[jdk21u-dev] RFR: 8321075: RISC-V: UseSystemMemoryBarrier lacking proper OS support

[Ludovic Henry]

8321075: RISC-V: UseSystemMemoryBarrier lacking proper OS support

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Commit messages:
 - Backport 68eb5a1df5afdc011aa467f1c723a8792532dd3f

Changes: https://git.openjdk.org/jdk21u-dev/pull/294/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u-dev&pr=294&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8321075
  Stats: 40 lines in 3 files changed: 39 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk21u-dev/pull/294.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u-dev.git pull/294/head:pull/294

PR: https://git.openjdk.org/jdk21u-dev/pull/294