RFR: 8263107: PSPromotionManager::copy_and_push_safe_barrier needs acquire memory barrier [v2]

[Kim Barrett]

On Mon, 7 Jun 2021 14:48:11 GMT, Albert Mingkun Yang <ayang at openjdk.org> wrote:

>> Kim Barrett has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   avoid reloading forwardee
>
> src/hotspot/share/gc/parallel/psPromotionManager.inline.hpp line 308:
> 
>> 306:     }
>> 307: 
>> 308:     // don't update this before the unallocation!
> 
> This comment gives me the impression that there is some racy going on here, and deallocation and update to `new_obj` must be ordered this way. However, the actual reason is that  the old value of`new_obj` is used for deallocation. I think it's best to remove this comment; it doesn't really say anything interesting.

That comment went away as part of latest change to avoid reloading the forwardee.

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PR: https://git.openjdk.java.net/jdk/pull/4371