GEgeertj·Sep 24, 2023
A disadvantage of the ‘no function coloring’ in fibers is that it makes lockless programming harder. A nested function call can switch from under you without your knowledge, making it hard to know where the preemption points are and whether to take locks when making updates to shared state. With function coloring you immediately see whether a function might switch as there’s a different calling syntax.
I’ve programmed both fiber based systems and coroutines. I even created my own fiber libraries for Python (https://github.com/geertj/gruvi) and C++ (https://github.com/geertj/cgreenlet, mostly an experiment, and incorrectly named coroutines for C++ while it’s really fibers). In the Python version I experimented with some features to help you know whether a nested function might switch.
In the end, for me and for the problem domains I worke
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d in, the explicit async/await co-routine style wins over fibers. It gives you most of the performance benefits of user mode switching, all of the memory benefits, while keeping your code mostly lock free.