[jdk21u] RFR: 8314551: More generic way to handshake GC threads with monitor deflation

[Roman Kennke]

On Mon, 2 Oct 2023 12:34:54 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Clean backport to to complement [JDK-8307236](https://bugs.openjdk.org/browse/JDK-8307236) that is already in JDK 21. There is no bugtail in JDK 22 so far. Attn @rkennke.
> 
> Additional testing:
>  - [x] macos-aarch64-server-fastdebug, `hotspot:tier1`

Looks good to me!

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Marked as reviewed by rkennke (Reviewer).

PR Review: https://git.openjdk.org/jdk21u/pull/222#pullrequestreview-1652730987