Comment by throwawaylinux

You do, but it's not a good implementation for a general API is all I was trying to say.

Do you really need an "asynchronous process creation" call? The rationale is that "blocking is bad", but a thread creation system call blocks the caller too until the thread is created. So it's not just "blocking", it's the amount of blocking if anything. Is posix_spawn or vfork+exec really too slow for your case?

Then multi-process and multi-threading seems like a reasonable solution. Asynchronous system calls are the exception not the rule in unix. So it wouldn't make sense as a traditional afork(2) system call. You could probably do a posix_spawn for io_uring, but do you really need to?