threads and garbage collection

Hi all,

Does any one knows, if I create a thread in a method and start some
processing in it, what happens when this thread object goes out of
scope.
Nothing in particular.
Is it garbage collected (I assume yes, as it is a regular object
and there is no reference to it).

Hi all,

Does any one knows, if I create a thread in a method and start some
processing in it, what happens when this thread object goes out of
scope. Is it garbage collected (I assume yes, as it is a regular object
and there is no reference to it). If it is, what happens with the
executed code inside the thread? What kind of exceptions can I receive
(if any) and how to capture them (AppDomain.UnhandledException may help,
but how do I recognize that this is in the collected thread?).

This is a sample:

using System;
using System.Threading;

namespace Test {

public class Test {

static ManualResetEvent evnt = new ManualResetEvent(false);

static void CreateThread()
{
Thread t = new Thread(new ThreadStart(ThreadMethod));
t.IsBackground = true;
t.Start();
}

static void ThreadMethod()
{
Console.WriteLine("Thread started");
evnt.Set();
while (true)
{
Console.WriteLine("From thread.");
Thread.Sleep(1000);
}
}

[STAThread]
public static void Main()
{
CreateThread();
evnt.WaitOne();
Console.WriteLine("press enter to GC");
Console.ReadLine();
GC.Collect();
GC.WaitForPendingFinalizers();
Console.WriteLine("press enter for exit");
Console.ReadLine();
}
}
}
The thread continues to run even after GC.Collect? Why? What holds a
reference?

And why TaskManager shows 6 threads running (before and after the
GC.Collect call) and 5 after that? I can count to 3 - the main one, GC
thread and my worker thread. What are the others?

Thanks
Sunny

"Sunny" <su***@newsgroups.nospam> wrote in message
news:e7**************@tk2msftngp13.phx.gbl...

Hi all,

Does any one knows, if I create a thread in a method and start some
processing in it, what happens when this thread object goes out of
scope.

Nothing in particular.

Is it garbage collected (I assume yes, as it is a regular object
and there is no reference to it).

No. The CLR (in effect, though perhaps not literally) keeps a pointer to
each active thread. Until the thread exits, it will not be collected.

Hi Sunny

Threads are considered GC Roots by the runtime, so they are not collected (otherwise you'd have to have a strong reference to every running thread).

Hope that helps
-Chris

--------------------

Hi all,

Does any one knows, if I create a thread in a method and start some
processing in it, what happens when this thread object goes out of
scope. Is it garbage collected (I assume yes, as it is a regular object
and there is no reference to it). If it is, what happens with the
executed code inside the thread? What kind of exceptions can I receive
(if any) and how to capture them (AppDomain.UnhandledException may help,
but how do I recognize that this is in the collected thread?).

This is a sample:

using System;
using System.Threading;

namespace Test {

public class Test {

static ManualResetEvent evnt = new ManualResetEvent(false);

static void CreateThread()
{
Thread t = new Thread(new ThreadStart(ThreadMethod));
t.IsBackground = true;
t.Start();
}

static void ThreadMethod()
{
Console.WriteLine("Thread started");
evnt.Set();
while (true)
{
Console.WriteLine("From thread.");
Thread.Sleep(1000);
}
}

[STAThread]
public static void Main()
{
CreateThread();
evnt.WaitOne();
Console.WriteLine("press enter to GC");
Console.ReadLine();
GC.Collect();
GC.WaitForPendingFinalizers();
Console.WriteLine("press enter for exit");
Console.ReadLine();
}
}
}
The thread continues to run even after GC.Collect? Why? What holds a
reference?

And why TaskManager shows 6 threads running (before and after the
GC.Collect call) and 5 after that? I can count to 3 - the main one, GC
thread and my worker thread. What are the others?

Thanks
Sunny

From: Sunny <su***@newsgroups.nospam>
Subject: RE: threads and garbage collection
Date: Tue, 27 Jul 2004 17:48:56 -0500
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Thanks Chris,

can you provide a link for more info, it is interesting subject :). I.e.
I'm interested when they are considered collectable, etc.

Sunny
In article <9s**************@cpmsftngxa10.phx.gbl>,
cl***@online.microsoft.com says...

Hi Sunny

Threads are considered GC Roots by the runtime, so they are not collected (otherwise you'd have to have a strong reference to every running thread).

Hope that helps
-Chris

--------------------

>
>Hi all,
>
>Does any one knows, if I create a thread in a method and start some
>processing in it, what happens when this thread object goes out of
>scope. Is it garbage collected (I assume yes, as it is a regular object
>and there is no reference to it). If it is, what happens with the
>executed code inside the thread? What kind of exceptions can I receive
>(if any) and how to capture them (AppDomain.UnhandledException may help,
>but how do I recognize that this is in the collected thread?).
>
>This is a sample:
>
>using System;
>using System.Threading;
>
>namespace Test {
>
>public class Test {
>
> static ManualResetEvent evnt = new ManualResetEvent(false);
>
> static void CreateThread()
> {
> Thread t = new Thread(new ThreadStart(ThreadMethod));
> t.IsBackground = true;
> t.Start();
> }
>
> static void ThreadMethod()
> {
> Console.WriteLine("Thread started");
> evnt.Set();
> while (true)
> {
> Console.WriteLine("From thread.");
> Thread.Sleep(1000);
> }
> }
>
> [STAThread]
> public static void Main()
> {
> CreateThread();
> evnt.WaitOne();
> Console.WriteLine("press enter to GC");
> Console.ReadLine();
> GC.Collect();
> GC.WaitForPendingFinalizers();
> Console.WriteLine("press enter for exit");
> Console.ReadLine();
> }
>}
>}
>
>
>The thread continues to run even after GC.Collect? Why? What holds a
>reference?
>
>And why TaskManager shows 6 threads running (before and after the
>GC.Collect call) and 5 after that? I can count to 3 - the main one, GC
>thread and my worker thread. What are the others?
>
>Thanks
>Sunny
>