diff --git a/src/hotspot/share/gc/z/zRootsIterator.cpp b/src/hotspot/share/gc/z/zRootsIterator.cpp
index 58493c2..35ba43f 100644
--- a/src/hotspot/share/gc/z/zRootsIterator.cpp
+++ b/src/hotspot/share/gc/z/zRootsIterator.cpp
@@ -29,6 +29,7 @@
 #include "compiler/oopMap.hpp"
 #include "gc/shared/oopStorageParState.inline.hpp"
 #include "gc/z/zGlobals.hpp"
+#include "gc/z/zNMethodBarrier.hpp"
 #include "gc/z/zNMethodTable.hpp"
 #include "gc/z/zOopClosures.inline.hpp"
 #include "gc/z/zRootsIterator.hpp"
@@ -134,7 +135,8 @@ void ZParallelWeakOopsDo<T, F>::weak_oops_do(BoolObjectClosure* is_alive, OopClo
   }
 }
 
-ZRootsIterator::ZRootsIterator() :
+ZRootsIterator::ZRootsIterator(bool strong_only) :
+    _strong_only(strong_only),
     _vm_weak_handles_iter(SystemDictionary::vm_weak_oop_storage()),
     _jni_handles_iter(JNIHandles::global_handles()),
     _jni_weak_handles_iter(JNIHandles::weak_global_handles()),
@@ -150,6 +152,7 @@ ZRootsIterator::ZRootsIterator() :
     _jni_handles(this),
     _jni_weak_handles(this),
     _class_loader_data_graph(this),
+    _class_loader_data_graph_strong_only(this),
     _threads(this),
     _code_cache(this),
     _string_table(this) {
@@ -158,16 +161,19 @@ ZRootsIterator::ZRootsIterator() :
   Threads::change_thread_claim_parity();
   ClassLoaderDataGraph::clear_claimed_marks();
   COMPILER2_PRESENT(DerivedPointerTable::clear());
-  CodeCache::gc_prologue();
-  ZNMethodTable::gc_prologue();
+  if (!ClassUnloading) {
+    ZNMethodTable::gc_prologue();
+  }
 }
 
 ZRootsIterator::~ZRootsIterator() {
   ZStatTimer timer(ZSubPhasePauseRootsTeardown);
   ResourceMark rm;
-  ZNMethodTable::gc_epilogue();
-  CodeCache::gc_epilogue();
+  if (!ClassUnloading) {
+    ZNMethodTable::gc_epilogue();
+  }
   JvmtiExport::gc_epilogue();
+
   COMPILER2_PRESENT(DerivedPointerTable::update_pointers());
   Threads::assert_all_threads_claimed();
 }
@@ -232,13 +238,32 @@ void ZRootsIterator::do_class_loader_data_graph(OopClosure* cl) {
   ClassLoaderDataGraph::cld_do(&cld_cl);
 }
 
+void ZRootsIterator::do_class_loader_data_graph_strong_only(OopClosure* cl) {
+  ZStatTimer timer(ZSubPhasePauseRootsClassLoaderDataGraph);
+  ClassLoaderDataGraph::always_strong_oops_do(cl, /* must_claim */ true);
+}
+
+class ZCodeBlobClosure : public CodeBlobToOopClosure {
+public:
+  ZCodeBlobClosure(OopClosure* cl) : CodeBlobToOopClosure(cl, true) {}
+  virtual void do_code_blob(CodeBlob* cb) {
+    CodeBlobToOopClosure::do_code_blob(cb);
+    if (cb->is_nmethod()) {
+      nmethod* nm = (nmethod*) cb;
+      nm->disarm_barrier();
+    }
+  }
+};
+
 class ZRootsIteratorThreadClosure : public ThreadClosure {
 private:
   OopClosure* const _cl;
+  CodeBlobClosure* const _code_cl;
 
 public:
-  ZRootsIteratorThreadClosure(OopClosure* cl) :
-      _cl(cl) {}
+  ZRootsIteratorThreadClosure(OopClosure* cl, CodeBlobClosure* code_cl) :
+      _cl(cl),
+      _code_cl(code_cl) {}
 
   virtual void do_thread(Thread* thread) {
     if (thread->is_Java_thread()) {
@@ -247,14 +272,16 @@ public:
     }
 
     // Process thread oops
-    thread->oops_do(_cl, NULL);
+    thread->oops_do(_cl, _code_cl);
   }
 };
 
 void ZRootsIterator::do_threads(OopClosure* cl) {
   ZStatTimer timer(ZSubPhasePauseRootsThreads);
   ResourceMark rm;
-  ZRootsIteratorThreadClosure thread_cl(cl);
+
+  ZCodeBlobClosure code_cl(cl);
+  ZRootsIteratorThreadClosure thread_cl(cl, ClassUnloading ? &code_cl : NULL);
   Threads::possibly_parallel_threads_do(true, &thread_cl);
 }
 
@@ -276,9 +303,18 @@ void ZRootsIterator::oops_do(OopClosure* cl, bool visit_jvmti_weak_export) {
   _jvmti_export.oops_do(cl);
   _system_dictionary.oops_do(cl);
   _jni_handles.oops_do(cl);
-  _class_loader_data_graph.oops_do(cl);
   _threads.oops_do(cl);
-  _code_cache.oops_do(cl);
+
+  if (!ClassUnloading) {
+    _code_cache.oops_do(cl);
+  }
+
+  if (!ClassUnloading || !ZWeakRoots || !_strong_only) {
+    _class_loader_data_graph.oops_do(cl);
+  } else {
+    _class_loader_data_graph_strong_only.oops_do(cl);
+  }
+
   if (!ZWeakRoots) {
     _jvmti_weak_export.oops_do(cl);
     _jfr_weak.oops_do(cl);
@@ -304,6 +340,7 @@ ZWeakRootsIterator::ZWeakRootsIterator() :
   assert(SafepointSynchronize::is_at_safepoint(), "Should be at safepoint");
   ZStatTimer timer(ZSubPhasePauseWeakRootsSetup);
   StringTable::reset_dead_counter();
+  ClassLoaderDataGraph::clear_claimed_marks();
 }
 
 ZWeakRootsIterator::~ZWeakRootsIterator() {