1 /*
2 * Copyright (c) 1997, 2017, 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.
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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.
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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 "oops/oopsHierarchy.hpp"
31
32 class CodeBlob;
33 class nmethod;
34 class ReferenceProcessor;
35 class DataLayout;
36 class KlassClosure;
37 class ClassLoaderData;
38 class Symbol;
39
40 // The following classes are C++ `closures` for iterating over objects, roots and spaces
41
42 class Closure : public StackObj { };
43
44 // OopClosure is used for iterating through references to Java objects.
45 class OopClosure : public Closure {
46 public:
47 virtual void do_oop(oop* o) = 0;
48 virtual void do_oop(narrowOop* o) = 0;
49 };
50
51 // ExtendedOopClosure adds extra code to be run during oop iterations.
52 // This is needed by the GC and is extracted to a separate type to not
53 // pollute the OopClosure interface.
54 class ExtendedOopClosure : public OopClosure {
55 private:
56 ReferenceProcessor* _ref_processor;
57
58 protected:
59 ExtendedOopClosure(ReferenceProcessor* rp) : _ref_processor(rp) { }
60 ExtendedOopClosure() : _ref_processor(NULL) { }
61 ~ExtendedOopClosure() { }
62
63 void set_ref_processor_internal(ReferenceProcessor* rp) { _ref_processor = rp; }
64
65 public:
66 ReferenceProcessor* ref_processor() const { return _ref_processor; }
67
68 // Iteration of InstanceRefKlasses differ depending on the closure,
69 // the below enum describes the different alternatives.
70 enum ReferenceIterationMode {
71 DO_DISCOVERY, // Apply closure and discover references
72 DO_DISCOVERED_AND_DISCOVERY, // Apply closure to discovered field and do discovery
73 DO_FIELDS // Apply closure to all fields
74 };
75
76 // The default iteration mode is to do discovery.
77 virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERY; }
78
79 // If the do_metadata functions return "true",
80 // we invoke the following when running oop_iterate():
81 //
82 // 1) do_klass on the header klass pointer.
83 // 2) do_klass on the klass pointer in the mirrors.
84 // 3) do_cld on the class loader data in class loaders.
85 //
86 // The virtual (without suffix) and the non-virtual (with _nv suffix) need
87 // to be updated together, or else the devirtualization will break.
88 //
89 // Providing default implementations of the _nv functions unfortunately
90 // removes the compile-time safeness, but reduces the clutter for the
91 // ExtendedOopClosures that don't need to walk the metadata.
92 // Currently, only CMS and G1 need these.
93
94 bool do_metadata_nv() { return false; }
95 virtual bool do_metadata() { return do_metadata_nv(); }
96
97 void do_klass_nv(Klass* k) { ShouldNotReachHere(); }
98 virtual void do_klass(Klass* k) { do_klass_nv(k); }
99
100 void do_cld_nv(ClassLoaderData* cld) { ShouldNotReachHere(); }
101 virtual void do_cld(ClassLoaderData* cld) { do_cld_nv(cld); }
102
103 // True iff this closure may be safely applied more than once to an oop
104 // location without an intervening "major reset" (like the end of a GC).
105 virtual bool idempotent() { return false; }
106
107 #ifdef ASSERT
108 // Default verification of each visited oop field.
109 template <typename T> void verify(T* p);
110
111 // Can be used by subclasses to turn off the default verification of oop fields.
112 virtual bool should_verify_oops() { return true; }
113 #endif
114 };
115
116 // Wrapper closure only used to implement oop_iterate_no_header().
117 class NoHeaderExtendedOopClosure : public ExtendedOopClosure {
118 OopClosure* _wrapped_closure;
119 public:
120 NoHeaderExtendedOopClosure(OopClosure* cl) : _wrapped_closure(cl) {}
121 // Warning: this calls the virtual version do_oop in the the wrapped closure.
122 void do_oop_nv(oop* p) { _wrapped_closure->do_oop(p); }
123 void do_oop_nv(narrowOop* p) { _wrapped_closure->do_oop(p); }
124
125 void do_oop(oop* p) { assert(false, "Only the _nv versions should be used");
126 _wrapped_closure->do_oop(p); }
127 void do_oop(narrowOop* p) { assert(false, "Only the _nv versions should be used");
128 _wrapped_closure->do_oop(p);}
129 };
130
131 class BufferedValueClosure : public Closure {
132 public:
133 virtual void do_buffered_value(oop* p) = 0;
134 };
135
136 class KlassClosure : public Closure {
137 public:
138 virtual void do_klass(Klass* k) = 0;
139 };
140
141 class CLDClosure : public Closure {
142 public:
143 virtual void do_cld(ClassLoaderData* cld) = 0;
144 };
145
146 class KlassToOopClosure : public KlassClosure {
147 friend class MetadataAwareOopClosure;
148 friend class MetadataAwareOopsInGenClosure;
149
150 OopClosure* _oop_closure;
151
152 // Used when _oop_closure couldn't be set in an initialization list.
153 void initialize(OopClosure* oop_closure) {
154 assert(_oop_closure == NULL, "Should only be called once");
155 _oop_closure = oop_closure;
156 }
157
158 public:
159 KlassToOopClosure(OopClosure* oop_closure = NULL) : _oop_closure(oop_closure) {}
160
161 virtual void do_klass(Klass* k);
162 };
163
164 class CLDToOopClosure : public CLDClosure {
165 OopClosure* _oop_closure;
166 KlassToOopClosure _klass_closure;
167 bool _must_claim_cld;
168
169 public:
170 CLDToOopClosure(OopClosure* oop_closure, bool must_claim_cld = true) :
171 _oop_closure(oop_closure),
172 _klass_closure(oop_closure),
173 _must_claim_cld(must_claim_cld) {}
174
175 void do_cld(ClassLoaderData* cld);
176 };
177
178 class CLDToKlassAndOopClosure : public CLDClosure {
179 friend class G1CollectedHeap;
180 protected:
181 OopClosure* _oop_closure;
182 KlassClosure* _klass_closure;
183 bool _must_claim_cld;
184 public:
185 CLDToKlassAndOopClosure(KlassClosure* klass_closure,
186 OopClosure* oop_closure,
187 bool must_claim_cld) :
188 _oop_closure(oop_closure),
189 _klass_closure(klass_closure),
190 _must_claim_cld(must_claim_cld) {}
191 void do_cld(ClassLoaderData* cld);
192 };
193
194 // The base class for all concurrent marking closures,
195 // that participates in class unloading.
196 // It's used to proxy through the metadata to the oops defined in them.
197 class MetadataAwareOopClosure: public ExtendedOopClosure {
198 KlassToOopClosure _klass_closure;
199
200 public:
201 MetadataAwareOopClosure() : ExtendedOopClosure() {
202 _klass_closure.initialize(this);
203 }
204 MetadataAwareOopClosure(ReferenceProcessor* rp) : ExtendedOopClosure(rp) {
205 _klass_closure.initialize(this);
206 }
207
208 bool do_metadata_nv() { return true; }
209 virtual bool do_metadata() { return do_metadata_nv(); }
210
211 void do_klass_nv(Klass* k);
212 virtual void do_klass(Klass* k) { do_klass_nv(k); }
213
214 void do_cld_nv(ClassLoaderData* cld);
215 virtual void do_cld(ClassLoaderData* cld) { do_cld_nv(cld); }
216 };
217
218 // ObjectClosure is used for iterating through an object space
219
220 class ObjectClosure : public Closure {
221 public:
222 // Called for each object.
223 virtual void do_object(oop obj) = 0;
224 };
225
226
227 class BoolObjectClosure : public Closure {
228 public:
229 virtual bool do_object_b(oop obj) = 0;
230 };
231
232 class AlwaysTrueClosure: public BoolObjectClosure {
233 public:
234 bool do_object_b(oop p) { return true; }
235 };
236
237 class AlwaysFalseClosure : public BoolObjectClosure {
238 public:
239 bool do_object_b(oop p) { return false; }
240 };
241
242 // Applies an oop closure to all ref fields in objects iterated over in an
243 // object iteration.
244 class ObjectToOopClosure: public ObjectClosure {
245 ExtendedOopClosure* _cl;
246 public:
247 void do_object(oop obj);
248 ObjectToOopClosure(ExtendedOopClosure* cl) : _cl(cl) {}
249 };
250
251 // A version of ObjectClosure that is expected to be robust
252 // in the face of possibly uninitialized objects.
253 class ObjectClosureCareful : public ObjectClosure {
254 public:
255 virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;
256 virtual size_t do_object_careful(oop p) = 0;
257 };
258
259 // The following are used in CompactibleFreeListSpace and
260 // ConcurrentMarkSweepGeneration.
261
262 // Blk closure (abstract class)
263 class BlkClosure : public StackObj {
264 public:
265 virtual size_t do_blk(HeapWord* addr) = 0;
266 };
267
268 // A version of BlkClosure that is expected to be robust
269 // in the face of possibly uninitialized objects.
270 class BlkClosureCareful : public BlkClosure {
271 public:
272 size_t do_blk(HeapWord* addr) {
273 guarantee(false, "call do_blk_careful instead");
274 return 0;
275 }
276 virtual size_t do_blk_careful(HeapWord* addr) = 0;
277 };
278
279 // SpaceClosure is used for iterating over spaces
280
281 class Space;
282 class CompactibleSpace;
283
284 class SpaceClosure : public StackObj {
285 public:
286 // Called for each space
287 virtual void do_space(Space* s) = 0;
288 };
289
290 class CompactibleSpaceClosure : public StackObj {
291 public:
292 // Called for each compactible space
293 virtual void do_space(CompactibleSpace* s) = 0;
294 };
295
296
297 // CodeBlobClosure is used for iterating through code blobs
298 // in the code cache or on thread stacks
299
300 class CodeBlobClosure : public Closure {
301 public:
302 // Called for each code blob.
303 virtual void do_code_blob(CodeBlob* cb) = 0;
304 };
305
306 // Applies an oop closure to all ref fields in code blobs
307 // iterated over in an object iteration.
308 class CodeBlobToOopClosure : public CodeBlobClosure {
309 OopClosure* _cl;
310 bool _fix_relocations;
311 protected:
312 void do_nmethod(nmethod* nm);
313 public:
314 // If fix_relocations(), then cl must copy objects to their new location immediately to avoid
315 // patching nmethods with the old locations.
316 CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}
317 virtual void do_code_blob(CodeBlob* cb);
318
319 bool fix_relocations() const { return _fix_relocations; }
320 const static bool FixRelocations = true;
321 };
322
323 class MarkingCodeBlobClosure : public CodeBlobToOopClosure {
324 public:
325 MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations) : CodeBlobToOopClosure(cl, fix_relocations) {}
326 // Called for each code blob, but at most once per unique blob.
327
328 virtual void do_code_blob(CodeBlob* cb);
329 };
330
331 // MonitorClosure is used for iterating over monitors in the monitors cache
332
333 class ObjectMonitor;
334
335 class MonitorClosure : public StackObj {
336 public:
337 // called for each monitor in cache
338 virtual void do_monitor(ObjectMonitor* m) = 0;
339 };
340
341 // A closure that is applied without any arguments.
342 class VoidClosure : public StackObj {
343 public:
344 // I would have liked to declare this a pure virtual, but that breaks
345 // in mysterious ways, for unknown reasons.
346 virtual void do_void();
347 };
348
349
350 // YieldClosure is intended for use by iteration loops
351 // to incrementalize their work, allowing interleaving
352 // of an interruptable task so as to allow other
353 // threads to run (which may not otherwise be able to access
354 // exclusive resources, for instance). Additionally, the
355 // closure also allows for aborting an ongoing iteration
356 // by means of checking the return value from the polling
357 // call.
358 class YieldClosure : public StackObj {
359 public:
360 virtual bool should_return() = 0;
361 };
362
363 // Abstract closure for serializing data (read or write).
364
365 class SerializeClosure : public Closure {
366 public:
367 // Return bool indicating whether closure implements read or write.
368 virtual bool reading() const = 0;
369
370 // Read/write the void pointer pointed to by p.
371 virtual void do_ptr(void** p) = 0;
372
373 // Read/write the 32-bit unsigned integer pointed to by p.
374 virtual void do_u4(u4* p) = 0;
375
376 // Read/write the region specified.
377 virtual void do_region(u_char* start, size_t size) = 0;
378
379 // Check/write the tag. If reading, then compare the tag against
380 // the passed in value and fail is they don't match. This allows
381 // for verification that sections of the serialized data are of the
382 // correct length.
383 virtual void do_tag(int tag) = 0;
384
385 bool writing() {
386 return !reading();
387 }
388 };
389
390 class SymbolClosure : public StackObj {
391 public:
392 virtual void do_symbol(Symbol**) = 0;
393
394 // Clear LSB in symbol address; it can be set by CPSlot.
395 static Symbol* load_symbol(Symbol** p) {
396 return (Symbol*)(intptr_t(*p) & ~1);
397 }
398
399 // Store symbol, adjusting new pointer if the original pointer was adjusted
400 // (symbol references in constant pool slots have their LSB set to 1).
401 static void store_symbol(Symbol** p, Symbol* sym) {
402 *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));
403 }
404 };
405
406 // The two class template specializations are used to dispatch calls
407 // to the ExtendedOopClosure functions. If use_non_virtual_call is true,
408 // the non-virtual versions are called (E.g. do_oop_nv), otherwise the
409 // virtual versions are called (E.g. do_oop).
410
411 template <bool use_non_virtual_call>
412 class Devirtualizer {};
413
414 // Dispatches to the non-virtual functions.
415 template <> class Devirtualizer<true> {
416 public:
417 template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
418 template <class OopClosureType> static void do_klass(OopClosureType* closure, Klass* k);
419 template <class OopClosureType> static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
420 template <class OopClosureType> static bool do_metadata(OopClosureType* closure);
421 };
422
423 // Dispatches to the virtual functions.
424 template <> class Devirtualizer<false> {
425 public:
426 template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
427 template <class OopClosureType> static void do_klass(OopClosureType* closure, Klass* k);
428 template <class OopClosureType> static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
429 template <class OopClosureType> static bool do_metadata(OopClosureType* closure);
430 };
431
432 #endif // SHARE_VM_MEMORY_ITERATOR_HPP