1 /* 2 * Copyright (c) 1997, 2015, 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_RUNTIME_HANDLES_HPP 26 #define SHARE_VM_RUNTIME_HANDLES_HPP 27 28 #include "oops/oop.hpp" 29 #include "oops/oopsHierarchy.hpp" 30 31 class InstanceKlass; 32 class Klass; 33 34 //------------------------------------------------------------------------------------------------------------------------ 35 // In order to preserve oops during garbage collection, they should be 36 // allocated and passed around via Handles within the VM. A handle is 37 // simply an extra indirection allocated in a thread local handle area. 38 // 39 // A handle is a ValueObj, so it can be passed around as a value, can 40 // be used as a parameter w/o using &-passing, and can be returned as a 41 // return value. 42 // 43 // oop parameters and return types should be Handles whenever feasible. 44 // 45 // Handles are declared in a straight-forward manner, e.g. 46 // 47 // oop obj = ...; 48 // Handle h1(obj); // allocate new handle 49 // Handle h2(thread, obj); // faster allocation when current thread is known 50 // Handle h3; // declare handle only, no allocation occurs 51 // ... 52 // h3 = h1; // make h3 refer to same indirection as h1 53 // oop obj2 = h2(); // get handle value 54 // h1->print(); // invoking operation on oop 55 // 56 // Handles are specialized for different oop types to provide extra type 57 // information and avoid unnecessary casting. For each oop type xxxOop 58 // there is a corresponding handle called xxxHandle, e.g. 59 // 60 // oop Handle 61 // Method* methodHandle 62 // instanceOop instanceHandle 63 64 //------------------------------------------------------------------------------------------------------------------------ 65 // Base class for all handles. Provides overloading of frequently 66 // used operators for ease of use. 67 68 class Handle VALUE_OBJ_CLASS_SPEC { 69 private: 70 oop* _handle; 71 72 protected: 73 oop obj() const { return _handle == NULL ? (oop)NULL : *_handle; } 74 oop non_null_obj() const { assert(_handle != NULL, "resolving NULL handle"); return *_handle; } 75 76 public: 77 // Constructors 78 Handle() { _handle = NULL; } 79 Handle(oop obj); 80 Handle(Thread* thread, oop obj); 81 82 // General access 83 oop operator () () const { return obj(); } 84 oop operator -> () const { return non_null_obj(); } 85 bool operator == (oop o) const { return obj() == o; } 86 bool operator == (const Handle& h) const { return obj() == h.obj(); } 87 88 // Null checks 89 bool is_null() const { return _handle == NULL; } 90 bool not_null() const { return _handle != NULL; } 91 92 // Debugging 93 void print() { obj()->print(); } 94 95 // Direct interface, use very sparingly. 96 // Used by JavaCalls to quickly convert handles and to create handles static data structures. 97 // Constructor takes a dummy argument to prevent unintentional type conversion in C++. 98 Handle(oop *handle, bool dummy) { _handle = handle; } 99 100 // Raw handle access. Allows easy duplication of Handles. This can be very unsafe 101 // since duplicates is only valid as long as original handle is alive. 102 oop* raw_value() { return _handle; } 103 static oop raw_resolve(oop *handle) { return handle == NULL ? (oop)NULL : *handle; } 104 }; 105 106 // Specific Handles for different oop types 107 #define DEF_HANDLE(type, is_a) \ 108 class type##Handle: public Handle { \ 109 protected: \ 110 type##Oop obj() const { return (type##Oop)Handle::obj(); } \ 111 type##Oop non_null_obj() const { return (type##Oop)Handle::non_null_obj(); } \ 112 \ 113 public: \ 114 /* Constructors */ \ 115 type##Handle () : Handle() {} \ 116 type##Handle (type##Oop obj) : Handle((oop)obj) { \ 117 assert(is_null() || ((oop)obj)->is_a(), \ 118 "illegal type"); \ 119 } \ 120 type##Handle (Thread* thread, type##Oop obj) : Handle(thread, (oop)obj) { \ 121 assert(is_null() || ((oop)obj)->is_a(), "illegal type"); \ 122 } \ 123 \ 124 /* Operators for ease of use */ \ 125 type##Oop operator () () const { return obj(); } \ 126 type##Oop operator -> () const { return non_null_obj(); } \ 127 }; 128 129 130 DEF_HANDLE(instance , is_instance_noinline ) 131 DEF_HANDLE(array , is_array_noinline ) 132 DEF_HANDLE(objArray , is_objArray_noinline ) 133 DEF_HANDLE(typeArray , is_typeArray_noinline ) 134 135 //------------------------------------------------------------------------------------------------------------------------ 136 137 // Metadata Handles. Unlike oop Handles these are needed to prevent metadata 138 // from being reclaimed by RedefineClasses. 139 140 // Specific Handles for different oop types 141 #define DEF_METADATA_HANDLE(name, type) \ 142 class name##Handle; \ 143 class name##Handle : public StackObj { \ 144 type* _value; \ 145 Thread* _thread; \ 146 protected: \ 147 type* obj() const { return _value; } \ 148 type* non_null_obj() const { assert(_value != NULL, "resolving NULL _value"); return _value; } \ 149 \ 150 public: \ 151 /* Constructors */ \ 152 name##Handle () : _value(NULL), _thread(NULL) {} \ 153 name##Handle (type* obj); \ 154 name##Handle (Thread* thread, type* obj); \ 155 \ 156 name##Handle (const name##Handle &h); \ 157 name##Handle& operator=(const name##Handle &s); \ 158 \ 159 /* Destructor */ \ 160 ~name##Handle (); \ 161 void remove(); \ 162 \ 163 /* Operators for ease of use */ \ 164 type* operator () () const { return obj(); } \ 165 type* operator -> () const { return non_null_obj(); } \ 166 \ 167 bool operator == (type* o) const { return obj() == o; } \ 168 bool operator == (const name##Handle& h) const { return obj() == h.obj(); } \ 169 \ 170 /* Null checks */ \ 171 bool is_null() const { return _value == NULL; } \ 172 bool not_null() const { return _value != NULL; } \ 173 }; 174 175 176 DEF_METADATA_HANDLE(method, Method) 177 DEF_METADATA_HANDLE(constantPool, ConstantPool) 178 179 // Writing this class explicitly, since DEF_METADATA_HANDLE(klass) doesn't 180 // provide the necessary Klass* <-> Klass* conversions. This Klass 181 // could be removed when we don't have the Klass* typedef anymore. 182 class KlassHandle : public StackObj { 183 Klass* _value; 184 protected: 185 Klass* obj() const { return _value; } 186 Klass* non_null_obj() const { assert(_value != NULL, "resolving NULL _value"); return _value; } 187 188 public: 189 KlassHandle() : _value(NULL) {} 190 KlassHandle(const Klass* obj) : _value(const_cast<Klass *>(obj)) {}; 191 KlassHandle(Thread* thread, const Klass* obj) : _value(const_cast<Klass *>(obj)) {}; 192 193 Klass* operator () () const { return obj(); } 194 Klass* operator -> () const { return non_null_obj(); } 195 196 bool operator == (Klass* o) const { return obj() == o; } 197 bool operator == (const KlassHandle& h) const { return obj() == h.obj(); } 198 199 bool is_null() const { return _value == NULL; } 200 bool not_null() const { return _value != NULL; } 201 }; 202 203 class instanceKlassHandle : public KlassHandle { 204 public: 205 /* Constructors */ 206 instanceKlassHandle () : KlassHandle() {} 207 instanceKlassHandle (const Klass* k) : KlassHandle(k) { 208 assert(k == NULL || is_instanceKlass(k), "illegal type"); 209 } 210 instanceKlassHandle (Thread* thread, const Klass* k) : KlassHandle(thread, k) { 211 assert(k == NULL || is_instanceKlass(k), "illegal type"); 212 } 213 /* Access to klass part */ 214 InstanceKlass* operator () () const { return (InstanceKlass*)obj(); } 215 InstanceKlass* operator -> () const { return (InstanceKlass*)obj(); } 216 217 debug_only(bool is_instanceKlass(const Klass* k)); 218 }; 219 220 221 //------------------------------------------------------------------------------------------------------------------------ 222 // Thread local handle area 223 class HandleArea: public Arena { 224 friend class HandleMark; 225 friend class NoHandleMark; 226 friend class ResetNoHandleMark; 227 #ifdef ASSERT 228 int _handle_mark_nesting; 229 int _no_handle_mark_nesting; 230 #endif 231 HandleArea* _prev; // link to outer (older) area 232 public: 233 // Constructor 234 HandleArea(HandleArea* prev) : Arena(mtThread, Chunk::tiny_size) { 235 debug_only(_handle_mark_nesting = 0); 236 debug_only(_no_handle_mark_nesting = 0); 237 _prev = prev; 238 } 239 240 // Handle allocation 241 private: 242 oop* real_allocate_handle(oop obj) { 243 #ifdef ASSERT 244 oop* handle = (oop*) (UseMallocOnly ? internal_malloc_4(oopSize) : Amalloc_4(oopSize)); 245 #else 246 oop* handle = (oop*) Amalloc_4(oopSize); 247 #endif 248 *handle = obj; 249 return handle; 250 } 251 public: 252 #ifdef ASSERT 253 oop* allocate_handle(oop obj); 254 #else 255 oop* allocate_handle(oop obj) { return real_allocate_handle(obj); } 256 #endif 257 258 // Garbage collection support 259 void oops_do(OopClosure* f); 260 261 // Number of handles in use 262 size_t used() const { return Arena::used() / oopSize; } 263 264 debug_only(bool no_handle_mark_active() { return _no_handle_mark_nesting > 0; }) 265 }; 266 267 268 //------------------------------------------------------------------------------------------------------------------------ 269 // Handles are allocated in a (growable) thread local handle area. Deallocation 270 // is managed using a HandleMark. It should normally not be necessary to use 271 // HandleMarks manually. 272 // 273 // A HandleMark constructor will record the current handle area top, and the 274 // destructor will reset the top, destroying all handles allocated in between. 275 // The following code will therefore NOT work: 276 // 277 // Handle h; 278 // { 279 // HandleMark hm; 280 // h = Handle(obj); 281 // } 282 // h()->print(); // WRONG, h destroyed by HandleMark destructor. 283 // 284 // If h has to be preserved, it can be converted to an oop or a local JNI handle 285 // across the HandleMark boundary. 286 287 // The base class of HandleMark should have been StackObj but we also heap allocate 288 // a HandleMark when a thread is created. The operator new is for this special case. 289 290 class HandleMark { 291 private: 292 Thread *_thread; // thread that owns this mark 293 HandleArea *_area; // saved handle area 294 Chunk *_chunk; // saved arena chunk 295 char *_hwm, *_max; // saved arena info 296 size_t _size_in_bytes; // size of handle area 297 // Link to previous active HandleMark in thread 298 HandleMark* _previous_handle_mark; 299 300 void initialize(Thread* thread); // common code for constructors 301 void set_previous_handle_mark(HandleMark* mark) { _previous_handle_mark = mark; } 302 HandleMark* previous_handle_mark() const { return _previous_handle_mark; } 303 304 size_t size_in_bytes() const { return _size_in_bytes; } 305 public: 306 HandleMark(); // see handles_inline.hpp 307 HandleMark(Thread* thread) { initialize(thread); } 308 ~HandleMark(); 309 310 // Functions used by HandleMarkCleaner 311 // called in the constructor of HandleMarkCleaner 312 void push(); 313 // called in the destructor of HandleMarkCleaner 314 void pop_and_restore(); 315 // overloaded operators 316 void* operator new(size_t size) throw(); 317 void* operator new [](size_t size) throw(); 318 void operator delete(void* p); 319 void operator delete[](void* p); 320 }; 321 322 //------------------------------------------------------------------------------------------------------------------------ 323 // A NoHandleMark stack object will verify that no handles are allocated 324 // in its scope. Enabled in debug mode only. 325 326 class NoHandleMark: public StackObj { 327 public: 328 #ifdef ASSERT 329 NoHandleMark(); 330 ~NoHandleMark(); 331 #else 332 NoHandleMark() {} 333 ~NoHandleMark() {} 334 #endif 335 }; 336 337 338 class ResetNoHandleMark: public StackObj { 339 int _no_handle_mark_nesting; 340 public: 341 #ifdef ASSERT 342 ResetNoHandleMark(); 343 ~ResetNoHandleMark(); 344 #else 345 ResetNoHandleMark() {} 346 ~ResetNoHandleMark() {} 347 #endif 348 }; 349 350 #endif // SHARE_VM_RUNTIME_HANDLES_HPP