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 "runtime/handles.hpp" 33 #include "runtime/mutex.hpp" 34 #include "utilities/growableArray.hpp" 35 #include "utilities/macros.hpp" 36 #if INCLUDE_TRACE 37 #include "utilities/ticks.hpp" 38 #endif 39 40 // 41 // A class loader represents a linkset. Conceptually, a linkset identifies 42 // the complete transitive closure of resolved links that a dynamic linker can 43 // produce. 44 // 45 // A ClassLoaderData also encapsulates the allocation space, called a metaspace, 46 // used by the dynamic linker to allocate the runtime representation of all 47 // the types it defines. 48 // 49 // ClassLoaderData are stored in the runtime representation of classes and the 50 // system dictionary, are roots of garbage collection, and provides iterators 51 // for root tracing and other GC operations. 52 53 class ClassLoaderData; 54 class JNIMethodBlock; 55 class Metadebug; 56 57 // GC root for walking class loader data created 58 59 class ClassLoaderDataGraph : public AllStatic { 60 friend class ClassLoaderData; 61 friend class ClassLoaderDataGraphMetaspaceIterator; 62 friend class ClassLoaderDataGraphKlassIteratorAtomic; 63 friend class VMStructs; 64 private: 65 // All CLDs (except the null CLD) can be reached by walking _head->_next->... 66 static ClassLoaderData* _head; 67 static ClassLoaderData* _unloading; 68 // CMS support. 69 static ClassLoaderData* _saved_head; 70 static ClassLoaderData* _saved_unloading; 71 static bool _should_purge; 72 73 static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS); 74 static void post_class_unload_events(void); 75 static void clean_metaspaces(); 76 public: 77 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS); 78 static void purge(); 79 static void clear_claimed_marks(); 80 // oops do 81 static void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim); 82 static void keep_alive_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim); 83 static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim); 84 // cld do 85 static void cld_do(CLDClosure* cl); 86 static void roots_cld_do(CLDClosure* strong, CLDClosure* weak); 87 static void keep_alive_cld_do(CLDClosure* cl); 88 static void always_strong_cld_do(CLDClosure* cl); 89 // klass do 90 static void classes_do(KlassClosure* klass_closure); 91 static void classes_do(void f(Klass* const)); 92 static void loaded_classes_do(KlassClosure* klass_closure); 93 static void classes_unloading_do(void f(Klass* const)); 94 static bool do_unloading(BoolObjectClosure* is_alive, bool clean_alive); 95 96 // CMS support. 97 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); } 98 static GrowableArray<ClassLoaderData*>* new_clds(); 99 100 static void set_should_purge(bool b) { _should_purge = b; } 101 static void purge_if_needed() { 102 // Only purge the CLDG for CMS if concurrent sweep is complete. 103 if (_should_purge) { 104 purge(); 105 // reset for next time. 106 set_should_purge(false); 107 } 108 } 109 110 static void free_deallocate_lists(); 111 112 static void dump_on(outputStream * const out) PRODUCT_RETURN; 113 static void dump() { dump_on(tty); } 114 static void verify(); 115 116 static bool unload_list_contains(const void* x); 117 #ifndef PRODUCT 118 static bool contains_loader_data(ClassLoaderData* loader_data); 119 #endif 120 121 #if INCLUDE_TRACE 122 private: 123 static Ticks _class_unload_time; 124 static void class_unload_event(Klass* const k); 125 #endif 126 }; 127 128 // ClassLoaderData class 129 130 class ClassLoaderData : public CHeapObj<mtClass> { 131 friend class VMStructs; 132 private: 133 class Dependencies VALUE_OBJ_CLASS_SPEC { 134 objArrayOop _list_head; 135 void locked_add(objArrayHandle last, 136 objArrayHandle new_dependency, 137 Thread* THREAD); 138 public: 139 Dependencies() : _list_head(NULL) {} 140 Dependencies(TRAPS) : _list_head(NULL) { 141 init(CHECK); 142 } 143 void add(Handle dependency, TRAPS); 144 void init(TRAPS); 145 void oops_do(OopClosure* f); 146 }; 147 148 class ChunkedHandleList VALUE_OBJ_CLASS_SPEC { 149 struct Chunk : public CHeapObj<mtClass> { 150 static const size_t CAPACITY = 32; 151 152 oop _data[CAPACITY]; 153 volatile juint _size; 154 Chunk* _next; 155 156 Chunk(Chunk* c) : _next(c), _size(0) { } 157 }; 158 159 Chunk* _head; 160 161 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size); 162 163 public: 164 ChunkedHandleList() : _head(NULL) {} 165 ~ChunkedHandleList(); 166 167 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock(). 168 // However, multiple threads can execute oops_do concurrently with add. 169 oop* add(oop o); 170 void oops_do(OopClosure* f); 171 }; 172 173 friend class ClassLoaderDataGraph; 174 friend class ClassLoaderDataGraphKlassIteratorAtomic; 175 friend class ClassLoaderDataGraphMetaspaceIterator; 176 friend class MetaDataFactory; 177 friend class Method; 178 179 static ClassLoaderData * _the_null_class_loader_data; 180 181 oop _class_loader; // oop used to uniquely identify a class loader 182 // class loader or a canonical class path 183 Dependencies _dependencies; // holds dependencies from this class loader 184 // data to others. 185 186 Metaspace * _metaspace; // Meta-space where meta-data defined by the 187 // classes in the class loader are allocated. 188 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup. 189 bool _unloading; // true if this class loader goes away 190 bool _keep_alive; // if this CLD is kept alive without a keep_alive_object(). 191 bool _is_anonymous; // if this CLD is for an anonymous class 192 volatile int _claimed; // true if claimed, for example during GC traces. 193 // To avoid applying oop closure more than once. 194 // Has to be an int because we cas it. 195 Klass* _klasses; // The classes defined by the class loader. 196 197 ChunkedHandleList _handles; // Handles to constant pool arrays, etc, which 198 // have the same life cycle of the corresponding ClassLoader. 199 200 // These method IDs are created for the class loader and set to NULL when the 201 // class loader is unloaded. They are rarely freed, only for redefine classes 202 // and if they lose a data race in InstanceKlass. 203 JNIMethodBlock* _jmethod_ids; 204 205 // Metadata to be deallocated when it's safe at class unloading, when 206 // this class loader isn't unloaded itself. 207 GrowableArray<Metadata*>* _deallocate_list; 208 209 // Support for walking class loader data objects 210 ClassLoaderData* _next; /// Next loader_datas created 211 212 // ReadOnly and ReadWrite metaspaces (static because only on the null 213 // class loader for now). 214 static Metaspace* _ro_metaspace; 215 static Metaspace* _rw_metaspace; 216 217 void set_next(ClassLoaderData* next) { _next = next; } 218 ClassLoaderData* next() const { return _next; } 219 220 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies); 221 ~ClassLoaderData(); 222 223 void set_metaspace(Metaspace* m) { _metaspace = m; } 224 225 Mutex* metaspace_lock() const { return _metaspace_lock; } 226 227 // GC interface. 228 void clear_claimed() { _claimed = 0; } 229 bool claimed() const { return _claimed == 1; } 230 bool claim(); 231 232 void unload(); 233 bool keep_alive() const { return _keep_alive; } 234 void classes_do(void f(Klass*)); 235 void loaded_classes_do(KlassClosure* klass_closure); 236 void classes_do(void f(InstanceKlass*)); 237 238 // Deallocate free list during class unloading. 239 void free_deallocate_list(); 240 241 // Allocate out of this class loader data 242 MetaWord* allocate(size_t size); 243 244 public: 245 246 bool is_alive(BoolObjectClosure* is_alive_closure) const; 247 248 // Accessors 249 Metaspace* metaspace_or_null() const { return _metaspace; } 250 251 static ClassLoaderData* the_null_class_loader_data() { 252 return _the_null_class_loader_data; 253 } 254 255 bool is_anonymous() const { return _is_anonymous; } 256 257 static void init_null_class_loader_data() { 258 assert(_the_null_class_loader_data == NULL, "cannot initialize twice"); 259 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice"); 260 261 // We explicitly initialize the Dependencies object at a later phase in the initialization 262 _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies()); 263 ClassLoaderDataGraph::_head = _the_null_class_loader_data; 264 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be"); 265 if (DumpSharedSpaces) { 266 _the_null_class_loader_data->initialize_shared_metaspaces(); 267 } 268 } 269 270 bool is_the_null_class_loader_data() const { 271 return this == _the_null_class_loader_data; 272 } 273 bool is_ext_class_loader_data() const; 274 275 // The Metaspace is created lazily so may be NULL. This 276 // method will allocate a Metaspace if needed. 277 Metaspace* metaspace_non_null(); 278 279 oop class_loader() const { return _class_loader; } 280 281 // The object the GC is using to keep this ClassLoaderData alive. 282 oop keep_alive_object() const; 283 284 // Returns true if this class loader data is for a loader going away. 285 bool is_unloading() const { 286 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded"); 287 return _unloading; 288 } 289 290 // Used to make sure that this CLD is not unloaded. 291 void set_keep_alive(bool value) { _keep_alive = value; } 292 293 unsigned int identity_hash() { 294 return _class_loader == NULL ? 0 : _class_loader->identity_hash(); 295 } 296 297 // Used when tracing from klasses. 298 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim); 299 300 void classes_do(KlassClosure* klass_closure); 301 302 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; } 303 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; } 304 305 void print_value() { print_value_on(tty); } 306 void print_value_on(outputStream* out) const; 307 void dump(outputStream * const out) PRODUCT_RETURN; 308 void verify(); 309 const char* loader_name(); 310 311 jobject add_handle(Handle h); 312 void add_class(Klass* k); 313 void remove_class(Klass* k); 314 bool contains_klass(Klass* k); 315 void record_dependency(Klass* to, TRAPS); 316 void init_dependencies(TRAPS); 317 318 void add_to_deallocate_list(Metadata* m); 319 320 static ClassLoaderData* class_loader_data(oop loader); 321 static ClassLoaderData* class_loader_data_or_null(oop loader); 322 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS); 323 static void print_loader(ClassLoaderData *loader_data, outputStream *out); 324 325 // CDS support 326 Metaspace* ro_metaspace(); 327 Metaspace* rw_metaspace(); 328 void initialize_shared_metaspaces(); 329 }; 330 331 // An iterator that distributes Klasses to parallel worker threads. 332 class ClassLoaderDataGraphKlassIteratorAtomic : public StackObj { 333 Klass* volatile _next_klass; 334 public: 335 ClassLoaderDataGraphKlassIteratorAtomic(); 336 Klass* next_klass(); 337 private: 338 static Klass* next_klass_in_cldg(Klass* klass); 339 }; 340 341 class ClassLoaderDataGraphMetaspaceIterator : public StackObj { 342 ClassLoaderData* _data; 343 public: 344 ClassLoaderDataGraphMetaspaceIterator(); 345 ~ClassLoaderDataGraphMetaspaceIterator(); 346 bool repeat() { return _data != NULL; } 347 Metaspace* get_next() { 348 assert(_data != NULL, "Should not be NULL in call to the iterator"); 349 Metaspace* result = _data->metaspace_or_null(); 350 _data = _data->next(); 351 // This result might be NULL for class loaders without metaspace 352 // yet. It would be nice to return only non-null results but 353 // there is no guarantee that there will be a non-null result 354 // down the list so the caller is going to have to check. 355 return result; 356 } 357 }; 358 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP