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 class ClassLoaderMetaspace; 66 67 // ClassLoaderData class 68 69 class ClassLoaderData : public CHeapObj<mtClass> { 70 friend class VMStructs; 71 72 private: 73 class ChunkedHandleList { 74 struct Chunk : public CHeapObj<mtClass> { 75 static const size_t CAPACITY = 32; 76 77 oop _data[CAPACITY]; 78 volatile juint _size; 79 Chunk* _next; 80 ChunkClassLoaderData::ChunkedHandleList::Chunk81 Chunk(Chunk* c) : _size(0), _next(c) { } 82 }; 83 84 Chunk* volatile _head; 85 86 void oops_do_chunk(OopClosure* f, Chunk* c, const juint size); 87 88 public: ChunkedHandleList()89 ChunkedHandleList() : _head(NULL) {} 90 ~ChunkedHandleList(); 91 92 // Only one thread at a time can add, guarded by ClassLoaderData::metaspace_lock(). 93 // However, multiple threads can execute oops_do concurrently with add. 94 OopHandle add(oop o); 95 bool contains(oop p); 96 NOT_PRODUCT(bool owner_of(oop* p);) 97 void oops_do(OopClosure* f); 98 99 int count() const; 100 }; 101 102 friend class ClassLoaderDataGraph; 103 friend class ClassLoaderDataGraphIterator; 104 friend class ClassLoaderDataGraphKlassIteratorAtomic; 105 friend class ClassLoaderDataGraphKlassIteratorStatic; 106 friend class ClassLoaderDataGraphMetaspaceIterator; 107 friend class Klass; 108 friend class MetaDataFactory; 109 friend class Method; 110 111 static ClassLoaderData * _the_null_class_loader_data; 112 113 WeakHandle _holder; // The oop that determines lifetime of this class loader 114 OopHandle _class_loader; // The instance of java/lang/ClassLoader associated with 115 // this ClassLoaderData 116 117 ClassLoaderMetaspace * volatile _metaspace; // Meta-space where meta-data defined by the 118 // classes in the class loader are allocated. 119 Mutex* _metaspace_lock; // Locks the metaspace for allocations and setup. 120 bool _unloading; // true if this class loader goes away 121 bool _has_class_mirror_holder; // If true, CLD is dedicated to one class and that class determines 122 // the CLDs lifecycle. For example, a non-strong hidden class or an 123 // unsafe anonymous class. Arrays of these classes are also assigned 124 // to these class loader datas. 125 126 // Remembered sets support for the oops in the class loader data. 127 bool _modified_oops; // Card Table Equivalent 128 129 int _keep_alive; // if this CLD is kept alive. 130 // Used for non-strong 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 non-strong hidden class 133 // or unsafe anonymous class. 134 135 volatile int _claim; // non-zero if claimed, for example during GC traces. 136 // To avoid applying oop closure more than once. 137 ChunkedHandleList _handles; // Handles to constant pool arrays, Modules, etc, which 138 // have the same life cycle of the corresponding ClassLoader. 139 140 NOT_PRODUCT(volatile int _dependency_count;) // number of class loader dependencies 141 142 Klass* volatile _klasses; // The classes defined by the class loader. 143 PackageEntryTable* volatile _packages; // The packages defined by the class loader. 144 ModuleEntryTable* volatile _modules; // The modules defined by the class loader. 145 ModuleEntry* _unnamed_module; // This class loader's unnamed module. 146 Dictionary* _dictionary; // The loaded InstanceKlasses, including initiated by this class loader 147 148 // These method IDs are created for the class loader and set to NULL when the 149 // class loader is unloaded. They are rarely freed, only for redefine classes 150 // and if they lose a data race in InstanceKlass. 151 JNIMethodBlock* _jmethod_ids; 152 153 // Metadata to be deallocated when it's safe at class unloading, when 154 // this class loader isn't unloaded itself. 155 GrowableArray<Metadata*>* _deallocate_list; 156 157 // Support for walking class loader data objects 158 ClassLoaderData* _next; /// Next loader_datas created 159 160 Klass* _class_loader_klass; 161 Symbol* _name; 162 Symbol* _name_and_id; JFR_ONLY(DEFINE_TRACE_ID_FIELD;)163 JFR_ONLY(DEFINE_TRACE_ID_FIELD;) 164 165 void set_next(ClassLoaderData* next) { _next = next; } next() const166 ClassLoaderData* next() const { return Atomic::load(&_next); } 167 168 ClassLoaderData(Handle h_class_loader, bool has_class_mirror_holder); 169 ~ClassLoaderData(); 170 171 // The CLD are not placed in the Heap, so the Card Table or 172 // the Mod Union Table can't be used to mark when CLD have modified oops. 173 // The CT and MUT bits saves this information for the whole class loader data. clear_modified_oops()174 void clear_modified_oops() { _modified_oops = false; } 175 public: record_modified_oops()176 void record_modified_oops() { _modified_oops = true; } has_modified_oops()177 bool has_modified_oops() { return _modified_oops; } 178 179 oop holder_no_keepalive() const; 180 oop holder_phantom() const; 181 182 private: 183 void unload(); keep_alive() const184 bool keep_alive() const { return _keep_alive > 0; } 185 186 void classes_do(void f(Klass* const)); 187 void loaded_classes_do(KlassClosure* klass_closure); 188 void classes_do(void f(InstanceKlass*)); 189 void methods_do(void f(Method*)); 190 void modules_do(void f(ModuleEntry*)); 191 void packages_do(void f(PackageEntry*)); 192 193 // Deallocate free list during class unloading. 194 void free_deallocate_list(); // for the classes that are not unloaded 195 void free_deallocate_list_C_heap_structures(); // for the classes that are unloaded 196 197 // Allocate out of this class loader data 198 MetaWord* allocate(size_t size); 199 200 Dictionary* create_dictionary(); 201 202 void initialize_name(Handle class_loader); 203 204 public: 205 // GC interface. 206 207 // The "claim" is typically used to check if oops_do needs to be applied on 208 // the CLD or not. Most GCs only perform strong marking during the marking phase. 209 enum Claim { 210 _claim_none = 0, 211 _claim_finalizable = 2, 212 _claim_strong = 3, 213 _claim_other = 4 214 }; clear_claim()215 void clear_claim() { _claim = 0; } 216 void clear_claim(int claim); claimed() const217 bool claimed() const { return _claim != 0; } claimed(int claim) const218 bool claimed(int claim) const { return (_claim & claim) == claim; } 219 bool try_claim(int claim); 220 221 // Computes if the CLD is alive or not. This is safe to call in concurrent 222 // contexts. 223 bool is_alive() const; 224 225 // Accessors metaspace_or_null() const226 ClassLoaderMetaspace* metaspace_or_null() const { return _metaspace; } 227 the_null_class_loader_data()228 static ClassLoaderData* the_null_class_loader_data() { 229 return _the_null_class_loader_data; 230 } 231 metaspace_lock() const232 Mutex* metaspace_lock() const { return _metaspace_lock; } 233 has_class_mirror_holder() const234 bool has_class_mirror_holder() const { return _has_class_mirror_holder; } 235 236 static void init_null_class_loader_data(); 237 is_the_null_class_loader_data() const238 bool is_the_null_class_loader_data() const { 239 return this == _the_null_class_loader_data; 240 } 241 242 // Returns true if this class loader data is for the system class loader. 243 // (Note that the class loader data may be for a non-strong hidden class or unsafe anonymous class) 244 bool is_system_class_loader_data() const; 245 246 // Returns true if this class loader data is for the platform class loader. 247 // (Note that the class loader data may be for a non-strong hidden class or unsafe anonymous class) 248 bool is_platform_class_loader_data() const; 249 250 // Returns true if this class loader data is for the boot class loader. 251 // (Note that the class loader data may be for a non-strong hidden class or unsafe anonymous class) 252 inline bool is_boot_class_loader_data() const; 253 254 bool is_builtin_class_loader_data() const; 255 bool is_permanent_class_loader_data() const; 256 257 // The Metaspace is created lazily so may be NULL. This 258 // method will allocate a Metaspace if needed. 259 ClassLoaderMetaspace* metaspace_non_null(); 260 261 inline oop class_loader() const; 262 263 // Returns true if this class loader data is for a loader going away. 264 // Note that this is only safe after the GC has computed if the CLD is 265 // unloading or not. In concurrent contexts where there are no such 266 // guarantees, is_alive() should be used instead. is_unloading() const267 bool is_unloading() const { 268 assert(!(is_the_null_class_loader_data() && _unloading), "The null class loader can never be unloaded"); 269 return _unloading; 270 } 271 272 // Used to refcount a non-strong hidden class's or unsafe anonymous class's CLD in order to 273 // indicate their aliveness. 274 void inc_keep_alive(); 275 void dec_keep_alive(); 276 277 void initialize_holder(Handle holder); 278 279 void oops_do(OopClosure* f, int claim_value, bool clear_modified_oops = false); 280 281 void classes_do(KlassClosure* klass_closure); klasses()282 Klass* klasses() { return _klasses; } 283 jmethod_ids() const284 JNIMethodBlock* jmethod_ids() const { return _jmethod_ids; } set_jmethod_ids(JNIMethodBlock * new_block)285 void set_jmethod_ids(JNIMethodBlock* new_block) { _jmethod_ids = new_block; } 286 287 void print() const; 288 void print_on(outputStream* out) const PRODUCT_RETURN; 289 void print_value() const; 290 void print_value_on(outputStream* out) const; 291 void verify(); 292 293 OopHandle add_handle(Handle h); 294 void remove_handle(OopHandle h); 295 void init_handle_locked(OopHandle& pd, Handle h); // used for concurrent access to ModuleEntry::_pd field 296 void add_class(Klass* k, bool publicize = true); 297 void remove_class(Klass* k); 298 bool contains_klass(Klass* k); 299 void record_dependency(const Klass* to); packages()300 PackageEntryTable* packages() { return _packages; } unnamed_module()301 ModuleEntry* unnamed_module() { return _unnamed_module; } 302 ModuleEntryTable* modules(); modules_defined()303 bool modules_defined() { return (_modules != NULL); } 304 305 // Offsets holder_offset()306 static ByteSize holder_offset() { return in_ByteSize(offset_of(ClassLoaderData, _holder)); } keep_alive_offset()307 static ByteSize keep_alive_offset() { return in_ByteSize(offset_of(ClassLoaderData, _keep_alive)); } 308 309 // Loaded class dictionary dictionary() const310 Dictionary* dictionary() const { return _dictionary; } 311 312 void add_to_deallocate_list(Metadata* m); 313 314 static ClassLoaderData* class_loader_data(oop loader); 315 static ClassLoaderData* class_loader_data_or_null(oop loader); 316 317 // Returns Klass* of associated class loader, or NULL if associated loader is 'bootstrap'. 318 // Also works if unloading. class_loader_klass() const319 Klass* class_loader_klass() const { return _class_loader_klass; } 320 321 // Returns the class loader's explict name as specified during 322 // construction or the class loader's qualified class name. 323 // Works during unloading. 324 const char* loader_name() const; 325 // Returns the explicitly specified class loader name or NULL. name() const326 Symbol* name() const { return _name; } 327 328 // Obtain the class loader's _name_and_id, works during unloading. 329 const char* loader_name_and_id() const; name_and_id() const330 Symbol* name_and_id() const { return _name_and_id; } 331 332 JFR_ONLY(DEFINE_TRACE_ID_METHODS;) 333 }; 334 335 #endif // SHARE_CLASSFILE_CLASSLOADERDATA_HPP 336