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 , forkIO -- :: IO a -> IO ThreadId
28 , forkOnIO -- :: Int -> IO a -> IO ThreadId
29 , childHandler -- :: Exception -> IO ()
30 , myThreadId -- :: IO ThreadId
31 , killThread -- :: ThreadId -> IO ()
32 , throwTo -- :: ThreadId -> Exception -> IO ()
33 , par -- :: a -> b -> b
34 , pseq -- :: a -> b -> b
36 , labelThread -- :: ThreadId -> String -> IO ()
39 , threadDelay -- :: Int -> IO ()
40 , registerDelay -- :: Int -> IO (TVar Bool)
41 , threadWaitRead -- :: Int -> IO ()
42 , threadWaitWrite -- :: Int -> IO ()
46 , newMVar -- :: a -> IO (MVar a)
47 , newEmptyMVar -- :: IO (MVar a)
48 , takeMVar -- :: MVar a -> IO a
49 , putMVar -- :: MVar a -> a -> IO ()
50 , tryTakeMVar -- :: MVar a -> IO (Maybe a)
51 , tryPutMVar -- :: MVar a -> a -> IO Bool
52 , isEmptyMVar -- :: MVar a -> IO Bool
53 , addMVarFinalizer -- :: MVar a -> IO () -> IO ()
57 , atomically -- :: STM a -> IO a
59 , orElse -- :: STM a -> STM a -> STM a
60 , catchSTM -- :: STM a -> (Exception -> STM a) -> STM a
62 , newTVar -- :: a -> STM (TVar a)
63 , newTVarIO -- :: a -> STM (TVar a)
64 , readTVar -- :: TVar a -> STM a
65 , writeTVar -- :: a -> TVar a -> STM ()
66 , unsafeIOToSTM -- :: IO a -> STM a
69 #ifdef mingw32_HOST_OS
70 , asyncRead -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
71 , asyncWrite -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
72 , asyncDoProc -- :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
74 , asyncReadBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
75 , asyncWriteBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
78 #ifndef mingw32_HOST_OS
79 , ensureIOManagerIsRunning
83 import System.Posix.Types
84 import System.Posix.Internals
89 import {-# SOURCE #-} GHC.TopHandler ( reportError, reportStackOverflow )
96 import GHC.Num ( Num(..) )
97 import GHC.Real ( fromIntegral, quot )
98 import GHC.Base ( Int(..) )
99 import GHC.Exception ( catchException, Exception(..), AsyncException(..) )
100 import GHC.Pack ( packCString# )
101 import GHC.Ptr ( Ptr(..), plusPtr, FunPtr(..) )
103 import GHC.Show ( Show(..), showString )
106 infixr 0 `par`, `pseq`
109 %************************************************************************
111 \subsection{@ThreadId@, @par@, and @fork@}
113 %************************************************************************
116 data ThreadId = ThreadId ThreadId# deriving( Typeable )
117 -- ToDo: data ThreadId = ThreadId (Weak ThreadId#)
118 -- But since ThreadId# is unlifted, the Weak type must use open
121 A 'ThreadId' is an abstract type representing a handle to a thread.
122 'ThreadId' is an instance of 'Eq', 'Ord' and 'Show', where
123 the 'Ord' instance implements an arbitrary total ordering over
124 'ThreadId's. The 'Show' instance lets you convert an arbitrary-valued
125 'ThreadId' to string form; showing a 'ThreadId' value is occasionally
126 useful when debugging or diagnosing the behaviour of a concurrent
129 /Note/: in GHC, if you have a 'ThreadId', you essentially have
130 a pointer to the thread itself. This means the thread itself can\'t be
131 garbage collected until you drop the 'ThreadId'.
132 This misfeature will hopefully be corrected at a later date.
134 /Note/: Hugs does not provide any operations on other threads;
135 it defines 'ThreadId' as a synonym for ().
138 instance Show ThreadId where
140 showString "ThreadId " .
141 showsPrec d (getThreadId (id2TSO t))
143 foreign import ccall unsafe "rts_getThreadId" getThreadId :: ThreadId# -> Int
145 id2TSO :: ThreadId -> ThreadId#
146 id2TSO (ThreadId t) = t
148 foreign import ccall unsafe "cmp_thread" cmp_thread :: ThreadId# -> ThreadId# -> CInt
151 cmpThread :: ThreadId -> ThreadId -> Ordering
153 case cmp_thread (id2TSO t1) (id2TSO t2) of
158 instance Eq ThreadId where
160 case t1 `cmpThread` t2 of
164 instance Ord ThreadId where
168 This sparks off a new thread to run the 'IO' computation passed as the
169 first argument, and returns the 'ThreadId' of the newly created
172 The new thread will be a lightweight thread; if you want to use a foreign
173 library that uses thread-local storage, use 'forkOS' instead.
175 forkIO :: IO () -> IO ThreadId
176 forkIO action = IO $ \ s ->
177 case (fork# action_plus s) of (# s1, id #) -> (# s1, ThreadId id #)
179 action_plus = catchException action childHandler
181 forkOnIO :: Int -> IO () -> IO ThreadId
182 forkOnIO (I# cpu) action = IO $ \ s ->
183 case (forkOn# cpu action_plus s) of (# s1, id #) -> (# s1, ThreadId id #)
185 action_plus = catchException action childHandler
187 childHandler :: Exception -> IO ()
188 childHandler err = catchException (real_handler err) childHandler
190 real_handler :: Exception -> IO ()
193 -- ignore thread GC and killThread exceptions:
194 BlockedOnDeadMVar -> return ()
195 BlockedIndefinitely -> return ()
196 AsyncException ThreadKilled -> return ()
198 -- report all others:
199 AsyncException StackOverflow -> reportStackOverflow
200 other -> reportError other
202 {- | 'killThread' terminates the given thread (GHC only).
203 Any work already done by the thread isn\'t
204 lost: the computation is suspended until required by another thread.
205 The memory used by the thread will be garbage collected if it isn\'t
206 referenced from anywhere. The 'killThread' function is defined in
209 > killThread tid = throwTo tid (AsyncException ThreadKilled)
212 killThread :: ThreadId -> IO ()
213 killThread tid = throwTo tid (AsyncException ThreadKilled)
215 {- | 'throwTo' raises an arbitrary exception in the target thread (GHC only).
217 'throwTo' does not return until the exception has been raised in the
218 target thread. The calling thread can thus be certain that the target
219 thread has received the exception. This is a useful property to know
220 when dealing with race conditions: eg. if there are two threads that
221 can kill each other, it is guaranteed that only one of the threads
222 will get to kill the other.
224 If the target thread is currently making a foreign call, then the
225 exception will not be raised (and hence 'throwTo' will not return)
226 until the call has completed. This is the case regardless of whether
227 the call is inside a 'block' or not.
229 throwTo :: ThreadId -> Exception -> IO ()
230 throwTo (ThreadId id) ex = IO $ \ s ->
231 case (killThread# id ex s) of s1 -> (# s1, () #)
233 -- | Returns the 'ThreadId' of the calling thread (GHC only).
234 myThreadId :: IO ThreadId
235 myThreadId = IO $ \s ->
236 case (myThreadId# s) of (# s1, id #) -> (# s1, ThreadId id #)
239 -- |The 'yield' action allows (forces, in a co-operative multitasking
240 -- implementation) a context-switch to any other currently runnable
241 -- threads (if any), and is occasionally useful when implementing
242 -- concurrency abstractions.
245 case (yield# s) of s1 -> (# s1, () #)
247 {- | 'labelThread' stores a string as identifier for this thread if
248 you built a RTS with debugging support. This identifier will be used in
249 the debugging output to make distinction of different threads easier
250 (otherwise you only have the thread state object\'s address in the heap).
252 Other applications like the graphical Concurrent Haskell Debugger
253 (<http://www.informatik.uni-kiel.de/~fhu/chd/>) may choose to overload
254 'labelThread' for their purposes as well.
257 labelThread :: ThreadId -> String -> IO ()
258 labelThread (ThreadId t) str = IO $ \ s ->
259 let ps = packCString# str
260 adr = byteArrayContents# ps in
261 case (labelThread# t adr s) of s1 -> (# s1, () #)
263 -- Nota Bene: 'pseq' used to be 'seq'
264 -- but 'seq' is now defined in PrelGHC
266 -- "pseq" is defined a bit weirdly (see below)
268 -- The reason for the strange "lazy" call is that
269 -- it fools the compiler into thinking that pseq and par are non-strict in
270 -- their second argument (even if it inlines pseq at the call site).
271 -- If it thinks pseq is strict in "y", then it often evaluates
272 -- "y" before "x", which is totally wrong.
276 pseq x y = x `seq` lazy y
280 par x y = case (par# x) of { _ -> lazy y }
284 %************************************************************************
286 \subsection[stm]{Transactional heap operations}
288 %************************************************************************
290 TVars are shared memory locations which support atomic memory
294 -- |A monad supporting atomic memory transactions.
295 newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #)) deriving( Typeable )
297 unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
300 instance Functor STM where
301 fmap f x = x >>= (return . f)
303 instance Monad STM where
304 {-# INLINE return #-}
308 return x = returnSTM x
309 m >>= k = bindSTM m k
311 bindSTM :: STM a -> (a -> STM b) -> STM b
312 bindSTM (STM m) k = STM ( \s ->
314 (# new_s, a #) -> unSTM (k a) new_s
317 thenSTM :: STM a -> STM b -> STM b
318 thenSTM (STM m) k = STM ( \s ->
320 (# new_s, a #) -> unSTM k new_s
323 returnSTM :: a -> STM a
324 returnSTM x = STM (\s -> (# s, x #))
326 -- | Unsafely performs IO in the STM monad.
327 unsafeIOToSTM :: IO a -> STM a
328 unsafeIOToSTM (IO m) = STM m
330 -- |Perform a series of STM actions atomically.
332 -- You cannot use 'atomically' inside an 'unsafePerformIO' or 'unsafeInterleaveIO'.
333 -- Any attempt to do so will result in a runtime error. (Reason: allowing
334 -- this would effectively allow a transaction inside a transaction, depending
335 -- on exactly when the thunk is evaluated.)
337 -- However, see 'newTVarIO', which can be called inside 'unsafePerformIO',
338 -- and which allows top-level TVars to be allocated.
340 atomically :: STM a -> IO a
341 atomically (STM m) = IO (\s -> (atomically# m) s )
343 -- |Retry execution of the current memory transaction because it has seen
344 -- values in TVars which mean that it should not continue (e.g. the TVars
345 -- represent a shared buffer that is now empty). The implementation may
346 -- block the thread until one of the TVars that it has read from has been
347 -- udpated. (GHC only)
349 retry = STM $ \s# -> retry# s#
351 -- |Compose two alternative STM actions (GHC only). If the first action
352 -- completes without retrying then it forms the result of the orElse.
353 -- Otherwise, if the first action retries, then the second action is
354 -- tried in its place. If both actions retry then the orElse as a
356 orElse :: STM a -> STM a -> STM a
357 orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
359 -- |Exception handling within STM actions.
360 catchSTM :: STM a -> (Exception -> STM a) -> STM a
361 catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
363 -- |Shared memory locations that support atomic memory transactions.
364 data TVar a = TVar (TVar# RealWorld a) deriving( Typeable )
366 instance Eq (TVar a) where
367 (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
369 -- |Create a new TVar holding a value supplied
370 newTVar :: a -> STM (TVar a)
371 newTVar val = STM $ \s1# ->
372 case newTVar# val s1# of
373 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
375 -- |@IO@ version of 'newTVar'. This is useful for creating top-level
376 -- 'TVar's using 'System.IO.Unsafe.unsafePerformIO', because using
377 -- 'atomically' inside 'System.IO.Unsafe.unsafePerformIO' isn't
379 newTVarIO :: a -> IO (TVar a)
380 newTVarIO val = IO $ \s1# ->
381 case newTVar# val s1# of
382 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
384 -- |Return the current value stored in a TVar
385 readTVar :: TVar a -> STM a
386 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
388 -- |Write the supplied value into a TVar
389 writeTVar :: TVar a -> a -> STM ()
390 writeTVar (TVar tvar#) val = STM $ \s1# ->
391 case writeTVar# tvar# val s1# of
396 %************************************************************************
398 \subsection[mvars]{M-Structures}
400 %************************************************************************
402 M-Vars are rendezvous points for concurrent threads. They begin
403 empty, and any attempt to read an empty M-Var blocks. When an M-Var
404 is written, a single blocked thread may be freed. Reading an M-Var
405 toggles its state from full back to empty. Therefore, any value
406 written to an M-Var may only be read once. Multiple reads and writes
407 are allowed, but there must be at least one read between any two
411 --Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
413 -- |Create an 'MVar' which is initially empty.
414 newEmptyMVar :: IO (MVar a)
415 newEmptyMVar = IO $ \ s# ->
417 (# s2#, svar# #) -> (# s2#, MVar svar# #)
419 -- |Create an 'MVar' which contains the supplied value.
420 newMVar :: a -> IO (MVar a)
422 newEmptyMVar >>= \ mvar ->
423 putMVar mvar value >>
426 -- |Return the contents of the 'MVar'. If the 'MVar' is currently
427 -- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
428 -- the 'MVar' is left empty.
430 -- There are two further important properties of 'takeMVar':
432 -- * 'takeMVar' is single-wakeup. That is, if there are multiple
433 -- threads blocked in 'takeMVar', and the 'MVar' becomes full,
434 -- only one thread will be woken up. The runtime guarantees that
435 -- the woken thread completes its 'takeMVar' operation.
437 -- * When multiple threads are blocked on an 'MVar', they are
438 -- woken up in FIFO order. This is useful for providing
439 -- fairness properties of abstractions built using 'MVar's.
441 takeMVar :: MVar a -> IO a
442 takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
444 -- |Put a value into an 'MVar'. If the 'MVar' is currently full,
445 -- 'putMVar' will wait until it becomes empty.
447 -- There are two further important properties of 'putMVar':
449 -- * 'putMVar' is single-wakeup. That is, if there are multiple
450 -- threads blocked in 'putMVar', and the 'MVar' becomes empty,
451 -- only one thread will be woken up. The runtime guarantees that
452 -- the woken thread completes its 'putMVar' operation.
454 -- * When multiple threads are blocked on an 'MVar', they are
455 -- woken up in FIFO order. This is useful for providing
456 -- fairness properties of abstractions built using 'MVar's.
458 putMVar :: MVar a -> a -> IO ()
459 putMVar (MVar mvar#) x = IO $ \ s# ->
460 case putMVar# mvar# x s# of
463 -- |A non-blocking version of 'takeMVar'. The 'tryTakeMVar' function
464 -- returns immediately, with 'Nothing' if the 'MVar' was empty, or
465 -- @'Just' a@ if the 'MVar' was full with contents @a@. After 'tryTakeMVar',
466 -- the 'MVar' is left empty.
467 tryTakeMVar :: MVar a -> IO (Maybe a)
468 tryTakeMVar (MVar m) = IO $ \ s ->
469 case tryTakeMVar# m s of
470 (# s, 0#, _ #) -> (# s, Nothing #) -- MVar is empty
471 (# s, _, a #) -> (# s, Just a #) -- MVar is full
473 -- |A non-blocking version of 'putMVar'. The 'tryPutMVar' function
474 -- attempts to put the value @a@ into the 'MVar', returning 'True' if
475 -- it was successful, or 'False' otherwise.
476 tryPutMVar :: MVar a -> a -> IO Bool
477 tryPutMVar (MVar mvar#) x = IO $ \ s# ->
478 case tryPutMVar# mvar# x s# of
479 (# s, 0# #) -> (# s, False #)
480 (# s, _ #) -> (# s, True #)
482 -- |Check whether a given 'MVar' is empty.
484 -- Notice that the boolean value returned is just a snapshot of
485 -- the state of the MVar. By the time you get to react on its result,
486 -- the MVar may have been filled (or emptied) - so be extremely
487 -- careful when using this operation. Use 'tryTakeMVar' instead if possible.
488 isEmptyMVar :: MVar a -> IO Bool
489 isEmptyMVar (MVar mv#) = IO $ \ s# ->
490 case isEmptyMVar# mv# s# of
491 (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
493 -- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
494 -- "System.Mem.Weak" for more about finalizers.
495 addMVarFinalizer :: MVar a -> IO () -> IO ()
496 addMVarFinalizer (MVar m) finalizer =
497 IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
501 %************************************************************************
503 \subsection{Thread waiting}
505 %************************************************************************
508 #ifdef mingw32_HOST_OS
510 -- Note: threadDelay, threadWaitRead and threadWaitWrite aren't really functional
511 -- on Win32, but left in there because lib code (still) uses them (the manner
512 -- in which they're used doesn't cause problems on a Win32 platform though.)
514 asyncRead :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
515 asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf) =
516 IO $ \s -> case asyncRead# fd isSock len buf s of
517 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
519 asyncWrite :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
520 asyncWrite (I# fd) (I# isSock) (I# len) (Ptr buf) =
521 IO $ \s -> case asyncWrite# fd isSock len buf s of
522 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
524 asyncDoProc :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
525 asyncDoProc (FunPtr proc) (Ptr param) =
526 -- the 'length' value is ignored; simplifies implementation of
527 -- the async*# primops to have them all return the same result.
528 IO $ \s -> case asyncDoProc# proc param s of
529 (# s, len#, err# #) -> (# s, I# err# #)
531 -- to aid the use of these primops by the IO Handle implementation,
532 -- provide the following convenience funs:
534 -- this better be a pinned byte array!
535 asyncReadBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
536 asyncReadBA fd isSock len off bufB =
537 asyncRead fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
539 asyncWriteBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
540 asyncWriteBA fd isSock len off bufB =
541 asyncWrite fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
545 -- -----------------------------------------------------------------------------
548 -- | Block the current thread until data is available to read on the
549 -- given file descriptor (GHC only).
550 threadWaitRead :: Fd -> IO ()
552 #ifndef mingw32_HOST_OS
553 | threaded = waitForReadEvent fd
555 | otherwise = IO $ \s ->
556 case fromIntegral fd of { I# fd# ->
557 case waitRead# fd# s of { s -> (# s, () #)
560 -- | Block the current thread until data can be written to the
561 -- given file descriptor (GHC only).
562 threadWaitWrite :: Fd -> IO ()
564 #ifndef mingw32_HOST_OS
565 | threaded = waitForWriteEvent fd
567 | otherwise = IO $ \s ->
568 case fromIntegral fd of { I# fd# ->
569 case waitWrite# fd# s of { s -> (# s, () #)
572 -- | Suspends the current thread for a given number of microseconds
575 -- Note that the resolution used by the Haskell runtime system's
576 -- internal timer is 1\/50 second, and 'threadDelay' will round its
577 -- argument up to the nearest multiple of this resolution.
579 -- There is no guarantee that the thread will be rescheduled promptly
580 -- when the delay has expired, but the thread will never continue to
581 -- run /earlier/ than specified.
583 threadDelay :: Int -> IO ()
585 #ifndef mingw32_HOST_OS
586 | threaded = waitForDelayEvent time
588 | threaded = c_Sleep (fromIntegral (time `quot` 1000))
590 | otherwise = IO $ \s ->
591 case fromIntegral time of { I# time# ->
592 case delay# time# s of { s -> (# s, () #)
595 registerDelay :: Int -> IO (TVar Bool)
597 #ifndef mingw32_HOST_OS
598 | threaded = waitForDelayEventSTM usecs
599 | otherwise = error "registerDelay: requires -threaded"
601 = error "registerDelay: not currently supported on Windows"
604 -- On Windows, we just make a safe call to 'Sleep' to implement threadDelay.
605 #ifdef mingw32_HOST_OS
606 foreign import stdcall safe "Sleep" c_Sleep :: CInt -> IO ()
609 foreign import ccall unsafe "rtsSupportsBoundThreads" threaded :: Bool
611 -- ----------------------------------------------------------------------------
612 -- Threaded RTS implementation of threadWaitRead, threadWaitWrite, threadDelay
614 -- In the threaded RTS, we employ a single IO Manager thread to wait
615 -- for all outstanding IO requests (threadWaitRead,threadWaitWrite)
616 -- and delays (threadDelay).
618 -- We can do this because in the threaded RTS the IO Manager can make
619 -- a non-blocking call to select(), so we don't have to do select() in
620 -- the scheduler as we have to in the non-threaded RTS. We get performance
621 -- benefits from doing it this way, because we only have to restart the select()
622 -- when a new request arrives, rather than doing one select() each time
623 -- around the scheduler loop. Furthermore, the scheduler can be simplified
624 -- by not having to check for completed IO requests.
626 -- Issues, possible problems:
628 -- - we might want bound threads to just do the blocking
629 -- operation rather than communicating with the IO manager
630 -- thread. This would prevent simgle-threaded programs which do
631 -- IO from requiring multiple OS threads. However, it would also
632 -- prevent bound threads waiting on IO from being killed or sent
635 -- - Apprently exec() doesn't work on Linux in a multithreaded program.
636 -- I couldn't repeat this.
638 -- - How do we handle signal delivery in the multithreaded RTS?
640 -- - forkProcess will kill the IO manager thread. Let's just
641 -- hope we don't need to do any blocking IO between fork & exec.
643 #ifndef mingw32_HOST_OS
646 = Read {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
647 | Write {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
650 = Delay {-# UNPACK #-} !Int {-# UNPACK #-} !(MVar ())
651 | DelaySTM {-# UNPACK #-} !Int {-# UNPACK #-} !(TVar Bool)
653 pendingEvents :: IORef [IOReq]
654 pendingDelays :: IORef [DelayReq]
655 -- could use a strict list or array here
656 {-# NOINLINE pendingEvents #-}
657 {-# NOINLINE pendingDelays #-}
658 (pendingEvents,pendingDelays) = unsafePerformIO $ do
663 -- the first time we schedule an IO request, the service thread
664 -- will be created (cool, huh?)
666 ensureIOManagerIsRunning :: IO ()
667 ensureIOManagerIsRunning
668 | threaded = seq pendingEvents $ return ()
669 | otherwise = return ()
671 startIOManagerThread :: IO ()
672 startIOManagerThread = do
673 allocaArray 2 $ \fds -> do
674 throwErrnoIfMinus1 "startIOManagerThread" (c_pipe fds)
675 rd_end <- peekElemOff fds 0
676 wr_end <- peekElemOff fds 1
677 writeIORef stick (fromIntegral wr_end)
678 c_setIOManagerPipe wr_end
680 allocaBytes sizeofFdSet $ \readfds -> do
681 allocaBytes sizeofFdSet $ \writefds -> do
682 allocaBytes sizeofTimeVal $ \timeval -> do
683 service_loop (fromIntegral rd_end) readfds writefds timeval [] []
687 :: Fd -- listen to this for wakeup calls
694 service_loop wakeup readfds writefds ptimeval old_reqs old_delays = do
696 -- pick up new IO requests
697 new_reqs <- atomicModifyIORef pendingEvents (\a -> ([],a))
698 let reqs = new_reqs ++ old_reqs
700 -- pick up new delay requests
701 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
702 let delays = foldr insertDelay old_delays new_delays
704 -- build the FDSets for select()
708 maxfd <- buildFdSets 0 readfds writefds reqs
710 -- perform the select()
711 let do_select delays = do
712 -- check the current time and wake up any thread in
713 -- threadDelay whose timeout has expired. Also find the
714 -- timeout value for the select() call.
716 (delays', timeout) <- getDelay now ptimeval delays
718 res <- c_select ((max wakeup maxfd)+1) readfds writefds
724 _ | err == eINTR -> do_select delays'
725 -- EINTR: just redo the select()
726 _ | err == eBADF -> return (True, delays)
727 -- EBADF: one of the file descriptors is closed or bad,
728 -- we don't know which one, so wake everyone up.
729 _ | otherwise -> throwErrno "select"
730 -- otherwise (ENOMEM or EINVAL) something has gone
731 -- wrong; report the error.
733 return (False,delays')
735 (wakeup_all,delays') <- do_select delays
738 if wakeup_all then return False
740 b <- fdIsSet wakeup readfds
743 else alloca $ \p -> do
744 c_read (fromIntegral wakeup) p 1; return ()
747 _ | s == io_MANAGER_WAKEUP -> return False
748 _ | s == io_MANAGER_DIE -> return True
749 _ -> do handler_tbl <- peek handlers
750 sp <- peekElemOff handler_tbl (fromIntegral s)
751 forkIO (do io <- deRefStablePtr sp; io)
754 if exit then return () else do
757 putMVar prodding False
759 reqs' <- if wakeup_all then do wakeupAll reqs; return []
760 else completeRequests reqs readfds writefds []
762 service_loop wakeup readfds writefds ptimeval reqs' delays'
765 {-# NOINLINE stick #-}
766 stick = unsafePerformIO (newIORef 0)
768 io_MANAGER_WAKEUP = 0xff :: CChar
769 io_MANAGER_DIE = 0xfe :: CChar
771 prodding :: MVar Bool
772 {-# NOINLINE prodding #-}
773 prodding = unsafePerformIO (newMVar False)
775 prodServiceThread :: IO ()
776 prodServiceThread = do
777 b <- takeMVar prodding
779 then do fd <- readIORef stick
780 with io_MANAGER_WAKEUP $ \pbuf -> do
781 c_write (fromIntegral fd) pbuf 1; return ()
783 putMVar prodding True
785 foreign import ccall "&signal_handlers" handlers :: Ptr (Ptr (StablePtr (IO ())))
787 foreign import ccall "setIOManagerPipe"
788 c_setIOManagerPipe :: CInt -> IO ()
790 -- -----------------------------------------------------------------------------
793 buildFdSets maxfd readfds writefds [] = return maxfd
794 buildFdSets maxfd readfds writefds (Read fd m : reqs)
795 | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
798 buildFdSets (max maxfd fd) readfds writefds reqs
799 buildFdSets maxfd readfds writefds (Write fd m : reqs)
800 | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
803 buildFdSets (max maxfd fd) readfds writefds reqs
805 completeRequests [] _ _ reqs' = return reqs'
806 completeRequests (Read fd m : reqs) readfds writefds reqs' = do
807 b <- fdIsSet fd readfds
809 then do putMVar m (); completeRequests reqs readfds writefds reqs'
810 else completeRequests reqs readfds writefds (Read fd m : reqs')
811 completeRequests (Write fd m : reqs) readfds writefds reqs' = do
812 b <- fdIsSet fd writefds
814 then do putMVar m (); completeRequests reqs readfds writefds reqs'
815 else completeRequests reqs readfds writefds (Write fd m : reqs')
817 wakeupAll [] = return ()
818 wakeupAll (Read fd m : reqs) = do putMVar m (); wakeupAll reqs
819 wakeupAll (Write fd m : reqs) = do putMVar m (); wakeupAll reqs
821 waitForReadEvent :: Fd -> IO ()
822 waitForReadEvent fd = do
824 atomicModifyIORef pendingEvents (\xs -> (Read fd m : xs, ()))
828 waitForWriteEvent :: Fd -> IO ()
829 waitForWriteEvent fd = do
831 atomicModifyIORef pendingEvents (\xs -> (Write fd m : xs, ()))
835 -- XXX: move into GHC.IOBase from Data.IORef?
836 atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
837 atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
839 -- -----------------------------------------------------------------------------
842 waitForDelayEvent :: Int -> IO ()
843 waitForDelayEvent usecs = do
846 let target = now + usecs `quot` tick_usecs
847 atomicModifyIORef pendingDelays (\xs -> (Delay target m : xs, ()))
851 -- Delays for use in STM
852 waitForDelayEventSTM :: Int -> IO (TVar Bool)
853 waitForDelayEventSTM usecs = do
854 t <- atomically $ newTVar False
856 let target = now + usecs `quot` tick_usecs
857 atomicModifyIORef pendingDelays (\xs -> (DelaySTM target t : xs, ()))
861 -- Walk the queue of pending delays, waking up any that have passed
862 -- and return the smallest delay to wait for. The queue of pending
863 -- delays is kept ordered.
864 getDelay :: Ticks -> Ptr CTimeVal -> [DelayReq] -> IO ([DelayReq], Ptr CTimeVal)
865 getDelay now ptimeval [] = return ([],nullPtr)
866 getDelay now ptimeval all@(d : rest)
868 Delay time m | now >= time -> do
870 getDelay now ptimeval rest
871 DelaySTM time t | now >= time -> do
872 atomically $ writeTVar t True
873 getDelay now ptimeval rest
875 setTimevalTicks ptimeval (delayTime d - now)
876 return (all,ptimeval)
878 insertDelay :: DelayReq -> [DelayReq] -> [DelayReq]
879 insertDelay d [] = [d]
880 insertDelay d1 ds@(d2 : rest)
881 | delayTime d1 <= delayTime d2 = d1 : ds
882 | otherwise = d2 : insertDelay d1 rest
884 delayTime (Delay t _) = t
885 delayTime (DelaySTM t _) = t
888 tick_freq = 50 :: Ticks -- accuracy of threadDelay (ticks per sec)
889 tick_usecs = 1000000 `quot` tick_freq :: Int
891 newtype CTimeVal = CTimeVal ()
893 foreign import ccall unsafe "sizeofTimeVal"
896 foreign import ccall unsafe "getTicksOfDay"
897 getTicksOfDay :: IO Ticks
899 foreign import ccall unsafe "setTimevalTicks"
900 setTimevalTicks :: Ptr CTimeVal -> Ticks -> IO ()
902 -- ----------------------------------------------------------------------------
903 -- select() interface
905 -- ToDo: move to System.Posix.Internals?
907 newtype CFdSet = CFdSet ()
909 foreign import ccall safe "select"
910 c_select :: Fd -> Ptr CFdSet -> Ptr CFdSet -> Ptr CFdSet -> Ptr CTimeVal
913 foreign import ccall unsafe "hsFD_SETSIZE"
916 foreign import ccall unsafe "hsFD_CLR"
917 fdClr :: Fd -> Ptr CFdSet -> IO ()
919 foreign import ccall unsafe "hsFD_ISSET"
920 fdIsSet :: Fd -> Ptr CFdSet -> IO CInt
922 foreign import ccall unsafe "hsFD_SET"
923 fdSet :: Fd -> Ptr CFdSet -> IO ()
925 foreign import ccall unsafe "hsFD_ZERO"
926 fdZero :: Ptr CFdSet -> IO ()
928 foreign import ccall unsafe "sizeof_fd_set"