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.
331 atomically :: STM a -> IO a
332 atomically (STM m) = IO (\s -> (atomically# m) s )
334 -- |Retry execution of the current memory transaction because it has seen
335 -- values in TVars which mean that it should not continue (e.g. the TVars
336 -- represent a shared buffer that is now empty). The implementation may
337 -- block the thread until one of the TVars that it has read from has been
338 -- udpated. (GHC only)
340 retry = STM $ \s# -> retry# s#
342 -- |Compose two alternative STM actions (GHC only). If the first action
343 -- completes without retrying then it forms the result of the orElse.
344 -- Otherwise, if the first action retries, then the second action is
345 -- tried in its place. If both actions retry then the orElse as a
347 orElse :: STM a -> STM a -> STM a
348 orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
350 -- |Exception handling within STM actions.
351 catchSTM :: STM a -> (Exception -> STM a) -> STM a
352 catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
354 -- |Shared memory locations that support atomic memory transactions.
355 data TVar a = TVar (TVar# RealWorld a) deriving( Typeable )
357 instance Eq (TVar a) where
358 (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
360 -- |Create a new TVar holding a value supplied
361 newTVar :: a -> STM (TVar a)
362 newTVar val = STM $ \s1# ->
363 case newTVar# val s1# of
364 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
366 -- |@IO@ version of 'newTVar'. This is useful for creating top-level
367 -- 'TVar's using 'System.IO.Unsafe.unsafePerformIO', because using
368 -- 'atomically' inside 'System.IO.Unsafe.unsafePerformIO' isn't
370 newTVarIO :: a -> IO (TVar a)
371 newTVarIO val = IO $ \s1# ->
372 case newTVar# val s1# of
373 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
375 -- |Return the current value stored in a TVar
376 readTVar :: TVar a -> STM a
377 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
379 -- |Write the supplied value into a TVar
380 writeTVar :: TVar a -> a -> STM ()
381 writeTVar (TVar tvar#) val = STM $ \s1# ->
382 case writeTVar# tvar# val s1# of
387 %************************************************************************
389 \subsection[mvars]{M-Structures}
391 %************************************************************************
393 M-Vars are rendezvous points for concurrent threads. They begin
394 empty, and any attempt to read an empty M-Var blocks. When an M-Var
395 is written, a single blocked thread may be freed. Reading an M-Var
396 toggles its state from full back to empty. Therefore, any value
397 written to an M-Var may only be read once. Multiple reads and writes
398 are allowed, but there must be at least one read between any two
402 --Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
404 -- |Create an 'MVar' which is initially empty.
405 newEmptyMVar :: IO (MVar a)
406 newEmptyMVar = IO $ \ s# ->
408 (# s2#, svar# #) -> (# s2#, MVar svar# #)
410 -- |Create an 'MVar' which contains the supplied value.
411 newMVar :: a -> IO (MVar a)
413 newEmptyMVar >>= \ mvar ->
414 putMVar mvar value >>
417 -- |Return the contents of the 'MVar'. If the 'MVar' is currently
418 -- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
419 -- the 'MVar' is left empty.
421 -- There are two further important properties of 'takeMVar':
423 -- * 'takeMVar' is single-wakeup. That is, if there are multiple
424 -- threads blocked in 'takeMVar', and the 'MVar' becomes full,
425 -- only one thread will be woken up. The runtime guarantees that
426 -- the woken thread completes its 'takeMVar' operation.
428 -- * When multiple threads are blocked on an 'MVar', they are
429 -- woken up in FIFO order. This is useful for providing
430 -- fairness properties of abstractions built using 'MVar's.
432 takeMVar :: MVar a -> IO a
433 takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
435 -- |Put a value into an 'MVar'. If the 'MVar' is currently full,
436 -- 'putMVar' will wait until it becomes empty.
438 -- There are two further important properties of 'putMVar':
440 -- * 'putMVar' is single-wakeup. That is, if there are multiple
441 -- threads blocked in 'putMVar', and the 'MVar' becomes empty,
442 -- only one thread will be woken up. The runtime guarantees that
443 -- the woken thread completes its 'putMVar' operation.
445 -- * When multiple threads are blocked on an 'MVar', they are
446 -- woken up in FIFO order. This is useful for providing
447 -- fairness properties of abstractions built using 'MVar's.
449 putMVar :: MVar a -> a -> IO ()
450 putMVar (MVar mvar#) x = IO $ \ s# ->
451 case putMVar# mvar# x s# of
454 -- |A non-blocking version of 'takeMVar'. The 'tryTakeMVar' function
455 -- returns immediately, with 'Nothing' if the 'MVar' was empty, or
456 -- @'Just' a@ if the 'MVar' was full with contents @a@. After 'tryTakeMVar',
457 -- the 'MVar' is left empty.
458 tryTakeMVar :: MVar a -> IO (Maybe a)
459 tryTakeMVar (MVar m) = IO $ \ s ->
460 case tryTakeMVar# m s of
461 (# s, 0#, _ #) -> (# s, Nothing #) -- MVar is empty
462 (# s, _, a #) -> (# s, Just a #) -- MVar is full
464 -- |A non-blocking version of 'putMVar'. The 'tryPutMVar' function
465 -- attempts to put the value @a@ into the 'MVar', returning 'True' if
466 -- it was successful, or 'False' otherwise.
467 tryPutMVar :: MVar a -> a -> IO Bool
468 tryPutMVar (MVar mvar#) x = IO $ \ s# ->
469 case tryPutMVar# mvar# x s# of
470 (# s, 0# #) -> (# s, False #)
471 (# s, _ #) -> (# s, True #)
473 -- |Check whether a given 'MVar' is empty.
475 -- Notice that the boolean value returned is just a snapshot of
476 -- the state of the MVar. By the time you get to react on its result,
477 -- the MVar may have been filled (or emptied) - so be extremely
478 -- careful when using this operation. Use 'tryTakeMVar' instead if possible.
479 isEmptyMVar :: MVar a -> IO Bool
480 isEmptyMVar (MVar mv#) = IO $ \ s# ->
481 case isEmptyMVar# mv# s# of
482 (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
484 -- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
485 -- "System.Mem.Weak" for more about finalizers.
486 addMVarFinalizer :: MVar a -> IO () -> IO ()
487 addMVarFinalizer (MVar m) finalizer =
488 IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
492 %************************************************************************
494 \subsection{Thread waiting}
496 %************************************************************************
499 #ifdef mingw32_HOST_OS
501 -- Note: threadDelay, threadWaitRead and threadWaitWrite aren't really functional
502 -- on Win32, but left in there because lib code (still) uses them (the manner
503 -- in which they're used doesn't cause problems on a Win32 platform though.)
505 asyncRead :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
506 asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf) =
507 IO $ \s -> case asyncRead# fd isSock len buf s of
508 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
510 asyncWrite :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
511 asyncWrite (I# fd) (I# isSock) (I# len) (Ptr buf) =
512 IO $ \s -> case asyncWrite# fd isSock len buf s of
513 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
515 asyncDoProc :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
516 asyncDoProc (FunPtr proc) (Ptr param) =
517 -- the 'length' value is ignored; simplifies implementation of
518 -- the async*# primops to have them all return the same result.
519 IO $ \s -> case asyncDoProc# proc param s of
520 (# s, len#, err# #) -> (# s, I# err# #)
522 -- to aid the use of these primops by the IO Handle implementation,
523 -- provide the following convenience funs:
525 -- this better be a pinned byte array!
526 asyncReadBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
527 asyncReadBA fd isSock len off bufB =
528 asyncRead fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
530 asyncWriteBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
531 asyncWriteBA fd isSock len off bufB =
532 asyncWrite fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
536 -- -----------------------------------------------------------------------------
539 -- | Block the current thread until data is available to read on the
540 -- given file descriptor (GHC only).
541 threadWaitRead :: Fd -> IO ()
543 #ifndef mingw32_HOST_OS
544 | threaded = waitForReadEvent fd
546 | otherwise = IO $ \s ->
547 case fromIntegral fd of { I# fd# ->
548 case waitRead# fd# s of { s -> (# s, () #)
551 -- | Block the current thread until data can be written to the
552 -- given file descriptor (GHC only).
553 threadWaitWrite :: Fd -> IO ()
555 #ifndef mingw32_HOST_OS
556 | threaded = waitForWriteEvent fd
558 | otherwise = IO $ \s ->
559 case fromIntegral fd of { I# fd# ->
560 case waitWrite# fd# s of { s -> (# s, () #)
563 -- | Suspends the current thread for a given number of microseconds
566 -- Note that the resolution used by the Haskell runtime system's
567 -- internal timer is 1\/50 second, and 'threadDelay' will round its
568 -- argument up to the nearest multiple of this resolution.
570 -- There is no guarantee that the thread will be rescheduled promptly
571 -- when the delay has expired, but the thread will never continue to
572 -- run /earlier/ than specified.
574 threadDelay :: Int -> IO ()
576 #ifndef mingw32_HOST_OS
577 | threaded = waitForDelayEvent time
579 | threaded = c_Sleep (fromIntegral (time `quot` 1000))
581 | otherwise = IO $ \s ->
582 case fromIntegral time of { I# time# ->
583 case delay# time# s of { s -> (# s, () #)
587 #ifndef mingw32_HOST_OS
588 | threaded = waitForDelayEventSTM usecs
589 | otherwise = error "registerDelay: requires -threaded"
591 = error "registerDelay: not currently supported on Windows"
594 -- On Windows, we just make a safe call to 'Sleep' to implement threadDelay.
595 #ifdef mingw32_HOST_OS
596 foreign import stdcall safe "Sleep" c_Sleep :: CInt -> IO ()
599 foreign import ccall unsafe "rtsSupportsBoundThreads" threaded :: Bool
601 -- ----------------------------------------------------------------------------
602 -- Threaded RTS implementation of threadWaitRead, threadWaitWrite, threadDelay
604 -- In the threaded RTS, we employ a single IO Manager thread to wait
605 -- for all outstanding IO requests (threadWaitRead,threadWaitWrite)
606 -- and delays (threadDelay).
608 -- We can do this because in the threaded RTS the IO Manager can make
609 -- a non-blocking call to select(), so we don't have to do select() in
610 -- the scheduler as we have to in the non-threaded RTS. We get performance
611 -- benefits from doing it this way, because we only have to restart the select()
612 -- when a new request arrives, rather than doing one select() each time
613 -- around the scheduler loop. Furthermore, the scheduler can be simplified
614 -- by not having to check for completed IO requests.
616 -- Issues, possible problems:
618 -- - we might want bound threads to just do the blocking
619 -- operation rather than communicating with the IO manager
620 -- thread. This would prevent simgle-threaded programs which do
621 -- IO from requiring multiple OS threads. However, it would also
622 -- prevent bound threads waiting on IO from being killed or sent
625 -- - Apprently exec() doesn't work on Linux in a multithreaded program.
626 -- I couldn't repeat this.
628 -- - How do we handle signal delivery in the multithreaded RTS?
630 -- - forkProcess will kill the IO manager thread. Let's just
631 -- hope we don't need to do any blocking IO between fork & exec.
633 #ifndef mingw32_HOST_OS
636 = Read {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
637 | Write {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
640 = Delay {-# UNPACK #-} !Int {-# UNPACK #-} !(MVar ())
641 | DelaySTM {-# UNPACK #-} !Int {-# UNPACK #-} !(TVar Bool)
643 pendingEvents :: IORef [IOReq]
644 pendingDelays :: IORef [DelayReq]
645 -- could use a strict list or array here
646 {-# NOINLINE pendingEvents #-}
647 {-# NOINLINE pendingDelays #-}
648 (pendingEvents,pendingDelays) = unsafePerformIO $ do
653 -- the first time we schedule an IO request, the service thread
654 -- will be created (cool, huh?)
656 ensureIOManagerIsRunning :: IO ()
657 ensureIOManagerIsRunning
658 | threaded = seq pendingEvents $ return ()
659 | otherwise = return ()
661 startIOManagerThread :: IO ()
662 startIOManagerThread = do
663 allocaArray 2 $ \fds -> do
664 throwErrnoIfMinus1 "startIOManagerThread" (c_pipe fds)
665 rd_end <- peekElemOff fds 0
666 wr_end <- peekElemOff fds 1
667 writeIORef stick (fromIntegral wr_end)
668 c_setIOManagerPipe wr_end
670 allocaBytes sizeofFdSet $ \readfds -> do
671 allocaBytes sizeofFdSet $ \writefds -> do
672 allocaBytes sizeofTimeVal $ \timeval -> do
673 service_loop (fromIntegral rd_end) readfds writefds timeval [] []
677 :: Fd -- listen to this for wakeup calls
684 service_loop wakeup readfds writefds ptimeval old_reqs old_delays = do
686 -- pick up new IO requests
687 new_reqs <- atomicModifyIORef pendingEvents (\a -> ([],a))
688 let reqs = new_reqs ++ old_reqs
690 -- pick up new delay requests
691 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
692 let delays = foldr insertDelay old_delays new_delays
694 -- build the FDSets for select()
698 maxfd <- buildFdSets 0 readfds writefds reqs
700 -- perform the select()
701 let do_select delays = do
702 -- check the current time and wake up any thread in
703 -- threadDelay whose timeout has expired. Also find the
704 -- timeout value for the select() call.
706 (delays', timeout) <- getDelay now ptimeval delays
708 res <- c_select ((max wakeup maxfd)+1) readfds writefds
714 _ | err == eINTR -> do_select delays'
715 -- EINTR: just redo the select()
716 _ | err == eBADF -> return (True, delays)
717 -- EBADF: one of the file descriptors is closed or bad,
718 -- we don't know which one, so wake everyone up.
719 _ | otherwise -> throwErrno "select"
720 -- otherwise (ENOMEM or EINVAL) something has gone
721 -- wrong; report the error.
723 return (False,delays')
725 (wakeup_all,delays') <- do_select delays
728 if wakeup_all then return False
730 b <- fdIsSet wakeup readfds
733 else alloca $ \p -> do
734 c_read (fromIntegral wakeup) p 1; return ()
737 _ | s == io_MANAGER_WAKEUP -> return False
738 _ | s == io_MANAGER_DIE -> return True
739 _ -> do handler_tbl <- peek handlers
740 sp <- peekElemOff handler_tbl (fromIntegral s)
741 forkIO (do io <- deRefStablePtr sp; io)
744 if exit then return () else do
747 putMVar prodding False
749 reqs' <- if wakeup_all then do wakeupAll reqs; return []
750 else completeRequests reqs readfds writefds []
752 service_loop wakeup readfds writefds ptimeval reqs' delays'
755 {-# NOINLINE stick #-}
756 stick = unsafePerformIO (newIORef 0)
758 io_MANAGER_WAKEUP = 0xff :: CChar
759 io_MANAGER_DIE = 0xfe :: CChar
761 prodding :: MVar Bool
762 {-# NOINLINE prodding #-}
763 prodding = unsafePerformIO (newMVar False)
765 prodServiceThread :: IO ()
766 prodServiceThread = do
767 b <- takeMVar prodding
769 then do fd <- readIORef stick
770 with io_MANAGER_WAKEUP $ \pbuf -> do
771 c_write (fromIntegral fd) pbuf 1; return ()
773 putMVar prodding True
775 foreign import ccall "&signal_handlers" handlers :: Ptr (Ptr (StablePtr (IO ())))
777 foreign import ccall "setIOManagerPipe"
778 c_setIOManagerPipe :: CInt -> IO ()
780 -- -----------------------------------------------------------------------------
783 buildFdSets maxfd readfds writefds [] = return maxfd
784 buildFdSets maxfd readfds writefds (Read fd m : reqs)
785 | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
788 buildFdSets (max maxfd fd) readfds writefds reqs
789 buildFdSets maxfd readfds writefds (Write fd m : reqs)
790 | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
793 buildFdSets (max maxfd fd) readfds writefds reqs
795 completeRequests [] _ _ reqs' = return reqs'
796 completeRequests (Read fd m : reqs) readfds writefds reqs' = do
797 b <- fdIsSet fd readfds
799 then do putMVar m (); completeRequests reqs readfds writefds reqs'
800 else completeRequests reqs readfds writefds (Read fd m : reqs')
801 completeRequests (Write fd m : reqs) readfds writefds reqs' = do
802 b <- fdIsSet fd writefds
804 then do putMVar m (); completeRequests reqs readfds writefds reqs'
805 else completeRequests reqs readfds writefds (Write fd m : reqs')
807 wakeupAll [] = return ()
808 wakeupAll (Read fd m : reqs) = do putMVar m (); wakeupAll reqs
809 wakeupAll (Write fd m : reqs) = do putMVar m (); wakeupAll reqs
811 waitForReadEvent :: Fd -> IO ()
812 waitForReadEvent fd = do
814 atomicModifyIORef pendingEvents (\xs -> (Read fd m : xs, ()))
818 waitForWriteEvent :: Fd -> IO ()
819 waitForWriteEvent fd = do
821 atomicModifyIORef pendingEvents (\xs -> (Write fd m : xs, ()))
825 -- XXX: move into GHC.IOBase from Data.IORef?
826 atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
827 atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
829 -- -----------------------------------------------------------------------------
832 waitForDelayEvent :: Int -> IO ()
833 waitForDelayEvent usecs = do
836 let target = now + usecs `quot` tick_usecs
837 atomicModifyIORef pendingDelays (\xs -> (Delay target m : xs, ()))
841 -- Delays for use in STM
842 waitForDelayEventSTM :: Int -> IO (TVar Bool)
843 waitForDelayEventSTM usecs = do
844 t <- atomically $ newTVar False
846 let target = now + usecs `quot` tick_usecs
847 atomicModifyIORef pendingDelays (\xs -> (DelaySTM target t : xs, ()))
851 -- Walk the queue of pending delays, waking up any that have passed
852 -- and return the smallest delay to wait for. The queue of pending
853 -- delays is kept ordered.
854 getDelay :: Ticks -> Ptr CTimeVal -> [DelayReq] -> IO ([DelayReq], Ptr CTimeVal)
855 getDelay now ptimeval [] = return ([],nullPtr)
856 getDelay now ptimeval all@(d : rest)
858 Delay time m | now >= time -> do
860 getDelay now ptimeval rest
861 DelaySTM time t | now >= time -> do
862 atomically $ writeTVar t True
863 getDelay now ptimeval rest
865 setTimevalTicks ptimeval (delayTime d - now)
866 return (all,ptimeval)
868 insertDelay :: DelayReq -> [DelayReq] -> [DelayReq]
869 insertDelay d [] = [d]
870 insertDelay d1 ds@(d2 : rest)
871 | delayTime d1 <= delayTime d2 = d1 : ds
872 | otherwise = d2 : insertDelay d1 rest
874 delayTime (Delay t _) = t
875 delayTime (DelaySTM t _) = t
878 tick_freq = 50 :: Ticks -- accuracy of threadDelay (ticks per sec)
879 tick_usecs = 1000000 `quot` tick_freq :: Int
881 newtype CTimeVal = CTimeVal ()
883 foreign import ccall unsafe "sizeofTimeVal"
886 foreign import ccall unsafe "getTicksOfDay"
887 getTicksOfDay :: IO Ticks
889 foreign import ccall unsafe "setTimevalTicks"
890 setTimevalTicks :: Ptr CTimeVal -> Ticks -> IO ()
892 -- ----------------------------------------------------------------------------
893 -- select() interface
895 -- ToDo: move to System.Posix.Internals?
897 newtype CFdSet = CFdSet ()
899 foreign import ccall safe "select"
900 c_select :: Fd -> Ptr CFdSet -> Ptr CFdSet -> Ptr CFdSet -> Ptr CTimeVal
903 foreign import ccall unsafe "hsFD_SETSIZE"
906 foreign import ccall unsafe "hsFD_CLR"
907 fdClr :: Fd -> Ptr CFdSet -> IO ()
909 foreign import ccall unsafe "hsFD_ISSET"
910 fdIsSet :: Fd -> Ptr CFdSet -> IO CInt
912 foreign import ccall unsafe "hsFD_SET"
913 fdSet :: Fd -> Ptr CFdSet -> IO ()
915 foreign import ccall unsafe "hsFD_ZERO"
916 fdZero :: Ptr CFdSet -> IO ()
918 foreign import ccall unsafe "sizeof_fd_set"