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.
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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_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 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 bool _must_claim_cld;
131
132 public:
133 CLDToOopClosure(OopClosure* oop_closure, bool must_claim_cld = true) :
134 _oop_closure(oop_closure),
135 _must_claim_cld(must_claim_cld) {}
136
137 void do_cld(ClassLoaderData* cld);
138 };
139
140 // The base class for all concurrent marking closures,
141 // that participates in class unloading.
142 // It's used to proxy through the metadata to the oops defined in them.
143 class MetadataVisitingOopIterateClosure: public OopIterateClosure {
144 public:
145 MetadataVisitingOopIterateClosure(ReferenceDiscoverer* rd = NULL) : OopIterateClosure(rd) { }
146
147 virtual bool do_metadata() { return true; }
148 virtual void do_klass(Klass* k);
149 virtual void do_cld(ClassLoaderData* cld);
150 };
151
152 // ObjectClosure is used for iterating through an object space
153
154 class ObjectClosure : public Closure {
155 public:
156 // Called for each object.
157 virtual void do_object(oop obj) = 0;
158 };
159
160
161 class BoolObjectClosure : public Closure {
162 public:
163 virtual bool do_object_b(oop obj) = 0;
164 };
165
166 class AlwaysTrueClosure: public BoolObjectClosure {
167 public:
168 bool do_object_b(oop p) { return true; }
169 };
170
171 class AlwaysFalseClosure : public BoolObjectClosure {
172 public:
173 bool do_object_b(oop p) { return false; }
174 };
175
176 // Applies an oop closure to all ref fields in objects iterated over in an
177 // object iteration.
178 class ObjectToOopClosure: public ObjectClosure {
179 OopIterateClosure* _cl;
180 public:
181 void do_object(oop obj);
182 ObjectToOopClosure(OopIterateClosure* cl) : _cl(cl) {}
183 };
184
185 // A version of ObjectClosure that is expected to be robust
186 // in the face of possibly uninitialized objects.
187 class ObjectClosureCareful : public ObjectClosure {
188 public:
189 virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;
190 virtual size_t do_object_careful(oop p) = 0;
191 };
192
193 // The following are used in CompactibleFreeListSpace and
194 // ConcurrentMarkSweepGeneration.
195
196 // Blk closure (abstract class)
197 class BlkClosure : public StackObj {
198 public:
199 virtual size_t do_blk(HeapWord* addr) = 0;
200 };
201
202 // A version of BlkClosure that is expected to be robust
203 // in the face of possibly uninitialized objects.
204 class BlkClosureCareful : public BlkClosure {
205 public:
206 size_t do_blk(HeapWord* addr) {
207 guarantee(false, "call do_blk_careful instead");
208 return 0;
209 }
210 virtual size_t do_blk_careful(HeapWord* addr) = 0;
211 };
212
213 // SpaceClosure is used for iterating over spaces
214
215 class Space;
216 class CompactibleSpace;
217
218 class SpaceClosure : public StackObj {
219 public:
220 // Called for each space
221 virtual void do_space(Space* s) = 0;
222 };
223
224 class CompactibleSpaceClosure : public StackObj {
225 public:
226 // Called for each compactible space
227 virtual void do_space(CompactibleSpace* s) = 0;
228 };
229
230
231 // CodeBlobClosure is used for iterating through code blobs
232 // in the code cache or on thread stacks
233
234 class CodeBlobClosure : public Closure {
235 public:
236 // Called for each code blob.
237 virtual void do_code_blob(CodeBlob* cb) = 0;
238 };
239
240 // Applies an oop closure to all ref fields in code blobs
241 // iterated over in an object iteration.
242 class CodeBlobToOopClosure : public CodeBlobClosure {
243 OopClosure* _cl;
244 bool _fix_relocations;
245 protected:
246 void do_nmethod(nmethod* nm);
247 public:
248 // If fix_relocations(), then cl must copy objects to their new location immediately to avoid
249 // patching nmethods with the old locations.
250 CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}
251 virtual void do_code_blob(CodeBlob* cb);
252
253 bool fix_relocations() const { return _fix_relocations; }
254 const static bool FixRelocations = true;
255 };
256
257 class MarkingCodeBlobClosure : public CodeBlobToOopClosure {
258 public:
259 MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations) : CodeBlobToOopClosure(cl, fix_relocations) {}
260 // Called for each code blob, but at most once per unique blob.
261
262 virtual void do_code_blob(CodeBlob* cb);
263 };
264
265 // MonitorClosure is used for iterating over monitors in the monitors cache
266
267 class ObjectMonitor;
268
269 class MonitorClosure : public StackObj {
270 public:
271 // called for each monitor in cache
272 virtual void do_monitor(ObjectMonitor* m) = 0;
273 };
274
275 // A closure that is applied without any arguments.
276 class VoidClosure : public StackObj {
277 public:
278 // I would have liked to declare this a pure virtual, but that breaks
279 // in mysterious ways, for unknown reasons.
280 virtual void do_void();
281 };
282
283
284 // YieldClosure is intended for use by iteration loops
285 // to incrementalize their work, allowing interleaving
286 // of an interruptable task so as to allow other
287 // threads to run (which may not otherwise be able to access
288 // exclusive resources, for instance). Additionally, the
289 // closure also allows for aborting an ongoing iteration
290 // by means of checking the return value from the polling
291 // call.
292 class YieldClosure : public StackObj {
293 public:
294 virtual bool should_return() = 0;
295
296 // Yield on a fine-grain level. The check in case of not yielding should be very fast.
297 virtual bool should_return_fine_grain() { return false; }
298 };
299
300 // Abstract closure for serializing data (read or write).
301
302 class SerializeClosure : public Closure {
303 public:
304 // Return bool indicating whether closure implements read or write.
305 virtual bool reading() const = 0;
306
307 // Read/write the void pointer pointed to by p.
308 virtual void do_ptr(void** p) = 0;
309
310 // Read/write the 32-bit unsigned integer pointed to by p.
311 virtual void do_u4(u4* p) = 0;
312
313 // Read/write the region specified.
314 virtual void do_region(u_char* start, size_t size) = 0;
315
316 // Check/write the tag. If reading, then compare the tag against
317 // the passed in value and fail is they don't match. This allows
318 // for verification that sections of the serialized data are of the
319 // correct length.
320 virtual void do_tag(int tag) = 0;
321
322 // Read/write the oop
323 virtual void do_oop(oop* o) = 0;
324
325 bool writing() {
326 return !reading();
327 }
328 };
329
330 class SymbolClosure : public StackObj {
331 public:
332 virtual void do_symbol(Symbol**) = 0;
333
334 // Clear LSB in symbol address; it can be set by CPSlot.
335 static Symbol* load_symbol(Symbol** p) {
336 return (Symbol*)(intptr_t(*p) & ~1);
337 }
338
339 // Store symbol, adjusting new pointer if the original pointer was adjusted
340 // (symbol references in constant pool slots have their LSB set to 1).
341 static void store_symbol(Symbol** p, Symbol* sym) {
342 *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));
343 }
344 };
345
346 // Dispatches to the non-virtual functions if OopClosureType has
347 // a concrete implementation, otherwise a virtual call is taken.
348 class Devirtualizer {
349 public:
350 template <typename OopClosureType, typename T> static void do_oop_no_verify(OopClosureType* closure, T* p);
351 template <typename OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
352 template <typename OopClosureType> static void do_klass(OopClosureType* closure, Klass* k);
353 template <typename OopClosureType> static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
354 template <typename OopClosureType> static bool do_metadata(OopClosureType* closure);
355 };
356
357 class OopIteratorClosureDispatch {
358 public:
359 template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass);
360 template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass, MemRegion mr);
361 template <typename OopClosureType> static void oop_oop_iterate_backwards(OopClosureType* cl, oop obj, Klass* klass);
362 };
363
364 #endif // SHARE_VM_MEMORY_ITERATOR_HPP