1 /*
2 * Copyright (c) 2012, 2014, 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 #if INCLUDE_TRACE
35 # include "utilities/ticks.hpp"
36 #endif
37
38 //
39 // A class loader represents a linkset. Conceptually, a linkset identifies
40 // the complete transitive closure of resolved links that a dynamic linker can
41 // produce.
42 //
43 // A ClassLoaderData also encapsulates the allocation space, called a metaspace,
44 // used by the dynamic linker to allocate the runtime representation of all
45 // the types it defines.
46 //
47 // ClassLoaderData are stored in the runtime representation of classes and the
48 // system dictionary, are roots of garbage collection, and provides iterators
49 // for root tracing and other GC operations.
50
51 class ClassLoaderData;
52 class JNIMethodBlock;
53 class JNIHandleBlock;
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 friend class ClassLoaderDataGraph;
148 friend class ClassLoaderDataGraphKlassIteratorAtomic;
149 friend class ClassLoaderDataGraphMetaspaceIterator;
150 friend class MetaDataFactory;
151 friend class Method;
152
153 static ClassLoaderData * _the_null_class_loader_data;
154
155 oop _class_loader; // oop used to uniquely identify a class loader
156 // class loader or a canonical class path
157 Dependencies _dependencies; // holds dependencies from this class loader
158 // data to others.
159
160 Metaspace * _metaspace; // Meta-space where meta-data defined by the
161 // classes in the class loader are allocated.
162 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
163 bool _unloading; // true if this class loader goes away
164 bool _keep_alive; // if this CLD is kept alive without a keep_alive_object().
165 bool _is_anonymous; // if this CLD is for an anonymous class
166 volatile int _claimed; // true if claimed, for example during GC traces.
167 // To avoid applying oop closure more than once.
168 // Has to be an int because we cas it.
169 Klass* _klasses; // The classes defined by the class loader.
170
171 JNIHandleBlock* _handles; // Handles to constant pool arrays
172
173 // These method IDs are created for the class loader and set to NULL when the
174 // class loader is unloaded. They are rarely freed, only for redefine classes
175 // and if they lose a data race in InstanceKlass.
176 JNIMethodBlock* _jmethod_ids;
177
178 // Metadata to be deallocated when it's safe at class unloading, when
179 // this class loader isn't unloaded itself.
180 GrowableArray<Metadata*>* _deallocate_list;
181
182 // Support for walking class loader data objects
183 ClassLoaderData* _next; /// Next loader_datas created
184
185 // ReadOnly and ReadWrite metaspaces (static because only on the null
186 // class loader for now).
187 static Metaspace* _ro_metaspace;
188 static Metaspace* _rw_metaspace;
189
190 void set_next(ClassLoaderData* next) { _next = next; }
191 ClassLoaderData* next() const { return _next; }
192
193 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
194 ~ClassLoaderData();
195
196 void set_metaspace(Metaspace* m) { _metaspace = m; }
197
198 JNIHandleBlock* handles() const;
199 void set_handles(JNIHandleBlock* handles);
200
201 Mutex* metaspace_lock() const { return _metaspace_lock; }
202
203 // GC interface.
204 void clear_claimed() { _claimed = 0; }
205 bool claimed() const { return _claimed == 1; }
206 bool claim();
207
208 void unload();
209 bool keep_alive() const { return _keep_alive; }
210 void classes_do(void f(Klass*));
211 void loaded_classes_do(KlassClosure* klass_closure);
212 void classes_do(void f(InstanceKlass*));
213
214 // Deallocate free list during class unloading.
215 void free_deallocate_list();
216
217 // Allocate out of this class loader data
218 MetaWord* allocate(size_t size);
219
220 public:
221
222 bool is_alive(BoolObjectClosure* is_alive_closure) const;
223
224 // Accessors
225 Metaspace* metaspace_or_null() const { return _metaspace; }
226
227 static ClassLoaderData* the_null_class_loader_data() {
228 return _the_null_class_loader_data;
229 }
230
231 bool is_anonymous() const { return _is_anonymous; }
232
233 static void init_null_class_loader_data() {
234 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
235 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
236
237 // We explicitly initialize the Dependencies object at a later phase in the initialization
238 _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies());
239 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
240 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
241 if (DumpSharedSpaces) {
242 _the_null_class_loader_data->initialize_shared_metaspaces();
243 }
244 }
245
246 bool is_the_null_class_loader_data() const {
247 return this == _the_null_class_loader_data;
248 }
249 bool is_ext_class_loader_data() const;
250
251 // The Metaspace is created lazily so may be NULL. This
252 // method will allocate a Metaspace if needed.
253 Metaspace* metaspace_non_null();
254
255 oop class_loader() const { return _class_loader; }
256
257 // The object the GC is using to keep this ClassLoaderData alive.
258 oop keep_alive_object() const;
259
260 // Returns true if this class loader data is for a loader going away.
261 bool is_unloading() const {
262 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
263 return _unloading;
264 }
265
266 // Used to make sure that this CLD is not unloaded.
267 void set_keep_alive(bool value) { _keep_alive = value; }
268
269 unsigned int identity_hash() {
270 return _class_loader == NULL ? 0 : _class_loader->identity_hash();
271 }
272
273 // Used when tracing from klasses.
274 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
275
276 void classes_do(KlassClosure* klass_closure);
277
278 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
279 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
280
281 void print_value() { print_value_on(tty); }
282 void print_value_on(outputStream* out) const;
283 void dump(outputStream * const out) PRODUCT_RETURN;
284 void verify();
285 const char* loader_name();
286
287 jobject add_handle(Handle h);
288 void add_class(Klass* k);
289 void remove_class(Klass* k);
290 bool contains_klass(Klass* k);
291 void record_dependency(Klass* to, TRAPS);
292 void init_dependencies(TRAPS);
293
294 void add_to_deallocate_list(Metadata* m);
295
296 static ClassLoaderData* class_loader_data(oop loader);
297 static ClassLoaderData* class_loader_data_or_null(oop loader);
298 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
299 static void print_loader(ClassLoaderData *loader_data, outputStream *out);
300
301 // CDS support
302 Metaspace* ro_metaspace();
303 Metaspace* rw_metaspace();
304 void initialize_shared_metaspaces();
305 };
306
307 // An iterator that distributes Klasses to parallel worker threads.
308 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
309 volatile Klass* _next_klass;
310 public:
311 ClassLoaderDataGraphKlassIteratorAtomic();
312 Klass* next_klass();
313 private:
314 static Klass* next_klass_in_cldg(Klass* klass);
315 };
316
317 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
318 ClassLoaderData* _data;
319 public:
320 ClassLoaderDataGraphMetaspaceIterator();
321 ~ClassLoaderDataGraphMetaspaceIterator();
322 bool repeat() { return _data != NULL; }
323 Metaspace* get_next() {
324 assert(_data != NULL, "Should not be NULL in call to the iterator");
325 Metaspace* result = _data->metaspace_or_null();
326 _data = _data->next();
327 // This result might be NULL for class loaders without metaspace
328 // yet. It would be nice to return only non-null results but
329 // there is no guarantee that there will be a non-null result
330 // down the list so the caller is going to have to check.
331 return result;
332 }
333 };
334 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP