I have one background thread I use for processing separately from the GUI, and everything works fine between the threads. However when I close the application, the program "closes" but does not kill the process. The background thread is keeping the program alive it seems.
I have set "myThreadInstance.IsBackground = true;", and I thought this would require C# to kill it when it is killed.
I am testing this all in Visual Studio (2010, using .NET 4.0), and after the first build, the rest all fail because the exe is still in use so it cannot overwrite it. Looking in task manager, it is there. Killing Visual Studio releases the vbhost process which releases my exe. Killing my exe's process, makes vbhost respawn it in a second or two.
Actually, based on your description and other things you've tried (and their results), I believe the most likely cause is this:
You have another foreground thread in your application, other than the one you're examining.
Try using Application.Exit(0); in the form_closing/form_closed event.
Bug: I think this might be a bug. Look at the comments at the bottom of this MSDN page: http://msdn.microsoft.com/en-us/library/system.threading.thread.isbackground.aspx
Also, try using the BackgroundWorker. Here's a good description in the VisualStudio Magazine: http://visualstudiomagazine.com/articles/2007/09/01/simplify-background-threads.aspx
This type of problem usually requires code to figure out. Take your app and trim it down to the bare minimum necessary to show the issue.
However, most likely you are either not signaling the thread to terminate or the thread is such a long running beast that it doesn't ever see the signal.
Related
Is there any tool which gives you the view of current execution of you code? I need this because my WPF application's UI is hanging without any notification/exceptions. I am not able to debug the issue. System stays Idle and every time I have to kill the process explicitly. Any suggestions. FYI.. many third party tools are being used.
I am not sure what you have tested already and maybe I answer is invalid but:
Have you tried to use the pause function in Visual Studio. It pauses all threads of your application and you can see per Thread where it is paused. You can also step through each Thread to find possible issues.
Some issues I had in the past:
Too much actions where executed immediately from the UI Thread
Dispatch big chunk of work to background threads using the BackgroundWorker
Incorrect locking model so that the UI thread is not able to gather the information it wants
Make sure data in the ViewModel cannot be changed by background threads without locking properties.
Some interesting links to read about WPF and MultiThreading:
WPF Fundamentals - Threading Model
Debugging locks and deadlocks
Hopefully this helps you a bit
You can use windbg to fully investigate all aspects of a process. While there is a learning curve involved, in my opinion, becoming familiar with this tool is vital for a developer. To get started get a full memory dump of your running process via task manager & download & install debugging tools for windows. Once you've this done take a look at some tutorials & I'll try and help if you post a comment back
If you are doing Memory/CPU Consuming tasks using the main thread the UI will become Idle even without any exceptions.To solve this issue use a BackgroudWorker/a Separate thread to do the time consuming operations.So that UI will not freeze.
I have a multi-threaded application build in C# using VS2010 Professional. It's quite a large application and we've experienced the classing GUI cross-threading and deadlock issues before, but in the past month we've noticed the appears to lock up when left idle for around 20-30 minutes.
The application is irresponsive and although it will repaint itself when other windows are dragged in front of the application and over it, the GUI still appears to be locked... interstingly (unlike if the GUI thread is being used for a considerable amount of time) the Close, Maximise and minimise buttons are also irresponsive and when clicked the little (Not Responding...) text is not displayed in the title of the application i.e. Windows still seems to think it's running fine.
If I break/pause the application using the debugger, and view the threads that are running. There are 3 threads of our managed code that are running, and a few other worker threads whom the source code cannot be displayed for.
The 3 threads that run are:
The main/GUI thread
A thread that loops indefinitely
A thread that loops indefinitely
If I step into threads 2 and 3, they appear to be looping correctly. They do not share locks (even with the main GUI thread) and they are not using the GUI thread at all. When stepping into the main/GUI thread however, it's broken on Application.Run...
This problem screams deadlock to me, but what I don't understand is if it's deadlock, why can't I see the line of code the main/GUI thread is hanging on?
Any help will be greatly appreciated! Let me know if you need more information...
Cheers,
Roo
-----------------------------------------------------SOLUTION--------------------------------------------------
Okay, so the problem is now solved. Thanks to everyone for their suggestions! Much appreciated! I've marked the answer that solved my initial problem of determining where on the main/UI thread the application hangs (I handn't turned off the "Enable Just My Code" option).
The overall issue I was experiencing was indeed Deadlock, however. After obtaining the call-stack and popping the top half of it into Google I came across this which explains exactly what I was experiencing...
http://timl.net/
This references a lovely guide to debugging the issue...
http://www.aaronlerch.com/blog/2008/12/15/debugging-ui/
This identified a control I was constructing off the GUI thread. I did know this, however, and was marshalling calls correctly, but what I didn't realise was that behind the scenes this Control was subscribing to an event or set of events that are triggered when e.g. a Windows session is unlocked or the screensaver exits. These calls are always made on the main/UI thread and were blocking when it saw the call was made on the incorrect thread. Kim explains in more detail here...
http://krgreenlee.blogspot.com/2007/09/onuserpreferencechanged-hang.html
In the end I found an alternative solution which did not require this Control off the main/UI thread.
That appears to have solved the problem and the application no longer hangs. I hope this helps anyone who's confronted by a similar problem.
Thanks again to everyone on here who helped! (and indirectly, the delightful bloggers I've referenced above!)
Roo
-----------------------------------------------------SOLUTION II--------------------------------------------------
Aren't threading issues delightful...you think you've solved it, and a month down the line it pops back up again. I still believe the solution above resolved an issue that would cause simillar behaviour, but we encountered the problem again.
As we spent a while debugging this, I thought I'd update this question with our (hopefully) final solution:
The problem appears to have been a bug in the Infragistics components in the WinForms 2010.1 release (no hot fixes). We had been running from around the time the freeze issue appeared (but had also added a bunch of other stuff too). After upgrading to WinForms 2010.3, we've yet to reproduce the issue (deja vu). See my question here for a bit more information: '.NET 4.0 and the dreaded OnUserPreferenceChanged Hang'. Hans has given a nice summary of the general issue.
I hope this adds a little to the suggestions/information surrounding the nutorious OnUserPreferenceChanged Hang (or whatever you'd like to call it).
Cheers,
Roo
I would check to make sure there is no modal dialog that is being launched behind the main form. This can happen if the dialog is launched and some event causes the main form to steal back focus. You can avoid this by making sure the modal dialog has the main form as its Owner when you create it.
Check where it's hanging in Application.Run; disable Just My Code in Debugger Options, then look at the call stack.
I've fixed an application that deadlocked in Application.Run because it was trying to remove an event handler from an object that a different thread was locked on. (Until the C# 4.0 compiler, event handler accessors implicitly lock(this))
However, if you're using VS2010, that isn't the exact issue.
I am developing a multi-thread application and one of my threads is somehow blocked by something and thus it will occupy some resource such as a file forever. Is there a way to find out which thread is being blocked and more important what resouce is being held by that thread?
At last and as usual, thanks for your patience and reply. :)
---------new progress----------
Since all the resouces on the windows platform are accessed via "handles". I am thinking if there is a way to list all the handles a .NET thread is holding?
When you Create the Threads, you can Set a Name for each thread just before you start it. You can then use these in the Debugger to identify the Thread in question.
Then when your program doesn't close, you jump up to the debugger and Hit Pause, you can then via the active threads. Debug->Windows->Threads (CTRL-ALT+H)
If your threads are not critical, and you just want the system to Close upon Completion you can set .IsBackground on the thread and you don't need to perform any special operations to get your thread to close, often though this may lead to other conditions you were not expecting.
I personally also use System.Threading.AutoResetEvent(duration) instead of Sleep(duration) because if I wish to exit, I set mIsRunning=false then set the event which will cause the Stopping of the Event to Wake up, but Exit Immediately. A Sleep has to finish before it resumes.
The new Concurrency Profiler in Visual Studio 2010 was built to answer and solve this type of question.
Resource Contention Concurrency Profiling in Visual Studio 2010 – Performance Investigation Flows
I recommend downloading the trial version if you don't already have Visual Studio 2010. You won't be disappointed. :)
If you are familiar with dump analysis using WinDbg, you can also capture a hang dump when this issue happens, and then manually analyze the dump to see which thread hangs and why.
http://blogs.msdn.com/tess/archive/tags/Performance+issues+and+hangs/default.aspx
I am developing a WinForm multithreaded application with C#.
Sometimes it happens that my application hangs, or freezes or blocks.
When this happens and I am running in DEBUG mode, is there anyway to understand at what line of code my application is currently? Since it is freezed I expect to find a point where the application is locked or blocked or whatever.
Is it possible to do that someway?
When It is freezed I tried to open the CALL STACK window, but this doesn't display any info; is there some action that I might do? Some "pause and check" or whatever?
You may need to open the Threads window, and change the current thread. While debugging, choose Debug->Break All, and open the Threads window. If you go through each thread, by double clicking on the thread, you should be able to investigate the call stack for each thread.
That being said, if you can run your program in VS 2010 - this gets a lot easier. In VS 2010, you can use the new Concurrency Profiler, and run your code under the Concurrency Profiler with the option to Visualize the Behavior of a multithreaded application. Once your application locks up, kill it, and let the profiler churn -
Eventually, you'll get a diagram which shows each thread in your program, and when they're locked. The callstack for each blocked thread will be shown, as well as what lock is being held (with the line of source code). This makes it very easy to track down a dead lock.
When debugger is attached go to Debug menu and choose 'Break All'... Then you can examine call stacks for all thread.
You could press pause and see where it ends up (use the aforementioned call stack window). Chances are however that you'll end up in native code. You could try to step out a bit or just look at the stack for a managed function to debug.
Alternatively you could put a breakpoint after the application "freezes" and try to pinpoint a loop that doesn't end.
Both the above are assuming your application is busy (100% cpu usage). If your application is however stuck in a dead lock or just plain waiting for a mutex that won't tick, you'll have to manually re-read your code and try to figure it out on your own.
I keep having this problem, solving it, and then when I implement new code it comes back again. It's driving me crazy!
What I finally found was that if you instantiate a Window of any kind, even if you never call Show() or ShowDialog(), when you close your application, it will not terminate. So now I make sure to call Close() when appropriate, and the problem hasn't ever come back with all of the Windows that I've created.
I've implemented more new features that don't create windows (as far as I can tell!), yet now my app will not terminate again. Hitting pause in the VS IDE is useless, I think, because the threads don't have any context so I can't figure out what code caused the hanging.
Normally, I would expect that a thread executing in the background that hasn't exited (and wasn't set as a Background thread) would cause this behavior, but I am not creating any threads at this point.
Can anyone recommend a good tool (free or license required) that will help me quickly resolve these sorts of stupid problems? For now, I'm going to go back, comment out a ton of the new code, and then uncomment line by line until the problem reappears. Brute force is how I typically end up fixing these sorts of things, and would really appreciate a tool to make my life easier. :)
It sounds like you may be having other issues with background threads that the other answers are addressing but with regard to WPF Windows, have you tried changing the ShutdownMode of your App class? You can also try forcing the app to quit by calling Shutdown explicitly:
Application.Current.Shutdown();
You might get more information if you attached using both managed and unmanaged code. In Visual Studio 2008, you can change the mode in the Attach to Process form. Press the "Select..." button and specify debugging for both "Managed" and "Native".
(Before you do this, make sure your symbol path is setup. Go to Tools/Options, Debugging, Symbols. Enter http://msdl.microsoft.com/download/symbols in the list of symbol file locations. Cache the symbols locally in some directory.)
When you attach in both managed and unmanaged modes, you should get a larger call stack. I recommend right-clicking in the Call Stack debug window and choosing "Include Calls To/From Other Threads".
If your main thread shows System.Windows.Forms.Application.Run or ThreadContext.RunMessageLoop, then your UI thread's message pump is alive and still pumping messages. If, for some reason, it is transitioning to another thread, then it can't exit until it's done.
You can also see the full stack traces of the rest of the managed and unmanaged threads. You might want to look for a garbage collector thread and see what it's doing. Look for one that is has a stack with "GCHeap::FinalizerThreadStart" in it. That might be doing something.
There may also be a GID+ thread that's busy trying to do work.
I don't mean to over-simplify things, but have you tried setting the owner of the dialog window to the MainWindow? This will force the dialog window to close when the MainWindow is closed. In other words, it would look like this:
dialog.Owner = Window.GetWindow(this);
// Or...
dialog.Owner = Application.Current.MainWindow;
This may not be an option for you, but I just wanted to throw it out there since your post didn't mention you didn't want to set the window's owner.
While it may not help in your particular case, Process Explorer is an excellent tool for looking inside running processes and seeing how many threads etc. there are.