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