RFR (S) 8232112: MDO extra_data_lock leaks during class unloading

[coleen.phillimore at oracle.com]

Thank you, David and Erik, for the reviews, and for Erik for noticing 
this bug!
Coleen

On 10/17/19 7:31 AM, Erik Österlund wrote:
> Hi Coleen
>
> Looks good. Thanks for fixing!
>
> /Erik
>
> On 2019-10-16 15:48, coleen.phillimore at oracle.com wrote:
>> Summary: call the MDO destructor during class unloading.
>>
>> Also moved the other C heap deallocation from method_data to 
>> release_C_heap_structures.  Methods won't have method_data unless 
>> they're deallocated from the InstanceKlass.  The other paths to 
>> deallocate_contents are before the method is called.
>>
>> Tested with tier1 all Oracle platforms, and tier2-6 on linux-x64.
>>
>> open webrev at 
>> http://cr.openjdk.java.net/~coleenp/2019/8232112.01/webrev
>> bug link https://bugs.openjdk.java.net/browse/JDK-8232112
>>
>> Thanks,
>> Coleen
>>
>>