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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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* #forceTermination} is also available to abruptly release waiting |
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* threads and allow them to terminate. |
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* |
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* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged |
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* in tree structures) to reduce contention. Phasers with large |
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* numbers of parties that would otherwise experience heavy |
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* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., |
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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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* |
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* * parties -- the number of parties to wait (16 bits) |
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* * unarrived -- the number of parties yet to hit barrier (16 bits) |
232 |
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* * phase -- the generation of the barrier (31 bits) |
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* * 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. |
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*/ |
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private volatile long state; |
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|
243 |
< |
private static final int ushortMask = 0xffff; |
244 |
< |
private static final int phaseMask = 0x7fffffff; |
243 |
> |
private static final int MAX_PARTIES = 0xffff; |
244 |
> |
private static final int MAX_PHASE = 0x7fffffff; |
245 |
> |
private static final int PARTIES_SHIFT = 16; |
246 |
> |
private static final int PHASE_SHIFT = 32; |
247 |
> |
private static final int UNARRIVED_MASK = 0xffff; |
248 |
> |
private static final long PARTIES_MASK = 0xffff0000L; // for masking long |
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 |
> |
|
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// The following unpacking methods are usually manually inlined |
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|
255 |
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private static int unarrivedOf(long s) { |
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return (int) (s & ushortMask); |
256 |
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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; |
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return (int)s >>> PARTIES_SHIFT; |
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} |
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|
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private static int phaseOf(long s) { |
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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); |
269 |
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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) | |
267 |
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(long) unarrived); |
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} |
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|
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private static long trippedStateFor(int phase, int parties) { |
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long lp = (long) parties; |
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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. |
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*/ |
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private static String badBounds(int parties, int unarrived) { |
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return ("Attempt to set " + unarrived + |
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" unarrived of " + parties + " parties"); |
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} |
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|
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/** |
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* The parent of this phaser, or null if none |
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*/ |
279 |
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*/ |
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private final Phaser root; |
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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 |
284 |
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* contention while releasing some threads while adding others, we |
284 |
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* contention when releasing some threads while adding others, we |
285 |
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* use two of them, alternating across even and odd phases. |
286 |
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* Subphasers share queues with root to speed up releases. |
287 |
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*/ |
288 |
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private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>(); |
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private final AtomicReference<QNode> oddQ = new AtomicReference<QNode>(); |
288 |
> |
private final AtomicReference<QNode> evenQ; |
289 |
> |
private final AtomicReference<QNode> oddQ; |
290 |
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|
291 |
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private AtomicReference<QNode> queueFor(int phase) { |
292 |
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return ((phase & 1) == 0) ? evenQ : oddQ; |
293 |
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} |
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295 |
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/** |
296 |
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* Returns current state, first resolving lagged propagation from |
297 |
< |
* root if necessary. |
296 |
> |
* Main implementation for methods arrive and arriveAndDeregister. |
297 |
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* Manually tuned to speed up and minimize race windows for the |
298 |
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* common case of just decrementing unarrived field. |
299 |
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* |
300 |
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* @param adj - adjustment to apply to state -- either |
301 |
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* ONE_ARRIVAL (for arrive) or |
302 |
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* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister) |
303 |
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*/ |
304 |
< |
private long getReconciledState() { |
305 |
< |
return (parent == null) ? state : reconcileState(); |
304 |
> |
private int doArrive(long adj) { |
305 |
> |
for (;;) { |
306 |
> |
long s = state; |
307 |
> |
int phase = (int)(s >>> PHASE_SHIFT); |
308 |
> |
if (phase < 0) |
309 |
> |
return phase; |
310 |
> |
int unarrived = (int)s & UNARRIVED_MASK; |
311 |
> |
if (unarrived == 0) |
312 |
> |
checkBadArrive(s); |
313 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
314 |
> |
if (unarrived == 1) { |
315 |
> |
long p = s & PARTIES_MASK; // unshifted parties field |
316 |
> |
long lu = p >>> PARTIES_SHIFT; |
317 |
> |
int u = (int)lu; |
318 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
319 |
> |
long next = ((long)nextPhase << PHASE_SHIFT) | p | lu; |
320 |
> |
final Phaser parent = this.parent; |
321 |
> |
if (parent == null) { |
322 |
> |
if (onAdvance(phase, u)) |
323 |
> |
next |= TERMINATION_PHASE; // obliterate phase |
324 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
325 |
> |
releaseWaiters(phase); |
326 |
> |
} |
327 |
> |
else { |
328 |
> |
parent.doArrive((u == 0) ? |
329 |
> |
ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
330 |
> |
if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase || |
331 |
> |
((int)(state >>> PHASE_SHIFT) != nextPhase && |
332 |
> |
!UNSAFE.compareAndSwapLong(this, stateOffset, |
333 |
> |
s, next))) |
334 |
> |
reconcileState(); |
335 |
> |
} |
336 |
> |
} |
337 |
> |
return phase; |
338 |
> |
} |
339 |
> |
} |
340 |
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} |
341 |
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|
342 |
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/** |
343 |
< |
* Recursively resolves state. |
343 |
> |
* Rechecks state and throws bounds exceptions on arrival -- called |
344 |
> |
* only if unarrived is apparently zero. |
345 |
> |
*/ |
346 |
> |
private void checkBadArrive(long s) { |
347 |
> |
if (reconcileState() == s) |
348 |
> |
throw new IllegalStateException |
349 |
> |
("Attempted arrival of unregistered party for " + |
350 |
> |
stateToString(s)); |
351 |
> |
} |
352 |
> |
|
353 |
> |
/** |
354 |
> |
* Implementation of register, bulkRegister |
355 |
> |
* |
356 |
> |
* @param registrations number to add to both parties and |
357 |
> |
* unarrived fields. Must be greater than zero. |
358 |
> |
*/ |
359 |
> |
private int doRegister(int registrations) { |
360 |
> |
// adjustment to state |
361 |
> |
long adj = ((long)registrations << PARTIES_SHIFT) | registrations; |
362 |
> |
final Phaser parent = this.parent; |
363 |
> |
for (;;) { |
364 |
> |
long s = (parent == null) ? state : reconcileState(); |
365 |
> |
int parties = (int)s >>> PARTIES_SHIFT; |
366 |
> |
int phase = (int)(s >>> PHASE_SHIFT); |
367 |
> |
if (phase < 0) |
368 |
> |
return phase; |
369 |
> |
else if (parties != 0 && ((int)s & UNARRIVED_MASK) == 0) |
370 |
> |
internalAwaitAdvance(phase, null); // wait for onAdvance |
371 |
> |
else if (registrations > MAX_PARTIES - parties) |
372 |
> |
throw new IllegalStateException(badRegister(s)); |
373 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj)) |
374 |
> |
return phase; |
375 |
> |
} |
376 |
> |
} |
377 |
> |
|
378 |
> |
/** |
379 |
> |
* Returns message string for out of bounds exceptions on registration. |
380 |
> |
*/ |
381 |
> |
private String badRegister(long s) { |
382 |
> |
return "Attempt to register more than " + |
383 |
> |
MAX_PARTIES + " parties for " + stateToString(s); |
384 |
> |
} |
385 |
> |
|
386 |
> |
/** |
387 |
> |
* Recursively resolves lagged phase propagation from root if necessary. |
388 |
|
*/ |
389 |
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private long reconcileState() { |
390 |
< |
Phaser p = parent; |
390 |
> |
Phaser par = parent; |
391 |
|
long s = state; |
392 |
< |
if (p != null) { |
393 |
< |
while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) { |
394 |
< |
long parentState = p.getReconciledState(); |
395 |
< |
int parentPhase = phaseOf(parentState); |
396 |
< |
int phase = phaseOf(s = state); |
397 |
< |
if (phase != parentPhase) { |
398 |
< |
long next = trippedStateFor(parentPhase, partiesOf(s)); |
399 |
< |
if (casState(s, next)) { |
400 |
< |
releaseWaiters(phase); |
401 |
< |
s = next; |
402 |
< |
} |
392 |
> |
if (par != null) { |
393 |
> |
Phaser rt = root; |
394 |
> |
int phase, rPhase; |
395 |
> |
while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 && |
396 |
> |
(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) { |
397 |
> |
if ((int)(par.state >>> PHASE_SHIFT) != rPhase) |
398 |
> |
par.reconcileState(); |
399 |
> |
else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) { |
400 |
> |
long u = s & PARTIES_MASK; // reset unarrived to parties |
401 |
> |
long next = ((((long) rPhase) << PHASE_SHIFT) | u | |
402 |
> |
(u >>> PARTIES_SHIFT)); |
403 |
> |
if (state == s && |
404 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, |
405 |
> |
s, s = next)) |
406 |
> |
break; |
407 |
|
} |
408 |
+ |
s = state; |
409 |
|
} |
410 |
|
} |
411 |
|
return s; |
417 |
|
* phaser will need to first register for it. |
418 |
|
*/ |
419 |
|
public Phaser() { |
420 |
< |
this(null); |
420 |
> |
this(null, 0); |
421 |
|
} |
422 |
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|
423 |
|
/** |
433 |
|
} |
434 |
|
|
435 |
|
/** |
436 |
< |
* Creates a new phaser with the given parent, without any |
362 |
< |
* initially registered parties. If parent is non-null this phaser |
363 |
< |
* is registered with the parent and its initial phase number is |
364 |
< |
* the same as that of parent phaser. |
436 |
> |
* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}. |
437 |
|
* |
438 |
|
* @param parent the parent phaser |
439 |
|
*/ |
440 |
|
public Phaser(Phaser parent) { |
441 |
< |
int phase = 0; |
370 |
< |
this.parent = parent; |
371 |
< |
if (parent != null) { |
372 |
< |
this.root = parent.root; |
373 |
< |
phase = parent.register(); |
374 |
< |
} |
375 |
< |
else |
376 |
< |
this.root = this; |
377 |
< |
this.state = trippedStateFor(phase, 0); |
441 |
> |
this(parent, 0); |
442 |
|
} |
443 |
|
|
444 |
|
/** |
445 |
|
* Creates a new phaser with the given parent and number of |
446 |
< |
* registered unarrived parties. If parent is non-null, this phaser |
447 |
< |
* is registered with the parent and its initial phase number is |
448 |
< |
* the same as that of parent phaser. |
446 |
> |
* registered unarrived parties. If parent is non-null, this |
447 |
> |
* phaser is registered with the parent and its initial phase |
448 |
> |
* number is the same as that of parent phaser. If the number of |
449 |
> |
* parties is zero, the parent phaser will not proceed until this |
450 |
> |
* child phaser registers parties and advances, or this child |
451 |
> |
* phaser deregisters with its parent, or the parent is otherwise |
452 |
> |
* terminated. This child Phaser will be deregistered from its |
453 |
> |
* parent automatically upon any invocation of the child's {@link |
454 |
> |
* #arriveAndDeregister} method that results in the child's number |
455 |
> |
* of registered parties becoming zero. (Although rarely |
456 |
> |
* appropriate, this child may also explicity deregister from its |
457 |
> |
* parent using {@code getParent().arriveAndDeregister()}.) After |
458 |
> |
* deregistration, the child cannot re-register. (Instead, you can |
459 |
> |
* create a new child Phaser.) |
460 |
|
* |
461 |
|
* @param parent the parent phaser |
462 |
|
* @param parties the number of parties required to trip barrier |
464 |
|
* or greater than the maximum number of parties supported |
465 |
|
*/ |
466 |
|
public Phaser(Phaser parent, int parties) { |
467 |
< |
if (parties < 0 || parties > ushortMask) |
467 |
> |
if (parties >>> PARTIES_SHIFT != 0) |
468 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
469 |
< |
int phase = 0; |
469 |
> |
int phase; |
470 |
|
this.parent = parent; |
471 |
|
if (parent != null) { |
472 |
< |
this.root = parent.root; |
473 |
< |
phase = parent.register(); |
472 |
> |
Phaser r = parent.root; |
473 |
> |
this.root = r; |
474 |
> |
this.evenQ = r.evenQ; |
475 |
> |
this.oddQ = r.oddQ; |
476 |
> |
phase = parent.doRegister(1); |
477 |
|
} |
478 |
< |
else |
478 |
> |
else { |
479 |
|
this.root = this; |
480 |
< |
this.state = trippedStateFor(phase, parties); |
480 |
> |
this.evenQ = new AtomicReference<QNode>(); |
481 |
> |
this.oddQ = new AtomicReference<QNode>(); |
482 |
> |
phase = 0; |
483 |
> |
} |
484 |
> |
long p = (long)parties; |
485 |
> |
this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT); |
486 |
|
} |
487 |
|
|
488 |
|
/** |
489 |
|
* Adds a new unarrived party to this phaser. |
490 |
+ |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
491 |
+ |
* this method may wait until its completion before registering. |
492 |
|
* |
493 |
|
* @return the arrival phase number to which this registration applied |
494 |
|
* @throws IllegalStateException if attempting to register more |
500 |
|
|
501 |
|
/** |
502 |
|
* Adds the given number of new unarrived parties to this phaser. |
503 |
+ |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
504 |
+ |
* this method may wait until its completion before registering. |
505 |
|
* |
506 |
|
* @param parties the number of additional parties required to trip barrier |
507 |
|
* @return the arrival phase number to which this registration applied |
518 |
|
} |
519 |
|
|
520 |
|
/** |
434 |
– |
* Shared code for register, bulkRegister |
435 |
– |
*/ |
436 |
– |
private int doRegister(int registrations) { |
437 |
– |
int phase; |
438 |
– |
for (;;) { |
439 |
– |
long s = getReconciledState(); |
440 |
– |
phase = phaseOf(s); |
441 |
– |
int unarrived = unarrivedOf(s) + registrations; |
442 |
– |
int parties = partiesOf(s) + registrations; |
443 |
– |
if (phase < 0) |
444 |
– |
break; |
445 |
– |
if (parties > ushortMask || unarrived > ushortMask) |
446 |
– |
throw new IllegalStateException(badBounds(parties, unarrived)); |
447 |
– |
if (phase == phaseOf(root.state) && |
448 |
– |
casState(s, stateFor(phase, parties, unarrived))) |
449 |
– |
break; |
450 |
– |
} |
451 |
– |
return phase; |
452 |
– |
} |
453 |
– |
|
454 |
– |
/** |
521 |
|
* Arrives at the barrier, but does not wait for others. (You can |
522 |
|
* in turn wait for others via {@link #awaitAdvance}). It is an |
523 |
|
* unenforced usage error for an unregistered party to invoke this |
528 |
|
* of unarrived parties would become negative |
529 |
|
*/ |
530 |
|
public int arrive() { |
531 |
< |
int phase; |
466 |
< |
for (;;) { |
467 |
< |
long s = state; |
468 |
< |
phase = phaseOf(s); |
469 |
< |
if (phase < 0) |
470 |
< |
break; |
471 |
< |
int parties = partiesOf(s); |
472 |
< |
int unarrived = unarrivedOf(s) - 1; |
473 |
< |
if (unarrived > 0) { // Not the last arrival |
474 |
< |
if (casState(s, s - 1)) // s-1 adds one arrival |
475 |
< |
break; |
476 |
< |
} |
477 |
< |
else if (unarrived == 0) { // the last arrival |
478 |
< |
Phaser par = parent; |
479 |
< |
if (par == null) { // directly trip |
480 |
< |
if (casState |
481 |
< |
(s, |
482 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
483 |
< |
((phase + 1) & phaseMask), parties))) { |
484 |
< |
releaseWaiters(phase); |
485 |
< |
break; |
486 |
< |
} |
487 |
< |
} |
488 |
< |
else { // cascade to parent |
489 |
< |
if (casState(s, s - 1)) { // zeroes unarrived |
490 |
< |
par.arrive(); |
491 |
< |
reconcileState(); |
492 |
< |
break; |
493 |
< |
} |
494 |
< |
} |
495 |
< |
} |
496 |
< |
else if (phase != phaseOf(root.state)) // or if unreconciled |
497 |
< |
reconcileState(); |
498 |
< |
else |
499 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
500 |
< |
} |
501 |
< |
return phase; |
531 |
> |
return doArrive(ONE_ARRIVAL); |
532 |
|
} |
533 |
|
|
534 |
|
/** |
545 |
|
* of registered or unarrived parties would become negative |
546 |
|
*/ |
547 |
|
public int arriveAndDeregister() { |
548 |
< |
// similar code to arrive, but too different to merge |
519 |
< |
Phaser par = parent; |
520 |
< |
int phase; |
521 |
< |
for (;;) { |
522 |
< |
long s = state; |
523 |
< |
phase = phaseOf(s); |
524 |
< |
if (phase < 0) |
525 |
< |
break; |
526 |
< |
int parties = partiesOf(s) - 1; |
527 |
< |
int unarrived = unarrivedOf(s) - 1; |
528 |
< |
if (parties >= 0) { |
529 |
< |
if (unarrived > 0 || (unarrived == 0 && par != null)) { |
530 |
< |
if (casState |
531 |
< |
(s, |
532 |
< |
stateFor(phase, parties, unarrived))) { |
533 |
< |
if (unarrived == 0) { |
534 |
< |
par.arriveAndDeregister(); |
535 |
< |
reconcileState(); |
536 |
< |
} |
537 |
< |
break; |
538 |
< |
} |
539 |
< |
continue; |
540 |
< |
} |
541 |
< |
if (unarrived == 0) { |
542 |
< |
if (casState |
543 |
< |
(s, |
544 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
545 |
< |
((phase + 1) & phaseMask), parties))) { |
546 |
< |
releaseWaiters(phase); |
547 |
< |
break; |
548 |
< |
} |
549 |
< |
continue; |
550 |
< |
} |
551 |
< |
if (par != null && phase != phaseOf(root.state)) { |
552 |
< |
reconcileState(); |
553 |
< |
continue; |
554 |
< |
} |
555 |
< |
} |
556 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
557 |
< |
} |
558 |
< |
return phase; |
548 |
> |
return doArrive(ONE_ARRIVAL|ONE_PARTY); |
549 |
|
} |
550 |
|
|
551 |
|
/** |
569 |
|
* Awaits the phase of the barrier to advance from the given phase |
570 |
|
* value, returning immediately if the current phase of the |
571 |
|
* barrier is not equal to the given phase value or this barrier |
572 |
< |
* is terminated. It is an unenforced usage error for an |
583 |
< |
* unregistered party to invoke this method. |
572 |
> |
* is terminated. |
573 |
|
* |
574 |
|
* @param phase an arrival phase number, or negative value if |
575 |
|
* terminated; this argument is normally the value returned by a |
580 |
|
public int awaitAdvance(int phase) { |
581 |
|
if (phase < 0) |
582 |
|
return phase; |
583 |
< |
long s = getReconciledState(); |
584 |
< |
int p = phaseOf(s); |
585 |
< |
if (p != phase) |
597 |
< |
return p; |
598 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
599 |
< |
parent.awaitAdvance(phase); |
600 |
< |
// Fall here even if parent waited, to reconcile and help release |
601 |
< |
return untimedWait(phase); |
583 |
> |
long s = (parent == null) ? state : reconcileState(); |
584 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
585 |
> |
return (p != phase) ? p : internalAwaitAdvance(phase, null); |
586 |
|
} |
587 |
|
|
588 |
|
/** |
590 |
|
* value, throwing {@code InterruptedException} if interrupted |
591 |
|
* while waiting, or returning immediately if the current phase of |
592 |
|
* the barrier is not equal to the given phase value or this |
593 |
< |
* barrier is terminated. It is an unenforced usage error for an |
610 |
< |
* unregistered party to invoke this method. |
593 |
> |
* barrier is terminated. |
594 |
|
* |
595 |
|
* @param phase an arrival phase number, or negative value if |
596 |
|
* terminated; this argument is normally the value returned by a |
603 |
|
throws InterruptedException { |
604 |
|
if (phase < 0) |
605 |
|
return phase; |
606 |
< |
long s = getReconciledState(); |
607 |
< |
int p = phaseOf(s); |
608 |
< |
if (p != phase) |
609 |
< |
return p; |
610 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
611 |
< |
parent.awaitAdvanceInterruptibly(phase); |
612 |
< |
return interruptibleWait(phase); |
606 |
> |
long s = (parent == null) ? state : reconcileState(); |
607 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
608 |
> |
if (p == phase) { |
609 |
> |
QNode node = new QNode(this, phase, true, false, 0L); |
610 |
> |
p = internalAwaitAdvance(phase, node); |
611 |
> |
if (node.wasInterrupted) |
612 |
> |
throw new InterruptedException(); |
613 |
> |
} |
614 |
> |
return p; |
615 |
|
} |
616 |
|
|
617 |
|
/** |
620 |
|
* InterruptedException} if interrupted while waiting, or |
621 |
|
* returning immediately if the current phase of the barrier is |
622 |
|
* not equal to the given phase value or this barrier is |
623 |
< |
* terminated. It is an unenforced usage error for an |
639 |
< |
* unregistered party to invoke this method. |
623 |
> |
* terminated. |
624 |
|
* |
625 |
|
* @param phase an arrival phase number, or negative value if |
626 |
|
* terminated; this argument is normally the value returned by a |
639 |
|
throws InterruptedException, TimeoutException { |
640 |
|
if (phase < 0) |
641 |
|
return phase; |
642 |
< |
long s = getReconciledState(); |
643 |
< |
int p = phaseOf(s); |
644 |
< |
if (p != phase) |
645 |
< |
return p; |
646 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
647 |
< |
parent.awaitAdvanceInterruptibly(phase, timeout, unit); |
648 |
< |
return timedWait(phase, unit.toNanos(timeout)); |
642 |
> |
long s = (parent == null) ? state : reconcileState(); |
643 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
644 |
> |
if (p == phase) { |
645 |
> |
long nanos = unit.toNanos(timeout); |
646 |
> |
QNode node = new QNode(this, phase, true, true, nanos); |
647 |
> |
p = internalAwaitAdvance(phase, node); |
648 |
> |
if (node.wasInterrupted) |
649 |
> |
throw new InterruptedException(); |
650 |
> |
else if (p == phase) |
651 |
> |
throw new TimeoutException(); |
652 |
> |
} |
653 |
> |
return p; |
654 |
|
} |
655 |
|
|
656 |
|
/** |
657 |
< |
* Forces this barrier to enter termination state. Counts of |
658 |
< |
* arrived and registered parties are unaffected. If this phaser |
659 |
< |
* has a parent, it too is terminated. This method may be useful |
660 |
< |
* for coordinating recovery after one or more tasks encounter |
661 |
< |
* unexpected exceptions. |
657 |
> |
* Forces this barrier to enter termination state. Counts of |
658 |
> |
* arrived and registered parties are unaffected. If this phaser |
659 |
> |
* is a member of a tiered set of phasers, then all of the phasers |
660 |
> |
* in the set are terminated. If this phaser is already |
661 |
> |
* terminated, this method has no effect. This method may be |
662 |
> |
* useful for coordinating recovery after one or more tasks |
663 |
> |
* encounter unexpected exceptions. |
664 |
|
*/ |
665 |
|
public void forceTermination() { |
666 |
< |
for (;;) { |
667 |
< |
long s = getReconciledState(); |
668 |
< |
int phase = phaseOf(s); |
669 |
< |
int parties = partiesOf(s); |
670 |
< |
int unarrived = unarrivedOf(s); |
671 |
< |
if (phase < 0 || |
672 |
< |
casState(s, stateFor(-1, parties, unarrived))) { |
682 |
< |
releaseWaiters(0); |
666 |
> |
// Only need to change root state |
667 |
> |
final Phaser root = this.root; |
668 |
> |
long s; |
669 |
> |
while ((s = root.state) >= 0) { |
670 |
> |
if (UNSAFE.compareAndSwapLong(root, stateOffset, |
671 |
> |
s, s | TERMINATION_PHASE)) { |
672 |
> |
releaseWaiters(0); // signal all threads |
673 |
|
releaseWaiters(1); |
684 |
– |
if (parent != null) |
685 |
– |
parent.forceTermination(); |
674 |
|
return; |
675 |
|
} |
676 |
|
} |
684 |
|
* @return the phase number, or a negative value if terminated |
685 |
|
*/ |
686 |
|
public final int getPhase() { |
687 |
< |
return phaseOf(getReconciledState()); |
687 |
> |
return (int)(root.state >>> PHASE_SHIFT); |
688 |
|
} |
689 |
|
|
690 |
|
/** |
703 |
|
* @return the number of arrived parties |
704 |
|
*/ |
705 |
|
public int getArrivedParties() { |
706 |
< |
return arrivedOf(state); |
706 |
> |
return arrivedOf(parent==null? state : reconcileState()); |
707 |
|
} |
708 |
|
|
709 |
|
/** |
713 |
|
* @return the number of unarrived parties |
714 |
|
*/ |
715 |
|
public int getUnarrivedParties() { |
716 |
< |
return unarrivedOf(state); |
716 |
> |
return unarrivedOf(parent==null? state : reconcileState()); |
717 |
|
} |
718 |
|
|
719 |
|
/** |
741 |
|
* @return {@code true} if this barrier has been terminated |
742 |
|
*/ |
743 |
|
public boolean isTerminated() { |
744 |
< |
return getPhase() < 0; |
744 |
> |
return root.state < 0L; |
745 |
|
} |
746 |
|
|
747 |
|
/** |
757 |
|
* which case no advance occurs. |
758 |
|
* |
759 |
|
* <p>The arguments to this method provide the state of the phaser |
760 |
< |
* prevailing for the current transition. (When called from within |
761 |
< |
* an implementation of {@code onAdvance} the values returned by |
762 |
< |
* methods such as {@code getPhase} may or may not reliably |
763 |
< |
* indicate the state to which this transition applies.) |
760 |
> |
* prevailing for the current transition. The effects of invoking |
761 |
> |
* arrival, registration, and waiting methods on this Phaser from |
762 |
> |
* within {@code onAdvance} are unspecified and should not be |
763 |
> |
* relied on. |
764 |
> |
* |
765 |
> |
* <p>If this Phaser is a member of a tiered set of Phasers, then |
766 |
> |
* {@code onAdvance} is invoked only for its root Phaser on each |
767 |
> |
* advance. |
768 |
|
* |
769 |
|
* <p>The default version returns {@code true} when the number of |
770 |
|
* registered parties is zero. Normally, overrides that arrange |
771 |
|
* termination for other reasons should also preserve this |
772 |
|
* property. |
773 |
|
* |
782 |
– |
* <p>You may override this method to perform an action with side |
783 |
– |
* effects visible to participating tasks, but it is only sensible |
784 |
– |
* to do so in designs where all parties register before any |
785 |
– |
* arrive, and all {@link #awaitAdvance} at each phase. |
786 |
– |
* Otherwise, you cannot ensure lack of interference from other |
787 |
– |
* parties during the invocation of this method. Additionally, |
788 |
– |
* method {@code onAdvance} may be invoked more than once per |
789 |
– |
* transition if registrations are intermixed with arrivals. |
790 |
– |
* |
774 |
|
* @param phase the phase number on entering the barrier |
775 |
|
* @param registeredParties the current number of registered parties |
776 |
|
* @return {@code true} if this barrier should terminate |
789 |
|
* @return a string identifying this barrier, as well as its state |
790 |
|
*/ |
791 |
|
public String toString() { |
792 |
< |
long s = getReconciledState(); |
792 |
> |
return stateToString(reconcileState()); |
793 |
> |
} |
794 |
> |
|
795 |
> |
/** |
796 |
> |
* Implementation of toString and string-based error messages |
797 |
> |
*/ |
798 |
> |
private String stateToString(long s) { |
799 |
|
return super.toString() + |
800 |
|
"[phase = " + phaseOf(s) + |
801 |
|
" parties = " + partiesOf(s) + |
802 |
|
" arrived = " + arrivedOf(s) + "]"; |
803 |
|
} |
804 |
|
|
805 |
< |
// methods for waiting |
805 |
> |
// Waiting mechanics |
806 |
> |
|
807 |
> |
/** |
808 |
> |
* Removes and signals threads from queue for phase. |
809 |
> |
*/ |
810 |
> |
private void releaseWaiters(int phase) { |
811 |
> |
AtomicReference<QNode> head = queueFor(phase); |
812 |
> |
QNode q; |
813 |
> |
int p; |
814 |
> |
while ((q = head.get()) != null && |
815 |
> |
((p = q.phase) == phase || |
816 |
> |
(int)(root.state >>> PHASE_SHIFT) != p)) { |
817 |
> |
if (head.compareAndSet(q, q.next)) |
818 |
> |
q.signal(); |
819 |
> |
} |
820 |
> |
} |
821 |
> |
|
822 |
> |
/** The number of CPUs, for spin control */ |
823 |
> |
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
824 |
> |
|
825 |
> |
/** |
826 |
> |
* The number of times to spin before blocking while waiting for |
827 |
> |
* advance, per arrival while waiting. On multiprocessors, fully |
828 |
> |
* blocking and waking up a large number of threads all at once is |
829 |
> |
* usually a very slow process, so we use rechargeable spins to |
830 |
> |
* avoid it when threads regularly arrive: When a thread in |
831 |
> |
* internalAwaitAdvance notices another arrival before blocking, |
832 |
> |
* and there appear to be enough CPUs available, it spins |
833 |
> |
* SPINS_PER_ARRIVAL more times before blocking. Plus, even on |
834 |
> |
* uniprocessors, there is at least one intervening Thread.yield |
835 |
> |
* before blocking. The value trades off good-citizenship vs big |
836 |
> |
* unnecessary slowdowns. |
837 |
> |
*/ |
838 |
> |
static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8; |
839 |
> |
|
840 |
> |
/** |
841 |
> |
* Possibly blocks and waits for phase to advance unless aborted. |
842 |
> |
* |
843 |
> |
* @param phase current phase |
844 |
> |
* @param node if non-null, the wait node to track interrupt and timeout; |
845 |
> |
* if null, denotes noninterruptible wait |
846 |
> |
* @return current phase |
847 |
> |
*/ |
848 |
> |
private int internalAwaitAdvance(int phase, QNode node) { |
849 |
> |
Phaser current = this; // to eventually wait at root if tiered |
850 |
> |
boolean queued = false; // true when node is enqueued |
851 |
> |
int lastUnarrived = -1; // to increase spins upon change |
852 |
> |
int spins = SPINS_PER_ARRIVAL; |
853 |
> |
long s; |
854 |
> |
int p; |
855 |
> |
while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) { |
856 |
> |
Phaser par; |
857 |
> |
int unarrived = (int)s & UNARRIVED_MASK; |
858 |
> |
if (unarrived != lastUnarrived) { |
859 |
> |
if (lastUnarrived == -1) // ensure old queue clean |
860 |
> |
releaseWaiters(phase-1); |
861 |
> |
if ((lastUnarrived = unarrived) < NCPU) |
862 |
> |
spins += SPINS_PER_ARRIVAL; |
863 |
> |
} |
864 |
> |
else if (unarrived == 0 && (par = current.parent) != null) { |
865 |
> |
current = par; // if all arrived, use parent |
866 |
> |
par = par.parent; |
867 |
> |
lastUnarrived = -1; |
868 |
> |
} |
869 |
> |
else if (spins > 0) { |
870 |
> |
if (--spins == (SPINS_PER_ARRIVAL >>> 1)) |
871 |
> |
Thread.yield(); // yield midway through spin |
872 |
> |
} |
873 |
> |
else if (node == null) // must be noninterruptible |
874 |
> |
node = new QNode(this, phase, false, false, 0L); |
875 |
> |
else if (node.isReleasable()) { |
876 |
> |
if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase) |
877 |
> |
break; |
878 |
> |
else |
879 |
> |
return phase; // aborted |
880 |
> |
} |
881 |
> |
else if (!queued) { // push onto queue |
882 |
> |
AtomicReference<QNode> head = queueFor(phase); |
883 |
> |
QNode q = head.get(); |
884 |
> |
if (q == null || q.phase == phase) { |
885 |
> |
node.next = q; |
886 |
> |
if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase) |
887 |
> |
break; // recheck to avoid stale enqueue |
888 |
> |
else |
889 |
> |
queued = head.compareAndSet(q, node); |
890 |
> |
} |
891 |
> |
} |
892 |
> |
else { |
893 |
> |
try { |
894 |
> |
ForkJoinPool.managedBlock(node); |
895 |
> |
} catch (InterruptedException ie) { |
896 |
> |
node.wasInterrupted = true; |
897 |
> |
} |
898 |
> |
} |
899 |
> |
} |
900 |
> |
releaseWaiters(phase); |
901 |
> |
if (node != null) |
902 |
> |
node.onRelease(); |
903 |
> |
return p; |
904 |
> |
} |
905 |
|
|
906 |
|
/** |
907 |
|
* Wait nodes for Treiber stack representing wait queue |
909 |
|
static final class QNode implements ForkJoinPool.ManagedBlocker { |
910 |
|
final Phaser phaser; |
911 |
|
final int phase; |
824 |
– |
final long startTime; |
825 |
– |
final long nanos; |
826 |
– |
final boolean timed; |
912 |
|
final boolean interruptible; |
913 |
< |
volatile boolean wasInterrupted = false; |
913 |
> |
final boolean timed; |
914 |
> |
boolean wasInterrupted; |
915 |
> |
long nanos; |
916 |
> |
long lastTime; |
917 |
|
volatile Thread thread; // nulled to cancel wait |
918 |
|
QNode next; |
919 |
|
|
920 |
|
QNode(Phaser phaser, int phase, boolean interruptible, |
921 |
< |
boolean timed, long startTime, long nanos) { |
921 |
> |
boolean timed, long nanos) { |
922 |
|
this.phaser = phaser; |
923 |
|
this.phase = phase; |
836 |
– |
this.timed = timed; |
924 |
|
this.interruptible = interruptible; |
838 |
– |
this.startTime = startTime; |
925 |
|
this.nanos = nanos; |
926 |
+ |
this.timed = timed; |
927 |
+ |
this.lastTime = timed? System.nanoTime() : 0L; |
928 |
|
thread = Thread.currentThread(); |
929 |
|
} |
930 |
|
|
931 |
|
public boolean isReleasable() { |
932 |
< |
return (thread == null || |
933 |
< |
phaser.getPhase() != phase || |
934 |
< |
(interruptible && wasInterrupted) || |
935 |
< |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
932 |
> |
Thread t = thread; |
933 |
> |
if (t != null) { |
934 |
> |
if (phaser.getPhase() != phase) |
935 |
> |
t = null; |
936 |
> |
else { |
937 |
> |
if (Thread.interrupted()) |
938 |
> |
wasInterrupted = true; |
939 |
> |
if (interruptible && wasInterrupted) |
940 |
> |
t = null; |
941 |
> |
else if (timed) { |
942 |
> |
if (nanos > 0) { |
943 |
> |
long now = System.nanoTime(); |
944 |
> |
nanos -= now - lastTime; |
945 |
> |
lastTime = now; |
946 |
> |
} |
947 |
> |
if (nanos <= 0) |
948 |
> |
t = null; |
949 |
> |
} |
950 |
> |
} |
951 |
> |
if (t != null) |
952 |
> |
return false; |
953 |
> |
thread = null; |
954 |
> |
} |
955 |
> |
return true; |
956 |
|
} |
957 |
|
|
958 |
|
public boolean block() { |
959 |
< |
if (Thread.interrupted()) { |
960 |
< |
wasInterrupted = true; |
961 |
< |
if (interruptible) |
854 |
< |
return true; |
855 |
< |
} |
856 |
< |
if (!timed) |
959 |
> |
if (isReleasable()) |
960 |
> |
return true; |
961 |
> |
else if (!timed) |
962 |
|
LockSupport.park(this); |
963 |
< |
else { |
964 |
< |
long waitTime = nanos - (System.nanoTime() - startTime); |
860 |
< |
if (waitTime <= 0) |
861 |
< |
return true; |
862 |
< |
LockSupport.parkNanos(this, waitTime); |
863 |
< |
} |
963 |
> |
else if (nanos > 0) |
964 |
> |
LockSupport.parkNanos(this, nanos); |
965 |
|
return isReleasable(); |
966 |
|
} |
967 |
|
|
973 |
|
} |
974 |
|
} |
975 |
|
|
976 |
< |
boolean doWait() { |
977 |
< |
if (thread != null) { |
978 |
< |
try { |
979 |
< |
ForkJoinPool.managedBlock(this); |
980 |
< |
} catch (InterruptedException ie) { |
880 |
< |
wasInterrupted = true; // can't currently happen |
881 |
< |
} |
882 |
< |
} |
883 |
< |
return wasInterrupted; |
884 |
< |
} |
885 |
< |
} |
886 |
< |
|
887 |
< |
/** |
888 |
< |
* Removes and signals waiting threads from wait queue. |
889 |
< |
*/ |
890 |
< |
private void releaseWaiters(int phase) { |
891 |
< |
AtomicReference<QNode> head = queueFor(phase); |
892 |
< |
QNode q; |
893 |
< |
while ((q = head.get()) != null) { |
894 |
< |
if (head.compareAndSet(q, q.next)) |
895 |
< |
q.signal(); |
896 |
< |
} |
897 |
< |
} |
898 |
< |
|
899 |
< |
/** |
900 |
< |
* Tries to enqueue given node in the appropriate wait queue. |
901 |
< |
* |
902 |
< |
* @return true if successful |
903 |
< |
*/ |
904 |
< |
private boolean tryEnqueue(QNode node) { |
905 |
< |
AtomicReference<QNode> head = queueFor(node.phase); |
906 |
< |
return head.compareAndSet(node.next = head.get(), node); |
907 |
< |
} |
908 |
< |
|
909 |
< |
/** |
910 |
< |
* Enqueues node and waits unless aborted or signalled. |
911 |
< |
* |
912 |
< |
* @return current phase |
913 |
< |
*/ |
914 |
< |
private int untimedWait(int phase) { |
915 |
< |
QNode node = null; |
916 |
< |
boolean queued = false; |
917 |
< |
boolean interrupted = false; |
918 |
< |
int p; |
919 |
< |
while ((p = getPhase()) == phase) { |
920 |
< |
if (Thread.interrupted()) |
921 |
< |
interrupted = true; |
922 |
< |
else if (node == null) |
923 |
< |
node = new QNode(this, phase, false, false, 0, 0); |
924 |
< |
else if (!queued) |
925 |
< |
queued = tryEnqueue(node); |
926 |
< |
else if (node.doWait()) |
927 |
< |
interrupted = true; |
976 |
> |
void onRelease() { // actions upon return from internalAwaitAdvance |
977 |
> |
if (!interruptible && wasInterrupted) |
978 |
> |
Thread.currentThread().interrupt(); |
979 |
> |
if (thread != null) |
980 |
> |
thread = null; |
981 |
|
} |
929 |
– |
if (node != null) |
930 |
– |
node.thread = null; |
931 |
– |
releaseWaiters(phase); |
932 |
– |
if (interrupted) |
933 |
– |
Thread.currentThread().interrupt(); |
934 |
– |
return p; |
935 |
– |
} |
982 |
|
|
937 |
– |
/** |
938 |
– |
* Interruptible version |
939 |
– |
* @return current phase |
940 |
– |
*/ |
941 |
– |
private int interruptibleWait(int phase) throws InterruptedException { |
942 |
– |
QNode node = null; |
943 |
– |
boolean queued = false; |
944 |
– |
boolean interrupted = false; |
945 |
– |
int p; |
946 |
– |
while ((p = getPhase()) == phase && !interrupted) { |
947 |
– |
if (Thread.interrupted()) |
948 |
– |
interrupted = true; |
949 |
– |
else if (node == null) |
950 |
– |
node = new QNode(this, phase, true, false, 0, 0); |
951 |
– |
else if (!queued) |
952 |
– |
queued = tryEnqueue(node); |
953 |
– |
else if (node.doWait()) |
954 |
– |
interrupted = true; |
955 |
– |
} |
956 |
– |
if (node != null) |
957 |
– |
node.thread = null; |
958 |
– |
if (p != phase || (p = getPhase()) != phase) |
959 |
– |
releaseWaiters(phase); |
960 |
– |
if (interrupted) |
961 |
– |
throw new InterruptedException(); |
962 |
– |
return p; |
963 |
– |
} |
964 |
– |
|
965 |
– |
/** |
966 |
– |
* Timeout version. |
967 |
– |
* @return current phase |
968 |
– |
*/ |
969 |
– |
private int timedWait(int phase, long nanos) |
970 |
– |
throws InterruptedException, TimeoutException { |
971 |
– |
long startTime = System.nanoTime(); |
972 |
– |
QNode node = null; |
973 |
– |
boolean queued = false; |
974 |
– |
boolean interrupted = false; |
975 |
– |
int p; |
976 |
– |
while ((p = getPhase()) == phase && !interrupted) { |
977 |
– |
if (Thread.interrupted()) |
978 |
– |
interrupted = true; |
979 |
– |
else if (nanos - (System.nanoTime() - startTime) <= 0) |
980 |
– |
break; |
981 |
– |
else if (node == null) |
982 |
– |
node = new QNode(this, phase, true, true, startTime, nanos); |
983 |
– |
else if (!queued) |
984 |
– |
queued = tryEnqueue(node); |
985 |
– |
else if (node.doWait()) |
986 |
– |
interrupted = true; |
987 |
– |
} |
988 |
– |
if (node != null) |
989 |
– |
node.thread = null; |
990 |
– |
if (p != phase || (p = getPhase()) != phase) |
991 |
– |
releaseWaiters(phase); |
992 |
– |
if (interrupted) |
993 |
– |
throw new InterruptedException(); |
994 |
– |
if (p == phase) |
995 |
– |
throw new TimeoutException(); |
996 |
– |
return p; |
983 |
|
} |
984 |
|
|
985 |
|
// Unsafe mechanics |
988 |
|
private static final long stateOffset = |
989 |
|
objectFieldOffset("state", Phaser.class); |
990 |
|
|
1005 |
– |
private final boolean casState(long cmp, long val) { |
1006 |
– |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
1007 |
– |
} |
1008 |
– |
|
991 |
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
992 |
|
try { |
993 |
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |