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 #include "ghcconfig.h"
21 -- Forking and suchlike
22 , myThreadId -- :: IO ThreadId
23 , killThread -- :: ThreadId -> IO ()
24 , throwTo -- :: ThreadId -> Exception -> IO ()
25 , par -- :: a -> b -> b
26 , pseq -- :: a -> b -> b
28 , labelThread -- :: ThreadId -> String -> IO ()
31 , threadDelay -- :: Int -> IO ()
32 , threadWaitRead -- :: Int -> IO ()
33 , threadWaitWrite -- :: Int -> IO ()
37 , newMVar -- :: a -> IO (MVar a)
38 , newEmptyMVar -- :: IO (MVar a)
39 , takeMVar -- :: MVar a -> IO a
40 , putMVar -- :: MVar a -> a -> IO ()
41 , tryTakeMVar -- :: MVar a -> IO (Maybe a)
42 , tryPutMVar -- :: MVar a -> a -> IO Bool
43 , isEmptyMVar -- :: MVar a -> IO Bool
44 , addMVarFinalizer -- :: MVar a -> IO () -> IO ()
48 , atomically -- :: STM a -> IO a
50 , orElse -- :: STM a -> STM a -> STM a
51 , catchSTM -- :: STM a -> (Exception -> STM a) -> STM a
53 , newTVar -- :: a -> STM (TVar a)
54 , readTVar -- :: TVar a -> STM a
55 , writeTVar -- :: a -> TVar a -> STM ()
56 , unsafeIOToSTM -- :: IO a -> STM a
58 #ifdef mingw32_TARGET_OS
59 , asyncRead -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
60 , asyncWrite -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
61 , asyncDoProc -- :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
63 , asyncReadBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
64 , asyncWriteBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
68 import System.Posix.Types
69 import System.Posix.Internals
77 import GHC.Num ( Num(..) )
78 import GHC.Real ( fromIntegral, quot )
79 import GHC.Base ( Int(..) )
80 import GHC.Exception ( Exception(..), AsyncException(..) )
81 import GHC.Pack ( packCString# )
82 import GHC.Ptr ( Ptr(..), plusPtr, FunPtr(..) )
87 infixr 0 `par`, `pseq`
90 %************************************************************************
92 \subsection{@ThreadId@, @par@, and @fork@}
94 %************************************************************************
97 data ThreadId = ThreadId ThreadId#
98 -- ToDo: data ThreadId = ThreadId (Weak ThreadId#)
99 -- But since ThreadId# is unlifted, the Weak type must use open
102 A 'ThreadId' is an abstract type representing a handle to a thread.
103 'ThreadId' is an instance of 'Eq', 'Ord' and 'Show', where
104 the 'Ord' instance implements an arbitrary total ordering over
105 'ThreadId's. The 'Show' instance lets you convert an arbitrary-valued
106 'ThreadId' to string form; showing a 'ThreadId' value is occasionally
107 useful when debugging or diagnosing the behaviour of a concurrent
110 /Note/: in GHC, if you have a 'ThreadId', you essentially have
111 a pointer to the thread itself. This means the thread itself can\'t be
112 garbage collected until you drop the 'ThreadId'.
113 This misfeature will hopefully be corrected at a later date.
115 /Note/: Hugs does not provide any operations on other threads;
116 it defines 'ThreadId' as a synonym for ().
119 INSTANCE_TYPEABLE0(ThreadId,threadIdTc,"ThreadId")
122 --forkIO has now been hoisted out into the Concurrent library.
124 {- | 'killThread' terminates the given thread (GHC only).
125 Any work already done by the thread isn\'t
126 lost: the computation is suspended until required by another thread.
127 The memory used by the thread will be garbage collected if it isn\'t
128 referenced from anywhere. The 'killThread' function is defined in
131 > killThread tid = throwTo tid (AsyncException ThreadKilled)
134 killThread :: ThreadId -> IO ()
135 killThread tid = throwTo tid (AsyncException ThreadKilled)
137 {- | 'throwTo' raises an arbitrary exception in the target thread (GHC only).
139 'throwTo' does not return until the exception has been raised in the
140 target thread. The calling thread can thus be certain that the target
141 thread has received the exception. This is a useful property to know
142 when dealing with race conditions: eg. if there are two threads that
143 can kill each other, it is guaranteed that only one of the threads
144 will get to kill the other. -}
145 throwTo :: ThreadId -> Exception -> IO ()
146 throwTo (ThreadId id) ex = IO $ \ s ->
147 case (killThread# id ex s) of s1 -> (# s1, () #)
149 -- | Returns the 'ThreadId' of the calling thread (GHC only).
150 myThreadId :: IO ThreadId
151 myThreadId = IO $ \s ->
152 case (myThreadId# s) of (# s1, id #) -> (# s1, ThreadId id #)
155 -- |The 'yield' action allows (forces, in a co-operative multitasking
156 -- implementation) a context-switch to any other currently runnable
157 -- threads (if any), and is occasionally useful when implementing
158 -- concurrency abstractions.
161 case (yield# s) of s1 -> (# s1, () #)
163 {- | 'labelThread' stores a string as identifier for this thread if
164 you built a RTS with debugging support. This identifier will be used in
165 the debugging output to make distinction of different threads easier
166 (otherwise you only have the thread state object\'s address in the heap).
168 Other applications like the graphical Concurrent Haskell Debugger
169 (<http://www.informatik.uni-kiel.de/~fhu/chd/>) may choose to overload
170 'labelThread' for their purposes as well.
173 labelThread :: ThreadId -> String -> IO ()
174 labelThread (ThreadId t) str = IO $ \ s ->
175 let ps = packCString# str
176 adr = byteArrayContents# ps in
177 case (labelThread# t adr s) of s1 -> (# s1, () #)
179 -- Nota Bene: 'pseq' used to be 'seq'
180 -- but 'seq' is now defined in PrelGHC
182 -- "pseq" is defined a bit weirdly (see below)
184 -- The reason for the strange "lazy" call is that
185 -- it fools the compiler into thinking that pseq and par are non-strict in
186 -- their second argument (even if it inlines pseq at the call site).
187 -- If it thinks pseq is strict in "y", then it often evaluates
188 -- "y" before "x", which is totally wrong.
192 pseq x y = x `seq` lazy y
196 par x y = case (par# x) of { _ -> lazy y }
200 %************************************************************************
202 \subsection[stm]{Transactional heap operations}
204 %************************************************************************
206 TVars are shared memory locations which support atomic memory
210 newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #))
212 INSTANCE_TYPEABLE1(STM,stmTc,"STM" )
214 unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
217 instance Functor STM where
218 fmap f x = x >>= (return . f)
220 instance Monad STM where
221 {-# INLINE return #-}
225 return x = returnSTM x
226 m >>= k = bindSTM m k
228 bindSTM :: STM a -> (a -> STM b) -> STM b
229 bindSTM (STM m) k = STM ( \s ->
231 (# new_s, a #) -> unSTM (k a) new_s
234 thenSTM :: STM a -> STM b -> STM b
235 thenSTM (STM m) k = STM ( \s ->
237 (# new_s, a #) -> unSTM k new_s
240 returnSTM :: a -> STM a
241 returnSTM x = STM (\s -> (# s, x #))
243 -- | Unsafely performs IO in the STM monad.
244 unsafeIOToSTM :: IO a -> STM a
245 unsafeIOToSTM (IO m) = STM m
247 -- |Perform a series of STM actions atomically.
248 atomically :: STM a -> IO a
249 atomically (STM m) = IO (\s -> (atomically# m) s )
251 -- |Retry execution of the current memory transaction because it has seen
252 -- values in TVars which mean that it should not continue (e.g. the TVars
253 -- represent a shared buffer that is now empty). The implementation may
254 -- block the thread until one of the TVars that it has read from has been
257 retry = STM $ \s# -> retry# s#
259 -- |Compose two alternative STM actions. If the first action completes without
260 -- retrying then it forms the result of the orElse. Otherwise, if the first
261 -- action retries, then the second action is tried in its place. If both actions
262 -- retry then the orElse as a whole retries.
263 orElse :: STM a -> STM a -> STM a
264 orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
266 -- |Exception handling within STM actions.
267 catchSTM :: STM a -> (Exception -> STM a) -> STM a
268 catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
270 data TVar a = TVar (TVar# RealWorld a)
272 INSTANCE_TYPEABLE1(TVar,tvarTc,"TVar" )
274 instance Eq (TVar a) where
275 (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
277 -- |Create a new TVar holding a value supplied
278 newTVar :: a -> STM (TVar a)
279 newTVar val = STM $ \s1# ->
280 case newTVar# val s1# of
281 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
283 -- |Return the current value stored in a TVar
284 readTVar :: TVar a -> STM a
285 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
287 -- |Write the supplied value into a TVar
288 writeTVar :: TVar a -> a -> STM ()
289 writeTVar (TVar tvar#) val = STM $ \s1# ->
290 case writeTVar# tvar# val s1# of
295 %************************************************************************
297 \subsection[mvars]{M-Structures}
299 %************************************************************************
301 M-Vars are rendezvous points for concurrent threads. They begin
302 empty, and any attempt to read an empty M-Var blocks. When an M-Var
303 is written, a single blocked thread may be freed. Reading an M-Var
304 toggles its state from full back to empty. Therefore, any value
305 written to an M-Var may only be read once. Multiple reads and writes
306 are allowed, but there must be at least one read between any two
310 --Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
312 INSTANCE_TYPEABLE1(MVar,mvarTc,"MVar" )
314 -- |Create an 'MVar' which is initially empty.
315 newEmptyMVar :: IO (MVar a)
316 newEmptyMVar = IO $ \ s# ->
318 (# s2#, svar# #) -> (# s2#, MVar svar# #)
320 -- |Create an 'MVar' which contains the supplied value.
321 newMVar :: a -> IO (MVar a)
323 newEmptyMVar >>= \ mvar ->
324 putMVar mvar value >>
327 -- |Return the contents of the 'MVar'. If the 'MVar' is currently
328 -- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
329 -- the 'MVar' is left empty.
331 -- If several threads are competing to take the same 'MVar', one is chosen
332 -- to continue at random when the 'MVar' becomes full.
333 takeMVar :: MVar a -> IO a
334 takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
336 -- |Put a value into an 'MVar'. If the 'MVar' is currently full,
337 -- 'putMVar' will wait until it becomes empty.
339 -- If several threads are competing to fill the same 'MVar', one is
340 -- chosen to continue at random when the 'MVar' becomes empty.
341 putMVar :: MVar a -> a -> IO ()
342 putMVar (MVar mvar#) x = IO $ \ s# ->
343 case putMVar# mvar# x s# of
346 -- |A non-blocking version of 'takeMVar'. The 'tryTakeMVar' function
347 -- returns immediately, with 'Nothing' if the 'MVar' was empty, or
348 -- @'Just' a@ if the 'MVar' was full with contents @a@. After 'tryTakeMVar',
349 -- the 'MVar' is left empty.
350 tryTakeMVar :: MVar a -> IO (Maybe a)
351 tryTakeMVar (MVar m) = IO $ \ s ->
352 case tryTakeMVar# m s of
353 (# s, 0#, _ #) -> (# s, Nothing #) -- MVar is empty
354 (# s, _, a #) -> (# s, Just a #) -- MVar is full
356 -- |A non-blocking version of 'putMVar'. The 'tryPutMVar' function
357 -- attempts to put the value @a@ into the 'MVar', returning 'True' if
358 -- it was successful, or 'False' otherwise.
359 tryPutMVar :: MVar a -> a -> IO Bool
360 tryPutMVar (MVar mvar#) x = IO $ \ s# ->
361 case tryPutMVar# mvar# x s# of
362 (# s, 0# #) -> (# s, False #)
363 (# s, _ #) -> (# s, True #)
365 -- |Check whether a given 'MVar' is empty.
367 -- Notice that the boolean value returned is just a snapshot of
368 -- the state of the MVar. By the time you get to react on its result,
369 -- the MVar may have been filled (or emptied) - so be extremely
370 -- careful when using this operation. Use 'tryTakeMVar' instead if possible.
371 isEmptyMVar :: MVar a -> IO Bool
372 isEmptyMVar (MVar mv#) = IO $ \ s# ->
373 case isEmptyMVar# mv# s# of
374 (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
376 -- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
377 -- "System.Mem.Weak" for more about finalizers.
378 addMVarFinalizer :: MVar a -> IO () -> IO ()
379 addMVarFinalizer (MVar m) finalizer =
380 IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
384 %************************************************************************
386 \subsection{Thread waiting}
388 %************************************************************************
391 #ifdef mingw32_TARGET_OS
393 -- Note: threadDelay, threadWaitRead and threadWaitWrite aren't really functional
394 -- on Win32, but left in there because lib code (still) uses them (the manner
395 -- in which they're used doesn't cause problems on a Win32 platform though.)
397 asyncRead :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
398 asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf) = do
399 (l, rc) <- IO (\s -> case asyncRead# fd isSock len buf s of
400 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #))
401 -- special handling for Ctrl+C-aborted 'standard input' reads;
402 -- see rts/win32/ConsoleHandler.c for details.
403 if (l == 0 && rc == -2)
404 then asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf)
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_TARGET_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_TARGET_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_TARGET_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_TARGET_OS
485 foreign import ccall 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_TARGET_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 startIOServiceThread :: IO ()
545 startIOServiceThread = do
546 allocaArray 2 $ \fds -> do
547 throwErrnoIfMinus1 "startIOServiceThread" (c_pipe fds)
548 rd_end <- peekElemOff fds 0
549 wr_end <- peekElemOff fds 1
550 writeIORef stick (fromIntegral 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 -- check the current time and wake up any thread in threadDelay whose
587 -- timeout has expired. Also find the timeout value for the select() call.
589 (delays', timeout) <- getDelay now ptimeval delays
591 -- perform the select()
593 res <- c_select ((max wakeup maxfd)+1) readfds writefds
604 -- ToDo: check result
606 b <- takeMVar prodding
607 if b then alloca $ \p -> do c_read (fromIntegral wakeup) p 1; return ()
609 putMVar prodding False
611 reqs' <- completeRequests reqs readfds writefds []
612 service_loop wakeup readfds writefds ptimeval reqs' delays'
615 {-# NOINLINE stick #-}
616 stick = unsafePerformIO (newIORef 0)
618 prodding :: MVar Bool
619 {-# NOINLINE prodding #-}
620 prodding = unsafePerformIO (newMVar False)
622 prodServiceThread :: IO ()
623 prodServiceThread = do
624 b <- takeMVar prodding
626 then do fd <- readIORef stick
627 with 42 $ \pbuf -> do c_write (fromIntegral fd) pbuf 1; return ()
629 putMVar prodding True
631 -- -----------------------------------------------------------------------------
634 buildFdSets maxfd readfds writefds [] = return maxfd
635 buildFdSets maxfd readfds writefds (Read fd m : reqs) = do
637 buildFdSets (max maxfd fd) readfds writefds reqs
638 buildFdSets maxfd readfds writefds (Write fd m : reqs) = do
640 buildFdSets (max maxfd fd) readfds writefds reqs
642 completeRequests [] _ _ reqs' = return reqs'
643 completeRequests (Read fd m : reqs) readfds writefds reqs' = do
644 b <- fdIsSet fd readfds
646 then do putMVar m (); completeRequests reqs readfds writefds reqs'
647 else completeRequests reqs readfds writefds (Read fd m : reqs')
648 completeRequests (Write fd m : reqs) readfds writefds reqs' = do
649 b <- fdIsSet fd writefds
651 then do putMVar m (); completeRequests reqs readfds writefds reqs'
652 else completeRequests reqs readfds writefds (Write fd m : reqs')
654 waitForReadEvent :: Fd -> IO ()
655 waitForReadEvent fd = do
657 atomicModifyIORef pendingEvents (\xs -> (Read fd m : xs, ()))
661 waitForWriteEvent :: Fd -> IO ()
662 waitForWriteEvent fd = do
664 atomicModifyIORef pendingEvents (\xs -> (Write fd m : xs, ()))
668 -- XXX: move into GHC.IOBase from Data.IORef?
669 atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
670 atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
672 -- -----------------------------------------------------------------------------
675 waitForDelayEvent :: Int -> IO ()
676 waitForDelayEvent usecs = do
679 let target = now + usecs `quot` tick_usecs
680 atomicModifyIORef pendingDelays (\xs -> (Delay target m : xs, ()))
684 -- Walk the queue of pending delays, waking up any that have passed
685 -- and return the smallest delay to wait for. The queue of pending
686 -- delays is kept ordered.
687 getDelay :: Ticks -> Ptr CTimeVal -> [DelayReq] -> IO ([DelayReq], Ptr CTimeVal)
688 getDelay now ptimeval [] = return ([],nullPtr)
689 getDelay now ptimeval all@(Delay time m : rest)
692 getDelay now ptimeval rest
694 setTimevalTicks ptimeval (time - now)
695 return (all,ptimeval)
697 insertDelay :: DelayReq -> [DelayReq] -> [DelayReq]
698 insertDelay d@(Delay time m) [] = [d]
699 insertDelay d1@(Delay time m) ds@(d2@(Delay time' m') : rest)
700 | time <= time' = d1 : ds
701 | otherwise = d2 : insertDelay d1 rest
704 tick_freq = 50 :: Ticks -- accuracy of threadDelay (ticks per sec)
705 tick_usecs = 1000000 `quot` tick_freq :: Int
707 newtype CTimeVal = CTimeVal ()
709 foreign import ccall unsafe "sizeofTimeVal"
712 foreign import ccall unsafe "getTicksOfDay"
713 getTicksOfDay :: IO Ticks
715 foreign import ccall unsafe "setTimevalTicks"
716 setTimevalTicks :: Ptr CTimeVal -> Ticks -> IO ()
718 -- ----------------------------------------------------------------------------
719 -- select() interface
721 -- ToDo: move to System.Posix.Internals?
723 newtype CFdSet = CFdSet ()
725 foreign import ccall safe "select"
726 c_select :: Fd -> Ptr CFdSet -> Ptr CFdSet -> Ptr CFdSet -> Ptr CTimeVal
729 foreign import ccall unsafe "hsFD_CLR"
730 fdClr :: Fd -> Ptr CFdSet -> IO ()
732 foreign import ccall unsafe "hsFD_ISSET"
733 fdIsSet :: Fd -> Ptr CFdSet -> IO CInt
735 foreign import ccall unsafe "hsFD_SET"
736 fdSet :: Fd -> Ptr CFdSet -> IO ()
738 foreign import ccall unsafe "hsFD_ZERO"
739 fdZero :: Ptr CFdSet -> IO ()
741 foreign import ccall unsafe "sizeof_fd_set"