{-# LANGUAGE Trustworthy #-} {-# LANGUAGE BangPatterns, NoImplicitPrelude #-} module GHC.Event.Thread ( getSystemEventManager , getSystemTimerManager , ensureIOManagerIsRunning , ioManagerCapabilitiesChanged , threadWaitRead , threadWaitWrite , threadWaitReadSTM , threadWaitWriteSTM , closeFdWith , threadDelay , registerDelay ) where import Control.Exception (finally) import Control.Monad (forM, forM_, sequence_, zipWithM, when) import Data.IORef (IORef, newIORef, readIORef, writeIORef) import Data.List (zipWith3) import Data.Maybe (Maybe(..)) import Data.Tuple (snd) import Foreign.C.Error (eBADF, errnoToIOError) import Foreign.Ptr (Ptr) import GHC.Base import GHC.Conc.Sync (TVar, ThreadId, ThreadStatus(..), atomically, forkIO, labelThread, modifyMVar_, withMVar, newTVar, sharedCAF, getNumCapabilities, threadCapability, myThreadId, forkOn, threadStatus, writeTVar, newTVarIO, readTVar, retry,throwSTM,STM) import GHC.IO (mask_, onException) import GHC.IO.Exception (ioError) import GHC.IOArray (IOArray, newIOArray, readIOArray, writeIOArray, boundsIOArray) import GHC.MVar (MVar, newEmptyMVar, newMVar, putMVar, takeMVar) import GHC.Event.Internal (eventIs, evtClose) import GHC.Event.Manager (Event, EventManager, evtRead, evtWrite, loop, new, registerFd, unregisterFd_) import qualified GHC.Event.Manager as M import qualified GHC.Event.TimerManager as TM import GHC.Num ((-), (+)) import System.IO.Unsafe (unsafePerformIO) import System.Posix.Types (Fd) -- | Suspends the current thread for a given number of microseconds -- (GHC only). -- -- There is no guarantee that the thread will be rescheduled promptly -- when the delay has expired, but the thread will never continue to -- run /earlier/ than specified. threadDelay :: Int -> IO () threadDelay usecs = mask_ $ do mgr <- getSystemTimerManager m <- newEmptyMVar reg <- TM.registerTimeout mgr usecs (putMVar m ()) takeMVar m `onException` TM.unregisterTimeout mgr reg -- | Set the value of returned TVar to True after a given number of -- microseconds. The caveats associated with threadDelay also apply. -- registerDelay :: Int -> IO (TVar Bool) registerDelay usecs = do t <- atomically $ newTVar False mgr <- getSystemTimerManager _ <- TM.registerTimeout mgr usecs . atomically $ writeTVar t True return t -- | Block the current thread until data is available to read from the -- given file descriptor. -- -- This will throw an 'IOError' if the file descriptor was closed -- while this thread was blocked. To safely close a file descriptor -- that has been used with 'threadWaitRead', use 'closeFdWith'. threadWaitRead :: Fd -> IO () threadWaitRead = threadWait evtRead {-# INLINE threadWaitRead #-} -- | Block the current thread until the given file descriptor can -- accept data to write. -- -- This will throw an 'IOError' if the file descriptor was closed -- while this thread was blocked. To safely close a file descriptor -- that has been used with 'threadWaitWrite', use 'closeFdWith'. threadWaitWrite :: Fd -> IO () threadWaitWrite = threadWait evtWrite {-# INLINE threadWaitWrite #-} -- | Close a file descriptor in a concurrency-safe way. -- -- Any threads that are blocked on the file descriptor via -- 'threadWaitRead' or 'threadWaitWrite' will be unblocked by having -- IO exceptions thrown. closeFdWith :: (Fd -> IO ()) -- ^ Action that performs the close. -> Fd -- ^ File descriptor to close. -> IO () closeFdWith close fd = do eventManagerArray <- readIORef eventManager let (low, high) = boundsIOArray eventManagerArray mgrs <- forM [low..high] $ \i -> do Just (_,!mgr) <- readIOArray eventManagerArray i return mgr mask_ $ do tables <- forM mgrs $ \mgr -> takeMVar $ M.callbackTableVar mgr fd cbApps <- zipWithM (\mgr table -> M.closeFd_ mgr table fd) mgrs tables close fd `finally` sequence_ (zipWith3 finish mgrs tables cbApps) where finish mgr table cbApp = putMVar (M.callbackTableVar mgr fd) table >> cbApp threadWait :: Event -> Fd -> IO () threadWait evt fd = mask_ $ do m <- newEmptyMVar mgr <- getSystemEventManager_ reg <- registerFd mgr (\_ e -> putMVar m e) fd evt evt' <- takeMVar m `onException` unregisterFd_ mgr reg if evt' `eventIs` evtClose then ioError $ errnoToIOError "threadWait" eBADF Nothing Nothing else return () threadWaitSTM :: Event -> Fd -> IO (STM (), IO ()) threadWaitSTM evt fd = mask_ $ do m <- newTVarIO Nothing mgr <- getSystemEventManager_ reg <- registerFd mgr (\_ e -> atomically (writeTVar m (Just e))) fd evt let waitAction = do mevt <- readTVar m case mevt of Nothing -> retry Just evt' -> if evt' `eventIs` evtClose then throwSTM $ errnoToIOError "threadWaitSTM" eBADF Nothing Nothing else return () return (waitAction, unregisterFd_ mgr reg >> return ()) -- | Allows a thread to use an STM action to wait for a file descriptor to be readable. -- The STM action will retry until the file descriptor has data ready. -- The second element of the return value pair is an IO action that can be used -- to deregister interest in the file descriptor. -- -- The STM action will throw an 'IOError' if the file descriptor was closed -- while the STM action is being executed. To safely close a file descriptor -- that has been used with 'threadWaitReadSTM', use 'closeFdWith'. threadWaitReadSTM :: Fd -> IO (STM (), IO ()) threadWaitReadSTM = threadWaitSTM evtRead {-# INLINE threadWaitReadSTM #-} -- | Allows a thread to use an STM action to wait until a file descriptor can accept a write. -- The STM action will retry while the file until the given file descriptor can accept a write. -- The second element of the return value pair is an IO action that can be used to deregister -- interest in the file descriptor. -- -- The STM action will throw an 'IOError' if the file descriptor was closed -- while the STM action is being executed. To safely close a file descriptor -- that has been used with 'threadWaitWriteSTM', use 'closeFdWith'. threadWaitWriteSTM :: Fd -> IO (STM (), IO ()) threadWaitWriteSTM = threadWaitSTM evtWrite {-# INLINE threadWaitWriteSTM #-} -- | Retrieve the system event manager for the capability on which the -- calling thread is running. -- -- This function always returns 'Just' the current thread's event manager -- when using the threaded RTS and 'Nothing' otherwise. getSystemEventManager :: IO (Maybe EventManager) getSystemEventManager = do t <- myThreadId (cap, _) <- threadCapability t eventManagerArray <- readIORef eventManager mmgr <- readIOArray eventManagerArray cap return $ fmap snd mmgr getSystemEventManager_ :: IO EventManager getSystemEventManager_ = do Just mgr <- getSystemEventManager return mgr {-# INLINE getSystemEventManager_ #-} foreign import ccall unsafe "getOrSetSystemEventThreadEventManagerStore" getOrSetSystemEventThreadEventManagerStore :: Ptr a -> IO (Ptr a) eventManager :: IORef (IOArray Int (Maybe (ThreadId, EventManager))) eventManager = unsafePerformIO $ do numCaps <- getNumCapabilities eventManagerArray <- newIOArray (0, numCaps - 1) Nothing em <- newIORef eventManagerArray sharedCAF em getOrSetSystemEventThreadEventManagerStore {-# NOINLINE eventManager #-} numEnabledEventManagers :: IORef Int numEnabledEventManagers = unsafePerformIO $ do newIORef 0 {-# NOINLINE numEnabledEventManagers #-} foreign import ccall unsafe "getOrSetSystemEventThreadIOManagerThreadStore" getOrSetSystemEventThreadIOManagerThreadStore :: Ptr a -> IO (Ptr a) -- | The ioManagerLock protects the 'eventManager' value: -- Only one thread at a time can start or shutdown event managers. {-# NOINLINE ioManagerLock #-} ioManagerLock :: MVar () ioManagerLock = unsafePerformIO $ do m <- newMVar () sharedCAF m getOrSetSystemEventThreadIOManagerThreadStore getSystemTimerManager :: IO TM.TimerManager getSystemTimerManager = do Just mgr <- readIORef timerManager return mgr foreign import ccall unsafe "getOrSetSystemTimerThreadEventManagerStore" getOrSetSystemTimerThreadEventManagerStore :: Ptr a -> IO (Ptr a) timerManager :: IORef (Maybe TM.TimerManager) timerManager = unsafePerformIO $ do em <- newIORef Nothing sharedCAF em getOrSetSystemTimerThreadEventManagerStore {-# NOINLINE timerManager #-} foreign import ccall unsafe "getOrSetSystemTimerThreadIOManagerThreadStore" getOrSetSystemTimerThreadIOManagerThreadStore :: Ptr a -> IO (Ptr a) {-# NOINLINE timerManagerThreadVar #-} timerManagerThreadVar :: MVar (Maybe ThreadId) timerManagerThreadVar = unsafePerformIO $ do m <- newMVar Nothing sharedCAF m getOrSetSystemTimerThreadIOManagerThreadStore ensureIOManagerIsRunning :: IO () ensureIOManagerIsRunning | not threaded = return () | otherwise = do startIOManagerThreads startTimerManagerThread startIOManagerThreads :: IO () startIOManagerThreads = withMVar ioManagerLock $ \_ -> do eventManagerArray <- readIORef eventManager let (_, high) = boundsIOArray eventManagerArray forM_ [0..high] (startIOManagerThread eventManagerArray) writeIORef numEnabledEventManagers (high+1) restartPollLoop :: EventManager -> Int -> IO ThreadId restartPollLoop mgr i = do M.release mgr !t <- forkOn i $ loop mgr labelThread t "IOManager" return t startIOManagerThread :: IOArray Int (Maybe (ThreadId, EventManager)) -> Int -> IO () startIOManagerThread eventManagerArray i = do let create = do !mgr <- new True !t <- forkOn i $ loop mgr labelThread t "IOManager" writeIOArray eventManagerArray i (Just (t,mgr)) old <- readIOArray eventManagerArray i case old of Nothing -> create Just (t,em) -> do s <- threadStatus t case s of ThreadFinished -> create ThreadDied -> do -- Sanity check: if the thread has died, there is a chance -- that event manager is still alive. This could happend during -- the fork, for example. In this case we should clean up -- open pipes and everything else related to the event manager. -- See #4449 M.cleanup em create _other -> return () startTimerManagerThread :: IO () startTimerManagerThread = modifyMVar_ timerManagerThreadVar $ \old -> do let create = do !mgr <- TM.new writeIORef timerManager $ Just mgr !t <- forkIO $ TM.loop mgr `finally` shutdownManagers labelThread t "TimerManager" return $ Just t case old of Nothing -> create st@(Just t) -> do s <- threadStatus t case s of ThreadFinished -> create ThreadDied -> do -- Sanity check: if the thread has died, there is a chance -- that event manager is still alive. This could happend during -- the fork, for example. In this case we should clean up -- open pipes and everything else related to the event manager. -- See #4449 mem <- readIORef timerManager _ <- case mem of Nothing -> return () Just em -> TM.cleanup em create _other -> return st shutdownManagers :: IO () shutdownManagers = withMVar ioManagerLock $ \_ -> do eventManagerArray <- readIORef eventManager let (_, high) = boundsIOArray eventManagerArray forM_ [0..high] $ \i -> do mmgr <- readIOArray eventManagerArray i case mmgr of Nothing -> return () Just (_,mgr) -> M.shutdown mgr foreign import ccall unsafe "rtsSupportsBoundThreads" threaded :: Bool ioManagerCapabilitiesChanged :: IO () ioManagerCapabilitiesChanged = do withMVar ioManagerLock $ \_ -> do new_n_caps <- getNumCapabilities numEnabled <- readIORef numEnabledEventManagers writeIORef numEnabledEventManagers new_n_caps eventManagerArray <- readIORef eventManager let (_, high) = boundsIOArray eventManagerArray let old_n_caps = high + 1 if new_n_caps > old_n_caps then do new_eventManagerArray <- newIOArray (0, new_n_caps - 1) Nothing -- copy the existing values into the new array: forM_ [0..high] $ \i -> do Just (tid,mgr) <- readIOArray eventManagerArray i if i < numEnabled then writeIOArray new_eventManagerArray i (Just (tid,mgr)) else do tid' <- restartPollLoop mgr i writeIOArray new_eventManagerArray i (Just (tid',mgr)) -- create new IO managers for the new caps: forM_ [old_n_caps..new_n_caps-1] $ startIOManagerThread new_eventManagerArray -- update the event manager array reference: writeIORef eventManager new_eventManagerArray else when (new_n_caps > numEnabled) $ forM_ [numEnabled..new_n_caps-1] $ \i -> do Just (_,mgr) <- readIOArray eventManagerArray i tid <- restartPollLoop mgr i writeIOArray eventManagerArray i (Just (tid,mgr))