src/hotspot/share/gc/shared/preservedMarks.hpp

/*
 * Copyright (c) 2016, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
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#ifndef SHARE_VM_GC_SHARED_PRESERVEDMARKS_HPP
#define SHARE_VM_GC_SHARED_PRESERVEDMARKS_HPP

#include "memory/allocation.hpp"
#include "memory/padded.hpp"
#include "oops/oop.hpp"
#include "utilities/stack.hpp"

class PreservedMarksSet;
class WorkGang;

class PreservedMarks {
private:
  class OopAndMarkOop {
  private:
    oop _o;
    markOop _m;

  public:
    OopAndMarkOop(oop obj, markOop m) : _o(obj), _m(m) { }

    oop get_oop() { return _o; }
    inline void set_mark() const;
    void set_oop(oop obj) { _o = obj; }
  };
  typedef Stack<OopAndMarkOop, mtGC> OopAndMarkOopStack;

  OopAndMarkOopStack _stack;

  inline bool should_preserve_mark(oop obj, markOop m) const;

public:
  size_t size() const { return _stack.size(); }
  inline void push(oop obj, markOop m);
  inline void push_if_necessary(oop obj, markOop m);
  // Iterate over the stack, restore all preserved marks, and
  // reclaim the memory taken up by the stack segments.
  void restore();
  // Iterate over the stack, adjust all preserved marks according
  // to their forwarding location stored in the mark.
  void adjust_during_full_gc();

  void restore_and_increment(volatile size_t* const _total_size_addr);
  inline static void init_forwarded_mark(oop obj);

  // Assert the stack is empty and has no cached segments.
  void assert_empty() PRODUCT_RETURN;

  inline PreservedMarks();
  ~PreservedMarks() { assert_empty(); }
};

class RemoveForwardedPointerClosure: public ObjectClosure {
public:
  virtual void do_object(oop obj);
};

class RestorePreservedMarksTaskExecutor {
public:
  void virtual restore(PreservedMarksSet* preserved_marks_set,
                       volatile size_t* total_size_addr) = 0;
};

class SharedRestorePreservedMarksTaskExecutor : public RestorePreservedMarksTaskExecutor {
private:
    WorkGang* _workers;

public:
    SharedRestorePreservedMarksTaskExecutor(WorkGang* workers) : _workers(workers) { }

    void restore(PreservedMarksSet* preserved_marks_set,
                 volatile size_t* total_size_addr);

};

class PreservedMarksSet : public CHeapObj<mtGC> {
private:
  // true -> _stacks will be allocated in the C heap
  // false -> _stacks will be allocated in the resource arena
  const bool _in_c_heap;

  // Number of stacks we have allocated (typically, one stack per GC worker).
  // This should be >= 1 if the stacks have been initialized,
  // or == 0 if they have not.
  uint _num;

  // Stack array (typically, one stack per GC worker) of length _num.
  // This should be != NULL if the stacks have been initialized,
  // or == NULL if they have not.
  Padded<PreservedMarks>* _stacks;

public:
  uint num() const { return _num; }

  // Return the i'th stack.
  PreservedMarks* get(uint i = 0) const {
    assert(_num > 0 && _stacks != NULL, "stacks should have been initialized");
    assert(i < _num, "pre-condition");
    return (_stacks + i);
  }

  // Allocate stack array.
  void init(uint num);

  // Iterate over all stacks, restore all preserved marks, and reclaim
  // the memory taken up by the stack segments.
  // Supported executors: SharedRestorePreservedMarksTaskExecutor (Serial, CMS, G1),
  // PSRestorePreservedMarksTaskExecutor (PS).
  inline void restore(RestorePreservedMarksTaskExecutor* executor);

  // Reclaim stack array.
  void reclaim();

  // Assert all the stacks are empty and have no cached segments.
  void assert_empty() PRODUCT_RETURN;

  PreservedMarksSet(bool in_c_heap)
      : _in_c_heap(in_c_heap), _num(0), _stacks(NULL) { }

  ~PreservedMarksSet() {
    assert(_stacks == NULL && _num == 0, "stacks should have been reclaimed");
  }
};

#endif // SHARE_VM_GC_SHARED_PRESERVEDMARKS_HPP