{-# LANGUAGE Trustworthy #-} {-# LANGUAGE BangPatterns , CPP , ExistentialQuantification , NoImplicitPrelude , RecordWildCards , TypeSynonymInstances , FlexibleInstances #-} module GHC.Event.Manager ( -- * Types EventManager -- * Creation , new , newWith , newDefaultBackend -- * Running , finished , loop , step , shutdown , release , cleanup , wakeManager -- * State , callbackTableVar -- * Registering interest in I/O events , Event , evtRead , evtWrite , IOCallback , FdKey(keyFd) , FdData , registerFd_ , registerFd , unregisterFd_ , unregisterFd , closeFd , closeFd_ ) where #include "EventConfig.h" ------------------------------------------------------------------------ -- Imports import Control.Concurrent.MVar (MVar, newMVar, readMVar, putMVar, tryPutMVar, takeMVar, withMVar) import Control.Exception (onException) import Control.Monad ((=<<), forM_, liftM, when, replicateM, void) import Data.Bits ((.&.)) import Data.IORef (IORef, atomicModifyIORef', mkWeakIORef, newIORef, readIORef, writeIORef) import Data.Maybe (Maybe(..), maybe) import Data.Monoid (mappend, mconcat, mempty) import GHC.Arr (Array, (!), listArray) import GHC.Base import GHC.Conc.Signal (runHandlers) import GHC.Conc.Sync (yield) import GHC.List (filter) import GHC.Num (Num(..)) import GHC.Real (fromIntegral) import GHC.Show (Show(..)) import GHC.Event.Control import GHC.Event.IntTable (IntTable) import GHC.Event.Internal (Backend, Event, evtClose, evtRead, evtWrite, Timeout(..)) import GHC.Event.Unique (Unique, UniqueSource, newSource, newUnique) import System.Posix.Types (Fd) import qualified GHC.Event.IntTable as IT import qualified GHC.Event.Internal as I #if defined(HAVE_KQUEUE) import qualified GHC.Event.KQueue as KQueue #elif defined(HAVE_EPOLL) import qualified GHC.Event.EPoll as EPoll #elif defined(HAVE_POLL) import qualified GHC.Event.Poll as Poll #else # error not implemented for this operating system #endif ------------------------------------------------------------------------ -- Types data FdData = FdData { fdKey :: {-# UNPACK #-} !FdKey , fdEvents :: {-# UNPACK #-} !Event , _fdCallback :: !IOCallback } -- | A file descriptor registration cookie. data FdKey = FdKey { keyFd :: {-# UNPACK #-} !Fd , keyUnique :: {-# UNPACK #-} !Unique } deriving (Eq, Show) -- | Callback invoked on I/O events. type IOCallback = FdKey -> Event -> IO () data State = Created | Running | Dying | Releasing | Finished deriving (Eq, Show) -- | The event manager state. data EventManager = EventManager { emBackend :: !Backend , emFds :: {-# UNPACK #-} !(Array Int (MVar (IntTable [FdData]))) , emState :: {-# UNPACK #-} !(IORef State) , emUniqueSource :: {-# UNPACK #-} !UniqueSource , emControl :: {-# UNPACK #-} !Control , emOneShot :: !Bool , emLock :: {-# UNPACK #-} !(MVar ()) } -- must be power of 2 callbackArraySize :: Int callbackArraySize = 32 hashFd :: Fd -> Int hashFd fd = fromIntegral fd .&. (callbackArraySize - 1) {-# INLINE hashFd #-} callbackTableVar :: EventManager -> Fd -> MVar (IntTable [FdData]) callbackTableVar mgr fd = emFds mgr ! hashFd fd {-# INLINE callbackTableVar #-} haveOneShot :: Bool {-# INLINE haveOneShot #-} #if defined(darwin_HOST_OS) || defined(ios_HOST_OS) haveOneShot = False #elif defined(HAVE_EPOLL) || defined(HAVE_KQUEUE) haveOneShot = True #else haveOneShot = False #endif ------------------------------------------------------------------------ -- Creation handleControlEvent :: EventManager -> Fd -> Event -> IO () handleControlEvent mgr fd _evt = do msg <- readControlMessage (emControl mgr) fd case msg of CMsgWakeup -> return () CMsgDie -> writeIORef (emState mgr) Finished CMsgSignal fp s -> runHandlers fp s newDefaultBackend :: IO Backend #if defined(HAVE_KQUEUE) newDefaultBackend = KQueue.new #elif defined(HAVE_EPOLL) newDefaultBackend = EPoll.new #elif defined(HAVE_POLL) newDefaultBackend = Poll.new #else newDefaultBackend = error "no back end for this platform" #endif -- | Create a new event manager. new :: Bool -> IO EventManager new oneShot = newWith oneShot =<< newDefaultBackend newWith :: Bool -> Backend -> IO EventManager newWith oneShot be = do iofds <- fmap (listArray (0, callbackArraySize-1)) $ replicateM callbackArraySize (newMVar =<< IT.new 8) ctrl <- newControl False state <- newIORef Created us <- newSource _ <- mkWeakIORef state $ do st <- atomicModifyIORef' state $ \s -> (Finished, s) when (st /= Finished) $ do I.delete be closeControl ctrl lockVar <- newMVar () let mgr = EventManager { emBackend = be , emFds = iofds , emState = state , emUniqueSource = us , emControl = ctrl , emOneShot = oneShot , emLock = lockVar } registerControlFd mgr (controlReadFd ctrl) evtRead registerControlFd mgr (wakeupReadFd ctrl) evtRead return mgr failOnInvalidFile :: String -> Fd -> IO Bool -> IO () failOnInvalidFile loc fd m = do ok <- m when (not ok) $ let msg = "Failed while attempting to modify registration of file " ++ show fd ++ " at location " ++ loc in error msg registerControlFd :: EventManager -> Fd -> Event -> IO () registerControlFd mgr fd evs = failOnInvalidFile "registerControlFd" fd $ I.modifyFd (emBackend mgr) fd mempty evs -- | Asynchronously shuts down the event manager, if running. shutdown :: EventManager -> IO () shutdown mgr = do state <- atomicModifyIORef' (emState mgr) $ \s -> (Dying, s) when (state == Running) $ sendDie (emControl mgr) -- | Asynchronously tell the thread executing the event -- manager loop to exit. release :: EventManager -> IO () release EventManager{..} = do state <- atomicModifyIORef' emState $ \s -> (Releasing, s) when (state == Running) $ sendWakeup emControl finished :: EventManager -> IO Bool finished mgr = (== Finished) `liftM` readIORef (emState mgr) cleanup :: EventManager -> IO () cleanup EventManager{..} = do writeIORef emState Finished void $ tryPutMVar emLock () I.delete emBackend closeControl emControl ------------------------------------------------------------------------ -- Event loop -- | Start handling events. This function loops until told to stop, -- using 'shutdown'. -- -- /Note/: This loop can only be run once per 'EventManager', as it -- closes all of its control resources when it finishes. loop :: EventManager -> IO () loop mgr@EventManager{..} = do void $ takeMVar emLock state <- atomicModifyIORef' emState $ \s -> case s of Created -> (Running, s) Releasing -> (Running, s) _ -> (s, s) case state of Created -> go `onException` cleanup mgr Releasing -> go `onException` cleanup mgr Dying -> cleanup mgr -- While a poll loop is never forked when the event manager is in the -- 'Finished' state, its state could read 'Finished' once the new thread -- actually runs. This is not an error, just an unfortunate race condition -- in Thread.restartPollLoop. See #8235 Finished -> return () _ -> do cleanup mgr error $ "GHC.Event.Manager.loop: state is already " ++ show state where go = do state <- step mgr case state of Running -> yield >> go Releasing -> putMVar emLock () _ -> cleanup mgr -- | To make a step, we first do a non-blocking poll, in case -- there are already events ready to handle. This improves performance -- because we can make an unsafe foreign C call, thereby avoiding -- forcing the current Task to release the Capability and forcing a context switch. -- If the poll fails to find events, we yield, putting the poll loop thread at -- end of the Haskell run queue. When it comes back around, we do one more -- non-blocking poll, in case we get lucky and have ready events. -- If that also returns no events, then we do a blocking poll. step :: EventManager -> IO State step mgr@EventManager{..} = do waitForIO state <- readIORef emState state `seq` return state where waitForIO = do n1 <- I.poll emBackend Nothing (onFdEvent mgr) when (n1 <= 0) $ do yield n2 <- I.poll emBackend Nothing (onFdEvent mgr) when (n2 <= 0) $ do _ <- I.poll emBackend (Just Forever) (onFdEvent mgr) return () ------------------------------------------------------------------------ -- Registering interest in I/O events -- | Register interest in the given events, without waking the event -- manager thread. The 'Bool' return value indicates whether the -- event manager ought to be woken. registerFd_ :: EventManager -> IOCallback -> Fd -> Event -> IO (FdKey, Bool) registerFd_ mgr@(EventManager{..}) cb fd evs = do u <- newUnique emUniqueSource let fd' = fromIntegral fd reg = FdKey fd u !fdd = FdData reg evs cb (modify,ok) <- withMVar (callbackTableVar mgr fd) $ \tbl -> if haveOneShot && emOneShot then do oldFdd <- IT.insertWith (++) fd' [fdd] tbl let evs' = maybe evs (combineEvents evs) oldFdd ok <- I.modifyFdOnce emBackend fd evs' if ok then return (False, True) else IT.reset fd' oldFdd tbl >> return (False, False) else do oldFdd <- IT.insertWith (++) fd' [fdd] tbl let (oldEvs, newEvs) = case oldFdd of Nothing -> (mempty, evs) Just prev -> (eventsOf prev, combineEvents evs prev) modify = oldEvs /= newEvs ok <- if modify then I.modifyFd emBackend fd oldEvs newEvs else return True if ok then return (modify, True) else IT.reset fd' oldFdd tbl >> return (False, False) -- this simulates behavior of old IO manager: -- i.e. just call the callback if the registration fails. when (not ok) (cb reg evs) return (reg,modify) {-# INLINE registerFd_ #-} combineEvents :: Event -> [FdData] -> Event combineEvents ev [fdd] = mappend ev (fdEvents fdd) combineEvents ev fdds = mappend ev (eventsOf fdds) {-# INLINE combineEvents #-} -- | @registerFd mgr cb fd evs@ registers interest in the events @evs@ -- on the file descriptor @fd@. @cb@ is called for each event that -- occurs. Returns a cookie that can be handed to 'unregisterFd'. registerFd :: EventManager -> IOCallback -> Fd -> Event -> IO FdKey registerFd mgr cb fd evs = do (r, wake) <- registerFd_ mgr cb fd evs when wake $ wakeManager mgr return r {-# INLINE registerFd #-} {- Building GHC with parallel IO manager on Mac freezes when compiling the dph libraries in the phase 2. As workaround, we don't use oneshot and we wake up an IO manager on Mac every time when we register an event. For more information, please read: http://hackage.haskell.org/trac/ghc/ticket/7651 -} -- | Wake up the event manager. wakeManager :: EventManager -> IO () #if defined(darwin_HOST_OS) || defined(ios_HOST_OS) wakeManager mgr = sendWakeup (emControl mgr) #elif defined(HAVE_EPOLL) || defined(HAVE_KQUEUE) wakeManager _ = return () #else wakeManager mgr = sendWakeup (emControl mgr) #endif eventsOf :: [FdData] -> Event eventsOf = mconcat . map fdEvents -- | Drop a previous file descriptor registration, without waking the -- event manager thread. The return value indicates whether the event -- manager ought to be woken. unregisterFd_ :: EventManager -> FdKey -> IO Bool unregisterFd_ mgr@(EventManager{..}) (FdKey fd u) = withMVar (callbackTableVar mgr fd) $ \tbl -> do let dropReg = nullToNothing . filter ((/= u) . keyUnique . fdKey) fd' = fromIntegral fd pairEvents prev = do r <- maybe mempty eventsOf `fmap` IT.lookup fd' tbl return (eventsOf prev, r) (oldEvs, newEvs) <- IT.updateWith dropReg fd' tbl >>= maybe (return (mempty, mempty)) pairEvents let modify = oldEvs /= newEvs when modify $ failOnInvalidFile "unregisterFd_" fd $ if haveOneShot && emOneShot && newEvs /= mempty then I.modifyFdOnce emBackend fd newEvs else I.modifyFd emBackend fd oldEvs newEvs return modify -- | Drop a previous file descriptor registration. unregisterFd :: EventManager -> FdKey -> IO () unregisterFd mgr reg = do wake <- unregisterFd_ mgr reg when wake $ wakeManager mgr -- | Close a file descriptor in a race-safe way. closeFd :: EventManager -> (Fd -> IO ()) -> Fd -> IO () closeFd mgr close fd = do fds <- withMVar (callbackTableVar mgr fd) $ \tbl -> do prev <- IT.delete (fromIntegral fd) tbl case prev of Nothing -> close fd >> return [] Just fds -> do let oldEvs = eventsOf fds when (oldEvs /= mempty) $ do _ <- I.modifyFd (emBackend mgr) fd oldEvs mempty wakeManager mgr close fd return fds forM_ fds $ \(FdData reg ev cb) -> cb reg (ev `mappend` evtClose) -- | Close a file descriptor in a race-safe way. -- It assumes the caller will update the callback tables and that the caller -- holds the callback table lock for the fd. It must hold this lock because -- this command executes a backend command on the fd. closeFd_ :: EventManager -> IntTable [FdData] -> Fd -> IO (IO ()) closeFd_ mgr tbl fd = do prev <- IT.delete (fromIntegral fd) tbl case prev of Nothing -> return (return ()) Just fds -> do let oldEvs = eventsOf fds when (oldEvs /= mempty) $ do _ <- I.modifyFd (emBackend mgr) fd oldEvs mempty wakeManager mgr return $ forM_ fds $ \(FdData reg ev cb) -> cb reg (ev `mappend` evtClose) ------------------------------------------------------------------------ -- Utilities -- | Call the callbacks corresponding to the given file descriptor. onFdEvent :: EventManager -> Fd -> Event -> IO () onFdEvent mgr fd evs = if fd == controlReadFd (emControl mgr) || fd == wakeupReadFd (emControl mgr) then handleControlEvent mgr fd evs else if emOneShot mgr then do fdds <- withMVar (callbackTableVar mgr fd) $ \tbl -> IT.delete fd' tbl >>= maybe (return []) (selectCallbacks tbl) forM_ fdds $ \(FdData reg _ cb) -> cb reg evs else do found <- IT.lookup fd' =<< readMVar (callbackTableVar mgr fd) case found of Just cbs -> forM_ cbs $ \(FdData reg ev cb) -> do when (evs `I.eventIs` ev) $ cb reg evs Nothing -> return () where fd' :: Int fd' = fromIntegral fd selectCallbacks :: IntTable [FdData] -> [FdData] -> IO [FdData] selectCallbacks tbl cbs = aux cbs [] [] where -- nothing to rearm. aux [] _ [] = if haveOneShot then return cbs else do _ <- I.modifyFd (emBackend mgr) fd (eventsOf cbs) mempty return cbs -- reinsert and rearm; note that we already have the lock on the -- callback table for this fd, and we deleted above, so we know there -- is no entry in the table for this fd. aux [] fdds saved@(_:_) = do _ <- if haveOneShot then I.modifyFdOnce (emBackend mgr) fd $ eventsOf saved else I.modifyFd (emBackend mgr) fd (eventsOf cbs) $ eventsOf saved _ <- IT.insertWith (\_ _ -> saved) fd' saved tbl return fdds -- continue, saving those callbacks that don't match the event aux (fdd@(FdData _ evs' _) : cbs') fdds saved | evs `I.eventIs` evs' = aux cbs' (fdd:fdds) saved | otherwise = aux cbs' fdds (fdd:saved) nullToNothing :: [a] -> Maybe [a] nullToNothing [] = Nothing nullToNothing xs@(_:_) = Just xs