1 /*
 2  * Copyright (c) 2017, 2018, 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 ScopedDisabledBiasedLocking {
30   bool _orig;
31 public:
32   ScopedDisabledBiasedLocking() : _orig(UseBiasedLocking) { UseBiasedLocking = false; }
33   ~ScopedDisabledBiasedLocking() { UseBiasedLocking = _orig; }
34 };
35 
36 // Class to create a "fake" oop with a mark that will
37 // return true for calls to must_be_preserved().
38 class FakeOop {
39   oopDesc _oop;
40 
41 public:
42   FakeOop() : _oop() { _oop.set_mark(originalMark()); }
43 
44   oop get_oop() { return &_oop; }
45   markWord mark() { return _oop.mark(); }
46   void set_mark(markWord m) { _oop.set_mark(m); }
47   void forward_to(oop obj) {
48     markWord m = markWord::encode_pointer_as_mark(obj);
49     _oop.set_mark(m);
50   }
51 
52   static markWord originalMark() { return markWord(markWord::lock_mask_in_place); }
53   static markWord changedMark()  { return markWord(0x4711); }
54 };
55 
56 #define ASSERT_MARK_WORD_EQ(a, b) ASSERT_EQ((a).value(), (b).value())
57 
58 TEST_VM(PreservedMarks, iterate_and_restore) {
59   // Need to disable biased locking to easily
60   // create oops that "must_be_preseved"
61   ScopedDisabledBiasedLocking dbl;
62 
63   PreservedMarks pm;
64   FakeOop o1;
65   FakeOop o2;
66   FakeOop o3;
67   FakeOop o4;
68 
69   // Make sure initial marks are correct.
70   ASSERT_MARK_WORD_EQ(o1.mark(), FakeOop::originalMark());
71   ASSERT_MARK_WORD_EQ(o2.mark(), FakeOop::originalMark());
72   ASSERT_MARK_WORD_EQ(o3.mark(), FakeOop::originalMark());
73   ASSERT_MARK_WORD_EQ(o4.mark(), FakeOop::originalMark());
74 
75   // Change the marks and verify change.
76   o1.set_mark(FakeOop::changedMark());
77   o2.set_mark(FakeOop::changedMark());
78   ASSERT_MARK_WORD_EQ(o1.mark(), FakeOop::changedMark());
79   ASSERT_MARK_WORD_EQ(o2.mark(), FakeOop::changedMark());
80 
81   // Push o1 and o2 to have their marks preserved.
82   pm.push(o1.get_oop(), o1.mark());
83   pm.push(o2.get_oop(), o2.mark());
84 
85   // Fake a move from o1->o3 and o2->o4.
86   o1.forward_to(o3.get_oop());
87   o2.forward_to(o4.get_oop());
88   ASSERT_EQ(o1.get_oop()->forwardee(), o3.get_oop());
89   ASSERT_EQ(o2.get_oop()->forwardee(), o4.get_oop());
90   // Adjust will update the PreservedMarks stack to
91   // make sure the mark is updated at the new location.
92   pm.adjust_during_full_gc();
93 
94   // Restore all preserved and verify that the changed
95   // mark is now present at o3 and o4.
96   pm.restore();
97   ASSERT_MARK_WORD_EQ(o3.mark(), FakeOop::changedMark());
98   ASSERT_MARK_WORD_EQ(o4.mark(), FakeOop::changedMark());
99 }