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

[David Holmes]

On Thu, 1 Feb 2024 18:25:33 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.

Excluding Xcomp mode seems the most practical/expedient solution.

Please update the 2023 copyright year to 2024.

Thanks.

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Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17675#pullrequestreview-1858173944