src/share/classes/java/util/concurrent/Phaser.java
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*** 33,42 ****
--- 33,44 ----
* http://creativecommons.org/licenses/publicdomain
*/
package java.util.concurrent;
+ import java.util.concurrent.TimeUnit;
+ import java.util.concurrent.TimeoutException;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.locks.LockSupport;
/**
* A reusable synchronization barrier, similar in functionality to
*** 59,123 ****
*
* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
* Phaser} may be repeatedly awaited. Method {@link
* #arriveAndAwaitAdvance} has effect analogous to {@link
* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
! * generation of a {@code Phaser} has an associated phase number. The
! * phase number starts at zero, and advances when all parties arrive
! * at the barrier, wrapping around to zero after reaching {@code
* Integer.MAX_VALUE}. The use of phase numbers enables independent
! * control of actions upon arrival at a barrier and upon awaiting
* others, via two kinds of methods that may be invoked by any
* registered party:
*
* <ul>
*
* <li> <b>Arrival.</b> Methods {@link #arrive} and
! * {@link #arriveAndDeregister} record arrival at a
! * barrier. These methods do not block, but return an associated
! * <em>arrival phase number</em>; that is, the phase number of
! * the barrier to which the arrival applied. When the final
! * party for a given phase arrives, an optional barrier action
! * is performed and the phase advances. Barrier actions,
! * performed by the party triggering a phase advance, are
! * arranged by overriding method {@link #onAdvance(int, int)},
! * which also controls termination. Overriding this method is
! * similar to, but more flexible than, providing a barrier
! * action to a {@code CyclicBarrier}.
*
* <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
* argument indicating an arrival phase number, and returns when
! * the barrier advances to (or is already at) a different phase.
* Unlike similar constructions using {@code CyclicBarrier},
* method {@code awaitAdvance} continues to wait even if the
* waiting thread is interrupted. Interruptible and timeout
* versions are also available, but exceptions encountered while
* tasks wait interruptibly or with timeout do not change the
! * state of the barrier. If necessary, you can perform any
* associated recovery within handlers of those exceptions,
* often after invoking {@code forceTermination}. Phasers may
* also be used by tasks executing in a {@link ForkJoinPool},
* which will ensure sufficient parallelism to execute tasks
* when others are blocked waiting for a phase to advance.
*
* </ul>
*
! * <p> <b>Termination.</b> A {@code Phaser} may enter a
! * <em>termination</em> state in which all synchronization methods
! * immediately return without updating phaser state or waiting for
! * advance, and indicating (via a negative phase value) that execution
! * is complete. Termination is triggered when an invocation of {@code
! * onAdvance} returns {@code true}. As illustrated below, when
! * phasers control actions with a fixed number of iterations, it is
! * often convenient to override this method to cause termination when
! * the current phase number reaches a threshold. Method {@link
! * #forceTermination} is also available to abruptly release waiting
! * threads and allow them to terminate.
*
! * <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
! * in tree structures) to reduce contention. Phasers with large
! * numbers of parties that would otherwise experience heavy
* synchronization contention costs may instead be set up so that
* groups of sub-phasers share a common parent. This may greatly
* increase throughput even though it incurs greater per-operation
* overhead.
*
--- 61,127 ----
*
* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code
* Phaser} may be repeatedly awaited. Method {@link
* #arriveAndAwaitAdvance} has effect analogous to {@link
* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each
! * generation of a phaser has an associated phase number. The phase
! * number starts at zero, and advances when all parties arrive at the
! * phaser, wrapping around to zero after reaching {@code
* Integer.MAX_VALUE}. The use of phase numbers enables independent
! * control of actions upon arrival at a phaser and upon awaiting
* others, via two kinds of methods that may be invoked by any
* registered party:
*
* <ul>
*
* <li> <b>Arrival.</b> Methods {@link #arrive} and
! * {@link #arriveAndDeregister} record arrival. These methods
! * do not block, but return an associated <em>arrival phase
! * number</em>; that is, the phase number of the phaser to which
! * the arrival applied. When the final party for a given phase
! * arrives, an optional action is performed and the phase
! * advances. These actions are performed by the party
! * triggering a phase advance, and are arranged by overriding
! * method {@link #onAdvance(int, int)}, which also controls
! * termination. Overriding this method is similar to, but more
! * flexible than, providing a barrier action to a {@code
! * CyclicBarrier}.
*
* <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an
* argument indicating an arrival phase number, and returns when
! * the phaser advances to (or is already at) a different phase.
* Unlike similar constructions using {@code CyclicBarrier},
* method {@code awaitAdvance} continues to wait even if the
* waiting thread is interrupted. Interruptible and timeout
* versions are also available, but exceptions encountered while
* tasks wait interruptibly or with timeout do not change the
! * state of the phaser. If necessary, you can perform any
* associated recovery within handlers of those exceptions,
* often after invoking {@code forceTermination}. Phasers may
* also be used by tasks executing in a {@link ForkJoinPool},
* which will ensure sufficient parallelism to execute tasks
* when others are blocked waiting for a phase to advance.
*
* </ul>
*
! * <p> <b>Termination.</b> A phaser may enter a <em>termination</em>
! * state in which all synchronization methods immediately return
! * without updating phaser state or waiting for advance, and
! * indicating (via a negative phase value) that execution is complete.
! * Termination is triggered when an invocation of {@code onAdvance}
! * returns {@code true}. The default implementation returns {@code
! * true} if a deregistration has caused the number of registered
! * parties to become zero. As illustrated below, when phasers control
! * actions with a fixed number of iterations, it is often convenient
! * to override this method to cause termination when the current phase
! * number reaches a threshold. Method {@link #forceTermination} is
! * also available to abruptly release waiting threads and allow them
! * to terminate.
*
! * <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
! * constructed in tree structures) to reduce contention. Phasers with
! * large numbers of parties that would otherwise experience heavy
* synchronization contention costs may instead be set up so that
* groups of sub-phasers share a common parent. This may greatly
* increase throughput even though it incurs greater per-operation
* overhead.
*
*** 134,146 ****
* informal monitoring.
*
* <p><b>Sample usages:</b>
*
* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
! * to control a one-shot action serving a variable number of
! * parties. The typical idiom is for the method setting this up to
! * first register, then start the actions, then deregister, as in:
*
* <pre> {@code
* void runTasks(List<Runnable> tasks) {
* final Phaser phaser = new Phaser(1); // "1" to register self
* // create and start threads
--- 138,150 ----
* informal monitoring.
*
* <p><b>Sample usages:</b>
*
* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch}
! * to control a one-shot action serving a variable number of parties.
! * The typical idiom is for the method setting this up to first
! * register, then start the actions, then deregister, as in:
*
* <pre> {@code
* void runTasks(List<Runnable> tasks) {
* final Phaser phaser = new Phaser(1); // "1" to register self
* // create and start threads
*** 208,219 ****
* }}</pre>
*
*
* <p>To create a set of tasks using a tree of phasers,
* you could use code of the following form, assuming a
! * Task class with a constructor accepting a phaser that
! * it registers for upon construction:
*
* <pre> {@code
* void build(Task[] actions, int lo, int hi, Phaser ph) {
* if (hi - lo > TASKS_PER_PHASER) {
* for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
--- 212,223 ----
* }}</pre>
*
*
* <p>To create a set of tasks using a tree of phasers,
* you could use code of the following form, assuming a
! * Task class with a constructor accepting a {@code Phaser} that
! * it registers with upon construction:
*
* <pre> {@code
* void build(Task[] actions, int lo, int hi, Phaser ph) {
* if (hi - lo > TASKS_PER_PHASER) {
* for (int i = lo; i < hi; i += TASKS_PER_PHASER) {
*** 228,243 ****
* }
* // .. initially called, for n tasks via
* build(new Task[n], 0, n, new Phaser());}</pre>
*
* The best value of {@code TASKS_PER_PHASER} depends mainly on
! * expected barrier synchronization rates. A value as low as four may
! * be appropriate for extremely small per-barrier task bodies (thus
* high rates), or up to hundreds for extremely large ones.
*
- * </pre>
- *
* <p><b>Implementation notes</b>: This implementation restricts the
* maximum number of parties to 65535. Attempts to register additional
* parties result in {@code IllegalStateException}. However, you can and
* should create tiered phasers to accommodate arbitrarily large sets
* of participants.
--- 232,245 ----
* }
* // .. initially called, for n tasks via
* build(new Task[n], 0, n, new Phaser());}</pre>
*
* The best value of {@code TASKS_PER_PHASER} depends mainly on
! * expected synchronization rates. A value as low as four may
! * be appropriate for extremely small per-phase task bodies (thus
* high rates), or up to hundreds for extremely large ones.
*
* <p><b>Implementation notes</b>: This implementation restricts the
* maximum number of parties to 65535. Attempts to register additional
* parties result in {@code IllegalStateException}. However, you can and
* should create tiered phasers to accommodate arbitrarily large sets
* of participants.
*** 251,317 ****
* Vijay Saraswat for the idea, and to Vivek Sarkar for
* enhancements to extend functionality.
*/
/**
! * Barrier state representation. Conceptually, a barrier contains
! * four values:
*
! * * parties -- the number of parties to wait (16 bits)
! * * unarrived -- the number of parties yet to hit barrier (16 bits)
! * * phase -- the generation of the barrier (31 bits)
! * * terminated -- set if barrier is terminated (1 bit)
*
* However, to efficiently maintain atomicity, these values are
* packed into a single (atomic) long. Termination uses the sign
* bit of 32 bit representation of phase, so phase is set to -1 on
* termination. Good performance relies on keeping state decoding
* and encoding simple, and keeping race windows short.
- *
- * Note: there are some cheats in arrive() that rely on unarrived
- * count being lowest 16 bits.
*/
private volatile long state;
! private static final int ushortMask = 0xffff;
! private static final int phaseMask = 0x7fffffff;
private static int unarrivedOf(long s) {
! return (int) (s & ushortMask);
}
private static int partiesOf(long s) {
! return ((int) s) >>> 16;
}
private static int phaseOf(long s) {
! return (int) (s >>> 32);
}
private static int arrivedOf(long s) {
return partiesOf(s) - unarrivedOf(s);
}
- private static long stateFor(int phase, int parties, int unarrived) {
- return ((((long) phase) << 32) | (((long) parties) << 16) |
- (long) unarrived);
- }
-
- private static long trippedStateFor(int phase, int parties) {
- long lp = (long) parties;
- return (((long) phase) << 32) | (lp << 16) | lp;
- }
-
/**
- * Returns message string for bad bounds exceptions.
- */
- private static String badBounds(int parties, int unarrived) {
- return ("Attempt to set " + unarrived +
- " unarrived of " + parties + " parties");
- }
-
- /**
* The parent of this phaser, or null if none
*/
private final Phaser parent;
/**
--- 253,306 ----
* Vijay Saraswat for the idea, and to Vivek Sarkar for
* enhancements to extend functionality.
*/
/**
! * Primary state representation, holding four fields:
*
! * * unarrived -- the number of parties yet to hit barrier (bits 0-15)
! * * parties -- the number of parties to wait (bits 16-31)
! * * phase -- the generation of the barrier (bits 32-62)
! * * terminated -- set if barrier is terminated (bit 63 / sign)
*
* However, to efficiently maintain atomicity, these values are
* packed into a single (atomic) long. Termination uses the sign
* bit of 32 bit representation of phase, so phase is set to -1 on
* termination. Good performance relies on keeping state decoding
* and encoding simple, and keeping race windows short.
*/
private volatile long state;
! private static final int MAX_PARTIES = 0xffff;
! private static final int MAX_PHASE = 0x7fffffff;
! private static final int PARTIES_SHIFT = 16;
! private static final int PHASE_SHIFT = 32;
! private static final int UNARRIVED_MASK = 0xffff; // to mask ints
! private static final long PARTIES_MASK = 0xffff0000L; // to mask longs
! private static final long ONE_ARRIVAL = 1L;
! private static final long ONE_PARTY = 1L << PARTIES_SHIFT;
! private static final long TERMINATION_BIT = 1L << 63;
+ // The following unpacking methods are usually manually inlined
+
private static int unarrivedOf(long s) {
! return (int)s & UNARRIVED_MASK;
}
private static int partiesOf(long s) {
! return (int)s >>> PARTIES_SHIFT;
}
private static int phaseOf(long s) {
! return (int) (s >>> PHASE_SHIFT);
}
private static int arrivedOf(long s) {
return partiesOf(s) - unarrivedOf(s);
}
/**
* The parent of this phaser, or null if none
*/
private final Phaser parent;
/**
*** 318,440 ****
* The root of phaser tree. Equals this if not in a tree. Used to
* support faster state push-down.
*/
private final Phaser root;
- // Wait queues
-
/**
* Heads of Treiber stacks for waiting threads. To eliminate
! * contention while releasing some threads while adding others, we
* use two of them, alternating across even and odd phases.
*/
! private final AtomicReference<QNode> evenQ = new AtomicReference<QNode>();
! private final AtomicReference<QNode> oddQ = new AtomicReference<QNode>();
private AtomicReference<QNode> queueFor(int phase) {
return ((phase & 1) == 0) ? evenQ : oddQ;
}
/**
! * Returns current state, first resolving lagged propagation from
! * root if necessary.
*/
! private long getReconciledState() {
! return (parent == null) ? state : reconcileState();
}
/**
! * Recursively resolves state.
*/
! private long reconcileState() {
! Phaser p = parent;
long s = state;
! if (p != null) {
! while (unarrivedOf(s) == 0 && phaseOf(s) != phaseOf(root.state)) {
! long parentState = p.getReconciledState();
! int parentPhase = phaseOf(parentState);
! int phase = phaseOf(s = state);
! if (phase != parentPhase) {
! long next = trippedStateFor(parentPhase, partiesOf(s));
! if (casState(s, next)) {
releaseWaiters(phase);
- s = next;
}
}
}
}
return s;
}
/**
! * Creates a new phaser without any initially registered parties,
! * initial phase number 0, and no parent. Any thread using this
* phaser will need to first register for it.
*/
public Phaser() {
! this(null);
}
/**
! * Creates a new phaser with the given numbers of registered
! * unarrived parties, initial phase number 0, and no parent.
*
! * @param parties the number of parties required to trip barrier
* @throws IllegalArgumentException if parties less than zero
* or greater than the maximum number of parties supported
*/
public Phaser(int parties) {
this(null, parties);
}
/**
! * Creates a new phaser with the given parent, without any
! * initially registered parties. If parent is non-null this phaser
! * is registered with the parent and its initial phase number is
! * the same as that of parent phaser.
*
* @param parent the parent phaser
*/
public Phaser(Phaser parent) {
! int phase = 0;
! this.parent = parent;
! if (parent != null) {
! this.root = parent.root;
! phase = parent.register();
}
- else
- this.root = this;
- this.state = trippedStateFor(phase, 0);
- }
/**
! * Creates a new phaser with the given parent and numbers of
! * registered unarrived parties. If parent is non-null, this phaser
! * is registered with the parent and its initial phase number is
! * the same as that of parent phaser.
*
* @param parent the parent phaser
! * @param parties the number of parties required to trip barrier
* @throws IllegalArgumentException if parties less than zero
* or greater than the maximum number of parties supported
*/
public Phaser(Phaser parent, int parties) {
! if (parties < 0 || parties > ushortMask)
throw new IllegalArgumentException("Illegal number of parties");
! int phase = 0;
this.parent = parent;
if (parent != null) {
! this.root = parent.root;
! phase = parent.register();
}
! else
this.root = this;
! this.state = trippedStateFor(phase, parties);
}
/**
! * Adds a new unarrived party to this phaser.
*
* @return the arrival phase number to which this registration applied
* @throws IllegalStateException if attempting to register more
* than the maximum supported number of parties
*/
--- 307,538 ----
* The root of phaser tree. Equals this if not in a tree. Used to
* support faster state push-down.
*/
private final Phaser root;
/**
* Heads of Treiber stacks for waiting threads. To eliminate
! * contention when releasing some threads while adding others, we
* use two of them, alternating across even and odd phases.
+ * Subphasers share queues with root to speed up releases.
*/
! private final AtomicReference<QNode> evenQ;
! private final AtomicReference<QNode> oddQ;
private AtomicReference<QNode> queueFor(int phase) {
return ((phase & 1) == 0) ? evenQ : oddQ;
}
/**
! * Returns message string for bounds exceptions on arrival.
*/
! private String badArrive(long s) {
! return "Attempted arrival of unregistered party for " +
! stateToString(s);
}
/**
! * Returns message string for bounds exceptions on registration.
*/
! private String badRegister(long s) {
! return "Attempt to register more than " +
! MAX_PARTIES + " parties for " + stateToString(s);
! }
!
! /**
! * Main implementation for methods arrive and arriveAndDeregister.
! * Manually tuned to speed up and minimize race windows for the
! * common case of just decrementing unarrived field.
! *
! * @param adj - adjustment to apply to state -- either
! * ONE_ARRIVAL (for arrive) or
! * ONE_ARRIVAL|ONE_PARTY (for arriveAndDeregister)
! */
! private int doArrive(long adj) {
! for (;;) {
long s = state;
! int unarrived = (int)s & UNARRIVED_MASK;
! int phase = (int)(s >>> PHASE_SHIFT);
! if (phase < 0)
! return phase;
! else if (unarrived == 0) {
! if (reconcileState() == s) // recheck
! throw new IllegalStateException(badArrive(s));
! }
! else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
! if (unarrived == 1) {
! long p = s & PARTIES_MASK; // unshifted parties field
! long lu = p >>> PARTIES_SHIFT;
! int u = (int)lu;
! int nextPhase = (phase + 1) & MAX_PHASE;
! long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
! final Phaser parent = this.parent;
! if (parent == null) {
! if (onAdvance(phase, u))
! next |= TERMINATION_BIT;
! UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
releaseWaiters(phase);
}
+ else {
+ parent.doArrive((u == 0) ?
+ ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
+ if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase)
+ reconcileState();
+ else if (state == s)
+ UNSAFE.compareAndSwapLong(this, stateOffset, s,
+ next);
}
}
+ return phase;
}
+ }
+ }
+
+ /**
+ * Implementation of register, bulkRegister
+ *
+ * @param registrations number to add to both parties and
+ * unarrived fields. Must be greater than zero.
+ */
+ private int doRegister(int registrations) {
+ // adjustment to state
+ long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
+ final Phaser parent = this.parent;
+ for (;;) {
+ long s = (parent == null) ? state : reconcileState();
+ int parties = (int)s >>> PARTIES_SHIFT;
+ int phase = (int)(s >>> PHASE_SHIFT);
+ if (phase < 0)
+ return phase;
+ else if (registrations > MAX_PARTIES - parties)
+ throw new IllegalStateException(badRegister(s));
+ else if ((parties == 0 && parent == null) || // first reg of root
+ ((int)s & UNARRIVED_MASK) != 0) { // not advancing
+ if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
+ return phase;
+ }
+ else if (parties != 0) // wait for onAdvance
+ root.internalAwaitAdvance(phase, null);
+ else { // 1st registration of child
+ synchronized (this) { // register parent first
+ if (reconcileState() == s) { // recheck under lock
+ parent.doRegister(1); // OK if throws IllegalState
+ for (;;) { // simpler form of outer loop
+ s = reconcileState();
+ phase = (int)(s >>> PHASE_SHIFT);
+ if (phase < 0 ||
+ UNSAFE.compareAndSwapLong(this, stateOffset,
+ s, s + adj))
+ return phase;
+ }
+ }
+ }
+ }
+ }
+ }
+
+ /**
+ * Recursively resolves lagged phase propagation from root if necessary.
+ */
+ private long reconcileState() {
+ Phaser par = parent;
+ long s = state;
+ if (par != null) {
+ Phaser rt = root;
+ int phase, rPhase;
+ while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
+ (rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
+ if (par != rt && (int)(par.state >>> PHASE_SHIFT) != rPhase)
+ par.reconcileState();
+ else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
+ long u = s & PARTIES_MASK; // reset unarrived to parties
+ long next = ((((long) rPhase) << PHASE_SHIFT) | u |
+ (u >>> PARTIES_SHIFT));
+ UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
+ }
+ s = state;
+ }
+ }
return s;
}
/**
! * Creates a new phaser with no initially registered parties, no
! * parent, and initial phase number 0. Any thread using this
* phaser will need to first register for it.
*/
public Phaser() {
! this(null, 0);
}
/**
! * Creates a new phaser with the given number of registered
! * unarrived parties, no parent, and initial phase number 0.
*
! * @param parties the number of parties required to advance to the
! * next phase
* @throws IllegalArgumentException if parties less than zero
* or greater than the maximum number of parties supported
*/
public Phaser(int parties) {
this(null, parties);
}
/**
! * Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
*
* @param parent the parent phaser
*/
public Phaser(Phaser parent) {
! this(parent, 0);
}
/**
! * Creates a new phaser with the given parent and number of
! * registered unarrived parties. Registration and deregistration
! * of this child phaser with its parent are managed automatically.
! * If the given parent is non-null, whenever this child phaser has
! * any registered parties (as established in this constructor,
! * {@link #register}, or {@link #bulkRegister}), this child phaser
! * is registered with its parent. Whenever the number of
! * registered parties becomes zero as the result of an invocation
! * of {@link #arriveAndDeregister}, this child phaser is
! * deregistered from its parent.
*
* @param parent the parent phaser
! * @param parties the number of parties required to advance to the
! * next phase
* @throws IllegalArgumentException if parties less than zero
* or greater than the maximum number of parties supported
*/
public Phaser(Phaser parent, int parties) {
! if (parties >>> PARTIES_SHIFT != 0)
throw new IllegalArgumentException("Illegal number of parties");
! long s = ((long) parties) | (((long) parties) << PARTIES_SHIFT);
this.parent = parent;
if (parent != null) {
! Phaser r = parent.root;
! this.root = r;
! this.evenQ = r.evenQ;
! this.oddQ = r.oddQ;
! if (parties != 0)
! s |= ((long)(parent.doRegister(1))) << PHASE_SHIFT;
}
! else {
this.root = this;
! this.evenQ = new AtomicReference<QNode>();
! this.oddQ = new AtomicReference<QNode>();
}
+ this.state = s;
+ }
/**
! * Adds a new unarrived party to this phaser. If an ongoing
! * invocation of {@link #onAdvance} is in progress, this method
! * may await its completion before returning. If this phaser has
! * a parent, and this phaser previously had no registered parties,
! * this phaser is also registered with its parent.
*
* @return the arrival phase number to which this registration applied
* @throws IllegalStateException if attempting to register more
* than the maximum supported number of parties
*/
*** 442,456 ****
return doRegister(1);
}
/**
* Adds the given number of new unarrived parties to this phaser.
*
! * @param parties the number of parties required to trip barrier
* @return the arrival phase number to which this registration applied
* @throws IllegalStateException if attempting to register more
* than the maximum supported number of parties
*/
public int bulkRegister(int parties) {
if (parties < 0)
throw new IllegalArgumentException();
if (parties == 0)
--- 540,561 ----
return doRegister(1);
}
/**
* Adds the given number of new unarrived parties to this phaser.
+ * If an ongoing invocation of {@link #onAdvance} is in progress,
+ * this method may await its completion before returning. If this
+ * phaser has a parent, and the given number of parities is
+ * greater than zero, and this phaser previously had no registered
+ * parties, this phaser is also registered with its parent.
*
! * @param parties the number of additional parties required to
! * advance to the next phase
* @return the arrival phase number to which this registration applied
* @throws IllegalStateException if attempting to register more
* than the maximum supported number of parties
+ * @throws IllegalArgumentException if {@code parties < 0}
*/
public int bulkRegister(int parties) {
if (parties < 0)
throw new IllegalArgumentException();
if (parties == 0)
*** 457,676 ****
return getPhase();
return doRegister(parties);
}
/**
! * Shared code for register, bulkRegister
! */
! private int doRegister(int registrations) {
! int phase;
! for (;;) {
! long s = getReconciledState();
! phase = phaseOf(s);
! int unarrived = unarrivedOf(s) + registrations;
! int parties = partiesOf(s) + registrations;
! if (phase < 0)
! break;
! if (parties > ushortMask || unarrived > ushortMask)
! throw new IllegalStateException(badBounds(parties, unarrived));
! if (phase == phaseOf(root.state) &&
! casState(s, stateFor(phase, parties, unarrived)))
! break;
! }
! return phase;
! }
!
! /**
! * Arrives at the barrier, but does not wait for others. (You can
! * in turn wait for others via {@link #awaitAdvance}). It is an
! * unenforced usage error for an unregistered party to invoke this
! * method.
*
* @return the arrival phase number, or a negative value if terminated
* @throws IllegalStateException if not terminated and the number
* of unarrived parties would become negative
*/
public int arrive() {
! int phase;
! for (;;) {
! long s = state;
! phase = phaseOf(s);
! if (phase < 0)
! break;
! int parties = partiesOf(s);
! int unarrived = unarrivedOf(s) - 1;
! if (unarrived > 0) { // Not the last arrival
! if (casState(s, s - 1)) // s-1 adds one arrival
! break;
}
- else if (unarrived == 0) { // the last arrival
- Phaser par = parent;
- if (par == null) { // directly trip
- if (casState
- (s,
- trippedStateFor(onAdvance(phase, parties) ? -1 :
- ((phase + 1) & phaseMask), parties))) {
- releaseWaiters(phase);
- break;
- }
- }
- else { // cascade to parent
- if (casState(s, s - 1)) { // zeroes unarrived
- par.arrive();
- reconcileState();
- break;
- }
- }
- }
- else if (phase != phaseOf(root.state)) // or if unreconciled
- reconcileState();
- else
- throw new IllegalStateException(badBounds(parties, unarrived));
- }
- return phase;
- }
/**
! * Arrives at the barrier and deregisters from it without waiting
! * for others. Deregistration reduces the number of parties
! * required to trip the barrier in future phases. If this phaser
* has a parent, and deregistration causes this phaser to have
! * zero parties, this phaser also arrives at and is deregistered
! * from its parent. It is an unenforced usage error for an
! * unregistered party to invoke this method.
*
* @return the arrival phase number, or a negative value if terminated
* @throws IllegalStateException if not terminated and the number
* of registered or unarrived parties would become negative
*/
public int arriveAndDeregister() {
! // similar code to arrive, but too different to merge
! Phaser par = parent;
! int phase;
! for (;;) {
! long s = state;
! phase = phaseOf(s);
! if (phase < 0)
! break;
! int parties = partiesOf(s) - 1;
! int unarrived = unarrivedOf(s) - 1;
! if (parties >= 0) {
! if (unarrived > 0 || (unarrived == 0 && par != null)) {
! if (casState
! (s,
! stateFor(phase, parties, unarrived))) {
! if (unarrived == 0) {
! par.arriveAndDeregister();
! reconcileState();
}
- break;
- }
- continue;
- }
- if (unarrived == 0) {
- if (casState
- (s,
- trippedStateFor(onAdvance(phase, parties) ? -1 :
- ((phase + 1) & phaseMask), parties))) {
- releaseWaiters(phase);
- break;
- }
- continue;
- }
- if (par != null && phase != phaseOf(root.state)) {
- reconcileState();
- continue;
- }
- }
- throw new IllegalStateException(badBounds(parties, unarrived));
- }
- return phase;
- }
/**
! * Arrives at the barrier and awaits others. Equivalent in effect
* to {@code awaitAdvance(arrive())}. If you need to await with
* interruption or timeout, you can arrange this with an analogous
! * construction using one of the other forms of the awaitAdvance
! * method. If instead you need to deregister upon arrival use
! * {@code arriveAndDeregister}. It is an unenforced usage error
! * for an unregistered party to invoke this method.
*
* @return the arrival phase number, or a negative number if terminated
* @throws IllegalStateException if not terminated and the number
* of unarrived parties would become negative
*/
public int arriveAndAwaitAdvance() {
! return awaitAdvance(arrive());
}
/**
! * Awaits the phase of the barrier to advance from the given phase
! * value, returning immediately if the current phase of the
! * barrier is not equal to the given phase value or this barrier
! * is terminated. It is an unenforced usage error for an
! * unregistered party to invoke this method.
*
* @param phase an arrival phase number, or negative value if
* terminated; this argument is normally the value returned by a
! * previous call to {@code arrive} or its variants
* @return the next arrival phase number, or a negative value
* if terminated or argument is negative
*/
public int awaitAdvance(int phase) {
if (phase < 0)
return phase;
! long s = getReconciledState();
! int p = phaseOf(s);
! if (p != phase)
return p;
- if (unarrivedOf(s) == 0 && parent != null)
- parent.awaitAdvance(phase);
- // Fall here even if parent waited, to reconcile and help release
- return untimedWait(phase);
}
/**
! * Awaits the phase of the barrier to advance from the given phase
* value, throwing {@code InterruptedException} if interrupted
! * while waiting, or returning immediately if the current phase of
! * the barrier is not equal to the given phase value or this
! * barrier is terminated. It is an unenforced usage error for an
! * unregistered party to invoke this method.
*
* @param phase an arrival phase number, or negative value if
* terminated; this argument is normally the value returned by a
! * previous call to {@code arrive} or its variants
* @return the next arrival phase number, or a negative value
* if terminated or argument is negative
* @throws InterruptedException if thread interrupted while waiting
*/
public int awaitAdvanceInterruptibly(int phase)
throws InterruptedException {
if (phase < 0)
return phase;
! long s = getReconciledState();
! int p = phaseOf(s);
! if (p != phase)
return p;
- if (unarrivedOf(s) == 0 && parent != null)
- parent.awaitAdvanceInterruptibly(phase);
- return interruptibleWait(phase);
}
/**
! * Awaits the phase of the barrier to advance from the given phase
* value or the given timeout to elapse, throwing {@code
* InterruptedException} if interrupted while waiting, or
! * returning immediately if the current phase of the barrier is
! * not equal to the given phase value or this barrier is
! * terminated. It is an unenforced usage error for an
! * unregistered party to invoke this method.
*
* @param phase an arrival phase number, or negative value if
* terminated; this argument is normally the value returned by a
! * previous call to {@code arrive} or its variants
* @param timeout how long to wait before giving up, in units of
* {@code unit}
* @param unit a {@code TimeUnit} determining how to interpret the
* {@code timeout} parameter
* @return the next arrival phase number, or a negative value
--- 562,689 ----
return getPhase();
return doRegister(parties);
}
/**
! * Arrives at this phaser, without waiting for others to arrive.
*
+ * <p>It is a usage error for an unregistered party to invoke this
+ * method. However, this error may result in an {@code
+ * IllegalStateException} only upon some subsequent operation on
+ * this phaser, if ever.
+ *
* @return the arrival phase number, or a negative value if terminated
* @throws IllegalStateException if not terminated and the number
* of unarrived parties would become negative
*/
public int arrive() {
! return doArrive(ONE_ARRIVAL);
}
/**
! * Arrives at this phaser and deregisters from it without waiting
! * for others to arrive. Deregistration reduces the number of
! * parties required to advance in future phases. If this phaser
* has a parent, and deregistration causes this phaser to have
! * zero parties, this phaser is also deregistered from its parent.
*
+ * <p>It is a usage error for an unregistered party to invoke this
+ * method. However, this error may result in an {@code
+ * IllegalStateException} only upon some subsequent operation on
+ * this phaser, if ever.
+ *
* @return the arrival phase number, or a negative value if terminated
* @throws IllegalStateException if not terminated and the number
* of registered or unarrived parties would become negative
*/
public int arriveAndDeregister() {
! return doArrive(ONE_ARRIVAL|ONE_PARTY);
}
/**
! * Arrives at this phaser and awaits others. Equivalent in effect
* to {@code awaitAdvance(arrive())}. If you need to await with
* interruption or timeout, you can arrange this with an analogous
! * construction using one of the other forms of the {@code
! * awaitAdvance} method. If instead you need to deregister upon
! * arrival, use {@code awaitAdvance(arriveAndDeregister())}.
*
+ * <p>It is a usage error for an unregistered party to invoke this
+ * method. However, this error may result in an {@code
+ * IllegalStateException} only upon some subsequent operation on
+ * this phaser, if ever.
+ *
* @return the arrival phase number, or a negative number if terminated
* @throws IllegalStateException if not terminated and the number
* of unarrived parties would become negative
*/
public int arriveAndAwaitAdvance() {
! return awaitAdvance(doArrive(ONE_ARRIVAL));
}
/**
! * Awaits the phase of this phaser to advance from the given phase
! * value, returning immediately if the current phase is not equal
! * to the given phase value or this phaser is terminated.
*
* @param phase an arrival phase number, or negative value if
* terminated; this argument is normally the value returned by a
! * previous call to {@code arrive} or {@code arriveAndDeregister}.
* @return the next arrival phase number, or a negative value
* if terminated or argument is negative
*/
public int awaitAdvance(int phase) {
+ Phaser rt;
+ int p = (int)(state >>> PHASE_SHIFT);
if (phase < 0)
return phase;
! if (p == phase &&
! (p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase)
! return rt.internalAwaitAdvance(phase, null);
return p;
}
/**
! * Awaits the phase of this phaser to advance from the given phase
* value, throwing {@code InterruptedException} if interrupted
! * while waiting, or returning immediately if the current phase is
! * not equal to the given phase value or this phaser is
! * terminated.
*
* @param phase an arrival phase number, or negative value if
* terminated; this argument is normally the value returned by a
! * previous call to {@code arrive} or {@code arriveAndDeregister}.
* @return the next arrival phase number, or a negative value
* if terminated or argument is negative
* @throws InterruptedException if thread interrupted while waiting
*/
public int awaitAdvanceInterruptibly(int phase)
throws InterruptedException {
+ Phaser rt;
+ int p = (int)(state >>> PHASE_SHIFT);
if (phase < 0)
return phase;
! if (p == phase &&
! (p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
! QNode node = new QNode(this, phase, true, false, 0L);
! p = rt.internalAwaitAdvance(phase, node);
! if (node.wasInterrupted)
! throw new InterruptedException();
! }
return p;
}
/**
! * Awaits the phase of this phaser to advance from the given phase
* value or the given timeout to elapse, throwing {@code
* InterruptedException} if interrupted while waiting, or
! * returning immediately if the current phase is not equal to the
! * given phase value or this phaser is terminated.
*
* @param phase an arrival phase number, or negative value if
* terminated; this argument is normally the value returned by a
! * previous call to {@code arrive} or {@code arriveAndDeregister}.
* @param timeout how long to wait before giving up, in units of
* {@code unit}
* @param unit a {@code TimeUnit} determining how to interpret the
* {@code timeout} parameter
* @return the next arrival phase number, or a negative value
*** 679,761 ****
* @throws TimeoutException if timed out while waiting
*/
public int awaitAdvanceInterruptibly(int phase,
long timeout, TimeUnit unit)
throws InterruptedException, TimeoutException {
if (phase < 0)
return phase;
! long s = getReconciledState();
! int p = phaseOf(s);
! if (p != phase)
return p;
- if (unarrivedOf(s) == 0 && parent != null)
- parent.awaitAdvanceInterruptibly(phase, timeout, unit);
- return timedWait(phase, unit.toNanos(timeout));
}
/**
! * Forces this barrier to enter termination state. Counts of
* arrived and registered parties are unaffected. If this phaser
! * has a parent, it too is terminated. This method may be useful
! * for coordinating recovery after one or more tasks encounter
! * unexpected exceptions.
*/
public void forceTermination() {
! for (;;) {
! long s = getReconciledState();
! int phase = phaseOf(s);
! int parties = partiesOf(s);
! int unarrived = unarrivedOf(s);
! if (phase < 0 ||
! casState(s, stateFor(-1, parties, unarrived))) {
! releaseWaiters(0);
releaseWaiters(1);
- if (parent != null)
- parent.forceTermination();
return;
}
}
}
/**
* Returns the current phase number. The maximum phase number is
* {@code Integer.MAX_VALUE}, after which it restarts at
! * zero. Upon termination, the phase number is negative.
*
* @return the phase number, or a negative value if terminated
*/
public final int getPhase() {
! return phaseOf(getReconciledState());
}
/**
! * Returns the number of parties registered at this barrier.
*
* @return the number of parties
*/
public int getRegisteredParties() {
return partiesOf(state);
}
/**
* Returns the number of registered parties that have arrived at
! * the current phase of this barrier.
*
* @return the number of arrived parties
*/
public int getArrivedParties() {
! return arrivedOf(state);
}
/**
* Returns the number of registered parties that have not yet
! * arrived at the current phase of this barrier.
*
* @return the number of unarrived parties
*/
public int getUnarrivedParties() {
! return unarrivedOf(state);
}
/**
* Returns the parent of this phaser, or {@code null} if none.
*
--- 692,786 ----
* @throws TimeoutException if timed out while waiting
*/
public int awaitAdvanceInterruptibly(int phase,
long timeout, TimeUnit unit)
throws InterruptedException, TimeoutException {
+ long nanos = unit.toNanos(timeout);
+ Phaser rt;
+ int p = (int)(state >>> PHASE_SHIFT);
if (phase < 0)
return phase;
! if (p == phase &&
! (p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) {
! QNode node = new QNode(this, phase, true, true, nanos);
! p = rt.internalAwaitAdvance(phase, node);
! if (node.wasInterrupted)
! throw new InterruptedException();
! else if (p == phase)
! throw new TimeoutException();
! }
return p;
}
/**
! * Forces this phaser to enter termination state. Counts of
* arrived and registered parties are unaffected. If this phaser
! * is a member of a tiered set of phasers, then all of the phasers
! * in the set are terminated. If this phaser is already
! * terminated, this method has no effect. This method may be
! * useful for coordinating recovery after one or more tasks
! * encounter unexpected exceptions.
*/
public void forceTermination() {
! // Only need to change root state
! final Phaser root = this.root;
! long s;
! while ((s = root.state) >= 0) {
! if (UNSAFE.compareAndSwapLong(root, stateOffset,
! s, s | TERMINATION_BIT)) {
! releaseWaiters(0); // signal all threads
releaseWaiters(1);
return;
}
}
}
/**
* Returns the current phase number. The maximum phase number is
* {@code Integer.MAX_VALUE}, after which it restarts at
! * zero. Upon termination, the phase number is negative,
! * in which case the prevailing phase prior to termination
! * may be obtained via {@code getPhase() + Integer.MIN_VALUE}.
*
* @return the phase number, or a negative value if terminated
*/
public final int getPhase() {
! return (int)(root.state >>> PHASE_SHIFT);
}
/**
! * Returns the number of parties registered at this phaser.
*
* @return the number of parties
*/
public int getRegisteredParties() {
return partiesOf(state);
}
/**
* Returns the number of registered parties that have arrived at
! * the current phase of this phaser.
*
* @return the number of arrived parties
*/
public int getArrivedParties() {
! long s = state;
! int u = unarrivedOf(s); // only reconcile if possibly needed
! return (u != 0 || parent == null) ?
! partiesOf(s) - u :
! arrivedOf(reconcileState());
}
/**
* Returns the number of registered parties that have not yet
! * arrived at the current phase of this phaser.
*
* @return the number of unarrived parties
*/
public int getUnarrivedParties() {
! int u = unarrivedOf(state);
! return (u != 0 || parent == null) ? u : unarrivedOf(reconcileState());
}
/**
* Returns the parent of this phaser, or {@code null} if none.
*
*** 774,1036 ****
public Phaser getRoot() {
return root;
}
/**
! * Returns {@code true} if this barrier has been terminated.
*
! * @return {@code true} if this barrier has been terminated
*/
public boolean isTerminated() {
! return getPhase() < 0;
}
/**
* Overridable method to perform an action upon impending phase
* advance, and to control termination. This method is invoked
! * upon arrival of the party tripping the barrier (when all other
* waiting parties are dormant). If this method returns {@code
! * true}, then, rather than advance the phase number, this barrier
* will be set to a final termination state, and subsequent calls
* to {@link #isTerminated} will return true. Any (unchecked)
* Exception or Error thrown by an invocation of this method is
! * propagated to the party attempting to trip the barrier, in
* which case no advance occurs.
*
* <p>The arguments to this method provide the state of the phaser
! * prevailing for the current transition. (When called from within
! * an implementation of {@code onAdvance} the values returned by
! * methods such as {@code getPhase} may or may not reliably
! * indicate the state to which this transition applies.)
*
! * <p>The default version returns {@code true} when the number of
! * registered parties is zero. Normally, overrides that arrange
! * termination for other reasons should also preserve this
! * property.
*
! * <p>You may override this method to perform an action with side
! * effects visible to participating tasks, but it is only sensible
! * to do so in designs where all parties register before any
! * arrive, and all {@link #awaitAdvance} at each phase.
! * Otherwise, you cannot ensure lack of interference from other
! * parties during the invocation of this method. Additionally,
! * method {@code onAdvance} may be invoked more than once per
! * transition if registrations are intermixed with arrivals.
*
! * @param phase the phase number on entering the barrier
* @param registeredParties the current number of registered parties
! * @return {@code true} if this barrier should terminate
*/
protected boolean onAdvance(int phase, int registeredParties) {
! return registeredParties <= 0;
}
/**
* Returns a string identifying this phaser, as well as its
* state. The state, in brackets, includes the String {@code
* "phase = "} followed by the phase number, {@code "parties = "}
* followed by the number of registered parties, and {@code
* "arrived = "} followed by the number of arrived parties.
*
! * @return a string identifying this barrier, as well as its state
*/
public String toString() {
! long s = getReconciledState();
return super.toString() +
"[phase = " + phaseOf(s) +
" parties = " + partiesOf(s) +
" arrived = " + arrivedOf(s) + "]";
}
! // methods for waiting
/**
! * Wait nodes for Treiber stack representing wait queue
*/
! static final class QNode implements ForkJoinPool.ManagedBlocker {
! final Phaser phaser;
! final int phase;
! final long startTime;
! final long nanos;
! final boolean timed;
! final boolean interruptible;
! volatile boolean wasInterrupted = false;
! volatile Thread thread; // nulled to cancel wait
! QNode next;
! QNode(Phaser phaser, int phase, boolean interruptible,
! boolean timed, long startTime, long nanos) {
! this.phaser = phaser;
! this.phase = phase;
! this.timed = timed;
! this.interruptible = interruptible;
! this.startTime = startTime;
! this.nanos = nanos;
! thread = Thread.currentThread();
! }
! public boolean isReleasable() {
! return (thread == null ||
! phaser.getPhase() != phase ||
! (interruptible && wasInterrupted) ||
! (timed && (nanos - (System.nanoTime() - startTime)) <= 0));
! }
! public boolean block() {
! if (Thread.interrupted()) {
! wasInterrupted = true;
! if (interruptible)
! return true;
! }
! if (!timed)
! LockSupport.park(this);
! else {
! long waitTime = nanos - (System.nanoTime() - startTime);
! if (waitTime <= 0)
! return true;
! LockSupport.parkNanos(this, waitTime);
! }
! return isReleasable();
! }
! void signal() {
! Thread t = thread;
! if (t != null) {
! thread = null;
LockSupport.unpark(t);
}
}
- boolean doWait() {
- if (thread != null) {
- try {
- ForkJoinPool.managedBlock(this);
- } catch (InterruptedException ie) {
}
- }
- return wasInterrupted;
- }
! }
/**
! * Removes and signals waiting threads from wait queue.
*/
! private void releaseWaiters(int phase) {
! AtomicReference<QNode> head = queueFor(phase);
! QNode q;
! while ((q = head.get()) != null) {
! if (head.compareAndSet(q, q.next))
! q.signal();
! }
! }
/**
! * Tries to enqueue given node in the appropriate wait queue.
*
! * @return true if successful
! */
! private boolean tryEnqueue(QNode node) {
! AtomicReference<QNode> head = queueFor(node.phase);
! return head.compareAndSet(node.next = head.get(), node);
! }
!
! /**
! * Enqueues node and waits unless aborted or signalled.
! *
* @return current phase
*/
! private int untimedWait(int phase) {
! QNode node = null;
! boolean queued = false;
! boolean interrupted = false;
int p;
! while ((p = getPhase()) == phase) {
! if (Thread.interrupted())
! interrupted = true;
! else if (node == null)
! node = new QNode(this, phase, false, false, 0, 0);
! else if (!queued)
! queued = tryEnqueue(node);
! else
! interrupted = node.doWait();
}
- if (node != null)
- node.thread = null;
- releaseWaiters(phase);
- if (interrupted)
- Thread.currentThread().interrupt();
- return p;
}
! /**
! * Interruptible version
! * @return current phase
! */
! private int interruptibleWait(int phase) throws InterruptedException {
! QNode node = null;
! boolean queued = false;
! boolean interrupted = false;
! int p;
! while ((p = getPhase()) == phase && !interrupted) {
! if (Thread.interrupted())
! interrupted = true;
! else if (node == null)
! node = new QNode(this, phase, true, false, 0, 0);
! else if (!queued)
! queued = tryEnqueue(node);
! else
! interrupted = node.doWait();
}
- if (node != null)
- node.thread = null;
- if (p != phase || (p = getPhase()) != phase)
releaseWaiters(phase);
- if (interrupted)
- throw new InterruptedException();
return p;
}
/**
! * Timeout version.
! * @return current phase
*/
! private int timedWait(int phase, long nanos)
! throws InterruptedException, TimeoutException {
! long startTime = System.nanoTime();
! QNode node = null;
! boolean queued = false;
! boolean interrupted = false;
! int p;
! while ((p = getPhase()) == phase && !interrupted) {
if (Thread.interrupted())
! interrupted = true;
! else if (nanos - (System.nanoTime() - startTime) <= 0)
! break;
! else if (node == null)
! node = new QNode(this, phase, true, true, startTime, nanos);
! else if (!queued)
! queued = tryEnqueue(node);
! else
! interrupted = node.doWait();
}
! if (node != null)
! node.thread = null;
! if (p != phase || (p = getPhase()) != phase)
! releaseWaiters(phase);
! if (interrupted)
! throw new InterruptedException();
! if (p == phase)
! throw new TimeoutException();
! return p;
}
// Unsafe mechanics
private static final sun.misc.Unsafe UNSAFE = sun.misc.Unsafe.getUnsafe();
private static final long stateOffset =
objectFieldOffset("state", Phaser.class);
- private final boolean casState(long cmp, long val) {
- return UNSAFE.compareAndSwapLong(this, stateOffset, cmp, val);
- }
-
private static long objectFieldOffset(String field, Class<?> klazz) {
try {
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
} catch (NoSuchFieldException e) {
// Convert Exception to corresponding Error
--- 799,1047 ----
public Phaser getRoot() {
return root;
}
/**
! * Returns {@code true} if this phaser has been terminated.
*
! * @return {@code true} if this phaser has been terminated
*/
public boolean isTerminated() {
! return root.state < 0L;
}
/**
* Overridable method to perform an action upon impending phase
* advance, and to control termination. This method is invoked
! * upon arrival of the party advancing this phaser (when all other
* waiting parties are dormant). If this method returns {@code
! * true}, then, rather than advance the phase number, this phaser
* will be set to a final termination state, and subsequent calls
* to {@link #isTerminated} will return true. Any (unchecked)
* Exception or Error thrown by an invocation of this method is
! * propagated to the party attempting to advance this phaser, in
* which case no advance occurs.
*
* <p>The arguments to this method provide the state of the phaser
! * prevailing for the current transition. The effects of invoking
! * arrival, registration, and waiting methods on this phaser from
! * within {@code onAdvance} are unspecified and should not be
! * relied on.
*
! * <p>If this phaser is a member of a tiered set of phasers, then
! * {@code onAdvance} is invoked only for its root phaser on each
! * advance.
*
! * <p>To support the most common use cases, the default
! * implementation of this method returns {@code true} when the
! * number of registered parties has become zero as the result of a
! * party invoking {@code arriveAndDeregister}. You can disable
! * this behavior, thus enabling continuation upon future
! * registrations, by overriding this method to always return
! * {@code false}:
*
! * <pre> {@code
! * Phaser phaser = new Phaser() {
! * protected boolean onAdvance(int phase, int parties) { return false; }
! * }}</pre>
! *
! * @param phase the current phase number on entry to this method,
! * before this phaser is advanced
* @param registeredParties the current number of registered parties
! * @return {@code true} if this phaser should terminate
*/
protected boolean onAdvance(int phase, int registeredParties) {
! return registeredParties == 0;
}
/**
* Returns a string identifying this phaser, as well as its
* state. The state, in brackets, includes the String {@code
* "phase = "} followed by the phase number, {@code "parties = "}
* followed by the number of registered parties, and {@code
* "arrived = "} followed by the number of arrived parties.
*
! * @return a string identifying this phaser, as well as its state
*/
public String toString() {
! return stateToString(reconcileState());
! }
!
! /**
! * Implementation of toString and string-based error messages
! */
! private String stateToString(long s) {
return super.toString() +
"[phase = " + phaseOf(s) +
" parties = " + partiesOf(s) +
" arrived = " + arrivedOf(s) + "]";
}
! // Waiting mechanics
/**
! * Removes and signals threads from queue for phase.
*/
! private void releaseWaiters(int phase) {
! QNode q; // first element of queue
! int p; // its phase
! Thread t; // its thread
! AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
! while ((q = head.get()) != null &&
! ((p = q.phase) == phase ||
! (int)(root.state >>> PHASE_SHIFT) != p)) {
! if (head.compareAndSet(q, q.next) &&
! (t = q.thread) != null) {
! q.thread = null;
LockSupport.unpark(t);
}
}
}
! /** The number of CPUs, for spin control */
! private static final int NCPU = Runtime.getRuntime().availableProcessors();
/**
! * The number of times to spin before blocking while waiting for
! * advance, per arrival while waiting. On multiprocessors, fully
! * blocking and waking up a large number of threads all at once is
! * usually a very slow process, so we use rechargeable spins to
! * avoid it when threads regularly arrive: When a thread in
! * internalAwaitAdvance notices another arrival before blocking,
! * and there appear to be enough CPUs available, it spins
! * SPINS_PER_ARRIVAL more times before blocking. The value trades
! * off good-citizenship vs big unnecessary slowdowns.
*/
! static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
/**
! * Possibly blocks and waits for phase to advance unless aborted.
! * Call only from root node.
*
! * @param phase current phase
! * @param node if non-null, the wait node to track interrupt and timeout;
! * if null, denotes noninterruptible wait
* @return current phase
*/
! private int internalAwaitAdvance(int phase, QNode node) {
! releaseWaiters(phase-1); // ensure old queue clean
! boolean queued = false; // true when node is enqueued
! int lastUnarrived = 0; // to increase spins upon change
! int spins = SPINS_PER_ARRIVAL;
! long s;
int p;
! while ((p = (int)((s = state) >>> PHASE_SHIFT)) == phase) {
! if (node == null) { // spinning in noninterruptible mode
! int unarrived = (int)s & UNARRIVED_MASK;
! if (unarrived != lastUnarrived &&
! (lastUnarrived = unarrived) < NCPU)
! spins += SPINS_PER_ARRIVAL;
! boolean interrupted = Thread.interrupted();
! if (interrupted || --spins < 0) { // need node to record intr
! node = new QNode(this, phase, false, false, 0L);
! node.wasInterrupted = interrupted;
}
}
+ else if (node.isReleasable()) // done or aborted
+ break;
+ else if (!queued) { // push onto queue
+ AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ;
+ QNode q = node.next = head.get();
+ if ((q == null || q.phase == phase) &&
+ (int)(state >>> PHASE_SHIFT) == phase) // avoid stale enq
+ queued = head.compareAndSet(q, node);
+ }
+ else {
+ try {
+ ForkJoinPool.managedBlock(node);
+ } catch (InterruptedException ie) {
+ node.wasInterrupted = true;
+ }
+ }
+ }
! if (node != null) {
! if (node.thread != null)
! node.thread = null; // avoid need for unpark()
! if (node.wasInterrupted && !node.interruptible)
! Thread.currentThread().interrupt();
! if ((p = (int)(state >>> PHASE_SHIFT)) == phase)
! return p; // recheck abort
}
releaseWaiters(phase);
return p;
}
/**
! * Wait nodes for Treiber stack representing wait queue
*/
! static final class QNode implements ForkJoinPool.ManagedBlocker {
! final Phaser phaser;
! final int phase;
! final boolean interruptible;
! final boolean timed;
! boolean wasInterrupted;
! long nanos;
! long lastTime;
! volatile Thread thread; // nulled to cancel wait
! QNode next;
!
! QNode(Phaser phaser, int phase, boolean interruptible,
! boolean timed, long nanos) {
! this.phaser = phaser;
! this.phase = phase;
! this.interruptible = interruptible;
! this.nanos = nanos;
! this.timed = timed;
! this.lastTime = timed ? System.nanoTime() : 0L;
! thread = Thread.currentThread();
! }
!
! public boolean isReleasable() {
! if (thread == null)
! return true;
! if (phaser.getPhase() != phase) {
! thread = null;
! return true;
! }
if (Thread.interrupted())
! wasInterrupted = true;
! if (wasInterrupted && interruptible) {
! thread = null;
! return true;
}
! if (timed) {
! if (nanos > 0L) {
! long now = System.nanoTime();
! nanos -= now - lastTime;
! lastTime = now;
}
+ if (nanos <= 0L) {
+ thread = null;
+ return true;
+ }
+ }
+ return false;
+ }
+ public boolean block() {
+ if (isReleasable())
+ return true;
+ else if (!timed)
+ LockSupport.park(this);
+ else if (nanos > 0)
+ LockSupport.parkNanos(this, nanos);
+ return isReleasable();
+ }
+ }
+
// Unsafe mechanics
private static final sun.misc.Unsafe UNSAFE = sun.misc.Unsafe.getUnsafe();
private static final long stateOffset =
objectFieldOffset("state", Phaser.class);
private static long objectFieldOffset(String field, Class<?> klazz) {
try {
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field));
} catch (NoSuchFieldException e) {
// Convert Exception to corresponding Error