1 /*
2 * Copyright (c) 2003, 2007, 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 "incls/_precompiled.incl"
26 # include "incls/_placeholders.cpp.incl"
27
28 // Placeholder methods
29
30 PlaceholderEntry* PlaceholderTable::new_entry(int hash, symbolOop name,
31 oop loader, bool havesupername,
32 symbolOop supername) {
33 PlaceholderEntry* entry = (PlaceholderEntry*)Hashtable::new_entry(hash, name);
34 entry->set_loader(loader);
35 entry->set_havesupername(havesupername);
36 entry->set_supername(supername);
37 entry->set_superThreadQ(NULL);
38 entry->set_loadInstanceThreadQ(NULL);
39 entry->set_defineThreadQ(NULL);
40 entry->set_definer(NULL);
41 entry->set_instanceKlass(NULL);
42 return entry;
43 }
44
45
46 // Placeholder objects represent classes currently being loaded.
47 // All threads examining the placeholder table must hold the
48 // SystemDictionary_lock, so we don't need special precautions
49 // on store ordering here.
50 void PlaceholderTable::add_entry(int index, unsigned int hash,
51 symbolHandle class_name, Handle class_loader,
52 bool havesupername, symbolHandle supername){
53 assert_locked_or_safepoint(SystemDictionary_lock);
54 assert(!class_name.is_null(), "adding NULL obj");
55
56 // Both readers and writers are locked so it's safe to just
57 // create the placeholder and insert it in the list without a membar.
58 PlaceholderEntry* entry = new_entry(hash, class_name(), class_loader(), havesupername, supername());
59 add_entry(index, entry);
60 }
61
62
63 // Remove a placeholder object.
64 void PlaceholderTable::remove_entry(int index, unsigned int hash,
65 symbolHandle class_name,
66 Handle class_loader) {
67 assert_locked_or_safepoint(SystemDictionary_lock);
68 PlaceholderEntry** p = bucket_addr(index);
69 while (*p) {
70 PlaceholderEntry *probe = *p;
71 if (probe->hash() == hash && probe->equals(class_name(), class_loader())) {
72 // Delete entry
73 *p = probe->next();
74 free_entry(probe);
75 return;
76 }
77 p = probe->next_addr();
78 }
79 }
80
81 PlaceholderEntry* PlaceholderTable::get_entry(int index, unsigned int hash,
82 symbolHandle class_name,
83 Handle class_loader) {
84 assert_locked_or_safepoint(SystemDictionary_lock);
85
86 symbolOop class_name_ = class_name();
87 oop class_loader_ = class_loader();
88
89 for (PlaceholderEntry *place_probe = bucket(index);
90 place_probe != NULL;
91 place_probe = place_probe->next()) {
92 if (place_probe->hash() == hash &&
93 place_probe->equals(class_name_, class_loader_)) {
94 return place_probe;
95 }
96 }
97 return NULL;
98 }
99
100 symbolOop PlaceholderTable::find_entry(int index, unsigned int hash,
101 symbolHandle class_name,
102 Handle class_loader) {
103 PlaceholderEntry* probe = get_entry(index, hash, class_name, class_loader);
104 return (probe? probe->klass(): symbolOop(NULL));
105 }
106
107 // find_and_add returns probe pointer - old or new
108 // If no entry exists, add a placeholder entry
109 // If entry exists, reuse entry
110 // For both, push SeenThread for classloadAction
111 // if havesupername: this is used for circularity for instanceklass loading
112 PlaceholderEntry* PlaceholderTable::find_and_add(int index, unsigned int hash, symbolHandle name, Handle loader, classloadAction action, symbolHandle supername, Thread* thread) {
113 PlaceholderEntry* probe = get_entry(index, hash, name, loader);
114 if (probe == NULL) {
115 // Nothing found, add place holder
116 add_entry(index, hash, name, loader, (action == LOAD_SUPER), supername);
117 probe = get_entry(index, hash, name, loader);
118 } else {
119 if (action == LOAD_SUPER) {
120 probe->set_havesupername(true);
121 probe->set_supername(supername());
122 }
123 }
124 if (probe) probe->add_seen_thread(thread, action);
125 return probe;
126 }
127
128
129 // placeholder used to track class loading internal states
130 // placeholder existence now for loading superclass/superinterface
131 // superthreadQ tracks class circularity, while loading superclass/superinterface
132 // loadInstanceThreadQ tracks load_instance_class calls
133 // definer() tracks the single thread that owns define token
134 // defineThreadQ tracks waiters on defining thread's results
135 // 1st claimant creates placeholder
136 // find_and_add adds SeenThread entry for appropriate queue
137 // All claimants remove SeenThread after completing action
138 // On removal: if definer and all queues empty, remove entry
139 // Note: you can be in both placeholders and systemDictionary
140 // see parse_stream for redefine classes
141 // Therefore - must always check SD first
142 // Ignores the case where entry is not found
143 void PlaceholderTable::find_and_remove(int index, unsigned int hash,
144 symbolHandle name, Handle loader, Thread* thread) {
145 assert_locked_or_safepoint(SystemDictionary_lock);
146 PlaceholderEntry *probe = get_entry(index, hash, name, loader);
147 if (probe != NULL) {
148 // No other threads using this entry
149 if ((probe->superThreadQ() == NULL) && (probe->loadInstanceThreadQ() == NULL)
150 && (probe->defineThreadQ() == NULL) && (probe->definer() == NULL)) {
151 remove_entry(index, hash, name, loader);
152 }
153 }
154 }
155
156 PlaceholderTable::PlaceholderTable(int table_size)
157 : TwoOopHashtable(table_size, sizeof(PlaceholderEntry)) {
158 }
159
160
161 void PlaceholderTable::oops_do(OopClosure* f) {
162 for (int index = 0; index < table_size(); index++) {
163 for (PlaceholderEntry* probe = bucket(index);
164 probe != NULL;
165 probe = probe->next()) {
166 probe->oops_do(f);
167 }
168 }
169 }
170
171
172 void PlaceholderEntry::oops_do(OopClosure* blk) {
173 assert(klass() != NULL, "should have a non-null klass");
174 blk->do_oop((oop*)klass_addr());
175 if (_loader != NULL) {
176 blk->do_oop(loader_addr());
177 }
178 if (_supername != NULL) {
179 blk->do_oop((oop*)supername_addr());
180 }
181 if (_instanceKlass != NULL) {
182 blk->do_oop((oop*)instanceKlass_addr());
183 }
184 }
185
186 // do all entries in the placeholder table
187 void PlaceholderTable::entries_do(void f(symbolOop, oop)) {
188 for (int index = 0; index < table_size(); index++) {
189 for (PlaceholderEntry* probe = bucket(index);
190 probe != NULL;
191 probe = probe->next()) {
192 f(probe->klass(), probe->loader());
193 }
194 }
195 }
196
197
198 #ifndef PRODUCT
199 // Note, doesn't append a cr
200 void PlaceholderEntry::print() const {
201 klass()->print_value();
202 if (loader() != NULL) {
203 tty->print(", loader ");
204 loader()->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 (instanceKlass() != NULL) {
215 tty->print(", instanceKlass ");
216 instanceKlass()->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() == NULL || loader()->is_instance(),
233 "checking type of _loader");
234 guarantee(instanceKlass() == NULL
235 || Klass::cast(instanceKlass())->oop_is_instance(),
236 "checking type of instanceKlass result");
237 klass()->verify();
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