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, KlassClosure* klass_closure, bool must_claim); 91 static void keep_alive_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim); 92 static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, 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 bool has_metaspace_oom() { return _metaspace_oom; } 147 static void set_metaspace_oom(bool value) { _metaspace_oom = value; } 148 149 static void dump_on(outputStream * const out) PRODUCT_RETURN; 150 static void dump() { dump_on(tty); } 151 static void verify(); 152 static void print_creation(outputStream* out, Handle loader, ClassLoaderData* cld, TRAPS); 153 154 static bool unload_list_contains(const void* x); 155 #ifndef PRODUCT 156 static bool contains_loader_data(ClassLoaderData* loader_data); 157 #endif 158 159 #if INCLUDE_TRACE 160 private: 161 static Ticks _class_unload_time; 162 static void class_unload_event(Klass* const k); 163 #endif 164 }; 165 166 // ClassLoaderData class 167 168 class ClassLoaderData : public CHeapObj<mtClass> { 169 friend class VMStructs; 170 private: 171 class Dependencies VALUE_OBJ_CLASS_SPEC { 172 objArrayOop _list_head; 173 void locked_add(objArrayHandle last, 174 objArrayHandle new_dependency, 175 Thread* THREAD); 176 public: 177 Dependencies() : _list_head(NULL) {} 178 Dependencies(TRAPS) : _list_head(NULL) { 179 init(CHECK); 180 } 181 void add(Handle dependency, TRAPS); 182 void init(TRAPS); 183 void oops_do(OopClosure* f); 184 }; 185 186 class ChunkedHandleList VALUE_OBJ_CLASS_SPEC { 187 struct Chunk : public CHeapObj<mtClass> { 188 static const size_t CAPACITY = 32; 189 190 oop _data[CAPACITY]; 191 volatile juint _size; 192 Chunk* _next; 193 194 Chunk(Chunk* c) : _next(c), _size(0) { } 195 }; 196 197 Chunk* _head; 198 199 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size); 200 201 public: 202 ChunkedHandleList() : _head(NULL) {} 203 ~ChunkedHandleList(); 204 205 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock(). 206 // However, multiple threads can execute oops_do concurrently with add. 207 oop* add(oop o); 208 #ifdef ASSERT 209 bool contains(oop* p); 210 #endif 211 void oops_do(OopClosure* f); 212 }; 213 214 friend class ClassLoaderDataGraph; 215 friend class ClassLoaderDataGraphKlassIteratorAtomic; 216 friend class ClassLoaderDataGraphKlassIteratorStatic; 217 friend class ClassLoaderDataGraphMetaspaceIterator; 218 friend class MetaDataFactory; 219 friend class Method; 220 221 static ClassLoaderData * _the_null_class_loader_data; 222 223 oop _class_loader; // oop used to uniquely identify a class loader 224 // class loader or a canonical class path 225 Dependencies _dependencies; // holds dependencies from this class loader 226 // data to others. 227 228 Metaspace * volatile _metaspace; // Meta-space where meta-data defined by the 229 // classes in the class loader are allocated. 230 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup. 231 bool _unloading; // true if this class loader goes away 232 bool _is_anonymous; // if this CLD is for an anonymous class 233 s2 _keep_alive; // if this CLD is kept alive without a keep_alive_object(). 234 // Used for anonymous classes and the boot class 235 // loader. _keep_alive does not need to be volatile or 236 // atomic since there is one unique CLD per anonymous class. 237 volatile int _claimed; // true if claimed, for example during GC traces. 238 // To avoid applying oop closure more than once. 239 // Has to be an int because we cas it. 240 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which 241 // have the same life cycle of the corresponding ClassLoader. 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 // ReadOnly and ReadWrite metaspaces (static because only on the null 262 // class loader for now). 263 static Metaspace* _ro_metaspace; 264 static Metaspace* _rw_metaspace; 265 266 TRACE_DEFINE_TRACE_ID_FIELD; 267 268 void set_next(ClassLoaderData* next) { _next = next; } 269 ClassLoaderData* next() const { return _next; } 270 271 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies); 272 ~ClassLoaderData(); 273 274 // GC interface. 275 void clear_claimed() { _claimed = 0; } 276 bool claimed() const { return _claimed == 1; } 277 bool claim(); 278 279 void unload(); 280 bool keep_alive() const { return _keep_alive > 0; } 281 void classes_do(void f(Klass*)); 282 void loaded_classes_do(KlassClosure* klass_closure); 283 void classes_do(void f(InstanceKlass*)); 284 void methods_do(void f(Method*)); 285 void modules_do(void f(ModuleEntry*)); 286 void packages_do(void f(PackageEntry*)); 287 288 // Deallocate free list during class unloading. 289 void free_deallocate_list(); 290 291 // Allocate out of this class loader data 292 MetaWord* allocate(size_t size); 293 294 Dictionary* create_dictionary(); 295 public: 296 297 bool is_alive(BoolObjectClosure* is_alive_closure) const; 298 299 // Accessors 300 Metaspace* metaspace_or_null() const { return _metaspace; } 301 302 static ClassLoaderData* the_null_class_loader_data() { 303 return _the_null_class_loader_data; 304 } 305 306 Mutex* metaspace_lock() const { return _metaspace_lock; } 307 308 bool is_anonymous() const { return _is_anonymous; } 309 310 static void init_null_class_loader_data() { 311 assert(_the_null_class_loader_data == NULL, "cannot initialize twice"); 312 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice"); 313 314 // We explicitly initialize the Dependencies object at a later phase in the initialization 315 _the_null_class_loader_data = new ClassLoaderData(Handle(), false, Dependencies()); 316 ClassLoaderDataGraph::_head = _the_null_class_loader_data; 317 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be"); 318 } 319 320 bool is_the_null_class_loader_data() const { 321 return this == _the_null_class_loader_data; 322 } 323 bool is_system_class_loader_data() const; 324 bool is_platform_class_loader_data() const; 325 bool is_builtin_class_loader_data() const; 326 327 // The Metaspace is created lazily so may be NULL. This 328 // method will allocate a Metaspace if needed. 329 Metaspace* metaspace_non_null(); 330 331 oop class_loader() const { return _class_loader; } 332 333 // The object the GC is using to keep this ClassLoaderData alive. 334 oop keep_alive_object() const; 335 336 // Returns true if this class loader data is for a loader going away. 337 bool is_unloading() const { 338 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded"); 339 return _unloading; 340 } 341 342 // Used to refcount an anonymous class's CLD in order to 343 // indicate their aliveness without a keep_alive_object(). 344 void inc_keep_alive(); 345 void dec_keep_alive(); 346 347 inline unsigned int identity_hash() const { return (unsigned int)(((intptr_t)this) >> 3); } 348 349 // Used when tracing from klasses. 350 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim); 351 352 void classes_do(KlassClosure* klass_closure); 353 Klass* klasses() { return _klasses; } 354 355 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; } 356 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; } 357 358 void print() { print_on(tty); } 359 void print_on(outputStream* out) const; 360 void print_value() { print_value_on(tty); } 361 void print_value_on(outputStream* out) const; 362 void dump(outputStream * const out) PRODUCT_RETURN; 363 void verify(); 364 const char* loader_name(); 365 366 OopHandle add_handle(Handle h); 367 void remove_handle(OopHandle h); 368 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field 369 void add_class(Klass* k, bool publicize = true); 370 void remove_class(Klass* k); 371 bool contains_klass(Klass* k); 372 void record_dependency(const Klass* to, TRAPS); 373 void init_dependencies(TRAPS); 374 PackageEntryTable* packages() { return _packages; } 375 ModuleEntry* unnamed_module() { return _unnamed_module; } 376 ModuleEntryTable* modules(); 377 bool modules_defined() { return (_modules != NULL); } 378 379 // Loaded class dictionary 380 Dictionary* dictionary() const { return _dictionary; } 381 382 void add_to_deallocate_list(Metadata* m); 383 384 static ClassLoaderData* class_loader_data(oop loader); 385 static ClassLoaderData* class_loader_data_or_null(oop loader); 386 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS); 387 static void print_loader(ClassLoaderData *loader_data, outputStream *out); 388 389 TRACE_DEFINE_TRACE_ID_METHODS; 390 }; 391 392 // An iterator that distributes Klasses to parallel worker threads. 393 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj { 394 Klass* volatile _next_klass; 395 public: 396 ClassLoaderDataGraphKlassIteratorAtomic(); 397 Klass* next_klass(); 398 private: 399 static Klass* next_klass_in_cldg(Klass* klass); 400 }; 401 402 class ClassLoaderDataGraphMetaspaceIterator : public StackObj { 403 ClassLoaderData* _data; 404 public: 405 ClassLoaderDataGraphMetaspaceIterator(); 406 ~ClassLoaderDataGraphMetaspaceIterator(); 407 bool repeat() { return _data != NULL; } 408 Metaspace* get_next() { 409 assert(_data != NULL, "Should not be NULL in call to the iterator"); 410 Metaspace* result = _data->metaspace_or_null(); 411 _data = _data->next(); 412 // This result might be NULL for class loaders without metaspace 413 // yet. It would be nice to return only non-null results but 414 // there is no guarantee that there will be a non-null result 415 // down the list so the caller is going to have to check. 416 return result; 417 } 418 }; 419 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP