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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.36 by dl, Sun Aug 23 20:12:24 2009 UTC vs.
Revision 1.64 by jsr166, Mon Nov 29 20:58:06 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	<	import java.util.concurrent.*;
10	<
9	>	import java.util.concurrent.TimeUnit;
10	>	import java.util.concurrent.TimeoutException;
11		import java.util.concurrent.atomic.AtomicReference;
12		import java.util.concurrent.locks.LockSupport;
13
14		/**
15	<	* A reusable synchronization barrier, similar in functionality to a
15	>	* A reusable synchronization barrier, similar in functionality to
16		* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and
17		* {@link java.util.concurrent.CountDownLatch CountDownLatch}
18		* but supporting more flexible usage.
19		*
20	<	* <ul>
21	<	*
22	<	* <li> The number of parties <em>registered</em> to synchronize on a
23	<	* phaser may vary over time.  Tasks may be registered at any time
24	<	* (using methods {@link #register}, {@link #bulkRegister}, or forms
25	<	* of constructors establishing initial numbers of parties), and may
26	<	* optionally be deregistered upon any arrival (using {@link
20	>	* <p> <b>Registration.</b> Unlike the case for other barriers, the
21	>	* number of parties <em>registered</em> to synchronize on a phaser
22	>	* may vary over time.  Tasks may be registered at any time (using
23	>	* methods {@link #register}, {@link #bulkRegister}, or forms of
24	>	* constructors establishing initial numbers of parties), and
25	>	* optionally deregistered upon any arrival (using {@link
26		* #arriveAndDeregister}).  As is the case with most basic
27		* synchronization constructs, registration and deregistration affect
28		* only internal counts; they do not establish any further internal
29	<	* bookkeeping, so tasks cannot query whether they are
30	<	* registered. (However, you can introduce such bookkeeping by
31	<	* subclassing this class.)
32	<	*
33	<	* <li> Each generation has an associated phase number. The phase
34	<	* number starts at zero, amd advances when all parties arrive at the
35	<	* barrier, wrapping around to zero after reaching {@code
36	<	* Integer.MAX_VALUE}.
37	<	*
38	<	* <li> Like a {@code CyclicBarrier}, a phaser may be repeatedly
39	<	* awaited.  Method {@link #arriveAndAwaitAdvance} has effect
40	<	* analogous to {@link java.util.concurrent.CyclicBarrier#await
41	<	* CyclicBarrier.await}.  However, phasers separate two aspects of
42	<	* coordination, which may also be invoked independently:
29	>	* bookkeeping, so tasks cannot query whether they are registered.
30	>	* (However, you can introduce such bookkeeping by subclassing this
31	>	* class.)
32	>	*
33	>	* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
34	>	* Phaser} may be repeatedly awaited.  Method {@link
35	>	* #arriveAndAwaitAdvance} has effect analogous to {@link
36	>	* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
37	>	* generation of a phaser has an associated phase number. The phase
38	>	* number starts at zero, and advances when all parties arrive at the
39	>	* phaser, wrapping around to zero after reaching {@code
40	>	* Integer.MAX_VALUE}. The use of phase numbers enables independent
41	>	* control of actions upon arrival at a phaser and upon awaiting
42	>	* others, via two kinds of methods that may be invoked by any
43	>	* registered party:
44		*
45		* <ul>
46		*
47	<	*   <li> Arriving at a barrier. Methods {@link #arrive} and
48	<	*       {@link #arriveAndDeregister} do not block, but return
49	<	*       an associated <em>arrival phase number</em>;
50	<	*       that is, the phase number of the barrier to which the
51	<	*       arrival applied.
52	<	*
53	<	*   <li> Awaiting others. Method {@link #awaitAdvance} requires an
54	<	*       argument indicating an arrival phase number, and returns
55	<	*       when the barrier advances to a new phase.
56	<	* </ul>
47	>	*   <li> <b>Arrival.</b> Methods {@link #arrive} and
48	>	*       {@link #arriveAndDeregister} record arrival.  These methods
49	>	*       do not block, but return an associated <em>arrival phase
50	>	*       number</em>; that is, the phase number of the phaser to which
51	>	*       the arrival applied. When the final party for a given phase
52	>	*       arrives, an optional action is performed and the phase
53	>	*       advances.  These actions are performed by the party
54	>	*       triggering a phase advance, and are arranged by overriding
55	>	*       method {@link #onAdvance(int, int)}, which also controls
56	>	*       termination. Overriding this method is similar to, but more
57	>	*       flexible than, providing a barrier action to a {@code
58	>	*       CyclicBarrier}.
59	>	*
60	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61	>	*       argument indicating an arrival phase number, and returns when
62	>	*       the phaser advances to (or is already at) a different phase.
63	>	*       Unlike similar constructions using {@code CyclicBarrier},
64	>	*       method {@code awaitAdvance} continues to wait even if the
65	>	*       waiting thread is interrupted. Interruptible and timeout
66	>	*       versions are also available, but exceptions encountered while
67	>	*       tasks wait interruptibly or with timeout do not change the
68	>	*       state of the phaser. If necessary, you can perform any
69	>	*       associated recovery within handlers of those exceptions,
70	>	*       often after invoking {@code forceTermination}.  Phasers may
71	>	*       also be used by tasks executing in a {@link ForkJoinPool},
72	>	*       which will ensure sufficient parallelism to execute tasks
73	>	*       when others are blocked waiting for a phase to advance.
74		*
75	<	* <li> Barrier actions, performed by the task triggering a phase
59	<	* advance, are arranged by overriding method {@link #onAdvance(int,
60	<	* int)}, which also controls termination. Overriding this method is
61	<	* similar to, but more flexible than, providing a barrier action to a
62	<	* {@code CyclicBarrier}.
63	<	*
64	<	* <li> Phasers may enter a <em>termination</em> state in which all
65	<	* actions immediately return without updating phaser state or waiting
66	<	* for advance, and indicating (via a negative phase value) that
67	<	* execution is complete.  Termination is triggered when an invocation
68	<	* of {@code onAdvance} returns {@code true}.  When a phaser is
69	<	* controlling an action with a fixed number of iterations, it is
70	<	* often convenient to override this method to cause termination when
71	<	* the current phase number reaches a threshold. Method {@link
72	<	* #forceTermination} is also available to abruptly release waiting
73	<	* threads and allow them to terminate.
74	<	*
75	<	* <li> Phasers may be tiered to reduce contention. Phasers with large
76	<	* numbers of parties that would otherwise experience heavy
77	<	* synchronization contention costs may instead be arranged in trees.
78	<	* This will typically greatly increase throughput even though it
79	<	* incurs somewhat greater per-operation overhead.
80	<	*
81	<	* <li> By default, {@code awaitAdvance} continues to wait even if
82	<	* the waiting thread is interrupted. And unlike the case in
83	<	* {@code CyclicBarrier}, exceptions encountered while tasks wait
84	<	* interruptibly or with timeout do not change the state of the
85	<	* barrier. If necessary, you can perform any associated recovery
86	<	* within handlers of those exceptions, often after invoking
87	<	* {@code forceTermination}.
88	<	*
89	<	* <li>Phasers may be used to coordinate tasks executing in a {@link
90	<	* ForkJoinPool}, which will ensure sufficient parallelism to execute
91	<	* tasks when others are blocked waiting for a phase to advance.
75	>	* </ul>
76		*
77	<	* <li>The current state of a phaser may be monitored.  At any given
78	<	* moment there are {@link #getRegisteredParties}, where {@link
77	>	* <p> <b>Termination.</b> A phaser may enter a <em>termination</em>
78	>	* state in which all synchronization methods immediately return
79	>	* without updating phaser state or waiting for advance, and
80	>	* indicating (via a negative phase value) that execution is complete.
81	>	* Termination is triggered when an invocation of {@code onAdvance}
82	>	* returns {@code true}. The default implementation returns {@code
83	>	* true} if a deregistration has caused the number of registered
84	>	* parties to become zero.  As illustrated below, when phasers control
85	>	* actions with a fixed number of iterations, it is often convenient
86	>	* to override this method to cause termination when the current phase
87	>	* number reaches a threshold. Method {@link #forceTermination} is
88	>	* also available to abruptly release waiting threads and allow them
89	>	* to terminate.
90	>	*
91	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
92	>	* constructed in tree structures) to reduce contention. Phasers with
93	>	* large numbers of parties that would otherwise experience heavy
94	>	* synchronization contention costs may instead be set up so that
95	>	* groups of sub-phasers share a common parent.  This may greatly
96	>	* increase throughput even though it incurs greater per-operation
97	>	* overhead.
98	>	*
99	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
100	>	* only by registered parties, the current state of a phaser may be
101	>	* monitored by any caller.  At any given moment there are {@link
102	>	* #getRegisteredParties} parties in total, of which {@link
103		* #getArrivedParties} have arrived at the current phase ({@link
104	<	* #getPhase}). When the remaining {@link #getUnarrivedParties})
105	<	* arrive, the phase advances. Method {@link #toString} returns
106	<	* snapshots of these state queries in a form convenient for
104	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
105	>	* parties arrive, the phase advances.  The values returned by these
106	>	* methods may reflect transient states and so are not in general
107	>	* useful for synchronization control.  Method {@link #toString}
108	>	* returns snapshots of these state queries in a form convenient for
109		* informal monitoring.
110		*
101	–	* </ul>
102	–	*
111		* <p><b>Sample usages:</b>
112		*
113		* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
114	<	* to control a one-shot action serving a variable number of
115	<	* parties. The typical idiom is for the method setting this up to
116	<	* first register, then start the actions, then deregister, as in:
114	>	* to control a one-shot action serving a variable number of parties.
115	>	* The typical idiom is for the method setting this up to first
116	>	* register, then start the actions, then deregister, as in:
117		*
118		*  <pre> {@code
119		* void runTasks(List<Runnable> tasks) {
#	Line 131 | Line 139 | import java.util.concurrent.locks.LockSu
139		*  <pre> {@code
140		* void startTasks(List<Runnable> tasks, final int iterations) {
141		*   final Phaser phaser = new Phaser() {
142	<	*     public boolean onAdvance(int phase, int registeredParties) {
142	>	*     protected boolean onAdvance(int phase, int registeredParties) {
143		*       return phase >= iterations || registeredParties == 0;
144		*     }
145		*   };
146		*   phaser.register();
147	<	*   for (Runnable task : tasks) {
147	>	*   for (final Runnable task : tasks) {
148		*     phaser.register();
149		*     new Thread() {
150		*       public void run() {
151		*         do {
152		*           task.run();
153		*           phaser.arriveAndAwaitAdvance();
154	<	*         } while(!phaser.isTerminated();
154	>	*         } while (!phaser.isTerminated());
155		*       }
156		*     }.start();
157		*   }
158		*   phaser.arriveAndDeregister(); // deregister self, don't wait
159		* }}</pre>
160		*
161	+	* If the main task must later await termination, it
162	+	* may re-register and then execute a similar loop:
163	+	*  <pre> {@code
164	+	*   // ...
165	+	*   phaser.register();
166	+	*   while (!phaser.isTerminated())
167	+	*     phaser.arriveAndAwaitAdvance();}</pre>
168	+	*
169	+	* <p>Related constructions may be used to await particular phase numbers
170	+	* in contexts where you are sure that the phase will never wrap around
171	+	* {@code Integer.MAX_VALUE}. For example:
172	+	*
173	+	*  <pre> {@code
174	+	* void awaitPhase(Phaser phaser, int phase) {
175	+	*   int p = phaser.register(); // assumes caller not already registered
176	+	*   while (p < phase) {
177	+	*     if (phaser.isTerminated())
178	+	*       // ... deal with unexpected termination
179	+	*     else
180	+	*       p = phaser.arriveAndAwaitAdvance();
181	+	*   }
182	+	*   phaser.arriveAndDeregister();
183	+	* }}</pre>
184	+	*
185	+	*
186		* <p>To create a set of tasks using a tree of phasers,
187		* you could use code of the following form, assuming a
188	<	* Task class with a constructor accepting a phaser that
189	<	* it registers for upon construction:
188	>	* Task class with a constructor accepting a {@code Phaser} that
189	>	* it registers with upon construction:
190	>	*
191		*  <pre> {@code
192	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
193	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
194	<	*   if (step > 1) {
195	<	*     int i = lo;
196	<	*     while (i < hi) {
163	<	*       int r = Math.min(i + step, hi);
164	<	*       build(actions, i, r, new Phaser(b));
165	<	*       i = r;
192	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
193	>	*   if (hi - lo > TASKS_PER_PHASER) {
194	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
195	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
196	>	*       build(actions, i, j, new Phaser(ph));
197		*     }
198		*   } else {
199		*     for (int i = lo; i < hi; ++i)
200	<	*       actions[i] = new Task(b);
201	<	*       // assumes new Task(b) performs b.register()
200	>	*       actions[i] = new Task(ph);
201	>	*       // assumes new Task(ph) performs ph.register()
202		*   }
203		* }
204		* // .. initially called, for n tasks via
205		* build(new Task[n], 0, n, new Phaser());}</pre>
206		*
207		* The best value of {@code TASKS_PER_PHASER} depends mainly on
208	<	* expected barrier synchronization rates. A value as low as four may
209	<	* be appropriate for extremely small per-barrier task bodies (thus
208	>	* expected synchronization rates. A value as low as four may
209	>	* be appropriate for extremely small per-phase task bodies (thus
210		* high rates), or up to hundreds for extremely large ones.
211		*
181	–	* </pre>
182	–	*
212		* <p><b>Implementation notes</b>: This implementation restricts the
213		* maximum number of parties to 65535. Attempts to register additional
214		* parties result in {@code IllegalStateException}. However, you can and
#	Line 197 | Line 226 | public class Phaser {
226		*/
227
228		/**
229	<	* Barrier state representation. Conceptually, a barrier contains
201	<	* four values:
229	>	* Primary state representation, holding four fields:
230		*
231	<	* * parties -- the number of parties to wait (16 bits)
232	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
233	<	* * phase -- the generation of the barrier (31 bits)
234	<	* * terminated -- set if barrier is terminated (1 bit)
231	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
232	>	* * parties -- the number of parties to wait              (bits 16-31)
233	>	* * phase -- the generation of the barrier                (bits 32-62)
234	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
235		*
236		* However, to efficiently maintain atomicity, these values are
237		* packed into a single (atomic) long. Termination uses the sign
238		* bit of 32 bit representation of phase, so phase is set to -1 on
239		* termination. Good performance relies on keeping state decoding
240		* and encoding simple, and keeping race windows short.
213	–	*
214	–	* Note: there are some cheats in arrive() that rely on unarrived
215	–	* count being lowest 16 bits.
241		*/
242		private volatile long state;
243
244	<	private static final int ushortBits = 16;
245	<	private static final int ushortMask = 0xffff;
246	<	private static final int phaseMask  = 0x7fffffff;
244	>	private static final int  MAX_PARTIES     = 0xffff;
245	>	private static final int  MAX_PHASE       = 0x7fffffff;
246	>	private static final int  PARTIES_SHIFT   = 16;
247	>	private static final int  PHASE_SHIFT     = 32;
248	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
249	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
250	>	private static final long ONE_ARRIVAL     = 1L;
251	>	private static final long ONE_PARTY       = 1L << PARTIES_SHIFT;
252	>	private static final long TERMINATION_BIT = 1L << 63;
253	>
254	>	// The following unpacking methods are usually manually inlined
255
256		private static int unarrivedOf(long s) {
257	<	return (int) (s & ushortMask);
257	>	return (int)s & UNARRIVED_MASK;
258		}
259
260		private static int partiesOf(long s) {
261	<	return ((int) s) >>> 16;
261	>	return (int)s >>> PARTIES_SHIFT;
262		}
263
264		private static int phaseOf(long s) {
265	<	return (int) (s >>> 32);
265	>	return (int) (s >>> PHASE_SHIFT);
266		}
267
268		private static int arrivedOf(long s) {
269		return partiesOf(s) - unarrivedOf(s);
270		}
271
239	–	private static long stateFor(int phase, int parties, int unarrived) {
240	–	return ((((long) phase) << 32) | (((long) parties) << 16) |
241	–	(long) unarrived);
242	–	}
243	–
244	–	private static long trippedStateFor(int phase, int parties) {
245	–	long lp = (long) parties;
246	–	return (((long) phase) << 32) | (lp << 16) | lp;
247	–	}
248	–
249	–	/**
250	–	* Returns message string for bad bounds exceptions.
251	–	*/
252	–	private static String badBounds(int parties, int unarrived) {
253	–	return ("Attempt to set " + unarrived +
254	–	" unarrived of " + parties + " parties");
255	–	}
256	–
272		/**
273		* The parent of this phaser, or null if none
274		*/
#	Line 265 | Line 280 | public class Phaser {
280		*/
281		private final Phaser root;
282
268	–	// Wait queues
269	–
283		/**
284		* Heads of Treiber stacks for waiting threads. To eliminate
285	<	* contention while releasing some threads while adding others, we
285	>	* contention when releasing some threads while adding others, we
286		* use two of them, alternating across even and odd phases.
287	+	* Subphasers share queues with root to speed up releases.
288		*/
289	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
290	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
289	>	private final AtomicReference<QNode> evenQ;
290	>	private final AtomicReference<QNode> oddQ;
291
292		private AtomicReference<QNode> queueFor(int phase) {
293		return ((phase & 1) == 0) ? evenQ : oddQ;
294		}
295
296		/**
297	<	* Returns current state, first resolving lagged propagation from
284	<	* root if necessary.
297	>	* Returns message string for bounds exceptions on arrival.
298		*/
299	<	private long getReconciledState() {
300	<	return (parent == null) ? state : reconcileState();
299	>	private String badArrive(long s) {
300	>	return "Attempted arrival of unregistered party for " +
301	>	stateToString(s);
302		}
303
304		/**
305	<	* Recursively resolves state.
305	>	* Returns message string for bounds exceptions on registration.
306		*/
307	<	private long reconcileState() {
308	<	Phaser p = parent;
309	<	long s = state;
310	<	if (p != null) {
311	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
312	<	long parentState = p.getReconciledState();
313	<	int parentPhase = phaseOf(parentState);
314	<	int phase = phaseOf(s = state);
315	<	if (phase != parentPhase) {
316	<	long next = trippedStateFor(parentPhase, partiesOf(s));
317	<	if (casState(s, next)) {
307	>	private String badRegister(long s) {
308	>	return "Attempt to register more than " +
309	>	MAX_PARTIES + " parties for " + stateToString(s);
310	>	}
311	>
312	>	/**
313	>	* Main implementation for methods arrive and arriveAndDeregister.
314	>	* Manually tuned to speed up and minimize race windows for the
315	>	* common case of just decrementing unarrived field.
316	>	*
317	>	* @param adj - adjustment to apply to state -- either
318	>	* ONE_ARRIVAL (for arrive) or
319	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
320	>	*/
321	>	private int doArrive(long adj) {
322	>	for (;;) {
323	>	long s = state;
324	>	int unarrived = (int)s & UNARRIVED_MASK;
325	>	int phase = (int)(s >>> PHASE_SHIFT);
326	>	if (phase < 0)
327	>	return phase;
328	>	else if (unarrived == 0) {
329	>	if (reconcileState() == s)     // recheck
330	>	throw new IllegalStateException(badArrive(s));
331	>	}
332	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
333	>	if (unarrived == 1) {
334	>	long p = s & PARTIES_MASK; // unshifted parties field
335	>	long lu = p >>> PARTIES_SHIFT;
336	>	int u = (int)lu;
337	>	int nextPhase = (phase + 1) & MAX_PHASE;
338	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
339	>	final Phaser parent = this.parent;
340	>	if (parent == null) {
341	>	if (onAdvance(phase, u))
342	>	next |= TERMINATION_BIT;
343	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
344		releaseWaiters(phase);
305	–	s = next;
345		}
346	+	else {
347	+	parent.doArrive((u == 0) ?
348	+	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
349	+	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase)
350	+	reconcileState();
351	+	else if (state == s)
352	+	UNSAFE.compareAndSwapLong(this, stateOffset, s,
353	+	next);
354	+	}
355	+	}
356	+	return phase;
357	+	}
358	+	}
359	+	}
360	+
361	+	/**
362	+	* Implementation of register, bulkRegister
363	+	*
364	+	* @param registrations number to add to both parties and
365	+	* unarrived fields. Must be greater than zero.
366	+	*/
367	+	private int doRegister(int registrations) {
368	+	// adjustment to state
369	+	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
370	+	final Phaser parent = this.parent;
371	+	for (;;) {
372	+	long s = (parent == null) ? state : reconcileState();
373	+	int parties = (int)s >>> PARTIES_SHIFT;
374	+	int phase = (int)(s >>> PHASE_SHIFT);
375	+	if (phase < 0)
376	+	return phase;
377	+	else if (registrations > MAX_PARTIES - parties)
378	+	throw new IllegalStateException(badRegister(s));
379	+	else if ((parties == 0 && parent == null) || // first reg of root
380	+	((int)s & UNARRIVED_MASK) != 0) {   // not advancing
381	+	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
382	+	return phase;
383	+	}
384	+	else if (parties != 0)               // wait for onAdvance
385	+	root.internalAwaitAdvance(phase, null);
386	+	else {                               // 1st registration of child
387	+	synchronized (this) {            // register parent first
388	+	if (reconcileState() == s) { // recheck under lock
389	+	parent.doRegister(1);    // OK if throws IllegalState
390	+	for (;;) {               // simpler form of outer loop
391	+	s = reconcileState();
392	+	phase = (int)(s >>> PHASE_SHIFT);
393	+	if (phase < 0 ||
394	+	UNSAFE.compareAndSwapLong(this, stateOffset,
395	+	s, s + adj))
396	+	return phase;
397	+	}
398	+	}
399	+	}
400	+	}
401	+	}
402	+	}
403	+
404	+	/**
405	+	* Recursively resolves lagged phase propagation from root if necessary.
406	+	*/
407	+	private long reconcileState() {
408	+	Phaser par = parent;
409	+	long s = state;
410	+	if (par != null) {
411	+	Phaser rt = root;
412	+	int phase, rPhase;
413	+	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
414	+	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
415	+	if (par != rt && (int)(par.state >>> PHASE_SHIFT) != rPhase)
416	+	par.reconcileState();
417	+	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
418	+	long u = s & PARTIES_MASK; // reset unarrived to parties
419	+	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
420	+	(u >>> PARTIES_SHIFT));
421	+	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
422		}
423	+	s = state;
424		}
425		}
426		return s;
427		}
428
429		/**
430	<	* Creates a new phaser without any initially registered parties,
431	<	* initial phase number 0, and no parent. Any thread using this
430	>	* Creates a new phaser with no initially registered parties, no
431	>	* parent, and initial phase number 0. Any thread using this
432		* phaser will need to first register for it.
433		*/
434		public Phaser() {
435	<	this(null);
435	>	this(null, 0);
436		}
437
438		/**
439	<	* Creates a new phaser with the given numbers of registered
440	<	* unarrived parties, initial phase number 0, and no parent.
439	>	* Creates a new phaser with the given number of registered
440	>	* unarrived parties, no parent, and initial phase number 0.
441		*
442	<	* @param parties the number of parties required to trip barrier
442	>	* @param parties the number of parties required to advance to the
443	>	* next phase
444		* @throws IllegalArgumentException if parties less than zero
445		* or greater than the maximum number of parties supported
446		*/
#	Line 332 | Line 449 | public class Phaser {
449		}
450
451		/**
452	<	* Creates a new phaser with the given parent, without any
336	<	* initially registered parties. If parent is non-null this phaser
337	<	* is registered with the parent and its initial phase number is
338	<	* the same as that of parent phaser.
452	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
453		*
454		* @param parent the parent phaser
455		*/
456		public Phaser(Phaser parent) {
457	<	int phase = 0;
344	<	this.parent = parent;
345	<	if (parent != null) {
346	<	this.root = parent.root;
347	<	phase = parent.register();
348	<	}
349	<	else
350	<	this.root = this;
351	<	this.state = trippedStateFor(phase, 0);
457	>	this(parent, 0);
458		}
459
460		/**
461	<	* Creates a new phaser with the given parent and numbers of
462	<	* registered unarrived parties. If parent is non-null, this phaser
463	<	* is registered with the parent and its initial phase number is
464	<	* the same as that of parent phaser.
461	>	* Creates a new phaser with the given parent and number of
462	>	* registered unarrived parties. Registration and deregistration
463	>	* of this child phaser with its parent are managed automatically.
464	>	* 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.
471		*
472		* @param parent the parent phaser
473	<	* @param parties the number of parties required to trip barrier
473	>	* @param parties the number of parties required to advance to the
474	>	* next phase
475		* @throws IllegalArgumentException if parties less than zero
476		* or greater than the maximum number of parties supported
477		*/
478		public Phaser(Phaser parent, int parties) {
479	<	if (parties < 0 || parties > ushortMask)
479	>	if (parties >>> PARTIES_SHIFT != 0)
480		throw new IllegalArgumentException("Illegal number of parties");
481	<	int phase = 0;
481	>	long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT);
482		this.parent = parent;
483		if (parent != null) {
484	<	this.root = parent.root;
485	<	phase = parent.register();
484	>	Phaser r = parent.root;
485	>	this.root = r;
486	>	this.evenQ = r.evenQ;
487	>	this.oddQ = r.oddQ;
488	>	if (parties != 0)
489	>	s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT;
490		}
491	<	else
491	>	else {
492		this.root = this;
493	<	this.state = trippedStateFor(phase, parties);
493	>	this.evenQ = new AtomicReference<QNode>();
494	>	this.oddQ = new AtomicReference<QNode>();
495	>	}
496	>	this.state = s;
497		}
498
499		/**
500	<	* Adds a new unarrived party to this phaser.
500	>	* Adds a new unarrived party to this phaser.  If an ongoing
501	>	* invocation of {@link #onAdvance} is in progress, this method
502	>	* may await its completion before returning.  If this phaser has
503	>	* a parent, and this phaser previously had no registered parties,
504	>	* this phaser is also registered with its parent.
505		*
506		* @return the arrival phase number to which this registration applied
507		* @throws IllegalStateException if attempting to register more
#	Line 389 | Line 513 | public class Phaser {
513
514		/**
515		* Adds the given number of new unarrived parties to this phaser.
516	+	* If an ongoing invocation of {@link #onAdvance} is in progress,
517	+	* this method may await its completion before returning.  If this
518	+	* phaser has a parent, and the given number of parities is
519	+	* greater than zero, and this phaser previously had no registered
520	+	* parties, this phaser is also registered with its parent.
521		*
522	<	* @param parties the number of parties required to trip barrier
522	>	* @param parties the number of additional parties required to
523	>	* advance to the next phase
524		* @return the arrival phase number to which this registration applied
525		* @throws IllegalStateException if attempting to register more
526		* than the maximum supported number of parties
527	+	* @throws IllegalArgumentException if {@code parties < 0}
528		*/
529		public int bulkRegister(int parties) {
530		if (parties < 0)
#	Line 404 | Line 535 | public class Phaser {
535		}
536
537		/**
538	<	* Shared code for register, bulkRegister
539	<	*/
540	<	private int doRegister(int registrations) {
541	<	int phase;
542	<	for (;;) {
543	<	long s = getReconciledState();
413	<	phase = phaseOf(s);
414	<	int unarrived = unarrivedOf(s) + registrations;
415	<	int parties = partiesOf(s) + registrations;
416	<	if (phase < 0)
417	<	break;
418	<	if (parties > ushortMask || unarrived > ushortMask)
419	<	throw new IllegalStateException(badBounds(parties, unarrived));
420	<	if (phase == phaseOf(root.state) &&
421	<	casState(s, stateFor(phase, parties, unarrived)))
422	<	break;
423	<	}
424	<	return phase;
425	<	}
426	<
427	<	/**
428	<	* Arrives at the barrier, but does not wait for others.  (You can
429	<	* in turn wait for others via {@link #awaitAdvance}).
538	>	* Arrives at this phaser, without waiting for others to arrive.
539	>	*
540	>	* <p>It is a usage error for an unregistered party to invoke this
541	>	* method.  However, this error may result in an {@code
542	>	* IllegalStateException} only upon some subsequent operation on
543	>	* this phaser, if ever.
544		*
545		* @return the arrival phase number, or a negative value if terminated
546		* @throws IllegalStateException if not terminated and the number
547		* of unarrived parties would become negative
548		*/
549		public int arrive() {
550	<	int phase;
437	<	for (;;) {
438	<	long s = state;
439	<	phase = phaseOf(s);
440	<	if (phase < 0)
441	<	break;
442	<	int parties = partiesOf(s);
443	<	int unarrived = unarrivedOf(s) - 1;
444	<	if (unarrived > 0) {        // Not the last arrival
445	<	if (casState(s, s - 1)) // s-1 adds one arrival
446	<	break;
447	<	}
448	<	else if (unarrived == 0) {  // the last arrival
449	<	Phaser par = parent;
450	<	if (par == null) {      // directly trip
451	<	if (casState
452	<	(s,
453	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
454	<	((phase + 1) & phaseMask), parties))) {
455	<	releaseWaiters(phase);
456	<	break;
457	<	}
458	<	}
459	<	else {                  // cascade to parent
460	<	if (casState(s, s - 1)) { // zeroes unarrived
461	<	par.arrive();
462	<	reconcileState();
463	<	break;
464	<	}
465	<	}
466	<	}
467	<	else if (phase != phaseOf(root.state)) // or if unreconciled
468	<	reconcileState();
469	<	else
470	<	throw new IllegalStateException(badBounds(parties, unarrived));
471	<	}
472	<	return phase;
550	>	return doArrive(ONE_ARRIVAL);
551		}
552
553		/**
554	<	* Arrives at the barrier and deregisters from it without waiting
555	<	* for others. Deregistration reduces the number of parties
556	<	* required to trip the barrier in future phases.  If this phaser
554	>	* Arrives at this phaser and deregisters from it without waiting
555	>	* for others to arrive. Deregistration reduces the number of
556	>	* parties required to advance in future phases.  If this phaser
557		* has a parent, and deregistration causes this phaser to have
558	<	* zero parties, this phaser also arrives at and is deregistered
559	<	* from its parent.
558	>	* zero parties, this phaser is also deregistered from its parent.
559	>	*
560	>	* <p>It is a usage error for an unregistered party to invoke this
561	>	* method.  However, this error may result in an {@code
562	>	* IllegalStateException} only upon some subsequent operation on
563	>	* this phaser, if ever.
564		*
565		* @return the arrival phase number, or a negative value if terminated
566		* @throws IllegalStateException if not terminated and the number
567		* of registered or unarrived parties would become negative
568		*/
569		public int arriveAndDeregister() {
570	<	// similar code to arrive, but too different to merge
489	<	Phaser par = parent;
490	<	int phase;
491	<	for (;;) {
492	<	long s = state;
493	<	phase = phaseOf(s);
494	<	if (phase < 0)
495	<	break;
496	<	int parties = partiesOf(s) - 1;
497	<	int unarrived = unarrivedOf(s) - 1;
498	<	if (parties >= 0) {
499	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
500	<	if (casState
501	<	(s,
502	<	stateFor(phase, parties, unarrived))) {
503	<	if (unarrived == 0) {
504	<	par.arriveAndDeregister();
505	<	reconcileState();
506	<	}
507	<	break;
508	<	}
509	<	continue;
510	<	}
511	<	if (unarrived == 0) {
512	<	if (casState
513	<	(s,
514	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
515	<	((phase + 1) & phaseMask), parties))) {
516	<	releaseWaiters(phase);
517	<	break;
518	<	}
519	<	continue;
520	<	}
521	<	if (par != null && phase != phaseOf(root.state)) {
522	<	reconcileState();
523	<	continue;
524	<	}
525	<	}
526	<	throw new IllegalStateException(badBounds(parties, unarrived));
527	<	}
528	<	return phase;
570	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
571		}
572
573		/**
574	<	* Arrives at the barrier and awaits others. Equivalent in effect
574	>	* Arrives at this phaser and awaits others. Equivalent in effect
575		* to {@code awaitAdvance(arrive())}.  If you need to await with
576		* interruption or timeout, you can arrange this with an analogous
577	<	* construction using one of the other forms of the awaitAdvance
578	<	* method.  If instead you need to deregister upon arrival use
579	<	* {@code arriveAndDeregister}.
577	>	* construction using one of the other forms of the {@code
578	>	* awaitAdvance} method.  If instead you need to deregister upon
579	>	* arrival, use {@code awaitAdvance(arriveAndDeregister())}.
580	>	*
581	>	* <p>It is a usage error for an unregistered party to invoke this
582	>	* method.  However, this error may result in an {@code
583	>	* IllegalStateException} only upon some subsequent operation on
584	>	* this phaser, if ever.
585		*
586		* @return the arrival phase number, or a negative number if terminated
587		* @throws IllegalStateException if not terminated and the number
588		* of unarrived parties would become negative
589		*/
590		public int arriveAndAwaitAdvance() {
591	<	return awaitAdvance(arrive());
591	>	return awaitAdvance(doArrive(ONE_ARRIVAL));
592		}
593
594		/**
595	<	* Awaits the phase of the barrier to advance from the given phase
596	<	* value, returning immediately if the current phase of the
597	<	* barrier is not equal to the given phase value or this barrier
551	<	* is terminated.
595	>	* Awaits the phase of this phaser to advance from the given phase
596	>	* value, returning immediately if the current phase is not equal
597	>	* to the given phase value or this phaser is terminated.
598		*
599		* @param phase an arrival phase number, or negative value if
600		* terminated; this argument is normally the value returned by a
601	<	* previous call to {@code arrive} or its variants
601	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
602		* @return the next arrival phase number, or a negative value
603		* if terminated or argument is negative
604		*/
605		public int awaitAdvance(int phase) {
606	+	Phaser rt;
607	+	int p = (int)(state >>> PHASE_SHIFT);
608		if (phase < 0)
609		return phase;
610	<	long s = getReconciledState();
611	<	int p = phaseOf(s);
612	<	if (p != phase)
613	<	return p;
566	<	if (unarrivedOf(s) == 0 && parent != null)
567	<	parent.awaitAdvance(phase);
568	<	// Fall here even if parent waited, to reconcile and help release
569	<	return untimedWait(phase);
610	>	if (p == phase &&
611	>	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase)
612	>	return rt.internalAwaitAdvance(phase, null);
613	>	return p;
614		}
615
616		/**
617	<	* Awaits the phase of the barrier to advance from the given phase
618	<	* value, throwing {@code InterruptedException} if interrupted while
619	<	* waiting, or returning immediately if the current phase of the
620	<	* barrier is not equal to the given phase value or this barrier
621	<	* is terminated.
617	>	* Awaits the phase of this phaser to advance from the given phase
618	>	* value, throwing {@code InterruptedException} if interrupted
619	>	* while waiting, or returning immediately if the current phase is
620	>	* not equal to the given phase value or this phaser is
621	>	* terminated.
622		*
623		* @param phase an arrival phase number, or negative value if
624		* terminated; this argument is normally the value returned by a
625	<	* previous call to {@code arrive} or its variants
625	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
626		* @return the next arrival phase number, or a negative value
627		* if terminated or argument is negative
628		* @throws InterruptedException if thread interrupted while waiting
629		*/
630		public int awaitAdvanceInterruptibly(int phase)
631		throws InterruptedException {
632	+	Phaser rt;
633	+	int p = (int)(state >>> PHASE_SHIFT);
634		if (phase < 0)
635		return phase;
636	<	long s = getReconciledState();
637	<	int p = phaseOf(s);
638	<	if (p != phase)
639	<	return p;
640	<	if (unarrivedOf(s) == 0 && parent != null)
641	<	parent.awaitAdvanceInterruptibly(phase);
642	<	return interruptibleWait(phase);
636	>	if (p == phase &&
637	>	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
638	>	QNode node = new QNode(this, phase, true, false, 0L);
639	>	p = rt.internalAwaitAdvance(phase, node);
640	>	if (node.wasInterrupted)
641	>	throw new InterruptedException();
642	>	}
643	>	return p;
644		}
645
646		/**
647	<	* Awaits the phase of the barrier to advance from the given phase
648	<	* value or the given timeout to elapse, throwing
649	<	* {@code InterruptedException} if interrupted while waiting, or
650	<	* returning immediately if the current phase of the barrier is not
651	<	* equal to the given phase value or this barrier is terminated.
647	>	* Awaits the phase of this phaser to advance from the given phase
648	>	* value or the given timeout to elapse, throwing {@code
649	>	* InterruptedException} if interrupted while waiting, or
650	>	* returning immediately if the current phase is not equal to the
651	>	* given phase value or this phaser is terminated.
652		*
653		* @param phase an arrival phase number, or negative value if
654		* terminated; this argument is normally the value returned by a
655	<	* previous call to {@code arrive} or its variants
655	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
656		* @param timeout how long to wait before giving up, in units of
657		*        {@code unit}
658		* @param unit a {@code TimeUnit} determining how to interpret the
#	Line 618 | Line 665 | public class Phaser {
665		public int awaitAdvanceInterruptibly(int phase,
666		long timeout, TimeUnit unit)
667		throws InterruptedException, TimeoutException {
668	+	long nanos = unit.toNanos(timeout);
669	+	Phaser rt;
670	+	int p = (int)(state >>> PHASE_SHIFT);
671		if (phase < 0)
672		return phase;
673	<	long s = getReconciledState();
674	<	int p = phaseOf(s);
675	<	if (p != phase)
676	<	return p;
677	<	if (unarrivedOf(s) == 0 && parent != null)
678	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
679	<	return timedWait(phase, unit.toNanos(timeout));
673	>	if (p == phase &&
674	>	(p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
675	>	QNode node = new QNode(this, phase, true, true, nanos);
676	>	p = rt.internalAwaitAdvance(phase, node);
677	>	if (node.wasInterrupted)
678	>	throw new InterruptedException();
679	>	else if (p == phase)
680	>	throw new TimeoutException();
681	>	}
682	>	return p;
683		}
684
685		/**
686	<	* Forces this barrier to enter termination state. Counts of
687	<	* arrived and registered parties are unaffected. If this phaser
688	<	* has a parent, it too is terminated. This method may be useful
689	<	* for coordinating recovery after one or more tasks encounter
690	<	* unexpected exceptions.
686	>	* Forces this phaser to enter termination state.  Counts of
687	>	* arrived and registered parties are unaffected.  If this phaser
688	>	* is a member of a tiered set of phasers, then all of the phasers
689	>	* in the set are terminated.  If this phaser is already
690	>	* terminated, this method has no effect.  This method may be
691	>	* useful for coordinating recovery after one or more tasks
692	>	* encounter unexpected exceptions.
693		*/
694		public void forceTermination() {
695	<	for (;;) {
696	<	long s = getReconciledState();
697	<	int phase = phaseOf(s);
698	<	int parties = partiesOf(s);
699	<	int unarrived = unarrivedOf(s);
700	<	if (phase < 0 ||
701	<	casState(s, stateFor(-1, parties, unarrived))) {
647	<	releaseWaiters(0);
695	>	// Only need to change root state
696	>	final Phaser root = this.root;
697	>	long s;
698	>	while ((s = root.state) >= 0) {
699	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
700	>	s, s | TERMINATION_BIT)) {
701	>	releaseWaiters(0); // signal all threads
702		releaseWaiters(1);
649	–	if (parent != null)
650	–	parent.forceTermination();
703		return;
704		}
705		}
#	Line 656 | Line 708 | public class Phaser {
708		/**
709		* Returns the current phase number. The maximum phase number is
710		* {@code Integer.MAX_VALUE}, after which it restarts at
711	<	* zero. Upon termination, the phase number is negative.
711	>	* zero. Upon termination, the phase number is negative,
712	>	* in which case the prevailing phase prior to termination
713	>	* may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
714		*
715		* @return the phase number, or a negative value if terminated
716		*/
717		public final int getPhase() {
718	<	return phaseOf(getReconciledState());
718	>	return (int)(root.state >>> PHASE_SHIFT);
719		}
720
721		/**
722	<	* Returns the number of parties registered at this barrier.
722	>	* Returns the number of parties registered at this phaser.
723		*
724		* @return the number of parties
725		*/
#	Line 675 | Line 729 | public class Phaser {
729
730		/**
731		* Returns the number of registered parties that have arrived at
732	<	* the current phase of this barrier.
732	>	* the current phase of this phaser.
733		*
734		* @return the number of arrived parties
735		*/
736		public int getArrivedParties() {
737	<	return arrivedOf(state);
737	>	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());
742		}
743
744		/**
745		* Returns the number of registered parties that have not yet
746	<	* arrived at the current phase of this barrier.
746	>	* arrived at the current phase of this phaser.
747		*
748		* @return the number of unarrived parties
749		*/
750		public int getUnarrivedParties() {
751	<	return unarrivedOf(state);
751	>	int u = unarrivedOf(state);
752	>	return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState());
753		}
754
755		/**
#	Line 713 | Line 772 | public class Phaser {
772		}
773
774		/**
775	<	* Returns {@code true} if this barrier has been terminated.
775	>	* Returns {@code true} if this phaser has been terminated.
776		*
777	<	* @return {@code true} if this barrier has been terminated
777	>	* @return {@code true} if this phaser has been terminated
778		*/
779		public boolean isTerminated() {
780	<	return getPhase() < 0;
780	>	return root.state < 0L;
781		}
782
783		/**
784	<	* Overridable method to perform an action upon phase advance, and
785	<	* to control termination. This method is invoked whenever the
786	<	* barrier is tripped (and thus all other waiting parties are
787	<	* dormant). If it returns {@code true}, then, rather than advance
788	<	* the phase number, this barrier will be set to a final
789	<	* termination state, and subsequent calls to {@link #isTerminated}
790	<	* will return true.
791	<	*
792	<	* <p>The default version returns {@code true} when the number of
793	<	* registered parties is zero. Normally, overrides that arrange
794	<	* termination for other reasons should also preserve this
795	<	* property.
796	<	*
797	<	* <p>You may override this method to perform an action with side
798	<	* effects visible to participating tasks, but it is in general
799	<	* only sensible to do so in designs where all parties register
800	<	* before any arrive, and all {@link #awaitAdvance} at each phase.
801	<	* Otherwise, you cannot ensure lack of interference from other
802	<	* parties during the invocation of this method.
784	>	* Overridable method to perform an action upon impending phase
785	>	* advance, and to control termination. This method is invoked
786	>	* upon arrival of the party advancing this phaser (when all other
787	>	* waiting parties are dormant).  If this method returns {@code
788	>	* true}, then, rather than advance the phase number, this phaser
789	>	* will be set to a final termination state, and subsequent calls
790	>	* to {@link #isTerminated} will return true. Any (unchecked)
791	>	* Exception or Error thrown by an invocation of this method is
792	>	* propagated to the party attempting to advance this phaser, in
793	>	* which case no advance occurs.
794	>	*
795	>	* <p>The arguments to this method provide the state of the phaser
796	>	* prevailing for the current transition.  The effects of invoking
797	>	* arrival, registration, and waiting methods on this phaser from
798	>	* within {@code onAdvance} are unspecified and should not be
799	>	* relied on.
800	>	*
801	>	* <p>If this phaser is a member of a tiered set of phasers, then
802	>	* {@code onAdvance} is invoked only for its root phaser on each
803	>	* advance.
804	>	*
805	>	* <p>To support the most common use cases, the default
806	>	* implementation of this method returns {@code true} when the
807	>	* number of registered parties has become zero as the result of a
808	>	* party invoking {@code arriveAndDeregister}.  You can disable
809	>	* this behavior, thus enabling continuation upon future
810	>	* registrations, by overriding this method to always return
811	>	* {@code false}:
812	>	*
813	>	* <pre> {@code
814	>	* Phaser phaser = new Phaser() {
815	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
816	>	* }}</pre>
817		*
818	<	* @param phase the phase number on entering the barrier
818	>	* @param phase the current phase number on entry to this method,
819	>	* before this phaser is advanced
820		* @param registeredParties the current number of registered parties
821	<	* @return {@code true} if this barrier should terminate
821	>	* @return {@code true} if this phaser should terminate
822		*/
823		protected boolean onAdvance(int phase, int registeredParties) {
824	<	return registeredParties <= 0;
824	>	return registeredParties == 0;
825		}
826
827		/**
#	Line 757 | Line 831 | public class Phaser {
831		* followed by the number of registered parties, and {@code
832		* "arrived = "} followed by the number of arrived parties.
833		*
834	<	* @return a string identifying this barrier, as well as its state
834	>	* @return a string identifying this phaser, as well as its state
835		*/
836		public String toString() {
837	<	long s = getReconciledState();
837	>	return stateToString(reconcileState());
838	>	}
839	>
840	>	/**
841	>	* Implementation of toString and string-based error messages
842	>	*/
843	>	private String stateToString(long s) {
844		return super.toString() +
845		"[phase = " + phaseOf(s) +
846		" parties = " + partiesOf(s) +
847		" arrived = " + arrivedOf(s) + "]";
848		}
849
850	<	// methods for waiting
850	>	// Waiting mechanics
851
852		/**
853	<	* Wait nodes for Treiber stack representing wait queue
853	>	* Removes and signals threads from queue for phase.
854		*/
855	<	static final class QNode implements ForkJoinPool.ManagedBlocker {
856	<	final Phaser phaser;
857	<	final int phase;
858	<	final long startTime;
859	<	final long nanos;
860	<	final boolean timed;
861	<	final boolean interruptible;
862	<	volatile boolean wasInterrupted = false;
863	<	volatile Thread thread; // nulled to cancel wait
864	<	QNode next;
865	<	QNode(Phaser phaser, int phase, boolean interruptible,
786	<	boolean timed, long startTime, long nanos) {
787	<	this.phaser = phaser;
788	<	this.phase = phase;
789	<	this.timed = timed;
790	<	this.interruptible = interruptible;
791	<	this.startTime = startTime;
792	<	this.nanos = nanos;
793	<	thread = Thread.currentThread();
794	<	}
795	<	public boolean isReleasable() {
796	<	return (thread == null ||
797	<	phaser.getPhase() != phase ||
798	<	(interruptible && wasInterrupted) ||
799	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
800	<	}
801	<	public boolean block() {
802	<	if (Thread.interrupted()) {
803	<	wasInterrupted = true;
804	<	if (interruptible)
805	<	return true;
806	<	}
807	<	if (!timed)
808	<	LockSupport.park(this);
809	<	else {
810	<	long waitTime = nanos - (System.nanoTime() - startTime);
811	<	if (waitTime <= 0)
812	<	return true;
813	<	LockSupport.parkNanos(this, waitTime);
814	<	}
815	<	return isReleasable();
816	<	}
817	<	void signal() {
818	<	Thread t = thread;
819	<	if (t != null) {
820	<	thread = null;
855	>	private void releaseWaiters(int phase) {
856	>	QNode q;   // first element of queue
857	>	int p;     // its phase
858	>	Thread t;  // its thread
859	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
860	>	while ((q = head.get()) != null &&
861	>	((p = q.phase) == phase ||
862	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
863	>	if (head.compareAndSet(q, q.next) &&
864	>	(t = q.thread) != null) {
865	>	q.thread = null;
866		LockSupport.unpark(t);
867		}
868		}
824	–	boolean doWait() {
825	–	if (thread != null) {
826	–	try {
827	–	ForkJoinPool.managedBlock(this, false);
828	–	} catch (InterruptedException ie) {
829	–	}
830	–	}
831	–	return wasInterrupted;
832	–	}
833	–
869		}
870
871	<	/**
872	<	* Removes and signals waiting threads from wait queue.
838	<	*/
839	<	private void releaseWaiters(int phase) {
840	<	AtomicReference<QNode> head = queueFor(phase);
841	<	QNode q;
842	<	while ((q = head.get()) != null) {
843	<	if (head.compareAndSet(q, q.next))
844	<	q.signal();
845	<	}
846	<	}
871	>	/** The number of CPUs, for spin control */
872	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
873
874		/**
875	<	* Tries to enqueue given node in the appropriate wait queue.
876	<	*
877	<	* @return true if successful
875	>	* The number of times to spin before blocking while waiting for
876	>	* advance, per arrival while waiting. On multiprocessors, fully
877	>	* blocking and waking up a large number of threads all at once is
878	>	* usually a very slow process, so we use rechargeable spins to
879	>	* avoid it when threads regularly arrive: When a thread in
880	>	* internalAwaitAdvance notices another arrival before blocking,
881	>	* and there appear to be enough CPUs available, it spins
882	>	* SPINS_PER_ARRIVAL more times before blocking. The value trades
883	>	* off good-citizenship vs big unnecessary slowdowns.
884		*/
885	<	private boolean tryEnqueue(QNode node) {
854	<	AtomicReference<QNode> head = queueFor(node.phase);
855	<	return head.compareAndSet(node.next = head.get(), node);
856	<	}
885	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
886
887		/**
888	<	* Enqueues node and waits unless aborted or signalled.
888	>	* Possibly blocks and waits for phase to advance unless aborted.
889	>	* Call only from root node.
890		*
891	+	* @param phase current phase
892	+	* @param node if non-null, the wait node to track interrupt and timeout;
893	+	* if null, denotes noninterruptible wait
894		* @return current phase
895		*/
896	<	private int untimedWait(int phase) {
897	<	QNode node = null;
898	<	boolean queued = false;
899	<	boolean interrupted = false;
896	>	private int internalAwaitAdvance(int phase, QNode node) {
897	>	releaseWaiters(phase-1);          // ensure old queue clean
898	>	boolean queued = false;           // true when node is enqueued
899	>	int lastUnarrived = 0;            // to increase spins upon change
900	>	int spins = SPINS_PER_ARRIVAL;
901	>	long s;
902		int p;
903	<	while ((p = getPhase()) == phase) {
904	<	if (Thread.interrupted())
905	<	interrupted = true;
906	<	else if (node == null)
907	<	node = new QNode(this, phase, false, false, 0, 0);
908	<	else if (!queued)
909	<	queued = tryEnqueue(node);
910	<	else
911	<	interrupted = node.doWait();
903	>	while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
904	>	if (node == null) {           // spinning in noninterruptible mode
905	>	int unarrived = (int)s & UNARRIVED_MASK;
906	>	if (unarrived != lastUnarrived &&
907	>	(lastUnarrived = unarrived) < NCPU)
908	>	spins += SPINS_PER_ARRIVAL;
909	>	boolean interrupted = Thread.interrupted();
910	>	if (interrupted || --spins < 0) { // need node to record intr
911	>	node = new QNode(this, phase, false, false, 0L);
912	>	node.wasInterrupted = interrupted;
913	>	}
914	>	}
915	>	else if (node.isReleasable()) // done or aborted
916	>	break;
917	>	else if (!queued) {           // push onto queue
918	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
919	>	QNode q = node.next = head.get();
920	>	if ((q == null || q.phase == phase) &&
921	>	(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
922	>	queued = head.compareAndSet(q, node);
923	>	}
924	>	else {
925	>	try {
926	>	ForkJoinPool.managedBlock(node);
927	>	} catch (InterruptedException ie) {
928	>	node.wasInterrupted = true;
929	>	}
930	>	}
931	>	}
932	>
933	>	if (node != null) {
934	>	if (node.thread != null)
935	>	node.thread = null;       // avoid need for unpark()
936	>	if (node.wasInterrupted && !node.interruptible)
937	>	Thread.currentThread().interrupt();
938	>	if ((p = (int)(state >>> PHASE_SHIFT)) == phase)
939	>	return p;                 // recheck abort
940		}
878	–	if (node != null)
879	–	node.thread = null;
941		releaseWaiters(phase);
881	–	if (interrupted)
882	–	Thread.currentThread().interrupt();
942		return p;
943		}
944
945		/**
946	<	* Interruptible version
888	<	* @return current phase
946	>	* Wait nodes for Treiber stack representing wait queue
947		*/
948	<	private int interruptibleWait(int phase) throws InterruptedException {
949	<	QNode node = null;
950	<	boolean queued = false;
951	<	boolean interrupted = false;
952	<	int p;
953	<	while ((p = getPhase()) == phase && !interrupted) {
954	<	if (Thread.interrupted())
955	<	interrupted = true;
956	<	else if (node == null)
957	<	node = new QNode(this, phase, true, false, 0, 0);
900	<	else if (!queued)
901	<	queued = tryEnqueue(node);
902	<	else
903	<	interrupted = node.doWait();
904	<	}
905	<	if (node != null)
906	<	node.thread = null;
907	<	if (p != phase || (p = getPhase()) != phase)
908	<	releaseWaiters(phase);
909	<	if (interrupted)
910	<	throw new InterruptedException();
911	<	return p;
912	<	}
948	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
949	>	final Phaser phaser;
950	>	final int phase;
951	>	final boolean interruptible;
952	>	final boolean timed;
953	>	boolean wasInterrupted;
954	>	long nanos;
955	>	long lastTime;
956	>	volatile Thread thread; // nulled to cancel wait
957	>	QNode next;
958
959	<	/**
960	<	* Timeout version.
961	<	* @return current phase
962	<	*/
963	<	private int timedWait(int phase, long nanos)
964	<	throws InterruptedException, TimeoutException {
965	<	long startTime = System.nanoTime();
966	<	QNode node = null;
967	<	boolean queued = false;
968	<	boolean interrupted = false;
969	<	int p;
970	<	while ((p = getPhase()) == phase && !interrupted) {
959	>	QNode(Phaser phaser, int phase, boolean interruptible,
960	>	boolean timed, long nanos) {
961	>	this.phaser = phaser;
962	>	this.phase = phase;
963	>	this.interruptible = interruptible;
964	>	this.nanos = nanos;
965	>	this.timed = timed;
966	>	this.lastTime = timed ? System.nanoTime() : 0L;
967	>	thread = Thread.currentThread();
968	>	}
969	>
970	>	public boolean isReleasable() {
971	>	if (thread == null)
972	>	return true;
973	>	if (phaser.getPhase() != phase) {
974	>	thread = null;
975	>	return true;
976	>	}
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
986	<	interrupted = node.doWait();
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;
978	>	wasInterrupted = true;
979	>	if (wasInterrupted && interruptible) {
980	>	thread = null;
981	>	return true;
982	>	}
983	>	if (timed) {
984	>	if (nanos > 0L) {
985	>	long now = System.nanoTime();
986	>	nanos -= now - lastTime;
987	>	lastTime = now;
988	>	}
989	>	if (nanos <= 0L) {
990	>	thread = null;
991	>	return true;
992	>	}
993	>	}
994	>	return false;
995	>	}
996	>
997	>	public boolean block() {
998	>	if (isReleasable())
999	>	return true;
1000	>	else if (!timed)
1001	>	LockSupport.park(this);
1002	>	else if (nanos > 0)
1003	>	LockSupport.parkNanos(this, nanos);
1004	>	return isReleasable();
1005	>	}
1006		}
1007
1008		// Unsafe mechanics
#	Line 951 | Line 1011 | public class Phaser {
1011		private static final long stateOffset =
1012		objectFieldOffset("state", Phaser.class);
1013
954	–	private final boolean casState(long cmp, long val) {
955	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
956	–	}
957	–
1014		private static long objectFieldOffset(String field, Class<?> klazz) {
1015		try {
1016		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

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