RFR: 8350572: ZGC: Enhance z_verify_safepoints_are_blocked interactions with VMError

[Stefan Karlsson]

On Thu, 27 Feb 2025 11:15:52 GMT, Axel Boldt-Christmas <aboldtch at openjdk.org> wrote:

> If VMError reporting is triggered from a disallowed  thread state `z_verify_safepoints_are_blocked` will cause reentrant assertions to be triggered, when for example when loading the thread oop as part of thread printing. This extends the verification to be ignored if triggered from the thread doing the error reporting. In most cases performing the load barriers from disallowed thread states during error reporting will work.
> 
> Testing:
>  - tier 1 Oracle supported platforms
>  - GHA

Marked as reviewed by stefank (Reviewer).

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PR Review: https://git.openjdk.org/jdk/pull/23820#pullrequestreview-2664717938