| 75 |
|
* </ul> |
| 76 |
|
* |
| 77 |
|
* <p> <b>Termination.</b> A phaser may enter a <em>termination</em> |
| 78 |
< |
* state in which all synchronization methods immediately return |
| 79 |
< |
* without updating phaser state or waiting for advance, and |
| 80 |
< |
* indicating (via a negative phase value) that execution is complete. |
| 81 |
< |
* Termination is triggered when an invocation of {@code onAdvance} |
| 82 |
< |
* returns {@code true}. The default implementation returns {@code |
| 83 |
< |
* true} if a deregistration has caused the number of registered |
| 84 |
< |
* parties to become zero. As illustrated below, when phasers control |
| 85 |
< |
* actions with a fixed number of iterations, it is often convenient |
| 86 |
< |
* to override this method to cause termination when the current phase |
| 87 |
< |
* number reaches a threshold. Method {@link #forceTermination} is |
| 88 |
< |
* also available to abruptly release waiting threads and allow them |
| 89 |
< |
* to terminate. |
| 78 |
> |
* state, that may be checked using method {@link #isTerminated}. Upon |
| 79 |
> |
* termination, all synchronization methods immediately return without |
| 80 |
> |
* waiting for advance, as indicated by a negative return |
| 81 |
> |
* value. Similarly, attempts to register upon termination have no |
| 82 |
> |
* effect. Termination is triggered when an invocation of {@code |
| 83 |
> |
* onAdvance} returns {@code true}. The default implementation returns |
| 84 |
> |
* {@code true} if a deregistration has caused the number of |
| 85 |
> |
* registered parties to become zero. As illustrated below, when |
| 86 |
> |
* phasers control actions with a fixed number of iterations, it is |
| 87 |
> |
* often convenient to override this method to cause termination when |
| 88 |
> |
* the current phase number reaches a threshold. Method {@link |
| 89 |
> |
* #forceTermination} is also available to abruptly release waiting |
| 90 |
> |
* threads and allow them to terminate. |
| 91 |
|
* |
| 92 |
|
* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., |
| 93 |
|
* constructed in tree structures) to reduce contention. Phasers with |
| 97 |
|
* increase throughput even though it incurs greater per-operation |
| 98 |
|
* overhead. |
| 99 |
|
* |
| 100 |
+ |
* <p>In a tree of tiered phasers, registration and deregistration of |
| 101 |
+ |
* child phasers with their parent are managed automatically. |
| 102 |
+ |
* Whenever the number of registered parties of a child phaser becomes |
| 103 |
+ |
* non-zero (as established in the {@link #Phaser(Phaser,int)} |
| 104 |
+ |
* constructor, {@link #register}, or {@link #bulkRegister}), the |
| 105 |
+ |
* child phaser is registered with its parent. Whenever the number of |
| 106 |
+ |
* registered parties becomes zero as the result of an invocation of |
| 107 |
+ |
* {@link #arriveAndDeregister}, the child phaser is deregistered |
| 108 |
+ |
* from its parent. |
| 109 |
+ |
* |
| 110 |
|
* <p><b>Monitoring.</b> While synchronization methods may be invoked |
| 111 |
|
* only by registered parties, the current state of a phaser may be |
| 112 |
|
* monitored by any caller. At any given moment there are {@link |
| 194 |
|
* }}</pre> |
| 195 |
|
* |
| 196 |
|
* |
| 197 |
< |
* <p>To create a set of tasks using a tree of phasers, |
| 198 |
< |
* you could use code of the following form, assuming a |
| 199 |
< |
* Task class with a constructor accepting a {@code Phaser} that |
| 200 |
< |
* it registers with upon construction: |
| 197 |
> |
* <p>To create a set of {@code n} tasks using a tree of phasers, you |
| 198 |
> |
* could use code of the following form, assuming a Task class with a |
| 199 |
> |
* constructor accepting a {@code Phaser} that it registers with upon |
| 200 |
> |
* construction. After invocation of {@code build(new Task[n], 0, n, |
| 201 |
> |
* new Phaser())}, these tasks could then be started, for example by |
| 202 |
> |
* submitting to a pool: |
| 203 |
|
* |
| 204 |
|
* <pre> {@code |
| 205 |
< |
* void build(Task[] actions, int lo, int hi, Phaser ph) { |
| 205 |
> |
* void build(Task[] tasks, int lo, int hi, Phaser ph) { |
| 206 |
|
* if (hi - lo > TASKS_PER_PHASER) { |
| 207 |
|
* for (int i = lo; i < hi; i += TASKS_PER_PHASER) { |
| 208 |
|
* int j = Math.min(i + TASKS_PER_PHASER, hi); |
| 209 |
< |
* build(actions, i, j, new Phaser(ph)); |
| 209 |
> |
* build(tasks, i, j, new Phaser(ph)); |
| 210 |
|
* } |
| 211 |
|
* } else { |
| 212 |
|
* for (int i = lo; i < hi; ++i) |
| 213 |
< |
* actions[i] = new Task(ph); |
| 213 |
> |
* tasks[i] = new Task(ph); |
| 214 |
|
* // assumes new Task(ph) performs ph.register() |
| 215 |
|
* } |
| 216 |
< |
* } |
| 204 |
< |
* // .. initially called, for n tasks via |
| 205 |
< |
* build(new Task[n], 0, n, new Phaser());}</pre> |
| 216 |
> |
* }}</pre> |
| 217 |
|
* |
| 218 |
|
* The best value of {@code TASKS_PER_PHASER} depends mainly on |
| 219 |
|
* expected synchronization rates. A value as low as four may |
| 244 |
|
* * phase -- the generation of the barrier (bits 32-62) |
| 245 |
|
* * terminated -- set if barrier is terminated (bit 63 / sign) |
| 246 |
|
* |
| 247 |
< |
* However, to efficiently maintain atomicity, these values are |
| 248 |
< |
* packed into a single (atomic) long. Termination uses the sign |
| 249 |
< |
* bit of 32 bit representation of phase, so phase is set to -1 on |
| 250 |
< |
* termination. Good performance relies on keeping state decoding |
| 251 |
< |
* and encoding simple, and keeping race windows short. |
| 247 |
> |
* Except that a phaser with no registered parties is |
| 248 |
> |
* distinguished with 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 |
| 252 |
> |
* a single (atomic) long. Good performance relies on keeping |
| 253 |
> |
* state decoding and encoding simple, and keeping race windows |
| 254 |
> |
* short. |
| 255 |
> |
* |
| 256 |
> |
* All state updates are performed via CAS except initial |
| 257 |
> |
* registration of a sub-phaser (i.e., one with a non-null |
| 258 |
> |
* parent). In this (relatively rare) case, we use built-in |
| 259 |
> |
* synchronization to lock while first registering with its |
| 260 |
> |
* parent. |
| 261 |
> |
* |
| 262 |
> |
* The phase of a subphaser is allowed to lag that of its |
| 263 |
> |
* ancestors until it is actually accessed. Method reconcileState |
| 264 |
> |
* is usually attempted only only when the number of unarrived |
| 265 |
> |
* parties appears to be zero, which indicates a potential lag in |
| 266 |
> |
* updating phase after the root advanced. |
| 267 |
|
*/ |
| 268 |
|
private volatile long state; |
| 269 |
|
|
| 273 |
|
private static final int PHASE_SHIFT = 32; |
| 274 |
|
private static final int UNARRIVED_MASK = 0xffff; // to mask ints |
| 275 |
|
private static final long PARTIES_MASK = 0xffff0000L; // to mask longs |
| 250 |
– |
private static final long ONE_ARRIVAL = 1L; |
| 251 |
– |
private static final long ONE_PARTY = 1L << PARTIES_SHIFT; |
| 276 |
|
private static final long TERMINATION_BIT = 1L << 63; |
| 277 |
|
|
| 278 |
+ |
// some special values |
| 279 |
+ |
private static final int ONE_ARRIVAL = 1; |
| 280 |
+ |
private static final int ONE_PARTY = 1 << PARTIES_SHIFT; |
| 281 |
+ |
private static final int EMPTY = 1; |
| 282 |
+ |
|
| 283 |
|
// The following unpacking methods are usually manually inlined |
| 284 |
|
|
| 285 |
|
private static int unarrivedOf(long s) { |
| 286 |
< |
return (int)s & UNARRIVED_MASK; |
| 286 |
> |
int counts = (int)s; |
| 287 |
> |
return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK; |
| 288 |
|
} |
| 289 |
|
|
| 290 |
|
private static int partiesOf(long s) { |
| 296 |
|
} |
| 297 |
|
|
| 298 |
|
private static int arrivedOf(long s) { |
| 299 |
< |
return partiesOf(s) - unarrivedOf(s); |
| 299 |
> |
int counts = (int)s; |
| 300 |
> |
return (counts == EMPTY) ? 0 : |
| 301 |
> |
(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK); |
| 302 |
|
} |
| 303 |
|
|
| 304 |
|
/** |
| 307 |
|
private final Phaser parent; |
| 308 |
|
|
| 309 |
|
/** |
| 310 |
< |
* The root of phaser tree. Equals this if not in a tree. Used to |
| 279 |
< |
* support faster state push-down. |
| 310 |
> |
* The root of phaser tree. Equals this if not in a tree. |
| 311 |
|
*/ |
| 312 |
|
private final Phaser root; |
| 313 |
|
|
| 345 |
|
* Manually tuned to speed up and minimize race windows for the |
| 346 |
|
* common case of just decrementing unarrived field. |
| 347 |
|
* |
| 348 |
< |
* @param adj - adjustment to apply to state -- either |
| 318 |
< |
* ONE_ARRIVAL (for arrive) or |
| 319 |
< |
* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister) |
| 348 |
> |
* @param deregister false for arrive, true for arriveAndDeregister |
| 349 |
|
*/ |
| 350 |
< |
private int doArrive(long adj) { |
| 350 |
> |
private int doArrive(boolean deregister) { |
| 351 |
> |
int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL; |
| 352 |
> |
final Phaser root = this.root; |
| 353 |
|
for (;;) { |
| 354 |
< |
long s = state; |
| 324 |
< |
int unarrived = (int)s & UNARRIVED_MASK; |
| 354 |
> |
long s = (root == this) ? state : reconcileState(); |
| 355 |
|
int phase = (int)(s >>> PHASE_SHIFT); |
| 356 |
+ |
int counts = (int)s; |
| 357 |
+ |
int unarrived = (counts & UNARRIVED_MASK) - 1; |
| 358 |
|
if (phase < 0) |
| 359 |
|
return phase; |
| 360 |
< |
else if (unarrived == 0) { |
| 361 |
< |
if (reconcileState() == s) // recheck |
| 360 |
> |
else if (counts == EMPTY || unarrived < 0) { |
| 361 |
> |
if (root == this || reconcileState() == s) |
| 362 |
|
throw new IllegalStateException(badArrive(s)); |
| 363 |
|
} |
| 364 |
|
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
| 365 |
< |
if (unarrived == 1) { |
| 366 |
< |
long p = s & PARTIES_MASK; // unshifted parties field |
| 367 |
< |
long lu = p >>> PARTIES_SHIFT; |
| 368 |
< |
int u = (int)lu; |
| 369 |
< |
int nextPhase = (phase + 1) & MAX_PHASE; |
| 370 |
< |
long next = ((long)nextPhase << PHASE_SHIFT) | p | lu; |
| 371 |
< |
final Phaser parent = this.parent; |
| 372 |
< |
if (parent == null) { |
| 373 |
< |
if (onAdvance(phase, u)) |
| 374 |
< |
next |= TERMINATION_BIT; |
| 375 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
| 376 |
< |
releaseWaiters(phase); |
| 377 |
< |
} |
| 378 |
< |
else { |
| 347 |
< |
parent.doArrive((u == 0) ? |
| 348 |
< |
ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
| 349 |
< |
if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase) |
| 350 |
< |
reconcileState(); |
| 351 |
< |
else if (state == s) |
| 352 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, |
| 353 |
< |
next); |
| 354 |
< |
} |
| 365 |
> |
if (unarrived == 0) { |
| 366 |
> |
long n = s & PARTIES_MASK; // base of next state |
| 367 |
> |
int nextUnarrived = ((int)n) >>> PARTIES_SHIFT; |
| 368 |
> |
if (root != this) |
| 369 |
> |
return parent.doArrive(nextUnarrived == 0); |
| 370 |
> |
if (onAdvance(phase, nextUnarrived)) |
| 371 |
> |
n |= TERMINATION_BIT; |
| 372 |
> |
else if (nextUnarrived == 0) |
| 373 |
> |
n |= EMPTY; |
| 374 |
> |
else |
| 375 |
> |
n |= nextUnarrived; |
| 376 |
> |
n |= ((long)((phase + 1) & MAX_PHASE)) << PHASE_SHIFT; |
| 377 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, n); |
| 378 |
> |
releaseWaiters(phase); |
| 379 |
|
} |
| 380 |
|
return phase; |
| 381 |
|
} |
| 391 |
|
private int doRegister(int registrations) { |
| 392 |
|
// adjustment to state |
| 393 |
|
long adj = ((long)registrations << PARTIES_SHIFT) | registrations; |
| 394 |
< |
final Phaser parent = this.parent; |
| 394 |
> |
Phaser par = parent; |
| 395 |
> |
int phase; |
| 396 |
|
for (;;) { |
| 397 |
< |
long s = (parent == null) ? state : reconcileState(); |
| 398 |
< |
int parties = (int)s >>> PARTIES_SHIFT; |
| 399 |
< |
int phase = (int)(s >>> PHASE_SHIFT); |
| 400 |
< |
if (phase < 0) |
| 401 |
< |
return phase; |
| 377 |
< |
else if (registrations > MAX_PARTIES - parties) |
| 397 |
> |
long s = state; |
| 398 |
> |
int counts = (int)s; |
| 399 |
> |
int parties = counts >>> PARTIES_SHIFT; |
| 400 |
> |
int unarrived = counts & UNARRIVED_MASK; |
| 401 |
> |
if (registrations > MAX_PARTIES - parties) |
| 402 |
|
throw new IllegalStateException(badRegister(s)); |
| 403 |
< |
else if ((parties == 0 && parent == null) || // first reg of root |
| 404 |
< |
((int)s & UNARRIVED_MASK) != 0) { // not advancing |
| 405 |
< |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj)) |
| 406 |
< |
return phase; |
| 407 |
< |
} |
| 408 |
< |
else if (parties != 0) // wait for onAdvance |
| 409 |
< |
root.internalAwaitAdvance(phase, null); |
| 410 |
< |
else { // 1st registration of child |
| 411 |
< |
synchronized (this) { // register parent first |
| 412 |
< |
if (reconcileState() == s) { // recheck under lock |
| 413 |
< |
parent.doRegister(1); // OK if throws IllegalState |
| 414 |
< |
for (;;) { // simpler form of outer loop |
| 415 |
< |
s = reconcileState(); |
| 416 |
< |
phase = (int)(s >>> PHASE_SHIFT); |
| 417 |
< |
if (phase < 0 || |
| 418 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, |
| 419 |
< |
s, s + adj)) |
| 420 |
< |
return phase; |
| 421 |
< |
} |
| 403 |
> |
else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0) |
| 404 |
> |
break; |
| 405 |
> |
else if (counts != EMPTY) { // not 1st registration |
| 406 |
> |
if (par == null || reconcileState() == s) { |
| 407 |
> |
if (unarrived == 0) // wait out advance |
| 408 |
> |
root.internalAwaitAdvance(phase, null); |
| 409 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, |
| 410 |
> |
s, s + adj)) |
| 411 |
> |
break; |
| 412 |
> |
} |
| 413 |
> |
} |
| 414 |
> |
else if (par == null) { // 1st root registration |
| 415 |
> |
long next = (((long) phase) << PHASE_SHIFT) | adj; |
| 416 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
| 417 |
> |
break; |
| 418 |
> |
} |
| 419 |
> |
else { |
| 420 |
> |
synchronized (this) { // 1st sub registration |
| 421 |
> |
if (state == s) { // recheck under lock |
| 422 |
> |
par.doRegister(1); |
| 423 |
> |
do { // force current phase |
| 424 |
> |
phase = (int)(root.state >>> PHASE_SHIFT); |
| 425 |
> |
// assert phase < 0 || (int)state == EMPTY; |
| 426 |
> |
} while (!UNSAFE.compareAndSwapLong |
| 427 |
> |
(this, stateOffset, state, |
| 428 |
> |
(((long) phase) << PHASE_SHIFT) | adj)); |
| 429 |
> |
break; |
| 430 |
|
} |
| 431 |
|
} |
| 432 |
|
} |
| 433 |
|
} |
| 434 |
+ |
return phase; |
| 435 |
|
} |
| 436 |
|
|
| 437 |
|
/** |
| 438 |
< |
* Recursively resolves lagged phase propagation from root if necessary. |
| 438 |
> |
* Resolves lagged phase propagation from root if necessary. |
| 439 |
|
*/ |
| 440 |
|
private long reconcileState() { |
| 441 |
< |
Phaser par = parent; |
| 441 |
> |
Phaser rt = root; |
| 442 |
|
long s = state; |
| 443 |
< |
if (par != null) { |
| 444 |
< |
Phaser rt = root; |
| 445 |
< |
int phase, rPhase; |
| 446 |
< |
while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 && |
| 447 |
< |
(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) { |
| 448 |
< |
if (par != rt && (int)(par.state >>> PHASE_SHIFT) != rPhase) |
| 449 |
< |
par.reconcileState(); |
| 450 |
< |
else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) { |
| 451 |
< |
long u = s & PARTIES_MASK; // reset unarrived to parties |
| 452 |
< |
long next = ((((long) rPhase) << PHASE_SHIFT) | u | |
| 453 |
< |
(u >>> PARTIES_SHIFT)); |
| 454 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
| 443 |
> |
if (rt != this) { |
| 444 |
> |
int phase; |
| 445 |
> |
while ((phase = (int)(rt.state >>> PHASE_SHIFT)) != |
| 446 |
> |
(int)(s >>> PHASE_SHIFT)) { |
| 447 |
> |
// assert phase < 0 || unarrivedOf(s) == 0 |
| 448 |
> |
long t; // to reread s |
| 449 |
> |
long p = s & PARTIES_MASK; // unshifted parties field |
| 450 |
> |
long n = (((long) phase) << PHASE_SHIFT) | p; |
| 451 |
> |
if (phase >= 0) { |
| 452 |
> |
if (p == 0L) |
| 453 |
> |
n |= EMPTY; // reset to empty |
| 454 |
> |
else |
| 455 |
> |
n |= p >>> PARTIES_SHIFT; // set unarr to parties |
| 456 |
|
} |
| 457 |
< |
s = state; |
| 457 |
> |
if ((t = state) == s && |
| 458 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, s = n)) |
| 459 |
> |
break; |
| 460 |
> |
s = t; |
| 461 |
|
} |
| 462 |
|
} |
| 463 |
|
return s; |
| 496 |
|
|
| 497 |
|
/** |
| 498 |
|
* Creates a new phaser with the given parent and number of |
| 499 |
< |
* registered unarrived parties. Registration and deregistration |
| 500 |
< |
* of this child phaser with its parent are managed automatically. |
| 501 |
< |
* If the given parent is non-null, whenever this child phaser has |
| 465 |
< |
* any registered parties (as established in this constructor, |
| 466 |
< |
* {@link #register}, or {@link #bulkRegister}), this child phaser |
| 467 |
< |
* is registered with its parent. Whenever the number of |
| 468 |
< |
* registered parties becomes zero as the result of an invocation |
| 469 |
< |
* of {@link #arriveAndDeregister}, this child phaser is |
| 470 |
< |
* deregistered from its parent. |
| 499 |
> |
* registered unarrived parties. When the given parent is non-null |
| 500 |
> |
* and the given number of parties is greater than zero, this |
| 501 |
> |
* child phaser is registered with its parent. |
| 502 |
|
* |
| 503 |
|
* @param parent the parent phaser |
| 504 |
|
* @param parties the number of parties required to advance to the |
| 509 |
|
public Phaser(Phaser parent, int parties) { |
| 510 |
|
if (parties >>> PARTIES_SHIFT != 0) |
| 511 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
| 512 |
< |
long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT); |
| 512 |
> |
int phase = 0; |
| 513 |
|
this.parent = parent; |
| 514 |
|
if (parent != null) { |
| 515 |
< |
Phaser r = parent.root; |
| 516 |
< |
this.root = r; |
| 517 |
< |
this.evenQ = r.evenQ; |
| 518 |
< |
this.oddQ = r.oddQ; |
| 515 |
> |
final Phaser root = parent.root; |
| 516 |
> |
this.root = root; |
| 517 |
> |
this.evenQ = root.evenQ; |
| 518 |
> |
this.oddQ = root.oddQ; |
| 519 |
|
if (parties != 0) |
| 520 |
< |
s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT; |
| 520 |
> |
phase = parent.doRegister(1); |
| 521 |
|
} |
| 522 |
|
else { |
| 523 |
|
this.root = this; |
| 524 |
|
this.evenQ = new AtomicReference<QNode>(); |
| 525 |
|
this.oddQ = new AtomicReference<QNode>(); |
| 526 |
|
} |
| 527 |
< |
this.state = s; |
| 527 |
> |
this.state = (parties == 0) ? (long) EMPTY : |
| 528 |
> |
((((long) phase) << PHASE_SHIFT) | |
| 529 |
> |
(((long) parties) << PARTIES_SHIFT) | |
| 530 |
> |
((long) parties)); |
| 531 |
|
} |
| 532 |
|
|
| 533 |
|
/** |
| 535 |
|
* invocation of {@link #onAdvance} is in progress, this method |
| 536 |
|
* may await its completion before returning. If this phaser has |
| 537 |
|
* a parent, and this phaser previously had no registered parties, |
| 538 |
< |
* this phaser is also registered with its parent. |
| 539 |
< |
* |
| 540 |
< |
* @return the arrival phase number to which this registration applied |
| 538 |
> |
* this child phaser is also registered with its parent. If |
| 539 |
> |
* this phaser is terminated, the attempt to register has |
| 540 |
> |
* no effect, and a negative value is returned. |
| 541 |
> |
* |
| 542 |
> |
* @return the arrival phase number to which this registration |
| 543 |
> |
* applied. If this value is negative, then this phaser has |
| 544 |
> |
* terminated, in which casem registration has no effect. |
| 545 |
|
* @throws IllegalStateException if attempting to register more |
| 546 |
|
* than the maximum supported number of parties |
| 547 |
|
*/ |
| 553 |
|
* Adds the given number of new unarrived parties to this phaser. |
| 554 |
|
* If an ongoing invocation of {@link #onAdvance} is in progress, |
| 555 |
|
* this method may await its completion before returning. If this |
| 556 |
< |
* phaser has a parent, and the given number of parities is |
| 557 |
< |
* greater than zero, and this phaser previously had no registered |
| 558 |
< |
* parties, this phaser is also registered with its parent. |
| 556 |
> |
* phaser has a parent, and the given number of parties is greater |
| 557 |
> |
* than zero, and this phaser previously had no registered |
| 558 |
> |
* parties, this child phaser is also registered with its parent. |
| 559 |
> |
* If this phaser is terminated, the attempt to register has no |
| 560 |
> |
* effect, and a negative value is returned. |
| 561 |
|
* |
| 562 |
|
* @param parties the number of additional parties required to |
| 563 |
|
* advance to the next phase |
| 564 |
< |
* @return the arrival phase number to which this registration applied |
| 564 |
> |
* @return the arrival phase number to which this registration |
| 565 |
> |
* applied. If this value is negative, then this phaser has |
| 566 |
> |
* terminated, in which casem registration has no effect. |
| 567 |
|
* @throws IllegalStateException if attempting to register more |
| 568 |
|
* than the maximum supported number of parties |
| 569 |
|
* @throws IllegalArgumentException if {@code parties < 0} |
| 589 |
|
* of unarrived parties would become negative |
| 590 |
|
*/ |
| 591 |
|
public int arrive() { |
| 592 |
< |
return doArrive(ONE_ARRIVAL); |
| 592 |
> |
return doArrive(false); |
| 593 |
|
} |
| 594 |
|
|
| 595 |
|
/** |
| 609 |
|
* of registered or unarrived parties would become negative |
| 610 |
|
*/ |
| 611 |
|
public int arriveAndDeregister() { |
| 612 |
< |
return doArrive(ONE_ARRIVAL|ONE_PARTY); |
| 612 |
> |
return doArrive(true); |
| 613 |
|
} |
| 614 |
|
|
| 615 |
|
/** |
| 625 |
|
* IllegalStateException} only upon some subsequent operation on |
| 626 |
|
* this phaser, if ever. |
| 627 |
|
* |
| 628 |
< |
* @return the arrival phase number, or a negative number if terminated |
| 628 |
> |
* @return the arrival phase number, or the (negative) |
| 629 |
> |
* {@linkplain #getPhase() current phase} if terminated |
| 630 |
|
* @throws IllegalStateException if not terminated and the number |
| 631 |
|
* of unarrived parties would become negative |
| 632 |
|
*/ |
| 633 |
|
public int arriveAndAwaitAdvance() { |
| 634 |
< |
return awaitAdvance(doArrive(ONE_ARRIVAL)); |
| 634 |
> |
// Specialization of doArrive+awaitAdvance eliminating some reads/paths |
| 635 |
> |
final Phaser root = this.root; |
| 636 |
> |
for (;;) { |
| 637 |
> |
long s = (root == this) ? state : reconcileState(); |
| 638 |
> |
int phase = (int)(s >>> PHASE_SHIFT); |
| 639 |
> |
int counts = (int)s; |
| 640 |
> |
int unarrived = (counts & UNARRIVED_MASK) - 1; |
| 641 |
> |
if (phase < 0) |
| 642 |
> |
return phase; |
| 643 |
> |
else if (counts == EMPTY || unarrived < 0) { |
| 644 |
> |
if (reconcileState() == s) |
| 645 |
> |
throw new IllegalStateException(badArrive(s)); |
| 646 |
> |
} |
| 647 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, |
| 648 |
> |
s -= ONE_ARRIVAL)) { |
| 649 |
> |
if (unarrived != 0) |
| 650 |
> |
return root.internalAwaitAdvance(phase, null); |
| 651 |
> |
if (root != this) |
| 652 |
> |
return parent.arriveAndAwaitAdvance(); |
| 653 |
> |
long n = s & PARTIES_MASK; // base of next state |
| 654 |
> |
int nextUnarrived = ((int)n) >>> PARTIES_SHIFT; |
| 655 |
> |
if (onAdvance(phase, nextUnarrived)) |
| 656 |
> |
n |= TERMINATION_BIT; |
| 657 |
> |
else if (nextUnarrived == 0) |
| 658 |
> |
n |= EMPTY; |
| 659 |
> |
else |
| 660 |
> |
n |= nextUnarrived; |
| 661 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
| 662 |
> |
n |= (long)nextPhase << PHASE_SHIFT; |
| 663 |
> |
if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n)) |
| 664 |
> |
return (int)(state >>> PHASE_SHIFT); // terminated |
| 665 |
> |
releaseWaiters(phase); |
| 666 |
> |
return nextPhase; |
| 667 |
> |
} |
| 668 |
> |
} |
| 669 |
|
} |
| 670 |
|
|
| 671 |
|
/** |
| 676 |
|
* @param phase an arrival phase number, or negative value if |
| 677 |
|
* terminated; this argument is normally the value returned by a |
| 678 |
|
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
| 679 |
< |
* @return the next arrival phase number, or a negative value |
| 680 |
< |
* if terminated or argument is negative |
| 679 |
> |
* @return the next arrival phase number, or the argument if it is |
| 680 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
| 681 |
> |
* if terminated |
| 682 |
|
*/ |
| 683 |
|
public int awaitAdvance(int phase) { |
| 684 |
< |
Phaser rt; |
| 685 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
| 684 |
> |
final Phaser root = this.root; |
| 685 |
> |
int p = (int)((root == this? state : reconcileState()) >>> PHASE_SHIFT); |
| 686 |
|
if (phase < 0) |
| 687 |
|
return phase; |
| 688 |
< |
if (p == phase && |
| 689 |
< |
(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) |
| 612 |
< |
return rt.internalAwaitAdvance(phase, null); |
| 688 |
> |
if (p == phase) |
| 689 |
> |
return root.internalAwaitAdvance(phase, null); |
| 690 |
|
return p; |
| 691 |
|
} |
| 692 |
|
|
| 700 |
|
* @param phase an arrival phase number, or negative value if |
| 701 |
|
* terminated; this argument is normally the value returned by a |
| 702 |
|
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
| 703 |
< |
* @return the next arrival phase number, or a negative value |
| 704 |
< |
* if terminated or argument is negative |
| 703 |
> |
* @return the next arrival phase number, or the argument if it is |
| 704 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
| 705 |
> |
* if terminated |
| 706 |
|
* @throws InterruptedException if thread interrupted while waiting |
| 707 |
|
*/ |
| 708 |
|
public int awaitAdvanceInterruptibly(int phase) |
| 709 |
|
throws InterruptedException { |
| 710 |
< |
Phaser rt; |
| 711 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
| 710 |
> |
final Phaser root = this.root; |
| 711 |
> |
int p = (int)((root == this? state : reconcileState()) >>> PHASE_SHIFT); |
| 712 |
|
if (phase < 0) |
| 713 |
|
return phase; |
| 714 |
< |
if (p == phase && |
| 637 |
< |
(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) { |
| 714 |
> |
if (p == phase) { |
| 715 |
|
QNode node = new QNode(this, phase, true, false, 0L); |
| 716 |
< |
p = rt.internalAwaitAdvance(phase, node); |
| 716 |
> |
p = root.internalAwaitAdvance(phase, node); |
| 717 |
|
if (node.wasInterrupted) |
| 718 |
|
throw new InterruptedException(); |
| 719 |
|
} |
| 734 |
|
* {@code unit} |
| 735 |
|
* @param unit a {@code TimeUnit} determining how to interpret the |
| 736 |
|
* {@code timeout} parameter |
| 737 |
< |
* @return the next arrival phase number, or a negative value |
| 738 |
< |
* if terminated or argument is negative |
| 737 |
> |
* @return the next arrival phase number, or the argument if it is |
| 738 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
| 739 |
> |
* if terminated |
| 740 |
|
* @throws InterruptedException if thread interrupted while waiting |
| 741 |
|
* @throws TimeoutException if timed out while waiting |
| 742 |
|
*/ |
| 744 |
|
long timeout, TimeUnit unit) |
| 745 |
|
throws InterruptedException, TimeoutException { |
| 746 |
|
long nanos = unit.toNanos(timeout); |
| 747 |
< |
Phaser rt; |
| 748 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
| 747 |
> |
final Phaser root = this.root; |
| 748 |
> |
int p = (int)((root == this? state : reconcileState()) >>> PHASE_SHIFT); |
| 749 |
|
if (phase < 0) |
| 750 |
|
return phase; |
| 751 |
< |
if (p == phase && |
| 674 |
< |
(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) { |
| 751 |
> |
if (p == phase) { |
| 752 |
|
QNode node = new QNode(this, phase, true, true, nanos); |
| 753 |
< |
p = rt.internalAwaitAdvance(phase, node); |
| 753 |
> |
p = root.internalAwaitAdvance(phase, node); |
| 754 |
|
if (node.wasInterrupted) |
| 755 |
|
throw new InterruptedException(); |
| 756 |
|
else if (p == phase) |
| 761 |
|
|
| 762 |
|
/** |
| 763 |
|
* Forces this phaser to enter termination state. Counts of |
| 764 |
< |
* arrived and registered parties are unaffected. If this phaser |
| 765 |
< |
* is a member of a tiered set of phasers, then all of the phasers |
| 766 |
< |
* in the set are terminated. If this phaser is already |
| 767 |
< |
* terminated, this method has no effect. This method may be |
| 768 |
< |
* useful for coordinating recovery after one or more tasks |
| 769 |
< |
* encounter unexpected exceptions. |
| 764 |
> |
* registered parties are unaffected. If this phaser is a member |
| 765 |
> |
* of a tiered set of phasers, then all of the phasers in the set |
| 766 |
> |
* are terminated. If this phaser is already terminated, this |
| 767 |
> |
* method has no effect. This method may be useful for |
| 768 |
> |
* coordinating recovery after one or more tasks encounter |
| 769 |
> |
* unexpected exceptions. |
| 770 |
|
*/ |
| 771 |
|
public void forceTermination() { |
| 772 |
|
// Only need to change root state |
| 773 |
|
final Phaser root = this.root; |
| 774 |
|
long s; |
| 775 |
|
while ((s = root.state) >= 0) { |
| 776 |
< |
if (UNSAFE.compareAndSwapLong(root, stateOffset, |
| 777 |
< |
s, s | TERMINATION_BIT)) { |
| 778 |
< |
releaseWaiters(0); // signal all threads |
| 776 |
> |
long next = (s & ~((long)UNARRIVED_MASK)) | TERMINATION_BIT; |
| 777 |
> |
if (UNSAFE.compareAndSwapLong(root, stateOffset, s, next)) { |
| 778 |
> |
// signal all threads |
| 779 |
> |
releaseWaiters(0); |
| 780 |
|
releaseWaiters(1); |
| 781 |
|
return; |
| 782 |
|
} |
| 812 |
|
* @return the number of arrived parties |
| 813 |
|
*/ |
| 814 |
|
public int getArrivedParties() { |
| 815 |
< |
long s = state; |
| 738 |
< |
int u = unarrivedOf(s); // only reconcile if possibly needed |
| 739 |
< |
return (u != 0 || parent == null) ? |
| 740 |
< |
partiesOf(s) - u : |
| 741 |
< |
arrivedOf(reconcileState()); |
| 815 |
> |
return arrivedOf(reconcileState()); |
| 816 |
|
} |
| 817 |
|
|
| 818 |
|
/** |
| 822 |
|
* @return the number of unarrived parties |
| 823 |
|
*/ |
| 824 |
|
public int getUnarrivedParties() { |
| 825 |
< |
int u = unarrivedOf(state); |
| 752 |
< |
return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState()); |
| 825 |
> |
return unarrivedOf(reconcileState()); |
| 826 |
|
} |
| 827 |
|
|
| 828 |
|
/** |
| 858 |
|
* advance, and to control termination. This method is invoked |
| 859 |
|
* upon arrival of the party advancing this phaser (when all other |
| 860 |
|
* waiting parties are dormant). If this method returns {@code |
| 861 |
< |
* true}, then, rather than advance the phase number, this phaser |
| 862 |
< |
* will be set to a final termination state, and subsequent calls |
| 863 |
< |
* to {@link #isTerminated} will return true. Any (unchecked) |
| 864 |
< |
* Exception or Error thrown by an invocation of this method is |
| 865 |
< |
* propagated to the party attempting to advance this phaser, in |
| 866 |
< |
* which case no advance occurs. |
| 861 |
> |
* true}, this phaser will be set to a final termination state |
| 862 |
> |
* upon advance, and subsequent calls to {@link #isTerminated} |
| 863 |
> |
* will return true. Any (unchecked) Exception or Error thrown by |
| 864 |
> |
* an invocation of this method is propagated to the party |
| 865 |
> |
* attempting to advance this phaser, in which case no advance |
| 866 |
> |
* occurs. |
| 867 |
|
* |
| 868 |
|
* <p>The arguments to this method provide the state of the phaser |
| 869 |
|
* prevailing for the current transition. The effects of invoking |
| 927 |
|
*/ |
| 928 |
|
private void releaseWaiters(int phase) { |
| 929 |
|
QNode q; // first element of queue |
| 857 |
– |
int p; // its phase |
| 930 |
|
Thread t; // its thread |
| 931 |
|
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
| 932 |
|
while ((q = head.get()) != null && |
| 933 |
< |
((p = q.phase) == phase || |
| 862 |
< |
(int)(root.state >>> PHASE_SHIFT) != p)) { |
| 933 |
> |
q.phase != (int)(root.state >>> PHASE_SHIFT)) { |
| 934 |
|
if (head.compareAndSet(q, q.next) && |
| 935 |
|
(t = q.thread) != null) { |
| 936 |
|
q.thread = null; |
| 939 |
|
} |
| 940 |
|
} |
| 941 |
|
|
| 942 |
+ |
/** |
| 943 |
+ |
* Variant of releaseWaiters that additionally tries to remove any |
| 944 |
+ |
* nodes no longer waiting for advance due to timeout or |
| 945 |
+ |
* interrupt. Currently, nodes are removed only if they are at |
| 946 |
+ |
* head of queue, which suffices to reduce memory footprint in |
| 947 |
+ |
* most usages. |
| 948 |
+ |
* |
| 949 |
+ |
* @return current phase on exit |
| 950 |
+ |
*/ |
| 951 |
+ |
private int abortWait(int phase) { |
| 952 |
+ |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
| 953 |
+ |
for (;;) { |
| 954 |
+ |
Thread t; |
| 955 |
+ |
QNode q = head.get(); |
| 956 |
+ |
int p = (int)(root.state >>> PHASE_SHIFT); |
| 957 |
+ |
if (q == null || ((t = q.thread) != null && q.phase == p)) |
| 958 |
+ |
return p; |
| 959 |
+ |
if (head.compareAndSet(q, q.next) && t != null) { |
| 960 |
+ |
q.thread = null; |
| 961 |
+ |
LockSupport.unpark(t); |
| 962 |
+ |
} |
| 963 |
+ |
} |
| 964 |
+ |
} |
| 965 |
+ |
|
| 966 |
|
/** The number of CPUs, for spin control */ |
| 967 |
|
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
| 968 |
|
|
| 1030 |
|
node.thread = null; // avoid need for unpark() |
| 1031 |
|
if (node.wasInterrupted && !node.interruptible) |
| 1032 |
|
Thread.currentThread().interrupt(); |
| 1033 |
< |
if ((p = (int)(state >>> PHASE_SHIFT)) == phase) |
| 1034 |
< |
return p; // recheck abort |
| 1033 |
> |
if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase) |
| 1034 |
> |
return abortWait(phase); // possibly clean up on abort |
| 1035 |
|
} |
| 1036 |
|
releaseWaiters(phase); |
| 1037 |
|
return p; |
