1 /*
2 * Copyright (c) 2016, 2020, 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_SHARED_PRESERVEDMARKS_HPP
26 #define SHARE_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 AbstractGangTask;
34 class PreservedMarksSet;
35 class WorkGang;
36
37 class PreservedMarks {
38 private:
39 class OopAndMarkWord {
40 private:
41 oop _o;
42 markWord _m;
43
44 public:
45 OopAndMarkWord(oop obj, markWord m) : _o(obj), _m(m) { }
46
47 oop get_oop() { return _o; }
48 inline void set_mark() const;
49 void set_oop(oop obj) { _o = obj; }
50 };
51 typedef Stack<OopAndMarkWord, mtGC> OopAndMarkWordStack;
52
53 OopAndMarkWordStack _stack;
54
55 inline bool should_preserve_mark(oop obj, markWord m) const;
56
57 template <bool ALT_FWD>
58 void adjust_during_full_gc_impl();
59
60 public:
61 size_t size() const { return _stack.size(); }
62 inline void push(oop obj, markWord m);
63 inline void push_if_necessary(oop obj, markWord m);
64 // Iterate over the stack, restore all preserved marks, and
65 // reclaim the memory taken up by the stack segments.
66 void restore();
67 // Iterate over the stack, adjust all preserved marks according
68 // to their forwarding location stored in the mark.
69 void adjust_during_full_gc();
70
71 void restore_and_increment(volatile size_t* const _total_size_addr);
72 inline static void init_forwarded_mark(oop obj);
73
74 // Assert the stack is empty and has no cached segments.
75 void assert_empty() PRODUCT_RETURN;
76
77 inline PreservedMarks();
78 ~PreservedMarks() { assert_empty(); }
79 };
80
81 class RemoveForwardedPointerClosure: public ObjectClosure {
82 public:
83 virtual void do_object(oop obj);
84 };
85
86 class PreservedMarksSet : public CHeapObj<mtGC> {
87 private:
88 // true -> _stacks will be allocated in the C heap
89 // false -> _stacks will be allocated in the resource arena
90 const bool _in_c_heap;
91
92 // Number of stacks we have allocated (typically, one stack per GC worker).
93 // This should be >= 1 if the stacks have been initialized,
94 // or == 0 if they have not.
95 uint _num;
96
97 // Stack array (typically, one stack per GC worker) of length _num.
98 // This should be != NULL if the stacks have been initialized,
99 // or == NULL if they have not.
100 Padded<PreservedMarks>* _stacks;
101
102 public:
103 uint num() const { return _num; }
104
105 // Return the i'th stack.
106 PreservedMarks* get(uint i = 0) const {
107 assert(_num > 0 && _stacks != NULL, "stacks should have been initialized");
108 assert(i < _num, "pre-condition");
109 return (_stacks + i);
110 }
111
112 // Allocate stack array.
113 void init(uint num);
114
115 // Iterate over all stacks, restore all preserved marks, and reclaim
116 // the memory taken up by the stack segments using the given WorkGang. If the WorkGang
117 // is NULL, perform the work serially in the current thread.
118 void restore(WorkGang* workers);
119
120 AbstractGangTask* create_task();
121
122 // Reclaim stack array.
123 void reclaim();
124
125 // Assert all the stacks are empty and have no cached segments.
126 void assert_empty() PRODUCT_RETURN;
127
128 PreservedMarksSet(bool in_c_heap)
129 : _in_c_heap(in_c_heap), _num(0), _stacks(NULL) { }
130
131 ~PreservedMarksSet() {
132 assert(_stacks == NULL && _num == 0, "stacks should have been reclaimed");
133 }
134 };
135
136 #endif // SHARE_GC_SHARED_PRESERVEDMARKS_HPP