RFR (S) JDK-8162553: Crash in class unloading due to null CLD having a zero _keep_alive value

[Lois Foltan]

Thanks David!
Lois

On 8/9/2016 7:34 PM, David Holmes wrote:
> On 10/08/2016 8:09 AM, Lois Foltan wrote:
>>
>> On 8/9/2016 5:57 PM, Karen Kinnear wrote:
>>> Code looks good. Agree with David about comment about use - for the
>>> _keep_alive field: for
>>> loaders never unloaded (boot now, platform and application I would
>>> expect us to add), and for
>>> anonymous classes via reference count methods.
>>
>> Thank you Karen for the review.  I have improved upon the comments as
>> requested.
>>
>> Updated webrev at:
>>     http://cr.openjdk.java.net/~lfoltan/bug_jdk8162553.1/webrev/
>
> Looks ok.
>
> Thanks,
> David
>
>> Lois
>>
>>>
>>> thanks,
>>> Karen
>>>
>>>> On Aug 8, 2016, at 3:41 PM, Lois Foltan <lois.foltan at oracle.com> 
>>>> wrote:
>>>>
>>>> Hello,
>>>>
>>>> Please review the following fix:
>>>>
>>>> Webrev:
>>>> http://cr.openjdk.java.net/~lfoltan/bug_jdk8162553/webrev/
>>>>
>>>> Bug: Crash in class unloading due to null CLD having a zero
>>>> _keep_alive value
>>>> https://bugs.openjdk.java.net/browse/JDK-8162553
>>>>
>>>> Summary:
>>>> Limit the increment/decrement of the ClassLoaderData _keep_alive
>>>> field to just ClassLoaderData(s) created specifically for an
>>>> anonymous class.  Due to the uniqueness that no other class shares an
>>>> anonymous class' ClassLoaderData, no other non-GC thread has
>>>> knowledge of the anonymous class while it is being defined. By
>>>> limiting the increment/decrement to just ClassLoaderData(s) dedicated
>>>> to anonymous classes, the need to make this an atomic operation is
>>>> avoided.  This bug was exposed since java_lang_Class::create_mirror()
>>>> is multi-threaded once java.lang.Class is loaded during JVM start up.
>>>>
>>>> Testing:
>>>> Several runs of hotspot nightly testing and several iterations of
>>>> various tests that have exposed this issue.
>>>>
>>>> Thanks,
>>>> Lois
>>