1 /* 2 * Copyright (c) 2012, 2020, 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_CLASSFILE_CLASSLOADERDATA_HPP 26 #define SHARE_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/atomic.hpp" 34 #include "runtime/mutex.hpp" 35 #include "utilities/growableArray.hpp" 36 #include "utilities/macros.hpp" 37 #if INCLUDE_JFR 38 #include "jfr/support/jfrTraceIdExtension.hpp" 39 #endif 40 41 // external name (synthetic) for the primordial "bootstrap" class loader instance 42 #define BOOTSTRAP_LOADER_NAME "bootstrap" 43 #define BOOTSTRAP_LOADER_NAME_LEN 9 44 45 // 46 // A class loader represents a linkset. Conceptually, a linkset identifies 47 // the complete transitive closure of resolved links that a dynamic linker can 48 // produce. 49 // 50 // A ClassLoaderData also encapsulates the allocation space, called a metaspace, 51 // used by the dynamic linker to allocate the runtime representation of all 52 // the types it defines. 53 // 54 // ClassLoaderData are stored in the runtime representation of classes, 55 // and provides iterators for root tracing and other GC operations. 56 57 class ClassLoaderDataGraph; 58 class JNIMethodBlock; 59 class ModuleEntry; 60 class PackageEntry; 61 class ModuleEntryTable; 62 class PackageEntryTable; 63 class DictionaryEntry; 64 class Dictionary; 65 66 // ClassLoaderData class 67 68 class ClassLoaderData : public CHeapObj<mtClass> { 69 friend class VMStructs; 70 71 private: 72 class ChunkedHandleList { 73 struct Chunk : public CHeapObj<mtClass> { 74 static const size_t CAPACITY = 32; 75 76 oop _data[CAPACITY]; 77 volatile juint _size; 78 Chunk* _next; 79 80 Chunk(Chunk* c) : _size(0), _next(c) { } 81 }; 82 83 Chunk* volatile _head; 84 85 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size); 86 87 public: 88 ChunkedHandleList() : _head(NULL) {} 89 ~ChunkedHandleList(); 90 91 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock(). 92 // However, multiple threads can execute oops_do concurrently with add. 93 oop* add(oop o); 94 bool contains(oop p); 95 NOT_PRODUCT(bool owner_of(oop* p);) 96 void oops_do(OopClosure* f); 97 98 int count() const; 99 }; 100 101 friend class ClassLoaderDataGraph; 102 friend class ClassLoaderDataGraphIterator; 103 friend class ClassLoaderDataGraphKlassIteratorAtomic; 104 friend class ClassLoaderDataGraphKlassIteratorStatic; 105 friend class ClassLoaderDataGraphMetaspaceIterator; 106 friend class Klass; 107 friend class MetaDataFactory; 108 friend class Method; 109 110 static ClassLoaderData * _the_null_class_loader_data; 111 112 WeakHandle<vm_class_loader_data> _holder; // The oop that determines lifetime of this class loader 113 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with 114 // this ClassLoaderData 115 116 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the 117 // classes in the class loader are allocated. 118 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup. 119 bool _unloading; // true if this class loader goes away 120 bool _has_class_mirror_holder; // If true, CLD is dedicated to one class and that class determines 121 // the CLDs lifecycle. For example, a non-strong hidden class or an 122 // unsafe anonymous class. Arrays of these classes are also assigned 123 // to these class loader datas. 124 125 // Remembered sets support for the oops in the class loader data. 126 bool _modified_oops; // Card Table Equivalent (YC/CMS support) 127 bool _accumulated_modified_oops; // Mod Union Equivalent (CMS support) 128 129 int _keep_alive; // if this CLD is kept alive. 130 // Used for weak hidden classes, unsafe anonymous classes and the 131 // boot class loader. _keep_alive does not need to be volatile or 132 // atomic since there is one unique CLD per weak hidden or unsafe anonymous class. 133 134 volatile int _claim; // non-zero if claimed, for example during GC traces. 135 // To avoid applying oop closure more than once. 136 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which 137 // have the same life cycle of the corresponding ClassLoader. 138 139 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies 140 141 Klass* volatile _klasses; // The classes defined by the class loader. 142 PackageEntryTable* volatile _packages; // The packages defined by the class loader. 143 ModuleEntryTable* volatile _modules; // The modules defined by the class loader. 144 ModuleEntry* _unnamed_module; // This class loader's unnamed module. 145 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader 146 147 // These method IDs are created for the class loader and set to NULL when the 148 // class loader is unloaded. They are rarely freed, only for redefine classes 149 // and if they lose a data race in InstanceKlass. 150 JNIMethodBlock* _jmethod_ids; 151 152 // Metadata to be deallocated when it's safe at class unloading, when 153 // this class loader isn't unloaded itself. 154 GrowableArray<Metadata*>* _deallocate_list; 155 156 // Support for walking class loader data objects 157 ClassLoaderData* _next; /// Next loader_datas created 158 159 Klass* _class_loader_klass; 160 Symbol* _name; 161 Symbol* _name_and_id; 162 JFR_ONLY(DEFINE_TRACE_ID_FIELD;) 163 164 void set_next(ClassLoaderData* next) { _next = next; } 165 ClassLoaderData* next() const { return Atomic::load(&_next); } 166 167 ClassLoaderData(Handle h_class_loader, bool has_class_mirror_holder); 168 ~ClassLoaderData(); 169 170 // The CLD are not placed in the Heap, so the Card Table or 171 // the Mod Union Table can't be used to mark when CLD have modified oops. 172 // The CT and MUT bits saves this information for the whole class loader data. 173 void clear_modified_oops() { _modified_oops = false; } 174 public: 175 void record_modified_oops() { _modified_oops = true; } 176 bool has_modified_oops() { return _modified_oops; } 177 178 void accumulate_modified_oops() { if (has_modified_oops()) _accumulated_modified_oops = true; } 179 void clear_accumulated_modified_oops() { _accumulated_modified_oops = false; } 180 bool has_accumulated_modified_oops() { return _accumulated_modified_oops; } 181 oop holder_no_keepalive() const; 182 oop holder_phantom() const; 183 184 private: 185 void unload(); 186 bool keep_alive() const { return _keep_alive > 0; } 187 188 void classes_do(void f(Klass* const)); 189 void loaded_classes_do(KlassClosure* klass_closure); 190 void classes_do(void f(InstanceKlass*)); 191 void methods_do(void f(Method*)); 192 void modules_do(void f(ModuleEntry*)); 193 void packages_do(void f(PackageEntry*)); 194 195 // Deallocate free list during class unloading. 196 void free_deallocate_list(); // for the classes that are not unloaded 197 void free_deallocate_list_C_heap_structures(); // for the classes that are unloaded 198 199 // Allocate out of this class loader data 200 MetaWord* allocate(size_t size); 201 202 Dictionary* create_dictionary(); 203 204 void initialize_name(Handle class_loader); 205 206 public: 207 // GC interface. 208 209 // The "claim" is typically used to check if oops_do needs to be applied on 210 // the CLD or not. Most GCs only perform strong marking during the marking phase. 211 enum Claim { 212 _claim_none = 0, 213 _claim_finalizable = 2, 214 _claim_strong = 3, 215 _claim_other = 4 216 }; 217 void clear_claim() { _claim = 0; } 218 void clear_claim(int claim); 219 bool claimed() const { return _claim != 0; } 220 bool claimed(int claim) const { return (_claim & claim) == claim; } 221 bool try_claim(int claim); 222 223 // Computes if the CLD is alive or not. This is safe to call in concurrent 224 // contexts. 225 bool is_alive() const; 226 227 // Accessors 228 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; } 229 230 static ClassLoaderData* the_null_class_loader_data() { 231 return _the_null_class_loader_data; 232 } 233 234 Mutex* metaspace_lock() const { return _metaspace_lock; } 235 236 bool has_class_mirror_holder() const { return _has_class_mirror_holder; } 237 238 static void init_null_class_loader_data(); 239 240 bool is_the_null_class_loader_data() const { 241 return this == _the_null_class_loader_data; 242 } 243 244 // Returns true if this class loader data is for the system class loader. 245 // (Note that the class loader data may be for an weak hidden or unsafe anonymous class) 246 bool is_system_class_loader_data() const; 247 248 // Returns true if this class loader data is for the platform class loader. 249 // (Note that the class loader data may be for an weak hidden or unsafe anonymous class) 250 bool is_platform_class_loader_data() const; 251 252 // Returns true if this class loader data is for the boot class loader. 253 // (Note that the class loader data may be for an weak hidden unsafe anonymous class) 254 inline bool is_boot_class_loader_data() const; 255 256 bool is_builtin_class_loader_data() const; 257 bool is_permanent_class_loader_data() const; 258 259 // The Metaspace is created lazily so may be NULL. This 260 // method will allocate a Metaspace if needed. 261 ClassLoaderMetaspace* metaspace_non_null(); 262 263 inline oop class_loader() const; 264 265 // Returns true if this class loader data is for a loader going away. 266 // Note that this is only safe after the GC has computed if the CLD is 267 // unloading or not. In concurrent contexts where there are no such 268 // guarantees, is_alive() should be used instead. 269 bool is_unloading() const { 270 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded"); 271 return _unloading; 272 } 273 274 // Used to refcount an weak hidden or unsafe anonymous class's CLD in order to 275 // indicate their aliveness. 276 void inc_keep_alive(); 277 void dec_keep_alive(); 278 279 void initialize_holder(Handle holder); 280 281 void oops_do(OopClosure* f, int claim_value, bool clear_modified_oops = false); 282 283 void classes_do(KlassClosure* klass_closure); 284 Klass* klasses() { return _klasses; } 285 286 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; } 287 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; } 288 289 void print() const; 290 void print_on(outputStream* out) const PRODUCT_RETURN; 291 void print_value() const; 292 void print_value_on(outputStream* out) const; 293 void verify(); 294 295 OopHandle add_handle(Handle h); 296 void remove_handle(OopHandle h); 297 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field 298 void add_class(Klass* k, bool publicize = true); 299 void remove_class(Klass* k); 300 bool contains_klass(Klass* k); 301 void record_dependency(const Klass* to); 302 PackageEntryTable* packages() { return _packages; } 303 ModuleEntry* unnamed_module() { return _unnamed_module; } 304 ModuleEntryTable* modules(); 305 bool modules_defined() { return (_modules != NULL); } 306 307 // Offsets 308 static ByteSize holder_offset() { return in_ByteSize(offset_of(ClassLoaderData, _holder)); } 309 static ByteSize keep_alive_offset() { return in_ByteSize(offset_of(ClassLoaderData, _keep_alive)); } 310 311 // Loaded class dictionary 312 Dictionary* dictionary() const { return _dictionary; } 313 314 void add_to_deallocate_list(Metadata* m); 315 316 static ClassLoaderData* class_loader_data(oop loader); 317 static ClassLoaderData* class_loader_data_or_null(oop loader); 318 static ClassLoaderData* has_class_mirror_holder_cld(Handle loader); 319 320 // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'. 321 // Also works if unloading. 322 Klass* class_loader_klass() const { return _class_loader_klass; } 323 324 // Returns the class loader's explict name as specified during 325 // construction or the class loader's qualified class name. 326 // Works during unloading. 327 const char* loader_name() const; 328 // Returns the explicitly specified class loader name or NULL. 329 Symbol* name() const { return _name; } 330 331 // Obtain the class loader's _name_and_id, works during unloading. 332 const char* loader_name_and_id() const; 333 Symbol* name_and_id() const { return _name_and_id; } 334 335 JFR_ONLY(DEFINE_TRACE_ID_METHODS;) 336 }; 337 338 #endif // SHARE_CLASSFILE_CLASSLOADERDATA_HPP