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