Need to synchronize worker thread exit with main thread, but worker thread uses Invok

This is a discussion on Need to synchronize worker thread exit with main thread, but worker thread uses Invok within the C# Programming forums, part of the General Programming Boards category; I have a problem for which I have a solution, but the solution feels like a hack. I am not ...

  1. #1
    Captain Crash brewbuck's Avatar
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    Need to synchronize worker thread exit with main thread, but worker thread uses Invok

    I have a problem for which I have a solution, but the solution feels like a hack. I am not a seasoned .NET programmer, let's just get that out there right away.

    I have a worker thread which accesses (reads) a container. The container is also accessed (updated) by the UI thread. Instead of locking the container, I actually shut the worker thread down completely, change the container, then spin up the worker thread again. The worker thread only does read accesses to the container, so this ensures mutual exclusion during updates.

    To synchronize with the termination of the worker thread, I wait on an AutoResetEvent in the main thread.

    Problem: The worker thread does some updates to a DataSet which is bound to some UI controls. The updates cause events to fire which are connected to the UI controls. Thus the updates need to be performed on the UI thread -- I use Invoke to do this. The problem is, this can deadlock during shutdown of the worker thread because it might be in the middle of an Invoke on the UI thread, while the UI thread goes to sleep waiting on the AutoResetEvent. Oops.

    My current workaround is for the UI thread to call WaitOne() with a timeout of zero, and while the event is not set, I call Application.DoEvents() to pump the main thread's event loop.

    This works, but I have a feeling it sucks and I'm missing something. Any suggestions?
    Last edited by brewbuck; 11-19-2011 at 07:34 PM.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  2. #2
    Gawking at stupidity
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    Instead of locking the container, I actually shut the worker thread down completely, change the container, then spin up the worker thread again.
    I think you might have answered your own question...
    If you understand what you're doing, you're not learning anything.

  3. #3
    Captain Crash brewbuck's Avatar
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    Quote Originally Posted by itsme86 View Post
    I think you might have answered your own question...
    Locking the container really sucks because the worker thread iterates over it constantly, but the UI thread only changes it very rarely. The container would almost always be locked by the worker, and the UI thread would have to wait to gain the lock before it could update the container, and this causes the UI to freeze.

    When the container changes, a lot of other stuff is also changing and rather than protect all these data structures with locks it is far simpler design to just stop the worker thread while making the changes and then restart it.

    But yes, something smells about the whole way I'm doing this.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

  4. #4
    Captain Crash brewbuck's Avatar
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    I solved my problem by eliminating the worker thread altogether.

    Ho hum.
    Code:
    //try
    //{
    	if (a) do { f( b); } while(1);
    	else   do { f(!b); } while(1);
    //}

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