RFR: JDK-8131600: heapdump/JMapHeap EXCEPTION_ACCESS_VIOLATION

Kim Barrett kim.barrett at oracle.com
Wed Jul 22 18:03:31 UTC 2015


On Jul 22, 2015, at 12:11 PM, Bengt Rutisson <bengt.rutisson at oracle.com> wrote:
> 
> On 2015-07-22 17:11, Kim Barrett wrote:
>> On Jul 22, 2015, at 8:12 AM, Bengt Rutisson <bengt.rutisson at oracle.com> wrote:
>>> 
>>> Hi everyone,
>>> 
>>> Could I have a couple of reviews for this patch to fix one of the critical nightly issues we are currently having?
>>> 
>>> http://cr.openjdk.java.net/~brutisso/8131600/webrev.00/
>>> https://bugs.openjdk.java.net/browse/JDK-8131600
>>> 
>>> Background
>>> […]
>> 
>>> Now, DumperSupport::dump_class_and_array_classes() actually calls InstanceKlass::signers() twice. The second time around we don't have an InstanceKlass but just a Klass. The Klass does not have the is_linked() method. I haven't tried to provoke that code to fail, but I assume it has the same problem. So, I added a java_class() != NULL check to that code to make it handle this case as well.
>> I think this change shouldn't be needed.
>> 
>> The klass involved is the result of array_klass_or_null(). That
>> shouldn't be able to return an incompletely initialized (array) klass.
> 
> Yes, I was discussing this a bit with Mikael and we weren't really sure. I think you are right, I'm just a bit worried about how fragile the class initialization seems to be.
> 
> But I'll remove this part of the fix. Let's just keep our eyes open if a crash in this area comes up again.

With that part backed out, change looks good to me.



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