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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.13 by jsr166, Mon Jul 20 22:40:09 2009 UTC vs.
Revision 1.51 by dl, Sat Nov 13 00:55:51 2010 UTC

#	Line 6 | Line 6
6
7		package jsr166y;
8
9	<	import java.util.concurrent.*;
10	<	import java.util.concurrent.atomic.*;
9	>	import java.util.concurrent.TimeUnit;
10	>	import java.util.concurrent.TimeoutException;
11	>	import java.util.concurrent.atomic.AtomicReference;
12		import java.util.concurrent.locks.LockSupport;
12	–	import sun.misc.Unsafe;
13	–	import java.lang.reflect.*;
13
14		/**
15	<	* A reusable synchronization barrier, similar in functionality to a
15	>	* A reusable synchronization barrier, similar in functionality to
16		* {@link java.util.concurrent.CyclicBarrier CyclicBarrier} and
17		* {@link java.util.concurrent.CountDownLatch CountDownLatch}
18		* but supporting more flexible usage.
19		*
20	<	* <ul>
21	<	*
22	<	* <li> The number of parties synchronizing on a phaser may vary over
23	<	* time.  A task may register to be a party at any time, and may
24	<	* deregister upon arriving at the barrier.  As is the case with most
25	<	* basic synchronization constructs, registration and deregistration
26	<	* affect only internal counts; they do not establish any further
27	<	* internal bookkeeping, so tasks cannot query whether they are
28	<	* registered. (However, you can introduce such bookkeeping by
29	<	* subclassing this class.)
30	<	*
31	<	* <li> Each generation has an associated phase value, starting at
32	<	* zero, and advancing when all parties reach the barrier (wrapping
33	<	* around to zero after reaching {@code Integer.MAX_VALUE}).
34	<	*
35	<	* <li> Like a CyclicBarrier, a Phaser may be repeatedly awaited.
36	<	* Method {@code arriveAndAwaitAdvance} has effect analogous to
37	<	* {@code CyclicBarrier.await}.  However, Phasers separate two
38	<	* aspects of coordination, that may also be invoked independently:
20	>	* <p> <b>Registration.</b> Unlike the case for other barriers, the
21	>	* number of parties <em>registered</em> to synchronize on a phaser
22	>	* may vary over time.  Tasks may be registered at any time (using
23	>	* methods {@link #register}, {@link #bulkRegister}, or forms of
24	>	* constructors establishing initial numbers of parties), and
25	>	* optionally deregistered upon any arrival (using {@link
26	>	* #arriveAndDeregister}).  As is the case with most basic
27	>	* synchronization constructs, registration and deregistration affect
28	>	* only internal counts; they do not establish any further internal
29	>	* bookkeeping, so tasks cannot query whether they are registered.
30	>	* (However, you can introduce such bookkeeping by subclassing this
31	>	* class.)
32	>	*
33	>	* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
34	>	* Phaser} may be repeatedly awaited.  Method {@link
35	>	* #arriveAndAwaitAdvance} has effect analogous to {@link
36	>	* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
37	>	* generation of a {@code Phaser} has an associated phase number. The
38	>	* phase number starts at zero, and advances when all parties arrive
39	>	* at the barrier, wrapping around to zero after reaching {@code
40	>	* Integer.MAX_VALUE}. The use of phase numbers enables independent
41	>	* control of actions upon arrival at a barrier and upon awaiting
42	>	* others, via two kinds of methods that may be invoked by any
43	>	* registered party:
44		*
45		* <ul>
46		*
47	<	*   <li> Arriving at a barrier. Methods {@code arrive} and
48	<	*       {@code arriveAndDeregister} do not block, but return
49	<	*       the phase value current upon entry to the method.
50	<	*
51	<	*   <li> Awaiting others. Method {@code awaitAdvance} requires an
52	<	*       argument indicating the entry phase, and returns when the
53	<	*       barrier advances to a new phase.
54	<	* </ul>
47	>	*   <li> <b>Arrival.</b> Methods {@link #arrive} and
48	>	*       {@link #arriveAndDeregister} record arrival at a
49	>	*       barrier. These methods do not block, but return an associated
50	>	*       <em>arrival phase number</em>; that is, the phase number of
51	>	*       the barrier to which the arrival applied. When the final
52	>	*       party for a given phase arrives, an optional barrier action
53	>	*       is performed and the phase advances.  Barrier actions,
54	>	*       performed by the party triggering a phase advance, are
55	>	*       arranged by overriding method {@link #onAdvance(int, int)},
56	>	*       which also controls termination. Overriding this method is
57	>	*       similar to, but more flexible than, providing a barrier
58	>	*       action to a {@code CyclicBarrier}.
59	>	*
60	>	*   <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
61	>	*       argument indicating an arrival phase number, and returns when
62	>	*       the barrier advances to (or is already at) a different phase.
63	>	*       Unlike similar constructions using {@code CyclicBarrier},
64	>	*       method {@code awaitAdvance} continues to wait even if the
65	>	*       waiting thread is interrupted. Interruptible and timeout
66	>	*       versions are also available, but exceptions encountered while
67	>	*       tasks wait interruptibly or with timeout do not change the
68	>	*       state of the barrier. If necessary, you can perform any
69	>	*       associated recovery within handlers of those exceptions,
70	>	*       often after invoking {@code forceTermination}.  Phasers may
71	>	*       also be used by tasks executing in a {@link ForkJoinPool},
72	>	*       which will ensure sufficient parallelism to execute tasks
73	>	*       when others are blocked waiting for a phase to advance.
74		*
75	+	* </ul>
76		*
77	<	* <li> Barrier actions, performed by the task triggering a phase
78	<	* advance while others may be waiting, are arranged by overriding
79	<	* method {@code onAdvance}, that also controls termination.
80	<	* Overriding this method may be used to similar but more flexible
81	<	* effect as providing a barrier action to a CyclicBarrier.
82	<	*
83	<	* <li> Phasers may enter a <em>termination</em> state in which all
84	<	* actions immediately return without updating phaser state or waiting
85	<	* for advance, and indicating (via a negative phase value) that
86	<	* execution is complete.  Termination is triggered by executing the
87	<	* overridable {@code onAdvance} method that is invoked each time the
64	<	* barrier is about to be tripped. When a Phaser is controlling an
65	<	* action with a fixed number of iterations, it is often convenient to
66	<	* override this method to cause termination when the current phase
67	<	* number reaches a threshold. Method {@code forceTermination} is also
68	<	* available to abruptly release waiting threads and allow them to
69	<	* terminate.
77	>	* <p> <b>Termination.</b> A {@code Phaser} may enter a
78	>	* <em>termination</em> state in which all 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 {@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	<	* <li>Phasers ensure lack of starvation when used by ForkJoinTasks.
105	<	*
106	<	* </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:
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> list) {
117	>	* void runTasks(List<Runnable> tasks) {
118		*   final Phaser phaser = new Phaser(1); // "1" to register self
119	<	*   for (Runnable r : list) {
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	<	*         r.run();
105	<	*         phaser.arriveAndDeregister();   // signal completion
125	>	*         task.run();
126		*       }
127		*     }.start();
128		*   }
129		*
130	<	*   doSomethingOnBehalfOfWorkers();
131	<	*   phaser.arrive(); // allow threads to start
112	<	*   int p = phaser.arriveAndDeregister(); // deregister self  ...
113	<	*   p = phaser.awaitAdvance(p); // ... and await arrival
114	<	*   otherActions(); // do other things while tasks execute
115	<	*   phaser.awaitAdvance(p); // await final completion
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> {@code
138	<	* void startTasks(List<Runnable> list, final int iterations) {
138	>	* void startTasks(List<Runnable> tasks, final int iterations) {
139		*   final Phaser phaser = new Phaser() {
140	<	*     public boolean onAdvance(int phase, int registeredParties) {
140	>	*     protected boolean onAdvance(int phase, int registeredParties) {
141		*       return phase >= iterations || registeredParties == 0;
142		*     }
143		*   };
144		*   phaser.register();
145	<	*   for (Runnable r : list) {
145	>	*   for (final Runnable task : tasks) {
146		*     phaser.register();
147		*     new Thread() {
148		*       public void run() {
149		*         do {
150	<	*           r.run();
150	>	*           task.run();
151		*           phaser.arriveAndAwaitAdvance();
152	<	*         } while(!phaser.isTerminated();
152	>	*         } while (!phaser.isTerminated());
153		*       }
154		*     }.start();
155		*   }
156		*   phaser.arriveAndDeregister(); // deregister self, don't wait
157		* }}</pre>
158		*
159	<	* <p> To create a set of tasks using a tree of Phasers,
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,
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:
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 b) {
191	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
192	<	*   if (step > 1) {
193	<	*     int i = lo;
194	<	*     while (i < hi) {
153	<	*       int r = Math.min(i + step, hi);
154	<	*       build(actions, i, r, new Phaser(b));
155	<	*       i = r;
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(b);
199	<	*       // assumes new Task(b) performs b.register()
198	>	*       actions[i] = new Task(ph);
199	>	*       // assumes new Task(ph) performs ph.register()
200		*   }
201		* }
202		* // .. initially called, for n tasks via
#	Line 168 | Line 207 | import java.lang.reflect.*;
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 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	–	* count being lowest 16 bits.
240		*/
241		private volatile long state;
242
243	<	private static final int ushortBits = 16;
244	<	private static final int ushortMask = 0xffff;
245	<	private static final int phaseMask  = 0x7fffffff;
243	>	private static final int  MAX_COUNT      = 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 long UNARRIVED_MASK = 0xffffL;
248	>	private static final long PARTIES_MASK   = 0xffff0000L;
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) >>> 16;
260	>	return ((int) (s & PARTIES_MASK)) >>> 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) | (((long)parties) << 16) |
228	–	(long)unarrived);
229	–	}
230	–
231	–	private static long trippedStateFor(int phase, int parties) {
232	–	long lp = (long)parties;
233	–	return (((long)phase) << 32) | (lp << 16) | lp;
234	–	}
235	–
236	–	/**
237	–	* Returns message string for bad bounds exceptions
238	–	*/
239	–	private static String badBounds(int parties, int unarrived) {
240	–	return ("Attempt to set " + unarrived +
241	–	" unarrived of " + parties + " parties");
242	–	}
243	–
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
255	–	// Wait queues
256	–
282		/**
283		* Heads of Treiber stacks for waiting threads. To eliminate
284	<	* contention while releasing some threads while adding others, we
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 int doArrive(long adj) {
305	>	long s;
306	>	int phase, unarrived;
307	>	while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0) {
308	>	if ((unarrived = (int)(s & UNARRIVED_MASK)) != 0) {
309	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s -= adj)) {
310	>	if (unarrived == 1) {
311	>	Phaser par;
312	>	long p = s & PARTIES_MASK; // unshifted parties field
313	>	long lu = p >>> PARTIES_SHIFT;
314	>	int u = (int)lu;
315	>	int nextPhase = (phase + 1) & MAX_PHASE;
316	>	long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
317	>	if ((par = parent) == null) {
318	>	UNSAFE.compareAndSwapLong
319	>	(this, stateOffset, s, onAdvance(phase, u)?
320	>	next | TERMINATION_PHASE : next);
321	>	releaseWaiters(phase);
322	>	}
323	>	else {
324	>	par.doArrive(u == 0?
325	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
326	>	if ((int)(par.state >>> PHASE_SHIFT) != nextPhase ||
327	>	((int)(state >>> PHASE_SHIFT) != nextPhase &&
328	>	!UNSAFE.compareAndSwapLong(this, stateOffset,
329	>	s, next)))
330	>	reconcileState();
331	>	}
332	>	}
333	>	break;
334	>	}
335	>	}
336	>	else if (state == s && reconcileState() == s) // recheck
337	>	throw new IllegalStateException(badArrive());
338	>	}
339	>	return phase;
340	>	}
341	>
342	>	/**
343	>	* Returns message string for bounds exceptions on arrival.
344	>	* Declared out of-line from doArrive to reduce string op bulk.
345		*/
346	<	private long getReconciledState() {
347	<	return parent == null? state : reconcileState();
346	>	private String badArrive() {
347	>	return ("Attempted arrival of unregistered party for " +
348	>	this.toString());
349		}
350
351		/**
352	<	* Recursively resolves state.
352	>	* Implementation of register, bulkRegister
353	>	*
354	>	* @param registrations number to add to both parties and unarrived fields
355	>	*/
356	>	private int doRegister(int registrations) {
357	>	long adj = (long)registrations; // adjustment to state
358	>	adj |= adj << PARTIES_SHIFT;
359	>	Phaser par = parent;
360	>	long s;
361	>	int phase;
362	>	while ((phase = (int)((s = (par == null? state : reconcileState()))
363	>	>>> PHASE_SHIFT)) >= 0) {
364	>	int parties = ((int)(s & PARTIES_MASK)) >>> PARTIES_SHIFT;
365	>	if (parties != 0 && (s & UNARRIVED_MASK) == 0)
366	>	internalAwaitAdvance(phase, null); // wait for onAdvance
367	>	else if (parties + registrations > MAX_COUNT)
368	>	throw new IllegalStateException(badRegister());
369	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
370	>	break;
371	>	}
372	>	return phase;
373	>	}
374	>
375	>	/**
376	>	* Returns message string for bounds exceptions on registration
377	>	*/
378	>	private String badRegister() {
379	>	return ("Attempt to register more than " + MAX_COUNT + " parties for "+
380	>	this.toString());
381	>	}
382	>
383	>	/**
384	>	* Recursively resolves lagged phase propagation from root if
385	>	* necessary.
386		*/
387		private long reconcileState() {
388	<	Phaser p = parent;
389	<	long s = state;
390	<	if (p != null) {
391	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
392	<	long parentState = p.getReconciledState();
393	<	int parentPhase = phaseOf(parentState);
394	<	int phase = phaseOf(s = state);
395	<	if (phase != parentPhase) {
396	<	long next = trippedStateFor(parentPhase, partiesOf(s));
397	<	if (casState(s, next)) {
398	<	releaseWaiters(phase);
399	<	s = next;
400	<	}
388	>	Phaser par = parent;
389	>	if (par == null)
390	>	return state;
391	>	Phaser rt = root;
392	>	long s;
393	>	int phase, rPhase;
394	>	while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0 &&
395	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
396	>	if (rPhase < 0 || (s & UNARRIVED_MASK) == 0) {
397	>	long ps = par.parent == null? par.state : par.reconcileState();
398	>	int pPhase = (int)(ps >>> PHASE_SHIFT);
399	>	if (pPhase < 0 || pPhase == ((phase + 1) & MAX_PHASE)) {
400	>	if (state != s)
401	>	continue;
402	>	long p = s & PARTIES_MASK;
403	>	long next = ((((long) pPhase) << PHASE_SHIFT) |
404	>	(p >>> PARTIES_SHIFT) | p);
405	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
406	>	return next;
407		}
408		}
409	+	if (state == s)
410	+	releaseWaiters(phase); // help release others
411		}
412		return s;
413		}
414
415		/**
416	<	* Creates a new Phaser without any initially registered parties,
416	>	* Creates a new phaser without any initially registered parties,
417		* initial phase number 0, and no parent. Any thread using this
418	<	* Phaser will need to first register for it.
418	>	* phaser will need to first register for it.
419		*/
420		public Phaser() {
421	<	this(null);
421	>	this(null, 0);
422		}
423
424		/**
425	<	* Creates a new Phaser with the given numbers of registered
425	>	* Creates a new phaser with the given number of registered
426		* unarrived parties, initial phase number 0, and no parent.
427	<	* @param parties the number of parties required to trip barrier.
427	>	*
428	>	* @param parties the number of parties required to trip barrier
429		* @throws IllegalArgumentException if parties less than zero
430	<	* or greater than the maximum number of parties supported.
430	>	* or greater than the maximum number of parties supported
431		*/
432		public Phaser(int parties) {
433		this(null, parties);
434		}
435
436		/**
437	<	* Creates a new Phaser with the given parent, without any
437	>	* Creates a new phaser with the given parent, without any
438		* initially registered parties. If parent is non-null this phaser
439		* is registered with the parent and its initial phase number is
440		* the same as that of parent phaser.
441	<	* @param parent the parent phaser.
441	>	*
442	>	* @param parent the parent phaser
443		*/
444		public Phaser(Phaser parent) {
445	<	int phase = 0;
329	<	this.parent = parent;
330	<	if (parent != null) {
331	<	this.root = parent.root;
332	<	phase = parent.register();
333	<	}
334	<	else
335	<	this.root = this;
336	<	this.state = trippedStateFor(phase, 0);
445	>	this(parent, 0);
446		}
447
448		/**
449	<	* Creates a new Phaser with the given parent and numbers of
450	<	* registered unarrived parties. If parent is non-null this phaser
449	>	* Creates a new phaser with the given parent and number of
450	>	* registered unarrived parties. If parent is non-null, this phaser
451		* is registered with the parent and its initial phase number is
452		* the same as that of parent phaser.
453	<	* @param parent the parent phaser.
454	<	* @param parties the number of parties required to trip barrier.
453	>	*
454	>	* @param parent the parent phaser
455	>	* @param parties the number of parties required to trip barrier
456		* @throws IllegalArgumentException if parties less than zero
457	<	* or greater than the maximum number of parties supported.
457	>	* or greater than the maximum number of parties supported
458		*/
459		public Phaser(Phaser parent, int parties) {
460	<	if (parties < 0 || parties > ushortMask)
460	>	if (parties < 0 || parties > MAX_COUNT)
461		throw new IllegalArgumentException("Illegal number of parties");
462	<	int phase = 0;
462	>	int phase;
463		this.parent = parent;
464		if (parent != null) {
465	<	this.root = parent.root;
465	>	Phaser r = parent.root;
466	>	this.root = r;
467	>	this.evenQ = r.evenQ;
468	>	this.oddQ = r.oddQ;
469		phase = parent.register();
470		}
471	<	else
471	>	else {
472		this.root = this;
473	<	this.state = trippedStateFor(phase, parties);
473	>	this.evenQ = new AtomicReference<QNode>();
474	>	this.oddQ = new AtomicReference<QNode>();
475	>	phase = 0;
476	>	}
477	>	long p = (long)parties;
478	>	this.state = (((long) phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
479		}
480
481		/**
482		* Adds a new unarrived party to this phaser.
483	<	* @return the current barrier phase number upon registration
483	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
484	>	* this method may wait until its completion before registering.
485	>	*
486	>	* @return the arrival phase number to which this registration applied
487		* @throws IllegalStateException if attempting to register more
488	<	* than the maximum supported number of parties.
488	>	* than the maximum supported number of parties
489		*/
490		public int register() {
491		return doRegister(1);
#	Line 372 | Line 493 | public class Phaser {
493
494		/**
495		* Adds the given number of new unarrived parties to this phaser.
496	<	* @param parties the number of parties required to trip barrier.
497	<	* @return the current barrier phase number upon registration
496	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
497	>	* this method may wait until its completion before registering.
498	>	*
499	>	* @param parties the number of additional parties required to trip barrier
500	>	* @return the arrival phase number to which this registration applied
501		* @throws IllegalStateException if attempting to register more
502	<	* than the maximum supported number of parties.
502	>	* than the maximum supported number of parties
503	>	* @throws IllegalArgumentException if {@code parties < 0}
504		*/
505		public int bulkRegister(int parties) {
506		if (parties < 0)
507		throw new IllegalArgumentException();
508	+	if (parties > MAX_COUNT)
509	+	throw new IllegalStateException(badRegister());
510		if (parties == 0)
511		return getPhase();
512		return doRegister(parties);
513		}
514
515		/**
389	–	* Shared code for register, bulkRegister
390	–	*/
391	–	private int doRegister(int registrations) {
392	–	int phase;
393	–	for (;;) {
394	–	long s = getReconciledState();
395	–	phase = phaseOf(s);
396	–	int unarrived = unarrivedOf(s) + registrations;
397	–	int parties = partiesOf(s) + registrations;
398	–	if (phase < 0)
399	–	break;
400	–	if (parties > ushortMask || unarrived > ushortMask)
401	–	throw new IllegalStateException(badBounds(parties, unarrived));
402	–	if (phase == phaseOf(root.state) &&
403	–	casState(s, stateFor(phase, parties, unarrived)))
404	–	break;
405	–	}
406	–	return phase;
407	–	}
408	–
409	–	/**
516		* Arrives at the barrier, but does not wait for others.  (You can
517	<	* in turn wait for others via {@link #awaitAdvance}).
517	>	* in turn wait for others via {@link #awaitAdvance}).  It is an
518	>	* unenforced usage error for an unregistered party to invoke this
519	>	* method.
520		*
521	<	* @return the barrier phase number upon entry to this method, or a
414	<	* negative value if terminated;
521	>	* @return the arrival phase number, or a negative value if terminated
522		* @throws IllegalStateException if not terminated and the number
523	<	* of unarrived parties would become negative.
523	>	* of unarrived parties would become negative
524		*/
525		public int arrive() {
526	<	int phase;
420	<	for (;;) {
421	<	long s = state;
422	<	phase = phaseOf(s);
423	<	if (phase < 0)
424	<	break;
425	<	int parties = partiesOf(s);
426	<	int unarrived = unarrivedOf(s) - 1;
427	<	if (unarrived > 0) {        // Not the last arrival
428	<	if (casState(s, s - 1)) // s-1 adds one arrival
429	<	break;
430	<	}
431	<	else if (unarrived == 0) {  // the last arrival
432	<	Phaser par = parent;
433	<	if (par == null) {      // directly trip
434	<	if (casState
435	<	(s,
436	<	trippedStateFor(onAdvance(phase, parties)? -1 :
437	<	((phase + 1) & phaseMask), parties))) {
438	<	releaseWaiters(phase);
439	<	break;
440	<	}
441	<	}
442	<	else {                  // cascade to parent
443	<	if (casState(s, s - 1)) { // zeroes unarrived
444	<	par.arrive();
445	<	reconcileState();
446	<	break;
447	<	}
448	<	}
449	<	}
450	<	else if (phase != phaseOf(root.state)) // or if unreconciled
451	<	reconcileState();
452	<	else
453	<	throw new IllegalStateException(badBounds(parties, unarrived));
454	<	}
455	<	return phase;
526	>	return doArrive(ONE_ARRIVAL);
527		}
528
529		/**
530	<	* Arrives at the barrier, and deregisters from it, without
531	<	* waiting for others. Deregistration reduces number of parties
530	>	* Arrives at the barrier and deregisters from it without waiting
531	>	* for others. Deregistration reduces the number of parties
532		* required to trip the barrier in future phases.  If this phaser
533		* has a parent, and deregistration causes this phaser to have
534	<	* zero parties, this phaser is also deregistered from its parent.
534	>	* zero parties, this phaser also arrives at and is deregistered
535	>	* from its parent.  It is an unenforced usage error for an
536	>	* unregistered party to invoke this method.
537		*
538	<	* @return the current barrier phase number upon entry to
466	<	* this method, or a negative value if terminated;
538	>	* @return the arrival phase number, or a negative value if terminated
539		* @throws IllegalStateException if not terminated and the number
540	<	* of registered or unarrived parties would become negative.
540	>	* of registered or unarrived parties would become negative
541		*/
542		public int arriveAndDeregister() {
543	<	// similar code to arrive, but too different to merge
472	<	Phaser par = parent;
473	<	int phase;
474	<	for (;;) {
475	<	long s = state;
476	<	phase = phaseOf(s);
477	<	if (phase < 0)
478	<	break;
479	<	int parties = partiesOf(s) - 1;
480	<	int unarrived = unarrivedOf(s) - 1;
481	<	if (parties >= 0) {
482	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
483	<	if (casState
484	<	(s,
485	<	stateFor(phase, parties, unarrived))) {
486	<	if (unarrived == 0) {
487	<	par.arriveAndDeregister();
488	<	reconcileState();
489	<	}
490	<	break;
491	<	}
492	<	continue;
493	<	}
494	<	if (unarrived == 0) {
495	<	if (casState
496	<	(s,
497	<	trippedStateFor(onAdvance(phase, parties)? -1 :
498	<	((phase + 1) & phaseMask), parties))) {
499	<	releaseWaiters(phase);
500	<	break;
501	<	}
502	<	continue;
503	<	}
504	<	if (par != null && phase != phaseOf(root.state)) {
505	<	reconcileState();
506	<	continue;
507	<	}
508	<	}
509	<	throw new IllegalStateException(badBounds(parties, unarrived));
510	<	}
511	<	return phase;
543	>	return doArrive(ONE_ARRIVAL|ONE_PARTY);
544		}
545
546		/**
547		* Arrives at the barrier and awaits others. Equivalent in effect
548	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
549	<	* await with interruption of timeout, and/or deregister upon
550	<	* arrival, you can arrange them using analogous constructions.
551	<	* @return the phase on entry to this method
548	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
549	>	* interruption or timeout, you can arrange this with an analogous
550	>	* construction using one of the other forms of the {@code
551	>	* awaitAdvance} method.  If instead you need to deregister upon
552	>	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
553	>	* usage error for an unregistered party to invoke this method.
554	>	*
555	>	* @return the arrival phase number, or a negative number if terminated
556		* @throws IllegalStateException if not terminated and the number
557	<	* of unarrived parties would become negative.
557	>	* of unarrived parties would become negative
558		*/
559		public int arriveAndAwaitAdvance() {
560		return awaitAdvance(arrive());
561		}
562
563		/**
564	<	* Awaits the phase of the barrier to advance from the given
565	<	* value, or returns immediately if argument is negative or this
566	<	* barrier is terminated.
567	<	* @param phase the phase on entry to this method
568	<	* @return the phase on exit from this method
564	>	* Awaits the phase of the barrier to advance from the given phase
565	>	* value, returning immediately if the current phase of the
566	>	* barrier is not equal to the given phase value or this barrier
567	>	* is terminated.
568	>	*
569	>	* @param phase an arrival phase number, or negative value if
570	>	* terminated; this argument is normally the value returned by a
571	>	* previous call to {@code arrive} or its variants
572	>	* @return the next arrival phase number, or a negative value
573	>	* if terminated or argument is negative
574		*/
575		public int awaitAdvance(int phase) {
576		if (phase < 0)
577		return phase;
578	<	long s = getReconciledState();
538	<	int p = phaseOf(s);
578	>	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
579		if (p != phase)
580		return p;
581	<	if (unarrivedOf(s) == 0 && parent != null)
542	<	parent.awaitAdvance(phase);
543	<	// Fall here even if parent waited, to reconcile and help release
544	<	return untimedWait(phase);
581	>	return internalAwaitAdvance(phase, null);
582		}
583
584		/**
585	<	* Awaits the phase of the barrier to advance from the given
586	<	* value, or returns immediately if argument is negative or this
587	<	* barrier is terminated, or throws InterruptedException if
588	<	* interrupted while waiting.
589	<	* @param phase the phase on entry to this method
590	<	* @return the phase on exit from this method
585	>	* Awaits the phase of the barrier to advance from the given phase
586	>	* value, throwing {@code InterruptedException} if interrupted
587	>	* while waiting, or returning immediately if the current phase of
588	>	* the barrier is not equal to the given phase value or this
589	>	* barrier is terminated.
590	>	*
591	>	* @param phase an arrival phase number, or negative value if
592	>	* terminated; this argument is normally the value returned by a
593	>	* previous call to {@code arrive} or its variants
594	>	* @return the next arrival phase number, or a negative value
595	>	* if terminated or argument is negative
596		* @throws InterruptedException if thread interrupted while waiting
597		*/
598		public int awaitAdvanceInterruptibly(int phase)
599		throws InterruptedException {
600		if (phase < 0)
601		return phase;
602	<	long s = getReconciledState();
561	<	int p = phaseOf(s);
602	>	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
603		if (p != phase)
604		return p;
605	<	if (unarrivedOf(s) == 0 && parent != null)
606	<	parent.awaitAdvanceInterruptibly(phase);
607	<	return interruptibleWait(phase);
605	>	QNode node = new QNode(this, phase, true, false, 0L);
606	>	p = internalAwaitAdvance(phase, node);
607	>	if (node.wasInterrupted)
608	>	throw new InterruptedException();
609	>	else
610	>	return p;
611		}
612
613		/**
614	<	* Awaits the phase of the barrier to advance from the given value
615	<	* or the given timeout elapses, or returns immediately if
616	<	* argument is negative or this barrier is terminated.
617	<	* @param phase the phase on entry to this method
618	<	* @return the phase on exit from this method
614	>	* Awaits the phase of the barrier to advance from the given phase
615	>	* value or the given timeout to elapse, throwing {@code
616	>	* InterruptedException} if interrupted while waiting, or
617	>	* returning immediately if the current phase of the barrier is
618	>	* not equal to the given phase value or this barrier is
619	>	* terminated.
620	>	*
621	>	* @param phase an arrival phase number, or negative value if
622	>	* terminated; this argument is normally the value returned by a
623	>	* previous call to {@code arrive} or its variants
624	>	* @param timeout how long to wait before giving up, in units of
625	>	*        {@code unit}
626	>	* @param unit a {@code TimeUnit} determining how to interpret the
627	>	*        {@code timeout} parameter
628	>	* @return the next arrival phase number, or a negative value
629	>	* if terminated or argument is negative
630		* @throws InterruptedException if thread interrupted while waiting
631		* @throws TimeoutException if timed out while waiting
632		*/
633	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
633	>	public int awaitAdvanceInterruptibly(int phase,
634	>	long timeout, TimeUnit unit)
635		throws InterruptedException, TimeoutException {
636	+	long nanos = unit.toNanos(timeout);
637		if (phase < 0)
638		return phase;
639	<	long s = getReconciledState();
583	<	int p = phaseOf(s);
639	>	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
640		if (p != phase)
641		return p;
642	<	if (unarrivedOf(s) == 0 && parent != null)
643	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
644	<	return timedWait(phase, unit.toNanos(timeout));
642	>	QNode node = new QNode(this, phase, true, true, nanos);
643	>	p = internalAwaitAdvance(phase, node);
644	>	if (node.wasInterrupted)
645	>	throw new InterruptedException();
646	>	else if (p == phase)
647	>	throw new TimeoutException();
648	>	else
649	>	return p;
650		}
651
652		/**
#	Line 596 | Line 657 | public class Phaser {
657		* unexpected exceptions.
658		*/
659		public void forceTermination() {
660	<	for (;;) {
661	<	long s = getReconciledState();
662	<	int phase = phaseOf(s);
663	<	int parties = partiesOf(s);
664	<	int unarrived = unarrivedOf(s);
665	<	if (phase < 0 ||
666	<	casState(s, stateFor(-1, parties, unarrived))) {
606	<	releaseWaiters(0);
607	<	releaseWaiters(1);
608	<	if (parent != null)
609	<	parent.forceTermination();
610	<	return;
611	<	}
612	<	}
660	>	Phaser r = root;    // force at root then reconcile
661	>	long s;
662	>	while ((s = r.state) >= 0)
663	>	UNSAFE.compareAndSwapLong(r, stateOffset, s, s | TERMINATION_PHASE);
664	>	reconcileState();
665	>	releaseWaiters(0); // signal all threads
666	>	releaseWaiters(1);
667		}
668
669		/**
670		* Returns the current phase number. The maximum phase number is
671		* {@code Integer.MAX_VALUE}, after which it restarts at
672		* zero. Upon termination, the phase number is negative.
673	+	*
674		* @return the phase number, or a negative value if terminated
675		*/
676		public final int getPhase() {
677	<	return phaseOf(getReconciledState());
623	<	}
624	<
625	<	/**
626	<	* Returns {@code true} if the current phase number equals the given phase.
627	<	* @param phase the phase
628	<	* @return {@code true} if the current phase number equals the given phase
629	<	*/
630	<	public final boolean hasPhase(int phase) {
631	<	return phaseOf(getReconciledState()) == phase;
677	>	return (int)((parent == null? state : reconcileState()) >>> PHASE_SHIFT);
678		}
679
680		/**
681		* Returns the number of parties registered at this barrier.
682	+	*
683		* @return the number of parties
684		*/
685		public int getRegisteredParties() {
686	<	return partiesOf(state);
686	>	return partiesOf(parent == null? state : reconcileState());
687		}
688
689		/**
690	<	* Returns the number of parties that have arrived at the current
691	<	* phase of this barrier.
690	>	* Returns the number of registered parties that have arrived at
691	>	* the current phase of this barrier.
692	>	*
693		* @return the number of arrived parties
694		*/
695		public int getArrivedParties() {
696	<	return arrivedOf(state);
696	>	return arrivedOf(parent == null? state : reconcileState());
697		}
698
699		/**
700		* Returns the number of registered parties that have not yet
701		* arrived at the current phase of this barrier.
702	+	*
703		* @return the number of unarrived parties
704		*/
705		public int getUnarrivedParties() {
706	<	return unarrivedOf(state);
706	>	return unarrivedOf(parent == null? state : reconcileState());
707		}
708
709		/**
710	<	* Returns the parent of this phaser, or null if none.
711	<	* @return the parent of this phaser, or null if none
710	>	* Returns the parent of this phaser, or {@code null} if none.
711	>	*
712	>	* @return the parent of this phaser, or {@code null} if none
713		*/
714		public Phaser getParent() {
715		return parent;
#	Line 668 | Line 718 | public class Phaser {
718		/**
719		* Returns the root ancestor of this phaser, which is the same as
720		* this phaser if it has no parent.
721	+	*
722		* @return the root ancestor of this phaser
723		*/
724		public Phaser getRoot() {
#	Line 676 | Line 727 | public class Phaser {
727
728		/**
729		* Returns {@code true} if this barrier has been terminated.
730	+	*
731		* @return {@code true} if this barrier has been terminated
732		*/
733		public boolean isTerminated() {
734	<	return getPhase() < 0;
734	>	return (parent == null? state : reconcileState()) < 0;
735		}
736
737		/**
738	<	* Overridable method to perform an action upon phase advance, and
739	<	* to control termination. This method is invoked whenever the
740	<	* barrier is tripped (and thus all other waiting parties are
741	<	* dormant). If it returns true, then, rather than advance the
742	<	* phase number, this barrier will be set to a final termination
743	<	* state, and subsequent calls to {@code isTerminated} will
744	<	* return true.
738	>	* Overridable method to perform an action upon impending phase
739	>	* advance, and to control termination. This method is invoked
740	>	* upon arrival of the party tripping the barrier (when all other
741	>	* waiting parties are dormant).  If this method returns {@code
742	>	* true}, then, rather than advance the phase number, this barrier
743	>	* will be set to a final termination state, and subsequent calls
744	>	* to {@link #isTerminated} will return true. Any (unchecked)
745	>	* Exception or Error thrown by an invocation of this method is
746	>	* propagated to the party attempting to trip the barrier, in
747	>	* which case no advance occurs.
748		*
749	<	* <p> The default version returns true when the number of
749	>	* <p>The arguments to this method provide the state of the phaser
750	>	* prevailing for the current transition.  The effects of invoking
751	>	* arrival, registration, and waiting methods on this Phaser from
752	>	* within {@code onAdvance} are unspecified and should not be
753	>	* relied on.
754	>	*
755	>	* <p>If this Phaser is a member of a tiered set of Phasers, then
756	>	* {@code onAdvance} is invoked only for its root Phaser on each
757	>	* advance.
758	>	*
759	>	* <p>The default version returns {@code true} when the number of
760		* registered parties is zero. Normally, overrides that arrange
761		* termination for other reasons should also preserve this
762		* property.
763		*
699	–	* <p> You may override this method to perform an action with side
700	–	* effects visible to participating tasks, but it is in general
701	–	* only sensible to do so in designs where all parties register
702	–	* before any arrive, and all {@code awaitAdvance} at each phase.
703	–	* Otherwise, you cannot ensure lack of interference. In
704	–	* particular, this method may be invoked more than once per
705	–	* transition if other parties successfully register while the
706	–	* invocation of this method is in progress, thus postponing the
707	–	* transition until those parties also arrive, re-triggering this
708	–	* method.
709	–	*
764		* @param phase the phase number on entering the barrier
765		* @param registeredParties the current number of registered parties
766		* @return {@code true} if this barrier should terminate
#	Line 725 | Line 779 | public class Phaser {
779		* @return a string identifying this barrier, as well as its state
780		*/
781		public String toString() {
782	<	long s = getReconciledState();
782	>	long s = reconcileState();
783		return super.toString() +
784		"[phase = " + phaseOf(s) +
785		" parties = " + partiesOf(s) +
786		" arrived = " + arrivedOf(s) + "]";
787		}
788
789	<	// methods for waiting
789	>	/**
790	>	* Removes and signals threads from queue for phase
791	>	*/
792	>	private void releaseWaiters(int phase) {
793	>	AtomicReference<QNode> head = queueFor(phase);
794	>	QNode q;
795	>	int p;
796	>	while ((q = head.get()) != null &&
797	>	((p = q.phase) == phase ||
798	>	(int)(root.state >>> PHASE_SHIFT) != p)) {
799	>	if (head.compareAndSet(q, q.next))
800	>	q.signal();
801	>	}
802	>	}
803	>
804	>	/**
805	>	* Tries to enqueue given node in the appropriate wait queue.
806	>	*
807	>	* @return true if successful
808	>	*/
809	>	private boolean tryEnqueue(int phase, QNode node) {
810	>	releaseWaiters(phase-1); // ensure old queue clean
811	>	AtomicReference<QNode> head = queueFor(phase);
812	>	QNode q = head.get();
813	>	return ((q == null || q.phase == phase) &&
814	>	(int)(root.state >>> PHASE_SHIFT) == phase &&
815	>	head.compareAndSet(node.next = q, node));
816	>	}
817	>
818	>	/** The number of CPUs, for spin control */
819	>	private static final int NCPU = Runtime.getRuntime().availableProcessors();
820	>
821	>	/**
822	>	* The number of times to spin before blocking while waiting for
823	>	* advance, per arrival while waiting. On multiprocessors, fully
824	>	* blocking and waking up a large number of threads all at once is
825	>	* usually a very slow process, so we use rechargeable spins to
826	>	* avoid it when threads regularly arrive: When a thread in
827	>	* internalAwaitAdvance notices another arrival before blocking,
828	>	* and there appear to be enough CPUs available, it spins
829	>	* SPINS_PER_ARRIVAL more times before continuing to try to
830	>	* block. The value trades off good-citizenship vs big unnecessary
831	>	* slowdowns.
832	>	*/
833	>	static final int SPINS_PER_ARRIVAL = NCPU < 2? 1 : 1 << 8;
834	>
835	>	/**
836	>	* Possibly blocks and waits for phase to advance unless aborted.
837	>	*
838	>	* @param phase current phase
839	>	* @param node if nonnull, the wait node to track interrupt and timeout;
840	>	* if null, denotes noninterruptible wait
841	>	* @return current phase
842	>	*/
843	>	private int internalAwaitAdvance(int phase, QNode node) {
844	>	Phaser current = this;       // to eventually wait at root if tiered
845	>	Phaser par = parent;
846	>	boolean queued = false;
847	>	int spins = SPINS_PER_ARRIVAL;
848	>	int lastUnarrived = -1;      // to increase spins upon change
849	>	long s;
850	>	int p;
851	>	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
852	>	int unarrived = (int)(s & UNARRIVED_MASK);
853	>	if (unarrived != lastUnarrived) {
854	>	if ((lastUnarrived = unarrived) < NCPU)
855	>	spins += SPINS_PER_ARRIVAL;
856	>	}
857	>	else if (unarrived == 0 && par != null) {
858	>	current = par;       // if all arrived, use parent
859	>	par = par.parent;
860	>	}
861	>	else if (spins > 0)
862	>	--spins;
863	>	else if (node == null)
864	>	node = new QNode(this, phase, false, false, 0L);
865	>	else if (node.isReleasable())
866	>	break;
867	>	else if (!queued)
868	>	queued = tryEnqueue(phase, node);
869	>	else {
870	>	try {
871	>	ForkJoinPool.managedBlock(node);
872	>	} catch (InterruptedException ie) {
873	>	node.wasInterrupted = true;
874	>	}
875	>	}
876	>	}
877	>	if (node != null) {
878	>	if (node.thread != null)
879	>	node.thread = null;
880	>	if (!node.interruptible && node.wasInterrupted)
881	>	Thread.currentThread().interrupt();
882	>	}
883	>	if (p == phase && parent != null)
884	>	p = (int)(reconcileState() >>> PHASE_SHIFT);
885	>	if (p != phase)
886	>	releaseWaiters(phase);
887	>	return p;
888	>	}
889
890		/**
891		* Wait nodes for Treiber stack representing wait queue
#	Line 740 | Line 893 | public class Phaser {
893		static final class QNode implements ForkJoinPool.ManagedBlocker {
894		final Phaser phaser;
895		final int phase;
743	–	final long startTime;
744	–	final long nanos;
745	–	final boolean timed;
896		final boolean interruptible;
897	<	volatile boolean wasInterrupted = false;
897	>	final boolean timed;
898	>	boolean wasInterrupted;
899	>	long nanos;
900	>	long lastTime;
901		volatile Thread thread; // nulled to cancel wait
902		QNode next;
903	+
904		QNode(Phaser phaser, int phase, boolean interruptible,
905	<	boolean timed, long startTime, long nanos) {
905	>	boolean timed, long nanos) {
906		this.phaser = phaser;
907		this.phase = phase;
754	–	this.timed = timed;
908		this.interruptible = interruptible;
756	–	this.startTime = startTime;
909		this.nanos = nanos;
910	+	this.timed = timed;
911	+	this.lastTime = timed? System.nanoTime() : 0L;
912		thread = Thread.currentThread();
913		}
914	+
915		public boolean isReleasable() {
916	<	return (thread == null ||
917	<	phaser.getPhase() != phase ||
918	<	(interruptible && wasInterrupted) ||
919	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
916	>	Thread t = thread;
917	>	if (t != null) {
918	>	if (phaser.getPhase() != phase)
919	>	t = null;
920	>	else {
921	>	if (Thread.interrupted())
922	>	wasInterrupted = true;
923	>	if (interruptible && wasInterrupted)
924	>	t = null;
925	>	else if (timed) {
926	>	if (nanos > 0) {
927	>	long now = System.nanoTime();
928	>	nanos -= now - lastTime;
929	>	lastTime = now;
930	>	}
931	>	if (nanos <= 0)
932	>	t = null;
933	>	}
934	>	}
935	>	if (t != null)
936	>	return false;
937	>	thread = null;
938	>	}
939	>	return true;
940		}
941	+
942		public boolean block() {
943	<	if (Thread.interrupted()) {
944	<	wasInterrupted = true;
945	<	if (interruptible)
770	<	return true;
771	<	}
772	<	if (!timed)
943	>	if (isReleasable())
944	>	return true;
945	>	else if (!timed)
946		LockSupport.park(this);
947	<	else {
948	<	long waitTime = nanos - (System.nanoTime() - startTime);
776	<	if (waitTime <= 0)
777	<	return true;
778	<	LockSupport.parkNanos(this, waitTime);
779	<	}
947	>	else if (nanos > 0)
948	>	LockSupport.parkNanos(this, nanos);
949		return isReleasable();
950		}
951	+
952		void signal() {
953		Thread t = thread;
954		if (t != null) {
#	Line 786 | Line 956 | public class Phaser {
956		LockSupport.unpark(t);
957		}
958		}
789	–	boolean doWait() {
790	–	if (thread != null) {
791	–	try {
792	–	ForkJoinPool.managedBlock(this, false);
793	–	} catch (InterruptedException ie) {
794	–	}
795	–	}
796	–	return wasInterrupted;
797	–	}
798	–
959		}
960
961	<	/**
802	<	* Removes and signals waiting threads from wait queue
803	<	*/
804	<	private void releaseWaiters(int phase) {
805	<	AtomicReference<QNode> head = queueFor(phase);
806	<	QNode q;
807	<	while ((q = head.get()) != null) {
808	<	if (head.compareAndSet(q, q.next))
809	<	q.signal();
810	<	}
811	<	}
961	>	// Unsafe mechanics
962
963	<	/**
964	<	* Tries to enqueue given node in the appropriate wait queue
965	<	* @return true if successful
816	<	*/
817	<	private boolean tryEnqueue(QNode node) {
818	<	AtomicReference<QNode> head = queueFor(node.phase);
819	<	return head.compareAndSet(node.next = head.get(), node);
820	<	}
821	<
822	<	/**
823	<	* Enqueues node and waits unless aborted or signalled.
824	<	* @return current phase
825	<	*/
826	<	private int untimedWait(int phase) {
827	<	QNode node = null;
828	<	boolean queued = false;
829	<	boolean interrupted = false;
830	<	int p;
831	<	while ((p = getPhase()) == phase) {
832	<	if (Thread.interrupted())
833	<	interrupted = true;
834	<	else if (node == null)
835	<	node = new QNode(this, phase, false, false, 0, 0);
836	<	else if (!queued)
837	<	queued = tryEnqueue(node);
838	<	else
839	<	interrupted = node.doWait();
840	<	}
841	<	if (node != null)
842	<	node.thread = null;
843	<	releaseWaiters(phase);
844	<	if (interrupted)
845	<	Thread.currentThread().interrupt();
846	<	return p;
847	<	}
963	>	private static final sun.misc.Unsafe UNSAFE = getUnsafe();
964	>	private static final long stateOffset =
965	>	objectFieldOffset("state", Phaser.class);
966
967	<	/**
968	<	* Interruptible version
969	<	* @return current phase
970	<	*/
971	<	private int interruptibleWait(int phase) throws InterruptedException {
972	<	QNode node = null;
973	<	boolean queued = false;
974	<	boolean interrupted = false;
975	<	int p;
858	<	while ((p = getPhase()) == phase && !interrupted) {
859	<	if (Thread.interrupted())
860	<	interrupted = true;
861	<	else if (node == null)
862	<	node = new QNode(this, phase, true, false, 0, 0);
863	<	else if (!queued)
864	<	queued = tryEnqueue(node);
865	<	else
866	<	interrupted = node.doWait();
867	<	}
868	<	if (node != null)
869	<	node.thread = null;
870	<	if (p != phase || (p = getPhase()) != phase)
871	<	releaseWaiters(phase);
872	<	if (interrupted)
873	<	throw new InterruptedException();
874	<	return p;
967	>	private static long objectFieldOffset(String field, Class<?> klazz) {
968	>	try {
969	>	return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
970	>	} catch (NoSuchFieldException e) {
971	>	// Convert Exception to corresponding Error
972	>	NoSuchFieldError error = new NoSuchFieldError(field);
973	>	error.initCause(e);
974	>	throw error;
975	>	}
976		}
977
978		/**
979	<	* Timeout version.
980	<	* @return current phase
979	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
980	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
981	>	* into a jdk.
982	>	*
983	>	* @return a sun.misc.Unsafe
984		*/
985	<	private int timedWait(int phase, long nanos)
882	<	throws InterruptedException, TimeoutException {
883	<	long startTime = System.nanoTime();
884	<	QNode node = null;
885	<	boolean queued = false;
886	<	boolean interrupted = false;
887	<	int p;
888	<	while ((p = getPhase()) == phase && !interrupted) {
889	<	if (Thread.interrupted())
890	<	interrupted = true;
891	<	else if (nanos - (System.nanoTime() - startTime) <= 0)
892	<	break;
893	<	else if (node == null)
894	<	node = new QNode(this, phase, true, true, startTime, nanos);
895	<	else if (!queued)
896	<	queued = tryEnqueue(node);
897	<	else
898	<	interrupted = node.doWait();
899	<	}
900	<	if (node != null)
901	<	node.thread = null;
902	<	if (p != phase || (p = getPhase()) != phase)
903	<	releaseWaiters(phase);
904	<	if (interrupted)
905	<	throw new InterruptedException();
906	<	if (p == phase)
907	<	throw new TimeoutException();
908	<	return p;
909	<	}
910	<
911	<	// Temporary Unsafe mechanics for preliminary release
912	<	private static Unsafe getUnsafe() throws Throwable {
985	>	private static sun.misc.Unsafe getUnsafe() {
986		try {
987	<	return Unsafe.getUnsafe();
987	>	return sun.misc.Unsafe.getUnsafe();
988		} catch (SecurityException se) {
989		try {
990		return java.security.AccessController.doPrivileged
991	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
992	<	public Unsafe run() throws Exception {
993	<	return getUnsafePrivileged();
991	>	(new java.security
992	>	.PrivilegedExceptionAction<sun.misc.Unsafe>() {
993	>	public sun.misc.Unsafe run() throws Exception {
994	>	java.lang.reflect.Field f = sun.misc
995	>	.Unsafe.class.getDeclaredField("theUnsafe");
996	>	f.setAccessible(true);
997	>	return (sun.misc.Unsafe) f.get(null);
998		}});
999		} catch (java.security.PrivilegedActionException e) {
1000	<	throw e.getCause();
1000	>	throw new RuntimeException("Could not initialize intrinsics",
1001	>	e.getCause());
1002		}
1003		}
1004		}
927	–
928	–	private static Unsafe getUnsafePrivileged()
929	–	throws NoSuchFieldException, IllegalAccessException {
930	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
931	–	f.setAccessible(true);
932	–	return (Unsafe) f.get(null);
933	–	}
934	–
935	–	private static long fieldOffset(String fieldName)
936	–	throws NoSuchFieldException {
937	–	return _unsafe.objectFieldOffset
938	–	(Phaser.class.getDeclaredField(fieldName));
939	–	}
940	–
941	–	static final Unsafe _unsafe;
942	–	static final long stateOffset;
943	–
944	–	static {
945	–	try {
946	–	_unsafe = getUnsafe();
947	–	stateOffset = fieldOffset("state");
948	–	} catch (Throwable e) {
949	–	throw new RuntimeException("Could not initialize intrinsics", e);
950	–	}
951	–	}
952	–
953	–	final boolean casState(long cmp, long val) {
954	–	return _unsafe.compareAndSwapLong(this, stateOffset, cmp, val);
955	–	}
1005		}

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