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 clean_module_and_package_info(); 101 static void purge(); 102 static void clear_claimed_marks(); 103 // oops do 104 static void oops_do(OopClosure* f, bool must_claim); 105 static void keep_alive_oops_do(OopClosure* blk, bool must_claim); 106 static void always_strong_oops_do(OopClosure* blk, bool must_claim); 107 // cld do 108 static void cld_do(CLDClosure* cl); 109 static void cld_unloading_do(CLDClosure* cl); 110 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak); 111 static void keep_alive_cld_do(CLDClosure* cl); 112 static void always_strong_cld_do(CLDClosure* cl); 113 // klass do 114 // Walking classes through the ClassLoaderDataGraph include array classes. It also includes 115 // classes that are allocated but not loaded, classes that have errors, and scratch classes 116 // for redefinition. These classes are removed during the next class unloading. 117 // Walking the ClassLoaderDataGraph also includes anonymous classes. 118 static void classes_do(KlassClosure* klass_closure); 119 static void classes_do(void f(Klass* const)); 120 static void methods_do(void f(Method*)); 121 static void modules_do(void f(ModuleEntry*)); 122 static void modules_unloading_do(void f(ModuleEntry*)); 123 static void packages_do(void f(PackageEntry*)); 124 static void packages_unloading_do(void f(PackageEntry*)); 125 static void loaded_classes_do(KlassClosure* klass_closure); 126 static void classes_unloading_do(void f(Klass* const)); 127 static bool do_unloading(bool do_cleaning); 128 129 // Expose state to avoid logging overhead in safepoint cleanup tasks. 130 static inline bool should_clean_metaspaces_and_reset(); 131 static void set_should_clean_deallocate_lists() { _should_clean_deallocate_lists = true; } 132 static void clean_deallocate_lists(bool purge_previous_versions); 133 static void walk_metadata_and_clean_metaspaces(); 134 135 // dictionary do 136 // Iterate over all klasses in dictionary, but 137 // just the classes from defining class loaders. 138 static void dictionary_classes_do(void f(InstanceKlass*)); 139 // Added for initialize_itable_for_klass to handle exceptions. 140 static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS); 141 142 // Iterate all classes and their class loaders, including initiating class loaders. 143 static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*)); 144 145 // VM_CounterDecay iteration support 146 static InstanceKlass* try_get_next_class(); 147 148 static void verify_dictionary(); 149 static void print_dictionary(outputStream* st); 150 static void print_dictionary_statistics(outputStream* st); 151 152 // CMS support. 153 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); } 154 static GrowableArray<ClassLoaderData*>* new_clds(); 155 156 static void set_should_purge(bool b) { _should_purge = b; } 157 static void purge_if_needed() { 158 // Only purge the CLDG for CMS if concurrent sweep is complete. 159 if (_should_purge) { 160 purge(); 161 // reset for next time. 162 set_should_purge(false); 163 } 164 } 165 166 static int resize_if_needed(); 167 168 static bool has_metaspace_oom() { return _metaspace_oom; } 169 static void set_metaspace_oom(bool value) { _metaspace_oom = value; } 170 171 static void print_on(outputStream * const out) PRODUCT_RETURN; 172 static void print() { print_on(tty); } 173 static void verify(); 174 175 // instance and array class counters 176 static inline size_t num_instance_classes(); 177 static inline size_t num_array_classes(); 178 static inline void inc_instance_classes(size_t count); 179 static inline void dec_instance_classes(size_t count); 180 static inline void inc_array_classes(size_t count); 181 static inline void dec_array_classes(size_t count); 182 183 #ifndef PRODUCT 184 static bool contains_loader_data(ClassLoaderData* loader_data); 185 #endif 186 }; 187 188 // ClassLoaderData class 189 190 class ClassLoaderData : public CHeapObj<mtClass> { 191 friend class VMStructs; 192 193 private: 194 class ChunkedHandleList { 195 struct Chunk : public CHeapObj<mtClass> { 196 static const size_t CAPACITY = 32; 197 198 oop _data[CAPACITY]; 199 volatile juint _size; 200 Chunk* _next; 201 202 Chunk(Chunk* c) : _size(0), _next(c) { } 203 }; 204 205 Chunk* volatile _head; 206 207 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size); 208 209 public: 210 ChunkedHandleList() : _head(NULL) {} 211 ~ChunkedHandleList(); 212 213 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock(). 214 // However, multiple threads can execute oops_do concurrently with add. 215 oop* add(oop o); 216 bool contains(oop p); 217 NOT_PRODUCT(bool owner_of(oop* p);) 218 void oops_do(OopClosure* f); 219 220 int count() const; 221 }; 222 223 friend class ClassLoaderDataGraph; 224 friend class ClassLoaderDataGraphKlassIteratorAtomic; 225 friend class ClassLoaderDataGraphKlassIteratorStatic; 226 friend class ClassLoaderDataGraphMetaspaceIterator; 227 friend class Klass; 228 friend class MetaDataFactory; 229 friend class Method; 230 231 static ClassLoaderData * _the_null_class_loader_data; 232 233 WeakHandle<vm_class_loader_data> _holder; // The oop that determines lifetime of this class loader 234 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with 235 // this ClassLoaderData 236 237 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the 238 // classes in the class loader are allocated. 239 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup. 240 bool _unloading; // true if this class loader goes away 241 bool _is_anonymous; // if this CLD is for an anonymous class 242 243 // Remembered sets support for the oops in the class loader data. 244 bool _modified_oops; // Card Table Equivalent (YC/CMS support) 245 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support) 246 247 s2 _keep_alive; // if this CLD is kept alive. 248 // Used for anonymous classes and the boot class 249 // loader. _keep_alive does not need to be volatile or 250 // atomic since there is one unique CLD per anonymous class. 251 252 volatile int _claimed; // true if claimed, for example during GC traces. 253 // To avoid applying oop closure more than once. 254 // Has to be an int because we cas it. 255 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which 256 // have the same life cycle of the corresponding ClassLoader. 257 258 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies 259 260 Klass* volatile _klasses; // The classes defined by the class loader. 261 PackageEntryTable* volatile _packages; // The packages defined by the class loader. 262 ModuleEntryTable* volatile _modules; // The modules defined by the class loader. 263 ModuleEntry* _unnamed_module; // This class loader's unnamed module. 264 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader 265 266 // These method IDs are created for the class loader and set to NULL when the 267 // class loader is unloaded. They are rarely freed, only for redefine classes 268 // and if they lose a data race in InstanceKlass. 269 JNIMethodBlock* _jmethod_ids; 270 271 // Metadata to be deallocated when it's safe at class unloading, when 272 // this class loader isn't unloaded itself. 273 GrowableArray<Metadata*>* _deallocate_list; 274 275 // Support for walking class loader data objects 276 ClassLoaderData* _next; /// Next loader_datas created 277 278 Klass* _class_loader_klass; 279 Symbol* _name; 280 Symbol* _name_and_id; 281 JFR_ONLY(DEFINE_TRACE_ID_FIELD;) 282 283 void set_next(ClassLoaderData* next) { _next = next; } 284 ClassLoaderData* next() const { return _next; } 285 286 ClassLoaderData(Handle h_class_loader, bool is_anonymous); 287 ~ClassLoaderData(); 288 289 // The CLD are not placed in the Heap, so the Card Table or 290 // the Mod Union Table can't be used to mark when CLD have modified oops. 291 // The CT and MUT bits saves this information for the whole class loader data. 292 void clear_modified_oops() { _modified_oops = false; } 293 public: 294 void record_modified_oops() { _modified_oops = true; } 295 bool has_modified_oops() { return _modified_oops; } 296 297 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; } 298 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; } 299 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; } 300 301 oop holder_no_keepalive() const; 302 bool keep_alive() const { return _keep_alive > 0; } 303 304 private: 305 void unload(); 306 oop holder_phantom() const; 307 308 void classes_do(void f(Klass*)); 309 void loaded_classes_do(KlassClosure* klass_closure); 310 void classes_do(void f(InstanceKlass*)); 311 void methods_do(void f(Method*)); 312 void modules_do(void f(ModuleEntry*)); 313 void packages_do(void f(PackageEntry*)); 314 315 // Deallocate free list during class unloading. 316 void free_deallocate_list(); // for the classes that are not unloaded 317 void free_deallocate_list_C_heap_structures(); // for the classes that are unloaded 318 319 // Allocate out of this class loader data 320 MetaWord* allocate(size_t size); 321 322 Dictionary* create_dictionary(); 323 324 void initialize_name(Handle class_loader); 325 public: 326 // GC interface. 327 void clear_claimed() { _claimed = 0; } 328 bool claimed() const { return _claimed != 0; } 329 bool claim(bool finalizable = false); 330 331 bool is_alive() const; 332 333 // Accessors 334 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; } 335 336 static ClassLoaderData* the_null_class_loader_data() { 337 return _the_null_class_loader_data; 338 } 339 340 Mutex* metaspace_lock() const { return _metaspace_lock; } 341 342 bool is_anonymous() const { return _is_anonymous; } 343 344 static void init_null_class_loader_data(); 345 346 bool is_the_null_class_loader_data() const { 347 return this == _the_null_class_loader_data; 348 } 349 350 // Returns true if this class loader data is for the system class loader. 351 // (Note that the class loader data may be anonymous.) 352 bool is_system_class_loader_data() const; 353 354 // Returns true if this class loader data is for the platform class loader. 355 // (Note that the class loader data may be anonymous.) 356 bool is_platform_class_loader_data() const; 357 358 // Returns true if this class loader data is for the boot class loader. 359 // (Note that the class loader data may be anonymous.) 360 bool is_boot_class_loader_data() const; 361 bool is_builtin_class_loader_data() const; 362 bool is_permanent_class_loader_data() const; 363 364 // The Metaspace is created lazily so may be NULL. This 365 // method will allocate a Metaspace if needed. 366 ClassLoaderMetaspace* metaspace_non_null(); 367 368 oop class_loader() const; 369 370 // Returns true if this class loader data is for a loader going away. 371 bool is_unloading() const { 372 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded"); 373 return _unloading; 374 } 375 376 // Used to refcount an anonymous class's CLD in order to 377 // indicate their aliveness. 378 void inc_keep_alive(); 379 void dec_keep_alive(); 380 381 void initialize_holder(Handle holder); 382 383 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false); 384 385 void classes_do(KlassClosure* klass_closure); 386 Klass* klasses() { return _klasses; } 387 388 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; } 389 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; } 390 391 void print() { print_on(tty); } 392 void print_on(outputStream* out) const PRODUCT_RETURN; 393 void print_value() { print_value_on(tty); } 394 void print_value_on(outputStream* out) const; 395 void verify(); 396 397 OopHandle add_handle(Handle h); 398 void remove_handle(OopHandle h); 399 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field 400 void add_class(Klass* k, bool publicize = true); 401 void remove_class(Klass* k); 402 bool contains_klass(Klass* k); 403 void record_dependency(const Klass* to); 404 PackageEntryTable* packages() { return _packages; } 405 ModuleEntry* unnamed_module() { return _unnamed_module; } 406 ModuleEntryTable* modules(); 407 bool modules_defined() { return (_modules != NULL); } 408 409 // Loaded class dictionary 410 Dictionary* dictionary() const { return _dictionary; } 411 412 void add_to_deallocate_list(Metadata* m); 413 414 static ClassLoaderData* class_loader_data(oop loader); 415 static ClassLoaderData* class_loader_data_or_null(oop loader); 416 static ClassLoaderData* anonymous_class_loader_data(Handle loader); 417 418 // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'. 419 // Also works if unloading. 420 Klass* class_loader_klass() const { return _class_loader_klass; } 421 422 // Returns the class loader's explict name as specified during 423 // construction or the class loader's qualified class name. 424 // Works during unloading. 425 const char* loader_name() const; 426 // Returns the explicitly specified class loader name or NULL. 427 Symbol* name() const { return _name; } 428 429 // Obtain the class loader's _name_and_id, works during unloading. 430 const char* loader_name_and_id() const; 431 Symbol* name_and_id() const { return _name_and_id; } 432 433 JFR_ONLY(DEFINE_TRACE_ID_METHODS;) 434 }; 435 436 // An iterator that distributes Klasses to parallel worker threads. 437 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj { 438 Klass* volatile _next_klass; 439 public: 440 ClassLoaderDataGraphKlassIteratorAtomic(); 441 Klass* next_klass(); 442 private: 443 static Klass* next_klass_in_cldg(Klass* klass); 444 }; 445 446 class ClassLoaderDataGraphMetaspaceIterator : public StackObj { 447 ClassLoaderData* _data; 448 public: 449 ClassLoaderDataGraphMetaspaceIterator(); 450 ~ClassLoaderDataGraphMetaspaceIterator(); 451 bool repeat() { return _data != NULL; } 452 ClassLoaderMetaspace* get_next() { 453 assert(_data != NULL, "Should not be NULL in call to the iterator"); 454 ClassLoaderMetaspace* result = _data->metaspace_or_null(); 455 _data = _data->next(); 456 // This result might be NULL for class loaders without metaspace 457 // yet. It would be nice to return only non-null results but 458 // there is no guarantee that there will be a non-null result 459 // down the list so the caller is going to have to check. 460 return result; 461 } 462 }; 463 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP