RFR: 8364343: Virtual Thread transition management needs to be independent of JVM TI [v3]

[Serguei Spitsyn]

On Thu, 20 Nov 2025 22:55:35 GMT, David Holmes <dholmes at openjdk.org> wrote:

>> Patricio Chilano Mateo has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   Add Alan's comment in VirtualThread
>
> src/hotspot/share/runtime/mountUnmountDisabler.cpp line 147:
> 
>> 145:       MonitorLocker ml(VTMSTransition_lock);
>> 146:       while (is_start_transition_disabled(current, vth())) {
>> 147:         ml.wait(200);
> 
> I see a lot of timed-waits throughout this code. Is that because we poll rather than synchronizing properly? All this potential busy-waiting is surely going to cause performance glitches.

The timeouts are for reliability purposes only. Technically, they are not needed and can be removed after this code becomes stable. The `wait()` calls are inside while loop which rechecks the loop-ending conditions.

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PR Review Comment: https://git.openjdk.org/jdk/pull/28361#discussion_r2552610777