RFR: 8038925: Java 7 with G1 crashes in dump_instance_fields using jmap or jcmd without fullgc

[Andreas Eriksson]

In addition, this particular test doesn't reproduce on jdk8 or jdk9 for 
some reason.
I will take a quick look and see if I can spot why.

/Andreas

On 2014-04-25 15:14, Mikael Gerdin wrote:
> On Friday 25 April 2014 14.53.29 Thomas Schatzl wrote:
>> Hi,
>>
>> On Fri, 2014-04-25 at 14:17 +0200, Andreas Eriksson wrote:
>>> Hi,
>>>
>>> Could I have a review for this G1 jdk7 only fix please?
>>    why is this change only necessary for jdk7?
> The idea was that for 9 and 8u40+ we will need a separate way to handle this
> anyway due to class unloading (as previously discussed).
>
> We may or may not want to get this fix into 8u20, I'd like to hear your input
> on that Thomas.
>
> /Mikael
>
>>> Description:
>>> When using G1 and doing a heap dump while no fullgc has been done,
>>> hotspot crashes.
>>> This is because G1CollectedHeap::safe_object_iterate uses
>>> ContiguousSpace::object_iterate_from, which does not avoid dead objects
>>> that can still be on the heap when using G1.
>>>
>>> The fix adds a G1 specific safe_object_iterate code path that avoids
>>> dead objects.
>>>
>>> http://cr.openjdk.java.net/~aeriksso/8038925/webrev.00/
>>> https://bugs.openjdk.java.net/browse/JDK-8038925
>>>
>>> Thanks to Mikael Gerdin for his help with this.
>> Thanks,
>> Thomas