1 /*
2 * Copyright (c) 1997, 2009, 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
21 * questions.
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23 */
24
25 // The following classes are C++ `closures` for iterating over objects, roots and spaces
26
27 class CodeBlob;
28 class nmethod;
29 class ReferenceProcessor;
30 class DataLayout;
31
32 // Closure provides abortability.
33
34 class Closure : public StackObj {
35 protected:
36 bool _abort;
37 void set_abort() { _abort = true; }
38 public:
39 Closure() : _abort(false) {}
40 // A subtype can use this mechanism to indicate to some iterator mapping
41 // functions that the iteration should cease.
42 bool abort() { return _abort; }
43 void clear_abort() { _abort = false; }
44 };
45
46 // OopClosure is used for iterating through roots (oop*)
47
48 class OopClosure : public Closure {
49 public:
50 ReferenceProcessor* _ref_processor;
51 OopClosure(ReferenceProcessor* rp) : _ref_processor(rp) { }
52 OopClosure() : _ref_processor(NULL) { }
53 virtual void do_oop(oop* o) = 0;
54 virtual void do_oop_v(oop* o) { do_oop(o); }
55 virtual void do_oop(narrowOop* o) = 0;
56 virtual void do_oop_v(narrowOop* o) { do_oop(o); }
57
58 // In support of post-processing of weak links of KlassKlass objects;
59 // see KlassKlass::oop_oop_iterate().
60
61 virtual const bool should_remember_klasses() const {
62 assert(!must_remember_klasses(), "Should have overriden this method.");
63 return false;
64 }
65
66 virtual void remember_klass(Klass* k) { /* do nothing */ }
67
68 // In support of post-processing of weak references in
69 // ProfileData (MethodDataOop) objects; see, for example,
70 // VirtualCallData::oop_iterate().
71 virtual const bool should_remember_mdo() const { return false; }
72 virtual void remember_mdo(DataLayout* v) { /* do nothing */ }
73
74 // The methods below control how object iterations invoking this closure
75 // should be performed:
76
77 // If "true", invoke on header klass field.
78 bool do_header() { return true; } // Note that this is non-virtual.
79 // Controls how prefetching is done for invocations of this closure.
80 Prefetch::style prefetch_style() { // Note that this is non-virtual.
81 return Prefetch::do_none;
82 }
83
84 // True iff this closure may be safely applied more than once to an oop
85 // location without an intervening "major reset" (like the end of a GC).
86 virtual bool idempotent() { return false; }
87 virtual bool apply_to_weak_ref_discovered_field() { return false; }
88
89 #ifdef ASSERT
90 static bool _must_remember_klasses;
91 static bool must_remember_klasses();
92 static void set_must_remember_klasses(bool v);
93 #endif
94 };
95
96 // ObjectClosure is used for iterating through an object space
97
98 class ObjectClosure : public Closure {
99 public:
100 // Called for each object.
101 virtual void do_object(oop obj) = 0;
102 };
103
104
105 class BoolObjectClosure : public ObjectClosure {
106 public:
107 virtual bool do_object_b(oop obj) = 0;
108 };
109
110 // Applies an oop closure to all ref fields in objects iterated over in an
111 // object iteration.
112 class ObjectToOopClosure: public ObjectClosure {
113 OopClosure* _cl;
114 public:
115 void do_object(oop obj);
116 ObjectToOopClosure(OopClosure* cl) : _cl(cl) {}
117 };
118
119 // A version of ObjectClosure with "memory" (see _previous_address below)
120 class UpwardsObjectClosure: public BoolObjectClosure {
121 HeapWord* _previous_address;
122 public:
123 UpwardsObjectClosure() : _previous_address(NULL) { }
124 void set_previous(HeapWord* addr) { _previous_address = addr; }
125 HeapWord* previous() { return _previous_address; }
126 // A return value of "true" can be used by the caller to decide
127 // if this object's end should *NOT* be recorded in
128 // _previous_address above.
129 virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
130 };
131
132 // A version of ObjectClosure that is expected to be robust
133 // in the face of possibly uninitialized objects.
134 class ObjectClosureCareful : public ObjectClosure {
135 public:
136 virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;
137 virtual size_t do_object_careful(oop p) = 0;
138 };
139
140 // The following are used in CompactibleFreeListSpace and
141 // ConcurrentMarkSweepGeneration.
142
143 // Blk closure (abstract class)
144 class BlkClosure : public StackObj {
145 public:
146 virtual size_t do_blk(HeapWord* addr) = 0;
147 };
148
149 // A version of BlkClosure that is expected to be robust
150 // in the face of possibly uninitialized objects.
151 class BlkClosureCareful : public BlkClosure {
152 public:
153 size_t do_blk(HeapWord* addr) {
154 guarantee(false, "call do_blk_careful instead");
155 return 0;
156 }
157 virtual size_t do_blk_careful(HeapWord* addr) = 0;
158 };
159
160 // SpaceClosure is used for iterating over spaces
161
162 class Space;
163 class CompactibleSpace;
164
165 class SpaceClosure : public StackObj {
166 public:
167 // Called for each space
168 virtual void do_space(Space* s) = 0;
169 };
170
171 class CompactibleSpaceClosure : public StackObj {
172 public:
173 // Called for each compactible space
174 virtual void do_space(CompactibleSpace* s) = 0;
175 };
176
177
178 // CodeBlobClosure is used for iterating through code blobs
179 // in the code cache or on thread stacks
180
181 class CodeBlobClosure : public Closure {
182 public:
183 // Called for each code blob.
184 virtual void do_code_blob(CodeBlob* cb) = 0;
185 };
186
187
188 class MarkingCodeBlobClosure : public CodeBlobClosure {
189 public:
190 // Called for each code blob, but at most once per unique blob.
191 virtual void do_newly_marked_nmethod(nmethod* nm) = 0;
192
193 virtual void do_code_blob(CodeBlob* cb);
194 // = { if (!nmethod(cb)->test_set_oops_do_mark()) do_newly_marked_nmethod(cb); }
195
196 class MarkScope : public StackObj {
197 protected:
198 bool _active;
199 public:
200 MarkScope(bool activate = true);
201 // = { if (active) nmethod::oops_do_marking_prologue(); }
202 ~MarkScope();
203 // = { if (active) nmethod::oops_do_marking_epilogue(); }
204 };
205 };
206
207
208 // Applies an oop closure to all ref fields in code blobs
209 // iterated over in an object iteration.
210 class CodeBlobToOopClosure: public MarkingCodeBlobClosure {
211 OopClosure* _cl;
212 bool _do_marking;
213 public:
214 virtual void do_newly_marked_nmethod(nmethod* cb);
215 // = { cb->oops_do(_cl); }
216 virtual void do_code_blob(CodeBlob* cb);
217 // = { if (_do_marking) super::do_code_blob(cb); else cb->oops_do(_cl); }
218 CodeBlobToOopClosure(OopClosure* cl, bool do_marking)
219 : _cl(cl), _do_marking(do_marking) {}
220 };
221
222
223
224 // MonitorClosure is used for iterating over monitors in the monitors cache
225
226 class ObjectMonitor;
227
228 class MonitorClosure : public StackObj {
229 public:
230 // called for each monitor in cache
231 virtual void do_monitor(ObjectMonitor* m) = 0;
232 };
233
234 // A closure that is applied without any arguments.
235 class VoidClosure : public StackObj {
236 public:
237 // I would have liked to declare this a pure virtual, but that breaks
238 // in mysterious ways, for unknown reasons.
239 virtual void do_void();
240 };
241
242
243 // YieldClosure is intended for use by iteration loops
244 // to incrementalize their work, allowing interleaving
245 // of an interruptable task so as to allow other
246 // threads to run (which may not otherwise be able to access
247 // exclusive resources, for instance). Additionally, the
248 // closure also allows for aborting an ongoing iteration
249 // by means of checking the return value from the polling
250 // call.
251 class YieldClosure : public StackObj {
252 public:
253 virtual bool should_return() = 0;
254 };
255
256 // Abstract closure for serializing data (read or write).
257
258 class SerializeOopClosure : public OopClosure {
259 public:
260 // Return bool indicating whether closure implements read or write.
261 virtual bool reading() const = 0;
262
263 // Read/write the int pointed to by i.
264 virtual void do_int(int* i) = 0;
265
266 // Read/write the size_t pointed to by i.
267 virtual void do_size_t(size_t* i) = 0;
268
269 // Read/write the void pointer pointed to by p.
270 virtual void do_ptr(void** p) = 0;
271
272 // Read/write the HeapWord pointer pointed to be p.
273 virtual void do_ptr(HeapWord** p) = 0;
274
275 // Read/write the region specified.
276 virtual void do_region(u_char* start, size_t size) = 0;
277
278 // Check/write the tag. If reading, then compare the tag against
279 // the passed in value and fail is they don't match. This allows
280 // for verification that sections of the serialized data are of the
281 // correct length.
282 virtual void do_tag(int tag) = 0;
283 };
284
285 #ifdef ASSERT
286 // This class is used to flag phases of a collection that
287 // can unload classes and which should override the
288 // should_remember_klasses() and remember_klass() of OopClosure.
289 // The _must_remember_klasses is set in the contructor and restored
290 // in the destructor. _must_remember_klasses is checked in assertions
291 // in the OopClosure implementations of should_remember_klasses() and
292 // remember_klass() and the expectation is that the OopClosure
293 // implementation should not be in use if _must_remember_klasses is set.
294 // Instances of RememberKlassesChecker can be place in
295 // marking phases of collections which can do class unloading.
296 // RememberKlassesChecker can be passed "false" to turn off checking.
297 // It is used by CMS when CMS yields to a different collector.
298 class RememberKlassesChecker: StackObj {
299 bool _saved_state;
300 bool _do_check;
301 public:
302 RememberKlassesChecker(bool checking_on) : _saved_state(false),
303 _do_check(true) {
304 // The ClassUnloading unloading flag affects the collectors except
305 // for CMS.
306 // CMS unloads classes if CMSClassUnloadingEnabled is true or
307 // if ExplicitGCInvokesConcurrentAndUnloadsClasses is true and
308 // the current collection is an explicit collection. Turning
309 // on the checking in general for
310 // ExplicitGCInvokesConcurrentAndUnloadsClasses and
311 // UseConcMarkSweepGC should not lead to false positives.
312 _do_check =
313 ClassUnloading && !UseConcMarkSweepGC ||
314 CMSClassUnloadingEnabled && UseConcMarkSweepGC ||
315 ExplicitGCInvokesConcurrentAndUnloadsClasses && UseConcMarkSweepGC;
316 if (_do_check) {
317 _saved_state = OopClosure::must_remember_klasses();
318 OopClosure::set_must_remember_klasses(checking_on);
319 }
320 }
321 ~RememberKlassesChecker() {
322 if (_do_check) {
323 OopClosure::set_must_remember_klasses(_saved_state);
324 }
325 }
326 };
327 #endif // ASSERT