1 /*
 2  * Copyright (c) 2017, 2021, 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 #include "precompiled.hpp"
25 #include "gc/shared/preservedMarks.inline.hpp"
26 #include "oops/oop.inline.hpp"
27 #include "unittest.hpp"
28 
29 // Class to create a "fake" oop with a mark that will
30 // return true for calls to must_be_preserved().
31 class FakeOop {
32   oopDesc _oop;
33 
34 public:
35   FakeOop() : _oop() { _oop.set_mark(originalMark()); }
36 
37   oop get_oop() { return &_oop; }
38   markWord mark() { return _oop.mark(); }
39   void set_mark(markWord m) { _oop.set_mark(m); }
40   void forward_to(oop obj) {
41     markWord m = markWord::encode_pointer_as_mark(obj);
42     _oop.set_mark(m);
43   }
44 
45   static markWord originalMark() { return markWord(markWord::lock_mask_in_place); }
46   static markWord changedMark()  { return markWord(0x4711); }
47 };
48 
49 #define ASSERT_MARK_WORD_EQ(a, b) ASSERT_EQ((a).value(), (b).value())
50 
51 TEST_VM(PreservedMarks, iterate_and_restore) {
52   PreservedMarks pm;
53   FakeOop o1;
54   FakeOop o2;
55   FakeOop o3;
56   FakeOop o4;
57 
58   // Make sure initial marks are correct.
59   ASSERT_MARK_WORD_EQ(o1.mark(), FakeOop::originalMark());
60   ASSERT_MARK_WORD_EQ(o2.mark(), FakeOop::originalMark());
61   ASSERT_MARK_WORD_EQ(o3.mark(), FakeOop::originalMark());
62   ASSERT_MARK_WORD_EQ(o4.mark(), FakeOop::originalMark());
63 
64   // Change the marks and verify change.
65   o1.set_mark(FakeOop::changedMark());
66   o2.set_mark(FakeOop::changedMark());
67   ASSERT_MARK_WORD_EQ(o1.mark(), FakeOop::changedMark());
68   ASSERT_MARK_WORD_EQ(o2.mark(), FakeOop::changedMark());
69 
70   // Push o1 and o2 to have their marks preserved.
71   pm.push(o1.get_oop(), o1.mark());
72   pm.push(o2.get_oop(), o2.mark());
73 
74   // Fake a move from o1->o3 and o2->o4.
75   o1.forward_to(o3.get_oop());
76   o2.forward_to(o4.get_oop());
77   ASSERT_EQ(o1.get_oop()->forwardee(), o3.get_oop());
78   ASSERT_EQ(o2.get_oop()->forwardee(), o4.get_oop());
79   // Adjust will update the PreservedMarks stack to
80   // make sure the mark is updated at the new location.
81   pm.adjust_during_full_gc();
82 
83   // Restore all preserved and verify that the changed
84   // mark is now present at o3 and o4.
85   pm.restore();
86   ASSERT_MARK_WORD_EQ(o3.mark(), FakeOop::changedMark());
87   ASSERT_MARK_WORD_EQ(o4.mark(), FakeOop::changedMark());
88 }