-import GHC.Exception ( catchException, Exception(..), AsyncException(..) )
-import GHC.Pack ( packCString# )
-import GHC.Ptr ( Ptr(..), plusPtr, FunPtr(..) )
-import GHC.STRef
-import GHC.Show ( Show(..), showString )
-import Data.Typeable
-
-infixr 0 `par`, `pseq`
-\end{code}
-
-%************************************************************************
-%* *
-\subsection{@ThreadId@, @par@, and @fork@}
-%* *
-%************************************************************************
-
-\begin{code}
-data ThreadId = ThreadId ThreadId# deriving( Typeable )
--- ToDo: data ThreadId = ThreadId (Weak ThreadId#)
--- But since ThreadId# is unlifted, the Weak type must use open
--- type variables.
-{- ^
-A 'ThreadId' is an abstract type representing a handle to a thread.
-'ThreadId' is an instance of 'Eq', 'Ord' and 'Show', where
-the 'Ord' instance implements an arbitrary total ordering over
-'ThreadId's. The 'Show' instance lets you convert an arbitrary-valued
-'ThreadId' to string form; showing a 'ThreadId' value is occasionally
-useful when debugging or diagnosing the behaviour of a concurrent
-program.
-
-/Note/: in GHC, if you have a 'ThreadId', you essentially have
-a pointer to the thread itself. This means the thread itself can\'t be
-garbage collected until you drop the 'ThreadId'.
-This misfeature will hopefully be corrected at a later date.
-
-/Note/: Hugs does not provide any operations on other threads;
-it defines 'ThreadId' as a synonym for ().
--}
-
-instance Show ThreadId where
- showsPrec d t =
- showString "ThreadId " .
- showsPrec d (getThreadId (id2TSO t))
-
-foreign import ccall unsafe "rts_getThreadId" getThreadId :: ThreadId# -> Int
-
-id2TSO :: ThreadId -> ThreadId#
-id2TSO (ThreadId t) = t
-
-foreign import ccall unsafe "cmp_thread" cmp_thread :: ThreadId# -> ThreadId# -> CInt
--- Returns -1, 0, 1
-
-cmpThread :: ThreadId -> ThreadId -> Ordering
-cmpThread t1 t2 =
- case cmp_thread (id2TSO t1) (id2TSO t2) of
- -1 -> LT
- 0 -> EQ
- _ -> GT -- must be 1
-
-instance Eq ThreadId where
- t1 == t2 =
- case t1 `cmpThread` t2 of
- EQ -> True
- _ -> False
-
-instance Ord ThreadId where
- compare = cmpThread
-
-{- |
-This sparks off a new thread to run the 'IO' computation passed as the
-first argument, and returns the 'ThreadId' of the newly created
-thread.
-
-The new thread will be a lightweight thread; if you want to use a foreign
-library that uses thread-local storage, use 'forkOS' instead.
--}
-forkIO :: IO () -> IO ThreadId
-forkIO action = IO $ \ s ->
- case (fork# action_plus s) of (# s1, id #) -> (# s1, ThreadId id #)
- where
- action_plus = catchException action childHandler
-
-forkOnIO :: Int -> IO () -> IO ThreadId
-forkOnIO (I# cpu) action = IO $ \ s ->
- case (forkOn# cpu action_plus s) of (# s1, id #) -> (# s1, ThreadId id #)
- where
- action_plus = catchException action childHandler
-
-childHandler :: Exception -> IO ()
-childHandler err = catchException (real_handler err) childHandler
-
-real_handler :: Exception -> IO ()
-real_handler ex =
- case ex of
- -- ignore thread GC and killThread exceptions:
- BlockedOnDeadMVar -> return ()
- BlockedIndefinitely -> return ()
- AsyncException ThreadKilled -> return ()
-
- -- report all others:
- AsyncException StackOverflow -> reportStackOverflow
- other -> reportError other
-
-{- | 'killThread' terminates the given thread (GHC only).
-Any work already done by the thread isn\'t
-lost: the computation is suspended until required by another thread.
-The memory used by the thread will be garbage collected if it isn\'t
-referenced from anywhere. The 'killThread' function is defined in
-terms of 'throwTo':
-
-> killThread tid = throwTo tid (AsyncException ThreadKilled)
-
--}
-killThread :: ThreadId -> IO ()
-killThread tid = throwTo tid (AsyncException ThreadKilled)
-
-{- | 'throwTo' raises an arbitrary exception in the target thread (GHC only).
-
-'throwTo' does not return until the exception has been raised in the
-target thread.
-The calling thread can thus be certain that the target
-thread has received the exception. This is a useful property to know
-when dealing with race conditions: eg. if there are two threads that
-can kill each other, it is guaranteed that only one of the threads
-will get to kill the other.
-
-If the target thread is currently making a foreign call, then the
-exception will not be raised (and hence 'throwTo' will not return)
-until the call has completed. This is the case regardless of whether
-the call is inside a 'block' or not.
-
-Important note: the behaviour of 'throwTo' differs from that described in
-the paper "Asynchronous exceptions in Haskell"
-(<http://research.microsoft.com/~simonpj/Papers/asynch-exns.htm>).
-In the paper, 'throwTo' is non-blocking; but the library implementation adopts
-a more synchronous design in which 'throwTo' does not return until the exception
-is received by the target thread. The trade-off is discussed in Section 8 of the paper.
-Like any blocking operation, 'throwTo' is therefore interruptible (see Section 4.3 of
-the paper).
-
-There is currently no guarantee that the exception delivered by 'throwTo' will be
-delivered at the first possible opportunity. In particular, if a thread may
-unblock and then re-block exceptions (using 'unblock' and 'block') without receiving
-a pending 'throwTo'. This is arguably undesirable behaviour.
-
- -}
-throwTo :: ThreadId -> Exception -> IO ()
-throwTo (ThreadId id) ex = IO $ \ s ->
- case (killThread# id ex s) of s1 -> (# s1, () #)
-
--- | Returns the 'ThreadId' of the calling thread (GHC only).
-myThreadId :: IO ThreadId
-myThreadId = IO $ \s ->
- case (myThreadId# s) of (# s1, id #) -> (# s1, ThreadId id #)
-
-
--- |The 'yield' action allows (forces, in a co-operative multitasking
--- implementation) a context-switch to any other currently runnable
--- threads (if any), and is occasionally useful when implementing
--- concurrency abstractions.
-yield :: IO ()
-yield = IO $ \s ->
- case (yield# s) of s1 -> (# s1, () #)
-
-{- | 'labelThread' stores a string as identifier for this thread if
-you built a RTS with debugging support. This identifier will be used in
-the debugging output to make distinction of different threads easier
-(otherwise you only have the thread state object\'s address in the heap).
-
-Other applications like the graphical Concurrent Haskell Debugger
-(<http://www.informatik.uni-kiel.de/~fhu/chd/>) may choose to overload
-'labelThread' for their purposes as well.
--}
-
-labelThread :: ThreadId -> String -> IO ()
-labelThread (ThreadId t) str = IO $ \ s ->
- let ps = packCString# str
- adr = byteArrayContents# ps in
- case (labelThread# t adr s) of s1 -> (# s1, () #)
-
--- Nota Bene: 'pseq' used to be 'seq'
--- but 'seq' is now defined in PrelGHC
---
--- "pseq" is defined a bit weirdly (see below)
---
--- The reason for the strange "lazy" call is that
--- it fools the compiler into thinking that pseq and par are non-strict in
--- their second argument (even if it inlines pseq at the call site).
--- If it thinks pseq is strict in "y", then it often evaluates
--- "y" before "x", which is totally wrong.
-
-{-# INLINE pseq #-}
-pseq :: a -> b -> b
-pseq x y = x `seq` lazy y
-
-{-# INLINE par #-}
-par :: a -> b -> b
-par x y = case (par# x) of { _ -> lazy y }
-\end{code}
-
-
-%************************************************************************
-%* *
-\subsection[stm]{Transactional heap operations}
-%* *
-%************************************************************************
-
-TVars are shared memory locations which support atomic memory
-transactions.
-
-\begin{code}
--- |A monad supporting atomic memory transactions.
-newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #))
-
-unSTM :: STM a -> (State# RealWorld -> (# State# RealWorld, a #))
-unSTM (STM a) = a
-
-INSTANCE_TYPEABLE1(STM,stmTc,"STM")
-
-instance Functor STM where
- fmap f x = x >>= (return . f)
-
-instance Monad STM where
- {-# INLINE return #-}
- {-# INLINE (>>) #-}
- {-# INLINE (>>=) #-}
- m >> k = thenSTM m k
- return x = returnSTM x
- m >>= k = bindSTM m k
-
-bindSTM :: STM a -> (a -> STM b) -> STM b
-bindSTM (STM m) k = STM ( \s ->
- case m s of
- (# new_s, a #) -> unSTM (k a) new_s
- )
-
-thenSTM :: STM a -> STM b -> STM b
-thenSTM (STM m) k = STM ( \s ->
- case m s of
- (# new_s, a #) -> unSTM k new_s
- )
-
-returnSTM :: a -> STM a
-returnSTM x = STM (\s -> (# s, x #))
-
--- | Unsafely performs IO in the STM monad.
-unsafeIOToSTM :: IO a -> STM a
-unsafeIOToSTM (IO m) = STM m
-
--- |Perform a series of STM actions atomically.
---
--- You cannot use 'atomically' inside an 'unsafePerformIO' or 'unsafeInterleaveIO'.
--- Any attempt to do so will result in a runtime error. (Reason: allowing
--- this would effectively allow a transaction inside a transaction, depending
--- on exactly when the thunk is evaluated.)
---
--- However, see 'newTVarIO', which can be called inside 'unsafePerformIO',
--- and which allows top-level TVars to be allocated.
-
-atomically :: STM a -> IO a
-atomically (STM m) = IO (\s -> (atomically# m) s )
-
--- |Retry execution of the current memory transaction because it has seen
--- values in TVars which mean that it should not continue (e.g. the TVars
--- represent a shared buffer that is now empty). The implementation may
--- block the thread until one of the TVars that it has read from has been
--- udpated. (GHC only)
-retry :: STM a
-retry = STM $ \s# -> retry# s#
-
--- |Compose two alternative STM actions (GHC only). If the first action
--- completes without retrying then it forms the result of the orElse.
--- Otherwise, if the first action retries, then the second action is
--- tried in its place. If both actions retry then the orElse as a
--- whole retries.
-orElse :: STM a -> STM a -> STM a
-orElse (STM m) e = STM $ \s -> catchRetry# m (unSTM e) s
-
--- |Exception handling within STM actions.
-catchSTM :: STM a -> (Exception -> STM a) -> STM a
-catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
-
--- | Low-level primitive on which always and alwaysSucceeds are built.
--- checkInv differs form these in that (i) the invariant is not
--- checked when checkInv is called, only at the end of this and
--- subsequent transcations, (ii) the invariant failure is indicated
--- by raising an exception.
-checkInv :: STM a -> STM ()
-checkInv (STM m) = STM (\s -> (check# m) s)
-
--- | alwaysSucceeds adds a new invariant that must be true when passed
--- to alwaysSucceeds, at the end of the current transaction, and at
--- the end of every subsequent transaction. If it fails at any
--- of those points then the transaction violating it is aborted
--- and the exception raised by the invariant is propagated.
-alwaysSucceeds :: STM a -> STM ()
-alwaysSucceeds i = do ( do i ; retry ) `orElse` ( return () )
- checkInv i
-
--- | always is a variant of alwaysSucceeds in which the invariant is
--- expressed as an STM Bool action that must return True. Returning
--- False or raising an exception are both treated as invariant failures.
-always :: STM Bool -> STM ()
-always i = alwaysSucceeds ( do v <- i
- if (v) then return () else ( error "Transacional invariant violation" ) )
-
--- |Shared memory locations that support atomic memory transactions.
-data TVar a = TVar (TVar# RealWorld a)
-
-INSTANCE_TYPEABLE1(TVar,tvarTc,"TVar")
-
-instance Eq (TVar a) where
- (TVar tvar1#) == (TVar tvar2#) = sameTVar# tvar1# tvar2#
-
--- |Create a new TVar holding a value supplied
-newTVar :: a -> STM (TVar a)
-newTVar val = STM $ \s1# ->
- case newTVar# val s1# of
- (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
-
--- |@IO@ version of 'newTVar'. This is useful for creating top-level
--- 'TVar's using 'System.IO.Unsafe.unsafePerformIO', because using
--- 'atomically' inside 'System.IO.Unsafe.unsafePerformIO' isn't
--- possible.
-newTVarIO :: a -> IO (TVar a)
-newTVarIO val = IO $ \s1# ->
- case newTVar# val s1# of
- (# s2#, tvar# #) -> (# s2#, TVar tvar# #)
-
--- |Return the current value stored in a TVar
-readTVar :: TVar a -> STM a
-readTVar (TVar tvar#) = STM $ \s# -> readTVar# tvar# s#
-
--- |Write the supplied value into a TVar
-writeTVar :: TVar a -> a -> STM ()
-writeTVar (TVar tvar#) val = STM $ \s1# ->
- case writeTVar# tvar# val s1# of
- s2# -> (# s2#, () #)
-
-\end{code}
-
-%************************************************************************
-%* *
-\subsection[mvars]{M-Structures}
-%* *
-%************************************************************************
-
-M-Vars are rendezvous points for concurrent threads. They begin
-empty, and any attempt to read an empty M-Var blocks. When an M-Var
-is written, a single blocked thread may be freed. Reading an M-Var
-toggles its state from full back to empty. Therefore, any value
-written to an M-Var may only be read once. Multiple reads and writes
-are allowed, but there must be at least one read between any two
-writes.
-
-\begin{code}
---Defined in IOBase to avoid cycle: data MVar a = MVar (SynchVar# RealWorld a)
-
--- |Create an 'MVar' which is initially empty.
-newEmptyMVar :: IO (MVar a)
-newEmptyMVar = IO $ \ s# ->
- case newMVar# s# of
- (# s2#, svar# #) -> (# s2#, MVar svar# #)
-
--- |Create an 'MVar' which contains the supplied value.
-newMVar :: a -> IO (MVar a)
-newMVar value =
- newEmptyMVar >>= \ mvar ->
- putMVar mvar value >>
- return mvar
-
--- |Return the contents of the 'MVar'. If the 'MVar' is currently
--- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
--- the 'MVar' is left empty.
---
--- There are two further important properties of 'takeMVar':
---
--- * 'takeMVar' is single-wakeup. That is, if there are multiple
--- threads blocked in 'takeMVar', and the 'MVar' becomes full,
--- only one thread will be woken up. The runtime guarantees that
--- the woken thread completes its 'takeMVar' operation.
---
--- * When multiple threads are blocked on an 'MVar', they are
--- woken up in FIFO order. This is useful for providing
--- fairness properties of abstractions built using 'MVar's.
---
-takeMVar :: MVar a -> IO a
-takeMVar (MVar mvar#) = IO $ \ s# -> takeMVar# mvar# s#
-
--- |Put a value into an 'MVar'. If the 'MVar' is currently full,
--- 'putMVar' will wait until it becomes empty.
---
--- There are two further important properties of 'putMVar':
---
--- * 'putMVar' is single-wakeup. That is, if there are multiple
--- threads blocked in 'putMVar', and the 'MVar' becomes empty,
--- only one thread will be woken up. The runtime guarantees that
--- the woken thread completes its 'putMVar' operation.
---
--- * When multiple threads are blocked on an 'MVar', they are
--- woken up in FIFO order. This is useful for providing
--- fairness properties of abstractions built using 'MVar's.
---
-putMVar :: MVar a -> a -> IO ()
-putMVar (MVar mvar#) x = IO $ \ s# ->
- case putMVar# mvar# x s# of
- s2# -> (# s2#, () #)
-
--- |A non-blocking version of 'takeMVar'. The 'tryTakeMVar' function
--- returns immediately, with 'Nothing' if the 'MVar' was empty, or
--- @'Just' a@ if the 'MVar' was full with contents @a@. After 'tryTakeMVar',
--- the 'MVar' is left empty.
-tryTakeMVar :: MVar a -> IO (Maybe a)
-tryTakeMVar (MVar m) = IO $ \ s ->
- case tryTakeMVar# m s of
- (# s, 0#, _ #) -> (# s, Nothing #) -- MVar is empty
- (# s, _, a #) -> (# s, Just a #) -- MVar is full
-
--- |A non-blocking version of 'putMVar'. The 'tryPutMVar' function
--- attempts to put the value @a@ into the 'MVar', returning 'True' if
--- it was successful, or 'False' otherwise.
-tryPutMVar :: MVar a -> a -> IO Bool
-tryPutMVar (MVar mvar#) x = IO $ \ s# ->
- case tryPutMVar# mvar# x s# of
- (# s, 0# #) -> (# s, False #)
- (# s, _ #) -> (# s, True #)
-
--- |Check whether a given 'MVar' is empty.
---
--- Notice that the boolean value returned is just a snapshot of
--- the state of the MVar. By the time you get to react on its result,
--- the MVar may have been filled (or emptied) - so be extremely
--- careful when using this operation. Use 'tryTakeMVar' instead if possible.
-isEmptyMVar :: MVar a -> IO Bool
-isEmptyMVar (MVar mv#) = IO $ \ s# ->
- case isEmptyMVar# mv# s# of
- (# s2#, flg #) -> (# s2#, not (flg ==# 0#) #)
-
--- |Add a finalizer to an 'MVar' (GHC only). See "Foreign.ForeignPtr" and
--- "System.Mem.Weak" for more about finalizers.
-addMVarFinalizer :: MVar a -> IO () -> IO ()
-addMVarFinalizer (MVar m) finalizer =
- IO $ \s -> case mkWeak# m () finalizer s of { (# s1, w #) -> (# s1, () #) }
-\end{code}