RFR: 8291555: Implement alternative fast-locking scheme [v29]

[Dean Long]

On Tue, 28 Mar 2023 10:53:10 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> src/hotspot/share/runtime/threads.cpp line 1422:
>> 
>>> 1420: }
>>> 1421: 
>>> 1422: JavaThread* Threads::owning_thread_from_object(ThreadsList * t_list, oop obj) {
>> 
>> Is this thread-safe?
>
> My last commit changed that code to only run during safepoints. It should be safe now, and I added an assert that verifies that it is only run at safepoint.

I see the assert in `owning_thread_from_monitor` but not `owning_thread_from_object`.

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PR Review Comment: https://git.openjdk.org/jdk/pull/10907#discussion_r1150900864