RFR (S): 8182703: Correct G1 barrier queue lock orderings

[Erik Österlund]

Hi Thomas,

Thanks for the review.

On 2017-07-04 19:43, Thomas Schatzl wrote:
> Hi,
>
> On Mon, 2017-06-26 at 15:34 +0200, Erik Österlund wrote:
>> Hi,
>>
>> Webrev: http://cr.openjdk.java.net/~eosterlund/8182703/webrev.02/
>> Bug: https://bugs.openjdk.java.net/browse/JDK-8182703
>>
>    looks good apart from the comment at Monitor::event_types. It now
> contradicts itself from one sentence to the next ("special must be
> lowest" and then "oh no, after all access must be lowest"). Please try
> to find some better wording here :)

Agreed. Will fix and send out new webrev after I receive a reply to my 
reply to your other email. That turned into a more complicated sentence 
than I anticipated.

Thanks,
/Erik

>> The G1 barrier queues have very awkward lock orderings for the
>> following reasons:
>>
> [...]
>> I do recognize that long term, we *might* want a lock-free solution
>> or something (not saying we do or do not). But until then, the ranks
>> ought to be corrected so that they do not cause these problems
>> causing everyone to bash their head against the awkward G1 lock ranks
>> throughout the code and make hacks around it.
>>
>> Testing: JPRT with hotspot all and lots of local testing.
> Thanks,
>    Thomas
>