--- /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);
+ }
+ }
+}