[fixed] NRE on application exit (2 Viewers)

[breese]

When I did the test yesterday I set MP2 Client to minimize.
I just went back onto my machine, opened up the minimized client and then told it to close...
When I did I got an error message


The file MP2 Stopped Working is the text from the Popup and the 3 Application Events registered.
I can only assume it is related to the new file and test from yesterday because I have never had this happen before.

 

[morpheus_xx]

Thanks for reporting! I've experienced the same message when testing yesterday. Nice that you have the stacktrace, it makes debugging easier.

I will look into this issue.

Edit: Moved report into own thread

 

[breese]

Be aware.... over the past few days I upgraded my server to include all the .net 4.5.1

 

[morpheus_xx]

@MJGraf, I found the issue. It comes from the finalizer of the AMQ: it might happen after the ServiceRegistration finalizer was called.

Then the access to ServiceRegistration.Get<> will lead to a NRE, because "_instance" was set to null already.

at MediaPortal.Common.ServiceRegistration.Get[[System.__Canon, mscorlib, Version=4.0.0.0, Culture=neutral, PublicKeyToken=b77a5c561934e089]](Boolean)
at MediaPortal.Common.Messaging.MessageQueueBase.UnregisterFromAllMessageChannels()
at MediaPortal.Common.Messaging.AsynchronousMessageQueue.Terminate()
at MediaPortal.Common.Messaging.AsynchronousMessageQueue.Dispose()
at MediaPortal.Common.Messaging.MessageQueueBase.Finalize()

A possible solution would be to simply remove the ~ServiceRegistration { Dispose(); } call. What do you think?

 

[MJGraf]

Good spot!
I always asked myself why we have a destructor which calls Dispose() and dispose does nothing but setting our singleton instance to null.
If we want to do this, we should follow a proper dispose-pattern - which we did not. But since ServiceRegistration itself does not hold any non-managed resources, I think it should be safe to remove the destructor.
Just to mention it - There is (at least) one more thing that is strange with our ServiceRegistration:
There is a property called IsShuttingDown, which defaults to "false". In the ApplicationLauncher's Stop() method, we set it to true with the comment "Block ServiceRegistration from trying to load new services in shutdown phase". But ServiceRegistration does not care at all about this property...

 

[morpheus_xx]

I fixed the disposal in this branch https://github.com/MediaPortal/MediaPortal-2/commits/FIX_ServiceRegistration_DTOR.

If you like to fix the "Block ServiceRegistration from trying to load new services in shutdown phase" issue you can do it in this branch.