I have been googling about this and found some (outdated) documents saying that this is not possible ( http://www.crystalclearsoftware.com/soc/coroutine/coroutine/coroutine_thread.html ).

this is another library

However, I did not find this warning in the document of the current release. Is this limitation still there or not?

as long as you don't use TLS you can suspend a coroutine in thread A and resume in thread B