[gclist] Finalization and death notices
Tue, 9 Oct 2001 13:01:35 -0600
From: Boehm, Hans <email@example.com>
> > From: Greg Colvin [mailto:firstname.lastname@example.org]
> > From: Boehm, Hans <email@example.com>
> > > I think that some of what we're really talking about here
> > is the choice
> > > between three alternatives:
> > >
> > > 1) The collector directly runs finalizers from whichever
> > thread happened to
> > > allocate and invoke the collector. This is common in early Java
> > > implementations, but fundamentally broken. It leads to intermittent
> > > deadlocks and/or multiple threads in the same monitor.
> > Let's ignore this
> > > alternative. (Such a facility can sometimes be used to implement a
> > > reasonable one. But if it's there it shouldn't be exposed
> > to the user.)
> > Is this approach broken if it is done immediately after the last
> > pointer to an object goes away, as with reference counting?
> Yes. See http://www.hpl.hp.com/personal/Hans_Boehm/gc/det_destr.html .
> It breaks whenever the finalizer needs to acquire a lock that may be held
> during a pointer assignment. (Or when it should logically hold such a
> lock.) That's likely to happen whenever a finalizer updates a global
> user-level data structure.
OK. So this is why Limbo doesn't provide destructors except
for kernel objects?