C# Winform 在 SerialPort.Close 上卡住

Question

我有一个 winform 程序，它在 SerialPort 上执行一些异步 IO。但是，我会定期遇到程序在 SerialPort.Close() 调用时卡住的问题，这似乎是随机的。

我认为这是一个线程安全问题，但如果是，我不确定如何解决。我尝试使用端口打开/关闭功能添加/删除异步 DataReceived 处理程序并丢弃端口上的输入和输出缓冲区，但它似乎没有做任何事情。我认为重要的 SerialPort 代码如下:

using System;
using System.Collections.Generic;
using System.IO.Ports;

public class SerialComm
{
  private object locker = new object();

  private SerialPort port;
  private List<byte> receivedBytes;
  
  public SerialComm(string portName)
  {
    port = new SerialPort(portName);
    port.BaudRate = 57600;
    port.Parity = Parity.None;
    port.DataBits = 8;
    port.StopBits = StopBits.One;
    
    receivedBytes = new List<byte>();
  }

  public void OpenPort()
  {
    if(port!=null && !port.IsOpen){
      lock(locker){
        receivedBytes.Clear();
      }

      port.DataReceived += port_DataReceived;
      port.Open();
    }
  }

  public void ClosePort()
  {
    if(port!=null && port.IsOpen){
      port.DataReceived -= port_DataReceived;
      while(!(port.BytesToRead==0 && port.BytesToWrite==0)){
        port.DiscardInBuffer();
        port.DiscardOutBuffer();
      }
      port.Close();
    }
  }

  private void port_DataReceived(object sender, SerialDataReceivedEventArgs e)
  {
    try{
      byte[] buffer = new byte[port.BytesToRead];
      int rcvdBytes = port.Read(buffer, 0, buffer.Length);

      lock(locker){
        receivedBytes.AddRange(buffer);
      }

      //Do the more interesting handling of the receivedBytes list here.

    } catch (Exception ex) {
      System.Diagnostics.Debug.WriteLine(ex.ToString());
      //put other, more interesting error handling here.
    }
  }
}

更新

感谢@Afrin 的回答指出了 UI 线程的死锁情况(This blog post 很好地描述了它，并给出了其他几个很好的提示)，我做了一个简单的更改，但无法重现错误呢!

private void port_DataReceived(object sender, SerialDataReceivedEventArgs e)
{
  try{
    byte[] buffer = new byte[port.BytesToRead];
    int rcvdBytes = port.Read(buffer, 0, buffer.Length);
    
    lock(locker){
      receivedBytes.AddRange(buffer);
    }
    
    ThreadPool.QueueUserWorkItem(handleReceivedBytes);
    
  } catch (Exception ex) {
    System.Diagnostics.Debug.WriteLine(ex.ToString());
    //put other, more interesting error handling here.
  }
}

private void handleReceivedBytes(object state)
{
  //Do the more interesting handling of the receivedBytes list here.
}

Answer 1

关闭它时它会挂起的原因是因为在您的 SerialPort 对象的事件处理程序中

您正在与主线程同步调用(通常通过调用 invoke)。 SerialPort 的关闭方法等待触发 DataReceived/Error/PinChanged 事件的 EventLoopRunner 线程终止。但是由于事件中您自己的代码也在等待主线程响应，因此您遇到了死锁情况。

解决方案:使用 begininvoke 而不是调用: https://connect.microsoft.com/VisualStudio/feedback/details/202137/serialport-close-hangs-the-application

引用:http://stackoverflow.com/a/3176959/146622

编辑:Microsoft 链接已断开，因为他们已停用 Connect。尝试 web.archive.org: https://web.archive.org/web/20111210024101/https://connect.microsoft.com/VisualStudio/feedback/details/202137/serialport-close-hangs-the-application