为什么Windows窗体应用程序(C#)死锁?如何避免其锁定

本文关键字:何避免 锁定 死锁 窗体 Windows 应用程序 为什么 | 更新日期: 2023-09-27 18:01:03

根据文章Lock-Up Unlocked实现对死锁的C#Windows窗体应用程序的更改后,我仍然遇到与文章Lock-Up的前一段代码相同的问题!

也就是说,快速单击按钮几次后,应用程序就会挂断(变得没有响应(。

为什么
如何纠正?

using System;
using System.Windows.Forms;
using System.Threading;
namespace LockupUnlocked
{
  public partial class Form1 : Form
  {
    public Form1()
    {
      InitializeComponent();
      _t = new Thread(new ParameterizedThreadStart(WorkerThread));
    }
    private Thread _t;
    private object lockObject = new object();
    private bool StopThread = false;  ////changes added to avoid deadlock
    private void WorkerThread(object sender)
    {
      Thread.Sleep(1000);
      //while (true)
      while (!StopThread)//changes added to avoid deadlock
      {
        string result = "This is a Test";
        IAsyncResult aResult;////changes added to avoid deadlock
        lock (lockObject)
        {
          Thread.Sleep(25);
          //lblResult.Invoke(new MethodInvoker(delegate { lblResult.Text = result; }));
          aResult = lblResult.BeginInvoke//changes to avoid deadlock
            (new MethodInvoker(delegate { lblResult.Text = result; }));
        }
        lblResult.EndInvoke(aResult);//changes added to avoid deadlock
        Thread.Sleep(500);
      }
    }
    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
      StopThread = true;
    }
    private void Form1_Load(object sender, EventArgs e)
    {
      _t.Start();
    }
    private void button1_Click(object sender, EventArgs e)
    {
      lock (lockObject)//changes added to avoid deadlock
      {
        lblResult.Text = "Override the Test";
      }
    }
  }
}

为什么Windows窗体应用程序(C#)死锁?如何避免其锁定

对我来说,这看起来像是锁争用,而不一定是死锁。

你每25毫秒(不是25秒,也就是25000秒(迭代一次while循环,然后点击按钮会中断请求锁的过程,因为睡眠在锁的范围内,所以可能永远不会得到锁。

如果不单击按钮,这可能看起来有效,但是,等待锁定的按钮单击将阻塞UI线程,导致出现"未响应"消息,因为表单没有可用的时间自行绘制。

实际上,您不需要锁定即可更新文本值。当您从Control调用时,它只需将消息推送到UI消息队列中,该队列在UI线程上同步处理。你能做的最糟糕的事情就是种族条件,它不会破坏任何共享状态。

删除锁定,代码应该仍能正常工作。


我很犹豫是否提供任何示例代码,因为我不知道你想用这个示例实现什么。

在Windows中处理需要GUi访问的冲突线程的模式。Forms涉及InvokeRequired属性和Invoke函数。那么锁定就没有必要了。

namespace WindowsFormsApplication1
{
  using System;
  using System.Threading;
  using System.Windows.Forms;
  public partial class Form1 : Form
  {
    private Thread thread;
    public Form1()
    {
      this.InitializeComponent();
      this.thread = new Thread(this.WorkerThread);
    }
    private void WorkerThread(object sender)
    {
      Thread.Sleep(1000);
      while (true)
      {
        Thread.Sleep(25);
        this.SetText("from thread");
        Thread.Sleep(500);
      }
    }
    private void Form1_FormClosing(object sender, FormClosingEventArgs e)
    {
      this.thread.Abort();
    }
    private void Form1_Load(object sender, EventArgs e)
    {
      this.thread.Start();
    }
    /// <summary>
    /// This is a callback for the SetText Method.
    /// </summary>
    /// <param name="text">The text.</param>
    private delegate void SetTextCallback(string text);
    /// <summary>
    /// This sets a text. 
    /// It's thread safe, you can call this function from any thread. 
    /// If it's not called from the UI-thread, it will invoke itself
    /// on the UI thread.
    /// </summary>
    /// <param name="text">The text.</param>
    private void SetText(string text)
    {
      if (this.InvokeRequired)
      {
        this.Invoke(new SetTextCallback(this.SetText), text);
      }
      else
      {
        this.lblResult.Text = text;  
      }
    }
    private void Button1_Click(object sender, EventArgs e)
    {
      this.SetText("from button");
    }
  }
}