RFR 8055008: Clean up code that saves the previous versions of redefined classes

[serguei.spitsyn at oracle.com]

On 8/20/14 3:45 PM, Daniel D. Daugherty wrote:
> On 8/20/14 2:01 PM, Coleen Phillimore wrote:
>> On 8/20/14, 3:49 PM, serguei.spitsyn at oracle.com wrote:
>>>>
>>>> If an EMCP method is not running, should we save it on a previous 
>>>> version list anyway so that we can make it obsolete if it's 
>>>> redefined and made obsolete?
>>>
>>> I hope, Dan will catch me if I'm wrong...
>>>
>>> I think, we should not.
>>> An EMCP method can not be made obsolete if it is not running.
>>>
>>
>>
>> It should be this way otherwise we'd have to hang onto things forever.
>
> An EMCP method should only be made obsolete if a RedefineClasses() or
> RetransformClasses() operation made it so. We should not be leveraging
> off the obsolete-ness attribute to solve a life-cycle problem.
>
> In the pre-PGR world, we could trust GC to make a completely unused
> EMCP method collectible and eventually our weak reference would go
> away. Just because an EMCP method is not on a stack does not mean
> that it is not used so we need a different way to determine whether
> it is OK to no longer track an EMCP method.

Most likely, you are right.
But I'm not convinced yet. Sorry.
A convincing point would be a test that shows this behavior.
I understand that it is not an easy task to write such a test though.
However, such a test would serve nicely if we want a different way
to determine whether it is OK to no longer track an EMCP method.


Thanks,
Serguei

>
>
>>
>>> BTW, I'm reviewing the webrev too, but probably it'd be better to 
>>> switch to updated webrev after it is ready.
>>
>> Yes, this is a good idea.  I figured out why I made emcp methods 
>> obsolete, and I'm fixing that as well as Dan's comments. Thanks!
>
> Cool! I'm looking forward to the next review.
>
> Dan
>
>
>>
>> Coleen
>>
>>>
>>> Thanks,
>>> Serguei
>>
>