green thread have pitfalls too, like this: https://news.ycombinator.com/item?id=39008026

This was a known issue and was fixed in Java 24 [1].

[1] https://openjdk.org/jeps/491

FWIW this was largely fixed in 24 (I think there are still some edge cases relating to FFI functionality), and the 25 LTS should be coming this month.

This doesn't look like a problem with green threads so much as it is a problem with Java's implementation of them. Of course, Java is known for having problems with its implementations of many different things, such as sandboxing; this isn't special.