1 /*
2 * Copyright (c) 2001, 2020, 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 biasedLockBits = db.lookupLongConstant("markWord::biased_lock_bits").longValue();
53 maxHashBits = db.lookupLongConstant("markWord::max_hash_bits").longValue();
54 hashBits = db.lookupLongConstant("markWord::hash_bits").longValue();
55 lockShift = db.lookupLongConstant("markWord::lock_shift").longValue();
56 biasedLockShift = db.lookupLongConstant("markWord::biased_lock_shift").longValue();
57 ageShift = db.lookupLongConstant("markWord::age_shift").longValue();
58 hashShift = db.lookupLongConstant("markWord::hash_shift").longValue();
59 lockMask = db.lookupLongConstant("markWord::lock_mask").longValue();
60 lockMaskInPlace = db.lookupLongConstant("markWord::lock_mask_in_place").longValue();
61 biasedLockMask = db.lookupLongConstant("markWord::biased_lock_mask").longValue();
62 biasedLockMaskInPlace = db.lookupLongConstant("markWord::biased_lock_mask_in_place").longValue();
63 biasedLockBitInPlace = db.lookupLongConstant("markWord::biased_lock_bit_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 biasedLockAlignment = db.lookupLongConstant("markWord::biased_lock_alignment").longValue();
69 lockedValue = db.lookupLongConstant("markWord::locked_value").longValue();
70 unlockedValue = db.lookupLongConstant("markWord::unlocked_value").longValue();
71 monitorValue = db.lookupLongConstant("markWord::monitor_value").longValue();
72 markedValue = db.lookupLongConstant("markWord::marked_value").longValue();
73 biasedLockPattern = db.lookupLongConstant("markWord::biased_lock_pattern").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 biasedLockBits;
87 private static long maxHashBits;
88 private static long hashBits;
89
90 private static long lockShift;
91 private static long biasedLockShift;
92 private static long ageShift;
93 private static long hashShift;
94
95 private static long lockMask;
96 private static long lockMaskInPlace;
97 private static long biasedLockMask;
98 private static long biasedLockMaskInPlace;
99 private static long biasedLockBitInPlace;
100 private static long ageMask;
101 private static long ageMaskInPlace;
102 private static long hashMask;
103 private static long hashMaskInPlace;
104 private static long biasedLockAlignment;
105
106 private static long lockedValue;
107 private static long unlockedValue;
108 private static long monitorValue;
109 private static long markedValue;
110 private static long biasedLockPattern;
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 /* Constants in markWord used by CMS. */
120 private static long cmsShift;
121 private static long cmsMask;
122 private static long sizeShift;
123
124 public Mark(Address addr) {
125 super(addr);
126 }
127
128 public long value() {
129 return markField.getValue(addr);
130 }
131
132 public Address valueAsAddress() {
133 return addr.getAddressAt(markField.getOffset());
134 }
135
136 // Biased locking accessors
137 // These must be checked by all code which calls into the
138 // ObjectSynchoronizer and other code. The biasing is not understood
139 // by the lower-level CAS-based locking code, although the runtime
140 // fixes up biased locks to be compatible with it when a bias is
141 // revoked.
142 public boolean hasBiasPattern() {
143 return (Bits.maskBitsLong(value(), biasedLockMaskInPlace) == biasedLockPattern);
144 }
145
146 public JavaThread biasedLocker() {
147 Threads threads = VM.getVM().getThreads();
148 Address addr = valueAsAddress().andWithMask(~(biasedLockMaskInPlace & ageMaskInPlace));
149 return threads.createJavaThreadWrapper(addr);
150 }
151
152 // Indicates that the mark gas the bias bit set but that it has not
153 // yet been biased toward a particular thread
154 public boolean isBiasedAnonymously() {
155 return hasBiasPattern() && (biasedLocker() == null);
156 }
157
158 // lock accessors (note that these assume lock_shift == 0)
159 public boolean isLocked() {
160 return (Bits.maskBitsLong(value(), lockMaskInPlace) != unlockedValue);
161 }
162 public boolean isUnlocked() {
163 return (Bits.maskBitsLong(value(), biasedLockMaskInPlace) == unlockedValue);
164 }
165 public boolean isMarked() {
166 return (Bits.maskBitsLong(value(), lockMaskInPlace) == markedValue);
167 }
168
169 // Special temporary state of the markWord while being inflated.
170 // Code that looks at mark outside a lock need to take this into account.
171 public boolean isBeingInflated() {
172 return (value() == 0);
173 }
174
175 // Should this header be preserved during GC?
176 public boolean mustBePreserved() {
177 return (!isUnlocked() || !hasNoHash());
178 }
179
180 // WARNING: The following routines are used EXCLUSIVELY by
181 // synchronization functions. They are not really gc safe.
182 // They must get updated if markWord layout get changed.
183
184 public boolean hasLocker() {
185 return ((value() & lockMaskInPlace) == lockedValue);
186 }
187 public BasicLock locker() {
188 if (Assert.ASSERTS_ENABLED) {
189 Assert.that(hasLocker(), "check");
190 }
191 return new BasicLock(valueAsAddress());
192 }
193 public boolean hasMonitor() {
194 return ((value() & monitorValue) != 0);
195 }
196 public ObjectMonitor monitor() {
197 if (Assert.ASSERTS_ENABLED) {
198 Assert.that(hasMonitor(), "check");
199 }
200 // Use xor instead of &~ to provide one extra tag-bit check.
201 Address monAddr = valueAsAddress().xorWithMask(monitorValue);
202 return new ObjectMonitor(monAddr);
203 }
204 public boolean hasDisplacedMarkHelper() {
205 return ((value() & unlockedValue) == 0);
206 }
207 public Mark displacedMarkHelper() {
208 if (Assert.ASSERTS_ENABLED) {
209 Assert.that(hasDisplacedMarkHelper(), "check");
210 }
211 Address addr = valueAsAddress().andWithMask(~monitorValue);
212 return new Mark(addr.getAddressAt(0));
213 }
214 public int age() { return (int) Bits.maskBitsLong(value() >> ageShift, ageMask); }
215
216 // hash operations
217 public long hash() {
218 return Bits.maskBitsLong(value() >> hashShift, hashMask);
219 }
220
221 public boolean hasNoHash() {
222 return hash() == noHash;
223 }
224
225 // Debugging
226 public void printOn(PrintStream tty) {
227 if (isLocked()) {
228 tty.print("locked(0x" +
229 Long.toHexString(value()) + ")->");
230 displacedMarkHelper().printOn(tty);
231 } else {
232 if (Assert.ASSERTS_ENABLED) {
233 Assert.that(isUnlocked(), "just checking");
234 }
235 tty.print("mark(");
236 tty.print("hash " + Long.toHexString(hash()) + ",");
237 tty.print("age " + age() + ")");
238 }
239 }
240
241 public long getSize() { return (long)(value() >> sizeShift); }
242 }