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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.9 by jsr166, Mon Jan 5 09:11:26 2009 UTC vs.
Revision 1.55 by dl, Mon Nov 15 12:51:54 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	<	import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
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;
12	–	import sun.misc.Unsafe;
13	–	import java.lang.reflect.*;
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 {@code Phaser} has an associated phase number. The
38	>	* phase number starts at zero, and advances when all parties arrive
39	>	* at the barrier, 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 barrier 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>
47	>	*   <li> <b>Arrival.</b> Methods {@link #arrive} and
48	>	*       {@link #arriveAndDeregister} record arrival at a
49	>	*       barrier. These methods do not block, but return an associated
50	>	*       <em>arrival phase number</em>; that is, the phase number of
51	>	*       the barrier to which the arrival applied. When the final
52	>	*       party for a given phase arrives, an optional barrier action
53	>	*       is performed and the phase advances.  Barrier actions,
54	>	*       performed by the party triggering a phase advance, are
55	>	*       arranged by overriding method {@link #onAdvance(int, int)},
56	>	*       which also controls termination. Overriding this method is
57	>	*       similar to, but more flexible than, providing a barrier
58	>	*       action to a {@code CyclicBarrier}.
59	>	*
60	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61	>	*       argument indicating an arrival phase number, and returns when
62	>	*       the barrier 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 barrier. 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	<	* <li> Barrier actions, performed by the task triggering a phase
78	<	* advance while others may be waiting, are arranged by overriding
79	<	* method {@code onAdvance}, that also controls termination.
80	<	* Overriding this method may be used to similar but more flexible
81	<	* effect as providing a barrier action to a CyclicBarrier.
82	<	*
83	<	* <li> Phasers may enter a <em>termination</em> state in which all
60	<	* await actions immediately return, indicating (via a negative phase
61	<	* value) that execution is complete.  Termination is triggered by
62	<	* executing the overridable {@code onAdvance} method that is invoked
63	<	* each time the barrier is about to be tripped. When a Phaser is
64	<	* controlling an action with a fixed number of iterations, it is
77	>	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	>	* <em>termination</em> state in which all synchronization methods
79	>	* immediately return without updating phaser state or waiting for
80	>	* advance, and indicating (via a negative phase value) that execution
81	>	* is complete.  Termination is triggered when an invocation of {@code
82	>	* onAdvance} returns {@code true}.  As illustrated below, when
83	>	* phasers control actions with a fixed number of iterations, it is
84		* often convenient to override this method to cause termination when
85	<	* the current phase number reaches a threshold. Method
86	<	* {@code forceTermination} is also available to abruptly release
87	<	* waiting threads and allow them to terminate.
85	>	* the current phase number reaches a threshold. Method {@link
86	>	* #forceTermination} is also available to abruptly release waiting
87	>	* threads and allow them to terminate.
88		*
89	<	* <li> Phasers may be tiered to reduce contention. Phasers with large
89	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
90	>	* in tree structures) to reduce contention. Phasers with large
91		* numbers of parties that would otherwise experience heavy
92	<	* synchronization contention costs may instead be arranged in trees.
93	<	* This will typically greatly increase throughput even though it
94	<	* incurs somewhat greater per-operation overhead.
95	<	*
96	<	* <li> By default, {@code awaitAdvance} continues to wait even if
97	<	* the waiting thread is interrupted. And unlike the case in
98	<	* CyclicBarriers, exceptions encountered while tasks wait
99	<	* interruptibly or with timeout do not change the state of the
100	<	* barrier. If necessary, you can perform any associated recovery
101	<	* within handlers of those exceptions, often after invoking
102	<	* {@code forceTermination}.
103	<	*
104	<	* </ul>
92	>	* synchronization contention costs may instead be set up so that
93	>	* groups of sub-phasers share a common parent.  This may greatly
94	>	* increase throughput even though it incurs greater per-operation
95	>	* overhead.
96	>	*
97	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
98	>	* only by registered parties, the current state of a phaser may be
99	>	* monitored by any caller.  At any given moment there are {@link
100	>	* #getRegisteredParties} parties in total, of which {@link
101	>	* #getArrivedParties} have arrived at the current phase ({@link
102	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
103	>	* parties arrive, the phase advances.  The values returned by these
104	>	* methods may reflect transient states and so are not in general
105	>	* useful for synchronization control.  Method {@link #toString}
106	>	* returns snapshots of these state queries in a form convenient for
107	>	* informal monitoring.
108		*
109		* <p><b>Sample usages:</b>
110		*
111	<	* <p>A Phaser may be used instead of a {@code CountDownLatch} to control
112	<	* a one-shot action serving a variable number of parties. The typical
113	<	* idiom is for the method setting this up to first register, then
114	<	* start the actions, then deregister, as in:
115	<	*
116	<	* <pre>
117	<	*  void runTasks(List&lt;Runnable&gt; list) {
118	<	*    final Phaser phaser = new Phaser(1); // "1" to register self
119	<	*    for (Runnable r : list) {
120	<	*      phaser.register();
121	<	*      new Thread() {
122	<	*        public void run() {
123	<	*          phaser.arriveAndAwaitAdvance(); // await all creation
124	<	*          r.run();
125	<	*          phaser.arriveAndDeregister();   // signal completion
126	<	*        }
127	<	*      }.start();
111	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
112	>	* to control a one-shot action serving a variable number of parties.
113	>	* The typical idiom is for the method setting this up to first
114	>	* register, then start the actions, then deregister, as in:
115	>	*
116	>	*  <pre> {@code
117	>	* void runTasks(List<Runnable> tasks) {
118	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
119	>	*   // create and start threads
120	>	*   for (Runnable task : tasks) {
121	>	*     phaser.register();
122	>	*     new Thread() {
123	>	*       public void run() {
124	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
125	>	*         task.run();
126	>	*       }
127	>	*     }.start();
128		*   }
129		*
130	<	*   doSomethingOnBehalfOfWorkers();
131	<	*   phaser.arrive(); // allow threads to start
132	<	*   int p = phaser.arriveAndDeregister(); // deregister self  ...
110	<	*   p = phaser.awaitAdvance(p); // ... and await arrival
111	<	*   otherActions(); // do other things while tasks execute
112	<	*   phaser.awaitAdvance(p); // await final completion
113	<	* }
114	<	* </pre>
130	>	*   // allow threads to start and deregister self
131	>	*   phaser.arriveAndDeregister();
132	>	* }}</pre>
133		*
134		* <p>One way to cause a set of threads to repeatedly perform actions
135		* for a given number of iterations is to override {@code onAdvance}:
136		*
137	<	* <pre>
138	<	*  void startTasks(List&lt;Runnable&gt; list, final int iterations) {
139	<	*    final Phaser phaser = new Phaser() {
140	<	*       public boolean onAdvance(int phase, int registeredParties) {
141	<	*         return phase &gt;= iterations || registeredParties == 0;
137	>	*  <pre> {@code
138	>	* void startTasks(List<Runnable> tasks, final int iterations) {
139	>	*   final Phaser phaser = new Phaser() {
140	>	*     protected boolean onAdvance(int phase, int registeredParties) {
141	>	*       return phase >= iterations || registeredParties == 0;
142	>	*     }
143	>	*   };
144	>	*   phaser.register();
145	>	*   for (final Runnable task : tasks) {
146	>	*     phaser.register();
147	>	*     new Thread() {
148	>	*       public void run() {
149	>	*         do {
150	>	*           task.run();
151	>	*           phaser.arriveAndAwaitAdvance();
152	>	*         } while (!phaser.isTerminated());
153		*       }
154	<	*    };
126	<	*    phaser.register();
127	<	*    for (Runnable r : list) {
128	<	*      phaser.register();
129	<	*      new Thread() {
130	<	*        public void run() {
131	<	*           do {
132	<	*             r.run();
133	<	*             phaser.arriveAndAwaitAdvance();
134	<	*           } while(!phaser.isTerminated();
135	<	*        }
136	<	*      }.start();
154	>	*     }.start();
155		*   }
156		*   phaser.arriveAndDeregister(); // deregister self, don't wait
157	<	* }
158	<	* </pre>
157	>	* }}</pre>
158	>	*
159	>	* If the main task must later await termination, it
160	>	* may re-register and then execute a similar loop:
161	>	*  <pre> {@code
162	>	*   // ...
163	>	*   phaser.register();
164	>	*   while (!phaser.isTerminated())
165	>	*     phaser.arriveAndAwaitAdvance();}</pre>
166	>	*
167	>	* <p>Related constructions may be used to await particular phase numbers
168	>	* in contexts where you are sure that the phase will never wrap around
169	>	* {@code Integer.MAX_VALUE}. For example:
170	>	*
171	>	*  <pre> {@code
172	>	* void awaitPhase(Phaser phaser, int phase) {
173	>	*   int p = phaser.register(); // assumes caller not already registered
174	>	*   while (p < phase) {
175	>	*     if (phaser.isTerminated())
176	>	*       // ... deal with unexpected termination
177	>	*     else
178	>	*       p = phaser.arriveAndAwaitAdvance();
179	>	*   }
180	>	*   phaser.arriveAndDeregister();
181	>	* }}</pre>
182	>	*
183		*
184	<	* <p> To create a set of tasks using a tree of Phasers,
184	>	* <p>To create a set of tasks using a tree of phasers,
185		* you could use code of the following form, assuming a
186	<	* Task class with a constructor accepting a Phaser that
187	<	* it registers for upon construction:
188	<	* <pre>
189	<	*  void build(Task[] actions, int lo, int hi, Phaser b) {
190	<	*    int step = (hi - lo) / TASKS_PER_PHASER;
191	<	*    if (step &gt; 1) {
192	<	*       int i = lo;
193	<	*       while (i &lt; hi) {
194	<	*         int r = Math.min(i + step, hi);
195	<	*         build(actions, i, r, new Phaser(b));
196	<	*         i = r;
197	<	*       }
198	<	*    }
199	<	*    else {
200	<	*      for (int i = lo; i &lt; hi; ++i)
201	<	*        actions[i] = new Task(b);
202	<	*        // assumes new Task(b) performs b.register()
203	<	*    }
162	<	*  }
163	<	*  // .. initially called, for n tasks via
164	<	*  build(new Task[n], 0, n, new Phaser());
165	<	* </pre>
186	>	* Task class with a constructor accepting a phaser that
187	>	* it registers with upon construction:
188	>	*
189	>	*  <pre> {@code
190	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
191	>	*   if (hi - lo > TASKS_PER_PHASER) {
192	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
193	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
194	>	*       build(actions, i, j, new Phaser(ph));
195	>	*     }
196	>	*   } else {
197	>	*     for (int i = lo; i < hi; ++i)
198	>	*       actions[i] = new Task(ph);
199	>	*       // assumes new Task(ph) performs ph.register()
200	>	*   }
201	>	* }
202	>	* // .. initially called, for n tasks via
203	>	* build(new Task[n], 0, n, new Phaser());}</pre>
204		*
205		* The best value of {@code TASKS_PER_PHASER} depends mainly on
206		* expected barrier synchronization rates. A value as low as four may
207		* be appropriate for extremely small per-barrier task bodies (thus
208		* high rates), or up to hundreds for extremely large ones.
209		*
172	–	* </pre>
173	–	*
210		* <p><b>Implementation notes</b>: This implementation restricts the
211		* maximum number of parties to 65535. Attempts to register additional
212	<	* parties result in IllegalStateExceptions. However, you can and
212	>	* parties result in {@code IllegalStateException}. However, you can and
213		* should create tiered phasers to accommodate arbitrarily large sets
214		* of participants.
215	+	*
216	+	* @since 1.7
217	+	* @author Doug Lea
218		*/
219		public class Phaser {
220		/*
#	Line 188 | Line 227 | public class Phaser {
227		* Barrier state representation. Conceptually, a barrier contains
228		* four values:
229		*
230	<	* * parties -- the number of parties to wait (16 bits)
231	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
232	<	* * phase -- the generation of the barrier (31 bits)
233	<	* * terminated -- set if barrier is terminated (1 bit)
230	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
231	>	* * parties -- the number of parties to wait              (bits 16-31)
232	>	* * phase -- the generation of the barrier                (bits 32-62)
233	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
234		*
235		* However, to efficiently maintain atomicity, these values are
236		* packed into a single (atomic) long. Termination uses the sign
237		* bit of 32 bit representation of phase, so phase is set to -1 on
238		* termination. Good performance relies on keeping state decoding
239		* and encoding simple, and keeping race windows short.
201	–	*
202	–	* Note: there are some cheats in arrive() that rely on unarrived
203	–	* being lowest 16 bits.
240		*/
241		private volatile long state;
242
243	<	private static final int ushortBits = 16;
244	<	private static final int ushortMask =  (1 << ushortBits) - 1;
245	<	private static final int phaseMask = 0x7fffffff;
243	>	private static final int  MAX_PARTIES    = 0xffff;
244	>	private static final int  MAX_PHASE      = 0x7fffffff;
245	>	private static final int  PARTIES_SHIFT  = 16;
246	>	private static final int  PHASE_SHIFT    = 32;
247	>	private static final int  UNARRIVED_MASK = 0xffff;
248	>	private static final int  PARTIES_MASK   = 0xffff0000;
249	>	private static final long LPARTIES_MASK  = 0xffff0000L; // long version
250	>	private static final long ONE_ARRIVAL    = 1L;
251	>	private static final long ONE_PARTY      = 1L << PARTIES_SHIFT;
252	>	private static final long TERMINATION_PHASE  = -1L << PHASE_SHIFT;
253	>
254	>	// The following unpacking methods are usually manually inlined
255
256		private static int unarrivedOf(long s) {
257	<	return (int)(s & ushortMask);
257	>	return ((int) s) & UNARRIVED_MASK;
258		}
259
260		private static int partiesOf(long s) {
261	<	return (int)(s & (ushortMask << 16)) >>> 16;
261	>	return (((int) s) & PARTIES_MASK) >>> PARTIES_SHIFT;
262		}
263
264		private static int phaseOf(long s) {
265	<	return (int)(s >>> 32);
265	>	return (int) (s >>> PHASE_SHIFT);
266		}
267
268		private static int arrivedOf(long s) {
269		return partiesOf(s) - unarrivedOf(s);
270		}
271
227	–	private static long stateFor(int phase, int parties, int unarrived) {
228	–	return (((long)phase) << 32) | ((parties << 16) | unarrived);
229	–	}
230	–
231	–	private static long trippedStateFor(int phase, int parties) {
232	–	return (((long)phase) << 32) | ((parties << 16) | parties);
233	–	}
234	–
235	–	private static IllegalStateException badBounds(int parties, int unarrived) {
236	–	return new IllegalStateException
237	–	("Attempt to set " + unarrived +
238	–	" unarrived of " + parties + " parties");
239	–	}
240	–
272		/**
273		* The parent of this phaser, or null if none
274		*/
275		private final Phaser parent;
276
277		/**
278	<	* The root of Phaser tree. Equals this if not in a tree.  Used to
278	>	* The root of phaser tree. Equals this if not in a tree.  Used to
279		* support faster state push-down.
280		*/
281		private final Phaser root;
282
252	–	// Wait queues
253	–
283		/**
284	<	* Heads of Treiber stacks waiting for nonFJ threads. To eliminate
285	<	* contention while releasing some threads while adding others, we
284	>	* Heads of Treiber stacks for waiting threads. To eliminate
285	>	* contention when releasing some threads while adding others, we
286		* use two of them, alternating across even and odd phases.
287	+	* Subphasers share queues with root to speed up releases.
288		*/
289	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
290	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
289	>	private final AtomicReference<QNode> evenQ;
290	>	private final AtomicReference<QNode> oddQ;
291
292		private AtomicReference<QNode> queueFor(int phase) {
293	<	return (phase & 1) == 0? evenQ : oddQ;
293	>	return ((phase & 1) == 0) ? evenQ : oddQ;
294		}
295
296		/**
297	<	* Returns current state, first resolving lagged propagation from
298	<	* root if necessary.
297	>	* Main implementation for methods arrive and arriveAndDeregister.
298	>	* Manually tuned to speed up and minimize race windows for the
299	>	* common case of just decrementing unarrived field.
300	>	*
301	>	* @param adj - adjustment to apply to state -- either
302	>	* ONE_ARRIVAL (for arrive) or
303	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
304		*/
305	<	private long getReconciledState() {
306	<	return parent == null? state : reconcileState();
305	>	private int doArrive(long adj) {
306	>	for (;;) {
307	>	long s;
308	>	int phase, unarrived;
309	>	if ((phase = (int)((s = state) >>> PHASE_SHIFT)) < 0)
310	>	return phase;
311	>	else if ((unarrived = ((int)s) & UNARRIVED_MASK) == 0)
312	>	checkBadArrive(s);
313	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
314	>	if (unarrived == 1) {
315	>	Phaser par;
316	>	long p = s & LPARTIES_MASK; // unshifted parties field
317	>	long lu = p >>> PARTIES_SHIFT;
318	>	int u = (int)lu;
319	>	int nextPhase = (phase + 1) & MAX_PHASE;
320	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
321	>	if ((par = parent) == null) {
322	>	if (onAdvance(phase, u))
323	>	next |= TERMINATION_PHASE; // obliterate phase
324	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
325	>	releaseWaiters(phase);
326	>	}
327	>	else {
328	>	par.doArrive(u == 0?
329	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
330	>	if ((int)(par.state >>> PHASE_SHIFT) != nextPhase ||
331	>	((int)(state >>> PHASE_SHIFT) != nextPhase &&
332	>	!UNSAFE.compareAndSwapLong(this, stateOffset,
333	>	s, next)))
334	>	reconcileState();
335	>	}
336	>	}
337	>	return phase;
338	>	}
339	>	}
340	>	}
341	>
342	>	/**
343	>	* Rechecks state and throws bounds exceptions on arrival -- called
344	>	* only if unarrived is apparently zero.
345	>	*/
346	>	private void checkBadArrive(long s) {
347	>	if (reconcileState() == s)
348	>	throw new IllegalStateException
349	>	("Attempted arrival of unregistered party for " +
350	>	stateToString(s));
351	>	}
352	>
353	>	/**
354	>	* Implementation of register, bulkRegister
355	>	*
356	>	* @param registrations number to add to both parties and unarrived fields
357	>	*/
358	>	private int doRegister(int registrations) {
359	>	long adj = (long)registrations; // adjustment to state
360	>	adj |= adj << PARTIES_SHIFT;
361	>	Phaser par = parent;
362	>	for (;;) {
363	>	int phase, parties;
364	>	long s = par == null? state : reconcileState();
365	>	if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
366	>	return phase;
367	>	if ((parties = (((int)s) & PARTIES_MASK) >>> PARTIES_SHIFT) != 0 &&
368	>	(((int)s) & UNARRIVED_MASK) == 0)
369	>	internalAwaitAdvance(phase, null); // wait for onAdvance
370	>	else if (parties + registrations > MAX_PARTIES)
371	>	throw new IllegalStateException(badRegister(s));
372	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
373	>	return phase;
374	>	}
375	>	}
376	>
377	>	/**
378	>	* Returns message string for out of bounds exceptions on registration.
379	>	*/
380	>	private String badRegister(long s) {
381	>	return "Attempt to register more than " +
382	>	MAX_PARTIES + " parties for " + stateToString(s);
383		}
384
385		/**
386	<	* Recursively resolves state.
386	>	* Recursively resolves lagged phase propagation from root if necessary.
387		*/
388		private long reconcileState() {
389	<	Phaser p = parent;
390	<	long s = state;
391	<	if (p != null) {
392	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
393	<	long parentState = p.getReconciledState();
394	<	int parentPhase = phaseOf(parentState);
395	<	int phase = phaseOf(s = state);
396	<	if (phase != parentPhase) {
397	<	long next = trippedStateFor(parentPhase, partiesOf(s));
398	<	if (casState(s, next)) {
399	<	releaseWaiters(phase);
400	<	s = next;
401	<	}
402	<	}
389	>	Phaser par = parent;
390	>	if (par == null)
391	>	return state;
392	>	Phaser rt = root;
393	>	for (;;) {
394	>	long s, u;
395	>	int phase, rPhase, pPhase;
396	>	if ((phase = (int)((s = state)>>> PHASE_SHIFT)) < 0 ||
397	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) == phase)
398	>	return s;
399	>	long pState = par.parent == null? par.state : par.reconcileState();
400	>	if (state == s) {
401	>	if ((rPhase < 0 || (((int)s) & UNARRIVED_MASK) == 0) &&
402	>	((pPhase = (int)(pState >>> PHASE_SHIFT)) < 0 ||
403	>	pPhase == ((phase + 1) & MAX_PHASE)))
404	>	UNSAFE.compareAndSwapLong
405	>	(this, stateOffset, s,
406	>	(((long) pPhase) << PHASE_SHIFT) |
407	>	(u = s & LPARTIES_MASK) |
408	>	(u >>> PARTIES_SHIFT)); // reset unarrived to parties
409	>	else
410	>	releaseWaiters(phase); // help release others
411		}
412		}
294	–	return s;
413		}
414
415		/**
416	<	* Creates a new Phaser without any initially registered parties,
417	<	* initial phase number 0, and no parent.
416	>	* Creates a new phaser without any initially registered parties,
417	>	* initial phase number 0, and no parent. Any thread using this
418	>	* phaser will need to first register for it.
419		*/
420		public Phaser() {
421	<	this(null);
421	>	this(null, 0);
422		}
423
424		/**
425	<	* Creates a new Phaser with the given numbers of registered
425	>	* Creates a new phaser with the given number of registered
426		* unarrived parties, initial phase number 0, and no parent.
427	<	* @param parties the number of parties required to trip barrier.
427	>	*
428	>	* @param parties the number of parties required to trip barrier
429		* @throws IllegalArgumentException if parties less than zero
430	<	* or greater than the maximum number of parties supported.
430	>	* or greater than the maximum number of parties supported
431		*/
432		public Phaser(int parties) {
433		this(null, parties);
434		}
435
436		/**
437	<	* Creates a new Phaser with the given parent, without any
437	>	* Creates a new phaser with the given parent, without any
438		* initially registered parties. If parent is non-null this phaser
439		* is registered with the parent and its initial phase number is
440		* the same as that of parent phaser.
441	<	* @param parent the parent phaser.
441	>	*
442	>	* @param parent the parent phaser
443		*/
444		public Phaser(Phaser parent) {
445	<	int phase = 0;
325	<	this.parent = parent;
326	<	if (parent != null) {
327	<	this.root = parent.root;
328	<	phase = parent.register();
329	<	}
330	<	else
331	<	this.root = this;
332	<	this.state = trippedStateFor(phase, 0);
445	>	this(parent, 0);
446		}
447
448		/**
449	<	* Creates a new Phaser with the given parent and numbers of
450	<	* registered unarrived parties. If parent is non-null this phaser
449	>	* Creates a new phaser with the given parent and number of
450	>	* registered unarrived parties. If parent is non-null, this phaser
451		* is registered with the parent and its initial phase number is
452		* the same as that of parent phaser.
453	<	* @param parent the parent phaser.
454	<	* @param parties the number of parties required to trip barrier.
453	>	*
454	>	* @param parent the parent phaser
455	>	* @param parties the number of parties required to trip barrier
456		* @throws IllegalArgumentException if parties less than zero
457	<	* or greater than the maximum number of parties supported.
457	>	* or greater than the maximum number of parties supported
458		*/
459		public Phaser(Phaser parent, int parties) {
460	<	if (parties < 0 || parties > ushortMask)
460	>	if (parties >>> PARTIES_SHIFT != 0)
461		throw new IllegalArgumentException("Illegal number of parties");
462	<	int phase = 0;
462	>	int phase;
463		this.parent = parent;
464		if (parent != null) {
465	<	this.root = parent.root;
465	>	Phaser r = parent.root;
466	>	this.root = r;
467	>	this.evenQ = r.evenQ;
468	>	this.oddQ = r.oddQ;
469		phase = parent.register();
470		}
471	<	else
471	>	else {
472		this.root = this;
473	<	this.state = trippedStateFor(phase, parties);
473	>	this.evenQ = new AtomicReference<QNode>();
474	>	this.oddQ = new AtomicReference<QNode>();
475	>	phase = 0;
476	>	}
477	>	long p = (long)parties;
478	>	this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
479		}
480
481		/**
482		* Adds a new unarrived party to this phaser.
483	<	* @return the current barrier phase number upon registration
483	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
484	>	* this method may wait until its completion before registering.
485	>	*
486	>	* @return the arrival phase number to which this registration applied
487		* @throws IllegalStateException if attempting to register more
488	<	* than the maximum supported number of parties.
488	>	* than the maximum supported number of parties
489		*/
490		public int register() {
491		return doRegister(1);
#	Line 368 | Line 493 | public class Phaser {
493
494		/**
495		* Adds the given number of new unarrived parties to this phaser.
496	<	* @param parties the number of parties required to trip barrier.
497	<	* @return the current barrier phase number upon registration
496	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
497	>	* this method may wait until its completion before registering.
498	>	*
499	>	* @param parties the number of additional parties required to trip barrier
500	>	* @return the arrival phase number to which this registration applied
501		* @throws IllegalStateException if attempting to register more
502	<	* than the maximum supported number of parties.
502	>	* than the maximum supported number of parties
503	>	* @throws IllegalArgumentException if {@code parties < 0}
504		*/
505		public int bulkRegister(int parties) {
506		if (parties < 0)
507		throw new IllegalArgumentException();
508	+	if (parties > MAX_PARTIES)
509	+	throw new IllegalStateException(badRegister(state));
510		if (parties == 0)
511		return getPhase();
512		return doRegister(parties);
513		}
514
515		/**
385	–	* Shared code for register, bulkRegister
386	–	*/
387	–	private int doRegister(int registrations) {
388	–	int phase;
389	–	for (;;) {
390	–	long s = getReconciledState();
391	–	phase = phaseOf(s);
392	–	int unarrived = unarrivedOf(s) + registrations;
393	–	int parties = partiesOf(s) + registrations;
394	–	if (phase < 0)
395	–	break;
396	–	if (parties > ushortMask || unarrived > ushortMask)
397	–	throw badBounds(parties, unarrived);
398	–	if (phase == phaseOf(root.state) &&
399	–	casState(s, stateFor(phase, parties, unarrived)))
400	–	break;
401	–	}
402	–	return phase;
403	–	}
404	–
405	–	/**
516		* Arrives at the barrier, but does not wait for others.  (You can
517	<	* in turn wait for others via {@link #awaitAdvance}).
517	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
518	>	* unenforced usage error for an unregistered party to invoke this
519	>	* method.
520		*
521	<	* @return the barrier phase number upon entry to this method, or a
410	<	* negative value if terminated;
521	>	* @return the arrival phase number, or a negative value if terminated
522		* @throws IllegalStateException if not terminated and the number
523	<	* of unarrived parties would become negative.
523	>	* of unarrived parties would become negative
524		*/
525		public int arrive() {
526	<	int phase;
416	<	for (;;) {
417	<	long s = state;
418	<	phase = phaseOf(s);
419	<	int parties = partiesOf(s);
420	<	int unarrived = unarrivedOf(s) - 1;
421	<	if (unarrived > 0) {        // Not the last arrival
422	<	if (casState(s, s - 1)) // s-1 adds one arrival
423	<	break;
424	<	}
425	<	else if (unarrived == 0) {  // the last arrival
426	<	Phaser par = parent;
427	<	if (par == null) {      // directly trip
428	<	if (casState
429	<	(s,
430	<	trippedStateFor(onAdvance(phase, parties)? -1 :
431	<	((phase + 1) & phaseMask), parties))) {
432	<	releaseWaiters(phase);
433	<	break;
434	<	}
435	<	}
436	<	else {                  // cascade to parent
437	<	if (casState(s, s - 1)) { // zeroes unarrived
438	<	par.arrive();
439	<	reconcileState();
440	<	break;
441	<	}
442	<	}
443	<	}
444	<	else if (phase < 0) // Don't throw exception if terminated
445	<	break;
446	<	else if (phase != phaseOf(root.state)) // or if unreconciled
447	<	reconcileState();
448	<	else
449	<	throw badBounds(parties, unarrived);
450	<	}
451	<	return phase;
526	>	return doArrive(ONE_ARRIVAL);
527		}
528
529		/**
530	<	* Arrives at the barrier, and deregisters from it, without
531	<	* waiting for others. Deregistration reduces number of parties
530	>	* Arrives at the barrier and deregisters from it without waiting
531	>	* for others. Deregistration reduces the number of parties
532		* required to trip the barrier in future phases.  If this phaser
533		* has a parent, and deregistration causes this phaser to have
534	<	* zero parties, this phaser is also deregistered from its parent.
534	>	* zero parties, this phaser also arrives at and is deregistered
535	>	* from its parent.  It is an unenforced usage error for an
536	>	* unregistered party to invoke this method.
537		*
538	<	* @return the current barrier phase number upon entry to
462	<	* this method, or a negative value if terminated;
538	>	* @return the arrival phase number, or a negative value if terminated
539		* @throws IllegalStateException if not terminated and the number
540	<	* of registered or unarrived parties would become negative.
540	>	* of registered or unarrived parties would become negative
541		*/
542		public int arriveAndDeregister() {
543	<	// similar code to arrive, but too different to merge
468	<	Phaser par = parent;
469	<	int phase;
470	<	for (;;) {
471	<	long s = state;
472	<	phase = phaseOf(s);
473	<	int parties = partiesOf(s) - 1;
474	<	int unarrived = unarrivedOf(s) - 1;
475	<	if (parties >= 0) {
476	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
477	<	if (casState
478	<	(s,
479	<	stateFor(phase, parties, unarrived))) {
480	<	if (unarrived == 0) {
481	<	par.arriveAndDeregister();
482	<	reconcileState();
483	<	}
484	<	break;
485	<	}
486	<	continue;
487	<	}
488	<	if (unarrived == 0) {
489	<	if (casState
490	<	(s,
491	<	trippedStateFor(onAdvance(phase, parties)? -1 :
492	<	((phase + 1) & phaseMask), parties))) {
493	<	releaseWaiters(phase);
494	<	break;
495	<	}
496	<	continue;
497	<	}
498	<	if (phase < 0)
499	<	break;
500	<	if (par != null && phase != phaseOf(root.state)) {
501	<	reconcileState();
502	<	continue;
503	<	}
504	<	}
505	<	throw badBounds(parties, unarrived);
506	<	}
507	<	return phase;
543	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
544		}
545
546		/**
547		* Arrives at the barrier and awaits others. Equivalent in effect
548	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
549	<	* await with interruption of timeout, and/or deregister upon
550	<	* arrival, you can arrange them using analogous constructions.
551	<	* @return the phase on entry to this method
548	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
549	>	* interruption or timeout, you can arrange this with an analogous
550	>	* construction using one of the other forms of the {@code
551	>	* awaitAdvance} method.  If instead you need to deregister upon
552	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
553	>	* usage error for an unregistered party to invoke this method.
554	>	*
555	>	* @return the arrival phase number, or a negative number if terminated
556		* @throws IllegalStateException if not terminated and the number
557	<	* of unarrived parties would become negative.
557	>	* of unarrived parties would become negative
558		*/
559		public int arriveAndAwaitAdvance() {
560		return awaitAdvance(arrive());
561		}
562
563		/**
564	<	* Awaits the phase of the barrier to advance from the given
565	<	* value, or returns immediately if argument is negative or this
566	<	* barrier is terminated.
567	<	* @param phase the phase on entry to this method
568	<	* @return the phase on exit from this method
564	>	* Awaits the phase of the barrier to advance from the given phase
565	>	* value, returning immediately if the current phase of the
566	>	* barrier is not equal to the given phase value or this barrier
567	>	* is terminated.
568	>	*
569	>	* @param phase an arrival phase number, or negative value if
570	>	* terminated; this argument is normally the value returned by a
571	>	* previous call to {@code arrive} or its variants
572	>	* @return the next arrival phase number, or a negative value
573	>	* if terminated or argument is negative
574		*/
575		public int awaitAdvance(int phase) {
576	+	int p;
577		if (phase < 0)
578		return phase;
579	<	long s = getReconciledState();
580	<	int p = phaseOf(s);
581	<	if (p != phase)
579	>	else if ((p = (int)((parent == null? state : reconcileState())
580	>	>>> PHASE_SHIFT)) == phase)
581	>	return internalAwaitAdvance(phase, null);
582	>	else
583		return p;
537	–	if (unarrivedOf(s) == 0)
538	–	parent.awaitAdvance(phase);
539	–	// Fall here even if parent waited, to reconcile and help release
540	–	return untimedWait(phase);
584		}
585
586		/**
587	<	* Awaits the phase of the barrier to advance from the given
588	<	* value, or returns immediately if argument is negative or this
589	<	* barrier is terminated, or throws InterruptedException if
590	<	* interrupted while waiting.
591	<	* @param phase the phase on entry to this method
592	<	* @return the phase on exit from this method
587	>	* Awaits the phase of the barrier to advance from the given phase
588	>	* value, throwing {@code InterruptedException} if interrupted
589	>	* while waiting, or returning immediately if the current phase of
590	>	* the barrier is not equal to the given phase value or this
591	>	* barrier is terminated.
592	>	*
593	>	* @param phase an arrival phase number, or negative value if
594	>	* terminated; this argument is normally the value returned by a
595	>	* previous call to {@code arrive} or its variants
596	>	* @return the next arrival phase number, or a negative value
597	>	* if terminated or argument is negative
598		* @throws InterruptedException if thread interrupted while waiting
599		*/
600	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
600	>	public int awaitAdvanceInterruptibly(int phase)
601	>	throws InterruptedException {
602	>	int p;
603		if (phase < 0)
604		return phase;
605	<	long s = getReconciledState();
606	<	int p = phaseOf(s);
607	<	if (p != phase)
608	<	return p;
609	<	if (unarrivedOf(s) != 0)
610	<	parent.awaitAdvanceInterruptibly(phase);
611	<	return interruptibleWait(phase);
605	>	if ((p = (int)((parent == null? state : reconcileState())
606	>	>>> PHASE_SHIFT)) == phase) {
607	>	QNode node = new QNode(this, phase, true, false, 0L);
608	>	p = internalAwaitAdvance(phase, node);
609	>	if (node.wasInterrupted)
610	>	throw new InterruptedException();
611	>	}
612	>	return p;
613		}
614
615		/**
616	<	* Awaits the phase of the barrier to advance from the given value
617	<	* or the given timeout elapses, or returns immediately if
618	<	* argument is negative or this barrier is terminated.
619	<	* @param phase the phase on entry to this method
620	<	* @return the phase on exit from this method
616	>	* Awaits the phase of the barrier to advance from the given phase
617	>	* value or the given timeout to elapse, throwing {@code
618	>	* InterruptedException} if interrupted while waiting, or
619	>	* returning immediately if the current phase of the barrier is
620	>	* not equal to the given phase value or this barrier is
621	>	* terminated.
622	>	*
623	>	* @param phase an arrival phase number, or negative value if
624	>	* terminated; this argument is normally the value returned by a
625	>	* previous call to {@code arrive} or its variants
626	>	* @param timeout how long to wait before giving up, in units of
627	>	*        {@code unit}
628	>	* @param unit a {@code TimeUnit} determining how to interpret the
629	>	*        {@code timeout} parameter
630	>	* @return the next arrival phase number, or a negative value
631	>	* if terminated or argument is negative
632		* @throws InterruptedException if thread interrupted while waiting
633		* @throws TimeoutException if timed out while waiting
634		*/
635	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
635	>	public int awaitAdvanceInterruptibly(int phase,
636	>	long timeout, TimeUnit unit)
637		throws InterruptedException, TimeoutException {
638	+	long nanos = unit.toNanos(timeout);
639	+	int p;
640		if (phase < 0)
641		return phase;
642	<	long s = getReconciledState();
643	<	int p = phaseOf(s);
644	<	if (p != phase)
645	<	return p;
646	<	if (unarrivedOf(s) == 0)
647	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
648	<	return timedWait(phase, unit.toNanos(timeout));
642	>	if ((p = (int)((parent == null? state : reconcileState())
643	>	>>> PHASE_SHIFT)) == phase) {
644	>	QNode node = new QNode(this, phase, true, true, nanos);
645	>	p = internalAwaitAdvance(phase, node);
646	>	if (node.wasInterrupted)
647	>	throw new InterruptedException();
648	>	else if (p == phase)
649	>	throw new TimeoutException();
650	>	}
651	>	return p;
652		}
653
654		/**
655	<	* Forces this barrier to enter termination state. Counts of
656	<	* arrived and registered parties are unaffected. If this phaser
657	<	* has a parent, it too is terminated. This method may be useful
658	<	* for coordinating recovery after one or more tasks encounter
659	<	* unexpected exceptions.
655	>	* Forces this barrier to enter termination state.  Counts of
656	>	* arrived and registered parties are unaffected.  If this phaser
657	>	* is a member of a tiered set of phasers, then all of the phasers
658	>	* in the set are terminated.  If this phaser is already
659	>	* terminated, this method has no effect.  This method may be
660	>	* useful for coordinating recovery after one or more tasks
661	>	* encounter unexpected exceptions.
662		*/
663		public void forceTermination() {
664	<	for (;;) {
665	<	long s = getReconciledState();
666	<	int phase = phaseOf(s);
667	<	int parties = partiesOf(s);
668	<	int unarrived = unarrivedOf(s);
669	<	if (phase < 0 ||
670	<	casState(s, stateFor(-1, parties, unarrived))) {
601	<	releaseWaiters(0);
664	>	// Only need to change root state
665	>	final Phaser root = this.root;
666	>	long s;
667	>	while ((s = root.state) >= 0) {
668	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
669	>	s, s | TERMINATION_PHASE)) {
670	>	releaseWaiters(0); // signal all threads
671		releaseWaiters(1);
603	–	if (parent != null)
604	–	parent.forceTermination();
672		return;
673		}
674		}
#	Line 611 | Line 678 | public class Phaser {
678		* Returns the current phase number. The maximum phase number is
679		* {@code Integer.MAX_VALUE}, after which it restarts at
680		* zero. Upon termination, the phase number is negative.
681	+	*
682		* @return the phase number, or a negative value if terminated
683		*/
684		public final int getPhase() {
685	<	return phaseOf(getReconciledState());
618	<	}
619	<
620	<	/**
621	<	* Returns {@code true} if the current phase number equals the given phase.
622	<	* @param phase the phase
623	<	* @return {@code true} if the current phase number equals the given phase
624	<	*/
625	<	public final boolean hasPhase(int phase) {
626	<	return phaseOf(getReconciledState()) == phase;
685	>	return (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
686		}
687
688		/**
689		* Returns the number of parties registered at this barrier.
690	+	*
691		* @return the number of parties
692		*/
693		public int getRegisteredParties() {
694	<	return partiesOf(state);
694	>	return partiesOf(parent==null? state : reconcileState());
695		}
696
697		/**
698	<	* Returns the number of parties that have arrived at the current
699	<	* phase of this barrier.
698	>	* Returns the number of registered parties that have arrived at
699	>	* the current phase of this barrier.
700	>	*
701		* @return the number of arrived parties
702		*/
703		public int getArrivedParties() {
704	<	return arrivedOf(state);
704	>	return arrivedOf(parent==null? state : reconcileState());
705		}
706
707		/**
708		* Returns the number of registered parties that have not yet
709		* arrived at the current phase of this barrier.
710	+	*
711		* @return the number of unarrived parties
712		*/
713		public int getUnarrivedParties() {
714	<	return unarrivedOf(state);
714	>	return unarrivedOf(parent==null? state : reconcileState());
715		}
716
717		/**
718	<	* Returns the parent of this phaser, or null if none.
719	<	* @return the parent of this phaser, or null if none
718	>	* Returns the parent of this phaser, or {@code null} if none.
719	>	*
720	>	* @return the parent of this phaser, or {@code null} if none
721		*/
722		public Phaser getParent() {
723		return parent;
#	Line 663 | Line 726 | public class Phaser {
726		/**
727		* Returns the root ancestor of this phaser, which is the same as
728		* this phaser if it has no parent.
729	+	*
730		* @return the root ancestor of this phaser
731		*/
732		public Phaser getRoot() {
#	Line 671 | Line 735 | public class Phaser {
735
736		/**
737		* Returns {@code true} if this barrier has been terminated.
738	+	*
739		* @return {@code true} if this barrier has been terminated
740		*/
741		public boolean isTerminated() {
742	<	return getPhase() < 0;
742	>	return (parent == null? state : reconcileState()) < 0;
743		}
744
745		/**
746	<	* Overridable method to perform an action upon phase advance, and
747	<	* to control termination. This method is invoked whenever the
748	<	* barrier is tripped (and thus all other waiting parties are
749	<	* dormant). If it returns true, then, rather than advance the
750	<	* phase number, this barrier will be set to a final termination
751	<	* state, and subsequent calls to {@code isTerminated} will
752	<	* return true.
746	>	* Overridable method to perform an action upon impending phase
747	>	* advance, and to control termination. This method is invoked
748	>	* upon arrival of the party tripping the barrier (when all other
749	>	* waiting parties are dormant).  If this method returns {@code
750	>	* true}, then, rather than advance the phase number, this barrier
751	>	* will be set to a final termination state, and subsequent calls
752	>	* to {@link #isTerminated} will return true. Any (unchecked)
753	>	* Exception or Error thrown by an invocation of this method is
754	>	* propagated to the party attempting to trip the barrier, in
755	>	* which case no advance occurs.
756	>	*
757	>	* <p>The arguments to this method provide the state of the phaser
758	>	* prevailing for the current transition.  The effects of invoking
759	>	* arrival, registration, and waiting methods on this Phaser from
760	>	* within {@code onAdvance} are unspecified and should not be
761	>	* relied on.
762		*
763	<	* <p> The default version returns true when the number of
763	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
764	>	* {@code onAdvance} is invoked only for its root Phaser on each
765	>	* advance.
766	>	*
767	>	* <p>The default version returns {@code true} when the number of
768		* registered parties is zero. Normally, overrides that arrange
769		* termination for other reasons should also preserve this
770		* property.
771		*
694	–	* <p> You may override this method to perform an action with side
695	–	* effects visible to participating tasks, but it is in general
696	–	* only sensible to do so in designs where all parties register
697	–	* before any arrive, and all {@code awaitAdvance} at each phase.
698	–	* Otherwise, you cannot ensure lack of interference. In
699	–	* particular, this method may be invoked more than once per
700	–	* transition if other parties successfully register while the
701	–	* invocation of this method is in progress, thus postponing the
702	–	* transition until those parties also arrive, re-triggering this
703	–	* method.
704	–	*
772		* @param phase the phase number on entering the barrier
773		* @param registeredParties the current number of registered parties
774		* @return {@code true} if this barrier should terminate
#	Line 720 | Line 787 | public class Phaser {
787		* @return a string identifying this barrier, as well as its state
788		*/
789		public String toString() {
790	<	long s = getReconciledState();
790	>	return stateToString(reconcileState());
791	>	}
792	>
793	>	/**
794	>	* Implementation of toString and string-based error messages
795	>	*/
796	>	private String stateToString(long s) {
797		return super.toString() +
798		"[phase = " + phaseOf(s) +
799		" parties = " + partiesOf(s) +
800		" arrived = " + arrivedOf(s) + "]";
801		}
802
803	<	// methods for waiting
731	<
732	<	/** The number of CPUs, for spin control */
733	<	static final int NCPUS = Runtime.getRuntime().availableProcessors();
734	<
735	<	/**
736	<	* The number of times to spin before blocking in timed waits.
737	<	* The value is empirically derived.
738	<	*/
739	<	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
740	<
741	<	/**
742	<	* The number of times to spin before blocking in untimed waits.
743	<	* This is greater than timed value because untimed waits spin
744	<	* faster since they don't need to check times on each spin.
745	<	*/
746	<	static final int maxUntimedSpins = maxTimedSpins * 32;
747	<
748	<	/**
749	<	* The number of nanoseconds for which it is faster to spin
750	<	* rather than to use timed park. A rough estimate suffices.
751	<	*/
752	<	static final long spinForTimeoutThreshold = 1000L;
753	<
754	<	/**
755	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
756	<	* tasks.
757	<	*/
758	<	static final class QNode {
759	<	QNode next;
760	<	volatile Thread thread; // nulled to cancel wait
761	<	QNode() {
762	<	thread = Thread.currentThread();
763	<	}
764	<	void signal() {
765	<	Thread t = thread;
766	<	if (t != null) {
767	<	thread = null;
768	<	LockSupport.unpark(t);
769	<	}
770	<	}
771	<	}
803	>	// Waiting mechanics
804
805		/**
806	<	* Removes and signals waiting threads from wait queue
806	>	* Removes and signals threads from queue for phase
807		*/
808		private void releaseWaiters(int phase) {
809		AtomicReference<QNode> head = queueFor(phase);
810		QNode q;
811	<	while ((q = head.get()) != null) {
811	>	int p;
812	>	while ((q = head.get()) != null &&
813	>	((p = q.phase) == phase ||
814	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
815		if (head.compareAndSet(q, q.next))
816		q.signal();
817		}
818		}
819
820		/**
821	<	* Enqueues node and waits unless aborted or signalled.
821	>	* Tries to enqueue given node in the appropriate wait queue.
822	>	*
823	>	* @return true if successful
824		*/
825	<	private int untimedWait(int phase) {
826	<	int spins = maxUntimedSpins;
827	<	QNode node = null;
828	<	boolean interrupted = false;
829	<	boolean queued = false;
830	<	int p;
831	<	while ((p = getPhase()) == phase) {
795	<	interrupted = Thread.interrupted();
796	<	if (node != null) {
797	<	if (!queued) {
798	<	AtomicReference<QNode> head = queueFor(phase);
799	<	queued = head.compareAndSet(node.next = head.get(), node);
800	<	}
801	<	else if (node.thread != null)
802	<	LockSupport.park(this);
803	<	}
804	<	else if (spins <= 0)
805	<	node = new QNode();
806	<	else
807	<	--spins;
808	<	}
809	<	if (node != null)
810	<	node.thread = null;
811	<	if (interrupted)
812	<	Thread.currentThread().interrupt();
813	<	releaseWaiters(phase);
814	<	return p;
825	>	private boolean tryEnqueue(int phase, QNode node) {
826	>	releaseWaiters(phase-1); // ensure old queue clean
827	>	AtomicReference<QNode> head = queueFor(phase);
828	>	QNode q = head.get();
829	>	return ((q == null || q.phase == phase) &&
830	>	(int)(root.state >>> PHASE_SHIFT) == phase &&
831	>	head.compareAndSet(node.next = q, node));
832		}
833
834	+	/** The number of CPUs, for spin control */
835	+	private static final int NCPU = Runtime.getRuntime().availableProcessors();
836	+
837		/**
838	<	* Messier interruptible version
838	>	* The number of times to spin before blocking while waiting for
839	>	* advance, per arrival while waiting. On multiprocessors, fully
840	>	* blocking and waking up a large number of threads all at once is
841	>	* usually a very slow process, so we use rechargeable spins to
842	>	* avoid it when threads regularly arrive: When a thread in
843	>	* internalAwaitAdvance notices another arrival before blocking,
844	>	* and there appear to be enough CPUs available, it spins
845	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
846	>	* uniprocessors, there is at least one intervening Thread.yield
847	>	* before blocking. The value trades off good-citizenship vs big
848	>	* unnecessary slowdowns.
849		*/
850	<	private int interruptibleWait(int phase) throws InterruptedException {
851	<	int spins = maxUntimedSpins;
852	<	QNode node = null;
853	<	boolean queued = false;
854	<	boolean interrupted = false;
855	<	int p;
856	<	while ((p = getPhase()) == phase) {
857	<	if (interrupted = Thread.interrupted())
858	<	break;
859	<	if (node != null) {
860	<	if (!queued) {
861	<	AtomicReference<QNode> head = queueFor(phase);
862	<	queued = head.compareAndSet(node.next = head.get(), node);
850	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
851	>
852	>	/**
853	>	* Possibly blocks and waits for phase to advance unless aborted.
854	>	*
855	>	* @param phase current phase
856	>	* @param node if non-null, the wait node to track interrupt and timeout;
857	>	* if null, denotes noninterruptible wait
858	>	* @return current phase
859	>	*/
860	>	private int internalAwaitAdvance(int phase, QNode node) {
861	>	Phaser current = this;       // to eventually wait at root if tiered
862	>	boolean queued = false;      // true when node is enqueued
863	>	int lastUnarrived = -1;      // to increase spins upon change
864	>	int spins = SPINS_PER_ARRIVAL;
865	>	for (;;) {
866	>	int p, unarrived;
867	>	Phaser par;
868	>	long s = current.state;
869	>	if ((p = (int)(s >>> PHASE_SHIFT)) != phase) {
870	>	if (node != null)
871	>	node.onRelease();
872	>	releaseWaiters(phase);
873	>	return p;
874	>	}
875	>	else if ((unarrived = ((int)s) & UNARRIVED_MASK) == 0 &&
876	>	(par = current.parent) != null) {
877	>	current = par;       // if all arrived, use parent
878	>	par = par.parent;
879	>	lastUnarrived = -1;
880	>	}
881	>	else if (unarrived != lastUnarrived) {
882	>	if ((lastUnarrived = unarrived) < NCPU)
883	>	spins += SPINS_PER_ARRIVAL;
884	>	}
885	>	else if (spins > 0) {
886	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
887	>	Thread.yield();  // yield midway through spin
888	>	}
889	>	else if (node == null)   // must be noninterruptible
890	>	node = new QNode(this, phase, false, false, 0L);
891	>	else if (node.isReleasable()) {
892	>	if ((int)(reconcileState() >>> PHASE_SHIFT) == phase)
893	>	return phase;    // aborted
894	>	}
895	>	else if (!queued)
896	>	queued = tryEnqueue(phase, node);
897	>	else {
898	>	try {
899	>	ForkJoinPool.managedBlock(node);
900	>	} catch (InterruptedException ie) {
901	>	node.wasInterrupted = true;
902		}
834	–	else if (node.thread != null)
835	–	LockSupport.park(this);
903		}
904	<	else if (spins <= 0)
838	<	node = new QNode();
839	<	else
840	<	--spins;
841	<	}
842	<	if (node != null)
843	<	node.thread = null;
844	<	if (interrupted)
845	<	throw new InterruptedException();
846	<	releaseWaiters(phase);
847	<	return p;
904	>	}
905		}
906
907		/**
908	<	* Even messier timeout version.
908	>	* Wait nodes for Treiber stack representing wait queue
909		*/
910	<	private int timedWait(int phase, long nanos)
911	<	throws InterruptedException, TimeoutException {
912	<	int p;
913	<	if ((p = getPhase()) == phase) {
914	<	long lastTime = System.nanoTime();
915	<	int spins = maxTimedSpins;
916	<	QNode node = null;
917	<	boolean queued = false;
918	<	boolean interrupted = false;
919	<	while ((p = getPhase()) == phase) {
920	<	if (interrupted = Thread.interrupted())
921	<	break;
922	<	long now = System.nanoTime();
923	<	if ((nanos -= now - lastTime) <= 0)
924	<	break;
925	<	lastTime = now;
926	<	if (node != null) {
927	<	if (!queued) {
928	<	AtomicReference<QNode> head = queueFor(phase);
929	<	queued = head.compareAndSet(node.next = head.get(), node);
930	<	}
931	<	else if (node.thread != null &&
932	<	nanos > spinForTimeoutThreshold) {
933	<	LockSupport.parkNanos(this, nanos);
910	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
911	>	final Phaser phaser;
912	>	final int phase;
913	>	final boolean interruptible;
914	>	final boolean timed;
915	>	boolean wasInterrupted;
916	>	long nanos;
917	>	long lastTime;
918	>	volatile Thread thread; // nulled to cancel wait
919	>	QNode next;
920	>
921	>	QNode(Phaser phaser, int phase, boolean interruptible,
922	>	boolean timed, long nanos) {
923	>	this.phaser = phaser;
924	>	this.phase = phase;
925	>	this.interruptible = interruptible;
926	>	this.nanos = nanos;
927	>	this.timed = timed;
928	>	this.lastTime = timed? System.nanoTime() : 0L;
929	>	thread = Thread.currentThread();
930	>	}
931	>
932	>	public boolean isReleasable() {
933	>	Thread t = thread;
934	>	if (t != null) {
935	>	if (phaser.getPhase() != phase)
936	>	t = null;
937	>	else {
938	>	if (Thread.interrupted())
939	>	wasInterrupted = true;
940	>	if (interruptible && wasInterrupted)
941	>	t = null;
942	>	else if (timed) {
943	>	if (nanos > 0) {
944	>	long now = System.nanoTime();
945	>	nanos -= now - lastTime;
946	>	lastTime = now;
947	>	}
948	>	if (nanos <= 0)
949	>	t = null;
950		}
951		}
952	<	else if (spins <= 0)
953	<	node = new QNode();
954	<	else
882	<	--spins;
952	>	if (t != null)
953	>	return false;
954	>	thread = null;
955		}
956	<	if (node != null)
885	<	node.thread = null;
886	<	if (interrupted)
887	<	throw new InterruptedException();
888	<	if (p == phase && (p = getPhase()) == phase)
889	<	throw new TimeoutException();
956	>	return true;
957		}
958	<	releaseWaiters(phase);
959	<	return p;
958	>
959	>	public boolean block() {
960	>	if (isReleasable())
961	>	return true;
962	>	else if (!timed)
963	>	LockSupport.park(this);
964	>	else if (nanos > 0)
965	>	LockSupport.parkNanos(this, nanos);
966	>	return isReleasable();
967	>	}
968	>
969	>	void signal() {
970	>	Thread t = thread;
971	>	if (t != null) {
972	>	thread = null;
973	>	LockSupport.unpark(t);
974	>	}
975	>	}
976	>
977	>	void onRelease() { // actions upon return from internalAwaitAdvance
978	>	if (!interruptible && wasInterrupted)
979	>	Thread.currentThread().interrupt();
980	>	if (thread != null)
981	>	thread = null;
982	>	}
983	>
984		}
985
986	<	// Temporary Unsafe mechanics for preliminary release
986	>	// Unsafe mechanics
987
988	<	static final Unsafe _unsafe;
989	<	static final long stateOffset;
988	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
989	>	private static final long stateOffset =
990	>	objectFieldOffset("state", Phaser.class);
991
992	<	static {
992	>	private static long objectFieldOffset(String field, Class<?> klazz) {
993		try {
994	<	if (Phaser.class.getClassLoader() != null) {
995	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
996	<	f.setAccessible(true);
997	<	_unsafe = (Unsafe)f.get(null);
998	<	}
999	<	else
908	<	_unsafe = Unsafe.getUnsafe();
909	<	stateOffset = _unsafe.objectFieldOffset
910	<	(Phaser.class.getDeclaredField("state"));
911	<	} catch (Exception e) {
912	<	throw new RuntimeException("Could not initialize intrinsics", e);
994	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
995	>	} catch (NoSuchFieldException e) {
996	>	// Convert Exception to corresponding Error
997	>	NoSuchFieldError error = new NoSuchFieldError(field);
998	>	error.initCause(e);
999	>	throw error;
1000		}
1001		}
1002
1003	<	final boolean casState(long cmp, long val) {
1004	<	return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val);
1003	>	/**
1004	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1005	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1006	>	* into a jdk.
1007	>	*
1008	>	* @return a sun.misc.Unsafe
1009	>	*/
1010	>	private static sun.misc.Unsafe getUnsafe() {
1011	>	try {
1012	>	return sun.misc.Unsafe.getUnsafe();
1013	>	} catch (SecurityException se) {
1014	>	try {
1015	>	return java.security.AccessController.doPrivileged
1016	>	(new java.security
1017	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1018	>	public sun.misc.Unsafe run() throws Exception {
1019	>	java.lang.reflect.Field f = sun.misc
1020	>	.Unsafe.class.getDeclaredField("theUnsafe");
1021	>	f.setAccessible(true);
1022	>	return (sun.misc.Unsafe) f.get(null);
1023	>	}});
1024	>	} catch (java.security.PrivilegedActionException e) {
1025	>	throw new RuntimeException("Could not initialize intrinsics",
1026	>	e.getCause());
1027	>	}
1028	>	}
1029		}
1030		}

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