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import Control.Concurrent
import GHC.Conc
import Data.List
import Data.Maybe
main = do
t1 <- forkIO (threadDelay 100000000)
m <- newEmptyMVar
t2 <- forkIO (takeMVar m)
t3 <- forkIO (let loop = do r <- tryTakeMVar m;
_ <- newEmptyMVar -- do some allocation :(
if isNothing r then loop else return ()
in loop)
t4 <- forkIO (return ())
yield
threadDelay 10000
print =<< mapM threadStatus [t1,t2,t3,t4]
putMVar m ()
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