RFR 8209184: JDK8 ResourceBundle vulnerable to GC (fix included)

[Hans Boehm]

FWIW, since there was agreement that empty static methods should work in
this context, that seems like the best option to me.

On Tue, Aug 14, 2018 at 4:54 PM mandy chung <mandy.chung at oracle.com> wrote:

> Thanks for the information.  Not sure what's the best option we can do
> in 8u.  I think it's acceptable to have a fix that works in the
> current context (like empty static method).
>
> Thoughts?
>
> Mandy
>
> On 8/14/18 4:22 PM, Hans Boehm wrote:
> > I haven't looked at the details here, but comparing against a volatile
> > is not in general a portable way to keep an object live. Like empty
> > static methods, it may be fine in the current (OpenJDK) context.
> >
> > Volatile loads have roach motel semantics and can be advanced past other
> > operations. The comparison can be done early, too, keeping only the
> > condition code. There is no guarantee the reference will still be around
> > when you expect it.
> >
> > I haven't come up with a great compiler-independent replacement for
> > reachabilityFence.
> >
> > On Tue, Aug 14, 2018 at 8:25 AM mandy chung <mandy.chung at oracle.com
> > <mailto:mandy.chung at oracle.com>> wrote:
> >
> >     Hi Adam,
> >
> >     Have you tried Peter's suggestion if an empty static method taking an
> >     Object parameter?  Does it work for you?
> >
> >     Your proposed approach seems fine and I would suggest to put the
> >     check in a static keepAlive method that will make it explicitly.
> >
> >     Mandy
> >
> >     On 8/10/18 8:42 AM, Adam Farley8 wrote:
> >      > Hi All,
> >      >
> >      > This bug could be fixed by comparing the Class Loader with a blank
> >      > static volatile Object (defined outside the method scope) at the
> >      > end of the getBundleImpl class.
> >      >
> >      > E.g.
> >      >
> >      > -----------------------------------------
> >      > +1322
> >      >      /**
> >      >       * volatile reference object to guard the ClassLoader object
> >      >       * being garbage collected before getBundleImpl() method
> >     completes
> >      >       * the caching and retrieving of requested Resourcebundle
> object
> >      >       */
> >      >      private static volatile Object vo = new Object();
> >      >
> >      >
> >      > +1400
> >      > //Should never be true. Using the loader here prevents it being
> GC'd.
> >      >              if (loader == vo) throw new Error("Unexpected
> error.");
> >      > -----------------------------------------
> >      >
> >      > Will upload a webrev after debate.
> >      >
> >      > - Adam
> >      > Unless stated otherwise above:
> >      > IBM United Kingdom Limited - Registered in England and Wales with
> >     number
> >      > 741598.
> >      > Registered office: PO Box 41, North Harbour, Portsmouth,
> >     Hampshire PO6 3AU
> >      >
> >
>