RFR: 8297286: runtime/vthread tests crashing after JDK-8296324 [v8]

[Patricio Chilano Mateo]

On Tue, 28 Mar 2023 18:57:23 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:
> 
>   fixed trailing spaces in two files

src/hotspot/share/prims/jvmtiEnvBase.cpp line 1550:

> 1548: 
> 1549:       if (jt->is_in_VTMS_transition()) {
> 1550:         count++;

For those threads that are in a transition when we enable the events, shouldn't we also set the jvmti_is_in_VTMS_transition field for the corresponding vthread as we do in JvmtiVTMSTransitionDisabler::start_VTMS_transition()? It seems a JvmtiVTMSTransitionDisabler that targets that particular vthread could otherwise proceed after the safepoint while that vthread is still in the transition. The "all" JvmtiVTMSTransitionDisabler won't proceed because that one does check the _VTMS_transition_count counter. I see that in general we won't have access to the vthread oop though.

-------------

PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1151313147