iterator.hpp revision 5776:de6a9e811145
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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_MEMORY_ITERATOR_HPP 26#define SHARE_VM_MEMORY_ITERATOR_HPP 27 28#include "memory/allocation.hpp" 29#include "memory/memRegion.hpp" 30#include "runtime/prefetch.hpp" 31#include "utilities/top.hpp" 32 33// The following classes are C++ `closures` for iterating over objects, roots and spaces 34 35class CodeBlob; 36class nmethod; 37class ReferenceProcessor; 38class DataLayout; 39class KlassClosure; 40class ClassLoaderData; 41 42// Closure provides abortability. 43 44class Closure : public StackObj { 45 protected: 46 bool _abort; 47 void set_abort() { _abort = true; } 48 public: 49 Closure() : _abort(false) {} 50 // A subtype can use this mechanism to indicate to some iterator mapping 51 // functions that the iteration should cease. 52 bool abort() { return _abort; } 53 void clear_abort() { _abort = false; } 54}; 55 56// OopClosure is used for iterating through references to Java objects. 57 58class OopClosure : public Closure { 59 public: 60 virtual void do_oop(oop* o) = 0; 61 virtual void do_oop_v(oop* o) { do_oop(o); } 62 virtual void do_oop(narrowOop* o) = 0; 63 virtual void do_oop_v(narrowOop* o) { do_oop(o); } 64}; 65 66// ExtendedOopClosure adds extra code to be run during oop iterations. 67// This is needed by the GC and is extracted to a separate type to not 68// pollute the OopClosure interface. 69class ExtendedOopClosure : public OopClosure { 70 public: 71 ReferenceProcessor* _ref_processor; 72 ExtendedOopClosure(ReferenceProcessor* rp) : _ref_processor(rp) { } 73 ExtendedOopClosure() : OopClosure(), _ref_processor(NULL) { } 74 75 // If the do_metadata functions return "true", 76 // we invoke the following when running oop_iterate(): 77 // 78 // 1) do_klass on the header klass pointer. 79 // 2) do_klass on the klass pointer in the mirrors. 80 // 3) do_class_loader_data on the class loader data in class loaders. 81 // 82 // The virtual (without suffix) and the non-virtual (with _nv suffix) need 83 // to be updated together, or else the devirtualization will break. 84 // 85 // Providing default implementations of the _nv functions unfortunately 86 // removes the compile-time safeness, but reduces the clutter for the 87 // ExtendedOopClosures that don't need to walk the metadata. Currently, 88 // only CMS needs these. 89 90 virtual bool do_metadata() { return do_metadata_nv(); } 91 bool do_metadata_v() { return do_metadata(); } 92 bool do_metadata_nv() { return false; } 93 94 virtual void do_klass(Klass* k) { do_klass_nv(k); } 95 void do_klass_v(Klass* k) { do_klass(k); } 96 void do_klass_nv(Klass* k) { ShouldNotReachHere(); } 97 98 virtual void do_class_loader_data(ClassLoaderData* cld) { ShouldNotReachHere(); } 99 100 // Controls how prefetching is done for invocations of this closure. 101 Prefetch::style prefetch_style() { // Note that this is non-virtual. 102 return Prefetch::do_none; 103 } 104 105 // True iff this closure may be safely applied more than once to an oop 106 // location without an intervening "major reset" (like the end of a GC). 107 virtual bool idempotent() { return false; } 108 virtual bool apply_to_weak_ref_discovered_field() { return false; } 109}; 110 111// Wrapper closure only used to implement oop_iterate_no_header(). 112class NoHeaderExtendedOopClosure : public ExtendedOopClosure { 113 OopClosure* _wrapped_closure; 114 public: 115 NoHeaderExtendedOopClosure(OopClosure* cl) : _wrapped_closure(cl) {} 116 // Warning: this calls the virtual version do_oop in the the wrapped closure. 117 void do_oop_nv(oop* p) { _wrapped_closure->do_oop(p); } 118 void do_oop_nv(narrowOop* p) { _wrapped_closure->do_oop(p); } 119 120 void do_oop(oop* p) { assert(false, "Only the _nv versions should be used"); 121 _wrapped_closure->do_oop(p); } 122 void do_oop(narrowOop* p) { assert(false, "Only the _nv versions should be used"); 123 _wrapped_closure->do_oop(p);} 124}; 125 126class KlassClosure : public Closure { 127 public: 128 virtual void do_klass(Klass* k) = 0; 129}; 130 131class KlassToOopClosure : public KlassClosure { 132 OopClosure* _oop_closure; 133 public: 134 KlassToOopClosure(OopClosure* oop_closure) : _oop_closure(oop_closure) {} 135 virtual void do_klass(Klass* k); 136}; 137 138class CLDToOopClosure { 139 OopClosure* _oop_closure; 140 KlassToOopClosure _klass_closure; 141 bool _must_claim_cld; 142 143 public: 144 CLDToOopClosure(OopClosure* oop_closure, bool must_claim_cld = true) : 145 _oop_closure(oop_closure), 146 _klass_closure(oop_closure), 147 _must_claim_cld(must_claim_cld) {} 148 149 void do_cld(ClassLoaderData* cld); 150}; 151 152// ObjectClosure is used for iterating through an object space 153 154class ObjectClosure : public Closure { 155 public: 156 // Called for each object. 157 virtual void do_object(oop obj) = 0; 158}; 159 160 161class BoolObjectClosure : public Closure { 162 public: 163 virtual bool do_object_b(oop obj) = 0; 164}; 165 166// Applies an oop closure to all ref fields in objects iterated over in an 167// object iteration. 168class ObjectToOopClosure: public ObjectClosure { 169 ExtendedOopClosure* _cl; 170public: 171 void do_object(oop obj); 172 ObjectToOopClosure(ExtendedOopClosure* cl) : _cl(cl) {} 173}; 174 175// A version of ObjectClosure with "memory" (see _previous_address below) 176class UpwardsObjectClosure: public BoolObjectClosure { 177 HeapWord* _previous_address; 178 public: 179 UpwardsObjectClosure() : _previous_address(NULL) { } 180 void set_previous(HeapWord* addr) { _previous_address = addr; } 181 HeapWord* previous() { return _previous_address; } 182 // A return value of "true" can be used by the caller to decide 183 // if this object's end should *NOT* be recorded in 184 // _previous_address above. 185 virtual bool do_object_bm(oop obj, MemRegion mr) = 0; 186}; 187 188// A version of ObjectClosure that is expected to be robust 189// in the face of possibly uninitialized objects. 190class ObjectClosureCareful : public ObjectClosure { 191 public: 192 virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0; 193 virtual size_t do_object_careful(oop p) = 0; 194}; 195 196// The following are used in CompactibleFreeListSpace and 197// ConcurrentMarkSweepGeneration. 198 199// Blk closure (abstract class) 200class BlkClosure : public StackObj { 201 public: 202 virtual size_t do_blk(HeapWord* addr) = 0; 203}; 204 205// A version of BlkClosure that is expected to be robust 206// in the face of possibly uninitialized objects. 207class BlkClosureCareful : public BlkClosure { 208 public: 209 size_t do_blk(HeapWord* addr) { 210 guarantee(false, "call do_blk_careful instead"); 211 return 0; 212 } 213 virtual size_t do_blk_careful(HeapWord* addr) = 0; 214}; 215 216// SpaceClosure is used for iterating over spaces 217 218class Space; 219class CompactibleSpace; 220 221class SpaceClosure : public StackObj { 222 public: 223 // Called for each space 224 virtual void do_space(Space* s) = 0; 225}; 226 227class CompactibleSpaceClosure : public StackObj { 228 public: 229 // Called for each compactible space 230 virtual void do_space(CompactibleSpace* s) = 0; 231}; 232 233 234// CodeBlobClosure is used for iterating through code blobs 235// in the code cache or on thread stacks 236 237class CodeBlobClosure : public Closure { 238 public: 239 // Called for each code blob. 240 virtual void do_code_blob(CodeBlob* cb) = 0; 241}; 242 243 244class MarkingCodeBlobClosure : public CodeBlobClosure { 245 public: 246 // Called for each code blob, but at most once per unique blob. 247 virtual void do_newly_marked_nmethod(nmethod* nm) = 0; 248 249 virtual void do_code_blob(CodeBlob* cb); 250 // = { if (!nmethod(cb)->test_set_oops_do_mark()) do_newly_marked_nmethod(cb); } 251 252 class MarkScope : public StackObj { 253 protected: 254 bool _active; 255 public: 256 MarkScope(bool activate = true); 257 // = { if (active) nmethod::oops_do_marking_prologue(); } 258 ~MarkScope(); 259 // = { if (active) nmethod::oops_do_marking_epilogue(); } 260 }; 261}; 262 263 264// Applies an oop closure to all ref fields in code blobs 265// iterated over in an object iteration. 266class CodeBlobToOopClosure: public MarkingCodeBlobClosure { 267 OopClosure* _cl; 268 bool _do_marking; 269public: 270 virtual void do_newly_marked_nmethod(nmethod* cb); 271 // = { cb->oops_do(_cl); } 272 virtual void do_code_blob(CodeBlob* cb); 273 // = { if (_do_marking) super::do_code_blob(cb); else cb->oops_do(_cl); } 274 CodeBlobToOopClosure(OopClosure* cl, bool do_marking) 275 : _cl(cl), _do_marking(do_marking) {} 276}; 277 278 279 280// MonitorClosure is used for iterating over monitors in the monitors cache 281 282class ObjectMonitor; 283 284class MonitorClosure : public StackObj { 285 public: 286 // called for each monitor in cache 287 virtual void do_monitor(ObjectMonitor* m) = 0; 288}; 289 290// A closure that is applied without any arguments. 291class VoidClosure : public StackObj { 292 public: 293 // I would have liked to declare this a pure virtual, but that breaks 294 // in mysterious ways, for unknown reasons. 295 virtual void do_void(); 296}; 297 298 299// YieldClosure is intended for use by iteration loops 300// to incrementalize their work, allowing interleaving 301// of an interruptable task so as to allow other 302// threads to run (which may not otherwise be able to access 303// exclusive resources, for instance). Additionally, the 304// closure also allows for aborting an ongoing iteration 305// by means of checking the return value from the polling 306// call. 307class YieldClosure : public StackObj { 308 public: 309 virtual bool should_return() = 0; 310}; 311 312// Abstract closure for serializing data (read or write). 313 314class SerializeClosure : public Closure { 315public: 316 // Return bool indicating whether closure implements read or write. 317 virtual bool reading() const = 0; 318 319 // Read/write the void pointer pointed to by p. 320 virtual void do_ptr(void** p) = 0; 321 322 // Read/write the region specified. 323 virtual void do_region(u_char* start, size_t size) = 0; 324 325 // Check/write the tag. If reading, then compare the tag against 326 // the passed in value and fail is they don't match. This allows 327 // for verification that sections of the serialized data are of the 328 // correct length. 329 virtual void do_tag(int tag) = 0; 330}; 331 332class SymbolClosure : public StackObj { 333 public: 334 virtual void do_symbol(Symbol**) = 0; 335 336 // Clear LSB in symbol address; it can be set by CPSlot. 337 static Symbol* load_symbol(Symbol** p) { 338 return (Symbol*)(intptr_t(*p) & ~1); 339 } 340 341 // Store symbol, adjusting new pointer if the original pointer was adjusted 342 // (symbol references in constant pool slots have their LSB set to 1). 343 static void store_symbol(Symbol** p, Symbol* sym) { 344 *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1)); 345 } 346}; 347 348#endif // SHARE_VM_MEMORY_ITERATOR_HPP 349