1 /*
2 * Copyright (c) 2001, 2025, 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 hashCtrlBits = db.lookupLongConstant("markWord::hashctrl_bits").longValue();
55 lockShift = db.lookupLongConstant("markWord::lock_shift").longValue();
56 ageShift = db.lookupLongConstant("markWord::age_shift").longValue();
57 hashShift = db.lookupLongConstant("markWord::hash_shift").longValue();
58 hashCtrlShift = db.lookupLongConstant("markWord::hashctrl_shift").longValue();
59 if (VM.getVM().isLP64()) {
60 klassShift = db.lookupLongConstant("markWord::klass_shift").longValue();
61 }
62 lockMask = db.lookupLongConstant("markWord::lock_mask").longValue();
63 lockMaskInPlace = db.lookupLongConstant("markWord::lock_mask_in_place").longValue();
64 ageMask = db.lookupLongConstant("markWord::age_mask").longValue();
65 ageMaskInPlace = db.lookupLongConstant("markWord::age_mask_in_place").longValue();
66 hashMask = db.lookupLongConstant("markWord::hash_mask").longValue();
67 hashMaskInPlace = db.lookupLongConstant("markWord::hash_mask_in_place").longValue();
68 hashCtrlMaskInPlace = db.lookupLongConstant("markWord::hashctrl_mask_in_place").longValue();
69 hashCtrlHashedMaskInPlace = db.lookupLongConstant("markWord::hashctrl_hashed_mask_in_place").longValue();
70 hashCtrlExpandedMaskInPlace = db.lookupLongConstant("markWord::hashctrl_expanded_mask_in_place").longValue();
71 lockedValue = db.lookupLongConstant("markWord::locked_value").longValue();
72 unlockedValue = db.lookupLongConstant("markWord::unlocked_value").longValue();
73 monitorValue = db.lookupLongConstant("markWord::monitor_value").longValue();
74 markedValue = db.lookupLongConstant("markWord::marked_value").longValue();
75 noHash = db.lookupLongConstant("markWord::no_hash").longValue();
76 noHashInPlace = db.lookupLongConstant("markWord::no_hash_in_place").longValue();
77 noLockInPlace = db.lookupLongConstant("markWord::no_lock_in_place").longValue();
78 maxAge = db.lookupLongConstant("markWord::max_age").longValue();
79 }
80
81 // Field accessors
82 private static CIntegerField markField;
83
84 // Constants -- read from VM
85 private static long ageBits;
86 private static long lockBits;
87 private static long maxHashBits;
88 private static long hashBits;
89 private static long hashCtrlBits;
90
91 private static long lockShift;
92 private static long ageShift;
93 private static long hashShift;
94 private static long hashCtrlShift;
95 private static long klassShift;
96
97 private static long lockMask;
98 private static long lockMaskInPlace;
99 private static long ageMask;
100 private static long ageMaskInPlace;
101 private static long hashMask;
102 private static long hashMaskInPlace;
103 private static long hashCtrlMaskInPlace;
104 private static long hashCtrlHashedMaskInPlace;
105 private static long hashCtrlExpandedMaskInPlace;
106
107 private static long lockedValue;
108 private static long unlockedValue;
109 private static long monitorValue;
110 private static long markedValue;
111
112 private static long noHash;
113
114 private static long noHashInPlace;
115 private static long noLockInPlace;
116
117 private static long maxAge;
118
119 public static long getKlassShift() {
120 return klassShift;
121 }
122
123 public Mark(Address addr) {
124 super(addr);
125 }
126
127 public long value() {
128 return markField.getValue(addr);
129 }
130
131 public Address valueAsAddress() {
132 return addr.getAddressAt(markField.getOffset());
133 }
134
135 // lock accessors (note that these assume lock_shift == 0)
136 public boolean isLocked() {
137 return (Bits.maskBitsLong(value(), lockMaskInPlace) != unlockedValue);
138 }
139 public boolean isUnlocked() {
140 return (Bits.maskBitsLong(value(), lockMaskInPlace) == unlockedValue);
141 }
142 public boolean isMarked() {
143 return (Bits.maskBitsLong(value(), lockMaskInPlace) == markedValue);
144 }
145
146 // Special temporary state of the markWord while being inflated.
147 // Code that looks at mark outside a lock need to take this into account.
148 public boolean isBeingInflated() {
149 return (value() == 0);
150 }
151
152 // Should this header be preserved during GC?
153 public boolean mustBePreserved() {
154 return (!isUnlocked() || !hasNoHash());
155 }
156
157 // WARNING: The following routines are used EXCLUSIVELY by
158 // synchronization functions. They are not really gc safe.
159 // They must get updated if markWord layout get changed.
160
161 public boolean hasLocker() {
162 return ((value() & lockMaskInPlace) == lockedValue);
163 }
164 public boolean hasMonitor() {
165 return ((value() & monitorValue) != 0);
166 }
167 public ObjectMonitor monitor() {
168 if (Assert.ASSERTS_ENABLED) {
169 Assert.that(hasMonitor(), "check");
170 }
171 if (VM.getVM().getCommandLineFlag("UseObjectMonitorTable").getBool()) {
172 Iterator it = ObjectSynchronizer.objectMonitorIterator();
173 while (it != null && it.hasNext()) {
174 ObjectMonitor mon = (ObjectMonitor)it.next();
175 if (getAddress().equals(mon.object())) {
176 return mon;
177 }
178 }
179 return null;
180 }
181 // Use xor instead of &~ to provide one extra tag-bit check.
182 Address monAddr = valueAsAddress().xorWithMask(monitorValue);
183 return new ObjectMonitor(monAddr);
184 }
185 public boolean hasDisplacedMarkHelper() {
186 return ((value() & unlockedValue) == 0);
187 }
188 public Mark displacedMarkHelper() {
189 if (Assert.ASSERTS_ENABLED) {
190 Assert.that(hasDisplacedMarkHelper(), "check");
191 }
192 Address addr = valueAsAddress().andWithMask(~monitorValue);
193 return new Mark(addr.getAddressAt(0));
194 }
195 public int age() { return (int) Bits.maskBitsLong(value() >> ageShift, ageMask); }
196
197 // hash operations
198 public long hash() {
199 if (VM.getVM().isCompactObjectHeadersEnabled()) {
200 System.exit(-23);
201 throw new RuntimeException("Compact I-Hash not yet implemented");
202 } else {
203 return Bits.maskBitsLong(value() >> hashShift, hashMask);
204 }
205 }
206
207 public boolean hasNoHash() {
208 return hash() == noHash;
209 }
210
211 public boolean isExpanded() {
212 assert(VM.getVM().isCompactObjectHeadersEnabled());
213 return Bits.maskBitsLong(value(), hashCtrlExpandedMaskInPlace) != 0;
214 }
215
216 public Klass getKlass() {
217 assert(VM.getVM().isCompactObjectHeadersEnabled());
218 return (Klass)Metadata.instantiateWrapperFor(addr.getCompKlassAddressAt(0));
219 }
220
221 // Debugging
222 public void printOn(PrintStream tty) {
223 if (isLocked()) {
224 tty.print("locked(0x" +
225 Long.toHexString(value()) + ")->");
226 displacedMarkHelper().printOn(tty);
227 } else {
228 if (Assert.ASSERTS_ENABLED) {
229 Assert.that(isUnlocked(), "just checking");
230 }
231 tty.print("mark(");
232 tty.print("hash " + Long.toHexString(hash()) + ",");
233 tty.print("age " + age() + ")");
234 }
235 }
236
237 public long getSize() { return (long)value(); }
238 }