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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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package jsr166y; |
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* </ul> |
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* |
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* <p> <b>Termination.</b> A phaser may enter a <em>termination</em> |
78 |
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* state in which all synchronization methods immediately return |
79 |
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* without updating phaser state or waiting for advance, and |
80 |
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* indicating (via a negative phase value) that execution is complete. |
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* state, that may be checked using method {@link #isTerminated}. Upon |
79 |
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* termination, all synchronization methods immediately return without |
80 |
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* waiting for advance, as indicated by a negative return value. |
81 |
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* Similarly, attempts to register upon termination have no effect. |
82 |
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* Termination is triggered when an invocation of {@code onAdvance} |
83 |
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* returns {@code true}. The default implementation returns {@code |
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* true} if a deregistration has caused the number of registered |
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* increase throughput even though it incurs greater per-operation |
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* overhead. |
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* |
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* <p>In a tree of tiered phasers, registration and deregistration of |
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* child phasers with their parent are managed automatically. |
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* Whenever the number of registered parties of a child phaser becomes |
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* non-zero (as established in the {@link #Phaser(Phaser,int)} |
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* constructor, {@link #register}, or {@link #bulkRegister}), the |
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* child phaser is registered with its parent. Whenever the number of |
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* registered parties becomes zero as the result of an invocation of |
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* {@link #arriveAndDeregister}, the child phaser is deregistered |
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* from its parent. |
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* |
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* <p><b>Monitoring.</b> While synchronization methods may be invoked |
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* only by registered parties, the current state of a phaser may be |
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* monitored by any caller. At any given moment there are {@link |
130 |
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* void runTasks(List<Runnable> tasks) { |
131 |
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* final Phaser phaser = new Phaser(1); // "1" to register self |
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* // create and start threads |
133 |
< |
* for (Runnable task : tasks) { |
133 |
> |
* for (final Runnable task : tasks) { |
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* phaser.register(); |
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* new Thread() { |
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* public void run() { |
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* }}</pre> |
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* |
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* |
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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 {@code Phaser} that |
200 |
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* it registers with upon construction: |
197 |
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* <p>To create a set of {@code n} tasks using a tree of phasers, you |
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* could use code of the following form, assuming a Task class with a |
199 |
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* constructor accepting a {@code Phaser} that it registers with upon |
200 |
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* construction. After invocation of {@code build(new Task[n], 0, n, |
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* new Phaser())}, these tasks could then be started, for example by |
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* submitting to a pool: |
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* |
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* <pre> {@code |
205 |
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* void build(Task[] actions, int lo, int hi, Phaser ph) { |
205 |
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* void build(Task[] tasks, int lo, int hi, Phaser ph) { |
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* if (hi - lo > TASKS_PER_PHASER) { |
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* for (int i = lo; i < hi; i += TASKS_PER_PHASER) { |
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* int j = Math.min(i + TASKS_PER_PHASER, hi); |
209 |
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* build(actions, i, j, new Phaser(ph)); |
209 |
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* build(tasks, i, j, new Phaser(ph)); |
210 |
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* } |
211 |
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* } else { |
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* for (int i = lo; i < hi; ++i) |
213 |
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* actions[i] = new Task(ph); |
213 |
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* tasks[i] = new Task(ph); |
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* // assumes new Task(ph) performs ph.register() |
215 |
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* } |
216 |
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* } |
204 |
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* // .. initially called, for n tasks via |
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* build(new Task[n], 0, n, new Phaser());}</pre> |
216 |
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* }}</pre> |
217 |
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* |
218 |
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* The best value of {@code TASKS_PER_PHASER} depends mainly on |
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* expected synchronization rates. A value as low as four may |
237 |
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*/ |
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|
239 |
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/** |
240 |
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* Primary state representation, holding four fields: |
240 |
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* Primary state representation, holding four bit-fields: |
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* |
242 |
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* * unarrived -- the number of parties yet to hit barrier (bits 0-15) |
243 |
< |
* * parties -- the number of parties to wait (bits 16-31) |
244 |
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* * phase -- the generation of the barrier (bits 32-62) |
245 |
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* * terminated -- set if barrier is terminated (bit 63 / sign) |
246 |
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* |
247 |
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* However, to efficiently maintain atomicity, these values are |
248 |
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* packed into a single (atomic) long. Termination uses the sign |
249 |
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* bit of 32 bit representation of phase, so phase is set to -1 on |
250 |
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* termination. Good performance relies on keeping state decoding |
251 |
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* and encoding simple, and keeping race windows short. |
242 |
> |
* unarrived -- the number of parties yet to hit barrier (bits 0-15) |
243 |
> |
* parties -- the number of parties to wait (bits 16-31) |
244 |
> |
* phase -- the generation of the barrier (bits 32-62) |
245 |
> |
* terminated -- set if barrier is terminated (bit 63 / sign) |
246 |
> |
* |
247 |
> |
* Except that a phaser with no registered parties is |
248 |
> |
* distinguished by the otherwise illegal state of having zero |
249 |
> |
* parties and one unarrived parties (encoded as EMPTY below). |
250 |
> |
* |
251 |
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* To efficiently maintain atomicity, these values are packed into |
252 |
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* a single (atomic) long. Good performance relies on keeping |
253 |
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* state decoding and encoding simple, and keeping race windows |
254 |
> |
* short. |
255 |
> |
* |
256 |
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* All state updates are performed via CAS except initial |
257 |
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* registration of a sub-phaser (i.e., one with a non-null |
258 |
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* parent). In this (relatively rare) case, we use built-in |
259 |
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* synchronization to lock while first registering with its |
260 |
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* parent. |
261 |
> |
* |
262 |
> |
* The phase of a subphaser is allowed to lag that of its |
263 |
> |
* ancestors until it is actually accessed -- see method |
264 |
> |
* reconcileState. |
265 |
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*/ |
266 |
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private volatile long state; |
267 |
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|
268 |
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private static final int MAX_PARTIES = 0xffff; |
269 |
< |
private static final int MAX_PHASE = 0x7fffffff; |
269 |
> |
private static final int MAX_PHASE = Integer.MAX_VALUE; |
270 |
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private static final int PARTIES_SHIFT = 16; |
271 |
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private static final int PHASE_SHIFT = 32; |
272 |
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private static final int UNARRIVED_MASK = 0xffff; // to mask ints |
273 |
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private static final long PARTIES_MASK = 0xffff0000L; // to mask longs |
250 |
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private static final long ONE_ARRIVAL = 1L; |
251 |
– |
private static final long ONE_PARTY = 1L << PARTIES_SHIFT; |
274 |
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private static final long TERMINATION_BIT = 1L << 63; |
275 |
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|
276 |
+ |
// some special values |
277 |
+ |
private static final int ONE_ARRIVAL = 1; |
278 |
+ |
private static final int ONE_PARTY = 1 << PARTIES_SHIFT; |
279 |
+ |
private static final int EMPTY = 1; |
280 |
+ |
|
281 |
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// The following unpacking methods are usually manually inlined |
282 |
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|
283 |
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private static int unarrivedOf(long s) { |
284 |
< |
return (int)s & UNARRIVED_MASK; |
284 |
> |
int counts = (int)s; |
285 |
> |
return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK; |
286 |
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} |
287 |
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|
288 |
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private static int partiesOf(long s) { |
290 |
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} |
291 |
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|
292 |
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private static int phaseOf(long s) { |
293 |
< |
return (int) (s >>> PHASE_SHIFT); |
293 |
> |
return (int)(s >>> PHASE_SHIFT); |
294 |
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} |
295 |
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|
296 |
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private static int arrivedOf(long s) { |
297 |
< |
return partiesOf(s) - unarrivedOf(s); |
297 |
> |
int counts = (int)s; |
298 |
> |
return (counts == EMPTY) ? 0 : |
299 |
> |
(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK); |
300 |
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} |
301 |
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|
302 |
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/** |
305 |
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private final Phaser parent; |
306 |
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|
307 |
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/** |
308 |
< |
* The root of phaser tree. Equals this if not in a tree. Used to |
279 |
< |
* support faster state push-down. |
308 |
> |
* The root of phaser tree. Equals this if not in a tree. |
309 |
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*/ |
310 |
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private final Phaser root; |
311 |
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|
343 |
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* Manually tuned to speed up and minimize race windows for the |
344 |
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* common case of just decrementing unarrived field. |
345 |
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* |
346 |
< |
* @param adj - adjustment to apply to state -- either |
318 |
< |
* ONE_ARRIVAL (for arrive) or |
319 |
< |
* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister) |
346 |
> |
* @param deregister false for arrive, true for arriveAndDeregister |
347 |
|
*/ |
348 |
< |
private int doArrive(long adj) { |
348 |
> |
private int doArrive(boolean deregister) { |
349 |
> |
int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL; |
350 |
> |
final Phaser root = this.root; |
351 |
|
for (;;) { |
352 |
< |
long s = state; |
324 |
< |
int unarrived = (int)s & UNARRIVED_MASK; |
352 |
> |
long s = (root == this) ? state : reconcileState(); |
353 |
|
int phase = (int)(s >>> PHASE_SHIFT); |
354 |
+ |
int counts = (int)s; |
355 |
+ |
int unarrived = (counts & UNARRIVED_MASK) - 1; |
356 |
|
if (phase < 0) |
357 |
|
return phase; |
358 |
< |
else if (unarrived == 0) { |
359 |
< |
if (reconcileState() == s) // recheck |
358 |
> |
else if (counts == EMPTY || unarrived < 0) { |
359 |
> |
if (root == this || reconcileState() == s) |
360 |
|
throw new IllegalStateException(badArrive(s)); |
361 |
|
} |
362 |
|
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
363 |
< |
if (unarrived == 1) { |
364 |
< |
long p = s & PARTIES_MASK; // unshifted parties field |
365 |
< |
long lu = p >>> PARTIES_SHIFT; |
366 |
< |
int u = (int)lu; |
367 |
< |
int nextPhase = (phase + 1) & MAX_PHASE; |
368 |
< |
long next = ((long)nextPhase << PHASE_SHIFT) | p | lu; |
369 |
< |
final Phaser parent = this.parent; |
370 |
< |
if (parent == null) { |
371 |
< |
if (onAdvance(phase, u)) |
372 |
< |
next |= TERMINATION_BIT; |
373 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
374 |
< |
releaseWaiters(phase); |
363 |
> |
long n = s & PARTIES_MASK; // base of next state |
364 |
> |
int nextUnarrived = (int)n >>> PARTIES_SHIFT; |
365 |
> |
if (unarrived == 0) { |
366 |
> |
if (root == this) { |
367 |
> |
if (onAdvance(phase, nextUnarrived)) |
368 |
> |
n |= TERMINATION_BIT; |
369 |
> |
else if (nextUnarrived == 0) |
370 |
> |
n |= EMPTY; |
371 |
> |
else |
372 |
> |
n |= nextUnarrived; |
373 |
> |
n |= (long)((phase + 1) & MAX_PHASE) << PHASE_SHIFT; |
374 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, s, n); |
375 |
|
} |
376 |
< |
else { |
377 |
< |
parent.doArrive((u == 0) ? |
378 |
< |
ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL); |
379 |
< |
if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase) |
350 |
< |
reconcileState(); |
351 |
< |
else if (state == s) |
352 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, |
353 |
< |
next); |
376 |
> |
else if (nextUnarrived == 0) { // propagate deregistration |
377 |
> |
phase = parent.doArrive(true); |
378 |
> |
UNSAFE.compareAndSwapLong(this, stateOffset, |
379 |
> |
s, s | EMPTY); |
380 |
|
} |
381 |
+ |
else |
382 |
+ |
phase = parent.doArrive(false); |
383 |
+ |
releaseWaiters(phase); |
384 |
|
} |
385 |
|
return phase; |
386 |
|
} |
397 |
|
// adjustment to state |
398 |
|
long adj = ((long)registrations << PARTIES_SHIFT) | registrations; |
399 |
|
final Phaser parent = this.parent; |
400 |
+ |
int phase; |
401 |
|
for (;;) { |
402 |
|
long s = (parent == null) ? state : reconcileState(); |
403 |
< |
int parties = (int)s >>> PARTIES_SHIFT; |
404 |
< |
int phase = (int)(s >>> PHASE_SHIFT); |
405 |
< |
if (phase < 0) |
406 |
< |
return phase; |
377 |
< |
else if (registrations > MAX_PARTIES - parties) |
403 |
> |
int counts = (int)s; |
404 |
> |
int parties = counts >>> PARTIES_SHIFT; |
405 |
> |
int unarrived = counts & UNARRIVED_MASK; |
406 |
> |
if (registrations > MAX_PARTIES - parties) |
407 |
|
throw new IllegalStateException(badRegister(s)); |
408 |
< |
else if ((parties == 0 && parent == null) || // first reg of root |
409 |
< |
((int)s & UNARRIVED_MASK) != 0) { // not advancing |
410 |
< |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj)) |
411 |
< |
return phase; |
408 |
> |
else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0) |
409 |
> |
break; |
410 |
> |
else if (counts != EMPTY) { // not 1st registration |
411 |
> |
if (parent == null || reconcileState() == s) { |
412 |
> |
if (unarrived == 0) // wait out advance |
413 |
> |
root.internalAwaitAdvance(phase, null); |
414 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, |
415 |
> |
s, s + adj)) |
416 |
> |
break; |
417 |
> |
} |
418 |
> |
} |
419 |
> |
else if (parent == null) { // 1st root registration |
420 |
> |
long next = ((long)phase << PHASE_SHIFT) | adj; |
421 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
422 |
> |
break; |
423 |
|
} |
424 |
< |
else if (parties != 0) // wait for onAdvance |
425 |
< |
root.internalAwaitAdvance(phase, null); |
426 |
< |
else { // 1st registration of child |
427 |
< |
synchronized (this) { // register parent first |
428 |
< |
if (reconcileState() == s) { // recheck under lock |
429 |
< |
parent.doRegister(1); // OK if throws IllegalState |
430 |
< |
for (;;) { // simpler form of outer loop |
431 |
< |
s = reconcileState(); |
432 |
< |
phase = (int)(s >>> PHASE_SHIFT); |
433 |
< |
if (phase < 0 || |
434 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, |
395 |
< |
s, s + adj)) |
396 |
< |
return phase; |
397 |
< |
} |
424 |
> |
else { |
425 |
> |
synchronized (this) { // 1st sub registration |
426 |
> |
if (state == s) { // recheck under lock |
427 |
> |
parent.doRegister(1); |
428 |
> |
do { // force current phase |
429 |
> |
phase = (int)(root.state >>> PHASE_SHIFT); |
430 |
> |
// assert phase < 0 || (int)state == EMPTY; |
431 |
> |
} while (!UNSAFE.compareAndSwapLong |
432 |
> |
(this, stateOffset, state, |
433 |
> |
((long)phase << PHASE_SHIFT) | adj)); |
434 |
> |
break; |
435 |
|
} |
436 |
|
} |
437 |
|
} |
438 |
|
} |
439 |
+ |
return phase; |
440 |
|
} |
441 |
|
|
442 |
|
/** |
443 |
< |
* Recursively resolves lagged phase propagation from root if necessary. |
443 |
> |
* Resolves lagged phase propagation from root if necessary. |
444 |
> |
* Reconciliation normally occurs when root has advanced but |
445 |
> |
* subphasers have not yet done so, in which case they must finish |
446 |
> |
* their own advance by setting unarrived to parties (or if |
447 |
> |
* parties is zero, resetting to unregistered EMPTY state). |
448 |
> |
* However, this method may also be called when "floating" |
449 |
> |
* subphasers with possibly some unarrived parties are merely |
450 |
> |
* catching up to current phase, in which case counts are |
451 |
> |
* unaffected. |
452 |
> |
* |
453 |
> |
* @return reconciled state |
454 |
|
*/ |
455 |
|
private long reconcileState() { |
456 |
< |
Phaser par = parent; |
456 |
> |
final Phaser root = this.root; |
457 |
|
long s = state; |
458 |
< |
if (par != null) { |
459 |
< |
Phaser rt = root; |
460 |
< |
int phase, rPhase; |
461 |
< |
while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 && |
462 |
< |
(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) { |
463 |
< |
if (par != rt && (int)(par.state >>> PHASE_SHIFT) != rPhase) |
464 |
< |
par.reconcileState(); |
465 |
< |
else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) { |
466 |
< |
long u = s & PARTIES_MASK; // reset unarrived to parties |
467 |
< |
long next = ((((long) rPhase) << PHASE_SHIFT) | u | |
468 |
< |
(u >>> PARTIES_SHIFT)); |
469 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, next); |
422 |
< |
} |
458 |
> |
if (root != this) { |
459 |
> |
int phase, u, p; |
460 |
> |
// CAS root phase with current parties; possibly trip unarrived |
461 |
> |
while ((phase = (int)(root.state >>> PHASE_SHIFT)) != |
462 |
> |
(int)(s >>> PHASE_SHIFT) && |
463 |
> |
!UNSAFE.compareAndSwapLong |
464 |
> |
(this, stateOffset, s, |
465 |
> |
s = (((long)phase << PHASE_SHIFT) | |
466 |
> |
(s & PARTIES_MASK) | |
467 |
> |
((p = (int)s >>> PARTIES_SHIFT) == 0 ? EMPTY : |
468 |
> |
((u = (int)s & UNARRIVED_MASK) == 0 && phase >= 0) ? |
469 |
> |
p : u)))) |
470 |
|
s = state; |
424 |
– |
} |
471 |
|
} |
472 |
|
return s; |
473 |
|
} |
505 |
|
|
506 |
|
/** |
507 |
|
* Creates a new phaser with the given parent and number of |
508 |
< |
* registered unarrived parties. Registration and deregistration |
509 |
< |
* of this child phaser with its parent are managed automatically. |
510 |
< |
* If the given parent is non-null, whenever this child phaser has |
465 |
< |
* any registered parties (as established in this constructor, |
466 |
< |
* {@link #register}, or {@link #bulkRegister}), this child phaser |
467 |
< |
* is registered with its parent. Whenever the number of |
468 |
< |
* registered parties becomes zero as the result of an invocation |
469 |
< |
* of {@link #arriveAndDeregister}, this child phaser is |
470 |
< |
* deregistered from its parent. |
508 |
> |
* registered unarrived parties. When the given parent is non-null |
509 |
> |
* and the given number of parties is greater than zero, this |
510 |
> |
* child phaser is registered with its parent. |
511 |
|
* |
512 |
|
* @param parent the parent phaser |
513 |
|
* @param parties the number of parties required to advance to the |
518 |
|
public Phaser(Phaser parent, int parties) { |
519 |
|
if (parties >>> PARTIES_SHIFT != 0) |
520 |
|
throw new IllegalArgumentException("Illegal number of parties"); |
521 |
< |
long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT); |
521 |
> |
int phase = 0; |
522 |
|
this.parent = parent; |
523 |
|
if (parent != null) { |
524 |
< |
Phaser r = parent.root; |
525 |
< |
this.root = r; |
526 |
< |
this.evenQ = r.evenQ; |
527 |
< |
this.oddQ = r.oddQ; |
524 |
> |
final Phaser root = parent.root; |
525 |
> |
this.root = root; |
526 |
> |
this.evenQ = root.evenQ; |
527 |
> |
this.oddQ = root.oddQ; |
528 |
|
if (parties != 0) |
529 |
< |
s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT; |
529 |
> |
phase = parent.doRegister(1); |
530 |
|
} |
531 |
|
else { |
532 |
|
this.root = this; |
533 |
|
this.evenQ = new AtomicReference<QNode>(); |
534 |
|
this.oddQ = new AtomicReference<QNode>(); |
535 |
|
} |
536 |
< |
this.state = s; |
536 |
> |
this.state = (parties == 0) ? (long)EMPTY : |
537 |
> |
((long)phase << PHASE_SHIFT) | |
538 |
> |
((long)parties << PARTIES_SHIFT) | |
539 |
> |
((long)parties); |
540 |
|
} |
541 |
|
|
542 |
|
/** |
544 |
|
* invocation of {@link #onAdvance} is in progress, this method |
545 |
|
* may await its completion before returning. If this phaser has |
546 |
|
* a parent, and this phaser previously had no registered parties, |
547 |
< |
* this phaser is also registered with its parent. |
548 |
< |
* |
549 |
< |
* @return the arrival phase number to which this registration applied |
547 |
> |
* this child phaser is also registered with its parent. If |
548 |
> |
* this phaser is terminated, the attempt to register has |
549 |
> |
* no effect, and a negative value is returned. |
550 |
> |
* |
551 |
> |
* @return the arrival phase number to which this registration |
552 |
> |
* applied. If this value is negative, then this phaser has |
553 |
> |
* terminated, in which case registration has no effect. |
554 |
|
* @throws IllegalStateException if attempting to register more |
555 |
|
* than the maximum supported number of parties |
556 |
|
*/ |
562 |
|
* Adds the given number of new unarrived parties to this phaser. |
563 |
|
* If an ongoing invocation of {@link #onAdvance} is in progress, |
564 |
|
* this method may await its completion before returning. If this |
565 |
< |
* phaser has a parent, and the given number of parities is |
566 |
< |
* greater than zero, and this phaser previously had no registered |
567 |
< |
* parties, this phaser is also registered with its parent. |
565 |
> |
* phaser has a parent, and the given number of parties is greater |
566 |
> |
* than zero, and this phaser previously had no registered |
567 |
> |
* parties, this child phaser is also registered with its parent. |
568 |
> |
* If this phaser is terminated, the attempt to register has no |
569 |
> |
* effect, and a negative value is returned. |
570 |
|
* |
571 |
|
* @param parties the number of additional parties required to |
572 |
|
* advance to the next phase |
573 |
< |
* @return the arrival phase number to which this registration applied |
573 |
> |
* @return the arrival phase number to which this registration |
574 |
> |
* applied. If this value is negative, then this phaser has |
575 |
> |
* terminated, in which case registration has no effect. |
576 |
|
* @throws IllegalStateException if attempting to register more |
577 |
|
* than the maximum supported number of parties |
578 |
|
* @throws IllegalArgumentException if {@code parties < 0} |
598 |
|
* of unarrived parties would become negative |
599 |
|
*/ |
600 |
|
public int arrive() { |
601 |
< |
return doArrive(ONE_ARRIVAL); |
601 |
> |
return doArrive(false); |
602 |
|
} |
603 |
|
|
604 |
|
/** |
618 |
|
* of registered or unarrived parties would become negative |
619 |
|
*/ |
620 |
|
public int arriveAndDeregister() { |
621 |
< |
return doArrive(ONE_ARRIVAL|ONE_PARTY); |
621 |
> |
return doArrive(true); |
622 |
|
} |
623 |
|
|
624 |
|
/** |
634 |
|
* IllegalStateException} only upon some subsequent operation on |
635 |
|
* this phaser, if ever. |
636 |
|
* |
637 |
< |
* @return the arrival phase number, or a negative number if terminated |
637 |
> |
* @return the arrival phase number, or the (negative) |
638 |
> |
* {@linkplain #getPhase() current phase} if terminated |
639 |
|
* @throws IllegalStateException if not terminated and the number |
640 |
|
* of unarrived parties would become negative |
641 |
|
*/ |
642 |
|
public int arriveAndAwaitAdvance() { |
643 |
< |
return awaitAdvance(doArrive(ONE_ARRIVAL)); |
643 |
> |
// Specialization of doArrive+awaitAdvance eliminating some reads/paths |
644 |
> |
final Phaser root = this.root; |
645 |
> |
for (;;) { |
646 |
> |
long s = (root == this) ? state : reconcileState(); |
647 |
> |
int phase = (int)(s >>> PHASE_SHIFT); |
648 |
> |
int counts = (int)s; |
649 |
> |
int unarrived = (counts & UNARRIVED_MASK) - 1; |
650 |
> |
if (phase < 0) |
651 |
> |
return phase; |
652 |
> |
else if (counts == EMPTY || unarrived < 0) { |
653 |
> |
if (reconcileState() == s) |
654 |
> |
throw new IllegalStateException(badArrive(s)); |
655 |
> |
} |
656 |
> |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, |
657 |
> |
s -= ONE_ARRIVAL)) { |
658 |
> |
if (unarrived != 0) |
659 |
> |
return root.internalAwaitAdvance(phase, null); |
660 |
> |
if (root != this) |
661 |
> |
return parent.arriveAndAwaitAdvance(); |
662 |
> |
long n = s & PARTIES_MASK; // base of next state |
663 |
> |
int nextUnarrived = (int)n >>> PARTIES_SHIFT; |
664 |
> |
if (onAdvance(phase, nextUnarrived)) |
665 |
> |
n |= TERMINATION_BIT; |
666 |
> |
else if (nextUnarrived == 0) |
667 |
> |
n |= EMPTY; |
668 |
> |
else |
669 |
> |
n |= nextUnarrived; |
670 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
671 |
> |
n |= (long)nextPhase << PHASE_SHIFT; |
672 |
> |
if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n)) |
673 |
> |
return (int)(state >>> PHASE_SHIFT); // terminated |
674 |
> |
releaseWaiters(phase); |
675 |
> |
return nextPhase; |
676 |
> |
} |
677 |
> |
} |
678 |
|
} |
679 |
|
|
680 |
|
/** |
685 |
|
* @param phase an arrival phase number, or negative value if |
686 |
|
* terminated; this argument is normally the value returned by a |
687 |
|
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
688 |
< |
* @return the next arrival phase number, or a negative value |
689 |
< |
* if terminated or argument is negative |
688 |
> |
* @return the next arrival phase number, or the argument if it is |
689 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
690 |
> |
* if terminated |
691 |
|
*/ |
692 |
|
public int awaitAdvance(int phase) { |
693 |
< |
Phaser rt; |
694 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
693 |
> |
final Phaser root = this.root; |
694 |
> |
long s = (root == this) ? state : reconcileState(); |
695 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
696 |
|
if (phase < 0) |
697 |
|
return phase; |
698 |
< |
if (p == phase && |
699 |
< |
(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) |
612 |
< |
return rt.internalAwaitAdvance(phase, null); |
698 |
> |
if (p == phase) |
699 |
> |
return root.internalAwaitAdvance(phase, null); |
700 |
|
return p; |
701 |
|
} |
702 |
|
|
710 |
|
* @param phase an arrival phase number, or negative value if |
711 |
|
* terminated; this argument is normally the value returned by a |
712 |
|
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
713 |
< |
* @return the next arrival phase number, or a negative value |
714 |
< |
* if terminated or argument is negative |
713 |
> |
* @return the next arrival phase number, or the argument if it is |
714 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
715 |
> |
* if terminated |
716 |
|
* @throws InterruptedException if thread interrupted while waiting |
717 |
|
*/ |
718 |
|
public int awaitAdvanceInterruptibly(int phase) |
719 |
|
throws InterruptedException { |
720 |
< |
Phaser rt; |
721 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
720 |
> |
final Phaser root = this.root; |
721 |
> |
long s = (root == this) ? state : reconcileState(); |
722 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
723 |
|
if (phase < 0) |
724 |
|
return phase; |
725 |
< |
if (p == phase && |
637 |
< |
(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) { |
725 |
> |
if (p == phase) { |
726 |
|
QNode node = new QNode(this, phase, true, false, 0L); |
727 |
< |
p = rt.internalAwaitAdvance(phase, node); |
727 |
> |
p = root.internalAwaitAdvance(phase, node); |
728 |
|
if (node.wasInterrupted) |
729 |
|
throw new InterruptedException(); |
730 |
|
} |
745 |
|
* {@code unit} |
746 |
|
* @param unit a {@code TimeUnit} determining how to interpret the |
747 |
|
* {@code timeout} parameter |
748 |
< |
* @return the next arrival phase number, or a negative value |
749 |
< |
* if terminated or argument is negative |
748 |
> |
* @return the next arrival phase number, or the argument if it is |
749 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
750 |
> |
* if terminated |
751 |
|
* @throws InterruptedException if thread interrupted while waiting |
752 |
|
* @throws TimeoutException if timed out while waiting |
753 |
|
*/ |
755 |
|
long timeout, TimeUnit unit) |
756 |
|
throws InterruptedException, TimeoutException { |
757 |
|
long nanos = unit.toNanos(timeout); |
758 |
< |
Phaser rt; |
759 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
758 |
> |
final Phaser root = this.root; |
759 |
> |
long s = (root == this) ? state : reconcileState(); |
760 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
761 |
|
if (phase < 0) |
762 |
|
return phase; |
763 |
< |
if (p == phase && |
674 |
< |
(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) { |
763 |
> |
if (p == phase) { |
764 |
|
QNode node = new QNode(this, phase, true, true, nanos); |
765 |
< |
p = rt.internalAwaitAdvance(phase, node); |
765 |
> |
p = root.internalAwaitAdvance(phase, node); |
766 |
|
if (node.wasInterrupted) |
767 |
|
throw new InterruptedException(); |
768 |
|
else if (p == phase) |
773 |
|
|
774 |
|
/** |
775 |
|
* Forces this phaser to enter termination state. Counts of |
776 |
< |
* arrived and registered parties are unaffected. If this phaser |
777 |
< |
* is a member of a tiered set of phasers, then all of the phasers |
778 |
< |
* in the set are terminated. If this phaser is already |
779 |
< |
* terminated, this method has no effect. This method may be |
780 |
< |
* useful for coordinating recovery after one or more tasks |
781 |
< |
* encounter unexpected exceptions. |
776 |
> |
* registered parties are unaffected. If this phaser is a member |
777 |
> |
* of a tiered set of phasers, then all of the phasers in the set |
778 |
> |
* are terminated. If this phaser is already terminated, this |
779 |
> |
* method has no effect. This method may be useful for |
780 |
> |
* coordinating recovery after one or more tasks encounter |
781 |
> |
* unexpected exceptions. |
782 |
|
*/ |
783 |
|
public void forceTermination() { |
784 |
|
// Only need to change root state |
787 |
|
while ((s = root.state) >= 0) { |
788 |
|
if (UNSAFE.compareAndSwapLong(root, stateOffset, |
789 |
|
s, s | TERMINATION_BIT)) { |
790 |
< |
releaseWaiters(0); // signal all threads |
790 |
> |
// signal all threads |
791 |
> |
releaseWaiters(0); |
792 |
|
releaseWaiters(1); |
793 |
|
return; |
794 |
|
} |
819 |
|
|
820 |
|
/** |
821 |
|
* Returns the number of registered parties that have arrived at |
822 |
< |
* the current phase of this phaser. |
822 |
> |
* the current phase of this phaser. If this phaser has terminated, |
823 |
> |
* the returned value is meaningless and arbitrary. |
824 |
|
* |
825 |
|
* @return the number of arrived parties |
826 |
|
*/ |
827 |
|
public int getArrivedParties() { |
828 |
< |
long s = state; |
738 |
< |
int u = unarrivedOf(s); // only reconcile if possibly needed |
739 |
< |
return (u != 0 || parent == null) ? |
740 |
< |
partiesOf(s) - u : |
741 |
< |
arrivedOf(reconcileState()); |
828 |
> |
return arrivedOf(reconcileState()); |
829 |
|
} |
830 |
|
|
831 |
|
/** |
832 |
|
* Returns the number of registered parties that have not yet |
833 |
< |
* arrived at the current phase of this phaser. |
833 |
> |
* arrived at the current phase of this phaser. If this phaser has |
834 |
> |
* terminated, the returned value is meaningless and arbitrary. |
835 |
|
* |
836 |
|
* @return the number of unarrived parties |
837 |
|
*/ |
838 |
|
public int getUnarrivedParties() { |
839 |
< |
int u = unarrivedOf(state); |
752 |
< |
return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState()); |
839 |
> |
return unarrivedOf(reconcileState()); |
840 |
|
} |
841 |
|
|
842 |
|
/** |
872 |
|
* advance, and to control termination. This method is invoked |
873 |
|
* upon arrival of the party advancing this phaser (when all other |
874 |
|
* waiting parties are dormant). If this method returns {@code |
875 |
< |
* true}, then, rather than advance the phase number, this phaser |
876 |
< |
* will be set to a final termination state, and subsequent calls |
877 |
< |
* to {@link #isTerminated} will return true. Any (unchecked) |
878 |
< |
* Exception or Error thrown by an invocation of this method is |
879 |
< |
* propagated to the party attempting to advance this phaser, in |
880 |
< |
* which case no advance occurs. |
875 |
> |
* true}, this phaser will be set to a final termination state |
876 |
> |
* upon advance, and subsequent calls to {@link #isTerminated} |
877 |
> |
* will return true. Any (unchecked) Exception or Error thrown by |
878 |
> |
* an invocation of this method is propagated to the party |
879 |
> |
* attempting to advance this phaser, in which case no advance |
880 |
> |
* occurs. |
881 |
|
* |
882 |
|
* <p>The arguments to this method provide the state of the phaser |
883 |
|
* prevailing for the current transition. The effects of invoking |
941 |
|
*/ |
942 |
|
private void releaseWaiters(int phase) { |
943 |
|
QNode q; // first element of queue |
857 |
– |
int p; // its phase |
944 |
|
Thread t; // its thread |
945 |
|
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
946 |
|
while ((q = head.get()) != null && |
947 |
< |
((p = q.phase) == phase || |
862 |
< |
(int)(root.state >>> PHASE_SHIFT) != p)) { |
947 |
> |
q.phase != (int)(root.state >>> PHASE_SHIFT)) { |
948 |
|
if (head.compareAndSet(q, q.next) && |
949 |
|
(t = q.thread) != null) { |
950 |
|
q.thread = null; |
953 |
|
} |
954 |
|
} |
955 |
|
|
956 |
+ |
/** |
957 |
+ |
* Variant of releaseWaiters that additionally tries to remove any |
958 |
+ |
* nodes no longer waiting for advance due to timeout or |
959 |
+ |
* interrupt. Currently, nodes are removed only if they are at |
960 |
+ |
* head of queue, which suffices to reduce memory footprint in |
961 |
+ |
* most usages. |
962 |
+ |
* |
963 |
+ |
* @return current phase on exit |
964 |
+ |
*/ |
965 |
+ |
private int abortWait(int phase) { |
966 |
+ |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
967 |
+ |
for (;;) { |
968 |
+ |
Thread t; |
969 |
+ |
QNode q = head.get(); |
970 |
+ |
int p = (int)(root.state >>> PHASE_SHIFT); |
971 |
+ |
if (q == null || ((t = q.thread) != null && q.phase == p)) |
972 |
+ |
return p; |
973 |
+ |
if (head.compareAndSet(q, q.next) && t != null) { |
974 |
+ |
q.thread = null; |
975 |
+ |
LockSupport.unpark(t); |
976 |
+ |
} |
977 |
+ |
} |
978 |
+ |
} |
979 |
+ |
|
980 |
|
/** The number of CPUs, for spin control */ |
981 |
|
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
982 |
|
|
1044 |
|
node.thread = null; // avoid need for unpark() |
1045 |
|
if (node.wasInterrupted && !node.interruptible) |
1046 |
|
Thread.currentThread().interrupt(); |
1047 |
< |
if ((p = (int)(state >>> PHASE_SHIFT)) == phase) |
1048 |
< |
return p; // recheck abort |
1047 |
> |
if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase) |
1048 |
> |
return abortWait(phase); // possibly clean up on abort |
1049 |
|
} |
1050 |
|
releaseWaiters(phase); |
1051 |
|
return p; |
1072 |
|
this.interruptible = interruptible; |
1073 |
|
this.nanos = nanos; |
1074 |
|
this.timed = timed; |
1075 |
< |
this.lastTime = timed? System.nanoTime() : 0L; |
1075 |
> |
this.lastTime = timed ? System.nanoTime() : 0L; |
1076 |
|
thread = Thread.currentThread(); |
1077 |
|
} |
1078 |
|
|
1116 |
|
|
1117 |
|
// Unsafe mechanics |
1118 |
|
|
1119 |
< |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
1120 |
< |
private static final long stateOffset = |
1121 |
< |
objectFieldOffset("state", Phaser.class); |
1013 |
< |
|
1014 |
< |
private static long objectFieldOffset(String field, Class<?> klazz) { |
1119 |
> |
private static final sun.misc.Unsafe UNSAFE; |
1120 |
> |
private static final long stateOffset; |
1121 |
> |
static { |
1122 |
|
try { |
1123 |
< |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
1124 |
< |
} catch (NoSuchFieldException e) { |
1125 |
< |
// Convert Exception to corresponding Error |
1126 |
< |
NoSuchFieldError error = new NoSuchFieldError(field); |
1127 |
< |
error.initCause(e); |
1128 |
< |
throw error; |
1123 |
> |
UNSAFE = getUnsafe(); |
1124 |
> |
Class<?> k = Phaser.class; |
1125 |
> |
stateOffset = UNSAFE.objectFieldOffset |
1126 |
> |
(k.getDeclaredField("state")); |
1127 |
> |
} catch (Exception e) { |
1128 |
> |
throw new Error(e); |
1129 |
|
} |
1130 |
|
} |
1131 |
|
|