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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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|
| 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) |
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> |
* * unarrived -- the number of parties yet to hit barrier (bits 0-15) |
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> |
* * parties -- the number of parties to wait (bits 16-31) |
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> |
* * phase -- the generation of the barrier (bits 32-62) |
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> |
* * terminated -- set if barrier is terminated (bit 63 / sign) |
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* |
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* However, to efficiently maintain atomicity, these values are |
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* packed into a single (atomic) long. Termination uses the sign |
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* bit of 32 bit representation of phase, so phase is set to -1 on |
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* termination. Good performance relies on keeping state decoding |
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* and encoding simple, and keeping race windows short. |
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* |
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– |
* Note: there are some cheats in arrive() that rely on unarrived |
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* count being lowest 16 bits. |
| 240 |
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*/ |
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private volatile long state; |
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|
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< |
private static final int ushortMask = 0xffff; |
| 244 |
< |
private static final int phaseMask = 0x7fffffff; |
| 243 |
> |
private static final int MAX_COUNT = 0xffff; |
| 244 |
> |
private static final int MAX_PHASE = 0x7fffffff; |
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> |
private static final int PARTIES_SHIFT = 16; |
| 246 |
> |
private static final int PHASE_SHIFT = 32; |
| 247 |
> |
private static final long UNARRIVED_MASK = 0xffffL; |
| 248 |
> |
private static final long PARTIES_MASK = 0xffff0000L; |
| 249 |
> |
private static final long ONE_ARRIVAL = 1L; |
| 250 |
> |
private static final long ONE_PARTY = 1L << PARTIES_SHIFT; |
| 251 |
> |
private static final long TERMINATION_PHASE = -1L << PHASE_SHIFT; |
| 252 |
> |
|
| 253 |
> |
// The following unpacking methods are usually manually inlined |
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|
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private static int unarrivedOf(long s) { |
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< |
return (int) (s & ushortMask); |
| 256 |
> |
return (int) (s & UNARRIVED_MASK); |
| 257 |
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} |
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|
| 259 |
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private static int partiesOf(long s) { |
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< |
return ((int) s) >>> 16; |
| 260 |
> |
return ((int) (s & PARTIES_MASK)) >>> PARTIES_SHIFT; |
| 261 |
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} |
| 262 |
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|
| 263 |
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private static int phaseOf(long s) { |
| 264 |
< |
return (int) (s >>> 32); |
| 264 |
> |
return (int) (s >>> PHASE_SHIFT); |
| 265 |
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} |
| 266 |
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|
| 267 |
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private static int arrivedOf(long s) { |
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return partiesOf(s) - unarrivedOf(s); |
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} |
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|
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– |
private static long stateFor(int phase, int parties, int unarrived) { |
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– |
return ((((long) phase) << 32) | (((long) parties) << 16) | |
| 266 |
– |
(long) unarrived); |
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– |
} |
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|
| 269 |
– |
private static long trippedStateFor(int phase, int parties) { |
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– |
long lp = (long) parties; |
| 271 |
– |
return (((long) phase) << 32) | (lp << 16) | lp; |
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– |
} |
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|
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– |
/** |
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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 |
– |
|
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/** |
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* The parent of this phaser, or null if none |
| 273 |
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*/ |
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*/ |
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private final Phaser root; |
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|
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// Wait queues |
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|
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/** |
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* Heads of Treiber stacks for waiting threads. To eliminate |
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* contention when releasing some threads while adding others, we |
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} |
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|
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/** |
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< |
* Returns current state, first resolving lagged propagation from |
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< |
* root if necessary. |
| 296 |
> |
* Main implementation for methods arrive and arriveAndDeregister. |
| 297 |
> |
* Manually tuned to speed up and minimize race windows for the |
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> |
* common case of just decrementing unarrived field. |
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> |
* |
| 300 |
> |
* @param adj - adjustment to apply to state -- either |
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> |
* ONE_ARRIVAL (for arrive) or |
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> |
* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister) |
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> |
*/ |
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> |
private int doArrive(long adj) { |
| 305 |
> |
long s; |
| 306 |
> |
int phase, unarrived; |
| 307 |
> |
while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0) { |
| 308 |
> |
if ((unarrived = (int)(s & UNARRIVED_MASK)) != 0) { |
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> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s -= adj)) { |
| 310 |
> |
if (unarrived == 1) { |
| 311 |
> |
Phaser par; |
| 312 |
> |
long p = s & PARTIES_MASK; // unshifted parties field |
| 313 |
> |
long lu = p >>> PARTIES_SHIFT; |
| 314 |
> |
int u = (int)lu; |
| 315 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
| 316 |
> |
long next = ((long)nextPhase << PHASE_SHIFT) | p | lu; |
| 317 |
> |
if ((par = parent) == null) { |
| 318 |
> |
UNSAFE.compareAndSwapLong |
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> |
(this, stateOffset, s, onAdvance(phase, u)? |
| 320 |
> |
next | TERMINATION_PHASE : next); |
| 321 |
> |
releaseWaiters(phase); |
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> |
} |
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> |
else { |
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> |
par.doArrive(u == 0? |
| 325 |
> |
ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
| 326 |
> |
if ((int)(par.state >>> PHASE_SHIFT) != nextPhase || |
| 327 |
> |
((int)(state >>> PHASE_SHIFT) != nextPhase && |
| 328 |
> |
!UNSAFE.compareAndSwapLong(this, stateOffset, |
| 329 |
> |
s, next))) |
| 330 |
> |
reconcileState(); |
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> |
} |
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> |
} |
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> |
break; |
| 334 |
> |
} |
| 335 |
> |
} |
| 336 |
> |
else if (state == s && reconcileState() == s) // recheck |
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> |
throw new IllegalStateException(badArrive()); |
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> |
} |
| 339 |
> |
return phase; |
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> |
} |
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> |
|
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> |
/** |
| 343 |
> |
* Returns message string for bounds exceptions on arrival. |
| 344 |
> |
* Declared out of-line from doArrive to reduce string op bulk. |
| 345 |
> |
*/ |
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> |
private String badArrive() { |
| 347 |
> |
return ("Attempted arrival of unregistered party for " + |
| 348 |
> |
this.toString()); |
| 349 |
> |
} |
| 350 |
> |
|
| 351 |
> |
/** |
| 352 |
> |
* Implementation of register, bulkRegister |
| 353 |
> |
* |
| 354 |
> |
* @param registrations number to add to both parties and unarrived fields |
| 355 |
|
*/ |
| 356 |
< |
private long getReconciledState() { |
| 357 |
< |
return (parent == null) ? state : reconcileState(); |
| 356 |
> |
private int doRegister(int registrations) { |
| 357 |
> |
long adj = (long)registrations; // adjustment to state |
| 358 |
> |
adj |= adj << PARTIES_SHIFT; |
| 359 |
> |
Phaser par = parent; |
| 360 |
> |
long s; |
| 361 |
> |
int phase; |
| 362 |
> |
while ((phase = (int)((s = (par == null? state : reconcileState())) |
| 363 |
> |
>>> PHASE_SHIFT)) >= 0) { |
| 364 |
> |
int parties = ((int)(s & PARTIES_MASK)) >>> PARTIES_SHIFT; |
| 365 |
> |
if (parties != 0 && (s & UNARRIVED_MASK) == 0) |
| 366 |
> |
internalAwaitAdvance(phase, null); // wait for onAdvance |
| 367 |
> |
else if (parties + registrations > MAX_COUNT) |
| 368 |
> |
throw new IllegalStateException(badRegister()); |
| 369 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj)) |
| 370 |
> |
break; |
| 371 |
> |
} |
| 372 |
> |
return phase; |
| 373 |
> |
} |
| 374 |
> |
|
| 375 |
> |
/** |
| 376 |
> |
* Returns message string for bounds exceptions on registration |
| 377 |
> |
*/ |
| 378 |
> |
private String badRegister() { |
| 379 |
> |
return ("Attempt to register more than " + MAX_COUNT + " parties for "+ |
| 380 |
> |
this.toString()); |
| 381 |
|
} |
| 382 |
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|
| 383 |
|
/** |
| 384 |
< |
* Recursively resolves state. |
| 384 |
> |
* Recursively resolves lagged phase propagation from root if |
| 385 |
> |
* necessary. |
| 386 |
|
*/ |
| 387 |
|
private long reconcileState() { |
| 388 |
|
Phaser par = parent; |
| 389 |
< |
long s = state; |
| 390 |
< |
if (par != null) { |
| 391 |
< |
int phase, rootPhase; |
| 392 |
< |
while ((phase = phaseOf(s)) >= 0 && |
| 393 |
< |
(rootPhase = phaseOf(root.state)) != phase && |
| 394 |
< |
(rootPhase < 0 || unarrivedOf(s) == 0)) { |
| 395 |
< |
int parentPhase = phaseOf(par.getReconciledState()); |
| 396 |
< |
if (parentPhase != phase) { |
| 397 |
< |
long next = trippedStateFor(parentPhase, partiesOf(s)); |
| 398 |
< |
if (state == s) |
| 399 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
| 389 |
> |
if (par == null) |
| 390 |
> |
return state; |
| 391 |
> |
Phaser rt = root; |
| 392 |
> |
long s; |
| 393 |
> |
int phase, rPhase; |
| 394 |
> |
while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0 && |
| 395 |
> |
(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) { |
| 396 |
> |
if (rPhase < 0 || (s & UNARRIVED_MASK) == 0) { |
| 397 |
> |
long ps = par.parent == null? par.state : par.reconcileState(); |
| 398 |
> |
int pPhase = (int)(ps >>> PHASE_SHIFT); |
| 399 |
> |
if (pPhase < 0 || pPhase == ((phase + 1) & MAX_PHASE)) { |
| 400 |
> |
if (state != s) |
| 401 |
> |
continue; |
| 402 |
> |
long p = s & PARTIES_MASK; |
| 403 |
> |
long next = ((((long) pPhase) << PHASE_SHIFT) | |
| 404 |
> |
(p >>> PARTIES_SHIFT) | p); |
| 405 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
| 406 |
> |
return next; |
| 407 |
|
} |
| 333 |
– |
s = state; |
| 408 |
|
} |
| 409 |
+ |
if (state == s) |
| 410 |
+ |
releaseWaiters(phase); // help release others |
| 411 |
|
} |
| 412 |
|
return s; |
| 413 |
|
} |
| 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 < 0 || parties > MAX_COUNT) |
| 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_COUNT) |
| 509 |
+ |
throw new IllegalStateException(badRegister()); |
| 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 |
|
/** |
| 575 |
|
public int awaitAdvance(int phase) { |
| 576 |
|
if (phase < 0) |
| 577 |
|
return phase; |
| 578 |
< |
int p = getPhase(); |
| 578 |
> |
int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
| 579 |
|
if (p != phase) |
| 580 |
|
return p; |
| 581 |
< |
return untimedWait(phase); |
| 581 |
> |
return internalAwaitAdvance(phase, null); |
| 582 |
|
} |
| 583 |
|
|
| 584 |
|
/** |
| 599 |
|
throws InterruptedException { |
| 600 |
|
if (phase < 0) |
| 601 |
|
return phase; |
| 602 |
< |
int p = getPhase(); |
| 602 |
> |
int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
| 603 |
|
if (p != phase) |
| 604 |
|
return p; |
| 605 |
< |
return interruptibleWait(phase); |
| 605 |
> |
QNode node = new QNode(this, phase, true, false, 0L); |
| 606 |
> |
p = internalAwaitAdvance(phase, node); |
| 607 |
> |
if (node.wasInterrupted) |
| 608 |
> |
throw new InterruptedException(); |
| 609 |
> |
else |
| 610 |
> |
return p; |
| 611 |
|
} |
| 612 |
|
|
| 613 |
|
/** |
| 636 |
|
long nanos = unit.toNanos(timeout); |
| 637 |
|
if (phase < 0) |
| 638 |
|
return phase; |
| 639 |
< |
int p = getPhase(); |
| 639 |
> |
int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
| 640 |
|
if (p != phase) |
| 641 |
|
return p; |
| 642 |
< |
return timedWait(phase, nanos); |
| 642 |
> |
QNode node = new QNode(this, phase, true, true, nanos); |
| 643 |
> |
p = internalAwaitAdvance(phase, node); |
| 644 |
> |
if (node.wasInterrupted) |
| 645 |
> |
throw new InterruptedException(); |
| 646 |
> |
else if (p == phase) |
| 647 |
> |
throw new TimeoutException(); |
| 648 |
> |
else |
| 649 |
> |
return p; |
| 650 |
|
} |
| 651 |
|
|
| 652 |
|
/** |
| 659 |
|
public void forceTermination() { |
| 660 |
|
Phaser r = root; // force at root then reconcile |
| 661 |
|
long s; |
| 662 |
< |
while (phaseOf(s = r.state) >= 0) |
| 663 |
< |
UNSAFE.compareAndSwapLong(r, stateOffset, s, |
| 661 |
< |
stateFor(-1, partiesOf(s), |
| 662 |
< |
unarrivedOf(s))); |
| 662 |
> |
while ((s = r.state) >= 0) |
| 663 |
> |
UNSAFE.compareAndSwapLong(r, stateOffset, s, s | TERMINATION_PHASE); |
| 664 |
|
reconcileState(); |
| 665 |
< |
releaseWaiters(0); // ensure wakeups on both queues |
| 665 |
> |
releaseWaiters(0); // signal all threads |
| 666 |
|
releaseWaiters(1); |
| 667 |
|
} |
| 668 |
|
|
| 674 |
|
* @return the phase number, or a negative value if terminated |
| 675 |
|
*/ |
| 676 |
|
public final int getPhase() { |
| 677 |
< |
return phaseOf(getReconciledState()); |
| 677 |
> |
return (int)((parent == null? state : reconcileState()) >>> PHASE_SHIFT); |
| 678 |
|
} |
| 679 |
|
|
| 680 |
|
/** |
| 683 |
|
* @return the number of parties |
| 684 |
|
*/ |
| 685 |
|
public int getRegisteredParties() { |
| 686 |
< |
return partiesOf(getReconciledState()); |
| 686 |
> |
return partiesOf(parent == null? state : reconcileState()); |
| 687 |
|
} |
| 688 |
|
|
| 689 |
|
/** |
| 693 |
|
* @return the number of arrived parties |
| 694 |
|
*/ |
| 695 |
|
public int getArrivedParties() { |
| 696 |
< |
return arrivedOf(getReconciledState()); |
| 696 |
> |
return arrivedOf(parent == null? state : reconcileState()); |
| 697 |
|
} |
| 698 |
|
|
| 699 |
|
/** |
| 703 |
|
* @return the number of unarrived parties |
| 704 |
|
*/ |
| 705 |
|
public int getUnarrivedParties() { |
| 706 |
< |
return unarrivedOf(getReconciledState()); |
| 706 |
> |
return unarrivedOf(parent == null? state : reconcileState()); |
| 707 |
|
} |
| 708 |
|
|
| 709 |
|
/** |
| 731 |
|
* @return {@code true} if this barrier has been terminated |
| 732 |
|
*/ |
| 733 |
|
public boolean isTerminated() { |
| 734 |
< |
return getPhase() < 0; |
| 734 |
> |
return (parent == null? state : reconcileState()) < 0; |
| 735 |
|
} |
| 736 |
|
|
| 737 |
|
/** |
| 747 |
|
* which case no advance occurs. |
| 748 |
|
* |
| 749 |
|
* <p>The arguments to this method provide the state of the phaser |
| 750 |
< |
* prevailing for the current transition. The results and effects |
| 751 |
< |
* of invoking phase-related methods (including {@code getPhase} |
| 751 |
< |
* as well as arrival, registration, and waiting methods) from |
| 750 |
> |
* prevailing for the current transition. The effects of invoking |
| 751 |
> |
* arrival, registration, and waiting methods on this Phaser from |
| 752 |
|
* within {@code onAdvance} are unspecified and should not be |
| 753 |
< |
* relied on. Similarly, while it is possible to override this |
| 754 |
< |
* method to produce side-effects visible to participating tasks, |
| 755 |
< |
* it is in general safe to do so only in designs in which all |
| 756 |
< |
* parties register before any arrive, and all {@link |
| 757 |
< |
* #awaitAdvance} at each phase. |
| 753 |
> |
* relied on. |
| 754 |
> |
* |
| 755 |
> |
* <p>If this Phaser is a member of a tiered set of Phasers, then |
| 756 |
> |
* {@code onAdvance} is invoked only for its root Phaser on each |
| 757 |
> |
* advance. |
| 758 |
|
* |
| 759 |
|
* <p>The default version returns {@code true} when the number of |
| 760 |
|
* registered parties is zero. Normally, overrides that arrange |
| 779 |
|
* @return a string identifying this barrier, as well as its state |
| 780 |
|
*/ |
| 781 |
|
public String toString() { |
| 782 |
< |
long s = getReconciledState(); |
| 782 |
> |
long s = reconcileState(); |
| 783 |
|
return super.toString() + |
| 784 |
|
"[phase = " + phaseOf(s) + |
| 785 |
|
" parties = " + partiesOf(s) + |
| 786 |
|
" arrived = " + arrivedOf(s) + "]"; |
| 787 |
|
} |
| 788 |
|
|
| 789 |
– |
// methods for waiting |
| 790 |
– |
|
| 789 |
|
/** |
| 790 |
< |
* Wait nodes for Treiber stack representing wait queue |
| 793 |
< |
*/ |
| 794 |
< |
static final class QNode implements ForkJoinPool.ManagedBlocker { |
| 795 |
< |
final Phaser phaser; |
| 796 |
< |
final int phase; |
| 797 |
< |
final long startTime; |
| 798 |
< |
final long nanos; |
| 799 |
< |
final boolean timed; |
| 800 |
< |
final boolean interruptible; |
| 801 |
< |
volatile boolean wasInterrupted = false; |
| 802 |
< |
volatile Thread thread; // nulled to cancel wait |
| 803 |
< |
QNode next; |
| 804 |
< |
|
| 805 |
< |
QNode(Phaser phaser, int phase, boolean interruptible, |
| 806 |
< |
boolean timed, long startTime, long nanos) { |
| 807 |
< |
this.phaser = phaser; |
| 808 |
< |
this.phase = phase; |
| 809 |
< |
this.timed = timed; |
| 810 |
< |
this.interruptible = interruptible; |
| 811 |
< |
this.startTime = startTime; |
| 812 |
< |
this.nanos = nanos; |
| 813 |
< |
thread = Thread.currentThread(); |
| 814 |
< |
} |
| 815 |
< |
|
| 816 |
< |
public boolean isReleasable() { |
| 817 |
< |
return (thread == null || |
| 818 |
< |
phaser.getPhase() != phase || |
| 819 |
< |
(interruptible && wasInterrupted) || |
| 820 |
< |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
| 821 |
< |
} |
| 822 |
< |
|
| 823 |
< |
public boolean block() { |
| 824 |
< |
if (Thread.interrupted()) { |
| 825 |
< |
wasInterrupted = true; |
| 826 |
< |
if (interruptible) |
| 827 |
< |
return true; |
| 828 |
< |
} |
| 829 |
< |
if (!timed) |
| 830 |
< |
LockSupport.park(this); |
| 831 |
< |
else { |
| 832 |
< |
long waitTime = nanos - (System.nanoTime() - startTime); |
| 833 |
< |
if (waitTime <= 0) |
| 834 |
< |
return true; |
| 835 |
< |
LockSupport.parkNanos(this, waitTime); |
| 836 |
< |
} |
| 837 |
< |
return isReleasable(); |
| 838 |
< |
} |
| 839 |
< |
|
| 840 |
< |
void signal() { |
| 841 |
< |
Thread t = thread; |
| 842 |
< |
if (t != null) { |
| 843 |
< |
thread = null; |
| 844 |
< |
LockSupport.unpark(t); |
| 845 |
< |
} |
| 846 |
< |
} |
| 847 |
< |
|
| 848 |
< |
boolean doWait() { |
| 849 |
< |
if (thread != null) { |
| 850 |
< |
try { |
| 851 |
< |
ForkJoinPool.managedBlock(this); |
| 852 |
< |
} 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. |
| 790 |
> |
* Removes and signals threads from queue for phase |
| 791 |
|
*/ |
| 792 |
|
private void releaseWaiters(int phase) { |
| 793 |
|
AtomicReference<QNode> head = queueFor(phase); |
| 794 |
|
QNode q; |
| 795 |
< |
while ((q = head.get()) != null) { |
| 795 |
> |
int p; |
| 796 |
> |
while ((q = head.get()) != null && |
| 797 |
> |
((p = q.phase) == phase || |
| 798 |
> |
(int)(root.state >>> PHASE_SHIFT) != p)) { |
| 799 |
|
if (head.compareAndSet(q, q.next)) |
| 800 |
|
q.signal(); |
| 801 |
|
} |
| 806 |
|
* |
| 807 |
|
* @return true if successful |
| 808 |
|
*/ |
| 809 |
< |
private boolean tryEnqueue(QNode node) { |
| 810 |
< |
AtomicReference<QNode> head = queueFor(node.phase); |
| 811 |
< |
return head.compareAndSet(node.next = head.get(), node); |
| 809 |
> |
private boolean tryEnqueue(int phase, QNode node) { |
| 810 |
> |
releaseWaiters(phase-1); // ensure old queue clean |
| 811 |
> |
AtomicReference<QNode> head = queueFor(phase); |
| 812 |
> |
QNode q = head.get(); |
| 813 |
> |
return ((q == null || q.phase == phase) && |
| 814 |
> |
(int)(root.state >>> PHASE_SHIFT) == phase && |
| 815 |
> |
head.compareAndSet(node.next = q, node)); |
| 816 |
|
} |
| 817 |
|
|
| 818 |
+ |
/** The number of CPUs, for spin control */ |
| 819 |
+ |
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
| 820 |
+ |
|
| 821 |
|
/** |
| 822 |
< |
* The number of times to spin before blocking waiting for advance. |
| 822 |
> |
* The number of times to spin before blocking while waiting for |
| 823 |
> |
* advance, per arrival while waiting. On multiprocessors, fully |
| 824 |
> |
* blocking and waking up a large number of threads all at once is |
| 825 |
> |
* usually a very slow process, so we use rechargeable spins to |
| 826 |
> |
* avoid it when threads regularly arrive: When a thread in |
| 827 |
> |
* internalAwaitAdvance notices another arrival before blocking, |
| 828 |
> |
* and there appear to be enough CPUs available, it spins |
| 829 |
> |
* SPINS_PER_ARRIVAL more times before continuing to try to |
| 830 |
> |
* block. The value trades off good-citizenship vs big unnecessary |
| 831 |
> |
* slowdowns. |
| 832 |
|
*/ |
| 833 |
< |
static final int MAX_SPINS = |
| 886 |
< |
Runtime.getRuntime().availableProcessors() == 1 ? 0 : 1 << 8; |
| 833 |
> |
static final int SPINS_PER_ARRIVAL = NCPU < 2? 1 : 1 << 8; |
| 834 |
|
|
| 835 |
|
/** |
| 836 |
< |
* Enqueues node and waits unless aborted or signalled. |
| 836 |
> |
* Possibly blocks and waits for phase to advance unless aborted. |
| 837 |
|
* |
| 838 |
+ |
* @param phase current phase |
| 839 |
+ |
* @param node if nonnull, the wait node to track interrupt and timeout; |
| 840 |
+ |
* if null, denotes noninterruptible wait |
| 841 |
|
* @return current phase |
| 842 |
|
*/ |
| 843 |
< |
private int untimedWait(int phase) { |
| 844 |
< |
QNode node = null; |
| 843 |
> |
private int internalAwaitAdvance(int phase, QNode node) { |
| 844 |
> |
Phaser current = this; // to eventually wait at root if tiered |
| 845 |
> |
Phaser par = parent; |
| 846 |
|
boolean queued = false; |
| 847 |
< |
boolean interrupted = false; |
| 848 |
< |
int spins = MAX_SPINS; |
| 847 |
> |
int spins = SPINS_PER_ARRIVAL; |
| 848 |
> |
int lastUnarrived = -1; // to increase spins upon change |
| 849 |
> |
long s; |
| 850 |
|
int p; |
| 851 |
< |
while ((p = getPhase()) == phase) { |
| 852 |
< |
if (Thread.interrupted()) |
| 853 |
< |
interrupted = true; |
| 854 |
< |
else if (spins > 0) { |
| 855 |
< |
if (--spins == 0) |
| 856 |
< |
Thread.yield(); |
| 851 |
> |
while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) { |
| 852 |
> |
int unarrived = (int)(s & UNARRIVED_MASK); |
| 853 |
> |
if (unarrived != lastUnarrived) { |
| 854 |
> |
if ((lastUnarrived = unarrived) < NCPU) |
| 855 |
> |
spins += SPINS_PER_ARRIVAL; |
| 856 |
> |
} |
| 857 |
> |
else if (unarrived == 0 && par != null) { |
| 858 |
> |
current = par; // if all arrived, use parent |
| 859 |
> |
par = par.parent; |
| 860 |
|
} |
| 861 |
+ |
else if (spins > 0) |
| 862 |
+ |
--spins; |
| 863 |
|
else if (node == null) |
| 864 |
< |
node = new QNode(this, phase, false, false, 0, 0); |
| 864 |
> |
node = new QNode(this, phase, false, false, 0L); |
| 865 |
> |
else if (node.isReleasable()) |
| 866 |
> |
break; |
| 867 |
|
else if (!queued) |
| 868 |
< |
queued = tryEnqueue(node); |
| 869 |
< |
else if (node.doWait()) |
| 870 |
< |
interrupted = true; |
| 871 |
< |
} |
| 872 |
< |
if (node != null) |
| 873 |
< |
node.thread = null; |
| 874 |
< |
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(); |
| 868 |
> |
queued = tryEnqueue(phase, node); |
| 869 |
> |
else { |
| 870 |
> |
try { |
| 871 |
> |
ForkJoinPool.managedBlock(node); |
| 872 |
> |
} catch (InterruptedException ie) { |
| 873 |
> |
node.wasInterrupted = true; |
| 874 |
> |
} |
| 875 |
|
} |
| 876 |
< |
else if (node == null) |
| 877 |
< |
node = new QNode(this, phase, true, false, 0, 0); |
| 878 |
< |
else if (!queued) |
| 879 |
< |
queued = tryEnqueue(node); |
| 880 |
< |
else if (node.doWait()) |
| 881 |
< |
interrupted = true; |
| 882 |
< |
} |
| 883 |
< |
if (node != null) |
| 884 |
< |
node.thread = null; |
| 885 |
< |
if (p != phase || (p = getPhase()) != phase) |
| 876 |
> |
} |
| 877 |
> |
if (node != null) { |
| 878 |
> |
if (node.thread != null) |
| 879 |
> |
node.thread = null; |
| 880 |
> |
if (!node.interruptible && node.wasInterrupted) |
| 881 |
> |
Thread.currentThread().interrupt(); |
| 882 |
> |
} |
| 883 |
> |
if (p == phase && parent != null) |
| 884 |
> |
p = (int)(reconcileState() >>> PHASE_SHIFT); |
| 885 |
> |
if (p != phase) |
| 886 |
|
releaseWaiters(phase); |
| 949 |
– |
if (interrupted) |
| 950 |
– |
throw new InterruptedException(); |
| 887 |
|
return p; |
| 888 |
|
} |
| 889 |
|
|
| 890 |
|
/** |
| 891 |
< |
* Timeout version. |
| 956 |
< |
* @return current phase |
| 891 |
> |
* Wait nodes for Treiber stack representing wait queue |
| 892 |
|
*/ |
| 893 |
< |
private int timedWait(int phase, long nanos) |
| 894 |
< |
throws InterruptedException, TimeoutException { |
| 895 |
< |
long startTime = System.nanoTime(); |
| 896 |
< |
QNode node = null; |
| 897 |
< |
boolean queued = false; |
| 898 |
< |
boolean interrupted = false; |
| 899 |
< |
int spins = MAX_SPINS; |
| 900 |
< |
int p; |
| 901 |
< |
while ((p = getPhase()) == phase && !interrupted) { |
| 902 |
< |
if (Thread.interrupted()) |
| 903 |
< |
interrupted = true; |
| 904 |
< |
else if (nanos - (System.nanoTime() - startTime) <= 0) |
| 905 |
< |
break; |
| 906 |
< |
else if (spins > 0) { |
| 907 |
< |
if (--spins == 0) |
| 908 |
< |
Thread.yield(); |
| 893 |
> |
static final class QNode implements ForkJoinPool.ManagedBlocker { |
| 894 |
> |
final Phaser phaser; |
| 895 |
> |
final int phase; |
| 896 |
> |
final boolean interruptible; |
| 897 |
> |
final boolean timed; |
| 898 |
> |
boolean wasInterrupted; |
| 899 |
> |
long nanos; |
| 900 |
> |
long lastTime; |
| 901 |
> |
volatile Thread thread; // nulled to cancel wait |
| 902 |
> |
QNode next; |
| 903 |
> |
|
| 904 |
> |
QNode(Phaser phaser, int phase, boolean interruptible, |
| 905 |
> |
boolean timed, long nanos) { |
| 906 |
> |
this.phaser = phaser; |
| 907 |
> |
this.phase = phase; |
| 908 |
> |
this.interruptible = interruptible; |
| 909 |
> |
this.nanos = nanos; |
| 910 |
> |
this.timed = timed; |
| 911 |
> |
this.lastTime = timed? System.nanoTime() : 0L; |
| 912 |
> |
thread = Thread.currentThread(); |
| 913 |
> |
} |
| 914 |
> |
|
| 915 |
> |
public boolean isReleasable() { |
| 916 |
> |
Thread t = thread; |
| 917 |
> |
if (t != null) { |
| 918 |
> |
if (phaser.getPhase() != phase) |
| 919 |
> |
t = null; |
| 920 |
> |
else { |
| 921 |
> |
if (Thread.interrupted()) |
| 922 |
> |
wasInterrupted = true; |
| 923 |
> |
if (interruptible && wasInterrupted) |
| 924 |
> |
t = null; |
| 925 |
> |
else if (timed) { |
| 926 |
> |
if (nanos > 0) { |
| 927 |
> |
long now = System.nanoTime(); |
| 928 |
> |
nanos -= now - lastTime; |
| 929 |
> |
lastTime = now; |
| 930 |
> |
} |
| 931 |
> |
if (nanos <= 0) |
| 932 |
> |
t = null; |
| 933 |
> |
} |
| 934 |
> |
} |
| 935 |
> |
if (t != null) |
| 936 |
> |
return false; |
| 937 |
> |
thread = null; |
| 938 |
|
} |
| 939 |
< |
else if (node == null) |
| 940 |
< |
node = new QNode(this, phase, true, true, startTime, nanos); |
| 941 |
< |
else if (!queued) |
| 942 |
< |
queued = tryEnqueue(node); |
| 943 |
< |
else if (node.doWait()) |
| 944 |
< |
interrupted = true; |
| 945 |
< |
} |
| 946 |
< |
if (node != null) |
| 947 |
< |
node.thread = null; |
| 948 |
< |
if (p != phase || (p = getPhase()) != phase) |
| 949 |
< |
releaseWaiters(phase); |
| 950 |
< |
if (interrupted) |
| 951 |
< |
throw new InterruptedException(); |
| 952 |
< |
if (p == phase) |
| 953 |
< |
throw new TimeoutException(); |
| 954 |
< |
return p; |
| 939 |
> |
return true; |
| 940 |
> |
} |
| 941 |
> |
|
| 942 |
> |
public boolean block() { |
| 943 |
> |
if (isReleasable()) |
| 944 |
> |
return true; |
| 945 |
> |
else if (!timed) |
| 946 |
> |
LockSupport.park(this); |
| 947 |
> |
else if (nanos > 0) |
| 948 |
> |
LockSupport.parkNanos(this, nanos); |
| 949 |
> |
return isReleasable(); |
| 950 |
> |
} |
| 951 |
> |
|
| 952 |
> |
void signal() { |
| 953 |
> |
Thread t = thread; |
| 954 |
> |
if (t != null) { |
| 955 |
> |
thread = null; |
| 956 |
> |
LockSupport.unpark(t); |
| 957 |
> |
} |
| 958 |
> |
} |
| 959 |
|
} |
| 960 |
|
|
| 961 |
|
// Unsafe mechanics |
