[jdk17u-dev] RFR: 8278389: SuspendibleThreadSet::_suspend_all should be volatile/atomic

[Aleksey Shipilev]

Clean backport for GC reliability. Will wait a bit for mainline testing to catch up.

Additional testing:
 - [x] Linux x86_64 fastdebug `tier1`
 - [x] Linux x86_64 fastdebug `tier2`

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Commit messages:
 - Backport aec1b039b35b73db17c943cdd86949a92e64fcb6

Changes: https://git.openjdk.java.net/jdk17u-dev/pull/54/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk17u-dev&pr=54&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8278389
  Stats: 20 lines in 2 files changed: 5 ins; 1 del; 14 mod
  Patch: https://git.openjdk.java.net/jdk17u-dev/pull/54.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk17u-dev pull/54/head:pull/54

PR: https://git.openjdk.java.net/jdk17u-dev/pull/54