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