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