Would rayon::ThreadPool::spawn surely spawn on another thread?

[nrbnlulu]

I have a usecase where it is required to run on another thread...

[cuviper]

No, if you call that when you're already on a thread in the pool, it will add to that local queue. Thus that may run locally if you ever block on rayon and it looks for more work, or it may run elsewhere if another thread steals it. But even if we put that on the pool's global queue, there's a chance it could be picked up by the current thread as well.

[cuviper]

I suppose if you spawn and then block in a non-rayon way until it's done, then you can be sure the current thread won't do anything. You'd better be careful not to tie up all your threads that way though.