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

[Stefan Karlsson]

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:
>  - [ ] Linux x86_64 service fastdebug, `all`
>  - [ ] Linux AArch64 service fastdebug, `all`

Looks good to me. Thanks for fixing this.

For those not reading the JBS entry: We might want to do a follow-up to limit the usage of the Service_lock so that we don't hold it while processing the JVMTI oops.

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Marked as reviewed by stefank (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/19800#pullrequestreview-2129957643