[kprotty]

Not sure I follow; the cancellation logic is on both threads/tasks 1) the operation itself waiting for either the result or a cancel notification and 2) the cancellation thread sending that notification.

The cancellation thread is generally the one doing the `select` so it spawns the operation thread(s) and waits for (one of) their results (i.e. through a channel/event). The others which lose the race are sent the cancellation signal and optionally joined if they need to be (i.e. they use intrusive memory).