> > I'd like to get forkProcess# fixed in 6.2, even if that
> means changing
> > the interface.
> >
> > First, could you explain exactly the problems with implementing the
> > current version of forkProcess? Do we only run into
> problems when we
> > try to implement forkProcess in the threaded RTS?
>
> We run into quite different problems whether we use the
> threaded RTS or
> not.
> With the non-threaded RTS, the current situation is that we keep not
> only the
> current thread, but also all other main threads.
> I think that we cannnot do better than that. Every main thread is due
> to a call-in into Haskell; all except the intial one are therefore
> indirectly caused by a safe foreign call out of Haskell.
> So we have the stack frames for each of these call-outs on the (only)
> OS thread's stack. As we can't remove a stack frame from the
> middle of
> the C stack, we cannot delete main threads. Period.
Couldn't we just fix this as follows:
Delete all other threads in the system (including main threads).
The thread that forked becomes a new main thread, but instead of
returning when it exits, the RTS will simply stop.
This is a small change to the semantics, but it should be easy to
implement and I doubt it will affect anybody currently using
forkProcess.
Cheers,
Simon
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