From be86081ff4a98b45e08921fdd0b8eba3fca7ea64 Mon Sep 17 00:00:00 2001
From: Joey Hess <joeyh@joeyh.name>
Date: Mon, 16 Nov 2015 14:27:23 -0400
Subject: [PATCH] avoid crashing in checkDaemon when fcntl locking is not
 supported

Instead, just assume the daemon isn't running. Since the pid file locking
fails on such a filesystem, we know it's not running.
---
 Utility/Daemon.hs | 20 +++++++++++---------
 1 file changed, 11 insertions(+), 9 deletions(-)

diff --git a/Utility/Daemon.hs b/Utility/Daemon.hs
index d7f0407bef..3cc2eb2613 100644
--- a/Utility/Daemon.hs
+++ b/Utility/Daemon.hs
@@ -119,16 +119,18 @@ alreadyRunning = error "Daemon is already running."
  - If it's running, returns its pid. -}
 checkDaemon :: FilePath -> IO (Maybe PID)
 #ifndef mingw32_HOST_OS
-checkDaemon pidfile = do
-	v <- catchMaybeIO $
-		openFd pidfile ReadOnly (Just stdFileMode) defaultFileFlags
-	case v of
-		Just fd -> do
-			locked <- getLock fd (ReadLock, AbsoluteSeek, 0, 0)
-			p <- readish <$> readFile pidfile
-			closeFd fd `after` return (check locked p)
-		Nothing -> return Nothing
+checkDaemon pidfile = bracket setup cleanup go
   where
+	setup = catchMaybeIO $
+		openFd pidfile ReadOnly (Just stdFileMode) defaultFileFlags
+	cleanup (Just fd) = closeFd fd
+	cleanup Nothing = return ()
+	go (Just fd) = catchDefaultIO Nothing $ do
+		locked <- getLock fd (ReadLock, AbsoluteSeek, 0, 0)
+		p <- readish <$> readFile pidfile
+		return (check locked p)
+	go Nothing = return Nothing
+
 	check Nothing _ = Nothing
 	check _ Nothing = Nothing
 	check (Just (pid, _)) (Just pid')