1 /*
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  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  *
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 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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 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 {
 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   virtual void do_oop_no_buffering(oop* o) { do_oop(o); }
 58   virtual void do_oop_no_buffering(narrowOop* o) { do_oop(o); }
 59 };
 60 
 61 class DoNothingClosure : public OopClosure {
 62  public:
 63   virtual void do_oop(oop* p)       {}
 64   virtual void do_oop(narrowOop* p) {}
 65 };
 66 extern DoNothingClosure do_nothing_cl;
 67 
 68 // OopIterateClosure adds extra code to be run during oop iterations.
 69 // This is needed by the GC and is extracted to a separate type to not
 70 // pollute the OopClosure interface.
 71 class OopIterateClosure : public OopClosure {
 72  private:
 73   ReferenceDiscoverer* _ref_discoverer;
 74 
 75  protected:
 76   OopIterateClosure(ReferenceDiscoverer* rd) : _ref_discoverer(rd) { }
 77   OopIterateClosure() : _ref_discoverer(nullptr) { }
 78   ~OopIterateClosure() { }
 79 
 80   void set_ref_discoverer_internal(ReferenceDiscoverer* rd) { _ref_discoverer = rd; }
 81 
 82  public:
 83   ReferenceDiscoverer* ref_discoverer() const { return _ref_discoverer; }
 84 
 85   // Iteration of InstanceRefKlasses differ depending on the closure,
 86   // the below enum describes the different alternatives.
 87   enum ReferenceIterationMode {
 88     DO_DISCOVERY,                // Apply closure and discover references
 89     DO_DISCOVERED_AND_DISCOVERY, // Apply closure to discovered field and do discovery
 90     DO_FIELDS,                   // Apply closure to all fields
 91     DO_FIELDS_EXCEPT_REFERENT    // Apply closure to all fields except the referent field
 92   };
 93 
 94   // The default iteration mode is to do discovery.
 95   virtual ReferenceIterationMode reference_iteration_mode() { return DO_DISCOVERY; }
 96 
 97   // If the do_metadata functions return "true",
 98   // we invoke the following when running oop_iterate():
 99   //
100   // 1) do_klass on the header klass pointer.
101   // 2) do_klass on the klass pointer in the mirrors.
102   // 3) do_cld   on the class loader data in class loaders.
103   //
104   // Used to determine metadata liveness for class unloading GCs.
105 
106   virtual bool do_metadata() = 0;
107   virtual void do_klass(Klass* k) = 0;
108   virtual void do_cld(ClassLoaderData* cld) = 0;
109 
110   // Class redefinition needs to get notified about methods from stackChunkOops
111   virtual void do_method(Method* m) = 0;
112   // The code cache unloading needs to get notified about methods from stackChunkOops
113   virtual void do_nmethod(nmethod* nm) = 0;
114 };
115 
116 // An OopIterateClosure that can be used when there's no need to visit the Metadata.
117 class BasicOopIterateClosure : public OopIterateClosure {
118 public:
119   BasicOopIterateClosure(ReferenceDiscoverer* rd = nullptr) : OopIterateClosure(rd) {}
120 
121   virtual bool do_metadata() { return false; }
122   virtual void do_klass(Klass* k) { ShouldNotReachHere(); }
123   virtual void do_cld(ClassLoaderData* cld) { ShouldNotReachHere(); }
124   virtual void do_method(Method* m) { ShouldNotReachHere(); }
125   virtual void do_nmethod(nmethod* nm) { ShouldNotReachHere(); }
126 };
127 
128 // Interface for applying an OopClosure to a set of oops.
129 class OopIterator {
130 public:
131   virtual void oops_do(OopClosure* cl) = 0;
132 };
133 
134 enum class derived_base : intptr_t;
135 enum class derived_pointer : intptr_t;
136 class DerivedOopClosure : public Closure {
137  public:
138   enum { SkipNull = true };
139   virtual void do_derived_oop(derived_base* base, derived_pointer* derived) = 0;
140 };
141 
142 class BufferedValueClosure : public Closure {
143 public:
144   virtual void do_buffered_value(oop* p) = 0;
145 };
146 
147 class KlassClosure : public Closure {
148  public:
149   virtual void do_klass(Klass* k) = 0;
150 };
151 
152 class CLDClosure : public Closure {
153  public:
154   virtual void do_cld(ClassLoaderData* cld) = 0;
155 };
156 
157 class MetadataClosure : public Closure {
158  public:
159   virtual void do_metadata(Metadata* md) = 0;
160 };
161 
162 
163 class CLDToOopClosure : public CLDClosure {
164   OopClosure*       _oop_closure;
165   int               _cld_claim;
166 
167  public:
168   CLDToOopClosure(OopClosure* oop_closure,
169                   int cld_claim) :
170       _oop_closure(oop_closure),
171       _cld_claim(cld_claim) {}
172 
173   void do_cld(ClassLoaderData* cld);
174 };
175 
176 template <int claim>
177 class ClaimingCLDToOopClosure : public CLDToOopClosure {
178 public:
179   ClaimingCLDToOopClosure(OopClosure* cl) : CLDToOopClosure(cl, claim) {}
180 };
181 
182 class ClaimMetadataVisitingOopIterateClosure : public OopIterateClosure {
183  protected:
184   const int _claim;
185 
186  public:
187   ClaimMetadataVisitingOopIterateClosure(int claim, ReferenceDiscoverer* rd = nullptr) :
188       OopIterateClosure(rd),
189       _claim(claim) { }
190 
191   virtual bool do_metadata() { return true; }
192   virtual void do_klass(Klass* k);
193   virtual void do_cld(ClassLoaderData* cld);
194   virtual void do_method(Method* m);
195   virtual void do_nmethod(nmethod* nm);
196 };
197 
198 // The base class for all concurrent marking closures,
199 // that participates in class unloading.
200 // It's used to proxy through the metadata to the oops defined in them.
201 class MetadataVisitingOopIterateClosure: public ClaimMetadataVisitingOopIterateClosure {
202  public:
203   MetadataVisitingOopIterateClosure(ReferenceDiscoverer* rd = nullptr);
204 };
205 
206 // ObjectClosure is used for iterating through an object space
207 
208 class ObjectClosure : public Closure {
209  public:
210   // Called for each object.
211   virtual void do_object(oop obj) = 0;
212 };
213 
214 class BoolObjectClosure : public Closure {
215  public:
216   virtual bool do_object_b(oop obj) = 0;
217 };
218 
219 class OopFieldClosure {
220 public:
221   virtual void do_field(oop base, oop* p) = 0;
222 };
223 
224 class AlwaysTrueClosure: public BoolObjectClosure {
225  public:
226   bool do_object_b(oop p) { return true; }
227 };
228 
229 class AlwaysFalseClosure : public BoolObjectClosure {
230  public:
231   bool do_object_b(oop p) { return false; }
232 };
233 
234 // Applies an oop closure to all ref fields in objects iterated over in an
235 // object iteration.
236 class ObjectToOopClosure: public ObjectClosure {
237   OopIterateClosure* _cl;
238 public:
239   void do_object(oop obj);
240   ObjectToOopClosure(OopIterateClosure* cl) : _cl(cl) {}
241 };
242 
243 // SpaceClosure is used for iterating over spaces
244 
245 class Space;
246 
247 class SpaceClosure : public StackObj {
248  public:
249   // Called for each space
250   virtual void do_space(Space* s) = 0;
251 };
252 
253 // CodeBlobClosure is used for iterating through code blobs
254 // in the code cache or on thread stacks
255 
256 class CodeBlobClosure : public Closure {
257  public:
258   // Called for each code blob.
259   virtual void do_code_blob(CodeBlob* cb) = 0;
260 };
261 
262 // Applies an oop closure to all ref fields in code blobs
263 // iterated over in an object iteration.
264 class CodeBlobToOopClosure : public CodeBlobClosure {
265  protected:
266   OopClosure* _cl;
267   bool _fix_relocations;
268   void do_nmethod(nmethod* nm);
269  public:
270   // If fix_relocations(), then cl must copy objects to their new location immediately to avoid
271   // patching nmethods with the old locations.
272   CodeBlobToOopClosure(OopClosure* cl, bool fix_relocations) : _cl(cl), _fix_relocations(fix_relocations) {}
273   virtual void do_code_blob(CodeBlob* cb);
274 
275   bool fix_relocations() const { return _fix_relocations; }
276   const static bool FixRelocations = true;
277 };
278 
279 class MarkingCodeBlobClosure : public CodeBlobToOopClosure {
280   bool _keepalive_nmethods;
281 
282  public:
283   MarkingCodeBlobClosure(OopClosure* cl, bool fix_relocations, bool keepalive_nmethods) :
284       CodeBlobToOopClosure(cl, fix_relocations),
285       _keepalive_nmethods(keepalive_nmethods) {}
286 
287   // Called for each code blob, but at most once per unique blob.
288   virtual void do_code_blob(CodeBlob* cb);
289 };
290 
291 class NMethodClosure : public Closure {
292  public:
293   virtual void do_nmethod(nmethod* n) = 0;
294 };
295 
296 class CodeBlobToNMethodClosure : public CodeBlobClosure {
297   NMethodClosure* const _nm_cl;
298 
299  public:
300   CodeBlobToNMethodClosure(NMethodClosure* nm_cl) : _nm_cl(nm_cl) {}
301 
302   virtual void do_code_blob(CodeBlob* cb);
303 };
304 
305 // MonitorClosure is used for iterating over monitors in the monitors cache
306 
307 class ObjectMonitor;
308 
309 class MonitorClosure : public StackObj {
310  public:
311   // called for each monitor in cache
312   virtual void do_monitor(ObjectMonitor* m) = 0;
313 };
314 
315 // A closure that is applied without any arguments.
316 class VoidClosure : public StackObj {
317  public:
318   virtual void do_void() = 0;
319 };
320 
321 
322 // YieldClosure is intended for use by iteration loops
323 // to incrementalize their work, allowing interleaving
324 // of an interruptible task so as to allow other
325 // threads to run (which may not otherwise be able to access
326 // exclusive resources, for instance). Additionally, the
327 // closure also allows for aborting an ongoing iteration
328 // by means of checking the return value from the polling
329 // call.
330 class YieldClosure : public StackObj {
331 public:
332  virtual bool should_return() = 0;
333 
334  // Yield on a fine-grain level. The check in case of not yielding should be very fast.
335  virtual bool should_return_fine_grain() { return false; }
336 };
337 
338 class SymbolClosure : public StackObj {
339  public:
340   virtual void do_symbol(Symbol**) = 0;
341 };
342 
343 template <typename E>
344 class CompareClosure : public Closure {
345 public:
346     virtual int do_compare(const E&, const E&) = 0;
347 };
348 
349 class OopIteratorClosureDispatch {
350  public:
351   template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass);
352   template <typename OopClosureType> static void oop_oop_iterate(OopClosureType* cl, oop obj, Klass* klass, MemRegion mr);
353   template <typename OopClosureType> static void oop_oop_iterate_backwards(OopClosureType* cl, oop obj, Klass* klass);
354 };
355 
356 #endif // SHARE_MEMORY_ITERATOR_HPP