1 /*
   2  * Copyright (c) 2016, 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_VM_GC_SHARED_PRESERVEDMARKS_HPP
  26 #define SHARE_VM_GC_SHARED_PRESERVEDMARKS_HPP
  27 
  28 #include "memory/allocation.hpp"
  29 #include "memory/padded.hpp"
  30 #include "oops/oop.hpp"
  31 #include "utilities/stack.hpp"
  32 
  33 class GCTaskManager;
  34 class WorkGang;
  35 
  36 class PreservedMarks VALUE_OBJ_CLASS_SPEC {
  37 private:
  38   class OopAndMarkOop {
  39   private:
  40     oop _o;
  41     markOop _m;
  42 
  43   public:
  44     OopAndMarkOop(oop obj, markOop m) : _o(obj), _m(m) { }
  45 
  46     void set_mark() const {
  47       _o->set_mark(_m);
  48     }
  49   };
  50   typedef Stack<OopAndMarkOop, mtGC> OopAndMarkOopStack;
  51 
  52   OopAndMarkOopStack _stack;
  53 
  54   inline bool should_preserve_mark(oop obj, markOop m) const;
  55   inline void push(oop obj, markOop m);
  56 
  57 public:
  58   size_t size() const { return _stack.size(); }
  59   inline void push_if_necessary(oop obj, markOop m);
  60   // Iterate over the stack, restore all preserved marks, and
  61   // reclaim the memory taken up by the stack segments.
  62   void restore();
  63 
  64   inline static void init_forwarded_mark(oop obj);
  65 
  66   // Assert the stack is empty and has no cached segments.
  67   void assert_empty() PRODUCT_RETURN;
  68 
  69   inline PreservedMarks();
  70   ~PreservedMarks() { assert_empty(); }
  71 };
  72 
  73 class RemoveForwardedPointerClosure: public ObjectClosure {
  74 public:
  75   virtual void do_object(oop obj);
  76 };
  77 
  78 class PreservedMarksSet : public CHeapObj<mtGC> {
  79 private:
  80   // true -> _stacks will be allocated in the C heap
  81   // false -> _stacks will be allocated in the resource arena
  82   const bool _in_c_heap;
  83 
  84   // Number of stacks we have allocated (typically, one stack per GC worker).
  85   // This should be >= 1 if the stacks have been initialized,
  86   // or == 0 if they have not.
  87   uint _num;
  88 
  89   // Stack array (typically, one stack per GC worker) of length _num.
  90   // This should be != NULL if the stacks have been initialized,
  91   // or == NULL if they have not.
  92   Padded<PreservedMarks>* _stacks;
  93 
  94   // Internal version of restore() that uses a WorkGang for parallelism.
  95   void restore_internal(WorkGang* workers, volatile size_t* total_size_addr);
  96 
  97   // Internal version of restore() that uses a GCTaskManager for parallelism.
  98   void restore_internal(GCTaskManager* gc_task_manager,
  99                         volatile size_t* total_size_addr);
 100 
 101 public:
 102   uint num() const { return _num; }
 103 
 104   // Return the i'th stack.
 105   PreservedMarks* get(uint i = 0) const {
 106     assert(_num > 0 && _stacks != NULL, "stacks should have been initialized");
 107     assert(i < _num, "pre-condition");
 108     return (_stacks + i);
 109   }
 110 
 111   // Allocate stack array.
 112   void init(uint num);
 113 
 114   // Itrerate over all stacks, restore all presered marks, and reclaim
 115   // the memory taken up by the stack segments. If the executor is
 116   // NULL, restoration will be done serially. If the executor is not
 117   // NULL, restoration could be done in parallel (when it makes
 118   // sense). Supported executors: WorkGang (Serial, CMS, G1),
 119   // GCTaskManager (PS).
 120   template <class E>
 121   inline void restore(E* executor);
 122 
 123   // Reclaim stack array.
 124   void reclaim();
 125 
 126   // Assert all the stacks are empty and have no cached segments.
 127   void assert_empty() PRODUCT_RETURN;
 128 
 129   PreservedMarksSet(bool in_c_heap)
 130       : _in_c_heap(in_c_heap), _num(0), _stacks(NULL) { }
 131 
 132   ~PreservedMarksSet() {
 133     assert(_stacks == NULL && _num == 0, "stacks should have been reclaimed");
 134   }
 135 };
 136 
 137 #endif // SHARE_VM_GC_SHARED_PRESERVEDMARKS_HPP