StampedLock 与 Thread 类的奇怪行为

Question

我在 Windows 上的 IntellijIDEA 社区中运行此代码

import static java.lang.Thread.sleep;

public class Main {
    public static void main(String[] args) {

        StampedLock lock = new StampedLock();
        Thread th = new Thread(() -> {
            long stamp = lock.tryOptimisticRead();
            try {
                System.out.println("Optimistic Lock Valid: " + lock.validate(stamp));
                sleep(1);
                System.out.println("Optimistic Lock Valid: " + lock.validate(stamp));
                sleep(2);
                System.out.println("Optimistic Lock Valid: " + lock.validate(stamp));
            } catch (InterruptedException ex) {
            } finally {
                lock.unlock(stamp);
            }
        });

        th.start();
        try {
            th.join();
        } catch (InterruptedException ex) {
            ex.printStackTrace();
        }
    }
}

我得到了有效的输出，但是有IllegalMonitorStateException

"C:\Program Files\Java\jdk1.8.0_171\bin\java.exe" "-javaagent:C:\Users\izotova\IntelliJ IDEA Community Edition 2019.3.3\lib\idea_rt.jar=54575:C:\Users\izotova\IntelliJ IDEA Community Edition 2019.3.3\bin" -Dfile.encoding=UTF-8 -classpath "C:\Program Files\Java\jdk1.8.0_171\jre\lib\charsets.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\deploy.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\access-bridge-64.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\cldrdata.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\dnsns.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\jaccess.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\jfxrt.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\localedata.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\nashorn.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\sunec.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\sunjce_provider.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\sunmscapi.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\sunpkcs11.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\ext\zipfs.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\javaws.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\jce.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\jfr.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\jfxswt.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\jsse.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\management-agent.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\plugin.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\resources.jar;C:\Program Files\Java\jdk1.8.0_171\jre\lib\rt.jar;C:\Users\izotova\Documents\case-study-java-backend\Tasks\out\production\tasks" Main
Optimistic Lock Valid: true
Optimistic Lock Valid: true
Optimistic Lock Valid: true
Exception in thread "Thread-0" java.lang.IllegalMonitorStateException
    at java.util.concurrent.locks.StampedLock.unlock(StampedLock.java:609)
    at Main.lambda$main$0(Main.java:22)
    at java.lang.Thread.run(Thread.java:748)

Process finished with exit code 0

老实说，我不知道是什么导致了这种情况，邮票和锁都很好，不知道我做错了什么。 也许您对加盖锁的内部工作方式有一些想法或见解？

Answer 1

我将在我上面的评论中加倍猜测，并说我不认为乐观锁可以被解锁（或需要被解锁）。

这是一个直接从StampedLock 文档中StampedLock 。 请注意，在代码的解锁部分，只有当标记已从乐观锁升级为读锁时，他们才会小心地调用unlock() 。 如果锁仍然是乐观锁，则该示例不会尝试解锁。

   // a read-only method
   // upgrade from optimistic read to read lock
   double distanceFromOrigin() {
     long stamp = sl.tryOptimisticRead();
     try {
       retryHoldingLock: for (;; stamp = sl.readLock()) {
         if (stamp == 0L)
           continue retryHoldingLock;
         // possibly racy reads
         double currentX = x;
         double currentY = y;
         if (!sl.validate(stamp))
           continue retryHoldingLock;
         return Math.hypot(currentX, currentY);
       }
     } finally {
       if (StampedLock.isReadLockStamp(stamp))
         sl.unlockRead(stamp);
     }
   }