Synchronization bugs in `RtlEnterCriticalSection`/`RtlLeaveCriticalSection`

[Markos-Th09]

Due to synchronization bugs in the implementation of critical sections which I have not been able to exactly pinpoint, various deadlocks have been observed exclusively on iOS in the execution blocks of RtlEnterCriticalSection and RtlLeaveCriticalSection. Under the conditions of the iOS kernel scheduler, which more aggressively parks and context-switches threads compared to desktop operating systems, various thread starvation patterns and deadlocks have been observed.

Prior to updating the implementation, the synchronization logic failed consistently across build configurations:

• Debug Builds: Permanent hang on the initial scene loading layout.
• Release Builds: Immediate deadlock at the early initialization sequence of the runtime application launch.

However, even after these changes, an infinite loading screen occurs when exiting back to the main menu.

Possible next steps

• Try conservative std::mutex / std::condition_variable implementation to see if it is resolved
• Profile thread interactions during scene teardown using Xcode Instruments.
• If conservative implementation works, try to refine the current implementation using atomics.

[Markos-Th09]

The std::mutex / std::conditional_variable implementation seems to have resolved all the synchronization issues, however it is probably not ideal for performance. I will try to continue refining it.

[Markos-Th09]

Technically this issue is resolved, however I am not content with keeping the current fix as a permanent solution. The performance impact will be investigated to determine whether it is worth investing time into a more complex lock-free solution