nmergeIO, -- :: [[a]] -> IO [a]
-- $merge
- -- * GHC\'s implementation of concurrency
+ -- * GHC's implementation of concurrency
- -- |This section describes features specific to GHC\'s
+ -- |This section describes features specific to GHC's
-- implementation of Concurrent Haskell.
-- ** Terminating the program
Concurrency is \"lightweight\", which means that both thread creation
and context switching overheads are extremely low. Scheduling of
Haskell threads is done internally in the Haskell runtime system, and
-doesn\'t make use of any operating system-supplied thread packages.
+doesn't make use of any operating system-supplied thread packages.
Haskell threads can communicate via 'MVar's, a kind of synchronised
mutable variable (see "Control.Concurrent.MVar"). Several common
as:
-> main = forkIO (write \'a\') >> write \'b\'
+> main = forkIO (write 'a') >> write 'b'
> where write c = putChar c >> write c
will print either @aaaaaaaaaaaaaa...@ or @bbbbbbbbbbbb...@,
Calling a foreign C procedure (such as @getchar@) that blocks waiting
for input will block /all/ threads, unless the @threadsafe@ attribute
is used on the foreign call (and your compiler \/ operating system
-supports it). GHC\'s I\/O system uses non-blocking I\/O internally to
+supports it). GHC's I\/O system uses non-blocking I\/O internally to
implement thread-friendly I\/O, so calling standard Haskell I\/O
-functions blocks only the thead making the call.
+functions blocks only the thread making the call.
-}
-- Thread Ids, specifically the instances of Eq and Ord for these things.
-- cmp_thread in the RTS.
#ifdef __GLASGOW_HASKELL__
-foreign import ccall unsafe "cmp_thread" cmp_thread :: Addr# -> Addr# -> Int
+id2TSO :: ThreadId -> ThreadId#
+id2TSO (ThreadId t) = t
+
+foreign import ccall unsafe "cmp_thread" cmp_thread :: ThreadId# -> ThreadId# -> Int
-- Returns -1, 0, 1
cmpThread :: ThreadId -> ThreadId -> Ordering
-cmpThread (ThreadId t1) (ThreadId t2) =
- case cmp_thread (unsafeCoerce# t1) (unsafeCoerce# t2) of
+cmpThread t1 t2 =
+ case cmp_thread (id2TSO t1) (id2TSO t2) of
-1 -> LT
0 -> EQ
_ -> GT -- must be 1
instance Ord ThreadId where
compare = cmpThread
-foreign import ccall unsafe "rts_getThreadId" getThreadId :: Addr# -> Int
+foreign import ccall unsafe "rts_getThreadId" getThreadId :: ThreadId# -> Int
instance Show ThreadId where
- showsPrec d (ThreadId t) =
+ showsPrec d t =
showString "ThreadId " .
- showsPrec d (getThreadId (unsafeCoerce# t))
+ showsPrec d (getThreadId (id2TSO t))
{- |
This sparks off a new thread to run the 'IO' computation passed as the
to the locking on a 'Handle'. Only one thread
may hold the lock on a 'Handle' at any one
time, so if a reschedule happens while a thread is holding the
- lock, the other thread won\'t be able to run. The upshot is that
+ lock, the other thread won't be able to run. The upshot is that
the switch from @aaaa@ to
@bbbbb@ happens infrequently. It can be
improved by lowering the reschedule tick period. We also have a
patch that causes a reschedule whenever a thread waiting on a
- lock is woken up, but haven\'t found it to be useful for anything
+ lock is woken up, but haven't found it to be useful for anything
other than this example :-)
-}