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
224 target thread. The calling thread can thus be certain that the target
225 thread has received the exception. This is a useful property to know
226 when dealing with race conditions: eg. if there are two threads that
227 can kill each other, it is guaranteed that only one of the threads
228 will get to kill the other.
230 If the target thread is currently making a foreign call, then the
231 exception will not be raised (and hence 'throwTo' will not return)
232 until the call has completed. This is the case regardless of whether
233 the call is inside a 'block' or not.
235 throwTo :: ThreadId -> Exception -> IO ()
236 throwTo (ThreadId id) ex = IO $ \ s ->
237 case (killThread# id ex s) of s1 -> (# s1, () #)
239 -- | Returns the 'ThreadId' of the calling thread (GHC only).
240 myThreadId :: IO ThreadId
241 myThreadId = IO $ \s ->
242 case (myThreadId# s) of (# s1, id #) -> (# s1, ThreadId id #)
245 -- |The 'yield' action allows (forces, in a co-operative multitasking
246 -- implementation) a context-switch to any other currently runnable
247 -- threads (if any), and is occasionally useful when implementing
248 -- concurrency abstractions.
251 case (yield# s) of s1 -> (# s1, () #)
253 {- | 'labelThread' stores a string as identifier for this thread if
254 you built a RTS with debugging support. This identifier will be used in
255 the debugging output to make distinction of different threads easier
256 (otherwise you only have the thread state object\'s address in the heap).
258 Other applications like the graphical Concurrent Haskell Debugger
259 (<http://www.informatik.uni-kiel.de/~fhu/chd/>) may choose to overload
260 'labelThread' for their purposes as well.
263 labelThread :: ThreadId -> String -> IO ()
264 labelThread (ThreadId t) str = IO $ \ s ->
265 let ps = packCString# str
266 adr = byteArrayContents# ps in
267 case (labelThread# t adr s) of s1 -> (# s1, () #)
269 -- Nota Bene: 'pseq' used to be 'seq'
270 -- but 'seq' is now defined in PrelGHC
272 -- "pseq" is defined a bit weirdly (see below)
274 -- The reason for the strange "lazy" call is that
275 -- it fools the compiler into thinking that pseq and par are non-strict in
276 -- their second argument (even if it inlines pseq at the call site).
277 -- If it thinks pseq is strict in "y", then it often evaluates
278 -- "y" before "x", which is totally wrong.
282 pseq x y = x `seq` lazy y
286 par x y = case (par# x) of { _ -> lazy y }
290 %************************************************************************
292 \subsection[stm]{Transactional heap operations}
294 %************************************************************************
296 TVars are shared memory locations which support atomic memory
300 -- |A monad supporting atomic memory transactions.
301 newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #))
303 unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
306 INSTANCE_TYPEABLE1(STM,stmTc,"STM")
308 instance Functor STM where
309 fmap f x = x >>= (return . f)
311 instance Monad STM where
312 {-# INLINE return #-}
316 return x = returnSTM x
317 m >>= k = bindSTM m k
319 bindSTM :: STM a -> (a -> STM b) -> STM b
320 bindSTM (STM m) k = STM ( \s ->
322 (# new_s, a #) -> unSTM (k a) new_s
325 thenSTM :: STM a -> STM b -> STM b
326 thenSTM (STM m) k = STM ( \s ->
328 (# new_s, a #) -> unSTM k new_s
331 returnSTM :: a -> STM a
332 returnSTM x = STM (\s -> (# s, x #))
334 -- | Unsafely performs IO in the STM monad.
335 unsafeIOToSTM :: IO a -> STM a
336 unsafeIOToSTM (IO m) = STM m
338 -- |Perform a series of STM actions atomically.
340 -- You cannot use 'atomically' inside an 'unsafePerformIO' or 'unsafeInterleaveIO'.
341 -- Any attempt to do so will result in a runtime error. (Reason: allowing
342 -- this would effectively allow a transaction inside a transaction, depending
343 -- on exactly when the thunk is evaluated.)
345 -- However, see 'newTVarIO', which can be called inside 'unsafePerformIO',
346 -- and which allows top-level TVars to be allocated.
348 atomically :: STM a -> IO a
349 atomically (STM m) = IO (\s -> (atomically# m) s )
351 -- |Retry execution of the current memory transaction because it has seen
352 -- values in TVars which mean that it should not continue (e.g. the TVars
353 -- represent a shared buffer that is now empty). The implementation may
354 -- block the thread until one of the TVars that it has read from has been
355 -- udpated. (GHC only)
357 retry = STM $ \s# -> retry# s#
359 -- |Compose two alternative STM actions (GHC only). If the first action
360 -- completes without retrying then it forms the result of the orElse.
361 -- Otherwise, if the first action retries, then the second action is
362 -- tried in its place. If both actions retry then the orElse as a
364 orElse :: STM a -> STM a -> STM a
365 orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
367 -- |Exception handling within STM actions.
368 catchSTM :: STM a -> (Exception -> STM a) -> STM a
369 catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
371 -- | Low-level primitive on which always and alwaysSucceeds are built.
372 -- checkInv differs form these in that (i) the invariant is not
373 -- checked when checkInv is called, only at the end of this and
374 -- subsequent transcations, (ii) the invariant failure is indicated
375 -- by raising an exception.
376 checkInv :: STM a -> STM ()
377 checkInv (STM m) = STM (\s -> (check# m) s)
379 -- | alwaysSucceeds adds a new invariant that must be true when passed
380 -- to alwaysSucceeds, at the end of the current transaction, and at
381 -- the end of every subsequent transaction. If it fails at any
382 -- of those points then the transaction violating it is aborted
383 -- and the exception raised by the invariant is propagated.
384 alwaysSucceeds :: STM a -> STM ()
385 alwaysSucceeds i = do ( do i ; retry ) `orElse` ( return () )
388 -- | always is a variant of alwaysSucceeds in which the invariant is
389 -- expressed as an STM Bool action that must return True. Returning
390 -- False or raising an exception are both treated as invariant failures.
391 always :: STM Bool -> STM ()
392 always i = alwaysSucceeds ( do v <- i
393 if (v) then return () else ( error "Transacional invariant violation" ) )
395 -- |Shared memory locations that support atomic memory transactions.
396 data TVar a = TVar (TVar# RealWorld a)
398 INSTANCE_TYPEABLE1(TVar,tvarTc,"TVar")
400 instance Eq (TVar a) where
401 (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
403 -- |Create a new TVar holding a value supplied
404 newTVar :: a -> STM (TVar a)
405 newTVar val = STM $ \s1# ->
406 case newTVar# val s1# of
407 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
409 -- |@IO@ version of 'newTVar'. This is useful for creating top-level
410 -- 'TVar's using 'System.IO.Unsafe.unsafePerformIO', because using
411 -- 'atomically' inside 'System.IO.Unsafe.unsafePerformIO' isn't
413 newTVarIO :: a -> IO (TVar a)
414 newTVarIO val = IO $ \s1# ->
415 case newTVar# val s1# of
416 (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
418 -- |Return the current value stored in a TVar
419 readTVar :: TVar a -> STM a
420 readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
422 -- |Write the supplied value into a TVar
423 writeTVar :: TVar a -> a -> STM ()
424 writeTVar (TVar tvar#) val = STM $ \s1# ->
425 case writeTVar# tvar# val s1# of
430 %************************************************************************
432 \subsection[mvars]{M-Structures}
434 %************************************************************************
436 M-Vars are rendezvous points for concurrent threads. They begin
437 empty, and any attempt to read an empty M-Var blocks. When an M-Var
438 is written, a single blocked thread may be freed. Reading an M-Var
439 toggles its state from full back to empty. Therefore, any value
440 written to an M-Var may only be read once. Multiple reads and writes
441 are allowed, but there must be at least one read between any two
445 --Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
447 -- |Create an 'MVar' which is initially empty.
448 newEmptyMVar :: IO (MVar a)
449 newEmptyMVar = IO $ \ s# ->
451 (# s2#, svar# #) -> (# s2#, MVar svar# #)
453 -- |Create an 'MVar' which contains the supplied value.
454 newMVar :: a -> IO (MVar a)
456 newEmptyMVar >>= \ mvar ->
457 putMVar mvar value >>
460 -- |Return the contents of the 'MVar'. If the 'MVar' is currently
461 -- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
462 -- the 'MVar' is left empty.
464 -- There are two further important properties of 'takeMVar':
466 -- * 'takeMVar' is single-wakeup. That is, if there are multiple
467 -- threads blocked in 'takeMVar', and the 'MVar' becomes full,
468 -- only one thread will be woken up. The runtime guarantees that
469 -- the woken thread completes its 'takeMVar' operation.
471 -- * When multiple threads are blocked on an 'MVar', they are
472 -- woken up in FIFO order. This is useful for providing
473 -- fairness properties of abstractions built using 'MVar's.
475 takeMVar :: MVar a -> IO a
476 takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
478 -- |Put a value into an 'MVar'. If the 'MVar' is currently full,
479 -- 'putMVar' will wait until it becomes empty.
481 -- There are two further important properties of 'putMVar':
483 -- * 'putMVar' is single-wakeup. That is, if there are multiple
484 -- threads blocked in 'putMVar', and the 'MVar' becomes empty,
485 -- only one thread will be woken up. The runtime guarantees that
486 -- the woken thread completes its 'putMVar' operation.
488 -- * When multiple threads are blocked on an 'MVar', they are
489 -- woken up in FIFO order. This is useful for providing
490 -- fairness properties of abstractions built using 'MVar's.
492 putMVar :: MVar a -> a -> IO ()
493 putMVar (MVar mvar#) x = IO $ \ s# ->
494 case putMVar# mvar# x s# of
497 -- |A non-blocking version of 'takeMVar'. The 'tryTakeMVar' function
498 -- returns immediately, with 'Nothing' if the 'MVar' was empty, or
499 -- @'Just' a@ if the 'MVar' was full with contents @a@. After 'tryTakeMVar',
500 -- the 'MVar' is left empty.
501 tryTakeMVar :: MVar a -> IO (Maybe a)
502 tryTakeMVar (MVar m) = IO $ \ s ->
503 case tryTakeMVar# m s of
504 (# s, 0#, _ #) -> (# s, Nothing #) -- MVar is empty
505 (# s, _, a #) -> (# s, Just a #) -- MVar is full
507 -- |A non-blocking version of 'putMVar'. The 'tryPutMVar' function
508 -- attempts to put the value @a@ into the 'MVar', returning 'True' if
509 -- it was successful, or 'False' otherwise.
510 tryPutMVar :: MVar a -> a -> IO Bool
511 tryPutMVar (MVar mvar#) x = IO $ \ s# ->
512 case tryPutMVar# mvar# x s# of
513 (# s, 0# #) -> (# s, False #)
514 (# s, _ #) -> (# s, True #)
516 -- |Check whether a given 'MVar' is empty.
518 -- Notice that the boolean value returned is just a snapshot of
519 -- the state of the MVar. By the time you get to react on its result,
520 -- the MVar may have been filled (or emptied) - so be extremely
521 -- careful when using this operation. Use 'tryTakeMVar' instead if possible.
522 isEmptyMVar :: MVar a -> IO Bool
523 isEmptyMVar (MVar mv#) = IO $ \ s# ->
524 case isEmptyMVar# mv# s# of
525 (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
527 -- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
528 -- "System.Mem.Weak" for more about finalizers.
529 addMVarFinalizer :: MVar a -> IO () -> IO ()
530 addMVarFinalizer (MVar m) finalizer =
531 IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
535 %************************************************************************
537 \subsection{Thread waiting}
539 %************************************************************************
542 #ifdef mingw32_HOST_OS
544 -- Note: threadDelay, threadWaitRead and threadWaitWrite aren't really functional
545 -- on Win32, but left in there because lib code (still) uses them (the manner
546 -- in which they're used doesn't cause problems on a Win32 platform though.)
548 asyncRead :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
549 asyncRead (I# fd) (I# isSock) (I# len) (Ptr buf) =
550 IO $ \s -> case asyncRead# fd isSock len buf s of
551 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
553 asyncWrite :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
554 asyncWrite (I# fd) (I# isSock) (I# len) (Ptr buf) =
555 IO $ \s -> case asyncWrite# fd isSock len buf s of
556 (# s, len#, err# #) -> (# s, (I# len#, I# err#) #)
558 asyncDoProc :: FunPtr (Ptr a -> IO Int) -> Ptr a -> IO Int
559 asyncDoProc (FunPtr proc) (Ptr param) =
560 -- the 'length' value is ignored; simplifies implementation of
561 -- the async*# primops to have them all return the same result.
562 IO $ \s -> case asyncDoProc# proc param s of
563 (# s, len#, err# #) -> (# s, I# err# #)
565 -- to aid the use of these primops by the IO Handle implementation,
566 -- provide the following convenience funs:
568 -- this better be a pinned byte array!
569 asyncReadBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
570 asyncReadBA fd isSock len off bufB =
571 asyncRead fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
573 asyncWriteBA :: Int -> Int -> Int -> Int -> MutableByteArray# RealWorld -> IO (Int,Int)
574 asyncWriteBA fd isSock len off bufB =
575 asyncWrite fd isSock len ((Ptr (byteArrayContents# (unsafeCoerce# bufB))) `plusPtr` off)
579 -- -----------------------------------------------------------------------------
582 -- | Block the current thread until data is available to read on the
583 -- given file descriptor (GHC only).
584 threadWaitRead :: Fd -> IO ()
586 #ifndef mingw32_HOST_OS
587 | threaded = waitForReadEvent fd
589 | otherwise = IO $ \s ->
590 case fromIntegral fd of { I# fd# ->
591 case waitRead# fd# s of { s -> (# s, () #)
594 -- | Block the current thread until data can be written to the
595 -- given file descriptor (GHC only).
596 threadWaitWrite :: Fd -> IO ()
598 #ifndef mingw32_HOST_OS
599 | threaded = waitForWriteEvent fd
601 | otherwise = IO $ \s ->
602 case fromIntegral fd of { I# fd# ->
603 case waitWrite# fd# s of { s -> (# s, () #)
606 -- | Suspends the current thread for a given number of microseconds
609 -- Note that the resolution used by the Haskell runtime system's
610 -- internal timer is 1\/50 second, and 'threadDelay' will round its
611 -- argument up to the nearest multiple of this resolution.
613 -- There is no guarantee that the thread will be rescheduled promptly
614 -- when the delay has expired, but the thread will never continue to
615 -- run /earlier/ than specified.
617 threadDelay :: Int -> IO ()
619 | threaded = waitForDelayEvent time
620 | otherwise = IO $ \s ->
621 case fromIntegral time of { I# time# ->
622 case delay# time# s of { s -> (# s, () #)
625 registerDelay :: Int -> IO (TVar Bool)
627 | threaded = waitForDelayEventSTM usecs
628 | otherwise = error "registerDelay: requires -threaded"
630 foreign import ccall unsafe "rtsSupportsBoundThreads" threaded :: Bool
632 waitForDelayEvent :: Int -> IO ()
633 waitForDelayEvent usecs = do
636 let target = now + usecs `quot` tick_usecs
637 atomicModifyIORef pendingDelays (\xs -> (Delay target m : xs, ()))
641 -- Delays for use in STM
642 waitForDelayEventSTM :: Int -> IO (TVar Bool)
643 waitForDelayEventSTM usecs = do
644 t <- atomically $ newTVar False
646 let target = now + usecs `quot` tick_usecs
647 atomicModifyIORef pendingDelays (\xs -> (DelaySTM target t : xs, ()))
651 calculateTarget :: Int -> IO Int
652 calculateTarget usecs = do
654 let -- Convert usecs to ticks, rounding up as we must wait /at least/
655 -- as long as we are told
656 usecs' = (usecs + tick_usecs - 1) `quot` tick_usecs
657 target = now + 1 -- getTicksOfDay will have rounded down, but
658 -- again we need to wait for /at least/ as long
659 -- as we are told, so add 1 to it
663 -- ----------------------------------------------------------------------------
664 -- Threaded RTS implementation of threadWaitRead, threadWaitWrite, threadDelay
666 -- In the threaded RTS, we employ a single IO Manager thread to wait
667 -- for all outstanding IO requests (threadWaitRead,threadWaitWrite)
668 -- and delays (threadDelay).
670 -- We can do this because in the threaded RTS the IO Manager can make
671 -- a non-blocking call to select(), so we don't have to do select() in
672 -- the scheduler as we have to in the non-threaded RTS. We get performance
673 -- benefits from doing it this way, because we only have to restart the select()
674 -- when a new request arrives, rather than doing one select() each time
675 -- around the scheduler loop. Furthermore, the scheduler can be simplified
676 -- by not having to check for completed IO requests.
678 -- Issues, possible problems:
680 -- - we might want bound threads to just do the blocking
681 -- operation rather than communicating with the IO manager
682 -- thread. This would prevent simgle-threaded programs which do
683 -- IO from requiring multiple OS threads. However, it would also
684 -- prevent bound threads waiting on IO from being killed or sent
687 -- - Apprently exec() doesn't work on Linux in a multithreaded program.
688 -- I couldn't repeat this.
690 -- - How do we handle signal delivery in the multithreaded RTS?
692 -- - forkProcess will kill the IO manager thread. Let's just
693 -- hope we don't need to do any blocking IO between fork & exec.
695 #ifndef mingw32_HOST_OS
697 = Read {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
698 | Write {-# UNPACK #-} !Fd {-# UNPACK #-} !(MVar ())
702 = Delay {-# UNPACK #-} !Int {-# UNPACK #-} !(MVar ())
703 | DelaySTM {-# UNPACK #-} !Int {-# UNPACK #-} !(TVar Bool)
705 #ifndef mingw32_HOST_OS
706 pendingEvents :: IORef [IOReq]
708 pendingDelays :: IORef [DelayReq]
709 -- could use a strict list or array here
710 {-# NOINLINE pendingEvents #-}
711 {-# NOINLINE pendingDelays #-}
712 (pendingEvents,pendingDelays) = unsafePerformIO $ do
717 -- the first time we schedule an IO request, the service thread
718 -- will be created (cool, huh?)
720 ensureIOManagerIsRunning :: IO ()
721 ensureIOManagerIsRunning
722 | threaded = seq pendingEvents $ return ()
723 | otherwise = return ()
725 insertDelay :: DelayReq -> [DelayReq] -> [DelayReq]
726 insertDelay d [] = [d]
727 insertDelay d1 ds@(d2 : rest)
728 | delayTime d1 <= delayTime d2 = d1 : ds
729 | otherwise = d2 : insertDelay d1 rest
731 delayTime (Delay t _) = t
732 delayTime (DelaySTM t _) = t
735 tick_freq = 50 :: Ticks -- accuracy of threadDelay (ticks per sec)
736 tick_usecs = 1000000 `quot` tick_freq :: Int
737 tick_msecs = 1000 `quot` tick_freq :: Int
739 -- XXX: move into GHC.IOBase from Data.IORef?
740 atomicModifyIORef :: IORef a -> (a -> (a,b)) -> IO b
741 atomicModifyIORef (IORef (STRef r#)) f = IO $ \s -> atomicModifyMutVar# r# f s
743 foreign import ccall unsafe "getTicksOfDay"
744 getTicksOfDay :: IO Ticks
746 #ifdef mingw32_HOST_OS
747 -- ----------------------------------------------------------------------------
748 -- Windows IO manager thread
750 startIOManagerThread :: IO ()
751 startIOManagerThread = do
752 wakeup <- c_getIOManagerEvent
753 forkIO $ service_loop wakeup []
756 service_loop :: HANDLE -- read end of pipe
757 -> [DelayReq] -- current delay requests
760 service_loop wakeup old_delays = do
761 -- pick up new delay requests
762 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
763 let delays = foldr insertDelay old_delays new_delays
766 (delays', timeout) <- getDelay now delays
768 r <- c_WaitForSingleObject wakeup timeout
770 0xffffffff -> do c_maperrno; throwErrno "service_loop"
772 r <- c_readIOManagerEvent
775 _ | r == io_MANAGER_WAKEUP -> return False
776 _ | r == io_MANAGER_DIE -> return True
777 0 -> return False -- spurious wakeup
778 r -> do start_console_handler (r `shiftR` 1); return False
781 else service_cont wakeup delays'
783 _other -> service_cont wakeup delays' -- probably timeout
785 service_cont wakeup delays = do
787 putMVar prodding False
788 service_loop wakeup delays
790 -- must agree with rts/win32/ThrIOManager.c
791 io_MANAGER_WAKEUP = 0xffffffff :: Word32
792 io_MANAGER_DIE = 0xfffffffe :: Word32
794 start_console_handler :: Word32 -> IO ()
795 start_console_handler r = do
796 stableptr <- peek console_handler
797 forkIO $ do io <- deRefStablePtr stableptr; io (fromIntegral r)
800 foreign import ccall "&console_handler"
801 console_handler :: Ptr (StablePtr (CInt -> IO ()))
803 stick :: IORef HANDLE
804 {-# NOINLINE stick #-}
805 stick = unsafePerformIO (newIORef nullPtr)
807 prodding :: MVar Bool
808 {-# NOINLINE prodding #-}
809 prodding = unsafePerformIO (newMVar False)
811 prodServiceThread :: IO ()
812 prodServiceThread = do
813 b <- takeMVar prodding
815 then do hdl <- readIORef stick
816 c_sendIOManagerEvent io_MANAGER_WAKEUP
818 putMVar prodding True
820 -- Walk the queue of pending delays, waking up any that have passed
821 -- and return the smallest delay to wait for. The queue of pending
822 -- delays is kept ordered.
823 getDelay :: Ticks -> [DelayReq] -> IO ([DelayReq], DWORD)
824 getDelay now [] = return ([], iNFINITE)
825 getDelay now all@(d : rest)
827 Delay time m | now >= time -> do
830 DelaySTM time t | now >= time -> do
831 atomically $ writeTVar t True
834 return (all, (fromIntegral (delayTime d - now) *
835 fromIntegral tick_msecs))
836 -- delay is in millisecs for WaitForSingleObject
838 -- ToDo: this just duplicates part of System.Win32.Types, which isn't
839 -- available yet. We should move some Win32 functionality down here,
840 -- maybe as part of the grand reorganisation of the base package...
844 iNFINITE = 0xFFFFFFFF :: DWORD -- urgh
846 foreign import ccall unsafe "getIOManagerEvent" -- in the RTS (ThrIOManager.c)
847 c_getIOManagerEvent :: IO HANDLE
849 foreign import ccall unsafe "readIOManagerEvent" -- in the RTS (ThrIOManager.c)
850 c_readIOManagerEvent :: IO Word32
852 foreign import ccall unsafe "sendIOManagerEvent" -- in the RTS (ThrIOManager.c)
853 c_sendIOManagerEvent :: Word32 -> IO ()
855 foreign import ccall unsafe "maperrno" -- in runProcess.c
858 foreign import stdcall "WaitForSingleObject"
859 c_WaitForSingleObject :: HANDLE -> DWORD -> IO DWORD
862 -- ----------------------------------------------------------------------------
863 -- Unix IO manager thread, using select()
865 startIOManagerThread :: IO ()
866 startIOManagerThread = do
867 allocaArray 2 $ \fds -> do
868 throwErrnoIfMinus1 "startIOManagerThread" (c_pipe fds)
869 rd_end <- peekElemOff fds 0
870 wr_end <- peekElemOff fds 1
871 writeIORef stick (fromIntegral wr_end)
872 c_setIOManagerPipe wr_end
874 allocaBytes sizeofFdSet $ \readfds -> do
875 allocaBytes sizeofFdSet $ \writefds -> do
876 allocaBytes sizeofTimeVal $ \timeval -> do
877 service_loop (fromIntegral rd_end) readfds writefds timeval [] []
881 :: Fd -- listen to this for wakeup calls
888 service_loop wakeup readfds writefds ptimeval old_reqs old_delays = do
890 -- pick up new IO requests
891 new_reqs <- atomicModifyIORef pendingEvents (\a -> ([],a))
892 let reqs = new_reqs ++ old_reqs
894 -- pick up new delay requests
895 new_delays <- atomicModifyIORef pendingDelays (\a -> ([],a))
896 let delays = foldr insertDelay old_delays new_delays
898 -- build the FDSets for select()
902 maxfd <- buildFdSets 0 readfds writefds reqs
904 -- perform the select()
905 let do_select delays = do
906 -- check the current time and wake up any thread in
907 -- threadDelay whose timeout has expired. Also find the
908 -- timeout value for the select() call.
910 (delays', timeout) <- getDelay now ptimeval delays
912 res <- c_select ((max wakeup maxfd)+1) readfds writefds
918 _ | err == eINTR -> do_select delays'
919 -- EINTR: just redo the select()
920 _ | err == eBADF -> return (True, delays)
921 -- EBADF: one of the file descriptors is closed or bad,
922 -- we don't know which one, so wake everyone up.
923 _ | otherwise -> throwErrno "select"
924 -- otherwise (ENOMEM or EINVAL) something has gone
925 -- wrong; report the error.
927 return (False,delays')
929 (wakeup_all,delays') <- do_select delays
932 if wakeup_all then return False
934 b <- fdIsSet wakeup readfds
937 else alloca $ \p -> do
938 c_read (fromIntegral wakeup) p 1; return ()
941 _ | s == io_MANAGER_WAKEUP -> return False
942 _ | s == io_MANAGER_DIE -> return True
943 _ -> do handler_tbl <- peek handlers
944 sp <- peekElemOff handler_tbl (fromIntegral s)
945 forkIO (do io <- deRefStablePtr sp; io)
948 if exit then return () else do
951 putMVar prodding False
953 reqs' <- if wakeup_all then do wakeupAll reqs; return []
954 else completeRequests reqs readfds writefds []
956 service_loop wakeup readfds writefds ptimeval reqs' delays'
958 io_MANAGER_WAKEUP = 0xff :: CChar
959 io_MANAGER_DIE = 0xfe :: CChar
962 {-# NOINLINE stick #-}
963 stick = unsafePerformIO (newIORef 0)
965 prodding :: MVar Bool
966 {-# NOINLINE prodding #-}
967 prodding = unsafePerformIO (newMVar False)
969 prodServiceThread :: IO ()
970 prodServiceThread = do
971 b <- takeMVar prodding
973 then do fd <- readIORef stick
974 with io_MANAGER_WAKEUP $ \pbuf -> do
975 c_write (fromIntegral fd) pbuf 1; return ()
977 putMVar prodding True
979 foreign import ccall "&signal_handlers" handlers :: Ptr (Ptr (StablePtr (IO ())))
981 foreign import ccall "setIOManagerPipe"
982 c_setIOManagerPipe :: CInt -> IO ()
984 -- -----------------------------------------------------------------------------
987 buildFdSets maxfd readfds writefds [] = return maxfd
988 buildFdSets maxfd readfds writefds (Read fd m : reqs)
989 | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
992 buildFdSets (max maxfd fd) readfds writefds reqs
993 buildFdSets maxfd readfds writefds (Write fd m : reqs)
994 | fd >= fD_SETSIZE = error "buildFdSets: file descriptor out of range"
997 buildFdSets (max maxfd fd) readfds writefds reqs
999 completeRequests [] _ _ reqs' = return reqs'
1000 completeRequests (Read fd m : reqs) readfds writefds reqs' = do
1001 b <- fdIsSet fd readfds
1003 then do putMVar m (); completeRequests reqs readfds writefds reqs'
1004 else completeRequests reqs readfds writefds (Read fd m : reqs')
1005 completeRequests (Write fd m : reqs) readfds writefds reqs' = do
1006 b <- fdIsSet fd writefds
1008 then do putMVar m (); completeRequests reqs readfds writefds reqs'
1009 else completeRequests reqs readfds writefds (Write fd m : reqs')
1011 wakeupAll [] = return ()
1012 wakeupAll (Read fd m : reqs) = do putMVar m (); wakeupAll reqs
1013 wakeupAll (Write fd m : reqs) = do putMVar m (); wakeupAll reqs
1015 waitForReadEvent :: Fd -> IO ()
1016 waitForReadEvent fd = do
1018 atomicModifyIORef pendingEvents (\xs -> (Read fd m : xs, ()))
1022 waitForWriteEvent :: Fd -> IO ()
1023 waitForWriteEvent fd = do
1025 atomicModifyIORef pendingEvents (\xs -> (Write fd m : xs, ()))
1029 -- -----------------------------------------------------------------------------
1032 -- Walk the queue of pending delays, waking up any that have passed
1033 -- and return the smallest delay to wait for. The queue of pending
1034 -- delays is kept ordered.
1035 getDelay :: Ticks -> Ptr CTimeVal -> [DelayReq] -> IO ([DelayReq], Ptr CTimeVal)
1036 getDelay now ptimeval [] = return ([],nullPtr)
1037 getDelay now ptimeval all@(d : rest)
1039 Delay time m | now >= time -> do
1041 getDelay now ptimeval rest
1042 DelaySTM time t | now >= time -> do
1043 atomically $ writeTVar t True
1044 getDelay now ptimeval rest
1046 setTimevalTicks ptimeval (delayTime d - now)
1047 return (all,ptimeval)
1049 newtype CTimeVal = CTimeVal ()
1051 foreign import ccall unsafe "sizeofTimeVal"
1052 sizeofTimeVal :: Int
1054 foreign import ccall unsafe "setTimevalTicks"
1055 setTimevalTicks :: Ptr CTimeVal -> Ticks -> IO ()
1058 On Win32 we're going to have a single Pipe, and a
1059 waitForSingleObject with the delay time. For signals, we send a
1060 byte down the pipe just like on Unix.
1063 -- ----------------------------------------------------------------------------
1064 -- select() interface
1066 -- ToDo: move to System.Posix.Internals?
1068 newtype CFdSet = CFdSet ()
1070 foreign import ccall safe "select"
1071 c_select :: Fd -> Ptr CFdSet -> Ptr CFdSet -> Ptr CFdSet -> Ptr CTimeVal
1074 foreign import ccall unsafe "hsFD_SETSIZE"
1077 foreign import ccall unsafe "hsFD_CLR"
1078 fdClr :: Fd -> Ptr CFdSet -> IO ()
1080 foreign import ccall unsafe "hsFD_ISSET"
1081 fdIsSet :: Fd -> Ptr CFdSet -> IO CInt
1083 foreign import ccall unsafe "hsFD_SET"
1084 fdSet :: Fd -> Ptr CFdSet -> IO ()
1086 foreign import ccall unsafe "hsFD_ZERO"
1087 fdZero :: Ptr CFdSet -> IO ()
1089 foreign import ccall unsafe "sizeof_fd_set"