use a TMVar

SampleMVar won't work; between getting the current value and changing
it, another thread could made a change, which would get lost.

TMVar works well; this update situation is handled by atomic transactions.

Assistant/Threads/Pusher.hs

@@ -17,27 +17,23 @@ import Utility.ThreadScheduler
 import Utility.Parallel
 
 import Data.Time.Clock
+import qualified Data.Map as M
 
 {- This thread retries pushes that failed before. -}
-pushRetryThread :: ThreadState -> FailedPushChan -> IO ()
-pushRetryThread st pushchan = runEvery (Seconds halfhour) $ do
+pushRetryThread :: ThreadState -> FailedPushMap -> IO ()
+pushRetryThread st pushmap = runEvery (Seconds halfhour) $ do
 	-- We already waited half an hour, now wait until there are failed
 	-- pushes to retry.
-	pushes <- getFailedPushes pushchan
-	-- Check times, to avoid repushing a push that's too new.
-	now <- getCurrentTime
-	let (newpushes, oldpushes) = partition (toorecent now . failedTimeStamp) pushes
-	unless (null newpushes) $
-		refillFailedPushes pushchan newpushes
-	unless (null oldpushes) $
-		pushToRemotes now st pushchan $ map failedRemote oldpushes
+	topush <- getFailedPushesBefore pushmap (fromIntegral halfhour)
+	unless (null topush) $ do
+		now <- getCurrentTime
+		pushToRemotes now st pushmap topush
 	where
 		halfhour = 1800
-		toorecent now time = now `diffUTCTime` time < fromIntegral halfhour
 
 {- This thread pushes git commits out to remotes soon after they are made. -}
-pushThread :: ThreadState -> CommitChan -> FailedPushChan -> IO ()
-pushThread st commitchan pushchan = do
+pushThread :: ThreadState -> CommitChan -> FailedPushMap -> IO ()
+pushThread st commitchan pushmap = do
 	remotes <- runThreadState st $ Command.Sync.syncRemotes []
 	runEvery (Seconds 2) $ do
 		-- We already waited two seconds as a simple rate limiter.
@@ -46,7 +42,7 @@ pushThread st commitchan pushchan = do
 		-- Now see if now's a good time to push.
 		now <- getCurrentTime
 		if shouldPush now commits
-			then pushToRemotes now st pushchan remotes
+			then pushToRemotes now st pushmap remotes
 			else refillCommits commitchan commits
 
 {- Decide if now is a good time to push to remotes.
@@ -65,23 +61,27 @@ shouldPush _now commits
  -
  - Avoids running possibly long-duration commands in the Annex monad, so
  - as not to block other threads. -}
-pushToRemotes :: UTCTime -> ThreadState -> FailedPushChan -> [Remote] -> IO ()
-pushToRemotes now st pushchan remotes = do
+pushToRemotes :: UTCTime -> ThreadState -> FailedPushMap -> [Remote] -> IO ()
+pushToRemotes now st pushmap remotes = do
 	(g, branch) <- runThreadState st $
 		(,) <$> fromRepo id <*> Command.Sync.currentBranch
 	go True branch g remotes
 	where
 		go shouldretry branch g rs = do
 			Command.Sync.updateBranch (Command.Sync.syncBranch branch) g
-			failed <- inParallel (push g branch) rs
-			unless (null failed) $
-				if shouldretry
-					then retry branch g rs
-					else refillFailedPushes pushchan $
-						map (`FailedPush` now) failed
+			(succeeded, failed) <- inParallel (push g branch) rs
+			changeFailedPushMap pushmap $ \m ->
+				M.union (makemap failed) $
+					M.difference m (makemap succeeded)
+			unless (null failed || not shouldretry) $
+				retry branch g failed
+
+		makemap l = M.fromList $ zip l (repeat now)
+
 		push g branch remote =
 			ifM (Command.Sync.pushBranch remote branch g)
 				( exitSuccess, exitFailure)
+
 		retry branch g rs = do
 			runThreadState st $ manualPull branch rs
 			go False branch g rs