RFR: 8297286: runtime/vthread tests crashing after JDK-8296324 [v13]

[Chris Plummer]

On Thu, 30 Mar 2023 17:10:16 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> The fix is to enable virtual threads support for late binding JVMTI agents.
>> The fix includes:
>> - New function `JvmtiEnvBase::enable_virtual_threads_notify_jvmti()` which does enabling JVMTI VTMS transition notifications in case of agent loaded into running VM. This function executes a VM operation counting VTMS transition bits in all `JavaThread`'s to correctly set the static counter `_VTMS_transition_count` needed for VTMS transition protocol.
>> - New function `JvmtiEnvBase::disable_virtual_threads_notify_jvmti()` which is needed for testing. It is used by the `WhiteBox` API.
>> - New WhiteBox function `WB_SetVirtualThreadsNotifyJvmtiMode(JNIEnv* env, jobject wb, jboolean enable)` needed for testing of this update.
>> - New regression test: `serviceability/jvmti/vthread/ToggleNotifyJvmtiTest`
>> 
>> Testing:
>> - New test: `serviceability/jvmti/vthread/ToggleNotifyJvmtiTest`
>> - The originally failed tests are expected to pass now:
>>   `runtime/vthread/RedefineClass.java`
>>   `runtime/vthread/TestObjectAllocationSampleEvent.java` 
>> - In progress: Run the tiers 1-6 to make sure there are no regression.
>
> Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review: tweak in count_transitions_and_correct_jvmti_thread_states

test/hotspot/jtreg/serviceability/jvmti/vthread/ToggleNotifyJvmtiTest/ToggleNotifyJvmtiTest.java line 90:

> 88:  *  - disable notifyJvmti events mode
> 89:  *  - start the platform launcher thread which starts N of virtual thread
> 90:  *  - enable notifyJvmti events mode after about hapf of virtual thread started

Suggestion:

 *  - enable notifyJvmti events mode after about half of the virtual threads have started

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PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1153843284