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

Andreas Eriksson andreas.eriksson at oracle.com
Wed May 21 09:36:47 UTC 2014


Thanks Mikael.

Could I have a review from a jdk7u Reviewer as well please?

/Andreas

On 2014-05-21 10:46, Mikael Gerdin wrote:
> Hi Andreas,
>
> On Tuesday 20 May 2014 16.26.40 Andreas Eriksson wrote:
>> Hi,
>>
>> Could I have a review for this G1 jdk7 only fix please?
>> (There is a related problem in jdk8 and jdk9, where an assert can fail
>> because of this problem. I have logged another bug for this.)
>>
>> Description:
>> Due to the marking cleanup reclaiming empty regions, and having stale
>> references a crash can occur when doing a heap dump.
>> The code tries to do an is_klass check on the object, which crashes the VM.
>> The fix is to add an is_perm check before doing the check, since is_perm
>> will do a bounds check on the oop and if it's in the perm gen we know
>> it's safe to look at it since G1 only ever does full compactions of the
>> perm gen.
>>
>> For more information, and a more in-depth analysis, please see the jira bug.
>>
>> http://cr.openjdk.java.net/~aeriksso/8038925/webrev.01/
> The change looks good to me.
>
> /Mikael
>
>> https://bugs.openjdk.java.net/browse/JDK-8038925
>>
>> Regards,
>> Andreas



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