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 "memory/metaspaceCounters.hpp" 32 #include "oops/oopHandle.hpp" 33 #include "runtime/mutex.hpp" 34 #include "trace/traceMacros.hpp" 35 #include "utilities/growableArray.hpp" 36 #include "utilities/macros.hpp" 37 #if INCLUDE_TRACE 38 #include "utilities/ticks.hpp" 39 #endif 40 41 // 42 // A class loader represents a linkset. Conceptually, a linkset identifies 43 // the complete transitive closure of resolved links that a dynamic linker can 44 // produce. 45 // 46 // A ClassLoaderData also encapsulates the allocation space, called a metaspace, 47 // used by the dynamic linker to allocate the runtime representation of all 48 // the types it defines. 49 // 50 // ClassLoaderData are stored in the runtime representation of classes, 51 // and provides iterators for root tracing and other GC operations. 52 53 class ClassLoaderData; 54 class JNIMethodBlock; 55 class Metadebug; 56 class ModuleEntry; 57 class PackageEntry; 58 class ModuleEntryTable; 59 class PackageEntryTable; 60 class DictionaryEntry; 61 class Dictionary; 62 63 // GC root for walking class loader data created 64 65 class ClassLoaderDataGraph : public AllStatic { 66 friend class ClassLoaderData; 67 friend class ClassLoaderDataGraphMetaspaceIterator; 68 friend class ClassLoaderDataGraphKlassIteratorAtomic; 69 friend class ClassLoaderDataGraphKlassIteratorStatic; 70 friend class VMStructs; 71 private: 72 // All CLDs (except the null CLD) can be reached by walking _head->_next->... 73 static ClassLoaderData* _head; 74 static ClassLoaderData* _unloading; 75 // CMS support. 76 static ClassLoaderData* _saved_head; 77 static ClassLoaderData* _saved_unloading; 78 static bool _should_purge; 79 // OOM has been seen in metaspace allocation. Used to prevent some 80 // allocations until class unloading 81 static bool _metaspace_oom; 82 83 static volatile size_t _num_instance_classes; 84 static volatile size_t _num_array_classes; 85 86 static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS); 87 static void post_class_unload_events(); 88 public: 89 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS); 90 static void purge(); 91 static void clear_claimed_marks(); 92 // oops do 93 static void oops_do(OopClosure* f, bool must_claim); 94 static void keep_alive_oops_do(OopClosure* blk, bool must_claim); 95 static void always_strong_oops_do(OopClosure* blk, bool must_claim); 96 // cld do 97 static void cld_do(CLDClosure* cl); 98 static void cld_unloading_do(CLDClosure* cl); 99 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak); 100 static void keep_alive_cld_do(CLDClosure* cl); 101 static void always_strong_cld_do(CLDClosure* cl); 102 // klass do 103 // Walking classes through the ClassLoaderDataGraph include array classes. It also includes 104 // classes that are allocated but not loaded, classes that have errors, and scratch classes 105 // for redefinition. These classes are removed during the next class unloading. 106 // Walking the ClassLoaderDataGraph also includes anonymous classes. 107 static void classes_do(KlassClosure* klass_closure); 108 static void classes_do(void f(Klass* const)); 109 static void methods_do(void f(Method*)); 110 static void modules_do(void f(ModuleEntry*)); 111 static void modules_unloading_do(void f(ModuleEntry*)); 112 static void packages_do(void f(PackageEntry*)); 113 static void packages_unloading_do(void f(PackageEntry*)); 114 static void loaded_classes_do(KlassClosure* klass_closure); 115 static void classes_unloading_do(void f(Klass* const)); 116 static bool do_unloading(BoolObjectClosure* is_alive, bool clean_previous_versions); 117 118 // dictionary do 119 // Iterate over all klasses in dictionary, but 120 // just the classes from defining class loaders. 121 static void dictionary_classes_do(void f(InstanceKlass*)); 122 // Added for initialize_itable_for_klass to handle exceptions. 123 static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS); 124 125 // Iterate all classes and their class loaders, including initiating class loaders. 126 static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*)); 127 128 // VM_CounterDecay iteration support 129 static InstanceKlass* try_get_next_class(); 130 131 static void verify_dictionary(); 132 static void print_dictionary(outputStream* st); 133 static void print_dictionary_statistics(outputStream* st); 134 135 // CMS support. 136 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); } 137 static GrowableArray<ClassLoaderData*>* new_clds(); 138 139 static void set_should_purge(bool b) { _should_purge = b; } 140 static void purge_if_needed() { 141 // Only purge the CLDG for CMS if concurrent sweep is complete. 142 if (_should_purge) { 143 purge(); 144 // reset for next time. 145 set_should_purge(false); 146 } 147 } 148 149 static int resize_if_needed(); 150 151 static bool has_metaspace_oom() { return _metaspace_oom; } 152 static void set_metaspace_oom(bool value) { _metaspace_oom = value; } 153 154 static void dump_on(outputStream * const out) PRODUCT_RETURN; 155 static void dump() { dump_on(tty); } 156 static void verify(); 157 static void print_creation(outputStream* out, Handle loader, ClassLoaderData* cld, TRAPS); 158 159 static bool unload_list_contains(const void* x); 160 161 // instance and array class counters 162 static inline size_t num_instance_classes(); 163 static inline size_t num_array_classes(); 164 static inline void inc_instance_classes(size_t count); 165 static inline void dec_instance_classes(size_t count); 166 static inline void inc_array_classes(size_t count); 167 static inline void dec_array_classes(size_t count); 168 169 #ifndef PRODUCT 170 static bool contains_loader_data(ClassLoaderData* loader_data); 171 #endif 172 173 #if INCLUDE_TRACE 174 private: 175 static Ticks _class_unload_time; 176 static void class_unload_event(Klass* const k); 177 #endif 178 }; 179 180 // ClassLoaderData class 181 182 class ClassLoaderData : public CHeapObj<mtClass> { 183 friend class VMStructs; 184 private: 185 class Dependencies VALUE_OBJ_CLASS_SPEC { 186 objArrayOop _list_head; 187 void locked_add(objArrayHandle last, 188 objArrayHandle new_dependency, 189 Thread* THREAD); 190 public: 191 Dependencies() : _list_head(NULL) {} 192 Dependencies(TRAPS) : _list_head(NULL) { 193 init(CHECK); 194 } 195 void add(Handle dependency, TRAPS); 196 void init(TRAPS); 197 void oops_do(OopClosure* f); 198 }; 199 200 class ChunkedHandleList VALUE_OBJ_CLASS_SPEC { 201 struct Chunk : public CHeapObj<mtClass> { 202 static const size_t CAPACITY = 32; 203 204 oop _data[CAPACITY]; 205 volatile juint _size; 206 Chunk* _next; 207 208 Chunk(Chunk* c) : _next(c), _size(0) { } 209 }; 210 211 Chunk* volatile _head; 212 213 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size); 214 215 public: 216 ChunkedHandleList() : _head(NULL) {} 217 ~ChunkedHandleList(); 218 219 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock(). 220 // However, multiple threads can execute oops_do concurrently with add. 221 oop* add(oop o); 222 #ifdef ASSERT 223 bool contains(oop* p); 224 #endif 225 void oops_do(OopClosure* f); 226 }; 227 228 friend class ClassLoaderDataGraph; 229 friend class ClassLoaderDataGraphKlassIteratorAtomic; 230 friend class ClassLoaderDataGraphKlassIteratorStatic; 231 friend class ClassLoaderDataGraphMetaspaceIterator; 232 friend class InstanceKlass; 233 friend class MetaDataFactory; 234 friend class Method; 235 236 static ClassLoaderData * _the_null_class_loader_data; 237 238 oop _class_loader; // oop used to uniquely identify a class loader 239 // class loader or a canonical class path 240 Dependencies _dependencies; // holds dependencies from this class loader 241 // data to others. 242 243 Metaspace * volatile _metaspace; // Meta-space where meta-data defined by the 244 // classes in the class loader are allocated. 245 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup. 246 bool _unloading; // true if this class loader goes away 247 bool _is_anonymous; // if this CLD is for an anonymous class 248 249 // Remembered sets support for the oops in the class loader data. 250 bool _modified_oops; // Card Table Equivalent (YC/CMS support) 251 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support) 252 253 s2 _keep_alive; // if this CLD is kept alive without a keep_alive_object(). 254 // Used for anonymous classes and the boot class 255 // loader. _keep_alive does not need to be volatile or 256 // atomic since there is one unique CLD per anonymous class. 257 258 volatile int _claimed; // true if claimed, for example during GC traces. 259 // To avoid applying oop closure more than once. 260 // Has to be an int because we cas it. 261 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which 262 // have the same life cycle of the corresponding ClassLoader. 263 264 Klass* volatile _klasses; // The classes defined by the class loader. 265 PackageEntryTable* volatile _packages; // The packages defined by the class loader. 266 ModuleEntryTable* volatile _modules; // The modules defined by the class loader. 267 ModuleEntry* _unnamed_module; // This class loader's unnamed module. 268 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader 269 270 // These method IDs are created for the class loader and set to NULL when the 271 // class loader is unloaded. They are rarely freed, only for redefine classes 272 // and if they lose a data race in InstanceKlass. 273 JNIMethodBlock* _jmethod_ids; 274 275 // Metadata to be deallocated when it's safe at class unloading, when 276 // this class loader isn't unloaded itself. 277 GrowableArray<Metadata*>* _deallocate_list; 278 279 // Support for walking class loader data objects 280 ClassLoaderData* _next; /// Next loader_datas created 281 282 // ReadOnly and ReadWrite metaspaces (static because only on the null 283 // class loader for now). 284 static Metaspace* _ro_metaspace; 285 static Metaspace* _rw_metaspace; 286 287 TRACE_DEFINE_TRACE_ID_FIELD; 288 289 void set_next(ClassLoaderData* next) { _next = next; } 290 ClassLoaderData* next() const { return _next; } 291 292 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies); 293 ~ClassLoaderData(); 294 295 // The CLD are not placed in the Heap, so the Card Table or 296 // the Mod Union Table can't be used to mark when CLD have modified oops. 297 // The CT and MUT bits saves this information for the whole class loader data. 298 void clear_modified_oops() { _modified_oops = false; } 299 public: 300 void record_modified_oops() { _modified_oops = true; } 301 bool has_modified_oops() { return _modified_oops; } 302 303 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; } 304 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; } 305 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; } 306 private: 307 308 void unload(); 309 bool keep_alive() const { return _keep_alive > 0; } 310 void classes_do(void f(Klass*)); 311 void loaded_classes_do(KlassClosure* klass_closure); 312 void classes_do(void f(InstanceKlass*)); 313 void methods_do(void f(Method*)); 314 void modules_do(void f(ModuleEntry*)); 315 void packages_do(void f(PackageEntry*)); 316 317 // Deallocate free list during class unloading. 318 void free_deallocate_list(); // for the classes that are not unloaded 319 void unload_deallocate_list(); // for the classes that are unloaded 320 321 // Allocate out of this class loader data 322 MetaWord* allocate(size_t size); 323 324 Dictionary* create_dictionary(); 325 public: 326 // GC interface. 327 void clear_claimed() { _claimed = 0; } 328 bool claimed() const { return _claimed == 1; } 329 bool claim(); 330 331 bool is_alive(BoolObjectClosure* is_alive_closure) const; 332 333 // Accessors 334 Metaspace* 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 assert(_the_null_class_loader_data == NULL, "cannot initialize twice"); 346 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice"); 347 348 // We explicitly initialize the Dependencies object at a later phase in the initialization 349 _the_null_class_loader_data = new ClassLoaderData(Handle(), false, Dependencies()); 350 ClassLoaderDataGraph::_head = _the_null_class_loader_data; 351 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be"); 352 } 353 354 bool is_the_null_class_loader_data() const { 355 return this == _the_null_class_loader_data; 356 } 357 bool is_system_class_loader_data() const; 358 bool is_platform_class_loader_data() const; 359 360 // Returns true if this class loader data is for the boot class loader. 361 // (Note that the class loader data may be anonymous.) 362 bool is_boot_class_loader_data() const { 363 return class_loader() == NULL; 364 } 365 366 bool is_builtin_class_loader_data() const; 367 bool is_permanent_class_loader_data() const; 368 369 // The Metaspace is created lazily so may be NULL. This 370 // method will allocate a Metaspace if needed. 371 Metaspace* metaspace_non_null(); 372 373 oop class_loader() const { return _class_loader; } 374 375 // The object the GC is using to keep this ClassLoaderData alive. 376 oop keep_alive_object() const; 377 378 // Returns true if this class loader data is for a loader going away. 379 bool is_unloading() const { 380 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded"); 381 return _unloading; 382 } 383 384 // Used to refcount an anonymous class's CLD in order to 385 // indicate their aliveness without a keep_alive_object(). 386 void inc_keep_alive(); 387 void dec_keep_alive(); 388 389 inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); } 390 391 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false); 392 393 void classes_do(KlassClosure* klass_closure); 394 Klass* klasses() { return _klasses; } 395 396 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; } 397 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; } 398 399 void print() { print_on(tty); } 400 void print_on(outputStream* out) const; 401 void print_value() { print_value_on(tty); } 402 void print_value_on(outputStream* out) const; 403 void dump(outputStream * const out) PRODUCT_RETURN; 404 void verify(); 405 const char* loader_name(); 406 407 OopHandle add_handle(Handle h); 408 void remove_handle(OopHandle h); 409 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field 410 void add_class(Klass* k, bool publicize = true); 411 void remove_class(Klass* k); 412 bool contains_klass(Klass* k); 413 void record_dependency(const Klass* to, TRAPS); 414 void init_dependencies(TRAPS); 415 PackageEntryTable* packages() { return _packages; } 416 ModuleEntry* unnamed_module() { return _unnamed_module; } 417 ModuleEntryTable* modules(); 418 bool modules_defined() { return (_modules != NULL); } 419 420 // Loaded class dictionary 421 Dictionary* dictionary() const { return _dictionary; } 422 423 void add_to_deallocate_list(Metadata* m); 424 425 static ClassLoaderData* class_loader_data(oop loader); 426 static ClassLoaderData* class_loader_data_or_null(oop loader); 427 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS); 428 static void print_loader(ClassLoaderData *loader_data, outputStream *out); 429 430 TRACE_DEFINE_TRACE_ID_METHODS; 431 }; 432 433 // An iterator that distributes Klasses to parallel worker threads. 434 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj { 435 Klass* volatile _next_klass; 436 public: 437 ClassLoaderDataGraphKlassIteratorAtomic(); 438 Klass* next_klass(); 439 private: 440 static Klass* next_klass_in_cldg(Klass* klass); 441 }; 442 443 class ClassLoaderDataGraphMetaspaceIterator : public StackObj { 444 ClassLoaderData* _data; 445 public: 446 ClassLoaderDataGraphMetaspaceIterator(); 447 ~ClassLoaderDataGraphMetaspaceIterator(); 448 bool repeat() { return _data != NULL; } 449 Metaspace* get_next() { 450 assert(_data != NULL, "Should not be NULL in call to the iterator"); 451 Metaspace* result = _data->metaspace_or_null(); 452 _data = _data->next(); 453 // This result might be NULL for class loaders without metaspace 454 // yet. It would be nice to return only non-null results but 455 // there is no guarantee that there will be a non-null result 456 // down the list so the caller is going to have to check. 457 return result; 458 } 459 }; 460 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP