Re: [Sablevm-developer] Question about _svmf_stopping_java()

[Archie C. <ar...@de...>]

Archie Cobbs wrote:
> > > However, I don't think this really gives you much advantage. It lets
> > > a thread continue in native mode instead of halting, but it probably
> > > is not going to get much further before having to come back to java mode
> > > and then halt anyway. Just a thought experiment really.
> > 
> > Theoretically, it could quite possibly work (I would have to think carefully
> > about all corner cases, but there's no deep reason it wouldn't work), but
> > practically, I don't see much benefit.  Current code simply depends on
> > the well tested _svmf_halt_if_requested().  Adding custom code for such critical
> > and difficult to write correctly code (even though it is short, it is very
> > tricky) is not something I look forward to. :-)
> 
> I hear you :-) Simplicity is sometimes it's own reward..

Actually I forgot to mention my original thought. I think the following
statement is true:

  If it is not safe to let halting threads enter native mode,
  then SableVM currently has a bug.

The reasoning is simple: pending_halt_thread_count only counts threads
that are running in Java mode. When it reaches zero, you consider the
world halted, yet there may very well be threads running in native mode
that had already entered native mode when stop_the_world() was called
(and so they didn't count in the pending_halt_thread_count total).

So if that's the case, then my idea of allowing halting threads to enter
native mode should not be adding any bugs that aren't already there.
Am I making any sense? :-)

Thanks,
-Archie

__________________________________________________________________________
Archie Cobbs     *    Halloo Communications    *     http://www.halloo.com