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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.12 by jsr166, Thu Mar 19 05:10:42 2009 UTC vs.
Revision 1.38 by dl, Mon Aug 24 12:11:00 2009 UTC

#	Line 7 | Line 7
7		package jsr166y;
8
9		import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
10	>
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, amd 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.)  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
84	<	* actions immediately return without updating phaser state or waiting
85	<	* for advance, and indicating (via a negative phase value) that
86	<	* execution is complete.  Termination is triggered by executing the
87	<	* overridable {@code onAdvance} method that is invoked each time the
64	<	* barrier is about to be tripped. When a Phaser is controlling an
65	<	* action with a fixed number of iterations, it is often convenient to
66	<	* override this method to cause termination when the current phase
67	<	* number reaches a threshold. Method {@code forceTermination} is also
68	<	* available to abruptly release waiting threads and allow them to
69	<	* terminate.
77	>	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	>	* <em>termination</em> state in which all actions immediately return
79	>	* without updating phaser state or waiting for advance, and
80	>	* indicating (via a negative phase value) that execution is complete.
81	>	* Termination is triggered when an invocation of {@code onAdvance}
82	>	* returns {@code true}.  As illustrated below, when phasers control
83	>	* actions with a fixed number of iterations, it is often convenient
84	>	* to override this method to cause termination when the current phase
85	>	* number reaches a threshold. Method {@link #forceTermination} is
86	>	* also available to abruptly release waiting threads and allow them
87	>	* 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	<	* <li>Phasers ensure lack of starvation when used by ForkJoinTasks.
86	<	*
87	<	* </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}, where {@link #getArrivedParties} have
101	>	* arrived at the current phase ({@link #getPhase}). When the
102	>	* remaining {@link #getUnarrivedParties}) arrive, the phase
103	>	* advances. Method {@link #toString} returns snapshots of these state
104	>	* queries in a form convenient for informal monitoring.
105		*
106		* <p><b>Sample usages:</b>
107		*
108	<	* <p>A Phaser may be used instead of a {@code CountDownLatch} to control
109	<	* a one-shot action serving a variable number of parties. The typical
110	<	* idiom is for the method setting this up to first register, then
111	<	* start the actions, then deregister, as in:
112	<	*
113	<	* <pre>
114	<	*  void runTasks(List&lt;Runnable&gt; list) {
115	<	*    final Phaser phaser = new Phaser(1); // "1" to register self
116	<	*    for (Runnable r : list) {
117	<	*      phaser.register();
118	<	*      new Thread() {
119	<	*        public void run() {
120	<	*          phaser.arriveAndAwaitAdvance(); // await all creation
121	<	*          r.run();
122	<	*          phaser.arriveAndDeregister();   // signal completion
123	<	*        }
124	<	*      }.start();
108	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
109	>	* to control a one-shot action serving a variable number of
110	>	* parties. The typical idiom is for the method setting this up to
111	>	* first register, then start the actions, then deregister, as in:
112	>	*
113	>	*  <pre> {@code
114	>	* void runTasks(List<Runnable> tasks) {
115	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
116	>	*   // create and start threads
117	>	*   for (Runnable task : tasks) {
118	>	*     phaser.register();
119	>	*     new Thread() {
120	>	*       public void run() {
121	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
122	>	*         task.run();
123	>	*       }
124	>	*     }.start();
125		*   }
126		*
127	<	*   doSomethingOnBehalfOfWorkers();
128	<	*   phaser.arrive(); // allow threads to start
129	<	*   int p = phaser.arriveAndDeregister(); // deregister self  ...
113	<	*   p = phaser.awaitAdvance(p); // ... and await arrival
114	<	*   otherActions(); // do other things while tasks execute
115	<	*   phaser.awaitAdvance(p); // await final completion
116	<	* }
117	<	* </pre>
127	>	*   // allow threads to start and deregister self
128	>	*   phaser.arriveAndDeregister();
129	>	* }}</pre>
130		*
131		* <p>One way to cause a set of threads to repeatedly perform actions
132		* for a given number of iterations is to override {@code onAdvance}:
133		*
134	<	* <pre>
135	<	*  void startTasks(List&lt;Runnable&gt; list, final int iterations) {
136	<	*    final Phaser phaser = new Phaser() {
137	<	*       public boolean onAdvance(int phase, int registeredParties) {
138	<	*         return phase &gt;= iterations || registeredParties == 0;
134	>	*  <pre> {@code
135	>	* void startTasks(List<Runnable> tasks, final int iterations) {
136	>	*   final Phaser phaser = new Phaser() {
137	>	*     protected boolean onAdvance(int phase, int registeredParties) {
138	>	*       return phase >= iterations || registeredParties == 0;
139	>	*     }
140	>	*   };
141	>	*   phaser.register();
142	>	*   for (Runnable task : tasks) {
143	>	*     phaser.register();
144	>	*     new Thread() {
145	>	*       public void run() {
146	>	*         do {
147	>	*           task.run();
148	>	*           phaser.arriveAndAwaitAdvance();
149	>	*         } while(!phaser.isTerminated();
150		*       }
151	<	*    };
129	<	*    phaser.register();
130	<	*    for (Runnable r : list) {
131	<	*      phaser.register();
132	<	*      new Thread() {
133	<	*        public void run() {
134	<	*           do {
135	<	*             r.run();
136	<	*             phaser.arriveAndAwaitAdvance();
137	<	*           } while(!phaser.isTerminated();
138	<	*        }
139	<	*      }.start();
151	>	*     }.start();
152		*   }
153		*   phaser.arriveAndDeregister(); // deregister self, don't wait
154	<	* }
143	<	* </pre>
154	>	* }}</pre>
155		*
156	<	* <p> To create a set of tasks using a tree of Phasers,
156	>	* If the main task must later await termination, it
157	>	* may re-register and then execute a similar loop:
158	>	* <pre> {@code
159	>	*   // ...
160	>	*   phaser.register();
161	>	*   while (!phaser.isTerminated())
162	>	*     phaser.arriveAndAwaitAdvance();
163	>	* }</pre>
164	>	*
165	>	* Related constructions may be used to await particular phase numbers
166	>	* in contexts where you are sure that the phase will never wrap around
167	>	* {@code Integer.MAX_VALUE}. For example:
168	>	*
169	>	* <pre> {@code
170	>	*   void awaitPhase(Phaser phaser, int phase) {
171	>	*     int p = phaser.register(); // assumes caller not already registered
172	>	*     while (p < phase) {
173	>	*       if (phaser.isTerminated())
174	>	*         // ... deal with unexpected termination
175	>	*       else
176	>	*         p = phaser.arriveAndAwaitAdvance();
177	>	*     }
178	>	*     phaser.arriveAndDeregister();
179	>	*   }
180	>	* }</pre>
181	>	*
182	>	*
183	>	* <p>To create a set of tasks using a tree of phasers,
184		* you could use code of the following form, assuming a
185	<	* Task class with a constructor accepting a Phaser that
185	>	* Task class with a constructor accepting a phaser that
186		* it registers for upon construction:
187	<	* <pre>
188	<	*  void build(Task[] actions, int lo, int hi, Phaser b) {
189	<	*    int step = (hi - lo) / TASKS_PER_PHASER;
190	<	*    if (step &gt; 1) {
191	<	*       int i = lo;
192	<	*       while (i &lt; hi) {
193	<	*         int r = Math.min(i + step, hi);
194	<	*         build(actions, i, r, new Phaser(b));
195	<	*         i = r;
196	<	*       }
197	<	*    }
198	<	*    else {
199	<	*      for (int i = lo; i &lt; hi; ++i)
200	<	*        actions[i] = new Task(b);
201	<	*        // assumes new Task(b) performs b.register()
202	<	*    }
203	<	*  }
204	<	*  // .. initially called, for n tasks via
167	<	*  build(new Task[n], 0, n, new Phaser());
168	<	* </pre>
187	>	*  <pre> {@code
188	>	* void build(Task[] actions, int lo, int hi, Phaser b) {
189	>	*   int step = (hi - lo) / TASKS_PER_PHASER;
190	>	*   if (step > 1) {
191	>	*     int i = lo;
192	>	*     while (i < hi) {
193	>	*       int r = Math.min(i + step, hi);
194	>	*       build(actions, i, r, new Phaser(b));
195	>	*       i = r;
196	>	*     }
197	>	*   } else {
198	>	*     for (int i = lo; i < hi; ++i)
199	>	*       actions[i] = new Task(b);
200	>	*       // assumes new Task(b) performs b.register()
201	>	*   }
202	>	* }
203	>	* // .. initially called, for n tasks via
204	>	* build(new Task[n], 0, n, new Phaser());}</pre>
205		*
206		* The best value of {@code TASKS_PER_PHASER} depends mainly on
207		* expected barrier synchronization rates. A value as low as four may
#	Line 176 | Line 212 | import java.lang.reflect.*;
212		*
213		* <p><b>Implementation notes</b>: This implementation restricts the
214		* maximum number of parties to 65535. Attempts to register additional
215	<	* parties result in IllegalStateExceptions. However, you can and
215	>	* parties result in {@code IllegalStateException}. However, you can and
216		* should create tiered phasers to accommodate arbitrarily large sets
217		* of participants.
218	+	*
219	+	* @since 1.7
220	+	* @author Doug Lea
221		*/
222		public class Phaser {
223		/*
#	Line 212 | Line 251 | public class Phaser {
251		private static final int phaseMask  = 0x7fffffff;
252
253		private static int unarrivedOf(long s) {
254	<	return (int)(s & ushortMask);
254	>	return (int) (s & ushortMask);
255		}
256
257		private static int partiesOf(long s) {
258	<	return ((int)s) >>> 16;
258	>	return ((int) s) >>> 16;
259		}
260
261		private static int phaseOf(long s) {
262	<	return (int)(s >>> 32);
262	>	return (int) (s >>> 32);
263		}
264
265		private static int arrivedOf(long s) {
#	Line 228 | Line 267 | public class Phaser {
267		}
268
269		private static long stateFor(int phase, int parties, int unarrived) {
270	<	return ((((long)phase) << 32) | (((long)parties) << 16) |
271	<	(long)unarrived);
270	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
271	>	(long) unarrived);
272		}
273
274		private static long trippedStateFor(int phase, int parties) {
275	<	long lp = (long)parties;
276	<	return (((long)phase) << 32) | (lp << 16) | lp;
275	>	long lp = (long) parties;
276	>	return (((long) phase) << 32) | (lp << 16) | lp;
277		}
278
279		/**
280	<	* Returns message string for bad bounds exceptions
280	>	* Returns message string for bad bounds exceptions.
281		*/
282		private static String badBounds(int parties, int unarrived) {
283		return ("Attempt to set " + unarrived +
#	Line 251 | Line 290 | public class Phaser {
290		private final Phaser parent;
291
292		/**
293	<	* The root of Phaser tree. Equals this if not in a tree.  Used to
293	>	* The root of phaser tree. Equals this if not in a tree.  Used to
294		* support faster state push-down.
295		*/
296		private final Phaser root;
#	Line 267 | Line 306 | public class Phaser {
306		private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
307
308		private AtomicReference<QNode> queueFor(int phase) {
309	<	return (phase & 1) == 0? evenQ : oddQ;
309	>	return ((phase & 1) == 0) ? evenQ : oddQ;
310		}
311
312		/**
#	Line 275 | Line 314 | public class Phaser {
314		* root if necessary.
315		*/
316		private long getReconciledState() {
317	<	return parent == null? state : reconcileState();
317	>	return (parent == null) ? state : reconcileState();
318		}
319
320		/**
#	Line 302 | Line 341 | public class Phaser {
341		}
342
343		/**
344	<	* Creates a new Phaser without any initially registered parties,
344	>	* Creates a new phaser without any initially registered parties,
345		* initial phase number 0, and no parent. Any thread using this
346	<	* Phaser will need to first register for it.
346	>	* phaser will need to first register for it.
347		*/
348		public Phaser() {
349		this(null);
350		}
351
352		/**
353	<	* Creates a new Phaser with the given numbers of registered
353	>	* Creates a new phaser with the given numbers of registered
354		* unarrived parties, initial phase number 0, and no parent.
355	<	* @param parties the number of parties required to trip barrier.
355	>	*
356	>	* @param parties the number of parties required to trip barrier
357		* @throws IllegalArgumentException if parties less than zero
358	<	* or greater than the maximum number of parties supported.
358	>	* or greater than the maximum number of parties supported
359		*/
360		public Phaser(int parties) {
361		this(null, parties);
362		}
363
364		/**
365	<	* Creates a new Phaser with the given parent, without any
365	>	* Creates a new phaser with the given parent, without any
366		* initially registered parties. If parent is non-null this phaser
367		* is registered with the parent and its initial phase number is
368		* the same as that of parent phaser.
369	<	* @param parent the parent phaser.
369	>	*
370	>	* @param parent the parent phaser
371		*/
372		public Phaser(Phaser parent) {
373		int phase = 0;
#	Line 341 | Line 382 | public class Phaser {
382		}
383
384		/**
385	<	* Creates a new Phaser with the given parent and numbers of
386	<	* registered unarrived parties. If parent is non-null this phaser
385	>	* Creates a new phaser with the given parent and numbers of
386	>	* registered unarrived parties. If parent is non-null, this phaser
387		* is registered with the parent and its initial phase number is
388		* the same as that of parent phaser.
389	<	* @param parent the parent phaser.
390	<	* @param parties the number of parties required to trip barrier.
389	>	*
390	>	* @param parent the parent phaser
391	>	* @param parties the number of parties required to trip barrier
392		* @throws IllegalArgumentException if parties less than zero
393	<	* or greater than the maximum number of parties supported.
393	>	* or greater than the maximum number of parties supported
394		*/
395		public Phaser(Phaser parent, int parties) {
396		if (parties < 0 || parties > ushortMask)
#	Line 366 | Line 408 | public class Phaser {
408
409		/**
410		* Adds a new unarrived party to this phaser.
411	<	* @return the current barrier phase number upon registration
411	>	*
412	>	* @return the arrival phase number to which this registration applied
413		* @throws IllegalStateException if attempting to register more
414	<	* than the maximum supported number of parties.
414	>	* than the maximum supported number of parties
415		*/
416		public int register() {
417		return doRegister(1);
#	Line 376 | Line 419 | public class Phaser {
419
420		/**
421		* Adds the given number of new unarrived parties to this phaser.
422	<	* @param parties the number of parties required to trip barrier.
423	<	* @return the current barrier phase number upon registration
422	>	*
423	>	* @param parties the number of parties required to trip barrier
424	>	* @return the arrival phase number to which this registration applied
425		* @throws IllegalStateException if attempting to register more
426	<	* than the maximum supported number of parties.
426	>	* than the maximum supported number of parties
427		*/
428		public int bulkRegister(int parties) {
429		if (parties < 0)
#	Line 412 | Line 456 | public class Phaser {
456
457		/**
458		* Arrives at the barrier, but does not wait for others.  (You can
459	<	* in turn wait for others via {@link #awaitAdvance}).
459	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
460	>	* unenforced usage error for an unregistered party to invoke this
461	>	* method.
462		*
463	<	* @return the barrier phase number upon entry to this method, or a
418	<	* negative value if terminated;
463	>	* @return the arrival phase number, or a negative value if terminated
464		* @throws IllegalStateException if not terminated and the number
465	<	* of unarrived parties would become negative.
465	>	* of unarrived parties would become negative
466		*/
467		public int arrive() {
468		int phase;
#	Line 437 | Line 482 | public class Phaser {
482		if (par == null) {      // directly trip
483		if (casState
484		(s,
485	<	trippedStateFor(onAdvance(phase, parties)? -1 :
485	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
486		((phase + 1) & phaseMask), parties))) {
487		releaseWaiters(phase);
488		break;
#	Line 460 | Line 505 | public class Phaser {
505		}
506
507		/**
508	<	* Arrives at the barrier, and deregisters from it, without
509	<	* waiting for others. Deregistration reduces number of parties
508	>	* Arrives at the barrier and deregisters from it without waiting
509	>	* for others. Deregistration reduces the number of parties
510		* required to trip the barrier in future phases.  If this phaser
511		* has a parent, and deregistration causes this phaser to have
512	<	* zero parties, this phaser is also deregistered from its parent.
512	>	* zero parties, this phaser also arrives at and is deregistered
513	>	* from its parent.  It is an unenforced usage error for an
514	>	* unregistered party to invoke this method.
515		*
516	<	* @return the current barrier phase number upon entry to
470	<	* this method, or a negative value if terminated;
516	>	* @return the arrival phase number, or a negative value if terminated
517		* @throws IllegalStateException if not terminated and the number
518	<	* of registered or unarrived parties would become negative.
518	>	* of registered or unarrived parties would become negative
519		*/
520		public int arriveAndDeregister() {
521		// similar code to arrive, but too different to merge
#	Line 498 | Line 544 | public class Phaser {
544		if (unarrived == 0) {
545		if (casState
546		(s,
547	<	trippedStateFor(onAdvance(phase, parties)? -1 :
547	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
548		((phase + 1) & phaseMask), parties))) {
549		releaseWaiters(phase);
550		break;
#	Line 517 | Line 563 | public class Phaser {
563
564		/**
565		* Arrives at the barrier and awaits others. Equivalent in effect
566	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
567	<	* await with interruption of timeout, and/or deregister upon
568	<	* arrival, you can arrange them using analogous constructions.
569	<	* @return the phase on entry to this method
566	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
567	>	* interruption or timeout, you can arrange this with an analogous
568	>	* construction using one of the other forms of the awaitAdvance
569	>	* method.  If instead you need to deregister upon arrival use
570	>	* {@code arriveAndDeregister}. It is an unenforced usage error
571	>	* for an unregistered party to invoke this method.
572	>	*
573	>	* @return the arrival phase number, or a negative number if terminated
574		* @throws IllegalStateException if not terminated and the number
575	<	* of unarrived parties would become negative.
575	>	* of unarrived parties would become negative
576		*/
577		public int arriveAndAwaitAdvance() {
578		return awaitAdvance(arrive());
579		}
580
581		/**
582	<	* Awaits the phase of the barrier to advance from the given
583	<	* value, or returns immediately if argument is negative or this
584	<	* barrier is terminated.
585	<	* @param phase the phase on entry to this method
586	<	* @return the phase on exit from this method
582	>	* Awaits the phase of the barrier to advance from the given phase
583	>	* value, returning immediately if the current phase of the
584	>	* barrier is not equal to the given phase value or this barrier
585	>	* is terminated.  It is an unenforced usage error for an
586	>	* unregistered party to invoke this method.
587	>	*
588	>	* @param phase an arrival phase number, or negative value if
589	>	* terminated; this argument is normally the value returned by a
590	>	* previous call to {@code arrive} or its variants
591	>	* @return the next arrival phase number, or a negative value
592	>	* if terminated or argument is negative
593		*/
594		public int awaitAdvance(int phase) {
595		if (phase < 0)
#	Line 549 | Line 605 | public class Phaser {
605		}
606
607		/**
608	<	* Awaits the phase of the barrier to advance from the given
609	<	* value, or returns immediately if argument is negative or this
610	<	* barrier is terminated, or throws InterruptedException if
611	<	* interrupted while waiting.
612	<	* @param phase the phase on entry to this method
613	<	* @return the phase on exit from this method
608	>	* Awaits the phase of the barrier to advance from the given phase
609	>	* value, throwing {@code InterruptedException} if interrupted
610	>	* while waiting, or returning immediately if the current phase of
611	>	* the barrier is not equal to the given phase value or this
612	>	* barrier is terminated. It is an unenforced usage error for an
613	>	* unregistered party to invoke this method.
614	>	*
615	>	* @param phase an arrival phase number, or negative value if
616	>	* terminated; this argument is normally the value returned by a
617	>	* previous call to {@code arrive} or its variants
618	>	* @return the next arrival phase number, or a negative value
619	>	* if terminated or argument is negative
620		* @throws InterruptedException if thread interrupted while waiting
621		*/
622		public int awaitAdvanceInterruptibly(int phase)
#	Line 571 | Line 633 | public class Phaser {
633		}
634
635		/**
636	<	* Awaits the phase of the barrier to advance from the given value
637	<	* or the given timeout elapses, or returns immediately if
638	<	* argument is negative or this barrier is terminated.
639	<	* @param phase the phase on entry to this method
640	<	* @return the phase on exit from this method
636	>	* Awaits the phase of the barrier to advance from the given phase
637	>	* value or the given timeout to elapse, throwing {@code
638	>	* InterruptedException} if interrupted while waiting, or
639	>	* returning immediately if the current phase of the barrier is
640	>	* not equal to the given phase value or this barrier is
641	>	* terminated.  It is an unenforced usage error for an
642	>	* unregistered party to invoke this method.
643	>	*
644	>	* @param phase an arrival phase number, or negative value if
645	>	* terminated; this argument is normally the value returned by a
646	>	* previous call to {@code arrive} or its variants
647	>	* @param timeout how long to wait before giving up, in units of
648	>	*        {@code unit}
649	>	* @param unit a {@code TimeUnit} determining how to interpret the
650	>	*        {@code timeout} parameter
651	>	* @return the next arrival phase number, or a negative value
652	>	* if terminated or argument is negative
653		* @throws InterruptedException if thread interrupted while waiting
654		* @throws TimeoutException if timed out while waiting
655		*/
656	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
656	>	public int awaitAdvanceInterruptibly(int phase,
657	>	long timeout, TimeUnit unit)
658		throws InterruptedException, TimeoutException {
659		if (phase < 0)
660		return phase;
#	Line 620 | Line 695 | public class Phaser {
695		* Returns the current phase number. The maximum phase number is
696		* {@code Integer.MAX_VALUE}, after which it restarts at
697		* zero. Upon termination, the phase number is negative.
698	+	*
699		* @return the phase number, or a negative value if terminated
700		*/
701		public final int getPhase() {
#	Line 627 | Line 703 | public class Phaser {
703		}
704
705		/**
630	–	* Returns {@code true} if the current phase number equals the given phase.
631	–	* @param phase the phase
632	–	* @return {@code true} if the current phase number equals the given phase
633	–	*/
634	–	public final boolean hasPhase(int phase) {
635	–	return phaseOf(getReconciledState()) == phase;
636	–	}
637	–
638	–	/**
706		* Returns the number of parties registered at this barrier.
707	+	*
708		* @return the number of parties
709		*/
710		public int getRegisteredParties() {
#	Line 644 | Line 712 | public class Phaser {
712		}
713
714		/**
715	<	* Returns the number of parties that have arrived at the current
716	<	* phase of this barrier.
715	>	* Returns the number of registered parties that have arrived at
716	>	* the current phase of this barrier.
717	>	*
718		* @return the number of arrived parties
719		*/
720		public int getArrivedParties() {
#	Line 655 | Line 724 | public class Phaser {
724		/**
725		* Returns the number of registered parties that have not yet
726		* arrived at the current phase of this barrier.
727	+	*
728		* @return the number of unarrived parties
729		*/
730		public int getUnarrivedParties() {
#	Line 662 | Line 732 | public class Phaser {
732		}
733
734		/**
735	<	* Returns the parent of this phaser, or null if none.
736	<	* @return the parent of this phaser, or null if none
735	>	* Returns the parent of this phaser, or {@code null} if none.
736	>	*
737	>	* @return the parent of this phaser, or {@code null} if none
738		*/
739		public Phaser getParent() {
740		return parent;
#	Line 672 | Line 743 | public class Phaser {
743		/**
744		* Returns the root ancestor of this phaser, which is the same as
745		* this phaser if it has no parent.
746	+	*
747		* @return the root ancestor of this phaser
748		*/
749		public Phaser getRoot() {
#	Line 680 | Line 752 | public class Phaser {
752
753		/**
754		* Returns {@code true} if this barrier has been terminated.
755	+	*
756		* @return {@code true} if this barrier has been terminated
757		*/
758		public boolean isTerminated() {
#	Line 690 | Line 763 | public class Phaser {
763		* Overridable method to perform an action upon phase advance, and
764		* to control termination. This method is invoked whenever the
765		* barrier is tripped (and thus all other waiting parties are
766	<	* dormant). If it returns true, then, rather than advance the
767	<	* phase number, this barrier will be set to a final termination
768	<	* state, and subsequent calls to {@code isTerminated} will
769	<	* return true.
766	>	* dormant). If it returns {@code true}, then, rather than advance
767	>	* the phase number, this barrier will be set to a final
768	>	* termination state, and subsequent calls to {@link #isTerminated}
769	>	* will return true.
770		*
771	<	* <p> The default version returns true when the number of
771	>	* <p>The default version returns {@code true} when the number of
772		* registered parties is zero. Normally, overrides that arrange
773		* termination for other reasons should also preserve this
774		* property.
775		*
776	<	* <p> You may override this method to perform an action with side
776	>	* <p>You may override this method to perform an action with side
777		* effects visible to participating tasks, but it is in general
778		* only sensible to do so in designs where all parties register
779	<	* before any arrive, and all {@code awaitAdvance} at each phase.
780	<	* Otherwise, you cannot ensure lack of interference. In
781	<	* particular, this method may be invoked more than once per
709	<	* transition if other parties successfully register while the
710	<	* invocation of this method is in progress, thus postponing the
711	<	* transition until those parties also arrive, re-triggering this
712	<	* method.
779	>	* before any arrive, and all {@link #awaitAdvance} at each phase.
780	>	* Otherwise, you cannot ensure lack of interference from other
781	>	* parties during the invocation of this method.
782		*
783		* @param phase the phase number on entering the barrier
784		* @param registeredParties the current number of registered parties
#	Line 803 | Line 872 | public class Phaser {
872		}
873
874		/**
875	<	* Removes and signals waiting threads from wait queue
875	>	* Removes and signals waiting threads from wait queue.
876		*/
877		private void releaseWaiters(int phase) {
878		AtomicReference<QNode> head = queueFor(phase);
#	Line 815 | Line 884 | public class Phaser {
884		}
885
886		/**
887	<	* Tries to enqueue given node in the appropriate wait queue
887	>	* Tries to enqueue given node in the appropriate wait queue.
888	>	*
889		* @return true if successful
890		*/
891		private boolean tryEnqueue(QNode node) {
#	Line 825 | Line 895 | public class Phaser {
895
896		/**
897		* Enqueues node and waits unless aborted or signalled.
898	+	*
899		* @return current phase
900		*/
901		private int untimedWait(int phase) {
#	Line 912 | Line 983 | public class Phaser {
983		return p;
984		}
985
986	<	// Temporary Unsafe mechanics for preliminary release
916	<	private static Unsafe getUnsafe() throws Throwable {
917	<	try {
918	<	return Unsafe.getUnsafe();
919	<	} catch (SecurityException se) {
920	<	try {
921	<	return java.security.AccessController.doPrivileged
922	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
923	<	public Unsafe run() throws Exception {
924	<	return getUnsafePrivileged();
925	<	}});
926	<	} catch (java.security.PrivilegedActionException e) {
927	<	throw e.getCause();
928	<	}
929	<	}
930	<	}
986	>	// Unsafe mechanics
987
988	<	private static Unsafe getUnsafePrivileged()
989	<	throws NoSuchFieldException, IllegalAccessException {
990	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
935	<	f.setAccessible(true);
936	<	return (Unsafe) f.get(null);
937	<	}
988	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
989	>	private static final long stateOffset =
990	>	objectFieldOffset("state", Phaser.class);
991
992	<	private static long fieldOffset(String fieldName)
993	<	throws NoSuchFieldException {
941	<	return _unsafe.objectFieldOffset
942	<	(Phaser.class.getDeclaredField(fieldName));
992	>	private final boolean casState(long cmp, long val) {
993	>	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
994		}
995
996	<	static final Unsafe _unsafe;
946	<	static final long stateOffset;
947	<
948	<	static {
996	>	private static long objectFieldOffset(String field, Class<?> klazz) {
997		try {
998	<	_unsafe = getUnsafe();
999	<	stateOffset = fieldOffset("state");
1000	<	} catch (Throwable e) {
1001	<	throw new RuntimeException("Could not initialize intrinsics", e);
998	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
999	>	} catch (NoSuchFieldException e) {
1000	>	// Convert Exception to corresponding Error
1001	>	NoSuchFieldError error = new NoSuchFieldError(field);
1002	>	error.initCause(e);
1003	>	throw error;
1004		}
1005		}
1006
1007	<	final boolean casState(long cmp, long val) {
1008	<	return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val);
1007	>	/**
1008	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1009	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1010	>	* into a jdk.
1011	>	*
1012	>	* @return a sun.misc.Unsafe
1013	>	*/
1014	>	private static sun.misc.Unsafe getUnsafe() {
1015	>	try {
1016	>	return sun.misc.Unsafe.getUnsafe();
1017	>	} catch (SecurityException se) {
1018	>	try {
1019	>	return java.security.AccessController.doPrivileged
1020	>	(new java.security
1021	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1022	>	public sun.misc.Unsafe run() throws Exception {
1023	>	java.lang.reflect.Field f = sun.misc
1024	>	.Unsafe.class.getDeclaredField("theUnsafe");
1025	>	f.setAccessible(true);
1026	>	return (sun.misc.Unsafe) f.get(null);
1027	>	}});
1028	>	} catch (java.security.PrivilegedActionException e) {
1029	>	throw new RuntimeException("Could not initialize intrinsics",
1030	>	e.getCause());
1031	>	}
1032	>	}
1033		}
1034		}

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