Summary

Update the specification of the FollowReferences and IterateOverReachableObjects functions to make it clear that virtual threads are not heap roots.

Problem

Currently the FollowReferences and IterateOverReachableObjects functions specify that heap roots include references from thread stacks. Virtual Threads are just objects in the heap, they should not be reported to JVMTI agents as heap roots.

Solution

Update the descriptions of FollowReferences and IterateOverReachableObjects to say that heap roots include references from platform threads stacks (rather than just thread stacks).

Drop "heap root reference" from the descriptions of JVMTI_HEAP_REFERENCE_STACK_LOCAL and JVMTI_HEAP_REFERENCE_JNI_LOCAL.

Specification

diff --git a/src/hotspot/share/prims/jvmti.xml b/src/hotspot/share/prims/jvmti.xml
index 456876fbcb9..3788d3c5ce7 100644
--- a/src/hotspot/share/prims/jvmti.xml
+++ b/src/hotspot/share/prims/jvmti.xml
@@ -3517,10 +3517,10 @@ err = (*jvmti)->Deallocate(jvmti, stack_info);
         Heap root reference: monitor.
       </constant>
       <constant id="JVMTI_HEAP_REFERENCE_STACK_LOCAL" num="24">
-            Heap root reference: local variable on the stack.
+            Local variable on a thread stack.
       </constant>
       <constant id="JVMTI_HEAP_REFERENCE_JNI_LOCAL" num="25">
-            Heap root reference: JNI local reference.
+            JNI local reference.
       </constant>
       <constant id="JVMTI_HEAP_REFERENCE_THREAD" num="26">
         Heap root reference: Thread.
@@ -4535,7 +4535,7 @@ class C2 extends C1 implements I2 {
     if <code>initial_object</code> is not specified, all objects
     reachable from the heap roots.
     The heap root are the set of system classes,
-        JNI globals, references from thread stacks, and other objects used as roots
+        JNI globals, references from platform thread stacks, and other objects used as roots
     for the purposes of garbage collection.
     <p/>
     This function operates by traversing the reference graph.
@@ -5579,7 +5579,7 @@ class C2 extends C1 implements I2 {
     This function iterates over the root objects and all objects that
     are directly and indirectly reachable from the root objects.
     The root objects comprise the set of system classes,
-        JNI globals, references from thread stacks, and other objects used as roots
+        JNI globals, references from platform thread stacks, and other objects used as roots
     for the purposes of garbage collection.
     <p/>
     For each root the <paramlink id="heap_root_callback"></paramlink>