[Haskell-cafe] STM semantics

I have a doubt that this code works like I want because actual STM implementation exposes its effects import Control.Concurrent import Control.Concurrent.STM main = do     c <- atomically $ newTChan :: IO (TChan ())     r <- atomically $ newTVar False     forkIO $ do         atomically $ do             r0 <- readTVar r             case r0 of                 True -> return ()                 False -> readTChan c         myThreadId >>= killThread     threadDelay 1000000     atomically (writeTVar r True) The thread stops on readTChan, but exits when I change the TVar, which happens before the readTChan. Should I trust this is the correct STM behaviour , and will not change in different implementations ? thanks paolino