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

[David Holmes]

On Sat, 2 Dec 2023 17:15:57 GMT, Daniel D. Daugherty <dcubed at openjdk.org> wrote:

> In the fix for the following bug:
> 
> [JDK-8319935](https://bugs.openjdk.org/browse/JDK-8319935) Ensure only one JvmtiThreadState is created for one JavaThread associated with attached native thread
> 
> JvmtiThreadState::state_for_while_locked() was changed to
> return nullptr for attaching JNI threads regardless of whether
> that JNI thread/JavaThread had a java.lang.Thread object.
> 
> We should only filter out a JavaThread that's attaching via JNI
> if it has no java.lang.Thread object.
> 
> This fix has been tested with Mach5 Tier[1-7] and there are no related test failures.
> Mach5 Tier8 is in process.
> 
> I'm going to need @jianglizhou to rerun her testing for:
> 
> [JDK-8319935](https://bugs.openjdk.org/browse/JDK-8319935) Ensure only one JvmtiThreadState is created for one JavaThread associated with attached native thread
> 
> since the test(s) for that fix are not yet integrated in the jdk/jdk repo.

Initially I thought this was not the right fix as we should not be exposing an attaching thread that may still have a partially constructed `threadObj`. But this issue shows that we must expose such a thread because the constructor of the `Thread` object can trigger these events on the current thread so it must have a valid JVMTI state!

Thanks.

src/hotspot/share/prims/jvmtiThreadState.inline.hpp line 90:

> 88:     // Don't add a JvmtiThreadState to a thread that is exiting or is attaching.
> 89:     // When a thread is attaching, it may not have a Java level thread object
> 90:     // created yet.

The comment needs adjusting now - suggestion:

// Don't add a JvmtiThreadState to a thread that is exiting, or is attaching
// and does not yet have a Java level thread object allocated.

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

Marked as reviewed by dholmes (Reviewer).

PR Review: https://git.openjdk.org/jdk/pull/16934#pullrequestreview-1761678171
PR Review Comment: https://git.openjdk.org/jdk/pull/16934#discussion_r1413421607