[UWP] Application hangs when suspended in a loading screen

Hi,

we are porting a game to UWP which runs quite fine, though on some machines, we are seeing the reproducible issue that, when minimizing & suspending while in a loading screen, the game freezes. At some point this also happend while being in a scene, though we could fix that by disabling 'Application.RunInBackground'.

There is no specific error message that hints on something that could be wrong. I suspect that there's something blocking the engine from suspending the D3D device, because in most logs the line "Trimming D3D resources." is missing. Sometimes the game code is still running, so there is still log ouptut from the game after resuming the game.
Though, when suspending again, Windows will kill the game because it is not responding to the suspend call in time.

Is there anything we could have missed ? As far as I can see we don't have the option to retrieve the graphics device and call Trim() manually, without creating a native plugin (and I'd really like to avoid that).

I also tried to create a repo project, but I was unable to reproduce this in smaller projects til now. But I will continue working on that.

A bit of information about our configuration:
The Unity version is 5.3.5p8, I looked through all the patch/release notes for the newer versions, but could not find anything related.
The project is D3D and we are building master builds, so the code is .NET native.
Application.RunInBackground is disabled.
We are not doing anything in the suspend/resume handler.
We are changing scenes using LoadAsync.
The content is loaded from Assetbundles asynchronously..


Thanks,
Michael

 

Hi,

thanks for the hint. I created a couple of performance and network traces but still can't really see what is happening.
What I can see though is that, when resuming, the ApplicationFrameHost is running getting the focus first, just like usual alt-tabbing, but the game is never re-activated.
Another thing I just saw is that, whenever I break the application, I have a couple of Tasks named "WinRT operation as Task" beeing stuck in "Scheduled and waiting to run". They are most likely caused by opening files using GetFileFromPathAsync/OpenStreamForReadAsync..
Could this be a problem for suspending the app ?

One thing I forgot to mention is that we are using Xbox live services, including storage, achievements, and presence.

 

I'll try to make a shorter trace so I can send it to you, any particular trace options you need ?

 

Unfortunately, the WPR tool crashes on the laptop (where I can easily reproduce the issue), when I try to load any WPR profile. I'll have a look into that and will send you a PM when I managed to load and record.

 

I have the same problem .....