RFR: JDK-8276422 Add command-line option to disable finalization [v3]

[Stuart Marks]

On Thu, 18 Nov 2021 21:19:44 GMT, Stuart Marks <smarks at openjdk.org> wrote:

>> One typical way for VM to pass the arguments to the library is via private system properties.   System::initPhase1 will save the VM properties in `jdk.internal.misc.VM` and filters out the private properties from the system properties returned from System::getProperties (see System::createProperties).
>> 
>> You can query the flag via `jdk.internal.misc.VM.getProperty("jdk.finalization.disabled")` for example.
>> 
>> I don't see any issue moving the Finalizer class initialization after initPhase1 since there is no finalizer during VM startup.
>
> I renamed the function to `is_finalization_enabled` per previous comment, and I also made these cleanups.

Regarding using system properties, my initial prototype did this in the launcher, and it did run into the problem that the Finalizer class is initialized before system properties are available. That's why I created the Holder class, so that reading the property could be delayed until the first upcall to Finalizer::register. I suppose the initialization of Finalizer could be moved later, but that seems more invasive.

The flag needs to be available in the VM in order to avoid upcalls for instances-with-finalizers in the first place. Alan had [suggested](https://bugs.openjdk.java.net/browse/JDK-8276422?focusedCommentId=14456185&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-14456185) moving the argument processing into the VM, and David suggested putting the flag into InstanceKlass, which seems a sensible place to me. It's also reasonably accessible there to GC implementations, should they want to inspect it.

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PR: https://git.openjdk.java.net/jdk/pull/6442