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From "Rana Dasgupta" <rdasg...@gmail.com>
Subject Re: [drlvm][regression] FAILED Linux x86: jdktools-test debug
Date Tue, 20 Nov 2007 17:29:55 GMT
On 11/20/07, Gregory Shimansky <gshimansky@apache.org> wrote:
> Eugene Ostrovsky wrote:
> > It seems that we have a regression.
> >
> > org.apache.harmony.jpda.tests.jdwp.Events.ClassUnloadTest
> > starts to fail from r596304 to r596371
> >So it seems that now that class unloading is enabled, JVMTI extension
> >event for class unloading has to be implemented to let this test pass.
> >The problem that I see here is that Sun's implementation passes a
> >reference to the unloaded class into event callback, so the reference is
> >still live (maybe weak?) at this point.
> >In our implementation there are no live references to the class objects
> >in VM part of the class unloading. There is even an assertion that
> >checks this in classloader.cpp:564.
> >There are two ways to fix this. First one is to create our own
> >implementation of class unloading event that wouldn't pass a reference
> >to the class being unloaded, just its name.

I am not very good with JVMTI semantics, but if it is OK to support an event
with the name only, I would vote for this. It is least intrusive.

>Second is to make references available in the VM part of class
> >unloading. But in this case agent may create a strong reference to the
> >class object, and class unloading has to be canceled (Actually, since
> >this event is an extension, it is not specified whether or not a strong
> >reference may be created).

This may be difficult to do in this implementation, since by the time the VM
gets back control in the class unloading cycle, it is possibly too late to
do this.


> Gregory

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