死锁lock（）方法 [英] Deadlocking lock() method

问题描述

我正面临僵局，我的代码结构与此类似：

I'm facing a deadlock, my code structure is similar to this:

private delegate void UpdateControlDelegate(string value);

public void UpdateControl(string value)
{
    if (txtAddress.InvokeRequired)
    {
        txtAddress.Invoke(new UpdateControlDelegate(UpdateControl), value);
    }
    else
    {
        txtAddress.Text = value; // This is in GroupBox1
        txtValue.Text = value; // This is in GroupBox2
    }
}

class ThreadHandler
{
    List<string> _list = new List<string>();
    object _criticalSection = new object();

    public ThreadHandler()
    {
        new Thread(new ThreadStart(Run)).Start();
    }

    public static ThreadHandler _threadHandler = null;

    public static ThreadHandler GetThreadHandler()
    {
        if (_threadHandler == null)
        {
            _threadHandler = new ThreadHandler();
        }

        return _threadHandler;
    }

    public void Run()
    {
        while (true)
        {
            // some code

            lock (_criticalSection)
            {
                foreach (string str in _list)
                {
                    // some Code
                }
            }

            // some code
            Thread.Sleep(SomeTime);
        }
    }

    public void AddItem(string item)
    {
        lock (_criticalSection)
        {
            _list.Add(item);
        }
    }

    public void RemoveItem(string item)
    {
        lock (_criticalSection)
        {
            _list.Remove(item);
        }
    }

}

但是使用相同的代码，我只是像这样修改了UpdateControl方法：

But using the same code, I just modified the UpdateControl method like this:

private delegate void UpdateControlDelegate(string value);

public void UpdateControl(string value)
{
    if (InvokeRequired)
    {
        BeginInvoke(new UpdateControlDelegate(UpdateControl), value);
    }
    else
    {
        txtAddress.Text = value; // This is in GroupBox1
        txtValue.Text = value; // This is in GroupBox2
    }
}

这很好。是什么问题？

推荐答案

问题几乎可以肯定是，您正在后台线程中获取锁，然后调用 Control.Invoke ，并调用一个试图获取相同锁的委托（在UI线程上）。它不能这样做，因为另一个线程持有该锁-并且在等待UI操作完成时将一直持有该锁。

The problem is almost certainly that you're acquiring the lock within a background thread, then calling Control.Invoke, and invoking a delegate (on the UI thread) which tries to acquire the same lock. It can't do that, because the other thread holds the lock - and will keep holding the lock while it waits for the UI operation to complete.

诚然，没有锁定在您已发布的U​​pdateControl方法中，但我怀疑这不是完整的代码-并且您没有显示正在使用 AddItem 或的位置RemoveItem 。

Admittedly there's no locking within the UpdateControl method you've posted, but I suspect that's not the complete code - and you haven't shown where you're using AddItem or RemoveItem.

我注意到，顺便说一句，GetThreadHandler（）并不是线程安全的-对我来说似乎是个错误。

I note that GetThreadHandler() isn't thread-safe, by the way - that looks like a bug to me...

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