1 /*
2 * Copyright (c) 2003, 2017, 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 #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 Hashtable<Symbol*, mtClass> {
38
39 public:
40 PlaceholderTable(int table_size);
41
42 PlaceholderEntry* new_entry(int hash, Symbol* name, ClassLoaderData* loader_data, bool havesupername, Symbol* supername);
43 void free_entry(PlaceholderEntry* entry);
44
45 PlaceholderEntry* bucket(int i) {
46 return (PlaceholderEntry*)Hashtable<Symbol*, mtClass>::bucket(i);
47 }
48
49 PlaceholderEntry** bucket_addr(int i) {
50 return (PlaceholderEntry**)Hashtable<Symbol*, mtClass>::bucket_addr(i);
51 }
52
53 void add_entry(int index, PlaceholderEntry* new_entry) {
54 Hashtable<Symbol*, mtClass>::add_entry(index, (HashtableEntry<Symbol*, mtClass>*)new_entry);
55 }
56
57 void add_entry(int index, unsigned int hash, Symbol* name,
58 ClassLoaderData* loader_data, bool havesupername, Symbol* supername);
59
60 // This returns a Symbol* to match type for SystemDictionary
61 Symbol* find_entry(int index, unsigned int hash,
62 Symbol* name, ClassLoaderData* loader_data);
63
64 PlaceholderEntry* get_entry(int index, unsigned int hash,
65 Symbol* name, ClassLoaderData* loader_data);
66
67 // caller to create a placeholder entry must enumerate an action
68 // caller claims ownership of that action
69 // For parallel classloading:
70 // multiple LOAD_INSTANCE threads can proceed in parallel
71 // multiple LOAD_SUPER threads can proceed in parallel
72 // LOAD_SUPER needed to check for class circularity
73 // DEFINE_CLASS: ultimately define class must be single threaded
74 // on a class/classloader basis
75 // so the head of that queue owns the token
76 // and the rest of the threads return the result the first thread gets
77 enum classloadAction {
78 LOAD_INSTANCE = 1, // calling load_instance_class
79 LOAD_SUPER = 2, // loading superclass for this class
80 DEFINE_CLASS = 3 // find_or_define class
81 };
82
83 // find_and_add returns probe pointer - old or new
84 // If no entry exists, add a placeholder entry and push SeenThread for classloadAction
85 // If entry exists, reuse entry and push SeenThread for classloadAction
86 PlaceholderEntry* find_and_add(int index, unsigned int hash,
87 Symbol* name, ClassLoaderData* loader_data,
88 classloadAction action, Symbol* supername,
89 Thread* thread);
90
91 void remove_entry(int index, unsigned int hash,
92 Symbol* name, ClassLoaderData* loader_data);
93
94 // find_and_remove first removes SeenThread for classloadAction
95 // If all queues are empty and definer is null, remove the PlacheholderEntry completely
96 void find_and_remove(int index, unsigned int hash,
97 Symbol* name, ClassLoaderData* loader_data,
98 classloadAction action, Thread* thread);
99
100 #ifndef PRODUCT
101 void print();
102 #endif
103 void verify();
104 };
105
106 // SeenThread objects represent list of threads that are
107 // currently performing a load action on a class.
108 // For class circularity, set before loading a superclass.
109 // For bootclasssearchpath, set before calling load_instance_class.
110 // Defining must be single threaded on a class/classloader basis
111 // For DEFINE_CLASS, the head of the queue owns the
112 // define token and the rest of the threads wait to return the
113 // result the first thread gets.
114 class SeenThread: public CHeapObj<mtInternal> {
115 private:
116 Thread *_thread;
117 SeenThread* _stnext;
118 SeenThread* _stprev;
119 public:
120 SeenThread(Thread *thread) {
121 _thread = thread;
122 _stnext = NULL;
123 _stprev = NULL;
124 }
125 Thread* thread() const { return _thread;}
126 void set_thread(Thread *thread) { _thread = thread; }
127
128 SeenThread* next() const { return _stnext;}
129 void set_next(SeenThread *seen) { _stnext = seen; }
130 void set_prev(SeenThread *seen) { _stprev = seen; }
131
132 #ifndef PRODUCT
133 void printActionQ() {
134 SeenThread* seen = this;
135 while (seen != NULL) {
136 seen->thread()->print_value();
137 tty->print(", ");
138 seen = seen->next();
139 }
140 }
141 #endif // PRODUCT
142 };
143
144 // Placeholder objects represent classes currently being loaded.
145 // All threads examining the placeholder table must hold the
146 // SystemDictionary_lock, so we don't need special precautions
147 // on store ordering here.
148 // The system dictionary is the only user of this class.
149
150 class PlaceholderEntry : public HashtableEntry<Symbol*, mtClass> {
151
152 private:
153 ClassLoaderData* _loader_data; // initiating loader
154 bool _havesupername; // distinguish between null supername, and unknown
155 Symbol* _supername;
156 Thread* _definer; // owner of define token
157 InstanceKlass* _instanceKlass; // InstanceKlass from successful define
158 SeenThread* _superThreadQ; // doubly-linked queue of Threads loading a superclass for this class
159 SeenThread* _loadInstanceThreadQ; // loadInstance thread
160 // can be multiple threads if classloader object lock broken by application
161 // or if classloader supports parallel classloading
162
163 SeenThread* _defineThreadQ; // queue of Threads trying to define this class
164 // including _definer
165 // _definer owns token
166 // queue waits for and returns results from _definer
167
168 public:
169 // Simple accessors, used only by SystemDictionary
170 Symbol* klassname() const { return literal(); }
171
172 ClassLoaderData* loader_data() const { return _loader_data; }
173 void set_loader_data(ClassLoaderData* loader_data) { _loader_data = loader_data; }
174
175 bool havesupername() const { return _havesupername; }
176 void set_havesupername(bool havesupername) { _havesupername = havesupername; }
177
178 Symbol* supername() const { return _supername; }
179 void set_supername(Symbol* supername) {
180 _supername = supername;
181 if (_supername != NULL) _supername->increment_refcount();
182 }
183
184 Thread* definer() const {return _definer; }
185 void set_definer(Thread* definer) { _definer = definer; }
186
187 InstanceKlass* instance_klass() const {return _instanceKlass; }
188 void set_instance_klass(InstanceKlass* ik) { _instanceKlass = ik; }
189
190 SeenThread* superThreadQ() const { return _superThreadQ; }
191 void set_superThreadQ(SeenThread* SeenThread) { _superThreadQ = SeenThread; }
192
193 SeenThread* loadInstanceThreadQ() const { return _loadInstanceThreadQ; }
194 void set_loadInstanceThreadQ(SeenThread* SeenThread) { _loadInstanceThreadQ = SeenThread; }
195
196 SeenThread* defineThreadQ() const { return _defineThreadQ; }
197 void set_defineThreadQ(SeenThread* SeenThread) { _defineThreadQ = SeenThread; }
198
199 PlaceholderEntry* next() const {
200 return (PlaceholderEntry*)HashtableEntry<Symbol*, mtClass>::next();
201 }
202
203 PlaceholderEntry** next_addr() {
204 return (PlaceholderEntry**)HashtableEntry<Symbol*, mtClass>::next_addr();
205 }
206
207 // Test for equality
208 // Entries are unique for class/classloader name pair
209 bool equals(Symbol* class_name, ClassLoaderData* loader) const {
210 return (klassname() == class_name && loader_data() == loader);
211 }
212
213 SeenThread* actionToQueue(PlaceholderTable::classloadAction action) {
214 SeenThread* queuehead = NULL;
215 switch (action) {
216 case PlaceholderTable::LOAD_INSTANCE:
217 queuehead = _loadInstanceThreadQ;
218 break;
219 case PlaceholderTable::LOAD_SUPER:
220 queuehead = _superThreadQ;
221 break;
222 case PlaceholderTable::DEFINE_CLASS:
223 queuehead = _defineThreadQ;
224 break;
225 default: Unimplemented();
226 }
227 return queuehead;
228 }
229
230 void set_threadQ(SeenThread* seenthread, PlaceholderTable::classloadAction action) {
231 switch (action) {
232 case PlaceholderTable::LOAD_INSTANCE:
233 _loadInstanceThreadQ = seenthread;
234 break;
235 case PlaceholderTable::LOAD_SUPER:
236 _superThreadQ = seenthread;
237 break;
238 case PlaceholderTable::DEFINE_CLASS:
239 _defineThreadQ = seenthread;
240 break;
241 default: Unimplemented();
242 }
243 return;
244 }
245
246 bool super_load_in_progress() {
247 return (_superThreadQ != NULL);
248 }
249
250 bool instance_load_in_progress() {
251 return (_loadInstanceThreadQ != NULL);
252 }
253
254 bool define_class_in_progress() {
255 return (_defineThreadQ != NULL);
256 }
257
258 // Doubly-linked list of Threads per action for class/classloader pair
259 // Class circularity support: links in thread before loading superclass
260 // bootstrapsearchpath support: links in a thread before load_instance_class
261 // definers: use as queue of define requestors, including owner of
262 // define token. Appends for debugging of requestor order
263 void add_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {
264 assert_lock_strong(SystemDictionary_lock);
265 SeenThread* threadEntry = new SeenThread(thread);
266 SeenThread* seen = actionToQueue(action);
267
268 if (seen == NULL) {
269 set_threadQ(threadEntry, action);
270 return;
271 }
272 SeenThread* next;
273 while ((next = seen->next()) != NULL) {
274 seen = next;
275 }
276 seen->set_next(threadEntry);
277 threadEntry->set_prev(seen);
278 return;
279 }
280
281 bool check_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {
282 assert_lock_strong(SystemDictionary_lock);
283 SeenThread* threadQ = actionToQueue(action);
284 SeenThread* seen = threadQ;
285 while (seen) {
286 if (thread == seen->thread()) {
287 return true;
288 }
289 seen = seen->next();
290 }
291 return false;
292 }
293
294 // returns true if seenthreadQ is now empty
295 // Note, caller must ensure probe still exists while holding
296 // SystemDictionary_lock
297 // ignores if cleanup has already been done
298 // if found, deletes SeenThread
299 bool remove_seen_thread(Thread* thread, PlaceholderTable::classloadAction action) {
300 assert_lock_strong(SystemDictionary_lock);
301 SeenThread* threadQ = actionToQueue(action);
302 SeenThread* seen = threadQ;
303 SeenThread* prev = NULL;
304 while (seen) {
305 if (thread == seen->thread()) {
306 if (prev) {
307 prev->set_next(seen->next());
308 } else {
309 set_threadQ(seen->next(), action);
310 }
311 if (seen->next()) {
312 seen->next()->set_prev(prev);
313 }
314 delete seen;
315 break;
316 }
317 prev = seen;
318 seen = seen->next();
319 }
320 return (actionToQueue(action) == NULL);
321 }
322
323 // Print method doesn't append a cr
324 void print() const PRODUCT_RETURN;
325 void verify() const;
326 };
327
328 #endif // SHARE_VM_CLASSFILE_PLACEHOLDERS_HPP