RFR: 8261407: ReflectionFactory.checkInitted() is not thread-safe [v7]

[liach]

On Fri, 11 Feb 2022 13:51:38 GMT, liach <duke at openjdk.java.net> wrote:

>> Upon review of [8261407](https://bugs.openjdk.java.net/browse/JDK-8261407), by design, duplicate initialization of ReflectionFactory should be safe as it performs side-effect-free property read actions, and the suggesting of making the `initted` field volatile cannot prevent concurrent initialization either; however, having `initted == true` published without the other fields' values is a possibility, which this patch addresses.
>> 
>> This simulates what's done in `CallSite`'s constructor for `ConstantCallSite`. Please feel free to point out the problems with this patch, as I am relatively inexperienced in this field of fences and there are relatively less available documents. (Thanks to https://shipilev.net/blog/2014/on-the-fence-with-dependencies/)
>
> liach has updated the pull request incrementally with two additional commits since the last revision:
> 
>  - The fast path should always come first. good lesson learned!
>    restore config field comments
>  - Try making the config a record and see if it works

mandy, does this patch look good? i added a comment to warn about indy for records so as to avoid future unintended problems, while the current setup looks safe.

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PR: https://git.openjdk.java.net/jdk/pull/6889