take awasy the session in shutdown to prevent race condition

Author: soulomoon

ghcide/src/Development/IDE/Core/Shake.hs

@@ -75,6 +75,7 @@ module Development.IDE.Core.Shake(
     VFSModified(..), getClientConfigAction,
     ) where
 
+import           Control.Concurrent                     (withMVar)
 import           Control.Concurrent.Async
 import           Control.Concurrent.STM
 import           Control.Concurrent.STM.Stats           (atomicallyNamed)
@@ -724,14 +725,14 @@ shakeSessionInit recorder ide@IdeState{..} = do
     logWith recorder Debug LogSessionInitialised
 
 shakeShut :: IdeState -> IO ()
-shakeShut IdeState{..} = do
-    runner <- tryReadMVar shakeSession
-    -- Shake gets unhappy if you try to close when there is a running
-    -- request so we first abort that.
-    for_ runner cancelShakeSession
-    void $ shakeDatabaseProfile shakeDb
-    progressStop $ progress shakeExtras
-    stopMonitoring
+shakeShut IdeState{..} =
+    withMVar shakeSession $ \ runner -> do
+        -- Shake gets unhappy if you try to close when there is a running
+        -- request so we first abort that.
+        cancelShakeSession runner
+        void $ shakeDatabaseProfile shakeDb
+        progressStop $ progress shakeExtras
+        stopMonitoring
 
 
 -- | This is a variant of withMVar where the first argument is run unmasked and if it throws

ghcide/src/Development/IDE/LSP/LanguageServer.hs

@@ -262,13 +262,10 @@ shutdownHandler :: Recorder (WithPriority Log) -> IO () -> LSP.Handlers (ServerM
 shutdownHandler recorder stopReactor = LSP.requestHandler SMethod_Shutdown $ \_ resp -> do
     (_, ide) <- ask
     liftIO $ logWith recorder Debug LogServerShutdownMessage
-    -- we need to shut down the ide session before stopping the reactor
-    -- since SessionIO depends on the reactor, we may hang if we stop the reactor first
-
-    -- flush out the Shake session to record a Shake profile if applicable
-    liftIO $ shakeShut ide
     -- stop the reactor to free up the hiedb connection
     liftIO stopReactor
+    -- flush out the Shake session to record a Shake profile if applicable
+    liftIO $ shakeShut ide
     resp $ Right Null
 
 exitHandler :: IO () -> LSP.Handlers (ServerM c)