[master] RFR: OMWorld: Cleanup ObjectMonitor::_header [v4]

[Roman Kennke]

On Tue, 23 Apr 2024 17:24:50 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

>> This changes the `ObjectMonitor::_header` to `ObjectMonitor::_metadata` and cleans up the surrounding terminology. 
>> 
>> Parts of this could be upstreamed, but the distinction of this field between the different locking modes is introduced in OMWorld. 
>> 
>> This patch will conflict with Lilliput if rebased on-top of OMWorld because Lilliput introduces `static ByteSize header_offset()` which is not used after OMWorld.  They could probably be removed in both these patches.
>> 
>> This also changes all the fields to have the same access level (private) so that this can be a standard layout type.
>
> Axel Boldt-Christmas has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:
> 
>  - Merge remote-tracking branch 'upstream_lilliput/master' into lilliput-om-cleanup-objectmonitor-header
>  - Use variable directly in sizeof
>  - Update src/hotspot/share/runtime/objectMonitor.hpp
>    
>    Co-authored-by: Stefan Karlsson <stefan.karlsson at oracle.com>
>  - Cleanup ObjectMonitor::_header

Marked as reviewed by rkennke (Lead).

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PR Review: https://git.openjdk.org/lilliput/pull/161#pullrequestreview-2017875848