[pjmlp]

I am old enough to remeber when UNIX only had processes, and several thread designs were being discussed until eventually pthreads one design won.

POSIX predates adoption of threads in the UNIX world.

[loeg]

Yes, yes, but also post-dates adoption of threads. It's an ongoing standard.

[pjmlp]

Which only standardises existing practice, not inventing new ideas.

So first everyone implementing POSIX has to agree to move forward with thread safety where it fails short.