RFR: 8345543: Test serviceability/jvmti/vthread/StopThreadTest/StopThreadTest.java failed: expected JVMTI_ERROR_OPAQUE_FRAME instead of: 0

[Alan Bateman]

On Wed, 15 Jan 2025 07:48:07 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

> The problem is that the state of the target `vthread` is changed to `BLOCKED` too early. It is done in a constructor of helper object `JavaThreadBlockedOnMonitorEnterState` which sets the state of `vthread` to `JavaThreadStatus::BLOCKED_ON_MONITOR_ENTER`. The `vthread` is getting suspended in `try_preempt()` while calling `JvmtiVTMSTransitionDisabler::start_VTMS_transition()`, so does not become unmounted as it is expected by the failing test. Also, it seems that the base class of the `JavaThreadBlockedOnMonitorEnterState` is supporting just HotSpot  `JavaThread`'s and so, it is changing the carrier thread state only.
> 
> The fix is to move the definition of the `JavaThreadBlockedOnMonitorEnterState` object after block where `try_preempt()` is called.
> 
> Testing:
>  - Checked the failed test does not fail with the fix: `serviceability/jvmti/vthread/StopThreadTest/StopThreadTest.java`
>  - Ran mach5 tiers 1-6

Good to see that this turned out to be an easy change.

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Marked as reviewed by alanb (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/23125#pullrequestreview-2553416228