RFR: 8282475: SafeFetch should not rely on existence of Thread::current [v2]

[Johannes Bechberger]

On Mon, 7 Mar 2022 18:55:33 GMT, Johannes Bechberger <duke at openjdk.java.net> wrote:

>> The WXMode for the current thread (on MacOS aarch64) is currently stored in the thread class which is unnecessary as the WXMode is bound to the current OS thread, not the current instance of the thread class.
>> This pull request moves the storage of the current WXMode into a thread local global variable in `os` and changes all related code. SafeFetch depended on the existence of a thread object only because of the WXMode. This pull request therefore removes the dependency, making SafeFetch usable in more contexts.
>
> Johannes Bechberger has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Minor fixes

Thanks.

> All the WX related code should be buried in the os/cpu file for BSD/Aarch64 and the callsites all using MACOS_AARCH64_ONLY.

I'm currently finishing a fix that exactly does that :)

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PR: https://git.openjdk.java.net/jdk/pull/7727