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. -}
150 throwTo :: ThreadId -> Exception -> IO ()
151 throwTo (ThreadId id) ex = IO $ \ s ->
152 case (killThread# id ex s) of s1 -> (# s1, () #)
154 -- | Returns the 'ThreadId' of the calling thread (GHC only).
155 myThreadId :: IO ThreadId
156 myThreadId = IO $ \s ->
157 case (myThreadId# s) of (# s1, id #) -> (# s1, ThreadId id #)
160 -- |The 'yield' action allows (forces, in a co-operative multitasking
161 -- implementation) a context-switch to any other currently runnable
162 -- threads (if any), and is occasionally useful when implementing
163 -- concurrency abstractions.
166 case (yield# s) of s1 -> (# s1, () #)
168 {- | 'labelThread' stores a string as identifier for this thread if
169 you built a RTS with debugging support. This identifier will be used in
170 the debugging output to make distinction of different threads easier
171 (otherwise you only have the thread state object\'s address in the heap).
173 Other applications like the graphical Concurrent Haskell Debugger
174 (<http://www.informatik.uni-kiel.de/~fhu/chd/>) may choose to overload
175 'labelThread' for their purposes as well.
178 labelThread :: ThreadId -> String -> IO ()
179 labelThread (ThreadId t) str = IO $ \ s ->
180 let ps = packCString# str
181 adr = byteArrayContents# ps in
182 case (labelThread# t adr s) of s1 -> (# s1, () #)
184 -- Nota Bene: 'pseq' used to be 'seq'
185 -- but 'seq' is now defined in PrelGHC
187 -- "pseq" is defined a bit weirdly (see below)
189 -- The reason for the strange "lazy" call is that
190 -- it fools the compiler into thinking that pseq and par are non-strict in
191 -- their second argument (even if it inlines pseq at the call site).
192 -- If it thinks pseq is strict in "y", then it often evaluates
193 -- "y" before "x", which is totally wrong.
197 pseq x y = x `seq` lazy y
201 par x y = case (par# x) of { _ -> lazy y }
205 %************************************************************************
207 \subsection[stm]{Transactional heap operations}
209 %************************************************************************
211 TVars are shared memory locations which support atomic memory
215 newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #)) deriving( Typeable )
217 unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
220 instance Functor STM where
221 fmap f x = x >>= (return . f)
223 instance Monad STM where
224 {-# INLINE return #-}
228 return x = returnSTM x
229 m >>= k = bindSTM m k
231 bindSTM :: STM a -> (a -> STM b) -> STM b
232 bindSTM (STM m) k = STM ( \s ->
234 (# new_s, a #) -> unSTM (k a) new_s
237 thenSTM :: STM a -> STM b -> STM b
238 thenSTM (STM m) k = STM ( \s ->
240 (# new_s, a #) -> unSTM k new_s
243 returnSTM :: a -> STM a
244 returnSTM x = STM (\s -> (# s, x #))
246 -- | Unsafely performs IO in the STM monad.
247 unsafeIOToSTM :: IO a -> STM a
248 unsafeIOToSTM (IO m) = STM m
250 -- |Perform a series of STM actions atomically.
251 atomically :: STM a -> IO a
252 atomically (STM m) = IO (\s -> (atomically# m) s )
254 -- |Retry execution of the current memory transaction because it has seen
255 -- values in TVars which mean that it should not continue (e.g. the TVars
256 -- represent a shared buffer that is now empty). The implementation may
257 -- block the thread until one of the TVars that it has read from has been
260 retry = STM $ \s# -> retry# s#
262 -- |Compose two alternative STM actions. If the first action completes without
263 -- retrying then it forms the result of the orElse. Otherwise, if the first
264 -- action retries, then the second action is tried in its place. If both actions
265 -- retry then the orElse as a whole retries.
266 orElse :: STM a -> STM a -> STM a
267 orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
269 -- |Exception handling within STM actions.
270 catchSTM :: STM a -> (Exception -> STM a) -> STM a
271 catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
273 data TVar a = TVar (TVar# RealWorld a) deriving( Typeable )
275 instance Eq (TVar a) where
276 (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
278 -- |Create a new TVar holding a value supplied
279 newTVar :: a -> STM (TVar a)
280 newTVar val = STM $ \s1# ->
281 case newTVar# val s1# of
282 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
284 -- |Return the current value stored in a TVar
285 readTVar :: TVar a -> STM a
286 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
288 -- |Write the supplied value into a TVar
289 writeTVar :: TVar a -> a -> STM ()
290 writeTVar (TVar tvar#) val = STM $ \s1# ->
291 case writeTVar# tvar# val s1# of
296 %************************************************************************
298 \subsection[mvars]{M-Structures}
300 %************************************************************************
302 M-Vars are rendezvous points for concurrent threads. They begin
303 empty, and any attempt to read an empty M-Var blocks. When an M-Var
304 is written, a single blocked thread may be freed. Reading an M-Var
305 toggles its state from full back to empty. Therefore, any value
306 written to an M-Var may only be read once. Multiple reads and writes
307 are allowed, but there must be at least one read between any two
311 --Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
313 -- |Create an 'MVar' which is initially empty.
314 newEmptyMVar :: IO (MVar a)
315 newEmptyMVar = IO $ \ s# ->
317 (# s2#, svar# #) -> (# s2#, MVar svar# #)
319 -- |Create an 'MVar' which contains the supplied value.
320 newMVar :: a -> IO (MVar a)
322 newEmptyMVar >>= \ mvar ->
323 putMVar mvar value >>
326 -- |Return the contents of the 'MVar'. If the 'MVar' is currently
327 -- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
328 -- the 'MVar' is left empty.
330 -- If several threads are competing to take the same 'MVar', one is chosen
331 -- to continue at random when the 'MVar' becomes full.
332 takeMVar :: MVar a -> IO a
333 takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
335 -- |Put a value into an 'MVar'. If the 'MVar' is currently full,
336 -- 'putMVar' will wait until it becomes empty.
338 -- If several threads are competing to fill the same 'MVar', one is
339 -- chosen to continue at random when the 'MVar' becomes empty.
340 putMVar :: MVar a -> a -> IO ()
341 putMVar (MVar mvar#) x = IO $ \ s# ->
342 case putMVar# mvar# x s# of
345 -- |A non-blocking version of 'takeMVar'. The 'tryTakeMVar' function
346 -- returns immediately, with 'Nothing' if the 'MVar' was empty, or
347 -- @'Just' a@ if the 'MVar' was full with contents @a@. After 'tryTakeMVar',
348 -- the 'MVar' is left empty.
349 tryTakeMVar :: MVar a -> IO (Maybe a)
350 tryTakeMVar (MVar m) = IO $ \ s ->
351 case tryTakeMVar# m s of
352 (# s, 0#, _ #) -> (# s, Nothing #) -- MVar is empty
353 (# s, _, a #) -> (# s, Just a #) -- MVar is full
355 -- |A non-blocking version of 'putMVar'. The 'tryPutMVar' function
356 -- attempts to put the value @a@ into the 'MVar', returning 'True' if
357 -- it was successful, or 'False' otherwise.
358 tryPutMVar :: MVar a -> a -> IO Bool
359 tryPutMVar (MVar mvar#) x = IO $ \ s# ->
360 case tryPutMVar# mvar# x s# of
361 (# s, 0# #) -> (# s, False #)
362 (# s, _ #) -> (# s, True #)
364 -- |Check whether a given 'MVar' is empty.
366 -- Notice that the boolean value returned is just a snapshot of
367 -- the state of the MVar. By the time you get to react on its result,
368 -- the MVar may have been filled (or emptied) - so be extremely
369 -- careful when using this operation. Use 'tryTakeMVar' instead if possible.
370 isEmptyMVar :: MVar a -> IO Bool
371 isEmptyMVar (MVar mv#) = IO $ \ s# ->
372 case isEmptyMVar# mv# s# of
373 (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
375 -- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
376 -- "System.Mem.Weak" for more about finalizers.
377 addMVarFinalizer :: MVar a -> IO () -> IO ()
378 addMVarFinalizer (MVar m) finalizer =
379 IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
383 %************************************************************************
385 \subsection{Thread waiting}
387 %************************************************************************
390 #ifdef mingw32_HOST_OS
392 -- Note: threadDelay, threadWaitRead and threadWaitWrite aren't really functional
393 -- on Win32, but left in there because lib code (still) uses them (the manner
394 -- in which they're used doesn't cause problems on a Win32 platform though.)
396 asyncRead :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
397 asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf) =
398 IO $ \s -> case asyncRead# fd isSock len buf s of
399 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
401 asyncWrite :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
402 asyncWrite (I# fd) (I# isSock) (I# len) (Ptr buf) =
403 IO $ \s -> case asyncWrite# fd isSock len buf s of
404 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
406 asyncDoProc :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
407 asyncDoProc (FunPtr proc) (Ptr param) =
408 -- the 'length' value is ignored; simplifies implementation of
409 -- the async*# primops to have them all return the same result.
410 IO $ \s -> case asyncDoProc# proc param s of
411 (# s, len#, err# #) -> (# s, I# err# #)
413 -- to aid the use of these primops by the IO Handle implementation,
414 -- provide the following convenience funs:
416 -- this better be a pinned byte array!
417 asyncReadBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
418 asyncReadBA fd isSock len off bufB =
419 asyncRead fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
421 asyncWriteBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
422 asyncWriteBA fd isSock len off bufB =
423 asyncWrite fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
427 -- -----------------------------------------------------------------------------
430 -- | Block the current thread until data is available to read on the
431 -- given file descriptor (GHC only).
432 threadWaitRead :: Fd -> IO ()
434 #ifndef mingw32_HOST_OS
435 | threaded = waitForReadEvent fd
437 | otherwise = IO $ \s ->
438 case fromIntegral fd of { I# fd# ->
439 case waitRead# fd# s of { s -> (# s, () #)
442 -- | Block the current thread until data can be written to the
443 -- given file descriptor (GHC only).
444 threadWaitWrite :: Fd -> IO ()
446 #ifndef mingw32_HOST_OS
447 | threaded = waitForWriteEvent fd
449 | otherwise = IO $ \s ->
450 case fromIntegral fd of { I# fd# ->
451 case waitWrite# fd# s of { s -> (# s, () #)
454 -- | Suspends the current thread for a given number of microseconds
457 -- Note that the resolution used by the Haskell runtime system's
458 -- internal timer is 1\/50 second, and 'threadDelay' will round its
459 -- argument up to the nearest multiple of this resolution.
461 -- There is no guarantee that the thread will be rescheduled promptly
462 -- when the delay has expired, but the thread will never continue to
463 -- run /earlier/ than specified.
465 threadDelay :: Int -> IO ()
467 #ifndef mingw32_HOST_OS
468 | threaded = waitForDelayEvent time
470 | threaded = c_Sleep (fromIntegral (time `quot` 1000))
472 | otherwise = IO $ \s ->
473 case fromIntegral time of { I# time# ->
474 case delay# time# s of { s -> (# s, () #)
477 -- On Windows, we just make a safe call to 'Sleep' to implement threadDelay.
478 #ifdef mingw32_HOST_OS
479 foreign import ccall safe "Sleep" c_Sleep :: CInt -> IO ()
482 foreign import ccall unsafe "rtsSupportsBoundThreads" threaded :: Bool
484 -- ----------------------------------------------------------------------------
485 -- Threaded RTS implementation of threadWaitRead, threadWaitWrite, threadDelay
487 -- In the threaded RTS, we employ a single IO Manager thread to wait
488 -- for all outstanding IO requests (threadWaitRead,threadWaitWrite)
489 -- and delays (threadDelay).
491 -- We can do this because in the threaded RTS the IO Manager can make
492 -- a non-blocking call to select(), so we don't have to do select() in
493 -- the scheduler as we have to in the non-threaded RTS. We get performance
494 -- benefits from doing it this way, because we only have to restart the select()
495 -- when a new request arrives, rather than doing one select() each time
496 -- around the scheduler loop. Furthermore, the scheduler can be simplified
497 -- by not having to check for completed IO requests.
499 -- Issues, possible problems:
501 -- - we might want bound threads to just do the blocking
502 -- operation rather than communicating with the IO manager
503 -- thread. This would prevent simgle-threaded programs which do
504 -- IO from requiring multiple OS threads. However, it would also
505 -- prevent bound threads waiting on IO from being killed or sent
508 -- - Apprently exec() doesn't work on Linux in a multithreaded program.
509 -- I couldn't repeat this.
511 -- - How do we handle signal delivery in the multithreaded RTS?
513 -- - forkProcess will kill the IO manager thread. Let's just
514 -- hope we don't need to do any blocking IO between fork & exec.
516 #ifndef mingw32_HOST_OS
519 = Read {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
520 | Write {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
523 = Delay {-# UNPACK #-} !Int {-# UNPACK #-} !(MVar ())
525 pendingEvents :: IORef [IOReq]
526 pendingDelays :: IORef [DelayReq]
527 -- could use a strict list or array here
528 {-# NOINLINE pendingEvents #-}
529 {-# NOINLINE pendingDelays #-}
530 (pendingEvents,pendingDelays) = unsafePerformIO $ do
535 -- the first time we schedule an IO request, the service thread
536 -- will be created (cool, huh?)
538 ensureIOManagerIsRunning :: IO ()
539 ensureIOManagerIsRunning
540 | threaded = seq pendingEvents $ return ()
541 | otherwise = return ()
543 startIOManagerThread :: IO ()
544 startIOManagerThread = do
545 allocaArray 2 $ \fds -> do
546 throwErrnoIfMinus1 "startIOManagerThread" (c_pipe fds)
547 rd_end <- peekElemOff fds 0
548 wr_end <- peekElemOff fds 1
549 writeIORef stick (fromIntegral wr_end)
550 c_setIOManagerPipe wr_end
552 allocaBytes sizeofFdSet $ \readfds -> do
553 allocaBytes sizeofFdSet $ \writefds -> do
554 allocaBytes sizeofTimeVal $ \timeval -> do
555 service_loop (fromIntegral rd_end) readfds writefds timeval [] []
558 -- XXX: move real forkIO here from Control.Concurrent?
559 quickForkIO action = IO $ \s ->
560 case (fork# action s) of (# s1, id #) -> (# s1, ThreadId id #)
563 :: Fd -- listen to this for wakeup calls
570 service_loop wakeup readfds writefds ptimeval old_reqs old_delays = do
572 -- pick up new IO requests
573 new_reqs <- atomicModifyIORef pendingEvents (\a -> ([],a))
574 let reqs = new_reqs ++ old_reqs
576 -- pick up new delay requests
577 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
578 let delays = foldr insertDelay old_delays new_delays
580 -- build the FDSets for select()
584 maxfd <- buildFdSets 0 readfds writefds reqs
586 -- perform the select()
587 let do_select delays = do
588 -- check the current time and wake up any thread in
589 -- threadDelay whose timeout has expired. Also find the
590 -- timeout value for the select() call.
592 (delays', timeout) <- getDelay now ptimeval delays
594 res <- c_select ((max wakeup maxfd)+1) readfds writefds
600 then do_select delays'
601 else return (res,delays')
605 (res,delays') <- do_select delays
606 -- ToDo: check result
608 b <- fdIsSet wakeup readfds
611 else alloca $ \p -> do
612 c_read (fromIntegral wakeup) p 1; return ()
616 else c_startSignalHandler (fromIntegral s)
619 putMVar prodding False
621 reqs' <- completeRequests reqs readfds writefds []
622 service_loop wakeup readfds writefds ptimeval reqs' delays'
625 {-# NOINLINE stick #-}
626 stick = unsafePerformIO (newIORef 0)
628 prodding :: MVar Bool
629 {-# NOINLINE prodding #-}
630 prodding = unsafePerformIO (newMVar False)
632 prodServiceThread :: IO ()
633 prodServiceThread = do
634 b <- takeMVar prodding
636 then do fd <- readIORef stick
637 with 0xff $ \pbuf -> do c_write (fromIntegral fd) pbuf 1; return ()
639 putMVar prodding True
641 foreign import ccall unsafe "startSignalHandler"
642 c_startSignalHandler :: CInt -> IO ()
644 foreign import ccall "setIOManagerPipe"
645 c_setIOManagerPipe :: CInt -> IO ()
647 -- -----------------------------------------------------------------------------
650 buildFdSets maxfd readfds writefds [] = return maxfd
651 buildFdSets maxfd readfds writefds (Read fd m : reqs) = do
653 buildFdSets (max maxfd fd) readfds writefds reqs
654 buildFdSets maxfd readfds writefds (Write fd m : reqs) = do
656 buildFdSets (max maxfd fd) readfds writefds reqs
658 completeRequests [] _ _ reqs' = return reqs'
659 completeRequests (Read fd m : reqs) readfds writefds reqs' = do
660 b <- fdIsSet fd readfds
662 then do putMVar m (); completeRequests reqs readfds writefds reqs'
663 else completeRequests reqs readfds writefds (Read fd m : reqs')
664 completeRequests (Write fd m : reqs) readfds writefds reqs' = do
665 b <- fdIsSet fd writefds
667 then do putMVar m (); completeRequests reqs readfds writefds reqs'
668 else completeRequests reqs readfds writefds (Write fd m : reqs')
670 waitForReadEvent :: Fd -> IO ()
671 waitForReadEvent fd = do
673 atomicModifyIORef pendingEvents (\xs -> (Read fd m : xs, ()))
677 waitForWriteEvent :: Fd -> IO ()
678 waitForWriteEvent fd = do
680 atomicModifyIORef pendingEvents (\xs -> (Write fd m : xs, ()))
684 -- XXX: move into GHC.IOBase from Data.IORef?
685 atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
686 atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
688 -- -----------------------------------------------------------------------------
691 waitForDelayEvent :: Int -> IO ()
692 waitForDelayEvent usecs = do
695 let target = now + usecs `quot` tick_usecs
696 atomicModifyIORef pendingDelays (\xs -> (Delay target m : xs, ()))
700 -- Walk the queue of pending delays, waking up any that have passed
701 -- and return the smallest delay to wait for. The queue of pending
702 -- delays is kept ordered.
703 getDelay :: Ticks -> Ptr CTimeVal -> [DelayReq] -> IO ([DelayReq], Ptr CTimeVal)
704 getDelay now ptimeval [] = return ([],nullPtr)
705 getDelay now ptimeval all@(Delay time m : rest)
708 getDelay now ptimeval rest
710 setTimevalTicks ptimeval (time - now)
711 return (all,ptimeval)
713 insertDelay :: DelayReq -> [DelayReq] -> [DelayReq]
714 insertDelay d@(Delay time m) [] = [d]
715 insertDelay d1@(Delay time m) ds@(d2@(Delay time' m') : rest)
716 | time <= time' = d1 : ds
717 | otherwise = d2 : insertDelay d1 rest
720 tick_freq = 50 :: Ticks -- accuracy of threadDelay (ticks per sec)
721 tick_usecs = 1000000 `quot` tick_freq :: Int
723 newtype CTimeVal = CTimeVal ()
725 foreign import ccall unsafe "sizeofTimeVal"
728 foreign import ccall unsafe "getTicksOfDay"
729 getTicksOfDay :: IO Ticks
731 foreign import ccall unsafe "setTimevalTicks"
732 setTimevalTicks :: Ptr CTimeVal -> Ticks -> IO ()
734 -- ----------------------------------------------------------------------------
735 -- select() interface
737 -- ToDo: move to System.Posix.Internals?
739 newtype CFdSet = CFdSet ()
741 foreign import ccall safe "select"
742 c_select :: Fd -> Ptr CFdSet -> Ptr CFdSet -> Ptr CFdSet -> Ptr CTimeVal
745 foreign import ccall unsafe "hsFD_CLR"
746 fdClr :: Fd -> Ptr CFdSet -> IO ()
748 foreign import ccall unsafe "hsFD_ISSET"
749 fdIsSet :: Fd -> Ptr CFdSet -> IO CInt
751 foreign import ccall unsafe "hsFD_SET"
752 fdSet :: Fd -> Ptr CFdSet -> IO ()
754 foreign import ccall unsafe "hsFD_ZERO"
755 fdZero :: Ptr CFdSet -> IO ()
757 foreign import ccall unsafe "sizeof_fd_set"