New asynchronous exception control API (base parts)

  
As discussed on the libraries/haskell-cafe mailing lists
  http://www.haskell.org/pipermail/libraries/2010-April/013420.html

This is a replacement for block/unblock in the asychronous exceptions
API to fix a problem whereby a function could unblock asynchronous
exceptions even if called within a blocked context.

The new terminology is "mask" rather than "block" (to avoid confusion
due to overloaded meanings of the latter).

The following is the new API; the old API is deprecated but still
available for the time being.

Control.Exception
-----------------

mask  :: ((forall a. IO a -> IO a) -> IO b) -> IO b
mask_ :: IO a -> IO a

uninterruptibleMask :: ((forall a. IO a -> IO a) -> IO b) -> IO b
uninterruptibleMask_ :: IO a -> IO 

getMaskingState :: IO MaskingState

data MaskingState
  = Unmasked
  | MaskedInterruptible 
  | MaskedUninterruptible


Control.Concurrent
------------------

forkIOUnmasked :: IO () -> IO ThreadId

1 files changed, 2 insertions, 2 deletions

diff --git a/libraries/base/GHC/IO/Handle/Internals.hs b/libraries/base/GHC/IO/Handle/Internals.hs
index 2c0523f901..5568855ad4 100644
--- a/libraries/base/GHC/IO/Handle/Internals.hs
+++ b/libraries/base/GHC/IO/Handle/Internals.hs
@@ -124,7 +124,7 @@ withHandle fun h@(DuplexHandle _ m _) act = withHandle' fun h m act
 withHandle' :: String -> Handle -> MVar Handle__
    -> (Handle__ -> IO (Handle__,a)) -> IO a
 withHandle' fun h m act =
- block $ do
+ mask_ $ do
    (h',v)  <- do_operation fun h act m
    checkHandleInvariants h'
    putMVar m h'
@@ -149,7 +149,7 @@ withAllHandles__ fun h@(DuplexHandle _ r w) act = do
 withHandle__' :: String -> Handle -> MVar Handle__ -> (Handle__ -> IO Handle__)
               -> IO ()
 withHandle__' fun h m act =
- block $ do
+ mask_ $ do
    h'  <- do_operation fun h act m
    checkHandleInvariants h'
    putMVar m h'