mask +base

mask :: ((forall a. IO a -> IO a) -> IO b) -> IO b
base Control.Exception.Base, base Control.Exception
Executes an IO computation with asynchronous exceptions masked. That is, any thread which attempts to raise an exception in the current thread with Control.Exception.throwTo will be blocked until asynchronous exceptions are unmasked again. The argument passed to mask is a function that takes as its argument another function, which can be used to restore the prevailing masking state within the context of the masked computation. For example, a common way to use mask is to protect the acquisition of a resource: > mask $ \restore -> do > x <- acquire > restore (do_something_with x) `onException` release > release This code guarantees that acquire is paired with release, by masking asynchronous exceptions for the critical parts. (Rather than write this code yourself, it would be better to use Control.Exception.bracket which abstracts the general pattern). Note that the restore action passed to the argument to mask does not necessarily unmask asynchronous exceptions, it just restores the masking state to that of the enclosing context. Thus if asynchronous exceptions are already masked, mask cannot be used to unmask exceptions again. This is so that if you call a library function with exceptions masked, you can be sure that the library call will not be able to unmask exceptions again. If you are writing library code and need to use asynchronous exceptions, the only way is to create a new thread; see Control.Concurrent.forkIOUnmasked. Asynchronous exceptions may still be received while in the masked state if the masked thread blocks in certain ways; see Control.Exception#interruptible. Threads created by Control.Concurrent.forkIO inherit the masked state from the parent; that is, to start a thread in blocked mode, use mask_ $ forkIO .... This is particularly useful if you need to establish an exception handler in the forked thread before any asynchronous exceptions are received. To create a a new thread in an unmasked state use Control.Concurrent.forkIOUnmasked.
mask_ :: IO a -> IO a
base Control.Exception.Base, base Control.Exception
Like mask, but does not pass a restore action to the argument.
MaskedInterruptible :: MaskingState
base Control.Exception.Base, base Control.Exception
the state during mask: asynchronous exceptions are masked, but blocking operations may still be interrupted
MaskedUninterruptible :: MaskingState
base Control.Exception.Base, base Control.Exception
the state during uninterruptibleMask: asynchronous exceptions are masked, and blocking operations may not be interrupted
data MaskingState
base Control.Exception.Base, base Control.Exception
Describes the behaviour of a thread when an asynchronous exception is received.
forkIOUnmasked :: IO () -> IO ThreadId
base Control.Concurrent, base GHC.Conc.Sync, base GHC.Conc
Like forkIO, but the child thread is created with asynchronous exceptions unmasked (see Control.Exception.mask).
getMaskingState :: IO MaskingState
base Control.Exception.Base, base Control.Exception
Returns the MaskingState for the current thread.
uninterruptibleMask :: ((forall a. IO a -> IO a) -> IO b) -> IO b
base Control.Exception.Base, base Control.Exception
Like mask, but the masked computation is not interruptible (see Control.Exception#interruptible). THIS SHOULD BE USED WITH GREAT CARE, because if a thread executing in uninterruptibleMask blocks for any reason, then the thread (and possibly the program, if this is the main thread) will be unresponsive and unkillable. This function should only be necessary if you need to mask exceptions around an interruptible operation, and you can guarantee that the interruptible operation will only block for a short period of time.
uninterruptibleMask_ :: IO a -> IO a
base Control.Exception.Base, base Control.Exception
Like uninterruptibleMask, but does not pass a restore action to the argument.
Unmasked :: MaskingState
base Control.Exception.Base, base Control.Exception
asynchronous exceptions are unmasked (the normal state)
forkOnIOUnmasked :: Int -> IO () -> IO ThreadId
base GHC.Conc.Sync, base GHC.Conc
Like forkOnIO, but the child thread is created with asynchronous exceptions unmasked (see Control.Exception.mask).
tAG_MASK :: Int
base GHC.Constants