RFR: 8289220: Locale.forLanguageTag throws NPE due to soft ref used in locale cache being cleared [v3]

[Erik Österlund]

On Tue, 6 Jun 2023 02:31:19 GMT, SUN Guoyun <duke at openjdk.org> wrote:

>> I still don't see a clear explanation of how the proposed patch fixes the problem. Also, I would appreciate the reasoning in the comments.
>
> For hotspot, when GC occurs, it causes all threads to run to the nearest safepoint and then freeze. Generally, safepoints are generated at branch jumps, method ends(ret instructions), loops instructions, and so on. Therefore, the purpose of this patch is to make the creation and use of a softReferences in the same method without branch, jumps and loops in between, that is ensure that GC will not occur in the process of the sofeReferences be created and used.
> 
> That's why I didn't use `Reference.reachabilityFence(locale)`.

This reasoning seems invalid. There are method calls in there, and you rely on inlining heuristics for this not to break. Please use reachabilityFence instead.

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PR Review Comment: https://git.openjdk.org/jdk/pull/14211#discussion_r1220145376