Hi, I'm having problems with executeFile as it seems to clear the advisory locks using the threaded runtime. Consider the following snippet (a simplification of what I'm doing): import System.IO import Control.Monad import System.Posix.IO import Control.Concurrent import System.Posix.Files import System.Posix.Process main = do let lock = (WriteLock, AbsoluteSeek, 0, 0) fd <- openFd "/tmp/foobar" ReadWrite (Just stdFileMode) defaultFileFlags {trunc=True} pid <- forkProcess $ do setLock fd lock >> putStrLn "child: ok" executeFile "/usr/bin/sleep" False ["5"] Nothing threadDelay $ 1 * 1000 * 1000 setLock fd lock >> putStrLn "parent: fail!" void $ getProcessStatus True False pid Then I consistentlty get these results: $ ghc -threaded --make test.hs; ./test child: ok parent: fail! $ ghc -rtsopts --make test.hs; ./test child: ok test: setLock: resource exhausted (Resource temporarily unavailable) Any pointers? At first I though it might be an issue with the unix package but that doesn't seem to be the case. $ ghc-pkg list | grep unix unix-2.6.0.1 $ ./test +RTS --info [("GHC RTS", "YES") ,("GHC version", "7.6.3") ,("RTS way", "rts_thr") ,("Build platform", "x86_64-unknown-linux") ,("Build architecture", "x86_64") ,("Build OS", "linux") ,("Build vendor", "unknown") ,("Host platform", "x86_64-unknown-linux") ,("Host architecture", "x86_64") ,("Host OS", "linux") ,("Host vendor", "unknown") ,("Target platform", "x86_64-unknown-linux") ,("Target architecture", "x86_64") ,("Target OS", "linux") ,("Target vendor", "unknown") ,("Word size", "64") ,("Compiler unregisterised", "NO") ,("Tables next to code", "YES") ] Thanks! ~dsouza