2 issues and 1 proposal for runInUnboundThread

[Bas van Dijk]

On Fri, Oct 15, 2010 at 12:00 AM, Bas van Dijk <v.dijk.bas at gmail.com> wrote:
> Hello,
>
> I found two small issues in Control.Concurrent:
>
> * Both runInBoundThread and runInUnboundThread use throw instead of
> throwIO. It's nicer to use throwIO in an IO context instead of throw
> because it guarantees ordering with respect to other IO actions.
>
> * runInUnboundThread explicitly checks the blocked status of the
> current thread which is redundant because mask also performs this
> check.
>
> I also have a new proposal:
>
> When you throw an asynchronous exception to a thread which is
> executing: `runInUnboundThread m`, m will keep executing and there's
> no way to kill it.
>
> I propose to catch asynchronous exceptions in runInUnboundThread and
> throw them to the thread which is executing m. m in turn can decide to
> catch or ignore them. In case m decides to ignore them or to rethrow
> them, the exception will be rethrown in the current thread:
>
> runInUnboundThread :: IO a -> IO a
> runInUnboundThread action = do
>  bound <- isCurrentThreadBound
>  if bound
>    then do
>      mv <- newEmptyMVar
>      mask $ \restore -> do
>        tid <- forkIO $ Exception.try (restore action) >>= putMVar mv
>        let wait = takeMVar mv `Exception.catch` \(e :: SomeException) ->
>                     Exception.throwTo tid e >> wait
>        wait >>= unsafeResult
>    else action
>
> unsafeResult :: Either SomeException a -> IO a
> unsafeResult = either Exception.throwIO return
>
> The patch bundle attached to the ticket fixes the two issues and
> implements the above behavior.
>
> Discussion deadline:
>
> I don't think the fixes for the issues need discussion. They only need
> a review from one of the GHC devs.
>
> With regard to the proposal I propose a discussion deadline of 2 weeks
> from now: Thursday 28 October.
>
> Ticket: http://hackage.haskell.org/trac/ghc/ticket/4400
>
> Regards,
>
> Bas
>

There're 2 days left for this proposal. Any more opinions?

Thanks,

Bas