convert TMVars that are never left empty into TVars

This is probably more efficient, and it avoids mistakenly leaving them
empty.

Assistant/DaemonStatus.hs

@@ -30,7 +30,7 @@ import qualified Data.Set as S
 import qualified Data.Text as T
 
 getDaemonStatus :: Assistant DaemonStatus
-getDaemonStatus = (atomically . readTMVar) <<~ daemonStatusHandle
+getDaemonStatus = (atomically . readTVar) <<~ daemonStatusHandle
 
 modifyDaemonStatus_ :: (DaemonStatus -> DaemonStatus) -> Assistant ()
 modifyDaemonStatus_ a = modifyDaemonStatus $ \s -> (a s, ())
@@ -40,8 +40,8 @@ modifyDaemonStatus a = do
 	dstatus <- getAssistant daemonStatusHandle
 	liftIO $ do
 		(s, b) <- atomically $ do
-			r@(!s, _) <- a <$> takeTMVar dstatus
-			putTMVar dstatus s
+			r@(!s, _) <- a <$> readTVar dstatus
+			writeTVar dstatus s
 			return r
 		sendNotification $ changeNotifier s
 		return b
@@ -102,7 +102,7 @@ startDaemonStatus = do
 		flip catchDefaultIO (readDaemonStatusFile file) =<< newDaemonStatus
 	transfers <- M.fromList <$> getTransfers
 	addsync <- calcSyncRemotes
-	liftIO $ atomically $ newTMVar $ addsync $ status
+	liftIO $ atomically $ newTVar $ addsync $ status
 		{ scanComplete = False
 		, sanityCheckRunning = False
 		, currentTransfers = transfers
@@ -162,14 +162,14 @@ tenMinutes = 10 * 60
  - to the caller. -}
 adjustTransfersSTM :: DaemonStatusHandle -> (TransferMap -> TransferMap) -> STM ()
 adjustTransfersSTM dstatus a = do
-	s <- takeTMVar dstatus
+	s <- readTVar dstatus
 	let !v = a (currentTransfers s)
-	putTMVar dstatus $ s { currentTransfers = v }
+	writeTVar dstatus $ s { currentTransfers = v }
 
 {- Checks if a transfer is currently running. -}
 checkRunningTransferSTM :: DaemonStatusHandle -> Transfer -> STM Bool
 checkRunningTransferSTM dstatus t = M.member t . currentTransfers
-	<$> readTMVar dstatus
+	<$> readTVar dstatus
 
 {- Alters a transfer's info, if the transfer is in the map. -}
 alterTransferInfo :: Transfer -> (TransferInfo -> TransferInfo) -> Assistant ()
@@ -207,14 +207,14 @@ notifyTransfer :: Assistant ()
 notifyTransfer = do
 	dstatus <- getAssistant daemonStatusHandle
 	liftIO $ sendNotification
-		=<< transferNotifier <$> atomically (readTMVar dstatus)
+		=<< transferNotifier <$> atomically (readTVar dstatus)
 
 {- Send a notification when alerts are changed. -}
 notifyAlert :: Assistant ()
 notifyAlert = do
 	dstatus <- getAssistant daemonStatusHandle
 	liftIO $ sendNotification
-		=<< alertNotifier <$> atomically (readTMVar dstatus)
+		=<< alertNotifier <$> atomically (readTVar dstatus)
 
 {- Returns the alert's identifier, which can be used to remove it. -}
 addAlert :: Alert -> Assistant AlertId

Assistant/Types/DaemonStatus.hs

@@ -86,8 +86,7 @@ data DaemonStatus = DaemonStatus
 
 type TransferMap = M.Map Transfer TransferInfo
 
-{- This TMVar is never left empty, so accessing it will never block. -}
-type DaemonStatusHandle = TMVar DaemonStatus
+type DaemonStatusHandle = TVar DaemonStatus
 
 newDaemonStatus :: IO DaemonStatus
 newDaemonStatus = DaemonStatus

Assistant/Types/TransferrerPool.hs

@@ -13,8 +13,7 @@ import Assistant.Types.DaemonStatus
 
 import Control.Concurrent.STM hiding (check)
 
-{- This TMVar is never left empty. -}
-type TransferrerPool = TMVar (MkCheckTransferrer, [TransferrerPoolItem])
+type TransferrerPool = TVar (MkCheckTransferrer, [TransferrerPoolItem])
 
 type CheckTransferrer = IO Bool
 type MkCheckTransferrer = IO (IO Bool)
@@ -31,24 +30,22 @@ data Transferrer = Transferrer
 	}
 
 newTransferrerPool :: MkCheckTransferrer -> IO TransferrerPool
-newTransferrerPool c = newTMVarIO (c, [])
+newTransferrerPool c = newTVarIO (c, [])
 
 popTransferrerPool :: TransferrerPool -> STM (Maybe TransferrerPoolItem, Int)
 popTransferrerPool p = do
-	(c, l) <- takeTMVar p
+	(c, l) <- readTVar p
 	case l of
-		[] -> do
-			putTMVar p (c, [])
-			return (Nothing, 0)
+		[] -> return (Nothing, 0)
 		(i:is) -> do
-			putTMVar p (c, is)
+			writeTVar p (c, is)
 			return $ (Just i, length is)
 
 pushTransferrerPool :: TransferrerPool -> TransferrerPoolItem -> STM ()
 pushTransferrerPool p i = do
-	(c, l) <- takeTMVar p
+	(c, l) <- readTVar p
 	let l' = i:l
-	putTMVar p (c, l')
+	writeTVar p (c, l')
 
 {- Note that making a CheckTransferrer may allocate resources,
  - such as a NotificationHandle, so it's important that the returned
@@ -56,12 +53,12 @@ pushTransferrerPool p i = do
  - garbage collected. -}
 mkTransferrerPoolItem :: TransferrerPool -> Transferrer -> IO TransferrerPoolItem
 mkTransferrerPoolItem p t = do
-	mkcheck <- atomically $ fst <$> readTMVar p
+	mkcheck <- atomically $ fst <$> readTVar p
 	check <- mkcheck
 	return $ TransferrerPoolItem (Just t) check
 
 checkNetworkConnections :: DaemonStatusHandle -> MkCheckTransferrer
 checkNetworkConnections dstatushandle = do
-	dstatus <- atomically $ readTMVar dstatushandle
+	dstatus <- atomically $ readTVar dstatushandle
 	h <- newNotificationHandle False (networkConnectedNotifier dstatus)
 	return $ not <$> checkNotification h