RFR: 8300917: Regression 2x and bimodal startup on Mac aarch64 in b27

[Per Minborg]

On Wed, 1 Feb 2023 07:21:10 GMT, Viktor Klang <duke at openjdk.org> wrote:

>> This PR proposed to reduce contention in synchronized methods mainly by doing I/O operations outside synch blocks.
>
> src/java.base/share/classes/java/lang/Module.java line 281:
> 
>> 279: 
>> 280:     private static boolean isNativeAccessEnabled(Module target) {
>> 281:         if (target.enableNativeAccess)
> 
> @minborg It'd seem a bit easier to implement using VarHandle and not having to use `synchronized`? Is the reason that you don't want to init VarHandle in this class? 🤔

It is a bootstrap problem. We cannot use AtomicBoolean, VarHandle or Unsafe here.

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PR: https://git.openjdk.org/jdk/pull/12193