1 /* 2 * Copyright (c) 2012, 2013, 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/mutex.hpp" 33 #include "utilities/growableArray.hpp" 34 #if INCLUDE_TRACE 35 # include "utilities/ticks.hpp" 36 #endif 37 38 // 39 // A class loader represents a linkset. Conceptually, a linkset identifies 40 // the complete transitive closure of resolved links that a dynamic linker can 41 // produce. 42 // 43 // A ClassLoaderData also encapsulates the allocation space, called a metaspace, 44 // used by the dynamic linker to allocate the runtime representation of all 45 // the types it defines. 46 // 47 // ClassLoaderData are stored in the runtime representation of classes and the 48 // system dictionary, are roots of garbage collection, and provides iterators 49 // for root tracing and other GC operations. 50 51 class ClassLoaderData; 52 class JNIMethodBlock; 53 class JNIHandleBlock; 54 class Metadebug; 55 56 // GC root for walking class loader data created 57 58 class ClassLoaderDataGraph : public AllStatic { 59 friend class ClassLoaderData; 60 friend class ClassLoaderDataGraphMetaspaceIterator; 61 friend class VMStructs; 62 private: 63 // All CLDs (except the null CLD) can be reached by walking _head->_next->... 64 static ClassLoaderData* _head; 65 static ClassLoaderData* _unloading; 66 // CMS support. 67 static ClassLoaderData* _saved_head; 68 69 static ClassLoaderData* add(Handle class_loader, bool anonymous, TRAPS); 70 static void post_class_unload_events(void); 71 public: 72 static ClassLoaderData* find_or_create(Handle class_loader, TRAPS); 73 static void purge(); 74 static void clear_claimed_marks(); 75 static void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim); 76 static void always_strong_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim); 77 static void keep_alive_oops_do(OopClosure* blk, KlassClosure* klass_closure, bool must_claim); 78 static void classes_do(KlassClosure* klass_closure); 79 static void classes_do(void f(Klass* const)); 80 static void loaded_classes_do(KlassClosure* klass_closure); 81 static void classes_unloading_do(void f(Klass* const)); 82 static bool do_unloading(BoolObjectClosure* is_alive); 83 84 // CMS support. 85 static void remember_new_clds(bool remember) { _saved_head = (remember ? _head : NULL); } 86 static GrowableArray<ClassLoaderData*>* new_clds(); 87 88 static void dump_on(outputStream * const out) PRODUCT_RETURN; 89 static void dump() { dump_on(tty); } 90 static void verify(); 91 92 #ifndef PRODUCT 93 // expensive test for pointer in metaspace for debugging 94 static bool contains(address x); 95 static bool contains_loader_data(ClassLoaderData* loader_data); 96 #endif 97 98 #if INCLUDE_TRACE 99 private: 100 static Ticks _class_unload_time; 101 static void class_unload_event(Klass* const k); 102 #endif 103 }; 104 105 // ClassLoaderData class 106 107 class ClassLoaderData : public CHeapObj<mtClass> { 108 friend class VMStructs; 109 private: 110 class Dependencies VALUE_OBJ_CLASS_SPEC { 111 objArrayOop _list_head; 112 void locked_add(objArrayHandle last, 113 objArrayHandle new_dependency, 114 Thread* THREAD); 115 public: 116 Dependencies() : _list_head(NULL) {} 117 Dependencies(TRAPS) : _list_head(NULL) { 118 init(CHECK); 119 } 120 void add(Handle dependency, TRAPS); 121 void init(TRAPS); 122 void oops_do(OopClosure* f); 123 }; 124 125 friend class ClassLoaderDataGraph; 126 friend class ClassLoaderDataGraphMetaspaceIterator; 127 friend class MetaDataFactory; 128 friend class Method; 129 130 static ClassLoaderData * _the_null_class_loader_data; 131 132 oop _class_loader; // oop used to uniquely identify a class loader 133 // class loader or a canonical class path 134 Dependencies _dependencies; // holds dependencies from this class loader 135 // data to others. 136 137 Metaspace * _metaspace; // Meta-space where meta-data defined by the 138 // classes in the class loader are allocated. 139 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup. 140 bool _unloading; // true if this class loader goes away 141 bool _keep_alive; // if this CLD can be unloaded for anonymous loaders 142 bool _is_anonymous; // if this CLD is for an anonymous class 143 volatile int _claimed; // true if claimed, for example during GC traces. 144 // To avoid applying oop closure more than once. 145 // Has to be an int because we cas it. 146 Klass* _klasses; // The classes defined by the class loader. 147 148 JNIHandleBlock* _handles; // Handles to constant pool arrays 149 150 // These method IDs are created for the class loader and set to NULL when the 151 // class loader is unloaded. They are rarely freed, only for redefine classes 152 // and if they lose a data race in InstanceKlass. 153 JNIMethodBlock* _jmethod_ids; 154 155 // Metadata to be deallocated when it's safe at class unloading, when 156 // this class loader isn't unloaded itself. 157 GrowableArray<Metadata*>* _deallocate_list; 158 159 // Support for walking class loader data objects 160 ClassLoaderData* _next; /// Next loader_datas created 161 162 // ReadOnly and ReadWrite metaspaces (static because only on the null 163 // class loader for now). 164 static Metaspace* _ro_metaspace; 165 static Metaspace* _rw_metaspace; 166 167 void set_next(ClassLoaderData* next) { _next = next; } 168 ClassLoaderData* next() const { return _next; } 169 170 ClassLoaderData(Handle h_class_loader, bool is_anonymous, Dependencies dependencies); 171 ~ClassLoaderData(); 172 173 void set_metaspace(Metaspace* m) { _metaspace = m; } 174 175 JNIHandleBlock* handles() const; 176 void set_handles(JNIHandleBlock* handles); 177 178 Mutex* metaspace_lock() const { return _metaspace_lock; } 179 180 // GC interface. 181 void clear_claimed() { _claimed = 0; } 182 bool claimed() const { return _claimed == 1; } 183 bool claim(); 184 185 void unload(); 186 bool keep_alive() const { return _keep_alive; } 187 bool is_alive(BoolObjectClosure* is_alive_closure) const; 188 void classes_do(void f(Klass*)); 189 void loaded_classes_do(KlassClosure* klass_closure); 190 void classes_do(void f(InstanceKlass*)); 191 192 // Deallocate free list during class unloading. 193 void free_deallocate_list(); 194 195 // Allocate out of this class loader data 196 MetaWord* allocate(size_t size); 197 198 public: 199 // Accessors 200 Metaspace* metaspace_or_null() const { return _metaspace; } 201 202 static ClassLoaderData* the_null_class_loader_data() { 203 return _the_null_class_loader_data; 204 } 205 206 bool is_anonymous() const { return _is_anonymous; } 207 208 static void init_null_class_loader_data() { 209 assert(_the_null_class_loader_data == NULL, "cannot initialize twice"); 210 assert(ClassLoaderDataGraph::_head == NULL, "cannot initialize twice"); 211 212 // We explicitly initialize the Dependencies object at a later phase in the initialization 213 _the_null_class_loader_data = new ClassLoaderData((oop)NULL, false, Dependencies()); 214 ClassLoaderDataGraph::_head = _the_null_class_loader_data; 215 assert(_the_null_class_loader_data->is_the_null_class_loader_data(), "Must be"); 216 if (DumpSharedSpaces) { 217 _the_null_class_loader_data->initialize_shared_metaspaces(); 218 } 219 } 220 221 bool is_the_null_class_loader_data() const { 222 return this == _the_null_class_loader_data; 223 } 224 bool is_ext_class_loader_data() const; 225 226 // The Metaspace is created lazily so may be NULL. This 227 // method will allocate a Metaspace if needed. 228 Metaspace* metaspace_non_null(); 229 230 oop class_loader() const { return _class_loader; } 231 232 // Returns true if this class loader data is for a loader going away. 233 bool is_unloading() const { 234 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded"); 235 return _unloading; 236 } 237 // Anonymous class loader data doesn't have anything to keep them from 238 // being unloaded during parsing the anonymous class. 239 void set_keep_alive(bool value) { _keep_alive = value; } 240 241 unsigned int identity_hash() { 242 return _class_loader == NULL ? 0 : _class_loader->identity_hash(); 243 } 244 245 // Used when tracing from klasses. 246 void oops_do(OopClosure* f, KlassClosure* klass_closure, bool must_claim); 247 248 void classes_do(KlassClosure* klass_closure); 249 250 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; } 251 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; } 252 253 void print_value() { print_value_on(tty); } 254 void print_value_on(outputStream* out) const; 255 void dump(outputStream * const out) PRODUCT_RETURN; 256 void verify(); 257 const char* loader_name(); 258 259 jobject add_handle(Handle h); 260 void add_class(Klass* k); 261 void remove_class(Klass* k); 262 void record_dependency(Klass* to, TRAPS); 263 void init_dependencies(TRAPS); 264 265 void add_to_deallocate_list(Metadata* m); 266 267 static ClassLoaderData* class_loader_data(oop loader); 268 static ClassLoaderData* class_loader_data_or_null(oop loader); 269 static ClassLoaderData* anonymous_class_loader_data(oop loader, TRAPS); 270 static void print_loader(ClassLoaderData *loader_data, outputStream *out); 271 272 // CDS support 273 Metaspace* ro_metaspace(); 274 Metaspace* rw_metaspace(); 275 void initialize_shared_metaspaces(); 276 }; 277 278 class ClassLoaderDataGraphMetaspaceIterator : public StackObj { 279 ClassLoaderData* _data; 280 public: 281 ClassLoaderDataGraphMetaspaceIterator(); 282 ~ClassLoaderDataGraphMetaspaceIterator(); 283 bool repeat() { return _data != NULL; } 284 Metaspace* get_next() { 285 assert(_data != NULL, "Should not be NULL in call to the iterator"); 286 Metaspace* result = _data->metaspace_or_null(); 287 _data = _data->next(); 288 // This result might be NULL for class loaders without metaspace 289 // yet. It would be nice to return only non-null results but 290 // there is no guarantee that there will be a non-null result 291 // down the list so the caller is going to have to check. 292 return result; 293 } 294 }; 295 #endif // SHARE_VM_CLASSFILE_CLASSLOADERDATA_HPP