1 /*
2 * Copyright (c) 2012, 2019, 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
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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 #include "jfr/utilities/jfrLog.hpp"
39
40 //
41 // A class loader represents a linkset. Conceptually, a linkset identifies
42 // the complete transitive closure of resolved links that a dynamic linker can
43 // produce.
44 //
45 // A ClassLoaderData also encapsulates the allocation space, called a metaspace,
46 // used by the dynamic linker to allocate the runtime representation of all
47 // the types it defines.
48 //
49 // ClassLoaderData are stored in the runtime representation of classes and the
50 // system dictionary, are roots of garbage collection, and provides iterators
51 // for root tracing and other GC operations.
52
53 class ClassLoaderData;
54 class JNIMethodBlock;
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
73 static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS);
74 static void post_class_unload_events(void);
75 static void clean_metaspaces();
76 public:
77 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);
78 static void purge();
79 static void clear_claimed_marks();
80 // oops do
81 static void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
82 static void keep_alive_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
83 static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
84 // cld do
85 static void cld_do(CLDClosure* cl);
86 static void cld_unloading_do(CLDClosure* cl);
87 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);
88 static void keep_alive_cld_do(CLDClosure* cl);
89 static void always_strong_cld_do(CLDClosure* cl);
90 // klass do
91 static void classes_do(KlassClosure* klass_closure);
92 static void classes_do(void f(Klass* const));
93 static void loaded_classes_do(KlassClosure* klass_closure);
94 static void classes_unloading_do(void f(Klass* const));
95 static bool do_unloading(BoolObjectClosure* is_alive, bool clean_alive);
96
97 // CMS support.
98 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
99 static GrowableArray<ClassLoaderData*>* new_clds();
100
101 static void set_should_purge(bool b) { _should_purge = b; }
102 static void purge_if_needed() {
103 // Only purge the CLDG for CMS if concurrent sweep is complete.
104 if (_should_purge) {
105 purge();
106 // reset for next time.
107 set_should_purge(false);
108 }
109 }
110
111 static void free_deallocate_lists();
112
113 static void dump_on(outputStream * const out) PRODUCT_RETURN;
114 static void dump() { dump_on(tty); }
115 static void verify();
116
117 static bool unload_list_contains(const void* x);
118 #ifndef PRODUCT
119 static bool contains_loader_data(ClassLoaderData* loader_data);
120 #endif
121
122 #if INCLUDE_TRACE
123 private:
124 static Ticks _class_unload_time;
125 static void class_unload_event(Klass* const k);
126 #endif
127 };
128
129 // ClassLoaderData class
130
131 class ClassLoaderData : public CHeapObj<mtClass> {
132 friend class VMStructs;
133 friend class CLDClaimContext;
134 friend class CLDClaimStateClosure;
135 private:
136 class Dependencies VALUE_OBJ_CLASS_SPEC {
137 objArrayOop _list_head;
138 void locked_add(objArrayHandle last,
139 objArrayHandle new_dependency,
140 Thread* THREAD);
141 public:
142 Dependencies() : _list_head(NULL) {}
143 Dependencies(TRAPS) : _list_head(NULL) {
144 init(CHECK);
145 }
146 void add(Handle dependency, TRAPS);
147 void init(TRAPS);
148 void oops_do(OopClosure* f);
149 };
150
151 class ChunkedHandleList VALUE_OBJ_CLASS_SPEC {
152 struct Chunk : public CHeapObj<mtClass> {
153 static const size_t CAPACITY = 32;
154
155 oop _data[CAPACITY];
156 volatile juint _size;
157 Chunk* _next;
158
159 Chunk(Chunk* c) : _next(c), _size(0) { }
160 };
161
162 Chunk* _head;
163
164 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
165
166 public:
167 ChunkedHandleList() : _head(NULL) {}
168 ~ChunkedHandleList();
169
170 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
171 // However, multiple threads can execute oops_do concurrently with add.
172 oop* add(oop o);
173 void oops_do(OopClosure* f);
174 };
175
176 friend class ClassLoaderDataGraph;
177 friend class ClassLoaderDataGraphKlassIteratorAtomic;
178 friend class ClassLoaderDataGraphMetaspaceIterator;
179 friend class MetaDataFactory;
180 friend class Method;
181
182 static ClassLoaderData * _the_null_class_loader_data;
183
184 oop _class_loader; // oop used to uniquely identify a class loader
185 // class loader or a canonical class path
186 Dependencies _dependencies; // holds dependencies from this class loader
187 // data to others.
188
189 Metaspace * _metaspace; // Meta-space where meta-data defined by the
190 // classes in the class loader are allocated.
191 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
192 bool _unloading; // true if this class loader goes away
193 bool _keep_alive; // if this CLD is kept alive without a keep_alive_object().
194 bool _is_anonymous; // if this CLD is for an anonymous class
195 volatile int _claimed; // true if claimed, for example during GC traces.
196 // To avoid applying oop closure more than once.
197 // Has to be an int because we cas it.
198 Klass* _klasses; // The classes defined by the class loader.
199
200 ChunkedHandleList _handles; // Handles to constant pool arrays, etc, which
201 // have the same life cycle of the corresponding ClassLoader.
202
203 // These method IDs are created for the class loader and set to NULL when the
204 // class loader is unloaded. They are rarely freed, only for redefine classes
205 // and if they lose a data race in InstanceKlass.
206 JNIMethodBlock* _jmethod_ids;
207
208 // Metadata to be deallocated when it's safe at class unloading, when
209 // this class loader isn't unloaded itself.
210 GrowableArray<Metadata*>* _deallocate_list;
211
212 // Support for walking class loader data objects
213 ClassLoaderData* _next; /// Next loader_datas created
214
215 // ReadOnly and ReadWrite metaspaces (static because only on the null
216 // class loader for now).
217 static Metaspace* _ro_metaspace;
218 static Metaspace* _rw_metaspace;
219
220 TRACE_DEFINE_TRACE_ID_FIELD;
221
222 void set_next(ClassLoaderData* next) { _next = next; }
223 ClassLoaderData* next() const { return _next; }
224
225 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
226 ~ClassLoaderData();
227
228 void set_metaspace(Metaspace* m) { _metaspace = m; }
229
230 Mutex* metaspace_lock() const { return _metaspace_lock; }
231
232 // GC interface.
233 void clear_claimed() { _claimed = 0; }
234 bool claimed() const { return _claimed == 1; }
235 bool claim();
236
237 void unload();
238 bool keep_alive() const { return _keep_alive; }
239 void classes_do(void f(Klass*));
240 void loaded_classes_do(KlassClosure* klass_closure);
241 void classes_do(void f(InstanceKlass*));
242
243 // Deallocate free list during class unloading.
244 void free_deallocate_list();
245
246 // Allocate out of this class loader data
247 MetaWord* allocate(size_t size);
248
249 public:
250
251 bool is_alive(BoolObjectClosure* is_alive_closure) const;
252
253 // Accessors
254 Metaspace* metaspace_or_null() const { return _metaspace; }
255
256 static ClassLoaderData* the_null_class_loader_data() {
257 return _the_null_class_loader_data;
258 }
259
260 bool is_anonymous() const { return _is_anonymous; }
261
262 static void init_null_class_loader_data() {
263 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
264 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
265
266 // We explicitly initialize the Dependencies object at a later phase in the initialization
267 _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies());
268 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
269 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
270 if (DumpSharedSpaces) {
271 _the_null_class_loader_data->initialize_shared_metaspaces();
272 }
273 }
274
275 bool is_the_null_class_loader_data() const {
276 return this == _the_null_class_loader_data;
277 }
278 bool is_ext_class_loader_data() const;
279
280 // The Metaspace is created lazily so may be NULL. This
281 // method will allocate a Metaspace if needed.
282 Metaspace* metaspace_non_null();
283
284 oop class_loader() const { return _class_loader; }
285
286 // The object the GC is using to keep this ClassLoaderData alive.
287 oop keep_alive_object() const;
288
289 // Returns true if this class loader data is for a loader going away.
290 bool is_unloading() const {
291 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
292 return _unloading;
293 }
294
295 // Used to make sure that this CLD is not unloaded.
296 void set_keep_alive(bool value) { _keep_alive = value; }
297
298 unsigned int identity_hash() {
299 return _class_loader == NULL ? 0 : _class_loader->identity_hash();
300 }
301
302 // Used when tracing from klasses.
303 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
304
305 void classes_do(KlassClosure* klass_closure);
306
307 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
308 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
309
310 void print_value() { print_value_on(tty); }
311 void print_value_on(outputStream* out) const;
312 void dump(outputStream * const out) PRODUCT_RETURN;
313 void verify();
314 const char* loader_name();
315
316 jobject add_handle(Handle h);
317 void add_class(Klass* k);
318 void remove_class(Klass* k);
319 bool contains_klass(Klass* k);
320 void record_dependency(Klass* to, TRAPS);
321 void init_dependencies(TRAPS);
322
323 void add_to_deallocate_list(Metadata* m);
324
325 static ClassLoaderData* class_loader_data(oop loader);
326 static ClassLoaderData* class_loader_data_or_null(oop loader);
327 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
328 static void print_loader(ClassLoaderData *loader_data, outputStream *out);
329
330 // CDS support
331 Metaspace* ro_metaspace();
332 Metaspace* rw_metaspace();
333 void initialize_shared_metaspaces();
334
335 TRACE_DEFINE_TRACE_ID_METHODS;
336 };
337
338 // An iterator that distributes Klasses to parallel worker threads.
339 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
340 Klass* volatile _next_klass;
341 public:
342 ClassLoaderDataGraphKlassIteratorAtomic();
343 Klass* next_klass();
344 private:
345 static Klass* next_klass_in_cldg(Klass* klass);
346 };
347
348 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
349 ClassLoaderData* _data;
350 public:
351 ClassLoaderDataGraphMetaspaceIterator();
352 ~ClassLoaderDataGraphMetaspaceIterator();
353 bool repeat() { return _data != NULL; }
354 Metaspace* get_next() {
355 assert(_data != NULL, "Should not be NULL in call to the iterator");
356 Metaspace* result = _data->metaspace_or_null();
357 _data = _data->next();
358 // This result might be NULL for class loaders without metaspace
359 // yet. It would be nice to return only non-null results but
360 // there is no guarantee that there will be a non-null result
361 // down the list so the caller is going to have to check.
362 return result;
363 }
364 };
365 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP