[jdk17u-dev] RFR: 8288663: JFR: Disabling the JfrThreadSampler commits only a partially disabled state

[Paul Hohensee]

On Fri, 24 Nov 2023 14:24:25 GMT, Dmitry Chuyko <dchuyko at openjdk.org> wrote:

> On 17u JFR sometimes continues to sample threads after recordings are closed. In particular that happens on Linux aarch64 when JFR streaming is used and only jdk.ExecutionSample event is enabled. Symptoms:
> 
> 
> [76.403s][debug][jfr      ] Recording "Recording Stream: 2023-11-21T14:57:07.651509569Z" (2) added chunk /tmp/2023_11_21_14_56_06_9044/2023_11_21_14_57_07.jfr, current size=4397790
> [76.404s][trace][jfr      ] Disenrolling thread sampler
> [76.404s][trace][jfr      ] Enrolling thread sampler
> [76.404s][trace][jfr      ] Updated thread sampler for java: 1  ms, native 0 ms
> 
> 
> This fix cures that enrolling after disenrolling. I'm not sure if related JDK-8295274 should be backported as well.
> 
> The patch was mostly applied cleanly but few hunks were replicated by hand without changes in their code.
> 
> Testing: tier1, tier2, jdk_jfr, gc/stress/jfr on (linux-aarch64 fastdebug).

I'd backport JDK-8295274 too.

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Marked as reviewed by phh (Reviewer).

PR Review: https://git.openjdk.org/jdk17u-dev/pull/1986#pullrequestreview-1750920295