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