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.
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5 * This code is free software; you can redistribute it and/or modify it
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7 * published by the Free Software Foundation.
8 *
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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,
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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 KlassClosure : public Closure {
132 public:
133 virtual void do_klass(Klass* k) = 0;
134 };
135
136 class CLDClosure : public Closure {
137 public:
138 virtual void do_cld(ClassLoaderData* cld) = 0;
139 };
140
141
142 class CLDToOopClosure : public CLDClosure {
143 OopClosure* _oop_closure;
144 bool _must_claim_cld;
145
146 public:
147 CLDToOopClosure(OopClosure* oop_closure, bool must_claim_cld = true) :
148 _oop_closure(oop_closure),
149 _must_claim_cld(must_claim_cld) {}
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 MetadataAwareOopClosure: public ExtendedOopClosure {
158
159 public:
160 MetadataAwareOopClosure() : ExtendedOopClosure() { }
161 MetadataAwareOopClosure(ReferenceProcessor* rp) : ExtendedOopClosure(rp) { }
162
163 bool do_metadata_nv() { return true; }
164 virtual bool do_metadata() { return do_metadata_nv(); }
165
166 void do_klass_nv(Klass* k);
167 virtual void do_klass(Klass* k) { do_klass_nv(k); }
168
169 void do_cld_nv(ClassLoaderData* cld);
170 virtual void do_cld(ClassLoaderData* cld) { do_cld_nv(cld); }
171 };
172
173 // ObjectClosure is used for iterating through an object space
174
175 class ObjectClosure : public Closure {
176 public:
177 // Called for each object.
178 virtual void do_object(oop obj) = 0;
179 };
180
181
182 class BoolObjectClosure : public Closure {
183 public:
184 virtual bool do_object_b(oop obj) = 0;
185 };
186
187 class AlwaysTrueClosure: public BoolObjectClosure {
188 public:
189 bool do_object_b(oop p) { return true; }
190 };
191
192 class AlwaysFalseClosure : public BoolObjectClosure {
193 public:
194 bool do_object_b(oop p) { return false; }
195 };
196
197 // Applies an oop closure to all ref fields in objects iterated over in an
198 // object iteration.
199 class ObjectToOopClosure: public ObjectClosure {
200 ExtendedOopClosure* _cl;
201 public:
202 void do_object(oop obj);
203 ObjectToOopClosure(ExtendedOopClosure* cl) : _cl(cl) {}
204 };
205
206 // A version of ObjectClosure that is expected to be robust
207 // in the face of possibly uninitialized objects.
208 class ObjectClosureCareful : public ObjectClosure {
209 public:
210 virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;
211 virtual size_t do_object_careful(oop p) = 0;
212 };
213
214 // The following are used in CompactibleFreeListSpace and
215 // ConcurrentMarkSweepGeneration.
216
217 // Blk closure (abstract class)
218 class BlkClosure : public StackObj {
219 public:
220 virtual size_t do_blk(HeapWord* addr) = 0;
221 };
222
223 // A version of BlkClosure that is expected to be robust
224 // in the face of possibly uninitialized objects.
225 class BlkClosureCareful : public BlkClosure {
226 public:
227 size_t do_blk(HeapWord* addr) {
228 guarantee(false, "call do_blk_careful instead");
229 return 0;
230 }
231 virtual size_t do_blk_careful(HeapWord* addr) = 0;
232 };
233
234 // SpaceClosure is used for iterating over spaces
235
236 class Space;
237 class CompactibleSpace;
238
239 class SpaceClosure : public StackObj {
240 public:
241 // Called for each space
242 virtual void do_space(Space* s) = 0;
243 };
244
245 class CompactibleSpaceClosure : public StackObj {
246 public:
247 // Called for each compactible space
248 virtual void do_space(CompactibleSpace* s) = 0;
249 };
250
251
252 // CodeBlobClosure is used for iterating through code blobs
253 // in the code cache or on thread stacks
254
255 class CodeBlobClosure : public Closure {
256 public:
257 // Called for each code blob.
258 virtual void do_code_blob(CodeBlob* cb) = 0;
259 };
260
261 // Applies an oop closure to all ref fields in code blobs
262 // iterated over in an object iteration.
263 class CodeBlobToOopClosure : public CodeBlobClosure {
264 OopClosure* _cl;
265 bool _fix_relocations;
266 protected:
267 void do_nmethod(nmethod* nm);
268 public:
269 // If fix_relocations(), then cl must copy objects to their new location immediately to avoid
270 // patching nmethods with the old locations.
271 CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}
272 virtual void do_code_blob(CodeBlob* cb);
273
274 bool fix_relocations() const { return _fix_relocations; }
275 const static bool FixRelocations = true;
276 };
277
278 class MarkingCodeBlobClosure : public CodeBlobToOopClosure {
279 public:
280 MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations) : CodeBlobToOopClosure(cl, fix_relocations) {}
281 // Called for each code blob, but at most once per unique blob.
282
283 virtual void do_code_blob(CodeBlob* cb);
284 };
285
286 // MonitorClosure is used for iterating over monitors in the monitors cache
287
288 class ObjectMonitor;
289
290 class MonitorClosure : public StackObj {
291 public:
292 // called for each monitor in cache
293 virtual void do_monitor(ObjectMonitor* m) = 0;
294 };
295
296 // A closure that is applied without any arguments.
297 class VoidClosure : public StackObj {
298 public:
299 // I would have liked to declare this a pure virtual, but that breaks
300 // in mysterious ways, for unknown reasons.
301 virtual void do_void();
302 };
303
304
305 // YieldClosure is intended for use by iteration loops
306 // to incrementalize their work, allowing interleaving
307 // of an interruptable task so as to allow other
308 // threads to run (which may not otherwise be able to access
309 // exclusive resources, for instance). Additionally, the
310 // closure also allows for aborting an ongoing iteration
311 // by means of checking the return value from the polling
312 // call.
313 class YieldClosure : public StackObj {
314 public:
315 virtual bool should_return() = 0;
316 };
317
318 // Abstract closure for serializing data (read or write).
319
320 class SerializeClosure : public Closure {
321 public:
322 // Return bool indicating whether closure implements read or write.
323 virtual bool reading() const = 0;
324
325 // Read/write the void pointer pointed to by p.
326 virtual void do_ptr(void** p) = 0;
327
328 // Read/write the 32-bit unsigned integer pointed to by p.
329 virtual void do_u4(u4* p) = 0;
330
331 // Read/write the region specified.
332 virtual void do_region(u_char* start, size_t size) = 0;
333
334 // Check/write the tag. If reading, then compare the tag against
335 // the passed in value and fail is they don't match. This allows
336 // for verification that sections of the serialized data are of the
337 // correct length.
338 virtual void do_tag(int tag) = 0;
339
340 bool writing() {
341 return !reading();
342 }
343 };
344
345 class SymbolClosure : public StackObj {
346 public:
347 virtual void do_symbol(Symbol**) = 0;
348
349 // Clear LSB in symbol address; it can be set by CPSlot.
350 static Symbol* load_symbol(Symbol** p) {
351 return (Symbol*)(intptr_t(*p) & ~1);
352 }
353
354 // Store symbol, adjusting new pointer if the original pointer was adjusted
355 // (symbol references in constant pool slots have their LSB set to 1).
356 static void store_symbol(Symbol** p, Symbol* sym) {
357 *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));
358 }
359 };
360
361 // The two class template specializations are used to dispatch calls
362 // to the ExtendedOopClosure functions. If use_non_virtual_call is true,
363 // the non-virtual versions are called (E.g. do_oop_nv), otherwise the
364 // virtual versions are called (E.g. do_oop).
365
366 template <bool use_non_virtual_call>
367 class Devirtualizer {};
368
369 // Dispatches to the non-virtual functions.
370 template <> class Devirtualizer<true> {
371 public:
372 template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
373 template <class OopClosureType> static void do_klass(OopClosureType* closure, Klass* k);
374 template <class OopClosureType> static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
375 template <class OopClosureType> static bool do_metadata(OopClosureType* closure);
376 };
377
378 // Dispatches to the virtual functions.
379 template <> class Devirtualizer<false> {
380 public:
381 template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
382 template <class OopClosureType> static void do_klass(OopClosureType* closure, Klass* k);
383 template <class OopClosureType> static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
384 template <class OopClosureType> static bool do_metadata(OopClosureType* closure);
385 };
386
387 #endif // SHARE_VM_MEMORY_ITERATOR_HPP