控制启动时的竞争条件 [英] Controlling race condition at startup

问题描述

我有一些代码，我想有一些时间进行初始化。但是这个代码没有一个明确的生命周期，所以我的逻辑可能被潜在地由多个线程调用之前我的初始化完成。所以，我想基本上确保我的逻辑代码等待，直到初始化完成。

I have some code that I want to have some one time initialisation performed. But this code doesn't have a definite lifecycle, so my logic can be potentially invoked by multiple threads before my initialisation is done. So, I want to basically ensure that my logic code "waits" until initialisation is done.

这是我的第一次切割。

public class MyClass {
    private static final AtomicBoolean initialised = new AtomicBoolean(false);

    public void initialise() {
        synchronized(initialised) {
            initStuff();
            initialised.getAndSet(true);
            initialised.notifyAll();
        }
    }

    public void doStuff() {
        synchronized(initialised) {
            if (!initialised.get()) {
                try {
                    initialised.wait();
                } catch (InterruptedException ex) {
                    throw new RuntimeException("Uh oh!", ex);
                }
            }
        }

        doOtherStuff();
    }
}

我基本上希望确保这样做我认为它会做 - 阻塞doStuff直到初始化是真的，我不缺少一个竞争条件，其中doStuff可能会卡在一个Object.wait（）永远不会到达。

I basically want to make sure this is going to do what I think it's going to do -- block doStuff until the initialised is true, and that I'm not missing a race condition where doStuff might get stuck on a Object.wait() that will never arrive.

编辑：

我无法控制线程。我想要能够控制何时所有的初始化完成，这就是为什么doStuff（）不能调用initialise（）。

I have no control over the threads. And I want to be able to control when all of the initialisation is done, which is why doStuff() can't call initialise().

我使用AtomicBoolean它是一个值持有者和我可以同步的对象的组合。我可以简单地有一个public static final Object lock = new Object（）;和一个简单的布尔标志。 AtomicBoolean方便地给了我两个。不能修改布尔值。

I used an AtomicBoolean as it was a combination of a value holder, and an object I could synchronize. I could have also simply had a "public static final Object lock = new Object();" and a simple boolean flag. AtomicBoolean conveniently gave me both. A Boolean can not be modified.

CountDownLatch正是我在寻找的。我也考虑使用一个Sempahore 0许可证。但CountDownLatch是完美的只是这个任务。

The CountDownLatch is exactly what I was looking for. I also considered using a Sempahore with 0 permits. But the CountDownLatch is perfect for just this task.

推荐答案

这是库的一个奇怪的混合和内置的并发控制。这样的东西很干净：

That's a strange mix of library and built-in concurrency controls. Something like this is much cleaner:

public class MyClass {

  private static final CountDownLatch latch = new CountDownLatch(1);

  public void initialise() {
    initStuff();
    latch.countDown();
  }

  public void doStuff() {
    try {
      latch.await();
    } catch (InterruptedException ex) {
      throw new RuntimeException("Uh oh!", ex);
    }
    doOtherStuff();
  }

}

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