1 /* 2 * Copyright (c) 1997, 2019, 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_MEMORY_ITERATOR_HPP 26 #define SHARE_MEMORY_ITERATOR_HPP 27 28 #include "memory/allocation.hpp" 29 #include "memory/memRegion.hpp" 30 #include "oops/oopsHierarchy.hpp" 31 32 class CodeBlob; 33 class nmethod; 34 class ReferenceDiscoverer; 35 class DataLayout; 36 class KlassClosure; 37 class ClassLoaderData; 38 class Symbol; 39 class Metadata; 40 41 // The following classes are C++ `closures` for iterating over objects, roots and spaces 42 43 class Closure : public StackObj { }; 44 45 // OopClosure is used for iterating through references to Java objects. 46 class OopClosure : public Closure { 47 public: 48 virtual void do_oop(oop* o) = 0; 49 virtual void do_oop(narrowOop* o) = 0; 50 }; 51 52 class DoNothingClosure : public OopClosure { 53 public: 54 virtual void do_oop(oop* p) {} 55 virtual void do_oop(narrowOop* p) {} 56 }; 57 extern DoNothingClosure do_nothing_cl; 58 59 // OopIterateClosure adds extra code to be run during oop iterations. 60 // This is needed by the GC and is extracted to a separate type to not 61 // pollute the OopClosure interface. 62 class OopIterateClosure : public OopClosure { 63 private: 64 ReferenceDiscoverer* _ref_discoverer; 65 66 protected: 67 OopIterateClosure(ReferenceDiscoverer* rd) : _ref_discoverer(rd) { } 68 OopIterateClosure() : _ref_discoverer(NULL) { } 69 ~OopIterateClosure() { } 70 71 void set_ref_discoverer_internal(ReferenceDiscoverer* rd) { _ref_discoverer = rd; } 72 73 public: 74 ReferenceDiscoverer* ref_discoverer() const { return _ref_discoverer; } 75 76 // Iteration of InstanceRefKlasses differ depending on the closure, 77 // the below enum describes the different alternatives. 78 enum ReferenceIterationMode { 79 DO_DISCOVERY, // Apply closure and discover references 80 DO_DISCOVERED_AND_DISCOVERY, // Apply closure to discovered field and do discovery 81 DO_FIELDS, // Apply closure to all fields 82 DO_FIELDS_EXCEPT_REFERENT // Apply closure to all fields except the referent field 83 }; 84 85 // The default iteration mode is to do discovery. 86 virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERY; } 87 88 // If the do_metadata functions return "true", 89 // we invoke the following when running oop_iterate(): 90 // 91 // 1) do_klass on the header klass pointer. 92 // 2) do_klass on the klass pointer in the mirrors. 93 // 3) do_cld on the class loader data in class loaders. 94 95 virtual bool do_metadata() = 0; 96 virtual void do_klass(Klass* k) = 0; 97 virtual void do_cld(ClassLoaderData* cld) = 0; 98 99 #ifdef ASSERT 100 // Default verification of each visited oop field. 101 template <typename T> void verify(T* p); 102 103 // Can be used by subclasses to turn off the default verification of oop fields. 104 virtual bool should_verify_oops() { return true; } 105 #endif 106 }; 107 108 // An OopIterateClosure that can be used when there's no need to visit the Metadata. 109 class BasicOopIterateClosure : public OopIterateClosure { 110 public: 111 BasicOopIterateClosure(ReferenceDiscoverer* rd = NULL) : OopIterateClosure(rd) {} 112 113 virtual bool do_metadata() { return false; } 114 virtual void do_klass(Klass* k) { ShouldNotReachHere(); } 115 virtual void do_cld(ClassLoaderData* cld) { ShouldNotReachHere(); } 116 }; 117 118 class KlassClosure : public Closure { 119 public: 120 virtual void do_klass(Klass* k) = 0; 121 }; 122 123 class CLDClosure : public Closure { 124 public: 125 virtual void do_cld(ClassLoaderData* cld) = 0; 126 }; 127 128 class MetadataClosure : public Closure { 129 public: 130 virtual void do_metadata(Metadata* md) = 0; 131 }; 132 133 134 class CLDToOopClosure : public CLDClosure { 135 OopClosure* _oop_closure; 136 int _cld_claim; 137 138 public: 139 CLDToOopClosure(OopClosure* oop_closure, 140 int cld_claim) : 141 _oop_closure(oop_closure), 142 _cld_claim(cld_claim) {} 143 144 void do_cld(ClassLoaderData* cld); 145 }; 146 147 class ClaimMetadataVisitingOopIterateClosure : public OopIterateClosure { 148 protected: 149 const int _claim; 150 151 public: 152 ClaimMetadataVisitingOopIterateClosure(int claim, ReferenceDiscoverer* rd = NULL) : 153 OopIterateClosure(rd), 154 _claim(claim) { } 155 156 virtual bool do_metadata() { return true; } 157 virtual void do_klass(Klass* k); 158 virtual void do_cld(ClassLoaderData* cld); 159 }; 160 161 // The base class for all concurrent marking closures, 162 // that participates in class unloading. 163 // It's used to proxy through the metadata to the oops defined in them. 164 class MetadataVisitingOopIterateClosure: public ClaimMetadataVisitingOopIterateClosure { 165 public: 166 MetadataVisitingOopIterateClosure(ReferenceDiscoverer* rd = NULL); 167 }; 168 169 // ObjectClosure is used for iterating through an object space 170 171 class ObjectClosure : public Closure { 172 public: 173 // Called for each object. 174 virtual void do_object(oop obj) = 0; 175 }; 176 177 178 class BoolObjectClosure : public Closure { 179 public: 180 virtual bool do_object_b(oop obj) = 0; 181 }; 182 183 class AlwaysTrueClosure: public BoolObjectClosure { 184 public: 185 bool do_object_b(oop p) { return true; } 186 }; 187 188 class AlwaysFalseClosure : public BoolObjectClosure { 189 public: 190 bool do_object_b(oop p) { return false; } 191 }; 192 193 // Applies an oop closure to all ref fields in objects iterated over in an 194 // object iteration. 195 class ObjectToOopClosure: public ObjectClosure { 196 OopIterateClosure* _cl; 197 public: 198 void do_object(oop obj); 199 ObjectToOopClosure(OopIterateClosure* cl) : _cl(cl) {} 200 }; 201 202 // A version of ObjectClosure that is expected to be robust 203 // in the face of possibly uninitialized objects. 204 class ObjectClosureCareful : public ObjectClosure { 205 public: 206 virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0; 207 virtual size_t do_object_careful(oop p) = 0; 208 }; 209 210 // The following are used in CompactibleFreeListSpace and 211 // ConcurrentMarkSweepGeneration. 212 213 // Blk closure (abstract class) 214 class BlkClosure : public StackObj { 215 public: 216 virtual size_t do_blk(HeapWord* addr) = 0; 217 }; 218 219 // A version of BlkClosure that is expected to be robust 220 // in the face of possibly uninitialized objects. 221 class BlkClosureCareful : public BlkClosure { 222 public: 223 size_t do_blk(HeapWord* addr) { 224 guarantee(false, "call do_blk_careful instead"); 225 return 0; 226 } 227 virtual size_t do_blk_careful(HeapWord* addr) = 0; 228 }; 229 230 // SpaceClosure is used for iterating over spaces 231 232 class Space; 233 class CompactibleSpace; 234 235 class SpaceClosure : public StackObj { 236 public: 237 // Called for each space 238 virtual void do_space(Space* s) = 0; 239 }; 240 241 class CompactibleSpaceClosure : public StackObj { 242 public: 243 // Called for each compactible space 244 virtual void do_space(CompactibleSpace* s) = 0; 245 }; 246 247 248 // CodeBlobClosure is used for iterating through code blobs 249 // in the code cache or on thread stacks 250 251 class CodeBlobClosure : public Closure { 252 public: 253 // Called for each code blob. 254 virtual void do_code_blob(CodeBlob* cb) = 0; 255 }; 256 257 // Applies an oop closure to all ref fields in code blobs 258 // iterated over in an object iteration. 259 class CodeBlobToOopClosure : public CodeBlobClosure { 260 OopClosure* _cl; 261 bool _fix_relocations; 262 protected: 263 void do_nmethod(nmethod* nm); 264 public: 265 // If fix_relocations(), then cl must copy objects to their new location immediately to avoid 266 // patching nmethods with the old locations. 267 CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {} 268 virtual void do_code_blob(CodeBlob* cb); 269 270 bool fix_relocations() const { return _fix_relocations; } 271 const static bool FixRelocations = true; 272 }; 273 274 class MarkingCodeBlobClosure : public CodeBlobToOopClosure { 275 public: 276 MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations) : CodeBlobToOopClosure(cl, fix_relocations) {} 277 // Called for each code blob, but at most once per unique blob. 278 279 virtual void do_code_blob(CodeBlob* cb); 280 }; 281 282 class NMethodClosure : public Closure { 283 public: 284 virtual void do_nmethod(nmethod* n) = 0; 285 }; 286 287 // MonitorClosure is used for iterating over monitors in the monitors cache 288 289 class ObjectMonitor; 290 291 class MonitorClosure : public StackObj { 292 public: 293 // called for each monitor in cache 294 virtual void do_monitor(ObjectMonitor* m) = 0; 295 }; 296 297 // A closure that is applied without any arguments. 298 class VoidClosure : public StackObj { 299 public: 300 // I would have liked to declare this a pure virtual, but that breaks 301 // in mysterious ways, for unknown reasons. 302 virtual void do_void(); 303 }; 304 305 306 // YieldClosure is intended for use by iteration loops 307 // to incrementalize their work, allowing interleaving 308 // of an interruptable task so as to allow other 309 // threads to run (which may not otherwise be able to access 310 // exclusive resources, for instance). Additionally, the 311 // closure also allows for aborting an ongoing iteration 312 // by means of checking the return value from the polling 313 // call. 314 class YieldClosure : public StackObj { 315 public: 316 virtual bool should_return() = 0; 317 318 // Yield on a fine-grain level. The check in case of not yielding should be very fast. 319 virtual bool should_return_fine_grain() { return false; } 320 }; 321 322 // Abstract closure for serializing data (read or write). 323 324 class SerializeClosure : public Closure { 325 public: 326 // Return bool indicating whether closure implements read or write. 327 virtual bool reading() const = 0; 328 329 // Read/write the void pointer pointed to by p. 330 virtual void do_ptr(void** p) = 0; 331 332 // Read/write the 32-bit unsigned integer pointed to by p. 333 virtual void do_u4(u4* p) = 0; 334 335 // Read/write the bool pointed to by p. 336 virtual void do_bool(bool* p) = 0; 337 338 // Read/write the region specified. 339 virtual void do_region(u_char* start, size_t size) = 0; 340 341 // Check/write the tag. If reading, then compare the tag against 342 // the passed in value and fail is they don't match. This allows 343 // for verification that sections of the serialized data are of the 344 // correct length. 345 virtual void do_tag(int tag) = 0; 346 347 // Read/write the oop 348 virtual void do_oop(oop* o) = 0; 349 350 // Read/write a oop that's the type of java.lang.Class 351 virtual void do_mirror_oop(oop* o) = 0; 352 353 bool writing() { 354 return !reading(); 355 } 356 }; 357 358 class SymbolClosure : public StackObj { 359 public: 360 virtual void do_symbol(Symbol**) = 0; 361 362 // Clear LSB in symbol address; it can be set by CPSlot. 363 static Symbol* load_symbol(Symbol** p) { 364 return (Symbol*)(intptr_t(*p) & ~1); 365 } 366 367 // Store symbol, adjusting new pointer if the original pointer was adjusted 368 // (symbol references in constant pool slots have their LSB set to 1). 369 static void store_symbol(Symbol** p, Symbol* sym) { 370 *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1)); 371 } 372 }; 373 374 // Dispatches to the non-virtual functions if OopClosureType has 375 // a concrete implementation, otherwise a virtual call is taken. 376 class Devirtualizer { 377 public: 378 template <typename OopClosureType, typename T> static void do_oop_no_verify(OopClosureType* closure, T* p); 379 template <typename OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p); 380 template <typename OopClosureType> static void do_klass(OopClosureType* closure, Klass* k); 381 template <typename OopClosureType> static void do_cld(OopClosureType* closure, ClassLoaderData* cld); 382 template <typename OopClosureType> static bool do_metadata(OopClosureType* closure); 383 }; 384 385 class OopIteratorClosureDispatch { 386 public: 387 template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass); 388 template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass, MemRegion mr); 389 template <typename OopClosureType> static void oop_oop_iterate_backwards(OopClosureType* cl, oop obj, Klass* klass); 390 }; 391 392 #endif // SHARE_MEMORY_ITERATOR_HPP