Put it another way: does a static reference from a class to itself prevent that class from being garbage collected? Of course not. ClassValue is intended to be a way to inject pseudo-static data into either a class or a Class. Injecting that data, even if it has a reference back to the class, should not prevent the class from being collected.
On Fri, Mar 2, 2018 at 2:19 PM Charles Oliver Nutter <head...@headius.com> wrote: > I have posted a modified version of my description to the main bug report. > > TLDR: ClassValue should not root objects. > > - Charlie > > On Fri, Mar 2, 2018 at 2:13 PM Charles Oliver Nutter <head...@headius.com> > wrote: > >> Yes, it may be the same bug. >> >> In my case, the ClassValue is held by a utility object used for our Java >> integration. That utility object has to live somewhere, so it's held by the >> JRuby runtime instance. There's a strong reference chain leading to the >> ClassValue. >> >> The value is a Ruby representation of the class, with reflected methods >> parsed out and turned into Ruby endpoints. Obviously, the value also >> references the class, either directly or indirectly through reflected >> members. >> >> The Ruby class wrapper is only hard referenced directly if there's an >> instance of the object live and moving through JRuby. It may be referenced >> indirectly through inline caches. >> >> However...I do not believe this should prevent collection of the class >> associated with the ClassValue. >> >> The value referenced in the ClassValue should not constitute a hard >> reference. If it is alive *only* because of its associate with a given >> class, that should not be enough to root either the object or the class. >> >> ClassValue should work like ThreadLocal. If the Thread associated with a >> value goes away, the value reference goes away. ThreadLocal does nothing >> prevent it from being collected. If the Class associated with a Value goes >> away, the same should happen to that Value and it should be collectable >> once all other hard references are gone. >> >> Perhaps I've misunderstood? >> >> - Charlie >> >> On Fri, Mar 2, 2018 at 12:16 PM Vladimir Ivanov < >> vladimir.x.iva...@oracle.com> wrote: >> >>> Charlie, >>> >>> Does it look similar to the following bugs? >>> https://bugs.openjdk.java.net/browse/JDK-8136353 >>> https://bugs.openjdk.java.net/browse/JDK-8169425 >>> >>> If that's the same (and it seems so to me [1]), then speak up and >>> persuade Paul it's an important edge case (as stated in JDK-8169425). >>> >>> Best regards, >>> Vladimir Ivanov >>> >>> [1] new RubyClass(Ruby.this) in >>> >>> public static class Ruby { >>> private ClassValue<RubyClass> cache = new >>> ClassValue<RubyClass>() { >>> protected RubyClass computeValue(Class<?> type) { >>> return new RubyClass(Ruby.this); >>> } >>> }; >>> >>> On 3/1/18 2:25 AM, Charles Oliver Nutter wrote: >>> > So I don't think we ever closed the loop here. Did anyone on the JDK >>> > side confirm this, file an issue, or fix it? >>> > >>> > We still have ClassValue disabled in JRuby because of the rooting >>> issues >>> > described here and in https://github.com/jruby/jruby/pull/3228. >>> > >>> > - Charlie >>> > >>> > On Thu, Aug 27, 2015 at 7:04 AM Jochen Theodorou <blackd...@gmx.org >>> > <mailto:blackd...@gmx.org>> wrote: >>> > >>> > One more thing... >>> > >>> > Remi, I tried your link with my simplified scenario and it does >>> there >>> > not stop the collection of the classloader >>> > >>> > Am 27.08.2015 11:54, schrieb Jochen Theodorou: >>> > > Hi, >>> > > >>> > > In trying to reproduce the problem outside of Groovy I stumbled >>> > over a >>> > > case case which I think should work >>> > > >>> > > public class MyClassValue extends ClassValue { >>> > > protected Object computeValue(Class type) { >>> > > Dummy ret = new Dummy(); >>> > > Dummy.l.add (this); >>> > > return ret; >>> > > } >>> > > } >>> > > >>> > > class Dummy { >>> > > static final ArrayList l = new ArrayList(); >>> > > } >>> > > >>> > > basically this means there will be a hard reference on the >>> ClassValue >>> > > somewhere. It can be in a static or non-static field, direct or >>> > > indirect. But this won't collect. If I put for example a >>> > WeakReference >>> > > in between it works again. >>> > > >>> > > Finally I also tested to put the hard reference in a third class >>> > > instead, to avoid this self reference. But it can still not >>> collect. >>> > > >>> > > So I currently have the impression that if anything holds a hard >>> > > reference on the class value that the classloader cannot be >>> collected >>> > > anymore. >>> > > >>> > > Unless I misunderstand something here I see that as a bug >>> > > >>> > > bye blackdrag >>> > > >>> > >>> > >>> > -- >>> > Jochen "blackdrag" Theodorou >>> > blog: http://blackdragsview.blogspot.com/ >>> > >>> > _______________________________________________ >>> > mlvm-dev mailing list >>> > mlvm-dev@openjdk.java.net <mailto:mlvm-dev@openjdk.java.net> >>> > http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev >>> > >>> > -- >>> > >>> > - Charlie (mobile) >>> > >>> > >>> > >>> > _______________________________________________ >>> > mlvm-dev mailing list >>> > mlvm-dev@openjdk.java.net >>> > http://mail.openjdk.java.net/mailman/listinfo/mlvm-dev >>> > >>> >> -- >> >> - Charlie (mobile) >> > -- > > - Charlie (mobile) > -- - Charlie (mobile)
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