import Foreign.C import Foreign.Marshal.Array import Foreign.Storable import Control.Concurrent -- The test works only on UNIX like. -- unportable bits: import qualified System.Posix.Internals as SPI import qualified System.Posix.Types as SPT pipe :: IO (CInt, CInt) pipe = allocaArray 2 $ \fds -> do throwErrnoIfMinus1_ "pipe" $ SPI.c_pipe fds rd <- peekElemOff fds 0 wr <- peekElemOff fds 1 return (rd, wr) main :: IO () main = do (r1, w1) <- pipe (r2, _w2) <- pipe _ <- forkIO $ do -- thread A threadWaitRead (SPT.Fd r1) _ <- forkIO $ do -- thread B threadWaitRead (SPT.Fd r2) yield -- switch to A, then B -- now both are blocked _ <- SPI.c_close w1 -- unblocking thread A fd _ <- SPI.c_close r2 -- breaking thread B fd yield -- kick RTS IO manager {- #10590 exposed a bug as: T10590: internal error: removeThreadFromDeQueue: not found (GHC version 7.11.20150702 for x86_64_unknown_linux) Please report this as a GHC bug: http://www.haskell.org/ghc/reportabug -}