C# Winform 在 SerialPort.Close 上冻结 [英] C# Winform freezing on SerialPort.Close

问题描述

我有一个在 SerialPort 上执行异步 IO 的 winform 程序.但是，我会定期遇到程序在 SerialPort.Close() 调用上冻结的问题，似乎是随机的.

I have a winform program that does some asynchronous IO on a SerialPort. However, I'm periodically running into an issue with the program freezing on the SerialPort.Close() call, seemingly at random.

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:

I think it's a thread safety issue, but I'm not sure how to fix it if it is. I tried adding/removing the async DataReceived handler with the port open/close functions and discarding the in and out buffers on the port, but it doesn't seem to do anything. I think the important SerialPort code is below:

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(这篇博文很好地描述了它，并提供了其他几个很好的提示)，我做了一个简单的改变，但一直无法重现错误呢！

Thanks to @Afrin's answer pointing out the deadlock condition with the UI thread (This blog post does a good job describing it, and gives several other good tips), I made a simple change, and haven't been able to reproduce the error yet!

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.
}

推荐答案

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

The reason it would hang when you close it is because in the event handler of your SerialPort object

您正在将调用与主线程同步(通常通过调用调用).SerialPort 的 close 方法等待触发 DataReceived/Error/PinChanged 事件的 EventLoopRunner 线程终止.但是由于你自己在事件中的代码也在等待主线程响应，所以你遇到了死锁的情况.

You're synchronizing a call with the main thread (typically by calling invoke). SerialPort's close method waits for its EventLoopRunner thread which fires DataReceived/Error/PinChanged events to terminate. but since your own code in the event is also waiting for main thread to respond, you run into a dead lock situation.

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

solution: use begininvoke instead of invoke: https://connect.microsoft.com/VisualStudio/feedback/details/202137/serialport-close-hangs-the-application

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

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

the Microsoft link is broken as they have retired Connect. try web.archive.org: https://web.archive.org/web/20111210024101/https://connect.microsoft.com/VisualStudio/feedback/details/202137/serialport-close-hangs-the-application

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