-- 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 ()
, myThreadId -- :: IO ThreadId
, killThread -- :: ThreadId -> 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)
, readTVar -- :: TVar a -> STM 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)
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`
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
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
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 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#
-- empty, 'takeMVar' will wait until it is full. After a 'takeMVar',
-- the 'MVar' is left empty.
--
--- If several threads are competing to take the same 'MVar', one is chosen
--- to continue at random when the 'MVar' becomes full.
+-- 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.
--
--- If several threads are competing to fill the same 'MVar', one is
--- chosen to continue at random when the 'MVar' 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
case delay# time# s of { s -> (# s, () #)
}}
+registerDelay :: Int -> IO (TVar Bool)
registerDelay usecs
#ifndef mingw32_HOST_OS
| threaded = waitForDelayEventSTM usecs
if (res == -1)
then do
err <- getErrno
- if err == eINTR
- then do_select delays'
- else return (res,delays')
+ case err of
+ _ | err == eINTR -> do_select delays'
+ -- EINTR: just redo the select()
+ _ | err == eBADF -> return (True, delays)
+ -- EBADF: one of the file descriptors is closed or bad,
+ -- we don't know which one, so wake everyone up.
+ _ | otherwise -> throwErrno "select"
+ -- otherwise (ENOMEM or EINVAL) something has gone
+ -- wrong; report the error.
else
- return (res,delays')
-
- (res,delays') <- do_select delays
- -- ToDo: check result
-
- 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 ()
+ return (False,delays')
+
+ (wakeup_all,delays') <- do_select delays
+
+ 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
- reqs' <- completeRequests reqs readfds writefds []
+ reqs' <- if wakeup_all then do wakeupAll reqs; return []
+ else completeRequests reqs readfds writefds []
+
service_loop wakeup readfds writefds ptimeval reqs' delays'
stick :: IORef Fd
{-# 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
then do putMVar m (); completeRequests reqs readfds writefds reqs'
else completeRequests reqs readfds writefds (Write fd m : reqs')
+wakeupAll [] = return ()
+wakeupAll (Read fd m : reqs) = do putMVar m (); wakeupAll reqs
+wakeupAll (Write fd m : reqs) = do putMVar m (); wakeupAll reqs
+
waitForReadEvent :: Fd -> IO ()
waitForReadEvent fd = do
m <- newEmptyMVar
projects / haskell-directory.git / blobdiff