RFR: 8334594: Generational ZGC: Deadlock after OopMap rewrites in 8331572

[Aleksey Shipilev]

On Thu, 20 Jun 2024 09:11:04 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> As shown in the bug, there are cases when acquiring the `ServiceLock` for opportunistic notification leads to deadlock. We can untie the deadlock by checking if `ServiceLock` can be acquired on triggering path, and never blocking otherwise.
> 
> Additional testing:
>  - [x] Linux x86_64 service fastdebug, `all`
>  - [x] Linux AArch64 service fastdebug, `all`

All tests pass. I'll wait until 24 hours expire and then integrate.

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PR Comment: https://git.openjdk.org/jdk/pull/19800#issuecomment-2180802390