1 /*
2 * Copyright (c) 2012, 2018, 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 "oops/oopHandle.hpp"
33 #include "runtime/mutex.hpp"
34 #include "trace/traceMacros.hpp"
35 #include "utilities/growableArray.hpp"
36 #include "utilities/macros.hpp"
37 #if INCLUDE_TRACE
38 #include "utilities/ticks.hpp"
39 #endif
40
41 //
42 // A class loader represents a linkset. Conceptually, a linkset identifies
43 // the complete transitive closure of resolved links that a dynamic linker can
44 // produce.
45 //
46 // A ClassLoaderData also encapsulates the allocation space, called a metaspace,
47 // used by the dynamic linker to allocate the runtime representation of all
48 // the types it defines.
49 //
50 // ClassLoaderData are stored in the runtime representation of classes,
51 // and provides iterators for root tracing and other GC operations.
52
53 class ClassLoaderData;
54 class JNIMethodBlock;
55 class Metadebug;
56 class ModuleEntry;
57 class PackageEntry;
58 class ModuleEntryTable;
59 class PackageEntryTable;
60 class DictionaryEntry;
61 class Dictionary;
62
63 // GC root for walking class loader data created
64
65 class ClassLoaderDataGraph : public AllStatic {
66 friend class ClassLoaderData;
67 friend class ClassLoaderDataGraphMetaspaceIterator;
68 friend class ClassLoaderDataGraphKlassIteratorAtomic;
69 friend class ClassLoaderDataGraphKlassIteratorStatic;
70 friend class VMStructs;
71 private:
72 // All CLDs (except the null CLD) can be reached by walking _head->_next->...
73 static ClassLoaderData* _head;
74 static ClassLoaderData* _unloading;
75 // CMS support.
76 static ClassLoaderData* _saved_head;
77 static ClassLoaderData* _saved_unloading;
78 static bool _should_purge;
79 // OOM has been seen in metaspace allocation. Used to prevent some
80 // allocations until class unloading
81 static bool _metaspace_oom;
82
83 static volatile size_t _num_instance_classes;
84 static volatile size_t _num_array_classes;
85
86 static ClassLoaderData* add(Handle class_loader, bool anonymous);
87 static void post_class_unload_events();
88 public:
89 static ClassLoaderData* find_or_create(Handle class_loader);
90 static void purge();
91 static void clear_claimed_marks();
92 // oops do
93 static void oops_do(OopClosure* f, bool must_claim);
94 static void keep_alive_oops_do(OopClosure* blk, bool must_claim);
95 static void always_strong_oops_do(OopClosure* blk, bool must_claim);
96 // cld do
97 static void cld_do(CLDClosure* cl);
98 static void cld_unloading_do(CLDClosure* cl);
99 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);
100 static void keep_alive_cld_do(CLDClosure* cl);
101 static void always_strong_cld_do(CLDClosure* cl);
102 // klass do
103 // Walking classes through the ClassLoaderDataGraph include array classes. It also includes
104 // classes that are allocated but not loaded, classes that have errors, and scratch classes
105 // for redefinition. These classes are removed during the next class unloading.
106 // Walking the ClassLoaderDataGraph also includes anonymous classes.
107 static void classes_do(KlassClosure* klass_closure);
108 static void classes_do(void f(Klass* const));
109 static void methods_do(void f(Method*));
110 static void modules_do(void f(ModuleEntry*));
111 static void modules_unloading_do(void f(ModuleEntry*));
112 static void packages_do(void f(PackageEntry*));
113 static void packages_unloading_do(void f(PackageEntry*));
114 static void loaded_classes_do(KlassClosure* klass_closure);
115 static void classes_unloading_do(void f(Klass* const));
116 static bool do_unloading(BoolObjectClosure* is_alive, bool clean_previous_versions);
117
118 // dictionary do
119 // Iterate over all klasses in dictionary, but
120 // just the classes from defining class loaders.
121 static void dictionary_classes_do(void f(InstanceKlass*));
122 // Added for initialize_itable_for_klass to handle exceptions.
123 static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS);
124
125 // Iterate all classes and their class loaders, including initiating class loaders.
126 static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*));
127
128 // VM_CounterDecay iteration support
129 static InstanceKlass* try_get_next_class();
130
131 static void verify_dictionary();
132 static void print_dictionary(outputStream* st);
133 static void print_dictionary_statistics(outputStream* st);
134
135 // CMS support.
136 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
137 static GrowableArray<ClassLoaderData*>* new_clds();
138
139 static void set_should_purge(bool b) { _should_purge = b; }
140 static void purge_if_needed() {
141 // Only purge the CLDG for CMS if concurrent sweep is complete.
142 if (_should_purge) {
143 purge();
144 // reset for next time.
145 set_should_purge(false);
146 }
147 }
148
149 static int resize_if_needed();
150
151 static bool has_metaspace_oom() { return _metaspace_oom; }
152 static void set_metaspace_oom(bool value) { _metaspace_oom = value; }
153
154 static void print_on(outputStream * const out) PRODUCT_RETURN;
155 static void print() { print_on(tty); }
156 static void verify();
157
158 // instance and array class counters
159 static inline size_t num_instance_classes();
160 static inline size_t num_array_classes();
161 static inline void inc_instance_classes(size_t count);
162 static inline void dec_instance_classes(size_t count);
163 static inline void inc_array_classes(size_t count);
164 static inline void dec_array_classes(size_t count);
165
166 #ifndef PRODUCT
167 static bool contains_loader_data(ClassLoaderData* loader_data);
168 #endif
169
170 #if INCLUDE_TRACE
171 private:
172 static Ticks _class_unload_time;
173 static void class_unload_event(Klass* const k);
174 #endif
175 };
176
177 // ClassLoaderData class
178
179 class ClassLoaderData : public CHeapObj<mtClass> {
180 friend class VMStructs;
181
182 private:
183 class ChunkedHandleList {
184 struct Chunk : public CHeapObj<mtClass> {
185 static const size_t CAPACITY = 32;
186
187 oop _data[CAPACITY];
188 volatile juint _size;
189 Chunk* _next;
190
191 Chunk(Chunk* c) : _next(c), _size(0) { }
192 };
193
194 Chunk* volatile _head;
195
196 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
197
198 public:
199 ChunkedHandleList() : _head(NULL) {}
200 ~ChunkedHandleList();
201
202 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
203 // However, multiple threads can execute oops_do concurrently with add.
204 oop* add(oop o);
205 bool contains(oop p);
206 NOT_PRODUCT(bool owner_of(oop* p);)
207 void oops_do(OopClosure* f);
208
209 int count() const;
210 };
211
212 friend class ClassLoaderDataGraph;
213 friend class ClassLoaderDataGraphKlassIteratorAtomic;
214 friend class ClassLoaderDataGraphKlassIteratorStatic;
215 friend class ClassLoaderDataGraphMetaspaceIterator;
216 friend class InstanceKlass;
217 friend class MetaDataFactory;
218 friend class Method;
219
220 static ClassLoaderData * _the_null_class_loader_data;
221
222 oop _class_loader; // oop used to uniquely identify a class loader
223 // class loader or a canonical class path
224
225 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the
226 // classes in the class loader are allocated.
227 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
228 bool _unloading; // true if this class loader goes away
229 bool _is_anonymous; // if this CLD is for an anonymous class
230
231 // Remembered sets support for the oops in the class loader data.
232 bool _modified_oops; // Card Table Equivalent (YC/CMS support)
233 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
234
235 s2 _keep_alive; // if this CLD is kept alive without a keep_alive_object().
236 // Used for anonymous classes and the boot class
237 // loader. _keep_alive does not need to be volatile or
238 // atomic since there is one unique CLD per anonymous class.
239
240 volatile int _claimed; // true if claimed, for example during GC traces.
241 // To avoid applying oop closure more than once.
242 // Has to be an int because we cas it.
243 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
244 // have the same life cycle of the corresponding ClassLoader.
245
246 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies
247
248 Klass* volatile _klasses; // The classes defined by the class loader.
249 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
250 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
251 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
252 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
253
254 // These method IDs are created for the class loader and set to NULL when the
255 // class loader is unloaded. They are rarely freed, only for redefine classes
256 // and if they lose a data race in InstanceKlass.
257 JNIMethodBlock* _jmethod_ids;
258
259 // Metadata to be deallocated when it's safe at class unloading, when
260 // this class loader isn't unloaded itself.
261 GrowableArray<Metadata*>* _deallocate_list;
262
263 // Support for walking class loader data objects
264 ClassLoaderData* _next; /// Next loader_datas created
265
266 TRACE_DEFINE_TRACE_ID_FIELD;
267
268 void set_next(ClassLoaderData* next) { _next = next; }
269 ClassLoaderData* next() const { return _next; }
270
271 ClassLoaderData(Handle h_class_loader, bool is_anonymous);
272 ~ClassLoaderData();
273
274 // The CLD are not placed in the Heap, so the Card Table or
275 // the Mod Union Table can't be used to mark when CLD have modified oops.
276 // The CT and MUT bits saves this information for the whole class loader data.
277 void clear_modified_oops() { _modified_oops = false; }
278 public:
279 void record_modified_oops() { _modified_oops = true; }
280 bool has_modified_oops() { return _modified_oops; }
281
282 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
283 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
284 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; }
285 private:
286
287 void unload();
288 bool keep_alive() const { return _keep_alive > 0; }
289 oop holder_phantom();
290 void classes_do(void f(Klass*));
291 void loaded_classes_do(KlassClosure* klass_closure);
292 void classes_do(void f(InstanceKlass*));
293 void methods_do(void f(Method*));
294 void modules_do(void f(ModuleEntry*));
295 void packages_do(void f(PackageEntry*));
296
297 // Deallocate free list during class unloading.
298 void free_deallocate_list(); // for the classes that are not unloaded
299 void unload_deallocate_list(); // for the classes that are unloaded
300
301 // Allocate out of this class loader data
302 MetaWord* allocate(size_t size);
303
304 Dictionary* create_dictionary();
305 public:
306 // GC interface.
307 void clear_claimed() { _claimed = 0; }
308 bool claimed() const { return _claimed == 1; }
309 bool claim();
310
311 bool is_alive(BoolObjectClosure* is_alive_closure) const;
312
313 // Accessors
314 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }
315
316 static ClassLoaderData* the_null_class_loader_data() {
317 return _the_null_class_loader_data;
318 }
319
320 Mutex* metaspace_lock() const { return _metaspace_lock; }
321
322 bool is_anonymous() const { return _is_anonymous; }
323
324 static void init_null_class_loader_data();
325
326 bool is_the_null_class_loader_data() const {
327 return this == _the_null_class_loader_data;
328 }
329
330 // Returns true if this class loader data is for the system class loader.
331 // (Note that the class loader data may be anonymous.)
332 bool is_system_class_loader_data() const;
333
334 // Returns true if this class loader data is for the platform class loader.
335 // (Note that the class loader data may be anonymous.)
336 bool is_platform_class_loader_data() const;
337
338 // Returns true if this class loader data is for the boot class loader.
339 // (Note that the class loader data may be anonymous.)
340 bool is_boot_class_loader_data() const {
341 return class_loader() == NULL;
342 }
343
344 bool is_builtin_class_loader_data() const;
345 bool is_permanent_class_loader_data() const;
346
347 // The Metaspace is created lazily so may be NULL. This
348 // method will allocate a Metaspace if needed.
349 ClassLoaderMetaspace* metaspace_non_null();
350
351 oop class_loader() const { return _class_loader; }
352
353 // The object the GC is using to keep this ClassLoaderData alive.
354 oop keep_alive_object() const;
355
356 // Returns true if this class loader data is for a loader going away.
357 bool is_unloading() const {
358 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
359 return _unloading;
360 }
361
362 // Used to refcount an anonymous class's CLD in order to
363 // indicate their aliveness without a keep_alive_object().
364 void inc_keep_alive();
365 void dec_keep_alive();
366
367 inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); }
368
369 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);
370
371 void classes_do(KlassClosure* klass_closure);
372 Klass* klasses() { return _klasses; }
373
374 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
375 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
376
377 void print() { print_on(tty); }
378 void print_on(outputStream* out) const PRODUCT_RETURN;
379 void print_value() { print_value_on(tty); }
380 void print_value_on(outputStream* out) const;
381 void verify();
382 const char* loader_name() const;
383
384 OopHandle add_handle(Handle h);
385 void remove_handle(OopHandle h);
386 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
387 void add_class(Klass* k, bool publicize = true);
388 void remove_class(Klass* k);
389 bool contains_klass(Klass* k);
390 void record_dependency(const Klass* to);
391 PackageEntryTable* packages() { return _packages; }
392 ModuleEntry* unnamed_module() { return _unnamed_module; }
393 ModuleEntryTable* modules();
394 bool modules_defined() { return (_modules != NULL); }
395
396 // Loaded class dictionary
397 Dictionary* dictionary() const { return _dictionary; }
398
399 void add_to_deallocate_list(Metadata* m);
400
401 static ClassLoaderData* class_loader_data(oop loader);
402 static ClassLoaderData* class_loader_data_or_null(oop loader);
403 static ClassLoaderData* anonymous_class_loader_data(Handle loader);
404
405 TRACE_DEFINE_TRACE_ID_METHODS;
406 };
407
408 // An iterator that distributes Klasses to parallel worker threads.
409 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
410 Klass* volatile _next_klass;
411 public:
412 ClassLoaderDataGraphKlassIteratorAtomic();
413 Klass* next_klass();
414 private:
415 static Klass* next_klass_in_cldg(Klass* klass);
416 };
417
418 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
419 ClassLoaderData* _data;
420 public:
421 ClassLoaderDataGraphMetaspaceIterator();
422 ~ClassLoaderDataGraphMetaspaceIterator();
423 bool repeat() { return _data != NULL; }
424 ClassLoaderMetaspace* get_next() {
425 assert(_data != NULL, "Should not be NULL in call to the iterator");
426 ClassLoaderMetaspace* result = _data->metaspace_or_null();
427 _data = _data->next();
428 // This result might be NULL for class loaders without metaspace
429 // yet. It would be nice to return only non-null results but
430 // there is no guarantee that there will be a non-null result
431 // down the list so the caller is going to have to check.
432 return result;
433 }
434 };
435 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP