Is it possible to rewrite this without unsafeIOToSTM? unsafeIOToSTM is insanely unsafe, and can cause otherwise working STM code to do unpredictable and terrible things to the runtime. Cheers, Sterl. On Mar 30, 2009, at 4:27 PM, Alberto G. Corona wrote:
Control.Concurrent.STM.TMVar's combine the best of MVars and TVars:
-Unlike TVars, they permit blocking/early retry when the TMVar is being used by other process, so that complete processes are not retried at the end when happens that the TVars have been modified in the meantime.
- Unlike MVars, they have no deadlocks, specially when a process is trying to adquire exclusive access to more than one TMVar.
however, It happens that fails in my windows box with ghc 6.10.1 , single core
here is the code and the results:
-----------begin code:
module Main where
import Control.Concurrent.STM
import Control.Concurrent import System.IO.Unsafe import GHC.Conc
mtxs= unsafePerformIO $ mapM newTMVarIO $ take 5 $ repeat 0
proc i= atomically $ do unsafeIOToSTM $ putStr $ "init of process "++ show i++"\n" xs<- mapM takeTMVar mtxs
mapM (\(mtx,x) ->putTMVar mtx (x+1)) $ zip mtxs xs
xs' <- mapM readTMVar mtxs unsafeIOToSTM $ putStr $ "End of processs "++show i ++ " result= "+ + show xs'++"\n"
main=do mapM (forkIO . proc) [1..5] threadDelay 100000000
-------------end code
the rigth result must be (occasionally with some "init of process x" repeated)
init of process 1 init of process 2 End of processs 1 result= [1,1,1,1,1] init of process 2 -- retried End of processs 2 result= [2,2,2,2,2] init of process 3 End of processs 3 result= [3,3,3,3,3] init of process 4 End of processs 4 result= [4,4,4,4,4] init of process 5 End of processs 5 result= [5,5,5,5,5]
under windows the program produces strange results for example
init of process 1 init of process 2 init of process 3 init of process 4 init of process 5 End of processs 1 result= [1,1,1,1,1] End of processs 2 result= [1,1,1,1,1] (deadlock)
or this other:
init of process 1 init of process 2 init of process 3 init of process 4 init of process 5 End of processs 1 result= [1,1,1,1,1] End of processs 2 result= [1,1,1,1,1] init of process 3 init of process 4 init of process 5 init of process 2 End of processs 4 result= [2,2,2,2,2] End of processs 3 result= [2,2,2,2,2] End of processs 5 result= [2,2,2,2,2] End of processs 2 result= [2,2,2,2,2] init of process 3 init of process 5 init of process 2 End of processs 3 result= [3,3,3,3,3] End of processs 5 result= [3,3,3,3,3] _______________________________________________ Haskell-Cafe mailing list Haskell-Cafe@haskell.org http://www.haskell.org/mailman/listinfo/haskell-cafe