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|
{- git-annex lock files.
-
- Copyright 2012, 2014 Joey Hess <joey@kitenet.net>
-
- Licensed under the GNU GPL version 3 or higher.
-}
{-# LANGUAGE CPP #-}
module Annex.LockFile (
lockFileShared,
unlockFile,
getLockPool,
withExclusiveLock,
) where
import Common.Annex
import Annex
import Types.LockPool
import qualified Git
import Annex.Exception
import Annex.Perms
import qualified Data.Map as M
#ifdef mingw32_HOST_OS
import Utility.WinLock
#endif
{- Create a specified lock file, and takes a shared lock, which is retained
- in the pool. -}
lockFileShared :: FilePath -> Annex ()
lockFileShared file = go =<< fromLockPool file
where
go (Just _) = noop -- already locked
go Nothing = do
#ifndef mingw32_HOST_OS
mode <- annexFileMode
lockhandle <- liftIO $ noUmask mode $
openFd file ReadOnly (Just mode) defaultFileFlags
liftIO $ waitToSetLock lockhandle (ReadLock, AbsoluteSeek, 0, 0)
#else
lockhandle <- liftIO $ waitToLock $ lockShared file
#endif
changeLockPool $ M.insert file lockhandle
unlockFile :: FilePath -> Annex ()
unlockFile file = maybe noop go =<< fromLockPool file
where
go lockhandle = do
#ifndef mingw32_HOST_OS
liftIO $ closeFd lockhandle
#else
liftIO $ dropLock lockhandle
#endif
changeLockPool $ M.delete file
getLockPool :: Annex LockPool
getLockPool = getState lockpool
fromLockPool :: FilePath -> Annex (Maybe LockHandle)
fromLockPool file = M.lookup file <$> getLockPool
changeLockPool :: (LockPool -> LockPool) -> Annex ()
changeLockPool a = do
m <- getLockPool
changeState $ \s -> s { lockpool = a m }
{- Runs an action with an exclusive lock held. If the lock is already
- held, blocks until it becomes free. -}
withExclusiveLock :: (Git.Repo -> FilePath) -> Annex a -> Annex a
withExclusiveLock getlockfile a = do
lockfile <- fromRepo getlockfile
createAnnexDirectory $ takeDirectory lockfile
mode <- annexFileMode
bracketIO (lock lockfile mode) unlock (const a)
where
#ifndef mingw32_HOST_OS
lock lockfile mode = do
l <- noUmask mode $ createFile lockfile mode
waitToSetLock l (WriteLock, AbsoluteSeek, 0, 0)
return l
unlock = closeFd
#else
lock lockfile _mode = waitToLock $ lockExclusive lockfile
unlock = dropLock
#endif
|
