RFR: 8299414: JVMTI FollowReferences should support references from VirtualThread stack [v19]
Serguei Spitsyn
sspitsyn at openjdk.org
Fri May 12 22:16:00 UTC 2023
On Wed, 10 May 2023 23:41:07 GMT, Alex Menkov <amenkov at openjdk.org> wrote:
>> The fix updates JVMTI FollowReferences implementation to report references from virtual threads:
>> - unmounted vthreads are detected, their stack references for JVMTI_HEAP_REFERENCE_STACK_LOCAL/JVMTI_HEAP_REFERENCE_JNI_LOCAL;
>> - stacks of mounted vthreads are splitted into 2 parts (virtual thread stack and carrier thread stack), references are reported with correct thread id/class tag/object tags/frame depth;
>> - common code to handle stack frames are moved into separate class;
>>
>> Threads are reported as:
>> - platform threads: JVMTI_HEAP_REFERENCE_THREAD (as before);
>> - mounted vthreads (synthetic references, consider them as heap roots because carrier threads are roots): JVMTI_HEAP_REFERENCE_OTHER;
>> - unmounted vthreads: not reported as heap roots.
>
> Alex Menkov has updated the pull request incrementally with one additional commit since the last revision:
>
> some refactoring
>
> added StackRefCollector::process_frames;
> used single RegisterMap instance;
> used RegisterMap::WalkContinuation::include for RegisterMap;
Thank you for the updates.
Looks good to me - approved.
Expecting some comment cleanup before integration.
Thanks,
Serguei
-------------
Marked as reviewed by sspitsyn (Reviewer).
PR Review: https://git.openjdk.org/jdk/pull/13254#pullrequestreview-1425207958
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