RFR: 8309688: Data race on java.io.ClassCache$CacheRef.strongReferent [v2]

[Man Cao]

> Hi all,
> 
> Could anyone review this small fix for a data race in java.io.ClassCache$CacheRef? This fix makes the code safer by making the code data-race-free.

Man Cao has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains two additional commits since the last revision:

 - Merge branch 'master' into JDK8309688
 - 8309688: Data race on java.io.ClassCache.strongReferent

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

Changes:
  - all: https://git.openjdk.org/jdk/pull/14386/files
  - new: https://git.openjdk.org/jdk/pull/14386/files/daef2b22..3b6d0baf

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=14386&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=14386&range=00-01

  Stats: 6835 lines in 318 files changed: 3989 ins; 1447 del; 1399 mod
  Patch: https://git.openjdk.org/jdk/pull/14386.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/14386/head:pull/14386

PR: https://git.openjdk.org/jdk/pull/14386