1 /*
  2  * Copyright (c) 1997, 2022, 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.
 22  *
 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/referenceProcessor.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 DataLayout;
 40 class SerialOldTracer;
 41 class STWGCTimer;
 42 
 43 // MarkSweep takes care of global mark-compact garbage collection for a
 44 // GenCollectedHeap using a four-phase pointer forwarding algorithm.  All
 45 // generations are assumed to support marking; those that can also support
 46 // compaction.
 47 //
 48 // Class unloading will only occur when a full gc is invoked.
 49 
 50 // declared at end
 51 class PreservedMark;
 52 class MarkAndPushClosure;
 53 class AdjustPointerClosure;
 54 
 55 class MarkSweep : AllStatic {
 56   //
 57   // Inline closure decls
 58   //
 59   class FollowRootClosure: public BasicOopIterateClosure {
 60    public:
 61     virtual void do_oop(oop* p);
 62     virtual void do_oop(narrowOop* p);
 63   };
 64 
 65   class FollowStackClosure: public VoidClosure {
 66    public:
 67     virtual void do_void();
 68   };
 69 
 70   // Used for java/lang/ref handling
 71   class IsAliveClosure: public BoolObjectClosure {
 72    public:
 73     virtual bool do_object_b(oop p);
 74   };
 75 
 76   class KeepAliveClosure: public OopClosure {
 77    protected:
 78     template <class T> void do_oop_work(T* p);
 79    public:
 80     virtual void do_oop(oop* p);
 81     virtual void do_oop(narrowOop* p);
 82   };
 83 
 84   //
 85   // Friend decls
 86   //
 87   friend class AdjustPointerClosure;
 88   friend class KeepAliveClosure;
 89 
 90   //
 91   // Vars
 92   //
 93  protected:
 94   // Total invocations of a MarkSweep collection
 95   static uint _total_invocations;
 96 
 97   // Traversal stacks used during phase1
 98   static Stack<oop, mtGC>                      _marking_stack;
 99   static Stack<ObjArrayTask, mtGC>             _objarray_stack;
100 
101   // Space for storing/restoring mark word
102   static Stack<PreservedMark, mtGC>      _preserved_overflow_stack;
103   static size_t                          _preserved_count;
104   static size_t                          _preserved_count_max;
105   static PreservedMark*                  _preserved_marks;
106 
107   static AlwaysTrueClosure               _always_true_closure;
108   static ReferenceProcessor*             _ref_processor;
109 
110   static STWGCTimer*                     _gc_timer;
111   static SerialOldTracer*                _gc_tracer;
112 
113   static StringDedup::Requests* _string_dedup_requests;
114 
115   // Non public closures
116   static KeepAliveClosure keep_alive;
117 
118  public:
119   static void initialize();
120 
121   // Public closures
122   static IsAliveClosure       is_alive;
123   static FollowRootClosure    follow_root_closure;
124   static MarkAndPushClosure   mark_and_push_closure;
125   static FollowStackClosure   follow_stack_closure;
126   static CLDToOopClosure      follow_cld_closure;
127   static AdjustPointerClosure adjust_pointer_closure;
128   static CLDToOopClosure      adjust_cld_closure;
129 
130   // Accessors
131   static uint total_invocations() { return _total_invocations; }
132 
133   // Reference Processing
134   static ReferenceProcessor* const ref_processor() { return _ref_processor; }
135 
136   static STWGCTimer* gc_timer() { return _gc_timer; }
137   static SerialOldTracer* gc_tracer() { return _gc_tracer; }
138 
139   static void preserve_mark(oop p, markWord mark);
140                                 // Save the mark word so it can be restored later
141   static void adjust_marks();   // Adjust the pointers in the preserved marks table
142   static void restore_marks();  // Restore the marks that we saved in preserve_mark
143 

144   static size_t adjust_pointers(oop obj);
145 
146   static void follow_stack();   // Empty marking stack.
147 
148   template <class T> static inline void adjust_pointer(T* p);

149 
150   // Check mark and maybe push on marking stack
151   template <class T> static void mark_and_push(T* p);
152 
153  private:



154   // Call backs for marking
155   static void mark_object(oop obj);
156   // Mark pointer and follow contents.  Empty marking stack afterwards.
157   template <class T> static inline void follow_root(T* p);
158 
159   static inline void push_objarray(oop obj, size_t index);
160 
161   static void follow_object(oop obj);
162 
163   static void follow_array(objArrayOop array);
164 
165   static void follow_array_chunk(objArrayOop array, int index);
166 };
167 
168 class MarkAndPushClosure: public ClaimMetadataVisitingOopIterateClosure {
169 public:
170   MarkAndPushClosure(int claim) : ClaimMetadataVisitingOopIterateClosure(claim) {}
171 
172   template <typename T> void do_oop_work(T* p);
173   virtual void do_oop(      oop* p);
174   virtual void do_oop(narrowOop* p);
175 
176   void set_ref_discoverer(ReferenceDiscoverer* rd) {
177     set_ref_discoverer_internal(rd);
178   }
179 };
180 

181 class AdjustPointerClosure: public BasicOopIterateClosure {
182  public:
183   template <typename T> void do_oop_work(T* p);
184   virtual void do_oop(oop* p);
185   virtual void do_oop(narrowOop* p);
186   virtual ReferenceIterationMode reference_iteration_mode() { return DO_FIELDS; }
187 };
188 
189 class PreservedMark {
190 private:
191   oop _obj;
192   markWord _mark;
193 
194 public:
195   PreservedMark(oop obj, markWord mark) : _obj(obj), _mark(mark) {}

196   void adjust_pointer();
197   void restore();
198 };
199 
200 #endif // SHARE_GC_SERIAL_MARKSWEEP_HPP
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