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 NOT_PRODUCT(bool owner_of(oop* p);)
209 void oops_do(OopClosure* f);
210
211 int count() const;
212 };
213
214 friend class ClassLoaderDataGraph;
215 friend class ClassLoaderDataGraphKlassIteratorAtomic;
216 friend class ClassLoaderDataGraphKlassIteratorStatic;
217 friend class ClassLoaderDataGraphMetaspaceIterator;
218 friend class InstanceKlass;
219 friend class MetaDataFactory;
220 friend class Method;
221
222 static ClassLoaderData * _the_null_class_loader_data;
223
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 void classes_do(void f(Klass*));
292 void loaded_classes_do(KlassClosure* klass_closure);
293 void classes_do(void f(InstanceKlass*));
294 void methods_do(void f(Method*));
295 void modules_do(void f(ModuleEntry*));
296 void packages_do(void f(PackageEntry*));
297
298 // Deallocate free list during class unloading.
299 void free_deallocate_list(); // for the classes that are not unloaded
300 void unload_deallocate_list(); // for the classes that are unloaded
301
302 // Allocate out of this class loader data
303 MetaWord* allocate(size_t size);
304
305 Dictionary* create_dictionary();
306 public:
307 // GC interface.
308 void clear_claimed() { _claimed = 0; }
309 bool claimed() const { return _claimed == 1; }
310 bool claim();
311
312 bool is_alive(BoolObjectClosure* is_alive_closure) const;
313
314 // Accessors
315 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }
316
317 static ClassLoaderData* the_null_class_loader_data() {
318 return _the_null_class_loader_data;
319 }
320
321 Mutex* metaspace_lock() const { return _metaspace_lock; }
322
323 bool is_anonymous() const { return _is_anonymous; }
324
325 static void init_null_class_loader_data();
326
327 bool is_the_null_class_loader_data() const {
328 return this == _the_null_class_loader_data;
329 }
330
331 // Returns true if this class loader data is for the system class loader.
332 // (Note that the class loader data may be anonymous.)
333 bool is_system_class_loader_data() const;
334
335 // Returns true if this class loader data is for the platform class loader.
336 // (Note that the class loader data may be anonymous.)
337 bool is_platform_class_loader_data() const;
338
339 // Returns true if this class loader data is for the boot class loader.
340 // (Note that the class loader data may be anonymous.)
341 bool is_boot_class_loader_data() const {
342 return class_loader() == NULL;
343 }
344
345 bool is_builtin_class_loader_data() const;
346 bool is_permanent_class_loader_data() const;
347
348 // The Metaspace is created lazily so may be NULL. This
349 // method will allocate a Metaspace if needed.
350 ClassLoaderMetaspace* metaspace_non_null();
351
352 oop class_loader() const { return _class_loader; }
353
354 // The object the GC is using to keep this ClassLoaderData alive.
355 oop keep_alive_object() const;
356
357 // Returns true if this class loader data is for a loader going away.
358 bool is_unloading() const {
359 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
360 return _unloading;
361 }
362
363 // Used to refcount an anonymous class's CLD in order to
364 // indicate their aliveness without a keep_alive_object().
365 void inc_keep_alive();
366 void dec_keep_alive();
367
368 inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); }
369
370 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);
371
372 void classes_do(KlassClosure* klass_closure);
373 Klass* klasses() { return _klasses; }
374
375 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
376 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
377
378 void print() { print_on(tty); }
379 void print_on(outputStream* out) const PRODUCT_RETURN;
380 void print_value() { print_value_on(tty); }
381 void print_value_on(outputStream* out) const;
382 void verify();
383 const char* loader_name() const;
384
385 OopHandle add_handle(Handle h);
386 void remove_handle(OopHandle h);
387 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
388 void add_class(Klass* k, bool publicize = true);
389 void remove_class(Klass* k);
390 bool contains_klass(Klass* k);
391 void record_dependency(const Klass* to);
392 PackageEntryTable* packages() { return _packages; }
393 ModuleEntry* unnamed_module() { return _unnamed_module; }
394 ModuleEntryTable* modules();
395 bool modules_defined() { return (_modules != NULL); }
396
397 // Loaded class dictionary
398 Dictionary* dictionary() const { return _dictionary; }
399
400 void add_to_deallocate_list(Metadata* m);
401
402 static ClassLoaderData* class_loader_data(oop loader);
403 static ClassLoaderData* class_loader_data_or_null(oop loader);
404 static ClassLoaderData* anonymous_class_loader_data(Handle loader);
405
406 TRACE_DEFINE_TRACE_ID_METHODS;
407 };
408
409 // An iterator that distributes Klasses to parallel worker threads.
410 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
411 Klass* volatile _next_klass;
412 public:
413 ClassLoaderDataGraphKlassIteratorAtomic();
414 Klass* next_klass();
415 private:
416 static Klass* next_klass_in_cldg(Klass* klass);
417 };
418
419 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
420 ClassLoaderData* _data;
421 public:
422 ClassLoaderDataGraphMetaspaceIterator();
423 ~ClassLoaderDataGraphMetaspaceIterator();
424 bool repeat() { return _data != NULL; }
425 ClassLoaderMetaspace* get_next() {
426 assert(_data != NULL, "Should not be NULL in call to the iterator");
427 ClassLoaderMetaspace* result = _data->metaspace_or_null();
428 _data = _data->next();
429 // This result might be NULL for class loaders without metaspace
430 // yet. It would be nice to return only non-null results but
431 // there is no guarantee that there will be a non-null result
432 // down the list so the caller is going to have to check.
433 return result;
434 }
435 };
436 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP