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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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* <p><b>Sample usages:</b> |
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* |
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* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch} |
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* to control a one-shot action serving a variable number of |
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* parties. The typical idiom is for the method setting this up to |
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* first register, then start the actions, then deregister, as in: |
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* to control a one-shot action serving a variable number of parties. |
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* The typical idiom is for the method setting this up to first |
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* register, then start the actions, then deregister, as in: |
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* |
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* <pre> {@code |
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* void runTasks(List<Runnable> tasks) { |
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* <p>To create a set of tasks using a tree of phasers, |
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* you could use code of the following form, assuming a |
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* Task class with a constructor accepting a phaser that |
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* it registers for upon construction: |
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* it registers with upon construction: |
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* |
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* <pre> {@code |
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* void build(Task[] actions, int lo, int hi, Phaser ph) { |
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* be appropriate for extremely small per-barrier task bodies (thus |
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* high rates), or up to hundreds for extremely large ones. |
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* |
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* </pre> |
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* |
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* <p><b>Implementation notes</b>: This implementation restricts the |
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* maximum number of parties to 65535. Attempts to register additional |
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* parties result in {@code IllegalStateException}. However, you can and |
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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) |
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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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private static final int ushortMask = 0xffff; |
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private static final int phaseMask = 0x7fffffff; |
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private static final int MAX_COUNT = 0xffff; |
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private static final int MAX_PHASE = 0x7fffffff; |
245 |
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private static final int PARTIES_SHIFT = 16; |
246 |
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private static final int PHASE_SHIFT = 32; |
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private static final long UNARRIVED_MASK = 0xffffL; |
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private static final long PARTIES_MASK = 0xffff0000L; |
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private static final long ONE_ARRIVAL = 1L; |
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private static final long ONE_PARTY = 1L << PARTIES_SHIFT; |
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private static final long TERMINATION_PHASE = -1L << PHASE_SHIFT; |
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|
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// The following unpacking methods are usually manually inlined |
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private static int unarrivedOf(long s) { |
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return (int) (s & ushortMask); |
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return (int) (s & UNARRIVED_MASK); |
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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 |
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return ((int) (s & PARTIES_MASK)) >>> PARTIES_SHIFT; |
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} |
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private static int phaseOf(long s) { |
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return (int) (s >>> 32); |
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return (int) (s >>> PHASE_SHIFT); |
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} |
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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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private static long stateFor(int phase, int parties, int unarrived) { |
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return ((((long) phase) << 32) | (((long) parties) << 16) | |
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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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*/ |
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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 |
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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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*/ |
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private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>(); |
289 |
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private final AtomicReference<QNode> oddQ = new AtomicReference<QNode>(); |
288 |
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private final AtomicReference<QNode> evenQ; |
289 |
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private final AtomicReference<QNode> oddQ; |
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private AtomicReference<QNode> queueFor(int phase) { |
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return ((phase & 1) == 0) ? evenQ : oddQ; |
293 |
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} |
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/** |
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* Returns current state, first resolving lagged propagation from |
297 |
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* root if necessary. |
296 |
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* 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 int doArrive(long adj) { |
305 |
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long s; |
306 |
> |
int phase, unarrived; |
307 |
> |
while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0) { |
308 |
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if ((unarrived = (int)(s & UNARRIVED_MASK)) != 0) { |
309 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s -= adj)) { |
310 |
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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 |
319 |
> |
(this, stateOffset, s, onAdvance(phase, u)? |
320 |
> |
next | TERMINATION_PHASE : next); |
321 |
> |
releaseWaiters(phase); |
322 |
> |
} |
323 |
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else { |
324 |
> |
par.doArrive(u == 0? |
325 |
> |
ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
326 |
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if ((int)(par.state >>> PHASE_SHIFT) != nextPhase || |
327 |
> |
((int)(state >>> PHASE_SHIFT) != nextPhase && |
328 |
> |
!UNSAFE.compareAndSwapLong(this, stateOffset, |
329 |
> |
s, next))) |
330 |
> |
reconcileState(); |
331 |
> |
} |
332 |
> |
} |
333 |
> |
break; |
334 |
> |
} |
335 |
> |
} |
336 |
> |
else if (state == s && reconcileState() == s) // recheck |
337 |
> |
throw new IllegalStateException(badArrive()); |
338 |
> |
} |
339 |
> |
return phase; |
340 |
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} |
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|
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> |
/** |
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> |
* Returns message string for bounds exceptions on arrival. |
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* Declared out of-line from doArrive to reduce string op bulk. |
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*/ |
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private long getReconciledState() { |
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return (parent == null) ? state : reconcileState(); |
346 |
> |
private String badArrive() { |
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return ("Attempted arrival of unregistered party for " + |
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this.toString()); |
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} |
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/** |
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* Recursively resolves state. |
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* Implementation of register, bulkRegister |
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* |
354 |
> |
* @param registrations number to add to both parties and unarrived fields |
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*/ |
356 |
> |
private int doRegister(int registrations) { |
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> |
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 |
> |
|
383 |
> |
/** |
384 |
> |
* Recursively resolves lagged phase propagation from root if |
385 |
> |
* necessary. |
386 |
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*/ |
387 |
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private long reconcileState() { |
388 |
< |
Phaser p = parent; |
389 |
< |
long s = state; |
390 |
< |
if (p != null) { |
391 |
< |
while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) { |
392 |
< |
long parentState = p.getReconciledState(); |
393 |
< |
int parentPhase = phaseOf(parentState); |
394 |
< |
int phase = phaseOf(s = state); |
395 |
< |
if (phase != parentPhase) { |
396 |
< |
long next = trippedStateFor(parentPhase, partiesOf(s)); |
397 |
< |
if (casState(s, next)) { |
398 |
< |
releaseWaiters(phase); |
399 |
< |
s = next; |
400 |
< |
} |
388 |
> |
Phaser par = parent; |
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 |
|
} |
408 |
|
} |
409 |
+ |
if (state == s) |
410 |
+ |
releaseWaiters(phase); // help release others |
411 |
|
} |
412 |
|
return s; |
413 |
|
} |
418 |
|
* phaser will need to first register for it. |
419 |
|
*/ |
420 |
|
public Phaser() { |
421 |
< |
this(null); |
421 |
> |
this(null, 0); |
422 |
|
} |
423 |
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|
424 |
|
/** |
425 |
< |
* Creates a new phaser with the given numbers of registered |
425 |
> |
* Creates a new phaser with the given number of registered |
426 |
|
* unarrived parties, initial phase number 0, and no parent. |
427 |
|
* |
428 |
|
* @param parties the number of parties required to trip barrier |
442 |
|
* @param parent the parent phaser |
443 |
|
*/ |
444 |
|
public Phaser(Phaser parent) { |
445 |
< |
int phase = 0; |
372 |
< |
this.parent = parent; |
373 |
< |
if (parent != null) { |
374 |
< |
this.root = parent.root; |
375 |
< |
phase = parent.register(); |
376 |
< |
} |
377 |
< |
else |
378 |
< |
this.root = this; |
379 |
< |
this.state = trippedStateFor(phase, 0); |
445 |
> |
this(parent, 0); |
446 |
|
} |
447 |
|
|
448 |
|
/** |
449 |
< |
* Creates a new phaser with the given parent and numbers of |
449 |
> |
* Creates a new phaser with the given parent and number of |
450 |
|
* registered unarrived parties. If parent is non-null, this phaser |
451 |
|
* is registered with the parent and its initial phase number is |
452 |
|
* the same as that of parent phaser. |
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 = 0; |
462 |
> |
int phase; |
463 |
|
this.parent = parent; |
464 |
|
if (parent != null) { |
465 |
< |
this.root = parent.root; |
465 |
> |
Phaser r = parent.root; |
466 |
> |
this.root = r; |
467 |
> |
this.evenQ = r.evenQ; |
468 |
> |
this.oddQ = r.oddQ; |
469 |
|
phase = parent.register(); |
470 |
|
} |
471 |
< |
else |
471 |
> |
else { |
472 |
|
this.root = this; |
473 |
< |
this.state = trippedStateFor(phase, parties); |
473 |
> |
this.evenQ = new AtomicReference<QNode>(); |
474 |
> |
this.oddQ = new AtomicReference<QNode>(); |
475 |
> |
phase = 0; |
476 |
> |
} |
477 |
> |
long p = (long)parties; |
478 |
> |
this.state = (((long) phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT); |
479 |
|
} |
480 |
|
|
481 |
|
/** |
482 |
|
* Adds a new unarrived party to this phaser. |
483 |
+ |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
484 |
+ |
* this method may wait until its completion before registering. |
485 |
|
* |
486 |
|
* @return the arrival phase number to which this registration applied |
487 |
|
* @throws IllegalStateException if attempting to register more |
493 |
|
|
494 |
|
/** |
495 |
|
* Adds the given number of new unarrived parties to this phaser. |
496 |
+ |
* If an ongoing invocation of {@link #onAdvance} is in progress, |
497 |
+ |
* this method may wait until its completion before registering. |
498 |
|
* |
499 |
< |
* @param parties the number of parties required to trip barrier |
499 |
> |
* @param parties the number of additional parties required to trip barrier |
500 |
|
* @return the arrival phase number to which this registration applied |
501 |
|
* @throws IllegalStateException if attempting to register more |
502 |
|
* than the maximum supported number of parties |
503 |
+ |
* @throws IllegalArgumentException if {@code parties < 0} |
504 |
|
*/ |
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 |
|
/** |
435 |
– |
* Shared code for register, bulkRegister |
436 |
– |
*/ |
437 |
– |
private int doRegister(int registrations) { |
438 |
– |
int phase; |
439 |
– |
for (;;) { |
440 |
– |
long s = getReconciledState(); |
441 |
– |
phase = phaseOf(s); |
442 |
– |
int unarrived = unarrivedOf(s) + registrations; |
443 |
– |
int parties = partiesOf(s) + registrations; |
444 |
– |
if (phase < 0) |
445 |
– |
break; |
446 |
– |
if (parties > ushortMask || unarrived > ushortMask) |
447 |
– |
throw new IllegalStateException(badBounds(parties, unarrived)); |
448 |
– |
if (phase == phaseOf(root.state) && |
449 |
– |
casState(s, stateFor(phase, parties, unarrived))) |
450 |
– |
break; |
451 |
– |
} |
452 |
– |
return phase; |
453 |
– |
} |
454 |
– |
|
455 |
– |
/** |
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 |
< |
int phase; |
467 |
< |
for (;;) { |
468 |
< |
long s = state; |
469 |
< |
phase = phaseOf(s); |
470 |
< |
if (phase < 0) |
471 |
< |
break; |
472 |
< |
int parties = partiesOf(s); |
473 |
< |
int unarrived = unarrivedOf(s) - 1; |
474 |
< |
if (unarrived > 0) { // Not the last arrival |
475 |
< |
if (casState(s, s - 1)) // s-1 adds one arrival |
476 |
< |
break; |
477 |
< |
} |
478 |
< |
else if (unarrived == 0) { // the last arrival |
479 |
< |
Phaser par = parent; |
480 |
< |
if (par == null) { // directly trip |
481 |
< |
if (casState |
482 |
< |
(s, |
483 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
484 |
< |
((phase + 1) & phaseMask), parties))) { |
485 |
< |
releaseWaiters(phase); |
486 |
< |
break; |
487 |
< |
} |
488 |
< |
} |
489 |
< |
else { // cascade to parent |
490 |
< |
if (casState(s, s - 1)) { // zeroes unarrived |
491 |
< |
par.arrive(); |
492 |
< |
reconcileState(); |
493 |
< |
break; |
494 |
< |
} |
495 |
< |
} |
496 |
< |
} |
497 |
< |
else if (phase != phaseOf(root.state)) // or if unreconciled |
498 |
< |
reconcileState(); |
499 |
< |
else |
500 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
501 |
< |
} |
502 |
< |
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 code to arrive, but too different to merge |
520 |
< |
Phaser par = parent; |
521 |
< |
int phase; |
522 |
< |
for (;;) { |
523 |
< |
long s = state; |
524 |
< |
phase = phaseOf(s); |
525 |
< |
if (phase < 0) |
526 |
< |
break; |
527 |
< |
int parties = partiesOf(s) - 1; |
528 |
< |
int unarrived = unarrivedOf(s) - 1; |
529 |
< |
if (parties >= 0) { |
530 |
< |
if (unarrived > 0 || (unarrived == 0 && par != null)) { |
531 |
< |
if (casState |
532 |
< |
(s, |
533 |
< |
stateFor(phase, parties, unarrived))) { |
534 |
< |
if (unarrived == 0) { |
535 |
< |
par.arriveAndDeregister(); |
536 |
< |
reconcileState(); |
537 |
< |
} |
538 |
< |
break; |
539 |
< |
} |
540 |
< |
continue; |
541 |
< |
} |
542 |
< |
if (unarrived == 0) { |
543 |
< |
if (casState |
544 |
< |
(s, |
545 |
< |
trippedStateFor(onAdvance(phase, parties) ? -1 : |
546 |
< |
((phase + 1) & phaseMask), parties))) { |
547 |
< |
releaseWaiters(phase); |
548 |
< |
break; |
549 |
< |
} |
550 |
< |
continue; |
551 |
< |
} |
552 |
< |
if (par != null && phase != phaseOf(root.state)) { |
553 |
< |
reconcileState(); |
554 |
< |
continue; |
555 |
< |
} |
556 |
< |
} |
557 |
< |
throw new IllegalStateException(badBounds(parties, unarrived)); |
558 |
< |
} |
559 |
< |
return phase; |
543 |
> |
return doArrive(ONE_ARRIVAL|ONE_PARTY); |
544 |
|
} |
545 |
|
|
546 |
|
/** |
547 |
|
* Arrives at the barrier and awaits others. Equivalent in effect |
548 |
|
* to {@code awaitAdvance(arrive())}. If you need to await with |
549 |
|
* interruption or timeout, you can arrange this with an analogous |
550 |
< |
* construction using one of the other forms of the awaitAdvance |
551 |
< |
* method. If instead you need to deregister upon arrival use |
552 |
< |
* {@code arriveAndDeregister}. It is an unenforced usage error |
553 |
< |
* for an unregistered party to invoke this method. |
550 |
> |
* construction using one of the other forms of the {@code |
551 |
> |
* awaitAdvance} method. If instead you need to deregister upon |
552 |
> |
* arrival, use {@link #arriveAndDeregister}. It is an unenforced |
553 |
> |
* usage error for an unregistered party to invoke this method. |
554 |
|
* |
555 |
|
* @return the arrival phase number, or a negative number if terminated |
556 |
|
* @throws IllegalStateException if not terminated and the number |
564 |
|
* Awaits the phase of the barrier to advance from the given phase |
565 |
|
* value, returning immediately if the current phase of the |
566 |
|
* barrier is not equal to the given phase value or this barrier |
567 |
< |
* is terminated. It is an unenforced usage error for an |
584 |
< |
* unregistered party to invoke this method. |
567 |
> |
* is terminated. |
568 |
|
* |
569 |
|
* @param phase an arrival phase number, or negative value if |
570 |
|
* terminated; this argument is normally the value returned by a |
575 |
|
public int awaitAdvance(int phase) { |
576 |
|
if (phase < 0) |
577 |
|
return phase; |
578 |
< |
long s = getReconciledState(); |
596 |
< |
int p = phaseOf(s); |
578 |
> |
int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
579 |
|
if (p != phase) |
580 |
|
return p; |
581 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
600 |
< |
parent.awaitAdvance(phase); |
601 |
< |
// Fall here even if parent waited, to reconcile and help release |
602 |
< |
return untimedWait(phase); |
581 |
> |
return internalAwaitAdvance(phase, null); |
582 |
|
} |
583 |
|
|
584 |
|
/** |
586 |
|
* value, throwing {@code InterruptedException} if interrupted |
587 |
|
* while waiting, or returning immediately if the current phase of |
588 |
|
* the barrier is not equal to the given phase value or this |
589 |
< |
* barrier is terminated. It is an unenforced usage error for an |
611 |
< |
* unregistered party to invoke this method. |
589 |
> |
* barrier is terminated. |
590 |
|
* |
591 |
|
* @param phase an arrival phase number, or negative value if |
592 |
|
* terminated; this argument is normally the value returned by a |
599 |
|
throws InterruptedException { |
600 |
|
if (phase < 0) |
601 |
|
return phase; |
602 |
< |
long s = getReconciledState(); |
625 |
< |
int p = phaseOf(s); |
602 |
> |
int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
603 |
|
if (p != phase) |
604 |
|
return p; |
605 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
606 |
< |
parent.awaitAdvanceInterruptibly(phase); |
607 |
< |
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 |
|
/** |
616 |
|
* InterruptedException} if interrupted while waiting, or |
617 |
|
* returning immediately if the current phase of the barrier is |
618 |
|
* not equal to the given phase value or this barrier is |
619 |
< |
* terminated. It is an unenforced usage error for an |
640 |
< |
* unregistered party to invoke this method. |
619 |
> |
* terminated. |
620 |
|
* |
621 |
|
* @param phase an arrival phase number, or negative value if |
622 |
|
* terminated; this argument is normally the value returned by a |
633 |
|
public int awaitAdvanceInterruptibly(int phase, |
634 |
|
long timeout, TimeUnit unit) |
635 |
|
throws InterruptedException, TimeoutException { |
636 |
+ |
long nanos = unit.toNanos(timeout); |
637 |
|
if (phase < 0) |
638 |
|
return phase; |
639 |
< |
long s = getReconciledState(); |
660 |
< |
int p = phaseOf(s); |
639 |
> |
int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT); |
640 |
|
if (p != phase) |
641 |
|
return p; |
642 |
< |
if (unarrivedOf(s) == 0 && parent != null) |
643 |
< |
parent.awaitAdvanceInterruptibly(phase, timeout, unit); |
644 |
< |
return timedWait(phase, unit.toNanos(timeout)); |
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 |
|
/** |
657 |
|
* unexpected exceptions. |
658 |
|
*/ |
659 |
|
public void forceTermination() { |
660 |
< |
for (;;) { |
661 |
< |
long s = getReconciledState(); |
662 |
< |
int phase = phaseOf(s); |
663 |
< |
int parties = partiesOf(s); |
664 |
< |
int unarrived = unarrivedOf(s); |
665 |
< |
if (phase < 0 || |
666 |
< |
casState(s, stateFor(-1, parties, unarrived))) { |
683 |
< |
releaseWaiters(0); |
684 |
< |
releaseWaiters(1); |
685 |
< |
if (parent != null) |
686 |
< |
parent.forceTermination(); |
687 |
< |
return; |
688 |
< |
} |
689 |
< |
} |
660 |
> |
Phaser r = root; // force at root then reconcile |
661 |
> |
long s; |
662 |
> |
while ((s = r.state) >= 0) |
663 |
> |
UNSAFE.compareAndSwapLong(r, stateOffset, s, s | TERMINATION_PHASE); |
664 |
> |
reconcileState(); |
665 |
> |
releaseWaiters(0); // signal all threads |
666 |
> |
releaseWaiters(1); |
667 |
|
} |
668 |
|
|
669 |
|
/** |
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(state); |
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(state); |
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(state); |
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. (When called from within |
751 |
< |
* an implementation of {@code onAdvance} the values returned by |
752 |
< |
* methods such as {@code getPhase} may or may not reliably |
753 |
< |
* indicate the state to which this transition applies.) |
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. |
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 |
761 |
|
* termination for other reasons should also preserve this |
762 |
|
* property. |
763 |
|
* |
783 |
– |
* <p>You may override this method to perform an action with side |
784 |
– |
* effects visible to participating tasks, but it is only sensible |
785 |
– |
* to do so in designs where all parties register before any |
786 |
– |
* arrive, and all {@link #awaitAdvance} at each phase. |
787 |
– |
* Otherwise, you cannot ensure lack of interference from other |
788 |
– |
* parties during the invocation of this method. Additionally, |
789 |
– |
* method {@code onAdvance} may be invoked more than once per |
790 |
– |
* transition if registrations are intermixed with arrivals. |
791 |
– |
* |
764 |
|
* @param phase the phase number on entering the barrier |
765 |
|
* @param registeredParties the current number of registered parties |
766 |
|
* @return {@code true} if this barrier should terminate |
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 |
|
|
817 |
– |
// methods for waiting |
818 |
– |
|
819 |
– |
/** |
820 |
– |
* Wait nodes for Treiber stack representing wait queue |
821 |
– |
*/ |
822 |
– |
static final class QNode implements ForkJoinPool.ManagedBlocker { |
823 |
– |
final Phaser phaser; |
824 |
– |
final int phase; |
825 |
– |
final long startTime; |
826 |
– |
final long nanos; |
827 |
– |
final boolean timed; |
828 |
– |
final boolean interruptible; |
829 |
– |
volatile boolean wasInterrupted = false; |
830 |
– |
volatile Thread thread; // nulled to cancel wait |
831 |
– |
QNode next; |
832 |
– |
QNode(Phaser phaser, int phase, boolean interruptible, |
833 |
– |
boolean timed, long startTime, long nanos) { |
834 |
– |
this.phaser = phaser; |
835 |
– |
this.phase = phase; |
836 |
– |
this.timed = timed; |
837 |
– |
this.interruptible = interruptible; |
838 |
– |
this.startTime = startTime; |
839 |
– |
this.nanos = nanos; |
840 |
– |
thread = Thread.currentThread(); |
841 |
– |
} |
842 |
– |
public boolean isReleasable() { |
843 |
– |
return (thread == null || |
844 |
– |
phaser.getPhase() != phase || |
845 |
– |
(interruptible && wasInterrupted) || |
846 |
– |
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
847 |
– |
} |
848 |
– |
public boolean block() { |
849 |
– |
if (Thread.interrupted()) { |
850 |
– |
wasInterrupted = true; |
851 |
– |
if (interruptible) |
852 |
– |
return true; |
853 |
– |
} |
854 |
– |
if (!timed) |
855 |
– |
LockSupport.park(this); |
856 |
– |
else { |
857 |
– |
long waitTime = nanos - (System.nanoTime() - startTime); |
858 |
– |
if (waitTime <= 0) |
859 |
– |
return true; |
860 |
– |
LockSupport.parkNanos(this, waitTime); |
861 |
– |
} |
862 |
– |
return isReleasable(); |
863 |
– |
} |
864 |
– |
void signal() { |
865 |
– |
Thread t = thread; |
866 |
– |
if (t != null) { |
867 |
– |
thread = null; |
868 |
– |
LockSupport.unpark(t); |
869 |
– |
} |
870 |
– |
} |
871 |
– |
boolean doWait() { |
872 |
– |
if (thread != null) { |
873 |
– |
try { |
874 |
– |
ForkJoinPool.managedBlock(this); |
875 |
– |
} catch (InterruptedException ie) { |
876 |
– |
} |
877 |
– |
} |
878 |
– |
return wasInterrupted; |
879 |
– |
} |
880 |
– |
|
881 |
– |
} |
882 |
– |
|
789 |
|
/** |
790 |
< |
* 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 |
< |
* Enqueues node and waits unless aborted or signalled. |
823 |
< |
* |
824 |
< |
* @return current phase |
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 |
< |
private int untimedWait(int phase) { |
911 |
< |
QNode node = null; |
912 |
< |
boolean queued = false; |
913 |
< |
boolean interrupted = false; |
914 |
< |
int p; |
915 |
< |
while ((p = getPhase()) == phase) { |
916 |
< |
if (Thread.interrupted()) |
917 |
< |
interrupted = true; |
918 |
< |
else if (node == null) |
919 |
< |
node = new QNode(this, phase, false, false, 0, 0); |
920 |
< |
else if (!queued) |
921 |
< |
queued = tryEnqueue(node); |
922 |
< |
else |
923 |
< |
interrupted = node.doWait(); |
924 |
< |
} |
925 |
< |
if (node != null) |
926 |
< |
node.thread = null; |
927 |
< |
releaseWaiters(phase); |
928 |
< |
if (interrupted) |
929 |
< |
Thread.currentThread().interrupt(); |
930 |
< |
return p; |
931 |
< |
} |
833 |
> |
static final int SPINS_PER_ARRIVAL = NCPU < 2? 1 : 1 << 8; |
834 |
|
|
835 |
|
/** |
836 |
< |
* Interruptible version |
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 interruptibleWait(int phase) throws InterruptedException { |
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; |
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 && !interrupted) { |
852 |
< |
if (Thread.interrupted()) |
853 |
< |
interrupted = true; |
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, true, 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 |
870 |
< |
interrupted = node.doWait(); |
871 |
< |
} |
872 |
< |
if (node != null) |
873 |
< |
node.thread = null; |
874 |
< |
if (p != phase || (p = getPhase()) != phase) |
868 |
> |
queued = tryEnqueue(phase, node); |
869 |
> |
else { |
870 |
> |
try { |
871 |
> |
ForkJoinPool.managedBlock(node); |
872 |
> |
} catch (InterruptedException ie) { |
873 |
> |
node.wasInterrupted = true; |
874 |
> |
} |
875 |
> |
} |
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); |
956 |
– |
if (interrupted) |
957 |
– |
throw new InterruptedException(); |
887 |
|
return p; |
888 |
|
} |
889 |
|
|
890 |
|
/** |
891 |
< |
* Timeout version. |
963 |
< |
* @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 p; |
900 |
< |
while ((p = getPhase()) == phase && !interrupted) { |
901 |
< |
if (Thread.interrupted()) |
902 |
< |
interrupted = true; |
903 |
< |
else if (nanos - (System.nanoTime() - startTime) <= 0) |
904 |
< |
break; |
905 |
< |
else if (node == null) |
906 |
< |
node = new QNode(this, phase, true, true, startTime, nanos); |
907 |
< |
else if (!queued) |
908 |
< |
queued = tryEnqueue(node); |
909 |
< |
else |
910 |
< |
interrupted = node.doWait(); |
911 |
< |
} |
912 |
< |
if (node != null) |
913 |
< |
node.thread = null; |
914 |
< |
if (p != phase || (p = getPhase()) != phase) |
915 |
< |
releaseWaiters(phase); |
916 |
< |
if (interrupted) |
917 |
< |
throw new InterruptedException(); |
918 |
< |
if (p == phase) |
919 |
< |
throw new TimeoutException(); |
920 |
< |
return p; |
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 |
> |
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 |
964 |
|
private static final long stateOffset = |
965 |
|
objectFieldOffset("state", Phaser.class); |
966 |
|
|
1001 |
– |
private final boolean casState(long cmp, long val) { |
1002 |
– |
return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val); |
1003 |
– |
} |
1004 |
– |
|
967 |
|
private static long objectFieldOffset(String field, Class<?> klazz) { |
968 |
|
try { |
969 |
|
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |