-- bits it exports, we'd rather have Control.Concurrent and the other
-- higher level modules be the home. Hence:
+#include "Typeable.h"
+
-- #not-home
module GHC.Conc
( ThreadId(..)
- -- Forking and suchlike
+ -- * Forking and suchlike
, forkIO -- :: IO a -> IO ThreadId
, forkOnIO -- :: Int -> IO a -> IO ThreadId
, childHandler -- :: Exception -> IO ()
, yield -- :: IO ()
, labelThread -- :: ThreadId -> String -> IO ()
- -- Waiting
+ -- * Waiting
, threadDelay -- :: Int -> IO ()
, registerDelay -- :: Int -> IO (TVar Bool)
, threadWaitRead -- :: Int -> IO ()
, threadWaitWrite -- :: Int -> IO ()
- -- MVars
+ -- * MVars
, MVar -- abstract
, newMVar -- :: a -> IO (MVar a)
, newEmptyMVar -- :: IO (MVar a)
, isEmptyMVar -- :: MVar a -> IO Bool
, addMVarFinalizer -- :: MVar a -> IO () -> IO ()
- -- TVars
+ -- * TVars
, STM -- abstract
, atomically -- :: STM a -> IO a
, retry -- :: STM a
, orElse -- :: STM a -> STM a -> STM a
, catchSTM -- :: STM a -> (Exception -> STM a) -> STM a
+ , alwaysSucceeds -- :: STM a -> STM ()
+ , always -- :: STM Bool -> STM ()
, TVar -- abstract
, newTVar -- :: a -> STM (TVar a)
, newTVarIO -- :: a -> STM (TVar a)
, writeTVar -- :: a -> TVar a -> STM ()
, unsafeIOToSTM -- :: IO a -> STM a
+ -- * Miscellaneous
#ifdef mingw32_HOST_OS
, asyncRead -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
, asyncWrite -- :: Int -> Int -> Int -> Ptr a -> IO (Int, Int)
transactions.
\begin{code}
-newtype STM a = STM (State# RealWorld -> (# State# RealWorld, a #)) deriving( Typeable )
+-- |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)
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 )
-- 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.
+-- udpated. (GHC only)
retry :: STM a
retry = STM $ \s# -> retry# s#
--- |Compose two alternative STM actions. 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.
+-- |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
catchSTM :: STM a -> (Exception -> STM a) -> STM a
catchSTM (STM m) k = STM $ \s -> catchSTM# m (\ex -> unSTM (k ex)) s
-data TVar a = TVar (TVar# RealWorld a) deriving( Typeable )
+-- | 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#
case delay# time# s of { s -> (# s, () #)
}}
+registerDelay :: Int -> IO (TVar Bool)
registerDelay usecs
#ifndef mingw32_HOST_OS
| threaded = waitForDelayEventSTM usecs
(wakeup_all,delays') <- do_select delays
- if wakeup_all then return ()
- else do
- b <- fdIsSet wakeup readfds
- if b == 0
- then return ()
- else alloca $ \p -> do
- c_read (fromIntegral wakeup) p 1; return ()
- s <- peek p
- if (s == 0xff)
- then return ()
- else do handler_tbl <- peek handlers
- sp <- peekElemOff handler_tbl (fromIntegral s)
- forkIO (do io <- deRefStablePtr sp; io)
- return ()
+ exit <-
+ if wakeup_all then return False
+ else do
+ b <- fdIsSet wakeup readfds
+ if b == 0
+ then return False
+ else alloca $ \p -> do
+ c_read (fromIntegral wakeup) p 1; return ()
+ s <- peek p
+ case s of
+ _ | s == io_MANAGER_WAKEUP -> return False
+ _ | s == io_MANAGER_DIE -> return True
+ _ -> do handler_tbl <- peek handlers
+ sp <- peekElemOff handler_tbl (fromIntegral s)
+ forkIO (do io <- deRefStablePtr sp; io)
+ return False
+
+ if exit then return () else do
takeMVar prodding
putMVar prodding False
{-# NOINLINE stick #-}
stick = unsafePerformIO (newIORef 0)
+io_MANAGER_WAKEUP = 0xff :: CChar
+io_MANAGER_DIE = 0xfe :: CChar
+
prodding :: MVar Bool
{-# NOINLINE prodding #-}
prodding = unsafePerformIO (newMVar False)
b <- takeMVar prodding
if (not b)
then do fd <- readIORef stick
- with 0xff $ \pbuf -> do c_write (fromIntegral fd) pbuf 1; return ()
+ with io_MANAGER_WAKEUP $ \pbuf -> do
+ c_write (fromIntegral fd) pbuf 1; return ()
else return ()
putMVar prodding True
projects / haskell-directory.git / blobdiff