1 /*
2 * Copyright (c) 2012, 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.
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23 */
24
25 #ifndef SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP
26 #define SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP
27
28 #include "memory/allocation.hpp"
29 #include "memory/memRegion.hpp"
30 #include "memory/metaspace.hpp"
31 #include "memory/metaspaceCounters.hpp"
32 #include "runtime/handles.hpp"
33 #include "runtime/mutex.hpp"
34 #include "utilities/growableArray.hpp"
35 #include "utilities/macros.hpp"
36 #if INCLUDE_TRACE
37 #include "utilities/ticks.hpp"
38 #endif
39
40 //
41 // A class loader represents a linkset. Conceptually, a linkset identifies
42 // the complete transitive closure of resolved links that a dynamic linker can
43 // produce.
44 //
45 // A ClassLoaderData also encapsulates the allocation space, called a metaspace,
46 // used by the dynamic linker to allocate the runtime representation of all
47 // the types it defines.
48 //
49 // ClassLoaderData are stored in the runtime representation of classes and the
50 // system dictionary, are roots of garbage collection, and provides iterators
51 // for root tracing and other GC operations.
52
53 class ClassLoaderData;
54 class JNIMethodBlock;
55 class Metadebug;
56
57 // GC root for walking class loader data created
58
59 class ClassLoaderDataGraph : public AllStatic {
60 friend class ClassLoaderData;
61 friend class ClassLoaderDataGraphMetaspaceIterator;
62 friend class ClassLoaderDataGraphKlassIteratorAtomic;
63 friend class VMStructs;
64 private:
65 // All CLDs (except the null CLD) can be reached by walking _head->_next->...
66 static ClassLoaderData* _head;
67 static ClassLoaderData* _unloading;
68 // CMS support.
69 static ClassLoaderData* _saved_head;
70 static ClassLoaderData* _saved_unloading;
71 static bool _should_purge;
72
73 static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS);
74 static void post_class_unload_events(void);
75 static void clean_metaspaces();
76 public:
77 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);
78 static void purge();
79 static void clear_claimed_marks();
80 // oops do
81 static void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
82 static void keep_alive_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
83 static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
84 // cld do
85 static void cld_do(CLDClosure* cl);
86 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);
87 static void keep_alive_cld_do(CLDClosure* cl);
88 static void always_strong_cld_do(CLDClosure* cl);
89 // klass do
90 static void classes_do(KlassClosure* klass_closure);
91 static void classes_do(void f(Klass* const));
92 static void loaded_classes_do(KlassClosure* klass_closure);
93 static void classes_unloading_do(void f(Klass* const));
94 static bool do_unloading(BoolObjectClosure* is_alive, bool clean_alive);
95
96 // CMS support.
97 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
98 static GrowableArray<ClassLoaderData*>* new_clds();
99
100 static void set_should_purge(bool b) { _should_purge = b; }
101 static void purge_if_needed() {
102 // Only purge the CLDG for CMS if concurrent sweep is complete.
103 if (_should_purge) {
104 purge();
105 // reset for next time.
106 set_should_purge(false);
107 }
108 }
109
110 static void free_deallocate_lists();
111
112 static void dump_on(outputStream * const out) PRODUCT_RETURN;
113 static void dump() { dump_on(tty); }
114 static void verify();
115
116 static bool unload_list_contains(const void* x);
117 #ifndef PRODUCT
118 static bool contains_loader_data(ClassLoaderData* loader_data);
119 #endif
120
121 #if INCLUDE_TRACE
122 private:
123 static Ticks _class_unload_time;
124 static void class_unload_event(Klass* const k);
125 #endif
126 };
127
128 // ClassLoaderData class
129
130 class ClassLoaderData : public CHeapObj<mtClass> {
131 friend class VMStructs;
132 private:
133 class Dependencies VALUE_OBJ_CLASS_SPEC {
134 objArrayOop _list_head;
135 void locked_add(objArrayHandle last,
136 objArrayHandle new_dependency,
137 Thread* THREAD);
138 public:
139 Dependencies() : _list_head(NULL) {}
140 Dependencies(TRAPS) : _list_head(NULL) {
141 init(CHECK);
142 }
143 void add(Handle dependency, TRAPS);
144 void init(TRAPS);
145 void oops_do(OopClosure* f);
146 };
147
148 class ChunkedHandleList VALUE_OBJ_CLASS_SPEC {
149 struct Chunk : public CHeapObj<mtClass> {
150 static const size_t CAPACITY = 32;
151
152 oop _data[CAPACITY];
153 volatile juint _size;
154 Chunk* _next;
155
156 Chunk(Chunk* c) : _next(c), _size(0) { }
157 };
158
159 Chunk* _head;
160
161 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
162
163 public:
164 ChunkedHandleList() : _head(NULL) {}
165 ~ChunkedHandleList();
166
167 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
168 // However, multiple threads can execute oops_do concurrently with add.
169 oop* add(oop o);
170 void oops_do(OopClosure* f);
171 };
172
173 friend class ClassLoaderDataGraph;
174 friend class ClassLoaderDataGraphKlassIteratorAtomic;
175 friend class ClassLoaderDataGraphMetaspaceIterator;
176 friend class MetaDataFactory;
177 friend class Method;
178 friend class ParallelCLDRootIterator;
179
180 static ClassLoaderData * _the_null_class_loader_data;
181
182 oop _class_loader; // oop used to uniquely identify a class loader
183 // class loader or a canonical class path
184 Dependencies _dependencies; // holds dependencies from this class loader
185 // data to others.
186
187 Metaspace * _metaspace; // Meta-space where meta-data defined by the
188 // classes in the class loader are allocated.
189 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
190 bool _unloading; // true if this class loader goes away
191 bool _keep_alive; // if this CLD is kept alive without a keep_alive_object().
192 bool _is_anonymous; // if this CLD is for an anonymous class
193 volatile int _claimed; // true if claimed, for example during GC traces.
194 // To avoid applying oop closure more than once.
195 // Has to be an int because we cas it.
196 Klass* _klasses; // The classes defined by the class loader.
197
198 ChunkedHandleList _handles; // Handles to constant pool arrays, etc, which
199 // have the same life cycle of the corresponding ClassLoader.
200
201 // These method IDs are created for the class loader and set to NULL when the
202 // class loader is unloaded. They are rarely freed, only for redefine classes
203 // and if they lose a data race in InstanceKlass.
204 JNIMethodBlock* _jmethod_ids;
205
206 // Metadata to be deallocated when it's safe at class unloading, when
207 // this class loader isn't unloaded itself.
208 GrowableArray<Metadata*>* _deallocate_list;
209
210 // Support for walking class loader data objects
211 ClassLoaderData* _next; /// Next loader_datas created
212
213 // ReadOnly and ReadWrite metaspaces (static because only on the null
214 // class loader for now).
215 static Metaspace* _ro_metaspace;
216 static Metaspace* _rw_metaspace;
217
218 void set_next(ClassLoaderData* next) { _next = next; }
219 ClassLoaderData* next() const { return _next; }
220
221 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
222 ~ClassLoaderData();
223
224 void set_metaspace(Metaspace* m) { _metaspace = m; }
225
226 Mutex* metaspace_lock() const { return _metaspace_lock; }
227
228 // GC interface.
229 void clear_claimed() { _claimed = 0; }
230 bool claimed() const { return _claimed == 1; }
231 bool claim();
232
233 void unload();
234 bool keep_alive() const { return _keep_alive; }
235 void classes_do(void f(Klass*));
236 void loaded_classes_do(KlassClosure* klass_closure);
237 void classes_do(void f(InstanceKlass*));
238
239 // Deallocate free list during class unloading.
240 void free_deallocate_list();
241
242 // Allocate out of this class loader data
243 MetaWord* allocate(size_t size);
244
245 public:
246
247 bool is_alive(BoolObjectClosure* is_alive_closure) const;
248
249 // Accessors
250 Metaspace* metaspace_or_null() const { return _metaspace; }
251
252 static ClassLoaderData* the_null_class_loader_data() {
253 return _the_null_class_loader_data;
254 }
255
256 bool is_anonymous() const { return _is_anonymous; }
257
258 static void init_null_class_loader_data() {
259 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
260 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
261
262 // We explicitly initialize the Dependencies object at a later phase in the initialization
263 _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies());
264 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
265 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
266 if (DumpSharedSpaces) {
267 _the_null_class_loader_data->initialize_shared_metaspaces();
268 }
269 }
270
271 bool is_the_null_class_loader_data() const {
272 return this == _the_null_class_loader_data;
273 }
274 bool is_ext_class_loader_data() const;
275
276 // The Metaspace is created lazily so may be NULL. This
277 // method will allocate a Metaspace if needed.
278 Metaspace* metaspace_non_null();
279
280 oop class_loader() const { return _class_loader; }
281
282 // The object the GC is using to keep this ClassLoaderData alive.
283 oop keep_alive_object() const;
284
285 // Returns true if this class loader data is for a loader going away.
286 bool is_unloading() const {
287 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
288 return _unloading;
289 }
290
291 // Used to make sure that this CLD is not unloaded.
292 void set_keep_alive(bool value) { _keep_alive = value; }
293
294 unsigned int identity_hash() {
295 return _class_loader == NULL ? 0 : _class_loader->identity_hash();
296 }
297
298 // Used when tracing from klasses.
299 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
300
301 void classes_do(KlassClosure* klass_closure);
302
303 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
304 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
305
306 void print_value() { print_value_on(tty); }
307 void print_value_on(outputStream* out) const;
308 void dump(outputStream * const out) PRODUCT_RETURN;
309 void verify();
310 const char* loader_name();
311
312 jobject add_handle(Handle h);
313 void add_class(Klass* k);
314 void remove_class(Klass* k);
315 bool contains_klass(Klass* k);
316 void record_dependency(Klass* to, TRAPS);
317 void init_dependencies(TRAPS);
318
319 void add_to_deallocate_list(Metadata* m);
320
321 static ClassLoaderData* class_loader_data(oop loader);
322 static ClassLoaderData* class_loader_data_or_null(oop loader);
323 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
324 static void print_loader(ClassLoaderData *loader_data, outputStream *out);
325
326 // CDS support
327 Metaspace* ro_metaspace();
328 Metaspace* rw_metaspace();
329 void initialize_shared_metaspaces();
330 };
331
332 // An iterator that distributes Klasses to parallel worker threads.
333 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
334 Klass* volatile _next_klass;
335 public:
336 ClassLoaderDataGraphKlassIteratorAtomic();
337 Klass* next_klass();
338 private:
339 static Klass* next_klass_in_cldg(Klass* klass);
340 };
341
342 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
343 ClassLoaderData* _data;
344 public:
345 ClassLoaderDataGraphMetaspaceIterator();
346 ~ClassLoaderDataGraphMetaspaceIterator();
347 bool repeat() { return _data != NULL; }
348 Metaspace* get_next() {
349 assert(_data != NULL, "Should not be NULL in call to the iterator");
350 Metaspace* result = _data->metaspace_or_null();
351 _data = _data->next();
352 // This result might be NULL for class loaders without metaspace
353 // yet. It would be nice to return only non-null results but
354 // there is no guarantee that there will be a non-null result
355 // down the list so the caller is going to have to check.
356 return result;
357 }
358 };
359 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP