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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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 anonymous);
96 static ClassLoaderData* add(Handle class_loader, bool anonymous);
97
98 public:
99 static ClassLoaderData* find_or_create(Handle class_loader);
100 static void purge();
101 static void clear_claimed_marks();
102 // oops do
103 static void oops_do(OopClosure* f, bool must_claim);
104 static void keep_alive_oops_do(OopClosure* blk, bool must_claim);
105 static void always_strong_oops_do(OopClosure* blk, bool must_claim);
106 // cld do
107 static void cld_do(CLDClosure* cl);
108 static void cld_unloading_do(CLDClosure* cl);
109 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);
110 static void keep_alive_cld_do(CLDClosure* cl);
111 static void always_strong_cld_do(CLDClosure* cl);
112 // klass do
113 // Walking classes through the ClassLoaderDataGraph include array classes. It also includes
114 // classes that are allocated but not loaded, classes that have errors, and scratch classes
115 // for redefinition. These classes are removed during the next class unloading.
116 // Walking the ClassLoaderDataGraph also includes anonymous classes.
117 static void classes_do(KlassClosure* klass_closure);
118 static void classes_do(void f(Klass* const));
119 static void methods_do(void f(Method*));
120 static void modules_do(void f(ModuleEntry*));
121 static void modules_unloading_do(void f(ModuleEntry*));
122 static void packages_do(void f(PackageEntry*));
123 static void packages_unloading_do(void f(PackageEntry*));
124 static void loaded_classes_do(KlassClosure* klass_closure);
125 static void classes_unloading_do(void f(Klass* const));
126 static bool do_unloading(bool do_cleaning);
127
128 // Expose state to avoid logging overhead in safepoint cleanup tasks.
129 static inline bool should_clean_metaspaces();
130 static void set_should_clean_deallocate_lists() { _should_clean_deallocate_lists = true; }
131 static void clean_deallocate_lists(bool purge_previous_versions);
132 static void walk_metadata_and_clean_metaspaces();
133
134 // dictionary do
135 // Iterate over all klasses in dictionary, but
136 // just the classes from defining class loaders.
137 static void dictionary_classes_do(void f(InstanceKlass*));
138 // Added for initialize_itable_for_klass to handle exceptions.
139 static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS);
140
141 // Iterate all classes and their class loaders, including initiating class loaders.
142 static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*));
143
144 // VM_CounterDecay iteration support
145 static InstanceKlass* try_get_next_class();
146
147 static void verify_dictionary();
148 static void print_dictionary(outputStream* st);
149 static void print_dictionary_statistics(outputStream* st);
150
151 // CMS support.
152 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
153 static GrowableArray<ClassLoaderData*>* new_clds();
154
155 static void set_should_purge(bool b) { _should_purge = b; }
156 static void purge_if_needed() {
157 // Only purge the CLDG for CMS if concurrent sweep is complete.
158 if (_should_purge) {
159 purge();
160 // reset for next time.
161 set_should_purge(false);
162 }
163 }
164
165 static int resize_if_needed();
166
167 static bool has_metaspace_oom() { return _metaspace_oom; }
168 static void set_metaspace_oom(bool value) { _metaspace_oom = value; }
169
170 static void print_on(outputStream * const out) PRODUCT_RETURN;
171 static void print() { print_on(tty); }
172 static void verify();
173
174 // instance and array class counters
175 static inline size_t num_instance_classes();
176 static inline size_t num_array_classes();
177 static inline void inc_instance_classes(size_t count);
178 static inline void dec_instance_classes(size_t count);
179 static inline void inc_array_classes(size_t count);
180 static inline void dec_array_classes(size_t count);
181
182 #ifndef PRODUCT
183 static bool contains_loader_data(ClassLoaderData* loader_data);
184 #endif
185 };
186
187 // ClassLoaderData class
188
189 class ClassLoaderData : public CHeapObj<mtClass> {
190 friend class VMStructs;
191
192 private:
193 class ChunkedHandleList {
194 struct Chunk : public CHeapObj<mtClass> {
195 static const size_t CAPACITY = 32;
196
197 oop _data[CAPACITY];
198 volatile juint _size;
199 Chunk* _next;
200
201 Chunk(Chunk* c) : _next(c), _size(0) { }
202 };
203
204 Chunk* volatile _head;
205
206 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
207
208 public:
209 ChunkedHandleList() : _head(NULL) {}
210 ~ChunkedHandleList();
211
212 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
213 // However, multiple threads can execute oops_do concurrently with add.
214 oop* add(oop o);
215 bool contains(oop p);
216 NOT_PRODUCT(bool owner_of(oop* p);)
217 void oops_do(OopClosure* f);
218
219 int count() const;
220 };
221
222 friend class ClassLoaderDataGraph;
223 friend class ClassLoaderDataGraphKlassIteratorAtomic;
224 friend class ClassLoaderDataGraphKlassIteratorStatic;
225 friend class ClassLoaderDataGraphMetaspaceIterator;
226 friend class Klass;
227 friend class MetaDataFactory;
228 friend class Method;
229
230 static ClassLoaderData * _the_null_class_loader_data;
231
232 WeakHandle<vm_class_loader_data> _holder; // The oop that determines lifetime of this class loader
233 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with
234 // this ClassLoaderData
235
236 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the
237 // classes in the class loader are allocated.
238 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
239 bool _unloading; // true if this class loader goes away
240 bool _is_anonymous; // if this CLD is for an anonymous class
241
242 // Remembered sets support for the oops in the class loader data.
243 bool _modified_oops; // Card Table Equivalent (YC/CMS support)
244 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
245
246 s2 _keep_alive; // if this CLD is kept alive.
247 // Used for anonymous classes and the boot class
248 // loader. _keep_alive does not need to be volatile or
249 // atomic since there is one unique CLD per anonymous class.
250
251 volatile int _claimed; // true if claimed, for example during GC traces.
252 // To avoid applying oop closure more than once.
253 // Has to be an int because we cas it.
254 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
255 // have the same life cycle of the corresponding ClassLoader.
256
257 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies
258
259 Klass* volatile _klasses; // The classes defined by the class loader.
260 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
261 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
262 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
263 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
264
265 // These method IDs are created for the class loader and set to NULL when the
266 // class loader is unloaded. They are rarely freed, only for redefine classes
267 // and if they lose a data race in InstanceKlass.
268 JNIMethodBlock* _jmethod_ids;
269
270 // Metadata to be deallocated when it's safe at class unloading, when
271 // this class loader isn't unloaded itself.
272 GrowableArray<Metadata*>* _deallocate_list;
273
274 // Support for walking class loader data objects
275 ClassLoaderData* _next; /// Next loader_datas created
276
277 Klass* _class_loader_klass;
278 Symbol* _name;
279 Symbol* _name_and_id;
280 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
281
282 void set_next(ClassLoaderData* next) { _next = next; }
283 ClassLoaderData* next() const { return _next; }
284
285 ClassLoaderData(Handle h_class_loader, bool is_anonymous);
286 ~ClassLoaderData();
287
288 // The CLD are not placed in the Heap, so the Card Table or
289 // the Mod Union Table can't be used to mark when CLD have modified oops.
290 // The CT and MUT bits saves this information for the whole class loader data.
291 void clear_modified_oops() { _modified_oops = false; }
292 public:
293 void record_modified_oops() { _modified_oops = true; }
294 bool has_modified_oops() { return _modified_oops; }
295
296 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
297 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
298 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; }
299 private:
300
301 void unload();
302 bool keep_alive() const { return _keep_alive > 0; }
303
304 oop holder_phantom() const;
305 void classes_do(void f(Klass*));
306 void loaded_classes_do(KlassClosure* klass_closure);
307 void classes_do(void f(InstanceKlass*));
308 void methods_do(void f(Method*));
309 void modules_do(void f(ModuleEntry*));
310 void packages_do(void f(PackageEntry*));
311
312 // Deallocate free list during class unloading.
313 void free_deallocate_list(); // for the classes that are not unloaded
314 void free_deallocate_list_C_heap_structures(); // for the classes that are unloaded
315
316 // Allocate out of this class loader data
317 MetaWord* allocate(size_t size);
318
319 Dictionary* create_dictionary();
320
321 void initialize_name(Handle class_loader);
322 public:
323 // GC interface.
324 void clear_claimed() { _claimed = 0; }
325 bool claimed() const { return _claimed == 1; }
326 bool claim();
327
328 bool is_alive() const;
329
330 // Accessors
331 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }
332
333 static ClassLoaderData* the_null_class_loader_data() {
334 return _the_null_class_loader_data;
335 }
336
337 Mutex* metaspace_lock() const { return _metaspace_lock; }
338
339 bool is_anonymous() const { return _is_anonymous; }
340
341 static void init_null_class_loader_data();
342
343 bool is_the_null_class_loader_data() const {
344 return this == _the_null_class_loader_data;
345 }
346
347 // Returns true if this class loader data is for the system class loader.
348 // (Note that the class loader data may be anonymous.)
349 bool is_system_class_loader_data() const;
350
351 // Returns true if this class loader data is for the platform class loader.
352 // (Note that the class loader data may be anonymous.)
353 bool is_platform_class_loader_data() const;
354
355 // Returns true if this class loader data is for the boot class loader.
356 // (Note that the class loader data may be anonymous.)
357 inline bool is_boot_class_loader_data() const;
358
359 bool is_builtin_class_loader_data() const;
360 bool is_permanent_class_loader_data() const;
361
362 // The Metaspace is created lazily so may be NULL. This
363 // method will allocate a Metaspace if needed.
364 ClassLoaderMetaspace* metaspace_non_null();
365
366 inline oop class_loader() const;
367
368 // Returns true if this class loader data is for a loader going away.
369 bool is_unloading() const {
370 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
371 return _unloading;
372 }
373
374 // Used to refcount an anonymous class's CLD in order to
375 // indicate their aliveness.
376 void inc_keep_alive();
377 void dec_keep_alive();
378
379 void initialize_holder(Handle holder);
380
381 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false);
382
383 void classes_do(KlassClosure* klass_closure);
384 Klass* klasses() { return _klasses; }
385
386 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
387 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
388
389 void print() { print_on(tty); }
390 void print_on(outputStream* out) const PRODUCT_RETURN;
391 void print_value() { print_value_on(tty); }
392 void print_value_on(outputStream* out) const;
393 void verify();
394
395 OopHandle add_handle(Handle h);
396 void remove_handle(OopHandle h);
397 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
398 void add_class(Klass* k, bool publicize = true);
399 void remove_class(Klass* k);
400 bool contains_klass(Klass* k);
401 void record_dependency(const Klass* to);
402 PackageEntryTable* packages() { return _packages; }
403 ModuleEntry* unnamed_module() { return _unnamed_module; }
404 ModuleEntryTable* modules();
405 bool modules_defined() { return (_modules != NULL); }
406
407 // Loaded class dictionary
408 Dictionary* dictionary() const { return _dictionary; }
409
410 void add_to_deallocate_list(Metadata* m);
411
412 static ClassLoaderData* class_loader_data(oop loader);
413 static ClassLoaderData* class_loader_data_or_null(oop loader);
414 static ClassLoaderData* anonymous_class_loader_data(Handle loader);
415
416 // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'.
417 // Also works if unloading.
418 Klass* class_loader_klass() const { return _class_loader_klass; }
419
420 // Returns the class loader's explict name as specified during
421 // construction or the class loader's qualified class name.
422 // Works during unloading.
423 const char* loader_name() const;
424 // Returns the explicitly specified class loader name or NULL.
425 Symbol* name() const { return _name; }
426
427 // Obtain the class loader's _name_and_id, works during unloading.
428 const char* loader_name_and_id() const;
429 Symbol* name_and_id() const { return _name_and_id; }
430
431 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
432 };
433
434 // An iterator that distributes Klasses to parallel worker threads.
435 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
436 Klass* volatile _next_klass;
437 public:
438 ClassLoaderDataGraphKlassIteratorAtomic();
439 Klass* next_klass();
440 private:
441 static Klass* next_klass_in_cldg(Klass* klass);
442 };
443
444 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
445 ClassLoaderData* _data;
446 public:
447 ClassLoaderDataGraphMetaspaceIterator();
448 ~ClassLoaderDataGraphMetaspaceIterator();
449 bool repeat() { return _data != NULL; }
450 ClassLoaderMetaspace* get_next() {
451 assert(_data != NULL, "Should not be NULL in call to the iterator");
452 ClassLoaderMetaspace* result = _data->metaspace_or_null();
453 _data = _data->next();
454 // This result might be NULL for class loaders without metaspace
455 // yet. It would be nice to return only non-null results but
456 // there is no guarantee that there will be a non-null result
457 // down the list so the caller is going to have to check.
458 return result;
459 }
460 };
461 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP