+-- | Close a file descriptor in a concurrency-safe way (GHC only). If
+-- you are using 'threadWaitRead' or 'threadWaitWrite' to perform
+-- blocking I\/O, you /must/ use this function to close file
+-- descriptors, or blocked threads may not be woken.
+--
+-- Any threads that are blocked on the file descriptor via
+-- 'threadWaitRead' or 'threadWaitWrite' will be unblocked by having
+-- IO exceptions thrown.
+closeFd :: (Fd -> IO ()) -- ^ Low-level action that performs the real close.
+ -> Fd -- ^ File descriptor to close.
+ -> IO ()
+closeFd close fd
+#ifndef mingw32_HOST_OS
+ | threaded = Event.closeFd close fd
+#endif
+ | otherwise = close fd
+