RFR: 8288327: Executable.hasRealParameterData should not be volatile [v4]

[Сергей Цыпанов]

> If there are two threads calling `Executable.hasRealParameterData()` under race and the first one writes into volatile `Executable.parameters` field (doing _releasing store_) and the second thread reads non-null value from the same field (doing acquiring read) then it must read exactly the same value written into `hasRealParameterData` within `privateGetParameters()`. The reason for this is that we assign `hasRealParameterData` before  _releasing store_.
> 
> In the opposite case (_acquiring read_ reads null) the second thread writes the value itself and returns it from the method so there is no change in behavior.

Сергей Цыпанов has updated the pull request incrementally with one additional commit since the last revision:

  8288327: Mark ParameterData.parameters as @Stable and rename real -> isReal

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9143/files
  - new: https://git.openjdk.org/jdk/pull/9143/files/076cde01..8ead0357

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9143&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9143&range=02-03

  Stats: 2 lines in 1 file changed: 0 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/9143.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9143/head:pull/9143

PR: https://git.openjdk.org/jdk/pull/9143