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Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.16 by jsr166, Wed Jul 22 01:36:51 2009 UTC vs.
Revision 1.80 by jsr166, Sun Sep 13 16:28:14 2015 UTC

#	Line 1 | Line 1
1		/*
2		* Written by Doug Lea with assistance from members of JCP JSR-166
3		* Expert Group and released to the public domain, as explained at
4	<	* http://creativecommons.org/licenses/publicdomain
4	>	* http://creativecommons.org/publicdomain/zero/1.0/
5		*/
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 phaser has an associated phase number. The phase
38	>	* number starts at zero, and advances when all parties arrive at the
39	>	* phaser, 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 phaser 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>
55	<	*
56	<	*
57	<	* <li> Barrier actions, performed by the task triggering a phase
58	<	* advance while others may be waiting, are arranged by overriding
59	<	* method {@code onAdvance}, that also controls termination.
60	<	* Overriding this method may be used to similar but more flexible
61	<	* effect as providing a barrier action to a CyclicBarrier.
62	<	*
63	<	* <li> Phasers may enter a <em>termination</em> state in which all
64	<	* actions immediately return without updating phaser state or waiting
65	<	* for advance, and indicating (via a negative phase value) that
66	<	* execution is complete.  Termination is triggered by executing the
67	<	* overridable {@code onAdvance} method that is invoked each time the
68	<	* barrier is about to be tripped. When a Phaser is controlling an
69	<	* action with a fixed number of iterations, it is often convenient to
70	<	* override this method to cause termination when the current phase
71	<	* number reaches a threshold. Method {@code forceTermination} is also
72	<	* available to abruptly release waiting threads and allow them to
73	<	* terminate.
70	<	*
71	<	* <li> Phasers may be tiered to reduce contention. Phasers with large
72	<	* numbers of parties that would otherwise experience heavy
73	<	* synchronization contention costs may instead be arranged in trees.
74	<	* This will typically greatly increase throughput even though it
75	<	* incurs somewhat greater per-operation overhead.
76	<	*
77	<	* <li> By default, {@code awaitAdvance} continues to wait even if
78	<	* the waiting thread is interrupted. And unlike the case in
79	<	* CyclicBarriers, exceptions encountered while tasks wait
80	<	* interruptibly or with timeout do not change the state of the
81	<	* barrier. If necessary, you can perform any associated recovery
82	<	* within handlers of those exceptions, often after invoking
83	<	* {@code forceTermination}.
84	<	*
85	<	* <li>Phasers ensure lack of starvation when used by ForkJoinTasks.
47	>	*   <li><b>Arrival.</b> Methods {@link #arrive} and
48	>	*       {@link #arriveAndDeregister} record arrival.  These methods
49	>	*       do not block, but return an associated <em>arrival phase
50	>	*       number</em>; that is, the phase number of the phaser to which
51	>	*       the arrival applied. When the final party for a given phase
52	>	*       arrives, an optional action is performed and the phase
53	>	*       advances.  These actions are performed by the party
54	>	*       triggering a phase advance, and are arranged by overriding
55	>	*       method {@link #onAdvance(int, int)}, which also controls
56	>	*       termination. Overriding this method is similar to, but more
57	>	*       flexible than, providing a barrier action to a {@code
58	>	*       CyclicBarrier}.
59	>	*
60	>	*   <li><b>Waiting.</b> Method {@link #awaitAdvance} requires an
61	>	*       argument indicating an arrival phase number, and returns when
62	>	*       the phaser 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 phaser. 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	+	* <p><b>Termination.</b> A phaser may enter a <em>termination</em>
78	+	* state, that may be checked using method {@link #isTerminated}. Upon
79	+	* termination, all synchronization methods immediately return without
80	+	* waiting for advance, as indicated by a negative return value.
81	+	* Similarly, attempts to register upon termination have no effect.
82	+	* Termination is triggered when an invocation of {@code onAdvance}
83	+	* returns {@code true}. The default implementation returns {@code
84	+	* true} if a deregistration has caused the number of registered
85	+	* parties to become zero.  As illustrated below, when phasers control
86	+	* actions with a fixed number of iterations, it is often convenient
87	+	* to override this method to cause termination when the current phase
88	+	* number reaches a threshold. Method {@link #forceTermination} is
89	+	* also available to abruptly release waiting threads and allow them
90	+	* to terminate.
91	+	*
92	+	* <p><b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
93	+	* constructed in tree structures) to reduce contention. Phasers with
94	+	* large numbers of parties that would otherwise experience heavy
95	+	* synchronization contention costs may instead be set up so that
96	+	* groups of sub-phasers share a common parent.  This may greatly
97	+	* increase throughput even though it incurs greater per-operation
98	+	* overhead.
99	+	*
100	+	* <p>In a tree of tiered phasers, registration and deregistration of
101	+	* child phasers with their parent are managed automatically.
102	+	* Whenever the number of registered parties of a child phaser becomes
103	+	* non-zero (as established in the {@link #Phaser(Phaser,int)}
104	+	* constructor, {@link #register}, or {@link #bulkRegister}), the
105	+	* child phaser is registered with its parent.  Whenever the number of
106	+	* registered parties becomes zero as the result of an invocation of
107	+	* {@link #arriveAndDeregister}, the child phaser is deregistered
108	+	* from its parent.
109	+	*
110	+	* <p><b>Monitoring.</b> While synchronization methods may be invoked
111	+	* only by registered parties, the current state of a phaser may be
112	+	* monitored by any caller.  At any given moment there are {@link
113	+	* #getRegisteredParties} parties in total, of which {@link
114	+	* #getArrivedParties} have arrived at the current phase ({@link
115	+	* #getPhase}).  When the remaining ({@link #getUnarrivedParties})
116	+	* parties arrive, the phase advances.  The values returned by these
117	+	* methods may reflect transient states and so are not in general
118	+	* useful for synchronization control.  Method {@link #toString}
119	+	* returns snapshots of these state queries in a form convenient for
120	+	* informal monitoring.
121	+	*
122		* <p><b>Sample usages:</b>
123		*
124	<	* <p>A Phaser may be used instead of a {@code CountDownLatch} to control
125	<	* a one-shot action serving a variable number of parties. The typical
126	<	* idiom is for the method setting this up to first register, then
127	<	* start the actions, then deregister, as in:
124	>	* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
125	>	* to control a one-shot action serving a variable number of parties.
126	>	* The typical idiom is for the method setting this up to first
127	>	* register, then start the actions, then deregister, as in:
128		*
129		*  <pre> {@code
130	<	* void runTasks(List<Runnable> list) {
130	>	* void runTasks(List<Runnable> tasks) {
131		*   final Phaser phaser = new Phaser(1); // "1" to register self
132	<	*   for (Runnable r : list) {
132	>	*   // create and start threads
133	>	*   for (final Runnable task : tasks) {
134		*     phaser.register();
135		*     new Thread() {
136		*       public void run() {
137		*         phaser.arriveAndAwaitAdvance(); // await all creation
138	<	*         r.run();
105	<	*         phaser.arriveAndDeregister();   // signal completion
138	>	*         task.run();
139		*       }
140		*     }.start();
141		*   }
142		*
143	<	*   doSomethingOnBehalfOfWorkers();
144	<	*   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
143	>	*   // allow threads to start and deregister self
144	>	*   phaser.arriveAndDeregister();
145		* }}</pre>
146		*
147		* <p>One way to cause a set of threads to repeatedly perform actions
148		* for a given number of iterations is to override {@code onAdvance}:
149		*
150		*  <pre> {@code
151	<	* void startTasks(List<Runnable> list, final int iterations) {
151	>	* void startTasks(List<Runnable> tasks, final int iterations) {
152		*   final Phaser phaser = new Phaser() {
153	<	*     public boolean onAdvance(int phase, int registeredParties) {
153	>	*     protected boolean onAdvance(int phase, int registeredParties) {
154		*       return phase >= iterations || registeredParties == 0;
155		*     }
156		*   };
157		*   phaser.register();
158	<	*   for (Runnable r : list) {
158	>	*   for (final Runnable task : tasks) {
159		*     phaser.register();
160		*     new Thread() {
161		*       public void run() {
162		*         do {
163	<	*           r.run();
163	>	*           task.run();
164		*           phaser.arriveAndAwaitAdvance();
165	<	*         } while(!phaser.isTerminated();
165	>	*         } while (!phaser.isTerminated());
166		*       }
167		*     }.start();
168		*   }
169		*   phaser.arriveAndDeregister(); // deregister self, don't wait
170		* }}</pre>
171		*
172	<	* <p> To create a set of tasks using a tree of Phasers,
173	<	* you could use code of the following form, assuming a
174	<	* Task class with a constructor accepting a Phaser that
175	<	* it registers for upon construction:
172	>	* If the main task must later await termination, it
173	>	* may re-register and then execute a similar loop:
174	>	*  <pre> {@code
175	>	*   // ...
176	>	*   phaser.register();
177	>	*   while (!phaser.isTerminated())
178	>	*     phaser.arriveAndAwaitAdvance();}</pre>
179	>	*
180	>	* <p>Related constructions may be used to await particular phase numbers
181	>	* in contexts where you are sure that the phase will never wrap around
182	>	* {@code Integer.MAX_VALUE}. For example:
183	>	*
184	>	*  <pre> {@code
185	>	* void awaitPhase(Phaser phaser, int phase) {
186	>	*   int p = phaser.register(); // assumes caller not already registered
187	>	*   while (p < phase) {
188	>	*     if (phaser.isTerminated())
189	>	*       // ... deal with unexpected termination
190	>	*     else
191	>	*       p = phaser.arriveAndAwaitAdvance();
192	>	*   }
193	>	*   phaser.arriveAndDeregister();
194	>	* }}</pre>
195	>	*
196	>	*
197	>	* <p>To create a set of {@code n} tasks using a tree of phasers, you
198	>	* could use code of the following form, assuming a Task class with a
199	>	* constructor accepting a {@code Phaser} that it registers with upon
200	>	* construction. After invocation of {@code build(new Task[n], 0, n,
201	>	* new Phaser())}, these tasks could then be started, for example by
202	>	* submitting to a pool:
203	>	*
204		*  <pre> {@code
205	<	* void build(Task[] actions, int lo, int hi, Phaser b) {
206	<	*   int step = (hi - lo) / TASKS_PER_PHASER;
207	<	*   if (step > 1) {
208	<	*     int i = lo;
209	<	*     while (i < hi) {
153	<	*       int r = Math.min(i + step, hi);
154	<	*       build(actions, i, r, new Phaser(b));
155	<	*       i = r;
205	>	* void build(Task[] tasks, int lo, int hi, Phaser ph) {
206	>	*   if (hi - lo > TASKS_PER_PHASER) {
207	>	*     for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
208	>	*       int j = Math.min(i + TASKS_PER_PHASER, hi);
209	>	*       build(tasks, i, j, new Phaser(ph));
210		*     }
211		*   } else {
212		*     for (int i = lo; i < hi; ++i)
213	<	*       actions[i] = new Task(b);
214	<	*       // assumes new Task(b) performs b.register()
213	>	*       tasks[i] = new Task(ph);
214	>	*       // assumes new Task(ph) performs ph.register()
215		*   }
216	<	* }
163	<	* // .. initially called, for n tasks via
164	<	* build(new Task[n], 0, n, new Phaser());}</pre>
216	>	* }}</pre>
217		*
218		* The best value of {@code TASKS_PER_PHASER} depends mainly on
219	<	* expected barrier synchronization rates. A value as low as four may
220	<	* be appropriate for extremely small per-barrier task bodies (thus
219	>	* expected synchronization rates. A value as low as four may
220	>	* be appropriate for extremely small per-phase task bodies (thus
221		* high rates), or up to hundreds for extremely large ones.
222		*
171	–	* </pre>
172	–	*
223		* <p><b>Implementation notes</b>: This implementation restricts the
224		* maximum number of parties to 65535. Attempts to register additional
225	<	* parties result in IllegalStateExceptions. However, you can and
225	>	* parties result in {@code IllegalStateException}. However, you can and
226		* should create tiered phasers to accommodate arbitrarily large sets
227		* of participants.
228		*
#	Line 187 | Line 237 | public class Phaser {
237		*/
238
239		/**
240	<	* Barrier state representation. Conceptually, a barrier contains
191	<	* four values:
240	>	* Primary state representation, holding four bit-fields:
241		*
242	<	* * parties -- the number of parties to wait (16 bits)
243	<	* * unarrived -- the number of parties yet to hit barrier (16 bits)
244	<	* * phase -- the generation of the barrier (31 bits)
245	<	* * terminated -- set if barrier is terminated (1 bit)
246	<	*
247	<	* However, to efficiently maintain atomicity, these values are
248	<	* packed into a single (atomic) long. Termination uses the sign
249	<	* bit of 32 bit representation of phase, so phase is set to -1 on
250	<	* termination. Good performance relies on keeping state decoding
251	<	* and encoding simple, and keeping race windows short.
252	<	*
253	<	* Note: there are some cheats in arrive() that rely on unarrived
254	<	* count being lowest 16 bits.
242	>	* unarrived  -- the number of parties yet to hit barrier (bits  0-15)
243	>	* parties    -- the number of parties to wait            (bits 16-31)
244	>	* phase      -- the generation of the barrier            (bits 32-62)
245	>	* terminated -- set if barrier is terminated             (bit  63 / sign)
246	>	*
247	>	* Except that a phaser with no registered parties is
248	>	* distinguished by the otherwise illegal state of having zero
249	>	* parties and one unarrived parties (encoded as EMPTY below).
250	>	*
251	>	* To efficiently maintain atomicity, these values are packed into
252	>	* a single (atomic) long. Good performance relies on keeping
253	>	* state decoding and encoding simple, and keeping race windows
254	>	* short.
255	>	*
256	>	* All state updates are performed via CAS except initial
257	>	* registration of a sub-phaser (i.e., one with a non-null
258	>	* parent).  In this (relatively rare) case, we use built-in
259	>	* synchronization to lock while first registering with its
260	>	* parent.
261	>	*
262	>	* The phase of a subphaser is allowed to lag that of its
263	>	* ancestors until it is actually accessed -- see method
264	>	* reconcileState.
265		*/
266		private volatile long state;
267
268	<	private static final int ushortBits = 16;
269	<	private static final int ushortMask = 0xffff;
270	<	private static final int phaseMask  = 0x7fffffff;
268	>	private static final int  MAX_PARTIES     = 0xffff;
269	>	private static final int  MAX_PHASE       = Integer.MAX_VALUE;
270	>	private static final int  PARTIES_SHIFT   = 16;
271	>	private static final int  PHASE_SHIFT     = 32;
272	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
273	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
274	>	private static final long COUNTS_MASK     = 0xffffffffL;
275	>	private static final long TERMINATION_BIT = 1L << 63;
276	>
277	>	// some special values
278	>	private static final int  ONE_ARRIVAL     = 1;
279	>	private static final int  ONE_PARTY       = 1 << PARTIES_SHIFT;
280	>	private static final int  ONE_DEREGISTER  = ONE_ARRIVAL|ONE_PARTY;
281	>	private static final int  EMPTY           = 1;
282	>
283	>	// The following unpacking methods are usually manually inlined
284
285		private static int unarrivedOf(long s) {
286	<	return (int)(s & ushortMask);
286	>	int counts = (int)s;
287	>	return (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK);
288		}
289
290		private static int partiesOf(long s) {
291	<	return ((int)s) >>> 16;
291	>	return (int)s >>> PARTIES_SHIFT;
292		}
293
294		private static int phaseOf(long s) {
295	<	return (int)(s >>> 32);
295	>	return (int)(s >>> PHASE_SHIFT);
296		}
297
298		private static int arrivedOf(long s) {
299	<	return partiesOf(s) - unarrivedOf(s);
300	<	}
301	<
229	<	private static long stateFor(int phase, int parties, int unarrived) {
230	<	return ((((long)phase) << 32) | (((long)parties) << 16) |
231	<	(long)unarrived);
232	<	}
233	<
234	<	private static long trippedStateFor(int phase, int parties) {
235	<	long lp = (long)parties;
236	<	return (((long)phase) << 32) | (lp << 16) | lp;
237	<	}
238	<
239	<	/**
240	<	* Returns message string for bad bounds exceptions.
241	<	*/
242	<	private static String badBounds(int parties, int unarrived) {
243	<	return ("Attempt to set " + unarrived +
244	<	" unarrived of " + parties + " parties");
299	>	int counts = (int)s;
300	>	return (counts == EMPTY) ? 0 :
301	>	(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK);
302		}
303
304		/**
#	Line 250 | Line 307 | public class Phaser {
307		private final Phaser parent;
308
309		/**
310	<	* The root of Phaser tree. Equals this if not in a tree.  Used to
254	<	* support faster state push-down.
310	>	* The root of phaser tree. Equals this if not in a tree.
311		*/
312		private final Phaser root;
313
258	–	// Wait queues
259	–
314		/**
315		* Heads of Treiber stacks for waiting threads. To eliminate
316	<	* contention while releasing some threads while adding others, we
316	>	* contention when releasing some threads while adding others, we
317		* use two of them, alternating across even and odd phases.
318	+	* Subphasers share queues with root to speed up releases.
319		*/
320	<	private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
321	<	private final AtomicReference<QNode> oddQ  = new AtomicReference<QNode>();
320	>	private final AtomicReference<QNode> evenQ;
321	>	private final AtomicReference<QNode> oddQ;
322
323		private AtomicReference<QNode> queueFor(int phase) {
324	<	return (phase & 1) == 0? evenQ : oddQ;
324	>	return ((phase & 1) == 0) ? evenQ : oddQ;
325		}
326
327		/**
328	<	* Returns current state, first resolving lagged propagation from
274	<	* root if necessary.
328	>	* Returns message string for bounds exceptions on arrival.
329		*/
330	<	private long getReconciledState() {
331	<	return parent == null? state : reconcileState();
330	>	private String badArrive(long s) {
331	>	return "Attempted arrival of unregistered party for " +
332	>	stateToString(s);
333		}
334
335		/**
336	<	* Recursively resolves state.
336	>	* Returns message string for bounds exceptions on registration.
337		*/
338	<	private long reconcileState() {
339	<	Phaser p = parent;
340	<	long s = state;
341	<	if (p != null) {
342	<	while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
343	<	long parentState = p.getReconciledState();
344	<	int parentPhase = phaseOf(parentState);
345	<	int phase = phaseOf(s = state);
346	<	if (phase != parentPhase) {
347	<	long next = trippedStateFor(parentPhase, partiesOf(s));
348	<	if (casState(s, next)) {
338	>	private String badRegister(long s) {
339	>	return "Attempt to register more than " +
340	>	MAX_PARTIES + " parties for " + stateToString(s);
341	>	}
342	>
343	>	/**
344	>	* Main implementation for methods arrive and arriveAndDeregister.
345	>	* Manually tuned to speed up and minimize race windows for the
346	>	* common case of just decrementing unarrived field.
347	>	*
348	>	* @param adjust value to subtract from state;
349	>	*               ONE_ARRIVAL for arrive,
350	>	*               ONE_DEREGISTER for arriveAndDeregister
351	>	*/
352	>	private int doArrive(int adjust) {
353	>	final Phaser root = this.root;
354	>	for (;;) {
355	>	long s = (root == this) ? state : reconcileState();
356	>	int phase = (int)(s >>> PHASE_SHIFT);
357	>	if (phase < 0)
358	>	return phase;
359	>	int counts = (int)s;
360	>	int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK);
361	>	if (unarrived <= 0)
362	>	throw new IllegalStateException(badArrive(s));
363	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adjust)) {
364	>	if (unarrived == 1) {
365	>	long n = s & PARTIES_MASK;  // base of next state
366	>	int nextUnarrived = (int)n >>> PARTIES_SHIFT;
367	>	if (root == this) {
368	>	if (onAdvance(phase, nextUnarrived))
369	>	n |= TERMINATION_BIT;
370	>	else if (nextUnarrived == 0)
371	>	n |= EMPTY;
372	>	else
373	>	n |= nextUnarrived;
374	>	int nextPhase = (phase + 1) & MAX_PHASE;
375	>	n |= (long)nextPhase << PHASE_SHIFT;
376	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, n);
377		releaseWaiters(phase);
295	–	s = next;
378		}
379	+	else if (nextUnarrived == 0) { // propagate deregistration
380	+	phase = parent.doArrive(ONE_DEREGISTER);
381	+	UNSAFE.compareAndSwapLong(this, stateOffset,
382	+	s, s | EMPTY);
383	+	}
384	+	else
385	+	phase = parent.doArrive(ONE_ARRIVAL);
386		}
387	+	return phase;
388		}
389		}
390	+	}
391	+
392	+	/**
393	+	* Implementation of register, bulkRegister
394	+	*
395	+	* @param registrations number to add to both parties and
396	+	* unarrived fields. Must be greater than zero.
397	+	*/
398	+	private int doRegister(int registrations) {
399	+	// adjustment to state
400	+	long adjust = ((long)registrations << PARTIES_SHIFT) | registrations;
401	+	final Phaser parent = this.parent;
402	+	int phase;
403	+	for (;;) {
404	+	long s = (parent == null) ? state : reconcileState();
405	+	int counts = (int)s;
406	+	int parties = counts >>> PARTIES_SHIFT;
407	+	int unarrived = counts & UNARRIVED_MASK;
408	+	if (registrations > MAX_PARTIES - parties)
409	+	throw new IllegalStateException(badRegister(s));
410	+	phase = (int)(s >>> PHASE_SHIFT);
411	+	if (phase < 0)
412	+	break;
413	+	if (counts != EMPTY) {                  // not 1st registration
414	+	if (parent == null || reconcileState() == s) {
415	+	if (unarrived == 0)             // wait out advance
416	+	root.internalAwaitAdvance(phase, null);
417	+	else if (UNSAFE.compareAndSwapLong(this, stateOffset,
418	+	s, s + adjust))
419	+	break;
420	+	}
421	+	}
422	+	else if (parent == null) {              // 1st root registration
423	+	long next = ((long)phase << PHASE_SHIFT) | adjust;
424	+	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next))
425	+	break;
426	+	}
427	+	else {
428	+	synchronized (this) {               // 1st sub registration
429	+	if (state == s) {               // recheck under lock
430	+	phase = parent.doRegister(1);
431	+	if (phase < 0)
432	+	break;
433	+	// finish registration whenever parent registration
434	+	// succeeded, even when racing with termination,
435	+	// since these are part of the same "transaction".
436	+	while (!UNSAFE.compareAndSwapLong
437	+	(this, stateOffset, s,
438	+	((long)phase << PHASE_SHIFT) | adjust)) {
439	+	s = state;
440	+	phase = (int)(root.state >>> PHASE_SHIFT);
441	+	// assert (int)s == EMPTY;
442	+	}
443	+	break;
444	+	}
445	+	}
446	+	}
447	+	}
448	+	return phase;
449	+	}
450	+
451	+	/**
452	+	* Resolves lagged phase propagation from root if necessary.
453	+	* Reconciliation normally occurs when root has advanced but
454	+	* subphasers have not yet done so, in which case they must finish
455	+	* their own advance by setting unarrived to parties (or if
456	+	* parties is zero, resetting to unregistered EMPTY state).
457	+	*
458	+	* @return reconciled state
459	+	*/
460	+	private long reconcileState() {
461	+	final Phaser root = this.root;
462	+	long s = state;
463	+	if (root != this) {
464	+	int phase, p;
465	+	// CAS to root phase with current parties, tripping unarrived
466	+	while ((phase = (int)(root.state >>> PHASE_SHIFT)) !=
467	+	(int)(s >>> PHASE_SHIFT) &&
468	+	!UNSAFE.compareAndSwapLong
469	+	(this, stateOffset, s,
470	+	s = (((long)phase << PHASE_SHIFT) |
471	+	((phase < 0) ? (s & COUNTS_MASK) :
472	+	(((p = (int)s >>> PARTIES_SHIFT) == 0) ? EMPTY :
473	+	((s & PARTIES_MASK) | p))))))
474	+	s = state;
475	+	}
476		return s;
477		}
478
479		/**
480	<	* Creates a new Phaser without any initially registered parties,
481	<	* initial phase number 0, and no parent. Any thread using this
482	<	* Phaser will need to first register for it.
480	>	* Creates a new phaser with no initially registered parties, no
481	>	* parent, and initial phase number 0. Any thread using this
482	>	* phaser will need to first register for it.
483		*/
484		public Phaser() {
485	<	this(null);
485	>	this(null, 0);
486		}
487
488		/**
489	<	* Creates a new Phaser with the given numbers of registered
490	<	* unarrived parties, initial phase number 0, and no parent.
489	>	* Creates a new phaser with the given number of registered
490	>	* unarrived parties, no parent, and initial phase number 0.
491		*
492	<	* @param parties the number of parties required to trip barrier
492	>	* @param parties the number of parties required to advance to the
493	>	* next phase
494		* @throws IllegalArgumentException if parties less than zero
495		* or greater than the maximum number of parties supported
496		*/
#	Line 322 | Line 499 | public class Phaser {
499		}
500
501		/**
502	<	* Creates a new Phaser with the given parent, without any
326	<	* initially registered parties. If parent is non-null this phaser
327	<	* is registered with the parent and its initial phase number is
328	<	* the same as that of parent phaser.
502	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
503		*
504		* @param parent the parent phaser
505		*/
506		public Phaser(Phaser parent) {
507	<	int phase = 0;
334	<	this.parent = parent;
335	<	if (parent != null) {
336	<	this.root = parent.root;
337	<	phase = parent.register();
338	<	}
339	<	else
340	<	this.root = this;
341	<	this.state = trippedStateFor(phase, 0);
507	>	this(parent, 0);
508		}
509
510		/**
511	<	* Creates a new Phaser with the given parent and numbers of
512	<	* registered unarrived parties. If parent is non-null, this phaser
513	<	* is registered with the parent and its initial phase number is
514	<	* the same as that of parent phaser.
511	>	* Creates a new phaser with the given parent and number of
512	>	* registered unarrived parties.  When the given parent is non-null
513	>	* and the given number of parties is greater than zero, this
514	>	* child phaser is registered with its parent.
515		*
516		* @param parent the parent phaser
517	<	* @param parties the number of parties required to trip barrier
517	>	* @param parties the number of parties required to advance to the
518	>	* next phase
519		* @throws IllegalArgumentException if parties less than zero
520		* or greater than the maximum number of parties supported
521		*/
522		public Phaser(Phaser parent, int parties) {
523	<	if (parties < 0 || parties > ushortMask)
523	>	if (parties >>> PARTIES_SHIFT != 0)
524		throw new IllegalArgumentException("Illegal number of parties");
525		int phase = 0;
526		this.parent = parent;
527		if (parent != null) {
528	<	this.root = parent.root;
529	<	phase = parent.register();
528	>	final Phaser root = parent.root;
529	>	this.root = root;
530	>	this.evenQ = root.evenQ;
531	>	this.oddQ = root.oddQ;
532	>	if (parties != 0)
533	>	phase = parent.doRegister(1);
534		}
535	<	else
535	>	else {
536		this.root = this;
537	<	this.state = trippedStateFor(phase, parties);
537	>	this.evenQ = new AtomicReference<QNode>();
538	>	this.oddQ = new AtomicReference<QNode>();
539	>	}
540	>	this.state = (parties == 0) ? (long)EMPTY :
541	>	((long)phase << PHASE_SHIFT) |
542	>	((long)parties << PARTIES_SHIFT) |
543	>	((long)parties);
544		}
545
546		/**
547	<	* Adds a new unarrived party to this phaser.
548	<	*
549	<	* @return the current barrier phase number upon registration
547	>	* Adds a new unarrived party to this phaser.  If an ongoing
548	>	* invocation of {@link #onAdvance} is in progress, this method
549	>	* may await its completion before returning.  If this phaser has
550	>	* a parent, and this phaser previously had no registered parties,
551	>	* this child phaser is also registered with its parent. If
552	>	* this phaser is terminated, the attempt to register has
553	>	* no effect, and a negative value is returned.
554	>	*
555	>	* @return the arrival phase number to which this registration
556	>	* applied.  If this value is negative, then this phaser has
557	>	* terminated, in which case registration has no effect.
558		* @throws IllegalStateException if attempting to register more
559		* than the maximum supported number of parties
560		*/
#	Line 379 | Line 564 | public class Phaser {
564
565		/**
566		* Adds the given number of new unarrived parties to this phaser.
567	<	*
568	<	* @param parties the number of parties required to trip barrier
569	<	* @return the current barrier phase number upon registration
567	>	* If an ongoing invocation of {@link #onAdvance} is in progress,
568	>	* this method may await its completion before returning.  If this
569	>	* phaser has a parent, and the given number of parties is greater
570	>	* than zero, and this phaser previously had no registered
571	>	* parties, this child phaser is also registered with its parent.
572	>	* If this phaser is terminated, the attempt to register has no
573	>	* effect, and a negative value is returned.
574	>	*
575	>	* @param parties the number of additional parties required to
576	>	* advance to the next phase
577	>	* @return the arrival phase number to which this registration
578	>	* applied.  If this value is negative, then this phaser has
579	>	* terminated, in which case registration has no effect.
580		* @throws IllegalStateException if attempting to register more
581		* than the maximum supported number of parties
582	+	* @throws IllegalArgumentException if {@code parties < 0}
583		*/
584		public int bulkRegister(int parties) {
585		if (parties < 0)
#	Line 394 | Line 590 | public class Phaser {
590		}
591
592		/**
593	<	* Shared code for register, bulkRegister
398	<	*/
399	<	private int doRegister(int registrations) {
400	<	int phase;
401	<	for (;;) {
402	<	long s = getReconciledState();
403	<	phase = phaseOf(s);
404	<	int unarrived = unarrivedOf(s) + registrations;
405	<	int parties = partiesOf(s) + registrations;
406	<	if (phase < 0)
407	<	break;
408	<	if (parties > ushortMask || unarrived > ushortMask)
409	<	throw new IllegalStateException(badBounds(parties, unarrived));
410	<	if (phase == phaseOf(root.state) &&
411	<	casState(s, stateFor(phase, parties, unarrived)))
412	<	break;
413	<	}
414	<	return phase;
415	<	}
416	<
417	<	/**
418	<	* Arrives at the barrier, but does not wait for others.  (You can
419	<	* in turn wait for others via {@link #awaitAdvance}).
593	>	* Arrives at this phaser, without waiting for others to arrive.
594		*
595	<	* @return the barrier phase number upon entry to this method, or a
596	<	* negative value if terminated
595	>	* <p>It is a usage error for an unregistered party to invoke this
596	>	* method.  However, this error may result in an {@code
597	>	* IllegalStateException} only upon some subsequent operation on
598	>	* this phaser, if ever.
599	>	*
600	>	* @return the arrival phase number, or a negative value if terminated
601		* @throws IllegalStateException if not terminated and the number
602		* of unarrived parties would become negative
603		*/
604		public int arrive() {
605	<	int phase;
428	<	for (;;) {
429	<	long s = state;
430	<	phase = phaseOf(s);
431	<	if (phase < 0)
432	<	break;
433	<	int parties = partiesOf(s);
434	<	int unarrived = unarrivedOf(s) - 1;
435	<	if (unarrived > 0) {        // Not the last arrival
436	<	if (casState(s, s - 1)) // s-1 adds one arrival
437	<	break;
438	<	}
439	<	else if (unarrived == 0) {  // the last arrival
440	<	Phaser par = parent;
441	<	if (par == null) {      // directly trip
442	<	if (casState
443	<	(s,
444	<	trippedStateFor(onAdvance(phase, parties)? -1 :
445	<	((phase + 1) & phaseMask), parties))) {
446	<	releaseWaiters(phase);
447	<	break;
448	<	}
449	<	}
450	<	else {                  // cascade to parent
451	<	if (casState(s, s - 1)) { // zeroes unarrived
452	<	par.arrive();
453	<	reconcileState();
454	<	break;
455	<	}
456	<	}
457	<	}
458	<	else if (phase != phaseOf(root.state)) // or if unreconciled
459	<	reconcileState();
460	<	else
461	<	throw new IllegalStateException(badBounds(parties, unarrived));
462	<	}
463	<	return phase;
605	>	return doArrive(ONE_ARRIVAL);
606		}
607
608		/**
609	<	* Arrives at the barrier, and deregisters from it, without
610	<	* waiting for others. Deregistration reduces number of parties
611	<	* required to trip the barrier in future phases.  If this phaser
609	>	* Arrives at this phaser and deregisters from it without waiting
610	>	* for others to arrive. Deregistration reduces the number of
611	>	* parties required to advance in future phases.  If this phaser
612		* has a parent, and deregistration causes this phaser to have
613		* zero parties, this phaser is also deregistered from its parent.
614		*
615	<	* @return the current barrier phase number upon entry to
616	<	* this method, or a negative value if terminated
615	>	* <p>It is a usage error for an unregistered party to invoke this
616	>	* method.  However, this error may result in an {@code
617	>	* IllegalStateException} only upon some subsequent operation on
618	>	* this phaser, if ever.
619	>	*
620	>	* @return the arrival phase number, or a negative value if terminated
621		* @throws IllegalStateException if not terminated and the number
622		* of registered or unarrived parties would become negative
623		*/
624		public int arriveAndDeregister() {
625	<	// similar code to arrive, but too different to merge
480	<	Phaser par = parent;
481	<	int phase;
482	<	for (;;) {
483	<	long s = state;
484	<	phase = phaseOf(s);
485	<	if (phase < 0)
486	<	break;
487	<	int parties = partiesOf(s) - 1;
488	<	int unarrived = unarrivedOf(s) - 1;
489	<	if (parties >= 0) {
490	<	if (unarrived > 0 || (unarrived == 0 && par != null)) {
491	<	if (casState
492	<	(s,
493	<	stateFor(phase, parties, unarrived))) {
494	<	if (unarrived == 0) {
495	<	par.arriveAndDeregister();
496	<	reconcileState();
497	<	}
498	<	break;
499	<	}
500	<	continue;
501	<	}
502	<	if (unarrived == 0) {
503	<	if (casState
504	<	(s,
505	<	trippedStateFor(onAdvance(phase, parties)? -1 :
506	<	((phase + 1) & phaseMask), parties))) {
507	<	releaseWaiters(phase);
508	<	break;
509	<	}
510	<	continue;
511	<	}
512	<	if (par != null && phase != phaseOf(root.state)) {
513	<	reconcileState();
514	<	continue;
515	<	}
516	<	}
517	<	throw new IllegalStateException(badBounds(parties, unarrived));
518	<	}
519	<	return phase;
625	>	return doArrive(ONE_DEREGISTER);
626		}
627
628		/**
629	<	* Arrives at the barrier and awaits others. Equivalent in effect
630	<	* to {@code awaitAdvance(arrive())}.  If you instead need to
631	<	* await with interruption of timeout, and/or deregister upon
632	<	* arrival, you can arrange them using analogous constructions.
629	>	* Arrives at this phaser and awaits others. Equivalent in effect
630	>	* to {@code awaitAdvance(arrive())}.  If you need to await with
631	>	* interruption or timeout, you can arrange this with an analogous
632	>	* construction using one of the other forms of the {@code
633	>	* awaitAdvance} method.  If instead you need to deregister upon
634	>	* arrival, use {@code awaitAdvance(arriveAndDeregister())}.
635		*
636	<	* @return the phase on entry to this method
636	>	* <p>It is a usage error for an unregistered party to invoke this
637	>	* method.  However, this error may result in an {@code
638	>	* IllegalStateException} only upon some subsequent operation on
639	>	* this phaser, if ever.
640	>	*
641	>	* @return the arrival phase number, or the (negative)
642	>	* {@linkplain #getPhase() current phase} if terminated
643		* @throws IllegalStateException if not terminated and the number
644		* of unarrived parties would become negative
645		*/
646		public int arriveAndAwaitAdvance() {
647	<	return awaitAdvance(arrive());
647	>	// Specialization of doArrive+awaitAdvance eliminating some reads/paths
648	>	final Phaser root = this.root;
649	>	for (;;) {
650	>	long s = (root == this) ? state : reconcileState();
651	>	int phase = (int)(s >>> PHASE_SHIFT);
652	>	if (phase < 0)
653	>	return phase;
654	>	int counts = (int)s;
655	>	int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK);
656	>	if (unarrived <= 0)
657	>	throw new IllegalStateException(badArrive(s));
658	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s,
659	>	s -= ONE_ARRIVAL)) {
660	>	if (unarrived > 1)
661	>	return root.internalAwaitAdvance(phase, null);
662	>	if (root != this)
663	>	return parent.arriveAndAwaitAdvance();
664	>	long n = s & PARTIES_MASK;  // base of next state
665	>	int nextUnarrived = (int)n >>> PARTIES_SHIFT;
666	>	if (onAdvance(phase, nextUnarrived))
667	>	n |= TERMINATION_BIT;
668	>	else if (nextUnarrived == 0)
669	>	n |= EMPTY;
670	>	else
671	>	n |= nextUnarrived;
672	>	int nextPhase = (phase + 1) & MAX_PHASE;
673	>	n |= (long)nextPhase << PHASE_SHIFT;
674	>	if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n))
675	>	return (int)(state >>> PHASE_SHIFT); // terminated
676	>	releaseWaiters(phase);
677	>	return nextPhase;
678	>	}
679	>	}
680		}
681
682		/**
683	<	* Awaits the phase of the barrier to advance from the given
684	<	* value, or returns immediately if argument is negative or this
685	<	* barrier is terminated.
686	<	*
687	<	* @param phase the phase on entry to this method
688	<	* @return the phase on exit from this method
683	>	* Awaits the phase of this phaser to advance from the given phase
684	>	* value, returning immediately if the current phase is not equal
685	>	* to the given phase value or this phaser is terminated.
686	>	*
687	>	* @param phase an arrival phase number, or negative value if
688	>	* terminated; this argument is normally the value returned by a
689	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
690	>	* @return the next arrival phase number, or the argument if it is
691	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
692	>	* if terminated
693		*/
694		public int awaitAdvance(int phase) {
695	+	final Phaser root = this.root;
696	+	long s = (root == this) ? state : reconcileState();
697	+	int p = (int)(s >>> PHASE_SHIFT);
698		if (phase < 0)
699		return phase;
700	<	long s = getReconciledState();
701	<	int p = phaseOf(s);
702	<	if (p != phase)
550	<	return p;
551	<	if (unarrivedOf(s) == 0 && parent != null)
552	<	parent.awaitAdvance(phase);
553	<	// Fall here even if parent waited, to reconcile and help release
554	<	return untimedWait(phase);
700	>	if (p == phase)
701	>	return root.internalAwaitAdvance(phase, null);
702	>	return p;
703		}
704
705		/**
706	<	* Awaits the phase of the barrier to advance from the given
707	<	* value, or returns immediately if argument is negative or this
708	<	* barrier is terminated, or throws InterruptedException if
709	<	* interrupted while waiting.
710	<	*
711	<	* @param phase the phase on entry to this method
712	<	* @return the phase on exit from this method
706	>	* Awaits the phase of this phaser to advance from the given phase
707	>	* value, throwing {@code InterruptedException} if interrupted
708	>	* while waiting, or returning immediately if the current phase is
709	>	* not equal to the given phase value or this phaser is
710	>	* terminated.
711	>	*
712	>	* @param phase an arrival phase number, or negative value if
713	>	* terminated; this argument is normally the value returned by a
714	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
715	>	* @return the next arrival phase number, or the argument if it is
716	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
717	>	* if terminated
718		* @throws InterruptedException if thread interrupted while waiting
719		*/
720		public int awaitAdvanceInterruptibly(int phase)
721		throws InterruptedException {
722	+	final Phaser root = this.root;
723	+	long s = (root == this) ? state : reconcileState();
724	+	int p = (int)(s >>> PHASE_SHIFT);
725		if (phase < 0)
726		return phase;
727	<	long s = getReconciledState();
728	<	int p = phaseOf(s);
729	<	if (p != phase)
730	<	return p;
731	<	if (unarrivedOf(s) == 0 && parent != null)
732	<	parent.awaitAdvanceInterruptibly(phase);
733	<	return interruptibleWait(phase);
727	>	if (p == phase) {
728	>	QNode node = new QNode(this, phase, true, false, 0L);
729	>	p = root.internalAwaitAdvance(phase, node);
730	>	if (node.wasInterrupted)
731	>	throw new InterruptedException();
732	>	}
733	>	return p;
734		}
735
736		/**
737	<	* Awaits the phase of the barrier to advance from the given value
738	<	* or the given timeout elapses, or returns immediately if
739	<	* argument is negative or this barrier is terminated.
740	<	*
741	<	* @param phase the phase on entry to this method
742	<	* @return the phase on exit from this method
737	>	* Awaits the phase of this phaser to advance from the given phase
738	>	* value or the given timeout to elapse, throwing {@code
739	>	* InterruptedException} if interrupted while waiting, or
740	>	* returning immediately if the current phase is not equal to the
741	>	* given phase value or this phaser is terminated.
742	>	*
743	>	* @param phase an arrival phase number, or negative value if
744	>	* terminated; this argument is normally the value returned by a
745	>	* previous call to {@code arrive} or {@code arriveAndDeregister}.
746	>	* @param timeout how long to wait before giving up, in units of
747	>	*        {@code unit}
748	>	* @param unit a {@code TimeUnit} determining how to interpret the
749	>	*        {@code timeout} parameter
750	>	* @return the next arrival phase number, or the argument if it is
751	>	* negative, or the (negative) {@linkplain #getPhase() current phase}
752	>	* if terminated
753		* @throws InterruptedException if thread interrupted while waiting
754		* @throws TimeoutException if timed out while waiting
755		*/
756	<	public int awaitAdvanceInterruptibly(int phase, long timeout, TimeUnit unit)
756	>	public int awaitAdvanceInterruptibly(int phase,
757	>	long timeout, TimeUnit unit)
758		throws InterruptedException, TimeoutException {
759	+	long nanos = unit.toNanos(timeout);
760	+	final Phaser root = this.root;
761	+	long s = (root == this) ? state : reconcileState();
762	+	int p = (int)(s >>> PHASE_SHIFT);
763		if (phase < 0)
764		return phase;
765	<	long s = getReconciledState();
766	<	int p = phaseOf(s);
767	<	if (p != phase)
768	<	return p;
769	<	if (unarrivedOf(s) == 0 && parent != null)
770	<	parent.awaitAdvanceInterruptibly(phase, timeout, unit);
771	<	return timedWait(phase, unit.toNanos(timeout));
765	>	if (p == phase) {
766	>	QNode node = new QNode(this, phase, true, true, nanos);
767	>	p = root.internalAwaitAdvance(phase, node);
768	>	if (node.wasInterrupted)
769	>	throw new InterruptedException();
770	>	else if (p == phase)
771	>	throw new TimeoutException();
772	>	}
773	>	return p;
774		}
775
776		/**
777	<	* Forces this barrier to enter termination state. Counts of
778	<	* arrived and registered parties are unaffected. If this phaser
779	<	* has a parent, it too is terminated. This method may be useful
780	<	* for coordinating recovery after one or more tasks encounter
777	>	* Forces this phaser to enter termination state.  Counts of
778	>	* registered parties are unaffected.  If this phaser is a member
779	>	* of a tiered set of phasers, then all of the phasers in the set
780	>	* are terminated.  If this phaser is already terminated, this
781	>	* method has no effect.  This method may be useful for
782	>	* coordinating recovery after one or more tasks encounter
783		* unexpected exceptions.
784		*/
785		public void forceTermination() {
786	<	for (;;) {
787	<	long s = getReconciledState();
788	<	int phase = phaseOf(s);
789	<	int parties = partiesOf(s);
790	<	int unarrived = unarrivedOf(s);
791	<	if (phase < 0 ||
792	<	casState(s, stateFor(-1, parties, unarrived))) {
793	<	releaseWaiters(0);
794	<	releaseWaiters(1);
620	<	if (parent != null)
621	<	parent.forceTermination();
786	>	// Only need to change root state
787	>	final Phaser root = this.root;
788	>	long s;
789	>	while ((s = root.state) >= 0) {
790	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
791	>	s, s | TERMINATION_BIT)) {
792	>	// signal all threads
793	>	releaseWaiters(0); // Waiters on evenQ
794	>	releaseWaiters(1); // Waiters on oddQ
795		return;
796		}
797		}
#	Line 627 | Line 800 | public class Phaser {
800		/**
801		* Returns the current phase number. The maximum phase number is
802		* {@code Integer.MAX_VALUE}, after which it restarts at
803	<	* zero. Upon termination, the phase number is negative.
803	>	* zero. Upon termination, the phase number is negative,
804	>	* in which case the prevailing phase prior to termination
805	>	* may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
806		*
807		* @return the phase number, or a negative value if terminated
808		*/
809		public final int getPhase() {
810	<	return phaseOf(getReconciledState());
810	>	return (int)(root.state >>> PHASE_SHIFT);
811		}
812
813		/**
814	<	* Returns {@code true} if the current phase number equals the given phase.
640	<	*
641	<	* @param phase the phase
642	<	* @return {@code true} if the current phase number equals the given phase
643	<	*/
644	<	public final boolean hasPhase(int phase) {
645	<	return phaseOf(getReconciledState()) == phase;
646	<	}
647	<
648	<	/**
649	<	* Returns the number of parties registered at this barrier.
814	>	* Returns the number of parties registered at this phaser.
815		*
816		* @return the number of parties
817		*/
#	Line 655 | Line 820 | public class Phaser {
820		}
821
822		/**
823	<	* Returns the number of parties that have arrived at the current
824	<	* phase of this barrier.
823	>	* Returns the number of registered parties that have arrived at
824	>	* the current phase of this phaser. If this phaser has terminated,
825	>	* the returned value is meaningless and arbitrary.
826		*
827		* @return the number of arrived parties
828		*/
829		public int getArrivedParties() {
830	<	return arrivedOf(state);
830	>	return arrivedOf(reconcileState());
831		}
832
833		/**
834		* Returns the number of registered parties that have not yet
835	<	* arrived at the current phase of this barrier.
835	>	* arrived at the current phase of this phaser. If this phaser has
836	>	* terminated, the returned value is meaningless and arbitrary.
837		*
838		* @return the number of unarrived parties
839		*/
840		public int getUnarrivedParties() {
841	<	return unarrivedOf(state);
841	>	return unarrivedOf(reconcileState());
842		}
843
844		/**
845	<	* Returns the parent of this phaser, or null if none.
845	>	* Returns the parent of this phaser, or {@code null} if none.
846		*
847	<	* @return the parent of this phaser, or null if none
847	>	* @return the parent of this phaser, or {@code null} if none
848		*/
849		public Phaser getParent() {
850		return parent;
#	Line 694 | Line 861 | public class Phaser {
861		}
862
863		/**
864	<	* Returns {@code true} if this barrier has been terminated.
864	>	* Returns {@code true} if this phaser has been terminated.
865		*
866	<	* @return {@code true} if this barrier has been terminated
866	>	* @return {@code true} if this phaser has been terminated
867		*/
868		public boolean isTerminated() {
869	<	return getPhase() < 0;
869	>	return root.state < 0L;
870		}
871
872		/**
873	<	* Overridable method to perform an action upon phase advance, and
874	<	* to control termination. This method is invoked whenever the
875	<	* barrier is tripped (and thus all other waiting parties are
876	<	* dormant). If it returns true, then, rather than advance the
877	<	* phase number, this barrier will be set to a final termination
878	<	* state, and subsequent calls to {@code isTerminated} will
879	<	* return true.
880	<	*
881	<	* <p> The default version returns true when the number of
882	<	* registered parties is zero. Normally, overrides that arrange
883	<	* termination for other reasons should also preserve this
884	<	* property.
885	<	*
886	<	* <p> You may override this method to perform an action with side
887	<	* effects visible to participating tasks, but it is in general
888	<	* only sensible to do so in designs where all parties register
889	<	* before any arrive, and all {@code awaitAdvance} at each phase.
890	<	* Otherwise, you cannot ensure lack of interference. In
891	<	* particular, this method may be invoked more than once per
892	<	* transition if other parties successfully register while the
893	<	* invocation of this method is in progress, thus postponing the
894	<	* transition until those parties also arrive, re-triggering this
895	<	* method.
873	>	* Overridable method to perform an action upon impending phase
874	>	* advance, and to control termination. This method is invoked
875	>	* upon arrival of the party advancing this phaser (when all other
876	>	* waiting parties are dormant).  If this method returns {@code
877	>	* true}, this phaser will be set to a final termination state
878	>	* upon advance, and subsequent calls to {@link #isTerminated}
879	>	* will return true. Any (unchecked) Exception or Error thrown by
880	>	* an invocation of this method is propagated to the party
881	>	* attempting to advance this phaser, in which case no advance
882	>	* occurs.
883	>	*
884	>	* <p>The arguments to this method provide the state of the phaser
885	>	* prevailing for the current transition.  The effects of invoking
886	>	* arrival, registration, and waiting methods on this phaser from
887	>	* within {@code onAdvance} are unspecified and should not be
888	>	* relied on.
889	>	*
890	>	* <p>If this phaser is a member of a tiered set of phasers, then
891	>	* {@code onAdvance} is invoked only for its root phaser on each
892	>	* advance.
893	>	*
894	>	* <p>To support the most common use cases, the default
895	>	* implementation of this method returns {@code true} when the
896	>	* number of registered parties has become zero as the result of a
897	>	* party invoking {@code arriveAndDeregister}.  You can disable
898	>	* this behavior, thus enabling continuation upon future
899	>	* registrations, by overriding this method to always return
900	>	* {@code false}:
901	>	*
902	>	* <pre> {@code
903	>	* Phaser phaser = new Phaser() {
904	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
905	>	* }}</pre>
906		*
907	<	* @param phase the phase number on entering the barrier
907	>	* @param phase the current phase number on entry to this method,
908	>	* before this phaser is advanced
909		* @param registeredParties the current number of registered parties
910	<	* @return {@code true} if this barrier should terminate
910	>	* @return {@code true} if this phaser should terminate
911		*/
912		protected boolean onAdvance(int phase, int registeredParties) {
913	<	return registeredParties <= 0;
913	>	return registeredParties == 0;
914		}
915
916		/**
#	Line 742 | Line 920 | public class Phaser {
920		* followed by the number of registered parties, and {@code
921		* "arrived = "} followed by the number of arrived parties.
922		*
923	<	* @return a string identifying this barrier, as well as its state
923	>	* @return a string identifying this phaser, as well as its state
924		*/
925		public String toString() {
926	<	long s = getReconciledState();
926	>	return stateToString(reconcileState());
927	>	}
928	>
929	>	/**
930	>	* Implementation of toString and string-based error messages
931	>	*/
932	>	private String stateToString(long s) {
933		return super.toString() +
934		"[phase = " + phaseOf(s) +
935		" parties = " + partiesOf(s) +
936		" arrived = " + arrivedOf(s) + "]";
937		}
938
939	<	// methods for waiting
939	>	// Waiting mechanics
940
941		/**
942	<	* Wait nodes for Treiber stack representing wait queue
942	>	* Removes and signals threads from queue for phase.
943		*/
944	<	static final class QNode implements ForkJoinPool.ManagedBlocker {
945	<	final Phaser phaser;
946	<	final int phase;
947	<	final long startTime;
948	<	final long nanos;
949	<	final boolean timed;
950	<	final boolean interruptible;
951	<	volatile boolean wasInterrupted = false;
952	<	volatile Thread thread; // nulled to cancel wait
769	<	QNode next;
770	<	QNode(Phaser phaser, int phase, boolean interruptible,
771	<	boolean timed, long startTime, long nanos) {
772	<	this.phaser = phaser;
773	<	this.phase = phase;
774	<	this.timed = timed;
775	<	this.interruptible = interruptible;
776	<	this.startTime = startTime;
777	<	this.nanos = nanos;
778	<	thread = Thread.currentThread();
779	<	}
780	<	public boolean isReleasable() {
781	<	return (thread == null ||
782	<	phaser.getPhase() != phase ||
783	<	(interruptible && wasInterrupted) ||
784	<	(timed && (nanos - (System.nanoTime() - startTime)) <= 0));
785	<	}
786	<	public boolean block() {
787	<	if (Thread.interrupted()) {
788	<	wasInterrupted = true;
789	<	if (interruptible)
790	<	return true;
791	<	}
792	<	if (!timed)
793	<	LockSupport.park(this);
794	<	else {
795	<	long waitTime = nanos - (System.nanoTime() - startTime);
796	<	if (waitTime <= 0)
797	<	return true;
798	<	LockSupport.parkNanos(this, waitTime);
799	<	}
800	<	return isReleasable();
801	<	}
802	<	void signal() {
803	<	Thread t = thread;
804	<	if (t != null) {
805	<	thread = null;
944	>	private void releaseWaiters(int phase) {
945	>	QNode q;   // first element of queue
946	>	Thread t;  // its thread
947	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
948	>	while ((q = head.get()) != null &&
949	>	q.phase != (int)(root.state >>> PHASE_SHIFT)) {
950	>	if (head.compareAndSet(q, q.next) &&
951	>	(t = q.thread) != null) {
952	>	q.thread = null;
953		LockSupport.unpark(t);
954		}
955		}
809	–	boolean doWait() {
810	–	if (thread != null) {
811	–	try {
812	–	ForkJoinPool.managedBlock(this, false);
813	–	} catch (InterruptedException ie) {
814	–	}
815	–	}
816	–	return wasInterrupted;
817	–	}
818	–
956		}
957
958		/**
959	<	* Removes and signals waiting threads from wait queue.
959	>	* Variant of releaseWaiters that additionally tries to remove any
960	>	* nodes no longer waiting for advance due to timeout or
961	>	* interrupt. Currently, nodes are removed only if they are at
962	>	* head of queue, which suffices to reduce memory footprint in
963	>	* most usages.
964	>	*
965	>	* @return current phase on exit
966		*/
967	<	private void releaseWaiters(int phase) {
968	<	AtomicReference<QNode> head = queueFor(phase);
969	<	QNode q;
970	<	while ((q = head.get()) != null) {
971	<	if (head.compareAndSet(q, q.next))
972	<	q.signal();
967	>	private int abortWait(int phase) {
968	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
969	>	for (;;) {
970	>	Thread t;
971	>	QNode q = head.get();
972	>	int p = (int)(root.state >>> PHASE_SHIFT);
973	>	if (q == null || ((t = q.thread) != null && q.phase == p))
974	>	return p;
975	>	if (head.compareAndSet(q, q.next) && t != null) {
976	>	q.thread = null;
977	>	LockSupport.unpark(t);
978	>	}
979		}
980		}
981
982	+	/** The number of CPUs, for spin control */
983	+	private static final int NCPU = Runtime.getRuntime().availableProcessors();
984	+
985		/**
986	<	* Tries to enqueue given node in the appropriate wait queue.
987	<	*
988	<	* @return true if successful
986	>	* The number of times to spin before blocking while waiting for
987	>	* advance, per arrival while waiting. On multiprocessors, fully
988	>	* blocking and waking up a large number of threads all at once is
989	>	* usually a very slow process, so we use rechargeable spins to
990	>	* avoid it when threads regularly arrive: When a thread in
991	>	* internalAwaitAdvance notices another arrival before blocking,
992	>	* and there appear to be enough CPUs available, it spins
993	>	* SPINS_PER_ARRIVAL more times before blocking. The value trades
994	>	* off good-citizenship vs big unnecessary slowdowns.
995		*/
996	<	private boolean tryEnqueue(QNode node) {
839	<	AtomicReference<QNode> head = queueFor(node.phase);
840	<	return head.compareAndSet(node.next = head.get(), node);
841	<	}
996	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
997
998		/**
999	<	* Enqueues node and waits unless aborted or signalled.
999	>	* Possibly blocks and waits for phase to advance unless aborted.
1000	>	* Call only on root phaser.
1001		*
1002	+	* @param phase current phase
1003	+	* @param node if non-null, the wait node to track interrupt and timeout;
1004	+	* if null, denotes noninterruptible wait
1005		* @return current phase
1006		*/
1007	<	private int untimedWait(int phase) {
1008	<	QNode node = null;
1009	<	boolean queued = false;
1010	<	boolean interrupted = false;
1007	>	private int internalAwaitAdvance(int phase, QNode node) {
1008	>	// assert root == this;
1009	>	releaseWaiters(phase-1);          // ensure old queue clean
1010	>	boolean queued = false;           // true when node is enqueued
1011	>	int lastUnarrived = 0;            // to increase spins upon change
1012	>	int spins = SPINS_PER_ARRIVAL;
1013	>	long s;
1014		int p;
1015	<	while ((p = getPhase()) == phase) {
1016	<	if (Thread.interrupted())
1017	<	interrupted = true;
1018	<	else if (node == null)
1019	<	node = new QNode(this, phase, false, false, 0, 0);
1020	<	else if (!queued)
1021	<	queued = tryEnqueue(node);
1022	<	else
1023	<	interrupted = node.doWait();
1015	>	while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
1016	>	if (node == null) {           // spinning in noninterruptible mode
1017	>	int unarrived = (int)s & UNARRIVED_MASK;
1018	>	if (unarrived != lastUnarrived &&
1019	>	(lastUnarrived = unarrived) < NCPU)
1020	>	spins += SPINS_PER_ARRIVAL;
1021	>	boolean interrupted = Thread.interrupted();
1022	>	if (interrupted || --spins < 0) { // need node to record intr
1023	>	node = new QNode(this, phase, false, false, 0L);
1024	>	node.wasInterrupted = interrupted;
1025	>	}
1026	>	}
1027	>	else if (node.isReleasable()) // done or aborted
1028	>	break;
1029	>	else if (!queued) {           // push onto queue
1030	>	AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
1031	>	QNode q = node.next = head.get();
1032	>	if ((q == null || q.phase == phase) &&
1033	>	(int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
1034	>	queued = head.compareAndSet(q, node);
1035	>	}
1036	>	else {
1037	>	try {
1038	>	ForkJoinPool.managedBlock(node);
1039	>	} catch (InterruptedException ie) {
1040	>	node.wasInterrupted = true;
1041	>	}
1042	>	}
1043	>	}
1044	>
1045	>	if (node != null) {
1046	>	if (node.thread != null)
1047	>	node.thread = null;       // avoid need for unpark()
1048	>	if (node.wasInterrupted && !node.interruptible)
1049	>	Thread.currentThread().interrupt();
1050	>	if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase)
1051	>	return abortWait(phase); // possibly clean up on abort
1052		}
863	–	if (node != null)
864	–	node.thread = null;
1053		releaseWaiters(phase);
866	–	if (interrupted)
867	–	Thread.currentThread().interrupt();
1054		return p;
1055		}
1056
1057		/**
1058	<	* Interruptible version
873	<	* @return current phase
1058	>	* Wait nodes for Treiber stack representing wait queue
1059		*/
1060	<	private int interruptibleWait(int phase) throws InterruptedException {
1061	<	QNode node = null;
1062	<	boolean queued = false;
1063	<	boolean interrupted = false;
1064	<	int p;
1065	<	while ((p = getPhase()) == phase && !interrupted) {
1066	<	if (Thread.interrupted())
1067	<	interrupted = true;
1068	<	else if (node == null)
1069	<	node = new QNode(this, phase, true, false, 0, 0);
885	<	else if (!queued)
886	<	queued = tryEnqueue(node);
887	<	else
888	<	interrupted = node.doWait();
889	<	}
890	<	if (node != null)
891	<	node.thread = null;
892	<	if (p != phase || (p = getPhase()) != phase)
893	<	releaseWaiters(phase);
894	<	if (interrupted)
895	<	throw new InterruptedException();
896	<	return p;
897	<	}
1060	>	static final class QNode implements ForkJoinPool.ManagedBlocker {
1061	>	final Phaser phaser;
1062	>	final int phase;
1063	>	final boolean interruptible;
1064	>	final boolean timed;
1065	>	boolean wasInterrupted;
1066	>	long nanos;
1067	>	long lastTime;
1068	>	volatile Thread thread; // nulled to cancel wait
1069	>	QNode next;
1070
1071	<	/**
1072	<	* Timeout version.
1073	<	* @return current phase
1074	<	*/
1075	<	private int timedWait(int phase, long nanos)
1076	<	throws InterruptedException, TimeoutException {
1077	<	long startTime = System.nanoTime();
1078	<	QNode node = null;
1079	<	boolean queued = false;
1080	<	boolean interrupted = false;
909	<	int p;
910	<	while ((p = getPhase()) == phase && !interrupted) {
911	<	if (Thread.interrupted())
912	<	interrupted = true;
913	<	else if (nanos - (System.nanoTime() - startTime) <= 0)
914	<	break;
915	<	else if (node == null)
916	<	node = new QNode(this, phase, true, true, startTime, nanos);
917	<	else if (!queued)
918	<	queued = tryEnqueue(node);
919	<	else
920	<	interrupted = node.doWait();
921	<	}
922	<	if (node != null)
923	<	node.thread = null;
924	<	if (p != phase || (p = getPhase()) != phase)
925	<	releaseWaiters(phase);
926	<	if (interrupted)
927	<	throw new InterruptedException();
928	<	if (p == phase)
929	<	throw new TimeoutException();
930	<	return p;
931	<	}
1071	>	QNode(Phaser phaser, int phase, boolean interruptible,
1072	>	boolean timed, long nanos) {
1073	>	this.phaser = phaser;
1074	>	this.phase = phase;
1075	>	this.interruptible = interruptible;
1076	>	this.nanos = nanos;
1077	>	this.timed = timed;
1078	>	this.lastTime = timed ? System.nanoTime() : 0L;
1079	>	thread = Thread.currentThread();
1080	>	}
1081
1082	<	// Temporary Unsafe mechanics for preliminary release
1083	<	private static Unsafe getUnsafe() throws Throwable {
1084	<	try {
1085	<	return Unsafe.getUnsafe();
1086	<	} catch (SecurityException se) {
1087	<	try {
1088	<	return java.security.AccessController.doPrivileged
1089	<	(new java.security.PrivilegedExceptionAction<Unsafe>() {
1090	<	public Unsafe run() throws Exception {
1091	<	return getUnsafePrivileged();
1092	<	}});
1093	<	} catch (java.security.PrivilegedActionException e) {
1094	<	throw e.getCause();
1082	>	public boolean isReleasable() {
1083	>	if (thread == null)
1084	>	return true;
1085	>	if (phaser.getPhase() != phase) {
1086	>	thread = null;
1087	>	return true;
1088	>	}
1089	>	if (Thread.interrupted())
1090	>	wasInterrupted = true;
1091	>	if (wasInterrupted && interruptible) {
1092	>	thread = null;
1093	>	return true;
1094	>	}
1095	>	if (timed) {
1096	>	if (nanos > 0L) {
1097	>	long now = System.nanoTime();
1098	>	nanos -= now - lastTime;
1099	>	lastTime = now;
1100	>	}
1101	>	if (nanos <= 0L) {
1102	>	thread = null;
1103	>	return true;
1104	>	}
1105		}
1106	+	return false;
1107		}
948	–	}
949	–
950	–	private static Unsafe getUnsafePrivileged()
951	–	throws NoSuchFieldException, IllegalAccessException {
952	–	Field f = Unsafe.class.getDeclaredField("theUnsafe");
953	–	f.setAccessible(true);
954	–	return (Unsafe) f.get(null);
955	–	}
1108
1109	<	private static long fieldOffset(String fieldName)
1110	<	throws NoSuchFieldException {
1111	<	return UNSAFE.objectFieldOffset
1112	<	(Phaser.class.getDeclaredField(fieldName));
1109	>	public boolean block() {
1110	>	if (isReleasable())
1111	>	return true;
1112	>	else if (!timed)
1113	>	LockSupport.park(this);
1114	>	else if (nanos > 0)
1115	>	LockSupport.parkNanos(this, nanos);
1116	>	return isReleasable();
1117	>	}
1118		}
1119
1120	<	static final Unsafe UNSAFE;
964	<	static final long stateOffset;
1120	>	// Unsafe mechanics
1121
1122	+	private static final sun.misc.Unsafe UNSAFE;
1123	+	private static final long stateOffset;
1124		static {
1125		try {
1126		UNSAFE = getUnsafe();
1127	<	stateOffset = fieldOffset("state");
1128	<	} catch (Throwable e) {
1129	<	throw new RuntimeException("Could not initialize intrinsics", e);
1127	>	Class<?> k = Phaser.class;
1128	>	stateOffset = UNSAFE.objectFieldOffset
1129	>	(k.getDeclaredField("state"));
1130	>	} catch (Exception e) {
1131	>	throw new Error(e);
1132		}
1133		}
1134
1135	<	final boolean casState(long cmp, long val) {
1136	<	return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
1135	>	/**
1136	>	* Returns a sun.misc.Unsafe.  Suitable for use in a 3rd party package.
1137	>	* Replace with a simple call to Unsafe.getUnsafe when integrating
1138	>	* into a jdk.
1139	>	*
1140	>	* @return a sun.misc.Unsafe
1141	>	*/
1142	>	private static sun.misc.Unsafe getUnsafe() {
1143	>	try {
1144	>	return sun.misc.Unsafe.getUnsafe();
1145	>	} catch (SecurityException tryReflectionInstead) {}
1146	>	try {
1147	>	return java.security.AccessController.doPrivileged
1148	>	(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() {
1149	>	public sun.misc.Unsafe run() throws Exception {
1150	>	Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class;
1151	>	for (java.lang.reflect.Field f : k.getDeclaredFields()) {
1152	>	f.setAccessible(true);
1153	>	Object x = f.get(null);
1154	>	if (k.isInstance(x))
1155	>	return k.cast(x);
1156	>	}
1157	>	throw new NoSuchFieldError("the Unsafe");
1158	>	}});
1159	>	} catch (java.security.PrivilegedActionException e) {
1160	>	throw new RuntimeException("Could not initialize intrinsics",
1161	>	e.getCause());
1162	>	}
1163		}
1164		}

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