[Haskell-cafe] Race Condition in threads

[mukesh tiwari]

Hello All
I have two questions.
1. I wrote this code to create 10  simultaneous threads. Could some one
please tell me if this is correct or not ?

incr_count :: MVar () -> MVar Int -> IO ()
incr_count m n = ( forM_ [ 1..10000 ] $ \_ -> modifyMVar_ n ( return . ( +
10 ) ) ) >> putMVar m ()

main :: IO()
main = do
      count <- newMVar 0
      list <- forM [1..10] $ \_ -> newEmptyMVar
      forM_ list $ \var -> forkIO . incr_count var $ count
      forM_ list $ \var ->  takeMVar var
      val <- takeMVar count
      print val

2. I am trying to create  race condition which makes the variable in
inconsistent state. Could some one please tell me how to achieve this ? I
look at IORef but it does not have function like modifyMVar_.

Mukesh Tiwari
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