JDK21 requires JVM_VirtualThreadMount/JVM_VirtualThreadUnmount implementations

[JasonFengJ9]

8304303: implement VirtualThread class notifyJvmti methods as C2 intrinsics added two new JVM methods. [1]

/*
 * Virtual thread support.
 */
JNIEXPORT void JNICALL
JVM_VirtualThreadMount(JNIEnv* env, jobject vthread, jboolean hide, jboolean first_mount);

JNIEXPORT void JNICALL
JVM_VirtualThreadUnmount(JNIEnv* env, jobject vthread, jboolean hide, jboolean last_unmount);

In addition, it removed notifyJvmtiEvents which made the JCL patch Enable VirtualThread JVMTI natives by default redundant.

FYI @fengxue-IS @babsingh @tajila

[1] https://github.com/ibmruntimes/openj9-openjdk-jdk/blob/1e70d47e951486673ca369046dadc498ccba4a43/src/hotspot/share/include/jvm.h#L1143-L1150

[keithc-ca]

jdk21 also removes the need for these functions:

JVM_VirtualThreadMountBegin
JVM_VirtualThreadMountEnd
JVM_VirtualThreadUnmountBegin
JVM_VirtualThreadUnmountEnd

[babsingh]

From a functional perspective, the new functions are amalgamated forms of the old functions:

JVM_VirtualThreadMount:
   if (hide): JVM_VirtualThreadMountBegin
   else: JVM_VirtualThreadMountEnd

JVM_VirtualThreadUnmount:
   if (hide): JVM_VirtualThreadUnmountBegin
   else: JVM_VirtualThreadUnmountEnd

To avoid hindering the JDK19 release, this change should be applied on top of #16855.

removed notifyJvmtiEvents which made the JCL patch Enable VirtualThread JVMTI natives by default redundant.

This field has been moved to native. It is enabled from JNI GetEnv if Continuations are enabled.

[fengxue-IS]

@thallium can you take a look at this

[JasonFengJ9]

Updated the PR as per #16984 (comment) required by ibmruntimes/openj9-openjdk-jdk#572

• JDK21 adds JVM_VirtualThreadMount/JVM_VirtualThreadUnmount #16985

[JasonFengJ9]

#16985 (comment)

		JVM_VirtualThreadMountBegin
		JVM_VirtualThreadMountEnd
		JVM_VirtualThreadUnmountBegin
		JVM_VirtualThreadUnmountEnd

These exports are not needed by JDK21+.

[keithc-ca]

More changes coming from upstream, see

• 8306028: separate ThreadStart/ThreadEnd events posting code in JVMTI VTMS transitions

meaning the signature of two existing functions change and two new ones are introduced.

[babsingh]

re #16984 (comment): @keithc-ca Looking for a timeline to support the new changes. Are the new changes JDK21 specific or will they flow down to JDK20?

[keithc-ca]

I've only seen those changes in JDK21; I don't know whether those changes will get back-ported to JDK20.

[pshipton]

There are some changes in the jdk20u master branch. We won't integrate anything until there is a 20.0.2 build tag. No guarantee these changes will go in to 20.0.2 or that we'll integrate anything until July 18.

openjdk/jdk20u@jdk-20.0.1+9...master

[babsingh]

I don't see 8306028: separate ThreadStart/ThreadEnd events posting code in JVMTI VTMS transitions in openjdk/jdk20u@jdk-20.0.1+9...master. For the time being, I will assume that the new changes are JDK21-specific.

[babsingh]

8306028: separate ThreadStart/ThreadEnd events posting code in JVMTI VTMS transitions

Rough draft of the OpenJ9 changes to support the above upstream changes:

JNIEXPORT void JNICALL
JVM_VirtualThreadMount(JNIEnv* env, jobject vthread, jboolean hide)
{
	if (hide) {
		JVM_VirtualThreadMountBegin(env, vthread, false);
	} else {
		JVM_VirtualThreadMountEnd(env, vthread, false);
	}
}

JNIEXPORT void JNICALL
JVM_VirtualThreadUnmount(JNIEnv* env, jobject vthread, jboolean hide)
{
	if (hide) {
		JVM_VirtualThreadUnmountBegin(env, vthread, false);
	} else {
		JVM_VirtualThreadUnmountEnd(env, vthread, false);
	}
}

JNIEXPORT void JNICALL
JVM_VirtualThreadStart(JNIEnv* env, jobject vthread)
{
	JVM_VirtualThreadMountEnd(env, vthread, false);
	// All firstMount specific code should be extracted from JVM_VirtualThreadMount[Begin|End] and consolidated here
}

JNIEXPORT void JNICALL
JVM_VirtualThreadEnd(JNIEnv* env, jobject vthread)
{
	// All lastUnmount specific code should be extracted from JVM_VirtualThreadUnmount[Begin|End] and consolidated here
	JVM_VirtualThreadUnmountBegin
}

[fengxue-IS]

More changes coming from upstream, see

• 8306028: separate ThreadStart/ThreadEnd events posting code in JVMTI VTMS transitions

meaning the signature of two existing functions change and two new ones are introduced.

Is there any ETA on when this will be integrated into the extension-repo build branch? if we are expecting this to be done within this week, we should include the changes in #17125 rather than refactoring it shortly after merging.

[JasonFengJ9]

Is there any ETA on when this will be integrated into the extension-repo build branch?

The branch master/openj9-staging containing the changes in question will be promoted into openj9 branch after merging Update FFI specific code for compilation in JDK21, afterwards, the change is visible for usual JDK21 builds.

[keithc-ca]

In

• 8306028: separate ThreadStart/ThreadEnd events posting code in JVMTI VTMS transitions

the signature of these functions changed

• JVM_VirtualThreadMount
• JVM_VirtualThreadUnmount

and these functions are added

• JVM_VirtualThreadStart
• JVM_VirtualThreadEnd

[JasonFengJ9]

JVM_VirtualThreadStart
JVM_VirtualThreadEnd

A change to bring up latest Java 21 level including these two APIs is in progress.

[babsingh]

#17125 has support for the new changes mentioned in #16984 (comment). The PR title and description needs to be updated but it includes all the four functions: JVM_VirtualThread Mount, Unmount, Start and End.