Hello, We wrote a small library (1) which offers a few extra synchronization primitives. These primitives are found in the standard libraries of languages like Java and Python, but not in Haskell. Before releasing concurrent-extra on hackage, we would like some comments on its name, design, implementation, documentation (2) and general usefulness. All primitives are implemented with MVars and IORefs, except for Control.Concurrent.STM.Event. There is a small test suite which tests some properties: cabal configure -ftest cabal build cabal test The test suite still needs to be expanded a great deal. We found that testing concurrent algorithms is really hard. Now we test things like "this shouldn't deadlock" by checking if it doesn't take too long. But that doesn't feel very formal. Is there a more principled approach to testing concurrent algorithms in Haskell? After writing our version of a read-write lock we noticed the package rwlock (3) on hackage. But there is a difference: rwlock is implemented with STM while our version is implemented entirely with MVars. Regards, Roel & Bas van Dijk 1 - http://code.haskell.org/~roelvandijk/code/concurrent-extra/ 2 - http://code.haskell.org/~roelvandijk/code/concurrent-extra/doc/html/concurre... 3 - http://hackage.haskell.org/package/rwlock