This may be a hardware issue, as I'm not exactly sure how background workers are implemented, but here is the issue: I have 3 background workers running different threads. I've coded those threads to display when they start and end, and I am getting some very strange results.
On some executions, all 3 threads will start, but only 1 will end (and I've waited many minutes to see if the program was just executing very slow, and put breaks in the code - it's not running slow, the background worker just "dies"). Other executions I get 2 threads to finish. Other times I get only 2 threads starting, and both end, etc.
I am not changing the code (entered below) at all between runs, I am simply stopping the program and restarting it. As such, I suspect it may be a hardware issue (CPU maybe?). Unfortunately, I don't have another PC to test the program on right now, and the PC that I am using is ... "far from the best".
So, my question: Could there be hardware issues that cause a background worker (and the thread that it is working on) to just die off / not start at all? Or does it absolutely have to be something in the code?
(The following is obviously not really my code. It is a much simpler version that illustrates the problem) Code:
public partial class Form1 : Form
{
BackgroundWorker[] workers = new BackgroundWorker[3];
Stopwatch timeKeeper = new Stopwatch();
string text = "";
public Form1()
{
timeKeeper.Start();
InitializeComponent();
for (int i = 0; i < 3; i++)
{
workers[i] = new BackgroundWorker();
workers[i].DoWork += new System.ComponentModel.DoWorkEventHandler(this.BWWorker_DoWork);
workers[i].RunWorkerCompleted += new System.ComponentModel.RunWorkerCompletedEventHandler(this.BWWorker_WorkDone);
workers[i].RunWorkerAsync(i);
}
}
private void BWWorker_WorkDone(object sender, RunWorkerCompletedEventArgs e)
{
this.textBox1.Text = text;
}
private void BWWorker_DoWork(object sender, DoWorkEventArgs e)
{
switch (e.Argument.ToString())
{
case "0":
startThread1();
break;
case "1":
startThread2();
break;
case "2":
startThread3();
break;
}
}
void startThread1()
{
text += Environment.NewLine + "Starting thread 1" + Environment.NewLine + "at " + timeKeeper.Elapsed.ToString();
this.textBox1.Text = text;
for (int i = 0; i < 25000; i++)
{
}
text += Environment.NewLine + "Ending thread 1" + Environment.NewLine + "at " + timeKeeper.Elapsed.ToString();
}
void startThread2()
{
text += Environment.NewLine + "Starting thread 2" + Environment.NewLine + "at " + timeKeeper.Elapsed.ToString();
this.textBox1.Text = text;
for (int i = 0; i < 10000; i++)
{
}
text += Environment.NewLine + "Ending thread 2" + Environment.NewLine + "at " + timeKeeper.Elapsed.ToString();
}
void startThread3()
{
text += Environment.NewLine + "Starting thread 3" + Environment.NewLine + "at " + timeKeeper.Elapsed.ToString();
this.textBox1.Text = text;
for (int i = 0; i < 75000; i++)
{
}
text += Environment.NewLine + "Ending thread 3" + Environment.NewLine + "at " + timeKeeper.Elapsed.ToString();
}
}
The result on 3 back-to-back runs with no code changes is as follows : (The 3rd pic runs all 3, as desired. The first 2 run/finish some of the threads, but not all (again, I've let the program run for minutes, so I know it's not just running slow) ... ?)
So, my question: Could there be hardware issues that cause a background worker (and the thread that it is working on) to just die off / not start at all? Or does it absolutely have to be something in the code?
That is very, very unlikely.
I suspect the real issue is that you are updating text
from multiple theads. Concatenating strings like this is not a thread-safe operation, and the threads can be expected to complete at about the same time. Even though the loops have a different number of iterations, minor fluctuations in thread scheduling can cause them to step on each other. In particular, the line
text += Environment.NewLine + "Ending thread 1" + Environment.NewLine + "at " + timeKeeper.Elapsed.ToString();
could run such that
Try using lock
statements around changes to resources shared by the threads.