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
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 JNIHandleBlock;
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 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
70 static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS);
71 static void post_class_unload_events(void);
72 public:
73 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);
74 static void purge();
75 static void clear_claimed_marks();
76 static void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
77 static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
78 static void keep_alive_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
79 static void classes_do(KlassClosure* klass_closure);
80 static void classes_do(void f(Klass* const));
81 static void methods_do(void f(Method*));
82 static void loaded_classes_do(KlassClosure* klass_closure);
83 static void classes_unloading_do(void f(Klass* const));
84 static bool do_unloading(BoolObjectClosure* is_alive);
85
86 // CMS support.
87 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
88 static GrowableArray<ClassLoaderData*>* new_clds();
89
90 static void dump_on(outputStream * const out) PRODUCT_RETURN;
91 static void dump() { dump_on(tty); }
92 static void verify();
93
94 // expensive test for pointer in metaspace for debugging
95 static bool contains(const void* x);
96 #ifndef PRODUCT
97 static bool contains_loader_data(ClassLoaderData* loader_data);
98 #endif
99
100 #if INCLUDE_TRACE
101 private:
102 static Ticks _class_unload_time;
103 static void class_unload_event(Klass* const k);
104 #endif
105 };
106
107 // ClassLoaderData class
108
109 class ClassLoaderData : public CHeapObj<mtClass> {
110 friend class VMStructs;
111 private:
112 class Dependencies VALUE_OBJ_CLASS_SPEC {
113 objArrayOop _list_head;
114 void locked_add(objArrayHandle last,
115 objArrayHandle new_dependency,
116 Thread* THREAD);
117 public:
118 Dependencies() : _list_head(NULL) {}
119 Dependencies(TRAPS) : _list_head(NULL) {
120 init(CHECK);
121 }
122 void add(Handle dependency, TRAPS);
123 void init(TRAPS);
124 void oops_do(OopClosure* f);
125 };
126
127 friend class ClassLoaderDataGraph;
128 friend class ClassLoaderDataGraphMetaspaceIterator;
129 friend class MetaDataFactory;
130 friend class Method;
131
132 static ClassLoaderData * _the_null_class_loader_data;
133
134 oop _class_loader; // oop used to uniquely identify a class loader
135 // class loader or a canonical class path
136 Dependencies _dependencies; // holds dependencies from this class loader
137 // data to others.
138
139 Metaspace * _metaspace; // Meta-space where meta-data defined by the
140 // classes in the class loader are allocated.
141 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
142 bool _unloading; // true if this class loader goes away
143 bool _keep_alive; // if this CLD is kept alive without a keep_alive_object().
144 bool _is_anonymous; // if this CLD is for an anonymous class
145 volatile int _claimed; // true if claimed, for example during GC traces.
146 // To avoid applying oop closure more than once.
147 // Has to be an int because we cas it.
148 Klass* _klasses; // The classes defined by the class loader.
149
150 JNIHandleBlock* _handles; // Handles to constant pool arrays
151
152 // These method IDs are created for the class loader and set to NULL when the
153 // class loader is unloaded. They are rarely freed, only for redefine classes
154 // and if they lose a data race in InstanceKlass.
155 JNIMethodBlock* _jmethod_ids;
156
157 // Metadata to be deallocated when it's safe at class unloading, when
158 // this class loader isn't unloaded itself.
159 GrowableArray<Metadata*>* _deallocate_list;
160
161 // Support for walking class loader data objects
162 ClassLoaderData* _next; /// Next loader_datas created
163
164 // ReadOnly and ReadWrite metaspaces (static because only on the null
165 // class loader for now).
166 static Metaspace* _ro_metaspace;
167 static Metaspace* _rw_metaspace;
168
169 void set_next(ClassLoaderData* next) { _next = next; }
170 ClassLoaderData* next() const { return _next; }
171
172 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
173 ~ClassLoaderData();
174
175 void set_metaspace(Metaspace* m) { _metaspace = m; }
176
177 JNIHandleBlock* handles() const;
178 void set_handles(JNIHandleBlock* handles);
179
180 Mutex* metaspace_lock() const { return _metaspace_lock; }
181
182 // GC interface.
183 void clear_claimed() { _claimed = 0; }
184 bool claimed() const { return _claimed == 1; }
185 bool claim();
186
187 void unload();
188 bool keep_alive() const { return _keep_alive; }
189 bool is_alive(BoolObjectClosure* is_alive_closure) const;
190 void classes_do(void f(Klass*));
191 void loaded_classes_do(KlassClosure* klass_closure);
192 void classes_do(void f(InstanceKlass*));
193 void methods_do(void f(Method*));
194
195 // Deallocate free list during class unloading.
196 void free_deallocate_list();
197
198 // Allocate out of this class loader data
199 MetaWord* allocate(size_t size);
200
201 public:
202 // Accessors
203 Metaspace* metaspace_or_null() const { return _metaspace; }
204
205 static ClassLoaderData* the_null_class_loader_data() {
206 return _the_null_class_loader_data;
207 }
208
209 bool is_anonymous() const { return _is_anonymous; }
210
211 static void init_null_class_loader_data() {
212 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
213 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
214
215 // We explicitly initialize the Dependencies object at a later phase in the initialization
216 _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies());
217 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
218 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
219 if (DumpSharedSpaces) {
220 _the_null_class_loader_data->initialize_shared_metaspaces();
221 }
222 }
223
224 bool is_the_null_class_loader_data() const {
225 return this == _the_null_class_loader_data;
226 }
227 bool is_ext_class_loader_data() const;
228
229 // The Metaspace is created lazily so may be NULL. This
230 // method will allocate a Metaspace if needed.
231 Metaspace* metaspace_non_null();
232
233 oop class_loader() const { return _class_loader; }
234
235 // The object the GC is using to keep this ClassLoaderData alive.
236 oop keep_alive_object() const;
237
238 // Returns true if this class loader data is for a loader going away.
239 bool is_unloading() const {
240 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
241 return _unloading;
242 }
243
244 // Used to make sure that this CLD is not unloaded.
245 void set_keep_alive(bool value) { _keep_alive = value; }
246
247 unsigned int identity_hash() {
248 return _class_loader == NULL ? 0 : _class_loader->identity_hash();
249 }
250
251 // Used when tracing from klasses.
252 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
253
254 void classes_do(KlassClosure* klass_closure);
255
256 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
257 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
258
259 void print_value() { print_value_on(tty); }
260 void print_value_on(outputStream* out) const;
261 void dump(outputStream * const out) PRODUCT_RETURN;
262 void verify();
263 const char* loader_name();
264
265 jobject add_handle(Handle h);
266 void add_class(Klass* k);
267 void remove_class(Klass* k);
268 bool contains_klass(Klass* k);
269 void record_dependency(Klass* to, TRAPS);
270 void init_dependencies(TRAPS);
271
272 void add_to_deallocate_list(Metadata* m);
273
274 static ClassLoaderData* class_loader_data(oop loader);
275 static ClassLoaderData* class_loader_data_or_null(oop loader);
276 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
277 static void print_loader(ClassLoaderData *loader_data, outputStream *out);
278
279 // CDS support
280 Metaspace* ro_metaspace();
281 Metaspace* rw_metaspace();
282 void initialize_shared_metaspaces();
283 };
284
285 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
286 ClassLoaderData* _data;
287 public:
288 ClassLoaderDataGraphMetaspaceIterator();
289 ~ClassLoaderDataGraphMetaspaceIterator();
290 bool repeat() { return _data != NULL; }
291 Metaspace* get_next() {
292 assert(_data != NULL, "Should not be NULL in call to the iterator");
293 Metaspace* result = _data->metaspace_or_null();
294 _data = _data->next();
295 // This result might be NULL for class loaders without metaspace
296 // yet. It would be nice to return only non-null results but
297 // there is no guarantee that there will be a non-null result
298 // down the list so the caller is going to have to check.
299 return result;
300 }
301 };
302 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP