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

[Leonid Mesnik]

On Wed, 20 Mar 2024 22:03:30 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> The `JvmtiHandshake` and `JvmtiUnitedHandshakeClosure` classes were introduced in the JDK 22 to unify/simplify the JVM TI functions supporting implementation of the virtual threads. This enhancement is to refactor JVM TI functions `GetOwnedMonitorInfo` and `GetOwnedMonitorStackDepthInfo` on the base of `JvmtiHandshake and `JvmtiUnitedHandshakeClosure` classes.
>> 
>> Testing:
>>  - Ran mach5 tiers 1-6
>
> Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review: work around problem for vthreads in EscapeBarrier::deoptimize_objects

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.

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PR Review Comment: https://git.openjdk.org/jdk/pull/18332#discussion_r1532988358