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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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* http://creativecommons.org/publicdomain/zero/1.0/ |
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*/ |
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package jsr166y; |
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* {@link java.util.concurrent.CountDownLatch CountDownLatch} |
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* but supporting more flexible usage. |
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* |
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< |
* <p> <b>Registration.</b> Unlike the case for other barriers, the |
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* <p><b>Registration.</b> Unlike the case for other barriers, the |
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* number of parties <em>registered</em> to synchronize on a phaser |
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* may vary over time. Tasks may be registered at any time (using |
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* methods {@link #register}, {@link #bulkRegister}, or forms of |
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* (However, you can introduce such bookkeeping by subclassing this |
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* class.) |
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* |
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< |
* <p> <b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code |
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> |
* <p><b>Synchronization.</b> Like a {@code CyclicBarrier}, a {@code |
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* Phaser} may be repeatedly awaited. Method {@link |
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* #arriveAndAwaitAdvance} has effect analogous to {@link |
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* java.util.concurrent.CyclicBarrier#await CyclicBarrier.await}. Each |
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* |
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* <ul> |
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* |
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* <li> <b>Arrival.</b> Methods {@link #arrive} and |
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* <li><b>Arrival.</b> Methods {@link #arrive} and |
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* {@link #arriveAndDeregister} record arrival. These methods |
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* do not block, but return an associated <em>arrival phase |
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* number</em>; that is, the phase number of the phaser to which |
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* flexible than, providing a barrier action to a {@code |
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* CyclicBarrier}. |
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* |
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< |
* <li> <b>Waiting.</b> Method {@link #awaitAdvance} requires an |
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* <li><b>Waiting.</b> Method {@link #awaitAdvance} requires an |
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* argument indicating an arrival phase number, and returns when |
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* the phaser advances to (or is already at) a different phase. |
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* Unlike similar constructions using {@code CyclicBarrier}, |
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* |
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* </ul> |
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* |
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* <p> <b>Termination.</b> A phaser may enter a <em>termination</em> |
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* state in which all synchronization methods immediately return |
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* without updating phaser state or waiting for advance, and |
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* indicating (via a negative phase value) that execution is complete. |
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* <p><b>Termination.</b> A phaser may enter a <em>termination</em> |
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* state, that may be checked using method {@link #isTerminated}. Upon |
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* termination, all synchronization methods immediately return without |
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* waiting for advance, as indicated by a negative return value. |
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* Similarly, attempts to register upon termination have no effect. |
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* Termination is triggered when an invocation of {@code onAdvance} |
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* returns {@code true}. The default implementation returns {@code |
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* true} if a deregistration has caused the number of registered |
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* also available to abruptly release waiting threads and allow them |
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* to terminate. |
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* |
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* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., |
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* <p><b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., |
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* constructed in tree structures) to reduce contention. Phasers with |
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* large numbers of parties that would otherwise experience heavy |
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* synchronization contention costs may instead be set up so that |
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* increase throughput even though it incurs greater per-operation |
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* overhead. |
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* |
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* <p>In a tree of tiered phasers, registration and deregistration of |
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* child phasers with their parent are managed automatically. |
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* Whenever the number of registered parties of a child phaser becomes |
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* non-zero (as established in the {@link #Phaser(Phaser,int)} |
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* constructor, {@link #register}, or {@link #bulkRegister}), the |
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* child phaser is registered with its parent. Whenever the number of |
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* registered parties becomes zero as the result of an invocation of |
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* {@link #arriveAndDeregister}, the child phaser is deregistered |
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* from its parent. |
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* |
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* <p><b>Monitoring.</b> While synchronization methods may be invoked |
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* only by registered parties, the current state of a phaser may be |
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* monitored by any caller. At any given moment there are {@link |
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* void runTasks(List<Runnable> tasks) { |
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* final Phaser phaser = new Phaser(1); // "1" to register self |
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* // create and start threads |
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* for (Runnable task : tasks) { |
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* for (final Runnable task : tasks) { |
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* phaser.register(); |
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* new Thread() { |
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* public void run() { |
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*/ |
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/** |
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* Primary state representation, holding four fields: |
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> |
* Primary state representation, holding four bit-fields: |
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* |
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* * unarrived -- the number of parties yet to hit barrier (bits 0-15) |
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* * parties -- the number of parties to wait (bits 16-31) |
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* * phase -- the generation of the barrier (bits 32-62) |
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* * terminated -- set if barrier is terminated (bit 63 / sign) |
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* unarrived -- the number of parties yet to hit barrier (bits 0-15) |
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* parties -- the number of parties to wait (bits 16-31) |
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* phase -- the generation of the barrier (bits 32-62) |
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* terminated -- set if barrier is terminated (bit 63 / sign) |
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* |
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* Except that a phaser with no registered parties is |
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* distinguished with the otherwise illegal state of having zero |
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* distinguished by the otherwise illegal state of having zero |
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* parties and one unarrived parties (encoded as EMPTY below). |
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* |
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* To efficiently maintain atomicity, these values are packed into |
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* parent. |
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* |
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* The phase of a subphaser is allowed to lag that of its |
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* ancestors until it is actually accessed. Method reconcileState |
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* is usually attempted only only when the number of unarrived |
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* parties appears to be zero, which indicates a potential lag in |
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* updating phase after the root advanced. |
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* ancestors until it is actually accessed -- see method |
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* reconcileState. |
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*/ |
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private volatile long state; |
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|
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private static final int MAX_PARTIES = 0xffff; |
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< |
private static final int MAX_PHASE = 0x7fffffff; |
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> |
private static final int MAX_PHASE = Integer.MAX_VALUE; |
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private static final int PARTIES_SHIFT = 16; |
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private static final int PHASE_SHIFT = 32; |
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private static final int UNARRIVED_MASK = 0xffff; // to mask ints |
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private static final long PARTIES_MASK = 0xffff0000L; // to mask longs |
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+ |
private static final long COUNTS_MASK = 0xffffffffL; |
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private static final long TERMINATION_BIT = 1L << 63; |
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|
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// some special values |
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private static final int ONE_ARRIVAL = 1; |
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private static final int ONE_PARTY = 1 << PARTIES_SHIFT; |
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+ |
private static final int ONE_DEREGISTER = ONE_ARRIVAL|ONE_PARTY; |
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private static final int EMPTY = 1; |
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|
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// The following unpacking methods are usually manually inlined |
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|
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private static int unarrivedOf(long s) { |
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int counts = (int)s; |
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< |
return (counts == EMPTY)? 0 : counts & UNARRIVED_MASK; |
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> |
return (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK); |
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} |
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|
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private static int partiesOf(long s) { |
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< |
int counts = (int)s; |
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< |
return (counts == EMPTY)? 0 : counts >>> PARTIES_SHIFT; |
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> |
return (int)s >>> PARTIES_SHIFT; |
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} |
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|
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private static int phaseOf(long s) { |
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< |
return (int) (s >>> PHASE_SHIFT); |
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> |
return (int)(s >>> PHASE_SHIFT); |
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} |
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|
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private static int arrivedOf(long s) { |
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int counts = (int)s; |
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< |
return (counts == EMPTY)? 0 : |
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> |
return (counts == EMPTY) ? 0 : |
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(counts >>> PARTIES_SHIFT) - (counts & UNARRIVED_MASK); |
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} |
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|
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* Manually tuned to speed up and minimize race windows for the |
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* common case of just decrementing unarrived field. |
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* |
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< |
* @param deregister false for arrive, true for arriveAndDeregister |
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> |
* @param adjust value to subtract from state; |
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> |
* ONE_ARRIVAL for arrive, |
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> |
* ONE_DEREGISTER for arriveAndDeregister |
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*/ |
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< |
private int doArrive(boolean deregister) { |
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< |
int adj = deregister ? ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL; |
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< |
long s; |
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< |
int phase; |
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< |
while ((phase = (int)((s = state) >>> PHASE_SHIFT)) >= 0) { |
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> |
private int doArrive(int adjust) { |
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> |
final Phaser root = this.root; |
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> |
for (;;) { |
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> |
long s = (root == this) ? state : reconcileState(); |
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> |
int phase = (int)(s >>> PHASE_SHIFT); |
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> |
if (phase < 0) |
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> |
return phase; |
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int counts = (int)s; |
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< |
int unarrived = counts & UNARRIVED_MASK; |
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< |
if (counts == EMPTY || unarrived == 0) { |
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< |
if (reconcileState() == s) |
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< |
throw new IllegalStateException(badArrive(s)); |
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< |
} |
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< |
else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) { |
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> |
int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK); |
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> |
if (unarrived <= 0) |
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> |
throw new IllegalStateException(badArrive(s)); |
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> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adjust)) { |
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if (unarrived == 1) { |
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< |
long n = s & PARTIES_MASK; // unshifted parties field |
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< |
int u = ((int)n) >>> PARTIES_SHIFT; |
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< |
Phaser par = parent; |
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< |
if (par != null) { |
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< |
par.doArrive(u == 0); |
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< |
reconcileState(); |
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< |
} |
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< |
else { |
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< |
n |= (((long)((phase+1) & MAX_PHASE)) << PHASE_SHIFT); |
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< |
if (onAdvance(phase, u)) |
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> |
long n = s & PARTIES_MASK; // base of next state |
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> |
int nextUnarrived = (int)n >>> PARTIES_SHIFT; |
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> |
if (root == this) { |
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> |
if (onAdvance(phase, nextUnarrived)) |
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n |= TERMINATION_BIT; |
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< |
else if (u == 0) |
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< |
n |= EMPTY; // reset to unregistered |
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> |
else if (nextUnarrived == 0) |
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> |
n |= EMPTY; |
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else |
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< |
n |= (long)u; // reset unarr to parties |
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< |
// assert state == s || isTerminated(); |
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> |
n |= nextUnarrived; |
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> |
int nextPhase = (phase + 1) & MAX_PHASE; |
| 375 |
> |
n |= (long)nextPhase << PHASE_SHIFT; |
| 376 |
|
UNSAFE.compareAndSwapLong(this, stateOffset, s, n); |
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releaseWaiters(phase); |
| 378 |
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} |
| 379 |
+ |
else if (nextUnarrived == 0) { // propagate deregistration |
| 380 |
+ |
phase = parent.doArrive(ONE_DEREGISTER); |
| 381 |
+ |
UNSAFE.compareAndSwapLong(this, stateOffset, |
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+ |
s, s | EMPTY); |
| 383 |
+ |
} |
| 384 |
+ |
else |
| 385 |
+ |
phase = parent.doArrive(ONE_ARRIVAL); |
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} |
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< |
break; |
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> |
return phase; |
| 388 |
|
} |
| 389 |
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} |
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– |
return phase; |
| 390 |
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} |
| 391 |
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|
| 392 |
|
/** |
| 397 |
|
*/ |
| 398 |
|
private int doRegister(int registrations) { |
| 399 |
|
// adjustment to state |
| 400 |
< |
long adj = ((long)registrations << PARTIES_SHIFT) | registrations; |
| 401 |
< |
Phaser par = parent; |
| 400 |
> |
long adjust = ((long)registrations << PARTIES_SHIFT) | registrations; |
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> |
final Phaser parent = this.parent; |
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|
int phase; |
| 403 |
|
for (;;) { |
| 404 |
< |
long s = state; |
| 404 |
> |
long s = (parent == null) ? state : reconcileState(); |
| 405 |
|
int counts = (int)s; |
| 406 |
|
int parties = counts >>> PARTIES_SHIFT; |
| 407 |
|
int unarrived = counts & UNARRIVED_MASK; |
| 408 |
|
if (registrations > MAX_PARTIES - parties) |
| 409 |
|
throw new IllegalStateException(badRegister(s)); |
| 410 |
< |
else if ((phase = (int)(s >>> PHASE_SHIFT)) < 0) |
| 410 |
> |
phase = (int)(s >>> PHASE_SHIFT); |
| 411 |
> |
if (phase < 0) |
| 412 |
|
break; |
| 413 |
< |
else if (counts != EMPTY) { // not 1st registration |
| 414 |
< |
if (par == null || reconcileState() == s) { |
| 413 |
> |
if (counts != EMPTY) { // not 1st registration |
| 414 |
> |
if (parent == null || reconcileState() == s) { |
| 415 |
|
if (unarrived == 0) // wait out advance |
| 416 |
|
root.internalAwaitAdvance(phase, null); |
| 417 |
|
else if (UNSAFE.compareAndSwapLong(this, stateOffset, |
| 418 |
< |
s, s + adj)) |
| 418 |
> |
s, s + adjust)) |
| 419 |
|
break; |
| 420 |
|
} |
| 421 |
|
} |
| 422 |
< |
else if (par == null) { // 1st root registration |
| 423 |
< |
long next = (((long) phase) << PHASE_SHIFT) | adj; |
| 422 |
> |
else if (parent == null) { // 1st root registration |
| 423 |
> |
long next = ((long)phase << PHASE_SHIFT) | adjust; |
| 424 |
|
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, next)) |
| 425 |
|
break; |
| 426 |
|
} |
| 427 |
|
else { |
| 428 |
< |
synchronized(this) { // 1st sub registration |
| 428 |
> |
synchronized (this) { // 1st sub registration |
| 429 |
|
if (state == s) { // recheck under lock |
| 430 |
< |
par.doRegister(1); |
| 431 |
< |
do { // force current phase |
| 430 |
> |
phase = parent.doRegister(1); |
| 431 |
> |
if (phase < 0) |
| 432 |
> |
break; |
| 433 |
> |
// finish registration whenever parent registration |
| 434 |
> |
// succeeded, even when racing with termination, |
| 435 |
> |
// since these are part of the same "transaction". |
| 436 |
> |
while (!UNSAFE.compareAndSwapLong |
| 437 |
> |
(this, stateOffset, s, |
| 438 |
> |
((long)phase << PHASE_SHIFT) | adjust)) { |
| 439 |
> |
s = state; |
| 440 |
|
phase = (int)(root.state >>> PHASE_SHIFT); |
| 441 |
< |
// assert phase < 0 || (int)state == EMPTY; |
| 442 |
< |
} while (!UNSAFE.compareAndSwapLong |
| 421 |
< |
(this, stateOffset, state, |
| 422 |
< |
(((long) phase) << PHASE_SHIFT) | adj)); |
| 441 |
> |
// assert (int)s == EMPTY; |
| 442 |
> |
} |
| 443 |
|
break; |
| 444 |
|
} |
| 445 |
|
} |
| 450 |
|
|
| 451 |
|
/** |
| 452 |
|
* Resolves lagged phase propagation from root if necessary. |
| 453 |
+ |
* Reconciliation normally occurs when root has advanced but |
| 454 |
+ |
* subphasers have not yet done so, in which case they must finish |
| 455 |
+ |
* their own advance by setting unarrived to parties (or if |
| 456 |
+ |
* parties is zero, resetting to unregistered EMPTY state). |
| 457 |
+ |
* |
| 458 |
+ |
* @return reconciled state |
| 459 |
|
*/ |
| 460 |
|
private long reconcileState() { |
| 461 |
< |
Phaser rt = root; |
| 461 |
> |
final Phaser root = this.root; |
| 462 |
|
long s = state; |
| 463 |
< |
if (rt != this) { |
| 464 |
< |
int phase; |
| 465 |
< |
while ((phase = (int)(rt.state >>> PHASE_SHIFT)) != |
| 466 |
< |
(int)(s >>> PHASE_SHIFT)) { |
| 467 |
< |
// assert phase < 0 || unarrivedOf(s) == 0 |
| 468 |
< |
long t; // to reread s |
| 469 |
< |
long p = s & PARTIES_MASK; // unshifted parties field |
| 470 |
< |
long n = (((long) phase) << PHASE_SHIFT) | p; |
| 471 |
< |
if (phase >= 0) { |
| 472 |
< |
if (p == 0L) |
| 473 |
< |
n |= EMPTY; // reset to empty |
| 474 |
< |
else |
| 449 |
< |
n |= p >>> PARTIES_SHIFT; // set unarr to parties |
| 450 |
< |
} |
| 451 |
< |
if ((t = state) == s && |
| 452 |
< |
UNSAFE.compareAndSwapLong(this, stateOffset, s, s = n)) |
| 453 |
< |
break; |
| 454 |
< |
s = t; |
| 455 |
< |
} |
| 463 |
> |
if (root != this) { |
| 464 |
> |
int phase, p; |
| 465 |
> |
// CAS to root phase with current parties, tripping unarrived |
| 466 |
> |
while ((phase = (int)(root.state >>> PHASE_SHIFT)) != |
| 467 |
> |
(int)(s >>> PHASE_SHIFT) && |
| 468 |
> |
!UNSAFE.compareAndSwapLong |
| 469 |
> |
(this, stateOffset, s, |
| 470 |
> |
s = (((long)phase << PHASE_SHIFT) | |
| 471 |
> |
((phase < 0) ? (s & COUNTS_MASK) : |
| 472 |
> |
(((p = (int)s >>> PARTIES_SHIFT) == 0) ? EMPTY : |
| 473 |
> |
((s & PARTIES_MASK) | p)))))) |
| 474 |
> |
s = state; |
| 475 |
|
} |
| 476 |
|
return s; |
| 477 |
|
} |
| 509 |
|
|
| 510 |
|
/** |
| 511 |
|
* Creates a new phaser with the given parent and number of |
| 512 |
< |
* registered unarrived parties. Registration and deregistration |
| 513 |
< |
* of this child phaser with its parent are managed automatically. |
| 514 |
< |
* If the given parent is non-null, whenever this child phaser has |
| 496 |
< |
* any registered parties (as established in this constructor, |
| 497 |
< |
* {@link #register}, or {@link #bulkRegister}), this child phaser |
| 498 |
< |
* is registered with its parent. Whenever the number of |
| 499 |
< |
* registered parties becomes zero as the result of an invocation |
| 500 |
< |
* of {@link #arriveAndDeregister}, this child phaser is |
| 501 |
< |
* deregistered from its parent. |
| 512 |
> |
* registered unarrived parties. When the given parent is non-null |
| 513 |
> |
* and the given number of parties is greater than zero, this |
| 514 |
> |
* child phaser is registered with its parent. |
| 515 |
|
* |
| 516 |
|
* @param parent the parent phaser |
| 517 |
|
* @param parties the number of parties required to advance to the |
| 525 |
|
int phase = 0; |
| 526 |
|
this.parent = parent; |
| 527 |
|
if (parent != null) { |
| 528 |
< |
Phaser r = parent.root; |
| 529 |
< |
this.root = r; |
| 530 |
< |
this.evenQ = r.evenQ; |
| 531 |
< |
this.oddQ = r.oddQ; |
| 528 |
> |
final Phaser root = parent.root; |
| 529 |
> |
this.root = root; |
| 530 |
> |
this.evenQ = root.evenQ; |
| 531 |
> |
this.oddQ = root.oddQ; |
| 532 |
|
if (parties != 0) |
| 533 |
|
phase = parent.doRegister(1); |
| 534 |
|
} |
| 537 |
|
this.evenQ = new AtomicReference<QNode>(); |
| 538 |
|
this.oddQ = new AtomicReference<QNode>(); |
| 539 |
|
} |
| 540 |
< |
this.state = (parties == 0)? ((long) EMPTY) : |
| 541 |
< |
((((long) phase) << PHASE_SHIFT) | |
| 542 |
< |
(((long) parties) << PARTIES_SHIFT) | |
| 543 |
< |
((long) parties)); |
| 540 |
> |
this.state = (parties == 0) ? (long)EMPTY : |
| 541 |
> |
((long)phase << PHASE_SHIFT) | |
| 542 |
> |
((long)parties << PARTIES_SHIFT) | |
| 543 |
> |
((long)parties); |
| 544 |
|
} |
| 545 |
|
|
| 546 |
|
/** |
| 548 |
|
* invocation of {@link #onAdvance} is in progress, this method |
| 549 |
|
* may await its completion before returning. If this phaser has |
| 550 |
|
* a parent, and this phaser previously had no registered parties, |
| 551 |
< |
* this phaser is also registered with its parent. |
| 552 |
< |
* |
| 553 |
< |
* @return the arrival phase number to which this registration applied |
| 551 |
> |
* this child phaser is also registered with its parent. If |
| 552 |
> |
* this phaser is terminated, the attempt to register has |
| 553 |
> |
* no effect, and a negative value is returned. |
| 554 |
> |
* |
| 555 |
> |
* @return the arrival phase number to which this registration |
| 556 |
> |
* applied. If this value is negative, then this phaser has |
| 557 |
> |
* terminated, in which case registration has no effect. |
| 558 |
|
* @throws IllegalStateException if attempting to register more |
| 559 |
|
* than the maximum supported number of parties |
| 560 |
|
*/ |
| 566 |
|
* Adds the given number of new unarrived parties to this phaser. |
| 567 |
|
* If an ongoing invocation of {@link #onAdvance} is in progress, |
| 568 |
|
* this method may await its completion before returning. If this |
| 569 |
< |
* phaser has a parent, and the given number of parities is |
| 570 |
< |
* greater than zero, and this phaser previously had no registered |
| 571 |
< |
* parties, this phaser is also registered with its parent. |
| 569 |
> |
* phaser has a parent, and the given number of parties is greater |
| 570 |
> |
* than zero, and this phaser previously had no registered |
| 571 |
> |
* parties, this child phaser is also registered with its parent. |
| 572 |
> |
* If this phaser is terminated, the attempt to register has no |
| 573 |
> |
* effect, and a negative value is returned. |
| 574 |
|
* |
| 575 |
|
* @param parties the number of additional parties required to |
| 576 |
|
* advance to the next phase |
| 577 |
< |
* @return the arrival phase number to which this registration applied |
| 577 |
> |
* @return the arrival phase number to which this registration |
| 578 |
> |
* applied. If this value is negative, then this phaser has |
| 579 |
> |
* terminated, in which case registration has no effect. |
| 580 |
|
* @throws IllegalStateException if attempting to register more |
| 581 |
|
* than the maximum supported number of parties |
| 582 |
|
* @throws IllegalArgumentException if {@code parties < 0} |
| 602 |
|
* of unarrived parties would become negative |
| 603 |
|
*/ |
| 604 |
|
public int arrive() { |
| 605 |
< |
return doArrive(false); |
| 605 |
> |
return doArrive(ONE_ARRIVAL); |
| 606 |
|
} |
| 607 |
|
|
| 608 |
|
/** |
| 622 |
|
* of registered or unarrived parties would become negative |
| 623 |
|
*/ |
| 624 |
|
public int arriveAndDeregister() { |
| 625 |
< |
return doArrive(true); |
| 625 |
> |
return doArrive(ONE_DEREGISTER); |
| 626 |
|
} |
| 627 |
|
|
| 628 |
|
/** |
| 638 |
|
* IllegalStateException} only upon some subsequent operation on |
| 639 |
|
* this phaser, if ever. |
| 640 |
|
* |
| 641 |
< |
* @return the arrival phase number, or a negative number if terminated |
| 641 |
> |
* @return the arrival phase number, or the (negative) |
| 642 |
> |
* {@linkplain #getPhase() current phase} if terminated |
| 643 |
|
* @throws IllegalStateException if not terminated and the number |
| 644 |
|
* of unarrived parties would become negative |
| 645 |
|
*/ |
| 646 |
|
public int arriveAndAwaitAdvance() { |
| 647 |
< |
return awaitAdvance(doArrive(false)); |
| 647 |
> |
// Specialization of doArrive+awaitAdvance eliminating some reads/paths |
| 648 |
> |
final Phaser root = this.root; |
| 649 |
> |
for (;;) { |
| 650 |
> |
long s = (root == this) ? state : reconcileState(); |
| 651 |
> |
int phase = (int)(s >>> PHASE_SHIFT); |
| 652 |
> |
if (phase < 0) |
| 653 |
> |
return phase; |
| 654 |
> |
int counts = (int)s; |
| 655 |
> |
int unarrived = (counts == EMPTY) ? 0 : (counts & UNARRIVED_MASK); |
| 656 |
> |
if (unarrived <= 0) |
| 657 |
> |
throw new IllegalStateException(badArrive(s)); |
| 658 |
> |
if (UNSAFE.compareAndSwapLong(this, stateOffset, s, |
| 659 |
> |
s -= ONE_ARRIVAL)) { |
| 660 |
> |
if (unarrived > 1) |
| 661 |
> |
return root.internalAwaitAdvance(phase, null); |
| 662 |
> |
if (root != this) |
| 663 |
> |
return parent.arriveAndAwaitAdvance(); |
| 664 |
> |
long n = s & PARTIES_MASK; // base of next state |
| 665 |
> |
int nextUnarrived = (int)n >>> PARTIES_SHIFT; |
| 666 |
> |
if (onAdvance(phase, nextUnarrived)) |
| 667 |
> |
n |= TERMINATION_BIT; |
| 668 |
> |
else if (nextUnarrived == 0) |
| 669 |
> |
n |= EMPTY; |
| 670 |
> |
else |
| 671 |
> |
n |= nextUnarrived; |
| 672 |
> |
int nextPhase = (phase + 1) & MAX_PHASE; |
| 673 |
> |
n |= (long)nextPhase << PHASE_SHIFT; |
| 674 |
> |
if (!UNSAFE.compareAndSwapLong(this, stateOffset, s, n)) |
| 675 |
> |
return (int)(state >>> PHASE_SHIFT); // terminated |
| 676 |
> |
releaseWaiters(phase); |
| 677 |
> |
return nextPhase; |
| 678 |
> |
} |
| 679 |
> |
} |
| 680 |
|
} |
| 681 |
|
|
| 682 |
|
/** |
| 687 |
|
* @param phase an arrival phase number, or negative value if |
| 688 |
|
* terminated; this argument is normally the value returned by a |
| 689 |
|
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
| 690 |
< |
* @return the next arrival phase number, or a negative value |
| 691 |
< |
* if terminated or argument is negative |
| 690 |
> |
* @return the next arrival phase number, or the argument if it is |
| 691 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
| 692 |
> |
* if terminated |
| 693 |
|
*/ |
| 694 |
|
public int awaitAdvance(int phase) { |
| 695 |
< |
Phaser rt; |
| 696 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
| 695 |
> |
final Phaser root = this.root; |
| 696 |
> |
long s = (root == this) ? state : reconcileState(); |
| 697 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
| 698 |
|
if (phase < 0) |
| 699 |
|
return phase; |
| 700 |
< |
if (p == phase) { |
| 701 |
< |
if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) |
| 646 |
< |
return rt.internalAwaitAdvance(phase, null); |
| 647 |
< |
reconcileState(); |
| 648 |
< |
} |
| 700 |
> |
if (p == phase) |
| 701 |
> |
return root.internalAwaitAdvance(phase, null); |
| 702 |
|
return p; |
| 703 |
|
} |
| 704 |
|
|
| 712 |
|
* @param phase an arrival phase number, or negative value if |
| 713 |
|
* terminated; this argument is normally the value returned by a |
| 714 |
|
* previous call to {@code arrive} or {@code arriveAndDeregister}. |
| 715 |
< |
* @return the next arrival phase number, or a negative value |
| 716 |
< |
* if terminated or argument is negative |
| 715 |
> |
* @return the next arrival phase number, or the argument if it is |
| 716 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
| 717 |
> |
* if terminated |
| 718 |
|
* @throws InterruptedException if thread interrupted while waiting |
| 719 |
|
*/ |
| 720 |
|
public int awaitAdvanceInterruptibly(int phase) |
| 721 |
|
throws InterruptedException { |
| 722 |
< |
Phaser rt; |
| 723 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
| 722 |
> |
final Phaser root = this.root; |
| 723 |
> |
long s = (root == this) ? state : reconcileState(); |
| 724 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
| 725 |
|
if (phase < 0) |
| 726 |
|
return phase; |
| 727 |
|
if (p == phase) { |
| 728 |
< |
if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) { |
| 729 |
< |
QNode node = new QNode(this, phase, true, false, 0L); |
| 730 |
< |
p = rt.internalAwaitAdvance(phase, node); |
| 731 |
< |
if (node.wasInterrupted) |
| 677 |
< |
throw new InterruptedException(); |
| 678 |
< |
} |
| 679 |
< |
else |
| 680 |
< |
reconcileState(); |
| 728 |
> |
QNode node = new QNode(this, phase, true, false, 0L); |
| 729 |
> |
p = root.internalAwaitAdvance(phase, node); |
| 730 |
> |
if (node.wasInterrupted) |
| 731 |
> |
throw new InterruptedException(); |
| 732 |
|
} |
| 733 |
|
return p; |
| 734 |
|
} |
| 747 |
|
* {@code unit} |
| 748 |
|
* @param unit a {@code TimeUnit} determining how to interpret the |
| 749 |
|
* {@code timeout} parameter |
| 750 |
< |
* @return the next arrival phase number, or a negative value |
| 751 |
< |
* if terminated or argument is negative |
| 750 |
> |
* @return the next arrival phase number, or the argument if it is |
| 751 |
> |
* negative, or the (negative) {@linkplain #getPhase() current phase} |
| 752 |
> |
* if terminated |
| 753 |
|
* @throws InterruptedException if thread interrupted while waiting |
| 754 |
|
* @throws TimeoutException if timed out while waiting |
| 755 |
|
*/ |
| 757 |
|
long timeout, TimeUnit unit) |
| 758 |
|
throws InterruptedException, TimeoutException { |
| 759 |
|
long nanos = unit.toNanos(timeout); |
| 760 |
< |
Phaser rt; |
| 761 |
< |
int p = (int)(state >>> PHASE_SHIFT); |
| 760 |
> |
final Phaser root = this.root; |
| 761 |
> |
long s = (root == this) ? state : reconcileState(); |
| 762 |
> |
int p = (int)(s >>> PHASE_SHIFT); |
| 763 |
|
if (phase < 0) |
| 764 |
|
return phase; |
| 765 |
|
if (p == phase) { |
| 766 |
< |
if ((p = (int)((rt = root).state >>> PHASE_SHIFT)) == phase) { |
| 767 |
< |
QNode node = new QNode(this, phase, true, true, nanos); |
| 768 |
< |
p = rt.internalAwaitAdvance(phase, node); |
| 769 |
< |
if (node.wasInterrupted) |
| 770 |
< |
throw new InterruptedException(); |
| 771 |
< |
else if (p == phase) |
| 719 |
< |
throw new TimeoutException(); |
| 720 |
< |
} |
| 721 |
< |
else |
| 722 |
< |
reconcileState(); |
| 766 |
> |
QNode node = new QNode(this, phase, true, true, nanos); |
| 767 |
> |
p = root.internalAwaitAdvance(phase, node); |
| 768 |
> |
if (node.wasInterrupted) |
| 769 |
> |
throw new InterruptedException(); |
| 770 |
> |
else if (p == phase) |
| 771 |
> |
throw new TimeoutException(); |
| 772 |
|
} |
| 773 |
|
return p; |
| 774 |
|
} |
| 787 |
|
final Phaser root = this.root; |
| 788 |
|
long s; |
| 789 |
|
while ((s = root.state) >= 0) { |
| 790 |
< |
long next = (s & ~(long)(MAX_PARTIES)) | TERMINATION_BIT; |
| 791 |
< |
if (UNSAFE.compareAndSwapLong(root, stateOffset, s, next)) { |
| 792 |
< |
releaseWaiters(0); // signal all threads |
| 793 |
< |
releaseWaiters(1); |
| 790 |
> |
if (UNSAFE.compareAndSwapLong(root, stateOffset, |
| 791 |
> |
s, s | TERMINATION_BIT)) { |
| 792 |
> |
// signal all threads |
| 793 |
> |
releaseWaiters(0); // Waiters on evenQ |
| 794 |
> |
releaseWaiters(1); // Waiters on oddQ |
| 795 |
|
return; |
| 796 |
|
} |
| 797 |
|
} |
| 821 |
|
|
| 822 |
|
/** |
| 823 |
|
* Returns the number of registered parties that have arrived at |
| 824 |
< |
* the current phase of this phaser. |
| 824 |
> |
* the current phase of this phaser. If this phaser has terminated, |
| 825 |
> |
* the returned value is meaningless and arbitrary. |
| 826 |
|
* |
| 827 |
|
* @return the number of arrived parties |
| 828 |
|
*/ |
| 832 |
|
|
| 833 |
|
/** |
| 834 |
|
* Returns the number of registered parties that have not yet |
| 835 |
< |
* arrived at the current phase of this phaser. |
| 835 |
> |
* arrived at the current phase of this phaser. If this phaser has |
| 836 |
> |
* terminated, the returned value is meaningless and arbitrary. |
| 837 |
|
* |
| 838 |
|
* @return the number of unarrived parties |
| 839 |
|
*/ |
| 943 |
|
*/ |
| 944 |
|
private void releaseWaiters(int phase) { |
| 945 |
|
QNode q; // first element of queue |
| 894 |
– |
int p; // its phase |
| 946 |
|
Thread t; // its thread |
| 896 |
– |
// assert phase != phaseOf(root.state); |
| 947 |
|
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
| 948 |
|
while ((q = head.get()) != null && |
| 949 |
|
q.phase != (int)(root.state >>> PHASE_SHIFT)) { |
| 955 |
|
} |
| 956 |
|
} |
| 957 |
|
|
| 958 |
+ |
/** |
| 959 |
+ |
* Variant of releaseWaiters that additionally tries to remove any |
| 960 |
+ |
* nodes no longer waiting for advance due to timeout or |
| 961 |
+ |
* interrupt. Currently, nodes are removed only if they are at |
| 962 |
+ |
* head of queue, which suffices to reduce memory footprint in |
| 963 |
+ |
* most usages. |
| 964 |
+ |
* |
| 965 |
+ |
* @return current phase on exit |
| 966 |
+ |
*/ |
| 967 |
+ |
private int abortWait(int phase) { |
| 968 |
+ |
AtomicReference<QNode> head = (phase & 1) == 0 ? evenQ : oddQ; |
| 969 |
+ |
for (;;) { |
| 970 |
+ |
Thread t; |
| 971 |
+ |
QNode q = head.get(); |
| 972 |
+ |
int p = (int)(root.state >>> PHASE_SHIFT); |
| 973 |
+ |
if (q == null || ((t = q.thread) != null && q.phase == p)) |
| 974 |
+ |
return p; |
| 975 |
+ |
if (head.compareAndSet(q, q.next) && t != null) { |
| 976 |
+ |
q.thread = null; |
| 977 |
+ |
LockSupport.unpark(t); |
| 978 |
+ |
} |
| 979 |
+ |
} |
| 980 |
+ |
} |
| 981 |
+ |
|
| 982 |
|
/** The number of CPUs, for spin control */ |
| 983 |
|
private static final int NCPU = Runtime.getRuntime().availableProcessors(); |
| 984 |
|
|
| 997 |
|
|
| 998 |
|
/** |
| 999 |
|
* Possibly blocks and waits for phase to advance unless aborted. |
| 1000 |
< |
* Call only from root node. |
| 1000 |
> |
* Call only on root phaser. |
| 1001 |
|
* |
| 1002 |
|
* @param phase current phase |
| 1003 |
|
* @param node if non-null, the wait node to track interrupt and timeout; |
| 1005 |
|
* @return current phase |
| 1006 |
|
*/ |
| 1007 |
|
private int internalAwaitAdvance(int phase, QNode node) { |
| 1008 |
+ |
// assert root == this; |
| 1009 |
|
releaseWaiters(phase-1); // ensure old queue clean |
| 1010 |
|
boolean queued = false; // true when node is enqueued |
| 1011 |
|
int lastUnarrived = 0; // to increase spins upon change |
| 1048 |
|
if (node.wasInterrupted && !node.interruptible) |
| 1049 |
|
Thread.currentThread().interrupt(); |
| 1050 |
|
if (p == phase && (p = (int)(state >>> PHASE_SHIFT)) == phase) |
| 1051 |
< |
return p; // recheck abort |
| 1051 |
> |
return abortWait(phase); // possibly clean up on abort |
| 1052 |
|
} |
| 1053 |
|
releaseWaiters(phase); |
| 1054 |
|
return p; |
| 1119 |
|
|
| 1120 |
|
// Unsafe mechanics |
| 1121 |
|
|
| 1122 |
< |
private static final sun.misc.Unsafe UNSAFE = getUnsafe(); |
| 1123 |
< |
private static final long stateOffset = |
| 1124 |
< |
objectFieldOffset("state", Phaser.class); |
| 1050 |
< |
|
| 1051 |
< |
private static long objectFieldOffset(String field, Class<?> klazz) { |
| 1122 |
> |
private static final sun.misc.Unsafe UNSAFE; |
| 1123 |
> |
private static final long stateOffset; |
| 1124 |
> |
static { |
| 1125 |
|
try { |
| 1126 |
< |
return UNSAFE.objectFieldOffset(klazz.getDeclaredField(field)); |
| 1127 |
< |
} catch (NoSuchFieldException e) { |
| 1128 |
< |
// Convert Exception to corresponding Error |
| 1129 |
< |
NoSuchFieldError error = new NoSuchFieldError(field); |
| 1130 |
< |
error.initCause(e); |
| 1131 |
< |
throw error; |
| 1126 |
> |
UNSAFE = getUnsafe(); |
| 1127 |
> |
Class<?> k = Phaser.class; |
| 1128 |
> |
stateOffset = UNSAFE.objectFieldOffset |
| 1129 |
> |
(k.getDeclaredField("state")); |
| 1130 |
> |
} catch (Exception e) { |
| 1131 |
> |
throw new Error(e); |
| 1132 |
|
} |
| 1133 |
|
} |
| 1134 |
|
|
| 1142 |
|
private static sun.misc.Unsafe getUnsafe() { |
| 1143 |
|
try { |
| 1144 |
|
return sun.misc.Unsafe.getUnsafe(); |
| 1145 |
< |
} catch (SecurityException se) { |
| 1146 |
< |
try { |
| 1147 |
< |
return java.security.AccessController.doPrivileged |
| 1148 |
< |
(new java.security |
| 1149 |
< |
.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
| 1150 |
< |
public sun.misc.Unsafe run() throws Exception { |
| 1151 |
< |
java.lang.reflect.Field f = sun.misc |
| 1152 |
< |
.Unsafe.class.getDeclaredField("theUnsafe"); |
| 1153 |
< |
f.setAccessible(true); |
| 1154 |
< |
return (sun.misc.Unsafe) f.get(null); |
| 1155 |
< |
}}); |
| 1156 |
< |
} catch (java.security.PrivilegedActionException e) { |
| 1157 |
< |
throw new RuntimeException("Could not initialize intrinsics", |
| 1158 |
< |
e.getCause()); |
| 1159 |
< |
} |
| 1145 |
> |
} catch (SecurityException tryReflectionInstead) {} |
| 1146 |
> |
try { |
| 1147 |
> |
return java.security.AccessController.doPrivileged |
| 1148 |
> |
(new java.security.PrivilegedExceptionAction<sun.misc.Unsafe>() { |
| 1149 |
> |
public sun.misc.Unsafe run() throws Exception { |
| 1150 |
> |
Class<sun.misc.Unsafe> k = sun.misc.Unsafe.class; |
| 1151 |
> |
for (java.lang.reflect.Field f : k.getDeclaredFields()) { |
| 1152 |
> |
f.setAccessible(true); |
| 1153 |
> |
Object x = f.get(null); |
| 1154 |
> |
if (k.isInstance(x)) |
| 1155 |
> |
return k.cast(x); |
| 1156 |
> |
} |
| 1157 |
> |
throw new NoSuchFieldError("the Unsafe"); |
| 1158 |
> |
}}); |
| 1159 |
> |
} catch (java.security.PrivilegedActionException e) { |
| 1160 |
> |
throw new RuntimeException("Could not initialize intrinsics", |
| 1161 |
> |
e.getCause()); |
| 1162 |
|
} |
| 1163 |
|
} |
| 1164 |
|
} |
