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package jsr166y; |
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< |
import java.util.concurrent.*; |
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import java.util.concurrent.TimeUnit; |
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import java.util.concurrent.TimeoutException; |
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import java.util.concurrent.atomic.AtomicReference; |
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import java.util.concurrent.locks.LockSupport; |
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|
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* immediately return without updating phaser state or waiting for |
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* advance, and indicating (via a negative phase value) that execution |
81 |
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* is complete. Termination is triggered when an invocation of {@code |
82 |
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* onAdvance} returns {@code true}. As illustrated below, when |
82 |
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* onAdvance} returns {@code true}. The default implementation returns |
83 |
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* {@code true} if a deregistration has caused the number of |
84 |
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* registered parties to become zero. As illustrated below, when |
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* phasers control actions with a fixed number of iterations, it is |
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* often convenient to override this method to cause termination when |
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* the current phase number reaches a threshold. Method {@link |
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* #forceTermination} is also available to abruptly release waiting |
89 |
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* threads and allow them to terminate. |
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* |
91 |
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* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged |
92 |
< |
* in tree structures) to reduce contention. Phasers with large |
93 |
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* numbers of parties that would otherwise experience heavy |
91 |
> |
* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., |
92 |
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* constructed in tree structures) to reduce contention. Phasers with |
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* large numbers of parties that would otherwise experience heavy |
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* synchronization contention costs may instead be set up so that |
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* groups of sub-phasers share a common parent. This may greatly |
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* increase throughput even though it incurs greater per-operation |
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* Barrier state representation. Conceptually, a barrier contains |
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* four values: |
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* |
232 |
< |
* * parties -- the number of parties to wait (16 bits) |
233 |
< |
* * unarrived -- the number of parties yet to hit barrier (16 bits) |
234 |
< |
* * phase -- the generation of the barrier (31 bits) |
235 |
< |
* * terminated -- set if barrier is terminated (1 bit) |
232 |
> |
* * unarrived -- the number of parties yet to hit barrier (bits 0-15) |
233 |
> |
* * parties -- the number of parties to wait (bits 16-31) |
234 |
> |
* * phase -- the generation of the barrier (bits 32-62) |
235 |
> |
* * terminated -- set if barrier is terminated (bit 63 / sign) |
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* |
237 |
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* However, to efficiently maintain atomicity, these values are |
238 |
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* packed into a single (atomic) long. Termination uses the sign |
239 |
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* bit of 32 bit representation of phase, so phase is set to -1 on |
240 |
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* termination. Good performance relies on keeping state decoding |
241 |
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* and encoding simple, and keeping race windows short. |
239 |
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* |
240 |
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* Note: there are some cheats in arrive() that rely on unarrived |
241 |
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* count being lowest 16 bits. |
242 |
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*/ |
243 |
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private volatile long state; |
244 |
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|
245 |
< |
private static final int ushortMask = 0xffff; |
246 |
< |
private static final int phaseMask = 0x7fffffff; |
245 |
> |
private static final int MAX_PARTIES = 0xffff; |
246 |
> |
private static final int MAX_PHASE = 0x7fffffff; |
247 |
> |
private static final int PARTIES_SHIFT = 16; |
248 |
> |
private static final int PHASE_SHIFT = 32; |
249 |
> |
private static final int UNARRIVED_MASK = 0xffff; // to mask ints |
250 |
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private static final long PARTIES_MASK = 0xffff0000L; // to mask longs |
251 |
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private static final long ONE_ARRIVAL = 1L; |
252 |
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private static final long ONE_PARTY = 1L << PARTIES_SHIFT; |
253 |
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private static final long TERMINATION_BIT = 1L << 63; |
254 |
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|
255 |
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// The following unpacking methods are usually manually inlined |
256 |
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|
257 |
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private static int unarrivedOf(long s) { |
258 |
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return (int) (s & ushortMask); |
258 |
> |
return (int)s & UNARRIVED_MASK; |
259 |
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} |
260 |
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|
261 |
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private static int partiesOf(long s) { |
262 |
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return ((int) s) >>> 16; |
262 |
> |
return (int)s >>> PARTIES_SHIFT; |
263 |
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} |
264 |
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|
265 |
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private static int phaseOf(long s) { |
266 |
< |
return (int) (s >>> 32); |
266 |
> |
return (int) (s >>> PHASE_SHIFT); |
267 |
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} |
268 |
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269 |
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private static int arrivedOf(long s) { |
270 |
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return partiesOf(s) - unarrivedOf(s); |
271 |
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} |
272 |
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|
264 |
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private static long stateFor(int phase, int parties, int unarrived) { |
265 |
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return ((((long) phase) << 32) | (((long) parties) << 16) | |
266 |
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(long) unarrived); |
267 |
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} |
268 |
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|
269 |
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private static long trippedStateFor(int phase, int parties) { |
270 |
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long lp = (long) parties; |
271 |
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return (((long) phase) << 32) | (lp << 16) | lp; |
272 |
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} |
273 |
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|
274 |
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/** |
275 |
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* Returns message string for bad bounds exceptions. |
276 |
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*/ |
277 |
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private static String badBounds(int parties, int unarrived) { |
278 |
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return ("Attempt to set " + unarrived + |
279 |
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" unarrived of " + parties + " parties"); |
280 |
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} |
281 |
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|
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/** |
274 |
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* The parent of this phaser, or null if none |
275 |
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*/ |
281 |
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*/ |
282 |
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private final Phaser root; |
283 |
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|
293 |
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// Wait queues |
294 |
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|
284 |
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/** |
285 |
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* Heads of Treiber stacks for waiting threads. To eliminate |
286 |
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* contention when releasing some threads while adding others, we |
295 |
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} |
296 |
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|
297 |
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/** |
298 |
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* Returns current state, first resolving lagged propagation from |
299 |
< |
* root if necessary. |
298 |
> |
* Returns message string for bounds exceptions on arrival. |
299 |
> |
*/ |
300 |
> |
private String badArrive(long s) { |
301 |
> |
return "Attempted arrival of unregistered party for " + |
302 |
> |
stateToString(s); |
303 |
> |
} |
304 |
> |
|
305 |
> |
/** |
306 |
> |
* Returns message string for bounds exceptions on registration. |
307 |
> |
*/ |
308 |
> |
private String badRegister(long s) { |
309 |
> |
return "Attempt to register more than " + |
310 |
> |
MAX_PARTIES + " parties for " + stateToString(s); |
311 |
> |
} |
312 |
> |
|
313 |
> |
/** |
314 |
> |
* Main implementation for methods arrive and arriveAndDeregister. |
315 |
> |
* Manually tuned to speed up and minimize race windows for the |
316 |
> |
* common case of just decrementing unarrived field. |
317 |
> |
* |
318 |
> |
* @param adj - adjustment to apply to state -- either |
319 |
> |
* ONE_ARRIVAL (for arrive) or |
320 |
> |
* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister) |
321 |
> |
*/ |
322 |
> |
private int doArrive(long adj) { |
323 |
> |
for (;;) { |
324 |
> |
long s = state; |
325 |
> |
int unarrived = (int)s & UNARRIVED_MASK; |
326 |
> |
int phase = (int)(s >>> PHASE_SHIFT); |
327 |
> |
if (phase < 0) |
328 |
> |
return phase; |
329 |
> |
else if (unarrived == 0) { |
330 |
> |
if (reconcileState() == s) // recheck |
331 |
> |
throw new IllegalStateException(badArrive(s)); |
332 |
> |
} |
333 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
334 |
> |
if (unarrived == 1) { |
335 |
> |
long p = s & PARTIES_MASK; // unshifted parties field |
336 |
> |
long lu = p >>> PARTIES_SHIFT; |
337 |
> |
int u = (int)lu; |
338 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
339 |
> |
long next = ((long)nextPhase << PHASE_SHIFT) | p | lu; |
340 |
> |
final Phaser parent = this.parent; |
341 |
> |
if (parent == null) { |
342 |
> |
if (onAdvance(phase, u)) |
343 |
> |
next |= TERMINATION_BIT; |
344 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
345 |
> |
releaseWaiters(phase); |
346 |
> |
} |
347 |
> |
else { |
348 |
> |
parent.doArrive((u == 0) ? |
349 |
> |
ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
350 |
> |
if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase || |
351 |
> |
((int)(state >>> PHASE_SHIFT) != nextPhase && |
352 |
> |
!UNSAFE.compareAndSwapLong(this, stateOffset, |
353 |
> |
s, next))) |
354 |
> |
reconcileState(); |
355 |
> |
} |
356 |
> |
} |
357 |
> |
return phase; |
358 |
> |
} |
359 |
> |
} |
360 |
> |
} |
361 |
> |
|
362 |
> |
/** |
363 |
> |
* Implementation of register, bulkRegister |
364 |
> |
* |
365 |
> |
* @param registrations number to add to both parties and |
366 |
> |
* unarrived fields. Must be greater than zero. |
367 |
|
*/ |
368 |
< |
private long getReconciledState() { |
369 |
< |
return (parent == null) ? state : reconcileState(); |
368 |
> |
private int doRegister(int registrations) { |
369 |
> |
// adjustment to state |
370 |
> |
long adj = ((long)registrations << PARTIES_SHIFT) | registrations; |
371 |
> |
final Phaser parent = this.parent; |
372 |
> |
for (;;) { |
373 |
> |
long s = (parent == null) ? state : reconcileState(); |
374 |
> |
int parties = (int)s >>> PARTIES_SHIFT; |
375 |
> |
int phase = (int)(s >>> PHASE_SHIFT); |
376 |
> |
if (phase < 0) |
377 |
> |
return phase; |
378 |
> |
else if (registrations > MAX_PARTIES - parties) |
379 |
> |
throw new IllegalStateException(badRegister(s)); |
380 |
> |
else if ((parties == 0 && parent == null) || // first reg of root |
381 |
> |
((int)s & UNARRIVED_MASK) != 0) { // not advancing |
382 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj)) |
383 |
> |
return phase; |
384 |
> |
} |
385 |
> |
else if (parties != 0) // wait for onAdvance |
386 |
> |
internalAwaitAdvance(phase, null); |
387 |
> |
else { // 1st registration of child |
388 |
> |
synchronized(this) { // register parent first |
389 |
> |
if (reconcileState() == s) { // recheck under lock |
390 |
> |
parent.doRegister(1); // OK if throws IllegalState |
391 |
> |
for (;;) { // simpler form of outer loop |
392 |
> |
s = reconcileState(); |
393 |
> |
phase = (int)(s >>> PHASE_SHIFT); |
394 |
> |
if (phase < 0 || |
395 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, |
396 |
> |
s, s + adj)) |
397 |
> |
return phase; |
398 |
> |
} |
399 |
> |
} |
400 |
> |
} |
401 |
> |
} |
402 |
> |
} |
403 |
|
} |
404 |
|
|
405 |
|
/** |
406 |
< |
* Recursively resolves state. |
406 |
> |
* Recursively resolves lagged phase propagation from root if necessary. |
407 |
|
*/ |
408 |
|
private long reconcileState() { |
409 |
|
Phaser par = parent; |
410 |
|
long s = state; |
411 |
|
if (par != null) { |
412 |
< |
int phase, rootPhase; |
413 |
< |
while ((phase = phaseOf(s)) >= 0 && |
414 |
< |
(rootPhase = phaseOf(root.state)) != phase && |
415 |
< |
(rootPhase < 0 || unarrivedOf(s) == 0)) { |
416 |
< |
int parentPhase = phaseOf(par.getReconciledState()); |
417 |
< |
if (parentPhase != phase) { |
418 |
< |
long next = trippedStateFor(parentPhase, partiesOf(s)); |
419 |
< |
if (state == s) |
420 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
412 |
> |
Phaser rt = root; |
413 |
> |
int phase, rPhase; |
414 |
> |
while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 && |
415 |
> |
(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) { |
416 |
> |
if ((int)(par.state >>> PHASE_SHIFT) != rPhase) |
417 |
> |
par.reconcileState(); |
418 |
> |
else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) { |
419 |
> |
long u = s & PARTIES_MASK; // reset unarrived to parties |
420 |
> |
long next = ((((long) rPhase) << PHASE_SHIFT) | u | |
421 |
> |
(u >>> PARTIES_SHIFT)); |
422 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
423 |
|
} |
424 |
|
s = state; |
425 |
|
} |
449 |
|
} |
450 |
|
|
451 |
|
/** |
452 |
< |
* Creates a new phaser with the given parent, without any |
453 |
< |
* initially registered parties. If parent is non-null this phaser |
454 |
< |
* is registered with the parent and its initial phase number is |
455 |
< |
* the same as that of parent phaser. |
452 |
> |
* Creates a new phaser with the given parent, and without any |
453 |
> |
* initially registered parties. Any thread using this phaser |
454 |
> |
* will need to first register for it, at which point, if the |
455 |
> |
* given parent is non-null, this phaser will also be registered |
456 |
> |
* with the parent. |
457 |
> |
* |
458 |
> |
* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}. |
459 |
|
* |
460 |
|
* @param parent the parent phaser |
461 |
|
*/ |
465 |
|
|
466 |
|
/** |
467 |
|
* Creates a new phaser with the given parent and number of |
468 |
< |
* registered unarrived parties. If parent is non-null, this phaser |
469 |
< |
* is registered with the parent and its initial phase number is |
470 |
< |
* the same as that of parent phaser. |
468 |
> |
* registered unarrived parties. If parent is non-null and |
469 |
> |
* the number of parties is non-zero, this phaser is registered |
470 |
> |
* with the parent. |
471 |
|
* |
472 |
|
* @param parent the parent phaser |
473 |
|
* @param parties the number of parties required to trip barrier |
475 |
|
* or greater than the maximum number of parties supported |
476 |
|
*/ |
477 |
|
public Phaser(Phaser parent, int parties) { |
478 |
< |
if (parties < 0 || parties > ushortMask) |
478 |
> |
if (parties >>> PARTIES_SHIFT != 0) |
479 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
480 |
|
int phase; |
481 |
|
this.parent = parent; |
484 |
|
this.root = r; |
485 |
|
this.evenQ = r.evenQ; |
486 |
|
this.oddQ = r.oddQ; |
487 |
< |
phase = parent.register(); |
487 |
> |
phase = (parties == 0) ? parent.getPhase() : parent.doRegister(1); |
488 |
|
} |
489 |
|
else { |
490 |
|
this.root = this; |
492 |
|
this.oddQ = new AtomicReference<QNode>(); |
493 |
|
phase = 0; |
494 |
|
} |
495 |
< |
this.state = trippedStateFor(phase, parties); |
495 |
> |
long p = (long)parties; |
496 |
> |
this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT); |
497 |
|
} |
498 |
|
|
499 |
|
/** |
500 |
< |
* Adds a new unarrived party to this phaser. |
501 |
< |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
502 |
< |
* this method may wait until its completion before registering. |
500 |
> |
* Adds a new unarrived party to this phaser. If an ongoing |
501 |
> |
* invocation of {@link #onAdvance} is in progress, this method |
502 |
> |
* may wait until its completion before registering. If this |
503 |
> |
* phaser has a parent, and this phaser previously had no |
504 |
> |
* registered parties, this phaser is also registered with its |
505 |
> |
* parent. |
506 |
|
* |
507 |
|
* @return the arrival phase number to which this registration applied |
508 |
|
* @throws IllegalStateException if attempting to register more |
516 |
|
* Adds the given number of new unarrived parties to this phaser. |
517 |
|
* If an ongoing invocation of {@link #onAdvance} is in progress, |
518 |
|
* this method may wait until its completion before registering. |
519 |
+ |
* If this phaser has a parent, and the given number of parities |
520 |
+ |
* is greater than zero, and this phaser previously had no |
521 |
+ |
* registered parties, this phaser is also registered with its |
522 |
+ |
* parent. |
523 |
|
* |
524 |
|
* @param parties the number of additional parties required to trip barrier |
525 |
|
* @return the arrival phase number to which this registration applied |
530 |
|
public int bulkRegister(int parties) { |
531 |
|
if (parties < 0) |
532 |
|
throw new IllegalArgumentException(); |
533 |
< |
if (parties == 0) |
533 |
> |
else if (parties == 0) |
534 |
|
return getPhase(); |
535 |
|
return doRegister(parties); |
536 |
|
} |
537 |
|
|
538 |
|
/** |
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 |
– |
/** |
539 |
|
* Arrives at the barrier, but does not wait for others. (You can |
540 |
< |
* in turn wait for others via {@link #awaitAdvance}). It is an |
541 |
< |
* unenforced usage error for an unregistered party to invoke this |
542 |
< |
* method. |
540 |
> |
* in turn wait for others via {@link #awaitAdvance}). It is a |
541 |
> |
* usage error for an unregistered party to invoke this |
542 |
> |
* method. However, it is possible that this error will result in |
543 |
> |
* an {code IllegalStateException} only when some <em>other</em> |
544 |
> |
* party arrives. |
545 |
|
* |
546 |
|
* @return the arrival phase number, or a negative value if terminated |
547 |
|
* @throws IllegalStateException if not terminated and the number |
548 |
|
* of unarrived parties would become negative |
549 |
|
*/ |
550 |
|
public int arrive() { |
551 |
< |
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; |
551 |
> |
return doArrive(ONE_ARRIVAL); |
552 |
|
} |
553 |
|
|
554 |
|
/** |
557 |
|
* required to trip the barrier in future phases. If this phaser |
558 |
|
* has a parent, and deregistration causes this phaser to have |
559 |
|
* zero parties, this phaser also arrives at and is deregistered |
560 |
< |
* from its parent. It is an unenforced usage error for an |
561 |
< |
* unregistered party to invoke this method. |
560 |
> |
* from its parent. It is a usage error for an unregistered party |
561 |
> |
* to invoke this method. However, it is possible that this error |
562 |
> |
* will result in an {code IllegalStateException} only when some |
563 |
> |
* <em>other</em> party arrives. |
564 |
|
* |
565 |
|
* @return the arrival phase number, or a negative value if terminated |
566 |
|
* @throws IllegalStateException if not terminated and the number |
567 |
|
* of registered or unarrived parties would become negative |
568 |
|
*/ |
569 |
|
public int arriveAndDeregister() { |
570 |
< |
// 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; |
570 |
> |
return doArrive(ONE_ARRIVAL|ONE_PARTY); |
571 |
|
} |
572 |
|
|
573 |
|
/** |
576 |
|
* interruption or timeout, you can arrange this with an analogous |
577 |
|
* construction using one of the other forms of the {@code |
578 |
|
* awaitAdvance} method. If instead you need to deregister upon |
579 |
< |
* arrival, use {@link #arriveAndDeregister}. It is an unenforced |
580 |
< |
* usage error for an unregistered party to invoke this method. |
579 |
> |
* arrival, use {@link #arriveAndDeregister}. It is a usage error |
580 |
> |
* for an unregistered party to invoke this method. However, it is |
581 |
> |
* possible that this error will result in an {code |
582 |
> |
* IllegalStateException} only when some <em>other</em> party |
583 |
> |
* arrives. |
584 |
|
* |
585 |
|
* @return the arrival phase number, or a negative number if terminated |
586 |
|
* @throws IllegalStateException if not terminated and the number |
605 |
|
public int awaitAdvance(int phase) { |
606 |
|
if (phase < 0) |
607 |
|
return phase; |
608 |
< |
int p = getPhase(); |
609 |
< |
if (p != phase) |
610 |
< |
return p; |
590 |
< |
return untimedWait(phase); |
608 |
> |
long s = (parent == null) ? state : reconcileState(); |
609 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
610 |
> |
return (p != phase) ? p : internalAwaitAdvance(phase, null); |
611 |
|
} |
612 |
|
|
613 |
|
/** |
628 |
|
throws InterruptedException { |
629 |
|
if (phase < 0) |
630 |
|
return phase; |
631 |
< |
int p = getPhase(); |
632 |
< |
if (p != phase) |
633 |
< |
return p; |
634 |
< |
return interruptibleWait(phase); |
631 |
> |
long s = (parent == null) ? state : reconcileState(); |
632 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
633 |
> |
if (p == phase) { |
634 |
> |
QNode node = new QNode(this, phase, true, false, 0L); |
635 |
> |
p = internalAwaitAdvance(phase, node); |
636 |
> |
if (node.wasInterrupted) |
637 |
> |
throw new InterruptedException(); |
638 |
> |
} |
639 |
> |
return p; |
640 |
|
} |
641 |
|
|
642 |
|
/** |
662 |
|
public int awaitAdvanceInterruptibly(int phase, |
663 |
|
long timeout, TimeUnit unit) |
664 |
|
throws InterruptedException, TimeoutException { |
640 |
– |
long nanos = unit.toNanos(timeout); |
665 |
|
if (phase < 0) |
666 |
|
return phase; |
667 |
< |
int p = getPhase(); |
668 |
< |
if (p != phase) |
669 |
< |
return p; |
670 |
< |
return timedWait(phase, nanos); |
667 |
> |
long s = (parent == null) ? state : reconcileState(); |
668 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
669 |
> |
if (p == phase) { |
670 |
> |
long nanos = unit.toNanos(timeout); |
671 |
> |
QNode node = new QNode(this, phase, true, true, nanos); |
672 |
> |
p = internalAwaitAdvance(phase, node); |
673 |
> |
if (node.wasInterrupted) |
674 |
> |
throw new InterruptedException(); |
675 |
> |
else if (p == phase) |
676 |
> |
throw new TimeoutException(); |
677 |
> |
} |
678 |
> |
return p; |
679 |
|
} |
680 |
|
|
681 |
|
/** |
682 |
< |
* Forces this barrier to enter termination state. Counts of |
683 |
< |
* arrived and registered parties are unaffected. If this phaser |
684 |
< |
* has a parent, it too is terminated. This method may be useful |
685 |
< |
* for coordinating recovery after one or more tasks encounter |
686 |
< |
* unexpected exceptions. |
682 |
> |
* Forces this barrier to enter termination state. Counts of |
683 |
> |
* arrived and registered parties are unaffected. If this phaser |
684 |
> |
* is a member of a tiered set of phasers, then all of the phasers |
685 |
> |
* in the set are terminated. If this phaser is already |
686 |
> |
* terminated, this method has no effect. This method may be |
687 |
> |
* useful for coordinating recovery after one or more tasks |
688 |
> |
* encounter unexpected exceptions. |
689 |
|
*/ |
690 |
|
public void forceTermination() { |
691 |
< |
Phaser r = root; // force at root then reconcile |
691 |
> |
// Only need to change root state |
692 |
> |
final Phaser root = this.root; |
693 |
|
long s; |
694 |
< |
while (phaseOf(s = r.state) >= 0) |
695 |
< |
UNSAFE.compareAndSwapLong(r, stateOffset, s, |
696 |
< |
stateFor(-1, partiesOf(s), |
697 |
< |
unarrivedOf(s))); |
698 |
< |
reconcileState(); |
699 |
< |
releaseWaiters(0); // ensure wakeups on both queues |
700 |
< |
releaseWaiters(1); |
694 |
> |
while ((s = root.state) >= 0) { |
695 |
> |
if (UNSAFE.compareAndSwapLong(root, stateOffset, |
696 |
> |
s, s | TERMINATION_BIT)) { |
697 |
> |
releaseWaiters(0); // signal all threads |
698 |
> |
releaseWaiters(1); |
699 |
> |
return; |
700 |
> |
} |
701 |
> |
} |
702 |
|
} |
703 |
|
|
704 |
|
/** |
709 |
|
* @return the phase number, or a negative value if terminated |
710 |
|
*/ |
711 |
|
public final int getPhase() { |
712 |
< |
return phaseOf(getReconciledState()); |
712 |
> |
return (int)(root.state >>> PHASE_SHIFT); |
713 |
|
} |
714 |
|
|
715 |
|
/** |
718 |
|
* @return the number of parties |
719 |
|
*/ |
720 |
|
public int getRegisteredParties() { |
721 |
< |
return partiesOf(getReconciledState()); |
721 |
> |
return partiesOf(state); |
722 |
|
} |
723 |
|
|
724 |
|
/** |
728 |
|
* @return the number of arrived parties |
729 |
|
*/ |
730 |
|
public int getArrivedParties() { |
731 |
< |
return arrivedOf(getReconciledState()); |
731 |
> |
return arrivedOf(parent==null? state : reconcileState()); |
732 |
|
} |
733 |
|
|
734 |
|
/** |
738 |
|
* @return the number of unarrived parties |
739 |
|
*/ |
740 |
|
public int getUnarrivedParties() { |
741 |
< |
return unarrivedOf(getReconciledState()); |
741 |
> |
return unarrivedOf(parent==null? state : reconcileState()); |
742 |
|
} |
743 |
|
|
744 |
|
/** |
766 |
|
* @return {@code true} if this barrier has been terminated |
767 |
|
*/ |
768 |
|
public boolean isTerminated() { |
769 |
< |
return getPhase() < 0; |
769 |
> |
return root.state < 0L; |
770 |
|
} |
771 |
|
|
772 |
|
/** |
782 |
|
* which case no advance occurs. |
783 |
|
* |
784 |
|
* <p>The arguments to this method provide the state of the phaser |
785 |
< |
* prevailing for the current transition. The results and effects |
786 |
< |
* of invoking phase-related methods (including {@code getPhase} |
751 |
< |
* as well as arrival, registration, and waiting methods) from |
785 |
> |
* prevailing for the current transition. The effects of invoking |
786 |
> |
* arrival, registration, and waiting methods on this Phaser from |
787 |
|
* within {@code onAdvance} are unspecified and should not be |
788 |
< |
* relied on. Similarly, while it is possible to override this |
789 |
< |
* method to produce side-effects visible to participating tasks, |
790 |
< |
* it is in general safe to do so only in designs in which all |
791 |
< |
* parties register before any arrive, and all {@link |
792 |
< |
* #awaitAdvance} at each phase. |
793 |
< |
* |
794 |
< |
* <p>The default version returns {@code true} when the number of |
795 |
< |
* registered parties is zero. Normally, overrides that arrange |
796 |
< |
* termination for other reasons should also preserve this |
797 |
< |
* property. |
788 |
> |
* relied on. |
789 |
> |
* |
790 |
> |
* <p>If this Phaser is a member of a tiered set of Phasers, then |
791 |
> |
* {@code onAdvance} is invoked only for its root Phaser on each |
792 |
> |
* advance. |
793 |
> |
* |
794 |
> |
* <p>To support the most common use cases, the default |
795 |
> |
* implementation of this method returns {@code true} when the |
796 |
> |
* number of registered parties has become zero as the result of a |
797 |
> |
* party invoking {@code arriveAndDeregister}. You can disable |
798 |
> |
* this behavior, thus enabling continuation upon future |
799 |
> |
* registrations, by overriding this method to always return |
800 |
> |
* {@code false}: |
801 |
> |
* |
802 |
> |
* <pre> {@code |
803 |
> |
* Phaser phaser = new Phaser() { |
804 |
> |
* protected boolean onAdvance(int phase, int parties) { return false; } |
805 |
> |
* }}</pre> |
806 |
|
* |
807 |
|
* @param phase the phase number on entering the barrier |
808 |
|
* @param registeredParties the current number of registered parties |
822 |
|
* @return a string identifying this barrier, as well as its state |
823 |
|
*/ |
824 |
|
public String toString() { |
825 |
< |
long s = getReconciledState(); |
825 |
> |
return stateToString(reconcileState()); |
826 |
> |
} |
827 |
> |
|
828 |
> |
/** |
829 |
> |
* Implementation of toString and string-based error messages |
830 |
> |
*/ |
831 |
> |
private String stateToString(long s) { |
832 |
|
return super.toString() + |
833 |
|
"[phase = " + phaseOf(s) + |
834 |
|
" parties = " + partiesOf(s) + |
835 |
|
" arrived = " + arrivedOf(s) + "]"; |
836 |
|
} |
837 |
|
|
838 |
< |
// methods for waiting |
838 |
> |
// Waiting mechanics |
839 |
> |
|
840 |
> |
/** |
841 |
> |
* Removes and signals threads from queue for phase. |
842 |
> |
*/ |
843 |
> |
private void releaseWaiters(int phase) { |
844 |
> |
AtomicReference<QNode> head = queueFor(phase); |
845 |
> |
QNode q; |
846 |
> |
int p; |
847 |
> |
while ((q = head.get()) != null && |
848 |
> |
((p = q.phase) == phase || |
849 |
> |
(int)(root.state >>> PHASE_SHIFT) != p)) { |
850 |
> |
if (head.compareAndSet(q, q.next)) |
851 |
> |
q.signal(); |
852 |
> |
} |
853 |
> |
} |
854 |
> |
|
855 |
> |
/** The number of CPUs, for spin control */ |
856 |
> |
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
857 |
> |
|
858 |
> |
/** |
859 |
> |
* The number of times to spin before blocking while waiting for |
860 |
> |
* advance, per arrival while waiting. On multiprocessors, fully |
861 |
> |
* blocking and waking up a large number of threads all at once is |
862 |
> |
* usually a very slow process, so we use rechargeable spins to |
863 |
> |
* avoid it when threads regularly arrive: When a thread in |
864 |
> |
* internalAwaitAdvance notices another arrival before blocking, |
865 |
> |
* and there appear to be enough CPUs available, it spins |
866 |
> |
* SPINS_PER_ARRIVAL more times before blocking. Plus, even on |
867 |
> |
* uniprocessors, there is at least one intervening Thread.yield |
868 |
> |
* before blocking. The value trades off good-citizenship vs big |
869 |
> |
* unnecessary slowdowns. |
870 |
> |
*/ |
871 |
> |
static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8; |
872 |
> |
|
873 |
> |
/** |
874 |
> |
* Possibly blocks and waits for phase to advance unless aborted. |
875 |
> |
* |
876 |
> |
* @param phase current phase |
877 |
> |
* @param node if non-null, the wait node to track interrupt and timeout; |
878 |
> |
* if null, denotes noninterruptible wait |
879 |
> |
* @return current phase |
880 |
> |
*/ |
881 |
> |
private int internalAwaitAdvance(int phase, QNode node) { |
882 |
> |
Phaser current = this; // to eventually wait at root if tiered |
883 |
> |
boolean queued = false; // true when node is enqueued |
884 |
> |
int lastUnarrived = -1; // to increase spins upon change |
885 |
> |
int spins = SPINS_PER_ARRIVAL; |
886 |
> |
long s; |
887 |
> |
int p; |
888 |
> |
while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) { |
889 |
> |
Phaser par; |
890 |
> |
int unarrived = (int)s & UNARRIVED_MASK; |
891 |
> |
if (unarrived != lastUnarrived) { |
892 |
> |
if (lastUnarrived == -1) // ensure old queue clean |
893 |
> |
releaseWaiters(phase-1); |
894 |
> |
if ((lastUnarrived = unarrived) < NCPU) |
895 |
> |
spins += SPINS_PER_ARRIVAL; |
896 |
> |
} |
897 |
> |
else if (unarrived == 0 && (par = current.parent) != null) { |
898 |
> |
current = par; // if all arrived, use parent |
899 |
> |
par = par.parent; |
900 |
> |
lastUnarrived = -1; |
901 |
> |
} |
902 |
> |
else if (spins > 0) { |
903 |
> |
if (--spins == (SPINS_PER_ARRIVAL >>> 1)) |
904 |
> |
Thread.yield(); // yield midway through spin |
905 |
> |
} |
906 |
> |
else if (node == null) // must be noninterruptible |
907 |
> |
node = new QNode(this, phase, false, false, 0L); |
908 |
> |
else if (node.isReleasable()) { |
909 |
> |
if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase) |
910 |
> |
break; |
911 |
> |
else |
912 |
> |
return phase; // aborted |
913 |
> |
} |
914 |
> |
else if (!queued) { // push onto queue |
915 |
> |
AtomicReference<QNode> head = queueFor(phase); |
916 |
> |
QNode q = head.get(); |
917 |
> |
if (q == null || q.phase == phase) { |
918 |
> |
node.next = q; |
919 |
> |
if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase) |
920 |
> |
break; // recheck to avoid stale enqueue |
921 |
> |
else |
922 |
> |
queued = head.compareAndSet(q, node); |
923 |
> |
} |
924 |
> |
} |
925 |
> |
else { |
926 |
> |
try { |
927 |
> |
ForkJoinPool.managedBlock(node); |
928 |
> |
} catch (InterruptedException ie) { |
929 |
> |
node.wasInterrupted = true; |
930 |
> |
} |
931 |
> |
} |
932 |
> |
} |
933 |
> |
releaseWaiters(phase); |
934 |
> |
if (node != null) |
935 |
> |
node.onRelease(); |
936 |
> |
return p; |
937 |
> |
} |
938 |
|
|
939 |
|
/** |
940 |
|
* Wait nodes for Treiber stack representing wait queue |
942 |
|
static final class QNode implements ForkJoinPool.ManagedBlocker { |
943 |
|
final Phaser phaser; |
944 |
|
final int phase; |
797 |
– |
final long startTime; |
798 |
– |
final long nanos; |
799 |
– |
final boolean timed; |
945 |
|
final boolean interruptible; |
946 |
< |
volatile boolean wasInterrupted = false; |
946 |
> |
final boolean timed; |
947 |
> |
boolean wasInterrupted; |
948 |
> |
long nanos; |
949 |
> |
long lastTime; |
950 |
|
volatile Thread thread; // nulled to cancel wait |
951 |
|
QNode next; |
952 |
|
|
953 |
|
QNode(Phaser phaser, int phase, boolean interruptible, |
954 |
< |
boolean timed, long startTime, long nanos) { |
954 |
> |
boolean timed, long nanos) { |
955 |
|
this.phaser = phaser; |
956 |
|
this.phase = phase; |
809 |
– |
this.timed = timed; |
957 |
|
this.interruptible = interruptible; |
811 |
– |
this.startTime = startTime; |
958 |
|
this.nanos = nanos; |
959 |
+ |
this.timed = timed; |
960 |
+ |
this.lastTime = timed? System.nanoTime() : 0L; |
961 |
|
thread = Thread.currentThread(); |
962 |
|
} |
963 |
|
|
964 |
|
public boolean isReleasable() { |
965 |
< |
return (thread == null || |
966 |
< |
phaser.getPhase() != phase || |
967 |
< |
(interruptible && wasInterrupted) || |
968 |
< |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
965 |
> |
Thread t = thread; |
966 |
> |
if (t != null) { |
967 |
> |
if (phaser.getPhase() != phase) |
968 |
> |
t = null; |
969 |
> |
else { |
970 |
> |
if (Thread.interrupted()) |
971 |
> |
wasInterrupted = true; |
972 |
> |
if (interruptible && wasInterrupted) |
973 |
> |
t = null; |
974 |
> |
else if (timed) { |
975 |
> |
if (nanos > 0) { |
976 |
> |
long now = System.nanoTime(); |
977 |
> |
nanos -= now - lastTime; |
978 |
> |
lastTime = now; |
979 |
> |
} |
980 |
> |
if (nanos <= 0) |
981 |
> |
t = null; |
982 |
> |
} |
983 |
> |
} |
984 |
> |
if (t != null) |
985 |
> |
return false; |
986 |
> |
thread = null; |
987 |
> |
} |
988 |
> |
return true; |
989 |
|
} |
990 |
|
|
991 |
|
public boolean block() { |
992 |
< |
if (Thread.interrupted()) { |
993 |
< |
wasInterrupted = true; |
994 |
< |
if (interruptible) |
827 |
< |
return true; |
828 |
< |
} |
829 |
< |
if (!timed) |
992 |
> |
if (isReleasable()) |
993 |
> |
return true; |
994 |
> |
else if (!timed) |
995 |
|
LockSupport.park(this); |
996 |
< |
else { |
997 |
< |
long waitTime = nanos - (System.nanoTime() - startTime); |
833 |
< |
if (waitTime <= 0) |
834 |
< |
return true; |
835 |
< |
LockSupport.parkNanos(this, waitTime); |
836 |
< |
} |
996 |
> |
else if (nanos > 0) |
997 |
> |
LockSupport.parkNanos(this, nanos); |
998 |
|
return isReleasable(); |
999 |
|
} |
1000 |
|
|
1006 |
|
} |
1007 |
|
} |
1008 |
|
|
1009 |
< |
boolean doWait() { |
1010 |
< |
if (thread != null) { |
1011 |
< |
try { |
1012 |
< |
ForkJoinPool.managedBlock(this); |
1013 |
< |
} 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(); |
869 |
< |
} |
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 |
< |
} |
881 |
< |
|
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; |
1009 |
> |
void onRelease() { // actions upon return from internalAwaitAdvance |
1010 |
> |
if (!interruptible && wasInterrupted) |
1011 |
> |
Thread.currentThread().interrupt(); |
1012 |
> |
if (thread != null) |
1013 |
> |
thread = null; |
1014 |
|
} |
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 |
– |
} |
1015 |
|
|
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; |
1016 |
|
} |
1017 |
|
|
1018 |
|
// Unsafe mechanics |