2 {-# OPTIONS_GHC -fno-implicit-prelude #-}
3 -----------------------------------------------------------------------------
6 -- Copyright : (c) The University of Glasgow, 1994-2002
7 -- License : see libraries/base/LICENSE
9 -- Maintainer : cvs-ghc@haskell.org
10 -- Stability : internal
11 -- Portability : non-portable (GHC extensions)
13 -- Basic concurrency stuff.
15 -----------------------------------------------------------------------------
17 -- No: #hide, because bits of this module are exposed by the stm package.
18 -- However, we don't want this module to be the home location for the
19 -- bits it exports, we'd rather have Control.Concurrent and the other
20 -- higher level modules be the home. Hence:
26 -- Forking and suchlike
27 , myThreadId -- :: IO ThreadId
28 , killThread -- :: ThreadId -> IO ()
29 , throwTo -- :: ThreadId -> Exception -> IO ()
30 , par -- :: a -> b -> b
31 , pseq -- :: a -> b -> b
33 , labelThread -- :: ThreadId -> String -> IO ()
36 , threadDelay -- :: Int -> IO ()
37 , threadWaitRead -- :: Int -> IO ()
38 , threadWaitWrite -- :: Int -> IO ()
42 , newMVar -- :: a -> IO (MVar a)
43 , newEmptyMVar -- :: IO (MVar a)
44 , takeMVar -- :: MVar a -> IO a
45 , putMVar -- :: MVar a -> a -> IO ()
46 , tryTakeMVar -- :: MVar a -> IO (Maybe a)
47 , tryPutMVar -- :: MVar a -> a -> IO Bool
48 , isEmptyMVar -- :: MVar a -> IO Bool
49 , addMVarFinalizer -- :: MVar a -> IO () -> IO ()
53 , atomically -- :: STM a -> IO a
55 , orElse -- :: STM a -> STM a -> STM a
56 , catchSTM -- :: STM a -> (Exception -> STM a) -> STM a
58 , newTVar -- :: a -> STM (TVar a)
59 , readTVar -- :: TVar a -> STM a
60 , writeTVar -- :: a -> TVar a -> STM ()
61 , unsafeIOToSTM -- :: IO a -> STM a
63 #ifdef mingw32_HOST_OS
64 , asyncRead -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
65 , asyncWrite -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
66 , asyncDoProc -- :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
68 , asyncReadBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
69 , asyncWriteBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
72 #ifndef mingw32_HOST_OS
73 , ensureIOManagerIsRunning
77 import System.Posix.Types
78 import System.Posix.Internals
86 import GHC.Num ( Num(..) )
87 import GHC.Real ( fromIntegral, quot )
88 import GHC.Base ( Int(..) )
89 import GHC.Exception ( Exception(..), AsyncException(..) )
90 import GHC.Pack ( packCString# )
91 import GHC.Ptr ( Ptr(..), plusPtr, FunPtr(..) )
95 infixr 0 `par`, `pseq`
98 %************************************************************************
100 \subsection{@ThreadId@, @par@, and @fork@}
102 %************************************************************************
105 data ThreadId = ThreadId ThreadId# deriving( Typeable )
106 -- ToDo: data ThreadId = ThreadId (Weak ThreadId#)
107 -- But since ThreadId# is unlifted, the Weak type must use open
110 A 'ThreadId' is an abstract type representing a handle to a thread.
111 'ThreadId' is an instance of 'Eq', 'Ord' and 'Show', where
112 the 'Ord' instance implements an arbitrary total ordering over
113 'ThreadId's. The 'Show' instance lets you convert an arbitrary-valued
114 'ThreadId' to string form; showing a 'ThreadId' value is occasionally
115 useful when debugging or diagnosing the behaviour of a concurrent
118 /Note/: in GHC, if you have a 'ThreadId', you essentially have
119 a pointer to the thread itself. This means the thread itself can\'t be
120 garbage collected until you drop the 'ThreadId'.
121 This misfeature will hopefully be corrected at a later date.
123 /Note/: Hugs does not provide any operations on other threads;
124 it defines 'ThreadId' as a synonym for ().
127 --forkIO has now been hoisted out into the Concurrent library.
129 {- | 'killThread' terminates the given thread (GHC only).
130 Any work already done by the thread isn\'t
131 lost: the computation is suspended until required by another thread.
132 The memory used by the thread will be garbage collected if it isn\'t
133 referenced from anywhere. The 'killThread' function is defined in
136 > killThread tid = throwTo tid (AsyncException ThreadKilled)
139 killThread :: ThreadId -> IO ()
140 killThread tid = throwTo tid (AsyncException ThreadKilled)
142 {- | 'throwTo' raises an arbitrary exception in the target thread (GHC only).
144 'throwTo' does not return until the exception has been raised in the
145 target thread. The calling thread can thus be certain that the target
146 thread has received the exception. This is a useful property to know
147 when dealing with race conditions: eg. if there are two threads that
148 can kill each other, it is guaranteed that only one of the threads
149 will get to kill the other.
151 If the target thread is currently making a foreign call, then the
152 exception will not be raised (and hence 'throwTo' will not return)
153 until the call has completed. This is the case regardless of whether
154 the call is inside a 'block' or not.
156 throwTo :: ThreadId -> Exception -> IO ()
157 throwTo (ThreadId id) ex = IO $ \ s ->
158 case (killThread# id ex s) of s1 -> (# s1, () #)
160 -- | Returns the 'ThreadId' of the calling thread (GHC only).
161 myThreadId :: IO ThreadId
162 myThreadId = IO $ \s ->
163 case (myThreadId# s) of (# s1, id #) -> (# s1, ThreadId id #)
166 -- |The 'yield' action allows (forces, in a co-operative multitasking
167 -- implementation) a context-switch to any other currently runnable
168 -- threads (if any), and is occasionally useful when implementing
169 -- concurrency abstractions.
172 case (yield# s) of s1 -> (# s1, () #)
174 {- | 'labelThread' stores a string as identifier for this thread if
175 you built a RTS with debugging support. This identifier will be used in
176 the debugging output to make distinction of different threads easier
177 (otherwise you only have the thread state object\'s address in the heap).
179 Other applications like the graphical Concurrent Haskell Debugger
180 (<http://www.informatik.uni-kiel.de/~fhu/chd/>) may choose to overload
181 'labelThread' for their purposes as well.
184 labelThread :: ThreadId -> String -> IO ()
185 labelThread (ThreadId t) str = IO $ \ s ->
186 let ps = packCString# str
187 adr = byteArrayContents# ps in
188 case (labelThread# t adr s) of s1 -> (# s1, () #)
190 -- Nota Bene: 'pseq' used to be 'seq'
191 -- but 'seq' is now defined in PrelGHC
193 -- "pseq" is defined a bit weirdly (see below)
195 -- The reason for the strange "lazy" call is that
196 -- it fools the compiler into thinking that pseq and par are non-strict in
197 -- their second argument (even if it inlines pseq at the call site).
198 -- If it thinks pseq is strict in "y", then it often evaluates
199 -- "y" before "x", which is totally wrong.
203 pseq x y = x `seq` lazy y
207 par x y = case (par# x) of { _ -> lazy y }
211 %************************************************************************
213 \subsection[stm]{Transactional heap operations}
215 %************************************************************************
217 TVars are shared memory locations which support atomic memory
221 newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #)) deriving( Typeable )
223 unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
226 instance Functor STM where
227 fmap f x = x >>= (return . f)
229 instance Monad STM where
230 {-# INLINE return #-}
234 return x = returnSTM x
235 m >>= k = bindSTM m k
237 bindSTM :: STM a -> (a -> STM b) -> STM b
238 bindSTM (STM m) k = STM ( \s ->
240 (# new_s, a #) -> unSTM (k a) new_s
243 thenSTM :: STM a -> STM b -> STM b
244 thenSTM (STM m) k = STM ( \s ->
246 (# new_s, a #) -> unSTM k new_s
249 returnSTM :: a -> STM a
250 returnSTM x = STM (\s -> (# s, x #))
252 -- | Unsafely performs IO in the STM monad.
253 unsafeIOToSTM :: IO a -> STM a
254 unsafeIOToSTM (IO m) = STM m
256 -- |Perform a series of STM actions atomically.
257 atomically :: STM a -> IO a
258 atomically (STM m) = IO (\s -> (atomically# m) s )
260 -- |Retry execution of the current memory transaction because it has seen
261 -- values in TVars which mean that it should not continue (e.g. the TVars
262 -- represent a shared buffer that is now empty). The implementation may
263 -- block the thread until one of the TVars that it has read from has been
266 retry = STM $ \s# -> retry# s#
268 -- |Compose two alternative STM actions. If the first action completes without
269 -- retrying then it forms the result of the orElse. Otherwise, if the first
270 -- action retries, then the second action is tried in its place. If both actions
271 -- retry then the orElse as a whole retries.
272 orElse :: STM a -> STM a -> STM a
273 orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
275 -- |Exception handling within STM actions.
276 catchSTM :: STM a -> (Exception -> STM a) -> STM a
277 catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
279 data TVar a = TVar (TVar# RealWorld a) deriving( Typeable )
281 instance Eq (TVar a) where
282 (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
284 -- |Create a new TVar holding a value supplied
285 newTVar :: a -> STM (TVar a)
286 newTVar val = STM $ \s1# ->
287 case newTVar# val s1# of
288 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
290 -- |Return the current value stored in a TVar
291 readTVar :: TVar a -> STM a
292 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
294 -- |Write the supplied value into a TVar
295 writeTVar :: TVar a -> a -> STM ()
296 writeTVar (TVar tvar#) val = STM $ \s1# ->
297 case writeTVar# tvar# val s1# of
302 %************************************************************************
304 \subsection[mvars]{M-Structures}
306 %************************************************************************
308 M-Vars are rendezvous points for concurrent threads. They begin
309 empty, and any attempt to read an empty M-Var blocks. When an M-Var
310 is written, a single blocked thread may be freed. Reading an M-Var
311 toggles its state from full back to empty. Therefore, any value
312 written to an M-Var may only be read once. Multiple reads and writes
313 are allowed, but there must be at least one read between any two
317 --Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
319 -- |Create an 'MVar' which is initially empty.
320 newEmptyMVar :: IO (MVar a)
321 newEmptyMVar = IO $ \ s# ->
323 (# s2#, svar# #) -> (# s2#, MVar svar# #)
325 -- |Create an 'MVar' which contains the supplied value.
326 newMVar :: a -> IO (MVar a)
328 newEmptyMVar >>= \ mvar ->
329 putMVar mvar value >>
332 -- |Return the contents of the 'MVar'. If the 'MVar' is currently
333 -- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
334 -- the 'MVar' is left empty.
336 -- If several threads are competing to take the same 'MVar', one is chosen
337 -- to continue at random when the 'MVar' becomes full.
338 takeMVar :: MVar a -> IO a
339 takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
341 -- |Put a value into an 'MVar'. If the 'MVar' is currently full,
342 -- 'putMVar' will wait until it becomes empty.
344 -- If several threads are competing to fill the same 'MVar', one is
345 -- chosen to continue at random when the 'MVar' becomes empty.
346 putMVar :: MVar a -> a -> IO ()
347 putMVar (MVar mvar#) x = IO $ \ s# ->
348 case putMVar# mvar# x s# of
351 -- |A non-blocking version of 'takeMVar'. The 'tryTakeMVar' function
352 -- returns immediately, with 'Nothing' if the 'MVar' was empty, or
353 -- @'Just' a@ if the 'MVar' was full with contents @a@. After 'tryTakeMVar',
354 -- the 'MVar' is left empty.
355 tryTakeMVar :: MVar a -> IO (Maybe a)
356 tryTakeMVar (MVar m) = IO $ \ s ->
357 case tryTakeMVar# m s of
358 (# s, 0#, _ #) -> (# s, Nothing #) -- MVar is empty
359 (# s, _, a #) -> (# s, Just a #) -- MVar is full
361 -- |A non-blocking version of 'putMVar'. The 'tryPutMVar' function
362 -- attempts to put the value @a@ into the 'MVar', returning 'True' if
363 -- it was successful, or 'False' otherwise.
364 tryPutMVar :: MVar a -> a -> IO Bool
365 tryPutMVar (MVar mvar#) x = IO $ \ s# ->
366 case tryPutMVar# mvar# x s# of
367 (# s, 0# #) -> (# s, False #)
368 (# s, _ #) -> (# s, True #)
370 -- |Check whether a given 'MVar' is empty.
372 -- Notice that the boolean value returned is just a snapshot of
373 -- the state of the MVar. By the time you get to react on its result,
374 -- the MVar may have been filled (or emptied) - so be extremely
375 -- careful when using this operation. Use 'tryTakeMVar' instead if possible.
376 isEmptyMVar :: MVar a -> IO Bool
377 isEmptyMVar (MVar mv#) = IO $ \ s# ->
378 case isEmptyMVar# mv# s# of
379 (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
381 -- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
382 -- "System.Mem.Weak" for more about finalizers.
383 addMVarFinalizer :: MVar a -> IO () -> IO ()
384 addMVarFinalizer (MVar m) finalizer =
385 IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
389 %************************************************************************
391 \subsection{Thread waiting}
393 %************************************************************************
396 #ifdef mingw32_HOST_OS
398 -- Note: threadDelay, threadWaitRead and threadWaitWrite aren't really functional
399 -- on Win32, but left in there because lib code (still) uses them (the manner
400 -- in which they're used doesn't cause problems on a Win32 platform though.)
402 asyncRead :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
403 asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf) =
404 IO $ \s -> case asyncRead# fd isSock len buf s of
405 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
407 asyncWrite :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
408 asyncWrite (I# fd) (I# isSock) (I# len) (Ptr buf) =
409 IO $ \s -> case asyncWrite# fd isSock len buf s of
410 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
412 asyncDoProc :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
413 asyncDoProc (FunPtr proc) (Ptr param) =
414 -- the 'length' value is ignored; simplifies implementation of
415 -- the async*# primops to have them all return the same result.
416 IO $ \s -> case asyncDoProc# proc param s of
417 (# s, len#, err# #) -> (# s, I# err# #)
419 -- to aid the use of these primops by the IO Handle implementation,
420 -- provide the following convenience funs:
422 -- this better be a pinned byte array!
423 asyncReadBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
424 asyncReadBA fd isSock len off bufB =
425 asyncRead fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
427 asyncWriteBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
428 asyncWriteBA fd isSock len off bufB =
429 asyncWrite fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
433 -- -----------------------------------------------------------------------------
436 -- | Block the current thread until data is available to read on the
437 -- given file descriptor (GHC only).
438 threadWaitRead :: Fd -> IO ()
440 #ifndef mingw32_HOST_OS
441 | threaded = waitForReadEvent fd
443 | otherwise = IO $ \s ->
444 case fromIntegral fd of { I# fd# ->
445 case waitRead# fd# s of { s -> (# s, () #)
448 -- | Block the current thread until data can be written to the
449 -- given file descriptor (GHC only).
450 threadWaitWrite :: Fd -> IO ()
452 #ifndef mingw32_HOST_OS
453 | threaded = waitForWriteEvent fd
455 | otherwise = IO $ \s ->
456 case fromIntegral fd of { I# fd# ->
457 case waitWrite# fd# s of { s -> (# s, () #)
460 -- | Suspends the current thread for a given number of microseconds
463 -- Note that the resolution used by the Haskell runtime system's
464 -- internal timer is 1\/50 second, and 'threadDelay' will round its
465 -- argument up to the nearest multiple of this resolution.
467 -- There is no guarantee that the thread will be rescheduled promptly
468 -- when the delay has expired, but the thread will never continue to
469 -- run /earlier/ than specified.
471 threadDelay :: Int -> IO ()
473 #ifndef mingw32_HOST_OS
474 | threaded = waitForDelayEvent time
476 | threaded = c_Sleep (fromIntegral (time `quot` 1000))
478 | otherwise = IO $ \s ->
479 case fromIntegral time of { I# time# ->
480 case delay# time# s of { s -> (# s, () #)
483 -- On Windows, we just make a safe call to 'Sleep' to implement threadDelay.
484 #ifdef mingw32_HOST_OS
485 foreign import stdcall safe "Sleep" c_Sleep :: CInt -> IO ()
488 foreign import ccall unsafe "rtsSupportsBoundThreads" threaded :: Bool
490 -- ----------------------------------------------------------------------------
491 -- Threaded RTS implementation of threadWaitRead, threadWaitWrite, threadDelay
493 -- In the threaded RTS, we employ a single IO Manager thread to wait
494 -- for all outstanding IO requests (threadWaitRead,threadWaitWrite)
495 -- and delays (threadDelay).
497 -- We can do this because in the threaded RTS the IO Manager can make
498 -- a non-blocking call to select(), so we don't have to do select() in
499 -- the scheduler as we have to in the non-threaded RTS. We get performance
500 -- benefits from doing it this way, because we only have to restart the select()
501 -- when a new request arrives, rather than doing one select() each time
502 -- around the scheduler loop. Furthermore, the scheduler can be simplified
503 -- by not having to check for completed IO requests.
505 -- Issues, possible problems:
507 -- - we might want bound threads to just do the blocking
508 -- operation rather than communicating with the IO manager
509 -- thread. This would prevent simgle-threaded programs which do
510 -- IO from requiring multiple OS threads. However, it would also
511 -- prevent bound threads waiting on IO from being killed or sent
514 -- - Apprently exec() doesn't work on Linux in a multithreaded program.
515 -- I couldn't repeat this.
517 -- - How do we handle signal delivery in the multithreaded RTS?
519 -- - forkProcess will kill the IO manager thread. Let's just
520 -- hope we don't need to do any blocking IO between fork & exec.
522 #ifndef mingw32_HOST_OS
525 = Read {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
526 | Write {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
529 = Delay {-# UNPACK #-} !Int {-# UNPACK #-} !(MVar ())
531 pendingEvents :: IORef [IOReq]
532 pendingDelays :: IORef [DelayReq]
533 -- could use a strict list or array here
534 {-# NOINLINE pendingEvents #-}
535 {-# NOINLINE pendingDelays #-}
536 (pendingEvents,pendingDelays) = unsafePerformIO $ do
541 -- the first time we schedule an IO request, the service thread
542 -- will be created (cool, huh?)
544 ensureIOManagerIsRunning :: IO ()
545 ensureIOManagerIsRunning
546 | threaded = seq pendingEvents $ return ()
547 | otherwise = return ()
549 startIOManagerThread :: IO ()
550 startIOManagerThread = do
551 allocaArray 2 $ \fds -> do
552 throwErrnoIfMinus1 "startIOManagerThread" (c_pipe fds)
553 rd_end <- peekElemOff fds 0
554 wr_end <- peekElemOff fds 1
555 writeIORef stick (fromIntegral wr_end)
556 c_setIOManagerPipe wr_end
558 allocaBytes sizeofFdSet $ \readfds -> do
559 allocaBytes sizeofFdSet $ \writefds -> do
560 allocaBytes sizeofTimeVal $ \timeval -> do
561 service_loop (fromIntegral rd_end) readfds writefds timeval [] []
564 -- XXX: move real forkIO here from Control.Concurrent?
565 quickForkIO action = IO $ \s ->
566 case (fork# action s) of (# s1, id #) -> (# s1, ThreadId id #)
569 :: Fd -- listen to this for wakeup calls
576 service_loop wakeup readfds writefds ptimeval old_reqs old_delays = do
578 -- pick up new IO requests
579 new_reqs <- atomicModifyIORef pendingEvents (\a -> ([],a))
580 let reqs = new_reqs ++ old_reqs
582 -- pick up new delay requests
583 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
584 let delays = foldr insertDelay old_delays new_delays
586 -- build the FDSets for select()
590 maxfd <- buildFdSets 0 readfds writefds reqs
592 -- perform the select()
593 let do_select delays = do
594 -- check the current time and wake up any thread in
595 -- threadDelay whose timeout has expired. Also find the
596 -- timeout value for the select() call.
598 (delays', timeout) <- getDelay now ptimeval delays
600 res <- c_select ((max wakeup maxfd)+1) readfds writefds
606 then do_select delays'
607 else return (res,delays')
611 (res,delays') <- do_select delays
612 -- ToDo: check result
614 b <- fdIsSet wakeup readfds
617 else alloca $ \p -> do
618 c_read (fromIntegral wakeup) p 1; return ()
622 else do handler_tbl <- peek handlers
623 sp <- peekElemOff handler_tbl (fromIntegral s)
624 quickForkIO (do io <- deRefStablePtr sp; io)
628 putMVar prodding False
630 reqs' <- completeRequests reqs readfds writefds []
631 service_loop wakeup readfds writefds ptimeval reqs' delays'
634 {-# NOINLINE stick #-}
635 stick = unsafePerformIO (newIORef 0)
637 prodding :: MVar Bool
638 {-# NOINLINE prodding #-}
639 prodding = unsafePerformIO (newMVar False)
641 prodServiceThread :: IO ()
642 prodServiceThread = do
643 b <- takeMVar prodding
645 then do fd <- readIORef stick
646 with 0xff $ \pbuf -> do c_write (fromIntegral fd) pbuf 1; return ()
648 putMVar prodding True
650 foreign import ccall "&signal_handlers" handlers :: Ptr (Ptr (StablePtr (IO ())))
652 foreign import ccall "setIOManagerPipe"
653 c_setIOManagerPipe :: CInt -> IO ()
655 -- -----------------------------------------------------------------------------
658 buildFdSets maxfd readfds writefds [] = return maxfd
659 buildFdSets maxfd readfds writefds (Read fd m : reqs) = do
661 buildFdSets (max maxfd fd) readfds writefds reqs
662 buildFdSets maxfd readfds writefds (Write fd m : reqs) = do
664 buildFdSets (max maxfd fd) readfds writefds reqs
666 completeRequests [] _ _ reqs' = return reqs'
667 completeRequests (Read fd m : reqs) readfds writefds reqs' = do
668 b <- fdIsSet fd readfds
670 then do putMVar m (); completeRequests reqs readfds writefds reqs'
671 else completeRequests reqs readfds writefds (Read fd m : reqs')
672 completeRequests (Write fd m : reqs) readfds writefds reqs' = do
673 b <- fdIsSet fd writefds
675 then do putMVar m (); completeRequests reqs readfds writefds reqs'
676 else completeRequests reqs readfds writefds (Write fd m : reqs')
678 waitForReadEvent :: Fd -> IO ()
679 waitForReadEvent fd = do
681 atomicModifyIORef pendingEvents (\xs -> (Read fd m : xs, ()))
685 waitForWriteEvent :: Fd -> IO ()
686 waitForWriteEvent fd = do
688 atomicModifyIORef pendingEvents (\xs -> (Write fd m : xs, ()))
692 -- XXX: move into GHC.IOBase from Data.IORef?
693 atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
694 atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
696 -- -----------------------------------------------------------------------------
699 waitForDelayEvent :: Int -> IO ()
700 waitForDelayEvent usecs = do
703 let target = now + usecs `quot` tick_usecs
704 atomicModifyIORef pendingDelays (\xs -> (Delay target m : xs, ()))
708 -- Walk the queue of pending delays, waking up any that have passed
709 -- and return the smallest delay to wait for. The queue of pending
710 -- delays is kept ordered.
711 getDelay :: Ticks -> Ptr CTimeVal -> [DelayReq] -> IO ([DelayReq], Ptr CTimeVal)
712 getDelay now ptimeval [] = return ([],nullPtr)
713 getDelay now ptimeval all@(Delay time m : rest)
716 getDelay now ptimeval rest
718 setTimevalTicks ptimeval (time - now)
719 return (all,ptimeval)
721 insertDelay :: DelayReq -> [DelayReq] -> [DelayReq]
722 insertDelay d@(Delay time m) [] = [d]
723 insertDelay d1@(Delay time m) ds@(d2@(Delay time' m') : rest)
724 | time <= time' = d1 : ds
725 | otherwise = d2 : insertDelay d1 rest
728 tick_freq = 50 :: Ticks -- accuracy of threadDelay (ticks per sec)
729 tick_usecs = 1000000 `quot` tick_freq :: Int
731 newtype CTimeVal = CTimeVal ()
733 foreign import ccall unsafe "sizeofTimeVal"
736 foreign import ccall unsafe "getTicksOfDay"
737 getTicksOfDay :: IO Ticks
739 foreign import ccall unsafe "setTimevalTicks"
740 setTimevalTicks :: Ptr CTimeVal -> Ticks -> IO ()
742 -- ----------------------------------------------------------------------------
743 -- select() interface
745 -- ToDo: move to System.Posix.Internals?
747 newtype CFdSet = CFdSet ()
749 foreign import ccall safe "select"
750 c_select :: Fd -> Ptr CFdSet -> Ptr CFdSet -> Ptr CFdSet -> Ptr CTimeVal
753 foreign import ccall unsafe "hsFD_CLR"
754 fdClr :: Fd -> Ptr CFdSet -> IO ()
756 foreign import ccall unsafe "hsFD_ISSET"
757 fdIsSet :: Fd -> Ptr CFdSet -> IO CInt
759 foreign import ccall unsafe "hsFD_SET"
760 fdSet :: Fd -> Ptr CFdSet -> IO ()
762 foreign import ccall unsafe "hsFD_ZERO"
763 fdZero :: Ptr CFdSet -> IO ()
765 foreign import ccall unsafe "sizeof_fd_set"