RFR: 8299240: rank of JvmtiVTMSTransition_lock can be safepoint

[Coleen Phillimore]

On Tue, 21 Feb 2023 14:38:21 GMT, Coleen Phillimore <coleenp 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/jvmtiEnv.cpp line 932:
> 
>> 930:   JavaThread* current = JavaThread::current();
>> 931:   HandleMark hm(current);
>> 932:   Handle self_tobj = Handle(current, nullptr);
> 
> This doesn't have to have the assignment, which the compiler will optimize away anyway.
> 
> Handle self_tobj;
> 
> does the same thing.

Both local variables java_thread and thread_oop should be declared before line 939 so we don't have to worry about the oop being unhandled and java_thread is only used locally.

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