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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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 static bool unload_list_contains(const void* x);
159
160 // instance and array class counters
161 static inline size_t num_instance_classes();
162 static inline size_t num_array_classes();
163 static inline void inc_instance_classes(size_t count);
164 static inline void dec_instance_classes(size_t count);
165 static inline void inc_array_classes(size_t count);
166 static inline void dec_array_classes(size_t count);
167
168 #ifndef PRODUCT
169 static bool contains_loader_data(ClassLoaderData* loader_data);
170 #endif
171
172 #if INCLUDE_TRACE
173 private:
174 static Ticks _class_unload_time;
175 static void class_unload_event(Klass* const k);
176 #endif
177 };
178
179 // ClassLoaderData class
180
181 class ClassLoaderData : public CHeapObj<mtClass> {
182 friend class VMStructs;
183
184 private:
185 class ChunkedHandleList {
186 struct Chunk : public CHeapObj<mtClass> {
187 static const size_t CAPACITY = 32;
188
189 oop _data[CAPACITY];
190 volatile juint _size;
191 Chunk* _next;
192
193 Chunk(Chunk* c) : _next(c), _size(0) { }
194 };
195
196 Chunk* volatile _head;
197
198 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
199
200 public:
201 ChunkedHandleList() : _head(NULL) {}
202 ~ChunkedHandleList();
203
204 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
205 // However, multiple threads can execute oops_do concurrently with add.
206 oop* add(oop o);
207 bool contains(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 oop _class_loader; // oop used to uniquely identify a class loader
224 // class loader or a canonical class path
225
226 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the
227 // classes in the class loader are allocated.
228 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
229 bool _unloading; // true if this class loader goes away
230 bool _is_anonymous; // if this CLD is for an anonymous class
231
232 // Remembered sets support for the oops in the class loader data.
233 bool _modified_oops; // Card Table Equivalent (YC/CMS support)
234 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
235
236 s2 _keep_alive; // if this CLD is kept alive without a keep_alive_object().
237 // Used for anonymous classes and the boot class
238 // loader. _keep_alive does not need to be volatile or
239 // atomic since there is one unique CLD per anonymous class.
240
241 volatile int _claimed; // true if claimed, for example during GC traces.
242 // To avoid applying oop closure more than once.
243 // Has to be an int because we cas it.
244 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
245 // have the same life cycle of the corresponding ClassLoader.
246
247 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies
248
249 Klass* volatile _klasses; // The classes defined by the class loader.
250 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
251 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
252 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
253 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
254
255 // These method IDs are created for the class loader and set to NULL when the
256 // class loader is unloaded. They are rarely freed, only for redefine classes
257 // and if they lose a data race in InstanceKlass.
258 JNIMethodBlock* _jmethod_ids;
259
260 // Metadata to be deallocated when it's safe at class unloading, when
261 // this class loader isn't unloaded itself.
262 GrowableArray<Metadata*>* _deallocate_list;
263
264 // Support for walking class loader data objects
265 ClassLoaderData* _next; /// Next loader_datas created
266
267 // ReadOnly and ReadWrite metaspaces (static because only on the null
268 // class loader for now).
269 static ClassLoaderMetaspace* _ro_metaspace;
270 static ClassLoaderMetaspace* _rw_metaspace;
271
272 TRACE_DEFINE_TRACE_ID_FIELD;
273
274 void set_next(ClassLoaderData* next) { _next = next; }
275 ClassLoaderData* next() const { return _next; }
276
277 ClassLoaderData(Handle h_class_loader, bool is_anonymous);
278 ~ClassLoaderData();
279
280 // The CLD are not placed in the Heap, so the Card Table or
281 // the Mod Union Table can't be used to mark when CLD have modified oops.
282 // The CT and MUT bits saves this information for the whole class loader data.
283 void clear_modified_oops() { _modified_oops = false; }
284 public:
285 void record_modified_oops() { _modified_oops = true; }
286 bool has_modified_oops() { return _modified_oops; }
287
288 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
289 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
290 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; }
291 private:
292
293 void unload();
294 bool keep_alive() const { return _keep_alive > 0; }
295 void classes_do(void f(Klass*));
296 void loaded_classes_do(KlassClosure* klass_closure);
297 void classes_do(void f(InstanceKlass*));
298 void methods_do(void f(Method*));
299 void modules_do(void f(ModuleEntry*));
300 void packages_do(void f(PackageEntry*));
301
302 // Deallocate free list during class unloading.
303 void free_deallocate_list(); // for the classes that are not unloaded
304 void unload_deallocate_list(); // for the classes that are unloaded
305
306 // Allocate out of this class loader data
307 MetaWord* allocate(size_t size);
308
309 Dictionary* create_dictionary();
310 public:
311 // GC interface.
312 void clear_claimed() { _claimed = 0; }
313 bool claimed() const { return _claimed == 1; }
314 bool claim();
315
316 bool is_alive(BoolObjectClosure* is_alive_closure) const;
317
318 // Accessors
319 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }
320
321 static ClassLoaderData* the_null_class_loader_data() {
322 return _the_null_class_loader_data;
323 }
324
325 Mutex* metaspace_lock() const { return _metaspace_lock; }
326
327 bool is_anonymous() const { return _is_anonymous; }
328
329 static void init_null_class_loader_data();
330
331 bool is_the_null_class_loader_data() const {
332 return this == _the_null_class_loader_data;
333 }
334
335 // Returns true if this class loader data is for the system class loader.
336 // (Note that the class loader data may be anonymous.)
337 bool is_system_class_loader_data() const;
338
339 // Returns true if this class loader data is for the platform class loader.
340 // (Note that the class loader data may be anonymous.)
341 bool is_platform_class_loader_data() const;
342
343 // Returns true if this class loader data is for the boot class loader.
344 // (Note that the class loader data may be anonymous.)
345 bool is_boot_class_loader_data() const {
346 return class_loader() == NULL;
347 }
348
349 bool is_builtin_class_loader_data() const;
350 bool is_permanent_class_loader_data() const;
351
352 // The Metaspace is created lazily so may be NULL. This
353 // method will allocate a Metaspace if needed.
354 ClassLoaderMetaspace* metaspace_non_null();
355
356 oop class_loader() const { return _class_loader; }
357
358 // The object the GC is using to keep this ClassLoaderData alive.
359 oop keep_alive_object() const;
360
361 // Returns true if this class loader data is for a loader going away.
362 bool is_unloading() const {
363 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
364 return _unloading;
365 }
366
367 // Used to refcount an anonymous class's CLD in order to
368 // indicate their aliveness without a keep_alive_object().
369 void inc_keep_alive();
370 void dec_keep_alive();
371
372 inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); }
373
374 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);
375
376 void classes_do(KlassClosure* klass_closure);
377 Klass* klasses() { return _klasses; }
378
379 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
380 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
381
382 void print() { print_on(tty); }
383 void print_on(outputStream* out) const PRODUCT_RETURN;
384 void print_value() { print_value_on(tty); }
385 void print_value_on(outputStream* out) const;
386 void verify();
387 const char* loader_name() const;
388
389 OopHandle add_handle(Handle h);
390 void remove_handle(OopHandle h);
391 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
392 void add_class(Klass* k, bool publicize = true);
393 void remove_class(Klass* k);
394 bool contains_klass(Klass* k);
395 void record_dependency(const Klass* to);
396 PackageEntryTable* packages() { return _packages; }
397 ModuleEntry* unnamed_module() { return _unnamed_module; }
398 ModuleEntryTable* modules();
399 bool modules_defined() { return (_modules != NULL); }
400
401 // Loaded class dictionary
402 Dictionary* dictionary() const { return _dictionary; }
403
404 void add_to_deallocate_list(Metadata* m);
405
406 static ClassLoaderData* class_loader_data(oop loader);
407 static ClassLoaderData* class_loader_data_or_null(oop loader);
408 static ClassLoaderData* anonymous_class_loader_data(Handle loader);
409
410 TRACE_DEFINE_TRACE_ID_METHODS;
411 };
412
413 // An iterator that distributes Klasses to parallel worker threads.
414 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
415 Klass* volatile _next_klass;
416 public:
417 ClassLoaderDataGraphKlassIteratorAtomic();
418 Klass* next_klass();
419 private:
420 static Klass* next_klass_in_cldg(Klass* klass);
421 };
422
423 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
424 ClassLoaderData* _data;
425 public:
426 ClassLoaderDataGraphMetaspaceIterator();
427 ~ClassLoaderDataGraphMetaspaceIterator();
428 bool repeat() { return _data != NULL; }
429 ClassLoaderMetaspace* get_next() {
430 assert(_data != NULL, "Should not be NULL in call to the iterator");
431 ClassLoaderMetaspace* result = _data->metaspace_or_null();
432 _data = _data->next();
433 // This result might be NULL for class loaders without metaspace
434 // yet. It would be nice to return only non-null results but
435 // there is no guarantee that there will be a non-null result
436 // down the list so the caller is going to have to check.
437 return result;
438 }
439 };
440 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP