Thread.Join()导致死锁

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问题描述

我总共有三个线程.第一个是主UI线程，它启动System.Threading.Thread(ExperimentThread)，然后启动BackgroundWorker(WorkerThread).

I have three threads in total. The first is the main UI thread, which starts a System.Threading.Thread (ExperimentThread), which in turn starts a BackgroundWorker (WorkerThread).

MainThread和WorkerThread都访问共享资源.我使用以下对象同步对该资源的访问:

MainThread and WorkerThread both access a shared resource. I synchronise access to this resource with the following object:

private static readonly Object LockObject = new Object();

在每个线程的主循环中按如下方式使用:

which I use as follows in the main loop of each thread:

lock (LockObject)
{
    // Do something with shared resource here.
}

ExperimentThread的简化版本如下:

public void RunExperiment
{
    while (!bStopThread)
    {

        lock (LockObject)
        {
            // Do something with shared resource here.
        }

        if (bStopThread)
        {
            break;
        }
        else
        {
            Application.DoEvents();
            Thread.Sleep(250);
        }
    }
}

为完整起见，这里是WorkerThread的DoWork方法:

And for completeness here is the DoWork method of WorkerThread:

private void Worker_DoWork(object sender, DoWorkEventArgs e)
{
    BackgroundWorker Worker = sender as BackgroundWorker;

    for (int X = 0; X < 200; X++)
    {
        if (Worker.CancellationPending)
        {
            e.Cancel = true;
            return;
        }

        lock (LockObject)
        {
            // Do something with shared resource here.
        }
    }
}

当两个线程都自由运行时，这似乎工作正常.

This seems to work fine when both threads are running freely.

在某个时候，UI线程会通过将其布尔字段之一设置为true来终止ExperimentThread，然后等待其结束，如下所示:

At some point the UI thread will terminate the ExperimentThread by setting one of its boolean fields to true and then wait for it to end, as follows:

if (ExperimentThread.IsAlive)
{
    ExperimentThread.StopThread = true;
    ExperimentThread.Join();    // this line seems to cause the deadlock?
}

一旦调用Join()，ExperimentThread和WorkerThread正在访问的共享资源就会发生死锁，并且我的应用程序会无限期挂起.这种情况可能发生10次中的9次.

As soon as Join() is called, a deadlock occurs on the shared resource being accessed by ExperimentThread and WorkerThread, and my application hangs indefinitely. This happens maybe 9 out of 10 times.

如果我从上面的代码片段中删除了ExperimentThread.Join()，则永远不会发生死锁，并且ExperimentThread似乎会优雅地终止(然后继续通过调用CancelAsync()终止WorkerThread).

If I remove ExperimentThread.Join() from the code snippet above, the deadlock never occurs, and ExperimentThread appears to terminate gracefully (it then goes on to terminate WorkerThread by calling CancelAsync()).

任何想法在这里可能是什么问题?

Any ideas what could be the problem here?

(PS我一直在使用Console.WriteLine()来确定何时获取和释放锁，这使我相信存在死锁.是否有更好的方法来确定这一点，我可能是错的吗?)

(P.S. I've been using Console.WriteLine() to determine when locks are taken and released, which is what has lead me to believe there's a deadlock. Is there a better to determine this, I could be wrong?)

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Thread.Join()导致死锁

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