RFR 8038797: JVMTI FollowReferences does not report roots reachable from nmethods

[Coleen Phillimore]

Thanks, Mikael,
Coleen

On 8/22/16 4:22 AM, Mikael Gerdin wrote:
> Hi Coleen,
>
> On 2016-08-11 22:34, Coleen Phillimore wrote:
>>
>> Thanks, Dean.
>> Coleen
>>
>> On 8/11/16 4:10 PM, dean.long at oracle.com wrote:
>>> On 8/11/16 12:54 PM, Coleen Phillimore wrote:
>>>
>>>>
>>>>
>>>> On 8/11/16 2:32 PM, dean.long at oracle.com wrote:
>>>>> Can you make it work for any CompiledMethod and not just nmethods?
>>>>
>>>> Dean, I tried to do this but CompiledMethod didn't have any oops_do
>>>> function.
>>>
>>> Oh right, I was thinking it did because of some experiments I had made
>>> in that area.
>>>
>>>>>
>>>>> I believe oops_do() also picks up klass_holder() oops that were
>>>>> added to keep metadata references alive.
>>>>
>>>> Yes, it does.
>>>>
>>>>> So for those you will most likely get a ClassLoader and not the
>>>>> Class object.  To get the Class object I think you would need to use
>>>>> something like metadata_do(). Does FollowReferences care either way?
>>>>
>>>> No, FollowReferences really wants the oops and you can use the oops
>>>> to find out which Class objects (java.lang.Class) and ClassLoaders
>>>> are alive.   FollowReferences doesn't follow any metadata for 
>>>> anything.
>>>>
>>>
>>> OK, this change looks good to me.
>>>
>>> dl
>>>
>>>> Coleen
>>>>
>>>>>
>>>>> dl
>>>>>
>>>>> On 8/11/16 10:44 AM, Coleen Phillimore wrote:
>>>>>> Summary: Also follow nmethods found on the execution stack.
>>>>>>
>>>>>> I have this fix to follow nmethods found on the execution stack but
>>>>>> not really a good way to test it.  There are two tests internally
>>>>>> that exercise this code and with some printing, I verified that
>>>>>> they do the right thing.   I am open to suggestions how to test
>>>>>> this, it requires compiled methods on the stack with oops that are
>>>>>> only referenced from said methods in the oop section (not in locals
>>>>>> or on stack).
>>>>>>
>>>>>> Also ran the tonga colocated/non-colocated internal tests,
>>>>>> jdk/test/com/sun/jdi.
>>>>>>
>>>>>> scp -r /home/cphillim/home/public_html/webrev/8038797.01
>>>>>> coleenp at cr.openjdk.java.net:
>>>>>> open webrev at http://cr.openjdk.java.net/~coleenp/8038797.01/webrev
>
> Looks ok to me.
>
> Thanks for taking care of this.
> /Mikael
>
>>>>>>
>>>>>>
>>>>>> thanks,
>>>>>> Coleen
>>>>>
>>>>
>>>
>>