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 , registerDelay -- :: Int -> IO (TVar Bool)
38 , threadWaitRead -- :: Int -> IO ()
39 , threadWaitWrite -- :: Int -> IO ()
43 , newMVar -- :: a -> IO (MVar a)
44 , newEmptyMVar -- :: IO (MVar a)
45 , takeMVar -- :: MVar a -> IO a
46 , putMVar -- :: MVar a -> a -> IO ()
47 , tryTakeMVar -- :: MVar a -> IO (Maybe a)
48 , tryPutMVar -- :: MVar a -> a -> IO Bool
49 , isEmptyMVar -- :: MVar a -> IO Bool
50 , addMVarFinalizer -- :: MVar a -> IO () -> IO ()
54 , atomically -- :: STM a -> IO a
56 , orElse -- :: STM a -> STM a -> STM a
57 , catchSTM -- :: STM a -> (Exception -> STM a) -> STM a
59 , newTVar -- :: a -> STM (TVar a)
60 , readTVar -- :: TVar a -> STM a
61 , writeTVar -- :: a -> TVar a -> STM ()
62 , unsafeIOToSTM -- :: IO a -> STM a
64 #ifdef mingw32_HOST_OS
65 , asyncRead -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
66 , asyncWrite -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
67 , asyncDoProc -- :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
69 , asyncReadBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
70 , asyncWriteBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
73 #ifndef mingw32_HOST_OS
74 , ensureIOManagerIsRunning
78 import System.Posix.Types
79 import System.Posix.Internals
87 import GHC.Num ( Num(..) )
88 import GHC.Real ( fromIntegral, quot )
89 import GHC.Base ( Int(..) )
90 import GHC.Exception ( Exception(..), AsyncException(..) )
91 import GHC.Pack ( packCString# )
92 import GHC.Ptr ( Ptr(..), plusPtr, FunPtr(..) )
96 infixr 0 `par`, `pseq`
99 %************************************************************************
101 \subsection{@ThreadId@, @par@, and @fork@}
103 %************************************************************************
106 data ThreadId = ThreadId ThreadId# deriving( Typeable )
107 -- ToDo: data ThreadId = ThreadId (Weak ThreadId#)
108 -- But since ThreadId# is unlifted, the Weak type must use open
111 A 'ThreadId' is an abstract type representing a handle to a thread.
112 'ThreadId' is an instance of 'Eq', 'Ord' and 'Show', where
113 the 'Ord' instance implements an arbitrary total ordering over
114 'ThreadId's. The 'Show' instance lets you convert an arbitrary-valued
115 'ThreadId' to string form; showing a 'ThreadId' value is occasionally
116 useful when debugging or diagnosing the behaviour of a concurrent
119 /Note/: in GHC, if you have a 'ThreadId', you essentially have
120 a pointer to the thread itself. This means the thread itself can\'t be
121 garbage collected until you drop the 'ThreadId'.
122 This misfeature will hopefully be corrected at a later date.
124 /Note/: Hugs does not provide any operations on other threads;
125 it defines 'ThreadId' as a synonym for ().
128 --forkIO has now been hoisted out into the Concurrent library.
130 {- | 'killThread' terminates the given thread (GHC only).
131 Any work already done by the thread isn\'t
132 lost: the computation is suspended until required by another thread.
133 The memory used by the thread will be garbage collected if it isn\'t
134 referenced from anywhere. The 'killThread' function is defined in
137 > killThread tid = throwTo tid (AsyncException ThreadKilled)
140 killThread :: ThreadId -> IO ()
141 killThread tid = throwTo tid (AsyncException ThreadKilled)
143 {- | 'throwTo' raises an arbitrary exception in the target thread (GHC only).
145 'throwTo' does not return until the exception has been raised in the
146 target thread. The calling thread can thus be certain that the target
147 thread has received the exception. This is a useful property to know
148 when dealing with race conditions: eg. if there are two threads that
149 can kill each other, it is guaranteed that only one of the threads
150 will get to kill the other.
152 If the target thread is currently making a foreign call, then the
153 exception will not be raised (and hence 'throwTo' will not return)
154 until the call has completed. This is the case regardless of whether
155 the call is inside a 'block' or not.
157 throwTo :: ThreadId -> Exception -> IO ()
158 throwTo (ThreadId id) ex = IO $ \ s ->
159 case (killThread# id ex s) of s1 -> (# s1, () #)
161 -- | Returns the 'ThreadId' of the calling thread (GHC only).
162 myThreadId :: IO ThreadId
163 myThreadId = IO $ \s ->
164 case (myThreadId# s) of (# s1, id #) -> (# s1, ThreadId id #)
167 -- |The 'yield' action allows (forces, in a co-operative multitasking
168 -- implementation) a context-switch to any other currently runnable
169 -- threads (if any), and is occasionally useful when implementing
170 -- concurrency abstractions.
173 case (yield# s) of s1 -> (# s1, () #)
175 {- | 'labelThread' stores a string as identifier for this thread if
176 you built a RTS with debugging support. This identifier will be used in
177 the debugging output to make distinction of different threads easier
178 (otherwise you only have the thread state object\'s address in the heap).
180 Other applications like the graphical Concurrent Haskell Debugger
181 (<http://www.informatik.uni-kiel.de/~fhu/chd/>) may choose to overload
182 'labelThread' for their purposes as well.
185 labelThread :: ThreadId -> String -> IO ()
186 labelThread (ThreadId t) str = IO $ \ s ->
187 let ps = packCString# str
188 adr = byteArrayContents# ps in
189 case (labelThread# t adr s) of s1 -> (# s1, () #)
191 -- Nota Bene: 'pseq' used to be 'seq'
192 -- but 'seq' is now defined in PrelGHC
194 -- "pseq" is defined a bit weirdly (see below)
196 -- The reason for the strange "lazy" call is that
197 -- it fools the compiler into thinking that pseq and par are non-strict in
198 -- their second argument (even if it inlines pseq at the call site).
199 -- If it thinks pseq is strict in "y", then it often evaluates
200 -- "y" before "x", which is totally wrong.
204 pseq x y = x `seq` lazy y
208 par x y = case (par# x) of { _ -> lazy y }
212 %************************************************************************
214 \subsection[stm]{Transactional heap operations}
216 %************************************************************************
218 TVars are shared memory locations which support atomic memory
222 newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #)) deriving( Typeable )
224 unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
227 instance Functor STM where
228 fmap f x = x >>= (return . f)
230 instance Monad STM where
231 {-# INLINE return #-}
235 return x = returnSTM x
236 m >>= k = bindSTM m k
238 bindSTM :: STM a -> (a -> STM b) -> STM b
239 bindSTM (STM m) k = STM ( \s ->
241 (# new_s, a #) -> unSTM (k a) new_s
244 thenSTM :: STM a -> STM b -> STM b
245 thenSTM (STM m) k = STM ( \s ->
247 (# new_s, a #) -> unSTM k new_s
250 returnSTM :: a -> STM a
251 returnSTM x = STM (\s -> (# s, x #))
253 -- | Unsafely performs IO in the STM monad.
254 unsafeIOToSTM :: IO a -> STM a
255 unsafeIOToSTM (IO m) = STM m
257 -- |Perform a series of STM actions atomically.
258 atomically :: STM a -> IO a
259 atomically (STM m) = IO (\s -> (atomically# m) s )
261 -- |Retry execution of the current memory transaction because it has seen
262 -- values in TVars which mean that it should not continue (e.g. the TVars
263 -- represent a shared buffer that is now empty). The implementation may
264 -- block the thread until one of the TVars that it has read from has been
267 retry = STM $ \s# -> retry# s#
269 -- |Compose two alternative STM actions. If the first action completes without
270 -- retrying then it forms the result of the orElse. Otherwise, if the first
271 -- action retries, then the second action is tried in its place. If both actions
272 -- retry then the orElse as a whole retries.
273 orElse :: STM a -> STM a -> STM a
274 orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
276 -- |Exception handling within STM actions.
277 catchSTM :: STM a -> (Exception -> STM a) -> STM a
278 catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
280 data TVar a = TVar (TVar# RealWorld a) deriving( Typeable )
282 instance Eq (TVar a) where
283 (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
285 -- |Create a new TVar holding a value supplied
286 newTVar :: a -> STM (TVar a)
287 newTVar val = STM $ \s1# ->
288 case newTVar# val s1# of
289 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
291 -- |Return the current value stored in a TVar
292 readTVar :: TVar a -> STM a
293 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
295 -- |Write the supplied value into a TVar
296 writeTVar :: TVar a -> a -> STM ()
297 writeTVar (TVar tvar#) val = STM $ \s1# ->
298 case writeTVar# tvar# val s1# of
303 %************************************************************************
305 \subsection[mvars]{M-Structures}
307 %************************************************************************
309 M-Vars are rendezvous points for concurrent threads. They begin
310 empty, and any attempt to read an empty M-Var blocks. When an M-Var
311 is written, a single blocked thread may be freed. Reading an M-Var
312 toggles its state from full back to empty. Therefore, any value
313 written to an M-Var may only be read once. Multiple reads and writes
314 are allowed, but there must be at least one read between any two
318 --Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
320 -- |Create an 'MVar' which is initially empty.
321 newEmptyMVar :: IO (MVar a)
322 newEmptyMVar = IO $ \ s# ->
324 (# s2#, svar# #) -> (# s2#, MVar svar# #)
326 -- |Create an 'MVar' which contains the supplied value.
327 newMVar :: a -> IO (MVar a)
329 newEmptyMVar >>= \ mvar ->
330 putMVar mvar value >>
333 -- |Return the contents of the 'MVar'. If the 'MVar' is currently
334 -- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
335 -- the 'MVar' is left empty.
337 -- If several threads are competing to take the same 'MVar', one is chosen
338 -- to continue at random when the 'MVar' becomes full.
339 takeMVar :: MVar a -> IO a
340 takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
342 -- |Put a value into an 'MVar'. If the 'MVar' is currently full,
343 -- 'putMVar' will wait until it becomes empty.
345 -- If several threads are competing to fill the same 'MVar', one is
346 -- chosen to continue at random when the 'MVar' becomes empty.
347 putMVar :: MVar a -> a -> IO ()
348 putMVar (MVar mvar#) x = IO $ \ s# ->
349 case putMVar# mvar# x s# of
352 -- |A non-blocking version of 'takeMVar'. The 'tryTakeMVar' function
353 -- returns immediately, with 'Nothing' if the 'MVar' was empty, or
354 -- @'Just' a@ if the 'MVar' was full with contents @a@. After 'tryTakeMVar',
355 -- the 'MVar' is left empty.
356 tryTakeMVar :: MVar a -> IO (Maybe a)
357 tryTakeMVar (MVar m) = IO $ \ s ->
358 case tryTakeMVar# m s of
359 (# s, 0#, _ #) -> (# s, Nothing #) -- MVar is empty
360 (# s, _, a #) -> (# s, Just a #) -- MVar is full
362 -- |A non-blocking version of 'putMVar'. The 'tryPutMVar' function
363 -- attempts to put the value @a@ into the 'MVar', returning 'True' if
364 -- it was successful, or 'False' otherwise.
365 tryPutMVar :: MVar a -> a -> IO Bool
366 tryPutMVar (MVar mvar#) x = IO $ \ s# ->
367 case tryPutMVar# mvar# x s# of
368 (# s, 0# #) -> (# s, False #)
369 (# s, _ #) -> (# s, True #)
371 -- |Check whether a given 'MVar' is empty.
373 -- Notice that the boolean value returned is just a snapshot of
374 -- the state of the MVar. By the time you get to react on its result,
375 -- the MVar may have been filled (or emptied) - so be extremely
376 -- careful when using this operation. Use 'tryTakeMVar' instead if possible.
377 isEmptyMVar :: MVar a -> IO Bool
378 isEmptyMVar (MVar mv#) = IO $ \ s# ->
379 case isEmptyMVar# mv# s# of
380 (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
382 -- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
383 -- "System.Mem.Weak" for more about finalizers.
384 addMVarFinalizer :: MVar a -> IO () -> IO ()
385 addMVarFinalizer (MVar m) finalizer =
386 IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
390 %************************************************************************
392 \subsection{Thread waiting}
394 %************************************************************************
397 #ifdef mingw32_HOST_OS
399 -- Note: threadDelay, threadWaitRead and threadWaitWrite aren't really functional
400 -- on Win32, but left in there because lib code (still) uses them (the manner
401 -- in which they're used doesn't cause problems on a Win32 platform though.)
403 asyncRead :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
404 asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf) =
405 IO $ \s -> case asyncRead# fd isSock len buf s of
406 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
408 asyncWrite :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
409 asyncWrite (I# fd) (I# isSock) (I# len) (Ptr buf) =
410 IO $ \s -> case asyncWrite# fd isSock len buf s of
411 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
413 asyncDoProc :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
414 asyncDoProc (FunPtr proc) (Ptr param) =
415 -- the 'length' value is ignored; simplifies implementation of
416 -- the async*# primops to have them all return the same result.
417 IO $ \s -> case asyncDoProc# proc param s of
418 (# s, len#, err# #) -> (# s, I# err# #)
420 -- to aid the use of these primops by the IO Handle implementation,
421 -- provide the following convenience funs:
423 -- this better be a pinned byte array!
424 asyncReadBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
425 asyncReadBA fd isSock len off bufB =
426 asyncRead fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
428 asyncWriteBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
429 asyncWriteBA fd isSock len off bufB =
430 asyncWrite fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
434 -- -----------------------------------------------------------------------------
437 -- | Block the current thread until data is available to read on the
438 -- given file descriptor (GHC only).
439 threadWaitRead :: Fd -> IO ()
441 #ifndef mingw32_HOST_OS
442 | threaded = waitForReadEvent fd
444 | otherwise = IO $ \s ->
445 case fromIntegral fd of { I# fd# ->
446 case waitRead# fd# s of { s -> (# s, () #)
449 -- | Block the current thread until data can be written to the
450 -- given file descriptor (GHC only).
451 threadWaitWrite :: Fd -> IO ()
453 #ifndef mingw32_HOST_OS
454 | threaded = waitForWriteEvent fd
456 | otherwise = IO $ \s ->
457 case fromIntegral fd of { I# fd# ->
458 case waitWrite# fd# s of { s -> (# s, () #)
461 -- | Suspends the current thread for a given number of microseconds
464 -- Note that the resolution used by the Haskell runtime system's
465 -- internal timer is 1\/50 second, and 'threadDelay' will round its
466 -- argument up to the nearest multiple of this resolution.
468 -- There is no guarantee that the thread will be rescheduled promptly
469 -- when the delay has expired, but the thread will never continue to
470 -- run /earlier/ than specified.
472 threadDelay :: Int -> IO ()
474 #ifndef mingw32_HOST_OS
475 | threaded = waitForDelayEvent time
477 | threaded = c_Sleep (fromIntegral (time `quot` 1000))
479 | otherwise = IO $ \s ->
480 case fromIntegral time of { I# time# ->
481 case delay# time# s of { s -> (# s, () #)
485 #ifndef mingw32_HOST_OS
486 | threaded = waitForDelayEventSTM usecs
487 | otherwise = error "registerDelay: requires -threaded"
489 = error "registerDelay: not currently supported on Windows"
492 -- On Windows, we just make a safe call to 'Sleep' to implement threadDelay.
493 #ifdef mingw32_HOST_OS
494 foreign import stdcall safe "Sleep" c_Sleep :: CInt -> IO ()
497 foreign import ccall unsafe "rtsSupportsBoundThreads" threaded :: Bool
499 -- ----------------------------------------------------------------------------
500 -- Threaded RTS implementation of threadWaitRead, threadWaitWrite, threadDelay
502 -- In the threaded RTS, we employ a single IO Manager thread to wait
503 -- for all outstanding IO requests (threadWaitRead,threadWaitWrite)
504 -- and delays (threadDelay).
506 -- We can do this because in the threaded RTS the IO Manager can make
507 -- a non-blocking call to select(), so we don't have to do select() in
508 -- the scheduler as we have to in the non-threaded RTS. We get performance
509 -- benefits from doing it this way, because we only have to restart the select()
510 -- when a new request arrives, rather than doing one select() each time
511 -- around the scheduler loop. Furthermore, the scheduler can be simplified
512 -- by not having to check for completed IO requests.
514 -- Issues, possible problems:
516 -- - we might want bound threads to just do the blocking
517 -- operation rather than communicating with the IO manager
518 -- thread. This would prevent simgle-threaded programs which do
519 -- IO from requiring multiple OS threads. However, it would also
520 -- prevent bound threads waiting on IO from being killed or sent
523 -- - Apprently exec() doesn't work on Linux in a multithreaded program.
524 -- I couldn't repeat this.
526 -- - How do we handle signal delivery in the multithreaded RTS?
528 -- - forkProcess will kill the IO manager thread. Let's just
529 -- hope we don't need to do any blocking IO between fork & exec.
531 #ifndef mingw32_HOST_OS
534 = Read {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
535 | Write {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
538 = Delay {-# UNPACK #-} !Int {-# UNPACK #-} !(MVar ())
539 | DelaySTM {-# UNPACK #-} !Int {-# UNPACK #-} !(TVar Bool)
541 pendingEvents :: IORef [IOReq]
542 pendingDelays :: IORef [DelayReq]
543 -- could use a strict list or array here
544 {-# NOINLINE pendingEvents #-}
545 {-# NOINLINE pendingDelays #-}
546 (pendingEvents,pendingDelays) = unsafePerformIO $ do
551 -- the first time we schedule an IO request, the service thread
552 -- will be created (cool, huh?)
554 ensureIOManagerIsRunning :: IO ()
555 ensureIOManagerIsRunning
556 | threaded = seq pendingEvents $ return ()
557 | otherwise = return ()
559 startIOManagerThread :: IO ()
560 startIOManagerThread = do
561 allocaArray 2 $ \fds -> do
562 throwErrnoIfMinus1 "startIOManagerThread" (c_pipe fds)
563 rd_end <- peekElemOff fds 0
564 wr_end <- peekElemOff fds 1
565 writeIORef stick (fromIntegral wr_end)
566 c_setIOManagerPipe wr_end
568 allocaBytes sizeofFdSet $ \readfds -> do
569 allocaBytes sizeofFdSet $ \writefds -> do
570 allocaBytes sizeofTimeVal $ \timeval -> do
571 service_loop (fromIntegral rd_end) readfds writefds timeval [] []
574 -- XXX: move real forkIO here from Control.Concurrent?
575 quickForkIO action = IO $ \s ->
576 case (fork# action s) of (# s1, id #) -> (# s1, ThreadId id #)
579 :: Fd -- listen to this for wakeup calls
586 service_loop wakeup readfds writefds ptimeval old_reqs old_delays = do
588 -- pick up new IO requests
589 new_reqs <- atomicModifyIORef pendingEvents (\a -> ([],a))
590 let reqs = new_reqs ++ old_reqs
592 -- pick up new delay requests
593 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
594 let delays = foldr insertDelay old_delays new_delays
596 -- build the FDSets for select()
600 maxfd <- buildFdSets 0 readfds writefds reqs
602 -- perform the select()
603 let do_select delays = do
604 -- check the current time and wake up any thread in
605 -- threadDelay whose timeout has expired. Also find the
606 -- timeout value for the select() call.
608 (delays', timeout) <- getDelay now ptimeval delays
610 res <- c_select ((max wakeup maxfd)+1) readfds writefds
616 then do_select delays'
617 else return (res,delays')
621 (res,delays') <- do_select delays
622 -- ToDo: check result
624 b <- fdIsSet wakeup readfds
627 else alloca $ \p -> do
628 c_read (fromIntegral wakeup) p 1; return ()
632 else do handler_tbl <- peek handlers
633 sp <- peekElemOff handler_tbl (fromIntegral s)
634 quickForkIO (do io <- deRefStablePtr sp; io)
638 putMVar prodding False
640 reqs' <- completeRequests reqs readfds writefds []
641 service_loop wakeup readfds writefds ptimeval reqs' delays'
644 {-# NOINLINE stick #-}
645 stick = unsafePerformIO (newIORef 0)
647 prodding :: MVar Bool
648 {-# NOINLINE prodding #-}
649 prodding = unsafePerformIO (newMVar False)
651 prodServiceThread :: IO ()
652 prodServiceThread = do
653 b <- takeMVar prodding
655 then do fd <- readIORef stick
656 with 0xff $ \pbuf -> do c_write (fromIntegral fd) pbuf 1; return ()
658 putMVar prodding True
660 foreign import ccall "&signal_handlers" handlers :: Ptr (Ptr (StablePtr (IO ())))
662 foreign import ccall "setIOManagerPipe"
663 c_setIOManagerPipe :: CInt -> IO ()
665 -- -----------------------------------------------------------------------------
668 buildFdSets maxfd readfds writefds [] = return maxfd
669 buildFdSets maxfd readfds writefds (Read fd m : reqs) = do
671 buildFdSets (max maxfd fd) readfds writefds reqs
672 buildFdSets maxfd readfds writefds (Write fd m : reqs) = do
674 buildFdSets (max maxfd fd) readfds writefds reqs
676 completeRequests [] _ _ reqs' = return reqs'
677 completeRequests (Read fd m : reqs) readfds writefds reqs' = do
678 b <- fdIsSet fd readfds
680 then do putMVar m (); completeRequests reqs readfds writefds reqs'
681 else completeRequests reqs readfds writefds (Read fd m : reqs')
682 completeRequests (Write fd m : reqs) readfds writefds reqs' = do
683 b <- fdIsSet fd writefds
685 then do putMVar m (); completeRequests reqs readfds writefds reqs'
686 else completeRequests reqs readfds writefds (Write fd m : reqs')
688 waitForReadEvent :: Fd -> IO ()
689 waitForReadEvent fd = do
691 atomicModifyIORef pendingEvents (\xs -> (Read fd m : xs, ()))
695 waitForWriteEvent :: Fd -> IO ()
696 waitForWriteEvent fd = do
698 atomicModifyIORef pendingEvents (\xs -> (Write fd m : xs, ()))
702 -- XXX: move into GHC.IOBase from Data.IORef?
703 atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
704 atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
706 -- -----------------------------------------------------------------------------
709 waitForDelayEvent :: Int -> IO ()
710 waitForDelayEvent usecs = do
713 let target = now + usecs `quot` tick_usecs
714 atomicModifyIORef pendingDelays (\xs -> (Delay target m : xs, ()))
718 -- Delays for use in STM
719 waitForDelayEventSTM :: Int -> IO (TVar Bool)
720 waitForDelayEventSTM usecs = do
721 t <- atomically $ newTVar False
723 let target = now + usecs `quot` tick_usecs
724 atomicModifyIORef pendingDelays (\xs -> (DelaySTM target t : xs, ()))
728 -- Walk the queue of pending delays, waking up any that have passed
729 -- and return the smallest delay to wait for. The queue of pending
730 -- delays is kept ordered.
731 getDelay :: Ticks -> Ptr CTimeVal -> [DelayReq] -> IO ([DelayReq], Ptr CTimeVal)
732 getDelay now ptimeval [] = return ([],nullPtr)
733 getDelay now ptimeval all@(d : rest)
735 Delay time m | now >= time -> do
737 getDelay now ptimeval rest
738 DelaySTM time t | now >= time -> do
739 atomically $ writeTVar t True
740 getDelay now ptimeval rest
742 setTimevalTicks ptimeval (delayTime d - now)
743 return (all,ptimeval)
745 insertDelay :: DelayReq -> [DelayReq] -> [DelayReq]
746 insertDelay d [] = [d]
747 insertDelay d1 ds@(d2 : rest)
748 | delayTime d1 <= delayTime d2 = d1 : ds
749 | otherwise = d2 : insertDelay d1 rest
751 delayTime (Delay t _) = t
752 delayTime (DelaySTM t _) = t
755 tick_freq = 50 :: Ticks -- accuracy of threadDelay (ticks per sec)
756 tick_usecs = 1000000 `quot` tick_freq :: Int
758 newtype CTimeVal = CTimeVal ()
760 foreign import ccall unsafe "sizeofTimeVal"
763 foreign import ccall unsafe "getTicksOfDay"
764 getTicksOfDay :: IO Ticks
766 foreign import ccall unsafe "setTimevalTicks"
767 setTimevalTicks :: Ptr CTimeVal -> Ticks -> IO ()
769 -- ----------------------------------------------------------------------------
770 -- select() interface
772 -- ToDo: move to System.Posix.Internals?
774 newtype CFdSet = CFdSet ()
776 foreign import ccall safe "select"
777 c_select :: Fd -> Ptr CFdSet -> Ptr CFdSet -> Ptr CFdSet -> Ptr CTimeVal
780 foreign import ccall unsafe "hsFD_CLR"
781 fdClr :: Fd -> Ptr CFdSet -> IO ()
783 foreign import ccall unsafe "hsFD_ISSET"
784 fdIsSet :: Fd -> Ptr CFdSet -> IO CInt
786 foreign import ccall unsafe "hsFD_SET"
787 fdSet :: Fd -> Ptr CFdSet -> IO ()
789 foreign import ccall unsafe "hsFD_ZERO"
790 fdZero :: Ptr CFdSet -> IO ()
792 foreign import ccall unsafe "sizeof_fd_set"