ViewVC Help

View File | Revision Log | Show Annotations | Download File | Root Listing

root/jsr166/jsr166/src/jsr166y/Phaser.java

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.28 by jsr166, Wed Aug 12 02:24:35 2009 UTC vs.
Revision 1.66 by jsr166, Wed Dec 1 19:12:53 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 synchronizing on a phaser may vary over
23	<	* time.  A task may register to be a party at any time, and may
24	<	* deregister upon arriving at the barrier.  As is the case with most
25	<	* basic synchronization constructs, registration and deregistration
26	<	* affect only internal counts; they do not establish any further
27	<	* internal bookkeeping, so tasks cannot query whether they are
28	<	* registered. (However, you can introduce such bookkeeping by
29	<	* subclassing this class.)
30	<	*
31	<	* <li> Each generation has an associated phase value, starting at
32	<	* zero, and advancing when all parties reach the barrier (wrapping
33	<	* around to zero after reaching {@code Integer.MAX_VALUE}).
34	<	*
35	<	* <li> Like a {@code CyclicBarrier}, a phaser may be repeatedly
36	<	* awaited.  Method {@link #arriveAndAwaitAdvance} has effect
37	<	* analogous to {@link java.util.concurrent.CyclicBarrier#await
38	<	* CyclicBarrier.await}.  However, phasers separate two aspects of
39	<	* coordination, which may also be invoked independently:
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 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	<	*       the phase value current upon entry to the method.
50	<	*
51	<	*   <li> Awaiting others. Method {@link #awaitAdvance} requires an
52	<	*       argument indicating the entry phase, and returns when the
53	<	*       barrier advances to a new phase.
54	<	* </ul>
55	<	*
56	<	*
57	<	* <li> Barrier actions, performed by the task triggering a phase
58	<	* advance, are arranged by overriding method {@link #onAdvance(int,
59	<	* int)}, which also controls termination. Overriding this method is
60	<	* similar to, but more flexible than, providing a barrier action to a
61	<	* {@code CyclicBarrier}.
62	<	*
63	<	* <li> Phasers may enter a <em>termination</em> state in which all
64	<	* actions immediately return without updating phaser state or waiting
65	<	* for advance, and indicating (via a negative phase value) that
66	<	* execution is complete.  Termination is triggered when an invocation
67	<	* of {@code onAdvance} returns {@code true}.  When a phaser is
68	<	* controlling an action with a fixed number of iterations, it is
69	<	* often convenient to override this method to cause termination when
70	<	* the current phase number reaches a threshold. Method {@link
71	<	* #forceTermination} is also available to abruptly release waiting
72	<	* threads and allow them to terminate.
73	<	*
70	<	* <li> Phasers may be tiered to reduce contention. Phasers with large
71	<	* numbers of parties that would otherwise experience heavy
72	<	* synchronization contention costs may instead be arranged in trees.
73	<	* This will typically greatly increase throughput even though it
74	<	* incurs somewhat greater per-operation overhead.
75	<	*
76	<	* <li> By default, {@code awaitAdvance} continues to wait even if
77	<	* the waiting thread is interrupted. And unlike the case in
78	<	* {@code CyclicBarrier}, exceptions encountered while tasks wait
79	<	* interruptibly or with timeout do not change the state of the
80	<	* barrier. If necessary, you can perform any associated recovery
81	<	* within handlers of those exceptions, often after invoking
82	<	* {@code forceTermination}.
83	<	*
84	<	* <li>Phasers may be used to coordinate tasks executing in a {@link
85	<	* ForkJoinPool}, which will ensure sufficient parallelism to execute
86	<	* tasks when others are blocked waiting for a phase to advance.
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		* </ul>
76		*
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	+	* 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	+	*
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> list) {
119	>	* void runTasks(List<Runnable> tasks) {
120		*   final Phaser phaser = new Phaser(1); // "1" to register self
121		*   // create and start threads
122	<	*   for (Runnable r : list) {
122	>	*   for (Runnable task : tasks) {
123		*     phaser.register();
124		*     new Thread() {
125		*       public void run() {
126		*         phaser.arriveAndAwaitAdvance(); // await all creation
127	<	*         r.run();
127	>	*         task.run();
128		*       }
129		*     }.start();
130		*   }
#	Line 116 | Line 137 | import java.util.concurrent.locks.LockSu
137		* for a given number of iterations is to override {@code onAdvance}:
138		*
139		*  <pre> {@code
140	<	* void startTasks(List<Runnable> list, final int iterations) {
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 r : list) {
147	>	*   for (final Runnable task : tasks) {
148		*     phaser.register();
149		*     new Thread() {
150		*       public void run() {
151		*         do {
152	<	*           r.run();
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	<	* <p>To create a set of tasks using a tree of phasers,
162	<	* you could use code of the following form, assuming a
163	<	* Task class with a constructor accepting a phaser that
164	<	* it registers for upon construction:
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 {@code n} tasks using a tree of phasers, you
187	>	* could use code of the following form, assuming a Task class with a
188	>	* constructor accepting a {@code Phaser} that it registers with upon
189	>	* construction. After invocation of {@code build(new Task[n], 0, n,
190	>	* new Phaser())}, these tasks could then be started, for example by
191	>	* submitting to a pool:
192	>	*
193		*  <pre> {@code
194	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
195	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
196	<	*   if (step > 1) {
197	<	*     int i = lo;
198	<	*     while (i < hi) {
150	<	*       int r = Math.min(i + step, hi);
151	<	*       build(actions, i, r, new Phaser(b));
152	<	*       i = r;
194	>	* void build(Task[] tasks, int lo, int hi, Phaser ph) {
195	>	*   if (hi - lo > TASKS_PER_PHASER) {
196	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
197	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
198	>	*       build(tasks, i, j, new Phaser(ph));
199		*     }
200		*   } else {
201		*     for (int i = lo; i < hi; ++i)
202	<	*       actions[i] = new Task(b);
203	<	*       // assumes new Task(b) performs b.register()
202	>	*       tasks[i] = new Task(ph);
203	>	*       // assumes new Task(ph) performs ph.register()
204		*   }
205	<	* }
160	<	* // .. initially called, for n tasks via
161	<	* build(new Task[n], 0, n, new Phaser());}</pre>
205	>	* }}</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		*
168	–	* </pre>
169	–	*
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 IllegalStateExceptions. However, you can and
214	>	* parties result in {@code IllegalStateException}. However, you can and
215		* should create tiered phasers to accommodate arbitrarily large sets
216		* of participants.
217		*
#	Line 184 | Line 226 | public class Phaser {
226		*/
227
228		/**
229	<	* Barrier state representation. Conceptually, a barrier contains
188	<	* 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)
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.
241	<	*
242	<	* Note: there are some cheats in arrive() that rely on unarrived
243	<	* count being lowest 16 bits.
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	>	* Except that a phaser with no registered parties is
237	>	* distinguished with the otherwise illegal state of having zero
238	>	* parties and one unarrived parties (encoded as EMPTY below).
239	>	*
240	>	* To efficiently maintain atomicity, these values are packed into
241	>	* a single (atomic) long. Good performance relies on keeping
242	>	* state decoding and encoding simple, and keeping race windows
243	>	* short.
244	>	*
245	>	* All state updates are performed via CAS except initial
246	>	* registration of a sub-phaser (i.e., one with a non-null
247	>	* parent).  In this (relatively rare) case, we use built-in
248	>	* synchronization to lock while first registering with its
249	>	* parent.
250	>	*
251	>	* The phase of a subphaser is allowed to lag that of its
252	>	* ancestors until it is actually accessed.  Method reconcileState
253	>	* is usually attempted only only when the number of unarrived
254	>	* parties appears to be zero, which indicates a potential lag in
255	>	* updating phase after the root advanced.
256		*/
257		private volatile long state;
258
259	<	private static final int ushortBits = 16;
260	<	private static final int ushortMask = 0xffff;
261	<	private static final int phaseMask  = 0x7fffffff;
259	>	private static final int  MAX_PARTIES     = 0xffff;
260	>	private static final int  MAX_PHASE       = 0x7fffffff;
261	>	private static final int  PARTIES_SHIFT   = 16;
262	>	private static final int  PHASE_SHIFT     = 32;
263	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
264	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
265	>	private static final long TERMINATION_BIT = 1L << 63;
266	>
267	>	// some special values
268	>	private static final int  ONE_ARRIVAL     = 1;
269	>	private static final int  ONE_PARTY       = 1 << PARTIES_SHIFT;
270	>	private static final int  EMPTY           = 1;
271	>
272	>	// The following unpacking methods are usually manually inlined
273
274		private static int unarrivedOf(long s) {
275	<	return (int) (s & ushortMask);
275	>	int counts = (int)s;
276	>	return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK;
277		}
278
279		private static int partiesOf(long s) {
280	<	return ((int) s) >>> 16;
280	>	int counts = (int)s;
281	>	return (counts == EMPTY) ? 0 : counts >>> PARTIES_SHIFT;
282		}
283
284		private static int phaseOf(long s) {
285	<	return (int) (s >>> 32);
285	>	return (int) (s >>> PHASE_SHIFT);
286		}
287
288		private static int arrivedOf(long s) {
289	<	return partiesOf(s) - unarrivedOf(s);
290	<	}
291	<
226	<	private static long stateFor(int phase, int parties, int unarrived) {
227	<	return ((((long) phase) << 32) | (((long) parties) << 16) |
228	<	(long) unarrived);
229	<	}
230	<
231	<	private static long trippedStateFor(int phase, int parties) {
232	<	long lp = (long) parties;
233	<	return (((long) phase) << 32) | (lp << 16) | lp;
234	<	}
235	<
236	<	/**
237	<	* Returns message string for bad bounds exceptions.
238	<	*/
239	<	private static String badBounds(int parties, int unarrived) {
240	<	return ("Attempt to set " + unarrived +
241	<	" unarrived of " + parties + " parties");
289	>	int counts = (int)s;
290	>	return (counts == EMPTY) ? 0 :
291	>	(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK);
292		}
293
294		/**
#	Line 247 | Line 297 | public class Phaser {
297		private final Phaser parent;
298
299		/**
300	<	* The root of phaser tree. Equals this if not in a tree.  Used to
251	<	* support faster state push-down.
300	>	* The root of phaser tree. Equals this if not in a tree.
301		*/
302		private final Phaser root;
303
255	–	// Wait queues
256	–
304		/**
305		* Heads of Treiber stacks for waiting threads. To eliminate
306	<	* contention while releasing some threads while adding others, we
306	>	* contention when releasing some threads while adding others, we
307		* use two of them, alternating across even and odd phases.
308	+	* Subphasers share queues with root to speed up releases.
309		*/
310	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
311	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
310	>	private final AtomicReference<QNode> evenQ;
311	>	private final AtomicReference<QNode> oddQ;
312
313		private AtomicReference<QNode> queueFor(int phase) {
314		return ((phase & 1) == 0) ? evenQ : oddQ;
315		}
316
317		/**
318	<	* Returns current state, first resolving lagged propagation from
271	<	* root if necessary.
318	>	* Returns message string for bounds exceptions on arrival.
319		*/
320	<	private long getReconciledState() {
321	<	return (parent == null) ? state : reconcileState();
320	>	private String badArrive(long s) {
321	>	return "Attempted arrival of unregistered party for " +
322	>	stateToString(s);
323		}
324
325		/**
326	<	* Recursively resolves state.
326	>	* Returns message string for bounds exceptions on registration.
327		*/
328	<	private long reconcileState() {
329	<	Phaser p = parent;
330	<	long s = state;
331	<	if (p != null) {
332	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
333	<	long parentState = p.getReconciledState();
334	<	int parentPhase = phaseOf(parentState);
335	<	int phase = phaseOf(s = state);
336	<	if (phase != parentPhase) {
337	<	long next = trippedStateFor(parentPhase, partiesOf(s));
338	<	if (casState(s, next)) {
328	>	private String badRegister(long s) {
329	>	return "Attempt to register more than " +
330	>	MAX_PARTIES + " parties for " + stateToString(s);
331	>	}
332	>
333	>	/**
334	>	* Main implementation for methods arrive and arriveAndDeregister.
335	>	* Manually tuned to speed up and minimize race windows for the
336	>	* common case of just decrementing unarrived field.
337	>	*
338	>	* @param deregister false for arrive, true for arriveAndDeregister
339	>	*/
340	>	private int doArrive(boolean deregister) {
341	>	int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL;
342	>	long s;
343	>	int phase;
344	>	while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0) {
345	>	int counts = (int)s;
346	>	int unarrived = counts & UNARRIVED_MASK;
347	>	if (counts == EMPTY || unarrived == 0) {
348	>	if (reconcileState() == s)
349	>	throw new IllegalStateException(badArrive(s));
350	>	}
351	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
352	>	if (unarrived == 1) {
353	>	long n = s & PARTIES_MASK;       // unshifted parties field
354	>	int u = ((int)n) >>> PARTIES_SHIFT;
355	>	Phaser par = parent;
356	>	if (par != null) {
357	>	par.doArrive(u == 0);
358	>	reconcileState();
359	>	}
360	>	else {
361	>	n |= (((long)((phase+1) & MAX_PHASE)) << PHASE_SHIFT);
362	>	if (onAdvance(phase, u))
363	>	n |= TERMINATION_BIT;
364	>	else if (u == 0)
365	>	n |= EMPTY;             // reset to unregistered
366	>	else
367	>	n |= (long)u;           // reset unarr to parties
368	>	// assert state == s || isTerminated();
369	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
370		releaseWaiters(phase);
292	–	s = next;
371		}
372		}
373	+	break;
374	+	}
375	+	}
376	+	return phase;
377	+	}
378	+
379	+	/**
380	+	* Implementation of register, bulkRegister
381	+	*
382	+	* @param registrations number to add to both parties and
383	+	* unarrived fields. Must be greater than zero.
384	+	*/
385	+	private int doRegister(int registrations) {
386	+	// adjustment to state
387	+	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
388	+	Phaser par = parent;
389	+	int phase;
390	+	for (;;) {
391	+	long s = state;
392	+	int counts = (int)s;
393	+	int parties = counts >>> PARTIES_SHIFT;
394	+	int unarrived = counts & UNARRIVED_MASK;
395	+	if (registrations > MAX_PARTIES - parties)
396	+	throw new IllegalStateException(badRegister(s));
397	+	else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
398	+	break;
399	+	else if (counts != EMPTY) {             // not 1st registration
400	+	if (par == null || reconcileState() == s) {
401	+	if (unarrived == 0)             // wait out advance
402	+	root.internalAwaitAdvance(phase, null);
403	+	else if (UNSAFE.compareAndSwapLong(this, stateOffset,
404	+	s, s + adj))
405	+	break;
406	+	}
407	+	}
408	+	else if (par == null) {                 // 1st root registration
409	+	long next = (((long) phase) << PHASE_SHIFT) | adj;
410	+	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
411	+	break;
412	+	}
413	+	else {
414	+	synchronized (this) {               // 1st sub registration
415	+	if (state == s) {               // recheck under lock
416	+	par.doRegister(1);
417	+	do {                        // force current phase
418	+	phase = (int)(root.state >>> PHASE_SHIFT);
419	+	// assert phase < 0 || (int)state == EMPTY;
420	+	} while (!UNSAFE.compareAndSwapLong
421	+	(this, stateOffset, state,
422	+	(((long) phase) << PHASE_SHIFT) | adj));
423	+	break;
424	+	}
425	+	}
426	+	}
427	+	}
428	+	return phase;
429	+	}
430	+
431	+	/**
432	+	* Resolves lagged phase propagation from root if necessary.
433	+	*/
434	+	private long reconcileState() {
435	+	Phaser rt = root;
436	+	long s = state;
437	+	if (rt != this) {
438	+	int phase;
439	+	while ((phase = (int)(rt.state >>> PHASE_SHIFT)) !=
440	+	(int)(s >>> PHASE_SHIFT)) {
441	+	// assert phase < 0 || unarrivedOf(s) == 0
442	+	long t;                             // to reread s
443	+	long p = s & PARTIES_MASK;          // unshifted parties field
444	+	long n = (((long) phase) << PHASE_SHIFT) | p;
445	+	if (phase >= 0) {
446	+	if (p == 0L)
447	+	n |= EMPTY;                 // reset to empty
448	+	else
449	+	n |= p >>> PARTIES_SHIFT;   // set unarr to parties
450	+	}
451	+	if ((t = state) == s &&
452	+	UNSAFE.compareAndSwapLong(this, stateOffset, s, s = n))
453	+	break;
454	+	s = t;
455		}
456		}
457		return s;
458		}
459
460		/**
461	<	* Creates a new phaser without any initially registered parties,
462	<	* initial phase number 0, and no parent. Any thread using this
461	>	* Creates a new phaser with no initially registered parties, no
462	>	* parent, and initial phase number 0. Any thread using this
463		* phaser will need to first register for it.
464		*/
465		public Phaser() {
466	<	this(null);
466	>	this(null, 0);
467		}
468
469		/**
470	<	* Creates a new phaser with the given numbers of registered
471	<	* unarrived parties, initial phase number 0, and no parent.
470	>	* Creates a new phaser with the given number of registered
471	>	* unarrived parties, no parent, and initial phase number 0.
472		*
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		*/
#	Line 319 | Line 480 | public class Phaser {
480		}
481
482		/**
483	<	* Creates a new phaser with the given parent, without any
323	<	* initially registered parties. If parent is non-null this phaser
324	<	* is registered with the parent and its initial phase number is
325	<	* the same as that of parent phaser.
483	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
484		*
485		* @param parent the parent phaser
486		*/
487		public Phaser(Phaser parent) {
488	<	int phase = 0;
331	<	this.parent = parent;
332	<	if (parent != null) {
333	<	this.root = parent.root;
334	<	phase = parent.register();
335	<	}
336	<	else
337	<	this.root = this;
338	<	this.state = trippedStateFor(phase, 0);
488	>	this(parent, 0);
489		}
490
491		/**
492	<	* Creates a new phaser with the given parent and numbers of
493	<	* registered unarrived parties. If parent is non-null, this phaser
494	<	* is registered with the parent and its initial phase number is
495	<	* the same as that of parent phaser.
492	>	* Creates a new phaser with the given parent and number of
493	>	* registered unarrived parties. Registration and deregistration
494	>	* of this child phaser with its parent are managed automatically.
495	>	* If the given parent is non-null, whenever this child phaser has
496	>	* any registered parties (as established in this constructor,
497	>	* {@link #register}, or {@link #bulkRegister}), this child phaser
498	>	* is registered with its parent. Whenever the number of
499	>	* registered parties becomes zero as the result of an invocation
500	>	* of {@link #arriveAndDeregister}, this child phaser is
501	>	* deregistered from its parent.
502		*
503		* @param parent the parent phaser
504	<	* @param parties the number of parties required to trip barrier
504	>	* @param parties the number of parties required to advance to the
505	>	* next phase
506		* @throws IllegalArgumentException if parties less than zero
507		* or greater than the maximum number of parties supported
508		*/
509		public Phaser(Phaser parent, int parties) {
510	<	if (parties < 0 || parties > ushortMask)
510	>	if (parties >>> PARTIES_SHIFT != 0)
511		throw new IllegalArgumentException("Illegal number of parties");
512		int phase = 0;
513		this.parent = parent;
514		if (parent != null) {
515	<	this.root = parent.root;
516	<	phase = parent.register();
515	>	Phaser r = parent.root;
516	>	this.root = r;
517	>	this.evenQ = r.evenQ;
518	>	this.oddQ = r.oddQ;
519	>	if (parties != 0)
520	>	phase = parent.doRegister(1);
521		}
522	<	else
522	>	else {
523		this.root = this;
524	<	this.state = trippedStateFor(phase, parties);
524	>	this.evenQ = new AtomicReference<QNode>();
525	>	this.oddQ = new AtomicReference<QNode>();
526	>	}
527	>	this.state = (parties == 0) ? ((long) EMPTY) :
528	>	((((long) phase) << PHASE_SHIFT) |
529	>	(((long) parties) << PARTIES_SHIFT) |
530	>	((long) parties));
531		}
532
533		/**
534	<	* Adds a new unarrived party to this phaser.
534	>	* Adds a new unarrived party to this phaser.  If an ongoing
535	>	* invocation of {@link #onAdvance} is in progress, this method
536	>	* may await its completion before returning.  If this phaser has
537	>	* a parent, and this phaser previously had no registered parties,
538	>	* this phaser is also registered with its parent.
539		*
540	<	* @return the current barrier phase number upon registration
540	>	* @return the arrival phase number to which this registration applied
541		* @throws IllegalStateException if attempting to register more
542		* than the maximum supported number of parties
543		*/
#	Line 376 | Line 547 | public class Phaser {
547
548		/**
549		* Adds the given number of new unarrived parties to this phaser.
550	<	*
551	<	* @param parties the number of parties required to trip barrier
552	<	* @return the current barrier phase number upon registration
550	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
551	>	* this method may await its completion before returning.  If this
552	>	* phaser has a parent, and the given number of parities is
553	>	* greater than zero, and this phaser previously had no registered
554	>	* parties, this phaser is also registered with its parent.
555	>	*
556	>	* @param parties the number of additional parties required to
557	>	* advance to the next phase
558	>	* @return the arrival phase number to which this registration applied
559		* @throws IllegalStateException if attempting to register more
560		* than the maximum supported number of parties
561	+	* @throws IllegalArgumentException if {@code parties < 0}
562		*/
563		public int bulkRegister(int parties) {
564		if (parties < 0)
#	Line 391 | Line 569 | public class Phaser {
569		}
570
571		/**
572	<	* Shared code for register, bulkRegister
573	<	*/
574	<	private int doRegister(int registrations) {
575	<	int phase;
576	<	for (;;) {
577	<	long s = getReconciledState();
400	<	phase = phaseOf(s);
401	<	int unarrived = unarrivedOf(s) + registrations;
402	<	int parties = partiesOf(s) + registrations;
403	<	if (phase < 0)
404	<	break;
405	<	if (parties > ushortMask || unarrived > ushortMask)
406	<	throw new IllegalStateException(badBounds(parties, unarrived));
407	<	if (phase == phaseOf(root.state) &&
408	<	casState(s, stateFor(phase, parties, unarrived)))
409	<	break;
410	<	}
411	<	return phase;
412	<	}
413	<
414	<	/**
415	<	* Arrives at the barrier, but does not wait for others.  (You can
416	<	* in turn wait for others via {@link #awaitAdvance}).
572	>	* Arrives at this phaser, without waiting for others to arrive.
573	>	*
574	>	* <p>It is a usage error for an unregistered party to invoke this
575	>	* method.  However, this error may result in an {@code
576	>	* IllegalStateException} only upon some subsequent operation on
577	>	* this phaser, if ever.
578		*
579	<	* @return the barrier phase number upon entry to this method, or a
419	<	* negative value if terminated
579	>	* @return the arrival phase number, or a negative value if terminated
580		* @throws IllegalStateException if not terminated and the number
581		* of unarrived parties would become negative
582		*/
583		public int arrive() {
584	<	int phase;
425	<	for (;;) {
426	<	long s = state;
427	<	phase = phaseOf(s);
428	<	if (phase < 0)
429	<	break;
430	<	int parties = partiesOf(s);
431	<	int unarrived = unarrivedOf(s) - 1;
432	<	if (unarrived > 0) {        // Not the last arrival
433	<	if (casState(s, s - 1)) // s-1 adds one arrival
434	<	break;
435	<	}
436	<	else if (unarrived == 0) {  // the last arrival
437	<	Phaser par = parent;
438	<	if (par == null) {      // directly trip
439	<	if (casState
440	<	(s,
441	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
442	<	((phase + 1) & phaseMask), parties))) {
443	<	releaseWaiters(phase);
444	<	break;
445	<	}
446	<	}
447	<	else {                  // cascade to parent
448	<	if (casState(s, s - 1)) { // zeroes unarrived
449	<	par.arrive();
450	<	reconcileState();
451	<	break;
452	<	}
453	<	}
454	<	}
455	<	else if (phase != phaseOf(root.state)) // or if unreconciled
456	<	reconcileState();
457	<	else
458	<	throw new IllegalStateException(badBounds(parties, unarrived));
459	<	}
460	<	return phase;
584	>	return doArrive(false);
585		}
586
587		/**
588	<	* Arrives at the barrier and deregisters from it without waiting
589	<	* for others. Deregistration reduces the number of parties
590	<	* required to trip the barrier in future phases.  If this phaser
588	>	* Arrives at this phaser and deregisters from it without waiting
589	>	* for others to arrive. Deregistration reduces the number of
590	>	* parties required to advance in future phases.  If this phaser
591		* has a parent, and deregistration causes this phaser to have
592	<	* zero parties, this phaser also arrives at and is deregistered
593	<	* from its parent.
592	>	* zero parties, this phaser is also deregistered from its parent.
593	>	*
594	>	* <p>It is a usage error for an unregistered party to invoke this
595	>	* method.  However, this error may result in an {@code
596	>	* IllegalStateException} only upon some subsequent operation on
597	>	* this phaser, if ever.
598		*
599	<	* @return the current barrier phase number upon entry to
472	<	* this method, or a negative value if terminated
599	>	* @return the arrival phase number, or a negative value if terminated
600		* @throws IllegalStateException if not terminated and the number
601		* of registered or unarrived parties would become negative
602		*/
603		public int arriveAndDeregister() {
604	<	// similar code to arrive, but too different to merge
478	<	Phaser par = parent;
479	<	int phase;
480	<	for (;;) {
481	<	long s = state;
482	<	phase = phaseOf(s);
483	<	if (phase < 0)
484	<	break;
485	<	int parties = partiesOf(s) - 1;
486	<	int unarrived = unarrivedOf(s) - 1;
487	<	if (parties >= 0) {
488	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
489	<	if (casState
490	<	(s,
491	<	stateFor(phase, parties, unarrived))) {
492	<	if (unarrived == 0) {
493	<	par.arriveAndDeregister();
494	<	reconcileState();
495	<	}
496	<	break;
497	<	}
498	<	continue;
499	<	}
500	<	if (unarrived == 0) {
501	<	if (casState
502	<	(s,
503	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
504	<	((phase + 1) & phaseMask), parties))) {
505	<	releaseWaiters(phase);
506	<	break;
507	<	}
508	<	continue;
509	<	}
510	<	if (par != null && phase != phaseOf(root.state)) {
511	<	reconcileState();
512	<	continue;
513	<	}
514	<	}
515	<	throw new IllegalStateException(badBounds(parties, unarrived));
516	<	}
517	<	return phase;
604	>	return doArrive(true);
605		}
606
607		/**
608	<	* Arrives at the barrier and awaits others. Equivalent in effect
608	>	* Arrives at this phaser and awaits others. Equivalent in effect
609		* to {@code awaitAdvance(arrive())}.  If you need to await with
610		* interruption or timeout, you can arrange this with an analogous
611	<	* construction using one of the other forms of the awaitAdvance
612	<	* method.  If instead you need to deregister upon arrival use
613	<	* {@code arriveAndDeregister}.
611	>	* construction using one of the other forms of the {@code
612	>	* awaitAdvance} method.  If instead you need to deregister upon
613	>	* arrival, use {@code awaitAdvance(arriveAndDeregister())}.
614	>	*
615	>	* <p>It is a usage error for an unregistered party to invoke this
616	>	* method.  However, this error may result in an {@code
617	>	* IllegalStateException} only upon some subsequent operation on
618	>	* this phaser, if ever.
619		*
620	<	* @return the phase on entry to this method
620	>	* @return the arrival phase number, or a negative number if terminated
621		* @throws IllegalStateException if not terminated and the number
622		* of unarrived parties would become negative
623		*/
624		public int arriveAndAwaitAdvance() {
625	<	return awaitAdvance(arrive());
625	>	return awaitAdvance(doArrive(false));
626		}
627
628		/**
629	<	* Awaits the phase of the barrier to advance from the given phase
630	<	* value, or returns immediately if the current phase of the barrier
631	<	* is not equal to the given phase value or this barrier is
540	<	* terminated.
629	>	* Awaits the phase of this phaser to advance from the given phase
630	>	* value, returning immediately if the current phase is not equal
631	>	* to the given phase value or this phaser is terminated.
632		*
633	<	* @param phase the phase on entry to this method
634	<	* @return the phase on exit from this method
633	>	* @param phase an arrival phase number, or negative value if
634	>	* terminated; this argument is normally the value returned by a
635	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
636	>	* @return the next arrival phase number, or a negative value
637	>	* if terminated or argument is negative
638		*/
639		public int awaitAdvance(int phase) {
640	+	Phaser rt;
641	+	int p = (int)(state >>> PHASE_SHIFT);
642		if (phase < 0)
643		return phase;
644	<	long s = getReconciledState();
645	<	int p = phaseOf(s);
646	<	if (p != phase)
647	<	return p;
648	<	if (unarrivedOf(s) == 0 && parent != null)
649	<	parent.awaitAdvance(phase);
554	<	// Fall here even if parent waited, to reconcile and help release
555	<	return untimedWait(phase);
644	>	if (p == phase) {
645	>	if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase)
646	>	return rt.internalAwaitAdvance(phase, null);
647	>	reconcileState();
648	>	}
649	>	return p;
650		}
651
652		/**
653	<	* Awaits the phase of the barrier to advance from the given
654	<	* value, or returns immediately if argument is negative or this
655	<	* barrier is terminated, or throws InterruptedException if
656	<	* interrupted while waiting.
653	>	* Awaits the phase of this phaser to advance from the given phase
654	>	* value, throwing {@code InterruptedException} if interrupted
655	>	* while waiting, or returning immediately if the current phase is
656	>	* not equal to the given phase value or this phaser is
657	>	* terminated.
658		*
659	<	* @param phase the phase on entry to this method
660	<	* @return the phase on exit from this method
659	>	* @param phase an arrival phase number, or negative value if
660	>	* terminated; this argument is normally the value returned by a
661	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
662	>	* @return the next arrival phase number, or a negative value
663	>	* if terminated or argument is negative
664		* @throws InterruptedException if thread interrupted while waiting
665		*/
666		public int awaitAdvanceInterruptibly(int phase)
667		throws InterruptedException {
668	+	Phaser rt;
669	+	int p = (int)(state >>> PHASE_SHIFT);
670		if (phase < 0)
671		return phase;
672	<	long s = getReconciledState();
673	<	int p = phaseOf(s);
674	<	if (p != phase)
675	<	return p;
676	<	if (unarrivedOf(s) == 0 && parent != null)
677	<	parent.awaitAdvanceInterruptibly(phase);
678	<	return interruptibleWait(phase);
672	>	if (p == phase) {
673	>	if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
674	>	QNode node = new QNode(this, phase, true, false, 0L);
675	>	p = rt.internalAwaitAdvance(phase, node);
676	>	if (node.wasInterrupted)
677	>	throw new InterruptedException();
678	>	}
679	>	else
680	>	reconcileState();
681	>	}
682	>	return p;
683		}
684
685		/**
686	<	* Awaits the phase of the barrier to advance from the given value
687	<	* or the given timeout elapses, or returns immediately if
688	<	* argument is negative or this barrier is terminated.
689	<	*
690	<	* @param phase the phase on entry to this method
691	<	* @return the phase on exit from this method
686	>	* Awaits the phase of this phaser to advance from the given phase
687	>	* value or the given timeout to elapse, throwing {@code
688	>	* InterruptedException} if interrupted while waiting, or
689	>	* returning immediately if the current phase is not equal to the
690	>	* given phase value or this phaser is terminated.
691	>	*
692	>	* @param phase an arrival phase number, or negative value if
693	>	* terminated; this argument is normally the value returned by a
694	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
695	>	* @param timeout how long to wait before giving up, in units of
696	>	*        {@code unit}
697	>	* @param unit a {@code TimeUnit} determining how to interpret the
698	>	*        {@code timeout} parameter
699	>	* @return the next arrival phase number, or a negative value
700	>	* if terminated or argument is negative
701		* @throws InterruptedException if thread interrupted while waiting
702		* @throws TimeoutException if timed out while waiting
703		*/
704		public int awaitAdvanceInterruptibly(int phase,
705		long timeout, TimeUnit unit)
706		throws InterruptedException, TimeoutException {
707	+	long nanos = unit.toNanos(timeout);
708	+	Phaser rt;
709	+	int p = (int)(state >>> PHASE_SHIFT);
710		if (phase < 0)
711		return phase;
712	<	long s = getReconciledState();
713	<	int p = phaseOf(s);
714	<	if (p != phase)
715	<	return p;
716	<	if (unarrivedOf(s) == 0 && parent != null)
717	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
718	<	return timedWait(phase, unit.toNanos(timeout));
712	>	if (p == phase) {
713	>	if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
714	>	QNode node = new QNode(this, phase, true, true, nanos);
715	>	p = rt.internalAwaitAdvance(phase, node);
716	>	if (node.wasInterrupted)
717	>	throw new InterruptedException();
718	>	else if (p == phase)
719	>	throw new TimeoutException();
720	>	}
721	>	else
722	>	reconcileState();
723	>	}
724	>	return p;
725		}
726
727		/**
728	<	* Forces this barrier to enter termination state. Counts of
729	<	* arrived and registered parties are unaffected. If this phaser
730	<	* has a parent, it too is terminated. This method may be useful
731	<	* for coordinating recovery after one or more tasks encounter
728	>	* Forces this phaser to enter termination state.  Counts of
729	>	* registered parties are unaffected.  If this phaser is a member
730	>	* of a tiered set of phasers, then all of the phasers in the set
731	>	* are terminated.  If this phaser is already terminated, this
732	>	* method has no effect.  This method may be useful for
733	>	* coordinating recovery after one or more tasks encounter
734		* unexpected exceptions.
735		*/
736		public void forceTermination() {
737	<	for (;;) {
738	<	long s = getReconciledState();
739	<	int phase = phaseOf(s);
740	<	int parties = partiesOf(s);
741	<	int unarrived = unarrivedOf(s);
742	<	if (phase < 0 ||
743	<	casState(s, stateFor(-1, parties, unarrived))) {
620	<	releaseWaiters(0);
737	>	// Only need to change root state
738	>	final Phaser root = this.root;
739	>	long s;
740	>	while ((s = root.state) >= 0) {
741	>	long next = (s & ~(long)(MAX_PARTIES)) | TERMINATION_BIT;
742	>	if (UNSAFE.compareAndSwapLong(root, stateOffset, s, next)) {
743	>	releaseWaiters(0); // signal all threads
744		releaseWaiters(1);
622	–	if (parent != null)
623	–	parent.forceTermination();
745		return;
746		}
747		}
#	Line 629 | Line 750 | public class Phaser {
750		/**
751		* Returns the current phase number. The maximum phase number is
752		* {@code Integer.MAX_VALUE}, after which it restarts at
753	<	* zero. Upon termination, the phase number is negative.
753	>	* zero. Upon termination, the phase number is negative,
754	>	* in which case the prevailing phase prior to termination
755	>	* may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
756		*
757		* @return the phase number, or a negative value if terminated
758		*/
759		public final int getPhase() {
760	<	return phaseOf(getReconciledState());
760	>	return (int)(root.state >>> PHASE_SHIFT);
761		}
762
763		/**
764	<	* Returns the number of parties registered at this barrier.
764	>	* Returns the number of parties registered at this phaser.
765		*
766		* @return the number of parties
767		*/
#	Line 647 | Line 770 | public class Phaser {
770		}
771
772		/**
773	<	* Returns the number of parties that have arrived at the current
774	<	* phase of this barrier.
773	>	* Returns the number of registered parties that have arrived at
774	>	* the current phase of this phaser.
775		*
776		* @return the number of arrived parties
777		*/
778		public int getArrivedParties() {
779	<	return arrivedOf(state);
779	>	return arrivedOf(reconcileState());
780		}
781
782		/**
783		* Returns the number of registered parties that have not yet
784	<	* arrived at the current phase of this barrier.
784	>	* arrived at the current phase of this phaser.
785		*
786		* @return the number of unarrived parties
787		*/
788		public int getUnarrivedParties() {
789	<	return unarrivedOf(state);
789	>	return unarrivedOf(reconcileState());
790		}
791
792		/**
#	Line 686 | Line 809 | public class Phaser {
809		}
810
811		/**
812	<	* Returns {@code true} if this barrier has been terminated.
812	>	* Returns {@code true} if this phaser has been terminated.
813		*
814	<	* @return {@code true} if this barrier has been terminated
814	>	* @return {@code true} if this phaser has been terminated
815		*/
816		public boolean isTerminated() {
817	<	return getPhase() < 0;
817	>	return root.state < 0L;
818		}
819
820		/**
821	<	* Overridable method to perform an action upon phase advance, and
822	<	* to control termination. This method is invoked whenever the
823	<	* barrier is tripped (and thus all other waiting parties are
824	<	* dormant). If it returns {@code true}, then, rather than advance
825	<	* the phase number, this barrier will be set to a final
826	<	* termination state, and subsequent calls to {@link #isTerminated}
827	<	* will return true.
828	<	*
829	<	* <p>The default version returns {@code true} when the number of
830	<	* registered parties is zero. Normally, overrides that arrange
831	<	* termination for other reasons should also preserve this
832	<	* property.
833	<	*
834	<	* <p>You may override this method to perform an action with side
835	<	* effects visible to participating tasks, but it is in general
836	<	* only sensible to do so in designs where all parties register
837	<	* before any arrive, and all {@link #awaitAdvance} at each phase.
838	<	* Otherwise, you cannot ensure lack of interference from other
839	<	* parties during the the invocation of this method.
821	>	* Overridable method to perform an action upon impending phase
822	>	* advance, and to control termination. This method is invoked
823	>	* upon arrival of the party advancing this phaser (when all other
824	>	* waiting parties are dormant).  If this method returns {@code
825	>	* true}, this phaser will be set to a final termination state
826	>	* upon advance, and subsequent calls to {@link #isTerminated}
827	>	* will return true. Any (unchecked) Exception or Error thrown by
828	>	* an invocation of this method is propagated to the party
829	>	* attempting to advance this phaser, in which case no advance
830	>	* occurs.
831	>	*
832	>	* <p>The arguments to this method provide the state of the phaser
833	>	* prevailing for the current transition.  The effects of invoking
834	>	* arrival, registration, and waiting methods on this phaser from
835	>	* within {@code onAdvance} are unspecified and should not be
836	>	* relied on.
837	>	*
838	>	* <p>If this phaser is a member of a tiered set of phasers, then
839	>	* {@code onAdvance} is invoked only for its root phaser on each
840	>	* advance.
841	>	*
842	>	* <p>To support the most common use cases, the default
843	>	* implementation of this method returns {@code true} when the
844	>	* number of registered parties has become zero as the result of a
845	>	* party invoking {@code arriveAndDeregister}.  You can disable
846	>	* this behavior, thus enabling continuation upon future
847	>	* registrations, by overriding this method to always return
848	>	* {@code false}:
849	>	*
850	>	* <pre> {@code
851	>	* Phaser phaser = new Phaser() {
852	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
853	>	* }}</pre>
854		*
855	<	* @param phase the phase number on entering the barrier
855	>	* @param phase the current phase number on entry to this method,
856	>	* before this phaser is advanced
857		* @param registeredParties the current number of registered parties
858	<	* @return {@code true} if this barrier should terminate
858	>	* @return {@code true} if this phaser should terminate
859		*/
860		protected boolean onAdvance(int phase, int registeredParties) {
861	<	return registeredParties <= 0;
861	>	return registeredParties == 0;
862		}
863
864		/**
#	Line 730 | Line 868 | public class Phaser {
868		* followed by the number of registered parties, and {@code
869		* "arrived = "} followed by the number of arrived parties.
870		*
871	<	* @return a string identifying this barrier, as well as its state
871	>	* @return a string identifying this phaser, as well as its state
872		*/
873		public String toString() {
874	<	long s = getReconciledState();
874	>	return stateToString(reconcileState());
875	>	}
876	>
877	>	/**
878	>	* Implementation of toString and string-based error messages
879	>	*/
880	>	private String stateToString(long s) {
881		return super.toString() +
882		"[phase = " + phaseOf(s) +
883		" parties = " + partiesOf(s) +
884		" arrived = " + arrivedOf(s) + "]";
885		}
886
887	<	// methods for waiting
887	>	// Waiting mechanics
888
889		/**
890	<	* Wait nodes for Treiber stack representing wait queue
890	>	* Removes and signals threads from queue for phase.
891		*/
892	<	static final class QNode implements ForkJoinPool.ManagedBlocker {
893	<	final Phaser phaser;
894	<	final int phase;
895	<	final long startTime;
896	<	final long nanos;
897	<	final boolean timed;
898	<	final boolean interruptible;
899	<	volatile boolean wasInterrupted = false;
900	<	volatile Thread thread; // nulled to cancel wait
901	<	QNode next;
902	<	QNode(Phaser phaser, int phase, boolean interruptible,
759	<	boolean timed, long startTime, long nanos) {
760	<	this.phaser = phaser;
761	<	this.phase = phase;
762	<	this.timed = timed;
763	<	this.interruptible = interruptible;
764	<	this.startTime = startTime;
765	<	this.nanos = nanos;
766	<	thread = Thread.currentThread();
767	<	}
768	<	public boolean isReleasable() {
769	<	return (thread == null ||
770	<	phaser.getPhase() != phase ||
771	<	(interruptible && wasInterrupted) ||
772	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
773	<	}
774	<	public boolean block() {
775	<	if (Thread.interrupted()) {
776	<	wasInterrupted = true;
777	<	if (interruptible)
778	<	return true;
779	<	}
780	<	if (!timed)
781	<	LockSupport.park(this);
782	<	else {
783	<	long waitTime = nanos - (System.nanoTime() - startTime);
784	<	if (waitTime <= 0)
785	<	return true;
786	<	LockSupport.parkNanos(this, waitTime);
787	<	}
788	<	return isReleasable();
789	<	}
790	<	void signal() {
791	<	Thread t = thread;
792	<	if (t != null) {
793	<	thread = null;
892	>	private void releaseWaiters(int phase) {
893	>	QNode q;   // first element of queue
894	>	int p;     // its phase
895	>	Thread t;  // its thread
896	>	//        assert phase != phaseOf(root.state);
897	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
898	>	while ((q = head.get()) != null &&
899	>	q.phase != (int)(root.state >>> PHASE_SHIFT)) {
900	>	if (head.compareAndSet(q, q.next) &&
901	>	(t = q.thread) != null) {
902	>	q.thread = null;
903		LockSupport.unpark(t);
904		}
905		}
797	–	boolean doWait() {
798	–	if (thread != null) {
799	–	try {
800	–	ForkJoinPool.managedBlock(this, false);
801	–	} catch (InterruptedException ie) {
802	–	}
803	–	}
804	–	return wasInterrupted;
805	–	}
806	–
906		}
907
908	<	/**
909	<	* Removes and signals waiting threads from wait queue.
811	<	*/
812	<	private void releaseWaiters(int phase) {
813	<	AtomicReference<QNode> head = queueFor(phase);
814	<	QNode q;
815	<	while ((q = head.get()) != null) {
816	<	if (head.compareAndSet(q, q.next))
817	<	q.signal();
818	<	}
819	<	}
908	>	/** The number of CPUs, for spin control */
909	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
910
911		/**
912	<	* Tries to enqueue given node in the appropriate wait queue.
913	<	*
914	<	* @return true if successful
912	>	* The number of times to spin before blocking while waiting for
913	>	* advance, per arrival while waiting. On multiprocessors, fully
914	>	* blocking and waking up a large number of threads all at once is
915	>	* usually a very slow process, so we use rechargeable spins to
916	>	* avoid it when threads regularly arrive: When a thread in
917	>	* internalAwaitAdvance notices another arrival before blocking,
918	>	* and there appear to be enough CPUs available, it spins
919	>	* SPINS_PER_ARRIVAL more times before blocking. The value trades
920	>	* off good-citizenship vs big unnecessary slowdowns.
921		*/
922	<	private boolean tryEnqueue(QNode node) {
827	<	AtomicReference<QNode> head = queueFor(node.phase);
828	<	return head.compareAndSet(node.next = head.get(), node);
829	<	}
922	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
923
924		/**
925	<	* Enqueues node and waits unless aborted or signalled.
925	>	* Possibly blocks and waits for phase to advance unless aborted.
926	>	* Call only from root node.
927		*
928	+	* @param phase current phase
929	+	* @param node if non-null, the wait node to track interrupt and timeout;
930	+	* if null, denotes noninterruptible wait
931		* @return current phase
932		*/
933	<	private int untimedWait(int phase) {
934	<	QNode node = null;
935	<	boolean queued = false;
936	<	boolean interrupted = false;
933	>	private int internalAwaitAdvance(int phase, QNode node) {
934	>	releaseWaiters(phase-1);          // ensure old queue clean
935	>	boolean queued = false;           // true when node is enqueued
936	>	int lastUnarrived = 0;            // to increase spins upon change
937	>	int spins = SPINS_PER_ARRIVAL;
938	>	long s;
939		int p;
940	<	while ((p = getPhase()) == phase) {
941	<	if (Thread.interrupted())
942	<	interrupted = true;
943	<	else if (node == null)
944	<	node = new QNode(this, phase, false, false, 0, 0);
945	<	else if (!queued)
946	<	queued = tryEnqueue(node);
947	<	else
948	<	interrupted = node.doWait();
940	>	while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
941	>	if (node == null) {           // spinning in noninterruptible mode
942	>	int unarrived = (int)s & UNARRIVED_MASK;
943	>	if (unarrived != lastUnarrived &&
944	>	(lastUnarrived = unarrived) < NCPU)
945	>	spins += SPINS_PER_ARRIVAL;
946	>	boolean interrupted = Thread.interrupted();
947	>	if (interrupted || --spins < 0) { // need node to record intr
948	>	node = new QNode(this, phase, false, false, 0L);
949	>	node.wasInterrupted = interrupted;
950	>	}
951	>	}
952	>	else if (node.isReleasable()) // done or aborted
953	>	break;
954	>	else if (!queued) {           // push onto queue
955	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
956	>	QNode q = node.next = head.get();
957	>	if ((q == null || q.phase == phase) &&
958	>	(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
959	>	queued = head.compareAndSet(q, node);
960	>	}
961	>	else {
962	>	try {
963	>	ForkJoinPool.managedBlock(node);
964	>	} catch (InterruptedException ie) {
965	>	node.wasInterrupted = true;
966	>	}
967	>	}
968	>	}
969	>
970	>	if (node != null) {
971	>	if (node.thread != null)
972	>	node.thread = null;       // avoid need for unpark()
973	>	if (node.wasInterrupted && !node.interruptible)
974	>	Thread.currentThread().interrupt();
975	>	if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase)
976	>	return p;                 // recheck abort
977		}
851	–	if (node != null)
852	–	node.thread = null;
978		releaseWaiters(phase);
854	–	if (interrupted)
855	–	Thread.currentThread().interrupt();
979		return p;
980		}
981
982		/**
983	<	* Interruptible version
861	<	* @return current phase
983	>	* Wait nodes for Treiber stack representing wait queue
984		*/
985	<	private int interruptibleWait(int phase) throws InterruptedException {
986	<	QNode node = null;
987	<	boolean queued = false;
988	<	boolean interrupted = false;
989	<	int p;
990	<	while ((p = getPhase()) == phase && !interrupted) {
991	<	if (Thread.interrupted())
992	<	interrupted = true;
993	<	else if (node == null)
994	<	node = new QNode(this, phase, true, false, 0, 0);
995	<	else if (!queued)
996	<	queued = tryEnqueue(node);
997	<	else
998	<	interrupted = node.doWait();
985	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
986	>	final Phaser phaser;
987	>	final int phase;
988	>	final boolean interruptible;
989	>	final boolean timed;
990	>	boolean wasInterrupted;
991	>	long nanos;
992	>	long lastTime;
993	>	volatile Thread thread; // nulled to cancel wait
994	>	QNode next;
995	>
996	>	QNode(Phaser phaser, int phase, boolean interruptible,
997	>	boolean timed, long nanos) {
998	>	this.phaser = phaser;
999	>	this.phase = phase;
1000	>	this.interruptible = interruptible;
1001	>	this.nanos = nanos;
1002	>	this.timed = timed;
1003	>	this.lastTime = timed ? System.nanoTime() : 0L;
1004	>	thread = Thread.currentThread();
1005		}
878	–	if (node != null)
879	–	node.thread = null;
880	–	if (p != phase || (p = getPhase()) != phase)
881	–	releaseWaiters(phase);
882	–	if (interrupted)
883	–	throw new InterruptedException();
884	–	return p;
885	–	}
1006
1007	<	/**
1008	<	* Timeout version.
1009	<	* @return current phase
1010	<	*/
1011	<	private int timedWait(int phase, long nanos)
1012	<	throws InterruptedException, TimeoutException {
1013	<	long startTime = System.nanoTime();
894	<	QNode node = null;
895	<	boolean queued = false;
896	<	boolean interrupted = false;
897	<	int p;
898	<	while ((p = getPhase()) == phase && !interrupted) {
1007	>	public boolean isReleasable() {
1008	>	if (thread == null)
1009	>	return true;
1010	>	if (phaser.getPhase() != phase) {
1011	>	thread = null;
1012	>	return true;
1013	>	}
1014		if (Thread.interrupted())
1015	<	interrupted = true;
1016	<	else if (nanos - (System.nanoTime() - startTime) <= 0)
1017	<	break;
1018	<	else if (node == null)
1019	<	node = new QNode(this, phase, true, true, startTime, nanos);
1020	<	else if (!queued)
1021	<	queued = tryEnqueue(node);
1022	<	else
1023	<	interrupted = node.doWait();
1015	>	wasInterrupted = true;
1016	>	if (wasInterrupted && interruptible) {
1017	>	thread = null;
1018	>	return true;
1019	>	}
1020	>	if (timed) {
1021	>	if (nanos > 0L) {
1022	>	long now = System.nanoTime();
1023	>	nanos -= now - lastTime;
1024	>	lastTime = now;
1025	>	}
1026	>	if (nanos <= 0L) {
1027	>	thread = null;
1028	>	return true;
1029	>	}
1030	>	}
1031	>	return false;
1032	>	}
1033	>
1034	>	public boolean block() {
1035	>	if (isReleasable())
1036	>	return true;
1037	>	else if (!timed)
1038	>	LockSupport.park(this);
1039	>	else if (nanos > 0)
1040	>	LockSupport.parkNanos(this, nanos);
1041	>	return isReleasable();
1042		}
910	–	if (node != null)
911	–	node.thread = null;
912	–	if (p != phase || (p = getPhase()) != phase)
913	–	releaseWaiters(phase);
914	–	if (interrupted)
915	–	throw new InterruptedException();
916	–	if (p == phase)
917	–	throw new TimeoutException();
918	–	return p;
1043		}
1044
1045		// Unsafe mechanics
#	Line 924 | Line 1048 | public class Phaser {
1048		private static final long stateOffset =
1049		objectFieldOffset("state", Phaser.class);
1050
927	–	private final boolean casState(long cmp, long val) {
928	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
929	–	}
930	–
1051		private static long objectFieldOffset(String field, Class<?> klazz) {
1052		try {
1053		return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));

Diff Legend

–	Removed lines
+	Added lines
<	Changed lines
>	Changed lines