On Mon, 25 Sep 2023 02:08:36 GMT, David Holmes <dhol...@openjdk.org> wrote:
>> Axel Boldt-Christmas has updated the pull request incrementally with one
>> additional commit since the last revision:
>>
>> Update copyright year
>
> src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/ObjectSynchronizer.java
> line 49:
>
>> 47: Type monitorListType = db.lookupType("MonitorList");
>> 48: Address monitorListAddr =
>> objectSynchronizerType.getField("_in_use_list").getStaticFieldAddress();
>> 49: inUseListHead =
>> monitorListType.getAddressField("_head").getAddress(monitorListAddr);
>
> So is `inUseListHead` effectively a "pointer" to the `_head` field of the
> `_in_use_list` `MonitorList`, which is dereferenced when we read it? Else I'm
> not seeing how we iterate the current set of in-use monitors.
It is not. It is the value of `_head` when ObjectSynchronizer is initialised.
My understanding of the serviceability agent is very limited, but from what I
understood the JVM does not run when we are attached. So no code should add to
the list.
If that was a requirement then both this and the previous implementation are
completely broken.
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PR Review Comment: https://git.openjdk.org/jdk/pull/15782#discussion_r1335673227
