[Haskell-cafe] Re: System.Timeout problems

[Simon Marlow]

Neil Mitchell wrote:
> Hi
> 
> I'm using the System.Timeout module from base, copied into my local
> repo, so that I can work with GHC 6.6.1. My copy is at:
> http://www.cs.york.ac.uk/fp/darcs/catch/catch_1/System/TimeoutGHC.hs
> (but it is identical to the one in base)
> 
> Sadly, it doesn't seem to work for me. Here are the tests I've been
> using, the results I get, and what I would have liked. All are GHC 6.6
> on Windows.
> 
> -- TEST 1
> import System.TimeoutGHC
> 
> main :: IO ()
> main = do
>    r <- timeout (5 * 10^6) (putStrLn "here")
>    print r
> 
> Without -threaded:
> here >> Just () >> wait 5 seconds
> 
> Without -threaded:
> here >> wait 5 seconds >> Just ()
> 
> So, either way, I get a 5 second delay - not something I want.

I think you're using GHC 6.6, right?  6.6.1 with -threaded has a new 
implementation of threadDelay on Windows that eliminates the final 5 second 
wait.  The problem was that threadDelay used to spawn a new OS thread to do the 
sleep, and the RTS would refuse to shut down until all the threads had finished 
(the latter requirement was introduced to fix bug with DLL shutdown, grrr).  We 
still have a similar bug that affects I/O: 
http://hackage.haskell.org/trac/ghc/ticket/1177

Cheers,
	Simon