About EndInvoke

Bob_Sun

I happened to find that in the provided libs of my program, many thread are invoked just by BeginInvoke without callback to do EndInvoke. Waht will happen to a thread in ThreadPool if EndInvoke is not all at all? Asyncs threads invoked by BeingInvoke are used in my program to send event, many I often enfront the problem that some events seem to heave disappeared in the middle of that thread. I will add EndInvoke code to all these threads. But I hope that I can get some confirmation befrore doing that. Thank you !

Ravi Bhavnani

As I understand it, EndInvoke() is used to obtain the return value of your delegate method. If your delegate method is of type void, a call to EndInvoke() may not be required. if you haven't already, see this[^] article. /ravi My new year's resolution: 2048 x 1536 Home | Music | Articles | Freeware | Trips ravib(at)ravib(dot)com

Bob_Sun

Thank you very much. But I was told that BeginInvoke and EndInvoke should be called in pair, otherwise memory leak may happen in program. I have checked topics on ThreadPool the other day, and I found that threads invoked by BeginInvoke are not so simple.

Ravi Bhavnani

Bob_Sun wrote:

BeginInvoke and EndInvoke should be called in pair,

Hmm, I don't believe that is correct (but could be wrong). See this[^] MSDN article. /ravi My new year's resolution: 2048 x 1536 Home | Music | Articles | Freeware | Trips ravib(at)ravib(dot)com

Bob_Sun

Of cause, I haven't found any such discription in MSDN articles, just on some forum. But the fact is that my program do stop at somethere in the invoked thread (maybe for some other reasons). As the detail of ThreadPool is not opened completely, now I am considering of writing a ThreadManager of my own, just start a thread by Thread.Start(), if necessary cancel it by Thread.Abort().

Bob_Sun

In the following artical, it says CAUTION Always call EndInvoke after your asynchronous call completes. http://msdn.microsoft.com/library/default.asp?url=/library/en-us/cpguide/html/cpovrasynchronousprogrammingoverview.asp?frame=true[^] http://www.interact-sw.co.uk/iangblog/2005/05/16/endinvokerequired[^] what will happen if EndInvoke is not called? Thank you!

Tehnoon

Rest assured. EndInvoke is ONLYused if your asyncronous method returns something. You call EndInvoke to retrieve that return value, since you can't get the return value in any other way. EndInvoke does not do anything else apart from giving you the return value. If you are not interested in the return value, you do not need to call EndInvoke. I have used BeginInvoke so many times in so many performance critical applications without using EndInvoke, it doesn't create a problem

Bob_Sun

Tehnoon wrote:

I have used BeginInvoke so many times in so many performance critical applications without using EndInvoke, it doesn't create a problem

Thank you for quick reply. In my case, this is the opposite, it seems to me that the thread invoked by BeginInvoke disappeared half way(only part of the log left). I am not sure whether a background thread will disappear half way if GC.Collect() happens during its process? I am investigating for the reason... Thank you

Daniel Grunwald

delegate.BeginInvoke (creates new thread [from thread-pool]) without delegate.EndInvoke will cause a memory leak. Control.BeginInvoke ('sends' call to main thread) without Control.EndInvoke is no problem.

Bob_Sun

Daniel Grunwald wrote:

delegate.BeginInvoke (creates new thread [from thread-pool]) without delegate.EndInvoke will cause a memory leak.

I am troubled by threads invoked from ThreadPool. Can you give me some hint about what the memory leak will bring about? Thank you.

Daniel Grunwald

I think you will leak one WaitHandle for each delegate.BeginInvoke call, plus any objects waiting to be returned (e.g. exceptions). When you want to use the thread-pool in "fire-and-forget" mode, use hreadPool.QueueUserWorkItem or provide a callback-method to delegate.BeginInvoke that in turn calls delegate.EndInvoke.

Tehnoon

Can you show the code in which you are invoking the thread which is creating the problem? Garbage collection will not be done unless the thread is finished with the execution. The only possibility that I am seeing here is that the system is not being able to provide all the requested resources by the program and hence the results are not coming out as expected. A look at the source code will give me a better idea of this.

Bob_Sun

Tehnoon wrote:

Can you show the code in which you are invoking the thread which is creating the problem? Garbage collection will not be done unless the thread is finished with the execution. The only possibility that I am seeing here is that the system is not being able to provide all the requested resources by the program and hence the results are not coming out as expected. A look at the source code will give me a better idea of this.

Sorry for a late response. A statemachine exists in my program, and all the events are dispatched to it by seperate threads.The code is something like the following.

public class Control
{
private StateMachine myStateMachine = new StateMachine();

public void EventProc1()
{
    ....
    EventHandler eventHandler = new EventHandler(this.Thread1);
    eventHandler.BeginInvoke(this,null,null,null);
}

public void EventProc2()
{
    ....
    EventHandler eventHandler = new EventHandler(this.Thread2);
    eventHandler.BeginInvoke(this,null,null,null);
}

protected void Thread1(object sender,EventArgs e)
{
    LogMessage("Start of thread1");
    this.myStateMachine.Dispatch(1);
}

protected void Thread2(object sender,EventArgs e)
{
    LogMessage("Start of thread2");
    this.myStateMachine.Dispatch(2);
}

}

public class StateMachine
{
public void Dispatch(event id)
{
switch(event id)
{
case 1:
....
break;
case 2:
....
break;
...
default:
break;
}
}
}

Up to now, many phenomena happened, such as although the LogMessage were logged in log file, the thread just stopped somewhere afterward. Or sometimes, one thread should be waiting for an AutoResetEvent which must be set in another thread as designed, but the previous thread moves on before the AutoResetEvent is Set()... Another important supplement is that GC.Collect() is executed in another thread, ie. in EventProc1(). I have written many test programs so as to find the real reason, and still don know where a memory leak brought by no-EndInvoke will lead to the above phenomena. Looking forword to your help. Thank you!