1 /*
2 * Copyright (c) 2003, 2013, 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.
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23 */
24
25 #ifndef SHARE_VM_CLASSFILE_PLACEHOLDERS_HPP
26 #define SHARE_VM_CLASSFILE_PLACEHOLDERS_HPP
27
28 #include "runtime/thread.hpp"
29 #include "utilities/hashtable.hpp"
30
31 class PlaceholderEntry;
32
33 // Placeholder objects. These represent classes currently
34 // being loaded, as well as arrays of primitives.
35 //
36
37 class PlaceholderTable : public TwoOopHashtable<Symbol*, mtClass> {
38 friend class VMStructs;
39
40 public:
41 PlaceholderTable(int table_size);
42
43 PlaceholderEntry* new_entry(int hash, Symbol* name, ClassLoaderData* loader_data, bool havesupername, Symbol* supername);
44 void free_entry(PlaceholderEntry* entry);
45
46 PlaceholderEntry* bucket(int i) {
47 return (PlaceholderEntry*)Hashtable<Symbol*, mtClass>::bucket(i);
48 }
49
50 PlaceholderEntry** bucket_addr(int i) {
51 return (PlaceholderEntry**)Hashtable<Symbol*, mtClass>::bucket_addr(i);
52 }
53
54 void add_entry(int index, PlaceholderEntry* new_entry) {
55 Hashtable<Symbol*, mtClass>::add_entry(index, (HashtableEntry<Symbol*, mtClass>*)new_entry);
56 }
57
58 void add_entry(int index, unsigned int hash, Symbol* name,
59 ClassLoaderData* loader_data, bool havesupername, Symbol* supername);
60
61 // This returns a Symbol* to match type for SystemDictionary
62 Symbol* find_entry(int index, unsigned int hash,
63 Symbol* name, ClassLoaderData* loader_data);
64
65 PlaceholderEntry* get_entry(int index, unsigned int hash,
66 Symbol* name, ClassLoaderData* loader_data);
67
68 // caller to create a placeholder entry must enumerate an action
69 // caller claims ownership of that action
70 // For parallel classloading:
71 // multiple LOAD_INSTANCE threads can proceed in parallel
72 // multiple LOAD_SUPER threads can proceed in parallel
73 // LOAD_SUPER needed to check for class circularity
74 // DEFINE_CLASS: ultimately define class must be single threaded
75 // on a class/classloader basis
76 // so the head of that queue owns the token
77 // and the rest of the threads return the result the first thread gets
78 enum classloadAction {
79 LOAD_INSTANCE = 1, // calling load_instance_class
80 LOAD_SUPER = 2, // loading superclass for this class
81 DEFINE_CLASS = 3 // find_or_define class
82 };
83
84 // find_and_add returns probe pointer - old or new
85 // If no entry exists, add a placeholder entry and push SeenThread for classloadAction
86 // If entry exists, reuse entry and push SeenThread for classloadAction
87 PlaceholderEntry* find_and_add(int index, unsigned int hash,
88 Symbol* name, ClassLoaderData* loader_data,
89 classloadAction action, Symbol* supername,
90 Thread* thread);
91
92 void remove_entry(int index, unsigned int hash,
93 Symbol* name, ClassLoaderData* loader_data);
94
95 // find_and_remove first removes SeenThread for classloadAction
96 // If all queues are empty and definer is null, remove the PlacheholderEntry completely
97 void find_and_remove(int index, unsigned int hash,
98 Symbol* name, ClassLoaderData* loader_data,
99 classloadAction action, Thread* thread);
100
101 // GC support.
102 void classes_do(KlassClosure* f);
103
104 #ifndef PRODUCT
105 void print();
106 #endif
107 void verify();
108 };
109
110 // SeenThread objects represent list of threads that are
111 // currently performing a load action on a class.
112 // For class circularity, set before loading a superclass.
113 // For bootclasssearchpath, set before calling load_instance_class.
114 // Defining must be single threaded on a class/classloader basis
115 // For DEFINE_CLASS, the head of the queue owns the
116 // define token and the rest of the threads wait to return the
117 // result the first thread gets.
118 class SeenThread: public CHeapObj<mtInternal> {
119 private:
120 Thread *_thread;
121 SeenThread* _stnext;
122 SeenThread* _stprev;
123 public:
124 SeenThread(Thread *thread) {
125 _thread = thread;
126 _stnext = NULL;
127 _stprev = NULL;
128 }
129 Thread* thread() const { return _thread;}
130 void set_thread(Thread *thread) { _thread = thread; }
131
132 SeenThread* next() const { return _stnext;}
133 void set_next(SeenThread *seen) { _stnext = seen; }
134 void set_prev(SeenThread *seen) { _stprev = seen; }
135
136 #ifndef PRODUCT
137 void printActionQ() {
138 SeenThread* seen = this;
139 while (seen != NULL) {
140 seen->thread()->print_value();
141 tty->print(", ");
142 seen = seen->next();
143 }
144 }
145 #endif // PRODUCT
146 };
147
148 // Placeholder objects represent classes currently being loaded.
149 // All threads examining the placeholder table must hold the
150 // SystemDictionary_lock, so we don't need special precautions
151 // on store ordering here.
152 // The system dictionary is the only user of this class.
153
154 class PlaceholderEntry : public HashtableEntry<Symbol*, mtClass> {
155 friend class VMStructs;
156
157
158 private:
159 ClassLoaderData* _loader_data; // initiating loader
160 bool _havesupername; // distinguish between null supername, and unknown
161 Symbol* _supername;
162 Thread* _definer; // owner of define token
163 Klass* _instanceKlass; // InstanceKlass from successful define
164 SeenThread* _superThreadQ; // doubly-linked queue of Threads loading a superclass for this class
165 SeenThread* _loadInstanceThreadQ; // loadInstance thread
166 // can be multiple threads if classloader object lock broken by application
167 // or if classloader supports parallel classloading
168
169 SeenThread* _defineThreadQ; // queue of Threads trying to define this class
170 // including _definer
171 // _definer owns token
172 // queue waits for and returns results from _definer
173
174 public:
175 // Simple accessors, used only by SystemDictionary
176 Symbol* klassname() const { return literal(); }
177
178 ClassLoaderData* loader_data() const { return _loader_data; }
179 void set_loader_data(ClassLoaderData* loader_data) { _loader_data = loader_data; }
180
181 bool havesupername() const { return _havesupername; }
182 void set_havesupername(bool havesupername) { _havesupername = havesupername; }
183
184 Symbol* supername() const { return _supername; }
185 void set_supername(Symbol* supername) {
186 _supername = supername;
187 if (_supername != NULL) _supername->increment_refcount();
188 }
189
190 Thread* definer() const {return _definer; }
191 void set_definer(Thread* definer) { _definer = definer; }
192
193 Klass* instance_klass() const {return _instanceKlass; }
194 void set_instance_klass(Klass* ik) { _instanceKlass = ik; }
195
196 SeenThread* superThreadQ() const { return _superThreadQ; }
197 void set_superThreadQ(SeenThread* SeenThread) { _superThreadQ = SeenThread; }
198
199 SeenThread* loadInstanceThreadQ() const { return _loadInstanceThreadQ; }
200 void set_loadInstanceThreadQ(SeenThread* SeenThread) { _loadInstanceThreadQ = SeenThread; }
201
202 SeenThread* defineThreadQ() const { return _defineThreadQ; }
203 void set_defineThreadQ(SeenThread* SeenThread) { _defineThreadQ = SeenThread; }
204
205 PlaceholderEntry* next() const {
206 return (PlaceholderEntry*)HashtableEntry<Symbol*, mtClass>::next();
207 }
208
209 PlaceholderEntry** next_addr() {
210 return (PlaceholderEntry**)HashtableEntry<Symbol*, mtClass>::next_addr();
211 }
212
213 // Test for equality
214 // Entries are unique for class/classloader name pair
215 bool equals(Symbol* class_name, ClassLoaderData* loader) const {
216 return (klassname() == class_name && loader_data() == loader);
217 }
218
219 SeenThread* actionToQueue(PlaceholderTable::classloadAction action) {
220 SeenThread* queuehead = NULL;
221 switch (action) {
222 case PlaceholderTable::LOAD_INSTANCE:
223 queuehead = _loadInstanceThreadQ;
224 break;
225 case PlaceholderTable::LOAD_SUPER:
226 queuehead = _superThreadQ;
227 break;
228 case PlaceholderTable::DEFINE_CLASS:
229 queuehead = _defineThreadQ;
230 break;
231 default: Unimplemented();
232 }
233 return queuehead;
234 }
235
236 void set_threadQ(SeenThread* seenthread, PlaceholderTable::classloadAction action) {
237 switch (action) {
238 case PlaceholderTable::LOAD_INSTANCE:
239 _loadInstanceThreadQ = seenthread;
240 break;
241 case PlaceholderTable::LOAD_SUPER:
242 _superThreadQ = seenthread;
243 break;
244 case PlaceholderTable::DEFINE_CLASS:
245 _defineThreadQ = seenthread;
246 break;
247 default: Unimplemented();
248 }
249 return;
250 }
251
252 bool super_load_in_progress() {
253 return (_superThreadQ != NULL);
254 }
255
256 bool instance_load_in_progress() {
257 return (_loadInstanceThreadQ != NULL);
258 }
259
260 bool define_class_in_progress() {
261 return (_defineThreadQ != NULL);
262 }
263
264 // Doubly-linked list of Threads per action for class/classloader pair
265 // Class circularity support: links in thread before loading superclass
266 // bootstrapsearchpath support: links in a thread before load_instance_class
267 // definers: use as queue of define requestors, including owner of
268 // define token. Appends for debugging of requestor order
269 void add_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {
270 assert_lock_strong(SystemDictionary_lock);
271 SeenThread* threadEntry = new SeenThread(thread);
272 SeenThread* seen = actionToQueue(action);
273
274 if (seen == NULL) {
275 set_threadQ(threadEntry, action);
276 return;
277 }
278 SeenThread* next;
279 while ((next = seen->next()) != NULL) {
280 seen = next;
281 }
282 seen->set_next(threadEntry);
283 threadEntry->set_prev(seen);
284 return;
285 }
286
287 bool check_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {
288 assert_lock_strong(SystemDictionary_lock);
289 SeenThread* threadQ = actionToQueue(action);
290 SeenThread* seen = threadQ;
291 while (seen) {
292 if (thread == seen->thread()) {
293 return true;
294 }
295 seen = seen->next();
296 }
297 return false;
298 }
299
300 // returns true if seenthreadQ is now empty
301 // Note, caller must ensure probe still exists while holding
302 // SystemDictionary_lock
303 // ignores if cleanup has already been done
304 // if found, deletes SeenThread
305 bool remove_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {
306 assert_lock_strong(SystemDictionary_lock);
307 SeenThread* threadQ = actionToQueue(action);
308 SeenThread* seen = threadQ;
309 SeenThread* prev = NULL;
310 while (seen) {
311 if (thread == seen->thread()) {
312 if (prev) {
313 prev->set_next(seen->next());
314 } else {
315 set_threadQ(seen->next(), action);
316 }
317 if (seen->next()) {
318 seen->next()->set_prev(prev);
319 }
320 delete seen;
321 break;
322 }
323 prev = seen;
324 seen = seen->next();
325 }
326 return (actionToQueue(action) == NULL);
327 }
328
329 // GC support
330 // Applies "f->do_oop" to all root oops in the placeholder table.
331 void classes_do(KlassClosure* closure);
332
333 // Print method doesn't append a cr
334 void print() const PRODUCT_RETURN;
335 void verify() const;
336 };
337
338 #endif // SHARE_VM_CLASSFILE_PLACEHOLDERS_HPP