RFR: 8253284: Zero OrderAccess barrier mappings are incorrect [v2]

[David Holmes]

On Thu, 17 Sep 2020 12:26:44 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> There are some jcstress failures with AArch64 Zero. It seems because to happen because `orderAccess_linux_zero.hpp`
>> defaults to compiler-only barriers for most OrderAccess::* calls. We need to defer to the strongest barriers by
>> default.   The code also needs some rearrangement to make the mappings clear.
>> 
>> jcstress seems to capture the bug, and seems to pass when bug is fixed. Since this is `zero`, we want only the
>> interpreter (compiler configs would be excessive). Release builds capture more samples.
>> $ wget https://builds.shipilev.net/jcstress/jcstress-tests-all-20200917.jar
>> $ build/linux-x86_64-server-release/images/jdk/bin/java -jar jcstress-tests-all-20200917.jar --jvmArgs "-Xint"
>> 
>> Testing:
>>  - [x] x86_64 Linux zero release jcstress run
>>  - [ ] x86_64 MacOS zero release jcstress run (volunteers, please?)
>>  - [x] AArch64 Linux zero release jcstress run
>>  - [x] PPC Linux zero release jcstress run
>>  - [ ] ARM32 Linux zero release jcstress run (don't have fast ARM32 hosts, ping @bulasevich ? It would seem ARM32 is
>>    broken already)
>
> Aleksey Shipilev has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Fix copy-paste omission in bsd_zero

Marked as reviewed by dholmes (Reviewer).

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PR: https://git.openjdk.java.net/jdk/pull/224