RFR (S) 8218851: JVM crash in custom classloader stress test, JDK 12 & 13

[coleen.phillimore at oracle.com]

On 2/14/19 8:54 PM, David Holmes wrote:
> Hi Coleen,
>
> On 15/02/2019 2:58 am, coleen.phillimore at oracle.com wrote:
>> Summary: Handle NULL and unloaded constraint class in loader 
>> constraint table, also cope with unloaded but not cleaned out klass 
>> in loader constraint entries.
>
> Pardon my ignorance but how can an unloaded class still be involved in 
> a loader constraint?

The class can be not loaded yet, because we apparently add the klass to 
the loader constraint table before the is_loaded flag is set.  It can be 
already unloaded with concurrent class unloading because the table 
hasn't been cleaned out yet.   I put interesting bits of the stack trace 
in the bug report.
thanks,
Coleen

>
> Thanks,
> David
>
>> Tested overnight with the application that caused the crash.  Tested 
>> with hs tier1-6.   Tested JCKs with ZGC.
>>
>> open webrev at 
>> http://cr.openjdk.java.net/~coleenp/2019/8218851.01/webrev
>> bug link https://bugs.openjdk.java.net/browse/JDK-8218851
>>
>> Thanks,
>> Coleen