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 static bool _should_purge;
70
71 static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS);
72 static void post_class_unload_events(void);
73 public:
74 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);
75 static void purge();
76 static void clear_claimed_marks();
77 static void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
78 static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
79 static void keep_alive_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
80 static void cld_do(CLDClosure* cl);
81 static void classes_do(KlassClosure* klass_closure);
82 static void classes_do(void f(Klass* const));
83 static void methods_do(void f(Method*));
84 static void loaded_classes_do(KlassClosure* klass_closure);
85 static void classes_unloading_do(void f(Klass* const));
86 static bool do_unloading(BoolObjectClosure* is_alive);
87
88 // CMS support.
89 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
90 static GrowableArray<ClassLoaderData*>* new_clds();
91
92 static void set_should_purge(bool b) { _should_purge = b; }
93 static void purge_if_needed() {
94 // Only purge the CLDG for CMS if concurrent sweep is complete.
95 if (_should_purge) {
96 purge();
97 // reset for next time.
98 set_should_purge(false);
99 }
100 }
101
102 static void dump_on(outputStream * const out) PRODUCT_RETURN;
103 static void dump() { dump_on(tty); }
104 static void verify();
105
106 #ifndef PRODUCT
107 static bool contains_loader_data(ClassLoaderData* loader_data);
108 #endif
109
110 #if INCLUDE_TRACE
111 private:
112 static Ticks _class_unload_time;
113 static void class_unload_event(Klass* const k);
114 #endif
115 };
116
117 // ClassLoaderData class
118
119 class ClassLoaderData : public CHeapObj<mtClass> {
120 friend class VMStructs;
121 private:
122 class Dependencies VALUE_OBJ_CLASS_SPEC {
123 objArrayOop _list_head;
124 void locked_add(objArrayHandle last,
125 objArrayHandle new_dependency,
126 Thread* THREAD);
127 public:
128 Dependencies() : _list_head(NULL) {}
129 Dependencies(TRAPS) : _list_head(NULL) {
130 init(CHECK);
131 }
132 void add(Handle dependency, TRAPS);
133 void init(TRAPS);
134 void oops_do(OopClosure* f);
135 };
136
137 friend class ClassLoaderDataGraph;
138 friend class ClassLoaderDataGraphMetaspaceIterator;
139 friend class MetaDataFactory;
140 friend class Method;
141
142 static ClassLoaderData * _the_null_class_loader_data;
143
144 oop _class_loader; // oop used to uniquely identify a class loader
145 // class loader or a canonical class path
146 Dependencies _dependencies; // holds dependencies from this class loader
147 // data to others.
148
149 Metaspace * _metaspace; // Meta-space where meta-data defined by the
150 // classes in the class loader are allocated.
151 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
152 bool _unloading; // true if this class loader goes away
153 bool _keep_alive; // if this CLD is kept alive without a keep_alive_object().
154 bool _is_anonymous; // if this CLD is for an anonymous class
155 volatile int _claimed; // true if claimed, for example during GC traces.
156 // To avoid applying oop closure more than once.
157 // Has to be an int because we cas it.
158 Klass* _klasses; // The classes defined by the class loader.
159
160 JNIHandleBlock* _handles; // Handles to constant pool arrays
161
162 // These method IDs are created for the class loader and set to NULL when the
163 // class loader is unloaded. They are rarely freed, only for redefine classes
164 // and if they lose a data race in InstanceKlass.
165 JNIMethodBlock* _jmethod_ids;
166
167 // Metadata to be deallocated when it's safe at class unloading, when
168 // this class loader isn't unloaded itself.
169 GrowableArray<Metadata*>* _deallocate_list;
170
171 // Support for walking class loader data objects
172 ClassLoaderData* _next; /// Next loader_datas created
173
174 // ReadOnly and ReadWrite metaspaces (static because only on the null
175 // class loader for now).
176 static Metaspace* _ro_metaspace;
177 static Metaspace* _rw_metaspace;
178
179 void set_next(ClassLoaderData* next) { _next = next; }
180 ClassLoaderData* next() const { return _next; }
181
182 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
183 ~ClassLoaderData();
184
185 void set_metaspace(Metaspace* m) { _metaspace = m; }
186
187 JNIHandleBlock* handles() const;
188 void set_handles(JNIHandleBlock* handles);
189
190 // GC interface.
191 void clear_claimed() { _claimed = 0; }
192 bool claimed() const { return _claimed == 1; }
193 bool claim();
194
195 void unload();
196 bool keep_alive() const { return _keep_alive; }
197 bool is_alive(BoolObjectClosure* is_alive_closure) const;
198 void classes_do(void f(Klass*));
199 void loaded_classes_do(KlassClosure* klass_closure);
200 void classes_do(void f(InstanceKlass*));
201 void methods_do(void f(Method*));
202
203 // Deallocate free list during class unloading.
204 void free_deallocate_list();
205
206 // Allocate out of this class loader data
207 MetaWord* allocate(size_t size);
208
209 public:
210 // Accessors
211 Metaspace* metaspace_or_null() const { return _metaspace; }
212
213 static ClassLoaderData* the_null_class_loader_data() {
214 return _the_null_class_loader_data;
215 }
216
217 Mutex* metaspace_lock() const { return _metaspace_lock; }
218
219 bool is_anonymous() const { return _is_anonymous; }
220
221 static void init_null_class_loader_data() {
222 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
223 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
224
225 // We explicitly initialize the Dependencies object at a later phase in the initialization
226 _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies());
227 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
228 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
229 if (DumpSharedSpaces) {
230 _the_null_class_loader_data->initialize_shared_metaspaces();
231 }
232 }
233
234 bool is_the_null_class_loader_data() const {
235 return this == _the_null_class_loader_data;
236 }
237 bool is_ext_class_loader_data() const;
238
239 // The Metaspace is created lazily so may be NULL. This
240 // method will allocate a Metaspace if needed.
241 Metaspace* metaspace_non_null();
242
243 oop class_loader() const { return _class_loader; }
244
245 // The object the GC is using to keep this ClassLoaderData alive.
246 oop keep_alive_object() const;
247
248 // Returns true if this class loader data is for a loader going away.
249 bool is_unloading() const {
250 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
251 return _unloading;
252 }
253
254 // Used to make sure that this CLD is not unloaded.
255 void set_keep_alive(bool value) { _keep_alive = value; }
256
257 unsigned int identity_hash() {
258 return _class_loader == NULL ? 0 : _class_loader->identity_hash();
259 }
260
261 // Used when tracing from klasses.
262 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
263
264 void classes_do(KlassClosure* klass_closure);
265
266 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
267 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
268
269 void print_value() { print_value_on(tty); }
270 void print_value_on(outputStream* out) const;
271 void dump(outputStream * const out) PRODUCT_RETURN;
272 void verify();
273 const char* loader_name();
274
275 jobject add_handle(Handle h);
276 void add_class(Klass* k);
277 void remove_class(Klass* k);
278 bool contains_klass(Klass* k);
279 void record_dependency(Klass* to, TRAPS);
280 void init_dependencies(TRAPS);
281
282 void add_to_deallocate_list(Metadata* m);
283
284 static ClassLoaderData* class_loader_data(oop loader);
285 static ClassLoaderData* class_loader_data_or_null(oop loader);
286 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
287 static void print_loader(ClassLoaderData *loader_data, outputStream *out);
288
289 // CDS support
290 Metaspace* ro_metaspace();
291 Metaspace* rw_metaspace();
292 void initialize_shared_metaspaces();
293 };
294
295 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
296 ClassLoaderData* _data;
297 public:
298 ClassLoaderDataGraphMetaspaceIterator();
299 ~ClassLoaderDataGraphMetaspaceIterator();
300 bool repeat() { return _data != NULL; }
301 Metaspace* get_next() {
302 assert(_data != NULL, "Should not be NULL in call to the iterator");
303 Metaspace* result = _data->metaspace_or_null();
304 _data = _data->next();
305 // This result might be NULL for class loaders without metaspace
306 // yet. It would be nice to return only non-null results but
307 // there is no guarantee that there will be a non-null result
308 // down the list so the caller is going to have to check.
309 return result;
310 }
311 };
312 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP