown Source)

  Locked ownable synchronizers:

        - None

"main" #1 prio=5 os_prio=0 tid=0x0000000004bc4000 nid=0x2c94 waiting on condition [0x000000000480f000]

  java.lang.Thread.State: WAITING (parking)

        at sun.misc.Unsafe.park(Native Method)

        - parking to wait for  <0x00000000d8198268> (a java.util.concurrent.locks.ReentrantLock$NonfairSync)

        at java.util.concurrent.locks.LockSupport.park(Unknown Source)

        at java.util.concurrent.locks.AbstractQueuedSynchronizer.parkAndCheckInterrupt(Unknown Source)

        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquireQueued(Unknown Source)

        at java.util.concurrent.locks.AbstractQueuedSynchronizer.acquire(Unknown Source)

        at java.util.concurrent.locks.ReentrantLock$NonfairSync.lock(Unknown Source)

        at java.util.concurrent.locks.ReentrantLock.lock(Unknown Source)

        at com.concurrent.testawait.TestAwaitMain.main(TestAwaitMain.java:27)

  Locked ownable synchronizers:

        - None

3.1 进行分析

t_B :这是线程名称

prio=5 ： 代表该线程的优先级

tid    ： thread id  即：线程id

nid    ：  native  thread id  即： 本地线程id

java.lang.Thread.State: WAITING (parking)  ： 表明线程目前的状态

    - parking to wait for  <0x00000000d8198268>  ：表明该线程处于Waiting状态，其正在等待获取0x00000000d8198268锁