Java多线程锁异常：IllegalMonitorStateException

2019年3月10日 226次阅读 来源: java锁

在项目多线程编程中用了ReentrantLock配合Condition来控制线程的加锁和解锁：

private void signalAllConnect() {
        final ReentrantLock lock = this.connectLock;
        try {
            lock.lockInterruptibly();

        } catch (InterruptedException e) {
            SyncLogUtil.e(e);
        } finally {
            connectCondition.signalAll();
                SyncLogUtil.d("notify the connect task...");
                lock.unlock();
            }
    }

之前的代码是这么写的，采用lockInterruptibly()来上锁，结果随机性出现以下异常：

java.lang.IllegalMonitorStateException
    at java.util.concurrent.locks.ReentrantLock$Sync.tryRelease(ReentrantLock.java:123)
    at java.util.concurrent.locks.AbstractQueuedSynchronizer.release(AbstractQueuedSynchronizer.java:1235)
    at java.util.concurrent.locks.ReentrantLock.unlock(ReentrantLock.java:429)
    at com.xtc.sync.connection.TCPConnection.putConnectTaskToQueue(TCPConnection.java:435)
    at com.xtc.sync.connection.TCPConnection.connect(TCPConnection.java:410)
    at com.xtc.sync.connection.TCPConnection.connect(TCPConnection.java:339)
    at com.xtc.sync.connection.ConnectionService.connect(ConnectionService.java:288)
    at com.xtc.sync.connection.ConnectionService.decodeData(ConnectionService.java:414)
    at com.xtc.sync.connection.ConnectionService.access$1600(ConnectionService.java:52)
    at com.xtc.sync.connection.ConnectionService$5.onRead(ConnectionService.java:381)
    at com.xtc.sync.connection.ReadAndWriteDataThread.onRead(ReadAndWriteDataThread.java:156)
    at com.xtc.sync.connection.ReadAndWriteDataThread.run(ReadAndWriteDataThread.java:109)

意思是该线程还未被lock，然后就调用了unLock造成的异常，跟进源码里面发现异常是这边报出来的：

protected final boolean tryRelease(int releases) {
            int c = getState() - releases;
            if (Thread.currentThread() != getExclusiveOwnerThread())
                throw new IllegalMonitorStateException();
            boolean free = false;
            if (c == 0) {
                free = true;
                setExclusiveOwnerThread(null);
            }
            setState(c);
            return free;
        }

而getExclusiveOwnerThread()会在线程被lock的时候调用的，也就是说线程确实还没被上锁就被unLock了，因为我用的是lockInterruptibly()，所以在线程调用interrupt()的时候这里会抛出InterruptedException异常，然后线程lock就失败，但是后面的finally里面却有对线程执行了unLock，所以就报错了，解决方法如下：

private void signalAllConnect() {
        final ReentrantLock lock = this.connectLock;
        try {
            lock.lockInterruptibly();
            try {
                connectCondition.signalAll();
            } finally {
                SyncLogUtil.d("notify the connect task...");
                lock.unlock();
            }
        } catch (InterruptedException e) {
            SyncLogUtil.e(e);
        }
    }

改成如上写法，当lockInterruptibly()抛出异常的时候就不会执行unlock()方法了，而且我看了BlockQueue的一些阻塞实现也是类似如上写法，它从来不会把unLock操作和lockInterruptibly操作放在同一级，而是把unlock操作放在lockInterruptibly操作的下一步，保证lockInterruptibly()抛出异常后，不执行unlock

    原文作者：java锁
    原文地址: https://blog.csdn.net/lhd201006/article/details/50986016
    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。
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