Fix potential bug when polling the Swarm

[tomaka]

In the situation where this.network.poll returns Poll::Ready(_) and then this.behaviour.poll returns Poll::Ready(NetworkBehaviourAction::NotifyHandler { .. }), we would return Poll::Pending.

That is wrong, as nothing in the stack has registered the Waker to wake it up later. In other words, the task would then get frozen forever.

Same problem if this.network.poll returns Ready and we have an event buffered up that we fail to deliver.

[romanb]

That is wrong, as nothing in the stack has registered the Waker to wake it up later. In other words, the task would then get frozen forever.

I'm not sure I follow, I will need to take a closer look later, but all the occurrences of return Poll::Pending that you removed here are in the context of notify_one / notify_any / notify_all having returned Some, which only happens when the current task is registered to be woken up because at least one connection returned Poll::Pending from poll_ready_notify_handler. At least that is the intention and how I documented it.

[tomaka]

Oh ok, I see. I admit that it didn't occur to me that notify was polling, as I still had the former design with the unbounded channels in my head.

[romanb]

No problem, I actually found an unrelated issue on re-reviewing the code: #1513.