--- jsr166/src/jsr166y/ForkJoinTask.java 2009/07/22 01:36:51 1.12
+++ jsr166/src/jsr166y/ForkJoinTask.java 2012/01/26 19:09:03 1.83
@@ -1,478 +1,639 @@
/*
* Written by Doug Lea with assistance from members of JCP JSR-166
* Expert Group and released to the public domain, as explained at
- * http://creativecommons.org/licenses/publicdomain
+ * http://creativecommons.org/publicdomain/zero/1.0/
*/
package jsr166y;
import java.io.Serializable;
-import java.util.*;
-import java.util.concurrent.*;
-import java.util.concurrent.atomic.*;
-import sun.misc.Unsafe;
-import java.lang.reflect.*;
+import java.util.Collection;
+import java.util.List;
+import java.util.RandomAccess;
+import java.lang.ref.WeakReference;
+import java.lang.ref.ReferenceQueue;
+import java.util.concurrent.Callable;
+import java.util.concurrent.CancellationException;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.Future;
+import java.util.concurrent.RejectedExecutionException;
+import java.util.concurrent.RunnableFuture;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.TimeoutException;
+import java.util.concurrent.locks.ReentrantLock;
+import java.lang.reflect.Constructor;
/**
- * Abstract base class for tasks that run within a {@link
- * ForkJoinPool}. A ForkJoinTask is a thread-like entity that is much
+ * Abstract base class for tasks that run within a {@link ForkJoinPool}.
+ * A {@code ForkJoinTask} is a thread-like entity that is much
* lighter weight than a normal thread. Huge numbers of tasks and
* subtasks may be hosted by a small number of actual threads in a
* ForkJoinPool, at the price of some usage limitations.
*
- *
A "main" ForkJoinTask begins execution when submitted to a
- * {@link ForkJoinPool}. Once started, it will usually in turn start
- * other subtasks. As indicated by the name of this class, many
- * programs using ForkJoinTasks employ only methods {@code fork}
- * and {@code join}, or derivatives such as
- * {@code invokeAll}. However, this class also provides a number
- * of other methods that can come into play in advanced usages, as
- * well as extension mechanics that allow support of new forms of
- * fork/join processing.
+ *
A "main" {@code ForkJoinTask} begins execution when submitted
+ * to a {@link ForkJoinPool}. Once started, it will usually in turn
+ * start other subtasks. As indicated by the name of this class,
+ * many programs using {@code ForkJoinTask} employ only methods
+ * {@link #fork} and {@link #join}, or derivatives such as {@link
+ * #invokeAll(ForkJoinTask...) invokeAll}. However, this class also
+ * provides a number of other methods that can come into play in
+ * advanced usages, as well as extension mechanics that allow
+ * support of new forms of fork/join processing.
*
- *
A ForkJoinTask is a lightweight form of {@link Future}. The
- * efficiency of ForkJoinTasks stems from a set of restrictions (that
- * are only partially statically enforceable) reflecting their
- * intended use as computational tasks calculating pure functions or
- * operating on purely isolated objects. The primary coordination
- * mechanisms are {@link #fork}, that arranges asynchronous execution,
- * and {@link #join}, that doesn't proceed until the task's result has
- * been computed. Computations should avoid {@code synchronized}
- * methods or blocks, and should minimize other blocking
- * synchronization apart from joining other tasks or using
- * synchronizers such as Phasers that are advertised to cooperate with
- * fork/join scheduling. Tasks should also not perform blocking IO,
- * and should ideally access variables that are completely independent
- * of those accessed by other running tasks. Minor breaches of these
- * restrictions, for example using shared output streams, may be
- * tolerable in practice, but frequent use may result in poor
- * performance, and the potential to indefinitely stall if the number
- * of threads not waiting for IO or other external synchronization
- * becomes exhausted. This usage restriction is in part enforced by
- * not permitting checked exceptions such as {@code IOExceptions}
- * to be thrown. However, computations may still encounter unchecked
- * exceptions, that are rethrown to callers attempting join
- * them. These exceptions may additionally include
- * RejectedExecutionExceptions stemming from internal resource
- * exhaustion such as failure to allocate internal task queues.
+ *
A {@code ForkJoinTask} is a lightweight form of {@link Future}.
+ * The efficiency of {@code ForkJoinTask}s stems from a set of
+ * restrictions (that are only partially statically enforceable)
+ * reflecting their main use as computational tasks calculating pure
+ * functions or operating on purely isolated objects. The primary
+ * coordination mechanisms are {@link #fork}, that arranges
+ * asynchronous execution, and {@link #join}, that doesn't proceed
+ * until the task's result has been computed. Computations should
+ * ideally avoid {@code synchronized} methods or blocks, and should
+ * minimize other blocking synchronization apart from joining other
+ * tasks or using synchronizers such as Phasers that are advertised to
+ * cooperate with fork/join scheduling. Subdividable tasks should also
+ * not perform blocking IO, and should ideally access variables that
+ * are completely independent of those accessed by other running
+ * tasks. These guidelines are loosely enforced by not permitting
+ * checked exceptions such as {@code IOExceptions} to be
+ * thrown. However, computations may still encounter unchecked
+ * exceptions, that are rethrown to callers attempting to join
+ * them. These exceptions may additionally include {@link
+ * RejectedExecutionException} stemming from internal resource
+ * exhaustion, such as failure to allocate internal task
+ * queues. Rethrown exceptions behave in the same way as regular
+ * exceptions, but, when possible, contain stack traces (as displayed
+ * for example using {@code ex.printStackTrace()}) of both the thread
+ * that initiated the computation as well as the thread actually
+ * encountering the exception; minimally only the latter.
+ *
+ *
It is possible to define and use ForkJoinTasks that may block,
+ * but doing do requires three further considerations: (1) Completion
+ * of few if any other tasks should be dependent on a task
+ * that blocks on external synchronization or IO. Event-style async
+ * tasks that are never joined often fall into this category. (2) To
+ * minimize resource impact, tasks should be small; ideally performing
+ * only the (possibly) blocking action. (3) Unless the {@link
+ * ForkJoinPool.ManagedBlocker} API is used, or the number of possibly
+ * blocked tasks is known to be less than the pool's {@link
+ * ForkJoinPool#getParallelism} level, the pool cannot guarantee that
+ * enough threads will be available to ensure progress or good
+ * performance.
*
*
The primary method for awaiting completion and extracting
* results of a task is {@link #join}, but there are several variants:
* The {@link Future#get} methods support interruptible and/or timed
* waits for completion and report results using {@code Future}
- * conventions. Method {@link #helpJoin} enables callers to actively
- * execute other tasks while awaiting joins, which is sometimes more
- * efficient but only applies when all subtasks are known to be
- * strictly tree-structured. Method {@link #invoke} is semantically
- * equivalent to {@code fork(); join()} but always attempts to
- * begin execution in the current thread. The "quiet" forms
- * of these methods do not extract results or report exceptions. These
+ * conventions. Method {@link #invoke} is semantically
+ * equivalent to {@code fork(); join()} but always attempts to begin
+ * execution in the current thread. The "quiet" forms of
+ * these methods do not extract results or report exceptions. These
* may be useful when a set of tasks are being executed, and you need
* to delay processing of results or exceptions until all complete.
* Method {@code invokeAll} (available in multiple versions)
* performs the most common form of parallel invocation: forking a set
* of tasks and joining them all.
*
- *
The ForkJoinTask class is not usually directly subclassed.
+ *
In the most typical usages, a fork-join pair act like a a call
+ * (fork) and return (join) from a parallel recursive function. As is
+ * the case with other forms of recursive calls, returns (joins)
+ * should be performed innermost-first. For example, {@code a.fork();
+ * b.fork(); b.join(); a.join();} is likely to be substantially more
+ * efficient than joining {@code a} before {@code b}.
+ *
+ *
The execution status of tasks may be queried at several levels
+ * of detail: {@link #isDone} is true if a task completed in any way
+ * (including the case where a task was cancelled without executing);
+ * {@link #isCompletedNormally} is true if a task completed without
+ * cancellation or encountering an exception; {@link #isCancelled} is
+ * true if the task was cancelled (in which case {@link #getException}
+ * returns a {@link java.util.concurrent.CancellationException}); and
+ * {@link #isCompletedAbnormally} is true if a task was either
+ * cancelled or encountered an exception, in which case {@link
+ * #getException} will return either the encountered exception or
+ * {@link java.util.concurrent.CancellationException}.
+ *
+ *
The ForkJoinTask class is not usually directly subclassed.
* Instead, you subclass one of the abstract classes that support a
- * particular style of fork/join processing. Normally, a concrete
+ * particular style of fork/join processing, typically {@link
+ * RecursiveAction} for computations that do not return results, or
+ * {@link RecursiveTask} for those that do. Normally, a concrete
* ForkJoinTask subclass declares fields comprising its parameters,
* established in a constructor, and then defines a {@code compute}
* method that somehow uses the control methods supplied by this base
* class. While these methods have {@code public} access (to allow
- * instances of different task subclasses to call each others
+ * instances of different task subclasses to call each other's
* methods), some of them may only be called from within other
- * ForkJoinTasks. Attempts to invoke them in other contexts result in
- * exceptions or errors possibly including ClassCastException.
+ * ForkJoinTasks (as may be determined using method {@link
+ * #inForkJoinPool}). Attempts to invoke them in other contexts
+ * result in exceptions or errors, possibly including
+ * {@code ClassCastException}.
*
- *
Most base support methods are {@code final} because their
- * implementations are intrinsically tied to the underlying
- * lightweight task scheduling framework, and so cannot be overridden.
- * Developers creating new basic styles of fork/join processing should
- * minimally implement {@code protected} methods
- * {@code exec}, {@code setRawResult}, and
- * {@code getRawResult}, while also introducing an abstract
- * computational method that can be implemented in its subclasses,
- * possibly relying on other {@code protected} methods provided
- * by this class.
+ *
Method {@link #join} and its variants are appropriate for use
+ * only when completion dependencies are acyclic; that is, the
+ * parallel computation can be described as a directed acyclic graph
+ * (DAG). Otherwise, executions may encounter a form of deadlock as
+ * tasks cyclically wait for each other. However, this framework
+ * supports other methods and techniques (for example the use of
+ * {@link Phaser}, {@link #helpQuiesce}, and {@link #complete}) that
+ * may be of use in constructing custom subclasses for problems that
+ * are not statically structured as DAGs. To support such usages a
+ * ForkJoinTask may be atomically marked using {@link
+ * #markForkJoinTask} and checked for marking using {@link
+ * #isMarkedForkJoinTask}. The ForkJoinTask implementation does not
+ * use these {@code protected} methods or marks for any purpose, but
+ * they may be of use in the construction of specialized subclasses.
+ * For example, parallel graph traversals can use the supplied methods
+ * to avoid revisiting nodes/tasks that have already been
+ * processed. Also, completion based designs can use them to record
+ * that one subtask has completed. (Method names for marking are bulky
+ * in part to encourage definition of methods that reflect their usage
+ * patterns.)
+ *
+ *
Most base support methods are {@code final}, to prevent
+ * overriding of implementations that are intrinsically tied to the
+ * underlying lightweight task scheduling framework. Developers
+ * creating new basic styles of fork/join processing should minimally
+ * implement {@code protected} methods {@link #exec}, {@link
+ * #setRawResult}, and {@link #getRawResult}, while also introducing
+ * an abstract computational method that can be implemented in its
+ * subclasses, possibly relying on other {@code protected} methods
+ * provided by this class.
*
*
ForkJoinTasks should perform relatively small amounts of
- * computations, otherwise splitting into smaller tasks. As a very
- * rough rule of thumb, a task should perform more than 100 and less
- * than 10000 basic computational steps. If tasks are too big, then
- * parallelism cannot improve throughput. If too small, then memory
- * and internal task maintenance overhead may overwhelm processing.
+ * computation. Large tasks should be split into smaller subtasks,
+ * usually via recursive decomposition. As a very rough rule of thumb,
+ * a task should perform more than 100 and less than 10000 basic
+ * computational steps, and should avoid indefinite looping. If tasks
+ * are too big, then parallelism cannot improve throughput. If too
+ * small, then memory and internal task maintenance overhead may
+ * overwhelm processing.
+ *
+ *
This class provides {@code adapt} methods for {@link Runnable}
+ * and {@link Callable}, that may be of use when mixing execution of
+ * {@code ForkJoinTasks} with other kinds of tasks. When all tasks are
+ * of this form, consider using a pool constructed in asyncMode.
*
- *
ForkJoinTasks are {@code Serializable}, which enables them
- * to be used in extensions such as remote execution frameworks. It is
- * in general sensible to serialize tasks only before or after, but
- * not during execution. Serialization is not relied on during
- * execution itself.
+ *
ForkJoinTasks are {@code Serializable}, which enables them to be
+ * used in extensions such as remote execution frameworks. It is
+ * sensible to serialize tasks only before or after, but not during,
+ * execution. Serialization is not relied on during execution itself.
*
* @since 1.7
* @author Doug Lea
*/
public abstract class ForkJoinTask implements Future, Serializable {
- /**
- * Run control status bits packed into a single int to minimize
- * footprint and to ensure atomicity (via CAS). Status is
- * initially zero, and takes on nonnegative values until
- * completed, upon which status holds COMPLETED. CANCELLED, or
- * EXCEPTIONAL, which use the top 3 bits. Tasks undergoing
- * blocking waits by other threads have SIGNAL_MASK bits set --
- * bit 15 for external (nonFJ) waits, and the rest a count of
- * waiting FJ threads. (This representation relies on
- * ForkJoinPool max thread limits). Completion of a stolen task
- * with SIGNAL_MASK bits set awakens waiter via notifyAll. Even
- * though suboptimal for some purposes, we use basic builtin
- * wait/notify to take advantage of "monitor inflation" in JVMs
- * that we would otherwise need to emulate to avoid adding further
- * per-task bookkeeping overhead. Note that bits 16-28 are
- * currently unused. Also value 0x80000000 is available as spare
- * completion value.
- */
- volatile int status; // accessed directly by pool and workers
-
- static final int COMPLETION_MASK = 0xe0000000;
- static final int NORMAL = 0xe0000000; // == mask
- static final int CANCELLED = 0xc0000000;
- static final int EXCEPTIONAL = 0xa0000000;
- static final int SIGNAL_MASK = 0x0000ffff;
- static final int INTERNAL_SIGNAL_MASK = 0x00007fff;
- static final int EXTERNAL_SIGNAL = 0x00008000; // top bit of low word
-
- /**
- * Table of exceptions thrown by tasks, to enable reporting by
- * callers. Because exceptions are rare, we don't directly keep
- * them with task objects, but instead use a weak ref table. Note
- * that cancellation exceptions don't appear in the table, but are
- * instead recorded as status values.
- * TODO: Use ConcurrentReferenceHashMap
- */
- static final Map, Throwable> exceptionMap =
- Collections.synchronizedMap
- (new WeakHashMap, Throwable>());
-
- // within-package utilities
-
- /**
- * Gets current worker thread, or null if not a worker thread.
+ /*
+ * See the internal documentation of class ForkJoinPool for a
+ * general implementation overview. ForkJoinTasks are mainly
+ * responsible for maintaining their "status" field amidst relays
+ * to methods in ForkJoinWorkerThread and ForkJoinPool.
+ *
+ * The methods of this class are more-or-less layered into
+ * (1) basic status maintenance
+ * (2) execution and awaiting completion
+ * (3) user-level methods that additionally report results.
+ * This is sometimes hard to see because this file orders exported
+ * methods in a way that flows well in javadocs.
*/
- static ForkJoinWorkerThread getWorker() {
- Thread t = Thread.currentThread();
- return ((t instanceof ForkJoinWorkerThread)?
- (ForkJoinWorkerThread)t : null);
- }
-
- final boolean casStatus(int cmp, int val) {
- return UNSAFE.compareAndSwapInt(this, statusOffset, cmp, val);
- }
/**
- * Workaround for not being able to rethrow unchecked exceptions.
+ * The number of times to try to help join a task without any
+ * apparent progress before giving up and blocking. The value is
+ * arbitrary but should be large enough to cope with transient
+ * stalls (due to GC etc) that can cause helping methods not to be
+ * able to proceed because other workers have not progressed to
+ * the point where subtasks can be found or taken.
+ */
+ private static final int HELP_RETRIES = 32;
+
+ /*
+ * The status field holds run control status bits packed into a
+ * single int to minimize footprint and to ensure atomicity (via
+ * CAS). Status is initially zero, and takes on nonnegative
+ * values until completed, upon which status holds value
+ * NORMAL, CANCELLED, or EXCEPTIONAL. Tasks undergoing blocking
+ * waits by other threads have the SIGNAL bit set. Completion of
+ * a stolen task with SIGNAL set awakens any waiters via
+ * notifyAll. Even though suboptimal for some purposes, we use
+ * basic builtin wait/notify to take advantage of "monitor
+ * inflation" in JVMs that we would otherwise need to emulate to
+ * avoid adding further per-task bookkeeping overhead. We want
+ * these monitors to be "fat", i.e., not use biasing or thin-lock
+ * techniques, so use some odd coding idioms that tend to avoid
+ * them.
*/
- static void rethrowException(Throwable ex) {
- if (ex != null)
- UNSAFE.throwException(ex);
- }
- // Setting completion status
+ /** The run status of this task */
+ volatile int status; // accessed directly by pool and workers
+ static final int NORMAL = 0xfffffffc; // negative with low 2 bits 0
+ static final int CANCELLED = 0xfffffff8; // must be < NORMAL
+ static final int EXCEPTIONAL = 0xfffffff4; // must be < CANCELLED
+ static final int SIGNAL = 0x00000001;
+ static final int MARKED = 0x00000002;
/**
- * Marks completion and wakes up threads waiting to join this task.
+ * Marks completion and wakes up threads waiting to join this
+ * task, also clearing signal request bits. A specialization for
+ * NORMAL completion is in method doExec.
*
* @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
+ * @return completion status on exit
*/
- final void setCompletion(int completion) {
- ForkJoinPool pool = getPool();
- if (pool != null) {
- int s; // Clear signal bits while setting completion status
- do;while ((s = status) >= 0 && !casStatus(s, completion));
-
- if ((s & SIGNAL_MASK) != 0) {
- if ((s &= INTERNAL_SIGNAL_MASK) != 0)
- pool.updateRunningCount(s);
- synchronized(this) { notifyAll(); }
+ private int setCompletion(int completion) {
+ for (int s;;) {
+ if ((s = status) < 0)
+ return s;
+ if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|completion)) {
+ if ((s & SIGNAL) != 0)
+ synchronized (this) { notifyAll(); }
+ return completion;
}
}
- else
- externallySetCompletion(completion);
}
/**
- * Version of setCompletion for non-FJ threads. Leaves signal
- * bits for unblocked threads to adjust, and always notifies.
- */
- private void externallySetCompletion(int completion) {
- int s;
- do;while ((s = status) >= 0 &&
- !casStatus(s, (s & SIGNAL_MASK) | completion));
- synchronized(this) { notifyAll(); }
- }
-
- /**
- * Sets status to indicate normal completion
- */
- final void setNormalCompletion() {
- // Try typical fast case -- single CAS, no signal, not already done.
- // Manually expand casStatus to improve chances of inlining it
- if (!UNSAFE.compareAndSwapInt(this, statusOffset, 0, NORMAL))
- setCompletion(NORMAL);
+ * Primary execution method for stolen tasks. Unless done, calls
+ * exec and records status if completed, but doesn't wait for
+ * completion otherwise.
+ *
+ * @return status on exit from this method
+ */
+ final int doExec() {
+ int s; boolean completed;
+ if ((s = status) >= 0) {
+ try {
+ completed = exec();
+ } catch (Throwable rex) {
+ return setExceptionalCompletion(rex);
+ }
+ while ((s = status) >= 0 && completed) {
+ if (U.compareAndSwapInt(this, STATUS, s, (s & ~SIGNAL)|NORMAL)) {
+ if ((s & SIGNAL) != 0)
+ synchronized (this) { notifyAll(); }
+ return NORMAL;
+ }
+ }
+ }
+ return s;
}
- // internal waiting and notification
-
/**
- * Performs the actual monitor wait for awaitDone
+ * Blocks a non-worker-thread until completion.
+ * @return status upon completion
*/
- private void doAwaitDone() {
- // Minimize lock bias and in/de-flation effects by maximizing
- // chances of waiting inside sync
- try {
- while (status >= 0)
- synchronized(this) { if (status >= 0) wait(); }
- } catch (InterruptedException ie) {
- onInterruptedWait();
+ private int externalAwaitDone() {
+ int s;
+ if ((s = status) >= 0) {
+ boolean interrupted = false;
+ synchronized (this) {
+ while ((s = status) >= 0) {
+ if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
+ try {
+ wait();
+ } catch (InterruptedException ie) {
+ interrupted = true;
+ }
+ }
+ }
+ }
+ if (interrupted)
+ Thread.currentThread().interrupt();
}
+ return s;
}
/**
- * Performs the actual monitor wait for awaitDone
+ * Blocks a non-worker-thread until completion or interruption or timeout.
*/
- private void doAwaitDone(long startTime, long nanos) {
- synchronized(this) {
- try {
- while (status >= 0) {
- long nt = nanos - System.nanoTime() - startTime;
- if (nt <= 0)
- break;
- wait(nt / 1000000, (int)(nt % 1000000));
+ private int externalInterruptibleAwaitDone(long millis)
+ throws InterruptedException {
+ int s;
+ if (Thread.interrupted())
+ throw new InterruptedException();
+ if ((s = status) >= 0) {
+ synchronized (this) {
+ while ((s = status) >= 0) {
+ if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
+ wait(millis);
+ if (millis > 0L)
+ break;
+ }
}
- } catch (InterruptedException ie) {
- onInterruptedWait();
}
}
+ return s;
}
- // Awaiting completion
/**
- * Sets status to indicate there is joiner, then waits for join,
- * surrounded with pool notifications.
+ * Implementation for join, get, quietlyJoin. Directly handles
+ * only cases of already-completed, external wait, and
+ * unfork+exec. Others are relayed to awaitJoin.
+ *
+ * @return status upon completion
+ */
+ private int doJoin() {
+ int s; Thread t; ForkJoinWorkerThread wt; ForkJoinPool.WorkQueue w;
+ if ((s = status) >= 0) {
+ if (!((t = Thread.currentThread()) instanceof ForkJoinWorkerThread))
+ s = externalAwaitDone();
+ else if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue).
+ tryUnpush(this) || (s = doExec()) >= 0)
+ s = awaitJoin(w, wt.pool);
+ }
+ return s;
+ }
+
+ /**
+ * Helps and/or blocks until joined.
*
- * @return status upon exit
+ * @param w the joiner
+ * @param p the pool
+ * @return status upon completion
*/
- private int awaitDone(ForkJoinWorkerThread w, boolean maintainParallelism) {
- ForkJoinPool pool = w == null? null : w.pool;
+ private int awaitJoin(ForkJoinPool.WorkQueue w, ForkJoinPool p) {
int s;
- while ((s = status) >= 0) {
- if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
- if (pool == null || !pool.preJoin(this, maintainParallelism))
- doAwaitDone();
- if (((s = status) & INTERNAL_SIGNAL_MASK) != 0)
- adjustPoolCountsOnUnblock(pool);
+ ForkJoinTask> prevJoin = w.currentJoin;
+ w.currentJoin = this;
+ for (int k = HELP_RETRIES; (s = status) >= 0;) {
+ if ((w.queueSize() > 0) ?
+ w.tryRemoveAndExec(this) : // self-help
+ p.tryHelpStealer(w, this)) // help process tasks
+ k = HELP_RETRIES; // reset if made progress
+ else if ((s = status) < 0) // recheck
break;
+ else if (--k > 0) {
+ if ((k & 3) == 1)
+ Thread.yield(); // occasionally yield
+ }
+ else if (k == 0)
+ p.tryPollForAndExec(w, this); // uncommon self-help case
+ else if (p.tryCompensate()) { // true if can block
+ try {
+ int ss = status;
+ if (ss >= 0 && // assert need signal
+ U.compareAndSwapInt(this, STATUS, ss, ss | SIGNAL)) {
+ synchronized (this) {
+ if (status >= 0) // block
+ wait();
+ }
+ }
+ } catch (InterruptedException ignore) {
+ } finally {
+ p.incrementActiveCount(); // re-activate
+ }
}
}
+ w.currentJoin = prevJoin;
return s;
}
/**
- * Timed version of awaitDone
- * @return status upon exit
+ * Implementation for invoke, quietlyInvoke.
+ *
+ * @return status upon completion
*/
- private int awaitDone(ForkJoinWorkerThread w, long nanos) {
- ForkJoinPool pool = w == null? null : w.pool;
- int s;
- while ((s = status) >= 0) {
- if (casStatus(s, pool == null? s|EXTERNAL_SIGNAL : s+1)) {
- long startTime = System.nanoTime();
- if (pool == null || !pool.preJoin(this, false))
- doAwaitDone(startTime, nanos);
- if ((s = status) >= 0) {
- adjustPoolCountsOnCancelledWait(pool);
- s = status;
- }
- if (s < 0 && (s & INTERNAL_SIGNAL_MASK) != 0)
- adjustPoolCountsOnUnblock(pool);
- break;
+ private int doInvoke() {
+ int s; Thread t;
+ if ((s = doExec()) >= 0) {
+ if (!((t = Thread.currentThread()) instanceof ForkJoinWorkerThread))
+ s = externalAwaitDone();
+ else {
+ ForkJoinWorkerThread wt = (ForkJoinWorkerThread)t;
+ s = awaitJoin(wt.workQueue, wt.pool);
}
}
return s;
}
+ // Exception table support
+
/**
- * Notifies pool that thread is unblocked. Called by signalled
- * threads when woken by non-FJ threads (which is atypical).
+ * Table of exceptions thrown by tasks, to enable reporting by
+ * callers. Because exceptions are rare, we don't directly keep
+ * them with task objects, but instead use a weak ref table. Note
+ * that cancellation exceptions don't appear in the table, but are
+ * instead recorded as status values.
+ *
+ * Note: These statics are initialized below in static block.
*/
- private void adjustPoolCountsOnUnblock(ForkJoinPool pool) {
- int s;
- do;while ((s = status) < 0 && !casStatus(s, s & COMPLETION_MASK));
- if (pool != null && (s &= INTERNAL_SIGNAL_MASK) != 0)
- pool.updateRunningCount(s);
- }
+ private static final ExceptionNode[] exceptionTable;
+ private static final ReentrantLock exceptionTableLock;
+ private static final ReferenceQueue