1 /*
2 * Copyright (c) 2012, 2013, 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/mutex.hpp"
33 #include "utilities/growableArray.hpp"
34
35 //
36 // A class loader represents a linkset. Conceptually, a linkset identifies
37 // the complete transitive closure of resolved links that a dynamic linker can
38 // produce.
39 //
40 // A ClassLoaderData also encapsulates the allocation space, called a metaspace,
41 // used by the dynamic linker to allocate the runtime representation of all
42 // the types it defines.
43 //
44 // ClassLoaderData are stored in the runtime representation of classes and the
45 // system dictionary, are roots of garbage collection, and provides iterators
46 // for root tracing and other GC operations.
47
48 class ClassLoaderData;
49 class JNIMethodBlock;
50 class JNIHandleBlock;
51 class Metadebug;
52 // GC root for walking class loader data created
53
54 class ClassLoaderDataGraph : public AllStatic {
55 friend class ClassLoaderData;
56 friend class ClassLoaderDataGraphMetaspaceIterator;
57 friend class VMStructs;
58 private:
59 // All CLDs (except the null CLD) can be reached by walking _head->_next->...
60 static ClassLoaderData* _head;
61 static ClassLoaderData* _unloading;
62 // CMS support.
63 static ClassLoaderData* _saved_head;
64
65 static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS);
66 public:
67 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);
68 static void purge();
69 static void clear_claimed_marks();
70 static void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
71 static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
72 static void keep_alive_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
73 static void classes_do(KlassClosure* klass_closure);
74 static bool do_unloading(BoolObjectClosure* is_alive);
75
76 // CMS support.
77 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
78 static GrowableArray<ClassLoaderData*>* new_clds();
79
80 static void dump_on(outputStream * const out) PRODUCT_RETURN;
81 static void dump() { dump_on(tty); }
82 static void verify();
83
84 #ifndef PRODUCT
85 // expensive test for pointer in metaspace for debugging
86 static bool contains(address x);
87 static bool contains_loader_data(ClassLoaderData* loader_data);
88 #endif
89 };
90
91 // ClassLoaderData class
92
93 class ClassLoaderData : public CHeapObj<mtClass> {
94 friend class VMStructs;
95 private:
96 class Dependencies VALUE_OBJ_CLASS_SPEC {
97 objArrayOop _list_head;
98 void locked_add(objArrayHandle last,
99 objArrayHandle new_dependency,
100 Thread* THREAD);
101 public:
102 Dependencies() : _list_head(NULL) {}
103 Dependencies(TRAPS) : _list_head(NULL) {
104 init(CHECK);
105 }
106 void add(Handle dependency, TRAPS);
107 void init(TRAPS);
108 void oops_do(OopClosure* f);
109 };
110
111 friend class ClassLoaderDataGraph;
112 friend class ClassLoaderDataGraphMetaspaceIterator;
113 friend class MetaDataFactory;
114 friend class Method;
115
116 static ClassLoaderData * _the_null_class_loader_data;
117
118 oop _class_loader; // oop used to uniquely identify a class loader
119 // class loader or a canonical class path
120 Dependencies _dependencies; // holds dependencies from this class loader
121 // data to others.
122
123 Metaspace * _metaspace; // Meta-space where meta-data defined by the
124 // classes in the class loader are allocated.
125 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
126 bool _unloading; // true if this class loader goes away
127 bool _keep_alive; // if this CLD can be unloaded for anonymous loaders
128 bool _is_anonymous; // if this CLD is for an anonymous class
129 volatile int _claimed; // true if claimed, for example during GC traces.
130 // To avoid applying oop closure more than once.
131 // Has to be an int because we cas it.
132 Klass* _klasses; // The classes defined by the class loader.
133
134 JNIHandleBlock* _handles; // Handles to constant pool arrays
135
136 // These method IDs are created for the class loader and set to NULL when the
137 // class loader is unloaded. They are rarely freed, only for redefine classes
138 // and if they lose a data race in InstanceKlass.
139 JNIMethodBlock* _jmethod_ids;
140
141 // Metadata to be deallocated when it's safe at class unloading, when
142 // this class loader isn't unloaded itself.
143 GrowableArray<Metadata*>* _deallocate_list;
144
145 // Support for walking class loader data objects
146 ClassLoaderData* _next; /// Next loader_datas created
147
148 // ReadOnly and ReadWrite metaspaces (static because only on the null
149 // class loader for now).
150 static Metaspace* _ro_metaspace;
151 static Metaspace* _rw_metaspace;
152
153 void set_next(ClassLoaderData* next) { _next = next; }
154 ClassLoaderData* next() const { return _next; }
155
156 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
157 ~ClassLoaderData();
158
159 void set_metaspace(Metaspace* m) { _metaspace = m; }
160
161 JNIHandleBlock* handles() const;
162 void set_handles(JNIHandleBlock* handles);
163
164 Mutex* metaspace_lock() const { return _metaspace_lock; }
165
166 // GC interface.
167 void clear_claimed() { _claimed = 0; }
168 bool claimed() const { return _claimed == 1; }
169 bool claim();
170
171 void unload();
172 bool keep_alive() const { return _keep_alive; }
173 bool is_alive(BoolObjectClosure* is_alive_closure) const;
174
175 void classes_do(void f(InstanceKlass*));
176
177 // Deallocate free list during class unloading.
178 void free_deallocate_list();
179
180 // Allocate out of this class loader data
181 MetaWord* allocate(size_t size);
182
183 public:
184 // Accessors
185 Metaspace* metaspace_or_null() const { return _metaspace; }
186
187 static ClassLoaderData* the_null_class_loader_data() {
188 return _the_null_class_loader_data;
189 }
190
191 bool is_anonymous() const { return _is_anonymous; }
192
193 static void init_null_class_loader_data() {
194 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
195 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
196
197 // We explicitly initialize the Dependencies object at a later phase in the initialization
198 _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies());
199 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
200 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
201 if (DumpSharedSpaces) {
202 _the_null_class_loader_data->initialize_shared_metaspaces();
203 }
204 }
205
206 bool is_the_null_class_loader_data() const {
207 return this == _the_null_class_loader_data;
208 }
209 bool is_ext_class_loader_data() const;
210
211 // The Metaspace is created lazily so may be NULL. This
212 // method will allocate a Metaspace if needed.
213 Metaspace* metaspace_non_null();
214
215 oop class_loader() const { return _class_loader; }
216
217 // Returns true if this class loader data is for a loader going away.
218 bool is_unloading() const {
219 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
220 return _unloading;
221 }
222 // Anonymous class loader data doesn't have anything to keep them from
223 // being unloaded during parsing the anonymous class.
224 void set_keep_alive(bool value) { _keep_alive = value; }
225
226 unsigned int identity_hash() {
227 return _class_loader == NULL ? 0 : _class_loader->identity_hash();
228 }
229
230 // Used when tracing from klasses.
231 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
232
233 void classes_do(KlassClosure* klass_closure);
234
235 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
236 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
237
238 void print_value() { print_value_on(tty); }
239 void print_value_on(outputStream* out) const;
240 void dump(outputStream * const out) PRODUCT_RETURN;
241 void verify();
242 const char* loader_name();
243
244 jobject add_handle(Handle h);
245 void add_class(Klass* k);
246 void remove_class(Klass* k);
247 void record_dependency(Klass* to, TRAPS);
248 void init_dependencies(TRAPS);
249
250 void add_to_deallocate_list(Metadata* m);
251
252 static ClassLoaderData* class_loader_data(oop loader);
253 static ClassLoaderData* class_loader_data_or_null(oop loader);
254 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
255 static void print_loader(ClassLoaderData *loader_data, outputStream *out);
256
257 // CDS support
258 Metaspace* ro_metaspace();
259 Metaspace* rw_metaspace();
260 void initialize_shared_metaspaces();
261 };
262
263 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
264 ClassLoaderData* _data;
265 public:
266 ClassLoaderDataGraphMetaspaceIterator();
267 ~ClassLoaderDataGraphMetaspaceIterator();
268 bool repeat() { return _data != NULL; }
269 Metaspace* get_next() {
270 assert(_data != NULL, "Should not be NULL in call to the iterator");
271 Metaspace* result = _data->metaspace_or_null();
272 _data = _data->next();
273 // This result might be NULL for class loaders without metaspace
274 // yet. It would be nice to return only non-null results but
275 // there is no guarantee that there will be a non-null result
276 // down the list so the caller is going to have to check.
277 return result;
278 }
279 };
280 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP