T5611 fails non-deterministically on OSX

Here is the test.

{-# LANGUAGE CPP,ForeignFunctionInterface #-}

import Control.Concurrent
import Foreign.C
import System.IO

#ifdef mingw32_HOST_OS
sleep n = sleepBlock (n*1000)
foreign import stdcall unsafe "Sleep" sleepBlock :: Int -> IO ()
#else
sleep n = sleepBlock n
foreign import ccall unsafe "sleep" sleepBlock :: Int -> IO ()
#endif

main :: IO ()
main = do
     hSetBuffering stdout LineBuffering

     tid <- forkIO $ do
         putStrLn "child: Sleeping"
         _ <- sleep 1

         -- The following lines should not happen after the killThread from the
         -- parent thread completes.  However, they do...
         -- putStrLn "child: Done sleeping"
         threadDelay 100000
         putStrLn "child: Done waiting"

     threadDelay 100000
     -- putStrLn $ "parent: Throwing exception to thread " ++ show tid
     throwTo tid $ userError "Exception delivered successfully"
     putStrLn "parent: Done throwing exception"

     threadDelay 200000

It occasionally fails with

=====> T5611(normal) 1 of 1 [0, 0, 0]
cd "./concurrent/should_run/T5611.run" &&  "/Users/matt/Documents/haskell/ghc/inplace/test   spaces/ghc-stage2" -o T5611 T5611.hs -dcore-lint -dcmm-lint -no-user-package-db -rtsopts -fno-warn-missed-specialisations -fshow-warning-groups -dno-debug-output  
cd "./concurrent/should_run/T5611.run" && ./T5611  
Actual stderr output differs from expected:
--- ./concurrent/should_run/T5611.run/T5611.stderr.normalised	2016-10-21 22:08:55.000000000 +0100
+++ ./concurrent/should_run/T5611.run/T5611.run.stderr.normalised	2016-10-21 22:08:55.000000000 +0100
@@ -1 +0,0 @@
-T5611: user error (Exception delivered successfully)
*** unexpected failure for T5611(normal)

Unexpected results from:
TEST="T5611"

I am marking it broken for now. Does anyone know why it is failing?

Trac metadata

Trac field	Value
Version	8.0.1
Type	Bug
TypeOfFailure	OtherFailure
Priority	normal
Resolution	Unresolved
Component	Compiler
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