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 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_to_graph(Handle class_loader, bool anonymous); 87 static ClassLoaderData* add(Handle class_loader, bool anonymous); 88 public: 89 static ClassLoaderData* find_or_create(Handle class_loader); 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(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 print_on(outputStream * const out) PRODUCT_RETURN; 155 static void print() { print_on(tty); } 156 static void verify(); 157 158 // instance and array class counters 159 static inline size_t num_instance_classes(); 160 static inline size_t num_array_classes(); 161 static inline void inc_instance_classes(size_t count); 162 static inline void dec_instance_classes(size_t count); 163 static inline void inc_array_classes(size_t count); 164 static inline void dec_array_classes(size_t count); 165 166 #ifndef PRODUCT 167 static bool contains_loader_data(ClassLoaderData* loader_data); 168 #endif 169 }; 170 171 // ClassLoaderData class 172 173 class ClassLoaderData : public CHeapObj<mtClass> { 174 friend class VMStructs; 175 176 private: 177 class ChunkedHandleList { 178 struct Chunk : public CHeapObj<mtClass> { 179 static const size_t CAPACITY = 32; 180 181 oop _data[CAPACITY]; 182 volatile juint _size; 183 Chunk* _next; 184 185 Chunk(Chunk* c) : _next(c), _size(0) { } 186 }; 187 188 Chunk* volatile _head; 189 190 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size); 191 192 public: 193 ChunkedHandleList() : _head(NULL) {} 194 ~ChunkedHandleList(); 195 196 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock(). 197 // However, multiple threads can execute oops_do concurrently with add. 198 oop* add(oop o); 199 bool contains(oop p); 200 NOT_PRODUCT(bool owner_of(oop* p);) 201 void oops_do(OopClosure* f); 202 203 int count() const; 204 }; 205 206 friend class ClassLoaderDataGraph; 207 friend class ClassLoaderDataGraphKlassIteratorAtomic; 208 friend class ClassLoaderDataGraphKlassIteratorStatic; 209 friend class ClassLoaderDataGraphMetaspaceIterator; 210 friend class InstanceKlass; 211 friend class MetaDataFactory; 212 friend class Method; 213 214 static ClassLoaderData * _the_null_class_loader_data; 215 216 WeakHandle<vm_class_loader_data> _holder; // The oop that determines lifetime of this class loader 217 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with 218 // this ClassLoaderData 219 220 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the 221 // classes in the class loader are allocated. 222 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup. 223 bool _unloading; // true if this class loader goes away 224 bool _is_anonymous; // if this CLD is for an anonymous class 225 226 // Remembered sets support for the oops in the class loader data. 227 bool _modified_oops; // Card Table Equivalent (YC/CMS support) 228 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support) 229 230 s2 _keep_alive; // if this CLD is kept alive. 231 // Used for anonymous classes and the boot class 232 // loader. _keep_alive does not need to be volatile or 233 // atomic since there is one unique CLD per anonymous class. 234 235 volatile int _claimed; // true if claimed, for example during GC traces. 236 // To avoid applying oop closure more than once. 237 // Has to be an int because we cas it. 238 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which 239 // have the same life cycle of the corresponding ClassLoader. 240 241 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies 242 243 Klass* volatile _klasses; // The classes defined by the class loader. 244 PackageEntryTable* volatile _packages; // The packages defined by the class loader. 245 ModuleEntryTable* volatile _modules; // The modules defined by the class loader. 246 ModuleEntry* _unnamed_module; // This class loader's unnamed module. 247 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader 248 249 // These method IDs are created for the class loader and set to NULL when the 250 // class loader is unloaded. They are rarely freed, only for redefine classes 251 // and if they lose a data race in InstanceKlass. 252 JNIMethodBlock* _jmethod_ids; 253 254 // Metadata to be deallocated when it's safe at class unloading, when 255 // this class loader isn't unloaded itself. 256 GrowableArray<Metadata*>* _deallocate_list; 257 258 // Support for walking class loader data objects 259 ClassLoaderData* _next; /// Next loader_datas created 260 261 // JFR support 262 Klass* _class_loader_klass; 263 Symbol* _class_loader_name; 264 JFR_ONLY(DEFINE_TRACE_ID_FIELD;) 265 266 void set_next(ClassLoaderData* next) { _next = next; } 267 ClassLoaderData* next() const { return _next; } 268 269 ClassLoaderData(Handle h_class_loader, bool is_anonymous); 270 ~ClassLoaderData(); 271 272 // The CLD are not placed in the Heap, so the Card Table or 273 // the Mod Union Table can't be used to mark when CLD have modified oops. 274 // The CT and MUT bits saves this information for the whole class loader data. 275 void clear_modified_oops() { _modified_oops = false; } 276 public: 277 void record_modified_oops() { _modified_oops = true; } 278 bool has_modified_oops() { return _modified_oops; } 279 280 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; } 281 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; } 282 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; } 283 private: 284 285 void unload(); 286 bool keep_alive() const { return _keep_alive > 0; } 287 288 oop holder_phantom() const; 289 void classes_do(void f(Klass*)); 290 void loaded_classes_do(KlassClosure* klass_closure); 291 void classes_do(void f(InstanceKlass*)); 292 void methods_do(void f(Method*)); 293 void modules_do(void f(ModuleEntry*)); 294 void packages_do(void f(PackageEntry*)); 295 296 // Deallocate free list during class unloading. 297 void free_deallocate_list(); // for the classes that are not unloaded 298 void unload_deallocate_list(); // for the classes that are unloaded 299 300 // Allocate out of this class loader data 301 MetaWord* allocate(size_t size); 302 303 Dictionary* create_dictionary(); 304 305 void initialize_name_and_klass(Handle class_loader); 306 public: 307 // GC interface. 308 void clear_claimed() { _claimed = 0; } 309 bool claimed() const { return _claimed == 1; } 310 bool claim(); 311 312 bool is_alive() const; 313 314 // Accessors 315 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; } 316 317 static ClassLoaderData* the_null_class_loader_data() { 318 return _the_null_class_loader_data; 319 } 320 321 Mutex* metaspace_lock() const { return _metaspace_lock; } 322 323 bool is_anonymous() const { return _is_anonymous; } 324 325 static void init_null_class_loader_data(); 326 327 bool is_the_null_class_loader_data() const { 328 return this == _the_null_class_loader_data; 329 } 330 331 // Returns true if this class loader data is for the system class loader. 332 // (Note that the class loader data may be anonymous.) 333 bool is_system_class_loader_data() const; 334 335 // Returns true if this class loader data is for the platform class loader. 336 // (Note that the class loader data may be anonymous.) 337 bool is_platform_class_loader_data() const; 338 339 // Returns true if this class loader data is for the boot class loader. 340 // (Note that the class loader data may be anonymous.) 341 inline bool is_boot_class_loader_data() const; 342 343 bool is_builtin_class_loader_data() const; 344 bool is_permanent_class_loader_data() const; 345 346 // The Metaspace is created lazily so may be NULL. This 347 // method will allocate a Metaspace if needed. 348 ClassLoaderMetaspace* metaspace_non_null(); 349 350 inline oop class_loader() const; 351 352 // Returns true if this class loader data is for a loader going away. 353 bool is_unloading() const { 354 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded"); 355 return _unloading; 356 } 357 358 // Used to refcount an anonymous class's CLD in order to 359 // indicate their aliveness. 360 void inc_keep_alive(); 361 void dec_keep_alive(); 362 363 void initialize_holder(Handle holder); 364 365 inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); } 366 367 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false); 368 369 void classes_do(KlassClosure* klass_closure); 370 Klass* klasses() { return _klasses; } 371 372 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; } 373 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; } 374 375 void print() { print_on(tty); } 376 void print_on(outputStream* out) const PRODUCT_RETURN; 377 void print_value() { print_value_on(tty); } 378 void print_value_on(outputStream* out) const; 379 void verify(); 380 const char* loader_name() const; 381 382 OopHandle add_handle(Handle h); 383 void remove_handle(OopHandle h); 384 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field 385 void add_class(Klass* k, bool publicize = true); 386 void remove_class(Klass* k); 387 bool contains_klass(Klass* k); 388 void record_dependency(const Klass* to); 389 PackageEntryTable* packages() { return _packages; } 390 ModuleEntry* unnamed_module() { return _unnamed_module; } 391 ModuleEntryTable* modules(); 392 bool modules_defined() { return (_modules != NULL); } 393 394 // Loaded class dictionary 395 Dictionary* dictionary() const { return _dictionary; } 396 397 void add_to_deallocate_list(Metadata* m); 398 399 static ClassLoaderData* class_loader_data(oop loader); 400 static ClassLoaderData* class_loader_data_or_null(oop loader); 401 static ClassLoaderData* anonymous_class_loader_data(Handle loader); 402 403 // Returns Klass* of associated class loader, or NULL if associated loader is <bootstrap>. 404 // Also works if unloading. 405 Klass* class_loader_klass() const { return _class_loader_klass; } 406 407 // Returns Name of associated class loader. 408 // Returns NULL if associated class loader is <bootstrap> or if no name has been set for 409 // this loader. 410 // Also works if unloading. 411 Symbol* class_loader_name() const { return _class_loader_name; } 412 413 JFR_ONLY(DEFINE_TRACE_ID_METHODS;) 414 }; 415 416 // An iterator that distributes Klasses to parallel worker threads. 417 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj { 418 Klass* volatile _next_klass; 419 public: 420 ClassLoaderDataGraphKlassIteratorAtomic(); 421 Klass* next_klass(); 422 private: 423 static Klass* next_klass_in_cldg(Klass* klass); 424 }; 425 426 class ClassLoaderDataGraphMetaspaceIterator : public StackObj { 427 ClassLoaderData* _data; 428 public: 429 ClassLoaderDataGraphMetaspaceIterator(); 430 ~ClassLoaderDataGraphMetaspaceIterator(); 431 bool repeat() { return _data != NULL; } 432 ClassLoaderMetaspace* get_next() { 433 assert(_data != NULL, "Should not be NULL in call to the iterator"); 434 ClassLoaderMetaspace* result = _data->metaspace_or_null(); 435 _data = _data->next(); 436 // This result might be NULL for class loaders without metaspace 437 // yet. It would be nice to return only non-null results but 438 // there is no guarantee that there will be a non-null result 439 // down the list so the caller is going to have to check. 440 return result; 441 } 442 }; 443 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP