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:
28 -- * Forking and suchlike
29 , forkIO -- :: IO a -> IO ThreadId
30 , forkOnIO -- :: Int -> IO a -> IO ThreadId
31 , childHandler -- :: Exception -> IO ()
32 , myThreadId -- :: IO ThreadId
33 , killThread -- :: ThreadId -> IO ()
34 , throwTo -- :: ThreadId -> Exception -> IO ()
35 , par -- :: a -> b -> b
36 , pseq -- :: a -> b -> b
38 , labelThread -- :: ThreadId -> String -> IO ()
41 , threadDelay -- :: Int -> IO ()
42 , registerDelay -- :: Int -> IO (TVar Bool)
43 , threadWaitRead -- :: Int -> IO ()
44 , threadWaitWrite -- :: Int -> IO ()
48 , newMVar -- :: a -> IO (MVar a)
49 , newEmptyMVar -- :: IO (MVar a)
50 , takeMVar -- :: MVar a -> IO a
51 , putMVar -- :: MVar a -> a -> IO ()
52 , tryTakeMVar -- :: MVar a -> IO (Maybe a)
53 , tryPutMVar -- :: MVar a -> a -> IO Bool
54 , isEmptyMVar -- :: MVar a -> IO Bool
55 , addMVarFinalizer -- :: MVar a -> IO () -> IO ()
59 , atomically -- :: STM a -> IO a
61 , orElse -- :: STM a -> STM a -> STM a
62 , catchSTM -- :: STM a -> (Exception -> STM a) -> STM a
63 , alwaysSucceeds -- :: STM a -> STM ()
64 , always -- :: STM Bool -> STM ()
66 , newTVar -- :: a -> STM (TVar a)
67 , newTVarIO -- :: a -> STM (TVar a)
68 , readTVar -- :: TVar a -> STM a
69 , writeTVar -- :: a -> TVar a -> STM ()
70 , unsafeIOToSTM -- :: IO a -> STM a
73 #ifdef mingw32_HOST_OS
74 , asyncRead -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
75 , asyncWrite -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
76 , asyncDoProc -- :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
78 , asyncReadBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
79 , asyncWriteBA -- :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int, Int)
82 , ensureIOManagerIsRunning
85 import System.Posix.Types
86 #ifndef mingw32_HOST_OS
87 import System.Posix.Internals
93 import {-# SOURCE #-} GHC.TopHandler ( reportError, reportStackOverflow )
100 import GHC.Num ( Num(..) )
101 import GHC.Real ( fromIntegral, quot )
102 #ifndef mingw32_HOST_OS
103 import GHC.Base ( Int(..) )
105 import GHC.Exception ( catchException, Exception(..), AsyncException(..) )
106 import GHC.Pack ( packCString# )
107 import GHC.Ptr ( Ptr(..), plusPtr, FunPtr(..) )
109 import GHC.Show ( Show(..), showString )
112 infixr 0 `par`, `pseq`
115 %************************************************************************
117 \subsection{@ThreadId@, @par@, and @fork@}
119 %************************************************************************
122 data ThreadId = ThreadId ThreadId# deriving( Typeable )
123 -- ToDo: data ThreadId = ThreadId (Weak ThreadId#)
124 -- But since ThreadId# is unlifted, the Weak type must use open
127 A 'ThreadId' is an abstract type representing a handle to a thread.
128 'ThreadId' is an instance of 'Eq', 'Ord' and 'Show', where
129 the 'Ord' instance implements an arbitrary total ordering over
130 'ThreadId's. The 'Show' instance lets you convert an arbitrary-valued
131 'ThreadId' to string form; showing a 'ThreadId' value is occasionally
132 useful when debugging or diagnosing the behaviour of a concurrent
135 /Note/: in GHC, if you have a 'ThreadId', you essentially have
136 a pointer to the thread itself. This means the thread itself can\'t be
137 garbage collected until you drop the 'ThreadId'.
138 This misfeature will hopefully be corrected at a later date.
140 /Note/: Hugs does not provide any operations on other threads;
141 it defines 'ThreadId' as a synonym for ().
144 instance Show ThreadId where
146 showString "ThreadId " .
147 showsPrec d (getThreadId (id2TSO t))
149 foreign import ccall unsafe "rts_getThreadId" getThreadId :: ThreadId# -> Int
151 id2TSO :: ThreadId -> ThreadId#
152 id2TSO (ThreadId t) = t
154 foreign import ccall unsafe "cmp_thread" cmp_thread :: ThreadId# -> ThreadId# -> CInt
157 cmpThread :: ThreadId -> ThreadId -> Ordering
159 case cmp_thread (id2TSO t1) (id2TSO t2) of
164 instance Eq ThreadId where
166 case t1 `cmpThread` t2 of
170 instance Ord ThreadId where
174 This sparks off a new thread to run the 'IO' computation passed as the
175 first argument, and returns the 'ThreadId' of the newly created
178 The new thread will be a lightweight thread; if you want to use a foreign
179 library that uses thread-local storage, use 'forkOS' instead.
181 forkIO :: IO () -> IO ThreadId
182 forkIO action = IO $ \ s ->
183 case (fork# action_plus s) of (# s1, id #) -> (# s1, ThreadId id #)
185 action_plus = catchException action childHandler
187 forkOnIO :: Int -> IO () -> IO ThreadId
188 forkOnIO (I# cpu) action = IO $ \ s ->
189 case (forkOn# cpu action_plus s) of (# s1, id #) -> (# s1, ThreadId id #)
191 action_plus = catchException action childHandler
193 childHandler :: Exception -> IO ()
194 childHandler err = catchException (real_handler err) childHandler
196 real_handler :: Exception -> IO ()
199 -- ignore thread GC and killThread exceptions:
200 BlockedOnDeadMVar -> return ()
201 BlockedIndefinitely -> return ()
202 AsyncException ThreadKilled -> return ()
204 -- report all others:
205 AsyncException StackOverflow -> reportStackOverflow
206 other -> reportError other
208 {- | 'killThread' terminates the given thread (GHC only).
209 Any work already done by the thread isn\'t
210 lost: the computation is suspended until required by another thread.
211 The memory used by the thread will be garbage collected if it isn\'t
212 referenced from anywhere. The 'killThread' function is defined in
215 > killThread tid = throwTo tid (AsyncException ThreadKilled)
218 killThread :: ThreadId -> IO ()
219 killThread tid = throwTo tid (AsyncException ThreadKilled)
221 {- | 'throwTo' raises an arbitrary exception in the target thread (GHC only).
223 'throwTo' does not return until the exception has been raised in the
225 The calling thread can thus be certain that the target
226 thread has received the exception. This is a useful property to know
227 when dealing with race conditions: eg. if there are two threads that
228 can kill each other, it is guaranteed that only one of the threads
229 will get to kill the other.
231 If the target thread is currently making a foreign call, then the
232 exception will not be raised (and hence 'throwTo' will not return)
233 until the call has completed. This is the case regardless of whether
234 the call is inside a 'block' or not.
236 Important note: the behaviour of 'throwTo' differs from that described in
237 the paper "Asynchronous exceptions in Haskell"
238 (<http://research.microsoft.com/~simonpj/Papers/asynch-exns.htm>).
239 In the paper, 'throwTo' is non-blocking; but the library implementation adopts
240 a more synchronous design in which 'throwTo' does not return until the exception
241 is received by the target thread. The trade-off is discussed in Section 8 of the paper.
242 Like any blocking operation, 'throwTo' is therefore interruptible (see Section 4.3 of
246 throwTo :: ThreadId -> Exception -> IO ()
247 throwTo (ThreadId id) ex = IO $ \ s ->
248 case (killThread# id ex s) of s1 -> (# s1, () #)
250 -- | Returns the 'ThreadId' of the calling thread (GHC only).
251 myThreadId :: IO ThreadId
252 myThreadId = IO $ \s ->
253 case (myThreadId# s) of (# s1, id #) -> (# s1, ThreadId id #)
256 -- |The 'yield' action allows (forces, in a co-operative multitasking
257 -- implementation) a context-switch to any other currently runnable
258 -- threads (if any), and is occasionally useful when implementing
259 -- concurrency abstractions.
262 case (yield# s) of s1 -> (# s1, () #)
264 {- | 'labelThread' stores a string as identifier for this thread if
265 you built a RTS with debugging support. This identifier will be used in
266 the debugging output to make distinction of different threads easier
267 (otherwise you only have the thread state object\'s address in the heap).
269 Other applications like the graphical Concurrent Haskell Debugger
270 (<http://www.informatik.uni-kiel.de/~fhu/chd/>) may choose to overload
271 'labelThread' for their purposes as well.
274 labelThread :: ThreadId -> String -> IO ()
275 labelThread (ThreadId t) str = IO $ \ s ->
276 let ps = packCString# str
277 adr = byteArrayContents# ps in
278 case (labelThread# t adr s) of s1 -> (# s1, () #)
280 -- Nota Bene: 'pseq' used to be 'seq'
281 -- but 'seq' is now defined in PrelGHC
283 -- "pseq" is defined a bit weirdly (see below)
285 -- The reason for the strange "lazy" call is that
286 -- it fools the compiler into thinking that pseq and par are non-strict in
287 -- their second argument (even if it inlines pseq at the call site).
288 -- If it thinks pseq is strict in "y", then it often evaluates
289 -- "y" before "x", which is totally wrong.
293 pseq x y = x `seq` lazy y
297 par x y = case (par# x) of { _ -> lazy y }
301 %************************************************************************
303 \subsection[stm]{Transactional heap operations}
305 %************************************************************************
307 TVars are shared memory locations which support atomic memory
311 -- |A monad supporting atomic memory transactions.
312 newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #))
314 unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
317 INSTANCE_TYPEABLE1(STM,stmTc,"STM")
319 instance Functor STM where
320 fmap f x = x >>= (return . f)
322 instance Monad STM where
323 {-# INLINE return #-}
327 return x = returnSTM x
328 m >>= k = bindSTM m k
330 bindSTM :: STM a -> (a -> STM b) -> STM b
331 bindSTM (STM m) k = STM ( \s ->
333 (# new_s, a #) -> unSTM (k a) new_s
336 thenSTM :: STM a -> STM b -> STM b
337 thenSTM (STM m) k = STM ( \s ->
339 (# new_s, a #) -> unSTM k new_s
342 returnSTM :: a -> STM a
343 returnSTM x = STM (\s -> (# s, x #))
345 -- | Unsafely performs IO in the STM monad.
346 unsafeIOToSTM :: IO a -> STM a
347 unsafeIOToSTM (IO m) = STM m
349 -- |Perform a series of STM actions atomically.
351 -- You cannot use 'atomically' inside an 'unsafePerformIO' or 'unsafeInterleaveIO'.
352 -- Any attempt to do so will result in a runtime error. (Reason: allowing
353 -- this would effectively allow a transaction inside a transaction, depending
354 -- on exactly when the thunk is evaluated.)
356 -- However, see 'newTVarIO', which can be called inside 'unsafePerformIO',
357 -- and which allows top-level TVars to be allocated.
359 atomically :: STM a -> IO a
360 atomically (STM m) = IO (\s -> (atomically# m) s )
362 -- |Retry execution of the current memory transaction because it has seen
363 -- values in TVars which mean that it should not continue (e.g. the TVars
364 -- represent a shared buffer that is now empty). The implementation may
365 -- block the thread until one of the TVars that it has read from has been
366 -- udpated. (GHC only)
368 retry = STM $ \s# -> retry# s#
370 -- |Compose two alternative STM actions (GHC only). If the first action
371 -- completes without retrying then it forms the result of the orElse.
372 -- Otherwise, if the first action retries, then the second action is
373 -- tried in its place. If both actions retry then the orElse as a
375 orElse :: STM a -> STM a -> STM a
376 orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
378 -- |Exception handling within STM actions.
379 catchSTM :: STM a -> (Exception -> STM a) -> STM a
380 catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
382 -- | Low-level primitive on which always and alwaysSucceeds are built.
383 -- checkInv differs form these in that (i) the invariant is not
384 -- checked when checkInv is called, only at the end of this and
385 -- subsequent transcations, (ii) the invariant failure is indicated
386 -- by raising an exception.
387 checkInv :: STM a -> STM ()
388 checkInv (STM m) = STM (\s -> (check# m) s)
390 -- | alwaysSucceeds adds a new invariant that must be true when passed
391 -- to alwaysSucceeds, at the end of the current transaction, and at
392 -- the end of every subsequent transaction. If it fails at any
393 -- of those points then the transaction violating it is aborted
394 -- and the exception raised by the invariant is propagated.
395 alwaysSucceeds :: STM a -> STM ()
396 alwaysSucceeds i = do ( do i ; retry ) `orElse` ( return () )
399 -- | always is a variant of alwaysSucceeds in which the invariant is
400 -- expressed as an STM Bool action that must return True. Returning
401 -- False or raising an exception are both treated as invariant failures.
402 always :: STM Bool -> STM ()
403 always i = alwaysSucceeds ( do v <- i
404 if (v) then return () else ( error "Transacional invariant violation" ) )
406 -- |Shared memory locations that support atomic memory transactions.
407 data TVar a = TVar (TVar# RealWorld a)
409 INSTANCE_TYPEABLE1(TVar,tvarTc,"TVar")
411 instance Eq (TVar a) where
412 (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
414 -- |Create a new TVar holding a value supplied
415 newTVar :: a -> STM (TVar a)
416 newTVar val = STM $ \s1# ->
417 case newTVar# val s1# of
418 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
420 -- |@IO@ version of 'newTVar'. This is useful for creating top-level
421 -- 'TVar's using 'System.IO.Unsafe.unsafePerformIO', because using
422 -- 'atomically' inside 'System.IO.Unsafe.unsafePerformIO' isn't
424 newTVarIO :: a -> IO (TVar a)
425 newTVarIO val = IO $ \s1# ->
426 case newTVar# val s1# of
427 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
429 -- |Return the current value stored in a TVar
430 readTVar :: TVar a -> STM a
431 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
433 -- |Write the supplied value into a TVar
434 writeTVar :: TVar a -> a -> STM ()
435 writeTVar (TVar tvar#) val = STM $ \s1# ->
436 case writeTVar# tvar# val s1# of
441 %************************************************************************
443 \subsection[mvars]{M-Structures}
445 %************************************************************************
447 M-Vars are rendezvous points for concurrent threads. They begin
448 empty, and any attempt to read an empty M-Var blocks. When an M-Var
449 is written, a single blocked thread may be freed. Reading an M-Var
450 toggles its state from full back to empty. Therefore, any value
451 written to an M-Var may only be read once. Multiple reads and writes
452 are allowed, but there must be at least one read between any two
456 --Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
458 -- |Create an 'MVar' which is initially empty.
459 newEmptyMVar :: IO (MVar a)
460 newEmptyMVar = IO $ \ s# ->
462 (# s2#, svar# #) -> (# s2#, MVar svar# #)
464 -- |Create an 'MVar' which contains the supplied value.
465 newMVar :: a -> IO (MVar a)
467 newEmptyMVar >>= \ mvar ->
468 putMVar mvar value >>
471 -- |Return the contents of the 'MVar'. If the 'MVar' is currently
472 -- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
473 -- the 'MVar' is left empty.
475 -- There are two further important properties of 'takeMVar':
477 -- * 'takeMVar' is single-wakeup. That is, if there are multiple
478 -- threads blocked in 'takeMVar', and the 'MVar' becomes full,
479 -- only one thread will be woken up. The runtime guarantees that
480 -- the woken thread completes its 'takeMVar' operation.
482 -- * When multiple threads are blocked on an 'MVar', they are
483 -- woken up in FIFO order. This is useful for providing
484 -- fairness properties of abstractions built using 'MVar's.
486 takeMVar :: MVar a -> IO a
487 takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
489 -- |Put a value into an 'MVar'. If the 'MVar' is currently full,
490 -- 'putMVar' will wait until it becomes empty.
492 -- There are two further important properties of 'putMVar':
494 -- * 'putMVar' is single-wakeup. That is, if there are multiple
495 -- threads blocked in 'putMVar', and the 'MVar' becomes empty,
496 -- only one thread will be woken up. The runtime guarantees that
497 -- the woken thread completes its 'putMVar' operation.
499 -- * When multiple threads are blocked on an 'MVar', they are
500 -- woken up in FIFO order. This is useful for providing
501 -- fairness properties of abstractions built using 'MVar's.
503 putMVar :: MVar a -> a -> IO ()
504 putMVar (MVar mvar#) x = IO $ \ s# ->
505 case putMVar# mvar# x s# of
508 -- |A non-blocking version of 'takeMVar'. The 'tryTakeMVar' function
509 -- returns immediately, with 'Nothing' if the 'MVar' was empty, or
510 -- @'Just' a@ if the 'MVar' was full with contents @a@. After 'tryTakeMVar',
511 -- the 'MVar' is left empty.
512 tryTakeMVar :: MVar a -> IO (Maybe a)
513 tryTakeMVar (MVar m) = IO $ \ s ->
514 case tryTakeMVar# m s of
515 (# s, 0#, _ #) -> (# s, Nothing #) -- MVar is empty
516 (# s, _, a #) -> (# s, Just a #) -- MVar is full
518 -- |A non-blocking version of 'putMVar'. The 'tryPutMVar' function
519 -- attempts to put the value @a@ into the 'MVar', returning 'True' if
520 -- it was successful, or 'False' otherwise.
521 tryPutMVar :: MVar a -> a -> IO Bool
522 tryPutMVar (MVar mvar#) x = IO $ \ s# ->
523 case tryPutMVar# mvar# x s# of
524 (# s, 0# #) -> (# s, False #)
525 (# s, _ #) -> (# s, True #)
527 -- |Check whether a given 'MVar' is empty.
529 -- Notice that the boolean value returned is just a snapshot of
530 -- the state of the MVar. By the time you get to react on its result,
531 -- the MVar may have been filled (or emptied) - so be extremely
532 -- careful when using this operation. Use 'tryTakeMVar' instead if possible.
533 isEmptyMVar :: MVar a -> IO Bool
534 isEmptyMVar (MVar mv#) = IO $ \ s# ->
535 case isEmptyMVar# mv# s# of
536 (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
538 -- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
539 -- "System.Mem.Weak" for more about finalizers.
540 addMVarFinalizer :: MVar a -> IO () -> IO ()
541 addMVarFinalizer (MVar m) finalizer =
542 IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
546 %************************************************************************
548 \subsection{Thread waiting}
550 %************************************************************************
553 #ifdef mingw32_HOST_OS
555 -- Note: threadDelay, threadWaitRead and threadWaitWrite aren't really functional
556 -- on Win32, but left in there because lib code (still) uses them (the manner
557 -- in which they're used doesn't cause problems on a Win32 platform though.)
559 asyncRead :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
560 asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf) =
561 IO $ \s -> case asyncRead# fd isSock len buf s of
562 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
564 asyncWrite :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
565 asyncWrite (I# fd) (I# isSock) (I# len) (Ptr buf) =
566 IO $ \s -> case asyncWrite# fd isSock len buf s of
567 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
569 asyncDoProc :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
570 asyncDoProc (FunPtr proc) (Ptr param) =
571 -- the 'length' value is ignored; simplifies implementation of
572 -- the async*# primops to have them all return the same result.
573 IO $ \s -> case asyncDoProc# proc param s of
574 (# s, len#, err# #) -> (# s, I# err# #)
576 -- to aid the use of these primops by the IO Handle implementation,
577 -- provide the following convenience funs:
579 -- this better be a pinned byte array!
580 asyncReadBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
581 asyncReadBA fd isSock len off bufB =
582 asyncRead fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
584 asyncWriteBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
585 asyncWriteBA fd isSock len off bufB =
586 asyncWrite fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
590 -- -----------------------------------------------------------------------------
593 -- | Block the current thread until data is available to read on the
594 -- given file descriptor (GHC only).
595 threadWaitRead :: Fd -> IO ()
597 #ifndef mingw32_HOST_OS
598 | threaded = waitForReadEvent fd
600 | otherwise = IO $ \s ->
601 case fromIntegral fd of { I# fd# ->
602 case waitRead# fd# s of { s -> (# s, () #)
605 -- | Block the current thread until data can be written to the
606 -- given file descriptor (GHC only).
607 threadWaitWrite :: Fd -> IO ()
609 #ifndef mingw32_HOST_OS
610 | threaded = waitForWriteEvent fd
612 | otherwise = IO $ \s ->
613 case fromIntegral fd of { I# fd# ->
614 case waitWrite# fd# s of { s -> (# s, () #)
617 -- | Suspends the current thread for a given number of microseconds
620 -- Note that the resolution used by the Haskell runtime system's
621 -- internal timer is 1\/50 second, and 'threadDelay' will round its
622 -- argument up to the nearest multiple of this resolution.
624 -- There is no guarantee that the thread will be rescheduled promptly
625 -- when the delay has expired, but the thread will never continue to
626 -- run /earlier/ than specified.
628 threadDelay :: Int -> IO ()
630 | threaded = waitForDelayEvent time
631 | otherwise = IO $ \s ->
632 case fromIntegral time of { I# time# ->
633 case delay# time# s of { s -> (# s, () #)
636 registerDelay :: Int -> IO (TVar Bool)
638 | threaded = waitForDelayEventSTM usecs
639 | otherwise = error "registerDelay: requires -threaded"
641 foreign import ccall unsafe "rtsSupportsBoundThreads" threaded :: Bool
643 waitForDelayEvent :: Int -> IO ()
644 waitForDelayEvent usecs = do
647 let target = now + usecs `quot` tick_usecs
648 atomicModifyIORef pendingDelays (\xs -> (Delay target m : xs, ()))
652 -- Delays for use in STM
653 waitForDelayEventSTM :: Int -> IO (TVar Bool)
654 waitForDelayEventSTM usecs = do
655 t <- atomically $ newTVar False
657 let target = now + usecs `quot` tick_usecs
658 atomicModifyIORef pendingDelays (\xs -> (DelaySTM target t : xs, ()))
662 calculateTarget :: Int -> IO Int
663 calculateTarget usecs = do
665 let -- Convert usecs to ticks, rounding up as we must wait /at least/
666 -- as long as we are told
667 usecs' = (usecs + tick_usecs - 1) `quot` tick_usecs
668 target = now + 1 -- getTicksOfDay will have rounded down, but
669 -- again we need to wait for /at least/ as long
670 -- as we are told, so add 1 to it
674 -- ----------------------------------------------------------------------------
675 -- Threaded RTS implementation of threadWaitRead, threadWaitWrite, threadDelay
677 -- In the threaded RTS, we employ a single IO Manager thread to wait
678 -- for all outstanding IO requests (threadWaitRead,threadWaitWrite)
679 -- and delays (threadDelay).
681 -- We can do this because in the threaded RTS the IO Manager can make
682 -- a non-blocking call to select(), so we don't have to do select() in
683 -- the scheduler as we have to in the non-threaded RTS. We get performance
684 -- benefits from doing it this way, because we only have to restart the select()
685 -- when a new request arrives, rather than doing one select() each time
686 -- around the scheduler loop. Furthermore, the scheduler can be simplified
687 -- by not having to check for completed IO requests.
689 -- Issues, possible problems:
691 -- - we might want bound threads to just do the blocking
692 -- operation rather than communicating with the IO manager
693 -- thread. This would prevent simgle-threaded programs which do
694 -- IO from requiring multiple OS threads. However, it would also
695 -- prevent bound threads waiting on IO from being killed or sent
698 -- - Apprently exec() doesn't work on Linux in a multithreaded program.
699 -- I couldn't repeat this.
701 -- - How do we handle signal delivery in the multithreaded RTS?
703 -- - forkProcess will kill the IO manager thread. Let's just
704 -- hope we don't need to do any blocking IO between fork & exec.
706 #ifndef mingw32_HOST_OS
708 = Read {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
709 | Write {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
713 = Delay {-# UNPACK #-} !Int {-# UNPACK #-} !(MVar ())
714 | DelaySTM {-# UNPACK #-} !Int {-# UNPACK #-} !(TVar Bool)
716 #ifndef mingw32_HOST_OS
717 pendingEvents :: IORef [IOReq]
719 pendingDelays :: IORef [DelayReq]
720 -- could use a strict list or array here
721 {-# NOINLINE pendingEvents #-}
722 {-# NOINLINE pendingDelays #-}
723 (pendingEvents,pendingDelays) = unsafePerformIO $ do
728 -- the first time we schedule an IO request, the service thread
729 -- will be created (cool, huh?)
731 ensureIOManagerIsRunning :: IO ()
732 ensureIOManagerIsRunning
733 | threaded = seq pendingEvents $ return ()
734 | otherwise = return ()
736 insertDelay :: DelayReq -> [DelayReq] -> [DelayReq]
737 insertDelay d [] = [d]
738 insertDelay d1 ds@(d2 : rest)
739 | delayTime d1 <= delayTime d2 = d1 : ds
740 | otherwise = d2 : insertDelay d1 rest
742 delayTime (Delay t _) = t
743 delayTime (DelaySTM t _) = t
746 tick_freq = 50 :: Ticks -- accuracy of threadDelay (ticks per sec)
747 tick_usecs = 1000000 `quot` tick_freq :: Int
748 tick_msecs = 1000 `quot` tick_freq :: Int
750 -- XXX: move into GHC.IOBase from Data.IORef?
751 atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
752 atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
754 foreign import ccall unsafe "getTicksOfDay"
755 getTicksOfDay :: IO Ticks
757 #ifdef mingw32_HOST_OS
758 -- ----------------------------------------------------------------------------
759 -- Windows IO manager thread
761 startIOManagerThread :: IO ()
762 startIOManagerThread = do
763 wakeup <- c_getIOManagerEvent
764 forkIO $ service_loop wakeup []
767 service_loop :: HANDLE -- read end of pipe
768 -> [DelayReq] -- current delay requests
771 service_loop wakeup old_delays = do
772 -- pick up new delay requests
773 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
774 let delays = foldr insertDelay old_delays new_delays
777 (delays', timeout) <- getDelay now delays
779 r <- c_WaitForSingleObject wakeup timeout
781 0xffffffff -> do c_maperrno; throwErrno "service_loop"
783 r <- c_readIOManagerEvent
786 _ | r == io_MANAGER_WAKEUP -> return False
787 _ | r == io_MANAGER_DIE -> return True
788 0 -> return False -- spurious wakeup
789 r -> do start_console_handler (r `shiftR` 1); return False
792 else service_cont wakeup delays'
794 _other -> service_cont wakeup delays' -- probably timeout
796 service_cont wakeup delays = do
798 putMVar prodding False
799 service_loop wakeup delays
801 -- must agree with rts/win32/ThrIOManager.c
802 io_MANAGER_WAKEUP = 0xffffffff :: Word32
803 io_MANAGER_DIE = 0xfffffffe :: Word32
805 start_console_handler :: Word32 -> IO ()
806 start_console_handler r = do
807 stableptr <- peek console_handler
808 forkIO $ do io <- deRefStablePtr stableptr; io (fromIntegral r)
811 foreign import ccall "&console_handler"
812 console_handler :: Ptr (StablePtr (CInt -> IO ()))
814 stick :: IORef HANDLE
815 {-# NOINLINE stick #-}
816 stick = unsafePerformIO (newIORef nullPtr)
818 prodding :: MVar Bool
819 {-# NOINLINE prodding #-}
820 prodding = unsafePerformIO (newMVar False)
822 prodServiceThread :: IO ()
823 prodServiceThread = do
824 b <- takeMVar prodding
826 then do hdl <- readIORef stick
827 c_sendIOManagerEvent io_MANAGER_WAKEUP
829 putMVar prodding True
831 -- Walk the queue of pending delays, waking up any that have passed
832 -- and return the smallest delay to wait for. The queue of pending
833 -- delays is kept ordered.
834 getDelay :: Ticks -> [DelayReq] -> IO ([DelayReq], DWORD)
835 getDelay now [] = return ([], iNFINITE)
836 getDelay now all@(d : rest)
838 Delay time m | now >= time -> do
841 DelaySTM time t | now >= time -> do
842 atomically $ writeTVar t True
845 return (all, (fromIntegral (delayTime d - now) *
846 fromIntegral tick_msecs))
847 -- delay is in millisecs for WaitForSingleObject
849 -- ToDo: this just duplicates part of System.Win32.Types, which isn't
850 -- available yet. We should move some Win32 functionality down here,
851 -- maybe as part of the grand reorganisation of the base package...
855 iNFINITE = 0xFFFFFFFF :: DWORD -- urgh
857 foreign import ccall unsafe "getIOManagerEvent" -- in the RTS (ThrIOManager.c)
858 c_getIOManagerEvent :: IO HANDLE
860 foreign import ccall unsafe "readIOManagerEvent" -- in the RTS (ThrIOManager.c)
861 c_readIOManagerEvent :: IO Word32
863 foreign import ccall unsafe "sendIOManagerEvent" -- in the RTS (ThrIOManager.c)
864 c_sendIOManagerEvent :: Word32 -> IO ()
866 foreign import ccall unsafe "maperrno" -- in runProcess.c
869 foreign import stdcall "WaitForSingleObject"
870 c_WaitForSingleObject :: HANDLE -> DWORD -> IO DWORD
873 -- ----------------------------------------------------------------------------
874 -- Unix IO manager thread, using select()
876 startIOManagerThread :: IO ()
877 startIOManagerThread = do
878 allocaArray 2 $ \fds -> do
879 throwErrnoIfMinus1 "startIOManagerThread" (c_pipe fds)
880 rd_end <- peekElemOff fds 0
881 wr_end <- peekElemOff fds 1
882 writeIORef stick (fromIntegral wr_end)
883 c_setIOManagerPipe wr_end
885 allocaBytes sizeofFdSet $ \readfds -> do
886 allocaBytes sizeofFdSet $ \writefds -> do
887 allocaBytes sizeofTimeVal $ \timeval -> do
888 service_loop (fromIntegral rd_end) readfds writefds timeval [] []
892 :: Fd -- listen to this for wakeup calls
899 service_loop wakeup readfds writefds ptimeval old_reqs old_delays = do
901 -- pick up new IO requests
902 new_reqs <- atomicModifyIORef pendingEvents (\a -> ([],a))
903 let reqs = new_reqs ++ old_reqs
905 -- pick up new delay requests
906 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
907 let delays = foldr insertDelay old_delays new_delays
909 -- build the FDSets for select()
913 maxfd <- buildFdSets 0 readfds writefds reqs
915 -- perform the select()
916 let do_select delays = do
917 -- check the current time and wake up any thread in
918 -- threadDelay whose timeout has expired. Also find the
919 -- timeout value for the select() call.
921 (delays', timeout) <- getDelay now ptimeval delays
923 res <- c_select ((max wakeup maxfd)+1) readfds writefds
929 _ | err == eINTR -> do_select delays'
930 -- EINTR: just redo the select()
931 _ | err == eBADF -> return (True, delays)
932 -- EBADF: one of the file descriptors is closed or bad,
933 -- we don't know which one, so wake everyone up.
934 _ | otherwise -> throwErrno "select"
935 -- otherwise (ENOMEM or EINVAL) something has gone
936 -- wrong; report the error.
938 return (False,delays')
940 (wakeup_all,delays') <- do_select delays
943 if wakeup_all then return False
945 b <- fdIsSet wakeup readfds
948 else alloca $ \p -> do
949 c_read (fromIntegral wakeup) p 1; return ()
952 _ | s == io_MANAGER_WAKEUP -> return False
953 _ | s == io_MANAGER_DIE -> return True
954 _ -> do handler_tbl <- peek handlers
955 sp <- peekElemOff handler_tbl (fromIntegral s)
956 forkIO (do io <- deRefStablePtr sp; io)
959 if exit then return () else do
962 putMVar prodding False
964 reqs' <- if wakeup_all then do wakeupAll reqs; return []
965 else completeRequests reqs readfds writefds []
967 service_loop wakeup readfds writefds ptimeval reqs' delays'
969 io_MANAGER_WAKEUP = 0xff :: CChar
970 io_MANAGER_DIE = 0xfe :: CChar
973 {-# NOINLINE stick #-}
974 stick = unsafePerformIO (newIORef 0)
976 prodding :: MVar Bool
977 {-# NOINLINE prodding #-}
978 prodding = unsafePerformIO (newMVar False)
980 prodServiceThread :: IO ()
981 prodServiceThread = do
982 b <- takeMVar prodding
984 then do fd <- readIORef stick
985 with io_MANAGER_WAKEUP $ \pbuf -> do
986 c_write (fromIntegral fd) pbuf 1; return ()
988 putMVar prodding True
990 foreign import ccall "&signal_handlers" handlers :: Ptr (Ptr (StablePtr (IO ())))
992 foreign import ccall "setIOManagerPipe"
993 c_setIOManagerPipe :: CInt -> IO ()
995 -- -----------------------------------------------------------------------------
998 buildFdSets maxfd readfds writefds [] = return maxfd
999 buildFdSets maxfd readfds writefds (Read fd m : reqs)
1000 | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
1003 buildFdSets (max maxfd fd) readfds writefds reqs
1004 buildFdSets maxfd readfds writefds (Write fd m : reqs)
1005 | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
1008 buildFdSets (max maxfd fd) readfds writefds reqs
1010 completeRequests [] _ _ reqs' = return reqs'
1011 completeRequests (Read fd m : reqs) readfds writefds reqs' = do
1012 b <- fdIsSet fd readfds
1014 then do putMVar m (); completeRequests reqs readfds writefds reqs'
1015 else completeRequests reqs readfds writefds (Read fd m : reqs')
1016 completeRequests (Write fd m : reqs) readfds writefds reqs' = do
1017 b <- fdIsSet fd writefds
1019 then do putMVar m (); completeRequests reqs readfds writefds reqs'
1020 else completeRequests reqs readfds writefds (Write fd m : reqs')
1022 wakeupAll [] = return ()
1023 wakeupAll (Read fd m : reqs) = do putMVar m (); wakeupAll reqs
1024 wakeupAll (Write fd m : reqs) = do putMVar m (); wakeupAll reqs
1026 waitForReadEvent :: Fd -> IO ()
1027 waitForReadEvent fd = do
1029 atomicModifyIORef pendingEvents (\xs -> (Read fd m : xs, ()))
1033 waitForWriteEvent :: Fd -> IO ()
1034 waitForWriteEvent fd = do
1036 atomicModifyIORef pendingEvents (\xs -> (Write fd m : xs, ()))
1040 -- -----------------------------------------------------------------------------
1043 -- Walk the queue of pending delays, waking up any that have passed
1044 -- and return the smallest delay to wait for. The queue of pending
1045 -- delays is kept ordered.
1046 getDelay :: Ticks -> Ptr CTimeVal -> [DelayReq] -> IO ([DelayReq], Ptr CTimeVal)
1047 getDelay now ptimeval [] = return ([],nullPtr)
1048 getDelay now ptimeval all@(d : rest)
1050 Delay time m | now >= time -> do
1052 getDelay now ptimeval rest
1053 DelaySTM time t | now >= time -> do
1054 atomically $ writeTVar t True
1055 getDelay now ptimeval rest
1057 setTimevalTicks ptimeval (delayTime d - now)
1058 return (all,ptimeval)
1060 newtype CTimeVal = CTimeVal ()
1062 foreign import ccall unsafe "sizeofTimeVal"
1063 sizeofTimeVal :: Int
1065 foreign import ccall unsafe "setTimevalTicks"
1066 setTimevalTicks :: Ptr CTimeVal -> Ticks -> IO ()
1069 On Win32 we're going to have a single Pipe, and a
1070 waitForSingleObject with the delay time. For signals, we send a
1071 byte down the pipe just like on Unix.
1074 -- ----------------------------------------------------------------------------
1075 -- select() interface
1077 -- ToDo: move to System.Posix.Internals?
1079 newtype CFdSet = CFdSet ()
1081 foreign import ccall safe "select"
1082 c_select :: Fd -> Ptr CFdSet -> Ptr CFdSet -> Ptr CFdSet -> Ptr CTimeVal
1085 foreign import ccall unsafe "hsFD_SETSIZE"
1088 foreign import ccall unsafe "hsFD_CLR"
1089 fdClr :: Fd -> Ptr CFdSet -> IO ()
1091 foreign import ccall unsafe "hsFD_ISSET"
1092 fdIsSet :: Fd -> Ptr CFdSet -> IO CInt
1094 foreign import ccall unsafe "hsFD_SET"
1095 fdSet :: Fd -> Ptr CFdSet -> IO ()
1097 foreign import ccall unsafe "hsFD_ZERO"
1098 fdZero :: Ptr CFdSet -> IO ()
1100 foreign import ccall unsafe "sizeof_fd_set"