Use onException for exception cleanup, and mask async exceptions

[ghc-base.git] / System / Event / Thread.hs

diff --git a/System/Event/Thread.hs b/System/Event/Thread.hs
index 66174cd..72343d9 100644 (file)
--- a/System/Event/Thread.hs
+++ b/System/Event/Thread.hs
@@ -5,12 +5,11 @@ module System.Event.Thread
       ensureIOManagerIsRunning
     , threadWaitRead
     , threadWaitWrite
-    , closeFd
+    , closeFdWith
     , threadDelay
     , registerDelay
     ) where
 
-import Control.Exception (SomeException, catch, throw)
 import Data.IORef (IORef, newIORef, readIORef, writeIORef)
 import Data.Maybe (Maybe(..))
 import Foreign.C.Error (eBADF, errnoToIOError)
@@ -19,6 +18,7 @@ import GHC.Base
 import GHC.Conc.Sync (TVar, ThreadId, ThreadStatus(..), atomically, forkIO,
                       labelThread, modifyMVar_, newTVar, sharedCAF,
                       threadStatus, writeTVar)
+import GHC.IO (mask_, onException)
 import GHC.IO.Exception (ioError)
 import GHC.MVar (MVar, newEmptyMVar, newMVar, putMVar, takeMVar)
 import GHC.Real (fromIntegral)
@@ -36,12 +36,11 @@ import System.Posix.Types (Fd)
 -- when the delay has expired, but the thread will never continue to
 -- run /earlier/ than specified.
 threadDelay :: Int -> IO ()
-threadDelay usecs = do
+threadDelay usecs = mask_ $ do
   Just mgr <- readIORef eventManager
   m <- newEmptyMVar
   reg <- registerTimeout mgr usecs (putMVar m ())
-  takeMVar m `catch` \(e::SomeException) ->
-    M.unregisterTimeout mgr reg >> throw e
+  takeMVar m `onException` M.unregisterTimeout mgr reg
 
 -- | Set the value of returned TVar to True after a given number of
 -- microseconds. The caveats associated with threadDelay also apply.
@@ -57,7 +56,8 @@ registerDelay usecs = do
 -- given file descriptor.
 --
 -- This will throw an 'IOError' if the file descriptor was closed
--- while this thread is blocked.
+-- while this thread was blocked.  To safely close a file descriptor
+-- that has been used with 'threadWaitRead', use 'closeFdWith'.
 threadWaitRead :: Fd -> IO ()
 threadWaitRead = threadWait evtRead
 {-# INLINE threadWaitRead #-}
@@ -66,7 +66,8 @@ threadWaitRead = threadWait evtRead
 -- accept data to write.
 --
 -- This will throw an 'IOError' if the file descriptor was closed
--- while this thread is blocked.
+-- while this thread was blocked.  To safely close a file descriptor
+-- that has been used with 'threadWaitWrite', use 'closeFdWith'.
 threadWaitWrite :: Fd -> IO ()
 threadWaitWrite = threadWait evtWrite
 {-# INLINE threadWaitWrite #-}
@@ -76,20 +77,19 @@ threadWaitWrite = threadWait evtWrite
 -- Any threads that are blocked on the file descriptor via
 -- 'threadWaitRead' or 'threadWaitWrite' will be unblocked by having
 -- IO exceptions thrown.
-closeFd :: (Fd -> IO ())        -- ^ Action that performs the close.
-        -> Fd                   -- ^ File descriptor to close.
-        -> IO ()
-closeFd close fd = do
+closeFdWith :: (Fd -> IO ())        -- ^ Action that performs the close.
+            -> Fd                   -- ^ File descriptor to close.
+            -> IO ()
+closeFdWith close fd = do
   Just mgr <- readIORef eventManager
   M.closeFd mgr close fd
 
 threadWait :: Event -> Fd -> IO ()
-threadWait evt fd = do
+threadWait evt fd = mask_ $ do
   m <- newEmptyMVar
   Just mgr <- readIORef eventManager
   reg <- registerFd mgr (\reg e -> unregisterFd_ mgr reg >> putMVar m e) fd evt
-  evt' <- takeMVar m `catch` \(e::SomeException) ->
-            unregisterFd_ mgr reg >> throw e
+  evt' <- takeMVar m `onException` unregisterFd_ mgr reg
   if evt' `eventIs` evtClose
     then ioError $ errnoToIOError "threadWait" eBADF Nothing Nothing
     else return ()