Hi. I have some doubts about errno handling in a Concurrent Haskell program. Let's suppose that GHC non threaded runtime is used, so that each Haskell thread is bound to an OS thread. Let's suppose there are two threads running (`A` and `B`). Thread `A` calls a function `f`, that, in turn, calls via FFI a C function `c_f`. Function `c_f` fails, settings errno; however the GHC scheduler suspends execution of thread `A` and switch to thread `B`, before the current value of errno is read. Now, let's suppose thread `B` calls a function `g`, that, in turn, calls via FFI a C function `c_g`. Function `c_g`, too, fails, setting errno. Is this possible? P.S.: I have found this is C.Foreign.Error.hs, in base package (not the latest version): throwErrnoIfRetry :: (a -> Bool) -> String -> IO a -> IO a throwErrnoIfRetry pred loc f = do res <- f if pred res then do err <- getErrno if err == eINTR then throwErrnoIfRetry pred loc f else throwErrno loc else return res This function calls getErrno two times. Is this safe? Why the throwErrno function does not accept errno as parameter? Thanks Manlio Perillo