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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.7 by jsr166, Mon Jan 5 03:53:26 2009 UTC vs.
Revision 1.57 by dl, Fri Nov 19 16:03:24 2010 UTC

#	Line 5 | Line 5
5		*/
6
7		package jsr166y;
8	<	import java.util.concurrent.*;
9	<	import java.util.concurrent.atomic.*;
8	>
9	>	import java.util.concurrent.TimeUnit;
10	>	import java.util.concurrent.TimeoutException;
11	>	import java.util.concurrent.atomic.AtomicReference;
12		import java.util.concurrent.locks.LockSupport;
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	>	* <p> <b>Registration.</b> Unlike the case for other barriers, the
21	>	* number of parties <em>registered</em> to synchronize on a phaser
22	>	* may vary over time.  Tasks may be registered at any time (using
23	>	* methods {@link #register}, {@link #bulkRegister}, or forms of
24	>	* constructors establishing initial numbers of parties), and
25	>	* optionally deregistered upon any arrival (using {@link
26	>	* #arriveAndDeregister}).  As is the case with most basic
27	>	* synchronization constructs, registration and deregistration affect
28	>	* only internal counts; they do not establish any further internal
29	>	* bookkeeping, so tasks cannot query whether they are registered.
30	>	* (However, you can introduce such bookkeeping by subclassing this
31	>	* class.)
32	>	*
33	>	* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
34	>	* Phaser} may be repeatedly awaited.  Method {@link
35	>	* #arriveAndAwaitAdvance} has effect analogous to {@link
36	>	* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
37	>	* generation of a {@code Phaser} has an associated phase number. The
38	>	* phase number starts at zero, and advances when all parties arrive
39	>	* at the barrier, wrapping around to zero after reaching {@code
40	>	* Integer.MAX_VALUE}. The use of phase numbers enables independent
41	>	* control of actions upon arrival at a barrier and upon awaiting
42	>	* others, via two kinds of methods that may be invoked by any
43	>	* registered party:
44		*
45		* <ul>
46		*
47	<	* <li> The number of parties synchronizing on a phaser may vary over
48	<	* time.  A task may register to be a party at any time, and may
49	<	* deregister upon arriving at the barrier.  As is the case with most
50	<	* basic synchronization constructs, registration and deregistration
51	<	* affect only internal counts; they do not establish any further
52	<	* internal bookkeeping, so tasks cannot query whether they are
53	<	* registered. (However, you can introduce such bookkeeping in by
54	<	* subclassing this class.)
55	<	*
56	<	* <li> Each generation has an associated phase value, starting at
57	<	* zero, and advancing when all parties reach the barrier (wrapping
58	<	* around to zero after reaching {@code Integer.MAX_VALUE}).
59	<	*
60	<	* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited.
61	<	* Method {@code arriveAndAwaitAdvance} has effect analogous to
62	<	* {@code CyclicBarrier.await}.  However, Phasers separate two
63	<	* aspects of coordination, that may also be invoked independently:
64	<	*
65	<	* <ul>
47	>	*   <li> <b>Arrival.</b> Methods {@link #arrive} and
48	>	*       {@link #arriveAndDeregister} record arrival at a
49	>	*       barrier. These methods do not block, but return an associated
50	>	*       <em>arrival phase number</em>; that is, the phase number of
51	>	*       the barrier to which the arrival applied. When the final
52	>	*       party for a given phase arrives, an optional barrier action
53	>	*       is performed and the phase advances.  Barrier actions,
54	>	*       performed by the party triggering a phase advance, are
55	>	*       arranged by overriding method {@link #onAdvance(int, int)},
56	>	*       which also controls termination. Overriding this method is
57	>	*       similar to, but more flexible than, providing a barrier
58	>	*       action to a {@code CyclicBarrier}.
59	>	*
60	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61	>	*       argument indicating an arrival phase number, and returns when
62	>	*       the barrier advances to (or is already at) a different phase.
63	>	*       Unlike similar constructions using {@code CyclicBarrier},
64	>	*       method {@code awaitAdvance} continues to wait even if the
65	>	*       waiting thread is interrupted. Interruptible and timeout
66	>	*       versions are also available, but exceptions encountered while
67	>	*       tasks wait interruptibly or with timeout do not change the
68	>	*       state of the barrier. If necessary, you can perform any
69	>	*       associated recovery within handlers of those exceptions,
70	>	*       often after invoking {@code forceTermination}.  Phasers may
71	>	*       also be used by tasks executing in a {@link ForkJoinPool},
72	>	*       which will ensure sufficient parallelism to execute tasks
73	>	*       when others are blocked waiting for a phase to advance.
74		*
42	–	*   <li> Arriving at a barrier. Methods {@code arrive} and
43	–	*       {@code arriveAndDeregister} do not block, but return
44	–	*       the phase value current upon entry to the method.
45	–	*
46	–	*   <li> Awaiting others. Method {@code awaitAdvance} requires an
47	–	*       argument indicating the entry phase, and returns when the
48	–	*       barrier advances to a new phase.
75		* </ul>
76		*
77	<	*
78	<	* <li> Barrier actions, performed by the task triggering a phase
79	<	* advance while others may be waiting, are arranged by overriding
80	<	* method {@code onAdvance}, that also controls termination.
81	<	* Overriding this method may be used to similar but more flexible
82	<	* effect as providing a barrier action to a CyclicBarrier.
83	<	*
58	<	* <li> Phasers may enter a <em>termination</em> state in which all
59	<	* await actions immediately return, indicating (via a negative phase
60	<	* value) that execution is complete.  Termination is triggered by
61	<	* executing the overridable {@code onAdvance} method that is invoked
62	<	* each time the barrier is about to be tripped. When a Phaser is
63	<	* controlling an action with a fixed number of iterations, it is
77	>	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	>	* <em>termination</em> state in which all synchronization methods
79	>	* immediately return without updating phaser state or waiting for
80	>	* advance, and indicating (via a negative phase value) that execution
81	>	* is complete.  Termination is triggered when an invocation of {@code
82	>	* onAdvance} returns {@code true}.  As illustrated below, when
83	>	* phasers control actions with a fixed number of iterations, it is
84		* often convenient to override this method to cause termination when
85	<	* the current phase number reaches a threshold. Method
86	<	* {@code forceTermination} is also available to abruptly release
87	<	* waiting threads and allow them to terminate.
85	>	* the current phase number reaches a threshold. Method {@link
86	>	* #forceTermination} is also available to abruptly release waiting
87	>	* threads and allow them to terminate.
88		*
89	<	* <li> Phasers may be tiered to reduce contention. Phasers with large
89	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
90	>	* in tree structures) to reduce contention. Phasers with large
91		* numbers of parties that would otherwise experience heavy
92	<	* synchronization contention costs may instead be arranged in trees.
93	<	* This will typically greatly increase throughput even though it
94	<	* incurs somewhat greater per-operation overhead.
95	<	*
96	<	* <li> By default, {@code awaitAdvance} continues to wait even if
97	<	* the waiting thread is interrupted. And unlike the case in
98	<	* CyclicBarriers, exceptions encountered while tasks wait
99	<	* interruptibly or with timeout do not change the state of the
100	<	* barrier. If necessary, you can perform any associated recovery
101	<	* within handlers of those exceptions, often after invoking
102	<	* {@code forceTermination}.
103	<	*
104	<	* </ul>
92	>	* synchronization contention costs may instead be set up so that
93	>	* groups of sub-phasers share a common parent.  This may greatly
94	>	* increase throughput even though it incurs greater per-operation
95	>	* overhead.
96	>	*
97	>	* <p><b>Monitoring.</b> While synchronization methods may be invoked
98	>	* only by registered parties, the current state of a phaser may be
99	>	* monitored by any caller.  At any given moment there are {@link
100	>	* #getRegisteredParties} parties in total, of which {@link
101	>	* #getArrivedParties} have arrived at the current phase ({@link
102	>	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
103	>	* parties arrive, the phase advances.  The values returned by these
104	>	* methods may reflect transient states and so are not in general
105	>	* useful for synchronization control.  Method {@link #toString}
106	>	* returns snapshots of these state queries in a form convenient for
107	>	* informal monitoring.
108		*
109		* <p><b>Sample usages:</b>
110		*
111	<	* <p>A Phaser may be used instead of a {@code CountdownLatch} to control
112	<	* a one-shot action serving a variable number of parties. The typical
113	<	* idiom is for the method setting this up to first register, then
114	<	* start the actions, then deregister, as in:
115	<	*
116	<	* <pre>
117	<	*  void runTasks(List&lt;Runnable&gt; list) {
118	<	*    final Phaser phaser = new Phaser(1); // "1" to register self
119	<	*    for (Runnable r : list) {
120	<	*      phaser.register();
121	<	*      new Thread() {
122	<	*        public void run() {
123	<	*          phaser.arriveAndAwaitAdvance(); // await all creation
124	<	*          r.run();
125	<	*          phaser.arriveAndDeregister();   // signal completion
126	<	*        }
127	<	*      }.start();
111	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
112	>	* to control a one-shot action serving a variable number of parties.
113	>	* The typical idiom is for the method setting this up to first
114	>	* register, then start the actions, then deregister, as in:
115	>	*
116	>	*  <pre> {@code
117	>	* void runTasks(List<Runnable> tasks) {
118	>	*   final Phaser phaser = new Phaser(1); // "1" to register self
119	>	*   // create and start threads
120	>	*   for (Runnable task : tasks) {
121	>	*     phaser.register();
122	>	*     new Thread() {
123	>	*       public void run() {
124	>	*         phaser.arriveAndAwaitAdvance(); // await all creation
125	>	*         task.run();
126	>	*       }
127	>	*     }.start();
128		*   }
129		*
130	<	*   doSomethingOnBehalfOfWorkers();
131	<	*   phaser.arrive(); // allow threads to start
132	<	*   int p = phaser.arriveAndDeregister(); // deregister self  ...
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>
130	>	*   // allow threads to start and deregister self
131	>	*   phaser.arriveAndDeregister();
132	>	* }}</pre>
133		*
134		* <p>One way to cause a set of threads to repeatedly perform actions
135		* for a given number of iterations is to override {@code onAdvance}:
136		*
137	<	* <pre>
138	<	*  void startTasks(List&lt;Runnable&gt; list, final int iterations) {
139	<	*    final Phaser phaser = new Phaser() {
140	<	*       public boolean onAdvance(int phase, int registeredParties) {
141	<	*         return phase &gt;= iterations || registeredParties == 0;
137	>	*  <pre> {@code
138	>	* void startTasks(List<Runnable> tasks, final int iterations) {
139	>	*   final Phaser phaser = new Phaser() {
140	>	*     protected boolean onAdvance(int phase, int registeredParties) {
141	>	*       return phase >= iterations || registeredParties == 0;
142	>	*     }
143	>	*   };
144	>	*   phaser.register();
145	>	*   for (final Runnable task : tasks) {
146	>	*     phaser.register();
147	>	*     new Thread() {
148	>	*       public void run() {
149	>	*         do {
150	>	*           task.run();
151	>	*           phaser.arriveAndAwaitAdvance();
152	>	*         } while (!phaser.isTerminated());
153		*       }
154	<	*    };
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();
154	>	*     }.start();
155		*   }
156		*   phaser.arriveAndDeregister(); // deregister self, don't wait
157	<	* }
158	<	* </pre>
157	>	* }}</pre>
158	>	*
159	>	* If the main task must later await termination, it
160	>	* may re-register and then execute a similar loop:
161	>	*  <pre> {@code
162	>	*   // ...
163	>	*   phaser.register();
164	>	*   while (!phaser.isTerminated())
165	>	*     phaser.arriveAndAwaitAdvance();}</pre>
166	>	*
167	>	* <p>Related constructions may be used to await particular phase numbers
168	>	* in contexts where you are sure that the phase will never wrap around
169	>	* {@code Integer.MAX_VALUE}. For example:
170	>	*
171	>	*  <pre> {@code
172	>	* void awaitPhase(Phaser phaser, int phase) {
173	>	*   int p = phaser.register(); // assumes caller not already registered
174	>	*   while (p < phase) {
175	>	*     if (phaser.isTerminated())
176	>	*       // ... deal with unexpected termination
177	>	*     else
178	>	*       p = phaser.arriveAndAwaitAdvance();
179	>	*   }
180	>	*   phaser.arriveAndDeregister();
181	>	* }}</pre>
182	>	*
183		*
184	<	* <p> To create a set of tasks using a tree of Phasers,
184	>	* <p>To create a set of tasks using a tree of phasers,
185		* you could use code of the following form, assuming a
186	<	* Task class with a constructor accepting a Phaser that
187	<	* it registers for upon construction:
188	<	* <pre>
189	<	*  void build(Task[] actions, int lo, int hi, Phaser b) {
190	<	*    int step = (hi - lo) / TASKS_PER_PHASER;
191	<	*    if (step &gt; 1) {
192	<	*       int i = lo;
193	<	*       while (i &lt; hi) {
194	<	*         int r = Math.min(i + step, hi);
195	<	*         build(actions, i, r, new Phaser(b));
196	<	*         i = r;
197	<	*       }
198	<	*    }
199	<	*    else {
200	<	*      for (int i = lo; i &lt; hi; ++i)
201	<	*        actions[i] = new Task(b);
202	<	*        // assumes new Task(b) performs b.register()
203	<	*    }
161	<	*  }
162	<	*  // .. initially called, for n tasks via
163	<	*  build(new Task[n], 0, n, new Phaser());
164	<	* </pre>
186	>	* Task class with a constructor accepting a phaser that
187	>	* it registers with upon construction:
188	>	*
189	>	*  <pre> {@code
190	>	* void build(Task[] actions, int lo, int hi, Phaser ph) {
191	>	*   if (hi - lo > TASKS_PER_PHASER) {
192	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
193	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
194	>	*       build(actions, i, j, new Phaser(ph));
195	>	*     }
196	>	*   } else {
197	>	*     for (int i = lo; i < hi; ++i)
198	>	*       actions[i] = new Task(ph);
199	>	*       // assumes new Task(ph) performs ph.register()
200	>	*   }
201	>	* }
202	>	* // .. initially called, for n tasks via
203	>	* build(new Task[n], 0, n, new Phaser());}</pre>
204		*
205		* The best value of {@code TASKS_PER_PHASER} depends mainly on
206		* expected barrier synchronization rates. A value as low as four may
207		* be appropriate for extremely small per-barrier task bodies (thus
208		* high rates), or up to hundreds for extremely large ones.
209		*
171	–	* </pre>
172	–	*
210		* <p><b>Implementation notes</b>: This implementation restricts the
211		* maximum number of parties to 65535. Attempts to register additional
212	<	* parties result in IllegalStateExceptions. However, you can and
212	>	* parties result in {@code IllegalStateException}. However, you can and
213		* should create tiered phasers to accommodate arbitrarily large sets
214		* of participants.
215	+	*
216	+	* @since 1.7
217	+	* @author Doug Lea
218		*/
219		public class Phaser {
220		/*
#	Line 187 | Line 227 | public class Phaser {
227		* Barrier state representation. Conceptually, a barrier contains
228		* four values:
229		*
230	<	* * parties -- the number of parties to wait (16 bits)
231	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
232	<	* * phase -- the generation of the barrier (31 bits)
233	<	* * terminated -- set if barrier is terminated (1 bit)
230	>	* * unarrived -- the number of parties yet to hit barrier (bits  0-15)
231	>	* * parties -- the number of parties to wait              (bits 16-31)
232	>	* * phase -- the generation of the barrier                (bits 32-62)
233	>	* * terminated -- set if barrier is terminated            (bit  63 / sign)
234		*
235		* However, to efficiently maintain atomicity, these values are
236		* packed into a single (atomic) long. Termination uses the sign
237		* bit of 32 bit representation of phase, so phase is set to -1 on
238	<	* termination. Good performace relies on keeping state decoding
238	>	* termination. Good performance relies on keeping state decoding
239		* and encoding simple, and keeping race windows short.
200	–	*
201	–	* Note: there are some cheats in arrive() that rely on unarrived
202	–	* being lowest 16 bits.
240		*/
241		private volatile long state;
242
243	<	private static final int ushortBits = 16;
244	<	private static final int ushortMask =  (1 << ushortBits) - 1;
245	<	private static final int phaseMask = 0x7fffffff;
243	>	private static final int  MAX_PARTIES    = 0xffff;
244	>	private static final int  MAX_PHASE      = 0x7fffffff;
245	>	private static final int  PARTIES_SHIFT  = 16;
246	>	private static final int  PHASE_SHIFT    = 32;
247	>	private static final int  UNARRIVED_MASK = 0xffff;
248	>	private static final long PARTIES_MASK   = 0xffff0000L; // for masking long
249	>	private static final long ONE_ARRIVAL    = 1L;
250	>	private static final long ONE_PARTY      = 1L << PARTIES_SHIFT;
251	>	private static final long TERMINATION_PHASE  = -1L << PHASE_SHIFT;
252	>
253	>	// The following unpacking methods are usually manually inlined
254
255		private static int unarrivedOf(long s) {
256	<	return (int)(s & ushortMask);
256	>	return (int)s & UNARRIVED_MASK;
257		}
258
259		private static int partiesOf(long s) {
260	<	return (int)(s & (ushortMask << 16)) >>> 16;
260	>	return (int)s >>> PARTIES_SHIFT;
261		}
262
263		private static int phaseOf(long s) {
264	<	return (int)(s >>> 32);
264	>	return (int) (s >>> PHASE_SHIFT);
265		}
266
267		private static int arrivedOf(long s) {
268		return partiesOf(s) - unarrivedOf(s);
269		}
270
226	–	private static long stateFor(int phase, int parties, int unarrived) {
227	–	return (((long)phase) << 32) | ((parties << 16) | unarrived);
228	–	}
229	–
230	–	private static long trippedStateFor(int phase, int parties) {
231	–	return (((long)phase) << 32) | ((parties << 16) | parties);
232	–	}
233	–
234	–	private static IllegalStateException badBounds(int parties, int unarrived) {
235	–	return new IllegalStateException
236	–	("Attempt to set " + unarrived +
237	–	" unarrived of " + parties + " parties");
238	–	}
239	–
271		/**
272		* The parent of this phaser, or null if none
273		*/
274		private final Phaser parent;
275
276		/**
277	<	* The root of Phaser tree. Equals this if not in a tree.  Used to
277	>	* The root of phaser tree. Equals this if not in a tree.  Used to
278		* support faster state push-down.
279		*/
280		private final Phaser root;
281
251	–	// Wait queues
252	–
282		/**
283	<	* Heads of Treiber stacks waiting for nonFJ threads. To eliminate
284	<	* contention while releasing some threads while adding others, we
283	>	* Heads of Treiber stacks for waiting threads. To eliminate
284	>	* contention when releasing some threads while adding others, we
285		* use two of them, alternating across even and odd phases.
286	+	* Subphasers share queues with root to speed up releases.
287		*/
288	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
289	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
288	>	private final AtomicReference<QNode> evenQ;
289	>	private final AtomicReference<QNode> oddQ;
290
291		private AtomicReference<QNode> queueFor(int phase) {
292	<	return (phase & 1) == 0? evenQ : oddQ;
292	>	return ((phase & 1) == 0) ? evenQ : oddQ;
293		}
294
295		/**
296	<	* Returns current state, first resolving lagged propagation from
297	<	* root if necessary.
296	>	* Main implementation for methods arrive and arriveAndDeregister.
297	>	* Manually tuned to speed up and minimize race windows for the
298	>	* common case of just decrementing unarrived field.
299	>	*
300	>	* @param adj - adjustment to apply to state -- either
301	>	* ONE_ARRIVAL (for arrive) or
302	>	* ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
303		*/
304	<	private long getReconciledState() {
305	<	return parent == null? state : reconcileState();
304	>	private int doArrive(long adj) {
305	>	for (;;) {
306	>	long s = state;
307	>	int phase = (int)(s >>> PHASE_SHIFT);
308	>	if (phase < 0)
309	>	return phase;
310	>	int unarrived = (int)s & UNARRIVED_MASK;
311	>	if (unarrived == 0)
312	>	checkBadArrive(s);
313	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
314	>	if (unarrived == 1) {
315	>	long p = s & PARTIES_MASK; // unshifted parties field
316	>	long lu = p >>> PARTIES_SHIFT;
317	>	int u = (int)lu;
318	>	int nextPhase = (phase + 1) & MAX_PHASE;
319	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
320	>	final Phaser parent = this.parent;
321	>	if (parent == null) {
322	>	if (onAdvance(phase, u))
323	>	next |= TERMINATION_PHASE; // obliterate phase
324	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
325	>	releaseWaiters(phase);
326	>	}
327	>	else {
328	>	parent.doArrive((u == 0) ?
329	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
330	>	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase ||
331	>	((int)(state >>> PHASE_SHIFT) != nextPhase &&
332	>	!UNSAFE.compareAndSwapLong(this, stateOffset,
333	>	s, next)))
334	>	reconcileState();
335	>	}
336	>	}
337	>	return phase;
338	>	}
339	>	}
340	>	}
341	>
342	>	/**
343	>	* Rechecks state and throws bounds exceptions on arrival -- called
344	>	* only if unarrived is apparently zero.
345	>	*/
346	>	private void checkBadArrive(long s) {
347	>	if (reconcileState() == s)
348	>	throw new IllegalStateException
349	>	("Attempted arrival of unregistered party for " +
350	>	stateToString(s));
351	>	}
352	>
353	>	/**
354	>	* Implementation of register, bulkRegister
355	>	*
356	>	* @param registrations number to add to both parties and unarrived fields
357	>	*/
358	>	private int doRegister(int registrations) {
359	>	// assert registrations > 0;
360	>	// adjustment to state
361	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
362	>	final Phaser parent = this.parent;
363	>	for (;;) {
364	>	long s = (parent == null) ? state : reconcileState();
365	>	int phase = (int)(s >>> PHASE_SHIFT);
366	>	if (phase < 0)
367	>	return phase;
368	>	int parties = (int)s >>> PARTIES_SHIFT;
369	>	if (parties != 0 && ((int)s & UNARRIVED_MASK) == 0)
370	>	internalAwaitAdvance(phase, null); // wait for onAdvance
371	>	else if (registrations > MAX_PARTIES - parties)
372	>	throw new IllegalStateException(badRegister(s));
373	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
374	>	return phase;
375	>	}
376		}
377
378		/**
379	<	* Recursively resolves state.
379	>	* Returns message string for out of bounds exceptions on registration.
380	>	*/
381	>	private String badRegister(long s) {
382	>	return "Attempt to register more than " +
383	>	MAX_PARTIES + " parties for " + stateToString(s);
384	>	}
385	>
386	>	/**
387	>	* Recursively resolves lagged phase propagation from root if necessary.
388		*/
389		private long reconcileState() {
390	<	Phaser p = parent;
390	>	Phaser par = parent;
391		long s = state;
392	<	if (p != null) {
393	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
394	<	long parentState = p.getReconciledState();
395	<	int parentPhase = phaseOf(parentState);
396	<	int phase = phaseOf(s = state);
397	<	if (phase != parentPhase) {
398	<	long next = trippedStateFor(parentPhase, partiesOf(s));
399	<	if (casState(s, next)) {
400	<	releaseWaiters(phase);
401	<	s = next;
402	<	}
392	>	if (par != null) {
393	>	Phaser rt = root;
394	>	int phase, rPhase;
395	>	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
396	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
397	>	if ((int)(par.state >>> PHASE_SHIFT) != rPhase)
398	>	par.reconcileState();
399	>	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
400	>	long u = s & PARTIES_MASK; // reset unarrived to parties
401	>	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
402	>	(u >>> PARTIES_SHIFT));
403	>	if (state == s &&
404	>	UNSAFE.compareAndSwapLong(this, stateOffset,
405	>	s, s = next))
406	>	break;
407		}
408	+	s = state;
409		}
410		}
411		return s;
412		}
413
414		/**
415	<	* Creates a new Phaser without any initially registered parties,
416	<	* initial phase number 0, and no parent.
415	>	* Creates a new phaser without any initially registered parties,
416	>	* initial phase number 0, and no parent. Any thread using this
417	>	* phaser will need to first register for it.
418		*/
419		public Phaser() {
420	<	this(null);
420	>	this(null, 0);
421		}
422
423		/**
424	<	* Creates a new Phaser with the given numbers of registered
424	>	* Creates a new phaser with the given number of registered
425		* unarrived parties, initial phase number 0, and no parent.
426	<	* @param parties the number of parties required to trip barrier.
426	>	*
427	>	* @param parties the number of parties required to trip barrier
428		* @throws IllegalArgumentException if parties less than zero
429	<	* or greater than the maximum number of parties supported.
429	>	* or greater than the maximum number of parties supported
430		*/
431		public Phaser(int parties) {
432		this(null, parties);
433		}
434
435		/**
436	<	* Creates a new Phaser with the given parent, without any
436	>	* Creates a new phaser with the given parent, without any
437		* initially registered parties. If parent is non-null this phaser
438		* is registered with the parent and its initial phase number is
439		* the same as that of parent phaser.
440	<	* @param parent the parent phaser.
440	>	*
441	>	* @param parent the parent phaser
442		*/
443		public Phaser(Phaser parent) {
444	<	int phase = 0;
324	<	this.parent = parent;
325	<	if (parent != null) {
326	<	this.root = parent.root;
327	<	phase = parent.register();
328	<	}
329	<	else
330	<	this.root = this;
331	<	this.state = trippedStateFor(phase, 0);
444	>	this(parent, 0);
445		}
446
447		/**
448	<	* Creates a new Phaser with the given parent and numbers of
449	<	* registered unarrived parties. If parent is non-null this phaser
448	>	* Creates a new phaser with the given parent and number of
449	>	* registered unarrived parties. If parent is non-null, this phaser
450		* is registered with the parent and its initial phase number is
451		* the same as that of parent phaser.
452	<	* @param parent the parent phaser.
453	<	* @param parties the number of parties required to trip barrier.
452	>	*
453	>	* @param parent the parent phaser
454	>	* @param parties the number of parties required to trip barrier
455		* @throws IllegalArgumentException if parties less than zero
456	<	* or greater than the maximum number of parties supported.
456	>	* or greater than the maximum number of parties supported
457		*/
458		public Phaser(Phaser parent, int parties) {
459	<	if (parties < 0 || parties > ushortMask)
459	>	if (parties >>> PARTIES_SHIFT != 0)
460		throw new IllegalArgumentException("Illegal number of parties");
461	<	int phase = 0;
461	>	int phase;
462		this.parent = parent;
463		if (parent != null) {
464	<	this.root = parent.root;
464	>	Phaser r = parent.root;
465	>	this.root = r;
466	>	this.evenQ = r.evenQ;
467	>	this.oddQ = r.oddQ;
468		phase = parent.register();
469		}
470	<	else
470	>	else {
471		this.root = this;
472	<	this.state = trippedStateFor(phase, parties);
472	>	this.evenQ = new AtomicReference<QNode>();
473	>	this.oddQ = new AtomicReference<QNode>();
474	>	phase = 0;
475	>	}
476	>	long p = (long)parties;
477	>	this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
478		}
479
480		/**
481		* Adds a new unarrived party to this phaser.
482	<	* @return the current barrier phase number upon registration
482	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
483	>	* this method may wait until its completion before registering.
484	>	*
485	>	* @return the arrival phase number to which this registration applied
486		* @throws IllegalStateException if attempting to register more
487	<	* than the maximum supported number of parties.
487	>	* than the maximum supported number of parties
488		*/
489		public int register() {
490		return doRegister(1);
#	Line 367 | Line 492 | public class Phaser {
492
493		/**
494		* Adds the given number of new unarrived parties to this phaser.
495	<	* @param parties the number of parties required to trip barrier.
496	<	* @return the current barrier phase number upon registration
495	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
496	>	* this method may wait until its completion before registering.
497	>	*
498	>	* @param parties the number of additional parties required to trip barrier
499	>	* @return the arrival phase number to which this registration applied
500		* @throws IllegalStateException if attempting to register more
501	<	* than the maximum supported number of parties.
501	>	* than the maximum supported number of parties
502	>	* @throws IllegalArgumentException if {@code parties < 0}
503		*/
504		public int bulkRegister(int parties) {
505		if (parties < 0)
#	Line 381 | Line 510 | public class Phaser {
510		}
511
512		/**
384	–	* Shared code for register, bulkRegister
385	–	*/
386	–	private int doRegister(int registrations) {
387	–	int phase;
388	–	for (;;) {
389	–	long s = getReconciledState();
390	–	phase = phaseOf(s);
391	–	int unarrived = unarrivedOf(s) + registrations;
392	–	int parties = partiesOf(s) + registrations;
393	–	if (phase < 0)
394	–	break;
395	–	if (parties > ushortMask || unarrived > ushortMask)
396	–	throw badBounds(parties, unarrived);
397	–	if (phase == phaseOf(root.state) &&
398	–	casState(s, stateFor(phase, parties, unarrived)))
399	–	break;
400	–	}
401	–	return phase;
402	–	}
403	–
404	–	/**
513		* Arrives at the barrier, but does not wait for others.  (You can
514	<	* in turn wait for others via {@link #awaitAdvance}).
514	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
515	>	* unenforced usage error for an unregistered party to invoke this
516	>	* method.
517		*
518	<	* @return the barrier phase number upon entry to this method, or a
409	<	* negative value if terminated;
518	>	* @return the arrival phase number, or a negative value if terminated
519		* @throws IllegalStateException if not terminated and the number
520	<	* of unarrived parties would become negative.
520	>	* of unarrived parties would become negative
521		*/
522		public int arrive() {
523	<	int phase;
415	<	for (;;) {
416	<	long s = state;
417	<	phase = phaseOf(s);
418	<	int parties = partiesOf(s);
419	<	int unarrived = unarrivedOf(s) - 1;
420	<	if (unarrived > 0) {        // Not the last arrival
421	<	if (casState(s, s - 1)) // s-1 adds one arrival
422	<	break;
423	<	}
424	<	else if (unarrived == 0) {  // the last arrival
425	<	Phaser par = parent;
426	<	if (par == null) {      // directly trip
427	<	if (casState
428	<	(s,
429	<	trippedStateFor(onAdvance(phase, parties)? -1 :
430	<	((phase + 1) & phaseMask), parties))) {
431	<	releaseWaiters(phase);
432	<	break;
433	<	}
434	<	}
435	<	else {                  // cascade to parent
436	<	if (casState(s, s - 1)) { // zeroes unarrived
437	<	par.arrive();
438	<	reconcileState();
439	<	break;
440	<	}
441	<	}
442	<	}
443	<	else if (phase < 0) // Don't throw exception if terminated
444	<	break;
445	<	else if (phase != phaseOf(root.state)) // or if unreconciled
446	<	reconcileState();
447	<	else
448	<	throw badBounds(parties, unarrived);
449	<	}
450	<	return phase;
523	>	return doArrive(ONE_ARRIVAL);
524		}
525
526		/**
527	<	* Arrives at the barrier, and deregisters from it, without
528	<	* waiting for others. Deregistration reduces number of parties
527	>	* Arrives at the barrier and deregisters from it without waiting
528	>	* for others. Deregistration reduces the number of parties
529		* required to trip the barrier in future phases.  If this phaser
530		* has a parent, and deregistration causes this phaser to have
531	<	* zero parties, this phaser is also deregistered from its parent.
531	>	* zero parties, this phaser also arrives at and is deregistered
532	>	* from its parent.  It is an unenforced usage error for an
533	>	* unregistered party to invoke this method.
534		*
535	<	* @return the current barrier phase number upon entry to
461	<	* this method, or a negative value if terminated;
535	>	* @return the arrival phase number, or a negative value if terminated
536		* @throws IllegalStateException if not terminated and the number
537	<	* of registered or unarrived parties would become negative.
537	>	* of registered or unarrived parties would become negative
538		*/
539		public int arriveAndDeregister() {
540	<	// similar code to arrive, but too different to merge
467	<	Phaser par = parent;
468	<	int phase;
469	<	for (;;) {
470	<	long s = state;
471	<	phase = phaseOf(s);
472	<	int parties = partiesOf(s) - 1;
473	<	int unarrived = unarrivedOf(s) - 1;
474	<	if (parties >= 0) {
475	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
476	<	if (casState
477	<	(s,
478	<	stateFor(phase, parties, unarrived))) {
479	<	if (unarrived == 0) {
480	<	par.arriveAndDeregister();
481	<	reconcileState();
482	<	}
483	<	break;
484	<	}
485	<	continue;
486	<	}
487	<	if (unarrived == 0) {
488	<	if (casState
489	<	(s,
490	<	trippedStateFor(onAdvance(phase, parties)? -1 :
491	<	((phase + 1) & phaseMask), parties))) {
492	<	releaseWaiters(phase);
493	<	break;
494	<	}
495	<	continue;
496	<	}
497	<	if (phase < 0)
498	<	break;
499	<	if (par != null && phase != phaseOf(root.state)) {
500	<	reconcileState();
501	<	continue;
502	<	}
503	<	}
504	<	throw badBounds(parties, unarrived);
505	<	}
506	<	return phase;
540	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
541		}
542
543		/**
544		* Arrives at the barrier and awaits others. Equivalent in effect
545	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
546	<	* await with interruption of timeout, and/or deregister upon
547	<	* arrival, you can arrange them using analogous constructions.
548	<	* @return the phase on entry to this method
545	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
546	>	* interruption or timeout, you can arrange this with an analogous
547	>	* construction using one of the other forms of the {@code
548	>	* awaitAdvance} method.  If instead you need to deregister upon
549	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
550	>	* usage error for an unregistered party to invoke this method.
551	>	*
552	>	* @return the arrival phase number, or a negative number if terminated
553		* @throws IllegalStateException if not terminated and the number
554	<	* of unarrived parties would become negative.
554	>	* of unarrived parties would become negative
555		*/
556		public int arriveAndAwaitAdvance() {
557		return awaitAdvance(arrive());
558		}
559
560		/**
561	<	* Awaits the phase of the barrier to advance from the given
562	<	* value, or returns immediately if argument is negative or this
563	<	* barrier is terminated.
564	<	* @param phase the phase on entry to this method
565	<	* @return the phase on exit from this method
561	>	* Awaits the phase of the barrier to advance from the given phase
562	>	* value, returning immediately if the current phase of the
563	>	* barrier is not equal to the given phase value or this barrier
564	>	* is terminated.
565	>	*
566	>	* @param phase an arrival phase number, or negative value if
567	>	* terminated; this argument is normally the value returned by a
568	>	* previous call to {@code arrive} or its variants
569	>	* @return the next arrival phase number, or a negative value
570	>	* if terminated or argument is negative
571		*/
572		public int awaitAdvance(int phase) {
573		if (phase < 0)
574		return phase;
575	<	long s = getReconciledState();
576	<	int p = phaseOf(s);
577	<	if (p != phase)
535	<	return p;
536	<	if (unarrivedOf(s) == 0)
537	<	parent.awaitAdvance(phase);
538	<	// Fall here even if parent waited, to reconcile and help release
539	<	return untimedWait(phase);
575	>	long s = (parent == null) ? state : reconcileState();
576	>	int p = (int)(s >>> PHASE_SHIFT);
577	>	return (p != phase) ? p : internalAwaitAdvance(phase, null);
578		}
579
580		/**
581	<	* Awaits the phase of the barrier to advance from the given
582	<	* value, or returns immediately if argumet is negative or this
583	<	* barrier is terminated, or throws InterruptedException if
584	<	* interrupted while waiting.
585	<	* @param phase the phase on entry to this method
586	<	* @return the phase on exit from this method
581	>	* Awaits the phase of the barrier to advance from the given phase
582	>	* value, throwing {@code InterruptedException} if interrupted
583	>	* while waiting, or returning immediately if the current phase of
584	>	* the barrier is not equal to the given phase value or this
585	>	* barrier is terminated.
586	>	*
587	>	* @param phase an arrival phase number, or negative value if
588	>	* terminated; this argument is normally the value returned by a
589	>	* previous call to {@code arrive} or its variants
590	>	* @return the next arrival phase number, or a negative value
591	>	* if terminated or argument is negative
592		* @throws InterruptedException if thread interrupted while waiting
593		*/
594	<	public int awaitAdvanceInterruptibly(int phase) throws InterruptedException {
594	>	public int awaitAdvanceInterruptibly(int phase)
595	>	throws InterruptedException {
596		if (phase < 0)
597		return phase;
598	<	long s = getReconciledState();
599	<	int p = phaseOf(s);
600	<	if (p != phase)
601	<	return p;
602	<	if (unarrivedOf(s) != 0)
603	<	parent.awaitAdvanceInterruptibly(phase);
604	<	return interruptibleWait(phase);
598	>	long s = (parent == null) ? state : reconcileState();
599	>	int p = (int)(s >>> PHASE_SHIFT);
600	>	if (p == phase) {
601	>	QNode node = new QNode(this, phase, true, false, 0L);
602	>	p = internalAwaitAdvance(phase, node);
603	>	if (node.wasInterrupted)
604	>	throw new InterruptedException();
605	>	}
606	>	return p;
607		}
608
609		/**
610	<	* Awaits the phase of the barrier to advance from the given value
611	<	* or the given timeout elapses, or returns immediately if
612	<	* argument is negative or this barrier is terminated.
613	<	* @param phase the phase on entry to this method
614	<	* @return the phase on exit from this method
610	>	* Awaits the phase of the barrier to advance from the given phase
611	>	* value or the given timeout to elapse, throwing {@code
612	>	* InterruptedException} if interrupted while waiting, or
613	>	* returning immediately if the current phase of the barrier is
614	>	* not equal to the given phase value or this barrier is
615	>	* terminated.
616	>	*
617	>	* @param phase an arrival phase number, or negative value if
618	>	* terminated; this argument is normally the value returned by a
619	>	* previous call to {@code arrive} or its variants
620	>	* @param timeout how long to wait before giving up, in units of
621	>	*        {@code unit}
622	>	* @param unit a {@code TimeUnit} determining how to interpret the
623	>	*        {@code timeout} parameter
624	>	* @return the next arrival phase number, or a negative value
625	>	* if terminated or argument is negative
626		* @throws InterruptedException if thread interrupted while waiting
627		* @throws TimeoutException if timed out while waiting
628		*/
629	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
629	>	public int awaitAdvanceInterruptibly(int phase,
630	>	long timeout, TimeUnit unit)
631		throws InterruptedException, TimeoutException {
632		if (phase < 0)
633		return phase;
634	<	long s = getReconciledState();
635	<	int p = phaseOf(s);
636	<	if (p != phase)
637	<	return p;
638	<	if (unarrivedOf(s) == 0)
639	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
640	<	return timedWait(phase, unit.toNanos(timeout));
634	>	long s = (parent == null) ? state : reconcileState();
635	>	int p = (int)(s >>> PHASE_SHIFT);
636	>	if (p == phase) {
637	>	long nanos = unit.toNanos(timeout);
638	>	QNode node = new QNode(this, phase, true, true, nanos);
639	>	p = internalAwaitAdvance(phase, node);
640	>	if (node.wasInterrupted)
641	>	throw new InterruptedException();
642	>	else if (p == phase)
643	>	throw new TimeoutException();
644	>	}
645	>	return p;
646		}
647
648		/**
649	<	* Forces this barrier to enter termination state. Counts of
650	<	* arrived and registered parties are unaffected. If this phaser
651	<	* has a parent, it too is terminated. This method may be useful
652	<	* for coordinating recovery after one or more tasks encounter
653	<	* unexpected exceptions.
649	>	* Forces this barrier to enter termination state.  Counts of
650	>	* arrived and registered parties are unaffected.  If this phaser
651	>	* is a member of a tiered set of phasers, then all of the phasers
652	>	* in the set are terminated.  If this phaser is already
653	>	* terminated, this method has no effect.  This method may be
654	>	* useful for coordinating recovery after one or more tasks
655	>	* encounter unexpected exceptions.
656		*/
657		public void forceTermination() {
658	<	for (;;) {
659	<	long s = getReconciledState();
660	<	int phase = phaseOf(s);
661	<	int parties = partiesOf(s);
662	<	int unarrived = unarrivedOf(s);
663	<	if (phase < 0 ||
664	<	casState(s, stateFor(-1, parties, unarrived))) {
600	<	releaseWaiters(0);
658	>	// Only need to change root state
659	>	final Phaser root = this.root;
660	>	long s;
661	>	while ((s = root.state) >= 0) {
662	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
663	>	s, s | TERMINATION_PHASE)) {
664	>	releaseWaiters(0); // signal all threads
665		releaseWaiters(1);
602	–	if (parent != null)
603	–	parent.forceTermination();
666		return;
667		}
668		}
#	Line 610 | Line 672 | public class Phaser {
672		* Returns the current phase number. The maximum phase number is
673		* {@code Integer.MAX_VALUE}, after which it restarts at
674		* zero. Upon termination, the phase number is negative.
675	+	*
676		* @return the phase number, or a negative value if terminated
677		*/
678		public final int getPhase() {
679	<	return phaseOf(getReconciledState());
617	<	}
618	<
619	<	/**
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;
679	>	return (int)(root.state >>> PHASE_SHIFT);
680		}
681
682		/**
683		* Returns the number of parties registered at this barrier.
684	+	*
685		* @return the number of parties
686		*/
687		public int getRegisteredParties() {
#	Line 634 | Line 689 | public class Phaser {
689		}
690
691		/**
692	<	* Returns the number of parties that have arrived at the current
693	<	* phase of this barrier.
692	>	* Returns the number of registered parties that have arrived at
693	>	* the current phase of this barrier.
694	>	*
695		* @return the number of arrived parties
696		*/
697		public int getArrivedParties() {
698	<	return arrivedOf(state);
698	>	return arrivedOf(parent==null? state : reconcileState());
699		}
700
701		/**
702		* Returns the number of registered parties that have not yet
703		* arrived at the current phase of this barrier.
704	+	*
705		* @return the number of unarrived parties
706		*/
707		public int getUnarrivedParties() {
708	<	return unarrivedOf(state);
708	>	return unarrivedOf(parent==null? state : reconcileState());
709		}
710
711		/**
712	<	* Returns the parent of this phaser, or null if none.
713	<	* @return the parent of this phaser, or null if none.
712	>	* Returns the parent of this phaser, or {@code null} if none.
713	>	*
714	>	* @return the parent of this phaser, or {@code null} if none
715		*/
716		public Phaser getParent() {
717		return parent;
#	Line 662 | Line 720 | public class Phaser {
720		/**
721		* Returns the root ancestor of this phaser, which is the same as
722		* this phaser if it has no parent.
723	<	* @return the root ancestor of this phaser.
723	>	*
724	>	* @return the root ancestor of this phaser
725		*/
726		public Phaser getRoot() {
727		return root;
728		}
729
730		/**
731	<	* Returns true if this barrier has been terminated.
732	<	* @return true if this barrier has been terminated
731	>	* Returns {@code true} if this barrier has been terminated.
732	>	*
733	>	* @return {@code true} if this barrier has been terminated
734		*/
735		public boolean isTerminated() {
736	<	return getPhase() < 0;
736	>	return root.state < 0L;
737		}
738
739		/**
740	<	* Overridable method to perform an action upon phase advance, and
741	<	* to control termination. This method is invoked whenever the
742	<	* barrier is tripped (and thus all other waiting parties are
743	<	* dormant). If it returns true, then, rather than advance the
744	<	* phase number, this barrier will be set to a final termination
745	<	* state, and subsequent calls to {@code isTerminated} will
746	<	* return true.
740	>	* Overridable method to perform an action upon impending phase
741	>	* advance, and to control termination. This method is invoked
742	>	* upon arrival of the party tripping the barrier (when all other
743	>	* waiting parties are dormant).  If this method returns {@code
744	>	* true}, then, rather than advance the phase number, this barrier
745	>	* will be set to a final termination state, and subsequent calls
746	>	* to {@link #isTerminated} will return true. Any (unchecked)
747	>	* Exception or Error thrown by an invocation of this method is
748	>	* propagated to the party attempting to trip the barrier, in
749	>	* which case no advance occurs.
750	>	*
751	>	* <p>The arguments to this method provide the state of the phaser
752	>	* prevailing for the current transition.  The effects of invoking
753	>	* arrival, registration, and waiting methods on this Phaser from
754	>	* within {@code onAdvance} are unspecified and should not be
755	>	* relied on.
756		*
757	<	* <p> The default version returns true when the number of
757	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
758	>	* {@code onAdvance} is invoked only for its root Phaser on each
759	>	* advance.
760	>	*
761	>	* <p>The default version returns {@code true} when the number of
762		* registered parties is zero. Normally, overrides that arrange
763		* termination for other reasons should also preserve this
764		* property.
765		*
693	–	* <p> You may override this method to perform an action with side
694	–	* effects visible to participating tasks, but it is in general
695	–	* only sensible to do so in designs where all parties register
696	–	* before any arrive, and all {@code awaitAdvance} at each phase.
697	–	* Otherwise, you cannot ensure lack of interference. In
698	–	* 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.
703	–	*
766		* @param phase the phase number on entering the barrier
767	<	* @param registeredParties the current number of registered
768	<	* parties.
707	<	* @return true if this barrier should terminate
767	>	* @param registeredParties the current number of registered parties
768	>	* @return {@code true} if this barrier should terminate
769		*/
770		protected boolean onAdvance(int phase, int registeredParties) {
771		return registeredParties <= 0;
#	Line 713 | Line 774 | public class Phaser {
774		/**
775		* Returns a string identifying this phaser, as well as its
776		* state.  The state, in brackets, includes the String {@code
777	<	* "phase ="} followed by the phase number, {@code "parties ="}
777	>	* "phase = "} followed by the phase number, {@code "parties = "}
778		* followed by the number of registered parties, and {@code
779	<	* "arrived ="} followed by the number of arrived parties
779	>	* "arrived = "} followed by the number of arrived parties.
780		*
781		* @return a string identifying this barrier, as well as its state
782		*/
783		public String toString() {
784	<	long s = getReconciledState();
724	<	return super.toString() + "[phase = " + phaseOf(s) + " parties = " + partiesOf(s) + " arrived = " + arrivedOf(s) + "]";
784	>	return stateToString(reconcileState());
785		}
786
727	–	// methods for waiting
728	–
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	–
787		/**
788	<	* The number of nanoseconds for which it is faster to spin
747	<	* rather than to use timed park. A rough estimate suffices.
788	>	* Implementation of toString and string-based error messages
789		*/
790	<	static final long spinForTimeoutThreshold = 1000L;
791	<
792	<	/**
793	<	* Wait nodes for Treiber stack representing wait queue for non-FJ
794	<	* tasks.
754	<	*/
755	<	static final class QNode {
756	<	QNode next;
757	<	volatile Thread thread; // nulled to cancel wait
758	<	QNode() {
759	<	thread = Thread.currentThread();
760	<	}
761	<	void signal() {
762	<	Thread t = thread;
763	<	if (t != null) {
764	<	thread = null;
765	<	LockSupport.unpark(t);
766	<	}
767	<	}
790	>	private String stateToString(long s) {
791	>	return super.toString() +
792	>	"[phase = " + phaseOf(s) +
793	>	" parties = " + partiesOf(s) +
794	>	" arrived = " + arrivedOf(s) + "]";
795		}
796
797	+	// Waiting mechanics
798	+
799		/**
800	<	* Removes and signals waiting threads from wait queue
800	>	* Removes and signals threads from queue for phase.
801		*/
802		private void releaseWaiters(int phase) {
803		AtomicReference<QNode> head = queueFor(phase);
804		QNode q;
805	<	while ((q = head.get()) != null) {
805	>	int p;
806	>	while ((q = head.get()) != null &&
807	>	((p = q.phase) == phase ||
808	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
809		if (head.compareAndSet(q, q.next))
810		q.signal();
811		}
812		}
813
814	+	/** The number of CPUs, for spin control */
815	+	private static final int NCPU = Runtime.getRuntime().availableProcessors();
816	+
817		/**
818	<	* Enqueues node and waits unless aborted or signalled.
818	>	* The number of times to spin before blocking while waiting for
819	>	* advance, per arrival while waiting. On multiprocessors, fully
820	>	* blocking and waking up a large number of threads all at once is
821	>	* usually a very slow process, so we use rechargeable spins to
822	>	* avoid it when threads regularly arrive: When a thread in
823	>	* internalAwaitAdvance notices another arrival before blocking,
824	>	* and there appear to be enough CPUs available, it spins
825	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
826	>	* uniprocessors, there is at least one intervening Thread.yield
827	>	* before blocking. The value trades off good-citizenship vs big
828	>	* unnecessary slowdowns.
829		*/
830	<	private int untimedWait(int phase) {
786	<	int spins = maxUntimedSpins;
787	<	QNode node = null;
788	<	boolean interrupted = false;
789	<	boolean queued = false;
790	<	int p;
791	<	while ((p = getPhase()) == phase) {
792	<	interrupted = Thread.interrupted();
793	<	if (node != null) {
794	<	if (!queued) {
795	<	AtomicReference<QNode> head = queueFor(phase);
796	<	queued = head.compareAndSet(node.next = head.get(), node);
797	<	}
798	<	else if (node.thread != null)
799	<	LockSupport.park(this);
800	<	}
801	<	else if (spins <= 0)
802	<	node = new QNode();
803	<	else
804	<	--spins;
805	<	}
806	<	if (node != null)
807	<	node.thread = null;
808	<	if (interrupted)
809	<	Thread.currentThread().interrupt();
810	<	releaseWaiters(phase);
811	<	return p;
812	<	}
830	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
831
832		/**
833	<	* Messier interruptible version
834	<	*/
835	<	private int interruptibleWait(int phase) throws InterruptedException {
836	<	int spins = maxUntimedSpins;
837	<	QNode node = null;
838	<	boolean queued = false;
839	<	boolean interrupted = false;
833	>	* Possibly blocks and waits for phase to advance unless aborted.
834	>	*
835	>	* @param phase current phase
836	>	* @param node if non-null, the wait node to track interrupt and timeout;
837	>	* if null, denotes noninterruptible wait
838	>	* @return current phase
839	>	*/
840	>	private int internalAwaitAdvance(int phase, QNode node) {
841	>	Phaser current = this;       // to eventually wait at root if tiered
842	>	boolean queued = false;      // true when node is enqueued
843	>	int lastUnarrived = -1;      // to increase spins upon change
844	>	int spins = SPINS_PER_ARRIVAL;
845	>	long s;
846		int p;
847	<	while ((p = getPhase()) == phase) {
848	<	if (interrupted = Thread.interrupted())
849	<	break;
850	<	if (node != null) {
851	<	if (!queued) {
852	<	AtomicReference<QNode> head = queueFor(phase);
853	<	queued = head.compareAndSet(node.next = head.get(), node);
847	>	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
848	>	Phaser par;
849	>	int unarrived = (int)s & UNARRIVED_MASK;
850	>	if (unarrived != lastUnarrived) {
851	>	if (lastUnarrived == -1) // ensure old queue clean
852	>	releaseWaiters(phase-1);
853	>	if ((lastUnarrived = unarrived) < NCPU)
854	>	spins += SPINS_PER_ARRIVAL;
855	>	}
856	>	else if (unarrived == 0 && (par = current.parent) != null) {
857	>	current = par;       // if all arrived, use parent
858	>	par = par.parent;
859	>	lastUnarrived = -1;
860	>	}
861	>	else if (spins > 0) {
862	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
863	>	Thread.yield();  // yield midway through spin
864	>	}
865	>	else if (node == null)   // must be noninterruptible
866	>	node = new QNode(this, phase, false, false, 0L);
867	>	else if (node.isReleasable()) {
868	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
869	>	break;
870	>	else
871	>	return phase;    // aborted
872	>	}
873	>	else if (!queued) {      // push onto queue
874	>	AtomicReference<QNode> head = queueFor(phase);
875	>	QNode q = head.get();
876	>	if (q == null || q.phase == phase) {
877	>	node.next = q;
878	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
879	>	break;       // recheck to avoid stale enqueue
880	>	else
881	>	queued = head.compareAndSet(q, node);
882	>	}
883	>	}
884	>	else {
885	>	try {
886	>	ForkJoinPool.managedBlock(node);
887	>	} catch (InterruptedException ie) {
888	>	node.wasInterrupted = true;
889		}
831	–	else if (node.thread != null)
832	–	LockSupport.park(this);
890		}
834	–	else if (spins <= 0)
835	–	node = new QNode();
836	–	else
837	–	--spins;
891		}
839	–	if (node != null)
840	–	node.thread = null;
841	–	if (interrupted)
842	–	throw new InterruptedException();
892		releaseWaiters(phase);
893	+	if (node != null)
894	+	node.onRelease();
895		return p;
896		}
897
898		/**
899	<	* Even messier timeout version.
899	>	* Wait nodes for Treiber stack representing wait queue
900		*/
901	<	private int timedWait(int phase, long nanos)
902	<	throws InterruptedException, TimeoutException {
903	<	int p;
904	<	if ((p = getPhase()) == phase) {
905	<	long lastTime = System.nanoTime();
906	<	int spins = maxTimedSpins;
907	<	QNode node = null;
908	<	boolean queued = false;
909	<	boolean interrupted = false;
910	<	while ((p = getPhase()) == phase) {
911	<	if (interrupted = Thread.interrupted())
912	<	break;
913	<	long now = System.nanoTime();
914	<	if ((nanos -= now - lastTime) <= 0)
915	<	break;
916	<	lastTime = now;
917	<	if (node != null) {
918	<	if (!queued) {
919	<	AtomicReference<QNode> head = queueFor(phase);
920	<	queued = head.compareAndSet(node.next = head.get(), node);
921	<	}
922	<	else if (node.thread != null &&
923	<	nanos > spinForTimeoutThreshold) {
924	<	LockSupport.parkNanos(this, nanos);
901	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
902	>	final Phaser phaser;
903	>	final int phase;
904	>	final boolean interruptible;
905	>	final boolean timed;
906	>	boolean wasInterrupted;
907	>	long nanos;
908	>	long lastTime;
909	>	volatile Thread thread; // nulled to cancel wait
910	>	QNode next;
911	>
912	>	QNode(Phaser phaser, int phase, boolean interruptible,
913	>	boolean timed, long nanos) {
914	>	this.phaser = phaser;
915	>	this.phase = phase;
916	>	this.interruptible = interruptible;
917	>	this.nanos = nanos;
918	>	this.timed = timed;
919	>	this.lastTime = timed? System.nanoTime() : 0L;
920	>	thread = Thread.currentThread();
921	>	}
922	>
923	>	public boolean isReleasable() {
924	>	Thread t = thread;
925	>	if (t != null) {
926	>	if (phaser.getPhase() != phase)
927	>	t = null;
928	>	else {
929	>	if (Thread.interrupted())
930	>	wasInterrupted = true;
931	>	if (interruptible && wasInterrupted)
932	>	t = null;
933	>	else if (timed) {
934	>	if (nanos > 0) {
935	>	long now = System.nanoTime();
936	>	nanos -= now - lastTime;
937	>	lastTime = now;
938	>	}
939	>	if (nanos <= 0)
940	>	t = null;
941		}
942		}
943	<	else if (spins <= 0)
944	<	node = new QNode();
945	<	else
879	<	--spins;
943	>	if (t != null)
944	>	return false;
945	>	thread = null;
946		}
947	<	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();
947	>	return true;
948		}
949	<	releaseWaiters(phase);
950	<	return p;
949	>
950	>	public boolean block() {
951	>	if (isReleasable())
952	>	return true;
953	>	else if (!timed)
954	>	LockSupport.park(this);
955	>	else if (nanos > 0)
956	>	LockSupport.parkNanos(this, nanos);
957	>	return isReleasable();
958	>	}
959	>
960	>	void signal() {
961	>	Thread t = thread;
962	>	if (t != null) {
963	>	thread = null;
964	>	LockSupport.unpark(t);
965	>	}
966	>	}
967	>
968	>	void onRelease() { // actions upon return from internalAwaitAdvance
969	>	if (!interruptible && wasInterrupted)
970	>	Thread.currentThread().interrupt();
971	>	if (thread != null)
972	>	thread = null;
973	>	}
974	>
975		}
976
977	<	// Temporary Unsafe mechanics for preliminary release
977	>	// Unsafe mechanics
978
979	<	static final Unsafe _unsafe;
980	<	static final long stateOffset;
979	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
980	>	private static final long stateOffset =
981	>	objectFieldOffset("state", Phaser.class);
982
983	<	static {
983	>	private static long objectFieldOffset(String field, Class<?> klazz) {
984		try {
985	<	if (Phaser.class.getClassLoader() != null) {
986	<	Field f = Unsafe.class.getDeclaredField("theUnsafe");
987	<	f.setAccessible(true);
988	<	_unsafe = (Unsafe)f.get(null);
989	<	}
990	<	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);
985	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
986	>	} catch (NoSuchFieldException e) {
987	>	// Convert Exception to corresponding Error
988	>	NoSuchFieldError error = new NoSuchFieldError(field);
989	>	error.initCause(e);
990	>	throw error;
991		}
992		}
993
994	<	final boolean casState(long cmp, long val) {
995	<	return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val);
994	>	/**
995	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
996	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
997	>	* into a jdk.
998	>	*
999	>	* @return a sun.misc.Unsafe
1000	>	*/
1001	>	private static sun.misc.Unsafe getUnsafe() {
1002	>	try {
1003	>	return sun.misc.Unsafe.getUnsafe();
1004	>	} catch (SecurityException se) {
1005	>	try {
1006	>	return java.security.AccessController.doPrivileged
1007	>	(new java.security
1008	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1009	>	public sun.misc.Unsafe run() throws Exception {
1010	>	java.lang.reflect.Field f = sun.misc
1011	>	.Unsafe.class.getDeclaredField("theUnsafe");
1012	>	f.setAccessible(true);
1013	>	return (sun.misc.Unsafe) f.get(null);
1014	>	}});
1015	>	} catch (java.security.PrivilegedActionException e) {
1016	>	throw new RuntimeException("Could not initialize intrinsics",
1017	>	e.getCause());
1018	>	}
1019	>	}
1020		}
1021		}

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