1 /*
2 * Copyright (c) 1997, 2018, 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.
18 *
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_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 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 // ExtendedOopClosure 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 ExtendedOopClosure : public OopClosure {
62 private:
63 ReferenceProcessor* _ref_processor;
64
65 protected:
66 ExtendedOopClosure(ReferenceProcessor* rp) : _ref_processor(rp) { }
67 ExtendedOopClosure() : _ref_processor(NULL) { }
68 ~ExtendedOopClosure() { }
69
70 void set_ref_processor_internal(ReferenceProcessor* rp) { _ref_processor = rp; }
71
72 public:
73 ReferenceProcessor* ref_processor() const { return _ref_processor; }
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 };
82
83 // The default iteration mode is to do discovery.
84 virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERY; }
85
86 // If the do_metadata functions return "true",
87 // we invoke the following when running oop_iterate():
88 //
89 // 1) do_klass on the header klass pointer.
90 // 2) do_klass on the klass pointer in the mirrors.
91 // 3) do_cld on the class loader data in class loaders.
92 //
93 // The virtual (without suffix) and the non-virtual (with _nv suffix) need
94 // to be updated together, or else the devirtualization will break.
95 //
96 // Providing default implementations of the _nv functions unfortunately
97 // removes the compile-time safeness, but reduces the clutter for the
98 // ExtendedOopClosures that don't need to walk the metadata.
99 // Currently, only CMS and G1 need these.
100
101 bool do_metadata_nv() { return false; }
102 virtual bool do_metadata() { return do_metadata_nv(); }
103
104 void do_klass_nv(Klass* k) { ShouldNotReachHere(); }
105 virtual void do_klass(Klass* k) { do_klass_nv(k); }
106
107 void do_cld_nv(ClassLoaderData* cld) { ShouldNotReachHere(); }
108 virtual void do_cld(ClassLoaderData* cld) { do_cld_nv(cld); }
109
110 // True iff this closure may be safely applied more than once to an oop
111 // location without an intervening "major reset" (like the end of a GC).
112 virtual bool idempotent() { return false; }
113
114 #ifdef ASSERT
115 // Default verification of each visited oop field.
116 template <typename T> void verify(T* p);
117
118 // Can be used by subclasses to turn off the default verification of oop fields.
119 virtual bool should_verify_oops() { return true; }
120 #endif
121 };
122
123 // Wrapper closure only used to implement oop_iterate_no_header().
124 class NoHeaderExtendedOopClosure : public ExtendedOopClosure {
125 OopClosure* _wrapped_closure;
126 public:
127 NoHeaderExtendedOopClosure(OopClosure* cl) : _wrapped_closure(cl) {}
128 // Warning: this calls the virtual version do_oop in the the wrapped closure.
129 void do_oop_nv(oop* p) { _wrapped_closure->do_oop(p); }
130 void do_oop_nv(narrowOop* p) { _wrapped_closure->do_oop(p); }
131
132 void do_oop(oop* p) { assert(false, "Only the _nv versions should be used");
133 _wrapped_closure->do_oop(p); }
134 void do_oop(narrowOop* p) { assert(false, "Only the _nv versions should be used");
135 _wrapped_closure->do_oop(p);}
136 #ifdef ASSERT
137 bool should_verify_oops() { return false; }
138 #endif
139 };
140
141 class KlassClosure : public Closure {
142 public:
143 virtual void do_klass(Klass* k) = 0;
144 };
145
146 class CLDClosure : public Closure {
147 public:
148 virtual void do_cld(ClassLoaderData* cld) = 0;
149 };
150
151
152 class CLDToOopClosure : public CLDClosure {
153 OopClosure* _oop_closure;
154 bool _must_claim_cld;
155
156 public:
157 CLDToOopClosure(OopClosure* oop_closure, bool must_claim_cld = true) :
158 _oop_closure(oop_closure),
159 _must_claim_cld(must_claim_cld) {}
160
161 void do_cld(ClassLoaderData* cld);
162 };
163
164 // The base class for all concurrent marking closures,
165 // that participates in class unloading.
166 // It's used to proxy through the metadata to the oops defined in them.
167 class MetadataAwareOopClosure: public ExtendedOopClosure {
168
169 public:
170 MetadataAwareOopClosure() : ExtendedOopClosure() { }
171 MetadataAwareOopClosure(ReferenceProcessor* rp) : ExtendedOopClosure(rp) { }
172
173 bool do_metadata_nv() { return true; }
174 virtual bool do_metadata() { return do_metadata_nv(); }
175
176 void do_klass_nv(Klass* k);
177 virtual void do_klass(Klass* k) { do_klass_nv(k); }
178
179 void do_cld_nv(ClassLoaderData* cld);
180 virtual void do_cld(ClassLoaderData* cld) { do_cld_nv(cld); }
181 };
182
183 // ObjectClosure is used for iterating through an object space
184
185 class ObjectClosure : public Closure {
186 public:
187 // Called for each object.
188 virtual void do_object(oop obj) = 0;
189 };
190
191
192 class BoolObjectClosure : public Closure {
193 public:
194 virtual bool do_object_b(oop obj) = 0;
195 };
196
197 class AlwaysTrueClosure: public BoolObjectClosure {
198 public:
199 bool do_object_b(oop p) { return true; }
200 };
201
202 class AlwaysFalseClosure : public BoolObjectClosure {
203 public:
204 bool do_object_b(oop p) { return false; }
205 };
206
207 // Applies an oop closure to all ref fields in objects iterated over in an
208 // object iteration.
209 class ObjectToOopClosure: public ObjectClosure {
210 ExtendedOopClosure* _cl;
211 public:
212 void do_object(oop obj);
213 ObjectToOopClosure(ExtendedOopClosure* cl) : _cl(cl) {}
214 };
215
216 // A version of ObjectClosure that is expected to be robust
217 // in the face of possibly uninitialized objects.
218 class ObjectClosureCareful : public ObjectClosure {
219 public:
220 virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;
221 virtual size_t do_object_careful(oop p) = 0;
222 };
223
224 // The following are used in CompactibleFreeListSpace and
225 // ConcurrentMarkSweepGeneration.
226
227 // Blk closure (abstract class)
228 class BlkClosure : public StackObj {
229 public:
230 virtual size_t do_blk(HeapWord* addr) = 0;
231 };
232
233 // A version of BlkClosure that is expected to be robust
234 // in the face of possibly uninitialized objects.
235 class BlkClosureCareful : public BlkClosure {
236 public:
237 size_t do_blk(HeapWord* addr) {
238 guarantee(false, "call do_blk_careful instead");
239 return 0;
240 }
241 virtual size_t do_blk_careful(HeapWord* addr) = 0;
242 };
243
244 // SpaceClosure is used for iterating over spaces
245
246 class Space;
247 class CompactibleSpace;
248
249 class SpaceClosure : public StackObj {
250 public:
251 // Called for each space
252 virtual void do_space(Space* s) = 0;
253 };
254
255 class CompactibleSpaceClosure : public StackObj {
256 public:
257 // Called for each compactible space
258 virtual void do_space(CompactibleSpace* s) = 0;
259 };
260
261
262 // CodeBlobClosure is used for iterating through code blobs
263 // in the code cache or on thread stacks
264
265 class CodeBlobClosure : public Closure {
266 public:
267 // Called for each code blob.
268 virtual void do_code_blob(CodeBlob* cb) = 0;
269 };
270
271 // Applies an oop closure to all ref fields in code blobs
272 // iterated over in an object iteration.
273 class CodeBlobToOopClosure : public CodeBlobClosure {
274 OopClosure* _cl;
275 bool _fix_relocations;
276 protected:
277 void do_nmethod(nmethod* nm);
278 public:
279 // If fix_relocations(), then cl must copy objects to their new location immediately to avoid
280 // patching nmethods with the old locations.
281 CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}
282 virtual void do_code_blob(CodeBlob* cb);
283
284 bool fix_relocations() const { return _fix_relocations; }
285 const static bool FixRelocations = true;
286 };
287
288 class MarkingCodeBlobClosure : public CodeBlobToOopClosure {
289 public:
290 MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations) : CodeBlobToOopClosure(cl, fix_relocations) {}
291 // Called for each code blob, but at most once per unique blob.
292
293 virtual void do_code_blob(CodeBlob* cb);
294 };
295
296 // MonitorClosure is used for iterating over monitors in the monitors cache
297
298 class ObjectMonitor;
299
300 class MonitorClosure : public StackObj {
301 public:
302 // called for each monitor in cache
303 virtual void do_monitor(ObjectMonitor* m) = 0;
304 };
305
306 // A closure that is applied without any arguments.
307 class VoidClosure : public StackObj {
308 public:
309 // I would have liked to declare this a pure virtual, but that breaks
310 // in mysterious ways, for unknown reasons.
311 virtual void do_void();
312 };
313
314
315 // YieldClosure is intended for use by iteration loops
316 // to incrementalize their work, allowing interleaving
317 // of an interruptable task so as to allow other
318 // threads to run (which may not otherwise be able to access
319 // exclusive resources, for instance). Additionally, the
320 // closure also allows for aborting an ongoing iteration
321 // by means of checking the return value from the polling
322 // call.
323 class YieldClosure : public StackObj {
324 public:
325 virtual bool should_return() = 0;
326 };
327
328 // Abstract closure for serializing data (read or write).
329
330 class SerializeClosure : public Closure {
331 public:
332 // Return bool indicating whether closure implements read or write.
333 virtual bool reading() const = 0;
334
335 // Read/write the void pointer pointed to by p.
336 virtual void do_ptr(void** p) = 0;
337
338 // Read/write the 32-bit unsigned integer pointed to by p.
339 virtual void do_u4(u4* p) = 0;
340
341 // Read/write the region specified.
342 virtual void do_region(u_char* start, size_t size) = 0;
343
344 // Check/write the tag. If reading, then compare the tag against
345 // the passed in value and fail is they don't match. This allows
346 // for verification that sections of the serialized data are of the
347 // correct length.
348 virtual void do_tag(int tag) = 0;
349
350 // Read/write the oop
351 virtual void do_oop(oop* o) = 0;
352
353 bool writing() {
354 return !reading();
355 }
356 };
357
358 class SymbolClosure : public StackObj {
359 public:
360 virtual void do_symbol(Symbol**) = 0;
361
362 // Clear LSB in symbol address; it can be set by CPSlot.
363 static Symbol* load_symbol(Symbol** p) {
364 return (Symbol*)(intptr_t(*p) & ~1);
365 }
366
367 // Store symbol, adjusting new pointer if the original pointer was adjusted
368 // (symbol references in constant pool slots have their LSB set to 1).
369 static void store_symbol(Symbol** p, Symbol* sym) {
370 *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));
371 }
372 };
373
374 // The two class template specializations are used to dispatch calls
375 // to the ExtendedOopClosure functions. If use_non_virtual_call is true,
376 // the non-virtual versions are called (E.g. do_oop_nv), otherwise the
377 // virtual versions are called (E.g. do_oop).
378
379 template <bool use_non_virtual_call>
380 class Devirtualizer {};
381
382 // Dispatches to the non-virtual functions.
383 template <> class Devirtualizer<true> {
384 public:
385 template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
386 template <class OopClosureType> static void do_klass(OopClosureType* closure, Klass* k);
387 template <class OopClosureType> static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
388 template <class OopClosureType> static bool do_metadata(OopClosureType* closure);
389 };
390
391 // Dispatches to the virtual functions.
392 template <> class Devirtualizer<false> {
393 public:
394 template <class OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
395 template <class OopClosureType> static void do_klass(OopClosureType* closure, Klass* k);
396 template <class OopClosureType> static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
397 template <class OopClosureType> static bool do_metadata(OopClosureType* closure);
398 };
399
400 #endif // SHARE_VM_MEMORY_ITERATOR_HPP