6992fe133b
When ssh connection caching is enabled (and when GIT_ANNEX_USE_GIT_SSH is not set), only one ssh password prompt will be made per host, and only one ssh password prompt will be made at a time. This also fixes a race in prepSocket's stale ssh connection stopping when run with -J. It was possible for one thread to start a cached ssh connection, and another thread to immediately stop it, resulting in excess connections being made. This commit was supported by the NSF-funded DataLad project.
92 lines
2.5 KiB
Haskell
92 lines
2.5 KiB
Haskell
{- git-annex lock files.
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-
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- Copyright 2012-2015 Joey Hess <id@joeyh.name>
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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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lockFileCached,
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unlockFile,
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getLockCache,
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fromLockCache,
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withExclusiveLock,
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tryExclusiveLock,
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) where
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import Annex.Common
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import Annex
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import Types.LockCache
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import qualified Git
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import Annex.Perms
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import Annex.LockPool
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import qualified Data.Map as M
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{- Create a specified lock file, and takes a shared lock, which is retained
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- in the cache. -}
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lockFileCached :: FilePath -> Annex ()
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lockFileCached file = go =<< fromLockCache 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 <- noUmask mode $ lockShared (Just mode) file
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#else
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lockhandle <- liftIO $ waitToLock $ lockShared file
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#endif
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changeLockCache $ M.insert file lockhandle
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unlockFile :: FilePath -> Annex ()
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unlockFile file = maybe noop go =<< fromLockCache file
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where
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go lockhandle = do
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liftIO $ dropLock lockhandle
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changeLockCache $ M.delete file
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getLockCache :: Annex LockCache
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getLockCache = getState lockcache
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fromLockCache :: FilePath -> Annex (Maybe LockHandle)
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fromLockCache file = M.lookup file <$> getLockCache
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changeLockCache :: (LockCache -> LockCache) -> Annex ()
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changeLockCache a = do
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m <- getLockCache
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changeState $ \s -> s { lockcache = 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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bracket (lock mode lockfile) (liftIO . dropLock) (const a)
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where
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#ifndef mingw32_HOST_OS
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lock mode = noUmask mode . lockExclusive (Just mode)
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#else
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lock _mode = liftIO . waitToLock . lockExclusive
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#endif
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{- Tries to take an exclusive lock and run an action. If the lock is
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- already held, returns Nothing. -}
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tryExclusiveLock :: (Git.Repo -> FilePath) -> Annex a -> Annex (Maybe a)
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tryExclusiveLock 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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bracket (lock mode lockfile) (liftIO . unlock) go
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where
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#ifndef mingw32_HOST_OS
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lock mode = noUmask mode . tryLockExclusive (Just mode)
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#else
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lock _mode = liftIO . lockExclusive
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#endif
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unlock = maybe noop dropLock
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go Nothing = return Nothing
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go (Just _) = Just <$> a
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