deadlock (when changing in between tabs)

[Luk Vloemans]

Hey Everyone,


I'm writing software to communicate with a GPS to a PDA.

So far, I've been quite lucky. All the data from the GPS is succefully
being read into my interface, and succesfully parsed.

However, I recently added an extra "settings"-tab to my program to spice
up usability.

The following problem occurs.

When I start the GPS and start playing with the tabs (going back and
foward between the "Main"-tab and the "Settings"-tab) my program hangs
itself up. (it might happen the first time, or after 10 times)

I've got no explenation for this..

I've got one thread updating all the textbox-fields in my "Main"-tab and
one thread reading all data from the PDA's COM-port (GPS). (plus the
main thread)

Should I stop updating the textbox-fields in my "Main"-tab when I check
out my "Settings"-tab ? (I found another tool made for a GPS on a PDA
and that tool didn't stop updating.. so I don't think I should stop
either..)

Anyone got a clue why this deadlock occurs?

PS: If I don't touch the tabs, the program works perfectly.

Thx for any help!

|Luk Vloemans
|IT student

 

[Ginny Caughey [MVP]]

Luk,

If you're updating the textbox data directly from a secondary thread, that could
well be your problem as this is not supported in any version of Windows. If
you're using a delegate to actually do the update on the same thread that the
form was created on, you should be ok.

 

[Ginny Caughey [MVP]]

Luk,

This is a great article with sample code:
http://msdn.microsoft.com/library/d...netcomp/html/BackgroundProcess.asp?frame=true

 

[RAVI KRISHNASWAMY [MSFT]]

When accessing control members from outside of the main thread that created
it, you need to call it via ControlInvoke in a thread safe manner. I have
attached a sample that I wrote for demonstration purpose, please use your
discretion.

Thx
-Ravi

using System;
using System.Drawing;
using System.Collections;
using System.ComponentModel;
using System.Windows.Forms;
using System.Threading;

public class Form1 : System.Windows.Forms.Form
{
Label lbl = new Label();
Button btn = new Button();
public bool fAlive;
int cHits = 0;
ArrayList m_alth = new ArrayList();

public Form1()
{
InitializeComponent();
}

private void InitializeComponent()
{
this.Text = "Form1";

lbl.Text = "Thread1";
this.Controls.Add(lbl);

btn.Location = new Point(50, 50);
btn.Text = "Start";
btn.Click += new EventHandler(this.OnStop);
this.Controls.Add(btn);
this.Closing += new CancelEventHandler(this.OnClosing);
this.ControlBox = true;
this.MinimizeBox = false;

}

private void OnStop(object sender, EventArgs e)
{
if (fAlive)
{
fAlive = false;
btn.Text = "Start";
m_alth.Clear();
}
else
{
fAlive = true;
btn.Text = "Stop";
Thread th;
for (int i=0; i<1; i++)
{
th = new Thread(new ThreadStart(new ThreadRunner(this, i+1).ThreadRun));
th.Start();
m_alth.Add(th);
}
}
}

private void OnClosing(object sender, CancelEventArgs e)
{
Console.WriteLine("inside dest");

foreach(Object obj in m_alth)
{
Thread th = (Thread)obj;
Console.WriteLine("stopping " + th);
//th.Abort();
}

fAlive = false;
//base.Dispose();
}


public void OnTextChange(object sender, System.EventArgs e)
{
this.cHits++;
this.Text = (cHits) + "Thread - " + sender;
//this.Refresh();
}

static void Main()
{
Application.Run(new Form1());
}
}

public class ThreadRunner
{
Form1 m_frm = null;
public int m_id;

public ThreadRunner(Form1 frm1, int id)
{
m_frm = frm1;
m_id = id;
}

public void ThreadRun()
{
while(m_frm.fAlive)
{
Console.WriteLine("heart beat from: " + m_id);
m_frm.Invoke(new EventHandler(m_frm.OnTextChange));
Thread.Sleep(300);
}
}
}


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