| 1 |
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/* |
| 2 |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
| 3 |
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* Expert Group and released to the public domain, as explained at |
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< |
* http://creativecommons.org/licenses/publicdomain |
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> |
* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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package jsr166y; |
| 130 |
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* void runTasks(List<Runnable> tasks) { |
| 131 |
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* final Phaser phaser = new Phaser(1); // "1" to register self |
| 132 |
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* // create and start threads |
| 133 |
< |
* for (Runnable task : tasks) { |
| 133 |
> |
* for (final Runnable task : tasks) { |
| 134 |
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* phaser.register(); |
| 135 |
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* new Thread() { |
| 136 |
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* public void run() { |
| 237 |
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*/ |
| 238 |
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|
| 239 |
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/** |
| 240 |
< |
* Primary state representation, holding four fields: |
| 240 |
> |
* Primary state representation, holding four bit-fields: |
| 241 |
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* |
| 242 |
< |
* * unarrived -- the number of parties yet to hit barrier (bits 0-15) |
| 243 |
< |
* * parties -- the number of parties to wait (bits 16-31) |
| 244 |
< |
* * phase -- the generation of the barrier (bits 32-62) |
| 245 |
< |
* * terminated -- set if barrier is terminated (bit 63 / sign) |
| 242 |
> |
* unarrived -- the number of parties yet to hit barrier (bits 0-15) |
| 243 |
> |
* parties -- the number of parties to wait (bits 16-31) |
| 244 |
> |
* phase -- the generation of the barrier (bits 32-62) |
| 245 |
> |
* terminated -- set if barrier is terminated (bit 63 / sign) |
| 246 |
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* |
| 247 |
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* Except that a phaser with no registered parties is |
| 248 |
< |
* distinguished with the otherwise illegal state of having zero |
| 248 |
> |
* distinguished by the otherwise illegal state of having zero |
| 249 |
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* parties and one unarrived parties (encoded as EMPTY below). |
| 250 |
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* |
| 251 |
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* To efficiently maintain atomicity, these values are packed into |
| 260 |
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* parent. |
| 261 |
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* |
| 262 |
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* The phase of a subphaser is allowed to lag that of its |
| 263 |
< |
* ancestors until it is actually accessed. Method reconcileState |
| 264 |
< |
* is usually attempted only only when the number of unarrived |
| 265 |
< |
* parties appears to be zero, which indicates a potential lag in |
| 266 |
< |
* updating phase after the root advanced. |
| 263 |
> |
* ancestors until it is actually accessed -- see method |
| 264 |
> |
* reconcileState. |
| 265 |
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*/ |
| 266 |
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private volatile long state; |
| 267 |
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|
| 268 |
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private static final int MAX_PARTIES = 0xffff; |
| 269 |
< |
private static final int MAX_PHASE = 0x7fffffff; |
| 269 |
> |
private static final int MAX_PHASE = Integer.MAX_VALUE; |
| 270 |
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private static final int PARTIES_SHIFT = 16; |
| 271 |
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private static final int PHASE_SHIFT = 32; |
| 272 |
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private static final int UNARRIVED_MASK = 0xffff; // to mask ints |
| 276 |
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// some special values |
| 277 |
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private static final int ONE_ARRIVAL = 1; |
| 278 |
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private static final int ONE_PARTY = 1 << PARTIES_SHIFT; |
| 279 |
+ |
private static final int ONE_DEREGISTER = ONE_ARRIVAL|ONE_PARTY; |
| 280 |
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private static final int EMPTY = 1; |
| 281 |
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|
| 282 |
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// The following unpacking methods are usually manually inlined |
| 283 |
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|
| 284 |
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private static int unarrivedOf(long s) { |
| 285 |
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int counts = (int)s; |
| 286 |
< |
return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK; |
| 286 |
> |
return (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK); |
| 287 |
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} |
| 288 |
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|
| 289 |
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private static int partiesOf(long s) { |
| 291 |
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} |
| 292 |
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|
| 293 |
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private static int phaseOf(long s) { |
| 294 |
< |
return (int) (s >>> PHASE_SHIFT); |
| 294 |
> |
return (int)(s >>> PHASE_SHIFT); |
| 295 |
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} |
| 296 |
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|
| 297 |
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private static int arrivedOf(long s) { |
| 344 |
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* Manually tuned to speed up and minimize race windows for the |
| 345 |
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* common case of just decrementing unarrived field. |
| 346 |
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* |
| 347 |
< |
* @param deregister false for arrive, true for arriveAndDeregister |
| 347 |
> |
* @param adjust value to subtract from state; |
| 348 |
> |
* ONE_ARRIVAL for arrive, |
| 349 |
> |
* ONE_DEREGISTER for arriveAndDeregister |
| 350 |
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*/ |
| 351 |
< |
private int doArrive(boolean deregister) { |
| 351 |
< |
int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL; |
| 351 |
> |
private int doArrive(int adjust) { |
| 352 |
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final Phaser root = this.root; |
| 353 |
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for (;;) { |
| 354 |
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long s = (root == this) ? state : reconcileState(); |
| 355 |
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int phase = (int)(s >>> PHASE_SHIFT); |
| 356 |
– |
int counts = (int)s; |
| 357 |
– |
int unarrived = (counts & UNARRIVED_MASK) - 1; |
| 356 |
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if (phase < 0) |
| 357 |
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return phase; |
| 358 |
< |
else if (counts == EMPTY || unarrived < 0) { |
| 359 |
< |
if (root == this || reconcileState() == s) |
| 360 |
< |
throw new IllegalStateException(badArrive(s)); |
| 361 |
< |
} |
| 362 |
< |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
| 363 |
< |
if (unarrived == 0) { |
| 358 |
> |
int counts = (int)s; |
| 359 |
> |
int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK); |
| 360 |
> |
if (unarrived <= 0) |
| 361 |
> |
throw new IllegalStateException(badArrive(s)); |
| 362 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adjust)) { |
| 363 |
> |
if (unarrived == 1) { |
| 364 |
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long n = s & PARTIES_MASK; // base of next state |
| 365 |
< |
int nextUnarrived = ((int)n) >>> PARTIES_SHIFT; |
| 366 |
< |
if (root != this) |
| 367 |
< |
return parent.doArrive(nextUnarrived == 0); |
| 368 |
< |
if (onAdvance(phase, nextUnarrived)) |
| 369 |
< |
n |= TERMINATION_BIT; |
| 370 |
< |
else if (nextUnarrived == 0) |
| 371 |
< |
n |= EMPTY; |
| 365 |
> |
int nextUnarrived = (int)n >>> PARTIES_SHIFT; |
| 366 |
> |
if (root == this) { |
| 367 |
> |
if (onAdvance(phase, nextUnarrived)) |
| 368 |
> |
n |= TERMINATION_BIT; |
| 369 |
> |
else if (nextUnarrived == 0) |
| 370 |
> |
n |= EMPTY; |
| 371 |
> |
else |
| 372 |
> |
n |= nextUnarrived; |
| 373 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
| 374 |
> |
n |= (long)nextPhase << PHASE_SHIFT; |
| 375 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, n); |
| 376 |
> |
releaseWaiters(phase); |
| 377 |
> |
} |
| 378 |
> |
else if (nextUnarrived == 0) { // propagate deregistration |
| 379 |
> |
phase = parent.doArrive(ONE_DEREGISTER); |
| 380 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, |
| 381 |
> |
s, s | EMPTY); |
| 382 |
> |
} |
| 383 |
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else |
| 384 |
< |
n |= nextUnarrived; |
| 376 |
< |
n |= ((long)((phase + 1) & MAX_PHASE)) << PHASE_SHIFT; |
| 377 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, n); |
| 378 |
< |
releaseWaiters(phase); |
| 384 |
> |
phase = parent.doArrive(ONE_ARRIVAL); |
| 385 |
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} |
| 386 |
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return phase; |
| 387 |
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} |
| 396 |
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*/ |
| 397 |
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private int doRegister(int registrations) { |
| 398 |
|
// adjustment to state |
| 399 |
< |
long adj = ((long)registrations << PARTIES_SHIFT) | registrations; |
| 400 |
< |
Phaser par = parent; |
| 399 |
> |
long adjust = ((long)registrations << PARTIES_SHIFT) | registrations; |
| 400 |
> |
final Phaser parent = this.parent; |
| 401 |
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int phase; |
| 402 |
|
for (;;) { |
| 403 |
< |
long s = state; |
| 403 |
> |
long s = (parent == null) ? state : reconcileState(); |
| 404 |
|
int counts = (int)s; |
| 405 |
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int parties = counts >>> PARTIES_SHIFT; |
| 406 |
|
int unarrived = counts & UNARRIVED_MASK; |
| 407 |
|
if (registrations > MAX_PARTIES - parties) |
| 408 |
|
throw new IllegalStateException(badRegister(s)); |
| 409 |
< |
else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0) |
| 409 |
> |
phase = (int)(s >>> PHASE_SHIFT); |
| 410 |
> |
if (phase < 0) |
| 411 |
|
break; |
| 412 |
< |
else if (counts != EMPTY) { // not 1st registration |
| 413 |
< |
if (par == null || reconcileState() == s) { |
| 412 |
> |
if (counts != EMPTY) { // not 1st registration |
| 413 |
> |
if (parent == null || reconcileState() == s) { |
| 414 |
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if (unarrived == 0) // wait out advance |
| 415 |
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root.internalAwaitAdvance(phase, null); |
| 416 |
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else if (UNSAFE.compareAndSwapLong(this, stateOffset, |
| 417 |
< |
s, s + adj)) |
| 417 |
> |
s, s + adjust)) |
| 418 |
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break; |
| 419 |
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} |
| 420 |
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} |
| 421 |
< |
else if (par == null) { // 1st root registration |
| 422 |
< |
long next = (((long) phase) << PHASE_SHIFT) | adj; |
| 421 |
> |
else if (parent == null) { // 1st root registration |
| 422 |
> |
long next = ((long)phase << PHASE_SHIFT) | adjust; |
| 423 |
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if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
| 424 |
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break; |
| 425 |
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} |
| 426 |
|
else { |
| 427 |
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synchronized (this) { // 1st sub registration |
| 428 |
|
if (state == s) { // recheck under lock |
| 429 |
< |
par.doRegister(1); |
| 430 |
< |
do { // force current phase |
| 429 |
> |
phase = parent.doRegister(1); |
| 430 |
> |
if (phase < 0) |
| 431 |
> |
break; |
| 432 |
> |
// finish registration whenever parent registration |
| 433 |
> |
// succeeded, even when racing with termination, |
| 434 |
> |
// since these are part of the same "transaction". |
| 435 |
> |
while (!UNSAFE.compareAndSwapLong |
| 436 |
> |
(this, stateOffset, s, |
| 437 |
> |
((long)phase << PHASE_SHIFT) | adjust)) { |
| 438 |
> |
s = state; |
| 439 |
|
phase = (int)(root.state >>> PHASE_SHIFT); |
| 440 |
< |
// assert phase < 0 || (int)state == EMPTY; |
| 441 |
< |
} while (!UNSAFE.compareAndSwapLong |
| 427 |
< |
(this, stateOffset, state, |
| 428 |
< |
(((long) phase) << PHASE_SHIFT) | adj)); |
| 440 |
> |
// assert (int)s == EMPTY; |
| 441 |
> |
} |
| 442 |
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break; |
| 443 |
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} |
| 444 |
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} |
| 449 |
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|
| 450 |
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/** |
| 451 |
|
* Resolves lagged phase propagation from root if necessary. |
| 452 |
+ |
* Reconciliation normally occurs when root has advanced but |
| 453 |
+ |
* subphasers have not yet done so, in which case they must finish |
| 454 |
+ |
* their own advance by setting unarrived to parties (or if |
| 455 |
+ |
* parties is zero, resetting to unregistered EMPTY state). |
| 456 |
+ |
* However, this method may also be called when "floating" |
| 457 |
+ |
* subphasers with possibly some unarrived parties are merely |
| 458 |
+ |
* catching up to current phase, in which case counts are |
| 459 |
+ |
* unaffected. |
| 460 |
+ |
* |
| 461 |
+ |
* @return reconciled state |
| 462 |
|
*/ |
| 463 |
|
private long reconcileState() { |
| 464 |
< |
Phaser rt = root; |
| 464 |
> |
final Phaser root = this.root; |
| 465 |
|
long s = state; |
| 466 |
< |
if (rt != this) { |
| 467 |
< |
int phase; |
| 468 |
< |
while ((phase = (int)(rt.state >>> PHASE_SHIFT)) != |
| 469 |
< |
(int)(s >>> PHASE_SHIFT)) { |
| 470 |
< |
// assert phase < 0 || unarrivedOf(s) == 0 |
| 471 |
< |
long t; // to reread s |
| 472 |
< |
long p = s & PARTIES_MASK; // unshifted parties field |
| 473 |
< |
long n = (((long) phase) << PHASE_SHIFT) | p; |
| 474 |
< |
if (phase >= 0) { |
| 475 |
< |
if (p == 0L) |
| 476 |
< |
n |= EMPTY; // reset to empty |
| 477 |
< |
else |
| 478 |
< |
n |= p >>> PARTIES_SHIFT; // set unarr to parties |
| 456 |
< |
} |
| 457 |
< |
if ((t = state) == s && |
| 458 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, s = n)) |
| 459 |
< |
break; |
| 460 |
< |
s = t; |
| 461 |
< |
} |
| 466 |
> |
if (root != this) { |
| 467 |
> |
int phase, u, p; |
| 468 |
> |
// CAS root phase with current parties; possibly trip unarrived |
| 469 |
> |
while ((phase = (int)(root.state >>> PHASE_SHIFT)) != |
| 470 |
> |
(int)(s >>> PHASE_SHIFT) && |
| 471 |
> |
!UNSAFE.compareAndSwapLong |
| 472 |
> |
(this, stateOffset, s, |
| 473 |
> |
s = (((long)phase << PHASE_SHIFT) | |
| 474 |
> |
(s & PARTIES_MASK) | |
| 475 |
> |
((p = (int)s >>> PARTIES_SHIFT) == 0 ? EMPTY : |
| 476 |
> |
((u = (int)s & UNARRIVED_MASK) == 0 && phase >= 0) ? |
| 477 |
> |
p : u)))) |
| 478 |
> |
s = state; |
| 479 |
|
} |
| 480 |
|
return s; |
| 481 |
|
} |
| 541 |
|
this.evenQ = new AtomicReference<QNode>(); |
| 542 |
|
this.oddQ = new AtomicReference<QNode>(); |
| 543 |
|
} |
| 544 |
< |
this.state = (parties == 0) ? (long) EMPTY : |
| 545 |
< |
((((long) phase) << PHASE_SHIFT) | |
| 546 |
< |
(((long) parties) << PARTIES_SHIFT) | |
| 547 |
< |
((long) parties)); |
| 544 |
> |
this.state = (parties == 0) ? (long)EMPTY : |
| 545 |
> |
((long)phase << PHASE_SHIFT) | |
| 546 |
> |
((long)parties << PARTIES_SHIFT) | |
| 547 |
> |
((long)parties); |
| 548 |
|
} |
| 549 |
|
|
| 550 |
|
/** |
| 606 |
|
* of unarrived parties would become negative |
| 607 |
|
*/ |
| 608 |
|
public int arrive() { |
| 609 |
< |
return doArrive(false); |
| 609 |
> |
return doArrive(ONE_ARRIVAL); |
| 610 |
|
} |
| 611 |
|
|
| 612 |
|
/** |
| 626 |
|
* of registered or unarrived parties would become negative |
| 627 |
|
*/ |
| 628 |
|
public int arriveAndDeregister() { |
| 629 |
< |
return doArrive(true); |
| 629 |
> |
return doArrive(ONE_DEREGISTER); |
| 630 |
|
} |
| 631 |
|
|
| 632 |
|
/** |
| 653 |
|
for (;;) { |
| 654 |
|
long s = (root == this) ? state : reconcileState(); |
| 655 |
|
int phase = (int)(s >>> PHASE_SHIFT); |
| 639 |
– |
int counts = (int)s; |
| 640 |
– |
int unarrived = (counts & UNARRIVED_MASK) - 1; |
| 656 |
|
if (phase < 0) |
| 657 |
|
return phase; |
| 658 |
< |
else if (counts == EMPTY || unarrived < 0) { |
| 659 |
< |
if (reconcileState() == s) |
| 660 |
< |
throw new IllegalStateException(badArrive(s)); |
| 661 |
< |
} |
| 662 |
< |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, |
| 663 |
< |
s -= ONE_ARRIVAL)) { |
| 664 |
< |
if (unarrived != 0) |
| 658 |
> |
int counts = (int)s; |
| 659 |
> |
int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK); |
| 660 |
> |
if (unarrived <= 0) |
| 661 |
> |
throw new IllegalStateException(badArrive(s)); |
| 662 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, |
| 663 |
> |
s -= ONE_ARRIVAL)) { |
| 664 |
> |
if (unarrived > 1) |
| 665 |
|
return root.internalAwaitAdvance(phase, null); |
| 666 |
|
if (root != this) |
| 667 |
|
return parent.arriveAndAwaitAdvance(); |
| 668 |
|
long n = s & PARTIES_MASK; // base of next state |
| 669 |
< |
int nextUnarrived = ((int)n) >>> PARTIES_SHIFT; |
| 669 |
> |
int nextUnarrived = (int)n >>> PARTIES_SHIFT; |
| 670 |
|
if (onAdvance(phase, nextUnarrived)) |
| 671 |
|
n |= TERMINATION_BIT; |
| 672 |
|
else if (nextUnarrived == 0) |
| 791 |
|
final Phaser root = this.root; |
| 792 |
|
long s; |
| 793 |
|
while ((s = root.state) >= 0) { |
| 794 |
< |
long next = (s & ~((long)UNARRIVED_MASK)) | TERMINATION_BIT; |
| 795 |
< |
if (UNSAFE.compareAndSwapLong(root, stateOffset, s, next)) { |
| 794 |
> |
if (UNSAFE.compareAndSwapLong(root, stateOffset, |
| 795 |
> |
s, s | TERMINATION_BIT)) { |
| 796 |
|
// signal all threads |
| 797 |
< |
releaseWaiters(0); |
| 798 |
< |
releaseWaiters(1); |
| 797 |
> |
releaseWaiters(0); // Waiters on evenQ |
| 798 |
> |
releaseWaiters(1); // Waiters on oddQ |
| 799 |
|
return; |
| 800 |
|
} |
| 801 |
|
} |
| 825 |
|
|
| 826 |
|
/** |
| 827 |
|
* Returns the number of registered parties that have arrived at |
| 828 |
< |
* the current phase of this phaser. |
| 828 |
> |
* the current phase of this phaser. If this phaser has terminated, |
| 829 |
> |
* the returned value is meaningless and arbitrary. |
| 830 |
|
* |
| 831 |
|
* @return the number of arrived parties |
| 832 |
|
*/ |
| 836 |
|
|
| 837 |
|
/** |
| 838 |
|
* Returns the number of registered parties that have not yet |
| 839 |
< |
* arrived at the current phase of this phaser. |
| 839 |
> |
* arrived at the current phase of this phaser. If this phaser has |
| 840 |
> |
* terminated, the returned value is meaningless and arbitrary. |
| 841 |
|
* |
| 842 |
|
* @return the number of unarrived parties |
| 843 |
|
*/ |
| 1001 |
|
|
| 1002 |
|
/** |
| 1003 |
|
* Possibly blocks and waits for phase to advance unless aborted. |
| 1004 |
< |
* Call only from root node. |
| 1004 |
> |
* Call only on root phaser. |
| 1005 |
|
* |
| 1006 |
|
* @param phase current phase |
| 1007 |
|
* @param node if non-null, the wait node to track interrupt and timeout; |
| 1009 |
|
* @return current phase |
| 1010 |
|
*/ |
| 1011 |
|
private int internalAwaitAdvance(int phase, QNode node) { |
| 1012 |
+ |
// assert root == this; |
| 1013 |
|
releaseWaiters(phase-1); // ensure old queue clean |
| 1014 |
|
boolean queued = false; // true when node is enqueued |
| 1015 |
|
int lastUnarrived = 0; // to increase spins upon change |
| 1123 |
|
|
| 1124 |
|
// Unsafe mechanics |
| 1125 |
|
|
| 1126 |
< |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
| 1127 |
< |
private static final long stateOffset = |
| 1128 |
< |
objectFieldOffset("state", Phaser.class); |
| 1111 |
< |
|
| 1112 |
< |
private static long objectFieldOffset(String field, Class<?> klazz) { |
| 1126 |
> |
private static final sun.misc.Unsafe UNSAFE; |
| 1127 |
> |
private static final long stateOffset; |
| 1128 |
> |
static { |
| 1129 |
|
try { |
| 1130 |
< |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
| 1131 |
< |
} catch (NoSuchFieldException e) { |
| 1132 |
< |
// Convert Exception to corresponding Error |
| 1133 |
< |
NoSuchFieldError error = new NoSuchFieldError(field); |
| 1134 |
< |
error.initCause(e); |
| 1135 |
< |
throw error; |
| 1130 |
> |
UNSAFE = getUnsafe(); |
| 1131 |
> |
Class<?> k = Phaser.class; |
| 1132 |
> |
stateOffset = UNSAFE.objectFieldOffset |
| 1133 |
> |
(k.getDeclaredField("state")); |
| 1134 |
> |
} catch (Exception e) { |
| 1135 |
> |
throw new Error(e); |
| 1136 |
|
} |
| 1137 |
|
} |
| 1138 |
|
|
