RFR: 8316401: sun/tools/jhsdb/JStackStressTest.java failed with "InternalError: We should have found a thread that owns the anonymous lock" [v2]

[David Holmes]

On Wed, 27 Sep 2023 17:54:51 GMT, Roman Kennke <rkennke at openjdk.org> wrote:

>> The SA can run concurrently with Java threads, SA code that inspects locking state should be able to deal with that. On the other hand, the particular code is only used in printing routine and is not expected to be precise. When resolving an anonymous owner, we may not find one, because Java threads may already have moved on. Instead of crashing with a stacktrace, we should gracefully return null here.
>> 
>> Testing:
>>  - [x] sun/tools/jhsdb/JStackStressTest.java
>>  - [x] sun/tools/jhsdb
>>  - [x] serviceability/sa
>
> Roman Kennke has updated the pull request incrementally with one additional commit since the last revision:
> 
>   Print warning when anonymous lock cannot be found

Changes requested by dholmes (Reviewer).

src/jdk.hotspot.agent/share/classes/sun/jvm/hotspot/runtime/Threads.java line 245:

> 243:                 }
> 244:                 // We should have found the owner. However, the code can run concurrently with
> 245:                 // Java code and locking state can change at any time. This code is not

The second sentence is not accurate as things are not running concurrently and cannot change state at any time. Suggestion:

// We should have found the owner, however, as the VM could be in any state, including the middle
// of performing GC, it is not always possible to do so. Just return null if we can't locate it.

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

PR Review: https://git.openjdk.org/jdk/pull/15907#pullrequestreview-1647736396
PR Review Comment: https://git.openjdk.org/jdk/pull/15907#discussion_r1339374587