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
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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 *
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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 ClassLoaderDataGraphIterator;
74 friend class VMStructs;
75 private:
76 // All CLDs (except the null CLD) can be reached by walking _head->_next->...
77 static ClassLoaderData* _head;
78 static ClassLoaderData* _unloading;
79 // CMS support.
80 static ClassLoaderData* _saved_head;
81 static ClassLoaderData* _saved_unloading;
82 static bool _should_purge;
83
84 // Set if there's anything to purge in the deallocate lists or previous versions
85 // during a safepoint after class unloading in a full GC.
86 static bool _should_clean_deallocate_lists;
87 static bool _safepoint_cleanup_needed;
88
89 // OOM has been seen in metaspace allocation. Used to prevent some
90 // allocations until class unloading
91 static bool _metaspace_oom;
92
93 static volatile size_t _num_instance_classes;
94 static volatile size_t _num_array_classes;
95
96 static ClassLoaderData* add_to_graph(Handle class_loader, bool is_unsafe_anonymous);
97 static ClassLoaderData* add(Handle class_loader, bool is_unsafe_anonymous);
98
99 public:
100 static ClassLoaderData* find_or_create(Handle class_loader);
101 static void clean_module_and_package_info();
102 static void purge();
103 static void clear_claimed_marks();
104 // Iteration through CLDG inside a safepoint; GC support
105 static void cld_do(CLDClosure* cl);
106 static void cld_unloading_do(CLDClosure* cl);
107 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak);
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 unlocked_loaded_classes_do(KlassClosure* klass_closure);
123 static void classes_unloading_do(void f(Klass* const));
124 static bool do_unloading(bool do_cleaning);
125
126 // Expose state to avoid logging overhead in safepoint cleanup tasks.
127 static inline bool should_clean_metaspaces_and_reset();
128 static void set_should_clean_deallocate_lists() { _should_clean_deallocate_lists = true; }
129 static void clean_deallocate_lists(bool purge_previous_versions);
130 static void walk_metadata_and_clean_metaspaces();
131
132 // dictionary do
133 // Iterate over all klasses in dictionary, but
134 // just the classes from defining class loaders.
135 static void dictionary_classes_do(void f(InstanceKlass*));
136 // Added for initialize_itable_for_klass to handle exceptions.
137 static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS);
138
139 // VM_CounterDecay iteration support
140 static InstanceKlass* try_get_next_class();
141
142 static void verify_dictionary();
143 static void print_dictionary(outputStream* st);
144 static void print_dictionary_statistics(outputStream* st);
145
146 // CMS support.
147 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); }
148 static GrowableArray<ClassLoaderData*>* new_clds();
149
150 static void set_should_purge(bool b) { _should_purge = b; }
151 static void purge_if_needed() {
152 // Only purge the CLDG for CMS if concurrent sweep is complete.
153 if (_should_purge) {
154 purge();
155 // reset for next time.
156 set_should_purge(false);
157 }
158 }
159
160 static int resize_if_needed();
161
162 static bool has_metaspace_oom() { return _metaspace_oom; }
163 static void set_metaspace_oom(bool value) { _metaspace_oom = value; }
164
165 static void print_on(outputStream * const out) PRODUCT_RETURN;
166 static void print() { print_on(tty); }
167 static void verify();
168
169 // instance and array class counters
170 static inline size_t num_instance_classes();
171 static inline size_t num_array_classes();
172 static inline void inc_instance_classes(size_t count);
173 static inline void dec_instance_classes(size_t count);
174 static inline void inc_array_classes(size_t count);
175 static inline void dec_array_classes(size_t count);
176
177 #ifndef PRODUCT
178 static bool contains_loader_data(ClassLoaderData* loader_data);
179 #endif
180 };
181
182 class LockedClassesDo : public KlassClosure {
183 typedef void (*classes_do_func_t)(Klass*);
184 classes_do_func_t _function;
185 public:
186 LockedClassesDo(); // For callers who provide their own do_klass
187 LockedClassesDo(classes_do_func_t function);
188 ~LockedClassesDo();
189
190 void do_klass(Klass* k) {
191 (*_function)(k);
192 }
193 };
194
195
196 // ClassLoaderData class
197
198 class ClassLoaderData : public CHeapObj<mtClass> {
199 friend class VMStructs;
200
201 private:
202 class ChunkedHandleList {
203 struct Chunk : public CHeapObj<mtClass> {
204 static const size_t CAPACITY = 32;
205
206 oop _data[CAPACITY];
207 volatile juint _size;
208 Chunk* _next;
209
210 Chunk(Chunk* c) : _size(0), _next(c) { }
211 };
212
213 Chunk* volatile _head;
214
215 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size);
216
217 public:
218 ChunkedHandleList() : _head(NULL) {}
219 ~ChunkedHandleList();
220
221 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock().
222 // However, multiple threads can execute oops_do concurrently with add.
223 oop* add(oop o);
224 bool contains(oop p);
225 NOT_PRODUCT(bool owner_of(oop* p);)
226 void oops_do(OopClosure* f);
227
228 int count() const;
229 };
230
231 friend class ClassLoaderDataGraph;
232 friend class ClassLoaderDataGraphIterator;
233 friend class ClassLoaderDataGraphKlassIteratorAtomic;
234 friend class ClassLoaderDataGraphKlassIteratorStatic;
235 friend class ClassLoaderDataGraphMetaspaceIterator;
236 friend class Klass;
237 friend class MetaDataFactory;
238 friend class Method;
239
240 static ClassLoaderData * _the_null_class_loader_data;
241
242 WeakHandle<vm_class_loader_data> _holder; // The oop that determines lifetime of this class loader
243 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with
244 // this ClassLoaderData
245
246 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the
247 // classes in the class loader are allocated.
248 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup.
249 bool _unloading; // true if this class loader goes away
250 bool _is_unsafe_anonymous; // CLD is dedicated to one class and that class determines the CLDs lifecycle.
251 // For example, an unsafe anonymous class.
252
253 // Remembered sets support for the oops in the class loader data.
254 bool _modified_oops; // Card Table Equivalent (YC/CMS support)
255 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support)
256
257 s2 _keep_alive; // if this CLD is kept alive.
258 // Used for unsafe anonymous classes and the boot class
259 // loader. _keep_alive does not need to be volatile or
260 // atomic since there is one unique CLD per unsafe anonymous class.
261
262 volatile int _claim; // non-zero if claimed, for example during GC traces.
263 // To avoid applying oop closure more than once.
264 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which
265 // have the same life cycle of the corresponding ClassLoader.
266
267 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies
268
269 Klass* volatile _klasses; // The classes defined by the class loader.
270 PackageEntryTable* volatile _packages; // The packages defined by the class loader.
271 ModuleEntryTable* volatile _modules; // The modules defined by the class loader.
272 ModuleEntry* _unnamed_module; // This class loader's unnamed module.
273 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader
274
275 // These method IDs are created for the class loader and set to NULL when the
276 // class loader is unloaded. They are rarely freed, only for redefine classes
277 // and if they lose a data race in InstanceKlass.
278 JNIMethodBlock* _jmethod_ids;
279
280 // Metadata to be deallocated when it's safe at class unloading, when
281 // this class loader isn't unloaded itself.
282 GrowableArray<Metadata*>* _deallocate_list;
283
284 // Support for walking class loader data objects
285 ClassLoaderData* _next; /// Next loader_datas created
286
287 Klass* _class_loader_klass;
288 Symbol* _name;
289 Symbol* _name_and_id;
290 JFR_ONLY(DEFINE_TRACE_ID_FIELD;)
291
292 void set_next(ClassLoaderData* next) { _next = next; }
293 ClassLoaderData* next() const { return _next; }
294
295 ClassLoaderData(Handle h_class_loader, bool is_unsafe_anonymous);
296 ~ClassLoaderData();
297
298 // The CLD are not placed in the Heap, so the Card Table or
299 // the Mod Union Table can't be used to mark when CLD have modified oops.
300 // The CT and MUT bits saves this information for the whole class loader data.
301 void clear_modified_oops() { _modified_oops = false; }
302 public:
303 void record_modified_oops() { _modified_oops = true; }
304 bool has_modified_oops() { return _modified_oops; }
305
306 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; }
307 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; }
308 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; }
309 oop holder_no_keepalive() const;
310
311 private:
312 void unload();
313 bool keep_alive() const { return _keep_alive > 0; }
314
315 oop holder_phantom() const;
316 void classes_do(void f(Klass*));
317 void loaded_classes_do(KlassClosure* klass_closure);
318 void classes_do(void f(InstanceKlass*));
319 void methods_do(void f(Method*));
320 void modules_do(void f(ModuleEntry*));
321 void packages_do(void f(PackageEntry*));
322
323 // Deallocate free list during class unloading.
324 void free_deallocate_list(); // for the classes that are not unloaded
325 void free_deallocate_list_C_heap_structures(); // for the classes that are unloaded
326
327 // Allocate out of this class loader data
328 MetaWord* allocate(size_t size);
329
330 Dictionary* create_dictionary();
331
332 void initialize_name(Handle class_loader);
333
334 public:
335 // GC interface.
336
337 // The "claim" is typically used to check if oops_do needs to be applied on
338 // the CLD or not. Most GCs only perform strong marking during the marking phase.
339 enum {
340 _claim_none = 0,
341 _claim_finalizable = 2,
342 _claim_strong = 3
343 };
344 void clear_claim() { _claim = 0; }
345 bool claimed() const { return _claim != 0; }
346 bool try_claim(int claim);
347 int get_claim() const { return _claim; }
348 void set_claim(int claim) { _claim = claim; }
349
350 // Computes if the CLD is alive or not. This is safe to call in concurrent
351 // contexts.
352 bool is_alive() const;
353
354 // Accessors
355 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; }
356
357 static ClassLoaderData* the_null_class_loader_data() {
358 return _the_null_class_loader_data;
359 }
360
361 Mutex* metaspace_lock() const { return _metaspace_lock; }
362
363 bool is_unsafe_anonymous() const { return _is_unsafe_anonymous; }
364
365 static void init_null_class_loader_data();
366
367 bool is_the_null_class_loader_data() const {
368 return this == _the_null_class_loader_data;
369 }
370
371 // Returns true if this class loader data is for the system class loader.
372 // (Note that the class loader data may be unsafe anonymous.)
373 bool is_system_class_loader_data() const;
374
375 // Returns true if this class loader data is for the platform class loader.
376 // (Note that the class loader data may be unsafe anonymous.)
377 bool is_platform_class_loader_data() const;
378
379 // Returns true if this class loader data is for the boot class loader.
380 // (Note that the class loader data may be unsafe anonymous.)
381 inline bool is_boot_class_loader_data() const;
382
383 bool is_builtin_class_loader_data() const;
384 bool is_permanent_class_loader_data() const;
385
386 // The Metaspace is created lazily so may be NULL. This
387 // method will allocate a Metaspace if needed.
388 ClassLoaderMetaspace* metaspace_non_null();
389
390 inline oop class_loader() const;
391
392 // Returns true if this class loader data is for a loader going away.
393 // Note that this is only safe after the GC has computed if the CLD is
394 // unloading or not. In concurrent contexts where there are no such
395 // guarantees, is_alive() should be used instead.
396 bool is_unloading() const {
397 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded");
398 return _unloading;
399 }
400
401 // Used to refcount an unsafe anonymous class's CLD in order to
402 // indicate their aliveness.
403 void inc_keep_alive();
404 void dec_keep_alive();
405
406 void initialize_holder(Handle holder);
407
408 void oops_do(OopClosure* f, int claim_value, bool clear_modified_oops = false);
409
410 void classes_do(KlassClosure* klass_closure);
411 Klass* klasses() { return _klasses; }
412
413 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; }
414 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; }
415
416 void print() { print_on(tty); }
417 void print_on(outputStream* out) const PRODUCT_RETURN;
418 void print_value() { print_value_on(tty); }
419 void print_value_on(outputStream* out) const;
420 void verify();
421
422 OopHandle add_handle(Handle h);
423 void remove_handle(OopHandle h);
424 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field
425 void add_class(Klass* k, bool publicize = true);
426 void remove_class(Klass* k);
427 bool contains_klass(Klass* k);
428 void record_dependency(const Klass* to);
429 PackageEntryTable* packages() { return _packages; }
430 ModuleEntry* unnamed_module() { return _unnamed_module; }
431 ModuleEntryTable* modules();
432 bool modules_defined() { return (_modules != NULL); }
433
434 // Loaded class dictionary
435 Dictionary* dictionary() const { return _dictionary; }
436
437 void add_to_deallocate_list(Metadata* m);
438
439 static ClassLoaderData* class_loader_data(oop loader);
440 static ClassLoaderData* class_loader_data_or_null(oop loader);
441 static ClassLoaderData* unsafe_anonymous_class_loader_data(Handle loader);
442
443 // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'.
444 // Also works if unloading.
445 Klass* class_loader_klass() const { return _class_loader_klass; }
446
447 // Returns the class loader's explict name as specified during
448 // construction or the class loader's qualified class name.
449 // Works during unloading.
450 const char* loader_name() const;
451 // Returns the explicitly specified class loader name or NULL.
452 Symbol* name() const { return _name; }
453
454 // Obtain the class loader's _name_and_id, works during unloading.
455 const char* loader_name_and_id() const;
456 Symbol* name_and_id() const { return _name_and_id; }
457
458 JFR_ONLY(DEFINE_TRACE_ID_METHODS;)
459 };
460
461 // An iterator that distributes Klasses to parallel worker threads.
462 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj {
463 Klass* volatile _next_klass;
464 public:
465 ClassLoaderDataGraphKlassIteratorAtomic();
466 Klass* next_klass();
467 private:
468 static Klass* next_klass_in_cldg(Klass* klass);
469 };
470
471 class ClassLoaderDataGraphMetaspaceIterator : public StackObj {
472 ClassLoaderData* _data;
473 public:
474 ClassLoaderDataGraphMetaspaceIterator();
475 ~ClassLoaderDataGraphMetaspaceIterator();
476 bool repeat() { return _data != NULL; }
477 ClassLoaderMetaspace* get_next() {
478 assert(_data != NULL, "Should not be NULL in call to the iterator");
479 ClassLoaderMetaspace* result = _data->metaspace_or_null();
480 _data = _data->next();
481 // This result might be NULL for class loaders without metaspace
482 // yet. It would be nice to return only non-null results but
483 // there is no guarantee that there will be a non-null result
484 // down the list so the caller is going to have to check.
485 return result;
486 }
487 };
488 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP