RFR: 8325303: Replace markWord.is_neutral() with markWord.is_unlocked()

[Stefan Karlsson]

On Wed, 7 Feb 2024 01:52:00 GMT, David Holmes <dholmes at openjdk.org> wrote:

> This is a small tidy up to try and remove confusion between checking `is_neutral` (a general state normally associated with a displaced markword in a "pristine" state) and `is_unlocked` (a specific state within the locking protocol). The underlying bit-pattern is the same and so these have been used somewhat synonymously/interchangeably.
> 
> A few comment tweaks too.
> 
> Testing: tiers 1-3 (sanity)
> 
> Thanks.

This seems reasonable to me. Are there any use-cases of `is_neutral()` left? Could you explain why we use `is_neutral()` there and not `is_locked()`?

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Marked as reviewed by stefank (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/17741#pullrequestreview-1979113931