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
 21  * questions.
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 23  */
 24 
 25 #ifndef SHARE_GC_SERIAL_MARKSWEEP_HPP
 26 #define SHARE_GC_SERIAL_MARKSWEEP_HPP
 27 
 28 #include "gc/shared/collectedHeap.hpp"
 29 #include "gc/shared/genOopClosures.hpp"
 30 #include "gc/shared/stringdedup/stringDedup.hpp"
 31 #include "gc/shared/taskqueue.hpp"
 32 #include "memory/iterator.hpp"
 33 #include "oops/markWord.hpp"
 34 #include "oops/oop.hpp"
 35 #include "runtime/timer.hpp"
 36 #include "utilities/growableArray.hpp"
 37 #include "utilities/stack.hpp"
 38 
 39 class ReferenceProcessor;
 40 class DataLayout;
 41 class SerialOldTracer;
 42 class STWGCTimer;
 43 
 44 // MarkSweep takes care of global mark-compact garbage collection for a
 45 // GenCollectedHeap using a four-phase pointer forwarding algorithm.  All
 46 // generations are assumed to support marking; those that can also support
 47 // compaction.
 48 //
 49 // Class unloading will only occur when a full gc is invoked.
 50 
 51 // declared at end
 52 class PreservedMark;
 53 class MarkAndPushClosure;
 54 class AdjustPointerClosure;
 55 
 56 class MarkSweep : AllStatic {
 57   //
 58   // Inline closure decls
 59   //
 60   class FollowRootClosure: public BasicOopIterateClosure {
 61    public:
 62     virtual void do_oop(oop* p);
 63     virtual void do_oop(narrowOop* p);
 64   };
 65 
 66   class FollowStackClosure: public VoidClosure {
 67    public:
 68     virtual void do_void();
 69   };
 70 
 71   // Used for java/lang/ref handling
 72   class IsAliveClosure: public BoolObjectClosure {
 73    public:
 74     virtual bool do_object_b(oop p);
 75   };
 76 
 77   class KeepAliveClosure: public OopClosure {
 78    protected:
 79     template <class T> void do_oop_work(T* p);
 80    public:
 81     virtual void do_oop(oop* p);
 82     virtual void do_oop(narrowOop* p);
 83   };
 84 
 85   //
 86   // Friend decls
 87   //
 88   friend class AdjustPointerClosure;
 89   friend class KeepAliveClosure;
 90   friend class VM_MarkSweep;
 91 
 92   //
 93   // Vars
 94   //
 95  protected:
 96   // Total invocations of a MarkSweep collection
 97   static uint _total_invocations;
 98 
 99   // Traversal stacks used during phase1
100   static Stack<oop, mtGC>                      _marking_stack;
101   static Stack<ObjArrayTask, mtGC>             _objarray_stack;
102 
103   // Space for storing/restoring mark word
104   static Stack<PreservedMark, mtGC>      _preserved_overflow_stack;
105   static size_t                          _preserved_count;
106   static size_t                          _preserved_count_max;
107   static PreservedMark*                  _preserved_marks;
108 
109   // Reference processing (used in ...follow_contents)
110   static ReferenceProcessor*             _ref_processor;
111 
112   static STWGCTimer*                     _gc_timer;
113   static SerialOldTracer*                _gc_tracer;
114 
115   static StringDedup::Requests* _string_dedup_requests;
116 
117   // Non public closures
118   static KeepAliveClosure keep_alive;
119 
120  public:
121   static void initialize();
122 
123   // Public closures
124   static IsAliveClosure       is_alive;
125   static FollowRootClosure    follow_root_closure;
126   static MarkAndPushClosure   mark_and_push_closure;
127   static FollowStackClosure   follow_stack_closure;
128   static CLDToOopClosure      follow_cld_closure;
129   static AdjustPointerClosure adjust_pointer_closure;
130   static CLDToOopClosure      adjust_cld_closure;
131 
132   // Accessors
133   static uint total_invocations() { return _total_invocations; }
134 
135   // Reference Processing
136   static ReferenceProcessor* const ref_processor() { return _ref_processor; }
137   static void set_ref_processor(ReferenceProcessor* rp);
138 
139   static STWGCTimer* gc_timer() { return _gc_timer; }
140   static SerialOldTracer* gc_tracer() { return _gc_tracer; }
141 
142   static void preserve_mark(oop p, markWord mark);
143                                 // Save the mark word so it can be restored later
144   static void adjust_marks();   // Adjust the pointers in the preserved marks table
145   static void restore_marks();  // Restore the marks that we saved in preserve_mark
146 
147   static int adjust_pointers(oop obj);
148 
149   static void follow_stack();   // Empty marking stack.
150 
151   static void follow_klass(Klass* klass);
152 
153   static void follow_cld(ClassLoaderData* cld);
154 
155   template <class T> static inline void adjust_pointer(T* p);
156 
157   // Check mark and maybe push on marking stack
158   template <class T> static void mark_and_push(T* p);
159 
160  private:
161   // Call backs for marking
162   static void mark_object(oop obj);
163   // Mark pointer and follow contents.  Empty marking stack afterwards.
164   template <class T> static inline void follow_root(T* p);
165 
166   static inline void push_objarray(oop obj, size_t index);
167 
168   static void follow_object(oop obj);
169 
170   static void follow_array(objArrayOop array);
171 
172   static void follow_array_chunk(objArrayOop array, int index);
173 };
174 
175 class MarkAndPushClosure: public OopIterateClosure {
176 public:
177   template <typename T> void do_oop_work(T* p);
178   virtual void do_oop(oop* p);
179   virtual void do_oop(narrowOop* p);
180 
181   virtual bool do_metadata() { return true; }
182   virtual void do_klass(Klass* k);
183   virtual void do_cld(ClassLoaderData* cld);
184 
185   void set_ref_discoverer(ReferenceDiscoverer* rd) {
186     set_ref_discoverer_internal(rd);
187   }
188 };
189 
190 class AdjustPointerClosure: public BasicOopIterateClosure {
191  public:
192   template <typename T> void do_oop_work(T* p);
193   virtual void do_oop(oop* p);
194   virtual void do_oop(narrowOop* p);
195   virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
196 };
197 
198 class PreservedMark {
199 private:
200   oop _obj;
201   markWord _mark;
202 
203 public:
204   PreservedMark(oop obj, markWord mark) : _obj(obj), _mark(mark) {}
205   void adjust_pointer();
206   void restore();
207 };
208 
209 #endif // SHARE_GC_SERIAL_MARKSWEEP_HPP