This issue primarily seems to affect Intel-based Macs without unified
memory: While an IOSurface is supposed to be shared via a mach port
with other processes, each process needs to lock the surface during
access (as is common with other shared resources).
Apple Silicon-based Macs seem to be less affected as a switch between
GPU and CPU memory (which can happen dynamically for IOSurfaces) would
still point to the same unified memory.
ee34d8fbfe