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{-# LANGUAGE CPP, MagicHash, BlockArguments, UnboxedTuples #-}
-- Test the atomic exchange primop.
-- We initialize a value with 1, and then perform exchanges on it
-- with two different values. At the end all the values should still
-- be present.
module Main ( main ) where
import Data.Bits
import GHC.Int
import GHC.Prim
import GHC.Word
import Control.Monad
import Control.Concurrent
import Foreign.Marshal.Alloc
import Foreign.Storable
import Data.List (sort)
import GHC.Exts
import GHC.Types
#include "MachDeps.h"
main = do
alloca $ \ptr_i -> do
poke ptr_i (1 :: Int)
w1 <- newEmptyMVar :: IO (MVar Int)
forkIO $ do
v <- swapN 50000 2 ptr_i
putMVar w1 v
v2 <- swapN 50000 3 ptr_i
v1 <- takeMVar w1
v0 <- peek ptr_i
-- Should be [1,2,3]
print $ sort [v0,v1,v2]
swapN :: Int -> Int -> Ptr Int -> IO Int
swapN 0 val ptr = return val
swapN n val ptr = do
val' <- swap ptr val
swapN (n-1) val' ptr
swap :: Ptr Int -> Int -> IO Int
swap (Ptr ptr) (I# val) = do
IO $ \s -> case (interlockedExchangeInt# ptr val s) of
(# s2, old_val #) -> (# s2, I# old_val #)
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