237 |
|
*/ |
238 |
|
|
239 |
|
/** |
240 |
< |
* Primary state representation, holding four fields: |
240 |
> |
* Primary state representation, holding four bit-fields: |
241 |
|
* |
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 |
|
* |
247 |
|
* 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 |
|
* parties and one unarrived parties (encoded as EMPTY below). |
250 |
|
* |
251 |
|
* To efficiently maintain atomicity, these values are packed into |
266 |
|
private volatile long state; |
267 |
|
|
268 |
|
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 |
|
private static final int PARTIES_SHIFT = 16; |
271 |
|
private static final int PHASE_SHIFT = 32; |
272 |
– |
private static final long PHASE_MASK = -1L << PHASE_SHIFT; |
272 |
|
private static final int UNARRIVED_MASK = 0xffff; // to mask ints |
273 |
|
private static final long PARTIES_MASK = 0xffff0000L; // to mask longs |
274 |
|
private static final long TERMINATION_BIT = 1L << 63; |
276 |
|
// some special values |
277 |
|
private static final int ONE_ARRIVAL = 1; |
278 |
|
private static final int ONE_PARTY = 1 << PARTIES_SHIFT; |
279 |
+ |
private static final int ONE_DEREGISTER = ONE_ARRIVAL|ONE_PARTY; |
280 |
|
private static final int EMPTY = 1; |
281 |
|
|
282 |
|
// The following unpacking methods are usually manually inlined |
283 |
|
|
284 |
|
private static int unarrivedOf(long s) { |
285 |
|
int counts = (int)s; |
286 |
< |
return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK; |
286 |
> |
return (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK); |
287 |
|
} |
288 |
|
|
289 |
|
private static int partiesOf(long s) { |
291 |
|
} |
292 |
|
|
293 |
|
private static int phaseOf(long s) { |
294 |
< |
return (int) (s >>> PHASE_SHIFT); |
294 |
> |
return (int)(s >>> PHASE_SHIFT); |
295 |
|
} |
296 |
|
|
297 |
|
private static int arrivedOf(long s) { |
344 |
|
* Manually tuned to speed up and minimize race windows for the |
345 |
|
* common case of just decrementing unarrived field. |
346 |
|
* |
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 |
|
*/ |
351 |
< |
private int doArrive(boolean deregister) { |
350 |
< |
int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL; |
351 |
> |
private int doArrive(int adjust) { |
352 |
|
final Phaser root = this.root; |
353 |
|
for (;;) { |
354 |
|
long s = (root == this) ? state : reconcileState(); |
355 |
|
int phase = (int)(s >>> PHASE_SHIFT); |
355 |
– |
int counts = (int)s; |
356 |
– |
int unarrived = (counts & UNARRIVED_MASK) - 1; |
356 |
|
if (phase < 0) |
357 |
|
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 |
|
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 |
|
else |
384 |
< |
n |= nextUnarrived; |
375 |
< |
n |= ((long)((phase + 1) & MAX_PHASE)) << PHASE_SHIFT; |
376 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, n); |
377 |
< |
releaseWaiters(phase); |
384 |
> |
phase = parent.doArrive(ONE_ARRIVAL); |
385 |
|
} |
386 |
|
return phase; |
387 |
|
} |
396 |
|
*/ |
397 |
|
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 |
|
int phase; |
402 |
|
for (;;) { |
403 |
< |
long s = state; |
403 |
> |
long s = (parent == null) ? state : reconcileState(); |
404 |
|
int counts = (int)s; |
405 |
|
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 |
|
if (unarrived == 0) // wait out advance |
415 |
|
root.internalAwaitAdvance(phase, null); |
416 |
|
else if (UNSAFE.compareAndSwapLong(this, stateOffset, |
417 |
< |
s, s + adj)) |
417 |
> |
s, s + adjust)) |
418 |
|
break; |
419 |
|
} |
420 |
|
} |
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 |
|
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
424 |
|
break; |
425 |
|
} |
426 |
|
else { |
427 |
|
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 |
426 |
< |
(this, stateOffset, state, |
427 |
< |
(((long) phase) << PHASE_SHIFT) | adj)); |
440 |
> |
// assert (int)s == EMPTY; |
441 |
> |
} |
442 |
|
break; |
443 |
|
} |
444 |
|
} |
470 |
|
(int)(s >>> PHASE_SHIFT) && |
471 |
|
!UNSAFE.compareAndSwapLong |
472 |
|
(this, stateOffset, s, |
473 |
< |
s = ((((long) phase) << PHASE_SHIFT) | (s & PARTIES_MASK) | |
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 ? p : u)))) |
476 |
> |
((u = (int)s & UNARRIVED_MASK) == 0 && phase >= 0) ? |
477 |
> |
p : u)))) |
478 |
|
s = state; |
479 |
|
} |
480 |
|
return s; |
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); |
640 |
– |
int counts = (int)s; |
641 |
– |
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) |
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 |
|
} |
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); |
1114 |
< |
|
1115 |
< |
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 |
|
|