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.NET Forum / .NET Framework / Interop / October 2004PInvoke threading issue
I have created a simple background thread to make one pinvoke call into a DLL I've created. My Winforms app spawns the thread in the form load event then go about it's business. The problem is that my form appears to be blocked while the background thread is running. I am very familir with threads in unmanaged code but am just getting into them in C#. Are there issues I need to be aware of with regards to threading a simple pinvoke call? As an experiment I replaced my pinvoke call with a simple Thread.Sleep(5000). This gave me the result I expected, my UI was responsive during the entire 5 seconds the thread was waiting. Changing the wait back into a pinvoke call caused my UI to not redraw until the pinvoke call completed. Any idea what's up? -Brett- What exactly are you doing in your PInvoke'd function? Looks like you are blocking the message pump or preventing the message loop to call the MSG handler because you are "monopolizing" the CPU. Willy. >I have created a simple background thread to make one pinvoke call into a > DLL I've created. My Winforms app spawns the thread in the form load [quoted text clipped - 16 lines] > > -Brett- My code is wrapping a 3rd party library so I honestly don't know fully what they are doing. So it is possible that something down in that unmanaged code could cause the main ui thread to block? I guess I was just looking to see if there were some fundamental issues with using pinvoke in a worker thread that I needed to be aware of. Sounds like that isn't the case. -Brett- > What exactly are you doing in your PInvoke'd function? Looks like you are > blocking the message pump or preventing the message loop to call the MSG [quoted text clipped - 22 lines] > > > > -Brett- Hi Brett, It is strange, can you post the code the main UI thread doing after you have created the working thread. Did the main UI threading doing something to wait for the working thread? Is there any race condition between the main UI thread and the working thread which will do the P/Invoke? Best regards, Peter Huang Microsoft Online Partner Support  SignatureGet Secure! - www.microsoft.com/security This posting is provided "AS IS" with no warranties, and confers no rights. No the main UI thread is not waiting on the worker thread in any way. I actually experiemented with join and other techniques for waiting on the thread and it acted exactly the same. This really brought me to the conclusion that the worker thread is somehow blocking the main ui thread. The code I'm calling in the worker thread is a code protection library by Aladdin. They have a technique where they encrypt a DLL using a hardware dongle (hasp). It is a very slow process to unencrypt it so I decided to thread the pinvoke call. I have no idea what they are doing down there but it definitely does not act like a good threaded citizen. -Brett- > Hi Brett, > [quoted text clipped - 11 lines] > Get Secure! - www.microsoft.com/security > This posting is provided "AS IS" with no warranties, and confers no rights. Hi Brett, So far it is hard to guess what had happen, I think there must be something underlying race condition which will cause the blcok. I think you would better contact MS PSS which will do further touble shooting about your issue. e..g live debugging or dump analysis which is beyond newsgroup support boundary. Thank you for you understanding! Best regards, Peter Huang Microsoft Online Partner Support SignatureGet Secure! - www.microsoft.com/security This posting is provided "AS IS" with no warranties, and confers no rights. Hi, One possibility is that if the third-party dll called a COM object which is main threaded that is to say we did not specified the thread model for the COM Object. In this way, the COM object will be created and running on the main thread, i.e. the main UI thread which may cause the main UI form thread blocked. Usually the main thread is the first thread in the process. So I think you may try to change your code as below. <code snippet> [STAThread] static void Main() { //run the winform in the second thread. Thread th = new Thread(new ThreadStart(ThreadProc)); th.Start(); //Run the P/Inovke code in the main thread, try to replace the three code lines below TestCOMP.COMPClass tcc = new TestCOMP.COMPClass(); tcc.SleepVB(1000); } public static void ThreadProc() { Application.Run(new Form1()); } </code snippet> Best regards, Peter Huang Microsoft Online Partner Support SignatureGet Secure! - www.microsoft.com/security This posting is provided "AS IS" with no warranties, and confers no rights. Free MagazinesGet these publications absolutely FREE for up to 12 months. There are no hidden fees and no obligation. Simply choose a title, complete the application form and submit it. Read more ...
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