git-annex/Annex/Concurrent.hs
Joey Hess 5c32196a37
fix process and FD leak
Fix process and file descriptor leak that was exposed when git-annex was
built with ghc 8.2.1. Apparently ghc has changed its behavior of GC
of open file handles that are pipes to running processes. That
broke git-annex test on OSX due to running out of FDs.

Audited for all uses of Annex.new and made stopCoProcesses be called
once it's done with the state. Fixed several places that might have
leaked in other situations than running the test suite.

This commit was sponsored by Ewen McNeill.
2017-09-29 22:36:08 -04:00

60 lines
1.6 KiB
Haskell

{- git-annex concurrent state
-
- Copyright 2015 Joey Hess <id@joeyh.name>
-
- Licensed under the GNU GPL version 3 or higher.
-}
module Annex.Concurrent where
import Annex
import Annex.Common
import Annex.Action
import qualified Annex.Queue
import qualified Data.Map as M
{- Allows forking off a thread that uses a copy of the current AnnexState
- to run an Annex action.
-
- The returned IO action can be used to start the thread.
- It returns an Annex action that must be run in the original
- calling context to merge the forked AnnexState back into the
- current AnnexState.
-}
forkState :: Annex a -> Annex (IO (Annex a))
forkState a = do
st <- dupState
return $ do
(ret, newst) <- run st a
return $ do
mergeState newst
return ret
{- Returns a copy of the current AnnexState that is safe to be
- used when forking off a thread.
-
- After an Annex action is run using this AnnexState, it
- should be merged back into the current Annex's state,
- by calling mergeState.
-}
dupState :: Annex AnnexState
dupState = do
st <- Annex.getState id
-- avoid sharing eg, open file handles
return $ st
{ Annex.workers = []
, Annex.catfilehandles = M.empty
, Annex.checkattrhandle = Nothing
, Annex.checkignorehandle = Nothing
}
{- Merges the passed AnnexState into the current Annex state.
- Also closes various handles in it. -}
mergeState :: AnnexState -> Annex ()
mergeState st = do
st' <- liftIO $ snd <$> run st stopCoProcesses
forM_ (M.toList $ Annex.cleanup st') $
uncurry addCleanup
Annex.Queue.mergeFrom st'
changeState $ \s -> s { errcounter = errcounter s + errcounter st' }