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