Re: [Haskell-cafe] Question about takeMVar

'takeMVar' documentation says "if there are multiple threads blocked in takeMVar, and the MVar becomes full, only one thread will be woken up."

Since 'takeMVar' is a reading function, i.e., it doesn't change the value of the "variable", why waking up only one thread? If we wake multiple threads, there's no risk of one changing the value while the other is reading.

Also in the docs: After a takeMVar, the MVar is left empty. The behaviour you describe is more like readMVar. Because readMVar does a takeMVar followed by a putMVar, it will wake up multiple threads. If you want to broadcast to multiple threads, you might also want to consider dupChan in Control.Concurrent.Chan.