RFR: 8202083: Remove explicit CMS checks in CardTableBarrierSet

[Kim Barrett]

> On Apr 27, 2018, at 4:41 AM, Erik Österlund <erik.osterlund at oracle.com> wrote:
> 
> Hi Kim,
> 
> Now that we reached an agreement on 8202082, may I assume we have reached an agreement here too?

Oh, right.  Yes.  Just needs the comment fix.

> 
> Thanks,
> /Erik
> 
> On 2018-04-23 23:29, Kim Barrett wrote:
>>> On Apr 20, 2018, at 10:50 AM, Erik Österlund <erik.osterlund at oracle.com> wrote:
>>> 
>>> Hi,
>>> 
>>> In CardTableBarrierSet, we sometimes need fencing due to the card table being scanned concurrently when using CMS with pre-cleaning. Rather than explicitly checking for those CMS flags in the generic CardTableBarrierSet class, it is preferrable to check the CardTable scanned_concurrently() property which reflects that better
>>> 
>>> Webrev:
>>> http://cr.openjdk.java.net/~eosterlund/8202083/webrev.00/
>>> 
>>> Bug:
>>> https://bugs.openjdk.java.net/browse/JDK-8202083
>>> 
>>> Thanks,
>>> /Erik
>> Isn't the correct predicate here
>> CardTableBarrierSet::card_mark_must_follow_store?
>> 
>> Also, the comment probably ought to be "generalized".
>> 
>> Also, CardTable::scanned_concurrently() seems misplaced. CardTable is
>> a data structure, scanned_concurrently is a usage policy. And the only
>> use of scanned_concurrently seems to be the implementation of
>> card_mark_must_follow_store. It seems like CardTableBarrierSet would
>> be a better place for that bit of information.