[jstclair]

Sounds like you're describing Microsoft Research's CHESS (2007), and a host of related projects (Google's ThreadWeaver for Java).

See http://research.microsoft.com/en-us/projects/chess/ and https://code.google.com/archive/p/thread-weaver/wikis/UsersG...

[jkot]

I made blogpost about thread weaver some time ago. Not very useful http://www.mapdb.org/news/thread_weaver/