1 /*
2 * Copyright (c) 2012, 2016, 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.
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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
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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 #include "utilities/macros.hpp"
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 ClassLoaderDataGraphKlassIteratorAtomic;
63 friend class VMStructs;
64 private:
65 // All CLDs (except the null CLD) can be reached by walking _head->_next->...
66 static ClassLoaderData* _head;
67 static ClassLoaderData* _unloading;
68 // CMS support.
69 static ClassLoaderData* _saved_head;
70 static ClassLoaderData* _saved_unloading;
71 static bool _should_purge;
72 // OOM has been seen in metaspace allocation. Used to prevent some
73 // allocations until class unloading
74 static bool _metaspace_oom;
75
76 static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS);
77 static void post_class_unload_events(void);
78 public:
79 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);
80 static void purge();
81 static void clear_claimed_marks();
82 // oops do
83 static void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
84 static void keep_alive_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
85 static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
86 // cld do
87 static void cld_do(CLDClosure* cl);
88 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);
89 static void keep_alive_cld_do(CLDClosure* cl);
90 static void always_strong_cld_do(CLDClosure* cl);
91 // klass do
92 static void classes_do(KlassClosure* klass_closure);
93 static void classes_do(void f(Klass* const));
94 static void methods_do(void f(Method*));
95 static void loaded_classes_do(KlassClosure* klass_closure);
96 static void classes_unloading_do(void f(Klass* const));
97 static bool do_unloading(BoolObjectClosure* is_alive, bool clean_previous_versions);
98
99 // CMS support.
100 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
101 static GrowableArray<ClassLoaderData*>* new_clds();
102
103 static void set_should_purge(bool b) { _should_purge = b; }
104 static void purge_if_needed() {
105 // Only purge the CLDG for CMS if concurrent sweep is complete.
106 if (_should_purge) {
107 purge();
108 // reset for next time.
109 set_should_purge(false);
110 }
111 }
112
113 static bool has_metaspace_oom() { return _metaspace_oom; }
114 static void set_metaspace_oom(bool value) { _metaspace_oom = value; }
115
116 static void dump_on(outputStream * const out) PRODUCT_RETURN;
117 static void dump() { dump_on(tty); }
118 static void verify();
119
120 static bool unload_list_contains(const void* x);
121 #ifndef PRODUCT
122 static bool contains_loader_data(ClassLoaderData* loader_data);
123 #endif
124
125 #if INCLUDE_TRACE
126 private:
127 static Ticks _class_unload_time;
128 static void class_unload_event(Klass* const k);
129 #endif
130 };
131
132 // ClassLoaderData class
133
134 class ClassLoaderData : public CHeapObj<mtClass> {
135 friend class VMStructs;
136 private:
137 class Dependencies VALUE_OBJ_CLASS_SPEC {
138 objArrayOop _list_head;
139 void locked_add(objArrayHandle last,
140 objArrayHandle new_dependency,
141 Thread* THREAD);
142 public:
143 Dependencies() : _list_head(NULL) {}
144 Dependencies(TRAPS) : _list_head(NULL) {
145 init(CHECK);
146 }
147 void add(Handle dependency, TRAPS);
148 void init(TRAPS);
149 void oops_do(OopClosure* f);
150 };
151
152 friend class ClassLoaderDataGraph;
153 friend class ClassLoaderDataGraphKlassIteratorAtomic;
154 friend class ClassLoaderDataGraphMetaspaceIterator;
155 friend class MetaDataFactory;
156 friend class Method;
157
158 static ClassLoaderData * _the_null_class_loader_data;
159
160 oop _class_loader; // oop used to uniquely identify a class loader
161 // class loader or a canonical class path
162 Dependencies _dependencies; // holds dependencies from this class loader
163 // data to others.
164
165 Metaspace * _metaspace; // Meta-space where meta-data defined by the
166 // classes in the class loader are allocated.
167 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
168 bool _unloading; // true if this class loader goes away
169 bool _keep_alive; // if this CLD is kept alive without a keep_alive_object().
170 bool _is_anonymous; // if this CLD is for an anonymous class
171 volatile int _claimed; // true if claimed, for example during GC traces.
172 // To avoid applying oop closure more than once.
173 // Has to be an int because we cas it.
174 Klass* _klasses; // The classes defined by the class loader.
175
176 JNIHandleBlock* _handles; // Handles to constant pool arrays
177
178 // These method IDs are created for the class loader and set to NULL when the
179 // class loader is unloaded. They are rarely freed, only for redefine classes
180 // and if they lose a data race in InstanceKlass.
181 JNIMethodBlock* _jmethod_ids;
182
183 // Metadata to be deallocated when it's safe at class unloading, when
184 // this class loader isn't unloaded itself.
185 GrowableArray<Metadata*>* _deallocate_list;
186
187 // Support for walking class loader data objects
188 ClassLoaderData* _next; /// Next loader_datas created
189
190 // CDS
191 int _shared_class_loader_id;
192
193 // ReadOnly and ReadWrite metaspaces (static because only on the null
194 // class loader for now).
195 static Metaspace* _ro_metaspace;
196 static Metaspace* _rw_metaspace;
197
198 void set_next(ClassLoaderData* next) { _next = next; }
199 ClassLoaderData* next() const { return _next; }
200
201 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
202 ~ClassLoaderData();
203
204 void set_metaspace(Metaspace* m) { _metaspace = m; }
205
206 JNIHandleBlock* handles() const;
207 void set_handles(JNIHandleBlock* handles);
208
209 // GC interface.
210 void clear_claimed() { _claimed = 0; }
211 bool claimed() const { return _claimed == 1; }
212 bool claim();
213
214 void unload();
215 bool keep_alive() const { return _keep_alive; }
216 void classes_do(void f(Klass*));
217 void loaded_classes_do(KlassClosure* klass_closure);
218 void classes_do(void f(InstanceKlass*));
219 void methods_do(void f(Method*));
220
221 // Deallocate free list during class unloading.
222 void free_deallocate_list();
223
224 // Allocate out of this class loader data
225 MetaWord* allocate(size_t size);
226
227 public:
228
229 bool is_alive(BoolObjectClosure* is_alive_closure) const;
230
231 // Accessors
232 Metaspace* metaspace_or_null() const { return _metaspace; }
233
234 static ClassLoaderData* the_null_class_loader_data() {
235 return _the_null_class_loader_data;
236 }
237
238 Mutex* metaspace_lock() const { return _metaspace_lock; }
239
240 bool is_anonymous() const { return _is_anonymous; }
241
242 static void init_null_class_loader_data() {
243 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
244 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
245
246 // We explicitly initialize the Dependencies object at a later phase in the initialization
247 _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies());
248 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
249 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
250 if (DumpSharedSpaces) {
251 _the_null_class_loader_data->initialize_shared_metaspaces();
252 }
253 }
254
255 bool is_the_null_class_loader_data() const {
256 return this == _the_null_class_loader_data;
257 }
258 bool is_ext_class_loader_data() const;
259
260 // The Metaspace is created lazily so may be NULL. This
261 // method will allocate a Metaspace if needed.
262 Metaspace* metaspace_non_null();
263
264 oop class_loader() const { return _class_loader; }
265
266 // The object the GC is using to keep this ClassLoaderData alive.
267 oop keep_alive_object() const;
268
269 // Returns true if this class loader data is for a loader going away.
270 bool is_unloading() const {
271 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
272 return _unloading;
273 }
274
275 // Used to make sure that this CLD is not unloaded.
276 void set_keep_alive(bool value) { _keep_alive = value; }
277
278 inline unsigned int identity_hash() const;
279
280 // Used when tracing from klasses.
281 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
282
283 void classes_do(KlassClosure* klass_closure);
284
285 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
286 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
287
288 void print_value() { print_value_on(tty); }
289 void print_value_on(outputStream* out) const;
290 void dump(outputStream * const out) PRODUCT_RETURN;
291 void verify();
292 const char* loader_name();
293
294 jobject add_handle(Handle h);
295 void add_class(Klass* k, bool publicize = true);
296 void remove_class(Klass* k);
297 bool contains_klass(Klass* k);
298 void record_dependency(const Klass* to, TRAPS);
299 void init_dependencies(TRAPS);
300
301 void add_to_deallocate_list(Metadata* m);
302
303 static ClassLoaderData* class_loader_data(oop loader);
304 static ClassLoaderData* class_loader_data_or_null(oop loader);
305 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
306 static void print_loader(ClassLoaderData *loader_data, outputStream *out);
307
308 // CDS support
309 Metaspace* ro_metaspace();
310 Metaspace* rw_metaspace();
311 void initialize_shared_metaspaces();
312
313 int shared_class_loader_id() const {
314 return _shared_class_loader_id;
315 }
316 void set_shared_class_loader_id(int id) {
317 assert(id >= 0, "sanity");
318 assert(_shared_class_loader_id <0, "cannot be assigned more than once");
319 _shared_class_loader_id = id;
320 }
321 };
322
323 // An iterator that distributes Klasses to parallel worker threads.
324 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
325 Klass* volatile _next_klass;
326 public:
327 ClassLoaderDataGraphKlassIteratorAtomic();
328 Klass* next_klass();
329 private:
330 static Klass* next_klass_in_cldg(Klass* klass);
331 };
332
333 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
334 ClassLoaderData* _data;
335 public:
336 ClassLoaderDataGraphMetaspaceIterator();
337 ~ClassLoaderDataGraphMetaspaceIterator();
338 bool repeat() { return _data != NULL; }
339 Metaspace* get_next() {
340 assert(_data != NULL, "Should not be NULL in call to the iterator");
341 Metaspace* result = _data->metaspace_or_null();
342 _data = _data->next();
343 // This result might be NULL for class loaders without metaspace
344 // yet. It would be nice to return only non-null results but
345 // there is no guarantee that there will be a non-null result
346 // down the list so the caller is going to have to check.
347 return result;
348 }
349 };
350 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP