1 /* 2 * Copyright (c) 2012, 2021, 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 "oops/oopHandle.hpp" 30 #include "oops/weakHandle.hpp" 31 #include "runtime/atomic.hpp" 32 #include "runtime/mutex.hpp" 33 #include "utilities/growableArray.hpp" 34 #include "utilities/macros.hpp" 35 #if INCLUDE_JFR 36 #include "jfr/support/jfrTraceIdExtension.hpp" 37 #endif 38 39 // external name (synthetic) for the primordial "bootstrap" class loader instance 40 #define BOOTSTRAP_LOADER_NAME "bootstrap" 41 #define BOOTSTRAP_LOADER_NAME_LEN 9 42 43 // 44 // A class loader represents a linkset. Conceptually, a linkset identifies 45 // the complete transitive closure of resolved links that a dynamic linker can 46 // produce. 47 // 48 // A ClassLoaderData also encapsulates the allocation space, called a metaspace, 49 // used by the dynamic linker to allocate the runtime representation of all 50 // the types it defines. 51 // 52 // ClassLoaderData are stored in the runtime representation of classes, 53 // and provides iterators for root tracing and other GC operations. 54 55 class ClassLoaderDataGraph; 56 class JNIMethodBlock; 57 class ModuleEntry; 58 class PackageEntry; 59 class ModuleEntryTable; 60 class PackageEntryTable; 61 class DictionaryEntry; 62 class Dictionary; 63 class ClassLoaderMetaspace; 64 65 // ClassLoaderData class 66 67 class ClassLoaderData : public CHeapObj<mtClass> { 68 friend class VMStructs; 69 70 private: 71 class ChunkedHandleList { 72 struct Chunk : public CHeapObj<mtClass> { 73 static const size_t CAPACITY = 32; 74 75 oop _data[CAPACITY]; 76 volatile juint _size; 77 Chunk* _next; 78 79 Chunk(Chunk* c) : _size(0), _next(c) { } 80 }; 81 82 Chunk* volatile _head; 83 84 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size); 85 86 public: 87 ChunkedHandleList() : _head(NULL) {} 88 ~ChunkedHandleList(); 89 90 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock(). 91 // However, multiple threads can execute oops_do concurrently with add. 92 OopHandle add(oop o); 93 bool contains(oop p); 94 NOT_PRODUCT(bool owner_of(oop* p);) 95 void oops_do(OopClosure* f); 96 97 int count() const; 98 }; 99 100 friend class ClassLoaderDataGraph; 101 friend class ClassLoaderDataGraphIterator; 102 friend class ClassLoaderDataGraphKlassIteratorAtomic; 103 friend class ClassLoaderDataGraphKlassIteratorStatic; 104 friend class ClassLoaderDataGraphMetaspaceIterator; 105 friend class Klass; 106 friend class MetaDataFactory; 107 friend class Method; 108 109 static ClassLoaderData * _the_null_class_loader_data; 110 111 WeakHandle _holder; // The oop that determines lifetime of this class loader 112 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with 113 // this ClassLoaderData 114 115 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the 116 // classes in the class loader are allocated. 117 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup. 118 bool _unloading; // true if this class loader goes away 119 bool _has_class_mirror_holder; // If true, CLD is dedicated to one class and that class determines 120 // the CLDs lifecycle. For example, a non-strong hidden class. 121 // Arrays of these classes are also assigned 122 // to these class loader datas. 123 124 // Remembered sets support for the oops in the class loader data. 125 bool _modified_oops; // Card Table Equivalent 126 127 int _keep_alive; // if this CLD is kept alive. 128 // Used for non-strong hidden classes and the 129 // boot class loader. _keep_alive does not need to be volatile or 130 // atomic since there is one unique CLD per non-strong hidden class. 131 132 volatile int _claim; // non-zero if claimed, for example during GC traces. 133 // To avoid applying oop closure more than once. 134 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which 135 // have the same life cycle of the corresponding ClassLoader. 136 137 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies 138 139 Klass* volatile _klasses; // The classes defined by the class loader. 140 PackageEntryTable* volatile _packages; // The packages defined by the class loader. 141 ModuleEntryTable* volatile _modules; // The modules defined by the class loader. 142 ModuleEntry* _unnamed_module; // This class loader's unnamed module. 143 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader 144 145 // These method IDs are created for the class loader and set to NULL when the 146 // class loader is unloaded. They are rarely freed, only for redefine classes 147 // and if they lose a data race in InstanceKlass. 148 JNIMethodBlock* _jmethod_ids; 149 150 // Metadata to be deallocated when it's safe at class unloading, when 151 // this class loader isn't unloaded itself. 152 GrowableArray<Metadata*>* _deallocate_list; 153 154 // Support for walking class loader data objects 155 ClassLoaderData* _next; /// Next loader_datas created 156 157 Klass* _class_loader_klass; 158 Symbol* _name; 159 Symbol* _name_and_id; 160 JFR_ONLY(DEFINE_TRACE_ID_FIELD;) 161 162 void set_next(ClassLoaderData* next) { _next = next; } 163 ClassLoaderData* next() const { return Atomic::load(&_next); } 164 165 ClassLoaderData(Handle h_class_loader, bool has_class_mirror_holder); 166 ~ClassLoaderData(); 167 168 // The CLD are not placed in the Heap, so the Card Table or 169 // the Mod Union Table can't be used to mark when CLD have modified oops. 170 // The CT and MUT bits saves this information for the whole class loader data. 171 void clear_modified_oops() { _modified_oops = false; } 172 public: 173 void record_modified_oops() { _modified_oops = true; } 174 bool has_modified_oops() { return _modified_oops; } 175 176 oop holder_no_keepalive() const; 177 oop holder() const; 178 179 private: 180 void unload(); 181 bool keep_alive() const { return _keep_alive > 0; } 182 183 void classes_do(void f(Klass* const)); 184 void loaded_classes_do(KlassClosure* klass_closure); 185 void classes_do(void f(InstanceKlass*)); 186 void methods_do(void f(Method*)); 187 void modules_do(void f(ModuleEntry*)); 188 void packages_do(void f(PackageEntry*)); 189 190 // Deallocate free list during class unloading. 191 void free_deallocate_list(); // for the classes that are not unloaded 192 void free_deallocate_list_C_heap_structures(); // for the classes that are unloaded 193 194 Dictionary* create_dictionary(); 195 196 void initialize_name(Handle class_loader); 197 198 public: 199 // GC interface. 200 201 // The "claim" is typically used to check if oops_do needs to be applied on 202 // the CLD or not. Most GCs only perform strong marking during the marking phase. 203 enum Claim { 204 _claim_none = 0, 205 _claim_finalizable = 2, 206 _claim_strong = 3, 207 _claim_other = 4 208 }; 209 void clear_claim() { _claim = 0; } 210 void clear_claim(int claim); 211 bool claimed() const { return _claim != 0; } 212 bool claimed(int claim) const { return (_claim & claim) == claim; } 213 bool try_claim(int claim); 214 215 // Computes if the CLD is alive or not. This is safe to call in concurrent 216 // contexts. 217 bool is_alive() const; 218 219 // Accessors 220 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; } 221 222 static ClassLoaderData* the_null_class_loader_data() { 223 return _the_null_class_loader_data; 224 } 225 226 Mutex* metaspace_lock() const { return _metaspace_lock; } 227 228 bool has_class_mirror_holder() const { return _has_class_mirror_holder; } 229 230 static void init_null_class_loader_data(); 231 232 bool is_the_null_class_loader_data() const { 233 return this == _the_null_class_loader_data; 234 } 235 236 // Returns true if this class loader data is for the system class loader. 237 // (Note that the class loader data may be for a non-strong hidden class) 238 bool is_system_class_loader_data() const; 239 240 // Returns true if this class loader data is for the platform class loader. 241 // (Note that the class loader data may be for a non-strong hidden class) 242 bool is_platform_class_loader_data() const; 243 244 // Returns true if this class loader data is for the boot class loader. 245 // (Note that the class loader data may be for a non-strong hidden class) 246 inline bool is_boot_class_loader_data() const; 247 248 bool is_builtin_class_loader_data() const; 249 bool is_permanent_class_loader_data() const; 250 251 // The Metaspace is created lazily so may be NULL. This 252 // method will allocate a Metaspace if needed. 253 ClassLoaderMetaspace* metaspace_non_null(); 254 255 inline oop class_loader() const; 256 257 // Returns true if this class loader data is for a loader going away. 258 // Note that this is only safe after the GC has computed if the CLD is 259 // unloading or not. In concurrent contexts where there are no such 260 // guarantees, is_alive() should be used instead. 261 bool is_unloading() const { 262 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded"); 263 return _unloading; 264 } 265 266 // Used to refcount a non-strong hidden class's s CLD in order to indicate their aliveness. 267 void inc_keep_alive(); 268 void dec_keep_alive(); 269 270 void initialize_holder(Handle holder); 271 272 void oops_do(OopClosure* f, int claim_value, bool clear_modified_oops = false); 273 274 void classes_do(KlassClosure* klass_closure); 275 Klass* klasses() { return _klasses; } 276 277 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; } 278 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; } 279 280 void print() const; 281 void print_on(outputStream* out) const PRODUCT_RETURN; 282 void print_value() const; 283 void print_value_on(outputStream* out) const; 284 void verify(); 285 286 OopHandle add_handle(Handle h); 287 void remove_handle(OopHandle h); 288 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field 289 void add_class(Klass* k, bool publicize = true); 290 void remove_class(Klass* k); 291 bool contains_klass(Klass* k); 292 void record_dependency(const Klass* to); 293 PackageEntryTable* packages() { return _packages; } 294 ModuleEntry* unnamed_module() { return _unnamed_module; } 295 ModuleEntryTable* modules(); 296 bool modules_defined() { return (_modules != NULL); } 297 298 // Offsets 299 static ByteSize holder_offset() { return in_ByteSize(offset_of(ClassLoaderData, _holder)); } 300 static ByteSize keep_alive_offset() { return in_ByteSize(offset_of(ClassLoaderData, _keep_alive)); } 301 302 // Loaded class dictionary 303 Dictionary* dictionary() const { return _dictionary; } 304 305 void add_to_deallocate_list(Metadata* m); 306 307 static ClassLoaderData* class_loader_data(oop loader); 308 static ClassLoaderData* class_loader_data_or_null(oop loader); 309 310 // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'. 311 // Also works if unloading. 312 Klass* class_loader_klass() const { return _class_loader_klass; } 313 314 // Returns the class loader's explict name as specified during 315 // construction or the class loader's qualified class name. 316 // Works during unloading. 317 const char* loader_name() const; 318 // Returns the explicitly specified class loader name or NULL. 319 Symbol* name() const { return _name; } 320 321 // Obtain the class loader's _name_and_id, works during unloading. 322 const char* loader_name_and_id() const; 323 Symbol* name_and_id() const { return _name_and_id; } 324 325 unsigned identity_hash() const { 326 return (unsigned)((uintptr_t)this >> LogBytesPerWord); 327 } 328 329 JFR_ONLY(DEFINE_TRACE_ID_METHODS;) 330 }; 331 332 #endif // SHARE_CLASSFILE_CLASSLOADERDATA_HPP