RFR: 8321069: JvmtiThreadState::state_for_while_locked() returns nullptr for an attached JNI thread with a java.lang.Thread object after JDK-8319935

[Daniel D. Daugherty]

On Mon, 4 Dec 2023 19:01:05 GMT, Jiangli Zhou <jiangli at openjdk.org> wrote:

>> @dcubed-ojdk Thanks for the notification. I just ran one of our affected test 100 times with JDK-8312174 change rolled back and with both following applied:
>> 
>> - https://git.openjdk.org/jdk/pull/16642
>> - https://github.com/openjdk/jdk/pull/16934
>> 
>> All 100 runs passed without failure. I'm going to run all tests tonight, will report back later tomorrow if I see any issue.
>
>> @jianglizhou - Thanks for doing the testing. Can you also do a review? We need two reviewers for this change.
> 
> Complete test run finished. Checking the results, looks like there's no issue related to JVMTIThreadState change. 
> 
> @dcubed-ojdk Reducing the check to `(thread->threadObj() == nullptr && thread->is_attaching_via_jni())` looks ok. 
> 
> I just rechecked all usages of setup_jvmti_thread_state(). Currently it's used in three cases:
> - JvmtiDynamicCodeEventCollector::JvmtiDynamicCodeEventCollector()
> - JvmtiVMObjectAllocEventCollector::JvmtiVMObjectAllocEventCollector()
> - JvmtiSampledObjectAllocEventCollector::start()
> 
> JDK-8319935 ran into issue with JvmtiSampledObjectAllocEventCollector::start() call path. We changed JvmtiSampledObjectAllocEventCollector::object_alloc_is_safe_to_sample() to avoid sampling if there is no thread obj allocated for the attaching thread. We also changed JvmtiThreadState::state_for_while_locked to handle the attaching case and return null. @dcubed-ojdk and @dholmes-ora, is there a case JvmtiVMObjectAllocEventCollector::JvmtiVMObjectAllocEventCollector() might also see an attaching thread without the thread obj allocated? 
> 
> JvmtiDynamicCodeEventCollector::JvmtiDynamicCodeEventCollector() call path probably is not affected by this case.

@jianglizhou and @sspitsyn - Thanks for the reviews.

In the interest of reducing the noise in the Mach5 CI, I'm going ahead with
integrating this fix without waiting for a reply to my comment above. If there
are remaining issues, then we'll deal with them in a follow-up bug/RFE.

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PR Comment: https://git.openjdk.org/jdk/pull/16934#issuecomment-1839457963