core/src/Streamly/Internal/Control/ForkIO.hs · streamly

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1{-# LANGUAGE UnboxedTuples #-}

3-- |

4-- Module : Streamly.Internal.Control.ForkIO

6-- License : BSD-3-Clause

7-- Maintainer : streamly@composewell.com

8-- Stability : experimental

9-- Portability : GHC

11module Streamly.Internal.Control.ForkIO

12 ( rawForkIO

13 , forkIOManaged

14 , forkManagedWith

15 )

16where

18import Control.Concurrent (ThreadId, forkIO, killThread)

19import Control.Monad.IO.Class (MonadIO(..))

20import GHC.Conc (ThreadId(..))

21import GHC.Exts

22import GHC.IO (IO(..))

23import System.Mem.Weak (addFinalizer)

25-- | Stolen from the async package. The perf improvement is modest, 2% on a

26-- thread heavy benchmark (parallel composition using noop computations).

27-- A version of forkIO that does not include the outer exception

28-- handler: saves a bit of time when we will be installing our own

29-- exception handler.

30{-# INLINE rawForkIO #-}

31rawForkIO :: IO () -> IO ThreadId

32rawForkIO (IO action) = IO $ \ s ->

33 case fork# action s of (# s1, tid #) -> (# s1, ThreadId tid #)

35-- | Fork a thread that is automatically killed as soon as the reference to the

36-- returned threadId is garbage collected.

38{-# INLINABLE forkManagedWith #-}

39forkManagedWith :: MonadIO m => (m () -> m ThreadId) -> m () -> m ThreadId

40forkManagedWith fork action = do

41 tid <- fork action

42 liftIO $ addFinalizer tid (killThread tid)

43 return tid

45-- | Fork a thread that is automatically killed as soon as the reference to the

46-- returned threadId is garbage collected.

48{-# INLINABLE forkIOManaged #-}

49forkIOManaged :: IO () -> IO ThreadId

50forkIOManaged = forkManagedWith forkIO