Mercurial > jdk8-mips64-public > hotspot / file revision

 /*

  * Copyright (c) 2003, 2013, 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)

     : TwoOopHashtable<Symbol*, mtClass>(table_size, sizeof(PlaceholderEntry)) {

 }

 void PlaceholderTable::classes_do(KlassClosure* f) {

   for (int index = 0; index < table_size(); index++) {

     for (PlaceholderEntry* probe = bucket(index);

                            probe != NULL;

                            probe = probe->next()) {

       probe->classes_do(f);

     }

   }

 }

 void PlaceholderEntry::classes_do(KlassClosure* closure) {

   assert(klassname() != NULL, "should have a non-null klass");

   if (_instanceKlass != NULL) {

     closure->do_klass(instance_klass());

   }

 }

 // do all entries in the placeholder table

 void PlaceholderTable::entries_do(void f(Symbol*)) {

   for (int index = 0; index < table_size(); index++) {

     for (PlaceholderEntry* probe = bucket(index);

                            probe != NULL;

                            probe = probe->next()) {

       f(probe->klassname());

     }

   }

 }

 #ifndef PRODUCT

 // Note, doesn't append a cr

 void PlaceholderEntry::print() const {

   klassname()->print_value();

   if (loader_data() != NULL) {

     tty->print(", loader ");

     loader_data()->print_value();

   }

   if (supername() != NULL) {

     tty->print(", supername ");

     supername()->print_value();

   }

   if (definer() != NULL) {

     tty->print(", definer ");

     definer()->print_value();

   }

   if (instance_klass() != NULL) {

     tty->print(", InstanceKlass ");

     instance_klass()->print_value();

   }

   tty->print("\n");

   tty->print("loadInstanceThreadQ threads:");

   loadInstanceThreadQ()->printActionQ();

   tty->print("\n");

   tty->print("superThreadQ threads:");

   superThreadQ()->printActionQ();

   tty->print("\n");

   tty->print("defineThreadQ threads:");

   defineThreadQ()->printActionQ();

   tty->print("\n");

 }

 #endif

 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()->oop_is_instance(),

             "checking type of instance_klass result");

 }

 void PlaceholderTable::verify() {

   int element_count = 0;

   for (int pindex = 0; pindex < table_size(); pindex++) {

     for (PlaceholderEntry* probe = bucket(pindex);

                            probe != NULL;

                            probe = probe->next()) {

       probe->verify();

       element_count++;  // both klasses and place holders count

     }

   }

   guarantee(number_of_entries() == element_count,

             "Verify of system dictionary failed");

 }

 #ifndef PRODUCT

 void PlaceholderTable::print() {

   for (int pindex = 0; pindex < table_size(); pindex++) {

     for (PlaceholderEntry* probe = bucket(pindex);

                            probe != NULL;

                            probe = probe->next()) {

       if (Verbose) tty->print("%4d: ", pindex);

       tty->print(" place holder ");

       probe->print();

       tty->cr();

     }

   }

 }

 #endif