RFR (S): 8011803: release_C_heap_structures is never called for anonymous classes.

Coleen Phillimore coleen.phillimore at oracle.com
Fri Apr 12 04:54:31 PDT 2013

On 4/11/2013 10:21 PM, David Holmes wrote:
> Hi Coleen,
> Can you clarify something for me please. ClassLoaderData::unload() is 
> what now cleans up the anonymous classes - correct? But 
> ClassLoaderData::unload() is only called when the ClassLoader is 
> unloaded - correct? And the whole point of anonymous classes is that 
> they get unloaded independent of the classloader lifecycle. Assuming 
> I'm correct so far it seems to me that if the classloader is never 
> unloaded, the anonymous classes still won't have 
> release_C_heap_structures called. And if it is unloaded it could be 
> well after the classes were unloaded.

Hi David,

Yes, anonymous classes do get unloaded independent of the class loader 
lifecycle, but they get their own ClassLoaderData when created.   This 
ClassLoaderData is tied to the lifetime of the anonymous class's mirror, 
so when the mirror is unreferenced, the CLD will get unloaded.    With 
anonymous classes there is not a 1-1 relationship between object of 
java/lang/ClassLoader and CLD.

I did it this way because otherwise the metadata for the anonymous 
classes is never reclaimed (or reclamation would have to walk the CLD 
graph and put holes in the metaspaces).


> David
> On 12/04/2013 6:52 AM, Coleen Phillimore wrote:
>> Summary: Call this function from CLD::unload()  now for anonymous 
>> classes.
>> Anonymous classes aren't in the system dictionary so
>> release_C_heap_structures isn't called for them if they are unloaded.  I
>> fixed this for jdk8 because they are in the class loader data graph but
>> for jdk7, I don't know how to fix this.  They are unloaded by being
>> garbage collected after the references are dropped.
>> Tested with ute tests vm.mvlm.testlist nsk.monitoring.testlist and
>> jdk/test/java/lang/invoke tests.
>> open webrev at http://cr.openjdk.java.net/~coleenp/8011803/
>> bug link at http://bugs.sun.com/view_bug.do?bug_id=8011803
>> Thanks,
>> Coleen

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