1 /* 2 * Copyright (c) 2003, 2015, Oracle and/or its affiliates. All rights reserved. 3 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER. 4 * 5 * This code is free software; you can redistribute it and/or modify it 6 * under the terms of the GNU General Public License version 2 only, as 7 * published by the Free Software Foundation. 8 * 9 * This code is distributed in the hope that it will be useful, but WITHOUT 10 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or 11 * FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License 12 * version 2 for more details (a copy is included in the LICENSE file that 13 * accompanied this code). 14 * 15 * You should have received a copy of the GNU General Public License version 16 * 2 along with this work; if not, write to the Free Software Foundation, 17 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 23 */ 24 25 #include "precompiled.hpp" 26 #include "classfile/placeholders.hpp" 27 #include "classfile/systemDictionary.hpp" 28 #include "oops/oop.inline.hpp" 29 #include "runtime/fieldType.hpp" 30 #include "utilities/hashtable.inline.hpp" 31 32 // Placeholder methods 33 34 PlaceholderEntry* PlaceholderTable::new_entry(int hash, Symbol* name, 35 ClassLoaderData* loader_data, 36 bool havesupername, 37 Symbol* supername) { 38 PlaceholderEntry* entry = (PlaceholderEntry*)Hashtable<Symbol*, mtClass>::new_entry(hash, name); 39 // Hashtable with Symbol* literal must increment and decrement refcount. 40 name->increment_refcount(); 41 entry->set_loader_data(loader_data); 42 entry->set_havesupername(havesupername); 43 entry->set_supername(supername); 44 entry->set_superThreadQ(NULL); 45 entry->set_loadInstanceThreadQ(NULL); 46 entry->set_defineThreadQ(NULL); 47 entry->set_definer(NULL); 48 entry->set_instance_klass(NULL); 49 return entry; 50 } 51 52 void PlaceholderTable::free_entry(PlaceholderEntry* entry) { 53 // decrement Symbol refcount here because Hashtable doesn't. 54 entry->literal()->decrement_refcount(); 55 if (entry->supername() != NULL) entry->supername()->decrement_refcount(); 56 Hashtable<Symbol*, mtClass>::free_entry(entry); 57 } 58 59 60 // Placeholder objects represent classes currently being loaded. 61 // All threads examining the placeholder table must hold the 62 // SystemDictionary_lock, so we don't need special precautions 63 // on store ordering here. 64 void PlaceholderTable::add_entry(int index, unsigned int hash, 65 Symbol* class_name, ClassLoaderData* loader_data, 66 bool havesupername, Symbol* supername){ 67 assert_locked_or_safepoint(SystemDictionary_lock); 68 assert(class_name != NULL, "adding NULL obj"); 69 70 // Both readers and writers are locked so it's safe to just 71 // create the placeholder and insert it in the list without a membar. 72 PlaceholderEntry* entry = new_entry(hash, class_name, loader_data, havesupername, supername); 73 add_entry(index, entry); 74 } 75 76 77 // Remove a placeholder object. 78 void PlaceholderTable::remove_entry(int index, unsigned int hash, 79 Symbol* class_name, 80 ClassLoaderData* loader_data) { 81 assert_locked_or_safepoint(SystemDictionary_lock); 82 PlaceholderEntry** p = bucket_addr(index); 83 while (*p) { 84 PlaceholderEntry *probe = *p; 85 if (probe->hash() == hash && probe->equals(class_name, loader_data)) { 86 // Delete entry 87 *p = probe->next(); 88 free_entry(probe); 89 return; 90 } 91 p = probe->next_addr(); 92 } 93 } 94 95 PlaceholderEntry* PlaceholderTable::get_entry(int index, unsigned int hash, 96 Symbol* class_name, 97 ClassLoaderData* loader_data) { 98 assert_locked_or_safepoint(SystemDictionary_lock); 99 100 for (PlaceholderEntry *place_probe = bucket(index); 101 place_probe != NULL; 102 place_probe = place_probe->next()) { 103 if (place_probe->hash() == hash && 104 place_probe->equals(class_name, loader_data)) { 105 return place_probe; 106 } 107 } 108 return NULL; 109 } 110 111 Symbol* PlaceholderTable::find_entry(int index, unsigned int hash, 112 Symbol* class_name, 113 ClassLoaderData* loader_data) { 114 PlaceholderEntry* probe = get_entry(index, hash, class_name, loader_data); 115 return (probe? probe->klassname(): (Symbol*)NULL); 116 } 117 118 // find_and_add returns probe pointer - old or new 119 // If no entry exists, add a placeholder entry 120 // If entry exists, reuse entry 121 // For both, push SeenThread for classloadAction 122 // if havesupername: this is used for circularity for instanceklass loading 123 PlaceholderEntry* PlaceholderTable::find_and_add(int index, unsigned int hash, 124 Symbol* name, 125 ClassLoaderData* loader_data, 126 classloadAction action, 127 Symbol* supername, 128 Thread* thread) { 129 PlaceholderEntry* probe = get_entry(index, hash, name, loader_data); 130 if (probe == NULL) { 131 // Nothing found, add place holder 132 add_entry(index, hash, name, loader_data, (action == LOAD_SUPER), supername); 133 probe = get_entry(index, hash, name, loader_data); 134 } else { 135 if (action == LOAD_SUPER) { 136 probe->set_havesupername(true); 137 probe->set_supername(supername); 138 } 139 } 140 if (probe) probe->add_seen_thread(thread, action); 141 return probe; 142 } 143 144 145 // placeholder is used to track class loading internal states 146 // placeholder existence now for loading superclass/superinterface 147 // superthreadQ tracks class circularity, while loading superclass/superinterface 148 // loadInstanceThreadQ tracks load_instance_class calls 149 // definer() tracks the single thread that owns define token 150 // defineThreadQ tracks waiters on defining thread's results 151 // 1st claimant creates placeholder 152 // find_and_add adds SeenThread entry for appropriate queue 153 // All claimants remove SeenThread after completing action 154 // On removal: if definer and all queues empty, remove entry 155 // Note: you can be in both placeholders and systemDictionary 156 // Therefore - must always check SD first 157 // Ignores the case where entry is not found 158 void PlaceholderTable::find_and_remove(int index, unsigned int hash, 159 Symbol* name, ClassLoaderData* loader_data, 160 classloadAction action, 161 Thread* thread) { 162 assert_locked_or_safepoint(SystemDictionary_lock); 163 PlaceholderEntry *probe = get_entry(index, hash, name, loader_data); 164 if (probe != NULL) { 165 probe->remove_seen_thread(thread, action); 166 // If no other threads using this entry, and this thread is not using this entry for other states 167 if ((probe->superThreadQ() == NULL) && (probe->loadInstanceThreadQ() == NULL) 168 && (probe->defineThreadQ() == NULL) && (probe->definer() == NULL)) { 169 remove_entry(index, hash, name, loader_data); 170 } 171 } 172 } 173 174 PlaceholderTable::PlaceholderTable(int table_size) 175 : TwoOopHashtable<Symbol*, mtClass>(table_size, sizeof(PlaceholderEntry)) { 176 } 177 178 179 void PlaceholderTable::classes_do(KlassClosure* f) { 180 for (int index = 0; index < table_size(); index++) { 181 for (PlaceholderEntry* probe = bucket(index); 182 probe != NULL; 183 probe = probe->next()) { 184 probe->classes_do(f); 185 } 186 } 187 } 188 189 190 void PlaceholderEntry::classes_do(KlassClosure* closure) { 191 assert(klassname() != NULL, "should have a non-null klass"); 192 if (_instanceKlass != NULL) { 193 closure->do_klass(instance_klass()); 194 } 195 } 196 197 198 #ifndef PRODUCT 199 // Note, doesn't append a cr 200 void PlaceholderEntry::print() const { 201 klassname()->print_value(); 202 if (loader_data() != NULL) { 203 tty->print(", loader "); 204 loader_data()->print_value(); 205 } 206 if (supername() != NULL) { 207 tty->print(", supername "); 208 supername()->print_value(); 209 } 210 if (definer() != NULL) { 211 tty->print(", definer "); 212 definer()->print_value(); 213 } 214 if (instance_klass() != NULL) { 215 tty->print(", InstanceKlass "); 216 instance_klass()->print_value(); 217 } 218 tty->print("\n"); 219 tty->print("loadInstanceThreadQ threads:"); 220 loadInstanceThreadQ()->printActionQ(); 221 tty->print("\n"); 222 tty->print("superThreadQ threads:"); 223 superThreadQ()->printActionQ(); 224 tty->print("\n"); 225 tty->print("defineThreadQ threads:"); 226 defineThreadQ()->printActionQ(); 227 tty->print("\n"); 228 } 229 #endif 230 231 void PlaceholderEntry::verify() const { 232 guarantee(loader_data() != NULL, "Must have been setup."); 233 guarantee(loader_data()->class_loader() == NULL || loader_data()->class_loader()->is_instance(), 234 "checking type of _loader"); 235 guarantee(instance_klass() == NULL 236 || instance_klass()->is_instance_klass(), 237 "checking type of instance_klass result"); 238 } 239 240 void PlaceholderTable::verify() { 241 int element_count = 0; 242 for (int pindex = 0; pindex < table_size(); pindex++) { 243 for (PlaceholderEntry* probe = bucket(pindex); 244 probe != NULL; 245 probe = probe->next()) { 246 probe->verify(); 247 element_count++; // both klasses and place holders count 248 } 249 } 250 guarantee(number_of_entries() == element_count, 251 "Verify of system dictionary failed"); 252 } 253 254 255 #ifndef PRODUCT 256 void PlaceholderTable::print() { 257 for (int pindex = 0; pindex < table_size(); pindex++) { 258 for (PlaceholderEntry* probe = bucket(pindex); 259 probe != NULL; 260 probe = probe->next()) { 261 if (Verbose) tty->print("%4d: ", pindex); 262 tty->print(" place holder "); 263 264 probe->print(); 265 tty->cr(); 266 } 267 } 268 } 269 #endif