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