RFR: 8315884: New Object to ObjectMonitor mapping [v6]

[Axel Boldt-Christmas]

On Tue, 23 Jul 2024 16:44:06 GMT, Coleen Phillimore <coleenp at openjdk.org> wrote:

>> I wanted to avoid having to add `NoSafepointVerifier` implementation details in the synchroniser code. I guess `ContinuationWrapper` already does this. 
>> 
>> Simply creating a `NoSafepointVerifier` when you expect no safepoint is more obvious to me, shows the intent better.
>
> This looks strange to me also, but it's be better than changing the no_safepoint_count directly, since NSV handles when the current thread isn't a JavaThread, so you'd have to duplicate that in this VerifyThreadState code too.
> 
>     NoSafepointVerifier::NoSafepointVerifier() : _thread(Thread::current()) {
>       if (_thread->is_Java_thread()) {
>         JavaThread::cast(_thread)->inc_no_safepoint_count();
>       }
>     }

It was the call to `[inc/dec]_no_safepoint_count` I wanted to avoid. But I will switch the conditionally created NSV to the `[inc/dec]_no_safepoint_count` calls instead.

>> Yeah. The only effect is has is that you cannot reassign the variable. It was the style taken from [synchronizer.hpp](https://github.com/openjdk/jdk/blob/15997bc3dfe9dddf21f20fa189f97291824892de/src/hotspot/share/runtime/synchronizer.hpp) where all `InflateCause` parameters are const.
>
> Do you get this for inflate_fast_locked_object also?

Yes. I'll just remove the const from all lightweightSynchronizer parameters.

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PR Review Comment: https://git.openjdk.org/jdk/pull/20067#discussion_r1713909267
PR Review Comment: https://git.openjdk.org/jdk/pull/20067#discussion_r1713909417