{-# LANGUAGE RankNTypes, NamedFieldPuns, BangPatterns, ExistentialQuantification, CPP, ScopedTypeVariables, TypeSynonymInstances, MultiParamTypeClasses, GeneralizedNewtypeDeriving, PackageImports, ParallelListComp #-} {- OPTIONS_GHC -Wall -fno-warn-name-shadowing -fno-warn-unused-do-bind -} -- {- LANGUAGE Trustworthy -} -- TODO: Before declaring this module TRUSTWORTHY/SAFE, we need to -- make the IVar type abstract. {-# LANGUAGE TypeFamilies #-} -- | A scheduler for the Par monad based on directly performing IO -- actions when Par methods are called (i.e. without using a lazy -- trace data structure). module Control.Monad.Par.Scheds.Direct ( Sched(..), Par, -- abstract: Constructor not exported. IVar(..), IVarContents(..), -- sched, runPar, runParIO, new, get, put_, fork, newFull, newFull_, put, spawn, spawn_, spawnP, spawn1_, fixPar, FixParException (..) -- runParAsync, runParAsyncHelper, -- yield, ) where import Control.Applicative import Control.Concurrent hiding (yield) import Data.IORef (IORef,newIORef,readIORef,writeIORef,atomicModifyIORef) import Text.Printf (printf) import GHC.Conc (numCapabilities,yield) import "mtl" Control.Monad.Cont as C import qualified "mtl" Control.Monad.Reader as RD import qualified System.Random.MWC as Random import System.IO.Unsafe (unsafePerformIO) import System.Mem.StableName (makeStableName, hashStableName) import qualified Control.Monad.Par.Class as PC import qualified Control.Monad.Par.Unsafe as UN import Control.Monad.Par.Scheds.DirectInternal (Par(..), Sched(..), HotVar, SessionID, Session(Session), newHotVar, readHotVar, modifyHotVar, modifyHotVar_, writeHotVarRaw, fixPar, FixParException (..)) #ifdef NEW_GENERIC import qualified Control.Par.Class as PN import qualified Control.Par.Class.Unsafe as PU #endif import Control.DeepSeq #ifdef NESTED_SCHEDS import qualified Data.Map as M #endif import qualified Data.Set as S import Data.Maybe (catMaybes) import Data.Word (Word64) -- import Data.Concurrent.Deque.Class (WSDeque) #ifdef USE_CHASELEV #warning "Note: using Chase-Lev lockfree workstealing deques..." import Data.Concurrent.Deque.ChaseLev.DequeInstance import Data.Concurrent.Deque.ChaseLev as R #else import Data.Concurrent.Deque.Reference.DequeInstance import Data.Concurrent.Deque.Reference as R #endif import qualified Control.Exception as E import Prelude hiding (null) import qualified Prelude #if __GLASGOW_HASKELL__ <= 700 import GHC.Conc (forkOnIO) forkOn = forkOnIO #endif -------------------------------------------------------------------------------- -- Configuration Toggles -------------------------------------------------------------------------------- -- [2012.08.30] This shows a 10X improvement on nested parfib: -- #define NESTED_SCHEDS #define PARPUTS #define FORKPARENT #define IDLING_ON -- Next, IF idling is on, should we do wakeups?: #define WAKEIDLE -- #define WAIT_FOR_WORKERS ------------------------------------------------------------------- -- Ifdefs for the above preprocessor defines. Try to MINIMIZE code -- that lives in this dangerous region, and instead do normal -- conditionals and trust dead-code-elimination. -------------------------------------------------------------------- #ifdef DEBUG_DIRECT #warning "DEBUG: Activating debugging for Direct.hs" import Debug.Trace (trace) import System.Environment (getEnvironment) theEnv = unsafePerformIO $ getEnvironment dbg = True dbglvl = 1 #else dbg = False dbglvl = 0 #endif dbg :: Bool dbglvl :: Int _PARPUTS :: Bool #ifdef PARPUTS _PARPUTS = True #else _PARPUTS = False #endif _FORKPARENT :: Bool #ifdef FORKPARENT _FORKPARENT = True #else #warning "FORKPARENT POLICY NOT USED; THIS IS GENERALLY WORSE" _FORKPARENT = False #endif _IDLING_ON :: Bool #ifdef IDLING_ON _IDLING_ON = True #else _IDLING_ON = False #endif _WAIT_FOR_WORKERS :: Bool #ifdef WAIT_FOR_WORKERS _WAIT_FOR_WORKERS = True #else _WAIT_FOR_WORKERS = False #endif -------------------------------------------------------------------------------- -- Core type definitions -------------------------------------------------------------------------------- type ROnly = RD.ReaderT Sched IO newtype IVar a = IVar (IORef (IVarContents a)) data IVarContents a = Full a | Empty | Blocked [a -> IO ()] unsafeParIO :: IO a -> Par a unsafeParIO iom = Par (lift$ lift iom) io :: IO a -> Par a io = unsafeParIO -- shorthand used below -------------------------------------------------------------------------------- -- Global State -------------------------------------------------------------------------------- -- This keeps track of ALL worker threads across all unreated -- `runPar` instantiations. This is used to detect nested invocations -- of `runPar` and avoid reinitialization. -- globalWorkerPool :: IORef (Data.IntMap ()) #ifdef NESTED_SCHEDS globalWorkerPool :: IORef (M.Map ThreadId Sched) globalWorkerPool = unsafePerformIO $ newIORef M.empty #endif -- TODO! Make this semi-local! (not shared between "top-level" runPars) {-# INLINE amINested #-} {-# INLINE registerWorker #-} {-# INLINE unregisterWorker #-} amINested :: ThreadId -> IO (Maybe Sched) registerWorker :: ThreadId -> Sched -> IO () unregisterWorker :: ThreadId -> IO () #ifdef NESTED_SCHEDS -- | If the current threadID is ALREADY a worker, return the corresponding Sched structure. amINested tid = do -- There is no race here. Each thread inserts itself before it -- becomes an active worker. wp <- readIORef globalWorkerPool return (M.lookup tid wp) registerWorker tid sched = atomicModifyIORef globalWorkerPool $ \ mp -> (M.insert tid sched mp, ()) unregisterWorker tid = atomicModifyIORef globalWorkerPool $ \ mp -> (M.delete tid mp, ()) #else amINested _ = return Nothing registerWorker _ _ = return () unregisterWorker _tid = return () #endif ----------------------------------------------------------------------------- -- Helpers #2: Pushing and popping work. ----------------------------------------------------------------------------- {-# INLINE popWork #-} popWork :: Sched -> IO (Maybe (Par ())) popWork Sched{ workpool, no } = do mb <- R.tryPopL workpool when dbg $ case mb of Nothing -> return () Just _ -> do sn <- makeStableName mb printf " [%d] -> POP work unit %d\n" no (hashStableName sn) return mb {-# INLINE pushWork #-} pushWork :: Sched -> Par () -> IO () pushWork Sched { workpool, idle, no } task = do R.pushL workpool task when dbg $ do sn <- makeStableName task printf " [%d] -> PUSH work unit %d\n" no (hashStableName sn) #if defined(IDLING_ON) && defined(WAKEIDLE) --when isMain$ -- Experimenting with reducing contention by doing this only from a single thread. -- TODO: We need to have a proper binary wakeup-tree. tryWakeIdle idle #endif return () tryWakeIdle :: HotVar [MVar Bool] -> IO () tryWakeIdle idle = do -- NOTE: I worry about having the idle var hammmered by all threads on their spawn-path: -- If any worker is idle, wake one up and give it work to do. idles <- readHotVar idle -- Optimistically do a normal read first. when (not (Prelude.null idles)) $ do when dbg$ printf "Waking %d idle thread(s).\n" (length idles) r <- modifyHotVar idle (\is -> case is of [] -> ([], return ()) (i:ils) -> (ils, putMVar i False)) r -- wake an idle worker up by putting an MVar. rand :: HotVar Random.GenIO -> IO Int rand ref = Random.uniformR (0, numCapabilities-1) =<< readHotVar ref -------------------------------------------------------------------------------- -- Running computations in the Par monad -------------------------------------------------------------------------------- instance NFData (IVar a) where rnf !_ = () {-# NOINLINE runPar #-} runPar = unsafePerformIO . runParIO -- | This procedure creates a new worker on the current thread (with a -- new session ID) and plugs it into the work-stealing environment. -- This new worker extracts itself from the work stealing pool when -- `userComp` has completed, thus freeing the current thread (this -- procedure) to return normally. runNewSessionAndWait :: String -> Sched -> Par b -> IO b runNewSessionAndWait name sched userComp = do tid <- myThreadId -- TODO: remove when done debugging sid <- modifyHotVar (sessionCounter sched) (\ x -> (x+1,x)) _ <- modifyHotVar (activeSessions sched) (\ set -> (S.insert sid set, ())) -- Here we have an extra IORef... ugly. ref <- newIORef (error$ "Empty session-result ref ("++name++") should never be touched (sid "++ show sid++", "++show tid ++")") newFlag <- newHotVar False -- Push the new session: _ <- modifyHotVar (sessions sched) (\ ls -> ((Session sid newFlag) : ls, ())) let userComp' = do when dbg$ io$ do tid2 <- myThreadId printf " [%d %s] Starting Par computation on %s.\n" (no sched) (show tid2) name ans <- userComp -- This add-on to userComp will run only after userComp has completed successfully, -- but that does NOT guarantee that userComp-forked computations have terminated: io$ do when (dbglvl>=1) $ do tid3 <- myThreadId printf " [%d %s] Continuation for %s called, finishing it up (%d)...\n" (no sched) (show tid3) name sid writeIORef ref ans writeHotVarRaw newFlag True modifyHotVar (activeSessions sched) (\ set -> (S.delete sid set, ())) kont :: Word64 -> a -> ROnly () kont n = trivialCont$ "("++name++", sid "++show sid++", round "++show n++")" loop :: Word64 -> ROnly () loop n = do flg <- liftIO$ readIORef newFlag unless flg $ do when dbg $ liftIO$ do tid4 <- myThreadId printf " [%d %s] BOUNCE %d... going into reschedule until finished.\n" (no sched) (show tid4) n rescheduleR 0 $ trivialCont$ "("++name++", sid "++show sid++")" loop (n+1) -- THIS IS RETURNING TOO EARLY!!: runReaderWith sched (C.runContT (unPar userComp') (kont 0)) -- Does this ASSUME child stealing? runReaderWith sched (loop 1) -- TODO: Ideally we would wait for ALL outstanding (stolen) work on this "team" to complete. when (dbglvl>=1)$ do active <- readHotVar (activeSessions sched) sess@True <- readHotVar newFlag -- ASSERT! printf " [%d %s] RETURN from %s (sessFin %s) runContT (%d) active set %s\n" (no sched) (show tid) name (show sess) sid (show active) -- Here we pop off the frame we added to the session stack: modifyHotVar_ (sessions sched) $ \ (Session sid2 _ : tl) -> if sid == sid2 then tl else error$ "Tried to pop the session stack and found we ("++show sid ++") were not on the top! (instead "++show sid2++")" -- By returning here we ARE implicitly reengaging the scheduler, since we -- are already inside the rescheduleR loop on this thread -- (before runParIO was called in a nested fashion). readIORef ref {-# NOINLINE runParIO #-} runParIO userComp = do tid <- myThreadId #if __GLASGOW_HASKELL__ >= 701 /* 20110301 */ -- -- We create a thread on each CPU with forkOn. The CPU on which -- the current thread is running will host the main thread; the -- other CPUs will host worker threads. -- -- Note: GHC 7.1.20110301 is required for this to work, because that -- is when threadCapability was added. -- (main_cpu, _) <- threadCapability tid #else -- -- Lacking threadCapability, we always pick CPU #0 to run the main -- thread. If the current thread is not running on CPU #0, this -- will require some data to be shipped over the memory bus, and -- hence will be slightly slower than the version above. -- let main_cpu = 0 #endif maybSched <- amINested tid tidorig <- myThreadId -- TODO: remove when done debugging case maybSched of Just (sched) -> do -- Here the current thread is ALREADY a worker. All we need to -- do is plug the users new computation in. sid0 <- readHotVar (sessionCounter sched) when (dbglvl>=1)$ printf " [%d %s] runPar called from existing worker thread, new session (%d)....\n" (no sched) (show tid) (sid0 + 1) runNewSessionAndWait "nested runPar" sched userComp ------------------------------------------------------------ -- Non-nested case, make a new set of worker threads: ------------------------------------------------------------ Nothing -> do allscheds <- makeScheds main_cpu [Session _ topSessFlag] <- readHotVar$ sessions$ head allscheds mfin <- newEmptyMVar doneFlags <- forM (zip [0..] allscheds) $ \(cpu,sched) -> do workerDone <- newEmptyMVar ---------------------------------------- let wname = ("(worker "++show cpu++" of originator "++show tidorig++")") -- forkOn cpu $ do _ <- forkWithExceptions (forkOn cpu) wname $ do ------------------------------------------------------------STRT WORKER THREAD tid2 <- myThreadId registerWorker tid2 sched if (cpu /= main_cpu) then do when dbg$ printf " [%d %s] Anonymous worker entering scheduling loop.\n" cpu (show tid2) runReaderWith sched $ rescheduleR 0 (trivialCont (wname++show tid2)) when dbg$ printf " [%d] Anonymous worker exited scheduling loop. FINISHED.\n" cpu putMVar workerDone cpu return () else do x <- runNewSessionAndWait "top-lvl main worker" sched userComp -- When the main worker finishes we can tell the anonymous "system" workers: writeIORef topSessFlag True when dbg$ do printf " *** Out of entire runContT user computation on main thread %s.\n" (show tid2) -- sanityCheck allscheds putMVar mfin x unregisterWorker tid ------------------------------------------------------------END WORKER THREAD return (if cpu == main_cpu then Nothing else Just workerDone) when _WAIT_FOR_WORKERS $ do when dbg$ printf " *** [%s] Originator thread: waiting for workers to complete." (show tidorig) forM_ (catMaybes doneFlags) $ \ mv -> do n <- readMVar mv -- n <- A.wait mv when dbg$ printf " * [%s] Worker %s completed\n" (show tidorig) (show n) when dbg$ do printf " *** [%s] Reading final MVar on originator thread.\n" (show tidorig) -- We don't directly use the thread we come in on. Rather, that thread waits -- waits. One reason for this is that the main/progenitor thread in -- GHC is expensive like a forkOS thread. ---------------------------------------- -- DEBUGGING -- #ifdef DEBUG_DIRECT busyTakeMVar (" The global wait "++ show tidorig) mfin -- Final value. -- dbgTakeMVar "global waiting thread" mfin -- Final value. #else takeMVar mfin -- Final value. #endif ---------------------------------------- -- Create the default scheduler(s) state: makeScheds :: Int -> IO [Sched] makeScheds main = do when dbg$ do tid <- myThreadId printf "[initialization] Creating %d worker threads, currently on %s\n" numCapabilities (show tid) workpools <- replicateM numCapabilities $ R.newQ rngs <- replicateM numCapabilities $ Random.create >>= newHotVar idle <- newHotVar [] -- The STACKs are per-worker.. but the root finished flag is shared between all anonymous system workers: sessionFinished <- newHotVar False sessionStacks <- mapM newHotVar (replicate numCapabilities [Session baseSessionID sessionFinished]) activeSessions <- newHotVar S.empty sessionCounter <- newHotVar (baseSessionID + 1) let allscheds = [ Sched { no=x, idle, isMain= (x==main), workpool=wp, scheds=allscheds, rng=rng, sessions = stck, activeSessions=activeSessions, sessionCounter=sessionCounter } -- | (x,wp,rng,stck) <- zip4 [0..] workpools rngs sessionStacks | x <- [0 .. numCapabilities-1] | wp <- workpools | rng <- rngs | stck <- sessionStacks ] return allscheds -- The ID of top-level runPar sessions. baseSessionID :: SessionID baseSessionID = 1000 -------------------------------------------------------------------------------- -- IVar operations -------------------------------------------------------------------------------- {-# INLINE new #-} -- | Creates a new @IVar@ new :: Par (IVar a) new = io$ do r <- newIORef Empty return (IVar r) {-# INLINE get #-} -- | Read the value in an @IVar@. The 'get' operation can only return when the -- value has been written by a prior or parallel @put@ to the same -- @IVar@. get (IVar vr) = do callCC $ \kont -> do e <- io$ readIORef vr case e of Full a -> return a _ -> do sch <- RD.ask # ifdef DEBUG_DIRECT sn <- io$ makeStableName vr -- Should probably do the MutVar inside... let resched = trace (" ["++ show (no sch) ++ "] - Rescheduling on unavailable ivar "++show (hashStableName sn)++"!") #else let resched = # endif longjmpSched -- Invariant: kont must not be lost. -- Because we continue on the same processor the Sched stays the same: -- TODO: Try NOT using monadic values as first class. Check for performance effect: r <- io$ atomicModifyIORef vr $ \x -> case x of Empty -> (Blocked [pushWork sch . kont], resched) Full a -> (Full a, return a) -- kont is implicit here. Blocked ks -> (Blocked (pushWork sch . kont:ks), resched) r -- | NOTE unsafePeek is NOT exposed directly through this module. (So -- this module remains SAFE in the Safe Haskell sense.) It can only -- be accessed by importing Control.Monad.Par.Unsafe. {-# INLINE unsafePeek #-} unsafePeek :: IVar a -> Par (Maybe a) unsafePeek (IVar v) = do e <- io$ readIORef v case e of Full a -> return (Just a) _ -> return Nothing ------------------------------------------------------------ {-# INLINE put_ #-} -- | @put_@ is a version of @put@ that is head-strict rather than fully-strict. -- In this scheduler, puts immediately execute woken work in the current thread. put_ (IVar vr) !content = do sched <- RD.ask ks <- io$ do ks <- atomicModifyIORef vr $ \e -> case e of Empty -> (Full content, []) Full _ -> error "multiple put" Blocked ks -> (Full content, ks) #ifdef DEBUG_DIRECT when (dbglvl >= 3) $ do sn <- makeStableName vr printf " [%d] Put value %s into IVar %d. Waking up %d continuations.\n" (no sched) (show content) (hashStableName sn) (length ks) return () #endif return ks wakeUp sched ks content -- | NOTE unsafeTryPut is NOT exposed directly through this module. (So -- this module remains SAFE in the Safe Haskell sense.) It can only -- be accessed by importing Control.Monad.Par.Unsafe. {-# INLINE unsafeTryPut #-} unsafeTryPut (IVar vr) !content = do -- Head strict rather than fully strict. sched <- RD.ask (ks,res) <- io$ do pr <- atomicModifyIORef vr $ \e -> case e of Empty -> (Full content, ([], content)) Full x -> (Full x, ([], x)) Blocked ks -> (Full content, (ks, content)) #ifdef DEBUG_DIRECT sn <- makeStableName vr printf " [%d] unsafeTryPut: value %s in IVar %d. Waking up %d continuations.\n" (no sched) (show content) (hashStableName sn) (length (fst pr)) #endif return pr wakeUp sched ks content return res -- | When an IVar is filled in, continuations wake up. {-# INLINE wakeUp #-} wakeUp :: Sched -> [a -> IO ()]-> a -> Par () wakeUp _sched ks arg = loop ks where loop [] = return () loop (kont:rest) = do -- FIXME -- without strict firewalls keeping ivars from moving -- between runPar sessions, if we allow nested scheduler use -- we could potentially wake up work belonging to a different -- runPar and thus bring it into our worker and delay our own -- continuation until its completion. if _PARPUTS then -- We do NOT force the putting thread to postpone its continuation. do _ <- spawn_$ pMap kont rest return () -- case rest of -- [] -> spawn_$ io$ kont arg -- _ -> spawn_$ do spawn_$ io$ kont arg -- io$ parchain rest -- error$"FINISHME - wake "++show (length ks)++" conts" else -- This version sacrifices a parallelism opportunity and -- imposes additional serialization. -- -- [2012.08.31] WARNING -- this serialzation CAN cause deadlock. -- This "optimization" should not be on the table. -- mapM_ ($arg) ks do io$ kont arg loop rest return () pMap kont [] = io$ kont arg pMap kont (more:rest) = do _ <- spawn_$ io$ kont arg pMap more rest -- parchain [kont] = kont arg -- parchain (kont:rest) = do spawn$ io$ kont arg -- parchain rest ------------------------------------------------------------ {-# INLINE fork #-} fork :: Par () -> Par () fork task = -- Forking the "parent" means offering up the continuation of the -- fork rather than the task argument for stealing: case _FORKPARENT of True -> do sched <- RD.ask callCC$ \parent -> do let wrapped = parent () io$ pushWork sched wrapped -- Then execute the child task and return to the scheduler when it is complete: task -- If we get to this point we have finished the child task: _ <- longjmpSched -- We reschedule to pop the cont we pushed. -- TODO... OPTIMIZATION: we could also try the pop directly, and if it succeeds return normally.... io$ printf " !!! ERROR: Should never reach this point #1\n" when dbg$ do sched2 <- RD.ask io$ printf " - called parent continuation... was on worker [%d] now on worker [%d]\n" (no sched) (no sched2) return () False -> do sch <- RD.ask when dbg$ io$ printf " [%d] forking task...\n" (no sch) io$ pushWork sch task -- This routine "longjmp"s to the scheduler, throwing out its own continuation. longjmpSched :: Par a -- longjmpSched = Par $ C.ContT rescheduleR longjmpSched = Par $ C.ContT (\ _k -> rescheduleR 0 (trivialCont "longjmpSched")) -- Reschedule the scheduler loop until it observes sessionFinished==True, and -- then it finally invokes its continuation. rescheduleR :: Word64 -> (a -> ROnly ()) -> ROnly () rescheduleR cnt kont = do mysched <- RD.ask when dbg$ liftIO$ do tid <- myThreadId sess <- readSessions mysched null <- R.nullQ (workpool mysched) printf " [%d %s] - Reschedule #%d... sessions %s, pool empty %s\n" (no mysched) (show tid) cnt (show sess) (show null) mtask <- liftIO$ popWork mysched case mtask of Nothing -> do (Session _ finRef):_ <- liftIO$ readIORef $ sessions mysched fin <- liftIO$ readIORef finRef if fin then do when (dbglvl >= 1) $ liftIO $ do tid <- myThreadId sess <- readSessions mysched printf " [%d %s] - DROP out of reschedule loop, sessionFinished=%s, all sessions %s\n" (no mysched) (show tid) (show fin) (show sess) empt <- R.nullQ$ workpool mysched when (not empt) $ do printf " [%d %s] - WARNING - leaving rescheduleR while local workpoll is nonempty\n" (no mysched) (show tid) kont (error "Direct.hs: The result value from rescheduleR should not be used.") else do -- when (dbglvl >= 1) $ liftIO $ do -- tid <- myThreadId -- sess <- readSessions mysched -- printf " [%d %s] - Apparently NOT finished with head session... trying to steal, all sessions %s\n" -- (no mysched) (show tid) (show sess) liftIO$ steal mysched #ifdef WAKEIDLE -- io$ tryWakeIdle (idle mysched) #endif liftIO yield rescheduleR (cnt+1) kont Just task -> do -- When popping work from our own queue the Sched (Reader value) stays the same: when dbg $ do sn <- liftIO$ makeStableName task liftIO$ printf " [%d] popped work %d from own queue\n" (no mysched) (hashStableName sn) let C.ContT fn = unPar task -- Run the stolen task with a continuation that returns to the scheduler if the task exits normally: fn (\ _ -> do sch <- RD.ask when dbg$ liftIO$ printf " + task finished successfully on cpu %d, calling reschedule continuation..\n" (no sch) rescheduleR 0 kont) -- | Attempt to steal work or, failing that, give up and go idle. -- -- The current policy is to do a burst of of N tries without -- yielding or pausing inbetween. steal :: Sched -> IO () steal mysched@Sched{ idle, scheds, rng, no=my_no } = do when (dbglvl>=2)$ do tid <- myThreadId printf " [%d %s] + stealing\n" my_no (show tid) i <- getnext (-1 :: Int) go maxtries i where -- maxtries = numCapabilities -- How many times should we attempt theft before going idle? maxtries = 20 * numCapabilities -- How many times should we attempt theft before going idle? getnext _ = rand rng ---------------------------------------- -- IDLING behavior: go 0 _ | _IDLING_ON = do m <- newEmptyMVar r <- modifyHotVar idle $ \is -> (m:is, is) if length r == numCapabilities - 1 then do when dbg$ printf " [%d] | waking up all threads\n" my_no writeHotVarRaw idle [] mapM_ (\vr -> putMVar vr True) r else do (Session _ finRef):_ <- readIORef $ sessions mysched fin <- readIORef finRef done <- if fin then pure True else takeMVar m if done then do when dbg$ printf " [%d] | shutting down\n" my_no return () else do when dbg$ printf " [%d] | woken up\n" my_no i <- getnext (-1::Int) go maxtries i -- We need to return from this loop to check sessionFinished and exit the scheduler if necessary. go 0 _i | _IDLING_ON == False = yield ---------------------------------------- go tries i | i == my_no = do i' <- getnext i go (tries-1) i' | otherwise = do -- We ONLY go through the global sched array to access victims: let schd = scheds!!i when (dbglvl>=2)$ printf " [%d] | trying steal from %d\n" my_no (no schd) -- let dq = workpool schd :: WSDeque (Par ()) let dq = workpool schd r <- R.tryPopR dq case r of Just task -> do when dbg$ do sn <- makeStableName task printf " [%d] | stole work (unit %d) from cpu %d\n" my_no (hashStableName sn) (no schd) runReaderWith mysched $ C.runContT (unPar task) (\_ -> do when dbg$ do sn <- liftIO$ makeStableName task liftIO$ printf " [%d] | DONE running stolen work (unit %d) from %d\n" my_no (hashStableName sn) (no schd) return ()) Nothing -> do i' <- getnext i go (tries-1) i' -- | The continuation which should not be called. _errK :: t _errK = error "Error cont: this closure shouldn't be used" trivialCont :: String -> a -> ROnly () #ifdef DEBUG_DIRECT trivialCont str _ = do -- trace (str ++" trivialCont evaluated!") liftIO$ printf " !! trivialCont evaluated, msg: %s\n" str #else trivialCont _str _ = do #endif return () ---------------------------------------------------------------------------------------------------- -------------------------------------------------------------------------------- -- -- TEMP: TODO: Factor out this boilerplate somehow. {-# INLINE spawn1_ #-} -- Spawn a one argument function instead of a thunk. This is good for debugging if the value supports "Show". spawn1_ f x = #ifdef DEBUG_DIRECT do sn <- io$ makeStableName f sch <- RD.ask; when dbg$ io$ printf " [%d] spawning fn %d with arg %s\n" (no sch) (hashStableName sn) (show x) #endif spawn_ (f x) -- The following is usually inefficient! newFull_ a = do v <- new put_ v a return v newFull a = deepseq a (newFull_ a) {-# INLINE put #-} put v a = deepseq a (put_ v a) spawn p = do r <- new; fork (p >>= put r); return r spawn_ p = do r <- new; fork (p >>= put_ r); return r spawnP a = spawn (return a) -- In Debug mode we require that IVar contents be Show-able: #ifdef DEBUG_DIRECT put :: (Show a, NFData a) => IVar a -> a -> Par () spawn :: (Show a, NFData a) => Par a -> Par (IVar a) spawn_ :: Show a => Par a -> Par (IVar a) spawn1_ :: (Show a, Show b) => (a -> Par b) -> a -> Par (IVar b) spawnP :: (Show a, NFData a) => a -> Par (IVar a) put_ :: Show a => IVar a -> a -> Par () get :: Show a => IVar a -> Par a runPar :: Show a => Par a -> a runParIO :: Show a => Par a -> IO a newFull :: (Show a, NFData a) => a -> Par (IVar a) newFull_ :: Show a => a -> Par (IVar a) unsafeTryPut :: Show b => IVar b -> b -> Par b #else spawn :: NFData a => Par a -> Par (IVar a) spawn_ :: Par a -> Par (IVar a) spawn1_ :: (a -> Par b) -> a -> Par (IVar b) spawnP :: NFData a => a -> Par (IVar a) put_ :: IVar a -> a -> Par () put :: NFData a => IVar a -> a -> Par () get :: IVar a -> Par a runPar :: Par a -> a runParIO :: Par a -> IO a newFull :: NFData a => a -> Par (IVar a) newFull_ :: a -> Par (IVar a) unsafeTryPut :: IVar b -> b -> Par b -- We can't make proper instances with the extra Show constraints: instance PC.ParFuture IVar Par where get = get spawn = spawn spawn_ = spawn_ spawnP = spawnP instance PC.ParIVar IVar Par where fork = fork new = new put_ = put_ newFull = newFull newFull_ = newFull_ instance UN.ParUnsafe IVar Par where unsafePeek = unsafePeek unsafeTryPut = unsafeTryPut unsafeParIO = unsafeParIO #endif #ifdef NEW_GENERIC instance PU.ParMonad Par where fork = fork internalLiftIO io = Par (lift $ lift io) instance PU.ParThreadSafe Par where unsafeParIO io = Par (lift $ lift io) instance PN.ParFuture Par where type Future Par = IVar type FutContents Par a = () get = get spawn = spawn spawn_ = spawn_ spawnP = spawnP instance PN.ParIVar Par where new = new put_ = put_ newFull = newFull newFull_ = newFull_ #endif -- -------------------------------------------------------------------------------- {-# INLINE runReaderWith #-} -- | Arguments flipped for convenience. runReaderWith :: r -> RD.ReaderT r m a -> m a runReaderWith state m = RD.runReaderT m state -------------------------------------------------------------------------------- -- DEBUGGING TOOLs -------------------------------------------------------------------------------- -- Make sure there is no work left in any deque after exiting. _sanityCheck :: [Sched] -> IO () _sanityCheck allscheds = do forM_ allscheds $ \ Sched{no, workpool} -> do b <- R.nullQ workpool when (not b) $ do () <- printf "WARNING: After main thread exited non-empty queue remains for worker %d\n" no return () printf "Sanity check complete.\n" -- | This tries to localize the blocked-indefinitely exception: _dbgTakeMVar :: String -> MVar a -> IO a _dbgTakeMVar msg mv = -- catch (takeMVar mv) ((\_ -> doDebugStuff) :: BlockedIndefinitelyOnMVar -> IO a) E.catch (takeMVar mv) (\(_::IOError) -> doDebugStuff) where doDebugStuff = do printf "This takeMVar blocked indefinitely!: %s\n" msg error "failed" -- | For debugging purposes. This can help us figure out (by an ugly -- process of elimination) which MVar reads are leading to a "Thread -- blocked indefinitely" exception. {- busyTakeMVar :: String -> MVar a -> IO a busyTakeMVar msg mv = try (10 * 1000 * 1000) where try 0 = do when dbg $ do tid <- myThreadId -- After we've failed enough times, start complaining: printf "%s not getting anywhere, msg: %s\n" (show tid) msg try (100 * 1000) try n = do x <- tryTakeMVar mv case x of Just y -> return y Nothing -> do yield; try (n-1) -} -- | Fork a thread but ALSO set up an error handler that suppresses -- MVar exceptions. _forkIO_Suppress :: Int -> IO () -> IO ThreadId _forkIO_Suppress whre action = forkOn whre $ E.handle (\e -> case (e :: E.BlockedIndefinitelyOnMVar) of _ -> do putStrLn$"CAUGHT child thread exception: "++show e return () ) action -- | Exceptions that walk up the fork tree of threads: forkWithExceptions :: (IO () -> IO ThreadId) -> String -> IO () -> IO ThreadId forkWithExceptions forkit descr action = do parent <- myThreadId forkit $ do tid <- myThreadId E.catch action (\ e -> case E.fromException e of Just E.ThreadKilled -> printf "\nThreadKilled exception inside child thread, %s (not propagating!): %s\n" (show tid) (show descr) _ -> do printf "\nException inside child thread %s, %s: %s\n" (show descr) (show tid) (show e) E.throwTo parent (e :: E.SomeException) ) -- Do all the memory reads to snapshot the current session stack: readSessions :: Sched -> IO [(SessionID, Bool)] readSessions sched = do ls <- readIORef (sessions sched) bools <- mapM (\ (Session _ r) -> readIORef r) ls return (zip (map (\ (Session sid _) -> sid) ls) bools)