RFR: 8377000: [BACKOUT] JDK-8376126 G1: Convert remaining volatiles in G1ConcurrentMark to Atomic<T>

[David Holmes]

Revert "8376126: G1: Convert remaining volatiles in G1ConcurrentMark to Atomic<T>"

This reverts commit b60249882cc511a7fc9cf9ae11e8beb1602ea10f.

Thanks

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Commit messages:
 - Revert "8376126: G1: Convert remaining volatiles in G1ConcurrentMark to Atomic<T>"

Changes: https://git.openjdk.org/jdk/pull/29535/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=29535&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8377000
  Stats: 64 lines in 4 files changed: 0 ins; 10 del; 54 mod
  Patch: https://git.openjdk.org/jdk/pull/29535.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/29535/head:pull/29535

PR: https://git.openjdk.org/jdk/pull/29535