RFR: 8328285: GetOwnedMonitorInfo functions should use JvmtiHandshake [v4]

[Leonid Mesnik]

On Thu, 21 Mar 2024 01:01:22 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> src/hotspot/share/prims/jvmtiEnv.cpp line 1366:
>> 
>>> 1364:   }
>>> 1365: 
>>> 1366:   if (java_thread != nullptr) {
>> 
>> I am not sure why this check is needed at this level. It is duplication.The GetOwnedMonitorInfoClosure::do_vthread checks if thread is null (no-op for unmounted threads). 
>> Currently, the unmounted threads can't own monitor. But if it's changed we need to update this check as well as the implementation of handshakes.
>
> This is needed to avoid using the `EscapeBarrier` for unmounted virtual threads.
> But you are right there is a duplication here - thanks.
> The following check can be removed:
> 
> +GetOwnedMonitorInfoClosure::do_vthread(Handle target_h) {
> +  if (_target_jt == nullptr) {
> +    _result = JVMTI_ERROR_NONE;
> +    return;
> +  }
> 
> I've replaced it with an assert:
> 
>   assert(_target_jt != nullptr, "sanity check");

Thanks, that should work!

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PR Review Comment: https://git.openjdk.org/jdk/pull/18332#discussion_r1533118435