diff options
| -rw-r--r-- | libraries/base/GHC/Event/Thread.hs | 6 |
1 files changed, 4 insertions, 2 deletions
diff --git a/libraries/base/GHC/Event/Thread.hs b/libraries/base/GHC/Event/Thread.hs index 19b6cd4117..fb40cde4d0 100644 --- a/libraries/base/GHC/Event/Thread.hs +++ b/libraries/base/GHC/Event/Thread.hs @@ -19,6 +19,7 @@ module GHC.Event.Thread import Control.Exception (finally, SomeException, toException) import Data.Foldable (forM_, mapM_, sequence_) import Data.IORef (IORef, newIORef, readIORef, writeIORef) +import Data.Maybe (fromMaybe) import Data.Tuple (snd) import Foreign.C.Error (eBADF, errnoToIOError) import Foreign.C.Types (CInt(..), CUInt(..)) @@ -213,8 +214,9 @@ ioManagerLock = unsafePerformIO $ do getSystemTimerManager :: IO TM.TimerManager getSystemTimerManager = do - Just mgr <- readIORef timerManager - return mgr + fromMaybe err `fmap` readIORef timerManager + where + err = error "GHC.Event.Thread.getSystemTimerManager: the TimerManager requires linking against the threaded runtime" foreign import ccall unsafe "getOrSetSystemTimerThreadEventManagerStore" getOrSetSystemTimerThreadEventManagerStore :: Ptr a -> IO (Ptr a) |