1 /*
2 * Copyright (c) 1997, 2012, 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 "runtime/prefetch.hpp"
31 #include "utilities/top.hpp"
32
33 // The following classes are C++ `closures` for iterating over objects, roots and spaces
34
35 class CodeBlob;
36 class nmethod;
37 class ReferenceProcessor;
38 class DataLayout;
39 class KlassClosure;
40 class ClassLoaderData;
41
42 // Closure provides abortability.
43
44 class Closure : public StackObj {
45 protected:
46 bool _abort;
47 void set_abort() { _abort = true; }
48 public:
49 Closure() : _abort(false) {}
50 // A subtype can use this mechanism to indicate to some iterator mapping
51 // functions that the iteration should cease.
52 bool abort() { return _abort; }
53 void clear_abort() { _abort = false; }
54 };
55
56 // OopClosure is used for iterating through references to Java objects.
57
58 class OopClosure : public Closure {
59 public:
60 virtual void do_oop(oop* o) = 0;
61 virtual void do_oop_v(oop* o) { do_oop(o); }
62 virtual void do_oop(narrowOop* o) = 0;
63 virtual void do_oop_v(narrowOop* o) { do_oop(o); }
64 };
65
66 // ExtendedOopClosure 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 ExtendedOopClosure : public OopClosure {
70 public:
71 ReferenceProcessor* _ref_processor;
72 ExtendedOopClosure(ReferenceProcessor* rp) : _ref_processor(rp) { }
73 ExtendedOopClosure() : OopClosure(), _ref_processor(NULL) { }
74
75 // If the do_metadata functions return "true",
76 // we invoke the following when running oop_iterate():
77 //
78 // 1) do_klass on the header klass pointer.
79 // 2) do_klass on the klass pointer in the mirrors.
80 // 3) do_class_loader_data on the class loader data in class loaders.
81 //
82 // The virtual (without suffix) and the non-virtual (with _nv suffix) need
83 // to be updated together, or else the devirtualization will break.
84 //
85 // Providing default implementations of the _nv functions unfortunately
86 // removes the compile-time safeness, but reduces the clutter for the
87 // ExtendedOopClosures that don't need to walk the metadata. Currently,
88 // only CMS needs these.
89
90 virtual bool do_metadata() { return do_metadata_nv(); }
91 bool do_metadata_v() { return do_metadata(); }
92 bool do_metadata_nv() { return false; }
93
94 virtual void do_klass(Klass* k) { do_klass_nv(k); }
95 void do_klass_v(Klass* k) { do_klass(k); }
96 void do_klass_nv(Klass* k) { ShouldNotReachHere(); }
97
98 virtual void do_class_loader_data(ClassLoaderData* cld) { ShouldNotReachHere(); }
99
100 // Controls how prefetching is done for invocations of this closure.
101 Prefetch::style prefetch_style() { // Note that this is non-virtual.
102 return Prefetch::do_none;
103 }
104
105 // True iff this closure may be safely applied more than once to an oop
106 // location without an intervening "major reset" (like the end of a GC).
107 virtual bool idempotent() { return false; }
108 virtual bool apply_to_weak_ref_discovered_field() { return false; }
109 };
110
111 // Wrapper closure only used to implement oop_iterate_no_header().
112 class NoHeaderExtendedOopClosure : public ExtendedOopClosure {
113 OopClosure* _wrapped_closure;
114 public:
115 NoHeaderExtendedOopClosure(OopClosure* cl) : _wrapped_closure(cl) {}
116 // Warning: this calls the virtual version do_oop in the the wrapped closure.
117 void do_oop_nv(oop* p) { _wrapped_closure->do_oop(p); }
118 void do_oop_nv(narrowOop* p) { _wrapped_closure->do_oop(p); }
119
120 void do_oop(oop* p) { assert(false, "Only the _nv versions should be used");
121 _wrapped_closure->do_oop(p); }
122 void do_oop(narrowOop* p) { assert(false, "Only the _nv versions should be used");
123 _wrapped_closure->do_oop(p);}
124 };
125
126 class KlassClosure : public Closure {
127 public:
128 virtual void do_klass(Klass* k) = 0;
129 };
130
131 class KlassToOopClosure : public KlassClosure {
132 OopClosure* _oop_closure;
133 public:
134 KlassToOopClosure(OopClosure* oop_closure) : _oop_closure(oop_closure) {}
135 virtual void do_klass(Klass* k);
136 };
137
138 class CLDToOopClosure {
139 OopClosure* _oop_closure;
140 KlassToOopClosure _default_klass_closure;
141 KlassClosure* _klass_closure;
142 bool _must_claim_cld;
143
144 public:
145 CLDToOopClosure(OopClosure* oop_closure, bool must_claim_cld = true) :
146 _oop_closure(oop_closure),
147 _default_klass_closure(oop_closure),
148 _klass_closure(&_default_klass_closure),
149 _must_claim_cld(must_claim_cld) {}
150 CLDToOopClosure(OopClosure* oop_closure, KlassClosure* klass_closure, bool must_claim_cld = true) :
151 _oop_closure(oop_closure),
152 _default_klass_closure(NULL), // Ignored
153 _klass_closure(klass_closure),
154 _must_claim_cld(must_claim_cld) {}
155
156 void do_cld(ClassLoaderData* cld);
157 };
158
159 // ObjectClosure is used for iterating through an object space
160
161 class ObjectClosure : public Closure {
162 public:
163 // Called for each object.
164 virtual void do_object(oop obj) = 0;
165 };
166
167
168 class BoolObjectClosure : public ObjectClosure {
169 public:
170 virtual bool do_object_b(oop obj) = 0;
171 };
172
173 // Applies an oop closure to all ref fields in objects iterated over in an
174 // object iteration.
175 class ObjectToOopClosure: public ObjectClosure {
176 ExtendedOopClosure* _cl;
177 public:
178 void do_object(oop obj);
179 ObjectToOopClosure(ExtendedOopClosure* cl) : _cl(cl) {}
180 };
181
182 // A version of ObjectClosure with "memory" (see _previous_address below)
183 class UpwardsObjectClosure: public BoolObjectClosure {
184 HeapWord* _previous_address;
185 public:
186 UpwardsObjectClosure() : _previous_address(NULL) { }
187 void set_previous(HeapWord* addr) { _previous_address = addr; }
188 HeapWord* previous() { return _previous_address; }
189 // A return value of "true" can be used by the caller to decide
190 // if this object's end should *NOT* be recorded in
191 // _previous_address above.
192 virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
193 };
194
195 // A version of ObjectClosure that is expected to be robust
196 // in the face of possibly uninitialized objects.
197 class ObjectClosureCareful : public ObjectClosure {
198 public:
199 virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;
200 virtual size_t do_object_careful(oop p) = 0;
201 };
202
203 // The following are used in CompactibleFreeListSpace and
204 // ConcurrentMarkSweepGeneration.
205
206 // Blk closure (abstract class)
207 class BlkClosure : public StackObj {
208 public:
209 virtual size_t do_blk(HeapWord* addr) = 0;
210 };
211
212 // A version of BlkClosure that is expected to be robust
213 // in the face of possibly uninitialized objects.
214 class BlkClosureCareful : public BlkClosure {
215 public:
216 size_t do_blk(HeapWord* addr) {
217 guarantee(false, "call do_blk_careful instead");
218 return 0;
219 }
220 virtual size_t do_blk_careful(HeapWord* addr) = 0;
221 };
222
223 // SpaceClosure is used for iterating over spaces
224
225 class Space;
226 class CompactibleSpace;
227
228 class SpaceClosure : public StackObj {
229 public:
230 // Called for each space
231 virtual void do_space(Space* s) = 0;
232 };
233
234 class CompactibleSpaceClosure : public StackObj {
235 public:
236 // Called for each compactible space
237 virtual void do_space(CompactibleSpace* s) = 0;
238 };
239
240
241 // CodeBlobClosure is used for iterating through code blobs
242 // in the code cache or on thread stacks
243
244 class CodeBlobClosure : public Closure {
245 public:
246 // Called for each code blob.
247 virtual void do_code_blob(CodeBlob* cb) = 0;
248 };
249
250
251 class MarkingCodeBlobClosure : public CodeBlobClosure {
252 public:
253 // Called for each code blob, but at most once per unique blob.
254 virtual void do_newly_marked_nmethod(nmethod* nm) = 0;
255
256 virtual void do_code_blob(CodeBlob* cb);
257 // = { if (!nmethod(cb)->test_set_oops_do_mark()) do_newly_marked_nmethod(cb); }
258
259 class MarkScope : public StackObj {
260 protected:
261 bool _active;
262 public:
263 MarkScope(bool activate = true);
264 // = { if (active) nmethod::oops_do_marking_prologue(); }
265 ~MarkScope();
266 // = { if (active) nmethod::oops_do_marking_epilogue(); }
267 };
268 };
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 MarkingCodeBlobClosure {
274 OopClosure* _cl;
275 bool _do_marking;
276 public:
277 virtual void do_newly_marked_nmethod(nmethod* cb);
278 // = { cb->oops_do(_cl); }
279 virtual void do_code_blob(CodeBlob* cb);
280 // = { if (_do_marking) super::do_code_blob(cb); else cb->oops_do(_cl); }
281 CodeBlobToOopClosure(OopClosure* cl, bool do_marking)
282 : _cl(cl), _do_marking(do_marking) {}
283 };
284
285
286
287 // MonitorClosure is used for iterating over monitors in the monitors cache
288
289 class ObjectMonitor;
290
291 class MonitorClosure : public StackObj {
292 public:
293 // called for each monitor in cache
294 virtual void do_monitor(ObjectMonitor* m) = 0;
295 };
296
297 // A closure that is applied without any arguments.
298 class VoidClosure : public StackObj {
299 public:
300 // I would have liked to declare this a pure virtual, but that breaks
301 // in mysterious ways, for unknown reasons.
302 virtual void do_void();
303 };
304
305
306 // YieldClosure is intended for use by iteration loops
307 // to incrementalize their work, allowing interleaving
308 // of an interruptable task so as to allow other
309 // threads to run (which may not otherwise be able to access
310 // exclusive resources, for instance). Additionally, the
311 // closure also allows for aborting an ongoing iteration
312 // by means of checking the return value from the polling
313 // call.
314 class YieldClosure : public StackObj {
315 public:
316 virtual bool should_return() = 0;
317 };
318
319 // Abstract closure for serializing data (read or write).
320
321 class SerializeClosure : public Closure {
322 public:
323 // Return bool indicating whether closure implements read or write.
324 virtual bool reading() const = 0;
325
326 // Read/write the void pointer pointed to by p.
327 virtual void do_ptr(void** p) = 0;
328
329 // Read/write the region specified.
330 virtual void do_region(u_char* start, size_t size) = 0;
331
332 // Check/write the tag. If reading, then compare the tag against
333 // the passed in value and fail is they don't match. This allows
334 // for verification that sections of the serialized data are of the
335 // correct length.
336 virtual void do_tag(int tag) = 0;
337 };
338
339 class SymbolClosure : public StackObj {
340 public:
341 virtual void do_symbol(Symbol**) = 0;
342
343 // Clear LSB in symbol address; it can be set by CPSlot.
344 static Symbol* load_symbol(Symbol** p) {
345 return (Symbol*)(intptr_t(*p) & ~1);
346 }
347
348 // Store symbol, adjusting new pointer if the original pointer was adjusted
349 // (symbol references in constant pool slots have their LSB set to 1).
350 static void store_symbol(Symbol** p, Symbol* sym) {
351 *p = (Symbol*)(intptr_t(sym) | (intptr_t(*p) & 1));
352 }
353 };
354
355 #endif // SHARE_VM_MEMORY_ITERATOR_HPP