| 63 |
|
* |
| 64 |
|
* <p>StampedLocks are designed for use as internal utilities in the |
| 65 |
|
* development of thread-safe components. Their use relies on |
| 66 |
< |
* knowledge of the internal properties of the the data, objects, and |
| 66 |
> |
* knowledge of the internal properties of the data, objects, and |
| 67 |
|
* methods they are protecting. They are not reentrant, so locked |
| 68 |
|
* bodies should not call other unknown methods that may try to |
| 69 |
|
* re-acquire locks (although you may pass a stamp to other methods |
| 125 |
|
* } |
| 126 |
|
* |
| 127 |
|
* double distanceFromOriginV2() { // combines code paths |
| 128 |
+ |
* double currentX = 0.0, currentY = 0.0; |
| 129 |
|
* for (long stamp = sl.tryOptimisticRead(); ; stamp = sl.readLock()) { |
| 129 |
– |
* double currentX = 0.0, currentY = 0.0; |
| 130 |
|
* try { |
| 131 |
|
* currentX = x; |
| 132 |
|
* currentY = y; |
| 133 |
|
* } finally { |
| 134 |
|
* if (sl.tryConvertToOptimisticRead(stamp) != 0L) // unlock or validate |
| 135 |
< |
* return Math.sqrt(currentX * currentX + currentY * currentY); |
| 135 |
> |
* break; |
| 136 |
|
* } |
| 137 |
|
* } |
| 138 |
+ |
* return Math.sqrt(currentX * currentX + currentY * currentY); |
| 139 |
|
* } |
| 140 |
|
* |
| 141 |
|
* void moveIfAtOrigin(double newX, double newY) { // upgrade |
| 156 |
|
* } |
| 157 |
|
* } |
| 158 |
|
* } finally { |
| 159 |
< |
* sl.unlock(stamp); |
| 159 |
> |
* sl.unlock(stamp); |
| 160 |
|
* } |
| 161 |
|
* } |
| 162 |
|
* }}</pre> |
| 226 |
|
* threads. Both await methods use a similar spin strategy: If |
| 227 |
|
* the associated queue appears to be empty, then the thread |
| 228 |
|
* spin-waits up to SPINS times (where each iteration decreases |
| 229 |
< |
* spin count with 50% probablility) before enqueing, and then, if |
| 229 |
> |
* spin count with 50% probability) before enqueuing, and then, if |
| 230 |
|
* it is the first thread to be enqueued, spins again up to SPINS |
| 231 |
|
* times before blocking. If, upon wakening it fails to obtain |
| 232 |
|
* lock, and is still (or becomes) the first waiting thread (which |
| 252 |
|
* be subject to future improvements. |
| 253 |
|
*/ |
| 254 |
|
|
| 255 |
+ |
private static final long serialVersionUID = -6001602636862214147L; |
| 256 |
+ |
|
| 257 |
|
/** Number of processors, for spin control */ |
| 258 |
|
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
| 259 |
|
|
| 997 |
|
else if ((time = deadline - System.nanoTime()) <= 0L) |
| 998 |
|
return cancelWriter(node, false); |
| 999 |
|
if (node.prev == p && p.status == WAITING && |
| 1000 |
< |
(p != whead || (state & WBIT) != 0L)) // recheck |
| 1000 |
> |
(p != whead || (state & ABITS) != 0L)) // recheck |
| 1001 |
|
U.park(false, time); |
| 1002 |
|
if (interruptible && Thread.interrupted()) |
| 1003 |
|
return cancelWriter(node, true); |
| 1010 |
|
/** |
| 1011 |
|
* If node non-null, forces cancel status and unsplices from queue |
| 1012 |
|
* if possible. This is a variant of cancellation methods in |
| 1013 |
< |
* AbstractQueuedSynchronizer (see its detailed explanation in |
| 1013 |
> |
* AbstractQueuedSynchronizer (see its detailed explanation in AQS |
| 1014 |
|
* internal documentation) that more conservatively wakes up other |
| 1015 |
< |
* threads that may have had their links changed so as to preserve |
| 1015 |
> |
* threads that may have had their links changed, so as to preserve |
| 1016 |
|
* liveness in the main signalling methods. |
| 1017 |
|
*/ |
| 1018 |
|
private long cancelWriter(WNode node, boolean interrupted) { |
| 1206 |
|
private static sun.misc.Unsafe getUnsafe() { |
| 1207 |
|
try { |
| 1208 |
|
return sun.misc.Unsafe.getUnsafe(); |
| 1209 |
< |
} catch (SecurityException se) { |
| 1210 |
< |
try { |
| 1211 |
< |
return java.security.AccessController.doPrivileged |
| 1212 |
< |
(new java.security |
| 1213 |
< |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
| 1214 |
< |
public sun.misc.Unsafe run() throws Exception { |
| 1215 |
< |
java.lang.reflect.Field f = sun.misc |
| 1216 |
< |
.Unsafe.class.getDeclaredField("theUnsafe"); |
| 1217 |
< |
f.setAccessible(true); |
| 1218 |
< |
return (sun.misc.Unsafe) f.get(null); |
| 1219 |
< |
}}); |
| 1220 |
< |
} catch (java.security.PrivilegedActionException e) { |
| 1221 |
< |
throw new RuntimeException("Could not initialize intrinsics", |
| 1222 |
< |
e.getCause()); |
| 1223 |
< |
} |
| 1209 |
> |
} catch (SecurityException tryReflectionInstead) {} |
| 1210 |
> |
try { |
| 1211 |
> |
return java.security.AccessController.doPrivileged |
| 1212 |
> |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
| 1213 |
> |
public sun.misc.Unsafe run() throws Exception { |
| 1214 |
> |
Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class; |
| 1215 |
> |
for (java.lang.reflect.Field f : k.getDeclaredFields()) { |
| 1216 |
> |
f.setAccessible(true); |
| 1217 |
> |
Object x = f.get(null); |
| 1218 |
> |
if (k.isInstance(x)) |
| 1219 |
> |
return k.cast(x); |
| 1220 |
> |
} |
| 1221 |
> |
throw new NoSuchFieldError("the Unsafe"); |
| 1222 |
> |
}}); |
| 1223 |
> |
} catch (java.security.PrivilegedActionException e) { |
| 1224 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
| 1225 |
> |
e.getCause()); |
| 1226 |
|
} |
| 1227 |
|
} |
| 1223 |
– |
|
| 1228 |
|
} |
