Using Threadpool in managed code run from a Runtime started by nethost

[Samuil1337]

Hello guys,

I am writing a scripting system for an Unreal Engine 3 game. My native host is loaded into the game using DLL injection. Then, I use hostfxr to load in the .NET Core Runtime and run my managed entry point. However, it seems like some features of .NET aren't inited properly. Specifically, doing anything async like creating tasks seem to freeze the application. I have tried using the relatively new System.Threading.ThreadPool.UseWindowsThreadPool runtime option which did fix Tasks. However, that only appears to be a workaround as other things like FileSystemWatchers still freeze the game.

Here's a link to my native host (~100 lines without boilerplate code) and here's a link to the function that it's running. I am using a modified version of the tutorial host. I also tried switching to the newer independent load_assembly_fn and get_function_pointer_fn but it didn't work.

I wanted to ask if this is a known issue or if I have something misconfigured. Are there any workarounds for this problem that I haven't tried yet? Thanks in advance.

Samuil1337

[AustinWise]

You are calling LoadLibrary from DllMain, some that is explicitly not allowed. See Dynamic-Link Library Best Practices. Using managed code is also on the list.

Perhaps on DLL_PROCESS_ATTACH use CreateThread to call your load_dll function, rather than calling it directly?

hostfxr_close potentially takes a lock and uses memory management functions ( see here ). Those are also not allowed in DllMain. And the host handle is not thread safe ( see here ). So I'm not sure what is the right way to clean that up.

[Samuil1337]

I have to load pretty early and do stuff on the main thread so I can manipulate the event loop properly but I'll see what I can do. Thanks for the heads up.

[Samuil1337]

Yup that was it. I implemented a hacky solution for it and that resolved the issue. Thank you very much!