Lumpio-: you have to do it that way, otherwise you can have a race condition deadlock if an interrupt happens at the right moment:

```rust
poll_fn(|cx| {
    if r.events_endtx.read().bits() != 0 {
        Poll::Ready(())
    } else {
        // INTERRUPT HAPPENS HERE
        s.endtx_waker.register(cx.waker());
        Poll::Pending
    }
}).await;