| 10 |
|
import java.util.concurrent.atomic.*; |
| 11 |
|
import java.util.*; |
| 12 |
|
import java.io.*; |
| 13 |
+ |
import sun.misc.Unsafe; |
| 14 |
+ |
import java.lang.reflect.*; |
| 15 |
|
|
| 16 |
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/** |
| 17 |
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* An unbounded {@linkplain TransferQueue} based on linked nodes. |
| 21 |
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* producer. The <em>tail</em> of the queue is that element that has |
| 22 |
|
* been on the queue the shortest time for some producer. |
| 23 |
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* |
| 24 |
< |
* <p>Beware that, unlike in most collections, the <tt>size</tt> |
| 24 |
> |
* <p>Beware that, unlike in most collections, the {@code size} |
| 25 |
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* method is <em>NOT</em> a constant-time operation. Because of the |
| 26 |
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* asynchronous nature of these queues, determining the current number |
| 27 |
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* of elements requires a traversal of the elements. |
| 51 |
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private static final long serialVersionUID = -3223113410248163686L; |
| 52 |
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|
| 53 |
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/* |
| 52 |
– |
* This is still a work in progress... |
| 53 |
– |
* |
| 54 |
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* This class extends the approach used in FIFO-mode |
| 55 |
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* SynchronousQueues. See the internal documentation, as well as |
| 56 |
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* the PPoPP 2006 paper "Scalable Synchronous Queues" by Scherer, |
| 57 |
|
* Lea & Scott |
| 58 |
|
* (http://www.cs.rice.edu/~wns1/papers/2006-PPoPP-SQ.pdf) |
| 59 |
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* |
| 60 |
< |
* The main extension is to provide different Wait modes |
| 61 |
< |
* for the main "xfer" method that puts or takes items. |
| 62 |
< |
* These don't impact the basic dual-queue logic, but instead |
| 63 |
< |
* control whether or how threads block upon insertion |
| 64 |
< |
* of request or data nodes into the dual queue. |
| 60 |
> |
* The main extension is to provide different Wait modes for the |
| 61 |
> |
* main "xfer" method that puts or takes items. These don't |
| 62 |
> |
* impact the basic dual-queue logic, but instead control whether |
| 63 |
> |
* or how threads block upon insertion of request or data nodes |
| 64 |
> |
* into the dual queue. It also uses slightly different |
| 65 |
> |
* conventions for tracking whether nodes are off-list or |
| 66 |
> |
* cancelled. |
| 67 |
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*/ |
| 68 |
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|
| 69 |
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// Wait modes for xfer method |
| 81 |
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* seems not to vary with number of CPUs (beyond 2) so is just |
| 82 |
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* a constant. |
| 83 |
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*/ |
| 84 |
< |
static final int maxTimedSpins = (NCPUS < 2)? 0 : 32; |
| 84 |
> |
static final int maxTimedSpins = (NCPUS < 2)? 0 : 32; |
| 85 |
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|
| 86 |
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/** |
| 87 |
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* The number of times to spin before blocking in untimed waits. |
| 96 |
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*/ |
| 97 |
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static final long spinForTimeoutThreshold = 1000L; |
| 98 |
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|
| 99 |
< |
/** |
| 100 |
< |
* Node class for LinkedTransferQueue. Opportunistically subclasses from |
| 101 |
< |
* AtomicReference to represent item. Uses Object, not E, to allow |
| 102 |
< |
* setting item to "this" after use, to avoid garbage |
| 103 |
< |
* retention. Similarly, setting the next field to this is used as |
| 104 |
< |
* sentinel that node is off list. |
| 99 |
> |
/** |
| 100 |
> |
* Node class for LinkedTransferQueue. Opportunistically |
| 101 |
> |
* subclasses from AtomicReference to represent item. Uses Object, |
| 102 |
> |
* not E, to allow setting item to "this" after use, to avoid |
| 103 |
> |
* garbage retention. Similarly, setting the next field to this is |
| 104 |
> |
* used as sentinel that node is off list. |
| 105 |
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*/ |
| 106 |
|
static final class QNode extends AtomicReference<Object> { |
| 107 |
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volatile QNode next; |
| 133 |
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} |
| 134 |
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|
| 135 |
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|
| 136 |
< |
private final QNode dummy = new QNode(null, false); |
| 137 |
< |
private final PaddedAtomicReference<QNode> head = |
| 138 |
< |
new PaddedAtomicReference<QNode>(dummy); |
| 139 |
< |
private final PaddedAtomicReference<QNode> tail = |
| 138 |
< |
new PaddedAtomicReference<QNode>(dummy); |
| 136 |
> |
/** head of the queue */ |
| 137 |
> |
private transient final PaddedAtomicReference<QNode> head; |
| 138 |
> |
/** tail of the queue */ |
| 139 |
> |
private transient final PaddedAtomicReference<QNode> tail; |
| 140 |
|
|
| 141 |
|
/** |
| 142 |
|
* Reference to a cancelled node that might not yet have been |
| 143 |
|
* unlinked from queue because it was the last inserted node |
| 144 |
|
* when it cancelled. |
| 145 |
|
*/ |
| 146 |
< |
private final PaddedAtomicReference<QNode> cleanMe = |
| 146 |
< |
new PaddedAtomicReference<QNode>(null); |
| 146 |
> |
private transient final PaddedAtomicReference<QNode> cleanMe; |
| 147 |
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|
| 148 |
|
/** |
| 149 |
|
* Tries to cas nh as new head; if successful, unlink |
| 156 |
|
} |
| 157 |
|
return false; |
| 158 |
|
} |
| 159 |
< |
|
| 159 |
> |
|
| 160 |
|
/** |
| 161 |
|
* Puts or takes an item. Used for most queue operations (except |
| 162 |
< |
* poll() and tryTransfer()) |
| 162 |
> |
* poll() and tryTransfer()). See the similar code in |
| 163 |
> |
* SynchronousQueue for detailed explanation. |
| 164 |
|
* @param e the item or if null, signifies that this is a take |
| 165 |
|
* @param mode the wait mode: NOWAIT, TIMEOUT, WAIT |
| 166 |
|
* @param nanos timeout in nanosecs, used only if mode is TIMEOUT |
| 189 |
|
return awaitFulfill(t, s, e, mode, nanos); |
| 190 |
|
} |
| 191 |
|
} |
| 192 |
< |
|
| 192 |
> |
|
| 193 |
|
else if (h != null) { |
| 194 |
|
QNode first = h.next; |
| 195 |
< |
if (t == tail.get() && first != null && |
| 195 |
> |
if (t == tail.get() && first != null && |
| 196 |
|
advanceHead(h, first)) { |
| 197 |
|
Object x = first.get(); |
| 198 |
|
if (x != first && first.compareAndSet(x, e)) { |
| 229 |
|
} |
| 230 |
|
else if (h != null) { |
| 231 |
|
QNode first = h.next; |
| 232 |
< |
if (t == tail.get() && |
| 232 |
> |
if (t == tail.get() && |
| 233 |
|
first != null && |
| 234 |
|
advanceHead(h, first)) { |
| 235 |
|
Object x = first.get(); |
| 253 |
|
* @param nanos timeout value |
| 254 |
|
* @return matched item, or s if cancelled |
| 255 |
|
*/ |
| 256 |
< |
private Object awaitFulfill(QNode pred, QNode s, Object e, |
| 256 |
> |
private Object awaitFulfill(QNode pred, QNode s, Object e, |
| 257 |
|
int mode, long nanos) { |
| 258 |
|
if (mode == NOWAIT) |
| 259 |
|
return null; |
| 267 |
|
Object x = s.get(); |
| 268 |
|
if (x != e) { // Node was matched or cancelled |
| 269 |
|
advanceHead(pred, s); // unlink if head |
| 270 |
< |
if (x == s) // was cancelled |
| 271 |
< |
return clean(pred, s); |
| 272 |
< |
else if (x != null) { |
| 270 |
> |
if (x == s) { // was cancelled |
| 271 |
> |
clean(pred, s); |
| 272 |
> |
return null; |
| 273 |
> |
} |
| 274 |
> |
else if (x != null) { |
| 275 |
|
s.set(s); // avoid garbage retention |
| 276 |
|
return x; |
| 277 |
|
} |
| 278 |
|
else |
| 279 |
|
return e; |
| 280 |
|
} |
| 278 |
– |
|
| 281 |
|
if (mode == TIMEOUT) { |
| 282 |
|
long now = System.nanoTime(); |
| 283 |
|
nanos -= now - lastTime; |
| 290 |
|
if (spins < 0) { |
| 291 |
|
QNode h = head.get(); // only spin if at head |
| 292 |
|
spins = ((h != null && h.next == s) ? |
| 293 |
< |
(mode == TIMEOUT? |
| 293 |
> |
(mode == TIMEOUT? |
| 294 |
|
maxTimedSpins : maxUntimedSpins) : 0); |
| 295 |
|
} |
| 296 |
|
if (spins > 0) |
| 298 |
|
else if (s.waiter == null) |
| 299 |
|
s.waiter = w; |
| 300 |
|
else if (mode != TIMEOUT) { |
| 301 |
< |
// LockSupport.park(this); |
| 300 |
< |
LockSupport.park(); // allows run on java5 |
| 301 |
> |
LockSupport.park(this); |
| 302 |
|
s.waiter = null; |
| 303 |
|
spins = -1; |
| 304 |
|
} |
| 305 |
|
else if (nanos > spinForTimeoutThreshold) { |
| 306 |
< |
// LockSupport.parkNanos(this, nanos); |
| 306 |
< |
LockSupport.parkNanos(nanos); |
| 306 |
> |
LockSupport.parkNanos(this, nanos); |
| 307 |
|
s.waiter = null; |
| 308 |
|
spins = -1; |
| 309 |
|
} |
| 311 |
|
} |
| 312 |
|
|
| 313 |
|
/** |
| 314 |
+ |
* Returns validated tail for use in cleaning methods |
| 315 |
+ |
*/ |
| 316 |
+ |
private QNode getValidatedTail() { |
| 317 |
+ |
for (;;) { |
| 318 |
+ |
QNode h = head.get(); |
| 319 |
+ |
QNode first = h.next; |
| 320 |
+ |
if (first != null && first.next == first) { // help advance |
| 321 |
+ |
advanceHead(h, first); |
| 322 |
+ |
continue; |
| 323 |
+ |
} |
| 324 |
+ |
QNode t = tail.get(); |
| 325 |
+ |
QNode last = t.next; |
| 326 |
+ |
if (t == tail.get()) { |
| 327 |
+ |
if (last != null) |
| 328 |
+ |
tail.compareAndSet(t, last); // help advance |
| 329 |
+ |
else |
| 330 |
+ |
return t; |
| 331 |
+ |
} |
| 332 |
+ |
} |
| 333 |
+ |
} |
| 334 |
+ |
|
| 335 |
+ |
/** |
| 336 |
|
* Gets rid of cancelled node s with original predecessor pred. |
| 337 |
< |
* @return null (to simplify use by callers) |
| 337 |
> |
* @param pred predecessor of cancelled node |
| 338 |
> |
* @param s the cancelled node |
| 339 |
|
*/ |
| 340 |
< |
private Object clean(QNode pred, QNode s) { |
| 340 |
> |
private void clean(QNode pred, QNode s) { |
| 341 |
|
Thread w = s.waiter; |
| 342 |
|
if (w != null) { // Wake up thread |
| 343 |
|
s.waiter = null; |
| 344 |
|
if (w != Thread.currentThread()) |
| 345 |
|
LockSupport.unpark(w); |
| 346 |
|
} |
| 347 |
< |
|
| 348 |
< |
for (;;) { |
| 349 |
< |
if (pred.next != s) // already cleaned |
| 350 |
< |
return null; |
| 351 |
< |
QNode h = head.get(); |
| 352 |
< |
QNode hn = h.next; // Absorb cancelled first node as head |
| 353 |
< |
if (hn != null && hn.next == hn) { |
| 354 |
< |
advanceHead(h, hn); |
| 355 |
< |
continue; |
| 356 |
< |
} |
| 357 |
< |
QNode t = tail.get(); // Ensure consistent read for tail |
| 358 |
< |
if (t == h) |
| 359 |
< |
return null; |
| 337 |
< |
QNode tn = t.next; |
| 338 |
< |
if (t != tail.get()) |
| 339 |
< |
continue; |
| 340 |
< |
if (tn != null) { // Help advance tail |
| 341 |
< |
tail.compareAndSet(t, tn); |
| 342 |
< |
continue; |
| 343 |
< |
} |
| 344 |
< |
if (s != t) { // If not tail, try to unsplice |
| 345 |
< |
QNode sn = s.next; |
| 347 |
> |
/* |
| 348 |
> |
* At any given time, exactly one node on list cannot be |
| 349 |
> |
* deleted -- the last inserted node. To accommodate this, if |
| 350 |
> |
* we cannot delete s, we save its predecessor as "cleanMe", |
| 351 |
> |
* processing the previously saved version first. At least one |
| 352 |
> |
* of node s or the node previously saved can always be |
| 353 |
> |
* processed, so this always terminates. |
| 354 |
> |
*/ |
| 355 |
> |
while (pred.next == s) { |
| 356 |
> |
QNode oldpred = reclean(); // First, help get rid of cleanMe |
| 357 |
> |
QNode t = getValidatedTail(); |
| 358 |
> |
if (s != t) { // If not tail, try to unsplice |
| 359 |
> |
QNode sn = s.next; // s.next == s means s already off list |
| 360 |
|
if (sn == s || pred.casNext(s, sn)) |
| 361 |
< |
return null; |
| 361 |
> |
break; |
| 362 |
|
} |
| 363 |
< |
QNode dp = cleanMe.get(); |
| 364 |
< |
if (dp != null) { // Try unlinking previous cancelled node |
| 365 |
< |
QNode d = dp.next; |
| 366 |
< |
QNode dn; |
| 367 |
< |
if (d == null || // d is gone or |
| 368 |
< |
d == dp || // d is off list or |
| 369 |
< |
d.get() != d || // d not cancelled or |
| 370 |
< |
(d != t && // d not tail and |
| 371 |
< |
(dn = d.next) != null && // has successor |
| 372 |
< |
dn != d && // that is on list |
| 373 |
< |
dp.casNext(d, dn))) // d unspliced |
| 374 |
< |
cleanMe.compareAndSet(dp, null); |
| 375 |
< |
if (dp == pred) |
| 376 |
< |
return null; // s is already saved node |
| 377 |
< |
} |
| 378 |
< |
else if (cleanMe.compareAndSet(null, pred)) |
| 379 |
< |
return null; // Postpone cleaning s |
| 363 |
> |
else if (oldpred == pred || // Already saved |
| 364 |
> |
(oldpred == null && cleanMe.compareAndSet(null, pred))) |
| 365 |
> |
break; // Postpone cleaning |
| 366 |
> |
} |
| 367 |
> |
} |
| 368 |
> |
|
| 369 |
> |
/** |
| 370 |
> |
* Tries to unsplice the cancelled node held in cleanMe that was |
| 371 |
> |
* previously uncleanable because it was at tail. |
| 372 |
> |
* @return current cleanMe node (or null) |
| 373 |
> |
*/ |
| 374 |
> |
private QNode reclean() { |
| 375 |
> |
/* |
| 376 |
> |
* cleanMe is, or at one time was, predecessor of cancelled |
| 377 |
> |
* node s that was the tail so could not be unspliced. If s |
| 378 |
> |
* is no longer the tail, try to unsplice if necessary and |
| 379 |
> |
* make cleanMe slot available. This differs from similar |
| 380 |
> |
* code in clean() because we must check that pred still |
| 381 |
> |
* points to a cancelled node that must be unspliced -- if |
| 382 |
> |
* not, we can (must) clear cleanMe without unsplicing. |
| 383 |
> |
* This can loop only due to contention on casNext or |
| 384 |
> |
* clearing cleanMe. |
| 385 |
> |
*/ |
| 386 |
> |
QNode pred; |
| 387 |
> |
while ((pred = cleanMe.get()) != null) { |
| 388 |
> |
QNode t = getValidatedTail(); |
| 389 |
> |
QNode s = pred.next; |
| 390 |
> |
if (s != t) { |
| 391 |
> |
QNode sn; |
| 392 |
> |
if (s == null || s == pred || s.get() != s || |
| 393 |
> |
(sn = s.next) == s || pred.casNext(s, sn)) |
| 394 |
> |
cleanMe.compareAndSet(pred, null); |
| 395 |
> |
} |
| 396 |
> |
else // s is still tail; cannot clean |
| 397 |
> |
break; |
| 398 |
|
} |
| 399 |
+ |
return pred; |
| 400 |
|
} |
| 401 |
< |
|
| 401 |
> |
|
| 402 |
|
/** |
| 403 |
< |
* Creates an initially empty <tt>LinkedTransferQueue</tt>. |
| 403 |
> |
* Creates an initially empty {@code LinkedTransferQueue}. |
| 404 |
|
*/ |
| 405 |
|
public LinkedTransferQueue() { |
| 406 |
+ |
QNode dummy = new QNode(null, false); |
| 407 |
+ |
head = new PaddedAtomicReference<QNode>(dummy); |
| 408 |
+ |
tail = new PaddedAtomicReference<QNode>(dummy); |
| 409 |
+ |
cleanMe = new PaddedAtomicReference<QNode>(null); |
| 410 |
|
} |
| 411 |
|
|
| 412 |
|
/** |
| 413 |
< |
* Creates a <tt>LinkedTransferQueue</tt> |
| 413 |
> |
* Creates a {@code LinkedTransferQueue} |
| 414 |
|
* initially containing the elements of the given collection, |
| 415 |
|
* added in traversal order of the collection's iterator. |
| 416 |
|
* @param c the collection of elements to initially contain |
| 418 |
|
* of its elements are null |
| 419 |
|
*/ |
| 420 |
|
public LinkedTransferQueue(Collection<? extends E> c) { |
| 421 |
+ |
this(); |
| 422 |
|
addAll(c); |
| 423 |
|
} |
| 424 |
|
|
| 428 |
|
xfer(e, NOWAIT, 0); |
| 429 |
|
} |
| 430 |
|
|
| 431 |
< |
public boolean offer(E e, long timeout, TimeUnit unit) |
| 431 |
> |
public boolean offer(E e, long timeout, TimeUnit unit) |
| 432 |
|
throws InterruptedException { |
| 433 |
|
if (e == null) throw new NullPointerException(); |
| 434 |
|
if (Thread.interrupted()) throw new InterruptedException(); |
| 445 |
|
public void transfer(E e) throws InterruptedException { |
| 446 |
|
if (e == null) throw new NullPointerException(); |
| 447 |
|
if (xfer(e, WAIT, 0) == null) { |
| 448 |
< |
Thread.interrupted(); |
| 448 |
> |
Thread.interrupted(); |
| 449 |
|
throw new InterruptedException(); |
| 450 |
< |
} |
| 450 |
> |
} |
| 451 |
|
} |
| 452 |
|
|
| 453 |
|
public boolean tryTransfer(E e, long timeout, TimeUnit unit) |
| 469 |
|
Object e = xfer(null, WAIT, 0); |
| 470 |
|
if (e != null) |
| 471 |
|
return (E)e; |
| 472 |
< |
Thread.interrupted(); |
| 472 |
> |
Thread.interrupted(); |
| 473 |
|
throw new InterruptedException(); |
| 474 |
|
} |
| 475 |
|
|
| 525 |
|
QNode last = t.next; |
| 526 |
|
QNode first = h.next; |
| 527 |
|
if (t == tail.get()) { |
| 528 |
< |
if (last != null) |
| 528 |
> |
if (last != null) |
| 529 |
|
tail.compareAndSet(t, last); |
| 530 |
|
else if (first != null) { |
| 531 |
|
Object x = first.get(); |
| 532 |
< |
if (x == first) |
| 533 |
< |
advanceHead(h, first); |
| 532 |
> |
if (x == first) |
| 533 |
> |
advanceHead(h, first); |
| 534 |
|
else |
| 535 |
|
return h; |
| 536 |
|
} |
| 558 |
|
QNode currentNode; // last returned node, for remove() |
| 559 |
|
QNode prevNode; // predecessor of last returned node |
| 560 |
|
E nextItem; // Cache of next item, once commited to in next |
| 561 |
< |
|
| 561 |
> |
|
| 562 |
|
Itr() { |
| 563 |
|
nextNode = traversalHead(); |
| 564 |
|
advance(); |
| 565 |
|
} |
| 566 |
< |
|
| 566 |
> |
|
| 567 |
|
E advance() { |
| 568 |
|
prevNode = currentNode; |
| 569 |
|
currentNode = nextNode; |
| 570 |
|
E x = nextItem; |
| 571 |
< |
|
| 571 |
> |
|
| 572 |
|
QNode p = nextNode.next; |
| 573 |
|
for (;;) { |
| 574 |
|
if (p == null || !p.isData) { |
| 581 |
|
nextNode = p; |
| 582 |
|
nextItem = (E)item; |
| 583 |
|
return x; |
| 584 |
< |
} |
| 584 |
> |
} |
| 585 |
|
prevNode = p; |
| 586 |
|
p = p.next; |
| 587 |
|
} |
| 588 |
|
} |
| 589 |
< |
|
| 589 |
> |
|
| 590 |
|
public boolean hasNext() { |
| 591 |
|
return nextNode != null; |
| 592 |
|
} |
| 593 |
< |
|
| 593 |
> |
|
| 594 |
|
public E next() { |
| 595 |
|
if (nextNode == null) throw new NoSuchElementException(); |
| 596 |
|
return advance(); |
| 597 |
|
} |
| 598 |
< |
|
| 598 |
> |
|
| 599 |
|
public void remove() { |
| 600 |
|
QNode p = currentNode; |
| 601 |
|
QNode prev = prevNode; |
| 602 |
< |
if (prev == null || p == null) |
| 602 |
> |
if (prev == null || p == null) |
| 603 |
|
throw new IllegalStateException(); |
| 604 |
|
Object x = p.get(); |
| 605 |
|
if (x != null && x != p && p.compareAndSet(x, p)) |
| 646 |
|
if (p == null) |
| 647 |
|
return false; |
| 648 |
|
Object x = p.get(); |
| 649 |
< |
if (p != x) |
| 649 |
> |
if (p != x) |
| 650 |
|
return !p.isData; |
| 651 |
|
} |
| 652 |
|
} |
| 653 |
< |
|
| 653 |
> |
|
| 654 |
|
/** |
| 655 |
|
* Returns the number of elements in this queue. If this queue |
| 656 |
< |
* contains more than <tt>Integer.MAX_VALUE</tt> elements, returns |
| 657 |
< |
* <tt>Integer.MAX_VALUE</tt>. |
| 656 |
> |
* contains more than {@code Integer.MAX_VALUE} elements, returns |
| 657 |
> |
* {@code Integer.MAX_VALUE}. |
| 658 |
|
* |
| 659 |
|
* <p>Beware that, unlike in most collections, this method is |
| 660 |
|
* <em>NOT</em> a constant-time operation. Because of the |
| 668 |
|
QNode h = traversalHead(); |
| 669 |
|
for (QNode p = h.next; p != null && p.isData; p = p.next) { |
| 670 |
|
Object x = p.get(); |
| 671 |
< |
if (x != null && x != p) { |
| 671 |
> |
if (x != null && x != p) { |
| 672 |
|
if (++count == Integer.MAX_VALUE) // saturated |
| 673 |
|
break; |
| 674 |
|
} |
| 695 |
|
/** |
| 696 |
|
* Save the state to a stream (that is, serialize it). |
| 697 |
|
* |
| 698 |
< |
* @serialData All of the elements (each an <tt>E</tt>) in |
| 698 |
> |
* @serialData All of the elements (each an {@code E}) in |
| 699 |
|
* the proper order, followed by a null |
| 700 |
|
* @param s the stream |
| 701 |
|
*/ |
| 716 |
|
private void readObject(java.io.ObjectInputStream s) |
| 717 |
|
throws java.io.IOException, ClassNotFoundException { |
| 718 |
|
s.defaultReadObject(); |
| 719 |
+ |
resetHeadAndTail(); |
| 720 |
|
for (;;) { |
| 721 |
|
E item = (E)s.readObject(); |
| 722 |
|
if (item == null) |
| 725 |
|
offer(item); |
| 726 |
|
} |
| 727 |
|
} |
| 728 |
+ |
|
| 729 |
+ |
|
| 730 |
+ |
// Support for resetting head/tail while deserializing |
| 731 |
+ |
private void resetHeadAndTail() { |
| 732 |
+ |
QNode dummy = new QNode(null, false); |
| 733 |
+ |
_unsafe.putObjectVolatile(this, headOffset, |
| 734 |
+ |
new PaddedAtomicReference<QNode>(dummy)); |
| 735 |
+ |
_unsafe.putObjectVolatile(this, tailOffset, |
| 736 |
+ |
new PaddedAtomicReference<QNode>(dummy)); |
| 737 |
+ |
_unsafe.putObjectVolatile(this, cleanMeOffset, |
| 738 |
+ |
new PaddedAtomicReference<QNode>(null)); |
| 739 |
+ |
} |
| 740 |
+ |
|
| 741 |
+ |
// Temporary Unsafe mechanics for preliminary release |
| 742 |
+ |
private static Unsafe getUnsafe() throws Throwable { |
| 743 |
+ |
try { |
| 744 |
+ |
return Unsafe.getUnsafe(); |
| 745 |
+ |
} catch (SecurityException se) { |
| 746 |
+ |
try { |
| 747 |
+ |
return java.security.AccessController.doPrivileged |
| 748 |
+ |
(new java.security.PrivilegedExceptionAction<Unsafe>() { |
| 749 |
+ |
public Unsafe run() throws Exception { |
| 750 |
+ |
return getUnsafePrivileged(); |
| 751 |
+ |
}}); |
| 752 |
+ |
} catch (java.security.PrivilegedActionException e) { |
| 753 |
+ |
throw e.getCause(); |
| 754 |
+ |
} |
| 755 |
+ |
} |
| 756 |
+ |
} |
| 757 |
+ |
|
| 758 |
+ |
private static Unsafe getUnsafePrivileged() |
| 759 |
+ |
throws NoSuchFieldException, IllegalAccessException { |
| 760 |
+ |
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
| 761 |
+ |
f.setAccessible(true); |
| 762 |
+ |
return (Unsafe) f.get(null); |
| 763 |
+ |
} |
| 764 |
+ |
|
| 765 |
+ |
private static long fieldOffset(String fieldName) |
| 766 |
+ |
throws NoSuchFieldException { |
| 767 |
+ |
return _unsafe.objectFieldOffset |
| 768 |
+ |
(LinkedTransferQueue.class.getDeclaredField(fieldName)); |
| 769 |
+ |
} |
| 770 |
+ |
|
| 771 |
+ |
private static final Unsafe _unsafe; |
| 772 |
+ |
private static final long headOffset; |
| 773 |
+ |
private static final long tailOffset; |
| 774 |
+ |
private static final long cleanMeOffset; |
| 775 |
+ |
static { |
| 776 |
+ |
try { |
| 777 |
+ |
_unsafe = getUnsafe(); |
| 778 |
+ |
headOffset = fieldOffset("head"); |
| 779 |
+ |
tailOffset = fieldOffset("tail"); |
| 780 |
+ |
cleanMeOffset = fieldOffset("cleanMe"); |
| 781 |
+ |
} catch (Throwable e) { |
| 782 |
+ |
throw new RuntimeException("Could not initialize intrinsics", e); |
| 783 |
+ |
} |
| 784 |
+ |
} |
| 785 |
+ |
|
| 786 |
|
} |
