On Mon, 9 Sep 2024 18:34:10 GMT, Chris Plummer <cjplum...@openjdk.org> wrote:
>> I've been looking into this. It's a bit hard to follow but I think you do >> need to do something more here. Can you run ClhsdbInspect.java and send me >> the output. In specific I need to know if the log includes the following: >> >> >> hsdb> + inspect 0x00000007cff154b8 >> instance of Oop for >> java/util/concurrent/locks/AbstractQueuedSynchronizer$ConditionObject @ >> 0x00000007cff154b8 (size = 24) >> _mark: 1 >> _metadata._compressed_klass: InstanceKlass for >> java/util/concurrent/locks/AbstractQueuedSynchronizer$ConditionObject >> firstWaiter: Oop for >> java/util/concurrent/locks/AbstractQueuedSynchronizer$ConditionNode @ >> 0x00000007cfff5f80 >> lastWaiter: Oop for >> java/util/concurrent/locks/AbstractQueuedSynchronizer$ConditionNode @ >> 0x00000007cfff5f80 >> this$0: Oop for java/util/concurrent/locks/ReentrantLock$NonfairSync @ >> 0x00000007cff15498 > > I pulled your changes and I see one slight difference in the output. The > following line is missing: > > `_metadata._compressed_klass: InstanceKlass for > java/util/concurrent/locks/AbstractQueuedSynchronizer$ConditionObject` > > I realize that there is no `_metadata._compressed_klass` when you have > compact headers, and that the Klass* is encoded in the `_mark` word, which is > now looks something like this in the output: > > _mark: 16294762323640321 > > So you can say that the Klass* is embedded in the _mark work, but this isn't > of much help to SA users. I think what is expected is that the visitor is > passed a MetadataField object that when getValue() is called on it, the Klass > mirror is returned. Maybe we need a new CompactKlassField type like we > current have a NarrowKlassField field type, and it will do the decoding of > the _mark work into a Klass. The current getKlass() is related to this. Thinking about this a bit more, maybe _mark needs to be a MetadataFile rather than CInt. This is a kind of odd situation. Basically we have a CInt field that is more than just simple bits used as flags or small integers. It also gets you to the Klass*. Possibly SA should treat _mark is two seprate fields; one that remains a CInt as it currently is and another that treats it as an encoded Klass* like the NarrowKlassField case. ------------- PR Review Comment: https://git.openjdk.org/jdk/pull/20677#discussion_r1750788243
