RFR: 8222422: vmTestbase/nsk/jdi/ClassLoaderReference/definedClasses tests failed with Unexpected Exception: null

[Jean Christophe Beyler]

Isn't that the point? The list returned could have unloaded classes  and we
can catch it via this exception (from the comment above the ReferenceType
interface):

 * Any method on <code>ReferenceType</code> or which directly or indirectly
takes
 * <code>ReferenceType</code> as parameter may throw
 * {@link ObjectCollectedException} if the mirrored type has been unloaded.

Turns out that even in the definedClasses, we can get that exception so we
should check for it while walking the reference types as well?
Jc

*From: *Chris Plummer <chris.plummer at oracle.com>
*Date: *Fri, May 10, 2019 at 9:09 PM
*To: *David Holmes, Daniil Titov, OpenJDK Serviceability

On 5/10/19 9:03 PM, Chris Plummer wrote:
> > On 5/10/19 8:59 PM, David Holmes wrote:
> >> Hi Daniil,
> >>
> >> On 11/05/2019 12:10 pm, Daniil Titov wrote:
> >>> Please review the change that fixes an intermittent failure of the
> >>> test.
> >>>
> >>> The tests checks the implementation of  the
> >>> com.sun.tools.jdi.ClassLoaderReference class. The problem here is
> >>> that while
> >>> com.sun.tools.jdi.ClassLoaderReferenceImpl.definedClasses() iterates
> >>> over all loaded classes to retrieve a classloader and compares it to
> >>> the current one, some of the classes might become unloaded and
> >>> garbage collected (e.g.
> >>> org.graalvm.compiler.nodes.InliningLog$$Lambda$41.899832640 or
> >>> jdk.internal.reflect.GeneratedConstructorAccessor1, etc.). If this
> >>> happens then the attempt to retrieve a classloader for the collected
> >>> class results in com.sun.jdi.ObjectCollectedException being thrown.
> >>
> >> That seems odd to me. If you have a reference to the Class then it
> >> can't be unloaded. I would not expect allClasses() to have
> >> weak-references, so a class should not be unloadable while you are
> >> examining it. Unless it is finding VM anonymous classes (which it
> >> should not!).
> >>
> > I was just typing up something similar. Shouldn't the test do a
> > vm.suspend() and then call disableCollection() on each class returned
> > by vm.allClasses()?
> Oh wait, this isn't a test. It's part of JDI. I guess it would be up to
> the user of ClassLoaderReference.definedClasses() to do the suspend. In
> fact I'm not sure there's much purpose in calling
> ClassLoaderReference.definedClasses() without suspending first. Even
> with your changes, the list returned can end up with references to
> unloaded classes.
>
> Chris
> >
> > Chris
> >> David
> >> -----
> >>
> >>> The fix catches this com.sun.jdi.ObjectCollectedException and
> >>> continues iterating over the rest of the classes.
> >>>
> >>> Webrev: http://cr.openjdk.java.net/~dtitov/8222422/webrev.01
> >>> Bug: https://bugs.openjdk.java.net/browse/JDK-8222422
> >>>
> >>> Thanks!
> >>> --Daniil
> >>>
> >>>
> >
> >
>
>
>

-- 

Thanks,
Jc
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