[jdk17u-dev] RFR: 8331735: UpcallLinker::on_exit races with GC when copying frame anchor

[Martin Balao]

On Thu, 3 Apr 2025 22:19:28 GMT, Andrew John Hughes <andrew at openjdk.org> wrote:

> Partial backport of a fix for a race condition in code adapted from JavaCallWrapper for the FFM API. This is more visible in 22 and later, where FFM is fully supported and the [OpenType implementation using HarfBuzz](https://bugs.openjdk.org/browse/JDK-8318364) has been ported to use it.
> 
> However, the copy in the native state seems to have been introduced as far back as [JDK-8269240](https://bugs.openjdk.org/browse/JDK-8269240) in 17 when the JavaCallWrapper code was ported to what was then universalUpcallHandler.cpp. That fix to `::on_exit` is included here.
> 
> The other hunk in the 24 and 21u versions is omitted as the `::on_entry` method has not been modified by [JDK-8272526](https://bugs.openjdk.org/browse/JDK-8272526) which is what moved the thread exception handling to native code.

Thanks for contributing this backport. Looks good to me.

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Marked as reviewed by mbalao (Reviewer).

PR Review: https://git.openjdk.org/jdk17u-dev/pull/3434#pullrequestreview-2744510532