Hi all, I'm writing a program that reads input from the user but should also handle a ctrl-c. My attempt is below; the program forks a thread to read one character of input, and kills that thread upon receiving a sigINT. It works fine compiled without -threaded, but with -threaded it blocks forever after a ctrl-c. I know that in general, foreign calls are not interruptible; but the documentation for Control.Concurrent and System.Timeout suggests that I/O operations are a special case. In particular, the documentation for System.Timeout.timeout says: "Standard I/O functions like hGetBuf, hPutBuf, Network.Socket.accept, or hWaitForInput appear to be blocking, but they really don't because the runtime system uses scheduling mechanisms like select(2) to perform asynchronous I/O, so it is possible to interrupt standard socket I/O or file I/O using this combinator." So is the behavior that I'm seeing correct? If so, it seems odd to get better concurrency without the threaded runtime. If not, I can file a bug for this. I used ghc-6.8.2 and HEAD on OS X 10.5 (x86). Thanks, -Judah -------------- module Main where import Control.Monad import System.Posix.Signals import Control.Concurrent import Control.Concurrent.MVar import System.IO main = do hSetBuffering stdin NoBuffering hSetEcho stdin False mv <- newEmptyMVar let handler = putMVar mv Nothing installHandler sigINT (CatchOnce handler) Nothing tid <- forkIO (myGetChar mv) c <- takeMVar mv when (c==Nothing) $ do killThread tid putStrLn ("Result: " ++ show c) myGetChar mv = do c <- getChar putMVar mv (Just c)