1 /*
2 * Copyright (c) 2001, 2023, 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 if (VM.getVM().isLP64()) {
58 klassShift = db.lookupLongConstant("markWord::klass_shift").longValue();
59 }
60 lockMask = db.lookupLongConstant("markWord::lock_mask").longValue();
61 lockMaskInPlace = db.lookupLongConstant("markWord::lock_mask_in_place").longValue();
62 ageMask = db.lookupLongConstant("markWord::age_mask").longValue();
63 ageMaskInPlace = db.lookupLongConstant("markWord::age_mask_in_place").longValue();
64 hashMask = db.lookupLongConstant("markWord::hash_mask").longValue();
65 hashMaskInPlace = db.lookupLongConstant("markWord::hash_mask_in_place").longValue();
66 lockedValue = db.lookupLongConstant("markWord::locked_value").longValue();
67 unlockedValue = db.lookupLongConstant("markWord::unlocked_value").longValue();
68 monitorValue = db.lookupLongConstant("markWord::monitor_value").longValue();
69 markedValue = db.lookupLongConstant("markWord::marked_value").longValue();
70 noHash = db.lookupLongConstant("markWord::no_hash").longValue();
71 noHashInPlace = db.lookupLongConstant("markWord::no_hash_in_place").longValue();
72 noLockInPlace = db.lookupLongConstant("markWord::no_lock_in_place").longValue();
73 maxAge = db.lookupLongConstant("markWord::max_age").longValue();
74 }
75
76 // Field accessors
77 private static CIntegerField markField;
78
79 // Constants -- read from VM
80 private static long ageBits;
81 private static long lockBits;
82 private static long maxHashBits;
83 private static long hashBits;
84
85 private static long lockShift;
86 private static long ageShift;
87 private static long hashShift;
88 private static long klassShift;
89
90 private static long lockMask;
91 private static long lockMaskInPlace;
92 private static long ageMask;
93 private static long ageMaskInPlace;
94 private static long hashMask;
95 private static long hashMaskInPlace;
96
97 private static long lockedValue;
98 private static long unlockedValue;
99 private static long monitorValue;
100 private static long markedValue;
101
102 private static long noHash;
103
104 private static long noHashInPlace;
105 private static long noLockInPlace;
106
107 private static long maxAge;
108
109 public static long getKlassShift() {
110 return klassShift;
111 }
112
113 public Mark(Address addr) {
114 super(addr);
115 }
116
117 public long value() {
118 return markField.getValue(addr);
119 }
120
121 public Address valueAsAddress() {
122 return addr.getAddressAt(markField.getOffset());
123 }
124
125 // lock accessors (note that these assume lock_shift == 0)
126 public boolean isLocked() {
127 return (Bits.maskBitsLong(value(), lockMaskInPlace) != unlockedValue);
128 }
129 public boolean isUnlocked() {
130 return (Bits.maskBitsLong(value(), lockMaskInPlace) == unlockedValue);
131 }
132 public boolean isMarked() {
133 return (Bits.maskBitsLong(value(), lockMaskInPlace) == markedValue);
134 }
135
136 // Special temporary state of the markWord while being inflated.
137 // Code that looks at mark outside a lock need to take this into account.
138 public boolean isBeingInflated() {
139 return (value() == 0);
140 }
141
142 // Should this header be preserved during GC?
143 public boolean mustBePreserved() {
144 return (!isUnlocked() || !hasNoHash());
145 }
146
147 // WARNING: The following routines are used EXCLUSIVELY by
148 // synchronization functions. They are not really gc safe.
149 // They must get updated if markWord layout get changed.
150
151 public boolean hasLocker() {
152 return ((value() & lockMaskInPlace) == lockedValue);
153 }
154 public BasicLock locker() {
155 if (Assert.ASSERTS_ENABLED) {
156 Assert.that(hasLocker(), "check");
157 }
158 return new BasicLock(valueAsAddress());
159 }
160 public boolean hasMonitor() {
161 return ((value() & monitorValue) != 0);
162 }
163 public ObjectMonitor monitor() {
164 if (Assert.ASSERTS_ENABLED) {
165 Assert.that(hasMonitor(), "check");
166 }
167 if (VM.getVM().getCommandLineFlag("UseObjectMonitorTable").getBool()) {
168 Iterator it = ObjectSynchronizer.objectMonitorIterator();
169 while (it != null && it.hasNext()) {
170 ObjectMonitor mon = (ObjectMonitor)it.next();
171 if (getAddress().equals(mon.object())) {
172 return mon;
173 }
174 }
175 return null;
176 }
177 // Use xor instead of &~ to provide one extra tag-bit check.
178 Address monAddr = valueAsAddress().xorWithMask(monitorValue);
179 return new ObjectMonitor(monAddr);
180 }
181 public boolean hasDisplacedMarkHelper() {
182 return ((value() & unlockedValue) == 0);
183 }
184 public Mark displacedMarkHelper() {
185 if (Assert.ASSERTS_ENABLED) {
186 Assert.that(hasDisplacedMarkHelper(), "check");
187 }
188 Address addr = valueAsAddress().andWithMask(~monitorValue);
189 return new Mark(addr.getAddressAt(0));
190 }
191 public int age() { return (int) Bits.maskBitsLong(value() >> ageShift, ageMask); }
192
193 // hash operations
194 public long hash() {
195 return Bits.maskBitsLong(value() >> hashShift, hashMask);
196 }
197
198 public boolean hasNoHash() {
199 return hash() == noHash;
200 }
201
202 public Klass getKlass() {
203 assert(VM.getVM().isCompactObjectHeadersEnabled());
204 return (Klass)Metadata.instantiateWrapperFor(addr.getCompKlassAddressAt(0));
205 }
206
207 // Debugging
208 public void printOn(PrintStream tty) {
209 if (isLocked()) {
210 tty.print("locked(0x" +
211 Long.toHexString(value()) + ")->");
212 displacedMarkHelper().printOn(tty);
213 } else {
214 if (Assert.ASSERTS_ENABLED) {
215 Assert.that(isUnlocked(), "just checking");
216 }
217 tty.print("mark(");
218 tty.print("hash " + Long.toHexString(hash()) + ",");
219 tty.print("age " + age() + ")");
220 }
221 }
222
223 public long getSize() { return (long)value(); }
224 }