On Mon, 18 Sep 2023 09:54:18 GMT, Axel Boldt-Christmas <abold...@openjdk.org> 
wrote:

> ObjectMonitorIterator fails to return the most resent monitor added. It start 
> with returning the `nextOM()` ObjectMonitor from the `_head` ObjectMonitor 
> but fails to ever return the `_head` ObjectMonitor.
> The current implementation can also not handle that the `_head` is nullptr 
> (no monitors in the system) and returns a null ObjectMonitorIterator. Which 
> is interpreted as `monitor list not supported, too old hotspot VM`.
> 
> Changed the iterator to keep return the current monitor (starts with `_head`) 
> and decoupled `_head == nullptr` from the question if ObjectMonitorIterator 
> is supported. 
> 
> Testing:
>   * Passes all `serviceability/sa` tests
>   * Currently running tier 1-3
>   * Currently running GHA

CDS tests are not happy with changing the class hierarchy of the LingeredApp. 
Unless it is easily solved for the CDS test I will revert those changes and 
have the 'TestObjectMonitorIterate' just do a less precise check of a lock on a 
Object. In the current JDK for LM_LEGACY and LM_LIGHTWEIGHT the 
`steadyStateObj` is the only object with a monitor when the SA agent queries.

-------------

PR Comment: https://git.openjdk.org/jdk/pull/15782#issuecomment-1723259794

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