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 *
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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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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 "oops/oopHandle.hpp"
32 #include "oops/weakHandle.hpp"
33 #include "runtime/mutex.hpp"
34 #include "utilities/growableArray.hpp"
35 #include "utilities/macros.hpp"
36 #if INCLUDE_JFR
37 #include "jfr/support/jfrTraceIdExtension.hpp"
38 #endif
39
40 // external name (synthetic) for the primordial "bootstrap" class loader instance
41 #define BOOTSTRAP_LOADER_NAME "bootstrap"
42 #define BOOTSTRAP_LOADER_NAME_LEN 9
43
44 //
45 // A class loader represents a linkset. Conceptually, a linkset identifies
46 // the complete transitive closure of resolved links that a dynamic linker can
47 // produce.
48 //
49 // A ClassLoaderData also encapsulates the allocation space, called a metaspace,
50 // used by the dynamic linker to allocate the runtime representation of all
51 // the types it defines.
52 //
53 // ClassLoaderData are stored in the runtime representation of classes,
54 // and provides iterators for root tracing and other GC operations.
55
56 class ClassLoaderData;
57 class JNIMethodBlock;
58 class Metadebug;
59 class ModuleEntry;
60 class PackageEntry;
61 class ModuleEntryTable;
62 class PackageEntryTable;
63 class DictionaryEntry;
64 class Dictionary;
65
66 // GC root for walking class loader data created
67
68 class ClassLoaderDataGraph : public AllStatic {
69 friend class ClassLoaderData;
70 friend class ClassLoaderDataGraphMetaspaceIterator;
71 friend class ClassLoaderDataGraphKlassIteratorAtomic;
72 friend class ClassLoaderDataGraphKlassIteratorStatic;
73 friend class VMStructs;
74 private:
75 // All CLDs (except the null CLD) can be reached by walking _head->_next->...
76 static ClassLoaderData* _head;
77 static ClassLoaderData* _unloading;
78 // CMS support.
79 static ClassLoaderData* _saved_head;
80 static ClassLoaderData* _saved_unloading;
81 static bool _should_purge;
82
83 // Set if there's anything to purge in the deallocate lists or previous versions
84 // during a safepoint after class unloading in a full GC.
85 static bool _should_clean_deallocate_lists;
86 static bool _safepoint_cleanup_needed;
87
88 // OOM has been seen in metaspace allocation. Used to prevent some
89 // allocations until class unloading
90 static bool _metaspace_oom;
91
92 static volatile size_t _num_instance_classes;
93 static volatile size_t _num_array_classes;
94
95 static ClassLoaderData* add_to_graph(Handle class_loader, bool is_unsafe_anonymous);
96 static ClassLoaderData* add(Handle class_loader, bool is_unsafe_anonymous);
97
98 public:
99 static ClassLoaderData* find_or_create(Handle class_loader);
100 static void clean_module_and_package_info();
101 static void purge();
102 static void clear_claimed_marks();
103 // Iteration through CLDG inside a safepoint; GC support
104 static void cld_do(CLDClosure* cl);
105 static void cld_unloading_do(CLDClosure* cl);
106 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);
107 static void keep_alive_cld_do(CLDClosure* cl);
108 static void always_strong_cld_do(CLDClosure* cl);
109 // klass do
110 // Walking classes through the ClassLoaderDataGraph include array classes. It also includes
111 // classes that are allocated but not loaded, classes that have errors, and scratch classes
112 // for redefinition. These classes are removed during the next class unloading.
113 // Walking the ClassLoaderDataGraph also includes unsafe anonymous classes.
114 static void classes_do(KlassClosure* klass_closure);
115 static void classes_do(void f(Klass* const));
116 static void methods_do(void f(Method*));
117 static void modules_do(void f(ModuleEntry*));
118 static void modules_unloading_do(void f(ModuleEntry*));
119 static void packages_do(void f(PackageEntry*));
120 static void packages_unloading_do(void f(PackageEntry*));
121 static void loaded_classes_do(KlassClosure* klass_closure);
122 static void classes_unloading_do(void f(Klass* const));
123 static bool do_unloading(bool do_cleaning);
124
125 // Expose state to avoid logging overhead in safepoint cleanup tasks.
126 static inline bool should_clean_metaspaces_and_reset();
127 static void set_should_clean_deallocate_lists() { _should_clean_deallocate_lists = true; }
128 static void clean_deallocate_lists(bool purge_previous_versions);
129 static void walk_metadata_and_clean_metaspaces();
130
131 // dictionary do
132 // Iterate over all klasses in dictionary, but
133 // just the classes from defining class loaders.
134 static void dictionary_classes_do(void f(InstanceKlass*));
135 // Added for initialize_itable_for_klass to handle exceptions.
136 static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS);
137
138 // Iterate all classes and their class loaders, including initiating class loaders.
139 static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*));
140
141 // VM_CounterDecay iteration support
142 static InstanceKlass* try_get_next_class();
143
144 static void verify_dictionary();
145 static void print_dictionary(outputStream* st);
146 static void print_dictionary_statistics(outputStream* st);
147
148 // CMS support.
149 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
150 static GrowableArray<ClassLoaderData*>* new_clds();
151
152 static void set_should_purge(bool b) { _should_purge = b; }
153 static void purge_if_needed() {
154 // Only purge the CLDG for CMS if concurrent sweep is complete.
155 if (_should_purge) {
156 purge();
157 // reset for next time.
158 set_should_purge(false);
159 }
160 }
161
162 static int resize_if_needed();
163
164 static bool has_metaspace_oom() { return _metaspace_oom; }
165 static void set_metaspace_oom(bool value) { _metaspace_oom = value; }
166
167 static void print_on(outputStream * const out) PRODUCT_RETURN;
168 static void print() { print_on(tty); }
169 static void verify();
170
171 // instance and array class counters
172 static inline size_t num_instance_classes();
173 static inline size_t num_array_classes();
174 static inline void inc_instance_classes(size_t count);
175 static inline void dec_instance_classes(size_t count);
176 static inline void inc_array_classes(size_t count);
177 static inline void dec_array_classes(size_t count);
178
179 #ifndef PRODUCT
180 static bool contains_loader_data(ClassLoaderData* loader_data);
181 #endif
182 };
183
184 // ClassLoaderData class
185
186 class ClassLoaderData : public CHeapObj<mtClass> {
187 friend class VMStructs;
188
189 private:
190 class ChunkedHandleList {
191 struct Chunk : public CHeapObj<mtClass> {
192 static const size_t CAPACITY = 32;
193
194 oop _data[CAPACITY];
195 volatile juint _size;
196 Chunk* _next;
197
198 Chunk(Chunk* c) : _size(0), _next(c) { }
199 };
200
201 Chunk* volatile _head;
202
203 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
204
205 public:
206 ChunkedHandleList() : _head(NULL) {}
207 ~ChunkedHandleList();
208
209 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
210 // However, multiple threads can execute oops_do concurrently with add.
211 oop* add(oop o);
212 bool contains(oop p);
213 NOT_PRODUCT(bool owner_of(oop* p);)
214 void oops_do(OopClosure* f);
215
216 int count() const;
217 };
218
219 friend class ClassLoaderDataGraph;
220 friend class ClassLoaderDataGraphKlassIteratorAtomic;
221 friend class ClassLoaderDataGraphKlassIteratorStatic;
222 friend class ClassLoaderDataGraphMetaspaceIterator;
223 friend class Klass;
224 friend class MetaDataFactory;
225 friend class Method;
226
227 static ClassLoaderData * _the_null_class_loader_data;
228
229 WeakHandle<vm_class_loader_data> _holder; // The oop that determines lifetime of this class loader
230 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with
231 // this ClassLoaderData
232
233 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the
234 // classes in the class loader are allocated.
235 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
236 bool _unloading; // true if this class loader goes away
237 bool _is_unsafe_anonymous; // CLD is dedicated to one class and that class determines the CLDs lifecycle.
238 // For example, an unsafe anonymous class.
239
240 // Remembered sets support for the oops in the class loader data.
241 bool _modified_oops; // Card Table Equivalent (YC/CMS support)
242 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
243
244 s2 _keep_alive; // if this CLD is kept alive.
245 // Used for unsafe anonymous classes and the boot class
246 // loader. _keep_alive does not need to be volatile or
247 // atomic since there is one unique CLD per unsafe anonymous class.
248
249 volatile int _claimed; // true if claimed, for example during GC traces.
250 // To avoid applying oop closure more than once.
251 // Has to be an int because we cas it.
252 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
253 // have the same life cycle of the corresponding ClassLoader.
254
255 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies
256
257 Klass* volatile _klasses; // The classes defined by the class loader.
258 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
259 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
260 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
261 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
262
263 // These method IDs are created for the class loader and set to NULL when the
264 // class loader is unloaded. They are rarely freed, only for redefine classes
265 // and if they lose a data race in InstanceKlass.
266 JNIMethodBlock* _jmethod_ids;
267
268 // Metadata to be deallocated when it's safe at class unloading, when
269 // this class loader isn't unloaded itself.
270 GrowableArray<Metadata*>* _deallocate_list;
271
272 // Support for walking class loader data objects
273 ClassLoaderData* _next; /// Next loader_datas created
274
275 Klass* _class_loader_klass;
276 Symbol* _name;
277 Symbol* _name_and_id;
278 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
279
280 void set_next(ClassLoaderData* next) { _next = next; }
281 ClassLoaderData* next() const { return _next; }
282
283 ClassLoaderData(Handle h_class_loader, bool is_unsafe_anonymous);
284 ~ClassLoaderData();
285
286 // The CLD are not placed in the Heap, so the Card Table or
287 // the Mod Union Table can't be used to mark when CLD have modified oops.
288 // The CT and MUT bits saves this information for the whole class loader data.
289 void clear_modified_oops() { _modified_oops = false; }
290 public:
291 void record_modified_oops() { _modified_oops = true; }
292 bool has_modified_oops() { return _modified_oops; }
293
294 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
295 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
296 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; }
297 private:
298
299 void unload();
300 bool keep_alive() const { return _keep_alive > 0; }
301
302 oop holder_phantom() const;
303 void classes_do(void f(Klass*));
304 void loaded_classes_do(KlassClosure* klass_closure);
305 void classes_do(void f(InstanceKlass*));
306 void methods_do(void f(Method*));
307 void modules_do(void f(ModuleEntry*));
308 void packages_do(void f(PackageEntry*));
309
310 // Deallocate free list during class unloading.
311 void free_deallocate_list(); // for the classes that are not unloaded
312 void free_deallocate_list_C_heap_structures(); // for the classes that are unloaded
313
314 // Allocate out of this class loader data
315 MetaWord* allocate(size_t size);
316
317 Dictionary* create_dictionary();
318
319 void initialize_name(Handle class_loader);
320 public:
321 // GC interface.
322 void clear_claimed() { _claimed = 0; }
323 bool claimed() const { return _claimed == 1; }
324 bool claim();
325
326 bool is_alive() const;
327
328 // Accessors
329 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }
330
331 static ClassLoaderData* the_null_class_loader_data() {
332 return _the_null_class_loader_data;
333 }
334
335 Mutex* metaspace_lock() const { return _metaspace_lock; }
336
337 bool is_unsafe_anonymous() const { return _is_unsafe_anonymous; }
338
339 static void init_null_class_loader_data();
340
341 bool is_the_null_class_loader_data() const {
342 return this == _the_null_class_loader_data;
343 }
344
345 // Returns true if this class loader data is for the system class loader.
346 // (Note that the class loader data may be unsafe anonymous.)
347 bool is_system_class_loader_data() const;
348
349 // Returns true if this class loader data is for the platform class loader.
350 // (Note that the class loader data may be unsafe anonymous.)
351 bool is_platform_class_loader_data() const;
352
353 // Returns true if this class loader data is for the boot class loader.
354 // (Note that the class loader data may be unsafe anonymous.)
355 inline bool is_boot_class_loader_data() const;
356
357 bool is_builtin_class_loader_data() const;
358 bool is_permanent_class_loader_data() const;
359
360 // The Metaspace is created lazily so may be NULL. This
361 // method will allocate a Metaspace if needed.
362 ClassLoaderMetaspace* metaspace_non_null();
363
364 inline oop class_loader() const;
365
366 // Returns true if this class loader data is for a loader going away.
367 bool is_unloading() const {
368 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
369 return _unloading;
370 }
371
372 // Used to refcount an unsafe anonymous class's CLD in order to
373 // indicate their aliveness.
374 void inc_keep_alive();
375 void dec_keep_alive();
376
377 void initialize_holder(Handle holder);
378
379 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);
380
381 void classes_do(KlassClosure* klass_closure);
382 Klass* klasses() { return _klasses; }
383
384 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
385 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
386
387 void print() { print_on(tty); }
388 void print_on(outputStream* out) const PRODUCT_RETURN;
389 void print_value() { print_value_on(tty); }
390 void print_value_on(outputStream* out) const;
391 void verify();
392
393 OopHandle add_handle(Handle h);
394 void remove_handle(OopHandle h);
395 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
396 void add_class(Klass* k, bool publicize = true);
397 void remove_class(Klass* k);
398 bool contains_klass(Klass* k);
399 void record_dependency(const Klass* to);
400 PackageEntryTable* packages() { return _packages; }
401 ModuleEntry* unnamed_module() { return _unnamed_module; }
402 ModuleEntryTable* modules();
403 bool modules_defined() { return (_modules != NULL); }
404
405 // Loaded class dictionary
406 Dictionary* dictionary() const { return _dictionary; }
407
408 void add_to_deallocate_list(Metadata* m);
409
410 static ClassLoaderData* class_loader_data(oop loader);
411 static ClassLoaderData* class_loader_data_or_null(oop loader);
412 static ClassLoaderData* unsafe_anonymous_class_loader_data(Handle loader);
413
414 // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'.
415 // Also works if unloading.
416 Klass* class_loader_klass() const { return _class_loader_klass; }
417
418 // Returns the class loader's explict name as specified during
419 // construction or the class loader's qualified class name.
420 // Works during unloading.
421 const char* loader_name() const;
422 // Returns the explicitly specified class loader name or NULL.
423 Symbol* name() const { return _name; }
424
425 // Obtain the class loader's _name_and_id, works during unloading.
426 const char* loader_name_and_id() const;
427 Symbol* name_and_id() const { return _name_and_id; }
428
429 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
430 };
431
432 // An iterator that distributes Klasses to parallel worker threads.
433 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
434 Klass* volatile _next_klass;
435 public:
436 ClassLoaderDataGraphKlassIteratorAtomic();
437 Klass* next_klass();
438 private:
439 static Klass* next_klass_in_cldg(Klass* klass);
440 };
441
442 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
443 ClassLoaderData* _data;
444 public:
445 ClassLoaderDataGraphMetaspaceIterator();
446 ~ClassLoaderDataGraphMetaspaceIterator();
447 bool repeat() { return _data != NULL; }
448 ClassLoaderMetaspace* get_next() {
449 assert(_data != NULL, "Should not be NULL in call to the iterator");
450 ClassLoaderMetaspace* result = _data->metaspace_or_null();
451 _data = _data->next();
452 // This result might be NULL for class loaders without metaspace
453 // yet. It would be nice to return only non-null results but
454 // there is no guarantee that there will be a non-null result
455 // down the list so the caller is going to have to check.
456 return result;
457 }
458 };
459 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP