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
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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 #ifdef ASSERT
107 // Default verification of each visited oop field.
108 template <typename T> void verify(T* p);
109
110 // Can be used by subclasses to turn off the default verification of oop fields.
111 virtual bool should_verify_oops() { return true; }
112 #endif
113 };
114
115 // An OopIterateClosure that can be used when there's no need to visit the Metadata.
116 class BasicOopIterateClosure : public OopIterateClosure {
117 public:
118 BasicOopIterateClosure(ReferenceDiscoverer* rd = NULL) : OopIterateClosure(rd) {}
119
120 virtual bool do_metadata() { return false; }
121 virtual void do_klass(Klass* k) { ShouldNotReachHere(); }
122 virtual void do_cld(ClassLoaderData* cld) { ShouldNotReachHere(); }
123 };
124
125 class KlassClosure : public Closure {
126 public:
127 virtual void do_klass(Klass* k) = 0;
128 };
129
130 class CLDClosure : public Closure {
131 public:
132 virtual void do_cld(ClassLoaderData* cld) = 0;
133 };
134
135 class MetadataClosure : public Closure {
136 public:
137 virtual void do_metadata(Metadata* md) = 0;
138 };
139
140
141 class CLDToOopClosure : public CLDClosure {
142 OopClosure* _oop_closure;
143 int _cld_claim;
144
145 public:
146 CLDToOopClosure(OopClosure* oop_closure,
147 int cld_claim) :
148 _oop_closure(oop_closure),
149 _cld_claim(cld_claim) {}
150
151 void do_cld(ClassLoaderData* cld);
152 };
153
154 class ClaimMetadataVisitingOopIterateClosure : public OopIterateClosure {
155 protected:
156 const int _claim;
157
158 public:
159 ClaimMetadataVisitingOopIterateClosure(int claim, ReferenceDiscoverer* rd = NULL) :
160 OopIterateClosure(rd),
161 _claim(claim) { }
162
163 virtual bool do_metadata() { return true; }
164 virtual void do_klass(Klass* k);
165 virtual void do_cld(ClassLoaderData* cld);
166 };
167
168 // The base class for all concurrent marking closures,
169 // that participates in class unloading.
170 // It's used to proxy through the metadata to the oops defined in them.
171 class MetadataVisitingOopIterateClosure: public ClaimMetadataVisitingOopIterateClosure {
172 public:
173 MetadataVisitingOopIterateClosure(ReferenceDiscoverer* rd = NULL);
174 };
175
176 // ObjectClosure is used for iterating through an object space
177
178 class ObjectClosure : public Closure {
179 public:
180 // Called for each object.
181 virtual void do_object(oop obj) = 0;
182 };
183
184
185 class BoolObjectClosure : public Closure {
186 public:
187 virtual bool do_object_b(oop obj) = 0;
188 };
189
190 class AlwaysTrueClosure: public BoolObjectClosure {
191 public:
192 bool do_object_b(oop p) { return true; }
193 };
194
195 class AlwaysFalseClosure : public BoolObjectClosure {
196 public:
197 bool do_object_b(oop p) { return false; }
198 };
199
200 // Applies an oop closure to all ref fields in objects iterated over in an
201 // object iteration.
202 class ObjectToOopClosure: public ObjectClosure {
203 OopIterateClosure* _cl;
204 public:
205 void do_object(oop obj);
206 ObjectToOopClosure(OopIterateClosure* cl) : _cl(cl) {}
207 };
208
209 // SpaceClosure is used for iterating over spaces
210
211 class Space;
212 class CompactibleSpace;
213
214 class SpaceClosure : public StackObj {
215 public:
216 // Called for each space
217 virtual void do_space(Space* s) = 0;
218 };
219
220 class CompactibleSpaceClosure : public StackObj {
221 public:
222 // Called for each compactible space
223 virtual void do_space(CompactibleSpace* s) = 0;
224 };
225
226
227 // CodeBlobClosure is used for iterating through code blobs
228 // in the code cache or on thread stacks
229
230 class CodeBlobClosure : public Closure {
231 public:
232 // Called for each code blob.
233 virtual void do_code_blob(CodeBlob* cb) = 0;
234 };
235
236 // Applies an oop closure to all ref fields in code blobs
237 // iterated over in an object iteration.
238 class CodeBlobToOopClosure : public CodeBlobClosure {
239 OopClosure* _cl;
240 bool _fix_relocations;
241 protected:
242 void do_nmethod(nmethod* nm);
243 public:
244 // If fix_relocations(), then cl must copy objects to their new location immediately to avoid
245 // patching nmethods with the old locations.
246 CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}
247 virtual void do_code_blob(CodeBlob* cb);
248
249 bool fix_relocations() const { return _fix_relocations; }
250 const static bool FixRelocations = true;
251 };
252
253 class MarkingCodeBlobClosure : public CodeBlobToOopClosure {
254 public:
255 MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations) : CodeBlobToOopClosure(cl, fix_relocations) {}
256 // Called for each code blob, but at most once per unique blob.
257
258 virtual void do_code_blob(CodeBlob* cb);
259 };
260
261 class NMethodClosure : public Closure {
262 public:
263 virtual void do_nmethod(nmethod* n) = 0;
264 };
265
266 // MonitorClosure is used for iterating over monitors in the monitors cache
267
268 class ObjectMonitor;
269
270 class MonitorClosure : public StackObj {
271 public:
272 // called for each monitor in cache
273 virtual void do_monitor(ObjectMonitor* m) = 0;
274 };
275
276 // A closure that is applied without any arguments.
277 class VoidClosure : public StackObj {
278 public:
279 // I would have liked to declare this a pure virtual, but that breaks
280 // in mysterious ways, for unknown reasons.
281 virtual void do_void();
282 };
283
284
285 // YieldClosure is intended for use by iteration loops
286 // to incrementalize their work, allowing interleaving
287 // of an interruptable task so as to allow other
288 // threads to run (which may not otherwise be able to access
289 // exclusive resources, for instance). Additionally, the
290 // closure also allows for aborting an ongoing iteration
291 // by means of checking the return value from the polling
292 // call.
293 class YieldClosure : public StackObj {
294 public:
295 virtual bool should_return() = 0;
296
297 // Yield on a fine-grain level. The check in case of not yielding should be very fast.
298 virtual bool should_return_fine_grain() { return false; }
299 };
300
301 // Abstract closure for serializing data (read or write).
302
303 class SerializeClosure : public Closure {
304 public:
305 // Return bool indicating whether closure implements read or write.
306 virtual bool reading() const = 0;
307
308 // Read/write the void pointer pointed to by p.
309 virtual void do_ptr(void** p) = 0;
310
311 // Read/write the 32-bit unsigned integer pointed to by p.
312 virtual void do_u4(u4* p) = 0;
313
314 // Read/write the bool pointed to by p.
315 virtual void do_bool(bool* p) = 0;
316
317 // Read/write the region specified.
318 virtual void do_region(u_char* start, size_t size) = 0;
319
320 // Check/write the tag. If reading, then compare the tag against
321 // the passed in value and fail is they don't match. This allows
322 // for verification that sections of the serialized data are of the
323 // correct length.
324 virtual void do_tag(int tag) = 0;
325
326 // Read/write the oop
327 virtual void do_oop(oop* o) = 0;
328
329 bool writing() {
330 return !reading();
331 }
332 };
333
334 class SymbolClosure : public StackObj {
335 public:
336 virtual void do_symbol(Symbol**) = 0;
337
338 // Clear LSB in symbol address; it can be set by CPSlot.
339 static Symbol* load_symbol(Symbol** p) {
340 return (Symbol*)(intptr_t(*p) & ~1);
341 }
342
343 // Store symbol, adjusting new pointer if the original pointer was adjusted
344 // (symbol references in constant pool slots have their LSB set to 1).
345 static void store_symbol(Symbol** p, Symbol* sym) {
346 *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));
347 }
348 };
349
350 // Dispatches to the non-virtual functions if OopClosureType has
351 // a concrete implementation, otherwise a virtual call is taken.
352 class Devirtualizer {
353 public:
354 template <typename OopClosureType, typename T> static void do_oop_no_verify(OopClosureType* closure, T* p);
355 template <typename OopClosureType, typename T> static void do_oop(OopClosureType* closure, T* p);
356 template <typename OopClosureType> static void do_klass(OopClosureType* closure, Klass* k);
357 template <typename OopClosureType> static void do_cld(OopClosureType* closure, ClassLoaderData* cld);
358 template <typename OopClosureType> static bool do_metadata(OopClosureType* closure);
359 };
360
361 class OopIteratorClosureDispatch {
362 public:
363 template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass);
364 template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass, MemRegion mr);
365 template <typename OopClosureType> static void oop_oop_iterate_backwards(OopClosureType* cl, oop obj, Klass* klass);
366 };
367
368 #endif // SHARE_MEMORY_ITERATOR_HPP