RFR: 8242440: use separate, destroyable JavaVM instances per libgraal compiler thread [v3]

[Doug Simon]

On Fri, 22 Apr 2022 05:20:20 GMT, Kim Barrett <kbarrett at openjdk.org> wrote:

>> Doug Simon has updated the pull request incrementally with one additional commit since the last revision:
>> 
>>   removed (incorrect) volatile modifier from JVMCIRuntime::_shared_library_javavm
>
> One more possible improvement suggestion.  As I said before, I've only reviewed the runtime parts (which looks okay), and just skimmed the rest.  So don't count me as the required 2nd reviewer.

Thanks @kimbarrett for the very helpful feedback on this PR.

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PR: https://git.openjdk.java.net/jdk/pull/8262