RFR: 8259021 avoid double racy reads from non-volatile fields of SharedSecrets

[Peter Levart]

See: https://bugs.openjdk.java.net/browse/JDK-8259021
See also discussion in thread: https://mail.openjdk.java.net/pipermail/core-libs-dev/2020-December/072798.html

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Commit messages:
 - 8259021 avoid double racy reads from non-volatile fields of SharedSecrets

Changes: https://git.openjdk.java.net/jdk/pull/1914/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=1914&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8259021
  Stats: 96 lines in 1 file changed: 50 ins; 0 del; 46 mod
  Patch: https://git.openjdk.java.net/jdk/pull/1914.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/1914/head:pull/1914

PR: https://git.openjdk.java.net/jdk/pull/1914