[Haskell-cafe] TMVar's are great but fail under ghc 6.10.1 windows

[Alberto G. Corona]

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]
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