RFR: 8299240: rank of JvmtiVTMSTransition_lock can be safepoint

[Serguei Spitsyn]

On Tue, 21 Feb 2023 17:57:36 GMT, Patricio Chilano Mateo <pchilanomate at openjdk.org> wrote:

>> The rank of JvmtiVTMSTransition_lock is better to be safepoint instead of nosafepoint.
>> The fix includes removal of the function `check_vthread_and_suspend_at_safepoint` which is not needed anymore.
>> 
>> Testing:
>> mach5 jobs are in progress:
>>  Kitchensink, tiers1-6 (all JVMTI, JDWP, JDI and JDB tests have to be included)
>
> src/hotspot/share/prims/jvmtiThreadState.cpp line 301:
> 
>> 299:   }
>> 300:   MonitorLocker ml(JvmtiVTMSTransition_lock);
>> 301: 
> 
> Ah, before we were accessing the vthread oop fields while being blocked so this change actually fixes that.

Right. It is really hard to catch and track, so it is much better to avoid being blocked as it is dangerous.

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PR: https://git.openjdk.org/jdk/pull/12550