> But it's worth noting pthread_cancel() is also rarely supported anywhere outside first-class pthreads-capable systems like modern linux

Having written some of the implementation for a non x86 commercial Unix well over 30 years ago now (yeah, I know), pthread_cancel is not that rare. A carve out like “modern linux” is io_uring or even inotify and epoll. AIX and HP-UX, fuck even OSF/1 had pthread_cancel.

Windows has TerminateThread. Most RTOS have some kind of thread level task killing interface.

While they have different semantics than pthread_cancel, that doesn’t really affect the example you’re giving - they can all be used for the “cpu-bound worker”

I’m not familiar with pthread_cancel, but I am with TerminateThread. It’s not something that can be used safely: ever. Raymond Chen has written a few times about it, including the history.

> Originally, there was no Terminate­Thread function. The original designers felt strongly that no such function should exist because there was no safe way to terminate a thread, and there’s no point having a function that cannot be called safely. But people screamed that they needed the Terminate­Thread function, even though it wasn’t safe, so the operating system designers caved and added the function because people demanded it. Of course, those people who insisted that they needed Terminate­Thread now regret having been given it.

pthreads has `pthread_kill`, which is like `TerminateThread`.

`pthread_cancel` is different