My long held belief: green/user-level/M:N threading schemes never work at first, and only work reliably after extreme effort has been put into fixing all the cases where blocking code gets called underneath. afaik there are only two modern working implementations: golang and erlang. This article is consistent with that belief.
There are many other implementations, although in less popular languages.
The trick is to include the green threads from the start, so there are no libraries that depend on real threading. That's why Go and Erlang are so successful.
It pins goroutine until it is explicitly released ensuring that multiple native calls will remain on the same platform thread and nothing else is going to use it.
This is critical for namespace manipulation on Linux.
Java only pins for duration of native call and synchronized blocks.
It looks like Java does not offer equivalent API?
For now could be achieved with synchronized but if synchronized will be changed in the future to not pin it would break.
