Not an Erlang user, but my understanding is that the Erlang VM (BEAM) schedules on function calls. Which works fine for that use, since Erlang does looping with tail calls, but is not a solution for procedural languages.
Erlang vm is fully preemptive and schedules on something called a reduction. You can call an external function with EFI that can screw things up, but otherwise it's not necessarily on what you might consider a function call .
In practice, it's enough to preempt at potentially-recursive function entry and loop backedges. A thread which doesn't recurse or loop has to come to an end pretty quickly, at which point the scheduler will get a go.
There's no fundamental difference between inserting a yield before a tail call and inserting a yield before a continue statement or closing bracket of the for block, is there?
Fundamentally no, but it's a more difficult thing to do in practice at least. Unless you want to give up other optimizations like loop unrolling and other things like that since you end up losing the fact that the loop exists after some optimization passes.
