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. 18 * 19 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA 20 * or visit www.oracle.com if you need additional information or have any 21 * questions. 22 * 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