RFR: 8075466: Address not aligned in Klass::decode_klass_not_null

Eric Caspole eric.caspole at oracle.com
Mon Apr 13 14:20:07 UTC 2015

Looks good to me, and nice job with the helpful comments.


   85   // Can obj really have it's mark word set?  It's not in young gen...

The first "it's" should be "its"

On 4/12/2015 10:47 PM, Kim Barrett wrote:
> Please review this change to the filtering of SATB queue contents.
> The problem is that a SATB queue may contain a stale reference to an
> eagerly reclaimed humongous object.  Assert-conditional verification
> during full queue processing that all entries are oop's can now fail.
> We deal with this by eliminating the pre-filtering verification
> (removed call to ObjPtrQueue::verify_oops_in_buffer and removed that
> now unused function).  Instead, ObjPtrQueue::filter has been revised
> to be more careful about oop-ness assumptions, and to assert the
> oop-ness of entries that are retained.
> This is related to
> https://bugs.openjdk.java.net/browse/JDK-8073717
> which is another failure due to unexpected stuff in SATB queues as a
> result of eager reclaim of a humongous object.
> As an aside, ObjPtrQueue is now poorly named.  A followup CR will be
> filed to rename it to something like SATBQueue.
> CR:
> https://bugs.openjdk.java.net/browse/JDK-8075466
> Webrev:
> http://cr.openjdk.java.net/~kbarrett/8075466/webrev.00/
> Testing:
> local RefWorkload with -XX:+UseG1GC
> Aurora GC Nightly and VM quicktests with -XX:+UseG1GC

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