RFR: 8292407: Improve Weak CAS VarHandle/Unsafe tests resilience under spurious failures [v4]

[Aleksey Shipilev]

On Fri, 19 Aug 2022 18:14:16 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

>> We have a few reports that existing Weak* VarHandle tests are still flaky, for example on large AArch64 machines or small RISC-V machines.
>> 
>> The flakiness is intrinsic to the nature of Weak* operations under tests, that can spuriously fail. The last attempt to fix these was [JDK-8155739](https://bugs.openjdk.org/browse/JDK-8155739). We need to strengthen these a bit more.
>> 
>> The actual values depend on the successful testing on known-failing platforms. I ballparked bumping the attempts 5x and introducing the delay would help without exploding test time in worst cases.
>
> Aleksey Shipilev has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains six commits:
> 
>  - Rework timeouts
>  - Merge branch 'master' into JDK-8292407-varhandle-weak-resilient
>  - Merge branch 'master' into JDK-8292407-varhandle-weak-resilient
>  - Update copyrights
>  - Also do Unsafe tests
>  - Fix

I have found the related RISC-V issue that makes the tests very slow -- https://github.com/openjdk/jdk/pull/9970 -- I think we should let that one first, and then reconsider what backoffs we do here. Looks to me with that patch, HiFive Unmatched is fine with 1ms backoff delay, not 100ms as this PR proposes.

-------------

PR: https://git.openjdk.org/jdk/pull/9889