[jdk25u] RFR: 8358735: GenShen: block_start() may be incorrect after class unloading

[Kelvin Nilsen]

On Thu, 13 Nov 2025 22:39:11 GMT, Rui Li <duke at openjdk.org> wrote:

> Backport of JDK-8358735.
> 
> Backport is almost clean except that `atomic.hpp` was renamed to `atomicAccess.hpp` in later versions, and I had to resolve the conflict by retaining `atomic.hpp` import.
> 
> Tier1 - Tier3 passed.

Marked as reviewed by kdnilsen (no project role).

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PR Review: https://git.openjdk.org/jdk25u/pull/378#pullrequestreview-3475059536