Hi everyone,
isEmptyTMVar :: TMVar a -> STM Bool Source
Check whether a given TMVar is empty.
Notice that the boolean value returned is just a snapshot of the state of the TMVar. By the time you get to react on its result, the TMVar may have been filled (or emptied) - so be extremely careful when using this operation. Use tryTakeTMVar instead if possible.
When I read this in the haddock to Control.Concurrent.STM.TMVar, I started to suspect that the behavior of TMVar and TChan might be worse than I imagined. Few questions on TMVar and TChan: (1) If 2 threads are sleeping-waiting for the output of TChan, and it gets filled, do they both wakeup, or just one? (2) Similar question about reading/writing TMVar. (3) If a thread is sleeping-waiting for the output of TChan, but transaction wants to restart due to the change in any of touched TVar, then does the thread wakeup and restart the transaction? (4) Similar question about TMVar. Also, if there is some paper on this, please, give me a link on it. Please help, Andrey -- View this message in context: http://old.nabble.com/Does-the-TMVar-and-TChan-really-obey-STM-rules--tp2691... Sent from the Haskell - Haskell-Cafe mailing list archive at Nabble.com.