src/share/classes/java/util/concurrent/Phaser.java

Print this page

        

*** 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