1 /*
2 * Copyright (c) 2001, 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
25 package sun.jvm.hotspot.oops;
26
27 import java.io.*;
28 import java.util.*;
29
30 import sun.jvm.hotspot.debugger.*;
31 import sun.jvm.hotspot.runtime.*;
32 import sun.jvm.hotspot.types.*;
33 import sun.jvm.hotspot.utilities.*;
34 import sun.jvm.hotspot.utilities.Observable;
35 import sun.jvm.hotspot.utilities.Observer;
36
37 public class Mark extends VMObject {
38 static {
39 VM.registerVMInitializedObserver(new Observer() {
40 public void update(Observable o, Object data) {
41 initialize(VM.getVM().getTypeDataBase());
42 }
43 });
44 }
45
46 private static synchronized void initialize(TypeDataBase db) throws WrongTypeException {
47 Type type = db.lookupType("oopDesc");
48 markField = type.getCIntegerField("_mark");
49
50 ageBits = db.lookupLongConstant("markWord::age_bits").longValue();
51 lockBits = db.lookupLongConstant("markWord::lock_bits").longValue();
52 maxHashBits = db.lookupLongConstant("markWord::max_hash_bits").longValue();
53 hashBits = db.lookupLongConstant("markWord::hash_bits").longValue();
54 lockShift = db.lookupLongConstant("markWord::lock_shift").longValue();
55 ageShift = db.lookupLongConstant("markWord::age_shift").longValue();
56 hashShift = db.lookupLongConstant("markWord::hash_shift").longValue();
57 lockMask = db.lookupLongConstant("markWord::lock_mask").longValue();
58 lockMaskInPlace = db.lookupLongConstant("markWord::lock_mask_in_place").longValue();
59 ageMask = db.lookupLongConstant("markWord::age_mask").longValue();
60 ageMaskInPlace = db.lookupLongConstant("markWord::age_mask_in_place").longValue();
61 hashMask = db.lookupLongConstant("markWord::hash_mask").longValue();
62 hashMaskInPlace = db.lookupLongConstant("markWord::hash_mask_in_place").longValue();
63 lockedValue = db.lookupLongConstant("markWord::locked_value").longValue();
64 unlockedValue = db.lookupLongConstant("markWord::unlocked_value").longValue();
65 monitorValue = db.lookupLongConstant("markWord::monitor_value").longValue();
66 markedValue = db.lookupLongConstant("markWord::marked_value").longValue();
67 noHash = db.lookupLongConstant("markWord::no_hash").longValue();
68 noHashInPlace = db.lookupLongConstant("markWord::no_hash_in_place").longValue();
69 noLockInPlace = db.lookupLongConstant("markWord::no_lock_in_place").longValue();
70 maxAge = db.lookupLongConstant("markWord::max_age").longValue();
71 }
72
73 // Field accessors
74 private static CIntegerField markField;
75
76 // Constants -- read from VM
77 private static long ageBits;
78 private static long lockBits;
79 private static long maxHashBits;
80 private static long hashBits;
81
82 private static long lockShift;
83 private static long ageShift;
84 private static long hashShift;
85
86 private static long lockMask;
87 private static long lockMaskInPlace;
88 private static long ageMask;
89 private static long ageMaskInPlace;
90 private static long hashMask;
91 private static long hashMaskInPlace;
92
93 private static long lockedValue;
94 private static long unlockedValue;
95 private static long monitorValue;
96 private static long markedValue;
97
98 private static long noHash;
99
100 private static long noHashInPlace;
101 private static long noLockInPlace;
102
103 private static long maxAge;
104
105 /* Constants in markWord used by CMS. */
106 private static long cmsShift;
107 private static long cmsMask;
108 private static long sizeShift;
109
110 public Mark(Address addr) {
111 super(addr);
112 }
113
114 public long value() {
115 return markField.getValue(addr);
116 }
117
118 public Address valueAsAddress() {
119 return addr.getAddressAt(markField.getOffset());
120 }
121
122 // lock accessors (note that these assume lock_shift == 0)
123 public boolean isLocked() {
124 return (Bits.maskBitsLong(value(), lockMaskInPlace) != unlockedValue);
125 }
126 public boolean isUnlocked() {
127 return (Bits.maskBitsLong(value(), lockMaskInPlace) == unlockedValue);
128 }
129 public boolean isMarked() {
130 return (Bits.maskBitsLong(value(), lockMaskInPlace) == markedValue);
131 }
132
133 // Special temporary state of the markWord while being inflated.
134 // Code that looks at mark outside a lock need to take this into account.
135 public boolean isBeingInflated() {
136 return (value() == 0);
137 }
138
139 // Should this header be preserved during GC?
140 public boolean mustBePreserved() {
141 return (!isUnlocked() || !hasNoHash());
142 }
143
144 // WARNING: The following routines are used EXCLUSIVELY by
145 // synchronization functions. They are not really gc safe.
146 // They must get updated if markWord layout get changed.
147
148 public boolean hasLocker() {
149 return ((value() & lockMaskInPlace) == lockedValue);
150 }
151 public BasicLock locker() {
152 if (Assert.ASSERTS_ENABLED) {
153 Assert.that(hasLocker(), "check");
154 }
155 return new BasicLock(valueAsAddress());
156 }
157 public boolean hasMonitor() {
158 return ((value() & monitorValue) != 0);
159 }
160 public ObjectMonitor monitor() {
161 if (Assert.ASSERTS_ENABLED) {
162 Assert.that(hasMonitor(), "check");
163 }
164 // Use xor instead of &~ to provide one extra tag-bit check.
165 Address monAddr = valueAsAddress().xorWithMask(monitorValue);
166 return new ObjectMonitor(monAddr);
167 }
168 public boolean hasDisplacedMarkHelper() {
169 return ((value() & unlockedValue) == 0);
170 }
171 public Mark displacedMarkHelper() {
172 if (Assert.ASSERTS_ENABLED) {
173 Assert.that(hasDisplacedMarkHelper(), "check");
174 }
175 Address addr = valueAsAddress().andWithMask(~monitorValue);
176 return new Mark(addr.getAddressAt(0));
177 }
178 public int age() { return (int) Bits.maskBitsLong(value() >> ageShift, ageMask); }
179
180 // hash operations
181 public long hash() {
182 return Bits.maskBitsLong(value() >> hashShift, hashMask);
183 }
184
185 public boolean hasNoHash() {
186 return hash() == noHash;
187 }
188
189 // Debugging
190 public void printOn(PrintStream tty) {
191 if (isLocked()) {
192 tty.print("locked(0x" +
193 Long.toHexString(value()) + ")->");
194 displacedMarkHelper().printOn(tty);
195 } else {
196 if (Assert.ASSERTS_ENABLED) {
197 Assert.that(isUnlocked(), "just checking");
198 }
199 tty.print("mark(");
200 tty.print("hash " + Long.toHexString(hash()) + ",");
201 tty.print("age " + age() + ")");
202 }
203 }
204
205 public long getSize() { return (long)(value() >> sizeShift); }
206 }