RFR: JDK-8273902: Memory leak in OopStorage due to bug in OopHandle::release()

[Volker Simonis]

On Thu, 16 Sep 2021 19:27:40 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> Currently, `OopHandle::release()` is implemented as follows:
>> 
>> inline void OopHandle::release(OopStorage* storage) {
>>   if (peek() != NULL) {
>>     // Clear the OopHandle first
>>     NativeAccess<>::oop_store(_obj, (oop)NULL);
>>     storage->release(_obj);
>>   }
>> }
>> 
>> However, peek() returns NULL not only if the oop* `_obj` is NULL, but also when `_obj` points to a zero oop. In the latter case, the oop* `_obj` will not be released from the corresponding OopStorage and the slot it occupies will remain alive forever.
>> 
>> This behavior can be easily triggered with the `LeakTestMinimal.java` test which is attached to the [JBS issue](https://bugs.openjdk.java.net/browse/JDK-8273902)(thanks to Oli Gillespie from the Amazon Profiler team for detecting the issue and providing a reproducer).
>> 
>> This fix should probably also be downported to jdk17 as quickly as possible.
>
> Yes, please backport.  Thank you for fixing this.

@coleenp, @sspitsyn thanks for the quick review!

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PR: https://git.openjdk.java.net/jdk/pull/5549