8340826: Should not send unload notification for scratch classes

Reviewed-by: sspitsyn, coleenp

src/hotspot/share/code/dependencyContext.cpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -227,6 +227,10 @@ void DependencyContext::remove_and_mark_for_deoptimization_all_dependents(Deopti
 }
 
 #ifndef PRODUCT
+bool DependencyContext::is_empty() {
+  return dependencies() == nullptr;
+}
+
 void DependencyContext::print_dependent_nmethods(bool verbose) {
   int idx = 0;
   for (nmethodBucket* b = dependencies_not_unloading(); b != nullptr; b = b->next_not_unloading()) {

src/hotspot/share/code/dependencyContext.hpp

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2015, 2023, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2015, 2024, Oracle and/or its affiliates. All rights reserved.
  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
  *
  * This code is free software; you can redistribute it and/or modify it
@@ -124,6 +124,7 @@ class DependencyContext : public StackObj {
 
 #ifndef PRODUCT
   void print_dependent_nmethods(bool verbose);
+  bool is_empty();
 #endif //PRODUCT
   bool is_dependent_nmethod(nmethod* nm);
 };

src/hotspot/share/jfr/recorder/checkpoint/types/jfrTypeSet.cpp

@@ -484,6 +484,9 @@ static void do_primitives() {
 static void do_unloading_klass(Klass* klass) {
   assert(klass != nullptr, "invariant");
   assert(_subsystem_callback != nullptr, "invariant");
+  if (klass->is_instance_klass() && InstanceKlass::cast(klass)->is_scratch_class()) {
+    return;
+  }
   if (JfrKlassUnloading::on_unload(klass)) {
     _subsystem_callback->do_artifact(klass);
   }

src/hotspot/share/oops/instanceKlass.cpp

@@ -2721,6 +2721,13 @@ static void clear_all_breakpoints(Method* m) {
 #endif
 
 void InstanceKlass::unload_class(InstanceKlass* ik) {
+
+  if (ik->is_scratch_class()) {
+    assert(ik->dependencies().is_empty(), "dependencies should be empty for scratch classes");
+    return;
+  }
+  assert(ik->is_loaded(), "class should be loaded " PTR_FORMAT, p2i(ik));
+
   // Release dependencies.
   ik->dependencies().remove_all_dependents();