1 /*
2 * Copyright 2001-2008 Sun Microsystems, Inc. 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 Sun Microsystems, Inc., 4150 Network Circle, Santa Clara,
20 * CA 95054 USA or visit www.sun.com if you need additional information or
21 * have any 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
35 /** Mark is the analogue of the VM's markOop. In this system it does
36 not subclass Oop but VMObject. For a mark on the stack, the mark's
37 address will be an Address; for a mark in the header of an object,
38 it will be an OopHandle. It is assumed in a couple of places in
39 this code that the mark is the first word in an object. */
40
41 public class Mark extends VMObject {
42 static {
43 VM.registerVMInitializedObserver(new Observer() {
44 public void update(Observable o, Object data) {
45 initialize(VM.getVM().getTypeDataBase());
46 }
47 });
48 }
49
50 private static synchronized void initialize(TypeDataBase db) throws WrongTypeException {
51 Type type = db.lookupType("oopDesc");
52 markField = type.getCIntegerField("_mark");
53
54 ageBits = db.lookupLongConstant("markOopDesc::age_bits").longValue();
55 lockBits = db.lookupLongConstant("markOopDesc::lock_bits").longValue();
56 biasedLockBits = db.lookupLongConstant("markOopDesc::biased_lock_bits").longValue();
57 maxHashBits = db.lookupLongConstant("markOopDesc::max_hash_bits").longValue();
58 hashBits = db.lookupLongConstant("markOopDesc::hash_bits").longValue();
59 lockShift = db.lookupLongConstant("markOopDesc::lock_shift").longValue();
60 biasedLockShift = db.lookupLongConstant("markOopDesc::biased_lock_shift").longValue();
61 ageShift = db.lookupLongConstant("markOopDesc::age_shift").longValue();
62 hashShift = db.lookupLongConstant("markOopDesc::hash_shift").longValue();
63 lockMask = db.lookupLongConstant("markOopDesc::lock_mask").longValue();
64 lockMaskInPlace = db.lookupLongConstant("markOopDesc::lock_mask_in_place").longValue();
65 biasedLockMask = db.lookupLongConstant("markOopDesc::biased_lock_mask").longValue();
66 biasedLockMaskInPlace = db.lookupLongConstant("markOopDesc::biased_lock_mask_in_place").longValue();
67 biasedLockBitInPlace = db.lookupLongConstant("markOopDesc::biased_lock_bit_in_place").longValue();
68 ageMask = db.lookupLongConstant("markOopDesc::age_mask").longValue();
69 ageMaskInPlace = db.lookupLongConstant("markOopDesc::age_mask_in_place").longValue();
70 hashMask = db.lookupLongConstant("markOopDesc::hash_mask").longValue();
71 hashMaskInPlace = db.lookupLongConstant("markOopDesc::hash_mask_in_place").longValue();
72 biasedLockAlignment = db.lookupLongConstant("markOopDesc::biased_lock_alignment").longValue();
73 lockedValue = db.lookupLongConstant("markOopDesc::locked_value").longValue();
74 unlockedValue = db.lookupLongConstant("markOopDesc::unlocked_value").longValue();
75 monitorValue = db.lookupLongConstant("markOopDesc::monitor_value").longValue();
76 markedValue = db.lookupLongConstant("markOopDesc::marked_value").longValue();
77 biasedLockPattern = db.lookupLongConstant("markOopDesc::biased_lock_pattern").longValue();
78 noHash = db.lookupLongConstant("markOopDesc::no_hash").longValue();
79 noHashInPlace = db.lookupLongConstant("markOopDesc::no_hash_in_place").longValue();
80 noLockInPlace = db.lookupLongConstant("markOopDesc::no_lock_in_place").longValue();
81 maxAge = db.lookupLongConstant("markOopDesc::max_age").longValue();
82
83 /* Constants in markOop used by CMS. */
84 cmsShift = db.lookupLongConstant("markOopDesc::cms_shift").longValue();
85 cmsMask = db.lookupLongConstant("markOopDesc::cms_mask").longValue();
86 sizeShift = db.lookupLongConstant("markOopDesc::size_shift").longValue();
87 }
88
89 // Field accessors
90 private static CIntegerField markField;
91
92 // Constants -- read from VM
93 private static long ageBits;
94 private static long lockBits;
95 private static long biasedLockBits;
96 private static long maxHashBits;
97 private static long hashBits;
98
99 private static long lockShift;
100 private static long biasedLockShift;
101 private static long ageShift;
102 private static long hashShift;
103
104 private static long lockMask;
105 private static long lockMaskInPlace;
106 private static long biasedLockMask;
107 private static long biasedLockMaskInPlace;
108 private static long biasedLockBitInPlace;
109 private static long ageMask;
110 private static long ageMaskInPlace;
111 private static long hashMask;
112 private static long hashMaskInPlace;
113 private static long biasedLockAlignment;
114
115 private static long lockedValue;
116 private static long unlockedValue;
117 private static long monitorValue;
118 private static long markedValue;
119 private static long biasedLockPattern;
120
121 private static long noHash;
122
123 private static long noHashInPlace;
124 private static long noLockInPlace;
125
126 private static long maxAge;
127
128 /* Constants in markOop used by CMS. */
129 private static long cmsShift;
130 private static long cmsMask;
131 private static long sizeShift;
132
133 public Mark(Address addr) {
134 super(addr);
135 }
136
137 public long value() {
138 return markField.getValue(addr);
139 }
140
141 public Address valueAsAddress() {
142 return addr.getAddressAt(markField.getOffset());
143 }
144
145 // Biased locking accessors
146 // These must be checked by all code which calls into the
147 // ObjectSynchoronizer and other code. The biasing is not understood
148 // by the lower-level CAS-based locking code, although the runtime
149 // fixes up biased locks to be compatible with it when a bias is
150 // revoked.
151 public boolean hasBiasPattern() {
152 return (Bits.maskBitsLong(value(), biasedLockMaskInPlace) == biasedLockPattern);
153 }
154
155 public JavaThread biasedLocker() {
156 Threads threads = VM.getVM().getThreads();
157 Address addr = valueAsAddress().andWithMask(~(biasedLockMaskInPlace & ageMaskInPlace));
158 return threads.createJavaThreadWrapper(addr);
159 }
160
161 // Indicates that the mark gas the bias bit set but that it has not
162 // yet been biased toward a particular thread
163 public boolean isBiasedAnonymously() {
164 return hasBiasPattern() && (biasedLocker() == null);
165 }
166
167 // lock accessors (note that these assume lock_shift == 0)
168 public boolean isLocked() {
169 return (Bits.maskBitsLong(value(), lockMaskInPlace) != unlockedValue);
170 }
171 public boolean isUnlocked() {
172 return (Bits.maskBitsLong(value(), biasedLockMaskInPlace) == unlockedValue);
173 }
174 public boolean isMarked() {
175 return (Bits.maskBitsLong(value(), lockMaskInPlace) == markedValue);
176 }
177
178 // Special temporary state of the markOop while being inflated.
179 // Code that looks at mark outside a lock need to take this into account.
180 public boolean isBeingInflated() {
181 return (value() == 0);
182 }
183
184 // Should this header be preserved during GC?
185 public boolean mustBePreserved() {
186 return (!isUnlocked() || !hasNoHash());
187 }
188
189 // WARNING: The following routines are used EXCLUSIVELY by
190 // synchronization functions. They are not really gc safe.
191 // They must get updated if markOop layout get changed.
192
193 // FIXME
194 // markOop set_unlocked() const {
195 // return markOop(value() | unlocked_value);
196 // }
197 public boolean hasLocker() {
198 return ((value() & lockMaskInPlace) == lockedValue);
199 }
200 public BasicLock locker() {
201 if (Assert.ASSERTS_ENABLED) {
202 Assert.that(hasLocker(), "check");
203 }
204 return new BasicLock(valueAsAddress());
205 }
206 public boolean hasMonitor() {
207 return ((value() & monitorValue) != 0);
208 }
209 public ObjectMonitor monitor() {
210 if (Assert.ASSERTS_ENABLED) {
211 Assert.that(hasMonitor(), "check");
212 }
213 // Use xor instead of &~ to provide one extra tag-bit check.
214 Address monAddr = valueAsAddress().xorWithMask(monitorValue);
215 return new ObjectMonitor(monAddr);
216 }
217 public boolean hasDisplacedMarkHelper() {
218 return ((value() & unlockedValue) == 0);
219 }
220 public Mark displacedMarkHelper() {
221 if (Assert.ASSERTS_ENABLED) {
222 Assert.that(hasDisplacedMarkHelper(), "check");
223 }
224 Address addr = valueAsAddress().andWithMask(~monitorValue);
225 return new Mark(addr.getAddressAt(0));
226 }
227 // FIXME
228 // void set_displaced_mark_helper(markOop m) const {
229 // assert(has_displaced_mark_helper(), "check");
230 // intptr_t ptr = (value() & ~monitor_value);
231 // *(markOop*)ptr = m;
232 // }
233 // markOop copy_set_hash(intptr_t hash) const {
234 // intptr_t tmp = value() & (~hash_mask_in_place);
235 // tmp |= ((hash & hash_mask) << hash_shift);
236 // return (markOop)tmp;
237 // }
238 // it is only used to be stored into BasicLock as the
239 // indicator that the lock is using heavyweight monitor
240 // static markOop unused_mark() {
241 // return (markOop) marked_value;
242 // }
243 // // the following two functions create the markOop to be
244 // // stored into object header, it encodes monitor info
245 // static markOop encode(BasicLock* lock) {
246 // return (markOop) lock;
247 // }
248 // static markOop encode(ObjectMonitor* monitor) {
249 // intptr_t tmp = (intptr_t) monitor;
250 // return (markOop) (tmp | monitor_value);
251 // }
252 // used for alignment-based marking to reuse the busy state to encode pointers
253 // (see markOop_alignment.hpp)
254 // markOop clear_lock_bits() { return markOop(value() & ~lock_mask_in_place); }
255 //
256 // // age operations
257 // markOop set_marked() { return markOop((value() & ~lock_mask_in_place) | marked_value); }
258 //
259 public int age() { return (int) Bits.maskBitsLong(value() >> ageShift, ageMask); }
260 // markOop set_age(int v) const {
261 // assert((v & ~age_mask) == 0, "shouldn't overflow age field");
262 // return markOop((value() & ~age_mask_in_place) | (((intptr_t)v & age_mask) << age_shift));
263 // }
264 // markOop incr_age() const { return age() == max_age ? markOop(this) : set_age(age() + 1); }
265
266 // hash operations
267 public long hash() {
268 return Bits.maskBitsLong(value() >> hashShift, hashMask);
269 }
270
271 public boolean hasNoHash() {
272 return hash() == noHash;
273 }
274
275 // FIXME
276 // Prototype mark for initialization
277 // static markOop prototype() {
278 // return markOop( no_hash_in_place | no_lock_in_place );
279 // }
280
281 // Debugging
282 public void printOn(PrintStream tty) {
283 if (isLocked()) {
284 tty.print("locked(0x" +
285 Long.toHexString(value()) + ")->");
286 displacedMarkHelper().printOn(tty);
287 } else {
288 if (Assert.ASSERTS_ENABLED) {
289 Assert.that(isUnlocked(), "just checking");
290 }
291 tty.print("mark(");
292 tty.print("hash " + Long.toHexString(hash()) + ",");
293 tty.print("age " + age() + ")");
294 }
295 }
296
297 // FIXME
298 // // Prepare address of oop for placement into mark
299 // inline static markOop encode_pointer_as_mark(void* p) { return markOop(p)->set_marked(); }
300 //
301 // // Recover address of oop from encoded form used in mark
302 // inline void* decode_pointer() { return clear_lock_bits(); }
303
304 // Copy markOop methods for CMS here.
305 public boolean isCmsFreeChunk() {
306 return isUnlocked() &&
307 (Bits.maskBitsLong(value() >> cmsShift, cmsMask) & 0x1L) == 0x1L;
308 }
309 public long getSize() { return (long)(value() >> sizeShift); }
310 }