RFR: 8325137: com/sun/management/ThreadMXBean/ThreadCpuTimeArray.java can fail in Xcomp with out of expected range [v2]

[Serguei Spitsyn]

On Fri, 2 Feb 2024 07:38:24 GMT, Doug Simon <dnsimon at openjdk.org> wrote:

>> The `com/sun/management/ThreadMXBean/ThreadCpuTimeArray.java` can transiently fail when run with `-Xcomp`. This happens when the compilation of methods on the worker threads interleaves with the 2 calls on the main thread to `mbean.getThreadCpuTime` to get the CPU time for all worker threads.
>> 
>> The way the test is currently written, the worker threads are all usually waiting on a shared monitor when the 2 timings are taken. That is, in a successful run, the delta between the timings is always 0. When `-Xcomp` compilations kick in at the "wrong" time or take sufficiently long, the expected delta of 100 nanoseconds is easily exceeded.
>> 
>> It does not make sense to run a timing test with such a small expected delta with `-Xcomp` so this PR simply ignores the test when `-Xcomp` is present.
>
> Doug Simon has updated the pull request incrementally with one additional commit since the last revision:
> 
>   fix date in header

Looks good. Thank you for fixing!

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Marked as reviewed by sspitsyn (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17675#pullrequestreview-1858895296