1 /*
2 * Copyright (c) 2003, 2010, 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, symbolOop name,
35 oop loader, bool havesupername,
36 symbolOop supername) {
37 PlaceholderEntry* entry = (PlaceholderEntry*)Hashtable::new_entry(hash, name);
38 entry->set_loader(loader);
39 entry->set_havesupername(havesupername);
40 entry->set_supername(supername);
41 entry->set_superThreadQ(NULL);
42 entry->set_loadInstanceThreadQ(NULL);
43 entry->set_defineThreadQ(NULL);
44 entry->set_definer(NULL);
45 entry->set_instanceKlass(NULL);
46 return entry;
47 }
48
49
50 // Placeholder objects represent classes currently being loaded.
51 // All threads examining the placeholder table must hold the
52 // SystemDictionary_lock, so we don't need special precautions
53 // on store ordering here.
54 void PlaceholderTable::add_entry(int index, unsigned int hash,
55 symbolHandle class_name, Handle class_loader,
56 bool havesupername, symbolHandle supername){
57 assert_locked_or_safepoint(SystemDictionary_lock);
58 assert(!class_name.is_null(), "adding NULL obj");
59
60 // Both readers and writers are locked so it's safe to just
61 // create the placeholder and insert it in the list without a membar.
62 PlaceholderEntry* entry = new_entry(hash, class_name(), class_loader(), havesupername, supername());
63 add_entry(index, entry);
64 }
65
66
67 // Remove a placeholder object.
68 void PlaceholderTable::remove_entry(int index, unsigned int hash,
69 symbolHandle class_name,
70 Handle class_loader) {
71 assert_locked_or_safepoint(SystemDictionary_lock);
72 PlaceholderEntry** p = bucket_addr(index);
73 while (*p) {
74 PlaceholderEntry *probe = *p;
75 if (probe->hash() == hash && probe->equals(class_name(), class_loader())) {
76 // Delete entry
77 *p = probe->next();
78 free_entry(probe);
79 return;
80 }
81 p = probe->next_addr();
82 }
83 }
84
85 PlaceholderEntry* PlaceholderTable::get_entry(int index, unsigned int hash,
86 symbolHandle class_name,
87 Handle class_loader) {
88 assert_locked_or_safepoint(SystemDictionary_lock);
89
90 symbolOop class_name_ = class_name();
91 oop class_loader_ = class_loader();
92
93 for (PlaceholderEntry *place_probe = bucket(index);
94 place_probe != NULL;
95 place_probe = place_probe->next()) {
96 if (place_probe->hash() == hash &&
97 place_probe->equals(class_name_, class_loader_)) {
98 return place_probe;
99 }
100 }
101 return NULL;
102 }
103
104 symbolOop PlaceholderTable::find_entry(int index, unsigned int hash,
105 symbolHandle class_name,
106 Handle class_loader) {
107 PlaceholderEntry* probe = get_entry(index, hash, class_name, class_loader);
108 return (probe? probe->klass(): symbolOop(NULL));
109 }
110
111 // find_and_add returns probe pointer - old or new
112 // If no entry exists, add a placeholder entry
113 // If entry exists, reuse entry
114 // For both, push SeenThread for classloadAction
115 // if havesupername: this is used for circularity for instanceklass loading
116 PlaceholderEntry* PlaceholderTable::find_and_add(int index, unsigned int hash, symbolHandle name, Handle loader, classloadAction action, symbolHandle supername, Thread* thread) {
117 PlaceholderEntry* probe = get_entry(index, hash, name, loader);
118 if (probe == NULL) {
119 // Nothing found, add place holder
120 add_entry(index, hash, name, loader, (action == LOAD_SUPER), supername);
121 probe = get_entry(index, hash, name, loader);
122 } else {
123 if (action == LOAD_SUPER) {
124 probe->set_havesupername(true);
125 probe->set_supername(supername());
126 }
127 }
128 if (probe) probe->add_seen_thread(thread, action);
129 return probe;
130 }
131
132
133 // placeholder used to track class loading internal states
134 // placeholder existence now for loading superclass/superinterface
135 // superthreadQ tracks class circularity, while loading superclass/superinterface
136 // loadInstanceThreadQ tracks load_instance_class calls
137 // definer() tracks the single thread that owns define token
138 // defineThreadQ tracks waiters on defining thread's results
139 // 1st claimant creates placeholder
140 // find_and_add adds SeenThread entry for appropriate queue
141 // All claimants remove SeenThread after completing action
142 // On removal: if definer and all queues empty, remove entry
143 // Note: you can be in both placeholders and systemDictionary
144 // see parse_stream for redefine classes
145 // Therefore - must always check SD first
146 // Ignores the case where entry is not found
147 void PlaceholderTable::find_and_remove(int index, unsigned int hash,
148 symbolHandle name, Handle loader, Thread* thread) {
149 assert_locked_or_safepoint(SystemDictionary_lock);
150 PlaceholderEntry *probe = get_entry(index, hash, name, loader);
151 if (probe != NULL) {
152 // No other threads using this entry
153 if ((probe->superThreadQ() == NULL) && (probe->loadInstanceThreadQ() == NULL)
154 && (probe->defineThreadQ() == NULL) && (probe->definer() == NULL)) {
155 remove_entry(index, hash, name, loader);
156 }
157 }
158 }
159
160 PlaceholderTable::PlaceholderTable(int table_size)
161 : TwoOopHashtable(table_size, sizeof(PlaceholderEntry)) {
162 }
163
164
165 void PlaceholderTable::oops_do(OopClosure* f) {
166 for (int index = 0; index < table_size(); index++) {
167 for (PlaceholderEntry* probe = bucket(index);
168 probe != NULL;
169 probe = probe->next()) {
170 probe->oops_do(f);
171 }
172 }
173 }
174
175
176 void PlaceholderEntry::oops_do(OopClosure* blk) {
177 assert(klass() != NULL, "should have a non-null klass");
178 blk->do_oop((oop*)klass_addr());
179 if (_loader != NULL) {
180 blk->do_oop(loader_addr());
181 }
182 if (_supername != NULL) {
183 blk->do_oop((oop*)supername_addr());
184 }
185 if (_instanceKlass != NULL) {
186 blk->do_oop((oop*)instanceKlass_addr());
187 }
188 }
189
190 // do all entries in the placeholder table
191 void PlaceholderTable::entries_do(void f(symbolOop, oop)) {
192 for (int index = 0; index < table_size(); index++) {
193 for (PlaceholderEntry* probe = bucket(index);
194 probe != NULL;
195 probe = probe->next()) {
196 f(probe->klass(), probe->loader());
197 }
198 }
199 }
200
201
202 #ifndef PRODUCT
203 // Note, doesn't append a cr
204 void PlaceholderEntry::print() const {
205 klass()->print_value();
206 if (loader() != NULL) {
207 tty->print(", loader ");
208 loader()->print_value();
209 }
210 if (supername() != NULL) {
211 tty->print(", supername ");
212 supername()->print_value();
213 }
214 if (definer() != NULL) {
215 tty->print(", definer ");
216 definer()->print_value();
217 }
218 if (instanceKlass() != NULL) {
219 tty->print(", instanceKlass ");
220 instanceKlass()->print_value();
221 }
222 tty->print("\n");
223 tty->print("loadInstanceThreadQ threads:");
224 loadInstanceThreadQ()->printActionQ();
225 tty->print("\n");
226 tty->print("superThreadQ threads:");
227 superThreadQ()->printActionQ();
228 tty->print("\n");
229 tty->print("defineThreadQ threads:");
230 defineThreadQ()->printActionQ();
231 tty->print("\n");
232 }
233 #endif
234
235 void PlaceholderEntry::verify() const {
236 guarantee(loader() == NULL || loader()->is_instance(),
237 "checking type of _loader");
238 guarantee(instanceKlass() == NULL
239 || Klass::cast(instanceKlass())->oop_is_instance(),
240 "checking type of instanceKlass result");
241 klass()->verify();
242 }
243
244 void PlaceholderTable::verify() {
245 int element_count = 0;
246 for (int pindex = 0; pindex < table_size(); pindex++) {
247 for (PlaceholderEntry* probe = bucket(pindex);
248 probe != NULL;
249 probe = probe->next()) {
250 probe->verify();
251 element_count++; // both klasses and place holders count
252 }
253 }
254 guarantee(number_of_entries() == element_count,
255 "Verify of system dictionary failed");
256 }
257
258
259 #ifndef PRODUCT
260 void PlaceholderTable::print() {
261 for (int pindex = 0; pindex < table_size(); pindex++) {
262 for (PlaceholderEntry* probe = bucket(pindex);
263 probe != NULL;
264 probe = probe->next()) {
265 if (Verbose) tty->print("%4d: ", pindex);
266 tty->print(" place holder ");
267
268 probe->print();
269 tty->cr();
270 }
271 }
272 }
273 #endif