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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.8 by jsr166, Mon Jan 5 05:50:47 2009 UTC vs.
Revision 1.35 by dl, Sun Aug 23 13:37:08 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.
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
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
31	>	* registered. (However, you can introduce such bookkeeping by
32		* subclassing this class.)
33		*
34		* <li> Each generation has an associated phase value, starting at
35	<	* zero, and advancing when all parties reach the barrier (wrapping
36	<	* around to zero after reaching {@code Integer.MAX_VALUE}).
35	>	* zero, and advancing when all parties arrive at the barrier
36	>	* (wrapping around to zero after reaching {@code Integer.MAX_VALUE}).
37		*
38	<	* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited.
39	<	* Method {@code arriveAndAwaitAdvance} has effect analogous to
40	<	* {@code CyclicBarrier.await}.  However, Phasers separate two
41	<	* aspects of coordination, that may also be invoked independently:
38	>	* <li> Like a {@code CyclicBarrier}, a phaser may be repeatedly
39	>	* awaited.  Method {@link #arriveAndAwaitAdvance} has effect
40	>	* analogous to {@link java.util.concurrent.CyclicBarrier#await
41	>	* CyclicBarrier.await}.  However, phasers separate two aspects of
42	>	* coordination, which may also be invoked independently:
43		*
44		* <ul>
45		*
46	<	*   <li> Arriving at a barrier. Methods {@code arrive} and
47	<	*       {@code arriveAndDeregister} do not block, but return
48	<	*       the phase value current upon entry to the method.
49	<	*
50	<	*   <li> Awaiting others. Method {@code awaitAdvance} requires an
51	<	*       argument indicating the entry phase, and returns when the
52	<	*       barrier advances to a new phase.
46	>	*   <li> Arriving at a barrier. Methods {@link #arrive} and
47	>	*       {@link #arriveAndDeregister} do not block, but return
48	>	*       an associated <em>arrival phase number</em>;
49	>	*       that is, the phase number of the barrier to which the
50	>	*       arrival applied.
51	>	*
52	>	*   <li> Awaiting others. Method {@link #awaitAdvance} requires an
53	>	*       argument indicating an arrival phase number, and returns
54	>	*       when the barrier advances to a new phase.
55		* </ul>
56		*
57		*
58		* <li> Barrier actions, performed by the task triggering a phase
59	<	* advance while others may be waiting, are arranged by overriding
60	<	* method {@code onAdvance}, 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 {@code onAdvance} 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	<	* {@code forceTermination} 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 74 | Line 80 | import java.lang.reflect.*;
80		*
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		* {@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		* </ul>
94		*
95		* <p><b>Sample usages:</b>
96		*
97	<	* <p>A Phaser may be used instead of a {@code CountDownLatch} to control
98	<	* a one-shot action serving a variable number of parties. The typical
99	<	* idiom is for the method setting this up to first register, then
100	<	* start the actions, then deregister, as in:
101	<	*
102	<	* <pre>
103	<	*  void runTasks(List&lt;Runnable&gt; list) {
104	<	*    final Phaser phaser = new Phaser(1); // "1" to register self
105	<	*    for (Runnable r : list) {
106	<	*      phaser.register();
107	<	*      new Thread() {
108	<	*        public void run() {
109	<	*          phaser.arriveAndAwaitAdvance(); // await all creation
110	<	*          r.run();
111	<	*          phaser.arriveAndDeregister();   // signal completion
112	<	*        }
113	<	*      }.start();
97	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
98	>	* to control a one-shot action serving a variable number of
99	>	* parties. The typical idiom is for the method setting this up to
100	>	* first register, then start the actions, then deregister, as in:
101	>	*
102	>	*  <pre> {@code
103	>	* void runTasks(List<Runnable> tasks) {
104	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
105	>	*   // create and start threads
106	>	*   for (Runnable task : tasks) {
107	>	*     phaser.register();
108	>	*     new Thread() {
109	>	*       public void run() {
110	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
111	>	*         task.run();
112	>	*       }
113	>	*     }.start();
114		*   }
115		*
116	<	*   doSomethingOnBehalfOfWorkers();
117	<	*   phaser.arrive(); // allow threads to start
118	<	*   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); // await final completion
112	<	* }
113	<	* </pre>
116	>	*   // allow threads to start and deregister self
117	>	*   phaser.arriveAndDeregister();
118	>	* }}</pre>
119		*
120		* <p>One way to cause a set of threads to repeatedly perform actions
121		* for a given number of iterations is to override {@code onAdvance}:
122		*
123	<	* <pre>
124	<	*  void startTasks(List&lt;Runnable&gt; list, final int iterations) {
125	<	*    final Phaser phaser = new Phaser() {
126	<	*       public boolean onAdvance(int phase, int registeredParties) {
127	<	*         return phase &gt;= iterations || registeredParties == 0;
123	>	*  <pre> {@code
124	>	* void startTasks(List<Runnable> tasks, final int iterations) {
125	>	*   final Phaser phaser = new Phaser() {
126	>	*     public boolean onAdvance(int phase, int registeredParties) {
127	>	*       return phase >= iterations || registeredParties == 0;
128	>	*     }
129	>	*   };
130	>	*   phaser.register();
131	>	*   for (Runnable task : tasks) {
132	>	*     phaser.register();
133	>	*     new Thread() {
134	>	*       public void run() {
135	>	*         do {
136	>	*           task.run();
137	>	*           phaser.arriveAndAwaitAdvance();
138	>	*         } while(!phaser.isTerminated();
139		*       }
140	<	*    };
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();
140	>	*     }.start();
141		*   }
142		*   phaser.arriveAndDeregister(); // deregister self, don't wait
143	<	* }
139	<	* </pre>
143	>	* }}</pre>
144		*
145	<	* <p> To create a set of tasks using a tree of Phasers,
145	>	* <p>To create a set of tasks using a tree of phasers,
146		* you could use code of the following form, assuming a
147	<	* Task class with a constructor accepting a Phaser that
147	>	* Task class with a constructor accepting a phaser that
148		* it registers for upon construction:
149	<	* <pre>
150	<	*  void build(Task[] actions, int lo, int hi, Phaser b) {
151	<	*    int step = (hi - lo) / TASKS_PER_PHASER;
152	<	*    if (step &gt; 1) {
153	<	*       int i = lo;
154	<	*       while (i &lt; hi) {
155	<	*         int r = Math.min(i + step, hi);
156	<	*         build(actions, i, r, new Phaser(b));
157	<	*         i = r;
158	<	*       }
159	<	*    }
160	<	*    else {
161	<	*      for (int i = lo; i &lt; hi; ++i)
162	<	*        actions[i] = new Task(b);
163	<	*        // assumes new Task(b) performs b.register()
164	<	*    }
165	<	*  }
166	<	*  // .. initially called, for n tasks via
163	<	*  build(new Task[n], 0, n, new Phaser());
164	<	* </pre>
149	>	*  <pre> {@code
150	>	* void build(Task[] actions, int lo, int hi, Phaser b) {
151	>	*   int step = (hi - lo) / TASKS_PER_PHASER;
152	>	*   if (step > 1) {
153	>	*     int i = lo;
154	>	*     while (i < hi) {
155	>	*       int r = Math.min(i + step, hi);
156	>	*       build(actions, i, r, new Phaser(b));
157	>	*       i = r;
158	>	*     }
159	>	*   } else {
160	>	*     for (int i = lo; i < hi; ++i)
161	>	*       actions[i] = new Task(b);
162	>	*       // assumes new Task(b) performs b.register()
163	>	*   }
164	>	* }
165	>	* // .. initially called, for n tasks via
166	>	* build(new Task[n], 0, n, new Phaser());}</pre>
167		*
168		* The best value of {@code TASKS_PER_PHASER} depends mainly on
169		* expected barrier synchronization rates. A value as low as four may
#	Line 172 | Line 174 | import java.lang.reflect.*;
174		*
175		* <p><b>Implementation notes</b>: This implementation restricts the
176		* maximum number of parties to 65535. Attempts to register additional
177	<	* parties result in IllegalStateExceptions. However, you can and
177	>	* parties result in {@code IllegalStateException}. However, you can and
178		* should create tiered phasers to accommodate arbitrarily large sets
179		* of participants.
180	+	*
181	+	* @since 1.7
182	+	* @author Doug Lea
183		*/
184		public class Phaser {
185		/*
#	Line 199 | Line 204 | public class Phaser {
204		* and encoding simple, and keeping race windows short.
205		*
206		* Note: there are some cheats in arrive() that rely on unarrived
207	<	* being lowest 16 bits.
207	>	* count being lowest 16 bits.
208		*/
209		private volatile long state;
210
211		private static final int ushortBits = 16;
212	<	private static final int ushortMask =  (1 << ushortBits) - 1;
213	<	private static final int phaseMask = 0x7fffffff;
212	>	private static final int ushortMask = 0xffff;
213	>	private static final int phaseMask  = 0x7fffffff;
214
215		private static int unarrivedOf(long s) {
216	<	return (int)(s & ushortMask);
216	>	return (int) (s & ushortMask);
217		}
218
219		private static int partiesOf(long s) {
220	<	return (int)(s & (ushortMask << 16)) >>> 16;
220	>	return ((int) s) >>> 16;
221		}
222
223		private static int phaseOf(long s) {
224	<	return (int)(s >>> 32);
224	>	return (int) (s >>> 32);
225		}
226
227		private static int arrivedOf(long s) {
#	Line 224 | Line 229 | public class Phaser {
229		}
230
231		private static long stateFor(int phase, int parties, int unarrived) {
232	<	return (((long)phase) << 32) | ((parties << 16) | unarrived);
232	>	return ((((long) phase) << 32) | (((long) parties) << 16) |
233	>	(long) unarrived);
234		}
235
236		private static long trippedStateFor(int phase, int parties) {
237	<	return (((long)phase) << 32) | ((parties << 16) | parties);
237	>	long lp = (long) parties;
238	>	return (((long) phase) << 32) | (lp << 16) | lp;
239		}
240
241	<	private static IllegalStateException badBounds(int parties, int unarrived) {
242	<	return new IllegalStateException
243	<	("Attempt to set " + unarrived +
244	<	" unarrived of " + parties + " parties");
241	>	/**
242	>	* Returns message string for bad bounds exceptions.
243	>	*/
244	>	private static String badBounds(int parties, int unarrived) {
245	>	return ("Attempt to set " + unarrived +
246	>	" unarrived of " + parties + " parties");
247		}
248
249		/**
#	Line 243 | Line 252 | public class Phaser {
252		private final Phaser parent;
253
254		/**
255	<	* The root of Phaser tree. Equals this if not in a tree.  Used to
255	>	* The root of phaser tree. Equals this if not in a tree.  Used to
256		* support faster state push-down.
257		*/
258		private final Phaser root;
#	Line 251 | Line 260 | public class Phaser {
260		// Wait queues
261
262		/**
263	<	* Heads of Treiber stacks waiting for nonFJ threads. To eliminate
263	>	* Heads of Treiber stacks for waiting threads. To eliminate
264		* contention while releasing some threads while adding others, we
265		* use two of them, alternating across even and odd phases.
266		*/
#	Line 259 | Line 268 | public class Phaser {
268		private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
269
270		private AtomicReference<QNode> queueFor(int phase) {
271	<	return (phase & 1) == 0? evenQ : oddQ;
271	>	return ((phase & 1) == 0) ? evenQ : oddQ;
272		}
273
274		/**
#	Line 267 | Line 276 | public class Phaser {
276		* root if necessary.
277		*/
278		private long getReconciledState() {
279	<	return parent == null? state : reconcileState();
279	>	return (parent == null) ? state : reconcileState();
280		}
281
282		/**
#	Line 294 | Line 303 | public class Phaser {
303		}
304
305		/**
306	<	* Creates a new Phaser without any initially registered parties,
307	<	* initial phase number 0, and no parent.
306	>	* Creates a new phaser without any initially registered parties,
307	>	* initial phase number 0, and no parent. Any thread using this
308	>	* phaser will need to first register for it.
309		*/
310		public Phaser() {
311		this(null);
312		}
313
314		/**
315	<	* Creates a new Phaser with the given numbers of registered
315	>	* Creates a new phaser with the given numbers of registered
316		* unarrived parties, initial phase number 0, and no parent.
317	<	* @param parties the number of parties required to trip barrier.
317	>	*
318	>	* @param parties the number of parties required to trip barrier
319		* @throws IllegalArgumentException if parties less than zero
320	<	* or greater than the maximum number of parties supported.
320	>	* or greater than the maximum number of parties supported
321		*/
322		public Phaser(int parties) {
323		this(null, parties);
324		}
325
326		/**
327	<	* Creates a new Phaser with the given parent, without any
327	>	* Creates a new phaser with the given parent, without any
328		* initially registered parties. If parent is non-null this phaser
329		* is registered with the parent and its initial phase number is
330		* the same as that of parent phaser.
331	<	* @param parent the parent phaser.
331	>	*
332	>	* @param parent the parent phaser
333		*/
334		public Phaser(Phaser parent) {
335		int phase = 0;
#	Line 332 | Line 344 | public class Phaser {
344		}
345
346		/**
347	<	* Creates a new Phaser with the given parent and numbers of
348	<	* registered unarrived parties. If parent is non-null this phaser
347	>	* Creates a new phaser with the given parent and numbers of
348	>	* registered unarrived parties. If parent is non-null, this phaser
349		* is registered with the parent and its initial phase number is
350		* the same as that of parent phaser.
351	<	* @param parent the parent phaser.
352	<	* @param parties the number of parties required to trip barrier.
351	>	*
352	>	* @param parent the parent phaser
353	>	* @param parties the number of parties required to trip barrier
354		* @throws IllegalArgumentException if parties less than zero
355	<	* or greater than the maximum number of parties supported.
355	>	* or greater than the maximum number of parties supported
356		*/
357		public Phaser(Phaser parent, int parties) {
358		if (parties < 0 || parties > ushortMask)
#	Line 357 | Line 370 | public class Phaser {
370
371		/**
372		* Adds a new unarrived party to this phaser.
373	<	* @return the current barrier phase number upon registration
373	>	*
374	>	* @return the arrival phase number to which this registration applied
375		* @throws IllegalStateException if attempting to register more
376	<	* than the maximum supported number of parties.
376	>	* than the maximum supported number of parties
377		*/
378		public int register() {
379		return doRegister(1);
#	Line 367 | Line 381 | public class Phaser {
381
382		/**
383		* Adds the given number of new unarrived parties to this phaser.
384	<	* @param parties the number of parties required to trip barrier.
385	<	* @return the current barrier phase number upon registration
384	>	*
385	>	* @param parties the number of parties required to trip barrier
386	>	* @return the arrival phase number to which this registration applied
387		* @throws IllegalStateException if attempting to register more
388	<	* than the maximum supported number of parties.
388	>	* than the maximum supported number of parties
389		*/
390		public int bulkRegister(int parties) {
391		if (parties < 0)
#	Line 393 | Line 408 | public class Phaser {
408		if (phase < 0)
409		break;
410		if (parties > ushortMask || unarrived > ushortMask)
411	<	throw badBounds(parties, unarrived);
411	>	throw new IllegalStateException(badBounds(parties, unarrived));
412		if (phase == phaseOf(root.state) &&
413		casState(s, stateFor(phase, parties, unarrived)))
414		break;
#	Line 405 | Line 420 | public class Phaser {
420		* Arrives at the barrier, but does not wait for others.  (You can
421		* in turn wait for others via {@link #awaitAdvance}).
422		*
423	<	* @return the barrier phase number upon entry to this method, or a
409	<	* negative value if terminated;
423	>	* @return the arrival phase number, or a negative value if terminated
424		* @throws IllegalStateException if not terminated and the number
425	<	* of unarrived parties would become negative.
425	>	* of unarrived parties would become negative
426		*/
427		public int arrive() {
428		int phase;
429		for (;;) {
430		long s = state;
431		phase = phaseOf(s);
432	+	if (phase < 0)
433	+	break;
434		int parties = partiesOf(s);
435		int unarrived = unarrivedOf(s) - 1;
436		if (unarrived > 0) {        // Not the last arrival
#	Line 426 | Line 442 | public class Phaser {
442		if (par == null) {      // directly trip
443		if (casState
444		(s,
445	<	trippedStateFor(onAdvance(phase, parties)? -1 :
445	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
446		((phase + 1) & phaseMask), parties))) {
447		releaseWaiters(phase);
448		break;
#	Line 440 | Line 456 | public class Phaser {
456		}
457		}
458		}
443	–	else if (phase < 0) // Don't throw exception if terminated
444	–	break;
459		else if (phase != phaseOf(root.state)) // or if unreconciled
460		reconcileState();
461		else
462	<	throw badBounds(parties, unarrived);
462	>	throw new IllegalStateException(badBounds(parties, unarrived));
463		}
464		return phase;
465		}
466
467		/**
468	<	* Arrives at the barrier, and deregisters from it, without
469	<	* waiting for others. Deregistration reduces number of parties
468	>	* Arrives at the barrier and deregisters from it without waiting
469	>	* for others. Deregistration reduces the number of parties
470		* required to trip the barrier in future phases.  If this phaser
471		* has a parent, and deregistration causes this phaser to have
472	<	* zero parties, this phaser is also deregistered from its parent.
472	>	* zero parties, this phaser also arrives at and is deregistered
473	>	* from its parent.
474		*
475	<	* @return the current barrier phase number upon entry to
461	<	* this method, or a negative value if terminated;
475	>	* @return the arrival phase number, or a negative value if terminated
476		* @throws IllegalStateException if not terminated and the number
477	<	* of registered or unarrived parties would become negative.
477	>	* of registered or unarrived parties would become negative
478		*/
479		public int arriveAndDeregister() {
480		// similar code to arrive, but too different to merge
#	Line 469 | Line 483 | public class Phaser {
483		for (;;) {
484		long s = state;
485		phase = phaseOf(s);
486	+	if (phase < 0)
487	+	break;
488		int parties = partiesOf(s) - 1;
489		int unarrived = unarrivedOf(s) - 1;
490		if (parties >= 0) {
#	Line 487 | Line 503 | public class Phaser {
503		if (unarrived == 0) {
504		if (casState
505		(s,
506	<	trippedStateFor(onAdvance(phase, parties)? -1 :
506	>	trippedStateFor(onAdvance(phase, parties) ? -1 :
507		((phase + 1) & phaseMask), parties))) {
508		releaseWaiters(phase);
509		break;
510		}
511		continue;
512		}
497	–	if (phase < 0)
498	–	break;
513		if (par != null && phase != phaseOf(root.state)) {
514		reconcileState();
515		continue;
516		}
517		}
518	<	throw badBounds(parties, unarrived);
518	>	throw new IllegalStateException(badBounds(parties, unarrived));
519		}
520		return phase;
521		}
522
523		/**
524		* Arrives at the barrier and awaits others. Equivalent in effect
525	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
526	<	* await with interruption of timeout, and/or deregister upon
527	<	* arrival, you can arrange them using analogous constructions.
528	<	* @return the phase on entry to this method
525	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
526	>	* interruption or timeout, you can arrange this with an analogous
527	>	* construction using one of the other forms of the awaitAdvance
528	>	* method.  If instead you need to deregister upon arrival use
529	>	* {@code arriveAndDeregister}.
530	>	*
531	>	* @return the arrival phase number, or a negative number if terminated
532		* @throws IllegalStateException if not terminated and the number
533	<	* of unarrived parties would become negative.
533	>	* of unarrived parties would become negative
534		*/
535		public int arriveAndAwaitAdvance() {
536		return awaitAdvance(arrive());
537		}
538
539		/**
540	<	* Awaits the phase of the barrier to advance from the given
541	<	* value, or returns immediately if argument is negative or this
542	<	* barrier is terminated.
543	<	* @param phase the phase on entry to this method
544	<	* @return the phase on exit from this method
540	>	* Awaits the phase of the barrier to advance from the given phase
541	>	* value, returning immediately if the current phase of the
542	>	* barrier is not equal to the given phase value or this barrier
543	>	* is terminated.
544	>	*
545	>	* @param phase an arrival phase number, or negative value if
546	>	* terminated; this argument is normally the value returned by a
547	>	* previous call to {@code arrive} or its variants
548	>	* @return the next arrival phase number, or a negative value
549	>	* if terminated or argument is negative
550		*/
551		public int awaitAdvance(int phase) {
552		if (phase < 0)
#	Line 533 | Line 555 | public class Phaser {
555		int p = phaseOf(s);
556		if (p != phase)
557		return p;
558	<	if (unarrivedOf(s) == 0)
558	>	if (unarrivedOf(s) == 0 && parent != null)
559		parent.awaitAdvance(phase);
560		// Fall here even if parent waited, to reconcile and help release
561		return untimedWait(phase);
562		}
563
564		/**
565	<	* Awaits the phase of the barrier to advance from the given
566	<	* value, or returns immediately if argument is negative or this
567	<	* barrier is terminated, or throws InterruptedException if
568	<	* interrupted while waiting.
569	<	* @param phase the phase on entry to this method
570	<	* @return the phase on exit from this method
565	>	* Awaits the phase of the barrier to advance from the given phase
566	>	* value, throwing {@code InterruptedException} if interrupted while
567	>	* waiting, or returning immediately if the current phase of the
568	>	* barrier is not equal to the given phase value or this barrier
569	>	* is terminated.
570	>	*
571	>	* @param phase an arrival phase number, or negative value if
572	>	* terminated; this argument is normally the value returned by a
573	>	* previous call to {@code arrive} or its variants
574	>	* @return the next arrival phase number, or a negative value
575	>	* if terminated or argument is negative
576		* @throws InterruptedException if thread interrupted while waiting
577		*/
578	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
578	>	public int awaitAdvanceInterruptibly(int phase)
579	>	throws InterruptedException {
580		if (phase < 0)
581		return phase;
582		long s = getReconciledState();
583		int p = phaseOf(s);
584		if (p != phase)
585		return p;
586	<	if (unarrivedOf(s) != 0)
586	>	if (unarrivedOf(s) == 0 && parent != null)
587		parent.awaitAdvanceInterruptibly(phase);
588		return interruptibleWait(phase);
589		}
590
591		/**
592	<	* Awaits the phase of the barrier to advance from the given value
593	<	* or the given timeout elapses, or returns immediately if
594	<	* argument is negative or this barrier is terminated.
595	<	* @param phase the phase on entry to this method
596	<	* @return the phase on exit from this method
592	>	* Awaits the phase of the barrier to advance from the given phase
593	>	* value or the given timeout to elapse, throwing
594	>	* {@code InterruptedException} if interrupted while waiting, or
595	>	* returning immediately if the current phase of the barrier is not
596	>	* equal to the given phase value or this barrier is terminated.
597	>	*
598	>	* @param phase an arrival phase number, or negative value if
599	>	* terminated; this argument is normally the value returned by a
600	>	* previous call to {@code arrive} or its variants
601	>	* @param timeout how long to wait before giving up, in units of
602	>	*        {@code unit}
603	>	* @param unit a {@code TimeUnit} determining how to interpret the
604	>	*        {@code timeout} parameter
605	>	* @return the next arrival phase number, or a negative value
606	>	* if terminated or argument is negative
607		* @throws InterruptedException if thread interrupted while waiting
608		* @throws TimeoutException if timed out while waiting
609		*/
610	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
610	>	public int awaitAdvanceInterruptibly(int phase,
611	>	long timeout, TimeUnit unit)
612		throws InterruptedException, TimeoutException {
613		if (phase < 0)
614		return phase;
#	Line 577 | Line 616 | public class Phaser {
616		int p = phaseOf(s);
617		if (p != phase)
618		return p;
619	<	if (unarrivedOf(s) == 0)
619	>	if (unarrivedOf(s) == 0 && parent != null)
620		parent.awaitAdvanceInterruptibly(phase, timeout, unit);
621		return timedWait(phase, unit.toNanos(timeout));
622		}
#	Line 610 | Line 649 | public class Phaser {
649		* Returns the current phase number. The maximum phase number is
650		* {@code Integer.MAX_VALUE}, after which it restarts at
651		* zero. Upon termination, the phase number is negative.
652	+	*
653		* @return the phase number, or a negative value if terminated
654		*/
655		public final int getPhase() {
#	Line 617 | Line 657 | public class Phaser {
657		}
658
659		/**
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	–	/**
660		* Returns the number of parties registered at this barrier.
661	+	*
662		* @return the number of parties
663		*/
664		public int getRegisteredParties() {
#	Line 636 | Line 668 | public class Phaser {
668		/**
669		* Returns the number of parties that have arrived at the current
670		* phase of this barrier.
671	+	*
672		* @return the number of arrived parties
673		*/
674		public int getArrivedParties() {
#	Line 645 | Line 678 | public class Phaser {
678		/**
679		* Returns the number of registered parties that have not yet
680		* arrived at the current phase of this barrier.
681	+	*
682		* @return the number of unarrived parties
683		*/
684		public int getUnarrivedParties() {
#	Line 652 | Line 686 | public class Phaser {
686		}
687
688		/**
689	<	* Returns the parent of this phaser, or null if none.
690	<	* @return the parent of this phaser, or null if none.
689	>	* Returns the parent of this phaser, or {@code null} if none.
690	>	*
691	>	* @return the parent of this phaser, or {@code null} if none
692		*/
693		public Phaser getParent() {
694		return parent;
#	Line 662 | Line 697 | public class Phaser {
697		/**
698		* Returns the root ancestor of this phaser, which is the same as
699		* this phaser if it has no parent.
700	<	* @return the root ancestor of this phaser.
700	>	*
701	>	* @return the root ancestor of this phaser
702		*/
703		public Phaser getRoot() {
704		return root;
705		}
706
707		/**
708	<	* Returns true if this barrier has been terminated.
709	<	* @return true if this barrier has been terminated
708	>	* Returns {@code true} if this barrier has been terminated.
709	>	*
710	>	* @return {@code true} if this barrier has been terminated
711		*/
712		public boolean isTerminated() {
713		return getPhase() < 0;
#	Line 680 | Line 717 | public class Phaser {
717		* Overridable method to perform an action upon phase advance, and
718		* to control termination. This method is invoked whenever the
719		* barrier is tripped (and thus all other waiting parties are
720	<	* dormant). If it returns true, then, rather than advance the
721	<	* phase number, this barrier will be set to a final termination
722	<	* state, and subsequent calls to {@code isTerminated} will
723	<	* return true.
720	>	* dormant). If it returns {@code true}, then, rather than advance
721	>	* the phase number, this barrier will be set to a final
722	>	* termination state, and subsequent calls to {@link #isTerminated}
723	>	* will return true.
724		*
725	<	* <p> The default version returns true when the number of
725	>	* <p>The default version returns {@code true} when the number of
726		* registered parties is zero. Normally, overrides that arrange
727		* termination for other reasons should also preserve this
728		* property.
729		*
730	<	* <p> You may override this method to perform an action with side
730	>	* <p>You may override this method to perform an action with side
731		* effects visible to participating tasks, but it is in general
732		* only sensible to do so in designs where all parties register
733	<	* before any arrive, and all {@code awaitAdvance} at each phase.
734	<	* Otherwise, you cannot ensure lack of interference. In
735	<	* 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.
733	>	* before any arrive, and all {@link #awaitAdvance} at each phase.
734	>	* Otherwise, you cannot ensure lack of interference from other
735	>	* parties during the invocation of this method.
736		*
737		* @param phase the phase number on entering the barrier
738	<	* @param registeredParties the current number of registered
739	<	* parties.
707	<	* @return true if this barrier should terminate
738	>	* @param registeredParties the current number of registered parties
739	>	* @return {@code true} if this barrier should terminate
740		*/
741		protected boolean onAdvance(int phase, int registeredParties) {
742		return registeredParties <= 0;
#	Line 713 | Line 745 | public class Phaser {
745		/**
746		* Returns a string identifying this phaser, as well as its
747		* state.  The state, in brackets, includes the String {@code
748	<	* "phase ="} followed by the phase number, {@code "parties ="}
748	>	* "phase = "} followed by the phase number, {@code "parties = "}
749		* followed by the number of registered parties, and {@code
750	<	* "arrived ="} followed by the number of arrived parties
750	>	* "arrived = "} followed by the number of arrived parties.
751		*
752		* @return a string identifying this barrier, as well as its state
753		*/
754		public String toString() {
755		long s = getReconciledState();
756	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
756	>	return super.toString() +
757	>	"[phase = " + phaseOf(s) +
758	>	" parties = " + partiesOf(s) +
759	>	" arrived = " + arrivedOf(s) + "]";
760		}
761
762		// methods for waiting
763
729	–	/** The number of CPUs, for spin control */
730	–	static final int NCPUS = Runtime.getRuntime().availableProcessors();
731	–
764		/**
765	<	* The number of times to spin before blocking in timed waits.
734	<	* The value is empirically derived.
765	>	* Wait nodes for Treiber stack representing wait queue
766		*/
767	<	static final int maxTimedSpins = (NCPUS < 2)? 0 : 32;
768	<
769	<	/**
770	<	* The number of times to spin before blocking in untimed waits.
771	<	* This is greater than timed value because untimed waits spin
772	<	* faster since they don't need to check times on each spin.
773	<	*/
774	<	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	<
751	<	/**
752	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
753	<	* tasks.
754	<	*/
755	<	static final class QNode {
756	<	QNode next;
767	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
768	>	final Phaser phaser;
769	>	final int phase;
770	>	final long startTime;
771	>	final long nanos;
772	>	final boolean timed;
773	>	final boolean interruptible;
774	>	volatile boolean wasInterrupted = false;
775		volatile Thread thread; // nulled to cancel wait
776	<	QNode() {
776	>	QNode next;
777	>	QNode(Phaser phaser, int phase, boolean interruptible,
778	>	boolean timed, long startTime, long nanos) {
779	>	this.phaser = phaser;
780	>	this.phase = phase;
781	>	this.timed = timed;
782	>	this.interruptible = interruptible;
783	>	this.startTime = startTime;
784	>	this.nanos = nanos;
785		thread = Thread.currentThread();
786		}
787	+	public boolean isReleasable() {
788	+	return (thread == null ||
789	+	phaser.getPhase() != phase ||
790	+	(interruptible && wasInterrupted) ||
791	+	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
792	+	}
793	+	public boolean block() {
794	+	if (Thread.interrupted()) {
795	+	wasInterrupted = true;
796	+	if (interruptible)
797	+	return true;
798	+	}
799	+	if (!timed)
800	+	LockSupport.park(this);
801	+	else {
802	+	long waitTime = nanos - (System.nanoTime() - startTime);
803	+	if (waitTime <= 0)
804	+	return true;
805	+	LockSupport.parkNanos(this, waitTime);
806	+	}
807	+	return isReleasable();
808	+	}
809		void signal() {
810		Thread t = thread;
811		if (t != null) {
#	Line 765 | Line 813 | public class Phaser {
813		LockSupport.unpark(t);
814		}
815		}
816	+	boolean doWait() {
817	+	if (thread != null) {
818	+	try {
819	+	ForkJoinPool.managedBlock(this, false);
820	+	} catch (InterruptedException ie) {
821	+	}
822	+	}
823	+	return wasInterrupted;
824	+	}
825	+
826		}
827
828		/**
829	<	* Removes and signals waiting threads from wait queue
829	>	* Removes and signals waiting threads from wait queue.
830		*/
831		private void releaseWaiters(int phase) {
832		AtomicReference<QNode> head = queueFor(phase);
#	Line 780 | Line 838 | public class Phaser {
838		}
839
840		/**
841	+	* Tries to enqueue given node in the appropriate wait queue.
842	+	*
843	+	* @return true if successful
844	+	*/
845	+	private boolean tryEnqueue(QNode node) {
846	+	AtomicReference<QNode> head = queueFor(node.phase);
847	+	return head.compareAndSet(node.next = head.get(), node);
848	+	}
849	+
850	+	/**
851		* Enqueues node and waits unless aborted or signalled.
852	+	*
853	+	* @return current phase
854		*/
855		private int untimedWait(int phase) {
786	–	int spins = maxUntimedSpins;
856		QNode node = null;
788	–	boolean interrupted = false;
857		boolean queued = false;
858	+	boolean interrupted = false;
859		int p;
860		while ((p = getPhase()) == phase) {
861	<	interrupted = Thread.interrupted();
862	<	if (node != null) {
863	<	if (!queued) {
864	<	AtomicReference<QNode> head = queueFor(phase);
865	<	queued = head.compareAndSet(node.next = head.get(), node);
866	<	}
798	<	else if (node.thread != null)
799	<	LockSupport.park(this);
800	<	}
801	<	else if (spins <= 0)
802	<	node = new QNode();
861	>	if (Thread.interrupted())
862	>	interrupted = true;
863	>	else if (node == null)
864	>	node = new QNode(this, phase, false, false, 0, 0);
865	>	else if (!queued)
866	>	queued = tryEnqueue(node);
867		else
868	<	--spins;
868	>	interrupted = node.doWait();
869		}
870		if (node != null)
871		node.thread = null;
872	+	releaseWaiters(phase);
873		if (interrupted)
874		Thread.currentThread().interrupt();
810	–	releaseWaiters(phase);
875		return p;
876		}
877
878		/**
879	<	* Messier interruptible version
879	>	* Interruptible version
880	>	* @return current phase
881		*/
882		private int interruptibleWait(int phase) throws InterruptedException {
818	–	int spins = maxUntimedSpins;
883		QNode node = null;
884		boolean queued = false;
885		boolean interrupted = false;
886		int p;
887	<	while ((p = getPhase()) == phase) {
888	<	if (interrupted = Thread.interrupted())
889	<	break;
890	<	if (node != null) {
891	<	if (!queued) {
892	<	AtomicReference<QNode> head = queueFor(phase);
893	<	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();
887	>	while ((p = getPhase()) == phase && !interrupted) {
888	>	if (Thread.interrupted())
889	>	interrupted = true;
890	>	else if (node == null)
891	>	node = new QNode(this, phase, true, false, 0, 0);
892	>	else if (!queued)
893	>	queued = tryEnqueue(node);
894		else
895	<	--spins;
895	>	interrupted = node.doWait();
896		}
897		if (node != null)
898		node.thread = null;
899	+	if (p != phase || (p = getPhase()) != phase)
900	+	releaseWaiters(phase);
901		if (interrupted)
902		throw new InterruptedException();
843	–	releaseWaiters(phase);
903		return p;
904		}
905
906		/**
907	<	* Even messier timeout version.
907	>	* Timeout version.
908	>	* @return current phase
909		*/
910		private int timedWait(int phase, long nanos)
911		throws InterruptedException, TimeoutException {
912	+	long startTime = System.nanoTime();
913	+	QNode node = null;
914	+	boolean queued = false;
915	+	boolean interrupted = false;
916		int p;
917	<	if ((p = getPhase()) == phase) {
918	<	long lastTime = System.nanoTime();
919	<	int spins = maxTimedSpins;
920	<	QNode node = null;
921	<	boolean queued = false;
922	<	boolean interrupted = false;
923	<	while ((p = getPhase()) == phase) {
924	<	if (interrupted = Thread.interrupted())
925	<	break;
926	<	long now = System.nanoTime();
927	<	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();
917	>	while ((p = getPhase()) == phase && !interrupted) {
918	>	if (Thread.interrupted())
919	>	interrupted = true;
920	>	else if (nanos - (System.nanoTime() - startTime) <= 0)
921	>	break;
922	>	else if (node == null)
923	>	node = new QNode(this, phase, true, true, startTime, nanos);
924	>	else if (!queued)
925	>	queued = tryEnqueue(node);
926	>	else
927	>	interrupted = node.doWait();
928		}
929	<	releaseWaiters(phase);
929	>	if (node != null)
930	>	node.thread = null;
931	>	if (p != phase || (p = getPhase()) != phase)
932	>	releaseWaiters(phase);
933	>	if (interrupted)
934	>	throw new InterruptedException();
935	>	if (p == phase)
936	>	throw new TimeoutException();
937		return p;
938		}
939
940	<	// Temporary Unsafe mechanics for preliminary release
940	>	// Unsafe mechanics
941	>
942	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
943	>	private static final long stateOffset =
944	>	objectFieldOffset("state", Phaser.class);
945
946	<	static final Unsafe _unsafe;
947	<	static final long stateOffset;
946	>	private final boolean casState(long cmp, long val) {
947	>	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
948	>	}
949
950	<	static {
950	>	private static long objectFieldOffset(String field, Class<?> klazz) {
951		try {
952	<	if (Phaser.class.getClassLoader() != null) {
953	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
954	<	f.setAccessible(true);
955	<	_unsafe = (Unsafe)f.get(null);
956	<	}
957	<	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);
952	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
953	>	} catch (NoSuchFieldException e) {
954	>	// Convert Exception to corresponding Error
955	>	NoSuchFieldError error = new NoSuchFieldError(field);
956	>	error.initCause(e);
957	>	throw error;
958		}
959		}
960
961	<	final boolean casState(long cmp, long val) {
962	<	return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val);
961	>	/**
962	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
963	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
964	>	* into a jdk.
965	>	*
966	>	* @return a sun.misc.Unsafe
967	>	*/
968	>	private static sun.misc.Unsafe getUnsafe() {
969	>	try {
970	>	return sun.misc.Unsafe.getUnsafe();
971	>	} catch (SecurityException se) {
972	>	try {
973	>	return java.security.AccessController.doPrivileged
974	>	(new java.security
975	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
976	>	public sun.misc.Unsafe run() throws Exception {
977	>	java.lang.reflect.Field f = sun.misc
978	>	.Unsafe.class.getDeclaredField("theUnsafe");
979	>	f.setAccessible(true);
980	>	return (sun.misc.Unsafe) f.get(null);
981	>	}});
982	>	} catch (java.security.PrivilegedActionException e) {
983	>	throw new RuntimeException("Could not initialize intrinsics",
984	>	e.getCause());
985	>	}
986	>	}
987		}
988		}

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