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
245 There is currently no guarantee that the exception delivered by 'throwTo' will be
246 delivered at the first possible opportunity. In particular, if a thread may
247 unblock and then re-block exceptions (using 'unblock' and 'block') without receiving
248 a pending 'throwTo'. This is arguably undesirable behaviour.
251 throwTo :: ThreadId -> Exception -> IO ()
252 throwTo (ThreadId id) ex = IO $ \ s ->
253 case (killThread# id ex s) of s1 -> (# s1, () #)
255 -- | Returns the 'ThreadId' of the calling thread (GHC only).
256 myThreadId :: IO ThreadId
257 myThreadId = IO $ \s ->
258 case (myThreadId# s) of (# s1, id #) -> (# s1, ThreadId id #)
261 -- |The 'yield' action allows (forces, in a co-operative multitasking
262 -- implementation) a context-switch to any other currently runnable
263 -- threads (if any), and is occasionally useful when implementing
264 -- concurrency abstractions.
267 case (yield# s) of s1 -> (# s1, () #)
269 {- | 'labelThread' stores a string as identifier for this thread if
270 you built a RTS with debugging support. This identifier will be used in
271 the debugging output to make distinction of different threads easier
272 (otherwise you only have the thread state object\'s address in the heap).
274 Other applications like the graphical Concurrent Haskell Debugger
275 (<http://www.informatik.uni-kiel.de/~fhu/chd/>) may choose to overload
276 'labelThread' for their purposes as well.
279 labelThread :: ThreadId -> String -> IO ()
280 labelThread (ThreadId t) str = IO $ \ s ->
281 let ps = packCString# str
282 adr = byteArrayContents# ps in
283 case (labelThread# t adr s) of s1 -> (# s1, () #)
285 -- Nota Bene: 'pseq' used to be 'seq'
286 -- but 'seq' is now defined in PrelGHC
288 -- "pseq" is defined a bit weirdly (see below)
290 -- The reason for the strange "lazy" call is that
291 -- it fools the compiler into thinking that pseq and par are non-strict in
292 -- their second argument (even if it inlines pseq at the call site).
293 -- If it thinks pseq is strict in "y", then it often evaluates
294 -- "y" before "x", which is totally wrong.
298 pseq x y = x `seq` lazy y
302 par x y = case (par# x) of { _ -> lazy y }
306 %************************************************************************
308 \subsection[stm]{Transactional heap operations}
310 %************************************************************************
312 TVars are shared memory locations which support atomic memory
316 -- |A monad supporting atomic memory transactions.
317 newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #))
319 unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
322 INSTANCE_TYPEABLE1(STM,stmTc,"STM")
324 instance Functor STM where
325 fmap f x = x >>= (return . f)
327 instance Monad STM where
328 {-# INLINE return #-}
332 return x = returnSTM x
333 m >>= k = bindSTM m k
335 bindSTM :: STM a -> (a -> STM b) -> STM b
336 bindSTM (STM m) k = STM ( \s ->
338 (# new_s, a #) -> unSTM (k a) new_s
341 thenSTM :: STM a -> STM b -> STM b
342 thenSTM (STM m) k = STM ( \s ->
344 (# new_s, a #) -> unSTM k new_s
347 returnSTM :: a -> STM a
348 returnSTM x = STM (\s -> (# s, x #))
350 -- | Unsafely performs IO in the STM monad.
351 unsafeIOToSTM :: IO a -> STM a
352 unsafeIOToSTM (IO m) = STM m
354 -- |Perform a series of STM actions atomically.
356 -- You cannot use 'atomically' inside an 'unsafePerformIO' or 'unsafeInterleaveIO'.
357 -- Any attempt to do so will result in a runtime error. (Reason: allowing
358 -- this would effectively allow a transaction inside a transaction, depending
359 -- on exactly when the thunk is evaluated.)
361 -- However, see 'newTVarIO', which can be called inside 'unsafePerformIO',
362 -- and which allows top-level TVars to be allocated.
364 atomically :: STM a -> IO a
365 atomically (STM m) = IO (\s -> (atomically# m) s )
367 -- |Retry execution of the current memory transaction because it has seen
368 -- values in TVars which mean that it should not continue (e.g. the TVars
369 -- represent a shared buffer that is now empty). The implementation may
370 -- block the thread until one of the TVars that it has read from has been
371 -- udpated. (GHC only)
373 retry = STM $ \s# -> retry# s#
375 -- |Compose two alternative STM actions (GHC only). If the first action
376 -- completes without retrying then it forms the result of the orElse.
377 -- Otherwise, if the first action retries, then the second action is
378 -- tried in its place. If both actions retry then the orElse as a
380 orElse :: STM a -> STM a -> STM a
381 orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
383 -- |Exception handling within STM actions.
384 catchSTM :: STM a -> (Exception -> STM a) -> STM a
385 catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
387 -- | Low-level primitive on which always and alwaysSucceeds are built.
388 -- checkInv differs form these in that (i) the invariant is not
389 -- checked when checkInv is called, only at the end of this and
390 -- subsequent transcations, (ii) the invariant failure is indicated
391 -- by raising an exception.
392 checkInv :: STM a -> STM ()
393 checkInv (STM m) = STM (\s -> (check# m) s)
395 -- | alwaysSucceeds adds a new invariant that must be true when passed
396 -- to alwaysSucceeds, at the end of the current transaction, and at
397 -- the end of every subsequent transaction. If it fails at any
398 -- of those points then the transaction violating it is aborted
399 -- and the exception raised by the invariant is propagated.
400 alwaysSucceeds :: STM a -> STM ()
401 alwaysSucceeds i = do ( do i ; retry ) `orElse` ( return () )
404 -- | always is a variant of alwaysSucceeds in which the invariant is
405 -- expressed as an STM Bool action that must return True. Returning
406 -- False or raising an exception are both treated as invariant failures.
407 always :: STM Bool -> STM ()
408 always i = alwaysSucceeds ( do v <- i
409 if (v) then return () else ( error "Transacional invariant violation" ) )
411 -- |Shared memory locations that support atomic memory transactions.
412 data TVar a = TVar (TVar# RealWorld a)
414 INSTANCE_TYPEABLE1(TVar,tvarTc,"TVar")
416 instance Eq (TVar a) where
417 (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
419 -- |Create a new TVar holding a value supplied
420 newTVar :: a -> STM (TVar a)
421 newTVar val = STM $ \s1# ->
422 case newTVar# val s1# of
423 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
425 -- |@IO@ version of 'newTVar'. This is useful for creating top-level
426 -- 'TVar's using 'System.IO.Unsafe.unsafePerformIO', because using
427 -- 'atomically' inside 'System.IO.Unsafe.unsafePerformIO' isn't
429 newTVarIO :: a -> IO (TVar a)
430 newTVarIO val = IO $ \s1# ->
431 case newTVar# val s1# of
432 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
434 -- |Return the current value stored in a TVar
435 readTVar :: TVar a -> STM a
436 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
438 -- |Write the supplied value into a TVar
439 writeTVar :: TVar a -> a -> STM ()
440 writeTVar (TVar tvar#) val = STM $ \s1# ->
441 case writeTVar# tvar# val s1# of
446 %************************************************************************
448 \subsection[mvars]{M-Structures}
450 %************************************************************************
452 M-Vars are rendezvous points for concurrent threads. They begin
453 empty, and any attempt to read an empty M-Var blocks. When an M-Var
454 is written, a single blocked thread may be freed. Reading an M-Var
455 toggles its state from full back to empty. Therefore, any value
456 written to an M-Var may only be read once. Multiple reads and writes
457 are allowed, but there must be at least one read between any two
461 --Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
463 -- |Create an 'MVar' which is initially empty.
464 newEmptyMVar :: IO (MVar a)
465 newEmptyMVar = IO $ \ s# ->
467 (# s2#, svar# #) -> (# s2#, MVar svar# #)
469 -- |Create an 'MVar' which contains the supplied value.
470 newMVar :: a -> IO (MVar a)
472 newEmptyMVar >>= \ mvar ->
473 putMVar mvar value >>
476 -- |Return the contents of the 'MVar'. If the 'MVar' is currently
477 -- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
478 -- the 'MVar' is left empty.
480 -- There are two further important properties of 'takeMVar':
482 -- * 'takeMVar' is single-wakeup. That is, if there are multiple
483 -- threads blocked in 'takeMVar', and the 'MVar' becomes full,
484 -- only one thread will be woken up. The runtime guarantees that
485 -- the woken thread completes its 'takeMVar' operation.
487 -- * When multiple threads are blocked on an 'MVar', they are
488 -- woken up in FIFO order. This is useful for providing
489 -- fairness properties of abstractions built using 'MVar's.
491 takeMVar :: MVar a -> IO a
492 takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
494 -- |Put a value into an 'MVar'. If the 'MVar' is currently full,
495 -- 'putMVar' will wait until it becomes empty.
497 -- There are two further important properties of 'putMVar':
499 -- * 'putMVar' is single-wakeup. That is, if there are multiple
500 -- threads blocked in 'putMVar', and the 'MVar' becomes empty,
501 -- only one thread will be woken up. The runtime guarantees that
502 -- the woken thread completes its 'putMVar' operation.
504 -- * When multiple threads are blocked on an 'MVar', they are
505 -- woken up in FIFO order. This is useful for providing
506 -- fairness properties of abstractions built using 'MVar's.
508 putMVar :: MVar a -> a -> IO ()
509 putMVar (MVar mvar#) x = IO $ \ s# ->
510 case putMVar# mvar# x s# of
513 -- |A non-blocking version of 'takeMVar'. The 'tryTakeMVar' function
514 -- returns immediately, with 'Nothing' if the 'MVar' was empty, or
515 -- @'Just' a@ if the 'MVar' was full with contents @a@. After 'tryTakeMVar',
516 -- the 'MVar' is left empty.
517 tryTakeMVar :: MVar a -> IO (Maybe a)
518 tryTakeMVar (MVar m) = IO $ \ s ->
519 case tryTakeMVar# m s of
520 (# s, 0#, _ #) -> (# s, Nothing #) -- MVar is empty
521 (# s, _, a #) -> (# s, Just a #) -- MVar is full
523 -- |A non-blocking version of 'putMVar'. The 'tryPutMVar' function
524 -- attempts to put the value @a@ into the 'MVar', returning 'True' if
525 -- it was successful, or 'False' otherwise.
526 tryPutMVar :: MVar a -> a -> IO Bool
527 tryPutMVar (MVar mvar#) x = IO $ \ s# ->
528 case tryPutMVar# mvar# x s# of
529 (# s, 0# #) -> (# s, False #)
530 (# s, _ #) -> (# s, True #)
532 -- |Check whether a given 'MVar' is empty.
534 -- Notice that the boolean value returned is just a snapshot of
535 -- the state of the MVar. By the time you get to react on its result,
536 -- the MVar may have been filled (or emptied) - so be extremely
537 -- careful when using this operation. Use 'tryTakeMVar' instead if possible.
538 isEmptyMVar :: MVar a -> IO Bool
539 isEmptyMVar (MVar mv#) = IO $ \ s# ->
540 case isEmptyMVar# mv# s# of
541 (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
543 -- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
544 -- "System.Mem.Weak" for more about finalizers.
545 addMVarFinalizer :: MVar a -> IO () -> IO ()
546 addMVarFinalizer (MVar m) finalizer =
547 IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
551 %************************************************************************
553 \subsection{Thread waiting}
555 %************************************************************************
558 #ifdef mingw32_HOST_OS
560 -- Note: threadDelay, threadWaitRead and threadWaitWrite aren't really functional
561 -- on Win32, but left in there because lib code (still) uses them (the manner
562 -- in which they're used doesn't cause problems on a Win32 platform though.)
564 asyncRead :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
565 asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf) =
566 IO $ \s -> case asyncRead# fd isSock len buf s of
567 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
569 asyncWrite :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
570 asyncWrite (I# fd) (I# isSock) (I# len) (Ptr buf) =
571 IO $ \s -> case asyncWrite# fd isSock len buf s of
572 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
574 asyncDoProc :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
575 asyncDoProc (FunPtr proc) (Ptr param) =
576 -- the 'length' value is ignored; simplifies implementation of
577 -- the async*# primops to have them all return the same result.
578 IO $ \s -> case asyncDoProc# proc param s of
579 (# s, len#, err# #) -> (# s, I# err# #)
581 -- to aid the use of these primops by the IO Handle implementation,
582 -- provide the following convenience funs:
584 -- this better be a pinned byte array!
585 asyncReadBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
586 asyncReadBA fd isSock len off bufB =
587 asyncRead fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
589 asyncWriteBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
590 asyncWriteBA fd isSock len off bufB =
591 asyncWrite fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
595 -- -----------------------------------------------------------------------------
598 -- | Block the current thread until data is available to read on the
599 -- given file descriptor (GHC only).
600 threadWaitRead :: Fd -> IO ()
602 #ifndef mingw32_HOST_OS
603 | threaded = waitForReadEvent fd
605 | otherwise = IO $ \s ->
606 case fromIntegral fd of { I# fd# ->
607 case waitRead# fd# s of { s -> (# s, () #)
610 -- | Block the current thread until data can be written to the
611 -- given file descriptor (GHC only).
612 threadWaitWrite :: Fd -> IO ()
614 #ifndef mingw32_HOST_OS
615 | threaded = waitForWriteEvent fd
617 | otherwise = IO $ \s ->
618 case fromIntegral fd of { I# fd# ->
619 case waitWrite# fd# s of { s -> (# s, () #)
622 -- | Suspends the current thread for a given number of microseconds
625 -- Note that the resolution used by the Haskell runtime system's
626 -- internal timer is 1\/50 second, and 'threadDelay' will round its
627 -- argument up to the nearest multiple of this resolution.
629 -- There is no guarantee that the thread will be rescheduled promptly
630 -- when the delay has expired, but the thread will never continue to
631 -- run /earlier/ than specified.
633 threadDelay :: Int -> IO ()
635 | threaded = waitForDelayEvent time
636 | otherwise = IO $ \s ->
637 case fromIntegral time of { I# time# ->
638 case delay# time# s of { s -> (# s, () #)
641 registerDelay :: Int -> IO (TVar Bool)
643 | threaded = waitForDelayEventSTM usecs
644 | otherwise = error "registerDelay: requires -threaded"
646 foreign import ccall unsafe "rtsSupportsBoundThreads" threaded :: Bool
648 waitForDelayEvent :: Int -> IO ()
649 waitForDelayEvent usecs = do
652 target <- calculateTarget usecs
653 atomicModifyIORef pendingDelays (\xs -> (Delay target m : xs, ()))
657 -- Delays for use in STM
658 waitForDelayEventSTM :: Int -> IO (TVar Bool)
659 waitForDelayEventSTM usecs = do
660 t <- atomically $ newTVar False
662 target <- calculateTarget usecs
663 atomicModifyIORef pendingDelays (\xs -> (DelaySTM target t : xs, ()))
667 calculateTarget :: Int -> IO Int
668 calculateTarget usecs = do
670 let -- Convert usecs to ticks, rounding up as we must wait /at least/
671 -- as long as we are told
672 usecs' = (usecs + tick_usecs - 1) `quot` tick_usecs
673 target = now + 1 -- getTicksOfDay will have rounded down, but
674 -- again we need to wait for /at least/ as long
675 -- as we are told, so add 1 to it
679 -- ----------------------------------------------------------------------------
680 -- Threaded RTS implementation of threadWaitRead, threadWaitWrite, threadDelay
682 -- In the threaded RTS, we employ a single IO Manager thread to wait
683 -- for all outstanding IO requests (threadWaitRead,threadWaitWrite)
684 -- and delays (threadDelay).
686 -- We can do this because in the threaded RTS the IO Manager can make
687 -- a non-blocking call to select(), so we don't have to do select() in
688 -- the scheduler as we have to in the non-threaded RTS. We get performance
689 -- benefits from doing it this way, because we only have to restart the select()
690 -- when a new request arrives, rather than doing one select() each time
691 -- around the scheduler loop. Furthermore, the scheduler can be simplified
692 -- by not having to check for completed IO requests.
694 -- Issues, possible problems:
696 -- - we might want bound threads to just do the blocking
697 -- operation rather than communicating with the IO manager
698 -- thread. This would prevent simgle-threaded programs which do
699 -- IO from requiring multiple OS threads. However, it would also
700 -- prevent bound threads waiting on IO from being killed or sent
703 -- - Apprently exec() doesn't work on Linux in a multithreaded program.
704 -- I couldn't repeat this.
706 -- - How do we handle signal delivery in the multithreaded RTS?
708 -- - forkProcess will kill the IO manager thread. Let's just
709 -- hope we don't need to do any blocking IO between fork & exec.
711 #ifndef mingw32_HOST_OS
713 = Read {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
714 | Write {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
718 = Delay {-# UNPACK #-} !Int {-# UNPACK #-} !(MVar ())
719 | DelaySTM {-# UNPACK #-} !Int {-# UNPACK #-} !(TVar Bool)
721 #ifndef mingw32_HOST_OS
722 pendingEvents :: IORef [IOReq]
724 pendingDelays :: IORef [DelayReq]
725 -- could use a strict list or array here
726 {-# NOINLINE pendingEvents #-}
727 {-# NOINLINE pendingDelays #-}
728 (pendingEvents,pendingDelays) = unsafePerformIO $ do
733 -- the first time we schedule an IO request, the service thread
734 -- will be created (cool, huh?)
736 ensureIOManagerIsRunning :: IO ()
737 ensureIOManagerIsRunning
738 | threaded = seq pendingEvents $ return ()
739 | otherwise = return ()
741 insertDelay :: DelayReq -> [DelayReq] -> [DelayReq]
742 insertDelay d [] = [d]
743 insertDelay d1 ds@(d2 : rest)
744 | delayTime d1 <= delayTime d2 = d1 : ds
745 | otherwise = d2 : insertDelay d1 rest
747 delayTime (Delay t _) = t
748 delayTime (DelaySTM t _) = t
751 tick_freq = 50 :: Ticks -- accuracy of threadDelay (ticks per sec)
752 tick_usecs = 1000000 `quot` tick_freq :: Int
753 tick_msecs = 1000 `quot` tick_freq :: Int
755 -- XXX: move into GHC.IOBase from Data.IORef?
756 atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
757 atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
759 foreign import ccall unsafe "getTicksOfDay"
760 getTicksOfDay :: IO Ticks
762 #ifdef mingw32_HOST_OS
763 -- ----------------------------------------------------------------------------
764 -- Windows IO manager thread
766 startIOManagerThread :: IO ()
767 startIOManagerThread = do
768 wakeup <- c_getIOManagerEvent
769 forkIO $ service_loop wakeup []
772 service_loop :: HANDLE -- read end of pipe
773 -> [DelayReq] -- current delay requests
776 service_loop wakeup old_delays = do
777 -- pick up new delay requests
778 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
779 let delays = foldr insertDelay old_delays new_delays
782 (delays', timeout) <- getDelay now delays
784 r <- c_WaitForSingleObject wakeup timeout
786 0xffffffff -> do c_maperrno; throwErrno "service_loop"
788 r <- c_readIOManagerEvent
791 _ | r == io_MANAGER_WAKEUP -> return False
792 _ | r == io_MANAGER_DIE -> return True
793 0 -> return False -- spurious wakeup
794 r -> do start_console_handler (r `shiftR` 1); return False
797 else service_cont wakeup delays'
799 _other -> service_cont wakeup delays' -- probably timeout
801 service_cont wakeup delays = do
803 putMVar prodding False
804 service_loop wakeup delays
806 -- must agree with rts/win32/ThrIOManager.c
807 io_MANAGER_WAKEUP = 0xffffffff :: Word32
808 io_MANAGER_DIE = 0xfffffffe :: Word32
810 start_console_handler :: Word32 -> IO ()
811 start_console_handler r = do
812 stableptr <- peek console_handler
813 forkIO $ do io <- deRefStablePtr stableptr; io (fromIntegral r)
816 foreign import ccall "&console_handler"
817 console_handler :: Ptr (StablePtr (CInt -> IO ()))
819 stick :: IORef HANDLE
820 {-# NOINLINE stick #-}
821 stick = unsafePerformIO (newIORef nullPtr)
823 prodding :: MVar Bool
824 {-# NOINLINE prodding #-}
825 prodding = unsafePerformIO (newMVar False)
827 prodServiceThread :: IO ()
828 prodServiceThread = do
829 b <- takeMVar prodding
831 then do hdl <- readIORef stick
832 c_sendIOManagerEvent io_MANAGER_WAKEUP
834 putMVar prodding True
836 -- Walk the queue of pending delays, waking up any that have passed
837 -- and return the smallest delay to wait for. The queue of pending
838 -- delays is kept ordered.
839 getDelay :: Ticks -> [DelayReq] -> IO ([DelayReq], DWORD)
840 getDelay now [] = return ([], iNFINITE)
841 getDelay now all@(d : rest)
843 Delay time m | now >= time -> do
846 DelaySTM time t | now >= time -> do
847 atomically $ writeTVar t True
850 return (all, (fromIntegral (delayTime d - now) *
851 fromIntegral tick_msecs))
852 -- delay is in millisecs for WaitForSingleObject
854 -- ToDo: this just duplicates part of System.Win32.Types, which isn't
855 -- available yet. We should move some Win32 functionality down here,
856 -- maybe as part of the grand reorganisation of the base package...
860 iNFINITE = 0xFFFFFFFF :: DWORD -- urgh
862 foreign import ccall unsafe "getIOManagerEvent" -- in the RTS (ThrIOManager.c)
863 c_getIOManagerEvent :: IO HANDLE
865 foreign import ccall unsafe "readIOManagerEvent" -- in the RTS (ThrIOManager.c)
866 c_readIOManagerEvent :: IO Word32
868 foreign import ccall unsafe "sendIOManagerEvent" -- in the RTS (ThrIOManager.c)
869 c_sendIOManagerEvent :: Word32 -> IO ()
871 foreign import ccall unsafe "maperrno" -- in runProcess.c
874 foreign import stdcall "WaitForSingleObject"
875 c_WaitForSingleObject :: HANDLE -> DWORD -> IO DWORD
878 -- ----------------------------------------------------------------------------
879 -- Unix IO manager thread, using select()
881 startIOManagerThread :: IO ()
882 startIOManagerThread = do
883 allocaArray 2 $ \fds -> do
884 throwErrnoIfMinus1 "startIOManagerThread" (c_pipe fds)
885 rd_end <- peekElemOff fds 0
886 wr_end <- peekElemOff fds 1
887 writeIORef stick (fromIntegral wr_end)
888 c_setIOManagerPipe wr_end
890 allocaBytes sizeofFdSet $ \readfds -> do
891 allocaBytes sizeofFdSet $ \writefds -> do
892 allocaBytes sizeofTimeVal $ \timeval -> do
893 service_loop (fromIntegral rd_end) readfds writefds timeval [] []
897 :: Fd -- listen to this for wakeup calls
904 service_loop wakeup readfds writefds ptimeval old_reqs old_delays = do
906 -- pick up new IO requests
907 new_reqs <- atomicModifyIORef pendingEvents (\a -> ([],a))
908 let reqs = new_reqs ++ old_reqs
910 -- pick up new delay requests
911 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
912 let delays = foldr insertDelay old_delays new_delays
914 -- build the FDSets for select()
918 maxfd <- buildFdSets 0 readfds writefds reqs
920 -- perform the select()
921 let do_select delays = do
922 -- check the current time and wake up any thread in
923 -- threadDelay whose timeout has expired. Also find the
924 -- timeout value for the select() call.
926 (delays', timeout) <- getDelay now ptimeval delays
928 res <- c_select ((max wakeup maxfd)+1) readfds writefds
934 _ | err == eINTR -> do_select delays'
935 -- EINTR: just redo the select()
936 _ | err == eBADF -> return (True, delays)
937 -- EBADF: one of the file descriptors is closed or bad,
938 -- we don't know which one, so wake everyone up.
939 _ | otherwise -> throwErrno "select"
940 -- otherwise (ENOMEM or EINVAL) something has gone
941 -- wrong; report the error.
943 return (False,delays')
945 (wakeup_all,delays') <- do_select delays
948 if wakeup_all then return False
950 b <- fdIsSet wakeup readfds
953 else alloca $ \p -> do
954 c_read (fromIntegral wakeup) p 1; return ()
957 _ | s == io_MANAGER_WAKEUP -> return False
958 _ | s == io_MANAGER_DIE -> return True
959 _ -> do handler_tbl <- peek handlers
960 sp <- peekElemOff handler_tbl (fromIntegral s)
961 forkIO (do io <- deRefStablePtr sp; io)
964 if exit then return () else do
967 putMVar prodding False
969 reqs' <- if wakeup_all then do wakeupAll reqs; return []
970 else completeRequests reqs readfds writefds []
972 service_loop wakeup readfds writefds ptimeval reqs' delays'
974 io_MANAGER_WAKEUP = 0xff :: CChar
975 io_MANAGER_DIE = 0xfe :: CChar
978 {-# NOINLINE stick #-}
979 stick = unsafePerformIO (newIORef 0)
981 prodding :: MVar Bool
982 {-# NOINLINE prodding #-}
983 prodding = unsafePerformIO (newMVar False)
985 prodServiceThread :: IO ()
986 prodServiceThread = do
987 b <- takeMVar prodding
989 then do fd <- readIORef stick
990 with io_MANAGER_WAKEUP $ \pbuf -> do
991 c_write (fromIntegral fd) pbuf 1; return ()
993 putMVar prodding True
995 foreign import ccall "&signal_handlers" handlers :: Ptr (Ptr (StablePtr (IO ())))
997 foreign import ccall "setIOManagerPipe"
998 c_setIOManagerPipe :: CInt -> IO ()
1000 -- -----------------------------------------------------------------------------
1003 buildFdSets maxfd readfds writefds [] = return maxfd
1004 buildFdSets maxfd readfds writefds (Read fd m : reqs)
1005 | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
1008 buildFdSets (max maxfd fd) readfds writefds reqs
1009 buildFdSets maxfd readfds writefds (Write fd m : reqs)
1010 | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
1013 buildFdSets (max maxfd fd) readfds writefds reqs
1015 completeRequests [] _ _ reqs' = return reqs'
1016 completeRequests (Read fd m : reqs) readfds writefds reqs' = do
1017 b <- fdIsSet fd readfds
1019 then do putMVar m (); completeRequests reqs readfds writefds reqs'
1020 else completeRequests reqs readfds writefds (Read fd m : reqs')
1021 completeRequests (Write fd m : reqs) readfds writefds reqs' = do
1022 b <- fdIsSet fd writefds
1024 then do putMVar m (); completeRequests reqs readfds writefds reqs'
1025 else completeRequests reqs readfds writefds (Write fd m : reqs')
1027 wakeupAll [] = return ()
1028 wakeupAll (Read fd m : reqs) = do putMVar m (); wakeupAll reqs
1029 wakeupAll (Write fd m : reqs) = do putMVar m (); wakeupAll reqs
1031 waitForReadEvent :: Fd -> IO ()
1032 waitForReadEvent fd = do
1034 atomicModifyIORef pendingEvents (\xs -> (Read fd m : xs, ()))
1038 waitForWriteEvent :: Fd -> IO ()
1039 waitForWriteEvent fd = do
1041 atomicModifyIORef pendingEvents (\xs -> (Write fd m : xs, ()))
1045 -- -----------------------------------------------------------------------------
1048 -- Walk the queue of pending delays, waking up any that have passed
1049 -- and return the smallest delay to wait for. The queue of pending
1050 -- delays is kept ordered.
1051 getDelay :: Ticks -> Ptr CTimeVal -> [DelayReq] -> IO ([DelayReq], Ptr CTimeVal)
1052 getDelay now ptimeval [] = return ([],nullPtr)
1053 getDelay now ptimeval all@(d : rest)
1055 Delay time m | now >= time -> do
1057 getDelay now ptimeval rest
1058 DelaySTM time t | now >= time -> do
1059 atomically $ writeTVar t True
1060 getDelay now ptimeval rest
1062 setTimevalTicks ptimeval (delayTime d - now)
1063 return (all,ptimeval)
1065 newtype CTimeVal = CTimeVal ()
1067 foreign import ccall unsafe "sizeofTimeVal"
1068 sizeofTimeVal :: Int
1070 foreign import ccall unsafe "setTimevalTicks"
1071 setTimevalTicks :: Ptr CTimeVal -> Ticks -> IO ()
1074 On Win32 we're going to have a single Pipe, and a
1075 waitForSingleObject with the delay time. For signals, we send a
1076 byte down the pipe just like on Unix.
1079 -- ----------------------------------------------------------------------------
1080 -- select() interface
1082 -- ToDo: move to System.Posix.Internals?
1084 newtype CFdSet = CFdSet ()
1086 foreign import ccall safe "select"
1087 c_select :: Fd -> Ptr CFdSet -> Ptr CFdSet -> Ptr CFdSet -> Ptr CTimeVal
1090 foreign import ccall unsafe "hsFD_SETSIZE"
1093 foreign import ccall unsafe "hsFD_CLR"
1094 fdClr :: Fd -> Ptr CFdSet -> IO ()
1096 foreign import ccall unsafe "hsFD_ISSET"
1097 fdIsSet :: Fd -> Ptr CFdSet -> IO CInt
1099 foreign import ccall unsafe "hsFD_SET"
1100 fdSet :: Fd -> Ptr CFdSet -> IO ()
1102 foreign import ccall unsafe "hsFD_ZERO"
1103 fdZero :: Ptr CFdSet -> IO ()
1105 foreign import ccall unsafe "sizeof_fd_set"