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

[Serguei Spitsyn]

On Wed, 29 Mar 2023 10:16:39 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> src/hotspot/share/prims/jvmtiEnvBase.cpp line 1554:
>> 
>>> 1552:       // Correct jt->jvmti_thread_state() and jt->jvmti_vthread() if necessary.
>>> 1553:       // It was not maintained while notifyJvmti was disabled.
>>> 1554:       if (jt_state != ct_state && jt_state != vt_state) {
>> 
>> Is it possible that jt_state == ct_state while the virtual thread is executed or vice versa? Just because jvmtt_state is outdated.
>> Shouldn't we always update (set to null) link/ jvmti_vthread if _enabled  == true?
>
> A1: Not sure, I understand your first question correctly. What does mean "vice versa" in this context?
> When `notifyJvmti` events is disabled then a call to `rebind_to_jvmti_thread_state_of` is omitted in VTMS transitions. So, we need to correct it if necessary. It can be `jt_state == ct_state` while the virtual thread is executed in a mount/unmount transition. I keep thinking on how to make this fixup more precise.
> 
> A better approach would be something like this:
> 
>       if (virt) {
>         if (jt_state != vt_state) {
>           jt->set_jvmti_thread_state(vt_state); // restore jt->jvmti_thread_state()
>           jt->set_jvmti_vthread(vt_oop);        // restore jt->jvmti_vthread()
>           if (vt_state != nullptr) {
>             vt_state->set_thread(jt);           // restore JavaThread link
>           }
>         }
>       } else { // !virt
>         if (jt_state != ct_state) {
>           jt->set_jvmti_thread_state(ct_state); // restore jt->jvmti_thread_state()
>           jt->set_jvmti_vthread(nullptr);       // reset jt->jvmti_vthread()
>         }
>       }
> 
> But it does not work correctly now. Some adjustment is needed to make it working.
> 
>> Shouldn't we always update (set to null) link/ jvmti_vthread if _enabled == true?
> 
> A2: Ideally, all these corrections are only needed for the case: `_enable == true.` I'm testing this now.

I've updated this part. Please. let me know if you still have some questions.

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PR Review Comment: https://git.openjdk.org/jdk/pull/13133#discussion_r1152304909