hGetContents and threadWaitRead?

Whilst everyone is discussing threads, does anybody know if hGetContents is well behaved with respect to threads - ie does it use threadWaitRead internally? I know it uses unsafePerfomIO, is a function that interleaves IO using unsafePerformIO automatically haskell-thread safe? - also do I need to use threadWaitWrite before any hPut - or do the hPut functions do this internally? Regards, Keean Schupke.