1 /*
2 * Copyright (c) 1997, 2010, 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
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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
40 // Closure provides abortability.
41
42 class Closure : public StackObj {
43 protected:
44 bool _abort;
45 void set_abort() { _abort = true; }
46 public:
47 Closure() : _abort(false) {}
48 // A subtype can use this mechanism to indicate to some iterator mapping
49 // functions that the iteration should cease.
50 bool abort() { return _abort; }
51 void clear_abort() { _abort = false; }
52 };
53
54 // OopClosure is used for iterating through roots (oop*)
55
56 class OopClosure : public Closure {
57 public:
58 ReferenceProcessor* _ref_processor;
59 OopClosure(ReferenceProcessor* rp) : _ref_processor(rp) { }
60 OopClosure() : _ref_processor(NULL) { }
61 virtual void do_oop(oop* o) = 0;
62 virtual void do_oop_v(oop* o) { do_oop(o); }
63 virtual void do_oop(narrowOop* o) = 0;
64 virtual void do_oop_v(narrowOop* o) { do_oop(o); }
65
66 // In support of post-processing of weak links of KlassKlass objects;
67 // see KlassKlass::oop_oop_iterate().
68
69 virtual const bool should_remember_klasses() const {
70 assert(!must_remember_klasses(), "Should have overriden this method.");
71 return false;
72 }
73
74 virtual void remember_klass(Klass* k) { /* do nothing */ }
75
76 // In support of post-processing of weak references in
77 // ProfileData (MethodDataOop) objects; see, for example,
78 // VirtualCallData::oop_iterate().
79 virtual const bool should_remember_mdo() const { return false; }
80 virtual void remember_mdo(DataLayout* v) { /* do nothing */ }
81
82 // The methods below control how object iterations invoking this closure
83 // should be performed:
84
85 // If "true", invoke on header klass field.
86 bool do_header() { return true; } // Note that this is non-virtual.
87 // Controls how prefetching is done for invocations of this closure.
88 Prefetch::style prefetch_style() { // Note that this is non-virtual.
89 return Prefetch::do_none;
90 }
91
92 // True iff this closure may be safely applied more than once to an oop
93 // location without an intervening "major reset" (like the end of a GC).
94 virtual bool idempotent() { return false; }
95 virtual bool apply_to_weak_ref_discovered_field() { return false; }
96
97 #ifdef ASSERT
98 static bool _must_remember_klasses;
99 static bool must_remember_klasses();
100 static void set_must_remember_klasses(bool v);
101 #endif
102 };
103
104 // ObjectClosure is used for iterating through an object space
105
106 class ObjectClosure : public Closure {
107 public:
108 // Called for each object.
109 virtual void do_object(oop obj) = 0;
110 };
111
112
113 class BoolObjectClosure : public ObjectClosure {
114 public:
115 virtual bool do_object_b(oop obj) = 0;
116 };
117
118 // Applies an oop closure to all ref fields in objects iterated over in an
119 // object iteration.
120 class ObjectToOopClosure: public ObjectClosure {
121 OopClosure* _cl;
122 public:
123 void do_object(oop obj);
124 ObjectToOopClosure(OopClosure* cl) : _cl(cl) {}
125 };
126
127 // A version of ObjectClosure with "memory" (see _previous_address below)
128 class UpwardsObjectClosure: public BoolObjectClosure {
129 HeapWord* _previous_address;
130 public:
131 UpwardsObjectClosure() : _previous_address(NULL) { }
132 void set_previous(HeapWord* addr) { _previous_address = addr; }
133 HeapWord* previous() { return _previous_address; }
134 // A return value of "true" can be used by the caller to decide
135 // if this object's end should *NOT* be recorded in
136 // _previous_address above.
137 virtual bool do_object_bm(oop obj, MemRegion mr) = 0;
138 };
139
140 // A version of ObjectClosure that is expected to be robust
141 // in the face of possibly uninitialized objects.
142 class ObjectClosureCareful : public ObjectClosure {
143 public:
144 virtual size_t do_object_careful_m(oop p, MemRegion mr) = 0;
145 virtual size_t do_object_careful(oop p) = 0;
146 };
147
148 // The following are used in CompactibleFreeListSpace and
149 // ConcurrentMarkSweepGeneration.
150
151 // Blk closure (abstract class)
152 class BlkClosure : public StackObj {
153 public:
154 virtual size_t do_blk(HeapWord* addr) = 0;
155 };
156
157 // A version of BlkClosure that is expected to be robust
158 // in the face of possibly uninitialized objects.
159 class BlkClosureCareful : public BlkClosure {
160 public:
161 size_t do_blk(HeapWord* addr) {
162 guarantee(false, "call do_blk_careful instead");
163 return 0;
164 }
165 virtual size_t do_blk_careful(HeapWord* addr) = 0;
166 };
167
168 // SpaceClosure is used for iterating over spaces
169
170 class Space;
171 class CompactibleSpace;
172
173 class SpaceClosure : public StackObj {
174 public:
175 // Called for each space
176 virtual void do_space(Space* s) = 0;
177 };
178
179 class CompactibleSpaceClosure : public StackObj {
180 public:
181 // Called for each compactible space
182 virtual void do_space(CompactibleSpace* s) = 0;
183 };
184
185
186 // CodeBlobClosure is used for iterating through code blobs
187 // in the code cache or on thread stacks
188
189 class CodeBlobClosure : public Closure {
190 public:
191 // Called for each code blob.
192 virtual void do_code_blob(CodeBlob* cb) = 0;
193 };
194
195
196 class MarkingCodeBlobClosure : public CodeBlobClosure {
197 public:
198 // Called for each code blob, but at most once per unique blob.
199 virtual void do_newly_marked_nmethod(nmethod* nm) = 0;
200
201 virtual void do_code_blob(CodeBlob* cb);
202 // = { if (!nmethod(cb)->test_set_oops_do_mark()) do_newly_marked_nmethod(cb); }
203
204 class MarkScope : public StackObj {
205 protected:
206 bool _active;
207 public:
208 MarkScope(bool activate = true);
209 // = { if (active) nmethod::oops_do_marking_prologue(); }
210 ~MarkScope();
211 // = { if (active) nmethod::oops_do_marking_epilogue(); }
212 };
213 };
214
215
216 // Applies an oop closure to all ref fields in code blobs
217 // iterated over in an object iteration.
218 class CodeBlobToOopClosure: public MarkingCodeBlobClosure {
219 OopClosure* _cl;
220 bool _do_marking;
221 public:
222 virtual void do_newly_marked_nmethod(nmethod* cb);
223 // = { cb->oops_do(_cl); }
224 virtual void do_code_blob(CodeBlob* cb);
225 // = { if (_do_marking) super::do_code_blob(cb); else cb->oops_do(_cl); }
226 CodeBlobToOopClosure(OopClosure* cl, bool do_marking)
227 : _cl(cl), _do_marking(do_marking) {}
228 };
229
230
231
232 // MonitorClosure is used for iterating over monitors in the monitors cache
233
234 class ObjectMonitor;
235
236 class MonitorClosure : public StackObj {
237 public:
238 // called for each monitor in cache
239 virtual void do_monitor(ObjectMonitor* m) = 0;
240 };
241
242 // A closure that is applied without any arguments.
243 class VoidClosure : public StackObj {
244 public:
245 // I would have liked to declare this a pure virtual, but that breaks
246 // in mysterious ways, for unknown reasons.
247 virtual void do_void();
248 };
249
250
251 // YieldClosure is intended for use by iteration loops
252 // to incrementalize their work, allowing interleaving
253 // of an interruptable task so as to allow other
254 // threads to run (which may not otherwise be able to access
255 // exclusive resources, for instance). Additionally, the
256 // closure also allows for aborting an ongoing iteration
257 // by means of checking the return value from the polling
258 // call.
259 class YieldClosure : public StackObj {
260 public:
261 virtual bool should_return() = 0;
262 };
263
264 // Abstract closure for serializing data (read or write).
265
266 class SerializeOopClosure : public OopClosure {
267 public:
268 // Return bool indicating whether closure implements read or write.
269 virtual bool reading() const = 0;
270
271 // Read/write the int pointed to by i.
272 virtual void do_int(int* i) = 0;
273
274 // Read/write the size_t pointed to by i.
275 virtual void do_size_t(size_t* i) = 0;
276
277 // Read/write the void pointer pointed to by p.
278 virtual void do_ptr(void** p) = 0;
279
280 // Read/write the HeapWord pointer pointed to be p.
281 virtual void do_ptr(HeapWord** p) = 0;
282
283 // Read/write the region specified.
284 virtual void do_region(u_char* start, size_t size) = 0;
285
286 // Check/write the tag. If reading, then compare the tag against
287 // the passed in value and fail is they don't match. This allows
288 // for verification that sections of the serialized data are of the
289 // correct length.
290 virtual void do_tag(int tag) = 0;
291 };
292
293 #ifdef ASSERT
294 // This class is used to flag phases of a collection that
295 // can unload classes and which should override the
296 // should_remember_klasses() and remember_klass() of OopClosure.
297 // The _must_remember_klasses is set in the contructor and restored
298 // in the destructor. _must_remember_klasses is checked in assertions
299 // in the OopClosure implementations of should_remember_klasses() and
300 // remember_klass() and the expectation is that the OopClosure
301 // implementation should not be in use if _must_remember_klasses is set.
302 // Instances of RememberKlassesChecker can be place in
303 // marking phases of collections which can do class unloading.
304 // RememberKlassesChecker can be passed "false" to turn off checking.
305 // It is used by CMS when CMS yields to a different collector.
306 class RememberKlassesChecker: StackObj {
307 bool _saved_state;
308 bool _do_check;
309 public:
310 RememberKlassesChecker(bool checking_on) : _saved_state(false),
311 _do_check(true) {
312 // The ClassUnloading unloading flag affects the collectors except
313 // for CMS.
314 // CMS unloads classes if CMSClassUnloadingEnabled is true or
315 // if ExplicitGCInvokesConcurrentAndUnloadsClasses is true and
316 // the current collection is an explicit collection. Turning
317 // on the checking in general for
318 // ExplicitGCInvokesConcurrentAndUnloadsClasses and
319 // UseConcMarkSweepGC should not lead to false positives.
320 _do_check =
321 ClassUnloading && !UseConcMarkSweepGC ||
322 CMSClassUnloadingEnabled && UseConcMarkSweepGC ||
323 ExplicitGCInvokesConcurrentAndUnloadsClasses && UseConcMarkSweepGC;
324 if (_do_check) {
325 _saved_state = OopClosure::must_remember_klasses();
326 OopClosure::set_must_remember_klasses(checking_on);
327 }
328 }
329 ~RememberKlassesChecker() {
330 if (_do_check) {
331 OopClosure::set_must_remember_klasses(_saved_state);
332 }
333 }
334 };
335 #endif // ASSERT
336
337 #endif // SHARE_VM_MEMORY_ITERATOR_HPP