diff -r 4ebc2e2fb97c -r 71c04702a3d5 src/hotspot/share/classfile/placeholders.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/src/hotspot/share/classfile/placeholders.cpp	Tue Sep 12 19:03:39 2017 +0200
@@ -0,0 +1,236 @@
+/*
+ * Copyright (c) 2003, 2017, 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 "classfile/placeholders.hpp"
+#include "classfile/systemDictionary.hpp"
+#include "oops/oop.inline.hpp"
+#include "runtime/fieldType.hpp"
+#include "utilities/hashtable.inline.hpp"
+
+// Placeholder methods
+
+PlaceholderEntry* PlaceholderTable::new_entry(int hash, Symbol* name,
+                                              ClassLoaderData* loader_data,
+                                              bool havesupername,
+                                              Symbol* supername) {
+  PlaceholderEntry* entry = (PlaceholderEntry*)Hashtable<Symbol*, mtClass>::new_entry(hash, name);
+  // Hashtable with Symbol* literal must increment and decrement refcount.
+  name->increment_refcount();
+  entry->set_loader_data(loader_data);
+  entry->set_havesupername(havesupername);
+  entry->set_supername(supername);
+  entry->set_superThreadQ(NULL);
+  entry->set_loadInstanceThreadQ(NULL);
+  entry->set_defineThreadQ(NULL);
+  entry->set_definer(NULL);
+  entry->set_instance_klass(NULL);
+  return entry;
+}
+
+void PlaceholderTable::free_entry(PlaceholderEntry* entry) {
+  // decrement Symbol refcount here because Hashtable doesn't.
+  entry->literal()->decrement_refcount();
+  if (entry->supername() != NULL) entry->supername()->decrement_refcount();
+  Hashtable<Symbol*, mtClass>::free_entry(entry);
+}
+
+
+// Placeholder objects represent classes currently being loaded.
+// All threads examining the placeholder table must hold the
+// SystemDictionary_lock, so we don't need special precautions
+// on store ordering here.
+void PlaceholderTable::add_entry(int index, unsigned int hash,
+                                 Symbol* class_name, ClassLoaderData* loader_data,
+                                 bool havesupername, Symbol* supername){
+  assert_locked_or_safepoint(SystemDictionary_lock);
+  assert(class_name != NULL, "adding NULL obj");
+
+  // Both readers and writers are locked so it's safe to just
+  // create the placeholder and insert it in the list without a membar.
+  PlaceholderEntry* entry = new_entry(hash, class_name, loader_data, havesupername, supername);
+  add_entry(index, entry);
+}
+
+
+// Remove a placeholder object.
+void PlaceholderTable::remove_entry(int index, unsigned int hash,
+                                    Symbol* class_name,
+                                    ClassLoaderData* loader_data) {
+  assert_locked_or_safepoint(SystemDictionary_lock);
+  PlaceholderEntry** p = bucket_addr(index);
+  while (*p) {
+    PlaceholderEntry *probe = *p;
+    if (probe->hash() == hash && probe->equals(class_name, loader_data)) {
+      // Delete entry
+      *p = probe->next();
+      free_entry(probe);
+      return;
+    }
+    p = probe->next_addr();
+  }
+}
+
+PlaceholderEntry* PlaceholderTable::get_entry(int index, unsigned int hash,
+                                       Symbol* class_name,
+                                       ClassLoaderData* loader_data) {
+  assert_locked_or_safepoint(SystemDictionary_lock);
+
+  for (PlaceholderEntry *place_probe = bucket(index);
+                         place_probe != NULL;
+                         place_probe = place_probe->next()) {
+    if (place_probe->hash() == hash &&
+        place_probe->equals(class_name, loader_data)) {
+      return place_probe;
+    }
+  }
+  return NULL;
+}
+
+Symbol* PlaceholderTable::find_entry(int index, unsigned int hash,
+                                       Symbol* class_name,
+                                       ClassLoaderData* loader_data) {
+  PlaceholderEntry* probe = get_entry(index, hash, class_name, loader_data);
+  return (probe? probe->klassname(): (Symbol*)NULL);
+}
+
+  // find_and_add returns probe pointer - old or new
+  // If no entry exists, add a placeholder entry
+  // If entry exists, reuse entry
+  // For both, push SeenThread for classloadAction
+  // if havesupername: this is used for circularity for instanceklass loading
+PlaceholderEntry* PlaceholderTable::find_and_add(int index, unsigned int hash,
+                                                 Symbol* name,
+                                                 ClassLoaderData* loader_data,
+                                                 classloadAction action,
+                                                 Symbol* supername,
+                                                 Thread* thread) {
+  PlaceholderEntry* probe = get_entry(index, hash, name, loader_data);
+  if (probe == NULL) {
+    // Nothing found, add place holder
+    add_entry(index, hash, name, loader_data, (action == LOAD_SUPER), supername);
+    probe = get_entry(index, hash, name, loader_data);
+  } else {
+    if (action == LOAD_SUPER) {
+      probe->set_havesupername(true);
+      probe->set_supername(supername);
+    }
+  }
+  if (probe) probe->add_seen_thread(thread, action);
+  return probe;
+}
+
+
+// placeholder is used to track class loading internal states
+// placeholder existence now for loading superclass/superinterface
+// superthreadQ tracks class circularity, while loading superclass/superinterface
+// loadInstanceThreadQ tracks load_instance_class calls
+// definer() tracks the single thread that owns define token
+// defineThreadQ tracks waiters on defining thread's results
+// 1st claimant creates placeholder
+// find_and_add adds SeenThread entry for appropriate queue
+// All claimants remove SeenThread after completing action
+// On removal: if definer and all queues empty, remove entry
+// Note: you can be in both placeholders and systemDictionary
+// Therefore - must always check SD first
+// Ignores the case where entry is not found
+void PlaceholderTable::find_and_remove(int index, unsigned int hash,
+                                       Symbol* name, ClassLoaderData* loader_data,
+                                       classloadAction action,
+                                       Thread* thread) {
+    assert_locked_or_safepoint(SystemDictionary_lock);
+    PlaceholderEntry *probe = get_entry(index, hash, name, loader_data);
+    if (probe != NULL) {
+       probe->remove_seen_thread(thread, action);
+       // If no other threads using this entry, and this thread is not using this entry for other states
+       if ((probe->superThreadQ() == NULL) && (probe->loadInstanceThreadQ() == NULL)
+          && (probe->defineThreadQ() == NULL) && (probe->definer() == NULL)) {
+         remove_entry(index, hash, name, loader_data);
+       }
+    }
+  }
+
+PlaceholderTable::PlaceholderTable(int table_size)
+    : Hashtable<Symbol*, mtClass>(table_size, sizeof(PlaceholderEntry)) {
+}
+
+void PlaceholderEntry::verify() const {
+  guarantee(loader_data() != NULL, "Must have been setup.");
+  guarantee(loader_data()->class_loader() == NULL || loader_data()->class_loader()->is_instance(),
+            "checking type of _loader");
+  guarantee(instance_klass() == NULL
+            || instance_klass()->is_instance_klass(),
+            "checking type of instance_klass result");
+}
+
+void PlaceholderTable::verify() {
+  verify_table<PlaceholderEntry>("Placeholder Table");
+}
+
+
+// Note, doesn't append a cr
+// Can't call this print_on because HashtableEntry doesn't initialize its vptr
+// and print_on is a virtual function so the vptr call crashes.
+void PlaceholderEntry::print_entry(outputStream* st) const {
+  klassname()->print_value_on(st);
+  if (loader_data() != NULL) {
+    st->print(", loader ");
+    loader_data()->print_value_on(st);
+  }
+  if (supername() != NULL) {
+    st->print(", supername ");
+    supername()->print_value_on(st);
+  }
+  if (definer() != NULL) {
+    st->print(", definer ");
+    definer()->print_value_on(st);
+  }
+  if (instance_klass() != NULL) {
+    st->print(", InstanceKlass ");
+    instance_klass()->print_value_on(st);
+  }
+  st->cr();
+  st->print("loadInstanceThreadQ threads:");
+  loadInstanceThreadQ()->print_action_queue(st);
+  st->cr();
+  st->print("superThreadQ threads:");
+  superThreadQ()->print_action_queue(st);
+  st->cr();
+  st->print("defineThreadQ threads:");
+  defineThreadQ()->print_action_queue(st);
+  st->cr();
+}
+
+void PlaceholderTable::print_on(outputStream* st) const {
+  st->print_cr("Placeholder table (table_size=%d, placeholders=%d)",
+                table_size(), number_of_entries());
+  for (int pindex = 0; pindex < table_size(); pindex++) {
+    for (PlaceholderEntry* probe = bucket(pindex);
+                           probe != NULL;
+                           probe = probe->next()) {
+      st->print("%4d: placeholder ", pindex);
+      probe->print_entry(st);
+    }
+  }
+}