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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.6 by dl, Tue Oct 28 23:03:24 2008 UTC vs.
Revision 1.37 by jsr166, Mon Aug 24 00:48:52 2009 UTC

#	Line 5 | Line 5
5		*/
6
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;
11	–	import sun.misc.Unsafe;
12	–	import java.lang.reflect.*;
13
14		/**
15	<	* A reusable synchronization barrier, similar in functionality to a
16	<	* {@link java.util.concurrent.CyclicBarrier} and {@link
17	<	* java.util.concurrent.CountDownLatch} but supporting more flexible
18	<	* usage.
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 in 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 <tt>Integer.MAX_VALUE</tt>).
34	<	*
35	<	* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited.
36	<	* Method <tt>arriveAndAwaitAdvance</tt> has effect analogous to
37	<	* <tt>CyclicBarrier.await</tt>.  However, Phasers separate two
38	<	* aspects of coordination, that may also be invoked independently:
22	>	* <li> The number of parties <em>registered</em> to synchronize on a
23	>	* phaser may vary over time.  Tasks may be registered at any time
24	>	* (using methods {@link #register}, {@link #bulkRegister}, or forms
25	>	* of constructors establishing initial numbers of parties), and may
26	>	* optionally be deregistered upon any arrival (using {@link
27	>	* #arriveAndDeregister}).  As is the case with most basic
28	>	* synchronization constructs, registration and deregistration affect
29	>	* only internal counts; they do not establish any further internal
30	>	* bookkeeping, so tasks cannot query whether they are registered.
31	>	* (However, you can introduce such bookkeeping by subclassing this
32	>	* class.)
33	>	*
34	>	* <li> Each generation has an associated phase number. The phase
35	>	* number starts at zero, amd advances when all parties arrive at the
36	>	* barrier, wrapping around to zero after reaching {@code
37	>	* Integer.MAX_VALUE}.
38	>	*
39	>	* <li> Like a {@code CyclicBarrier}, a phaser may be repeatedly
40	>	* awaited.  Method {@link #arriveAndAwaitAdvance} has effect
41	>	* analogous to {@link java.util.concurrent.CyclicBarrier#await
42	>	* CyclicBarrier.await}.  However, phasers separate two aspects of
43	>	* coordination, which may also be invoked independently:
44		*
45		* <ul>
46		*
47	<	*   <li> Arriving at a barrier. Methods <tt>arrive</tt> and
48	<	*       <tt>arriveAndDeregister</tt> do not block, but return
49	<	*       the phase value current upon entry to the method.
50	<	*
51	<	*   <li> Awaiting others. Method <tt>awaitAdvance</tt> requires an
52	<	*       argument indicating the entry phase, and returns when the
53	<	*       barrier advances to a new phase.
47	>	*   <li> Arriving at a barrier. Methods {@link #arrive} and
48	>	*       {@link #arriveAndDeregister} do not block, but return
49	>	*       an associated <em>arrival phase number</em>;
50	>	*       that is, the phase number of the barrier to which the
51	>	*       arrival applied.
52	>	*
53	>	*   <li> Awaiting others. Method {@link #awaitAdvance} requires an
54	>	*       argument indicating an arrival phase number, and returns
55	>	*       when the barrier advances to a new phase.
56		* </ul>
57		*
51	–	*
58		* <li> Barrier actions, performed by the task triggering a phase
59	<	* advance while others may be waiting, are arranged by overriding
60	<	* method <tt>onAdvance</tt>, that also controls termination.
61	<	* Overriding this method may be used to similar but more flexible
62	<	* effect as providing a barrier action to a CyclicBarrier.
59	>	* advance, are arranged by overriding method {@link #onAdvance(int,
60	>	* int)}, which also controls termination. Overriding this method is
61	>	* similar to, but more flexible than, providing a barrier action to a
62	>	* {@code CyclicBarrier}.
63		*
64		* <li> Phasers may enter a <em>termination</em> state in which all
65	<	* await actions immediately return, indicating (via a negative phase
66	<	* value) that execution is complete.  Termination is triggered by
67	<	* executing the overridable <tt>onAdvance</tt> method that is invoked
68	<	* each time the barrier is about to be tripped. When a Phaser is
65	>	* actions immediately return without updating phaser state or waiting
66	>	* for advance, and indicating (via a negative phase value) that
67	>	* execution is complete.  Termination is triggered when an invocation
68	>	* of {@code onAdvance} returns {@code true}.  When a phaser is
69		* controlling an action with a fixed number of iterations, it is
70		* often convenient to override this method to cause termination when
71	<	* the current phase number reaches a threshold. Method
72	<	* <tt>forceTermination</tt> is also available to abruptly release
73	<	* waiting threads and allow them to terminate.
71	>	* the current phase number reaches a threshold. Method {@link
72	>	* #forceTermination} is also available to abruptly release waiting
73	>	* threads and allow them to terminate.
74		*
75		* <li> Phasers may be tiered to reduce contention. Phasers with large
76		* numbers of parties that would otherwise experience heavy
#	Line 72 | Line 78 | import java.lang.reflect.*;
78		* This will typically greatly increase throughput even though it
79		* incurs somewhat greater per-operation overhead.
80		*
81	<	* <li> By default, <tt>awaitAdvance</tt> continues to wait even if
81	>	* <li> By default, {@code awaitAdvance} continues to wait even if
82		* the waiting thread is interrupted. And unlike the case in
83	<	* CyclicBarriers, exceptions encountered while tasks wait
83	>	* {@code CyclicBarrier}, exceptions encountered while tasks wait
84		* interruptibly or with timeout do not change the state of the
85		* barrier. If necessary, you can perform any associated recovery
86		* within handlers of those exceptions, often after invoking
87	<	* <tt>forceTermination</tt>.
87	>	* {@code forceTermination}.
88	>	*
89	>	* <li>Phasers may be used to coordinate tasks executing in a {@link
90	>	* ForkJoinPool}, which will ensure sufficient parallelism to execute
91	>	* tasks when others are blocked waiting for a phase to advance.
92	>	*
93	>	* <li>The current state of a phaser may be monitored.  At any given
94	>	* moment there are {@link #getRegisteredParties}, where {@link
95	>	* #getArrivedParties} have arrived at the current phase ({@link
96	>	* #getPhase}). When the remaining {@link #getUnarrivedParties})
97	>	* arrive, the phase advances. Method {@link #toString} returns
98	>	* snapshots of these state queries in a form convenient for
99	>	* informal monitoring.
100		*
101		* </ul>
102		*
103		* <p><b>Sample usages:</b>
104		*
105	<	* <p>A Phaser may be used instead of a <tt>CountdownLatch</tt> to control
106	<	* a one-shot action serving a variable number of parties. The typical
107	<	* idiom is for the method setting this up to first register, then
108	<	* start the actions, then deregister, as in:
109	<	*
110	<	* <pre>
111	<	*  void runTasks(List&lt;Runnable&gt; list) {
112	<	*    final Phaser phaser = new Phaser(1); // "1" to register self
113	<	*    for (Runnable r : list) {
114	<	*      phaser.register();
115	<	*      new Thread() {
116	<	*        public void run() {
117	<	*          phaser.arriveAndAwaitAdvance(); // await all creation
118	<	*          r.run();
119	<	*          phaser.arriveAndDeregister();   // signal completion
120	<	*        }
121	<	*      }.start();
105	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
106	>	* to control a one-shot action serving a variable number of
107	>	* parties. The typical idiom is for the method setting this up to
108	>	* first register, then start the actions, then deregister, as in:
109	>	*
110	>	*  <pre> {@code
111	>	* void runTasks(List<Runnable> tasks) {
112	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
113	>	*   // create and start threads
114	>	*   for (Runnable task : tasks) {
115	>	*     phaser.register();
116	>	*     new Thread() {
117	>	*       public void run() {
118	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
119	>	*         task.run();
120	>	*       }
121	>	*     }.start();
122		*   }
123		*
124	<	*   doSomethingOnBehalfOfWorkers();
125	<	*   phaser.arrive(); // allow threads to start
126	<	*   int p = phaser.arriveAndDeregister(); // deregister self  ...
109	<	*   p = phaser.awaitAdvance(p); // ... and await arrival
110	<	*   otherActions(); // do other things while tasks execute
111	<	*   phaser.awaitAdvance(p); // awit final completion
112	<	* }
113	<	* </pre>
124	>	*   // allow threads to start and deregister self
125	>	*   phaser.arriveAndDeregister();
126	>	* }}</pre>
127		*
128		* <p>One way to cause a set of threads to repeatedly perform actions
129	<	* for a given number of iterations is to override <tt>onAdvance</tt>:
129	>	* for a given number of iterations is to override {@code onAdvance}:
130		*
131	<	* <pre>
132	<	*  void startTasks(List&lt;Runnable&gt; list, final int iterations) {
133	<	*    final Phaser phaser = new Phaser() {
134	<	*       public boolean onAdvance(int phase, int registeredParties) {
135	<	*         return phase &gt;= iterations || registeredParties == 0;
131	>	*  <pre> {@code
132	>	* void startTasks(List<Runnable> tasks, final int iterations) {
133	>	*   final Phaser phaser = new Phaser() {
134	>	*     public boolean onAdvance(int phase, int registeredParties) {
135	>	*       return phase >= iterations || registeredParties == 0;
136	>	*     }
137	>	*   };
138	>	*   phaser.register();
139	>	*   for (Runnable task : tasks) {
140	>	*     phaser.register();
141	>	*     new Thread() {
142	>	*       public void run() {
143	>	*         do {
144	>	*           task.run();
145	>	*           phaser.arriveAndAwaitAdvance();
146	>	*         } while(!phaser.isTerminated();
147		*       }
148	<	*    };
125	<	*    phaser.register();
126	<	*    for (Runnable r : list) {
127	<	*      phaser.register();
128	<	*      new Thread() {
129	<	*        public void run() {
130	<	*           do {
131	<	*             r.run();
132	<	*             phaser.arriveAndAwaitAdvance();
133	<	*           } while(!phaser.isTerminated();
134	<	*        }
135	<	*      }.start();
148	>	*     }.start();
149		*   }
150		*   phaser.arriveAndDeregister(); // deregister self, don't wait
151	<	* }
139	<	* </pre>
151	>	* }}</pre>
152		*
153	<	* <p> To create a set of tasks using a tree of Phasers,
153	>	* <p>To create a set of tasks using a tree of phasers,
154		* you could use code of the following form, assuming a
155	<	* Task class with a constructor accepting a Phaser that
155	>	* Task class with a constructor accepting a phaser that
156		* it registers for upon construction:
157	<	* <pre>
158	<	*  void build(Task[] actions, int lo, int hi, Phaser b) {
159	<	*    int step = (hi - lo) / TASKS_PER_PHASER;
160	<	*    if (step &gt; 1) {
161	<	*       int i = lo;
162	<	*       while (i &lt; hi) {
163	<	*         int r = Math.min(i + step, hi);
164	<	*         build(actions, i, r, new Phaser(b));
165	<	*         i = r;
166	<	*       }
167	<	*    }
168	<	*    else {
169	<	*      for (int i = lo; i &lt; hi; ++i)
170	<	*        actions[i] = new Task(b);
171	<	*        // assumes new Task(b) performs b.register()
172	<	*    }
173	<	*  }
174	<	*  // .. initially called, for n tasks via
163	<	*  build(new Task[n], 0, n, new Phaser());
164	<	* </pre>
157	>	*  <pre> {@code
158	>	* void build(Task[] actions, int lo, int hi, Phaser b) {
159	>	*   int step = (hi - lo) / TASKS_PER_PHASER;
160	>	*   if (step > 1) {
161	>	*     int i = lo;
162	>	*     while (i < hi) {
163	>	*       int r = Math.min(i + step, hi);
164	>	*       build(actions, i, r, new Phaser(b));
165	>	*       i = r;
166	>	*     }
167	>	*   } else {
168	>	*     for (int i = lo; i < hi; ++i)
169	>	*       actions[i] = new Task(b);
170	>	*       // assumes new Task(b) performs b.register()
171	>	*   }
172	>	* }
173	>	* // .. initially called, for n tasks via
174	>	* build(new Task[n], 0, n, new Phaser());}</pre>
175		*
176	<	* The best value of <tt>TASKS_PER_PHASER</tt> depends mainly on
176	>	* The best value of {@code TASKS_PER_PHASER} depends mainly on
177		* expected barrier synchronization rates. A value as low as four may
178		* be appropriate for extremely small per-barrier task bodies (thus
179		* high rates), or up to hundreds for extremely large ones.
#	Line 172 | Line 182 | import java.lang.reflect.*;
182		*
183		* <p><b>Implementation notes</b>: This implementation restricts the
184		* maximum number of parties to 65535. Attempts to register additional
185	<	* parties result in IllegalStateExceptions. However, you can and
185	>	* parties result in {@code IllegalStateException}. However, you can and
186		* should create tiered phasers to accommodate arbitrarily large sets
187		* of participants.
188	+	*
189	+	* @since 1.7
190	+	* @author Doug Lea
191		*/
192		public class Phaser {
193		/*
#	Line 195 | Line 208 | public class Phaser {
208		* However, to efficiently maintain atomicity, these values are
209		* packed into a single (atomic) long. Termination uses the sign
210		* bit of 32 bit representation of phase, so phase is set to -1 on
211	<	* termination. Good performace relies on keeping state decoding
211	>	* termination. Good performance relies on keeping state decoding
212		* and encoding simple, and keeping race windows short.
213		*
214		* Note: there are some cheats in arrive() that rely on unarrived
215	<	* being lowest 16 bits.
215	>	* count being lowest 16 bits.
216		*/
217		private volatile long state;
218
219		private static final int ushortBits = 16;
220	<	private static final int ushortMask =  (1 << ushortBits) - 1;
221	<	private static final int phaseMask = 0x7fffffff;
220	>	private static final int ushortMask = 0xffff;
221	>	private static final int phaseMask  = 0x7fffffff;
222
223		private static int unarrivedOf(long s) {
224	<	return (int)(s & ushortMask);
224	>	return (int) (s & ushortMask);
225		}
226
227		private static int partiesOf(long s) {
228	<	return (int)(s & (ushortMask << 16)) >>> 16;
228	>	return ((int) s) >>> 16;
229		}
230
231		private static int phaseOf(long s) {
232	<	return (int)(s >>> 32);
232	>	return (int) (s >>> 32);
233		}
234
235		private static int arrivedOf(long s) {
#	Line 224 | Line 237 | public class Phaser {
237		}
238
239		private static long stateFor(int phase, int parties, int unarrived) {
240	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
240	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
241	>	(long) unarrived);
242		}
243
244		private static long trippedStateFor(int phase, int parties) {
245	<	return (((long)phase) << 32) | ((parties << 16) | parties);
245	>	long lp = (long) parties;
246	>	return (((long) phase) << 32) | (lp << 16) | lp;
247		}
248
249	<	private static IllegalStateException badBounds(int parties, int unarrived) {
250	<	return new IllegalStateException
251	<	("Attempt to set " + unarrived +
252	<	" unarrived of " + parties + " parties");
249	>	/**
250	>	* Returns message string for bad bounds exceptions.
251	>	*/
252	>	private static String badBounds(int parties, int unarrived) {
253	>	return ("Attempt to set " + unarrived +
254	>	" unarrived of " + parties + " parties");
255		}
256
257		/**
#	Line 243 | Line 260 | public class Phaser {
260		private final Phaser parent;
261
262		/**
263	<	* The root of Phaser tree. Equals this if not in a tree.  Used to
263	>	* The root of phaser tree. Equals this if not in a tree.  Used to
264		* support faster state push-down.
265		*/
266		private final Phaser root;
#	Line 251 | Line 268 | public class Phaser {
268		// Wait queues
269
270		/**
271	<	* Heads of Treiber stacks waiting for nonFJ threads. To eliminate
271	>	* Heads of Treiber stacks for waiting threads. To eliminate
272		* contention while releasing some threads while adding others, we
273		* use two of them, alternating across even and odd phases.
274		*/
#	Line 259 | Line 276 | public class Phaser {
276		private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
277
278		private AtomicReference<QNode> queueFor(int phase) {
279	<	return (phase & 1) == 0? evenQ : oddQ;
279	>	return ((phase & 1) == 0) ? evenQ : oddQ;
280		}
281
282		/**
#	Line 267 | Line 284 | public class Phaser {
284		* root if necessary.
285		*/
286		private long getReconciledState() {
287	<	return parent == null? state : reconcileState();
287	>	return (parent == null) ? state : reconcileState();
288		}
289
290		/**
#	Line 294 | Line 311 | public class Phaser {
311		}
312
313		/**
314	<	* Creates a new Phaser without any initially registered parties,
315	<	* initial phase number 0, and no parent.
314	>	* Creates a new phaser without any initially registered parties,
315	>	* initial phase number 0, and no parent. Any thread using this
316	>	* phaser will need to first register for it.
317		*/
318		public Phaser() {
319		this(null);
320		}
321
322		/**
323	<	* Creates a new Phaser with the given numbers of registered
323	>	* Creates a new phaser with the given numbers of registered
324		* unarrived parties, initial phase number 0, and no parent.
325	<	* @param parties the number of parties required to trip barrier.
325	>	*
326	>	* @param parties the number of parties required to trip barrier
327		* @throws IllegalArgumentException if parties less than zero
328	<	* or greater than the maximum number of parties supported.
328	>	* or greater than the maximum number of parties supported
329		*/
330		public Phaser(int parties) {
331		this(null, parties);
332		}
333
334		/**
335	<	* Creates a new Phaser with the given parent, without any
335	>	* Creates a new phaser with the given parent, without any
336		* initially registered parties. If parent is non-null this phaser
337		* is registered with the parent and its initial phase number is
338		* the same as that of parent phaser.
339	<	* @param parent the parent phaser.
339	>	*
340	>	* @param parent the parent phaser
341		*/
342		public Phaser(Phaser parent) {
343		int phase = 0;
#	Line 332 | Line 352 | public class Phaser {
352		}
353
354		/**
355	<	* Creates a new Phaser with the given parent and numbers of
356	<	* registered unarrived parties. If parent is non-null this phaser
355	>	* Creates a new phaser with the given parent and numbers of
356	>	* registered unarrived parties. If parent is non-null, this phaser
357		* is registered with the parent and its initial phase number is
358		* the same as that of parent phaser.
359	<	* @param parent the parent phaser.
360	<	* @param parties the number of parties required to trip barrier.
359	>	*
360	>	* @param parent the parent phaser
361	>	* @param parties the number of parties required to trip barrier
362		* @throws IllegalArgumentException if parties less than zero
363	<	* or greater than the maximum number of parties supported.
363	>	* or greater than the maximum number of parties supported
364		*/
365		public Phaser(Phaser parent, int parties) {
366		if (parties < 0 || parties > ushortMask)
#	Line 357 | Line 378 | public class Phaser {
378
379		/**
380		* Adds a new unarrived party to this phaser.
381	<	* @return the current barrier phase number upon registration
381	>	*
382	>	* @return the arrival phase number to which this registration applied
383		* @throws IllegalStateException if attempting to register more
384	<	* than the maximum supported number of parties.
384	>	* than the maximum supported number of parties
385		*/
386		public int register() {
387		return doRegister(1);
#	Line 367 | Line 389 | public class Phaser {
389
390		/**
391		* Adds the given number of new unarrived parties to this phaser.
392	<	* @param parties the number of parties required to trip barrier.
393	<	* @return the current barrier phase number upon registration
392	>	*
393	>	* @param parties the number of parties required to trip barrier
394	>	* @return the arrival phase number to which this registration applied
395		* @throws IllegalStateException if attempting to register more
396	<	* than the maximum supported number of parties.
396	>	* than the maximum supported number of parties
397		*/
398		public int bulkRegister(int parties) {
399		if (parties < 0)
#	Line 393 | Line 416 | public class Phaser {
416		if (phase < 0)
417		break;
418		if (parties > ushortMask || unarrived > ushortMask)
419	<	throw badBounds(parties, unarrived);
419	>	throw new IllegalStateException(badBounds(parties, unarrived));
420		if (phase == phaseOf(root.state) &&
421		casState(s, stateFor(phase, parties, unarrived)))
422		break;
#	Line 405 | Line 428 | public class Phaser {
428		* Arrives at the barrier, but does not wait for others.  (You can
429		* in turn wait for others via {@link #awaitAdvance}).
430		*
431	<	* @return the barrier phase number upon entry to this method, or a
409	<	* negative value if terminated;
431	>	* @return the arrival phase number, or a negative value if terminated
432		* @throws IllegalStateException if not terminated and the number
433	<	* of unarrived parties would become negative.
433	>	* of unarrived parties would become negative
434		*/
435		public int arrive() {
436		int phase;
437		for (;;) {
438		long s = state;
439		phase = phaseOf(s);
440	+	if (phase < 0)
441	+	break;
442		int parties = partiesOf(s);
443		int unarrived = unarrivedOf(s) - 1;
444		if (unarrived > 0) {        // Not the last arrival
#	Line 426 | Line 450 | public class Phaser {
450		if (par == null) {      // directly trip
451		if (casState
452		(s,
453	<	trippedStateFor(onAdvance(phase, parties)? -1 :
453	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
454		((phase + 1) & phaseMask), parties))) {
455		releaseWaiters(phase);
456		break;
#	Line 440 | Line 464 | public class Phaser {
464		}
465		}
466		}
443	–	else if (phase < 0) // Don't throw exception if terminated
444	–	break;
467		else if (phase != phaseOf(root.state)) // or if unreconciled
468		reconcileState();
469		else
470	<	throw badBounds(parties, unarrived);
470	>	throw new IllegalStateException(badBounds(parties, unarrived));
471		}
472		return phase;
473		}
474
475		/**
476	<	* Arrives at the barrier, and deregisters from it, without
477	<	* waiting for others. Deregistration reduces number of parties
476	>	* Arrives at the barrier and deregisters from it without waiting
477	>	* for others. Deregistration reduces the number of parties
478		* required to trip the barrier in future phases.  If this phaser
479		* has a parent, and deregistration causes this phaser to have
480	<	* zero parties, this phaser is also deregistered from its parent.
480	>	* zero parties, this phaser also arrives at and is deregistered
481	>	* from its parent.
482		*
483	<	* @return the current barrier phase number upon entry to
461	<	* this method, or a negative value if terminated;
483	>	* @return the arrival phase number, or a negative value if terminated
484		* @throws IllegalStateException if not terminated and the number
485	<	* of registered or unarrived parties would become negative.
485	>	* of registered or unarrived parties would become negative
486		*/
487		public int arriveAndDeregister() {
488		// similar code to arrive, but too different to merge
#	Line 469 | Line 491 | public class Phaser {
491		for (;;) {
492		long s = state;
493		phase = phaseOf(s);
494	+	if (phase < 0)
495	+	break;
496		int parties = partiesOf(s) - 1;
497		int unarrived = unarrivedOf(s) - 1;
498		if (parties >= 0) {
#	Line 487 | Line 511 | public class Phaser {
511		if (unarrived == 0) {
512		if (casState
513		(s,
514	<	trippedStateFor(onAdvance(phase, parties)? -1 :
514	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
515		((phase + 1) & phaseMask), parties))) {
516		releaseWaiters(phase);
517		break;
518		}
519		continue;
520		}
497	–	if (phase < 0)
498	–	break;
521		if (par != null && phase != phaseOf(root.state)) {
522		reconcileState();
523		continue;
524		}
525		}
526	<	throw badBounds(parties, unarrived);
526	>	throw new IllegalStateException(badBounds(parties, unarrived));
527		}
528		return phase;
529		}
530
531		/**
532		* Arrives at the barrier and awaits others. Equivalent in effect
533	<	* to <tt>awaitAdvance(arrive())</tt>.  If you instead need to
534	<	* await with interruption of timeout, and/or deregister upon
535	<	* arrival, you can arrange them using analogous constructions.
536	<	* @return the phase on entry to this method
533	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
534	>	* interruption or timeout, you can arrange this with an analogous
535	>	* construction using one of the other forms of the awaitAdvance
536	>	* method.  If instead you need to deregister upon arrival use
537	>	* {@code arriveAndDeregister}.
538	>	*
539	>	* @return the arrival phase number, or a negative number if terminated
540		* @throws IllegalStateException if not terminated and the number
541	<	* of unarrived parties would become negative.
541	>	* of unarrived parties would become negative
542		*/
543		public int arriveAndAwaitAdvance() {
544		return awaitAdvance(arrive());
545		}
546
547		/**
548	<	* Awaits the phase of the barrier to advance from the given
549	<	* value, or returns immediately if argument is negative or this
550	<	* barrier is terminated.
551	<	* @param phase the phase on entry to this method
552	<	* @return the phase on exit from this method
548	>	* Awaits the phase of the barrier to advance from the given phase
549	>	* value, returning immediately if the current phase of the
550	>	* barrier is not equal to the given phase value or this barrier
551	>	* is terminated.
552	>	*
553	>	* @param phase an arrival phase number, or negative value if
554	>	* terminated; this argument is normally the value returned by a
555	>	* previous call to {@code arrive} or its variants
556	>	* @return the next arrival phase number, or a negative value
557	>	* if terminated or argument is negative
558		*/
559		public int awaitAdvance(int phase) {
560		if (phase < 0)
#	Line 533 | Line 563 | public class Phaser {
563		int p = phaseOf(s);
564		if (p != phase)
565		return p;
566	<	if (unarrivedOf(s) == 0)
566	>	if (unarrivedOf(s) == 0 && parent != null)
567		parent.awaitAdvance(phase);
568		// Fall here even if parent waited, to reconcile and help release
569		return untimedWait(phase);
570		}
571
572		/**
573	<	* Awaits the phase of the barrier to advance from the given
574	<	* value, or returns immediately if argumet is negative or this
575	<	* barrier is terminated, or throws InterruptedException if
576	<	* interrupted while waiting.
577	<	* @param phase the phase on entry to this method
578	<	* @return the phase on exit from this method
573	>	* Awaits the phase of the barrier to advance from the given phase
574	>	* value, throwing {@code InterruptedException} if interrupted while
575	>	* waiting, or returning immediately if the current phase of the
576	>	* barrier is not equal to the given phase value or this barrier
577	>	* is terminated.
578	>	*
579	>	* @param phase an arrival phase number, or negative value if
580	>	* terminated; this argument is normally the value returned by a
581	>	* previous call to {@code arrive} or its variants
582	>	* @return the next arrival phase number, or a negative value
583	>	* if terminated or argument is negative
584		* @throws InterruptedException if thread interrupted while waiting
585		*/
586	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
586	>	public int awaitAdvanceInterruptibly(int phase)
587	>	throws InterruptedException {
588		if (phase < 0)
589		return phase;
590		long s = getReconciledState();
591		int p = phaseOf(s);
592		if (p != phase)
593		return p;
594	<	if (unarrivedOf(s) != 0)
594	>	if (unarrivedOf(s) == 0 && parent != null)
595		parent.awaitAdvanceInterruptibly(phase);
596		return interruptibleWait(phase);
597		}
598
599		/**
600	<	* Awaits the phase of the barrier to advance from the given value
601	<	* or the given timeout elapses, or returns immediately if
602	<	* argument is negative or this barrier is terminated.
603	<	* @param phase the phase on entry to this method
604	<	* @return the phase on exit from this method
600	>	* Awaits the phase of the barrier to advance from the given phase
601	>	* value or the given timeout to elapse, throwing
602	>	* {@code InterruptedException} if interrupted while waiting, or
603	>	* returning immediately if the current phase of the barrier is not
604	>	* equal to the given phase value or this barrier is terminated.
605	>	*
606	>	* @param phase an arrival phase number, or negative value if
607	>	* terminated; this argument is normally the value returned by a
608	>	* previous call to {@code arrive} or its variants
609	>	* @param timeout how long to wait before giving up, in units of
610	>	*        {@code unit}
611	>	* @param unit a {@code TimeUnit} determining how to interpret the
612	>	*        {@code timeout} parameter
613	>	* @return the next arrival phase number, or a negative value
614	>	* if terminated or argument is negative
615		* @throws InterruptedException if thread interrupted while waiting
616		* @throws TimeoutException if timed out while waiting
617		*/
618	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
618	>	public int awaitAdvanceInterruptibly(int phase,
619	>	long timeout, TimeUnit unit)
620		throws InterruptedException, TimeoutException {
621		if (phase < 0)
622		return phase;
#	Line 577 | Line 624 | public class Phaser {
624		int p = phaseOf(s);
625		if (p != phase)
626		return p;
627	<	if (unarrivedOf(s) == 0)
627	>	if (unarrivedOf(s) == 0 && parent != null)
628		parent.awaitAdvanceInterruptibly(phase, timeout, unit);
629		return timedWait(phase, unit.toNanos(timeout));
630		}
#	Line 608 | Line 655 | public class Phaser {
655
656		/**
657		* Returns the current phase number. The maximum phase number is
658	<	* <tt>Integer.MAX_VALUE</tt>, after which it restarts at
658	>	* {@code Integer.MAX_VALUE}, after which it restarts at
659		* zero. Upon termination, the phase number is negative.
660	+	*
661		* @return the phase number, or a negative value if terminated
662		*/
663		public final int getPhase() {
#	Line 617 | Line 665 | public class Phaser {
665		}
666
667		/**
620	–	* Returns true if the current phase number equals the given phase.
621	–	* @param phase the phase
622	–	* @return true if the current phase number equals the given phase.
623	–	*/
624	–	public final boolean hasPhase(int phase) {
625	–	return phaseOf(getReconciledState()) == phase;
626	–	}
627	–
628	–	/**
668		* Returns the number of parties registered at this barrier.
669	+	*
670		* @return the number of parties
671		*/
672		public int getRegisteredParties() {
#	Line 634 | Line 674 | public class Phaser {
674		}
675
676		/**
677	<	* Returns the number of parties that have arrived at the current
678	<	* phase of this barrier.
677	>	* Returns the number of registered parties that have arrived at
678	>	* the current phase of this barrier.
679	>	*
680		* @return the number of arrived parties
681		*/
682		public int getArrivedParties() {
#	Line 645 | Line 686 | public class Phaser {
686		/**
687		* Returns the number of registered parties that have not yet
688		* arrived at the current phase of this barrier.
689	+	*
690		* @return the number of unarrived parties
691		*/
692		public int getUnarrivedParties() {
#	Line 652 | Line 694 | public class Phaser {
694		}
695
696		/**
697	<	* Returns the parent of this phaser, or null if none.
698	<	* @return the parent of this phaser, or null if none.
697	>	* Returns the parent of this phaser, or {@code null} if none.
698	>	*
699	>	* @return the parent of this phaser, or {@code null} if none
700		*/
701		public Phaser getParent() {
702		return parent;
#	Line 662 | Line 705 | public class Phaser {
705		/**
706		* Returns the root ancestor of this phaser, which is the same as
707		* this phaser if it has no parent.
708	<	* @return the root ancestor of this phaser.
708	>	*
709	>	* @return the root ancestor of this phaser
710		*/
711		public Phaser getRoot() {
712		return root;
713		}
714
715		/**
716	<	* Returns true if this barrier has been terminated.
717	<	* @return true if this barrier has been terminated
716	>	* Returns {@code true} if this barrier has been terminated.
717	>	*
718	>	* @return {@code true} if this barrier has been terminated
719		*/
720		public boolean isTerminated() {
721		return getPhase() < 0;
#	Line 680 | Line 725 | public class Phaser {
725		* Overridable method to perform an action upon phase advance, and
726		* to control termination. This method is invoked whenever the
727		* barrier is tripped (and thus all other waiting parties are
728	<	* dormant). If it returns true, then, rather than advance the
729	<	* phase number, this barrier will be set to a final termination
730	<	* state, and subsequent calls to <tt>isTerminated</tt> will
731	<	* return true.
728	>	* dormant). If it returns {@code true}, then, rather than advance
729	>	* the phase number, this barrier will be set to a final
730	>	* termination state, and subsequent calls to {@link #isTerminated}
731	>	* will return true.
732		*
733	<	* <p> The default version returns true when the number of
733	>	* <p>The default version returns {@code true} when the number of
734		* registered parties is zero. Normally, overrides that arrange
735		* termination for other reasons should also preserve this
736		* property.
737		*
738	<	* <p> You may override this method to perform an action with side
738	>	* <p>You may override this method to perform an action with side
739		* effects visible to participating tasks, but it is in general
740		* only sensible to do so in designs where all parties register
741	<	* before any arrive, and all <tt>awaitAdvance</tt> at each phase.
742	<	* Otherwise, you cannot ensure lack of interference. In
743	<	* particular, this method may be invoked more than once per
699	<	* transition if other parties successfully register while the
700	<	* invocation of this method is in progress, thus postponing the
701	<	* transition until those parties also arrive, re-triggering this
702	<	* method.
741	>	* before any arrive, and all {@link #awaitAdvance} at each phase.
742	>	* Otherwise, you cannot ensure lack of interference from other
743	>	* parties during the invocation of this method.
744		*
745		* @param phase the phase number on entering the barrier
746	<	* @param registeredParties the current number of registered
747	<	* parties.
707	<	* @return true if this barrier should terminate
746	>	* @param registeredParties the current number of registered parties
747	>	* @return {@code true} if this barrier should terminate
748		*/
749		protected boolean onAdvance(int phase, int registeredParties) {
750		return registeredParties <= 0;
#	Line 713 | Line 753 | public class Phaser {
753		/**
754		* Returns a string identifying this phaser, as well as its
755		* state.  The state, in brackets, includes the String {@code
756	<	* "phase ="} followed by the phase number, {@code "parties ="}
756	>	* "phase = "} followed by the phase number, {@code "parties = "}
757		* followed by the number of registered parties, and {@code
758	<	* "arrived ="} followed by the number of arrived parties
758	>	* "arrived = "} followed by the number of arrived parties.
759		*
760		* @return a string identifying this barrier, as well as its state
761		*/
762		public String toString() {
763		long s = getReconciledState();
764	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
764	>	return super.toString() +
765	>	"[phase = " + phaseOf(s) +
766	>	" parties = " + partiesOf(s) +
767	>	" arrived = " + arrivedOf(s) + "]";
768		}
769
770		// methods for waiting
771
729	–	/** The number of CPUs, for spin control */
730	–	static final int NCPUS = Runtime.getRuntime().availableProcessors();
731	–
732	–	/**
733	–	* The number of times to spin before blocking in timed waits.
734	–	* The value is empirically derived.
735	–	*/
736	–	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
737	–
738	–	/**
739	–	* The number of times to spin before blocking in untimed waits.
740	–	* This is greater than timed value because untimed waits spin
741	–	* faster since they don't need to check times on each spin.
742	–	*/
743	–	static final int maxUntimedSpins = maxTimedSpins * 32;
744	–
745	–	/**
746	–	* The number of nanoseconds for which it is faster to spin
747	–	* rather than to use timed park. A rough estimate suffices.
748	–	*/
749	–	static final long spinForTimeoutThreshold = 1000L;
750	–
772		/**
773	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
753	<	* tasks.
773	>	* Wait nodes for Treiber stack representing wait queue
774		*/
775	<	static final class QNode {
776	<	QNode next;
775	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
776	>	final Phaser phaser;
777	>	final int phase;
778	>	final long startTime;
779	>	final long nanos;
780	>	final boolean timed;
781	>	final boolean interruptible;
782	>	volatile boolean wasInterrupted = false;
783		volatile Thread thread; // nulled to cancel wait
784	<	QNode() {
784	>	QNode next;
785	>	QNode(Phaser phaser, int phase, boolean interruptible,
786	>	boolean timed, long startTime, long nanos) {
787	>	this.phaser = phaser;
788	>	this.phase = phase;
789	>	this.timed = timed;
790	>	this.interruptible = interruptible;
791	>	this.startTime = startTime;
792	>	this.nanos = nanos;
793		thread = Thread.currentThread();
794		}
795	+	public boolean isReleasable() {
796	+	return (thread == null ||
797	+	phaser.getPhase() != phase ||
798	+	(interruptible && wasInterrupted) ||
799	+	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
800	+	}
801	+	public boolean block() {
802	+	if (Thread.interrupted()) {
803	+	wasInterrupted = true;
804	+	if (interruptible)
805	+	return true;
806	+	}
807	+	if (!timed)
808	+	LockSupport.park(this);
809	+	else {
810	+	long waitTime = nanos - (System.nanoTime() - startTime);
811	+	if (waitTime <= 0)
812	+	return true;
813	+	LockSupport.parkNanos(this, waitTime);
814	+	}
815	+	return isReleasable();
816	+	}
817		void signal() {
818		Thread t = thread;
819		if (t != null) {
#	Line 765 | Line 821 | public class Phaser {
821		LockSupport.unpark(t);
822		}
823		}
824	+	boolean doWait() {
825	+	if (thread != null) {
826	+	try {
827	+	ForkJoinPool.managedBlock(this, false);
828	+	} catch (InterruptedException ie) {
829	+	}
830	+	}
831	+	return wasInterrupted;
832	+	}
833	+
834		}
835
836		/**
837	<	* Removes and signals waiting threads from wait queue
837	>	* Removes and signals waiting threads from wait queue.
838		*/
839		private void releaseWaiters(int phase) {
840		AtomicReference<QNode> head = queueFor(phase);
#	Line 780 | Line 846 | public class Phaser {
846		}
847
848		/**
849	+	* Tries to enqueue given node in the appropriate wait queue.
850	+	*
851	+	* @return true if successful
852	+	*/
853	+	private boolean tryEnqueue(QNode node) {
854	+	AtomicReference<QNode> head = queueFor(node.phase);
855	+	return head.compareAndSet(node.next = head.get(), node);
856	+	}
857	+
858	+	/**
859		* Enqueues node and waits unless aborted or signalled.
860	+	*
861	+	* @return current phase
862		*/
863		private int untimedWait(int phase) {
786	–	int spins = maxUntimedSpins;
864		QNode node = null;
788	–	boolean interrupted = false;
865		boolean queued = false;
866	+	boolean interrupted = false;
867		int p;
868		while ((p = getPhase()) == phase) {
869	<	interrupted = Thread.interrupted();
870	<	if (node != null) {
871	<	if (!queued) {
872	<	AtomicReference<QNode> head = queueFor(phase);
873	<	queued = head.compareAndSet(node.next = head.get(), node);
874	<	}
798	<	else if (node.thread != null)
799	<	LockSupport.park(this);
800	<	}
801	<	else if (spins <= 0)
802	<	node = new QNode();
869	>	if (Thread.interrupted())
870	>	interrupted = true;
871	>	else if (node == null)
872	>	node = new QNode(this, phase, false, false, 0, 0);
873	>	else if (!queued)
874	>	queued = tryEnqueue(node);
875		else
876	<	--spins;
876	>	interrupted = node.doWait();
877		}
878		if (node != null)
879		node.thread = null;
880	+	releaseWaiters(phase);
881		if (interrupted)
882		Thread.currentThread().interrupt();
810	–	releaseWaiters(phase);
883		return p;
884		}
885
886		/**
887	<	* Messier interruptible version
887	>	* Interruptible version
888	>	* @return current phase
889		*/
890		private int interruptibleWait(int phase) throws InterruptedException {
818	–	int spins = maxUntimedSpins;
891		QNode node = null;
892		boolean queued = false;
893		boolean interrupted = false;
894		int p;
895	<	while ((p = getPhase()) == phase) {
896	<	if (interrupted = Thread.interrupted())
897	<	break;
898	<	if (node != null) {
899	<	if (!queued) {
900	<	AtomicReference<QNode> head = queueFor(phase);
901	<	queued = head.compareAndSet(node.next = head.get(), node);
830	<	}
831	<	else if (node.thread != null)
832	<	LockSupport.park(this);
833	<	}
834	<	else if (spins <= 0)
835	<	node = new QNode();
895	>	while ((p = getPhase()) == phase && !interrupted) {
896	>	if (Thread.interrupted())
897	>	interrupted = true;
898	>	else if (node == null)
899	>	node = new QNode(this, phase, true, false, 0, 0);
900	>	else if (!queued)
901	>	queued = tryEnqueue(node);
902		else
903	<	--spins;
903	>	interrupted = node.doWait();
904		}
905		if (node != null)
906		node.thread = null;
907	+	if (p != phase || (p = getPhase()) != phase)
908	+	releaseWaiters(phase);
909		if (interrupted)
910		throw new InterruptedException();
843	–	releaseWaiters(phase);
911		return p;
912		}
913
914		/**
915	<	* Even messier timeout version.
915	>	* Timeout version.
916	>	* @return current phase
917		*/
918		private int timedWait(int phase, long nanos)
919		throws InterruptedException, TimeoutException {
920	+	long startTime = System.nanoTime();
921	+	QNode node = null;
922	+	boolean queued = false;
923	+	boolean interrupted = false;
924		int p;
925	<	if ((p = getPhase()) == phase) {
926	<	long lastTime = System.nanoTime();
927	<	int spins = maxTimedSpins;
928	<	QNode node = null;
929	<	boolean queued = false;
930	<	boolean interrupted = false;
931	<	while ((p = getPhase()) == phase) {
932	<	if (interrupted = Thread.interrupted())
933	<	break;
934	<	long now = System.nanoTime();
935	<	if ((nanos -= now - lastTime) <= 0)
864	<	break;
865	<	lastTime = now;
866	<	if (node != null) {
867	<	if (!queued) {
868	<	AtomicReference<QNode> head = queueFor(phase);
869	<	queued = head.compareAndSet(node.next = head.get(), node);
870	<	}
871	<	else if (node.thread != null &&
872	<	nanos > spinForTimeoutThreshold) {
873	<	LockSupport.parkNanos(this, nanos);
874	<	}
875	<	}
876	<	else if (spins <= 0)
877	<	node = new QNode();
878	<	else
879	<	--spins;
880	<	}
881	<	if (node != null)
882	<	node.thread = null;
883	<	if (interrupted)
884	<	throw new InterruptedException();
885	<	if (p == phase && (p = getPhase()) == phase)
886	<	throw new TimeoutException();
925	>	while ((p = getPhase()) == phase && !interrupted) {
926	>	if (Thread.interrupted())
927	>	interrupted = true;
928	>	else if (nanos - (System.nanoTime() - startTime) <= 0)
929	>	break;
930	>	else if (node == null)
931	>	node = new QNode(this, phase, true, true, startTime, nanos);
932	>	else if (!queued)
933	>	queued = tryEnqueue(node);
934	>	else
935	>	interrupted = node.doWait();
936		}
937	<	releaseWaiters(phase);
937	>	if (node != null)
938	>	node.thread = null;
939	>	if (p != phase || (p = getPhase()) != phase)
940	>	releaseWaiters(phase);
941	>	if (interrupted)
942	>	throw new InterruptedException();
943	>	if (p == phase)
944	>	throw new TimeoutException();
945		return p;
946		}
947
948	<	// Temporary Unsafe mechanics for preliminary release
948	>	// Unsafe mechanics
949
950	<	static final Unsafe _unsafe;
951	<	static final long stateOffset;
950	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
951	>	private static final long stateOffset =
952	>	objectFieldOffset("state", Phaser.class);
953
954	<	static {
954	>	private final boolean casState(long cmp, long val) {
955	>	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
956	>	}
957	>
958	>	private static long objectFieldOffset(String field, Class<?> klazz) {
959		try {
960	<	if (Phaser.class.getClassLoader() != null) {
961	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
962	<	f.setAccessible(true);
963	<	_unsafe = (Unsafe)f.get(null);
964	<	}
965	<	else
905	<	_unsafe = Unsafe.getUnsafe();
906	<	stateOffset = _unsafe.objectFieldOffset
907	<	(Phaser.class.getDeclaredField("state"));
908	<	} catch (Exception e) {
909	<	throw new RuntimeException("Could not initialize intrinsics", e);
960	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
961	>	} catch (NoSuchFieldException e) {
962	>	// Convert Exception to corresponding Error
963	>	NoSuchFieldError error = new NoSuchFieldError(field);
964	>	error.initCause(e);
965	>	throw error;
966		}
967		}
968
969	<	final boolean casState(long cmp, long val) {
970	<	return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val);
969	>	/**
970	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
971	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
972	>	* into a jdk.
973	>	*
974	>	* @return a sun.misc.Unsafe
975	>	*/
976	>	private static sun.misc.Unsafe getUnsafe() {
977	>	try {
978	>	return sun.misc.Unsafe.getUnsafe();
979	>	} catch (SecurityException se) {
980	>	try {
981	>	return java.security.AccessController.doPrivileged
982	>	(new java.security
983	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
984	>	public sun.misc.Unsafe run() throws Exception {
985	>	java.lang.reflect.Field f = sun.misc
986	>	.Unsafe.class.getDeclaredField("theUnsafe");
987	>	f.setAccessible(true);
988	>	return (sun.misc.Unsafe) f.get(null);
989	>	}});
990	>	} catch (java.security.PrivilegedActionException e) {
991	>	throw new RuntimeException("Could not initialize intrinsics",
992	>	e.getCause());
993	>	}
994	>	}
995		}
996		}

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