206 lines
6.9 KiB
Haskell
206 lines
6.9 KiB
Haskell
{- git-annex concurrent state
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-
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- Copyright 2015-2020 Joey Hess <id@joeyh.name>
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-
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- Licensed under the GNU AGPL version 3 or higher.
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-}
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module Annex.Concurrent where
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import Annex
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import Annex.Common
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import qualified Annex.Queue
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import Annex.Action
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import Types.Concurrency
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import Types.WorkerPool
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import Types.CatFileHandles
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import Annex.CheckAttr
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import Annex.CheckIgnore
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import Remote.List
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import Control.Concurrent
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import Control.Concurrent.STM
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import qualified Data.Map as M
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setConcurrency :: Concurrency -> Annex ()
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setConcurrency NonConcurrent = Annex.changeState $ \s -> s
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{ Annex.concurrency = NonConcurrent
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}
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setConcurrency c = do
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cfh <- Annex.getState Annex.catfilehandles
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cfh' <- case cfh of
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CatFileHandlesNonConcurrent _ -> liftIO catFileHandlesPool
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CatFileHandlesPool _ -> pure cfh
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cah <- mkConcurrentCheckAttrHandle c
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cih <- mkConcurrentCheckIgnoreHandle c
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Annex.changeState $ \s -> s
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{ Annex.concurrency = c
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, Annex.catfilehandles = cfh'
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, Annex.checkattrhandle = Just cah
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, Annex.checkignorehandle = Just cih
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}
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{- Allows forking off a thread that uses a copy of the current AnnexState
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- to run an Annex action.
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-
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- The returned IO action can be used to start the thread.
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- It returns an Annex action that must be run in the original
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- calling context to merge the forked AnnexState back into the
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- current AnnexState.
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-}
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forkState :: Annex a -> Annex (IO (Annex a))
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forkState a = do
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st <- dupState
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return $ do
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(ret, newst) <- run st a
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return $ do
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mergeState newst
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return ret
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{- Returns a copy of the current AnnexState that is safe to be
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- used when forking off a thread.
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-
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- After an Annex action is run using this AnnexState, it
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- should be merged back into the current Annex's state,
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- by calling mergeState.
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-}
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dupState :: Annex AnnexState
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dupState = do
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-- Make sure that some expensive actions have been done before
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-- starting threads. This way the state has them already run,
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-- and each thread won't try to do them.
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_ <- remoteList
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st <- Annex.getState id
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-- Make sure that concurrency is enabled, if it was not already,
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-- so the concurrency-safe resource pools are set up.
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st' <- case Annex.concurrency st of
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NonConcurrent -> do
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setConcurrency (Concurrent 1)
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Annex.getState id
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_ -> return st
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return $ st'
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-- each thread has its own repoqueue
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{ Annex.repoqueue = Nothing
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}
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{- Merges the passed AnnexState into the current Annex state.
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- Also closes various handles in it. -}
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mergeState :: AnnexState -> Annex ()
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mergeState st = do
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st' <- liftIO $ snd <$> run st stopCoProcesses
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forM_ (M.toList $ Annex.cleanup st') $
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uncurry addCleanup
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Annex.Queue.mergeFrom st'
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changeState $ \s -> s { errcounter = errcounter s + errcounter st' }
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{- Runs an action and makes the current thread have the specified stage
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- while doing so. If too many other threads are running in the specified
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- stage, waits for one of them to become idle.
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-
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- Noop if the current thread already has the requested stage, or if the
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- current thread is not in the worker pool, or if concurrency is not
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- enabled.
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-
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- Also a noop if the stage is not one of the stages that the worker pool
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- uses.
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-}
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enteringStage :: WorkerStage -> Annex a -> Annex a
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enteringStage newstage a = Annex.getState Annex.workers >>= \case
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Nothing -> a
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Just tv -> do
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mytid <- liftIO myThreadId
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let set = changeStageTo mytid tv (const newstage)
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let restore = maybe noop (void . changeStageTo mytid tv . const)
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bracket set restore (const a)
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{- Transition the current thread to the initial stage.
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- This is done once the thread is ready to begin work.
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-}
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enteringInitialStage :: Annex ()
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enteringInitialStage = Annex.getState Annex.workers >>= \case
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Nothing -> noop
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Just tv -> do
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mytid <- liftIO myThreadId
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void $ changeStageTo mytid tv initialStage
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{- This needs to leave the WorkerPool with the same number of
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- idle and active threads, and with the same number of threads for each
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- WorkerStage. So, all it can do is swap the WorkerStage of our thread's
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- ActiveWorker with an IdleWorker.
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-
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- Must avoid a deadlock if all worker threads end up here at the same
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- time, or if there are no suitable IdleWorkers left. So if necessary
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- we first replace our ActiveWorker with an IdleWorker in the pool, to allow
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- some other thread to use it, before waiting for a suitable IdleWorker
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- for us to use.
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-
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- Note that the spareVals in the WorkerPool does not get anything added to
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- it when adding the IdleWorker, so there will for a while be more IdleWorkers
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- in the pool than spareVals. That does not prevent other threads that call
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- this from using them though, so it's fine.
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-}
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changeStageTo :: ThreadId -> TMVar (WorkerPool AnnexState) -> (UsedStages -> WorkerStage) -> Annex (Maybe WorkerStage)
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changeStageTo mytid tv getnewstage = liftIO $
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replaceidle >>= maybe
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(return Nothing)
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(either waitidle (return . Just))
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where
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replaceidle = atomically $ do
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pool <- takeTMVar tv
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let newstage = getnewstage (usedStages pool)
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let notchanging = do
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putTMVar tv pool
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return Nothing
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if memberStage newstage (usedStages pool)
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then case removeThreadIdWorkerPool mytid pool of
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Just ((myaid, oldstage), pool')
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| oldstage /= newstage -> case getIdleWorkerSlot newstage pool' of
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Nothing -> do
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putTMVar tv $
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addWorkerPool (IdleWorker oldstage) pool'
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return $ Just $ Left (myaid, newstage, oldstage)
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Just pool'' -> do
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-- optimisation
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putTMVar tv $
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addWorkerPool (IdleWorker oldstage) $
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addWorkerPool (ActiveWorker myaid newstage) pool''
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return $ Just $ Right oldstage
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| otherwise -> notchanging
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_ -> notchanging
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else notchanging
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waitidle (myaid, newstage, oldstage) = atomically $ do
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pool <- waitIdleWorkerSlot newstage =<< takeTMVar tv
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putTMVar tv $ addWorkerPool (ActiveWorker myaid newstage) pool
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return (Just oldstage)
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-- | Waits until there's an idle StartStage worker in the worker pool,
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-- removes it from the pool, and returns its state.
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--
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-- If the worker pool is not already allocated, returns Nothing.
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waitStartWorkerSlot :: TMVar (WorkerPool Annex.AnnexState) -> STM (Maybe (Annex.AnnexState, WorkerStage))
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waitStartWorkerSlot tv = do
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pool <- takeTMVar tv
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st <- go pool
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return $ Just (st, StartStage)
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where
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go pool = case spareVals pool of
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[] -> retry
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(v:vs) -> do
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let pool' = pool { spareVals = vs }
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putTMVar tv =<< waitIdleWorkerSlot StartStage pool'
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return v
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waitIdleWorkerSlot :: WorkerStage -> WorkerPool Annex.AnnexState -> STM (WorkerPool Annex.AnnexState)
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waitIdleWorkerSlot wantstage = maybe retry return . getIdleWorkerSlot wantstage
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getIdleWorkerSlot :: WorkerStage -> WorkerPool Annex.AnnexState -> Maybe (WorkerPool Annex.AnnexState)
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getIdleWorkerSlot wantstage pool = do
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l <- findidle [] (workerList pool)
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return $ pool { workerList = l }
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where
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findidle _ [] = Nothing
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findidle c ((IdleWorker stage):rest)
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| stage == wantstage = Just (c ++ rest)
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findidle c (w:rest) = findidle (w:c) rest
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