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.
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 #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 class ModuleEntry;
57 class PackageEntry;
58 class ModuleEntryTable;
59 class PackageEntryTable;
60
61 // GC root for walking class loader data created
62
63 class ClassLoaderDataGraph : public AllStatic {
64 friend class ClassLoaderData;
65 friend class ClassLoaderDataGraphMetaspaceIterator;
66 friend class ClassLoaderDataGraphKlassIteratorAtomic;
67 friend class VMStructs;
68 private:
69 // All CLDs (except the null CLD) can be reached by walking _head->_next->...
70 static ClassLoaderData* _head;
71 static ClassLoaderData* _unloading;
72 // CMS support.
73 static ClassLoaderData* _saved_head;
74 static ClassLoaderData* _saved_unloading;
75 static bool _should_purge;
76 // OOM has been seen in metaspace allocation. Used to prevent some
77 // allocations until class unloading
78 static bool _metaspace_oom;
79
80 static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS);
81 static void post_class_unload_events(void);
82 public:
83 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS);
84 static void purge();
85 static void clear_claimed_marks();
86 // oops do
87 static void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
88 static void keep_alive_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
89 static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim);
90 // cld do
91 static void cld_do(CLDClosure* cl);
92 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);
93 static void keep_alive_cld_do(CLDClosure* cl);
94 static void always_strong_cld_do(CLDClosure* cl);
95 // klass do
96 static void classes_do(KlassClosure* klass_closure);
97 static void classes_do(void f(Klass* const));
98 static void methods_do(void f(Method*));
99 static void modules_do(void f(ModuleEntry*));
100 static void modules_unloading_do(void f(ModuleEntry*));
101 static void packages_do(void f(PackageEntry*));
102 static void packages_unloading_do(void f(PackageEntry*));
103 static void loaded_classes_do(KlassClosure* klass_closure);
104 static void classes_unloading_do(void f(Klass* const));
105 static bool do_unloading(BoolObjectClosure* is_alive, bool clean_previous_versions);
106
107 // CMS support.
108 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
109 static GrowableArray<ClassLoaderData*>* new_clds();
110
111 static void set_should_purge(bool b) { _should_purge = b; }
112 static void purge_if_needed() {
113 // Only purge the CLDG for CMS if concurrent sweep is complete.
114 if (_should_purge) {
115 purge();
116 // reset for next time.
117 set_should_purge(false);
118 }
119 }
120
121 static bool has_metaspace_oom() { return _metaspace_oom; }
122 static void set_metaspace_oom(bool value) { _metaspace_oom = value; }
123
124 static void dump_on(outputStream * const out) PRODUCT_RETURN;
125 static void dump() { dump_on(tty); }
126 static void verify();
127 static void log_creation(Handle loader, ClassLoaderData* cld, TRAPS);
128
129 static bool unload_list_contains(const void* x);
130 #ifndef PRODUCT
131 static bool contains_loader_data(ClassLoaderData* loader_data);
132 #endif
133
134 #if INCLUDE_TRACE
135 private:
136 static Ticks _class_unload_time;
137 static void class_unload_event(Klass* const k);
138 #endif
139 };
140
141 // ClassLoaderData class
142
143 class ClassLoaderData : public CHeapObj<mtClass> {
144 friend class VMStructs;
145 private:
146 class Dependencies VALUE_OBJ_CLASS_SPEC {
147 objArrayOop _list_head;
148 void locked_add(objArrayHandle last,
149 objArrayHandle new_dependency,
150 Thread* THREAD);
151 public:
152 Dependencies() : _list_head(NULL) {}
153 Dependencies(TRAPS) : _list_head(NULL) {
154 init(CHECK);
155 }
156 void add(Handle dependency, TRAPS);
157 void init(TRAPS);
158 void oops_do(OopClosure* f);
159 };
160
161 friend class ClassLoaderDataGraph;
162 friend class ClassLoaderDataGraphKlassIteratorAtomic;
163 friend class ClassLoaderDataGraphMetaspaceIterator;
164 friend class MetaDataFactory;
165 friend class Method;
166
167 static ClassLoaderData * _the_null_class_loader_data;
168
169 oop _class_loader; // oop used to uniquely identify a class loader
170 // class loader or a canonical class path
171 Dependencies _dependencies; // holds dependencies from this class loader
172 // data to others.
173
174 Metaspace * _metaspace; // Meta-space where meta-data defined by the
175 // classes in the class loader are allocated.
176 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
177 bool _unloading; // true if this class loader goes away
178 bool _is_anonymous; // if this CLD is for an anonymous class
179 int _keep_alive; // if this CLD is kept alive without a keep_alive_object().
180 // Currently used solely for anonymous classes.
181 // _keep_alive does not need to be volatile or
182 // atomic since there is one unique CLD per anonymous class.
183 volatile int _claimed; // true if claimed, for example during GC traces.
184 // To avoid applying oop closure more than once.
185 // Has to be an int because we cas it.
186 JNIHandleBlock* _handles; // Handles to constant pool arrays, Modules, etc, which
187 // have the same life cycle of the corresponding ClassLoader.
188
189 Klass* _klasses; // The classes defined by the class loader.
190 PackageEntryTable* _packages; // The packages defined by the class loader.
191 ModuleEntryTable* _modules; // The modules defined by the class loader.
192
193 // These method IDs are created for the class loader and set to NULL when the
194 // class loader is unloaded. They are rarely freed, only for redefine classes
195 // and if they lose a data race in InstanceKlass.
196 JNIMethodBlock* _jmethod_ids;
197
198 // Metadata to be deallocated when it's safe at class unloading, when
199 // this class loader isn't unloaded itself.
200 GrowableArray<Metadata*>* _deallocate_list;
201
202 // Support for walking class loader data objects
203 ClassLoaderData* _next; /// Next loader_datas created
204
205 // CDS
206 int _shared_class_loader_id;
207
208 // ReadOnly and ReadWrite metaspaces (static because only on the null
209 // class loader for now).
210 static Metaspace* _ro_metaspace;
211 static Metaspace* _rw_metaspace;
212
213 void set_next(ClassLoaderData* next) { _next = next; }
214 ClassLoaderData* next() const { return _next; }
215
216 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies);
217 ~ClassLoaderData();
218
219 JNIHandleBlock* handles() const;
220 void set_handles(JNIHandleBlock* handles);
221
222 // GC interface.
223 void clear_claimed() { _claimed = 0; }
224 bool claimed() const { return _claimed == 1; }
225 bool claim();
226
227 void unload();
228 bool keep_alive() const { return _keep_alive > 0; }
229 void classes_do(void f(Klass*));
230 void loaded_classes_do(KlassClosure* klass_closure);
231 void classes_do(void f(InstanceKlass*));
232 void methods_do(void f(Method*));
233 void modules_do(void f(ModuleEntry*));
234 void packages_do(void f(PackageEntry*));
235
236 // Deallocate free list during class unloading.
237 void free_deallocate_list();
238
239 // Allocate out of this class loader data
240 MetaWord* allocate(size_t size);
241
242 public:
243
244 bool is_alive(BoolObjectClosure* is_alive_closure) const;
245
246 // Accessors
247 Metaspace* metaspace_or_null() const { return _metaspace; }
248
249 static ClassLoaderData* the_null_class_loader_data() {
250 return _the_null_class_loader_data;
251 }
252
253 Mutex* metaspace_lock() const { return _metaspace_lock; }
254
255 bool is_anonymous() const { return _is_anonymous; }
256
257 static void init_null_class_loader_data() {
258 assert(_the_null_class_loader_data == NULL, "cannot initialize twice");
259 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice");
260
261 // We explicitly initialize the Dependencies object at a later phase in the initialization
262 _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies());
263 ClassLoaderDataGraph::_head = _the_null_class_loader_data;
264 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be");
265 if (DumpSharedSpaces) {
266 _the_null_class_loader_data->initialize_shared_metaspaces();
267 }
268 }
269
270 bool is_the_null_class_loader_data() const {
271 return this == _the_null_class_loader_data;
272 }
273 bool is_platform_class_loader_data() const;
274
275 // The Metaspace is created lazily so may be NULL. This
276 // method will allocate a Metaspace if needed.
277 Metaspace* metaspace_non_null();
278
279 oop class_loader() const { return _class_loader; }
280
281 // The object the GC is using to keep this ClassLoaderData alive.
282 oop keep_alive_object() const;
283
284 // Returns true if this class loader data is for a loader going away.
285 bool is_unloading() const {
286 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
287 return _unloading;
288 }
289
290 void inc_keep_alive();
291 void dec_keep_alive();
292
293 inline unsigned int identity_hash() const;
294
295 // Used when tracing from klasses.
296 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim);
297
298 void classes_do(KlassClosure* klass_closure);
299
300 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
301 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
302
303 void print_value() { print_value_on(tty); }
304 void print_value_on(outputStream* out) const;
305 void dump(outputStream * const out) PRODUCT_RETURN;
306 void verify();
307 const char* loader_name();
308
309 jobject add_handle(Handle h);
310 void remove_handle(jobject h);
311 void add_class(Klass* k, bool publicize = true);
312 void remove_class(Klass* k);
313 bool contains_klass(Klass* k);
314 void record_dependency(const Klass* to, TRAPS);
315 void init_dependencies(TRAPS);
316 PackageEntryTable* packages();
317 bool packages_defined() { return (_packages != NULL); }
318 ModuleEntryTable* modules();
319 bool modules_defined() { return (_modules != NULL); }
320
321 void add_to_deallocate_list(Metadata* m);
322
323 static ClassLoaderData* class_loader_data(oop loader);
324 static ClassLoaderData* class_loader_data_or_null(oop loader);
325 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS);
326 static void print_loader(ClassLoaderData *loader_data, outputStream *out);
327
328 // CDS support
329 Metaspace* ro_metaspace();
330 Metaspace* rw_metaspace();
331 void initialize_shared_metaspaces();
332
333 int shared_class_loader_id() const {
334 return _shared_class_loader_id;
335 }
336 void set_shared_class_loader_id(int id) {
337 assert(id >= 0, "sanity");
338 assert(_shared_class_loader_id <0, "cannot be assigned more than once");
339 _shared_class_loader_id = id;
340 }
341 };
342
343 // An iterator that distributes Klasses to parallel worker threads.
344 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
345 Klass* volatile _next_klass;
346 public:
347 ClassLoaderDataGraphKlassIteratorAtomic();
348 Klass* next_klass();
349 private:
350 static Klass* next_klass_in_cldg(Klass* klass);
351 };
352
353 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
354 ClassLoaderData* _data;
355 public:
356 ClassLoaderDataGraphMetaspaceIterator();
357 ~ClassLoaderDataGraphMetaspaceIterator();
358 bool repeat() { return _data != NULL; }
359 Metaspace* get_next() {
360 assert(_data != NULL, "Should not be NULL in call to the iterator");
361 Metaspace* result = _data->metaspace_or_null();
362 _data = _data->next();
363 // This result might be NULL for class loaders without metaspace
364 // yet. It would be nice to return only non-null results but
365 // there is no guarantee that there will be a non-null result
366 // down the list so the caller is going to have to check.
367 return result;
368 }
369 };
370 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP