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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.20 by jsr166, Sat Jul 25 00:34:00 2009 UTC vs.
Revision 1.73 by jsr166, Wed May 25 16:08:03 2011 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
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 CyclicBarrier, a Phaser may be repeatedly awaited.
36	<	* Method {@code arriveAndAwaitAdvance} has effect analogous to
37	<	* {@code CyclicBarrier.await}.  However, Phasers separate two
38	<	* aspects of coordination, that 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 {@code arrive} and
48	<	*       {@code arriveAndDeregister} do not block, but return
49	<	*       the phase value current upon entry to the method.
50	<	*
51	<	*   <li> Awaiting others. Method {@code 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 while others may be waiting, are arranged by overriding
59	<	* method {@code onAdvance}, that also controls termination.
60	<	* Overriding this method may be used to similar but more flexible
61	<	* effect as providing a barrier action to a 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 by executing the
67	<	* overridable {@code onAdvance} method that is invoked each time the
68	<	* barrier is about to be tripped. When a Phaser is controlling an
69	<	* action with a fixed number of iterations, it is often convenient to
70	<	* override this method to cause termination when the current phase
71	<	* number reaches a threshold. Method {@code forceTermination} is also
72	<	* available to abruptly release waiting threads and allow them to
73	<	* terminate.
69	<	*
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	<	* CyclicBarriers, 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 ensure lack of starvation when used by ForkJoinTasks.
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, that may be checked using method {@link #isTerminated}. Upon
79	+	* termination, all synchronization methods immediately return without
80	+	* waiting for advance, as indicated by a negative return value.
81	+	* Similarly, attempts to register upon termination have no effect.
82	+	* Termination is triggered when an invocation of {@code onAdvance}
83	+	* returns {@code true}. The default implementation returns {@code
84	+	* true} if a deregistration has caused the number of registered
85	+	* parties to become zero.  As illustrated below, when phasers control
86	+	* actions with a fixed number of iterations, it is often convenient
87	+	* to override this method to cause termination when the current phase
88	+	* number reaches a threshold. Method {@link #forceTermination} is
89	+	* also available to abruptly release waiting threads and allow them
90	+	* to terminate.
91	+	*
92	+	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
93	+	* constructed in tree structures) to reduce contention. Phasers with
94	+	* large numbers of parties that would otherwise experience heavy
95	+	* synchronization contention costs may instead be set up so that
96	+	* groups of sub-phasers share a common parent.  This may greatly
97	+	* increase throughput even though it incurs greater per-operation
98	+	* overhead.
99	+	*
100	+	* <p>In a tree of tiered phasers, registration and deregistration of
101	+	* child phasers with their parent are managed automatically.
102	+	* Whenever the number of registered parties of a child phaser becomes
103	+	* non-zero (as established in the {@link #Phaser(Phaser,int)}
104	+	* constructor, {@link #register}, or {@link #bulkRegister}), the
105	+	* child phaser is registered with its parent.  Whenever the number of
106	+	* registered parties becomes zero as the result of an invocation of
107	+	* {@link #arriveAndDeregister}, the child phaser is deregistered
108	+	* from its parent.
109	+	*
110	+	* <p><b>Monitoring.</b> While synchronization methods may be invoked
111	+	* only by registered parties, the current state of a phaser may be
112	+	* monitored by any caller.  At any given moment there are {@link
113	+	* #getRegisteredParties} parties in total, of which {@link
114	+	* #getArrivedParties} have arrived at the current phase ({@link
115	+	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
116	+	* parties arrive, the phase advances.  The values returned by these
117	+	* methods may reflect transient states and so are not in general
118	+	* useful for synchronization control.  Method {@link #toString}
119	+	* returns snapshots of these state queries in a form convenient for
120	+	* informal monitoring.
121	+	*
122		* <p><b>Sample usages:</b>
123		*
124	<	* <p>A Phaser may be used instead of a {@code CountDownLatch} to control
125	<	* a one-shot action serving a variable number of parties. The typical
126	<	* idiom is for the method setting this up to first register, then
127	<	* start the actions, then deregister, as in:
124	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
125	>	* to control a one-shot action serving a variable number of parties.
126	>	* The typical idiom is for the method setting this up to first
127	>	* register, then start the actions, then deregister, as in:
128		*
129		*  <pre> {@code
130	<	* void runTasks(List<Runnable> list) {
130	>	* void runTasks(List<Runnable> tasks) {
131		*   final Phaser phaser = new Phaser(1); // "1" to register self
132	<	*   for (Runnable r : list) {
132	>	*   // create and start threads
133	>	*   for (final Runnable task : tasks) {
134		*     phaser.register();
135		*     new Thread() {
136		*       public void run() {
137		*         phaser.arriveAndAwaitAdvance(); // await all creation
138	<	*         r.run();
104	<	*         phaser.arriveAndDeregister();   // signal completion
138	>	*         task.run();
139		*       }
140		*     }.start();
141		*   }
142		*
143	<	*   doSomethingOnBehalfOfWorkers();
144	<	*   phaser.arrive(); // allow threads to start
111	<	*   int p = phaser.arriveAndDeregister(); // deregister self  ...
112	<	*   p = phaser.awaitAdvance(p); // ... and await arrival
113	<	*   otherActions(); // do other things while tasks execute
114	<	*   phaser.awaitAdvance(p); // await final completion
143	>	*   // allow threads to start and deregister self
144	>	*   phaser.arriveAndDeregister();
145		* }}</pre>
146		*
147		* <p>One way to cause a set of threads to repeatedly perform actions
148		* for a given number of iterations is to override {@code onAdvance}:
149		*
150		*  <pre> {@code
151	<	* void startTasks(List<Runnable> list, final int iterations) {
151	>	* void startTasks(List<Runnable> tasks, final int iterations) {
152		*   final Phaser phaser = new Phaser() {
153	<	*     public boolean onAdvance(int phase, int registeredParties) {
153	>	*     protected boolean onAdvance(int phase, int registeredParties) {
154		*       return phase >= iterations || registeredParties == 0;
155		*     }
156		*   };
157		*   phaser.register();
158	<	*   for (Runnable r : list) {
158	>	*   for (final Runnable task : tasks) {
159		*     phaser.register();
160		*     new Thread() {
161		*       public void run() {
162		*         do {
163	<	*           r.run();
163	>	*           task.run();
164		*           phaser.arriveAndAwaitAdvance();
165	<	*         } while(!phaser.isTerminated();
165	>	*         } while (!phaser.isTerminated());
166		*       }
167		*     }.start();
168		*   }
169		*   phaser.arriveAndDeregister(); // deregister self, don't wait
170		* }}</pre>
171		*
172	<	* <p> To create a set of tasks using a tree of Phasers,
173	<	* you could use code of the following form, assuming a
174	<	* Task class with a constructor accepting a Phaser that
175	<	* it registers for upon construction:
172	>	* If the main task must later await termination, it
173	>	* may re-register and then execute a similar loop:
174	>	*  <pre> {@code
175	>	*   // ...
176	>	*   phaser.register();
177	>	*   while (!phaser.isTerminated())
178	>	*     phaser.arriveAndAwaitAdvance();}</pre>
179	>	*
180	>	* <p>Related constructions may be used to await particular phase numbers
181	>	* in contexts where you are sure that the phase will never wrap around
182	>	* {@code Integer.MAX_VALUE}. For example:
183	>	*
184	>	*  <pre> {@code
185	>	* void awaitPhase(Phaser phaser, int phase) {
186	>	*   int p = phaser.register(); // assumes caller not already registered
187	>	*   while (p < phase) {
188	>	*     if (phaser.isTerminated())
189	>	*       // ... deal with unexpected termination
190	>	*     else
191	>	*       p = phaser.arriveAndAwaitAdvance();
192	>	*   }
193	>	*   phaser.arriveAndDeregister();
194	>	* }}</pre>
195	>	*
196	>	*
197	>	* <p>To create a set of {@code n} tasks using a tree of phasers, you
198	>	* could use code of the following form, assuming a Task class with a
199	>	* constructor accepting a {@code Phaser} that it registers with upon
200	>	* construction. After invocation of {@code build(new Task[n], 0, n,
201	>	* new Phaser())}, these tasks could then be started, for example by
202	>	* submitting to a pool:
203	>	*
204		*  <pre> {@code
205	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
206	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
207	<	*   if (step > 1) {
208	<	*     int i = lo;
209	<	*     while (i < hi) {
152	<	*       int r = Math.min(i + step, hi);
153	<	*       build(actions, i, r, new Phaser(b));
154	<	*       i = r;
205	>	* void build(Task[] tasks, int lo, int hi, Phaser ph) {
206	>	*   if (hi - lo > TASKS_PER_PHASER) {
207	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
208	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
209	>	*       build(tasks, i, j, new Phaser(ph));
210		*     }
211		*   } else {
212		*     for (int i = lo; i < hi; ++i)
213	<	*       actions[i] = new Task(b);
214	<	*       // assumes new Task(b) performs b.register()
213	>	*       tasks[i] = new Task(ph);
214	>	*       // assumes new Task(ph) performs ph.register()
215		*   }
216	<	* }
162	<	* // .. initially called, for n tasks via
163	<	* build(new Task[n], 0, n, new Phaser());}</pre>
216	>	* }}</pre>
217		*
218		* The best value of {@code TASKS_PER_PHASER} depends mainly on
219	<	* expected barrier synchronization rates. A value as low as four may
220	<	* be appropriate for extremely small per-barrier task bodies (thus
219	>	* expected synchronization rates. A value as low as four may
220	>	* be appropriate for extremely small per-phase task bodies (thus
221		* high rates), or up to hundreds for extremely large ones.
222		*
170	–	* </pre>
171	–	*
223		* <p><b>Implementation notes</b>: This implementation restricts the
224		* maximum number of parties to 65535. Attempts to register additional
225	<	* parties result in IllegalStateExceptions. However, you can and
225	>	* parties result in {@code IllegalStateException}. However, you can and
226		* should create tiered phasers to accommodate arbitrarily large sets
227		* of participants.
228		*
#	Line 186 | Line 237 | public class Phaser {
237		*/
238
239		/**
240	<	* Barrier state representation. Conceptually, a barrier contains
190	<	* four values:
240	>	* Primary state representation, holding four bit-fields:
241		*
242	<	* * parties -- the number of parties to wait (16 bits)
243	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
244	<	* * phase -- the generation of the barrier (31 bits)
245	<	* * terminated -- set if barrier is terminated (1 bit)
246	<	*
247	<	* However, to efficiently maintain atomicity, these values are
248	<	* packed into a single (atomic) long. Termination uses the sign
249	<	* bit of 32 bit representation of phase, so phase is set to -1 on
250	<	* termination. Good performance relies on keeping state decoding
251	<	* and encoding simple, and keeping race windows short.
252	<	*
253	<	* Note: there are some cheats in arrive() that rely on unarrived
254	<	* count being lowest 16 bits.
242	>	* unarrived  -- the number of parties yet to hit barrier (bits  0-15)
243	>	* parties    -- the number of parties to wait            (bits 16-31)
244	>	* phase      -- the generation of the barrier            (bits 32-62)
245	>	* terminated -- set if barrier is terminated             (bit  63 / sign)
246	>	*
247	>	* Except that a phaser with no registered parties is
248	>	* distinguished by the otherwise illegal state of having zero
249	>	* parties and one unarrived parties (encoded as EMPTY below).
250	>	*
251	>	* To efficiently maintain atomicity, these values are packed into
252	>	* a single (atomic) long. Good performance relies on keeping
253	>	* state decoding and encoding simple, and keeping race windows
254	>	* short.
255	>	*
256	>	* All state updates are performed via CAS except initial
257	>	* registration of a sub-phaser (i.e., one with a non-null
258	>	* parent).  In this (relatively rare) case, we use built-in
259	>	* synchronization to lock while first registering with its
260	>	* parent.
261	>	*
262	>	* The phase of a subphaser is allowed to lag that of its
263	>	* ancestors until it is actually accessed -- see method
264	>	* reconcileState.
265		*/
266		private volatile long state;
267
268	<	private static final int ushortBits = 16;
269	<	private static final int ushortMask = 0xffff;
270	<	private static final int phaseMask  = 0x7fffffff;
268	>	private static final int  MAX_PARTIES     = 0xffff;
269	>	private static final int  MAX_PHASE       = Integer.MAX_VALUE;
270	>	private static final int  PARTIES_SHIFT   = 16;
271	>	private static final int  PHASE_SHIFT     = 32;
272	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
273	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
274	>	private static final long TERMINATION_BIT = 1L << 63;
275	>
276	>	// some special values
277	>	private static final int  ONE_ARRIVAL     = 1;
278	>	private static final int  ONE_PARTY       = 1 << PARTIES_SHIFT;
279	>	private static final int  EMPTY           = 1;
280	>
281	>	// The following unpacking methods are usually manually inlined
282
283		private static int unarrivedOf(long s) {
284	<	return (int) (s & ushortMask);
284	>	int counts = (int)s;
285	>	return (counts == EMPTY) ? 0 : counts & UNARRIVED_MASK;
286		}
287
288		private static int partiesOf(long s) {
289	<	return ((int) s) >>> 16;
289	>	return (int)s >>> PARTIES_SHIFT;
290		}
291
292		private static int phaseOf(long s) {
293	<	return (int) (s >>> 32);
293	>	return (int)(s >>> PHASE_SHIFT);
294		}
295
296		private static int arrivedOf(long s) {
297	<	return partiesOf(s) - unarrivedOf(s);
298	<	}
299	<
228	<	private static long stateFor(int phase, int parties, int unarrived) {
229	<	return ((((long) phase) << 32) | (((long) parties) << 16) |
230	<	(long) unarrived);
231	<	}
232	<
233	<	private static long trippedStateFor(int phase, int parties) {
234	<	long lp = (long) parties;
235	<	return (((long) phase) << 32) | (lp << 16) | lp;
236	<	}
237	<
238	<	/**
239	<	* Returns message string for bad bounds exceptions.
240	<	*/
241	<	private static String badBounds(int parties, int unarrived) {
242	<	return ("Attempt to set " + unarrived +
243	<	" unarrived of " + parties + " parties");
297	>	int counts = (int)s;
298	>	return (counts == EMPTY) ? 0 :
299	>	(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK);
300		}
301
302		/**
#	Line 249 | Line 305 | public class Phaser {
305		private final Phaser parent;
306
307		/**
308	<	* The root of Phaser tree. Equals this if not in a tree.  Used to
253	<	* support faster state push-down.
308	>	* The root of phaser tree. Equals this if not in a tree.
309		*/
310		private final Phaser root;
311
257	–	// Wait queues
258	–
312		/**
313		* Heads of Treiber stacks for waiting threads. To eliminate
314	<	* contention while releasing some threads while adding others, we
314	>	* contention when releasing some threads while adding others, we
315		* use two of them, alternating across even and odd phases.
316	+	* Subphasers share queues with root to speed up releases.
317		*/
318	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
319	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
318	>	private final AtomicReference<QNode> evenQ;
319	>	private final AtomicReference<QNode> oddQ;
320
321		private AtomicReference<QNode> queueFor(int phase) {
322		return ((phase & 1) == 0) ? evenQ : oddQ;
323		}
324
325		/**
326	<	* Returns current state, first resolving lagged propagation from
273	<	* root if necessary.
326	>	* Returns message string for bounds exceptions on arrival.
327		*/
328	<	private long getReconciledState() {
329	<	return (parent == null) ? state : reconcileState();
328	>	private String badArrive(long s) {
329	>	return "Attempted arrival of unregistered party for " +
330	>	stateToString(s);
331		}
332
333		/**
334	<	* Recursively resolves state.
334	>	* Returns message string for bounds exceptions on registration.
335		*/
336	<	private long reconcileState() {
337	<	Phaser p = parent;
338	<	long s = state;
339	<	if (p != null) {
340	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
341	<	long parentState = p.getReconciledState();
342	<	int parentPhase = phaseOf(parentState);
343	<	int phase = phaseOf(s = state);
344	<	if (phase != parentPhase) {
345	<	long next = trippedStateFor(parentPhase, partiesOf(s));
346	<	if (casState(s, next)) {
347	<	releaseWaiters(phase);
348	<	s = next;
336	>	private String badRegister(long s) {
337	>	return "Attempt to register more than " +
338	>	MAX_PARTIES + " parties for " + stateToString(s);
339	>	}
340	>
341	>	/**
342	>	* Main implementation for methods arrive and arriveAndDeregister.
343	>	* Manually tuned to speed up and minimize race windows for the
344	>	* common case of just decrementing unarrived field.
345	>	*
346	>	* @param deregister false for arrive, true for arriveAndDeregister
347	>	*/
348	>	private int doArrive(boolean deregister) {
349	>	int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL;
350	>	final Phaser root = this.root;
351	>	for (;;) {
352	>	long s = (root == this) ? state : reconcileState();
353	>	int phase = (int)(s >>> PHASE_SHIFT);
354	>	int counts = (int)s;
355	>	int unarrived = (counts & UNARRIVED_MASK) - 1;
356	>	if (phase < 0)
357	>	return phase;
358	>	else if (counts == EMPTY || unarrived < 0) {
359	>	if (root == this || reconcileState() == s)
360	>	throw new IllegalStateException(badArrive(s));
361	>	}
362	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
363	>	if (unarrived == 0) {
364	>	long n = s & PARTIES_MASK;  // base of next state
365	>	int nextUnarrived = (int)n >>> PARTIES_SHIFT;
366	>	if (root != this)
367	>	return parent.doArrive(nextUnarrived == 0);
368	>	if (onAdvance(phase, nextUnarrived))
369	>	n |= TERMINATION_BIT;
370	>	else if (nextUnarrived == 0)
371	>	n |= EMPTY;
372	>	else
373	>	n |= nextUnarrived;
374	>	n |= (long)((phase + 1) & MAX_PHASE) << PHASE_SHIFT;
375	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
376	>	releaseWaiters(phase);
377	>	}
378	>	return phase;
379	>	}
380	>	}
381	>	}
382	>
383	>	/**
384	>	* Implementation of register, bulkRegister
385	>	*
386	>	* @param registrations number to add to both parties and
387	>	* unarrived fields. Must be greater than zero.
388	>	*/
389	>	private int doRegister(int registrations) {
390	>	// adjustment to state
391	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
392	>	final Phaser parent = this.parent;
393	>	int phase;
394	>	for (;;) {
395	>	long s = state;
396	>	int counts = (int)s;
397	>	int parties = counts >>> PARTIES_SHIFT;
398	>	int unarrived = counts & UNARRIVED_MASK;
399	>	if (registrations > MAX_PARTIES - parties)
400	>	throw new IllegalStateException(badRegister(s));
401	>	else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
402	>	break;
403	>	else if (counts != EMPTY) {             // not 1st registration
404	>	if (parent == null || reconcileState() == s) {
405	>	if (unarrived == 0)             // wait out advance
406	>	root.internalAwaitAdvance(phase, null);
407	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset,
408	>	s, s + adj))
409	>	break;
410	>	}
411	>	}
412	>	else if (parent == null) {              // 1st root registration
413	>	long next = ((long)phase << PHASE_SHIFT) | adj;
414	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
415	>	break;
416	>	}
417	>	else {
418	>	synchronized (this) {               // 1st sub registration
419	>	if (state == s) {               // recheck under lock
420	>	parent.doRegister(1);
421	>	do {                        // force current phase
422	>	phase = (int)(root.state >>> PHASE_SHIFT);
423	>	// assert phase < 0 || (int)state == EMPTY;
424	>	} while (!UNSAFE.compareAndSwapLong
425	>	(this, stateOffset, state,
426	>	((long)phase << PHASE_SHIFT) | adj));
427	>	break;
428		}
429		}
430		}
431		}
432	+	return phase;
433	+	}
434	+
435	+	/**
436	+	* Resolves lagged phase propagation from root if necessary.
437	+	* Reconciliation normally occurs when root has advanced but
438	+	* subphasers have not yet done so, in which case they must finish
439	+	* their own advance by setting unarrived to parties (or if
440	+	* parties is zero, resetting to unregistered EMPTY state).
441	+	* However, this method may also be called when "floating"
442	+	* subphasers with possibly some unarrived parties are merely
443	+	* catching up to current phase, in which case counts are
444	+	* unaffected.
445	+	*
446	+	* @return reconciled state
447	+	*/
448	+	private long reconcileState() {
449	+	final Phaser root = this.root;
450	+	long s = state;
451	+	if (root != this) {
452	+	int phase, u, p;
453	+	// CAS root phase with current parties; possibly trip unarrived
454	+	while ((phase = (int)(root.state >>> PHASE_SHIFT)) !=
455	+	(int)(s >>> PHASE_SHIFT) &&
456	+	!UNSAFE.compareAndSwapLong
457	+	(this, stateOffset, s,
458	+	s = (((long)phase << PHASE_SHIFT) |
459	+	(s & PARTIES_MASK) |
460	+	((p = (int)s >>> PARTIES_SHIFT) == 0 ? EMPTY :
461	+	(u = (int)s & UNARRIVED_MASK) == 0 ? p : u))))
462	+	s = state;
463	+	}
464		return s;
465		}
466
467		/**
468	<	* Creates a new Phaser without any initially registered parties,
469	<	* initial phase number 0, and no parent. Any thread using this
470	<	* Phaser will need to first register for it.
468	>	* Creates a new phaser with no initially registered parties, no
469	>	* parent, and initial phase number 0. Any thread using this
470	>	* phaser will need to first register for it.
471		*/
472		public Phaser() {
473	<	this(null);
473	>	this(null, 0);
474		}
475
476		/**
477	<	* Creates a new Phaser with the given numbers of registered
478	<	* unarrived parties, initial phase number 0, and no parent.
477	>	* Creates a new phaser with the given number of registered
478	>	* unarrived parties, no parent, and initial phase number 0.
479		*
480	<	* @param parties the number of parties required to trip barrier
480	>	* @param parties the number of parties required to advance to the
481	>	* next phase
482		* @throws IllegalArgumentException if parties less than zero
483		* or greater than the maximum number of parties supported
484		*/
#	Line 321 | Line 487 | public class Phaser {
487		}
488
489		/**
490	<	* Creates a new Phaser with the given parent, without any
325	<	* initially registered parties. If parent is non-null this phaser
326	<	* is registered with the parent and its initial phase number is
327	<	* the same as that of parent phaser.
490	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
491		*
492		* @param parent the parent phaser
493		*/
494		public Phaser(Phaser parent) {
495	<	int phase = 0;
333	<	this.parent = parent;
334	<	if (parent != null) {
335	<	this.root = parent.root;
336	<	phase = parent.register();
337	<	}
338	<	else
339	<	this.root = this;
340	<	this.state = trippedStateFor(phase, 0);
495	>	this(parent, 0);
496		}
497
498		/**
499	<	* Creates a new Phaser with the given parent and numbers of
500	<	* registered unarrived parties. If parent is non-null, this phaser
501	<	* is registered with the parent and its initial phase number is
502	<	* the same as that of parent phaser.
499	>	* Creates a new phaser with the given parent and number of
500	>	* registered unarrived parties.  When the given parent is non-null
501	>	* and the given number of parties is greater than zero, this
502	>	* child phaser is registered with its parent.
503		*
504		* @param parent the parent phaser
505	<	* @param parties the number of parties required to trip barrier
505	>	* @param parties the number of parties required to advance to the
506	>	* next phase
507		* @throws IllegalArgumentException if parties less than zero
508		* or greater than the maximum number of parties supported
509		*/
510		public Phaser(Phaser parent, int parties) {
511	<	if (parties < 0 || parties > ushortMask)
511	>	if (parties >>> PARTIES_SHIFT != 0)
512		throw new IllegalArgumentException("Illegal number of parties");
513		int phase = 0;
514		this.parent = parent;
515		if (parent != null) {
516	<	this.root = parent.root;
517	<	phase = parent.register();
516	>	final Phaser root = parent.root;
517	>	this.root = root;
518	>	this.evenQ = root.evenQ;
519	>	this.oddQ = root.oddQ;
520	>	if (parties != 0)
521	>	phase = parent.doRegister(1);
522		}
523	<	else
523	>	else {
524		this.root = this;
525	<	this.state = trippedStateFor(phase, parties);
525	>	this.evenQ = new AtomicReference<QNode>();
526	>	this.oddQ = new AtomicReference<QNode>();
527	>	}
528	>	this.state = (parties == 0) ? (long)EMPTY :
529	>	((long)phase << PHASE_SHIFT) |
530	>	((long)parties << PARTIES_SHIFT) |
531	>	((long)parties);
532		}
533
534		/**
535	<	* Adds a new unarrived party to this phaser.
536	<	*
537	<	* @return the current barrier phase number upon registration
535	>	* Adds a new unarrived party to this phaser.  If an ongoing
536	>	* invocation of {@link #onAdvance} is in progress, this method
537	>	* may await its completion before returning.  If this phaser has
538	>	* a parent, and this phaser previously had no registered parties,
539	>	* this child phaser is also registered with its parent. If
540	>	* this phaser is terminated, the attempt to register has
541	>	* no effect, and a negative value is returned.
542	>	*
543	>	* @return the arrival phase number to which this registration
544	>	* applied.  If this value is negative, then this phaser has
545	>	* terminated, in which case registration has no effect.
546		* @throws IllegalStateException if attempting to register more
547		* than the maximum supported number of parties
548		*/
#	Line 378 | Line 552 | public class Phaser {
552
553		/**
554		* Adds the given number of new unarrived parties to this phaser.
555	<	*
556	<	* @param parties the number of parties required to trip barrier
557	<	* @return the current barrier phase number upon registration
555	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
556	>	* this method may await its completion before returning.  If this
557	>	* phaser has a parent, and the given number of parties is greater
558	>	* than zero, and this phaser previously had no registered
559	>	* parties, this child phaser is also registered with its parent.
560	>	* If this phaser is terminated, the attempt to register has no
561	>	* effect, and a negative value is returned.
562	>	*
563	>	* @param parties the number of additional parties required to
564	>	* advance to the next phase
565	>	* @return the arrival phase number to which this registration
566	>	* applied.  If this value is negative, then this phaser has
567	>	* terminated, in which case registration has no effect.
568		* @throws IllegalStateException if attempting to register more
569		* than the maximum supported number of parties
570	+	* @throws IllegalArgumentException if {@code parties < 0}
571		*/
572		public int bulkRegister(int parties) {
573		if (parties < 0)
#	Line 393 | Line 578 | public class Phaser {
578		}
579
580		/**
581	<	* Shared code for register, bulkRegister
582	<	*/
583	<	private int doRegister(int registrations) {
584	<	int phase;
585	<	for (;;) {
586	<	long s = getReconciledState();
402	<	phase = phaseOf(s);
403	<	int unarrived = unarrivedOf(s) + registrations;
404	<	int parties = partiesOf(s) + registrations;
405	<	if (phase < 0)
406	<	break;
407	<	if (parties > ushortMask || unarrived > ushortMask)
408	<	throw new IllegalStateException(badBounds(parties, unarrived));
409	<	if (phase == phaseOf(root.state) &&
410	<	casState(s, stateFor(phase, parties, unarrived)))
411	<	break;
412	<	}
413	<	return phase;
414	<	}
415	<
416	<	/**
417	<	* Arrives at the barrier, but does not wait for others.  (You can
418	<	* in turn wait for others via {@link #awaitAdvance}).
581	>	* Arrives at this phaser, without waiting for others to arrive.
582	>	*
583	>	* <p>It is a usage error for an unregistered party to invoke this
584	>	* method.  However, this error may result in an {@code
585	>	* IllegalStateException} only upon some subsequent operation on
586	>	* this phaser, if ever.
587		*
588	<	* @return the barrier phase number upon entry to this method, or a
421	<	* negative value if terminated
588	>	* @return the arrival phase number, or a negative value if terminated
589		* @throws IllegalStateException if not terminated and the number
590		* of unarrived parties would become negative
591		*/
592		public int arrive() {
593	<	int phase;
427	<	for (;;) {
428	<	long s = state;
429	<	phase = phaseOf(s);
430	<	if (phase < 0)
431	<	break;
432	<	int parties = partiesOf(s);
433	<	int unarrived = unarrivedOf(s) - 1;
434	<	if (unarrived > 0) {        // Not the last arrival
435	<	if (casState(s, s - 1)) // s-1 adds one arrival
436	<	break;
437	<	}
438	<	else if (unarrived == 0) {  // the last arrival
439	<	Phaser par = parent;
440	<	if (par == null) {      // directly trip
441	<	if (casState
442	<	(s,
443	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
444	<	((phase + 1) & phaseMask), parties))) {
445	<	releaseWaiters(phase);
446	<	break;
447	<	}
448	<	}
449	<	else {                  // cascade to parent
450	<	if (casState(s, s - 1)) { // zeroes unarrived
451	<	par.arrive();
452	<	reconcileState();
453	<	break;
454	<	}
455	<	}
456	<	}
457	<	else if (phase != phaseOf(root.state)) // or if unreconciled
458	<	reconcileState();
459	<	else
460	<	throw new IllegalStateException(badBounds(parties, unarrived));
461	<	}
462	<	return phase;
593	>	return doArrive(false);
594		}
595
596		/**
597	<	* Arrives at the barrier, and deregisters from it, without
598	<	* waiting for others. Deregistration reduces number of parties
599	<	* required to trip the barrier in future phases.  If this phaser
597	>	* Arrives at this phaser and deregisters from it without waiting
598	>	* for others to arrive. Deregistration reduces the number of
599	>	* parties required to advance in future phases.  If this phaser
600		* has a parent, and deregistration causes this phaser to have
601		* zero parties, this phaser is also deregistered from its parent.
602		*
603	<	* @return the current barrier phase number upon entry to
604	<	* this method, or a negative value if terminated
603	>	* <p>It is a usage error for an unregistered party to invoke this
604	>	* method.  However, this error may result in an {@code
605	>	* IllegalStateException} only upon some subsequent operation on
606	>	* this phaser, if ever.
607	>	*
608	>	* @return the arrival phase number, or a negative value if terminated
609		* @throws IllegalStateException if not terminated and the number
610		* of registered or unarrived parties would become negative
611		*/
612		public int arriveAndDeregister() {
613	<	// similar code to arrive, but too different to merge
479	<	Phaser par = parent;
480	<	int phase;
481	<	for (;;) {
482	<	long s = state;
483	<	phase = phaseOf(s);
484	<	if (phase < 0)
485	<	break;
486	<	int parties = partiesOf(s) - 1;
487	<	int unarrived = unarrivedOf(s) - 1;
488	<	if (parties >= 0) {
489	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
490	<	if (casState
491	<	(s,
492	<	stateFor(phase, parties, unarrived))) {
493	<	if (unarrived == 0) {
494	<	par.arriveAndDeregister();
495	<	reconcileState();
496	<	}
497	<	break;
498	<	}
499	<	continue;
500	<	}
501	<	if (unarrived == 0) {
502	<	if (casState
503	<	(s,
504	<	trippedStateFor(onAdvance(phase, parties) ? -1 :
505	<	((phase + 1) & phaseMask), parties))) {
506	<	releaseWaiters(phase);
507	<	break;
508	<	}
509	<	continue;
510	<	}
511	<	if (par != null && phase != phaseOf(root.state)) {
512	<	reconcileState();
513	<	continue;
514	<	}
515	<	}
516	<	throw new IllegalStateException(badBounds(parties, unarrived));
517	<	}
518	<	return phase;
613	>	return doArrive(true);
614		}
615
616		/**
617	<	* Arrives at the barrier and awaits others. Equivalent in effect
618	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
619	<	* await with interruption of timeout, and/or deregister upon
620	<	* arrival, you can arrange them using analogous constructions.
617	>	* Arrives at this phaser and awaits others. Equivalent in effect
618	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
619	>	* interruption or timeout, you can arrange this with an analogous
620	>	* construction using one of the other forms of the {@code
621	>	* awaitAdvance} method.  If instead you need to deregister upon
622	>	* arrival, use {@code awaitAdvance(arriveAndDeregister())}.
623		*
624	<	* @return the phase on entry to this method
624	>	* <p>It is a usage error for an unregistered party to invoke this
625	>	* method.  However, this error may result in an {@code
626	>	* IllegalStateException} only upon some subsequent operation on
627	>	* this phaser, if ever.
628	>	*
629	>	* @return the arrival phase number, or the (negative)
630	>	* {@linkplain #getPhase() current phase} if terminated
631		* @throws IllegalStateException if not terminated and the number
632		* of unarrived parties would become negative
633		*/
634		public int arriveAndAwaitAdvance() {
635	<	return awaitAdvance(arrive());
635	>	// Specialization of doArrive+awaitAdvance eliminating some reads/paths
636	>	final Phaser root = this.root;
637	>	for (;;) {
638	>	long s = (root == this) ? state : reconcileState();
639	>	int phase = (int)(s >>> PHASE_SHIFT);
640	>	int counts = (int)s;
641	>	int unarrived = (counts & UNARRIVED_MASK) - 1;
642	>	if (phase < 0)
643	>	return phase;
644	>	else if (counts == EMPTY || unarrived < 0) {
645	>	if (reconcileState() == s)
646	>	throw new IllegalStateException(badArrive(s));
647	>	}
648	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s,
649	>	s -= ONE_ARRIVAL)) {
650	>	if (unarrived != 0)
651	>	return root.internalAwaitAdvance(phase, null);
652	>	if (root != this)
653	>	return parent.arriveAndAwaitAdvance();
654	>	long n = s & PARTIES_MASK;  // base of next state
655	>	int nextUnarrived = (int)n >>> PARTIES_SHIFT;
656	>	if (onAdvance(phase, nextUnarrived))
657	>	n |= TERMINATION_BIT;
658	>	else if (nextUnarrived == 0)
659	>	n |= EMPTY;
660	>	else
661	>	n |= nextUnarrived;
662	>	int nextPhase = (phase + 1) & MAX_PHASE;
663	>	n |= (long)nextPhase << PHASE_SHIFT;
664	>	if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n))
665	>	return (int)(state >>> PHASE_SHIFT); // terminated
666	>	releaseWaiters(phase);
667	>	return nextPhase;
668	>	}
669	>	}
670		}
671
672		/**
673	<	* Awaits the phase of the barrier to advance from the given
674	<	* value, or returns immediately if argument is negative or this
675	<	* barrier is terminated.
676	<	*
677	<	* @param phase the phase on entry to this method
678	<	* @return the phase on exit from this method
673	>	* Awaits the phase of this phaser to advance from the given phase
674	>	* value, returning immediately if the current phase is not equal
675	>	* to the given phase value or this phaser is terminated.
676	>	*
677	>	* @param phase an arrival phase number, or negative value if
678	>	* terminated; this argument is normally the value returned by a
679	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
680	>	* @return the next arrival phase number, or the argument if it is
681	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
682	>	* if terminated
683		*/
684		public int awaitAdvance(int phase) {
685	+	final Phaser root = this.root;
686	+	long s = (root == this) ? state : reconcileState();
687	+	int p = (int)(s >>> PHASE_SHIFT);
688		if (phase < 0)
689		return phase;
690	<	long s = getReconciledState();
691	<	int p = phaseOf(s);
692	<	if (p != phase)
549	<	return p;
550	<	if (unarrivedOf(s) == 0 && parent != null)
551	<	parent.awaitAdvance(phase);
552	<	// Fall here even if parent waited, to reconcile and help release
553	<	return untimedWait(phase);
690	>	if (p == phase)
691	>	return root.internalAwaitAdvance(phase, null);
692	>	return p;
693		}
694
695		/**
696	<	* Awaits the phase of the barrier to advance from the given
697	<	* value, or returns immediately if argument is negative or this
698	<	* barrier is terminated, or throws InterruptedException if
699	<	* interrupted while waiting.
700	<	*
701	<	* @param phase the phase on entry to this method
702	<	* @return the phase on exit from this method
696	>	* Awaits the phase of this phaser to advance from the given phase
697	>	* value, throwing {@code InterruptedException} if interrupted
698	>	* while waiting, or returning immediately if the current phase is
699	>	* not equal to the given phase value or this phaser is
700	>	* terminated.
701	>	*
702	>	* @param phase an arrival phase number, or negative value if
703	>	* terminated; this argument is normally the value returned by a
704	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
705	>	* @return the next arrival phase number, or the argument if it is
706	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
707	>	* if terminated
708		* @throws InterruptedException if thread interrupted while waiting
709		*/
710		public int awaitAdvanceInterruptibly(int phase)
711		throws InterruptedException {
712	+	final Phaser root = this.root;
713	+	long s = (root == this) ? state : reconcileState();
714	+	int p = (int)(s >>> PHASE_SHIFT);
715		if (phase < 0)
716		return phase;
717	<	long s = getReconciledState();
718	<	int p = phaseOf(s);
719	<	if (p != phase)
720	<	return p;
721	<	if (unarrivedOf(s) == 0 && parent != null)
722	<	parent.awaitAdvanceInterruptibly(phase);
723	<	return interruptibleWait(phase);
717	>	if (p == phase) {
718	>	QNode node = new QNode(this, phase, true, false, 0L);
719	>	p = root.internalAwaitAdvance(phase, node);
720	>	if (node.wasInterrupted)
721	>	throw new InterruptedException();
722	>	}
723	>	return p;
724		}
725
726		/**
727	<	* Awaits the phase of the barrier to advance from the given value
728	<	* or the given timeout elapses, or returns immediately if
729	<	* argument is negative or this barrier is terminated.
730	<	*
731	<	* @param phase the phase on entry to this method
732	<	* @return the phase on exit from this method
727	>	* Awaits the phase of this phaser to advance from the given phase
728	>	* value or the given timeout to elapse, throwing {@code
729	>	* InterruptedException} if interrupted while waiting, or
730	>	* returning immediately if the current phase is not equal to the
731	>	* given phase value or this phaser is terminated.
732	>	*
733	>	* @param phase an arrival phase number, or negative value if
734	>	* terminated; this argument is normally the value returned by a
735	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
736	>	* @param timeout how long to wait before giving up, in units of
737	>	*        {@code unit}
738	>	* @param unit a {@code TimeUnit} determining how to interpret the
739	>	*        {@code timeout} parameter
740	>	* @return the next arrival phase number, or the argument if it is
741	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
742	>	* if terminated
743		* @throws InterruptedException if thread interrupted while waiting
744		* @throws TimeoutException if timed out while waiting
745		*/
746		public int awaitAdvanceInterruptibly(int phase,
747		long timeout, TimeUnit unit)
748		throws InterruptedException, TimeoutException {
749	+	long nanos = unit.toNanos(timeout);
750	+	final Phaser root = this.root;
751	+	long s = (root == this) ? state : reconcileState();
752	+	int p = (int)(s >>> PHASE_SHIFT);
753		if (phase < 0)
754		return phase;
755	<	long s = getReconciledState();
756	<	int p = phaseOf(s);
757	<	if (p != phase)
758	<	return p;
759	<	if (unarrivedOf(s) == 0 && parent != null)
760	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
761	<	return timedWait(phase, unit.toNanos(timeout));
755	>	if (p == phase) {
756	>	QNode node = new QNode(this, phase, true, true, nanos);
757	>	p = root.internalAwaitAdvance(phase, node);
758	>	if (node.wasInterrupted)
759	>	throw new InterruptedException();
760	>	else if (p == phase)
761	>	throw new TimeoutException();
762	>	}
763	>	return p;
764		}
765
766		/**
767	<	* Forces this barrier to enter termination state. Counts of
768	<	* arrived and registered parties are unaffected. If this phaser
769	<	* has a parent, it too is terminated. This method may be useful
770	<	* for coordinating recovery after one or more tasks encounter
767	>	* Forces this phaser to enter termination state.  Counts of
768	>	* registered parties are unaffected.  If this phaser is a member
769	>	* of a tiered set of phasers, then all of the phasers in the set
770	>	* are terminated.  If this phaser is already terminated, this
771	>	* method has no effect.  This method may be useful for
772	>	* coordinating recovery after one or more tasks encounter
773		* unexpected exceptions.
774		*/
775		public void forceTermination() {
776	<	for (;;) {
777	<	long s = getReconciledState();
778	<	int phase = phaseOf(s);
779	<	int parties = partiesOf(s);
780	<	int unarrived = unarrivedOf(s);
781	<	if (phase < 0 ||
782	<	casState(s, stateFor(-1, parties, unarrived))) {
776	>	// Only need to change root state
777	>	final Phaser root = this.root;
778	>	long s;
779	>	while ((s = root.state) >= 0) {
780	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
781	>	s, s | TERMINATION_BIT)) {
782	>	// signal all threads
783		releaseWaiters(0);
784		releaseWaiters(1);
620	–	if (parent != null)
621	–	parent.forceTermination();
785		return;
786		}
787		}
#	Line 627 | Line 790 | public class Phaser {
790		/**
791		* Returns the current phase number. The maximum phase number is
792		* {@code Integer.MAX_VALUE}, after which it restarts at
793	<	* zero. Upon termination, the phase number is negative.
793	>	* zero. Upon termination, the phase number is negative,
794	>	* in which case the prevailing phase prior to termination
795	>	* may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
796		*
797		* @return the phase number, or a negative value if terminated
798		*/
799		public final int getPhase() {
800	<	return phaseOf(getReconciledState());
800	>	return (int)(root.state >>> PHASE_SHIFT);
801		}
802
803		/**
804	<	* Returns {@code true} if the current phase number equals the given phase.
640	<	*
641	<	* @param phase the phase
642	<	* @return {@code true} if the current phase number equals the given phase
643	<	*/
644	<	public final boolean hasPhase(int phase) {
645	<	return phaseOf(getReconciledState()) == phase;
646	<	}
647	<
648	<	/**
649	<	* Returns the number of parties registered at this barrier.
804	>	* Returns the number of parties registered at this phaser.
805		*
806		* @return the number of parties
807		*/
#	Line 655 | Line 810 | public class Phaser {
810		}
811
812		/**
813	<	* Returns the number of parties that have arrived at the current
814	<	* phase of this barrier.
813	>	* Returns the number of registered parties that have arrived at
814	>	* the current phase of this phaser. If this phaser has terminated,
815	>	* the returned value is meaningless and arbitrary.
816		*
817		* @return the number of arrived parties
818		*/
819		public int getArrivedParties() {
820	<	return arrivedOf(state);
820	>	return arrivedOf(reconcileState());
821		}
822
823		/**
824		* Returns the number of registered parties that have not yet
825	<	* arrived at the current phase of this barrier.
825	>	* arrived at the current phase of this phaser. If this phaser has
826	>	* terminated, the returned value is meaningless and arbitrary.
827		*
828		* @return the number of unarrived parties
829		*/
830		public int getUnarrivedParties() {
831	<	return unarrivedOf(state);
831	>	return unarrivedOf(reconcileState());
832		}
833
834		/**
835	<	* Returns the parent of this phaser, or null if none.
835	>	* Returns the parent of this phaser, or {@code null} if none.
836		*
837	<	* @return the parent of this phaser, or null if none
837	>	* @return the parent of this phaser, or {@code null} if none
838		*/
839		public Phaser getParent() {
840		return parent;
#	Line 694 | Line 851 | public class Phaser {
851		}
852
853		/**
854	<	* Returns {@code true} if this barrier has been terminated.
854	>	* Returns {@code true} if this phaser has been terminated.
855		*
856	<	* @return {@code true} if this barrier has been terminated
856	>	* @return {@code true} if this phaser has been terminated
857		*/
858		public boolean isTerminated() {
859	<	return getPhase() < 0;
859	>	return root.state < 0L;
860		}
861
862		/**
863	<	* Overridable method to perform an action upon phase advance, and
864	<	* to control termination. This method is invoked whenever the
865	<	* barrier is tripped (and thus all other waiting parties are
866	<	* dormant). If it returns true, then, rather than advance the
867	<	* phase number, this barrier will be set to a final termination
868	<	* state, and subsequent calls to {@code isTerminated} will
869	<	* return true.
870	<	*
871	<	* <p> The default version returns true when the number of
872	<	* registered parties is zero. Normally, overrides that arrange
873	<	* termination for other reasons should also preserve this
874	<	* property.
875	<	*
876	<	* <p> You may override this method to perform an action with side
877	<	* effects visible to participating tasks, but it is in general
878	<	* only sensible to do so in designs where all parties register
879	<	* before any arrive, and all {@code awaitAdvance} at each phase.
880	<	* Otherwise, you cannot ensure lack of interference. In
881	<	* particular, this method may be invoked more than once per
882	<	* transition if other parties successfully register while the
883	<	* invocation of this method is in progress, thus postponing the
884	<	* transition until those parties also arrive, re-triggering this
885	<	* method.
863	>	* Overridable method to perform an action upon impending phase
864	>	* advance, and to control termination. This method is invoked
865	>	* upon arrival of the party advancing this phaser (when all other
866	>	* waiting parties are dormant).  If this method returns {@code
867	>	* true}, this phaser will be set to a final termination state
868	>	* upon advance, and subsequent calls to {@link #isTerminated}
869	>	* will return true. Any (unchecked) Exception or Error thrown by
870	>	* an invocation of this method is propagated to the party
871	>	* attempting to advance this phaser, in which case no advance
872	>	* occurs.
873	>	*
874	>	* <p>The arguments to this method provide the state of the phaser
875	>	* prevailing for the current transition.  The effects of invoking
876	>	* arrival, registration, and waiting methods on this phaser from
877	>	* within {@code onAdvance} are unspecified and should not be
878	>	* relied on.
879	>	*
880	>	* <p>If this phaser is a member of a tiered set of phasers, then
881	>	* {@code onAdvance} is invoked only for its root phaser on each
882	>	* advance.
883	>	*
884	>	* <p>To support the most common use cases, the default
885	>	* implementation of this method returns {@code true} when the
886	>	* number of registered parties has become zero as the result of a
887	>	* party invoking {@code arriveAndDeregister}.  You can disable
888	>	* this behavior, thus enabling continuation upon future
889	>	* registrations, by overriding this method to always return
890	>	* {@code false}:
891	>	*
892	>	* <pre> {@code
893	>	* Phaser phaser = new Phaser() {
894	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
895	>	* }}</pre>
896		*
897	<	* @param phase the phase number on entering the barrier
897	>	* @param phase the current phase number on entry to this method,
898	>	* before this phaser is advanced
899		* @param registeredParties the current number of registered parties
900	<	* @return {@code true} if this barrier should terminate
900	>	* @return {@code true} if this phaser should terminate
901		*/
902		protected boolean onAdvance(int phase, int registeredParties) {
903	<	return registeredParties <= 0;
903	>	return registeredParties == 0;
904		}
905
906		/**
#	Line 742 | Line 910 | public class Phaser {
910		* followed by the number of registered parties, and {@code
911		* "arrived = "} followed by the number of arrived parties.
912		*
913	<	* @return a string identifying this barrier, as well as its state
913	>	* @return a string identifying this phaser, as well as its state
914		*/
915		public String toString() {
916	<	long s = getReconciledState();
916	>	return stateToString(reconcileState());
917	>	}
918	>
919	>	/**
920	>	* Implementation of toString and string-based error messages
921	>	*/
922	>	private String stateToString(long s) {
923		return super.toString() +
924		"[phase = " + phaseOf(s) +
925		" parties = " + partiesOf(s) +
926		" arrived = " + arrivedOf(s) + "]";
927		}
928
929	<	// methods for waiting
929	>	// Waiting mechanics
930	>
931	>	/**
932	>	* Removes and signals threads from queue for phase.
933	>	*/
934	>	private void releaseWaiters(int phase) {
935	>	QNode q;   // first element of queue
936	>	Thread t;  // its thread
937	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
938	>	while ((q = head.get()) != null &&
939	>	q.phase != (int)(root.state >>> PHASE_SHIFT)) {
940	>	if (head.compareAndSet(q, q.next) &&
941	>	(t = q.thread) != null) {
942	>	q.thread = null;
943	>	LockSupport.unpark(t);
944	>	}
945	>	}
946	>	}
947	>
948	>	/**
949	>	* Variant of releaseWaiters that additionally tries to remove any
950	>	* nodes no longer waiting for advance due to timeout or
951	>	* interrupt. Currently, nodes are removed only if they are at
952	>	* head of queue, which suffices to reduce memory footprint in
953	>	* most usages.
954	>	*
955	>	* @return current phase on exit
956	>	*/
957	>	private int abortWait(int phase) {
958	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
959	>	for (;;) {
960	>	Thread t;
961	>	QNode q = head.get();
962	>	int p = (int)(root.state >>> PHASE_SHIFT);
963	>	if (q == null || ((t = q.thread) != null && q.phase == p))
964	>	return p;
965	>	if (head.compareAndSet(q, q.next) && t != null) {
966	>	q.thread = null;
967	>	LockSupport.unpark(t);
968	>	}
969	>	}
970	>	}
971	>
972	>	/** The number of CPUs, for spin control */
973	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
974	>
975	>	/**
976	>	* The number of times to spin before blocking while waiting for
977	>	* advance, per arrival while waiting. On multiprocessors, fully
978	>	* blocking and waking up a large number of threads all at once is
979	>	* usually a very slow process, so we use rechargeable spins to
980	>	* avoid it when threads regularly arrive: When a thread in
981	>	* internalAwaitAdvance notices another arrival before blocking,
982	>	* and there appear to be enough CPUs available, it spins
983	>	* SPINS_PER_ARRIVAL more times before blocking. The value trades
984	>	* off good-citizenship vs big unnecessary slowdowns.
985	>	*/
986	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
987	>
988	>	/**
989	>	* Possibly blocks and waits for phase to advance unless aborted.
990	>	* Call only from root node.
991	>	*
992	>	* @param phase current phase
993	>	* @param node if non-null, the wait node to track interrupt and timeout;
994	>	* if null, denotes noninterruptible wait
995	>	* @return current phase
996	>	*/
997	>	private int internalAwaitAdvance(int phase, QNode node) {
998	>	releaseWaiters(phase-1);          // ensure old queue clean
999	>	boolean queued = false;           // true when node is enqueued
1000	>	int lastUnarrived = 0;            // to increase spins upon change
1001	>	int spins = SPINS_PER_ARRIVAL;
1002	>	long s;
1003	>	int p;
1004	>	while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
1005	>	if (node == null) {           // spinning in noninterruptible mode
1006	>	int unarrived = (int)s & UNARRIVED_MASK;
1007	>	if (unarrived != lastUnarrived &&
1008	>	(lastUnarrived = unarrived) < NCPU)
1009	>	spins += SPINS_PER_ARRIVAL;
1010	>	boolean interrupted = Thread.interrupted();
1011	>	if (interrupted || --spins < 0) { // need node to record intr
1012	>	node = new QNode(this, phase, false, false, 0L);
1013	>	node.wasInterrupted = interrupted;
1014	>	}
1015	>	}
1016	>	else if (node.isReleasable()) // done or aborted
1017	>	break;
1018	>	else if (!queued) {           // push onto queue
1019	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
1020	>	QNode q = node.next = head.get();
1021	>	if ((q == null || q.phase == phase) &&
1022	>	(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
1023	>	queued = head.compareAndSet(q, node);
1024	>	}
1025	>	else {
1026	>	try {
1027	>	ForkJoinPool.managedBlock(node);
1028	>	} catch (InterruptedException ie) {
1029	>	node.wasInterrupted = true;
1030	>	}
1031	>	}
1032	>	}
1033	>
1034	>	if (node != null) {
1035	>	if (node.thread != null)
1036	>	node.thread = null;       // avoid need for unpark()
1037	>	if (node.wasInterrupted && !node.interruptible)
1038	>	Thread.currentThread().interrupt();
1039	>	if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase)
1040	>	return abortWait(phase); // possibly clean up on abort
1041	>	}
1042	>	releaseWaiters(phase);
1043	>	return p;
1044	>	}
1045
1046		/**
1047		* Wait nodes for Treiber stack representing wait queue
#	Line 760 | Line 1049 | public class Phaser {
1049		static final class QNode implements ForkJoinPool.ManagedBlocker {
1050		final Phaser phaser;
1051		final int phase;
763	–	final long startTime;
764	–	final long nanos;
765	–	final boolean timed;
1052		final boolean interruptible;
1053	<	volatile boolean wasInterrupted = false;
1053	>	final boolean timed;
1054	>	boolean wasInterrupted;
1055	>	long nanos;
1056	>	long lastTime;
1057		volatile Thread thread; // nulled to cancel wait
1058		QNode next;
1059	+
1060		QNode(Phaser phaser, int phase, boolean interruptible,
1061	<	boolean timed, long startTime, long nanos) {
1061	>	boolean timed, long nanos) {
1062		this.phaser = phaser;
1063		this.phase = phase;
774	–	this.timed = timed;
1064		this.interruptible = interruptible;
776	–	this.startTime = startTime;
1065		this.nanos = nanos;
1066	+	this.timed = timed;
1067	+	this.lastTime = timed ? System.nanoTime() : 0L;
1068		thread = Thread.currentThread();
1069		}
1070	+
1071		public boolean isReleasable() {
1072	<	return (thread == null ||
1073	<	phaser.getPhase() != phase ||
1074	<	(interruptible && wasInterrupted) ||
1075	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
1076	<	}
786	<	public boolean block() {
787	<	if (Thread.interrupted()) {
788	<	wasInterrupted = true;
789	<	if (interruptible)
790	<	return true;
791	<	}
792	<	if (!timed)
793	<	LockSupport.park(this);
794	<	else {
795	<	long waitTime = nanos - (System.nanoTime() - startTime);
796	<	if (waitTime <= 0)
797	<	return true;
798	<	LockSupport.parkNanos(this, waitTime);
1072	>	if (thread == null)
1073	>	return true;
1074	>	if (phaser.getPhase() != phase) {
1075	>	thread = null;
1076	>	return true;
1077		}
1078	<	return isReleasable();
1079	<	}
1080	<	void signal() {
803	<	Thread t = thread;
804	<	if (t != null) {
1078	>	if (Thread.interrupted())
1079	>	wasInterrupted = true;
1080	>	if (wasInterrupted && interruptible) {
1081		thread = null;
1082	<	LockSupport.unpark(t);
1082	>	return true;
1083		}
1084	<	}
1085	<	boolean doWait() {
1086	<	if (thread != null) {
1087	<	try {
1088	<	ForkJoinPool.managedBlock(this, false);
1089	<	} catch (InterruptedException ie) {
1084	>	if (timed) {
1085	>	if (nanos > 0L) {
1086	>	long now = System.nanoTime();
1087	>	nanos -= now - lastTime;
1088	>	lastTime = now;
1089	>	}
1090	>	if (nanos <= 0L) {
1091	>	thread = null;
1092	>	return true;
1093		}
1094		}
1095	<	return wasInterrupted;
1095	>	return false;
1096		}
1097
1098	<	}
1099	<
1100	<	/**
1101	<	* Removes and signals waiting threads from wait queue.
1102	<	*/
1103	<	private void releaseWaiters(int phase) {
1104	<	AtomicReference<QNode> head = queueFor(phase);
1105	<	QNode q;
827	<	while ((q = head.get()) != null) {
828	<	if (head.compareAndSet(q, q.next))
829	<	q.signal();
1098	>	public boolean block() {
1099	>	if (isReleasable())
1100	>	return true;
1101	>	else if (!timed)
1102	>	LockSupport.park(this);
1103	>	else if (nanos > 0)
1104	>	LockSupport.parkNanos(this, nanos);
1105	>	return isReleasable();
1106		}
1107		}
1108
1109	<	/**
834	<	* Tries to enqueue given node in the appropriate wait queue.
835	<	*
836	<	* @return true if successful
837	<	*/
838	<	private boolean tryEnqueue(QNode node) {
839	<	AtomicReference<QNode> head = queueFor(node.phase);
840	<	return head.compareAndSet(node.next = head.get(), node);
841	<	}
1109	>	// Unsafe mechanics
1110
1111	<	/**
1112	<	* Enqueues node and waits unless aborted or signalled.
1113	<	*
1114	<	* @return current phase
1115	<	*/
1116	<	private int untimedWait(int phase) {
1117	<	QNode node = null;
1118	<	boolean queued = false;
1119	<	boolean interrupted = false;
1120	<	int p;
853	<	while ((p = getPhase()) == phase) {
854	<	if (Thread.interrupted())
855	<	interrupted = true;
856	<	else if (node == null)
857	<	node = new QNode(this, phase, false, false, 0, 0);
858	<	else if (!queued)
859	<	queued = tryEnqueue(node);
860	<	else
861	<	interrupted = node.doWait();
1111	>	private static final sun.misc.Unsafe UNSAFE;
1112	>	private static final long stateOffset;
1113	>	static {
1114	>	try {
1115	>	UNSAFE = getUnsafe();
1116	>	Class k = Phaser.class;
1117	>	stateOffset = UNSAFE.objectFieldOffset
1118	>	(k.getDeclaredField("state"));
1119	>	} catch (Exception e) {
1120	>	throw new Error(e);
1121		}
863	–	if (node != null)
864	–	node.thread = null;
865	–	releaseWaiters(phase);
866	–	if (interrupted)
867	–	Thread.currentThread().interrupt();
868	–	return p;
1122		}
1123
1124		/**
1125	<	* Interruptible version
1126	<	* @return current phase
1127	<	*/
1128	<	private int interruptibleWait(int phase) throws InterruptedException {
1129	<	QNode node = null;
877	<	boolean queued = false;
878	<	boolean interrupted = false;
879	<	int p;
880	<	while ((p = getPhase()) == phase && !interrupted) {
881	<	if (Thread.interrupted())
882	<	interrupted = true;
883	<	else if (node == null)
884	<	node = new QNode(this, phase, true, false, 0, 0);
885	<	else if (!queued)
886	<	queued = tryEnqueue(node);
887	<	else
888	<	interrupted = node.doWait();
889	<	}
890	<	if (node != null)
891	<	node.thread = null;
892	<	if (p != phase || (p = getPhase()) != phase)
893	<	releaseWaiters(phase);
894	<	if (interrupted)
895	<	throw new InterruptedException();
896	<	return p;
897	<	}
898	<
899	<	/**
900	<	* Timeout version.
901	<	* @return current phase
1125	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1126	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1127	>	* into a jdk.
1128	>	*
1129	>	* @return a sun.misc.Unsafe
1130		*/
903	–	private int timedWait(int phase, long nanos)
904	–	throws InterruptedException, TimeoutException {
905	–	long startTime = System.nanoTime();
906	–	QNode node = null;
907	–	boolean queued = false;
908	–	boolean interrupted = false;
909	–	int p;
910	–	while ((p = getPhase()) == phase && !interrupted) {
911	–	if (Thread.interrupted())
912	–	interrupted = true;
913	–	else if (nanos - (System.nanoTime() - startTime) <= 0)
914	–	break;
915	–	else if (node == null)
916	–	node = new QNode(this, phase, true, true, startTime, nanos);
917	–	else if (!queued)
918	–	queued = tryEnqueue(node);
919	–	else
920	–	interrupted = node.doWait();
921	–	}
922	–	if (node != null)
923	–	node.thread = null;
924	–	if (p != phase || (p = getPhase()) != phase)
925	–	releaseWaiters(phase);
926	–	if (interrupted)
927	–	throw new InterruptedException();
928	–	if (p == phase)
929	–	throw new TimeoutException();
930	–	return p;
931	–	}
932	–
933	–	// Unsafe mechanics for jsr166y 3rd party package.
1131		private static sun.misc.Unsafe getUnsafe() {
1132		try {
1133		return sun.misc.Unsafe.getUnsafe();
1134		} catch (SecurityException se) {
1135		try {
1136		return java.security.AccessController.doPrivileged
1137	<	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1137	>	(new java.security
1138	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1139		public sun.misc.Unsafe run() throws Exception {
1140	<	return getUnsafeByReflection();
1140	>	java.lang.reflect.Field f = sun.misc
1141	>	.Unsafe.class.getDeclaredField("theUnsafe");
1142	>	f.setAccessible(true);
1143	>	return (sun.misc.Unsafe) f.get(null);
1144		}});
1145		} catch (java.security.PrivilegedActionException e) {
1146		throw new RuntimeException("Could not initialize intrinsics",
#	Line 947 | Line 1148 | public class Phaser {
1148		}
1149		}
1150		}
950	–
951	–	private static sun.misc.Unsafe getUnsafeByReflection()
952	–	throws NoSuchFieldException, IllegalAccessException {
953	–	java.lang.reflect.Field f =
954	–	sun.misc.Unsafe.class.getDeclaredField("theUnsafe");
955	–	f.setAccessible(true);
956	–	return (sun.misc.Unsafe) f.get(null);
957	–	}
958	–
959	–	private static long fieldOffset(String fieldName, Class<?> klazz) {
960	–	try {
961	–	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(fieldName));
962	–	} catch (NoSuchFieldException e) {
963	–	// Convert Exception to Error
964	–	NoSuchFieldError error = new NoSuchFieldError(fieldName);
965	–	error.initCause(e);
966	–	throw error;
967	–	}
968	–	}
969	–
970	–	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
971	–	static final long stateOffset =
972	–	fieldOffset("state", Phaser.class);
973	–
974	–	final boolean casState(long cmp, long val) {
975	–	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
976	–	}
1151		}

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