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 class Thread;
41
42 // The following classes are C++ `closures` for iterating over objects, roots and spaces
43
44 class Closure : public StackObj { };
45
46 // Thread iterator
47 class ThreadClosure: public Closure {
48 public:
49 virtual void do_thread(Thread* thread) = 0;
50 };
51
52 // OopClosure is used for iterating through references to Java objects.
53 class OopClosure : public Closure {
54 public:
55 virtual void do_oop(oop* o) = 0;
56 virtual void do_oop(narrowOop* o) = 0;
57 };
58
59 class DoNothingClosure : public OopClosure {
60 public:
61 virtual void do_oop(oop* p) {}
62 virtual void do_oop(narrowOop* p) {}
63 };
64 extern DoNothingClosure do_nothing_cl;
65
66 // OopIterateClosure adds extra code to be run during oop iterations.
67 // This is needed by the GC and is extracted to a separate type to not
68 // pollute the OopClosure interface.
69 class OopIterateClosure : public OopClosure {
70 private:
71 ReferenceDiscoverer* _ref_discoverer;
72
73 protected:
74 OopIterateClosure(ReferenceDiscoverer* rd) : _ref_discoverer(rd) { }
75 OopIterateClosure() : _ref_discoverer(NULL) { }
76 ~OopIterateClosure() { }
77
78 void set_ref_discoverer_internal(ReferenceDiscoverer* rd) { _ref_discoverer = rd; }
79
80 public:
81 ReferenceDiscoverer* ref_discoverer() const { return _ref_discoverer; }
82
83 // Iteration of InstanceRefKlasses differ depending on the closure,
84 // the below enum describes the different alternatives.
85 enum ReferenceIterationMode {
86 DO_DISCOVERY, // Apply closure and discover references
87 DO_DISCOVERED_AND_DISCOVERY, // Apply closure to discovered field and do discovery
88 DO_FIELDS, // Apply closure to all fields
89 DO_FIELDS_EXCEPT_REFERENT // Apply closure to all fields except the referent field
90 };
91
92 // The default iteration mode is to do discovery.
93 virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERY; }
94
95 // If the do_metadata functions return "true",
96 // we invoke the following when running oop_iterate():
97 //
98 // 1) do_klass on the header klass pointer.
99 // 2) do_klass on the klass pointer in the mirrors.
100 // 3) do_cld on the class loader data in class loaders.
101
102 virtual bool do_metadata() = 0;
103 virtual void do_klass(Klass* k) = 0;
104 virtual void do_cld(ClassLoaderData* cld) = 0;
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 class MetadataClosure : public Closure {
128 public:
129 virtual void do_metadata(Metadata* md) = 0;
130 };
131
132
133 class CLDToOopClosure : public CLDClosure {
134 OopClosure* _oop_closure;
135 int _cld_claim;
136
137 public:
138 CLDToOopClosure(OopClosure* oop_closure,
139 int cld_claim) :
140 _oop_closure(oop_closure),
141 _cld_claim(cld_claim) {}
142
143 void do_cld(ClassLoaderData* cld);
144 };
145
146 class ClaimMetadataVisitingOopIterateClosure : public OopIterateClosure {
147 protected:
148 const int _claim;
149
150 public:
151 ClaimMetadataVisitingOopIterateClosure(int claim, ReferenceDiscoverer* rd = NULL) :
152 OopIterateClosure(rd),
153 _claim(claim) { }
154
155 virtual bool do_metadata() { return true; }
156 virtual void do_klass(Klass* k);
157 virtual void do_cld(ClassLoaderData* cld);
158 };
159
160 // The base class for all concurrent marking closures,
161 // that participates in class unloading.
162 // It's used to proxy through the metadata to the oops defined in them.
163 class MetadataVisitingOopIterateClosure: public ClaimMetadataVisitingOopIterateClosure {
164 public:
165 MetadataVisitingOopIterateClosure(ReferenceDiscoverer* rd = NULL);
166 };
167
168 // ObjectClosure is used for iterating through an object space
169
170 class ObjectClosure : public Closure {
171 public:
172 // Called for each object.
173 virtual void do_object(oop obj) = 0;
174 };
175
176
177 class BoolObjectClosure : public Closure {
178 public:
179 virtual bool do_object_b(oop obj) = 0;
180 };
181
182 class AlwaysTrueClosure: public BoolObjectClosure {
183 public:
184 bool do_object_b(oop p) { return true; }
185 };
186
187 class AlwaysFalseClosure : public BoolObjectClosure {
188 public:
189 bool do_object_b(oop p) { return false; }
190 };
191
192 // Applies an oop closure to all ref fields in objects iterated over in an
193 // object iteration.
194 class ObjectToOopClosure: public ObjectClosure {
195 OopIterateClosure* _cl;
196 public:
197 void do_object(oop obj);
198 ObjectToOopClosure(OopIterateClosure* cl) : _cl(cl) {}
199 };
200
201 // SpaceClosure is used for iterating over spaces
202
203 class Space;
204 class CompactibleSpace;
205
206 class SpaceClosure : public StackObj {
207 public:
208 // Called for each space
209 virtual void do_space(Space* s) = 0;
210 };
211
212 class CompactibleSpaceClosure : public StackObj {
213 public:
214 // Called for each compactible space
215 virtual void do_space(CompactibleSpace* s) = 0;
216 };
217
218
219 // CodeBlobClosure is used for iterating through code blobs
220 // in the code cache or on thread stacks
221
222 class CodeBlobClosure : public Closure {
223 public:
224 // Called for each code blob.
225 virtual void do_code_blob(CodeBlob* cb) = 0;
226 };
227
228 // Applies an oop closure to all ref fields in code blobs
229 // iterated over in an object iteration.
230 class CodeBlobToOopClosure : public CodeBlobClosure {
231 OopClosure* _cl;
232 bool _fix_relocations;
233 protected:
234 void do_nmethod(nmethod* nm);
235 public:
236 // If fix_relocations(), then cl must copy objects to their new location immediately to avoid
237 // patching nmethods with the old locations.
238 CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}
239 virtual void do_code_blob(CodeBlob* cb);
240
241 bool fix_relocations() const { return _fix_relocations; }
242 const static bool FixRelocations = true;
243 };
244
245 class MarkingCodeBlobClosure : public CodeBlobToOopClosure {
246 public:
247 MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations) : CodeBlobToOopClosure(cl, fix_relocations) {}
248 // Called for each code blob, but at most once per unique blob.
249
250 virtual void do_code_blob(CodeBlob* cb);
251 };
252
253 class NMethodClosure : public Closure {
254 public:
255 virtual void do_nmethod(nmethod* n) = 0;
256 };
257
258 // MonitorClosure is used for iterating over monitors in the monitors cache
259
260 class ObjectMonitor;
261
262 class MonitorClosure : public StackObj {
263 public:
264 // called for each monitor in cache
265 virtual void do_monitor(ObjectMonitor* m) = 0;
266 };
267
268 // A closure that is applied without any arguments.
269 class VoidClosure : public StackObj {
270 public:
271 // I would have liked to declare this a pure virtual, but that breaks
272 // in mysterious ways, for unknown reasons.
273 virtual void do_void();
274 };
275
276
277 // YieldClosure is intended for use by iteration loops
278 // to incrementalize their work, allowing interleaving
279 // of an interruptable task so as to allow other
280 // threads to run (which may not otherwise be able to access
281 // exclusive resources, for instance). Additionally, the
282 // closure also allows for aborting an ongoing iteration
283 // by means of checking the return value from the polling
284 // call.
285 class YieldClosure : public StackObj {
286 public:
287 virtual bool should_return() = 0;
288
289 // Yield on a fine-grain level. The check in case of not yielding should be very fast.
290 virtual bool should_return_fine_grain() { return false; }
291 };
292
293 // Abstract closure for serializing data (read or write).
294
295 class SerializeClosure : public Closure {
296 public:
297 // Return bool indicating whether closure implements read or write.
298 virtual bool reading() const = 0;
299
300 // Read/write the void pointer pointed to by p.
301 virtual void do_ptr(void** p) = 0;
302
303 // Read/write the 32-bit unsigned integer pointed to by p.
304 virtual void do_u4(u4* p) = 0;
305
306 // Read/write the bool pointed to by p.
307 virtual void do_bool(bool* p) = 0;
308
309 // Read/write the region specified.
310 virtual void do_region(u_char* start, size_t size) = 0;
311
312 // Check/write the tag. If reading, then compare the tag against
313 // the passed in value and fail is they don't match. This allows
314 // for verification that sections of the serialized data are of the
315 // correct length.
316 virtual void do_tag(int tag) = 0;
317
318 // Read/write the oop
319 virtual void do_oop(oop* o) = 0;
320
321 bool writing() {
322 return !reading();
323 }
324 };
325
326 class SymbolClosure : public StackObj {
327 public:
328 virtual void do_symbol(Symbol**) = 0;
329
330 // Clear LSB in symbol address; it can be set by CPSlot.
331 static Symbol* load_symbol(Symbol** p) {
332 return (Symbol*)(intptr_t(*p) & ~1);
333 }
334
335 // Store symbol, adjusting new pointer if the original pointer was adjusted
336 // (symbol references in constant pool slots have their LSB set to 1).
337 static void store_symbol(Symbol** p, Symbol* sym) {
338 *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));
339 }
340 };
341
342 // Dispatches to the non-virtual functions if OopClosureType has
343 // a concrete implementation, otherwise a virtual call is taken.
344 class Devirtualizer {
345 public:
346 template <typename OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
347 template <typename OopClosureType> static void do_klass(OopClosureType* closure, Klass* k);
348 template <typename OopClosureType> static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
349 template <typename OopClosureType> static bool do_metadata(OopClosureType* closure);
350 };
351
352 class OopIteratorClosureDispatch {
353 public:
354 template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass);
355 template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass, MemRegion mr);
356 template <typename OopClosureType> static void oop_oop_iterate_backwards(OopClosureType* cl, oop obj, Klass* klass);
357 };
358
359 #endif // SHARE_MEMORY_ITERATOR_HPP