RFR: 8352256: ObjectSynchronizer::quick_notify misses JFR event notification path

[David Holmes]

On Tue, 18 Mar 2025 11:42:39 GMT, Aleksey Shipilev <shade at openjdk.org> wrote:

> Noticed this while removing OM counters. When doing [JDK-8351187](https://bugs.openjdk.org/browse/JDK-8351187), I apparently forgot to cover a path from `ObjectSynchronizer::quick_notify`, probably due to concurrent renames. I think we can cover this gap while still simplifying the code: let `ObjectMonitor` handle all events, DTrace, JFR, OM stats.
> 
> Additional testing:
>  - [x] Linux x86_64 server fastdebug, `jdk_jfr`

The use of the quick variants is to avoid the checks that could lead to throwing an exception, as they would require that the thread be _thread_in_vm not _thread_in_java.

That said it is not clear to me that posting the event doesn't violate the requirements that the quick version must maintain: no safepoints, no blocking, no state transitions. ??

src/hotspot/share/runtime/synchronizer.cpp line 372:

> 370:     if (mon->first_waiter() != nullptr) {
> 371:       // We have one or more waiters. Since this is an inflated monitor
> 372:       // that we own, we quickly notify it here and now, avoiding the slow-path.

Suggestion:

      // that we own, we quickly notify them here and now, avoiding the slow-path.

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PR Review: https://git.openjdk.org/jdk/pull/24097#pullrequestreview-2701428216
PR Review Comment: https://git.openjdk.org/jdk/pull/24097#discussion_r2004904762