Is there a 'standard' read/write lock implementation for ruby?

Does anyone know of an existing ruby implementation of a read/write lock - http://en.wikipedia.org/wiki/Readers-writer_lock?

Preferably this would be in a popular library or some other implementation that's been used by enough people that it's fairly bulletproof at this point.

From stackoverflow Pete Hodgson

• There isn't a standard one to my knowledge, but they aren't terribly hard to write. Failing that, this guy has already written one. It looks right and he's provided tests.

  From Pesto