6 |
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package jsr166y; |
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9 |
< |
import java.util.concurrent.*; |
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> |
import java.util.concurrent.TimeUnit; |
10 |
> |
import java.util.concurrent.TimeoutException; |
11 |
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import java.util.concurrent.atomic.AtomicReference; |
12 |
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import java.util.concurrent.locks.LockSupport; |
13 |
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|
227 |
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* Barrier state representation. Conceptually, a barrier contains |
228 |
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* four values: |
229 |
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* |
230 |
< |
* * parties -- the number of parties to wait (16 bits) |
231 |
< |
* * unarrived -- the number of parties yet to hit barrier (16 bits) |
232 |
< |
* * phase -- the generation of the barrier (31 bits) |
233 |
< |
* * terminated -- set if barrier is terminated (1 bit) |
230 |
> |
* * unarrived -- the number of parties yet to hit barrier (bits 0-15) |
231 |
> |
* * parties -- the number of parties to wait (bits 16-31) |
232 |
> |
* * phase -- the generation of the barrier (bits 32-62) |
233 |
> |
* * terminated -- set if barrier is terminated (bit 63 / sign) |
234 |
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* |
235 |
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* However, to efficiently maintain atomicity, these values are |
236 |
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* packed into a single (atomic) long. Termination uses the sign |
237 |
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* bit of 32 bit representation of phase, so phase is set to -1 on |
238 |
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* termination. Good performance relies on keeping state decoding |
239 |
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* and encoding simple, and keeping race windows short. |
239 |
– |
* |
240 |
– |
* Note: there are some cheats in arrive() that rely on unarrived |
241 |
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* count being lowest 16 bits. |
240 |
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*/ |
241 |
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private volatile long state; |
242 |
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|
243 |
< |
private static final int ushortMask = 0xffff; |
244 |
< |
private static final int phaseMask = 0x7fffffff; |
243 |
> |
private static final int MAX_PARTIES = 0xffff; |
244 |
> |
private static final int MAX_PHASE = 0x7fffffff; |
245 |
> |
private static final int PARTIES_SHIFT = 16; |
246 |
> |
private static final int PHASE_SHIFT = 32; |
247 |
> |
private static final int UNARRIVED_MASK = 0xffff; |
248 |
> |
private static final int PARTIES_MASK = 0xffff0000; |
249 |
> |
private static final long LPARTIES_MASK = 0xffff0000L; // long version |
250 |
> |
private static final long ONE_ARRIVAL = 1L; |
251 |
> |
private static final long ONE_PARTY = 1L << PARTIES_SHIFT; |
252 |
> |
private static final long TERMINATION_PHASE = -1L << PHASE_SHIFT; |
253 |
> |
|
254 |
> |
// The following unpacking methods are usually manually inlined |
255 |
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|
256 |
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private static int unarrivedOf(long s) { |
257 |
< |
return (int) (s & ushortMask); |
257 |
> |
return ((int) s) & UNARRIVED_MASK; |
258 |
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} |
259 |
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|
260 |
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private static int partiesOf(long s) { |
261 |
< |
return ((int) s) >>> 16; |
261 |
> |
return (((int) s) & PARTIES_MASK) >>> PARTIES_SHIFT; |
262 |
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} |
263 |
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|
264 |
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private static int phaseOf(long s) { |
265 |
< |
return (int) (s >>> 32); |
265 |
> |
return (int) (s >>> PHASE_SHIFT); |
266 |
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} |
267 |
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|
268 |
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private static int arrivedOf(long s) { |
269 |
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return partiesOf(s) - unarrivedOf(s); |
270 |
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} |
271 |
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|
264 |
– |
private static long stateFor(int phase, int parties, int unarrived) { |
265 |
– |
return ((((long) phase) << 32) | (((long) parties) << 16) | |
266 |
– |
(long) unarrived); |
267 |
– |
} |
268 |
– |
|
269 |
– |
private static long trippedStateFor(int phase, int parties) { |
270 |
– |
long lp = (long) parties; |
271 |
– |
return (((long) phase) << 32) | (lp << 16) | lp; |
272 |
– |
} |
273 |
– |
|
274 |
– |
/** |
275 |
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* Returns message string for bad bounds exceptions. |
276 |
– |
*/ |
277 |
– |
private static String badBounds(int parties, int unarrived) { |
278 |
– |
return ("Attempt to set " + unarrived + |
279 |
– |
" unarrived of " + parties + " parties"); |
280 |
– |
} |
281 |
– |
|
272 |
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/** |
273 |
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* The parent of this phaser, or null if none |
274 |
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*/ |
280 |
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*/ |
281 |
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private final Phaser root; |
282 |
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|
293 |
– |
// Wait queues |
294 |
– |
|
283 |
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/** |
284 |
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* Heads of Treiber stacks for waiting threads. To eliminate |
285 |
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* contention when releasing some threads while adding others, we |
294 |
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} |
295 |
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|
296 |
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/** |
297 |
< |
* Returns current state, first resolving lagged propagation from |
298 |
< |
* root if necessary. |
297 |
> |
* Main implementation for methods arrive and arriveAndDeregister. |
298 |
> |
* Manually tuned to speed up and minimize race windows for the |
299 |
> |
* common case of just decrementing unarrived field. |
300 |
> |
* |
301 |
> |
* @param adj - adjustment to apply to state -- either |
302 |
> |
* ONE_ARRIVAL (for arrive) or |
303 |
> |
* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister) |
304 |
> |
*/ |
305 |
> |
private int doArrive(long adj) { |
306 |
> |
for (;;) { |
307 |
> |
long s; |
308 |
> |
int phase, unarrived; |
309 |
> |
if ((phase = (int)((s = state) >>> PHASE_SHIFT)) < 0) |
310 |
> |
return phase; |
311 |
> |
else if ((unarrived = ((int)s) & UNARRIVED_MASK) == 0) |
312 |
> |
checkBadArrive(s); |
313 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
314 |
> |
if (unarrived == 1) { |
315 |
> |
Phaser par; |
316 |
> |
long p = s & LPARTIES_MASK; // unshifted parties field |
317 |
> |
long lu = p >>> PARTIES_SHIFT; |
318 |
> |
int u = (int)lu; |
319 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
320 |
> |
long next = ((long)nextPhase << PHASE_SHIFT) | p | lu; |
321 |
> |
if ((par = parent) == null) { |
322 |
> |
if (onAdvance(phase, u)) |
323 |
> |
next |= TERMINATION_PHASE; // obliterate phase |
324 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
325 |
> |
releaseWaiters(phase); |
326 |
> |
} |
327 |
> |
else { |
328 |
> |
par.doArrive(u == 0? |
329 |
> |
ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
330 |
> |
if ((int)(par.state >>> PHASE_SHIFT) != nextPhase || |
331 |
> |
((int)(state >>> PHASE_SHIFT) != nextPhase && |
332 |
> |
!UNSAFE.compareAndSwapLong(this, stateOffset, |
333 |
> |
s, next))) |
334 |
> |
reconcileState(); |
335 |
> |
} |
336 |
> |
} |
337 |
> |
return phase; |
338 |
> |
} |
339 |
> |
} |
340 |
> |
} |
341 |
> |
|
342 |
> |
/** |
343 |
> |
* Rechecks state and throws bounds exceptions on arrival -- called |
344 |
> |
* only if unarrived is apparently zero. |
345 |
> |
*/ |
346 |
> |
private void checkBadArrive(long s) { |
347 |
> |
if (reconcileState() == s) |
348 |
> |
throw new IllegalStateException |
349 |
> |
("Attempted arrival of unregistered party for " + |
350 |
> |
stateToString(s)); |
351 |
> |
} |
352 |
> |
|
353 |
> |
/** |
354 |
> |
* Implementation of register, bulkRegister |
355 |
> |
* |
356 |
> |
* @param registrations number to add to both parties and unarrived fields |
357 |
> |
*/ |
358 |
> |
private int doRegister(int registrations) { |
359 |
> |
long adj = (long)registrations; // adjustment to state |
360 |
> |
adj |= adj << PARTIES_SHIFT; |
361 |
> |
Phaser par = parent; |
362 |
> |
for (;;) { |
363 |
> |
int phase, parties; |
364 |
> |
long s = par == null? state : reconcileState(); |
365 |
> |
if ((phase = (int)(s >>> PHASE_SHIFT)) < 0) |
366 |
> |
return phase; |
367 |
> |
if ((parties = (((int)s) & PARTIES_MASK) >>> PARTIES_SHIFT) != 0 && |
368 |
> |
(((int)s) & UNARRIVED_MASK) == 0) |
369 |
> |
internalAwaitAdvance(phase, null); // wait for onAdvance |
370 |
> |
else if (parties + registrations > MAX_PARTIES) |
371 |
> |
throw new IllegalStateException(badRegister(s)); |
372 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj)) |
373 |
> |
return phase; |
374 |
> |
} |
375 |
> |
} |
376 |
> |
|
377 |
> |
/** |
378 |
> |
* Returns message string for out of bounds exceptions on registration. |
379 |
|
*/ |
380 |
< |
private long getReconciledState() { |
381 |
< |
return (parent == null) ? state : reconcileState(); |
380 |
> |
private String badRegister(long s) { |
381 |
> |
return "Attempt to register more than " + |
382 |
> |
MAX_PARTIES + " parties for " + stateToString(s); |
383 |
|
} |
384 |
|
|
385 |
|
/** |
386 |
< |
* Recursively resolves state. |
386 |
> |
* Recursively resolves lagged phase propagation from root if necessary. |
387 |
|
*/ |
388 |
|
private long reconcileState() { |
389 |
|
Phaser par = parent; |
390 |
< |
long s = state; |
391 |
< |
if (par != null) { |
392 |
< |
int phase, rootPhase; |
393 |
< |
while ((phase = phaseOf(s)) >= 0 && |
394 |
< |
(rootPhase = phaseOf(root.state)) != phase && |
395 |
< |
(rootPhase < 0 || unarrivedOf(s) == 0)) { |
396 |
< |
int parentPhase = phaseOf(par.getReconciledState()); |
397 |
< |
if (parentPhase != phase) { |
398 |
< |
long next = trippedStateFor(parentPhase, partiesOf(s)); |
399 |
< |
if (state == s) |
400 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
401 |
< |
} |
402 |
< |
s = state; |
390 |
> |
if (par == null) |
391 |
> |
return state; |
392 |
> |
Phaser rt = root; |
393 |
> |
for (;;) { |
394 |
> |
long s, u; |
395 |
> |
int phase, rPhase, pPhase; |
396 |
> |
if ((phase = (int)((s = state)>>> PHASE_SHIFT)) < 0 || |
397 |
> |
(rPhase = (int)(rt.state >>> PHASE_SHIFT)) == phase) |
398 |
> |
return s; |
399 |
> |
long pState = par.parent == null? par.state : par.reconcileState(); |
400 |
> |
if (state == s) { |
401 |
> |
if ((rPhase < 0 || (((int)s) & UNARRIVED_MASK) == 0) && |
402 |
> |
((pPhase = (int)(pState >>> PHASE_SHIFT)) < 0 || |
403 |
> |
pPhase == ((phase + 1) & MAX_PHASE))) |
404 |
> |
UNSAFE.compareAndSwapLong |
405 |
> |
(this, stateOffset, s, |
406 |
> |
(((long) pPhase) << PHASE_SHIFT) | |
407 |
> |
(u = s & LPARTIES_MASK) | |
408 |
> |
(u >>> PARTIES_SHIFT)); // reset unarrived to parties |
409 |
> |
else |
410 |
> |
releaseWaiters(phase); // help release others |
411 |
|
} |
412 |
|
} |
336 |
– |
return s; |
413 |
|
} |
414 |
|
|
415 |
|
/** |
457 |
|
* or greater than the maximum number of parties supported |
458 |
|
*/ |
459 |
|
public Phaser(Phaser parent, int parties) { |
460 |
< |
if (parties < 0 || parties > ushortMask) |
460 |
> |
if (parties >>> PARTIES_SHIFT != 0) |
461 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
462 |
|
int phase; |
463 |
|
this.parent = parent; |
474 |
|
this.oddQ = new AtomicReference<QNode>(); |
475 |
|
phase = 0; |
476 |
|
} |
477 |
< |
this.state = trippedStateFor(phase, parties); |
477 |
> |
long p = (long)parties; |
478 |
> |
this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT); |
479 |
|
} |
480 |
|
|
481 |
|
/** |
505 |
|
public int bulkRegister(int parties) { |
506 |
|
if (parties < 0) |
507 |
|
throw new IllegalArgumentException(); |
508 |
+ |
if (parties > MAX_PARTIES) |
509 |
+ |
throw new IllegalStateException(badRegister(state)); |
510 |
|
if (parties == 0) |
511 |
|
return getPhase(); |
512 |
|
return doRegister(parties); |
513 |
|
} |
514 |
|
|
515 |
|
/** |
437 |
– |
* Shared code for register, bulkRegister |
438 |
– |
*/ |
439 |
– |
private int doRegister(int registrations) { |
440 |
– |
Phaser par = parent; |
441 |
– |
long s; |
442 |
– |
int phase; |
443 |
– |
while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) { |
444 |
– |
int p = partiesOf(s); |
445 |
– |
int u = unarrivedOf(s); |
446 |
– |
int unarrived = u + registrations; |
447 |
– |
int parties = p + registrations; |
448 |
– |
if (u == 0 && p != 0) // if tripped, wait for advance |
449 |
– |
untimedWait(phase); |
450 |
– |
else if (parties > ushortMask) |
451 |
– |
throw new IllegalStateException(badBounds(parties, unarrived)); |
452 |
– |
else if (par == null || phaseOf(root.state) == phase) { |
453 |
– |
long next = stateFor(phase, parties, unarrived); |
454 |
– |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
455 |
– |
break; |
456 |
– |
} |
457 |
– |
} |
458 |
– |
return phase; |
459 |
– |
} |
460 |
– |
|
461 |
– |
/** |
516 |
|
* Arrives at the barrier, but does not wait for others. (You can |
517 |
|
* in turn wait for others via {@link #awaitAdvance}). It is an |
518 |
|
* unenforced usage error for an unregistered party to invoke this |
523 |
|
* of unarrived parties would become negative |
524 |
|
*/ |
525 |
|
public int arrive() { |
526 |
< |
Phaser par = parent; |
473 |
< |
long s; |
474 |
< |
int phase; |
475 |
< |
while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) { |
476 |
< |
int parties = partiesOf(s); |
477 |
< |
int unarrived = unarrivedOf(s) - 1; |
478 |
< |
if (unarrived > 0) { // Not the last arrival |
479 |
< |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1)) |
480 |
< |
break; // s-1 adds one arrival |
481 |
< |
} |
482 |
< |
else if (unarrived < 0) |
483 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
484 |
< |
else if (par == null) { // directly trip |
485 |
< |
long next = trippedStateFor(onAdvance(phase, parties) ? -1 : |
486 |
< |
((phase + 1) & phaseMask), |
487 |
< |
parties); |
488 |
< |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) { |
489 |
< |
releaseWaiters(phase); |
490 |
< |
break; |
491 |
< |
} |
492 |
< |
} |
493 |
< |
else if (phaseOf(root.state) == phase && |
494 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, s - 1)) { |
495 |
< |
par.arrive(); // cascade to parent |
496 |
< |
reconcileState(); |
497 |
< |
break; |
498 |
< |
} |
499 |
< |
} |
500 |
< |
return phase; |
526 |
> |
return doArrive(ONE_ARRIVAL); |
527 |
|
} |
528 |
|
|
529 |
|
/** |
540 |
|
* of registered or unarrived parties would become negative |
541 |
|
*/ |
542 |
|
public int arriveAndDeregister() { |
543 |
< |
// similar to arrive, but too different to merge |
518 |
< |
Phaser par = parent; |
519 |
< |
long s; |
520 |
< |
int phase; |
521 |
< |
while ((phase = phaseOf(s = par==null? state:reconcileState())) >= 0) { |
522 |
< |
int parties = partiesOf(s) - 1; |
523 |
< |
int unarrived = unarrivedOf(s) - 1; |
524 |
< |
if (unarrived > 0) { |
525 |
< |
long next = stateFor(phase, parties, unarrived); |
526 |
< |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
527 |
< |
break; |
528 |
< |
} |
529 |
< |
else if (unarrived < 0) |
530 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
531 |
< |
else if (par == null) { |
532 |
< |
long next = trippedStateFor(onAdvance(phase, parties)? -1: |
533 |
< |
(phase + 1) & phaseMask, |
534 |
< |
parties); |
535 |
< |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) { |
536 |
< |
releaseWaiters(phase); |
537 |
< |
break; |
538 |
< |
} |
539 |
< |
} |
540 |
< |
else if (phaseOf(root.state) == phase) { |
541 |
< |
long next = stateFor(phase, parties, 0); |
542 |
< |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) { |
543 |
< |
if (parties == 0) |
544 |
< |
par.arriveAndDeregister(); |
545 |
< |
else |
546 |
< |
par.arrive(); |
547 |
< |
reconcileState(); |
548 |
< |
break; |
549 |
< |
} |
550 |
< |
} |
551 |
< |
} |
552 |
< |
return phase; |
543 |
> |
return doArrive(ONE_ARRIVAL|ONE_PARTY); |
544 |
|
} |
545 |
|
|
546 |
|
/** |
573 |
|
* if terminated or argument is negative |
574 |
|
*/ |
575 |
|
public int awaitAdvance(int phase) { |
576 |
+ |
int p; |
577 |
|
if (phase < 0) |
578 |
|
return phase; |
579 |
< |
int p = getPhase(); |
580 |
< |
if (p != phase) |
579 |
> |
else if ((p = (int)((parent == null? state : reconcileState()) |
580 |
> |
>>> PHASE_SHIFT)) == phase) |
581 |
> |
return internalAwaitAdvance(phase, null); |
582 |
> |
else |
583 |
|
return p; |
590 |
– |
return untimedWait(phase); |
584 |
|
} |
585 |
|
|
586 |
|
/** |
599 |
|
*/ |
600 |
|
public int awaitAdvanceInterruptibly(int phase) |
601 |
|
throws InterruptedException { |
602 |
+ |
int p; |
603 |
|
if (phase < 0) |
604 |
|
return phase; |
605 |
< |
int p = getPhase(); |
606 |
< |
if (p != phase) |
607 |
< |
return p; |
608 |
< |
return interruptibleWait(phase); |
605 |
> |
if ((p = (int)((parent == null? state : reconcileState()) |
606 |
> |
>>> PHASE_SHIFT)) == phase) { |
607 |
> |
QNode node = new QNode(this, phase, true, false, 0L); |
608 |
> |
p = internalAwaitAdvance(phase, node); |
609 |
> |
if (node.wasInterrupted) |
610 |
> |
throw new InterruptedException(); |
611 |
> |
} |
612 |
> |
return p; |
613 |
|
} |
614 |
|
|
615 |
|
/** |
636 |
|
long timeout, TimeUnit unit) |
637 |
|
throws InterruptedException, TimeoutException { |
638 |
|
long nanos = unit.toNanos(timeout); |
639 |
+ |
int p; |
640 |
|
if (phase < 0) |
641 |
|
return phase; |
642 |
< |
int p = getPhase(); |
643 |
< |
if (p != phase) |
644 |
< |
return p; |
645 |
< |
return timedWait(phase, nanos); |
642 |
> |
if ((p = (int)((parent == null? state : reconcileState()) |
643 |
> |
>>> PHASE_SHIFT)) == phase) { |
644 |
> |
QNode node = new QNode(this, phase, true, true, nanos); |
645 |
> |
p = internalAwaitAdvance(phase, node); |
646 |
> |
if (node.wasInterrupted) |
647 |
> |
throw new InterruptedException(); |
648 |
> |
else if (p == phase) |
649 |
> |
throw new TimeoutException(); |
650 |
> |
} |
651 |
> |
return p; |
652 |
|
} |
653 |
|
|
654 |
|
/** |
655 |
< |
* Forces this barrier to enter termination state. Counts of |
656 |
< |
* arrived and registered parties are unaffected. If this phaser |
657 |
< |
* has a parent, it too is terminated. This method may be useful |
658 |
< |
* for coordinating recovery after one or more tasks encounter |
659 |
< |
* unexpected exceptions. |
655 |
> |
* Forces this barrier to enter termination state. Counts of |
656 |
> |
* arrived and registered parties are unaffected. If this phaser |
657 |
> |
* is a member of a tiered set of phasers, then all of the phasers |
658 |
> |
* in the set are terminated. If this phaser is already |
659 |
> |
* terminated, this method has no effect. This method may be |
660 |
> |
* useful for coordinating recovery after one or more tasks |
661 |
> |
* encounter unexpected exceptions. |
662 |
|
*/ |
663 |
|
public void forceTermination() { |
664 |
< |
Phaser r = root; // force at root then reconcile |
664 |
> |
// Only need to change root state |
665 |
> |
final Phaser root = this.root; |
666 |
|
long s; |
667 |
< |
while (phaseOf(s = r.state) >= 0) |
668 |
< |
UNSAFE.compareAndSwapLong(r, stateOffset, s, |
669 |
< |
stateFor(-1, partiesOf(s), |
670 |
< |
unarrivedOf(s))); |
671 |
< |
reconcileState(); |
672 |
< |
releaseWaiters(0); // ensure wakeups on both queues |
673 |
< |
releaseWaiters(1); |
667 |
> |
while ((s = root.state) >= 0) { |
668 |
> |
if (UNSAFE.compareAndSwapLong(root, stateOffset, |
669 |
> |
s, s | TERMINATION_PHASE)) { |
670 |
> |
releaseWaiters(0); // signal all threads |
671 |
> |
releaseWaiters(1); |
672 |
> |
return; |
673 |
> |
} |
674 |
> |
} |
675 |
|
} |
676 |
|
|
677 |
|
/** |
682 |
|
* @return the phase number, or a negative value if terminated |
683 |
|
*/ |
684 |
|
public final int getPhase() { |
685 |
< |
return phaseOf(getReconciledState()); |
685 |
> |
return (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
686 |
|
} |
687 |
|
|
688 |
|
/** |
691 |
|
* @return the number of parties |
692 |
|
*/ |
693 |
|
public int getRegisteredParties() { |
694 |
< |
return partiesOf(getReconciledState()); |
694 |
> |
return partiesOf(parent==null? state : reconcileState()); |
695 |
|
} |
696 |
|
|
697 |
|
/** |
701 |
|
* @return the number of arrived parties |
702 |
|
*/ |
703 |
|
public int getArrivedParties() { |
704 |
< |
return arrivedOf(getReconciledState()); |
704 |
> |
return arrivedOf(parent==null? state : reconcileState()); |
705 |
|
} |
706 |
|
|
707 |
|
/** |
711 |
|
* @return the number of unarrived parties |
712 |
|
*/ |
713 |
|
public int getUnarrivedParties() { |
714 |
< |
return unarrivedOf(getReconciledState()); |
714 |
> |
return unarrivedOf(parent==null? state : reconcileState()); |
715 |
|
} |
716 |
|
|
717 |
|
/** |
739 |
|
* @return {@code true} if this barrier has been terminated |
740 |
|
*/ |
741 |
|
public boolean isTerminated() { |
742 |
< |
return getPhase() < 0; |
742 |
> |
return (parent == null? state : reconcileState()) < 0; |
743 |
|
} |
744 |
|
|
745 |
|
/** |
755 |
|
* which case no advance occurs. |
756 |
|
* |
757 |
|
* <p>The arguments to this method provide the state of the phaser |
758 |
< |
* prevailing for the current transition. The results and effects |
759 |
< |
* of invoking phase-related methods (including {@code getPhase} |
751 |
< |
* as well as arrival, registration, and waiting methods) from |
758 |
> |
* prevailing for the current transition. The effects of invoking |
759 |
> |
* arrival, registration, and waiting methods on this Phaser from |
760 |
|
* within {@code onAdvance} are unspecified and should not be |
761 |
< |
* relied on. Similarly, while it is possible to override this |
762 |
< |
* method to produce side-effects visible to participating tasks, |
763 |
< |
* it is in general safe to do so only in designs in which all |
764 |
< |
* parties register before any arrive, and all {@link |
765 |
< |
* #awaitAdvance} at each phase. |
761 |
> |
* relied on. |
762 |
> |
* |
763 |
> |
* <p>If this Phaser is a member of a tiered set of Phasers, then |
764 |
> |
* {@code onAdvance} is invoked only for its root Phaser on each |
765 |
> |
* advance. |
766 |
|
* |
767 |
|
* <p>The default version returns {@code true} when the number of |
768 |
|
* registered parties is zero. Normally, overrides that arrange |
787 |
|
* @return a string identifying this barrier, as well as its state |
788 |
|
*/ |
789 |
|
public String toString() { |
790 |
< |
long s = getReconciledState(); |
790 |
> |
return stateToString(reconcileState()); |
791 |
> |
} |
792 |
> |
|
793 |
> |
/** |
794 |
> |
* Implementation of toString and string-based error messages |
795 |
> |
*/ |
796 |
> |
private String stateToString(long s) { |
797 |
|
return super.toString() + |
798 |
|
"[phase = " + phaseOf(s) + |
799 |
|
" parties = " + partiesOf(s) + |
800 |
|
" arrived = " + arrivedOf(s) + "]"; |
801 |
|
} |
802 |
|
|
803 |
< |
// methods for waiting |
803 |
> |
// Waiting mechanics |
804 |
> |
|
805 |
> |
/** |
806 |
> |
* Removes and signals threads from queue for phase |
807 |
> |
*/ |
808 |
> |
private void releaseWaiters(int phase) { |
809 |
> |
AtomicReference<QNode> head = queueFor(phase); |
810 |
> |
QNode q; |
811 |
> |
int p; |
812 |
> |
while ((q = head.get()) != null && |
813 |
> |
((p = q.phase) == phase || |
814 |
> |
(int)(root.state >>> PHASE_SHIFT) != p)) { |
815 |
> |
if (head.compareAndSet(q, q.next)) |
816 |
> |
q.signal(); |
817 |
> |
} |
818 |
> |
} |
819 |
> |
|
820 |
> |
/** |
821 |
> |
* Tries to enqueue given node in the appropriate wait queue. |
822 |
> |
* |
823 |
> |
* @return true if successful |
824 |
> |
*/ |
825 |
> |
private boolean tryEnqueue(int phase, QNode node) { |
826 |
> |
releaseWaiters(phase-1); // ensure old queue clean |
827 |
> |
AtomicReference<QNode> head = queueFor(phase); |
828 |
> |
QNode q = head.get(); |
829 |
> |
return ((q == null || q.phase == phase) && |
830 |
> |
(int)(root.state >>> PHASE_SHIFT) == phase && |
831 |
> |
head.compareAndSet(node.next = q, node)); |
832 |
> |
} |
833 |
> |
|
834 |
> |
/** The number of CPUs, for spin control */ |
835 |
> |
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
836 |
> |
|
837 |
> |
/** |
838 |
> |
* The number of times to spin before blocking while waiting for |
839 |
> |
* advance, per arrival while waiting. On multiprocessors, fully |
840 |
> |
* blocking and waking up a large number of threads all at once is |
841 |
> |
* usually a very slow process, so we use rechargeable spins to |
842 |
> |
* avoid it when threads regularly arrive: When a thread in |
843 |
> |
* internalAwaitAdvance notices another arrival before blocking, |
844 |
> |
* and there appear to be enough CPUs available, it spins |
845 |
> |
* SPINS_PER_ARRIVAL more times before blocking. Plus, even on |
846 |
> |
* uniprocessors, there is at least one intervening Thread.yield |
847 |
> |
* before blocking. The value trades off good-citizenship vs big |
848 |
> |
* unnecessary slowdowns. |
849 |
> |
*/ |
850 |
> |
static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8; |
851 |
> |
|
852 |
> |
/** |
853 |
> |
* Possibly blocks and waits for phase to advance unless aborted. |
854 |
> |
* |
855 |
> |
* @param phase current phase |
856 |
> |
* @param node if non-null, the wait node to track interrupt and timeout; |
857 |
> |
* if null, denotes noninterruptible wait |
858 |
> |
* @return current phase |
859 |
> |
*/ |
860 |
> |
private int internalAwaitAdvance(int phase, QNode node) { |
861 |
> |
Phaser current = this; // to eventually wait at root if tiered |
862 |
> |
boolean queued = false; // true when node is enqueued |
863 |
> |
int lastUnarrived = -1; // to increase spins upon change |
864 |
> |
int spins = SPINS_PER_ARRIVAL; |
865 |
> |
for (;;) { |
866 |
> |
int p, unarrived; |
867 |
> |
Phaser par; |
868 |
> |
long s = current.state; |
869 |
> |
if ((p = (int)(s >>> PHASE_SHIFT)) != phase) { |
870 |
> |
if (node != null) |
871 |
> |
node.onRelease(); |
872 |
> |
releaseWaiters(phase); |
873 |
> |
return p; |
874 |
> |
} |
875 |
> |
else if ((unarrived = ((int)s) & UNARRIVED_MASK) == 0 && |
876 |
> |
(par = current.parent) != null) { |
877 |
> |
current = par; // if all arrived, use parent |
878 |
> |
par = par.parent; |
879 |
> |
lastUnarrived = -1; |
880 |
> |
} |
881 |
> |
else if (unarrived != lastUnarrived) { |
882 |
> |
if ((lastUnarrived = unarrived) < NCPU) |
883 |
> |
spins += SPINS_PER_ARRIVAL; |
884 |
> |
} |
885 |
> |
else if (spins > 0) { |
886 |
> |
if (--spins == (SPINS_PER_ARRIVAL >>> 1)) |
887 |
> |
Thread.yield(); // yield midway through spin |
888 |
> |
} |
889 |
> |
else if (node == null) // must be noninterruptible |
890 |
> |
node = new QNode(this, phase, false, false, 0L); |
891 |
> |
else if (node.isReleasable()) { |
892 |
> |
if ((int)(reconcileState() >>> PHASE_SHIFT) == phase) |
893 |
> |
return phase; // aborted |
894 |
> |
} |
895 |
> |
else if (!queued) |
896 |
> |
queued = tryEnqueue(phase, node); |
897 |
> |
else { |
898 |
> |
try { |
899 |
> |
ForkJoinPool.managedBlock(node); |
900 |
> |
} catch (InterruptedException ie) { |
901 |
> |
node.wasInterrupted = true; |
902 |
> |
} |
903 |
> |
} |
904 |
> |
} |
905 |
> |
} |
906 |
|
|
907 |
|
/** |
908 |
|
* Wait nodes for Treiber stack representing wait queue |
910 |
|
static final class QNode implements ForkJoinPool.ManagedBlocker { |
911 |
|
final Phaser phaser; |
912 |
|
final int phase; |
797 |
– |
final long startTime; |
798 |
– |
final long nanos; |
799 |
– |
final boolean timed; |
913 |
|
final boolean interruptible; |
914 |
< |
volatile boolean wasInterrupted = false; |
914 |
> |
final boolean timed; |
915 |
> |
boolean wasInterrupted; |
916 |
> |
long nanos; |
917 |
> |
long lastTime; |
918 |
|
volatile Thread thread; // nulled to cancel wait |
919 |
|
QNode next; |
920 |
|
|
921 |
|
QNode(Phaser phaser, int phase, boolean interruptible, |
922 |
< |
boolean timed, long startTime, long nanos) { |
922 |
> |
boolean timed, long nanos) { |
923 |
|
this.phaser = phaser; |
924 |
|
this.phase = phase; |
809 |
– |
this.timed = timed; |
925 |
|
this.interruptible = interruptible; |
811 |
– |
this.startTime = startTime; |
926 |
|
this.nanos = nanos; |
927 |
+ |
this.timed = timed; |
928 |
+ |
this.lastTime = timed? System.nanoTime() : 0L; |
929 |
|
thread = Thread.currentThread(); |
930 |
|
} |
931 |
|
|
932 |
|
public boolean isReleasable() { |
933 |
< |
return (thread == null || |
934 |
< |
phaser.getPhase() != phase || |
935 |
< |
(interruptible && wasInterrupted) || |
936 |
< |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
933 |
> |
Thread t = thread; |
934 |
> |
if (t != null) { |
935 |
> |
if (phaser.getPhase() != phase) |
936 |
> |
t = null; |
937 |
> |
else { |
938 |
> |
if (Thread.interrupted()) |
939 |
> |
wasInterrupted = true; |
940 |
> |
if (interruptible && wasInterrupted) |
941 |
> |
t = null; |
942 |
> |
else if (timed) { |
943 |
> |
if (nanos > 0) { |
944 |
> |
long now = System.nanoTime(); |
945 |
> |
nanos -= now - lastTime; |
946 |
> |
lastTime = now; |
947 |
> |
} |
948 |
> |
if (nanos <= 0) |
949 |
> |
t = null; |
950 |
> |
} |
951 |
> |
} |
952 |
> |
if (t != null) |
953 |
> |
return false; |
954 |
> |
thread = null; |
955 |
> |
} |
956 |
> |
return true; |
957 |
|
} |
958 |
|
|
959 |
|
public boolean block() { |
960 |
< |
if (Thread.interrupted()) { |
961 |
< |
wasInterrupted = true; |
962 |
< |
if (interruptible) |
827 |
< |
return true; |
828 |
< |
} |
829 |
< |
if (!timed) |
960 |
> |
if (isReleasable()) |
961 |
> |
return true; |
962 |
> |
else if (!timed) |
963 |
|
LockSupport.park(this); |
964 |
< |
else { |
965 |
< |
long waitTime = nanos - (System.nanoTime() - startTime); |
833 |
< |
if (waitTime <= 0) |
834 |
< |
return true; |
835 |
< |
LockSupport.parkNanos(this, waitTime); |
836 |
< |
} |
964 |
> |
else if (nanos > 0) |
965 |
> |
LockSupport.parkNanos(this, nanos); |
966 |
|
return isReleasable(); |
967 |
|
} |
968 |
|
|
974 |
|
} |
975 |
|
} |
976 |
|
|
977 |
< |
boolean doWait() { |
978 |
< |
if (thread != null) { |
979 |
< |
try { |
980 |
< |
ForkJoinPool.managedBlock(this); |
981 |
< |
} catch (InterruptedException ie) { |
853 |
< |
wasInterrupted = true; // can't currently happen |
854 |
< |
} |
855 |
< |
} |
856 |
< |
return wasInterrupted; |
857 |
< |
} |
858 |
< |
} |
859 |
< |
|
860 |
< |
/** |
861 |
< |
* Removes and signals waiting threads from wait queue. |
862 |
< |
*/ |
863 |
< |
private void releaseWaiters(int phase) { |
864 |
< |
AtomicReference<QNode> head = queueFor(phase); |
865 |
< |
QNode q; |
866 |
< |
while ((q = head.get()) != null) { |
867 |
< |
if (head.compareAndSet(q, q.next)) |
868 |
< |
q.signal(); |
977 |
> |
void onRelease() { // actions upon return from internalAwaitAdvance |
978 |
> |
if (!interruptible && wasInterrupted) |
979 |
> |
Thread.currentThread().interrupt(); |
980 |
> |
if (thread != null) |
981 |
> |
thread = null; |
982 |
|
} |
870 |
– |
} |
871 |
– |
|
872 |
– |
/** |
873 |
– |
* Tries to enqueue given node in the appropriate wait queue. |
874 |
– |
* |
875 |
– |
* @return true if successful |
876 |
– |
*/ |
877 |
– |
private boolean tryEnqueue(QNode node) { |
878 |
– |
AtomicReference<QNode> head = queueFor(node.phase); |
879 |
– |
return head.compareAndSet(node.next = head.get(), node); |
880 |
– |
} |
983 |
|
|
882 |
– |
/** |
883 |
– |
* The number of times to spin before blocking waiting for advance. |
884 |
– |
*/ |
885 |
– |
static final int MAX_SPINS = |
886 |
– |
Runtime.getRuntime().availableProcessors() == 1 ? 0 : 1 << 8; |
887 |
– |
|
888 |
– |
/** |
889 |
– |
* Enqueues node and waits unless aborted or signalled. |
890 |
– |
* |
891 |
– |
* @return current phase |
892 |
– |
*/ |
893 |
– |
private int untimedWait(int phase) { |
894 |
– |
QNode node = null; |
895 |
– |
boolean queued = false; |
896 |
– |
boolean interrupted = false; |
897 |
– |
int spins = MAX_SPINS; |
898 |
– |
int p; |
899 |
– |
while ((p = getPhase()) == phase) { |
900 |
– |
if (Thread.interrupted()) |
901 |
– |
interrupted = true; |
902 |
– |
else if (spins > 0) { |
903 |
– |
if (--spins == 0) |
904 |
– |
Thread.yield(); |
905 |
– |
} |
906 |
– |
else if (node == null) |
907 |
– |
node = new QNode(this, phase, false, false, 0, 0); |
908 |
– |
else if (!queued) |
909 |
– |
queued = tryEnqueue(node); |
910 |
– |
else if (node.doWait()) |
911 |
– |
interrupted = true; |
912 |
– |
} |
913 |
– |
if (node != null) |
914 |
– |
node.thread = null; |
915 |
– |
releaseWaiters(phase); |
916 |
– |
if (interrupted) |
917 |
– |
Thread.currentThread().interrupt(); |
918 |
– |
return p; |
919 |
– |
} |
920 |
– |
|
921 |
– |
/** |
922 |
– |
* Interruptible version |
923 |
– |
* @return current phase |
924 |
– |
*/ |
925 |
– |
private int interruptibleWait(int phase) throws InterruptedException { |
926 |
– |
QNode node = null; |
927 |
– |
boolean queued = false; |
928 |
– |
boolean interrupted = false; |
929 |
– |
int spins = MAX_SPINS; |
930 |
– |
int p; |
931 |
– |
while ((p = getPhase()) == phase && !interrupted) { |
932 |
– |
if (Thread.interrupted()) |
933 |
– |
interrupted = true; |
934 |
– |
else if (spins > 0) { |
935 |
– |
if (--spins == 0) |
936 |
– |
Thread.yield(); |
937 |
– |
} |
938 |
– |
else if (node == null) |
939 |
– |
node = new QNode(this, phase, true, false, 0, 0); |
940 |
– |
else if (!queued) |
941 |
– |
queued = tryEnqueue(node); |
942 |
– |
else if (node.doWait()) |
943 |
– |
interrupted = true; |
944 |
– |
} |
945 |
– |
if (node != null) |
946 |
– |
node.thread = null; |
947 |
– |
if (p != phase || (p = getPhase()) != phase) |
948 |
– |
releaseWaiters(phase); |
949 |
– |
if (interrupted) |
950 |
– |
throw new InterruptedException(); |
951 |
– |
return p; |
952 |
– |
} |
953 |
– |
|
954 |
– |
/** |
955 |
– |
* Timeout version. |
956 |
– |
* @return current phase |
957 |
– |
*/ |
958 |
– |
private int timedWait(int phase, long nanos) |
959 |
– |
throws InterruptedException, TimeoutException { |
960 |
– |
long startTime = System.nanoTime(); |
961 |
– |
QNode node = null; |
962 |
– |
boolean queued = false; |
963 |
– |
boolean interrupted = false; |
964 |
– |
int spins = MAX_SPINS; |
965 |
– |
int p; |
966 |
– |
while ((p = getPhase()) == phase && !interrupted) { |
967 |
– |
if (Thread.interrupted()) |
968 |
– |
interrupted = true; |
969 |
– |
else if (nanos - (System.nanoTime() - startTime) <= 0) |
970 |
– |
break; |
971 |
– |
else if (spins > 0) { |
972 |
– |
if (--spins == 0) |
973 |
– |
Thread.yield(); |
974 |
– |
} |
975 |
– |
else if (node == null) |
976 |
– |
node = new QNode(this, phase, true, true, startTime, nanos); |
977 |
– |
else if (!queued) |
978 |
– |
queued = tryEnqueue(node); |
979 |
– |
else if (node.doWait()) |
980 |
– |
interrupted = true; |
981 |
– |
} |
982 |
– |
if (node != null) |
983 |
– |
node.thread = null; |
984 |
– |
if (p != phase || (p = getPhase()) != phase) |
985 |
– |
releaseWaiters(phase); |
986 |
– |
if (interrupted) |
987 |
– |
throw new InterruptedException(); |
988 |
– |
if (p == phase) |
989 |
– |
throw new TimeoutException(); |
990 |
– |
return p; |
984 |
|
} |
985 |
|
|
986 |
|
// Unsafe mechanics |