Multithreading example crash using DX12 renderer

[duckdoom4]

When running the Multi-Threading example (in debug mode) using the DirectX12 renderer I got the following error:

D3D12 ERROR: ID3D12CommandQueue::ExecuteCommandLists: A command list, which writes to a swapchain back buffer, may only be executed when that back buffer is the back buffer that will be presented during the next call to Present*. Such a back buffer is also referred to as the "current back buffer". Swap Chain: 0x0000022962A35080:'Unnamed Object' - Current Back Buffer Buffer: 0x0000022961DA41B0:'Unnamed ID3D12Resource Object' - Attempted Write Buffer: 0x0000022961DA6880:'Unnamed ID3D12Resource Object' [ STATE_SETTING ERROR #907: EXECUTECOMMANDLISTS_WRONGSWAPCHAINBUFFERREFERENCE]
D3D12: Removing Device.
D3D12 ERROR: ID3D12Device::RemoveDevice: Device removal has been triggered for the following reason (DXGI_ERROR_ACCESS_DENIED: The application attempted to use a resource it does not access to.  This  could be, for example, rendering to a texture while only having read access.). [ EXECUTION ERROR #232: DEVICE_REMOVAL_PROCESS_AT_FAULT]

Console output:

selected renderer: Direct3D12
render system:
  renderer:           Direct3D 11.1
  device:             NVIDIA GeForce RTX 2060 SUPER
  vendor:             NVIDIA Corporation
  shading language:   HLSL 6.0

render context:
  resolution:         800 x 600
  samples:            8
  colorFormat:        RGBA8UNorm
  depthStencilFormat: D24UNormS8UInt

Enter thread: mainThread
Leave thread: mainThread
failed to present DXGI swap chain (error code = DXGI_ERROR_DEVICE_REMOVED)

[LukasBanana]

Multi-threading is in an experimental and unstable state. Ironically, the only backend that supports multi-threading in LLGL right now is OpenGL with the deferred command buffer. That being said, I just found out that the JIT compiler is broken, too (also more an experimental sub project). So make sure LLGL_ENABLE_JIT_COMPILER is disabled in CMake. It's not really essential anyway.

About the output renderer: Direct3D 11.1: that's another bug with the static lib build configuration. I tested the engine with dynamic libs most of the time, so some of those things slipped through. The macro LLGL_DX_ENABLE_D3D12 is defined for D3D12, but with the static lib configuration those definitions overlap with the different backends.

EDIT: I updated the TODO list accordingly.

[dmiller423]

How about some warning the entire library is not multithread friendly? You list features but that immediately burns 90% of usage for most people, and there is no mention of it on the page.

[LukasBanana]

@dmiller423 there are some multi-threading capabilities but not all renderers implement that. In what renderer did you run into MT problems? And please let me know where you found misleading information in the description.

[LukasBanana]

Several improvements have been implemented in recent commits to better support multi-threaded command recording in all backends. Please feel free to open a new ticket if any previously mentioned issues persist.