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