--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/z/zNMethodAllocator.cpp	Wed Feb 20 11:39:36 2019 +0100
@@ -0,0 +1,69 @@
+/*
+ * Copyright (c) 2019, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#include "precompiled.hpp"
+#include "gc/z/zArray.inline.hpp"
+#include "gc/z/zNMethodAllocator.hpp"
+#include "memory/allocation.hpp"
+
+ZArray<void*> ZNMethodAllocator::_deferred_frees;
+bool          ZNMethodAllocator::_defer_frees(false);
+
+void ZNMethodAllocator::immediate_free(void* data) {
+  FREE_C_HEAP_ARRAY(uint8_t, data);
+}
+
+void ZNMethodAllocator::deferred_free(void* data) {
+  _deferred_frees.add(data);
+}
+
+void* ZNMethodAllocator::allocate(size_t size) {
+  return NEW_C_HEAP_ARRAY(uint8_t, size, mtGC);
+}
+
+void ZNMethodAllocator::free(void* data) {
+  if (data == NULL) {
+    return;
+  }
+
+  if (_defer_frees) {
+    deferred_free(data);
+  } else {
+    immediate_free(data);
+  }
+}
+
+void ZNMethodAllocator::activate_deferred_frees() {
+  assert(_deferred_frees.is_empty(), "precondition");
+  _defer_frees = true;
+}
+
+void ZNMethodAllocator::deactivate_and_process_deferred_frees() {
+  _defer_frees = false;
+
+  ZArrayIterator<void*> iter(&_deferred_frees);
+  for (void* data; iter.next(&data);) {
+    immediate_free(data);
+  }
+  _deferred_frees.clear();
+}

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/gc/z/zNMethodAllocator.hpp	Wed Feb 20 11:39:36 2019 +0100
@@ -0,0 +1,46 @@
+/*
+ * Copyright (c) 2019, 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
+ * under the terms of the GNU General Public License version 2 only, as
+ * published by the Free Software Foundation.
+ *
+ * This code is distributed in the hope that it will be useful, but WITHOUT
+ * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
+ * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
+ * version 2 for more details (a copy is included in the LICENSE file that
+ * accompanied this code).
+ *
+ * You should have received a copy of the GNU General Public License version
+ * 2 along with this work; if not, write to the Free Software Foundation,
+ * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
+ *
+ * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
+ * or visit www.oracle.com if you need additional information or have any
+ * questions.
+ */
+
+#ifndef SHARE_GC_Z_ZNMETHODALLOCATOR_HPP
+#define SHARE_GC_Z_ZNMETHODALLOCATOR_HPP
+
+#include "memory/allocation.hpp"
+#include "gc/z/zArray.hpp"
+
+class ZNMethodAllocator : public AllStatic {
+private:
+  static ZArray<void*> _deferred_frees;
+  static bool          _defer_frees;
+
+  static void immediate_free(void* data);
+  static void deferred_free(void* data);
+
+public:
+  static void* allocate(size_t size);
+  static void free(void* data);
+
+  static void activate_deferred_frees();
+  static void deactivate_and_process_deferred_frees();
+};
+
+#endif // SHARE_GC_Z_ZNMETHODALLOCATOR_HPP

--- a/src/hotspot/share/gc/z/zNMethodTable.cpp	Wed Feb 20 10:47:03 2019 +0100
+++ b/src/hotspot/share/gc/z/zNMethodTable.cpp	Wed Feb 20 11:39:36 2019 +0100
@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2017, 2018, Oracle and/or its affiliates. All rights reserved.
+ * Copyright (c) 2017, 2019, 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
@@ -27,16 +27,16 @@
 #include "code/icBuffer.hpp"
 #include "gc/shared/barrierSet.hpp"
 #include "gc/shared/barrierSetNMethod.hpp"
-#include "gc/z/zArray.inline.hpp"
 #include "gc/z/zGlobals.hpp"
 #include "gc/z/zHash.inline.hpp"
 #include "gc/z/zLock.inline.hpp"
+#include "gc/z/zNMethodAllocator.hpp"
 #include "gc/z/zNMethodTable.hpp"
 #include "gc/z/zOopClosures.inline.hpp"
 #include "gc/z/zTask.hpp"
 #include "gc/z/zWorkers.hpp"
 #include "logging/log.hpp"
-#include "memory/allocation.inline.hpp"
+#include "memory/allocation.hpp"
 #include "memory/iterator.hpp"
 #include "memory/resourceArea.hpp"
 #include "runtime/atomic.hpp"
@@ -73,12 +73,12 @@
   // Allocate memory for the ZNMethodDataOops object
   // plus the immediate oop* array that follows right after.
   const size_t size = ZNMethodDataOops::header_size() + (sizeof(oop*) * immediates.length());
-  void* const data = NEW_C_HEAP_ARRAY(uint8_t, size, mtGC);
-  return ::new (data) ZNMethodDataOops(immediates, has_non_immediates);
+  void* const mem = ZNMethodAllocator::allocate(size);
+  return ::new (mem) ZNMethodDataOops(immediates, has_non_immediates);
 }
 
 void ZNMethodDataOops::destroy(ZNMethodDataOops* oops) {
-  ZNMethodTable::safe_delete(oops);
+  ZNMethodAllocator::free(oops);
 }
 
 ZNMethodDataOops::ZNMethodDataOops(const GrowableArray<oop*>& immediates, bool has_non_immediates) :
@@ -125,13 +125,13 @@
 };
 
 ZNMethodData* ZNMethodData::create(nmethod* nm) {
-  void* const method = NEW_C_HEAP_ARRAY(uint8_t, sizeof(ZNMethodData), mtGC);
-  return ::new (method) ZNMethodData(nm);
+  void* const mem = ZNMethodAllocator::allocate(sizeof(ZNMethodData));
+  return ::new (mem) ZNMethodData(nm);
 }
 
 void ZNMethodData::destroy(ZNMethodData* data) {
-  ZNMethodDataOops::destroy(data->oops());
-  ZNMethodTable::safe_delete(data);
+  ZNMethodAllocator::free(data->oops());
+  ZNMethodAllocator::free(data);
 }
 
 ZNMethodData::ZNMethodData(nmethod* nm) :
@@ -162,27 +162,10 @@
 size_t ZNMethodTable::_size = 0;
 ZNMethodTableEntry* ZNMethodTable::_iter_table = NULL;
 size_t ZNMethodTable::_iter_table_size = 0;
-ZArray<void*> ZNMethodTable::_iter_deferred_deletes;
 size_t ZNMethodTable::_nregistered = 0;
 size_t ZNMethodTable::_nunregistered = 0;
 volatile size_t ZNMethodTable::_claimed = 0;
 
-void ZNMethodTable::safe_delete(void* data) {
-  assert(CodeCache_lock->owned_by_self(), "Lock must be held");
-
-  if (data == NULL) {
-    return;
-  }
-
-  if (_iter_table != NULL) {
-    // Iteration in progress, defer delete
-    _iter_deferred_deletes.add(data);
-  } else {
-    // Iteration not in progress, delete now
-    FREE_C_HEAP_ARRAY(uint8_t, data);
-  }
-}
-
 void ZNMethodTable::attach_gc_data(nmethod* nm) {
   GrowableArray<oop*> immediate_oops;
   bool non_immediate_oops = false;
@@ -482,11 +465,13 @@
 void ZNMethodTable::nmethods_do_begin() {
   MutexLockerEx mu(CodeCache_lock, Mutex::_no_safepoint_check_flag);
 
+  // Make sure we don't free data while iterating
+  ZNMethodAllocator::activate_deferred_frees();
+
   // Prepare iteration
   _iter_table = _table;
   _iter_table_size = _size;
   _claimed = 0;
-  assert(_iter_deferred_deletes.is_empty(), "Should be emtpy");
 }
 
 void ZNMethodTable::nmethods_do_end() {
@@ -500,12 +485,8 @@
 
   assert(_claimed >= _iter_table_size, "Failed to claim all table entries");
 
-  // Process deferred deletes
-  ZArrayIterator<void*> iter(&_iter_deferred_deletes);
-  for (void* data; iter.next(&data);) {
-    FREE_C_HEAP_ARRAY(uint8_t, data);
-  }
-  _iter_deferred_deletes.clear();
+  // Process deferred frees
+  ZNMethodAllocator::deactivate_and_process_deferred_frees();
 
   // Notify iteration done
   CodeCache_lock->notify_all();

--- a/src/hotspot/share/gc/z/zNMethodTable.hpp	Wed Feb 20 10:47:03 2019 +0100
+++ b/src/hotspot/share/gc/z/zNMethodTable.hpp	Wed Feb 20 11:39:36 2019 +0100
@@ -31,6 +31,8 @@
 #include "memory/allocation.hpp"
 
 class NMethodClosure;
+class ZNMethodData;
+class ZNMethodDataOops;
 class ZWorkers;
 
 class ZNMethodTable : public AllStatic {
@@ -39,7 +41,6 @@
   static size_t              _size;
   static ZNMethodTableEntry* _iter_table;
   static size_t              _iter_table_size;
-  static ZArray<void*>       _iter_deferred_deletes;
   static size_t              _nregistered;
   static size_t              _nunregistered;
   static volatile size_t     _claimed ATTRIBUTE_ALIGNED(ZCacheLineSize);
@@ -62,8 +63,6 @@
   static void log_unregister(const nmethod* nm);
 
 public:
-  static void safe_delete(void* data);
-
   static size_t registered_nmethods();
   static size_t unregistered_nmethods();