I am always wondering who writes code so badly unaware of concurrency issues, to rely on the GIL. Wondering how many libraries and programs will actually break. But probably the number is way higher than even I imagine.
The race condition bugs are typically hidden by different software layers. For instance, we found one that involves OpenBLAS's pthreads-based thread pool management and maybe its scipy bindings:
We haven't managed to write minimal reproducers for either of those but as you can observe, those race conditions can only be triggered when composing many independently developed components.
