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