Discussion: Make pygame-ce thread safe with concurrent multi threading

[damusss]

Thread safety is a big topic like SDL3 porting, so I think a github issue can be helpful to discuss it, as discord messages get lost quickly.

[damusss]

Surface thread safety design proposal

Threads reading or writing to the same surface is something I can see happening easily. It's not inherently bad, but not the best practice or bad if they both write to it. Surface locking is not thread safe, so:

• Add a SDL_mutex field in the surface object struct, that is created when the surface is created and is destroyed when it is freed
• Create macros that when the python version is high enough and the gil is disabled lock the mutex before pixel access and unlock it after that

I know that atomic flags exist, but I'm not sure how reliable they are. If they are a better option we should use them.

[Starbuck5]

pgSurface_Lock could also be made thread safe by making it a critical section.

[damusss]

pgSurface_Lock could also be made thread safe by making it a critical section.

Yeah it makes sense. SDL_Surface s created inside the functions cannot be modified by other threads anyways, only pygame surface objects so we can embed the mutex/atomic thread safety within that function. We "just" need to check how it is used right now and correct it if needed.