RFR: 8298853: JvmtiVTMSTransitionDisabler should support disabling one virtual thread transitions [v2]

[David Holmes]

On Mon, 19 Dec 2022 12:50:11 GMT, Serguei Spitsyn <sspitsyn at openjdk.org> wrote:

>> Now the `JvmtiVTMSTransitionDisabler` mechanism supports disabling VTMS transitions for all virtual threads only. It should also support disabling transitions for any specific virtual thread as well. This will improve scalability of the JVMTI functions operating on target virtual threads as the functions can be executed concurrently without blocking each other execution when target virtual threads are different.
>> New constructor `JvmtiVTMSTransitionDisabler(jthread vthread)` is added which has jthread parameter of the target virtual thread.
>> 
>> Testing:
>>   mach5 jobs are TBD (preliminary testing was completed):
>>    - all JVMTI, JDWP, JDI and JDB tests have to be run
>>    - Kitchensink
>>    - tier5
>
> Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:
> 
>   review comments are addressed

src/hotspot/share/prims/jvmtiThreadState.hpp line 88:

> 86: 
> 87:   bool _is_SR;                                           // is suspender or resumer
> 88:   jthread _vthread;                                      // virtual thread to disable transitions for

Please don't call this `_vthread` as it may or may not be a virtual thread.

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PR: https://git.openjdk.org/jdk/pull/11690