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,
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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 "oops/oopHandle.hpp"
33 #include "oops/weakHandle.hpp"
34 #include "runtime/mutex.hpp"
35 #include "trace/traceMacros.hpp"
36 #include "utilities/growableArray.hpp"
37 #include "utilities/macros.hpp"
38 #if INCLUDE_TRACE
39 #include "utilities/ticks.hpp"
40 #endif
41
42 //
43 // A class loader represents a linkset. Conceptually, a linkset identifies
44 // the complete transitive closure of resolved links that a dynamic linker can
45 // produce.
46 //
47 // A ClassLoaderData also encapsulates the allocation space, called a metaspace,
48 // used by the dynamic linker to allocate the runtime representation of all
49 // the types it defines.
50 //
51 // ClassLoaderData are stored in the runtime representation of classes,
52 // and provides iterators for root tracing and other GC operations.
53
54 class ClassLoaderData;
55 class JNIMethodBlock;
56 class Metadebug;
57 class ModuleEntry;
58 class PackageEntry;
59 class ModuleEntryTable;
60 class PackageEntryTable;
61 class DictionaryEntry;
62 class Dictionary;
63
64 // GC root for walking class loader data created
65
66 class ClassLoaderDataGraph : public AllStatic {
67 friend class ClassLoaderData;
68 friend class ClassLoaderDataGraphMetaspaceIterator;
69 friend class ClassLoaderDataGraphKlassIteratorAtomic;
70 friend class ClassLoaderDataGraphKlassIteratorStatic;
71 friend class VMStructs;
72 private:
73 // All CLDs (except the null CLD) can be reached by walking _head->_next->...
74 static ClassLoaderData* _head;
75 static ClassLoaderData* _unloading;
76 // CMS support.
77 static ClassLoaderData* _saved_head;
78 static ClassLoaderData* _saved_unloading;
79 static bool _should_purge;
80 // OOM has been seen in metaspace allocation. Used to prevent some
81 // allocations until class unloading
82 static bool _metaspace_oom;
83
84 static volatile size_t _num_instance_classes;
85 static volatile size_t _num_array_classes;
86
87 static ClassLoaderData* add(Handle class_loader, bool anonymous);
88 static void post_class_unload_events();
89 public:
90 static ClassLoaderData* find_or_create(Handle class_loader);
91 static void purge();
92 static void clear_claimed_marks();
93 // oops do
94 static void oops_do(OopClosure* f, bool must_claim);
95 static void keep_alive_oops_do(OopClosure* blk, bool must_claim);
96 static void always_strong_oops_do(OopClosure* blk, bool must_claim);
97 // cld do
98 static void cld_do(CLDClosure* cl);
99 static void cld_unloading_do(CLDClosure* cl);
100 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);
101 static void keep_alive_cld_do(CLDClosure* cl);
102 static void always_strong_cld_do(CLDClosure* cl);
103 // klass do
104 // Walking classes through the ClassLoaderDataGraph include array classes. It also includes
105 // classes that are allocated but not loaded, classes that have errors, and scratch classes
106 // for redefinition. These classes are removed during the next class unloading.
107 // Walking the ClassLoaderDataGraph also includes anonymous classes.
108 static void classes_do(KlassClosure* klass_closure);
109 static void classes_do(void f(Klass* const));
110 static void methods_do(void f(Method*));
111 static void modules_do(void f(ModuleEntry*));
112 static void modules_unloading_do(void f(ModuleEntry*));
113 static void packages_do(void f(PackageEntry*));
114 static void packages_unloading_do(void f(PackageEntry*));
115 static void loaded_classes_do(KlassClosure* klass_closure);
116 static void classes_unloading_do(void f(Klass* const));
117 static bool do_unloading(BoolObjectClosure* is_alive_closure, bool clean_previous_versions);
118
119 // dictionary do
120 // Iterate over all klasses in dictionary, but
121 // just the classes from defining class loaders.
122 static void dictionary_classes_do(void f(InstanceKlass*));
123 // Added for initialize_itable_for_klass to handle exceptions.
124 static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS);
125
126 // Iterate all classes and their class loaders, including initiating class loaders.
127 static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*));
128
129 // VM_CounterDecay iteration support
130 static InstanceKlass* try_get_next_class();
131
132 static void verify_dictionary();
133 static void print_dictionary(outputStream* st);
134 static void print_dictionary_statistics(outputStream* st);
135
136 // CMS support.
137 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
138 static GrowableArray<ClassLoaderData*>* new_clds();
139
140 static void set_should_purge(bool b) { _should_purge = b; }
141 static void purge_if_needed() {
142 // Only purge the CLDG for CMS if concurrent sweep is complete.
143 if (_should_purge) {
144 purge();
145 // reset for next time.
146 set_should_purge(false);
147 }
148 }
149
150 static int resize_if_needed();
151
152 static bool has_metaspace_oom() { return _metaspace_oom; }
153 static void set_metaspace_oom(bool value) { _metaspace_oom = value; }
154
155 static void print_on(outputStream * const out) PRODUCT_RETURN;
156 static void print() { print_on(tty); }
157 static void verify();
158
159 // instance and array class counters
160 static inline size_t num_instance_classes();
161 static inline size_t num_array_classes();
162 static inline void inc_instance_classes(size_t count);
163 static inline void dec_instance_classes(size_t count);
164 static inline void inc_array_classes(size_t count);
165 static inline void dec_array_classes(size_t count);
166
167 #ifndef PRODUCT
168 static bool contains_loader_data(ClassLoaderData* loader_data);
169 #endif
170
171 #if INCLUDE_TRACE
172 private:
173 static Ticks _class_unload_time;
174 static void class_unload_event(Klass* const k);
175 #endif
176 };
177
178 // ClassLoaderData class
179
180 class ClassLoaderData : public CHeapObj<mtClass> {
181 friend class VMStructs;
182
183 private:
184 class ChunkedHandleList {
185 struct Chunk : public CHeapObj<mtClass> {
186 static const size_t CAPACITY = 32;
187
188 oop _data[CAPACITY];
189 volatile juint _size;
190 Chunk* _next;
191
192 Chunk(Chunk* c) : _next(c), _size(0) { }
193 };
194
195 Chunk* volatile _head;
196
197 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
198
199 public:
200 ChunkedHandleList() : _head(NULL) {}
201 ~ChunkedHandleList();
202
203 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
204 // However, multiple threads can execute oops_do concurrently with add.
205 oop* add(oop o);
206 bool contains(oop p);
207 NOT_PRODUCT(bool owner_of(oop* p);)
208 void oops_do(OopClosure* f);
209
210 int count() const;
211 };
212
213 friend class ClassLoaderDataGraph;
214 friend class ClassLoaderDataGraphKlassIteratorAtomic;
215 friend class ClassLoaderDataGraphKlassIteratorStatic;
216 friend class ClassLoaderDataGraphMetaspaceIterator;
217 friend class InstanceKlass;
218 friend class MetaDataFactory;
219 friend class Method;
220
221 static ClassLoaderData * _the_null_class_loader_data;
222
223 WeakHandle _holder; // The oop that determines lifetime of this class loader
224 oop _class_loader; // oop used to uniquely identify a class loader
225 // class loader or a canonical class path
226
227 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the
228 // classes in the class loader are allocated.
229 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
230 bool _unloading; // true if this class loader goes away
231 bool _is_anonymous; // if this CLD is for an anonymous class
232
233 // Remembered sets support for the oops in the class loader data.
234 bool _modified_oops; // Card Table Equivalent (YC/CMS support)
235 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
236
237 s2 _keep_alive; // if this CLD is kept alive without a keep_alive_object().
238 // Used for anonymous classes and the boot class
239 // loader. _keep_alive does not need to be volatile or
240 // atomic since there is one unique CLD per anonymous class.
241
242 volatile int _claimed; // true if claimed, for example during GC traces.
243 // To avoid applying oop closure more than once.
244 // Has to be an int because we cas it.
245 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
246 // have the same life cycle of the corresponding ClassLoader.
247
248 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies
249
250 Klass* volatile _klasses; // The classes defined by the class loader.
251 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
252 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
253 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
254 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
255
256 // These method IDs are created for the class loader and set to NULL when the
257 // class loader is unloaded. They are rarely freed, only for redefine classes
258 // and if they lose a data race in InstanceKlass.
259 JNIMethodBlock* _jmethod_ids;
260
261 // Metadata to be deallocated when it's safe at class unloading, when
262 // this class loader isn't unloaded itself.
263 GrowableArray<Metadata*>* _deallocate_list;
264
265 // Support for walking class loader data objects
266 ClassLoaderData* _next; /// Next loader_datas created
267
268 TRACE_DEFINE_TRACE_ID_FIELD;
269
270 void set_next(ClassLoaderData* next) { _next = next; }
271 ClassLoaderData* next() const { return _next; }
272
273 ClassLoaderData(Handle h_class_loader, bool is_anonymous);
274 ~ClassLoaderData();
275
276 // The CLD are not placed in the Heap, so the Card Table or
277 // the Mod Union Table can't be used to mark when CLD have modified oops.
278 // The CT and MUT bits saves this information for the whole class loader data.
279 void clear_modified_oops() { _modified_oops = false; }
280 public:
281 void record_modified_oops() { _modified_oops = true; }
282 bool has_modified_oops() { return _modified_oops; }
283
284 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
285 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
286 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; }
287 private:
288
289 void unload();
290 bool keep_alive() const { return _keep_alive > 0; }
291 oop holder_phantom();
292 void classes_do(void f(Klass*));
293 void loaded_classes_do(KlassClosure* klass_closure);
294 void classes_do(void f(InstanceKlass*));
295 void methods_do(void f(Method*));
296 void modules_do(void f(ModuleEntry*));
297 void packages_do(void f(PackageEntry*));
298
299 // Deallocate free list during class unloading.
300 void free_deallocate_list(); // for the classes that are not unloaded
301 void unload_deallocate_list(); // for the classes that are unloaded
302
303 // Allocate out of this class loader data
304 MetaWord* allocate(size_t size);
305
306 Dictionary* create_dictionary();
307 public:
308 // GC interface.
309 void clear_claimed() { _claimed = 0; }
310 bool claimed() const { return _claimed == 1; }
311 bool claim();
312
313 bool is_alive() const;
314
315 // Accessors
316 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }
317
318 static ClassLoaderData* the_null_class_loader_data() {
319 return _the_null_class_loader_data;
320 }
321
322 Mutex* metaspace_lock() const { return _metaspace_lock; }
323
324 bool is_anonymous() const { return _is_anonymous; }
325
326 static void init_null_class_loader_data();
327
328 bool is_the_null_class_loader_data() const {
329 return this == _the_null_class_loader_data;
330 }
331
332 // Returns true if this class loader data is for the system class loader.
333 // (Note that the class loader data may be anonymous.)
334 bool is_system_class_loader_data() const;
335
336 // Returns true if this class loader data is for the platform class loader.
337 // (Note that the class loader data may be anonymous.)
338 bool is_platform_class_loader_data() const;
339
340 // Returns true if this class loader data is for the boot class loader.
341 // (Note that the class loader data may be anonymous.)
342 bool is_boot_class_loader_data() const {
343 return class_loader() == NULL;
344 }
345
346 bool is_builtin_class_loader_data() const;
347 bool is_permanent_class_loader_data() const;
348
349 // The Metaspace is created lazily so may be NULL. This
350 // method will allocate a Metaspace if needed.
351 ClassLoaderMetaspace* metaspace_non_null();
352
353 oop class_loader() const { return _class_loader; }
354
355 // The object the GC is using to keep this ClassLoaderData alive.
356 oop keep_alive_object() const;
357
358 // Returns true if this class loader data is for a loader going away.
359 bool is_unloading() const {
360 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
361 return _unloading;
362 }
363
364 // Used to refcount an anonymous class's CLD in order to
365 // indicate their aliveness without a keep_alive_object().
366 void inc_keep_alive();
367 void dec_keep_alive();
368
369 void update_holder(Handle holder);
370
371 inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); }
372
373 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);
374
375 void classes_do(KlassClosure* klass_closure);
376 Klass* klasses() { return _klasses; }
377
378 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
379 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
380
381 void print() { print_on(tty); }
382 void print_on(outputStream* out) const PRODUCT_RETURN;
383 void print_value() { print_value_on(tty); }
384 void print_value_on(outputStream* out) const;
385 void verify();
386 const char* loader_name() const;
387
388 OopHandle add_handle(Handle h);
389 void remove_handle(OopHandle h);
390 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
391 void add_class(Klass* k, bool publicize = true);
392 void remove_class(Klass* k);
393 bool contains_klass(Klass* k);
394 void record_dependency(const Klass* to);
395 PackageEntryTable* packages() { return _packages; }
396 ModuleEntry* unnamed_module() { return _unnamed_module; }
397 ModuleEntryTable* modules();
398 bool modules_defined() { return (_modules != NULL); }
399
400 // Loaded class dictionary
401 Dictionary* dictionary() const { return _dictionary; }
402
403 void add_to_deallocate_list(Metadata* m);
404
405 static ClassLoaderData* class_loader_data(oop loader);
406 static ClassLoaderData* class_loader_data_or_null(oop loader);
407 static ClassLoaderData* anonymous_class_loader_data(Handle loader);
408
409 TRACE_DEFINE_TRACE_ID_METHODS;
410 };
411
412 // An iterator that distributes Klasses to parallel worker threads.
413 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
414 Klass* volatile _next_klass;
415 public:
416 ClassLoaderDataGraphKlassIteratorAtomic();
417 Klass* next_klass();
418 private:
419 static Klass* next_klass_in_cldg(Klass* klass);
420 };
421
422 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
423 ClassLoaderData* _data;
424 public:
425 ClassLoaderDataGraphMetaspaceIterator();
426 ~ClassLoaderDataGraphMetaspaceIterator();
427 bool repeat() { return _data != NULL; }
428 ClassLoaderMetaspace* get_next() {
429 assert(_data != NULL, "Should not be NULL in call to the iterator");
430 ClassLoaderMetaspace* result = _data->metaspace_or_null();
431 _data = _data->next();
432 // This result might be NULL for class loaders without metaspace
433 // yet. It would be nice to return only non-null results but
434 // there is no guarantee that there will be a non-null result
435 // down the list so the caller is going to have to check.
436 return result;
437 }
438 };
439 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP