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.
22 *
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_JFR
36 #include "jfr/support/jfrTraceIdExtension.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 clean_metaspaces();
74 public:
75 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);
76 static void purge();
77 static void clear_claimed_marks();
78 // oops do
79 static void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
80 static void keep_alive_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
81 static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
82 // cld do
83 static void cld_do(CLDClosure* cl);
84 static void cld_unloading_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
121 // ClassLoaderData class
122
123 class ClassLoaderData : public CHeapObj<mtClass> {
124 friend class VMStructs;
125 private:
126 class Dependencies VALUE_OBJ_CLASS_SPEC {
127 objArrayOop _list_head;
128 void locked_add(objArrayHandle last,
129 objArrayHandle new_dependency,
130 Thread* THREAD);
131 public:
132 Dependencies() : _list_head(NULL) {}
133 Dependencies(TRAPS) : _list_head(NULL) {
134 init(CHECK);
135 }
136 void add(Handle dependency, TRAPS);
137 void init(TRAPS);
138 void oops_do(OopClosure* f);
139 };
140
141 class ChunkedHandleList VALUE_OBJ_CLASS_SPEC {
142 struct Chunk : public CHeapObj<mtClass> {
143 static const size_t CAPACITY = 32;
144
145 oop _data[CAPACITY];
146 volatile juint _size;
147 Chunk* _next;
148
149 Chunk(Chunk* c) : _next(c), _size(0) { }
150 };
151
152 Chunk* _head;
153
154 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
155
156 public:
157 ChunkedHandleList() : _head(NULL) {}
158 ~ChunkedHandleList();
159
160 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
161 // However, multiple threads can execute oops_do concurrently with add.
162 oop* add(oop o);
163 void oops_do(OopClosure* f);
164 };
165
166 friend class ClassLoaderDataGraph;
167 friend class ClassLoaderDataGraphKlassIteratorAtomic;
168 friend class ClassLoaderDataGraphMetaspaceIterator;
169 friend class MetaDataFactory;
170 friend class Method;
171
172 static ClassLoaderData * _the_null_class_loader_data;
173
174 oop _class_loader; // oop used to uniquely identify a class loader
175 // class loader or a canonical class path
176 Dependencies _dependencies; // holds dependencies from this class loader
177 // data to others.
178
179 Metaspace * _metaspace; // Meta-space where meta-data defined by the
180 // classes in the class loader are allocated.
181 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
182 bool _unloading; // true if this class loader goes away
183 bool _keep_alive; // if this CLD is kept alive without a keep_alive_object().
184 bool _is_anonymous; // if this CLD is for an anonymous class
185 volatile int _claimed; // true if claimed, for example during GC traces.
186 // To avoid applying oop closure more than once.
187 // Has to be an int because we cas it.
188 Klass* _klasses; // The classes defined by the class loader.
189
190 ChunkedHandleList _handles; // Handles to constant pool arrays, etc, which
191 // have the same life cycle of the corresponding ClassLoader.
192
193 // These method IDs are created for the class loader and set to NULL when the
194 // class loader is unloaded. They are rarely freed, only for redefine classes
195 // and if they lose a data race in InstanceKlass.
196 JNIMethodBlock* _jmethod_ids;
197
198 // Metadata to be deallocated when it's safe at class unloading, when
199 // this class loader isn't unloaded itself.
200 GrowableArray<Metadata*>* _deallocate_list;
201
202 // Support for walking class loader data objects
203 ClassLoaderData* _next; /// Next loader_datas created
204
205 // ReadOnly and ReadWrite metaspaces (static because only on the null
206 // class loader for now).
207 static Metaspace* _ro_metaspace;
208 static Metaspace* _rw_metaspace;
209
210 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
211
212 void set_next(ClassLoaderData* next) { _next = next; }
213 ClassLoaderData* next() const { return _next; }
214
215 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
216 ~ClassLoaderData();
217
218 void set_metaspace(Metaspace* m) { _metaspace = m; }
219
220 Mutex* metaspace_lock() const { return _metaspace_lock; }
221
222 void unload();
223 bool keep_alive() const { return _keep_alive; }
224 void classes_do(void f(Klass*));
225 void loaded_classes_do(KlassClosure* klass_closure);
226 void classes_do(void f(InstanceKlass*));
227
228 // Deallocate free list during class unloading.
229 void free_deallocate_list();
230
231 // Allocate out of this class loader data
232 MetaWord* allocate(size_t size);
233
234 public:
235
236 // GC interface.
237 void clear_claimed() { _claimed = 0; }
238 bool claimed() const { return _claimed == 1; }
239 bool claim();
240
241 bool is_alive(BoolObjectClosure* is_alive_closure) const;
242
243 // Accessors
244 Metaspace* metaspace_or_null() const { return _metaspace; }
245
246 static ClassLoaderData* the_null_class_loader_data() {
247 return _the_null_class_loader_data;
248 }
249
250 bool is_anonymous() const { return _is_anonymous; }
251
252 static void init_null_class_loader_data() {
253 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
254 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
255
256 // We explicitly initialize the Dependencies object at a later phase in the initialization
257 _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies());
258 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
259 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
260 if (DumpSharedSpaces) {
261 _the_null_class_loader_data->initialize_shared_metaspaces();
262 }
263 }
264
265 bool is_the_null_class_loader_data() const {
266 return this == _the_null_class_loader_data;
267 }
268 bool is_ext_class_loader_data() const;
269
270 // The Metaspace is created lazily so may be NULL. This
271 // method will allocate a Metaspace if needed.
272 Metaspace* metaspace_non_null();
273
274 oop class_loader() const { return _class_loader; }
275
276 // The object the GC is using to keep this ClassLoaderData alive.
277 oop keep_alive_object() const;
278
279 // Returns true if this class loader data is for a loader going away.
280 bool is_unloading() const {
281 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
282 return _unloading;
283 }
284
285 // Used to make sure that this CLD is not unloaded.
286 void set_keep_alive(bool value) { _keep_alive = value; }
287
288 unsigned int identity_hash() {
289 return _class_loader == NULL ? 0 : _class_loader->identity_hash();
290 }
291
292 // Used when tracing from klasses.
293 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
294
295 void classes_do(KlassClosure* klass_closure);
296
297 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
298 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
299
300 void print_value() { print_value_on(tty); }
301 void print_value_on(outputStream* out) const;
302 void dump(outputStream * const out) PRODUCT_RETURN;
303 void verify();
304 const char* loader_name();
305
306 jobject add_handle(Handle h);
307 void add_class(Klass* k);
308 void remove_class(Klass* k);
309 bool contains_klass(Klass* k);
310 void record_dependency(Klass* to, TRAPS);
311 void init_dependencies(TRAPS);
312
313 void add_to_deallocate_list(Metadata* m);
314
315 static ClassLoaderData* class_loader_data(oop loader);
316 static ClassLoaderData* class_loader_data_or_null(oop loader);
317 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
318 static void print_loader(ClassLoaderData *loader_data, outputStream *out);
319
320 // CDS support
321 Metaspace* ro_metaspace();
322 Metaspace* rw_metaspace();
323 void initialize_shared_metaspaces();
324
325 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
326 };
327
328 // An iterator that distributes Klasses to parallel worker threads.
329 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
330 Klass* volatile _next_klass;
331 public:
332 ClassLoaderDataGraphKlassIteratorAtomic();
333 Klass* next_klass();
334 private:
335 static Klass* next_klass_in_cldg(Klass* klass);
336 };
337
338 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
339 ClassLoaderData* _data;
340 public:
341 ClassLoaderDataGraphMetaspaceIterator();
342 ~ClassLoaderDataGraphMetaspaceIterator();
343 bool repeat() { return _data != NULL; }
344 Metaspace* get_next() {
345 assert(_data != NULL, "Should not be NULL in call to the iterator");
346 Metaspace* result = _data->metaspace_or_null();
347 _data = _data->next();
348 // This result might be NULL for class loaders without metaspace
349 // yet. It would be nice to return only non-null results but
350 // there is no guarantee that there will be a non-null result
351 // down the list so the caller is going to have to check.
352 return result;
353 }
354 };
355 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP