1 /* 2 * Copyright (c) 2012, 2017, 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 ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS); 84 static void post_class_unload_events(); 85 public: 86 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS); 87 static void purge(); 88 static void clear_claimed_marks(); 89 // oops do 90 static void oops_do(OopClosure* f, bool must_claim); 91 static void keep_alive_oops_do(OopClosure* blk, bool must_claim); 92 static void always_strong_oops_do(OopClosure* blk, bool must_claim); 93 // cld do 94 static void cld_do(CLDClosure* cl); 95 static void cld_unloading_do(CLDClosure* cl); 96 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak); 97 static void keep_alive_cld_do(CLDClosure* cl); 98 static void always_strong_cld_do(CLDClosure* cl); 99 // klass do 100 // Walking classes through the ClassLoaderDataGraph include array classes. It also includes 101 // classes that are allocated but not loaded, classes that have errors, and scratch classes 102 // for redefinition. These classes are removed during the next class unloading. 103 // Walking the ClassLoaderDataGraph also includes anonymous classes. 104 static void classes_do(KlassClosure* klass_closure); 105 static void classes_do(void f(Klass* const)); 106 static void methods_do(void f(Method*)); 107 static void modules_do(void f(ModuleEntry*)); 108 static void modules_unloading_do(void f(ModuleEntry*)); 109 static void packages_do(void f(PackageEntry*)); 110 static void packages_unloading_do(void f(PackageEntry*)); 111 static void loaded_classes_do(KlassClosure* klass_closure); 112 static void classes_unloading_do(void f(Klass* const)); 113 static bool do_unloading(BoolObjectClosure* is_alive, bool clean_previous_versions); 114 115 // dictionary do 116 // Iterate over all klasses in dictionary, but 117 // just the classes from defining class loaders. 118 static void dictionary_classes_do(void f(InstanceKlass*)); 119 // Added for initialize_itable_for_klass to handle exceptions. 120 static void dictionary_classes_do(void f(InstanceKlass*, TRAPS), TRAPS); 121 122 // Iterate all classes and their class loaders, including initiating class loaders. 123 static void dictionary_all_entries_do(void f(InstanceKlass*, ClassLoaderData*)); 124 125 // VM_CounterDecay iteration support 126 static InstanceKlass* try_get_next_class(); 127 128 static void verify_dictionary(); 129 static void print_dictionary(outputStream* st); 130 static void print_dictionary_statistics(outputStream* st); 131 132 // CMS support. 133 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); } 134 static GrowableArray<ClassLoaderData*>* new_clds(); 135 136 static void set_should_purge(bool b) { _should_purge = b; } 137 static void purge_if_needed() { 138 // Only purge the CLDG for CMS if concurrent sweep is complete. 139 if (_should_purge) { 140 purge(); 141 // reset for next time. 142 set_should_purge(false); 143 } 144 } 145 146 static int resize_if_needed(); 147 148 static bool has_metaspace_oom() { return _metaspace_oom; } 149 static void set_metaspace_oom(bool value) { _metaspace_oom = value; } 150 151 static void dump_on(outputStream * const out) PRODUCT_RETURN; 152 static void dump() { dump_on(tty); } 153 static void verify(); 154 static void print_creation(outputStream* out, Handle loader, ClassLoaderData* cld, TRAPS); 155 156 static bool unload_list_contains(const void* x); 157 #ifndef PRODUCT 158 static bool contains_loader_data(ClassLoaderData* loader_data); 159 #endif 160 161 #if INCLUDE_TRACE 162 private: 163 static Ticks _class_unload_time; 164 static void class_unload_event(Klass* const k); 165 #endif 166 }; 167 168 // ClassLoaderData class 169 170 class ClassLoaderData : public CHeapObj<mtClass> { 171 friend class VMStructs; 172 private: 173 class Dependencies VALUE_OBJ_CLASS_SPEC { 174 objArrayOop _list_head; 175 void locked_add(objArrayHandle last, 176 objArrayHandle new_dependency, 177 Thread* THREAD); 178 public: 179 Dependencies() : _list_head(NULL) {} 180 Dependencies(TRAPS) : _list_head(NULL) { 181 init(CHECK); 182 } 183 void add(Handle dependency, TRAPS); 184 void init(TRAPS); 185 void oops_do(OopClosure* f); 186 }; 187 188 class ChunkedHandleList VALUE_OBJ_CLASS_SPEC { 189 struct Chunk : public CHeapObj<mtClass> { 190 static const size_t CAPACITY = 32; 191 192 oop _data[CAPACITY]; 193 volatile juint _size; 194 Chunk* _next; 195 196 Chunk(Chunk* c) : _next(c), _size(0) { } 197 }; 198 199 Chunk* volatile _head; 200 201 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size); 202 203 public: 204 ChunkedHandleList() : _head(NULL) {} 205 ~ChunkedHandleList(); 206 207 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock(). 208 // However, multiple threads can execute oops_do concurrently with add. 209 oop* add(oop o); 210 #ifdef ASSERT 211 bool contains(oop* p); 212 #endif 213 void oops_do(OopClosure* f); 214 }; 215 216 friend class ClassLoaderDataGraph; 217 friend class ClassLoaderDataGraphKlassIteratorAtomic; 218 friend class ClassLoaderDataGraphKlassIteratorStatic; 219 friend class ClassLoaderDataGraphMetaspaceIterator; 220 friend class MetaDataFactory; 221 friend class Method; 222 223 static ClassLoaderData * _the_null_class_loader_data; 224 225 oop _class_loader; // oop used to uniquely identify a class loader 226 // class loader or a canonical class path 227 Dependencies _dependencies; // holds dependencies from this class loader 228 // data to others. 229 230 Metaspace * volatile _metaspace; // Meta-space where meta-data defined by the 231 // classes in the class loader are allocated. 232 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup. 233 bool _unloading; // true if this class loader goes away 234 bool _is_anonymous; // if this CLD is for an anonymous class 235 236 // Remembered sets support for the oops in the class loader data. 237 bool _modified_oops; // Card Table Equivalent (YC/CMS support) 238 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support) 239 240 s2 _keep_alive; // if this CLD is kept alive without a keep_alive_object(). 241 // Used for anonymous classes and the boot class 242 // loader. _keep_alive does not need to be volatile or 243 // atomic since there is one unique CLD per anonymous class. 244 245 volatile int _claimed; // true if claimed, for example during GC traces. 246 // To avoid applying oop closure more than once. 247 // Has to be an int because we cas it. 248 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which 249 // have the same life cycle of the corresponding ClassLoader. 250 251 Klass* volatile _klasses; // The classes defined by the class loader. 252 PackageEntryTable* volatile _packages; // The packages defined by the class loader. 253 ModuleEntryTable* volatile _modules; // The modules defined by the class loader. 254 ModuleEntry* _unnamed_module; // This class loader's unnamed module. 255 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader 256 257 // These method IDs are created for the class loader and set to NULL when the 258 // class loader is unloaded. They are rarely freed, only for redefine classes 259 // and if they lose a data race in InstanceKlass. 260 JNIMethodBlock* _jmethod_ids; 261 262 // Metadata to be deallocated when it's safe at class unloading, when 263 // this class loader isn't unloaded itself. 264 GrowableArray<Metadata*>* _deallocate_list; 265 266 // Support for walking class loader data objects 267 ClassLoaderData* _next; /// Next loader_datas created 268 269 // ReadOnly and ReadWrite metaspaces (static because only on the null 270 // class loader for now). 271 static Metaspace* _ro_metaspace; 272 static Metaspace* _rw_metaspace; 273 274 TRACE_DEFINE_TRACE_ID_FIELD; 275 276 void set_next(ClassLoaderData* next) { _next = next; } 277 ClassLoaderData* next() const { return _next; } 278 279 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies); 280 ~ClassLoaderData(); 281 282 // GC interface. 283 void clear_claimed() { _claimed = 0; } 284 bool claimed() const { return _claimed == 1; } 285 bool claim(); 286 287 // The CLD are not placed in the Heap, so the Card Table or 288 // the Mod Union Table can't be used to mark when CLD have modified oops. 289 // The CT and MUT bits saves this information for the whole class loader data. 290 void clear_modified_oops() { _modified_oops = false; } 291 public: 292 void record_modified_oops() { _modified_oops = true; } 293 bool has_modified_oops() { return _modified_oops; } 294 295 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; } 296 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; } 297 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; } 298 private: 299 300 void unload(); 301 bool keep_alive() const { return _keep_alive > 0; } 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 unload_deallocate_list(); // 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 public: 318 319 bool is_alive(BoolObjectClosure* is_alive_closure) const; 320 321 // Accessors 322 Metaspace* 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 assert(_the_null_class_loader_data == NULL, "cannot initialize twice"); 334 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice"); 335 336 // We explicitly initialize the Dependencies object at a later phase in the initialization 337 _the_null_class_loader_data = new ClassLoaderData(Handle(), false, Dependencies()); 338 ClassLoaderDataGraph::_head = _the_null_class_loader_data; 339 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be"); 340 } 341 342 bool is_the_null_class_loader_data() const { 343 return this == _the_null_class_loader_data; 344 } 345 bool is_system_class_loader_data() const; 346 bool is_platform_class_loader_data() const; 347 bool is_builtin_class_loader_data() const; 348 349 // The Metaspace is created lazily so may be NULL. This 350 // method will allocate a Metaspace if needed. 351 Metaspace* metaspace_non_null(); 352 353 oop class_loader() const { return _class_loader; } 354 355 // The object the GC is using to keep this ClassLoaderData alive. 356 oop keep_alive_object() const; 357 358 // Returns true if this class loader data is for a loader going away. 359 bool is_unloading() const { 360 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded"); 361 return _unloading; 362 } 363 364 // Used to refcount an anonymous class's CLD in order to 365 // indicate their aliveness without a keep_alive_object(). 366 void inc_keep_alive(); 367 void dec_keep_alive(); 368 369 inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); } 370 371 void oops_do(OopClosure* f, bool must_claim, bool clear_modified_oops = false); 372 373 void classes_do(KlassClosure* klass_closure); 374 Klass* klasses() { return _klasses; } 375 376 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; } 377 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; } 378 379 void print() { print_on(tty); } 380 void print_on(outputStream* out) const; 381 void print_value() { print_value_on(tty); } 382 void print_value_on(outputStream* out) const; 383 void dump(outputStream * const out) PRODUCT_RETURN; 384 void verify(); 385 const char* loader_name(); 386 387 OopHandle add_handle(Handle h); 388 void remove_handle(OopHandle h); 389 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field 390 void add_class(Klass* k, bool publicize = true); 391 void remove_class(Klass* k); 392 bool contains_klass(Klass* k); 393 void record_dependency(const Klass* to, TRAPS); 394 void init_dependencies(TRAPS); 395 PackageEntryTable* packages() { return _packages; } 396 ModuleEntry* unnamed_module() { return _unnamed_module; } 397 ModuleEntryTable* modules(); 398 bool modules_defined() { return (_modules != NULL); } 399 400 // Loaded class dictionary 401 Dictionary* dictionary() const { return _dictionary; } 402 403 void add_to_deallocate_list(Metadata* m); 404 405 static ClassLoaderData* class_loader_data(oop loader); 406 static ClassLoaderData* class_loader_data_or_null(oop loader); 407 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS); 408 static void print_loader(ClassLoaderData *loader_data, outputStream *out); 409 410 TRACE_DEFINE_TRACE_ID_METHODS; 411 }; 412 413 // An iterator that distributes Klasses to parallel worker threads. 414 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj { 415 Klass* volatile _next_klass; 416 public: 417 ClassLoaderDataGraphKlassIteratorAtomic(); 418 Klass* next_klass(); 419 private: 420 static Klass* next_klass_in_cldg(Klass* klass); 421 }; 422 423 class ClassLoaderDataGraphMetaspaceIterator : public StackObj { 424 ClassLoaderData* _data; 425 public: 426 ClassLoaderDataGraphMetaspaceIterator(); 427 ~ClassLoaderDataGraphMetaspaceIterator(); 428 bool repeat() { return _data != NULL; } 429 Metaspace* get_next() { 430 assert(_data != NULL, "Should not be NULL in call to the iterator"); 431 Metaspace* result = _data->metaspace_or_null(); 432 _data = _data->next(); 433 // This result might be NULL for class loaders without metaspace 434 // yet. It would be nice to return only non-null results but 435 // there is no guarantee that there will be a non-null result 436 // down the list so the caller is going to have to check. 437 return result; 438 } 439 }; 440 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP