Pfthb

I've read the https://docs.microsoft.com/en-us/windows/desktop/direct3d11/overviews-direct3d-11-render-multi-thread-intro

And it states that I can make calls to ID3D11Device from multiple threads (unless D3D11_CREATE_DEVICE_SINGLETHREADED was used), but calls to ID3D11DeviceContext have to be surrounded with a critical section.

I haven't found any information about releasing resources, using their 'Release' method, for resources such as textures, render targets, vertex/index buffers, shaders.

ID3D11Texture2D, ID3D11Texture3D, ID3D11ShaderResourceView, ID3D11RenderTargetView, ID3D11DepthStencilView

ID3D11Buffer.

ID3D11VertexShader, ID3D11HullShader, ID3D11DomainShader, ID3D11PixelShader.

1) Can I call 'Release' for those resources at any time from any thread without using critical sections while they ARE NOT in use by the render thread's ID3D11DeviceContext?

2) Can I call 'Release' for those resources from other threads even while they ARE in use by ID3D11DeviceContext in the render thread?

Or do I need to surround the Release calls with the same critical section used for accessing ID3D11DeviceContext?

Generally the internal implementation of COM reference counts is done in a thread-safe manner (atomic increments/decrements), so it's safe to call AddRef and Release from multiple threads.

Of course, if the refcount goes to 0 then you have an object destruction so it's important that if you have multiple threads using the same resource, it has the appropriate number of reference counts to keep it live. In Direct3D, object destruction is typically deferred destruction so the actual object cleanup may not happen for a few frames, but you should still keep a non-zero refcount if anyone is referencing it.

Direct3D 11 uses the same rules as Direct3D 10. It uses 'weak references' for the pipeline set methods, so just having a resource set on the device context is not sufficient to increase it's reference count. IOW: if you have two threads both rendering with the same resource, then each thread must hold a reference count on the object to keep it 'live' whether or not it's 'actively set' on a device context at any given moment.

It works this way to avoid the overhead of constantly increment/decrementing reference counts every rendering frame. In Direct3D 9 this was happening thousands of times a frame or more.

Also, if the ID3D11Device reaches a zero ref-count, it and all it's child objects are released regardless of the individual device-child reference counts.

See Microsoft Docs.

The best answer is to use a smart-pointer like Microsoft::WRL::ComPtr and have each thread using a given resource have it's own ComPtr pointing to that resource. That way the only real special-case you'll have is when doing device tear-down (such as responding to a DXGI_ERROR_DEVICE_REMOVED or doing a 'clean exit').