RFR: 8302206: Factor out duplicate G1VerificationClosure [v2]

[Thomas Schatzl]

On Sat, 11 Feb 2023 09:07:25 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   kbarrett review, indentation
>
> src/hotspot/share/gc/g1/heapRegion.cpp line 499:
> 
>> 497:         LogStream ls(log.error());
>> 498: 
>> 499:         MutexLocker x(ParGCRareEvent_lock, Mutex::_no_safepoint_check_flag);
> 
> [pre-existing] That's a weird name for a mutex that seems to only be used by G1.

Historically it had been used in CMS and G1 (and Serial, but I think it just got victimized here because of shared code), but since CMS is dead now... I'll rename it in a separate CR.

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PR: https://git.openjdk.org/jdk/pull/12511