\begin{code}
-{-# OPTIONS -fno-implicit-prelude #-}
+{-# OPTIONS_GHC -fno-implicit-prelude #-}
-----------------------------------------------------------------------------
-- |
-- Module : GHC.Conc
--
-----------------------------------------------------------------------------
+-- No: #hide, because bits of this module are exposed by the stm package.
+-- However, we don't want this module to be the home location for the
+-- bits it exports, we'd rather have Control.Concurrent and the other
+-- higher level modules be the home. Hence:
+
+-- #not-home
module GHC.Conc
( ThreadId(..)
-- Forking and suchlike
+ , forkIO -- :: IO a -> IO ThreadId
+ , childHandler -- :: Exception -> IO ()
, myThreadId -- :: IO ThreadId
, killThread -- :: ThreadId -> IO ()
, throwTo -- :: ThreadId -> Exception -> IO ()
, pseq -- :: a -> b -> b
, yield -- :: IO ()
, labelThread -- :: ThreadId -> String -> IO ()
- , forkProcessPrim -- :: IO Int
- , forkProcess -- :: IO (Maybe Int)
-- Waiting
, threadDelay -- :: Int -> IO ()
+ , registerDelay -- :: Int -> IO (TVar Bool)
, threadWaitRead -- :: Int -> IO ()
, threadWaitWrite -- :: Int -> IO ()
, isEmptyMVar -- :: MVar a -> IO Bool
, addMVarFinalizer -- :: MVar a -> IO () -> IO ()
- ) where
+ -- TVars
+ , STM -- abstract
+ , atomically -- :: STM a -> IO a
+ , retry -- :: STM a
+ , orElse -- :: STM a -> STM a -> STM a
+ , catchSTM -- :: STM a -> (Exception -> STM a) -> STM a
+ , TVar -- abstract
+ , newTVar -- :: a -> STM (TVar a)
+ , newTVarIO -- :: a -> STM (TVar a)
+ , readTVar -- :: TVar a -> STM a
+ , writeTVar -- :: a -> TVar a -> STM ()
+ , unsafeIOToSTM -- :: IO a -> STM a
+
+#ifdef mingw32_HOST_OS
+ , asyncRead -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
+ , asyncWrite -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
+ , asyncDoProc -- :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
+
+ , asyncReadBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
+ , asyncWriteBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
+#endif
+
+#ifndef mingw32_HOST_OS
+ , ensureIOManagerIsRunning
+#endif
+ ) where
+
+import System.Posix.Types
+import System.Posix.Internals
+import Foreign
+import Foreign.C
+
+#ifndef __HADDOCK__
+import {-# SOURCE #-} GHC.TopHandler ( reportError, reportStackOverflow )
+#endif
import Data.Maybe
import GHC.Base
-import GHC.IOBase ( IO(..), MVar(..), ioException, IOException(..), IOErrorType(..) )
-import GHC.Num ( fromInteger, negate )
+import GHC.IOBase
+import GHC.Num ( Num(..) )
+import GHC.Real ( fromIntegral, quot )
import GHC.Base ( Int(..) )
-import GHC.Exception ( Exception(..), AsyncException(..) )
+import GHC.Exception ( catchException, Exception(..), AsyncException(..) )
import GHC.Pack ( packCString# )
+import GHC.Ptr ( Ptr(..), plusPtr, FunPtr(..) )
+import GHC.STRef
+import Data.Typeable
infixr 0 `par`, `pseq`
\end{code}
%************************************************************************
\begin{code}
-data ThreadId = ThreadId ThreadId#
+data ThreadId = ThreadId ThreadId# deriving( Typeable )
-- ToDo: data ThreadId = ThreadId (Weak ThreadId#)
-- But since ThreadId# is unlifted, the Weak type must use open
-- type variables.
useful when debugging or diagnosing the behaviour of a concurrent
program.
-NOTE: in GHC, if you have a 'ThreadId', you essentially have
+/Note/: in GHC, if you have a 'ThreadId', you essentially have
a pointer to the thread itself. This means the thread itself can\'t be
garbage collected until you drop the 'ThreadId'.
This misfeature will hopefully be corrected at a later date.
+
+/Note/: Hugs does not provide any operations on other threads;
+it defines 'ThreadId' as a synonym for ().
-}
---forkIO has now been hoisted out into the Concurrent library.
+{- |
+This sparks off a new thread to run the 'IO' computation passed as the
+first argument, and returns the 'ThreadId' of the newly created
+thread.
-{- | 'killThread' terminates the given thread (Note: 'killThread' is
-not implemented in Hugs). Any work already done by the thread isn\'t
+The new thread will be a lightweight thread; if you want to use a foreign
+library that uses thread-local storage, use 'forkOS' instead.
+-}
+forkIO :: IO () -> IO ThreadId
+forkIO action = IO $ \ s ->
+ case (fork# action_plus s) of (# s1, id #) -> (# s1, ThreadId id #)
+ where
+ action_plus = catchException action childHandler
+
+childHandler :: Exception -> IO ()
+childHandler err = catchException (real_handler err) childHandler
+
+real_handler :: Exception -> IO ()
+real_handler ex =
+ case ex of
+ -- ignore thread GC and killThread exceptions:
+ BlockedOnDeadMVar -> return ()
+ BlockedIndefinitely -> return ()
+ AsyncException ThreadKilled -> return ()
+
+ -- report all others:
+ AsyncException StackOverflow -> reportStackOverflow
+ other -> reportError other
+
+{- | 'killThread' terminates the given thread (GHC only).
+Any work already done by the thread isn\'t
lost: the computation is suspended until required by another thread.
The memory used by the thread will be garbage collected if it isn\'t
-referenced from anywhere. The 'killThread' function may be defined in
+referenced from anywhere. The 'killThread' function is defined in
terms of 'throwTo':
-> killThread tid = throwTo tid (AsyncException ThreadKilled)
+> killThread tid = throwTo tid (AsyncException ThreadKilled)
+
-}
killThread :: ThreadId -> IO ()
-killThread (ThreadId id) = IO $ \ s ->
- case (killThread# id (AsyncException ThreadKilled) s) of s1 -> (# s1, () #)
+killThread tid = throwTo tid (AsyncException ThreadKilled)
-{- | 'throwTo' raises an arbitrary exception in the target thread.
+{- | 'throwTo' raises an arbitrary exception in the target thread (GHC only).
'throwTo' does not return until the exception has been raised in the
target thread. The calling thread can thus be certain that the target
thread has received the exception. This is a useful property to know
when dealing with race conditions: eg. if there are two threads that
can kill each other, it is guaranteed that only one of the threads
-will get to kill the other. -}
+will get to kill the other.
+
+If the target thread is currently making a foreign call, then the
+exception will not be raised (and hence 'throwTo' will not return)
+until the call has completed. This is the case regardless of whether
+the call is inside a 'block' or not.
+ -}
throwTo :: ThreadId -> Exception -> IO ()
throwTo (ThreadId id) ex = IO $ \ s ->
case (killThread# id ex s) of s1 -> (# s1, () #)
--- | Returns the 'ThreadId' of the calling thread.
+-- | Returns the 'ThreadId' of the calling thread (GHC only).
myThreadId :: IO ThreadId
myThreadId = IO $ \s ->
case (myThreadId# s) of (# s1, id #) -> (# s1, ThreadId id #)
adr = byteArrayContents# ps in
case (labelThread# t adr s) of s1 -> (# s1, () #)
-{- | This function is a replacement for "Posix.forkProcess": This implementation
-/will stop all other Concurrent Haskell threads/ in the (heavyweight) forked copy.
-'forkProcessPrim' returns the pid of the child process to the parent, 0 to the child,
-and a value less than 0 in case of errors. See also: 'forkProcess'.
-
-Without this function, you need excessive and often impractical
-explicit synchronization using the regular Concurrent Haskell constructs to assure
-that only the desired thread is running after the fork().
-
-The stopped threads are /not/ garbage collected! This behaviour may change in
-future releases.
--}
-
-forkProcessPrim :: IO Int
-forkProcessPrim = IO $ \s -> case (forkProcess# s) of (# s1, id #) -> (# s1, (I# id) #)
-
-{- | 'forkProcess' is a wrapper around 'forkProcessPrim' similar to the one found in
-"Posix.forkProcess" which returns a Maybe-type. The child receives @Nothing@, the
-parent @Just (pid::Int)@. In case of an error, an exception is thrown.
--}
-
-forkProcess :: IO (Maybe Int)
-forkProcess = do
- pid <- forkProcessPrim
- case pid of
- -1 -> ioException (IOError Nothing -- stolen from hslibs/posix/PosixUtil
- SystemError
- "forkProcess"
- ""
- Nothing)
- 0 -> return Nothing
- _ -> return (Just pid)
-
-- Nota Bene: 'pseq' used to be 'seq'
-- but 'seq' is now defined in PrelGHC
--
par x y = case (par# x) of { _ -> lazy y }
\end{code}
+
+%************************************************************************
+%* *
+\subsection[stm]{Transactional heap operations}
+%* *
+%************************************************************************
+
+TVars are shared memory locations which support atomic memory
+transactions.
+
+\begin{code}
+newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #)) deriving( Typeable )
+
+unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
+unSTM (STM a) = a
+
+instance Functor STM where
+ fmap f x = x >>= (return . f)
+
+instance Monad STM where
+ {-# INLINE return #-}
+ {-# INLINE (>>) #-}
+ {-# INLINE (>>=) #-}
+ m >> k = thenSTM m k
+ return x = returnSTM x
+ m >>= k = bindSTM m k
+
+bindSTM :: STM a -> (a -> STM b) -> STM b
+bindSTM (STM m) k = STM ( \s ->
+ case m s of
+ (# new_s, a #) -> unSTM (k a) new_s
+ )
+
+thenSTM :: STM a -> STM b -> STM b
+thenSTM (STM m) k = STM ( \s ->
+ case m s of
+ (# new_s, a #) -> unSTM k new_s
+ )
+
+returnSTM :: a -> STM a
+returnSTM x = STM (\s -> (# s, x #))
+
+-- | Unsafely performs IO in the STM monad.
+unsafeIOToSTM :: IO a -> STM a
+unsafeIOToSTM (IO m) = STM m
+
+-- |Perform a series of STM actions atomically.
+atomically :: STM a -> IO a
+atomically (STM m) = IO (\s -> (atomically# m) s )
+
+-- |Retry execution of the current memory transaction because it has seen
+-- values in TVars which mean that it should not continue (e.g. the TVars
+-- represent a shared buffer that is now empty). The implementation may
+-- block the thread until one of the TVars that it has read from has been
+-- udpated.
+retry :: STM a
+retry = STM $ \s# -> retry# s#
+
+-- |Compose two alternative STM actions. If the first action completes without
+-- retrying then it forms the result of the orElse. Otherwise, if the first
+-- action retries, then the second action is tried in its place. If both actions
+-- retry then the orElse as a whole retries.
+orElse :: STM a -> STM a -> STM a
+orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
+
+-- |Exception handling within STM actions.
+catchSTM :: STM a -> (Exception -> STM a) -> STM a
+catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
+
+data TVar a = TVar (TVar# RealWorld a) deriving( Typeable )
+
+instance Eq (TVar a) where
+ (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
+
+-- |Create a new TVar holding a value supplied
+newTVar :: a -> STM (TVar a)
+newTVar val = STM $ \s1# ->
+ case newTVar# val s1# of
+ (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
+
+-- |@IO@ version of 'newTVar'. This is useful for creating top-level
+-- 'TVar's using 'System.IO.Unsafe.unsafePerformIO', because using
+-- 'atomically' inside 'System.IO.Unsafe.unsafePerformIO' isn't
+-- possible.
+newTVarIO :: a -> IO (TVar a)
+newTVarIO val = IO $ \s1# ->
+ case newTVar# val s1# of
+ (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
+
+-- |Return the current value stored in a TVar
+readTVar :: TVar a -> STM a
+readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
+
+-- |Write the supplied value into a TVar
+writeTVar :: TVar a -> a -> STM ()
+writeTVar (TVar tvar#) val = STM $ \s1# ->
+ case writeTVar# tvar# val s1# of
+ s2# -> (# s2#, () #)
+
+\end{code}
+
%************************************************************************
%* *
\subsection[mvars]{M-Structures}
-- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
-- the 'MVar' is left empty.
--
--- If several threads are competing to take the same 'MVar', one is chosen
--- to continue at random when the 'MVar' becomes full.
+-- There are two further important properties of 'takeMVar':
+--
+-- * 'takeMVar' is single-wakeup. That is, if there are multiple
+-- threads blocked in 'takeMVar', and the 'MVar' becomes full,
+-- only one thread will be woken up. The runtime guarantees that
+-- the woken thread completes its 'takeMVar' operation.
+--
+-- * When multiple threads are blocked on an 'MVar', they are
+-- woken up in FIFO order. This is useful for providing
+-- fairness properties of abstractions built using 'MVar's.
+--
takeMVar :: MVar a -> IO a
takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
-- |Put a value into an 'MVar'. If the 'MVar' is currently full,
-- 'putMVar' will wait until it becomes empty.
--
--- If several threads are competing to fill the same 'MVar', one is
--- chosen to continue at random with the 'MVar' becomes empty.
+-- There are two further important properties of 'putMVar':
+--
+-- * 'putMVar' is single-wakeup. That is, if there are multiple
+-- threads blocked in 'putMVar', and the 'MVar' becomes empty,
+-- only one thread will be woken up. The runtime guarantees that
+-- the woken thread completes its 'putMVar' operation.
+--
+-- * When multiple threads are blocked on an 'MVar', they are
+-- woken up in FIFO order. This is useful for providing
+-- fairness properties of abstractions built using 'MVar's.
+--
putMVar :: MVar a -> a -> IO ()
putMVar (MVar mvar#) x = IO $ \ s# ->
case putMVar# mvar# x s# of
case isEmptyMVar# mv# s# of
(# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
--- |Add a finalizer to an 'MVar'. See "Foreign.ForeignPtr" and
+-- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
-- "System.Mem.Weak" for more about finalizers.
addMVarFinalizer :: MVar a -> IO () -> IO ()
addMVarFinalizer (MVar m) finalizer =
%* *
%************************************************************************
-@threadWaitRead@ delays rescheduling of a thread until input on the
-specified file descriptor is available for reading (just like select).
-@threadWaitWrite@ is similar, but for writing on a file descriptor.
-
\begin{code}
--- |The 'threadDelay' operation will cause the current thread to
--- suspend for a given number of microseconds. Note that the resolution
--- used by the Haskell runtime system\'s internal timer together with the
--- fact that the thread may take some time to be rescheduled after the
--- time has expired, means that the accuracy is more like 1\/50 second.
-threadDelay :: Int -> IO ()
+#ifdef mingw32_HOST_OS
+
+-- Note: threadDelay, threadWaitRead and threadWaitWrite aren't really functional
+-- on Win32, but left in there because lib code (still) uses them (the manner
+-- in which they're used doesn't cause problems on a Win32 platform though.)
+
+asyncRead :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
+asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf) =
+ IO $ \s -> case asyncRead# fd isSock len buf s of
+ (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
+
+asyncWrite :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
+asyncWrite (I# fd) (I# isSock) (I# len) (Ptr buf) =
+ IO $ \s -> case asyncWrite# fd isSock len buf s of
+ (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
+
+asyncDoProc :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
+asyncDoProc (FunPtr proc) (Ptr param) =
+ -- the 'length' value is ignored; simplifies implementation of
+ -- the async*# primops to have them all return the same result.
+ IO $ \s -> case asyncDoProc# proc param s of
+ (# s, len#, err# #) -> (# s, I# err# #)
+
+-- to aid the use of these primops by the IO Handle implementation,
+-- provide the following convenience funs:
+
+-- this better be a pinned byte array!
+asyncReadBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
+asyncReadBA fd isSock len off bufB =
+ asyncRead fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
+
+asyncWriteBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
+asyncWriteBA fd isSock len off bufB =
+ asyncWrite fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
+
+#endif
+
+-- -----------------------------------------------------------------------------
+-- Thread IO API
-- | Block the current thread until data is available to read on the
--- given file descriptor.
-threadWaitRead :: Int -> IO ()
+-- given file descriptor (GHC only).
+threadWaitRead :: Fd -> IO ()
+threadWaitRead fd
+#ifndef mingw32_HOST_OS
+ | threaded = waitForReadEvent fd
+#endif
+ | otherwise = IO $ \s ->
+ case fromIntegral fd of { I# fd# ->
+ case waitRead# fd# s of { s -> (# s, () #)
+ }}
-- | Block the current thread until data can be written to the
--- given file descriptor.
-threadWaitWrite :: Int -> IO ()
-
-threadDelay (I# ms) = IO $ \s -> case delay# ms s of s -> (# s, () #)
-threadWaitRead (I# fd) = IO $ \s -> case waitRead# fd s of s -> (# s, () #)
-threadWaitWrite (I# fd) = IO $ \s -> case waitWrite# fd s of s -> (# s, () #)
+-- given file descriptor (GHC only).
+threadWaitWrite :: Fd -> IO ()
+threadWaitWrite fd
+#ifndef mingw32_HOST_OS
+ | threaded = waitForWriteEvent fd
+#endif
+ | otherwise = IO $ \s ->
+ case fromIntegral fd of { I# fd# ->
+ case waitWrite# fd# s of { s -> (# s, () #)
+ }}
+
+-- | Suspends the current thread for a given number of microseconds
+-- (GHC only).
+--
+-- Note that the resolution used by the Haskell runtime system's
+-- internal timer is 1\/50 second, and 'threadDelay' will round its
+-- argument up to the nearest multiple of this resolution.
+--
+-- 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 time
+#ifndef mingw32_HOST_OS
+ | threaded = waitForDelayEvent time
+#else
+ | threaded = c_Sleep (fromIntegral (time `quot` 1000))
+#endif
+ | otherwise = IO $ \s ->
+ case fromIntegral time of { I# time# ->
+ case delay# time# s of { s -> (# s, () #)
+ }}
+
+registerDelay usecs
+#ifndef mingw32_HOST_OS
+ | threaded = waitForDelayEventSTM usecs
+ | otherwise = error "registerDelay: requires -threaded"
+#else
+ = error "registerDelay: not currently supported on Windows"
+#endif
+
+-- On Windows, we just make a safe call to 'Sleep' to implement threadDelay.
+#ifdef mingw32_HOST_OS
+foreign import stdcall safe "Sleep" c_Sleep :: CInt -> IO ()
+#endif
+
+foreign import ccall unsafe "rtsSupportsBoundThreads" threaded :: Bool
+
+-- ----------------------------------------------------------------------------
+-- Threaded RTS implementation of threadWaitRead, threadWaitWrite, threadDelay
+
+-- In the threaded RTS, we employ a single IO Manager thread to wait
+-- for all outstanding IO requests (threadWaitRead,threadWaitWrite)
+-- and delays (threadDelay).
+--
+-- We can do this because in the threaded RTS the IO Manager can make
+-- a non-blocking call to select(), so we don't have to do select() in
+-- the scheduler as we have to in the non-threaded RTS. We get performance
+-- benefits from doing it this way, because we only have to restart the select()
+-- when a new request arrives, rather than doing one select() each time
+-- around the scheduler loop. Furthermore, the scheduler can be simplified
+-- by not having to check for completed IO requests.
+
+-- Issues, possible problems:
+--
+-- - we might want bound threads to just do the blocking
+-- operation rather than communicating with the IO manager
+-- thread. This would prevent simgle-threaded programs which do
+-- IO from requiring multiple OS threads. However, it would also
+-- prevent bound threads waiting on IO from being killed or sent
+-- exceptions.
+--
+-- - Apprently exec() doesn't work on Linux in a multithreaded program.
+-- I couldn't repeat this.
+--
+-- - How do we handle signal delivery in the multithreaded RTS?
+--
+-- - forkProcess will kill the IO manager thread. Let's just
+-- hope we don't need to do any blocking IO between fork & exec.
+
+#ifndef mingw32_HOST_OS
+
+data IOReq
+ = Read {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
+ | Write {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
+
+data DelayReq
+ = Delay {-# UNPACK #-} !Int {-# UNPACK #-} !(MVar ())
+ | DelaySTM {-# UNPACK #-} !Int {-# UNPACK #-} !(TVar Bool)
+
+pendingEvents :: IORef [IOReq]
+pendingDelays :: IORef [DelayReq]
+ -- could use a strict list or array here
+{-# NOINLINE pendingEvents #-}
+{-# NOINLINE pendingDelays #-}
+(pendingEvents,pendingDelays) = unsafePerformIO $ do
+ startIOManagerThread
+ reqs <- newIORef []
+ dels <- newIORef []
+ return (reqs, dels)
+ -- the first time we schedule an IO request, the service thread
+ -- will be created (cool, huh?)
+
+ensureIOManagerIsRunning :: IO ()
+ensureIOManagerIsRunning
+ | threaded = seq pendingEvents $ return ()
+ | otherwise = return ()
+
+startIOManagerThread :: IO ()
+startIOManagerThread = do
+ allocaArray 2 $ \fds -> do
+ throwErrnoIfMinus1 "startIOManagerThread" (c_pipe fds)
+ rd_end <- peekElemOff fds 0
+ wr_end <- peekElemOff fds 1
+ writeIORef stick (fromIntegral wr_end)
+ c_setIOManagerPipe wr_end
+ forkIO $ do
+ allocaBytes sizeofFdSet $ \readfds -> do
+ allocaBytes sizeofFdSet $ \writefds -> do
+ allocaBytes sizeofTimeVal $ \timeval -> do
+ service_loop (fromIntegral rd_end) readfds writefds timeval [] []
+ return ()
+
+service_loop
+ :: Fd -- listen to this for wakeup calls
+ -> Ptr CFdSet
+ -> Ptr CFdSet
+ -> Ptr CTimeVal
+ -> [IOReq]
+ -> [DelayReq]
+ -> IO ()
+service_loop wakeup readfds writefds ptimeval old_reqs old_delays = do
+
+ -- pick up new IO requests
+ new_reqs <- atomicModifyIORef pendingEvents (\a -> ([],a))
+ let reqs = new_reqs ++ old_reqs
+
+ -- pick up new delay requests
+ new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
+ let delays = foldr insertDelay old_delays new_delays
+
+ -- build the FDSets for select()
+ fdZero readfds
+ fdZero writefds
+ fdSet wakeup readfds
+ maxfd <- buildFdSets 0 readfds writefds reqs
+
+ -- perform the select()
+ let do_select delays = do
+ -- check the current time and wake up any thread in
+ -- threadDelay whose timeout has expired. Also find the
+ -- timeout value for the select() call.
+ now <- getTicksOfDay
+ (delays', timeout) <- getDelay now ptimeval delays
+
+ res <- c_select ((max wakeup maxfd)+1) readfds writefds
+ nullPtr timeout
+ if (res == -1)
+ then do
+ err <- getErrno
+ if err == eINTR
+ then do_select delays'
+ else return (res,delays')
+ else
+ return (res,delays')
+
+ (res,delays') <- do_select delays
+ -- ToDo: check result
+
+ b <- fdIsSet wakeup readfds
+ if b == 0
+ then return ()
+ else alloca $ \p -> do
+ c_read (fromIntegral wakeup) p 1; return ()
+ s <- peek p
+ if (s == 0xff)
+ then return ()
+ else do handler_tbl <- peek handlers
+ sp <- peekElemOff handler_tbl (fromIntegral s)
+ forkIO (do io <- deRefStablePtr sp; io)
+ return ()
+
+ takeMVar prodding
+ putMVar prodding False
+
+ reqs' <- completeRequests reqs readfds writefds []
+ service_loop wakeup readfds writefds ptimeval reqs' delays'
+
+stick :: IORef Fd
+{-# NOINLINE stick #-}
+stick = unsafePerformIO (newIORef 0)
+
+prodding :: MVar Bool
+{-# NOINLINE prodding #-}
+prodding = unsafePerformIO (newMVar False)
+
+prodServiceThread :: IO ()
+prodServiceThread = do
+ b <- takeMVar prodding
+ if (not b)
+ then do fd <- readIORef stick
+ with 0xff $ \pbuf -> do c_write (fromIntegral fd) pbuf 1; return ()
+ else return ()
+ putMVar prodding True
+
+foreign import ccall "&signal_handlers" handlers :: Ptr (Ptr (StablePtr (IO ())))
+
+foreign import ccall "setIOManagerPipe"
+ c_setIOManagerPipe :: CInt -> IO ()
+
+-- -----------------------------------------------------------------------------
+-- IO requests
+
+buildFdSets maxfd readfds writefds [] = return maxfd
+buildFdSets maxfd readfds writefds (Read fd m : reqs)
+ | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
+ | otherwise = do
+ fdSet fd readfds
+ buildFdSets (max maxfd fd) readfds writefds reqs
+buildFdSets maxfd readfds writefds (Write fd m : reqs)
+ | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
+ | otherwise = do
+ fdSet fd writefds
+ buildFdSets (max maxfd fd) readfds writefds reqs
+
+completeRequests [] _ _ reqs' = return reqs'
+completeRequests (Read fd m : reqs) readfds writefds reqs' = do
+ b <- fdIsSet fd readfds
+ if b /= 0
+ then do putMVar m (); completeRequests reqs readfds writefds reqs'
+ else completeRequests reqs readfds writefds (Read fd m : reqs')
+completeRequests (Write fd m : reqs) readfds writefds reqs' = do
+ b <- fdIsSet fd writefds
+ if b /= 0
+ then do putMVar m (); completeRequests reqs readfds writefds reqs'
+ else completeRequests reqs readfds writefds (Write fd m : reqs')
+
+waitForReadEvent :: Fd -> IO ()
+waitForReadEvent fd = do
+ m <- newEmptyMVar
+ atomicModifyIORef pendingEvents (\xs -> (Read fd m : xs, ()))
+ prodServiceThread
+ takeMVar m
+
+waitForWriteEvent :: Fd -> IO ()
+waitForWriteEvent fd = do
+ m <- newEmptyMVar
+ atomicModifyIORef pendingEvents (\xs -> (Write fd m : xs, ()))
+ prodServiceThread
+ takeMVar m
+
+-- XXX: move into GHC.IOBase from Data.IORef?
+atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
+atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
+
+-- -----------------------------------------------------------------------------
+-- Delays
+
+waitForDelayEvent :: Int -> IO ()
+waitForDelayEvent usecs = do
+ m <- newEmptyMVar
+ now <- getTicksOfDay
+ let target = now + usecs `quot` tick_usecs
+ atomicModifyIORef pendingDelays (\xs -> (Delay target m : xs, ()))
+ prodServiceThread
+ takeMVar m
+
+-- Delays for use in STM
+waitForDelayEventSTM :: Int -> IO (TVar Bool)
+waitForDelayEventSTM usecs = do
+ t <- atomically $ newTVar False
+ now <- getTicksOfDay
+ let target = now + usecs `quot` tick_usecs
+ atomicModifyIORef pendingDelays (\xs -> (DelaySTM target t : xs, ()))
+ prodServiceThread
+ return t
+
+-- Walk the queue of pending delays, waking up any that have passed
+-- and return the smallest delay to wait for. The queue of pending
+-- delays is kept ordered.
+getDelay :: Ticks -> Ptr CTimeVal -> [DelayReq] -> IO ([DelayReq], Ptr CTimeVal)
+getDelay now ptimeval [] = return ([],nullPtr)
+getDelay now ptimeval all@(d : rest)
+ = case d of
+ Delay time m | now >= time -> do
+ putMVar m ()
+ getDelay now ptimeval rest
+ DelaySTM time t | now >= time -> do
+ atomically $ writeTVar t True
+ getDelay now ptimeval rest
+ _otherwise -> do
+ setTimevalTicks ptimeval (delayTime d - now)
+ return (all,ptimeval)
+
+insertDelay :: DelayReq -> [DelayReq] -> [DelayReq]
+insertDelay d [] = [d]
+insertDelay d1 ds@(d2 : rest)
+ | delayTime d1 <= delayTime d2 = d1 : ds
+ | otherwise = d2 : insertDelay d1 rest
+
+delayTime (Delay t _) = t
+delayTime (DelaySTM t _) = t
+
+type Ticks = Int
+tick_freq = 50 :: Ticks -- accuracy of threadDelay (ticks per sec)
+tick_usecs = 1000000 `quot` tick_freq :: Int
+
+newtype CTimeVal = CTimeVal ()
+
+foreign import ccall unsafe "sizeofTimeVal"
+ sizeofTimeVal :: Int
+
+foreign import ccall unsafe "getTicksOfDay"
+ getTicksOfDay :: IO Ticks
+
+foreign import ccall unsafe "setTimevalTicks"
+ setTimevalTicks :: Ptr CTimeVal -> Ticks -> IO ()
+
+-- ----------------------------------------------------------------------------
+-- select() interface
+
+-- ToDo: move to System.Posix.Internals?
+
+newtype CFdSet = CFdSet ()
+
+foreign import ccall safe "select"
+ c_select :: Fd -> Ptr CFdSet -> Ptr CFdSet -> Ptr CFdSet -> Ptr CTimeVal
+ -> IO CInt
+
+foreign import ccall unsafe "hsFD_SETSIZE"
+ fD_SETSIZE :: Fd
+
+foreign import ccall unsafe "hsFD_CLR"
+ fdClr :: Fd -> Ptr CFdSet -> IO ()
+
+foreign import ccall unsafe "hsFD_ISSET"
+ fdIsSet :: Fd -> Ptr CFdSet -> IO CInt
+
+foreign import ccall unsafe "hsFD_SET"
+ fdSet :: Fd -> Ptr CFdSet -> IO ()
+
+foreign import ccall unsafe "hsFD_ZERO"
+ fdZero :: Ptr CFdSet -> IO ()
+
+foreign import ccall unsafe "sizeof_fd_set"
+ sizeofFdSet :: Int
+
+#endif
\end{code}
projects / haskell-directory.git / blobdiff