RFR: 8302354: InstanceKlass init state/thread should be atomic [v2]

[Robbin Ehn]

> Hi, please consider.
> 
> These states are read 'lock-less' should thus be atomic.
> Also the assert setting init thread state can be stricter.
> 
> Passes t1-4

Robbin Ehn has updated the pull request incrementally with one additional commit since the last revision:

  Re-align comments

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/12542/files
  - new: https://git.openjdk.org/jdk/pull/12542/files/595c2349..5cceddba

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=12542&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=12542&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/12542.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/12542/head:pull/12542

PR: https://git.openjdk.org/jdk/pull/12542