| 97 |
|
* <p><b>Monitoring.</b> While synchronization methods may be invoked |
| 98 |
|
* only by registered parties, the current state of a phaser may be |
| 99 |
|
* monitored by any caller. At any given moment there are {@link |
| 100 |
< |
* #getRegisteredParties}, where {@link #getArrivedParties} have |
| 101 |
< |
* arrived at the current phase ({@link #getPhase}). When the |
| 102 |
< |
* remaining {@link #getUnarrivedParties}) arrive, the phase |
| 103 |
< |
* advances. Method {@link #toString} returns snapshots of these state |
| 104 |
< |
* queries in a form convenient for informal monitoring. |
| 100 |
> |
* #getRegisteredParties} parties in total, of which {@link |
| 101 |
> |
* #getArrivedParties} have arrived at the current phase ({@link |
| 102 |
> |
* #getPhase}). When the remaining ({@link #getUnarrivedParties}) |
| 103 |
> |
* parties arrive, the phase advances. The values returned by these |
| 104 |
> |
* methods may reflect transient states and so are not in general |
| 105 |
> |
* useful for synchronization control. Method {@link #toString} |
| 106 |
> |
* returns snapshots of these state queries in a form convenient for |
| 107 |
> |
* informal monitoring. |
| 108 |
|
* |
| 109 |
|
* <p><b>Sample usages:</b> |
| 110 |
|
* |
| 111 |
|
* <p>A {@code Phaser} may be used instead of a {@code CountDownLatch} |
| 112 |
< |
* to control a one-shot action serving a variable number of |
| 113 |
< |
* parties. The typical idiom is for the method setting this up to |
| 114 |
< |
* first register, then start the actions, then deregister, as in: |
| 112 |
> |
* to control a one-shot action serving a variable number of parties. |
| 113 |
> |
* The typical idiom is for the method setting this up to first |
| 114 |
> |
* register, then start the actions, then deregister, as in: |
| 115 |
|
* |
| 116 |
|
* <pre> {@code |
| 117 |
|
* void runTasks(List<Runnable> tasks) { |
| 142 |
|
* } |
| 143 |
|
* }; |
| 144 |
|
* phaser.register(); |
| 145 |
< |
* for (Runnable task : tasks) { |
| 145 |
> |
* for (final Runnable task : tasks) { |
| 146 |
|
* phaser.register(); |
| 147 |
|
* new Thread() { |
| 148 |
|
* public void run() { |
| 149 |
|
* do { |
| 150 |
|
* task.run(); |
| 151 |
|
* phaser.arriveAndAwaitAdvance(); |
| 152 |
< |
* } while(!phaser.isTerminated(); |
| 152 |
> |
* } while (!phaser.isTerminated()); |
| 153 |
|
* } |
| 154 |
|
* }.start(); |
| 155 |
|
* } |
| 158 |
|
* |
| 159 |
|
* If the main task must later await termination, it |
| 160 |
|
* may re-register and then execute a similar loop: |
| 161 |
< |
* <pre> {@code |
| 161 |
> |
* <pre> {@code |
| 162 |
|
* // ... |
| 163 |
|
* phaser.register(); |
| 164 |
|
* while (!phaser.isTerminated()) |
| 165 |
< |
* phaser.arriveAndAwaitAdvance(); |
| 163 |
< |
* }</pre> |
| 165 |
> |
* phaser.arriveAndAwaitAdvance();}</pre> |
| 166 |
|
* |
| 167 |
< |
* Related constructions may be used to await particular phase numbers |
| 167 |
> |
* <p>Related constructions may be used to await particular phase numbers |
| 168 |
|
* in contexts where you are sure that the phase will never wrap around |
| 169 |
|
* {@code Integer.MAX_VALUE}. For example: |
| 170 |
|
* |
| 171 |
< |
* <pre> {@code |
| 172 |
< |
* void awaitPhase(Phaser phaser, int phase) { |
| 173 |
< |
* int p = phaser.register(); // assumes caller not already registered |
| 174 |
< |
* while (p < phase) { |
| 175 |
< |
* if (phaser.isTerminated()) |
| 176 |
< |
* // ... deal with unexpected termination |
| 177 |
< |
* else |
| 178 |
< |
* p = phaser.arriveAndAwaitAdvance(); |
| 177 |
< |
* } |
| 178 |
< |
* phaser.arriveAndDeregister(); |
| 171 |
> |
* <pre> {@code |
| 172 |
> |
* void awaitPhase(Phaser phaser, int phase) { |
| 173 |
> |
* int p = phaser.register(); // assumes caller not already registered |
| 174 |
> |
* while (p < phase) { |
| 175 |
> |
* if (phaser.isTerminated()) |
| 176 |
> |
* // ... deal with unexpected termination |
| 177 |
> |
* else |
| 178 |
> |
* p = phaser.arriveAndAwaitAdvance(); |
| 179 |
|
* } |
| 180 |
< |
* }</pre> |
| 180 |
> |
* phaser.arriveAndDeregister(); |
| 181 |
> |
* }}</pre> |
| 182 |
|
* |
| 183 |
|
* |
| 184 |
|
* <p>To create a set of tasks using a tree of phasers, |
| 185 |
|
* you could use code of the following form, assuming a |
| 186 |
|
* Task class with a constructor accepting a phaser that |
| 187 |
< |
* it registers for upon construction: |
| 187 |
> |
* it registers with upon construction: |
| 188 |
> |
* |
| 189 |
|
* <pre> {@code |
| 190 |
< |
* void build(Task[] actions, int lo, int hi, Phaser b) { |
| 191 |
< |
* int step = (hi - lo) / TASKS_PER_PHASER; |
| 192 |
< |
* if (step > 1) { |
| 193 |
< |
* int i = lo; |
| 194 |
< |
* while (i < hi) { |
| 193 |
< |
* int r = Math.min(i + step, hi); |
| 194 |
< |
* build(actions, i, r, new Phaser(b)); |
| 195 |
< |
* i = r; |
| 190 |
> |
* void build(Task[] actions, int lo, int hi, Phaser ph) { |
| 191 |
> |
* if (hi - lo > TASKS_PER_PHASER) { |
| 192 |
> |
* for (int i = lo; i < hi; i += TASKS_PER_PHASER) { |
| 193 |
> |
* int j = Math.min(i + TASKS_PER_PHASER, hi); |
| 194 |
> |
* build(actions, i, j, new Phaser(ph)); |
| 195 |
|
* } |
| 196 |
|
* } else { |
| 197 |
|
* for (int i = lo; i < hi; ++i) |
| 198 |
< |
* actions[i] = new Task(b); |
| 199 |
< |
* // assumes new Task(b) performs b.register() |
| 198 |
> |
* actions[i] = new Task(ph); |
| 199 |
> |
* // assumes new Task(ph) performs ph.register() |
| 200 |
|
* } |
| 201 |
|
* } |
| 202 |
|
* // .. initially called, for n tasks via |
| 207 |
|
* be appropriate for extremely small per-barrier task bodies (thus |
| 208 |
|
* high rates), or up to hundreds for extremely large ones. |
| 209 |
|
* |
| 211 |
– |
* </pre> |
| 212 |
– |
* |
| 210 |
|
* <p><b>Implementation notes</b>: This implementation restricts the |
| 211 |
|
* maximum number of parties to 65535. Attempts to register additional |
| 212 |
|
* parties result in {@code IllegalStateException}. However, you can and |
| 243 |
|
*/ |
| 244 |
|
private volatile long state; |
| 245 |
|
|
| 249 |
– |
private static final int ushortBits = 16; |
| 246 |
|
private static final int ushortMask = 0xffff; |
| 247 |
|
private static final int phaseMask = 0x7fffffff; |
| 248 |
|
|
| 346 |
|
} |
| 347 |
|
|
| 348 |
|
/** |
| 349 |
< |
* Creates a new phaser with the given numbers of registered |
| 349 |
> |
* Creates a new phaser with the given number of registered |
| 350 |
|
* unarrived parties, initial phase number 0, and no parent. |
| 351 |
|
* |
| 352 |
|
* @param parties the number of parties required to trip barrier |
| 378 |
|
} |
| 379 |
|
|
| 380 |
|
/** |
| 381 |
< |
* Creates a new phaser with the given parent and numbers of |
| 381 |
> |
* Creates a new phaser with the given parent and number of |
| 382 |
|
* registered unarrived parties. If parent is non-null, this phaser |
| 383 |
|
* is registered with the parent and its initial phase number is |
| 384 |
|
* the same as that of parent phaser. |
| 416 |
|
/** |
| 417 |
|
* Adds the given number of new unarrived parties to this phaser. |
| 418 |
|
* |
| 419 |
< |
* @param parties the number of parties required to trip barrier |
| 419 |
> |
* @param parties the number of additional parties required to trip barrier |
| 420 |
|
* @return the arrival phase number to which this registration applied |
| 421 |
|
* @throws IllegalStateException if attempting to register more |
| 422 |
|
* than the maximum supported number of parties |
| 423 |
+ |
* @throws IllegalArgumentException if {@code parties < 0} |
| 424 |
|
*/ |
| 425 |
|
public int bulkRegister(int parties) { |
| 426 |
|
if (parties < 0) |
| 562 |
|
* Arrives at the barrier and awaits others. Equivalent in effect |
| 563 |
|
* to {@code awaitAdvance(arrive())}. If you need to await with |
| 564 |
|
* interruption or timeout, you can arrange this with an analogous |
| 565 |
< |
* construction using one of the other forms of the awaitAdvance |
| 566 |
< |
* method. If instead you need to deregister upon arrival use |
| 567 |
< |
* {@code arriveAndDeregister}. It is an unenforced usage error |
| 568 |
< |
* for an unregistered party to invoke this method. |
| 565 |
> |
* construction using one of the other forms of the {@code |
| 566 |
> |
* awaitAdvance} method. If instead you need to deregister upon |
| 567 |
> |
* arrival, use {@link #arriveAndDeregister}. It is an unenforced |
| 568 |
> |
* usage error for an unregistered party to invoke this method. |
| 569 |
|
* |
| 570 |
|
* @return the arrival phase number, or a negative number if terminated |
| 571 |
|
* @throws IllegalStateException if not terminated and the number |
| 757 |
|
} |
| 758 |
|
|
| 759 |
|
/** |
| 760 |
< |
* Overridable method to perform an action upon phase advance, and |
| 761 |
< |
* to control termination. This method is invoked whenever the |
| 762 |
< |
* barrier is tripped (and thus all other waiting parties are |
| 763 |
< |
* dormant). If it returns {@code true}, then, rather than advance |
| 764 |
< |
* the phase number, this barrier will be set to a final |
| 765 |
< |
* termination state, and subsequent calls to {@link #isTerminated} |
| 766 |
< |
* will return true. |
| 760 |
> |
* Overridable method to perform an action upon impending phase |
| 761 |
> |
* advance, and to control termination. This method is invoked |
| 762 |
> |
* upon arrival of the party tripping the barrier (when all other |
| 763 |
> |
* waiting parties are dormant). If this method returns {@code |
| 764 |
> |
* true}, then, rather than advance the phase number, this barrier |
| 765 |
> |
* will be set to a final termination state, and subsequent calls |
| 766 |
> |
* to {@link #isTerminated} will return true. Any (unchecked) |
| 767 |
> |
* Exception or Error thrown by an invocation of this method is |
| 768 |
> |
* propagated to the party attempting to trip the barrier, in |
| 769 |
> |
* which case no advance occurs. |
| 770 |
> |
* |
| 771 |
> |
* <p>The arguments to this method provide the state of the phaser |
| 772 |
> |
* prevailing for the current transition. (When called from within |
| 773 |
> |
* an implementation of {@code onAdvance} the values returned by |
| 774 |
> |
* methods such as {@code getPhase} may or may not reliably |
| 775 |
> |
* indicate the state to which this transition applies.) |
| 776 |
|
* |
| 777 |
|
* <p>The default version returns {@code true} when the number of |
| 778 |
|
* registered parties is zero. Normally, overrides that arrange |
| 780 |
|
* property. |
| 781 |
|
* |
| 782 |
|
* <p>You may override this method to perform an action with side |
| 783 |
< |
* effects visible to participating tasks, but it is in general |
| 784 |
< |
* only sensible to do so in designs where all parties register |
| 785 |
< |
* before any arrive, and all {@link #awaitAdvance} at each phase. |
| 783 |
> |
* effects visible to participating tasks, but it is only sensible |
| 784 |
> |
* to do so in designs where all parties register before any |
| 785 |
> |
* arrive, and all {@link #awaitAdvance} at each phase. |
| 786 |
|
* Otherwise, you cannot ensure lack of interference from other |
| 787 |
< |
* parties during the invocation of this method. |
| 787 |
> |
* parties during the invocation of this method. Additionally, |
| 788 |
> |
* method {@code onAdvance} may be invoked more than once per |
| 789 |
> |
* transition if registrations are intermixed with arrivals. |
| 790 |
|
* |
| 791 |
|
* @param phase the phase number on entering the barrier |
| 792 |
|
* @param registeredParties the current number of registered parties |
| 828 |
|
volatile boolean wasInterrupted = false; |
| 829 |
|
volatile Thread thread; // nulled to cancel wait |
| 830 |
|
QNode next; |
| 831 |
+ |
|
| 832 |
|
QNode(Phaser phaser, int phase, boolean interruptible, |
| 833 |
|
boolean timed, long startTime, long nanos) { |
| 834 |
|
this.phaser = phaser; |
| 839 |
|
this.nanos = nanos; |
| 840 |
|
thread = Thread.currentThread(); |
| 841 |
|
} |
| 842 |
+ |
|
| 843 |
|
public boolean isReleasable() { |
| 844 |
|
return (thread == null || |
| 845 |
|
phaser.getPhase() != phase || |
| 846 |
|
(interruptible && wasInterrupted) || |
| 847 |
|
(timed && (nanos - (System.nanoTime() - startTime)) <= 0)); |
| 848 |
|
} |
| 849 |
+ |
|
| 850 |
|
public boolean block() { |
| 851 |
|
if (Thread.interrupted()) { |
| 852 |
|
wasInterrupted = true; |
| 863 |
|
} |
| 864 |
|
return isReleasable(); |
| 865 |
|
} |
| 866 |
+ |
|
| 867 |
|
void signal() { |
| 868 |
|
Thread t = thread; |
| 869 |
|
if (t != null) { |
| 871 |
|
LockSupport.unpark(t); |
| 872 |
|
} |
| 873 |
|
} |
| 874 |
+ |
|
| 875 |
|
boolean doWait() { |
| 876 |
|
if (thread != null) { |
| 877 |
|
try { |
| 878 |
< |
ForkJoinPool.managedBlock(this, false); |
| 878 |
> |
ForkJoinPool.managedBlock(this); |
| 879 |
|
} catch (InterruptedException ie) { |
| 880 |
+ |
wasInterrupted = true; // can't currently happen |
| 881 |
|
} |
| 882 |
|
} |
| 883 |
|
return wasInterrupted; |
| 884 |
|
} |
| 871 |
– |
|
| 885 |
|
} |
| 886 |
|
|
| 887 |
|
/** |
| 923 |
|
node = new QNode(this, phase, false, false, 0, 0); |
| 924 |
|
else if (!queued) |
| 925 |
|
queued = tryEnqueue(node); |
| 926 |
< |
else |
| 927 |
< |
interrupted = node.doWait(); |
| 926 |
> |
else if (node.doWait()) |
| 927 |
> |
interrupted = true; |
| 928 |
|
} |
| 929 |
|
if (node != null) |
| 930 |
|
node.thread = null; |
| 950 |
|
node = new QNode(this, phase, true, false, 0, 0); |
| 951 |
|
else if (!queued) |
| 952 |
|
queued = tryEnqueue(node); |
| 953 |
< |
else |
| 954 |
< |
interrupted = node.doWait(); |
| 953 |
> |
else if (node.doWait()) |
| 954 |
> |
interrupted = true; |
| 955 |
|
} |
| 956 |
|
if (node != null) |
| 957 |
|
node.thread = null; |
| 982 |
|
node = new QNode(this, phase, true, true, startTime, nanos); |
| 983 |
|
else if (!queued) |
| 984 |
|
queued = tryEnqueue(node); |
| 985 |
< |
else |
| 986 |
< |
interrupted = node.doWait(); |
| 985 |
> |
else if (node.doWait()) |
| 986 |
> |
interrupted = true; |
| 987 |
|
} |
| 988 |
|
if (node != null) |
| 989 |
|
node.thread = null; |
