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

[Mikael Gerdin]

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
>>>>
>>>
>>
>