RFR: 8298853: JvmtiVTMSTransitionDisabler should support disabling one virtual thread transitions [v5]

[Serguei Spitsyn]

On Wed, 8 Feb 2023 22:17:34 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

>> Serguei Spitsyn has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   fix race between VTMS_transition_disable_for_one and start_VTMS_transition
>
> src/hotspot/share/prims/jvmtiThreadState.cpp line 479:
> 
>> 477: 
>> 478:   // Unblock waiting VTMS transition disablers.
>> 479:   if (_VTMS_transition_disable_for_one_count > 0 ||
> 
> In here it would actually be the other way. If we would check java_lang_Thread::VTMS_transition_disable_count(vth()) > 0 instead of the global _VTMS_transition_disable_for_one_count we would avoid the notify in case there are singler disablers waiting but not for this thread.

Good comment.
Yes, I considered the same as you about to suggest.
It is on my plan to work on optimization of these fragments.
Will keep in mind this your comment.

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