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

[Martin Doerr]

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

In general, I appreciate making these tests more resilient.
However, I wonder about such large numbers for retry attempts. Smells like more than just sporadic failures. Are we sure there is no bug which causes more failures? Does it really make sense to have a weak implementation on platforms with such high failure rates?

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