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 // OOM has been seen in metaspace allocation. Used to prevent some 83 // allocations until class unloading 84 static bool _metaspace_oom; 85 86 static volatile size_t _num_instance_classes; 87 static volatile size_t _num_array_classes; 88 89 static ClassLoaderData* add_to_graph(Handle class_loader, bool anonymous); 90 static ClassLoaderData* add(Handle class_loader, bool anonymous); 91 public: 92 static ClassLoaderData* find_or_create(Handle class_loader); 93 static void purge(); 94 static void clear_claimed_marks(); 95 // oops do 96 static void oops_do(OopClosure* f, bool must_claim); 97 static void keep_alive_oops_do(OopClosure* blk, bool must_claim); 98 static void always_strong_oops_do(OopClosure* blk, bool must_claim); 99 // cld do 100 static void cld_do(CLDClosure* cl); 101 static void cld_unloading_do(CLDClosure* cl); 102 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak); 103 static void keep_alive_cld_do(CLDClosure* cl); 104 static void always_strong_cld_do(CLDClosure* cl); 105 // klass do 106 // Walking classes through the ClassLoaderDataGraph include array classes. It also includes 107 // classes that are allocated but not loaded, classes that have errors, and scratch classes 108 // for redefinition. These classes are removed during the next class unloading. 109 // Walking the ClassLoaderDataGraph also includes anonymous classes. 110 static void classes_do(KlassClosure* klass_closure); 111 static void classes_do(void f(Klass* const)); 112 static void methods_do(void f(Method*)); 113 static void modules_do(void f(ModuleEntry*)); 114 static void modules_unloading_do(void f(ModuleEntry*)); 115 static void packages_do(void f(PackageEntry*)); 116 static void packages_unloading_do(void f(PackageEntry*)); 117 static void loaded_classes_do(KlassClosure* klass_closure); 118 static void classes_unloading_do(void f(Klass* const)); 119 static bool do_unloading(bool clean_previous_versions); 120 121 // dictionary do 122 // Iterate over all klasses in dictionary, but 123 // just the classes from defining class loaders. 124 static void dictionary_classes_do(void f(InstanceKlass*)); 125 // Added for initialize_itable_for_klass to handle exceptions. 126 static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS); 127 128 // Iterate all classes and their class loaders, including initiating class loaders. 129 static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*)); 130 131 // VM_CounterDecay iteration support 132 static InstanceKlass* try_get_next_class(); 133 134 static void verify_dictionary(); 135 static void print_dictionary(outputStream* st); 136 static void print_dictionary_statistics(outputStream* st); 137 138 // CMS support. 139 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); } 140 static GrowableArray<ClassLoaderData*>* new_clds(); 141 142 static void set_should_purge(bool b) { _should_purge = b; } 143 static void purge_if_needed() { 144 // Only purge the CLDG for CMS if concurrent sweep is complete. 145 if (_should_purge) { 146 purge(); 147 // reset for next time. 148 set_should_purge(false); 149 } 150 } 151 152 static int resize_if_needed(); 153 154 static bool has_metaspace_oom() { return _metaspace_oom; } 155 static void set_metaspace_oom(bool value) { _metaspace_oom = value; } 156 157 static void print_on(outputStream * const out) PRODUCT_RETURN; 158 static void print() { print_on(tty); } 159 static void verify(); 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 // Check if ClassLoaderData is part of the ClassLoaderDataGraph (not unloaded) 174 // Usage without lock only allowed during error reporting. 175 static bool is_valid(ClassLoaderData* loader_data); 176 }; 177 178 // ClassLoaderData class 179 180 class ClassLoaderData : public CHeapObj<mtClass> { 181 friend class VMStructs; 182 183 private: 184 class ChunkedHandleList { 185 struct Chunk : public CHeapObj<mtClass> { 186 static const size_t CAPACITY = 32; 187 188 oop _data[CAPACITY]; 189 volatile juint _size; 190 Chunk* _next; 191 192 Chunk(Chunk* c) : _next(c), _size(0) { } 193 }; 194 195 Chunk* volatile _head; 196 197 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size); 198 199 public: 200 ChunkedHandleList() : _head(NULL) {} 201 ~ChunkedHandleList(); 202 203 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock(). 204 // However, multiple threads can execute oops_do concurrently with add. 205 oop* add(oop o); 206 bool contains(oop p); 207 NOT_PRODUCT(bool owner_of(oop* p);) 208 void oops_do(OopClosure* f); 209 210 int count() const; 211 }; 212 213 friend class ClassLoaderDataGraph; 214 friend class ClassLoaderDataGraphKlassIteratorAtomic; 215 friend class ClassLoaderDataGraphKlassIteratorStatic; 216 friend class ClassLoaderDataGraphMetaspaceIterator; 217 friend class Klass; 218 friend class MetaDataFactory; 219 friend class Method; 220 221 static ClassLoaderData * _the_null_class_loader_data; 222 223 WeakHandle<vm_class_loader_data> _holder; // The oop that determines lifetime of this class loader 224 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with 225 // this ClassLoaderData 226 227 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the 228 // classes in the class loader are allocated. 229 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup. 230 bool _unloading; // true if this class loader goes away 231 bool _is_anonymous; // if this CLD is for an anonymous class 232 233 // Remembered sets support for the oops in the class loader data. 234 bool _modified_oops; // Card Table Equivalent (YC/CMS support) 235 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support) 236 237 s2 _keep_alive; // if this CLD is kept alive. 238 // Used for anonymous classes and the boot class 239 // loader. _keep_alive does not need to be volatile or 240 // atomic since there is one unique CLD per anonymous class. 241 242 volatile int _claimed; // true if claimed, for example during GC traces. 243 // To avoid applying oop closure more than once. 244 // Has to be an int because we cas it. 245 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which 246 // have the same life cycle of the corresponding ClassLoader. 247 248 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies 249 250 Klass* volatile _klasses; // The classes defined by the class loader. 251 PackageEntryTable* volatile _packages; // The packages defined by the class loader. 252 ModuleEntryTable* volatile _modules; // The modules defined by the class loader. 253 ModuleEntry* _unnamed_module; // This class loader's unnamed module. 254 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader 255 256 // These method IDs are created for the class loader and set to NULL when the 257 // class loader is unloaded. They are rarely freed, only for redefine classes 258 // and if they lose a data race in InstanceKlass. 259 JNIMethodBlock* _jmethod_ids; 260 261 // Metadata to be deallocated when it's safe at class unloading, when 262 // this class loader isn't unloaded itself. 263 GrowableArray<Metadata*>* _deallocate_list; 264 265 // Support for walking class loader data objects 266 ClassLoaderData* _next; /// Next loader_datas created 267 268 Klass* _class_loader_klass; 269 Symbol* _name; 270 Symbol* _name_and_id; 271 JFR_ONLY(DEFINE_TRACE_ID_FIELD;) 272 273 void set_next(ClassLoaderData* next) { _next = next; } 274 ClassLoaderData* next() const { return _next; } 275 276 ClassLoaderData(Handle h_class_loader, bool is_anonymous); 277 ~ClassLoaderData(); 278 279 // The CLD are not placed in the Heap, so the Card Table or 280 // the Mod Union Table can't be used to mark when CLD have modified oops. 281 // The CT and MUT bits saves this information for the whole class loader data. 282 void clear_modified_oops() { _modified_oops = false; } 283 public: 284 void record_modified_oops() { _modified_oops = true; } 285 bool has_modified_oops() { return _modified_oops; } 286 287 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; } 288 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; } 289 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; } 290 private: 291 292 void unload(); 293 bool keep_alive() const { return _keep_alive > 0; } 294 295 oop holder_phantom() const; 296 void classes_do(void f(Klass*)); 297 void loaded_classes_do(KlassClosure* klass_closure); 298 void classes_do(void f(InstanceKlass*)); 299 void methods_do(void f(Method*)); 300 void modules_do(void f(ModuleEntry*)); 301 void packages_do(void f(PackageEntry*)); 302 303 // Deallocate free list during class unloading. 304 void free_deallocate_list(); // for the classes that are not unloaded 305 void unload_deallocate_list(); // for the classes that are unloaded 306 307 // Allocate out of this class loader data 308 MetaWord* allocate(size_t size); 309 310 Dictionary* create_dictionary(); 311 312 void initialize_name(Handle class_loader); 313 public: 314 // GC interface. 315 void clear_claimed() { _claimed = 0; } 316 bool claimed() const { return _claimed == 1; } 317 bool claim(); 318 319 bool is_alive() const; 320 321 // Accessors 322 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; } 323 324 static ClassLoaderData* the_null_class_loader_data() { 325 return _the_null_class_loader_data; 326 } 327 328 Mutex* metaspace_lock() const { return _metaspace_lock; } 329 330 bool is_anonymous() const { return _is_anonymous; } 331 332 static void init_null_class_loader_data(); 333 334 bool is_the_null_class_loader_data() const { 335 return this == _the_null_class_loader_data; 336 } 337 338 // Returns true if this class loader data is for the system class loader. 339 // (Note that the class loader data may be anonymous.) 340 bool is_system_class_loader_data() const; 341 342 // Returns true if this class loader data is for the platform class loader. 343 // (Note that the class loader data may be anonymous.) 344 bool is_platform_class_loader_data() const; 345 346 // Returns true if this class loader data is for the boot class loader. 347 // (Note that the class loader data may be anonymous.) 348 inline bool is_boot_class_loader_data() const; 349 350 bool is_builtin_class_loader_data() const; 351 bool is_permanent_class_loader_data() const; 352 353 // The Metaspace is created lazily so may be NULL. This 354 // method will allocate a Metaspace if needed. 355 ClassLoaderMetaspace* metaspace_non_null(); 356 357 inline oop class_loader() const; 358 359 // Returns true if this class loader data is for a loader going away. 360 bool is_unloading() const { 361 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded"); 362 return _unloading; 363 } 364 365 // Used to refcount an anonymous class's CLD in order to 366 // indicate their aliveness. 367 void inc_keep_alive(); 368 void dec_keep_alive(); 369 370 void initialize_holder(Handle holder); 371 372 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false); 373 374 void classes_do(KlassClosure* klass_closure); 375 Klass* klasses() { return _klasses; } 376 377 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; } 378 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; } 379 380 void print() { print_on(tty); } 381 void print_on(outputStream* out) const PRODUCT_RETURN; 382 void print_value() { print_value_on(tty); } 383 void print_value_on(outputStream* out) const; 384 void verify(); 385 386 OopHandle add_handle(Handle h); 387 void remove_handle(OopHandle h); 388 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field 389 void add_class(Klass* k, bool publicize = true); 390 void remove_class(Klass* k); 391 bool contains_klass(Klass* k); 392 void record_dependency(const Klass* to); 393 PackageEntryTable* packages() { return _packages; } 394 ModuleEntry* unnamed_module() { return _unnamed_module; } 395 ModuleEntryTable* modules(); 396 bool modules_defined() { return (_modules != NULL); } 397 398 // Loaded class dictionary 399 Dictionary* dictionary() const { return _dictionary; } 400 401 void add_to_deallocate_list(Metadata* m); 402 403 static ClassLoaderData* class_loader_data(oop loader); 404 static ClassLoaderData* class_loader_data_or_null(oop loader); 405 static ClassLoaderData* anonymous_class_loader_data(Handle loader); 406 407 // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'. 408 // Also works if unloading. 409 Klass* class_loader_klass() const { return _class_loader_klass; } 410 411 // Returns the class loader's explict name as specified during 412 // construction or the class loader's qualified class name. 413 // Works during unloading. 414 const char* loader_name() const; 415 // Returns the explicitly specified class loader name or NULL. 416 Symbol* name() const { return _name; } 417 418 // Obtain the class loader's _name_and_id, works during unloading. 419 const char* loader_name_and_id() const; 420 Symbol* name_and_id() const { return _name_and_id; } 421 422 JFR_ONLY(DEFINE_TRACE_ID_METHODS;) 423 }; 424 425 // An iterator that distributes Klasses to parallel worker threads. 426 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj { 427 Klass* volatile _next_klass; 428 public: 429 ClassLoaderDataGraphKlassIteratorAtomic(); 430 Klass* next_klass(); 431 private: 432 static Klass* next_klass_in_cldg(Klass* klass); 433 }; 434 435 class ClassLoaderDataGraphMetaspaceIterator : public StackObj { 436 ClassLoaderData* _data; 437 public: 438 ClassLoaderDataGraphMetaspaceIterator(); 439 ~ClassLoaderDataGraphMetaspaceIterator(); 440 bool repeat() { return _data != NULL; } 441 ClassLoaderMetaspace* get_next() { 442 assert(_data != NULL, "Should not be NULL in call to the iterator"); 443 ClassLoaderMetaspace* result = _data->metaspace_or_null(); 444 _data = _data->next(); 445 // This result might be NULL for class loaders without metaspace 446 // yet. It would be nice to return only non-null results but 447 // there is no guarantee that there will be a non-null result 448 // down the list so the caller is going to have to check. 449 return result; 450 } 451 }; 452 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP