diff --git a/akka-actor/src/main/java/akka/jsr166y/ForkJoinPool.java b/akka-actor/src/main/java/akka/jsr166y/ForkJoinPool.java
deleted file mode 100644
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--- a/akka-actor/src/main/java/akka/jsr166y/ForkJoinPool.java
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@@ -1,2858 +0,0 @@
-/*
- * 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/publicdomain/zero/1.0/
- */
-
-package akka.jsr166y;
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.List;
-import java.util.Random;
-import java.util.concurrent.AbstractExecutorService;
-import java.util.concurrent.Callable;
-import java.util.concurrent.ExecutorService;
-import java.util.concurrent.Future;
-import java.util.concurrent.RejectedExecutionException;
-import java.util.concurrent.RunnableFuture;
-import java.util.concurrent.TimeUnit;
-import java.util.concurrent.atomic.AtomicInteger;
-import java.util.concurrent.atomic.AtomicLong;
-import java.util.concurrent.locks.AbstractQueuedSynchronizer;
-import java.util.concurrent.locks.Condition;
-import akka.util.Unsafe;
-
-/**
- * An {@link ExecutorService} for running {@link ForkJoinTask}s.
- * A {@code ForkJoinPool} provides the entry point for submissions
- * from non-{@code ForkJoinTask} clients, as well as management and
- * monitoring operations.
- *
- *
A {@code ForkJoinPool} differs from other kinds of {@link
- * ExecutorService} mainly by virtue of employing
- * work-stealing: all threads in the pool attempt to find and
- * execute tasks submitted to the pool and/or created by other active
- * tasks (eventually blocking waiting for work if none exist). This
- * enables efficient processing when most tasks spawn other subtasks
- * (as do most {@code ForkJoinTask}s), as well as when many small
- * tasks are submitted to the pool from external clients. Especially
- * when setting asyncMode to true in constructors, {@code
- * ForkJoinPool}s may also be appropriate for use with event-style
- * tasks that are never joined.
- *
- *
A {@code ForkJoinPool} is constructed with a given target
- * parallelism level; by default, equal to the number of available
- * processors. The pool attempts to maintain enough active (or
- * available) threads by dynamically adding, suspending, or resuming
- * internal worker threads, even if some tasks are stalled waiting to
- * join others. However, no such adjustments are guaranteed in the
- * face of blocked IO or other unmanaged synchronization. The nested
- * {@link ManagedBlocker} interface enables extension of the kinds of
- * synchronization accommodated.
- *
- *
In addition to execution and lifecycle control methods, this
- * class provides status check methods (for example
- * {@link #getStealCount}) that are intended to aid in developing,
- * tuning, and monitoring fork/join applications. Also, method
- * {@link #toString} returns indications of pool state in a
- * convenient form for informal monitoring.
- *
- *
As is the case with other ExecutorServices, there are three
- * main task execution methods summarized in the following table.
- * These are designed to be used primarily by clients not already
- * engaged in fork/join computations in the current pool. The main
- * forms of these methods accept instances of {@code ForkJoinTask},
- * but overloaded forms also allow mixed execution of plain {@code
- * Runnable}- or {@code Callable}- based activities as well. However,
- * tasks that are already executing in a pool should normally instead
- * use the within-computation forms listed in the table unless using
- * async event-style tasks that are not usually joined, in which case
- * there is little difference among choice of methods.
- *
- *
- *
- *
- *
Call from non-fork/join clients
- *
Call from within fork/join computations
- *
- *
- *
Arrange async execution
- *
{@link #execute(ForkJoinTask)}
- *
{@link ForkJoinTask#fork}
- *
- *
- *
Await and obtain result
- *
{@link #invoke(ForkJoinTask)}
- *
{@link ForkJoinTask#invoke}
- *
- *
- *
Arrange exec and obtain Future
- *
{@link #submit(ForkJoinTask)}
- *
{@link ForkJoinTask#fork} (ForkJoinTasks are Futures)
- *
- *
- *
- *
Sample Usage. Normally a single {@code ForkJoinPool} is
- * used for all parallel task execution in a program or subsystem.
- * Otherwise, use would not usually outweigh the construction and
- * bookkeeping overhead of creating a large set of threads. For
- * example, a common pool could be used for the {@code SortTasks}
- * illustrated in {@link RecursiveAction}. Because {@code
- * ForkJoinPool} uses threads in {@linkplain java.lang.Thread#isDaemon
- * daemon} mode, there is typically no need to explicitly {@link
- * #shutdown} such a pool upon program exit.
- *
- *
{@code
- * static final ForkJoinPool mainPool = new ForkJoinPool();
- * ...
- * public void sort(long[] array) {
- * mainPool.invoke(new SortTask(array, 0, array.length));
- * }}
- *
- *
Implementation notes: This implementation restricts the
- * maximum number of running threads to 32767. Attempts to create
- * pools with greater than the maximum number result in
- * {@code IllegalArgumentException}.
- *
- *
This implementation rejects submitted tasks (that is, by throwing
- * {@link RejectedExecutionException}) only when the pool is shut down
- * or internal resources have been exhausted.
- *
- * @since 1.7
- * @author Doug Lea
- */
-public class ForkJoinPool extends AbstractExecutorService {
-
- /*
- * Implementation Overview
- *
- * This class and its nested classes provide the main
- * functionality and control for a set of worker threads:
- * Submissions from non-FJ threads enter into submission queues.
- * Workers take these tasks and typically split them into subtasks
- * that may be stolen by other workers. Preference rules give
- * first priority to processing tasks from their own queues (LIFO
- * or FIFO, depending on mode), then to randomized FIFO steals of
- * tasks in other queues.
- *
- * WorkQueues
- * ==========
- *
- * Most operations occur within work-stealing queues (in nested
- * class WorkQueue). These are special forms of Deques that
- * support only three of the four possible end-operations -- push,
- * pop, and poll (aka steal), under the further constraints that
- * push and pop are called only from the owning thread (or, as
- * extended here, under a lock), while poll may be called from
- * other threads. (If you are unfamiliar with them, you probably
- * want to read Herlihy and Shavit's book "The Art of
- * Multiprocessor programming", chapter 16 describing these in
- * more detail before proceeding.) The main work-stealing queue
- * design is roughly similar to those in the papers "Dynamic
- * Circular Work-Stealing Deque" by Chase and Lev, SPAA 2005
- * (http://research.sun.com/scalable/pubs/index.html) and
- * "Idempotent work stealing" by Michael, Saraswat, and Vechev,
- * PPoPP 2009 (http://portal.acm.org/citation.cfm?id=1504186).
- * The main differences ultimately stem from GC requirements that
- * we null out taken slots as soon as we can, to maintain as small
- * a footprint as possible even in programs generating huge
- * numbers of tasks. To accomplish this, we shift the CAS
- * arbitrating pop vs poll (steal) from being on the indices
- * ("base" and "top") to the slots themselves. So, both a
- * successful pop and poll mainly entail a CAS of a slot from
- * non-null to null. Because we rely on CASes of references, we
- * do not need tag bits on base or top. They are simple ints as
- * used in any circular array-based queue (see for example
- * ArrayDeque). Updates to the indices must still be ordered in a
- * way that guarantees that top == base means the queue is empty,
- * but otherwise may err on the side of possibly making the queue
- * appear nonempty when a push, pop, or poll have not fully
- * committed. Note that this means that the poll operation,
- * considered individually, is not wait-free. One thief cannot
- * successfully continue until another in-progress one (or, if
- * previously empty, a push) completes. However, in the
- * aggregate, we ensure at least probabilistic non-blockingness.
- * If an attempted steal fails, a thief always chooses a different
- * random victim target to try next. So, in order for one thief to
- * progress, it suffices for any in-progress poll or new push on
- * any empty queue to complete. (This is why we normally use
- * method pollAt and its variants that try once at the apparent
- * base index, else consider alternative actions, rather than
- * method poll.)
- *
- * This approach also enables support of a user mode in which local
- * task processing is in FIFO, not LIFO order, simply by using
- * poll rather than pop. This can be useful in message-passing
- * frameworks in which tasks are never joined. However neither
- * mode considers affinities, loads, cache localities, etc, so
- * rarely provide the best possible performance on a given
- * machine, but portably provide good throughput by averaging over
- * these factors. (Further, even if we did try to use such
- * information, we do not usually have a basis for exploiting it.
- * For example, some sets of tasks profit from cache affinities,
- * but others are harmed by cache pollution effects.)
- *
- * WorkQueues are also used in a similar way for tasks submitted
- * to the pool. We cannot mix these tasks in the same queues used
- * for work-stealing (this would contaminate lifo/fifo
- * processing). Instead, we loosely associate submission queues
- * with submitting threads, using a form of hashing. The
- * ThreadLocal Submitter class contains a value initially used as
- * a hash code for choosing existing queues, but may be randomly
- * repositioned upon contention with other submitters. In
- * essence, submitters act like workers except that they never
- * take tasks, and they are multiplexed on to a finite number of
- * shared work queues. However, classes are set up so that future
- * extensions could allow submitters to optionally help perform
- * tasks as well. Insertion of tasks in shared mode requires a
- * lock (mainly to protect in the case of resizing) but we use
- * only a simple spinlock (using bits in field runState), because
- * submitters encountering a busy queue move on to try or create
- * other queues -- they block only when creating and registering
- * new queues.
- *
- * Management
- * ==========
- *
- * The main throughput advantages of work-stealing stem from
- * decentralized control -- workers mostly take tasks from
- * themselves or each other. We cannot negate this in the
- * implementation of other management responsibilities. The main
- * tactic for avoiding bottlenecks is packing nearly all
- * essentially atomic control state into two volatile variables
- * that are by far most often read (not written) as status and
- * consistency checks.
- *
- * Field "ctl" contains 64 bits holding all the information needed
- * to atomically decide to add, inactivate, enqueue (on an event
- * queue), dequeue, and/or re-activate workers. To enable this
- * packing, we restrict maximum parallelism to (1<<15)-1 (which is
- * far in excess of normal operating range) to allow ids, counts,
- * and their negations (used for thresholding) to fit into 16bit
- * fields.
- *
- * Field "runState" contains 32 bits needed to register and
- * deregister WorkQueues, as well as to enable shutdown. It is
- * only modified under a lock (normally briefly held, but
- * occasionally protecting allocations and resizings) but even
- * when locked remains available to check consistency.
- *
- * Recording WorkQueues. WorkQueues are recorded in the
- * "workQueues" array that is created upon pool construction and
- * expanded if necessary. Updates to the array while recording
- * new workers and unrecording terminated ones are protected from
- * each other by a lock but the array is otherwise concurrently
- * readable, and accessed directly. To simplify index-based
- * operations, the array size is always a power of two, and all
- * readers must tolerate null slots. Shared (submission) queues
- * are at even indices, worker queues at odd indices. Grouping
- * them together in this way simplifies and speeds up task
- * scanning.
- *
- * All worker thread creation is on-demand, triggered by task
- * submissions, replacement of terminated workers, and/or
- * compensation for blocked workers. However, all other support
- * code is set up to work with other policies. To ensure that we
- * do not hold on to worker references that would prevent GC, ALL
- * accesses to workQueues are via indices into the workQueues
- * array (which is one source of some of the messy code
- * constructions here). In essence, the workQueues array serves as
- * a weak reference mechanism. Thus for example the wait queue
- * field of ctl stores indices, not references. Access to the
- * workQueues in associated methods (for example signalWork) must
- * both index-check and null-check the IDs. All such accesses
- * ignore bad IDs by returning out early from what they are doing,
- * since this can only be associated with termination, in which
- * case it is OK to give up. All uses of the workQueues array
- * also check that it is non-null (even if previously
- * non-null). This allows nulling during termination, which is
- * currently not necessary, but remains an option for
- * resource-revocation-based shutdown schemes. It also helps
- * reduce JIT issuance of uncommon-trap code, which tends to
- * unnecessarily complicate control flow in some methods.
- *
- * Event Queuing. Unlike HPC work-stealing frameworks, we cannot
- * let workers spin indefinitely scanning for tasks when none can
- * be found immediately, and we cannot start/resume workers unless
- * there appear to be tasks available. On the other hand, we must
- * quickly prod them into action when new tasks are submitted or
- * generated. In many usages, ramp-up time to activate workers is
- * the main limiting factor in overall performance (this is
- * compounded at program start-up by JIT compilation and
- * allocation). So we try to streamline this as much as possible.
- * We park/unpark workers after placing in an event wait queue
- * when they cannot find work. This "queue" is actually a simple
- * Treiber stack, headed by the "id" field of ctl, plus a 15bit
- * counter value (that reflects the number of times a worker has
- * been inactivated) to avoid ABA effects (we need only as many
- * version numbers as worker threads). Successors are held in
- * field WorkQueue.nextWait. Queuing deals with several intrinsic
- * races, mainly that a task-producing thread can miss seeing (and
- * signalling) another thread that gave up looking for work but
- * has not yet entered the wait queue. We solve this by requiring
- * a full sweep of all workers (via repeated calls to method
- * scan()) both before and after a newly waiting worker is added
- * to the wait queue. During a rescan, the worker might release
- * some other queued worker rather than itself, which has the same
- * net effect. Because enqueued workers may actually be rescanning
- * rather than waiting, we set and clear the "parker" field of
- * WorkQueues to reduce unnecessary calls to unpark. (This
- * requires a secondary recheck to avoid missed signals.) Note
- * the unusual conventions about Thread.interrupts surrounding
- * parking and other blocking: Because interrupts are used solely
- * to alert threads to check termination, which is checked anyway
- * upon blocking, we clear status (using Thread.interrupted)
- * before any call to park, so that park does not immediately
- * return due to status being set via some other unrelated call to
- * interrupt in user code.
- *
- * Signalling. We create or wake up workers only when there
- * appears to be at least one task they might be able to find and
- * execute. When a submission is added or another worker adds a
- * task to a queue that previously had fewer than two tasks, they
- * signal waiting workers (or trigger creation of new ones if
- * fewer than the given parallelism level -- see signalWork).
- * These primary signals are buttressed by signals during rescans;
- * together these cover the signals needed in cases when more
- * tasks are pushed but untaken, and improve performance compared
- * to having one thread wake up all workers.
- *
- * Trimming workers. To release resources after periods of lack of
- * use, a worker starting to wait when the pool is quiescent will
- * time out and terminate if the pool has remained quiescent for
- * SHRINK_RATE nanosecs. This will slowly propagate, eventually
- * terminating all workers after long periods of non-use.
- *
- * Shutdown and Termination. A call to shutdownNow atomically sets
- * a runState bit and then (non-atomically) sets each worker's
- * runState status, cancels all unprocessed tasks, and wakes up
- * all waiting workers. Detecting whether termination should
- * commence after a non-abrupt shutdown() call requires more work
- * and bookkeeping. We need consensus about quiescence (i.e., that
- * there is no more work). The active count provides a primary
- * indication but non-abrupt shutdown still requires a rechecking
- * scan for any workers that are inactive but not queued.
- *
- * Joining Tasks
- * =============
- *
- * Any of several actions may be taken when one worker is waiting
- * to join a task stolen (or always held) by another. Because we
- * are multiplexing many tasks on to a pool of workers, we can't
- * just let them block (as in Thread.join). We also cannot just
- * reassign the joiner's run-time stack with another and replace
- * it later, which would be a form of "continuation", that even if
- * possible is not necessarily a good idea since we sometimes need
- * both an unblocked task and its continuation to progress.
- * Instead we combine two tactics:
- *
- * Helping: Arranging for the joiner to execute some task that it
- * would be running if the steal had not occurred.
- *
- * Compensating: Unless there are already enough live threads,
- * method tryCompensate() may create or re-activate a spare
- * thread to compensate for blocked joiners until they unblock.
- *
- * A third form (implemented in tryRemoveAndExec and
- * tryPollForAndExec) amounts to helping a hypothetical
- * compensator: If we can readily tell that a possible action of a
- * compensator is to steal and execute the task being joined, the
- * joining thread can do so directly, without the need for a
- * compensation thread (although at the expense of larger run-time
- * stacks, but the tradeoff is typically worthwhile).
- *
- * The ManagedBlocker extension API can't use helping so relies
- * only on compensation in method awaitBlocker.
- *
- * The algorithm in tryHelpStealer entails a form of "linear"
- * helping: Each worker records (in field currentSteal) the most
- * recent task it stole from some other worker. Plus, it records
- * (in field currentJoin) the task it is currently actively
- * joining. Method tryHelpStealer uses these markers to try to
- * find a worker to help (i.e., steal back a task from and execute
- * it) that could hasten completion of the actively joined task.
- * In essence, the joiner executes a task that would be on its own
- * local deque had the to-be-joined task not been stolen. This may
- * be seen as a conservative variant of the approach in Wagner &
- * Calder "Leapfrogging: a portable technique for implementing
- * efficient futures" SIGPLAN Notices, 1993
- * (http://portal.acm.org/citation.cfm?id=155354). It differs in
- * that: (1) We only maintain dependency links across workers upon
- * steals, rather than use per-task bookkeeping. This sometimes
- * requires a linear scan of workQueues array to locate stealers,
- * but often doesn't because stealers leave hints (that may become
- * stale/wrong) of where to locate them. A stealHint is only a
- * hint because a worker might have had multiple steals and the
- * hint records only one of them (usually the most current).
- * Hinting isolates cost to when it is needed, rather than adding
- * to per-task overhead. (2) It is "shallow", ignoring nesting
- * and potentially cyclic mutual steals. (3) It is intentionally
- * racy: field currentJoin is updated only while actively joining,
- * which means that we miss links in the chain during long-lived
- * tasks, GC stalls etc (which is OK since blocking in such cases
- * is usually a good idea). (4) We bound the number of attempts
- * to find work (see MAX_HELP) and fall back to suspending the
- * worker and if necessary replacing it with another.
- *
- * It is impossible to keep exactly the target parallelism number
- * of threads running at any given time. Determining the
- * existence of conservatively safe helping targets, the
- * availability of already-created spares, and the apparent need
- * to create new spares are all racy, so we rely on multiple
- * retries of each. Compensation in the apparent absence of
- * helping opportunities is challenging to control on JVMs, where
- * GC and other activities can stall progress of tasks that in
- * turn stall out many other dependent tasks, without us being
- * able to determine whether they will ever require compensation.
- * Even though work-stealing otherwise encounters little
- * degradation in the presence of more threads than cores,
- * aggressively adding new threads in such cases entails risk of
- * unwanted positive feedback control loops in which more threads
- * cause more dependent stalls (as well as delayed progress of
- * unblocked threads to the point that we know they are available)
- * leading to more situations requiring more threads, and so
- * on. This aspect of control can be seen as an (analytically
- * intractable) game with an opponent that may choose the worst
- * (for us) active thread to stall at any time. We take several
- * precautions to bound losses (and thus bound gains), mainly in
- * methods tryCompensate and awaitJoin: (1) We only try
- * compensation after attempting enough helping steps (measured
- * via counting and timing) that we have already consumed the
- * estimated cost of creating and activating a new thread. (2) We
- * allow up to 50% of threads to be blocked before initially
- * adding any others, and unless completely saturated, check that
- * some work is available for a new worker before adding. Also, we
- * create up to only 50% more threads until entering a mode that
- * only adds a thread if all others are possibly blocked. All
- * together, this means that we might be half as fast to react,
- * and create half as many threads as possible in the ideal case,
- * but present vastly fewer anomalies in all other cases compared
- * to both more aggressive and more conservative alternatives.
- *
- * Style notes: There is a lot of representation-level coupling
- * among classes ForkJoinPool, ForkJoinWorkerThread, and
- * ForkJoinTask. The fields of WorkQueue maintain data structures
- * managed by ForkJoinPool, so are directly accessed. There is
- * little point trying to reduce this, since any associated future
- * changes in representations will need to be accompanied by
- * algorithmic changes anyway. Several methods intrinsically
- * sprawl because they must accumulate sets of consistent reads of
- * volatiles held in local variables. Methods signalWork() and
- * scan() are the main bottlenecks, so are especially heavily
- * micro-optimized/mangled. There are lots of inline assignments
- * (of form "while ((local = field) != 0)") which are usually the
- * simplest way to ensure the required read orderings (which are
- * sometimes critical). This leads to a "C"-like style of listing
- * declarations of these locals at the heads of methods or blocks.
- * There are several occurrences of the unusual "do {} while
- * (!cas...)" which is the simplest way to force an update of a
- * CAS'ed variable. There are also other coding oddities that help
- * some methods perform reasonably even when interpreted (not
- * compiled).
- *
- * The order of declarations in this file is:
- * (1) Static utility functions
- * (2) Nested (static) classes
- * (3) Static fields
- * (4) Fields, along with constants used when unpacking some of them
- * (5) Internal control methods
- * (6) Callbacks and other support for ForkJoinTask methods
- * (7) Exported methods
- * (8) Static block initializing statics in minimally dependent order
- */
-
- // Static utilities
-
- /**
- * If there is a security manager, makes sure caller has
- * permission to modify threads.
- */
- private static void checkPermission() {
- SecurityManager security = System.getSecurityManager();
- if (security != null)
- security.checkPermission(modifyThreadPermission);
- }
-
- // Nested classes
-
- /**
- * Factory for creating new {@link ForkJoinWorkerThread}s.
- * A {@code ForkJoinWorkerThreadFactory} must be defined and used
- * for {@code ForkJoinWorkerThread} subclasses that extend base
- * functionality or initialize threads with different contexts.
- */
- public static interface ForkJoinWorkerThreadFactory {
- /**
- * Returns a new worker thread operating in the given pool.
- *
- * @param pool the pool this thread works in
- * @throws NullPointerException if the pool is null
- */
- public ForkJoinWorkerThread newThread(ForkJoinPool pool);
- }
-
- /**
- * Default ForkJoinWorkerThreadFactory implementation; creates a
- * new ForkJoinWorkerThread.
- */
- static class DefaultForkJoinWorkerThreadFactory
- implements ForkJoinWorkerThreadFactory {
- public ForkJoinWorkerThread newThread(ForkJoinPool pool) {
- return new ForkJoinWorkerThread(pool);
- }
- }
-
- /**
- * A simple non-reentrant lock used for exclusion when managing
- * queues and workers. We use a custom lock so that we can readily
- * probe lock state in constructions that check among alternative
- * actions. The lock is normally only very briefly held, and
- * sometimes treated as a spinlock, but other usages block to
- * reduce overall contention in those cases where locked code
- * bodies perform allocation/resizing.
- */
- static final class Mutex extends AbstractQueuedSynchronizer {
- public final boolean tryAcquire(int ignore) {
- return compareAndSetState(0, 1);
- }
- public final boolean tryRelease(int ignore) {
- setState(0);
- return true;
- }
- public final void lock() { acquire(0); }
- public final void unlock() { release(0); }
- public final boolean isHeldExclusively() { return getState() == 1; }
- public final Condition newCondition() { return new ConditionObject(); }
- }
-
- /**
- * Class for artificial tasks that are used to replace the target
- * of local joins if they are removed from an interior queue slot
- * in WorkQueue.tryRemoveAndExec. We don't need the proxy to
- * actually do anything beyond having a unique identity.
- */
- static final class EmptyTask extends ForkJoinTask {
- EmptyTask() { status = ForkJoinTask.NORMAL; } // force done
- public final Void getRawResult() { return null; }
- public final void setRawResult(Void x) {}
- public final boolean exec() { return true; }
- }
-
- /**
- * Queues supporting work-stealing as well as external task
- * submission. See above for main rationale and algorithms.
- * Implementation relies heavily on "Unsafe" intrinsics
- * and selective use of "volatile":
- *
- * Field "base" is the index (mod array.length) of the least valid
- * queue slot, which is always the next position to steal (poll)
- * from if nonempty. Reads and writes require volatile orderings
- * but not CAS, because updates are only performed after slot
- * CASes.
- *
- * Field "top" is the index (mod array.length) of the next queue
- * slot to push to or pop from. It is written only by owner thread
- * for push, or under lock for trySharedPush, and accessed by
- * other threads only after reading (volatile) base. Both top and
- * base are allowed to wrap around on overflow, but (top - base)
- * (or more commonly -(base - top) to force volatile read of base
- * before top) still estimates size.
- *
- * The array slots are read and written using the emulation of
- * volatiles/atomics provided by Unsafe. Insertions must in
- * general use putOrderedObject as a form of releasing store to
- * ensure that all writes to the task object are ordered before
- * its publication in the queue. (Although we can avoid one case
- * of this when locked in trySharedPush.) All removals entail a
- * CAS to null. The array is always a power of two. To ensure
- * safety of Unsafe array operations, all accesses perform
- * explicit null checks and implicit bounds checks via
- * power-of-two masking.
- *
- * In addition to basic queuing support, this class contains
- * fields described elsewhere to control execution. It turns out
- * to work better memory-layout-wise to include them in this
- * class rather than a separate class.
- *
- * Performance on most platforms is very sensitive to placement of
- * instances of both WorkQueues and their arrays -- we absolutely
- * do not want multiple WorkQueue instances or multiple queue
- * arrays sharing cache lines. (It would be best for queue objects
- * and their arrays to share, but there is nothing available to
- * help arrange that). Unfortunately, because they are recorded
- * in a common array, WorkQueue instances are often moved to be
- * adjacent by garbage collectors. To reduce impact, we use field
- * padding that works OK on common platforms; this effectively
- * trades off slightly slower average field access for the sake of
- * avoiding really bad worst-case access. (Until better JVM
- * support is in place, this padding is dependent on transient
- * properties of JVM field layout rules.) We also take care in
- * allocating, sizing and resizing the array. Non-shared queue
- * arrays are initialized (via method growArray) by workers before
- * use. Others are allocated on first use.
- */
- static final class WorkQueue {
- /**
- * Capacity of work-stealing queue array upon initialization.
- * Must be a power of two; at least 4, but should be larger to
- * reduce or eliminate cacheline sharing among queues.
- * Currently, it is much larger, as a partial workaround for
- * the fact that JVMs often place arrays in locations that
- * share GC bookkeeping (especially cardmarks) such that
- * per-write accesses encounter serious memory contention.
- */
- static final int INITIAL_QUEUE_CAPACITY = 1 << 13;
-
- /**
- * Maximum size for queue arrays. Must be a power of two less
- * than or equal to 1 << (31 - width of array entry) to ensure
- * lack of wraparound of index calculations, but defined to a
- * value a bit less than this to help users trap runaway
- * programs before saturating systems.
- */
- static final int MAXIMUM_QUEUE_CAPACITY = 1 << 26; // 64M
-
- volatile long totalSteals; // cumulative number of steals
- int seed; // for random scanning; initialize nonzero
- volatile int eventCount; // encoded inactivation count; < 0 if inactive
- int nextWait; // encoded record of next event waiter
- int rescans; // remaining scans until block
- int nsteals; // top-level task executions since last idle
- final int mode; // lifo, fifo, or shared
- int poolIndex; // index of this queue in pool (or 0)
- int stealHint; // index of most recent known stealer
- volatile int runState; // 1: locked, -1: terminate; else 0
- volatile int base; // index of next slot for poll
- int top; // index of next slot for push
- ForkJoinTask[] array; // the elements (initially unallocated)
- final ForkJoinPool pool; // the containing pool (may be null)
- final ForkJoinWorkerThread owner; // owning thread or null if shared
- volatile Thread parker; // == owner during call to park; else null
- ForkJoinTask currentJoin; // task being joined in awaitJoin
- ForkJoinTask currentSteal; // current non-local task being executed
- // Heuristic padding to ameliorate unfortunate memory placements
- Object p00, p01, p02, p03, p04, p05, p06, p07;
- Object p08, p09, p0a, p0b, p0c, p0d, p0e;
-
- WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode) {
- this.mode = mode;
- this.pool = pool;
- this.owner = owner;
- // Place indices in the center of array (that is not yet allocated)
- base = top = INITIAL_QUEUE_CAPACITY >>> 1;
- }
-
- /**
- * Returns the approximate number of tasks in the queue.
- */
- final int queueSize() {
- int n = base - top; // non-owner callers must read base first
- return (n >= 0) ? 0 : -n; // ignore transient negative
- }
-
- /**
- * Provides a more accurate estimate of whether this queue has
- * any tasks than does queueSize, by checking whether a
- * near-empty queue has at least one unclaimed task.
- */
- final boolean isEmpty() {
- ForkJoinTask[] a; int m, s;
- int n = base - (s = top);
- return (n >= 0 ||
- (n == -1 &&
- ((a = array) == null ||
- (m = a.length - 1) < 0 ||
- U.getObjectVolatile
- (a, ((m & (s - 1)) << ASHIFT) + ABASE) == null)));
- }
-
- /**
- * Pushes a task. Call only by owner in unshared queues.
- *
- * @param task the task. Caller must ensure non-null.
- * @throw RejectedExecutionException if array cannot be resized
- */
- final void push(ForkJoinTask task) {
- ForkJoinTask[] a; ForkJoinPool p;
- int s = top, m, n;
- if ((a = array) != null) { // ignore if queue removed
- U.putOrderedObject
- (a, (((m = a.length - 1) & s) << ASHIFT) + ABASE, task);
- if ((n = (top = s + 1) - base) <= 2) {
- if ((p = pool) != null)
- p.signalWork();
- }
- else if (n >= m)
- growArray(true);
- }
- }
-
- /**
- * Pushes a task if lock is free and array is either big
- * enough or can be resized to be big enough.
- *
- * @param task the task. Caller must ensure non-null.
- * @return true if submitted
- */
- final boolean trySharedPush(ForkJoinTask task) {
- boolean submitted = false;
- if (runState == 0 && U.compareAndSwapInt(this, RUNSTATE, 0, 1)) {
- ForkJoinTask[] a = array;
- int s = top;
- try {
- if ((a != null && a.length > s + 1 - base) ||
- (a = growArray(false)) != null) { // must presize
- int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
- U.putObject(a, (long)j, task); // don't need "ordered"
- top = s + 1;
- submitted = true;
- }
- } finally {
- runState = 0; // unlock
- }
- }
- return submitted;
- }
-
- /**
- * Takes next task, if one exists, in LIFO order. Call only
- * by owner in unshared queues. (We do not have a shared
- * version of this method because it is never needed.)
- */
- final ForkJoinTask pop() {
- ForkJoinTask[] a; ForkJoinTask t; int m;
- if ((a = array) != null && (m = a.length - 1) >= 0) {
- for (int s; (s = top - 1) - base >= 0;) {
- long j = ((m & s) << ASHIFT) + ABASE;
- if ((t = (ForkJoinTask)U.getObject(a, j)) == null)
- break;
- if (U.compareAndSwapObject(a, j, t, null)) {
- top = s;
- return t;
- }
- }
- }
- return null;
- }
-
- /**
- * Takes a task in FIFO order if b is base of queue and a task
- * can be claimed without contention. Specialized versions
- * appear in ForkJoinPool methods scan and tryHelpStealer.
- */
- final ForkJoinTask pollAt(int b) {
- ForkJoinTask t; ForkJoinTask[] a;
- if ((a = array) != null) {
- int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
- if ((t = (ForkJoinTask)U.getObjectVolatile(a, j)) != null &&
- base == b &&
- U.compareAndSwapObject(a, j, t, null)) {
- base = b + 1;
- return t;
- }
- }
- return null;
- }
-
- /**
- * Takes next task, if one exists, in FIFO order.
- */
- final ForkJoinTask poll() {
- ForkJoinTask[] a; int b; ForkJoinTask t;
- while ((b = base) - top < 0 && (a = array) != null) {
- int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
- t = (ForkJoinTask)U.getObjectVolatile(a, j);
- if (t != null) {
- if (base == b &&
- U.compareAndSwapObject(a, j, t, null)) {
- base = b + 1;
- return t;
- }
- }
- else if (base == b) {
- if (b + 1 == top)
- break;
- Thread.yield(); // wait for lagging update
- }
- }
- return null;
- }
-
- /**
- * Takes next task, if one exists, in order specified by mode.
- */
- final ForkJoinTask nextLocalTask() {
- return mode == 0 ? pop() : poll();
- }
-
- /**
- * Returns next task, if one exists, in order specified by mode.
- */
- final ForkJoinTask peek() {
- ForkJoinTask[] a = array; int m;
- if (a == null || (m = a.length - 1) < 0)
- return null;
- int i = mode == 0 ? top - 1 : base;
- int j = ((i & m) << ASHIFT) + ABASE;
- return (ForkJoinTask)U.getObjectVolatile(a, j);
- }
-
- /**
- * Pops the given task only if it is at the current top.
- */
- final boolean tryUnpush(ForkJoinTask t) {
- ForkJoinTask[] a; int s;
- if ((a = array) != null && (s = top) != base &&
- U.compareAndSwapObject
- (a, (((a.length - 1) & --s) << ASHIFT) + ABASE, t, null)) {
- top = s;
- return true;
- }
- return false;
- }
-
- /**
- * Polls the given task only if it is at the current base.
- */
- final boolean pollFor(ForkJoinTask task) {
- ForkJoinTask[] a; int b;
- if ((b = base) - top < 0 && (a = array) != null) {
- int j = (((a.length - 1) & b) << ASHIFT) + ABASE;
- if (U.getObjectVolatile(a, j) == task && base == b &&
- U.compareAndSwapObject(a, j, task, null)) {
- base = b + 1;
- return true;
- }
- }
- return false;
- }
-
- /**
- * Initializes or doubles the capacity of array. Call either
- * by owner or with lock held -- it is OK for base, but not
- * top, to move while resizings are in progress.
- *
- * @param rejectOnFailure if true, throw exception if capacity
- * exceeded (relayed ultimately to user); else return null.
- */
- final ForkJoinTask[] growArray(boolean rejectOnFailure) {
- ForkJoinTask[] oldA = array;
- int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
- if (size <= MAXIMUM_QUEUE_CAPACITY) {
- int oldMask, t, b;
- ForkJoinTask[] a = array = new ForkJoinTask[size];
- if (oldA != null && (oldMask = oldA.length - 1) >= 0 &&
- (t = top) - (b = base) > 0) {
- int mask = size - 1;
- do {
- ForkJoinTask x;
- int oldj = ((b & oldMask) << ASHIFT) + ABASE;
- int j = ((b & mask) << ASHIFT) + ABASE;
- x = (ForkJoinTask)U.getObjectVolatile(oldA, oldj);
- if (x != null &&
- U.compareAndSwapObject(oldA, oldj, x, null))
- U.putObjectVolatile(a, j, x);
- } while (++b != t);
- }
- return a;
- }
- else if (!rejectOnFailure)
- return null;
- else
- throw new RejectedExecutionException("Queue capacity exceeded");
- }
-
- /**
- * Removes and cancels all known tasks, ignoring any exceptions.
- */
- final void cancelAll() {
- ForkJoinTask.cancelIgnoringExceptions(currentJoin);
- ForkJoinTask.cancelIgnoringExceptions(currentSteal);
- for (ForkJoinTask t; (t = poll()) != null; )
- ForkJoinTask.cancelIgnoringExceptions(t);
- }
-
- /**
- * Computes next value for random probes. Scans don't require
- * a very high quality generator, but also not a crummy one.
- * Marsaglia xor-shift is cheap and works well enough. Note:
- * This is manually inlined in its usages in ForkJoinPool to
- * avoid writes inside busy scan loops.
- */
- final int nextSeed() {
- int r = seed;
- r ^= r << 13;
- r ^= r >>> 17;
- return seed = r ^= r << 5;
- }
-
- // Execution methods
-
- /**
- * Pops and runs tasks until empty.
- */
- private void popAndExecAll() {
- // A bit faster than repeated pop calls
- ForkJoinTask[] a; int m, s; long j; ForkJoinTask t;
- while ((a = array) != null && (m = a.length - 1) >= 0 &&
- (s = top - 1) - base >= 0 &&
- (t = ((ForkJoinTask)
- U.getObject(a, j = ((m & s) << ASHIFT) + ABASE)))
- != null) {
- if (U.compareAndSwapObject(a, j, t, null)) {
- top = s;
- t.doExec();
- }
- }
- }
-
- /**
- * Polls and runs tasks until empty.
- */
- private void pollAndExecAll() {
- for (ForkJoinTask t; (t = poll()) != null;)
- t.doExec();
- }
-
- /**
- * If present, removes from queue and executes the given task, or
- * any other cancelled task. Returns (true) immediately on any CAS
- * or consistency check failure so caller can retry.
- *
- * @return false if no progress can be made
- */
- final boolean tryRemoveAndExec(ForkJoinTask task) {
- boolean removed = false, empty = true, progress = true;
- ForkJoinTask[] a; int m, s, b, n;
- if ((a = array) != null && (m = a.length - 1) >= 0 &&
- (n = (s = top) - (b = base)) > 0) {
- for (ForkJoinTask t;;) { // traverse from s to b
- int j = ((--s & m) << ASHIFT) + ABASE;
- t = (ForkJoinTask)U.getObjectVolatile(a, j);
- if (t == null) // inconsistent length
- break;
- else if (t == task) {
- if (s + 1 == top) { // pop
- if (!U.compareAndSwapObject(a, j, task, null))
- break;
- top = s;
- removed = true;
- }
- else if (base == b) // replace with proxy
- removed = U.compareAndSwapObject(a, j, task,
- new EmptyTask());
- break;
- }
- else if (t.status >= 0)
- empty = false;
- else if (s + 1 == top) { // pop and throw away
- if (U.compareAndSwapObject(a, j, t, null))
- top = s;
- break;
- }
- if (--n == 0) {
- if (!empty && base == b)
- progress = false;
- break;
- }
- }
- }
- if (removed)
- task.doExec();
- return progress;
- }
-
- /**
- * Executes a top-level task and any local tasks remaining
- * after execution.
- */
- final void runTask(ForkJoinTask t) {
- if (t != null) {
- currentSteal = t;
- t.doExec();
- if (top != base) { // process remaining local tasks
- if (mode == 0)
- popAndExecAll();
- else
- pollAndExecAll();
- }
- ++nsteals;
- currentSteal = null;
- }
- }
-
- /**
- * Executes a non-top-level (stolen) task.
- */
- final void runSubtask(ForkJoinTask t) {
- if (t != null) {
- ForkJoinTask ps = currentSteal;
- currentSteal = t;
- t.doExec();
- currentSteal = ps;
- }
- }
-
- /**
- * Returns true if owned and not known to be blocked.
- */
- final boolean isApparentlyUnblocked() {
- Thread wt; Thread.State s;
- return (eventCount >= 0 &&
- (wt = owner) != null &&
- (s = wt.getState()) != Thread.State.BLOCKED &&
- s != Thread.State.WAITING &&
- s != Thread.State.TIMED_WAITING);
- }
-
- /**
- * If this owned and is not already interrupted, try to
- * interrupt and/or unpark, ignoring exceptions.
- */
- final void interruptOwner() {
- Thread wt, p;
- if ((wt = owner) != null && !wt.isInterrupted()) {
- try {
- wt.interrupt();
- } catch (SecurityException ignore) {
- }
- }
- if ((p = parker) != null)
- U.unpark(p);
- }
-
- // Unsafe mechanics
- private static final sun.misc.Unsafe U;
- private static final long RUNSTATE;
- private static final int ABASE;
- private static final int ASHIFT;
- static {
- int s;
- try {
- U = getUnsafe();
- Class k = WorkQueue.class;
- Class ak = ForkJoinTask[].class;
- RUNSTATE = U.objectFieldOffset
- (k.getDeclaredField("runState"));
- ABASE = U.arrayBaseOffset(ak);
- s = U.arrayIndexScale(ak);
- } catch (Exception e) {
- throw new Error(e);
- }
- if ((s & (s-1)) != 0)
- throw new Error("data type scale not a power of two");
- ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
- }
- }
-
- /**
- * Per-thread records for threads that submit to pools. Currently
- * holds only pseudo-random seed / index that is used to choose
- * submission queues in method doSubmit. In the future, this may
- * also incorporate a means to implement different task rejection
- * and resubmission policies.
- *
- * Seeds for submitters and workers/workQueues work in basically
- * the same way but are initialized and updated using slightly
- * different mechanics. Both are initialized using the same
- * approach as in class ThreadLocal, where successive values are
- * unlikely to collide with previous values. This is done during
- * registration for workers, but requires a separate AtomicInteger
- * for submitters. Seeds are then randomly modified upon
- * collisions using xorshifts, which requires a non-zero seed.
- */
- static final class Submitter {
- int seed;
- Submitter() {
- int s = nextSubmitterSeed.getAndAdd(SEED_INCREMENT);
- seed = (s == 0) ? 1 : s; // ensure non-zero
- }
- }
-
- /** ThreadLocal class for Submitters */
- static final class ThreadSubmitter extends ThreadLocal {
- public Submitter initialValue() { return new Submitter(); }
- }
-
- // static fields (initialized in static initializer below)
-
- /**
- * Creates a new ForkJoinWorkerThread. This factory is used unless
- * overridden in ForkJoinPool constructors.
- */
- public static final ForkJoinWorkerThreadFactory
- defaultForkJoinWorkerThreadFactory;
-
- /**
- * Generator for assigning sequence numbers as pool names.
- */
- private static final AtomicInteger poolNumberGenerator;
-
- /**
- * Generator for initial hashes/seeds for submitters. Accessed by
- * Submitter class constructor.
- */
- static final AtomicInteger nextSubmitterSeed;
-
- /**
- * Permission required for callers of methods that may start or
- * kill threads.
- */
- private static final RuntimePermission modifyThreadPermission;
-
- /**
- * Per-thread submission bookeeping. Shared across all pools
- * to reduce ThreadLocal pollution and because random motion
- * to avoid contention in one pool is likely to hold for others.
- */
- private static final ThreadSubmitter submitters;
-
- // static constants
-
- /**
- * The wakeup interval (in nanoseconds) for a worker waiting for a
- * task when the pool is quiescent to instead try to shrink the
- * number of workers. The exact value does not matter too
- * much. It must be short enough to release resources during
- * sustained periods of idleness, but not so short that threads
- * are continually re-created.
- */
- private static final long SHRINK_RATE =
- 4L * 1000L * 1000L * 1000L; // 4 seconds
-
- /**
- * The timeout value for attempted shrinkage, includes
- * some slop to cope with system timer imprecision.
- */
- private static final long SHRINK_TIMEOUT = SHRINK_RATE - (SHRINK_RATE / 10);
-
- /**
- * The maximum stolen->joining link depth allowed in method
- * tryHelpStealer. Must be a power of two. This value also
- * controls the maximum number of times to try to help join a task
- * without any apparent progress or change in pool state before
- * giving up and blocking (see awaitJoin). Depths for legitimate
- * chains are unbounded, but we use a fixed constant to avoid
- * (otherwise unchecked) cycles and to bound staleness of
- * traversal parameters at the expense of sometimes blocking when
- * we could be helping.
- */
- private static final int MAX_HELP = 32;
-
- /**
- * Secondary time-based bound (in nanosecs) for helping attempts
- * before trying compensated blocking in awaitJoin. Used in
- * conjunction with MAX_HELP to reduce variance due to different
- * polling rates associated with different helping options. The
- * value should roughly approximate the time required to create
- * and/or activate a worker thread.
- */
- private static final long COMPENSATION_DELAY = 100L * 1000L; // 0.1 millisec
-
- /**
- * Increment for seed generators. See class ThreadLocal for
- * explanation.
- */
- private static final int SEED_INCREMENT = 0x61c88647;
-
- /**
- * Bits and masks for control variables
- *
- * Field ctl is a long packed with:
- * AC: Number of active running workers minus target parallelism (16 bits)
- * TC: Number of total workers minus target parallelism (16 bits)
- * ST: true if pool is terminating (1 bit)
- * EC: the wait count of top waiting thread (15 bits)
- * ID: poolIndex of top of Treiber stack of waiters (16 bits)
- *
- * When convenient, we can extract the upper 32 bits of counts and
- * the lower 32 bits of queue state, u = (int)(ctl >>> 32) and e =
- * (int)ctl. The ec field is never accessed alone, but always
- * together with id and st. The offsets of counts by the target
- * parallelism and the positionings of fields makes it possible to
- * perform the most common checks via sign tests of fields: When
- * ac is negative, there are not enough active workers, when tc is
- * negative, there are not enough total workers, and when e is
- * negative, the pool is terminating. To deal with these possibly
- * negative fields, we use casts in and out of "short" and/or
- * signed shifts to maintain signedness.
- *
- * When a thread is queued (inactivated), its eventCount field is
- * set negative, which is the only way to tell if a worker is
- * prevented from executing tasks, even though it must continue to
- * scan for them to avoid queuing races. Note however that
- * eventCount updates lag releases so usage requires care.
- *
- * Field runState is an int packed with:
- * SHUTDOWN: true if shutdown is enabled (1 bit)
- * SEQ: a sequence number updated upon (de)registering workers (30 bits)
- * INIT: set true after workQueues array construction (1 bit)
- *
- * The sequence number enables simple consistency checks:
- * Staleness of read-only operations on the workQueues array can
- * be checked by comparing runState before vs after the reads.
- */
-
- // bit positions/shifts for fields
- private static final int AC_SHIFT = 48;
- private static final int TC_SHIFT = 32;
- private static final int ST_SHIFT = 31;
- private static final int EC_SHIFT = 16;
-
- // bounds
- private static final int SMASK = 0xffff; // short bits
- private static final int MAX_CAP = 0x7fff; // max #workers - 1
- private static final int SQMASK = 0xfffe; // even short bits
- private static final int SHORT_SIGN = 1 << 15;
- private static final int INT_SIGN = 1 << 31;
-
- // masks
- private static final long STOP_BIT = 0x0001L << ST_SHIFT;
- private static final long AC_MASK = ((long)SMASK) << AC_SHIFT;
- private static final long TC_MASK = ((long)SMASK) << TC_SHIFT;
-
- // units for incrementing and decrementing
- private static final long TC_UNIT = 1L << TC_SHIFT;
- private static final long AC_UNIT = 1L << AC_SHIFT;
-
- // masks and units for dealing with u = (int)(ctl >>> 32)
- private static final int UAC_SHIFT = AC_SHIFT - 32;
- private static final int UTC_SHIFT = TC_SHIFT - 32;
- private static final int UAC_MASK = SMASK << UAC_SHIFT;
- private static final int UTC_MASK = SMASK << UTC_SHIFT;
- private static final int UAC_UNIT = 1 << UAC_SHIFT;
- private static final int UTC_UNIT = 1 << UTC_SHIFT;
-
- // masks and units for dealing with e = (int)ctl
- private static final int E_MASK = 0x7fffffff; // no STOP_BIT
- private static final int E_SEQ = 1 << EC_SHIFT;
-
- // runState bits
- private static final int SHUTDOWN = 1 << 31;
-
- // access mode for WorkQueue
- static final int LIFO_QUEUE = 0;
- static final int FIFO_QUEUE = 1;
- static final int SHARED_QUEUE = -1;
-
- // Instance fields
-
- /*
- * Field layout order in this class tends to matter more than one
- * would like. Runtime layout order is only loosely related to
- * declaration order and may differ across JVMs, but the following
- * empirically works OK on current JVMs.
- */
-
- volatile long ctl; // main pool control
- final int parallelism; // parallelism level
- final int localMode; // per-worker scheduling mode
- final int submitMask; // submit queue index bound
- int nextSeed; // for initializing worker seeds
- volatile int runState; // shutdown status and seq
- WorkQueue[] workQueues; // main registry
- final Mutex lock; // for registration
- final Condition termination; // for awaitTermination
- final ForkJoinWorkerThreadFactory factory; // factory for new workers
- final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
- final AtomicLong stealCount; // collect counts when terminated
- final AtomicInteger nextWorkerNumber; // to create worker name string
- final String workerNamePrefix; // to create worker name string
-
- // Creating, registering, and deregistering workers
-
- /**
- * Tries to create and start a worker
- */
- private void addWorker() {
- Throwable ex = null;
- ForkJoinWorkerThread wt = null;
- try {
- if ((wt = factory.newThread(this)) != null) {
- wt.start();
- return;
- }
- } catch (Throwable e) {
- ex = e;
- }
- deregisterWorker(wt, ex); // adjust counts etc on failure
- }
-
- /**
- * Callback from ForkJoinWorkerThread constructor to assign a
- * public name. This must be separate from registerWorker because
- * it is called during the "super" constructor call in
- * ForkJoinWorkerThread.
- */
- final String nextWorkerName() {
- return workerNamePrefix.concat
- (Integer.toString(nextWorkerNumber.addAndGet(1)));
- }
-
- /**
- * Callback from ForkJoinWorkerThread constructor to establish its
- * poolIndex and record its WorkQueue. To avoid scanning bias due
- * to packing entries in front of the workQueues array, we treat
- * the array as a simple power-of-two hash table using per-thread
- * seed as hash, expanding as needed.
- *
- * @param w the worker's queue
- */
- final void registerWorker(WorkQueue w) {
- Mutex lock = this.lock;
- lock.lock();
- try {
- WorkQueue[] ws = workQueues;
- if (w != null && ws != null) { // skip on shutdown/failure
- int rs, n = ws.length, m = n - 1;
- int s = nextSeed += SEED_INCREMENT; // rarely-colliding sequence
- w.seed = (s == 0) ? 1 : s; // ensure non-zero seed
- int r = (s << 1) | 1; // use odd-numbered indices
- if (ws[r &= m] != null) { // collision
- int probes = 0; // step by approx half size
- int step = (n <= 4) ? 2 : ((n >>> 1) & SQMASK) + 2;
- while (ws[r = (r + step) & m] != null) {
- if (++probes >= n) {
- workQueues = ws = Arrays.copyOf(ws, n <<= 1);
- m = n - 1;
- probes = 0;
- }
- }
- }
- w.eventCount = w.poolIndex = r; // establish before recording
- ws[r] = w; // also update seq
- runState = ((rs = runState) & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN);
- }
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * Final callback from terminating worker, as well as upon failure
- * to construct or start a worker in addWorker. Removes record of
- * worker from array, and adjusts counts. If pool is shutting
- * down, tries to complete termination.
- *
- * @param wt the worker thread or null if addWorker failed
- * @param ex the exception causing failure, or null if none
- */
- final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
- Mutex lock = this.lock;
- WorkQueue w = null;
- if (wt != null && (w = wt.workQueue) != null) {
- w.runState = -1; // ensure runState is set
- stealCount.getAndAdd(w.totalSteals + w.nsteals);
- int idx = w.poolIndex;
- lock.lock();
- try { // remove record from array
- WorkQueue[] ws = workQueues;
- if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
- ws[idx] = null;
- } finally {
- lock.unlock();
- }
- }
-
- long c; // adjust ctl counts
- do {} while (!U.compareAndSwapLong
- (this, CTL, c = ctl, (((c - AC_UNIT) & AC_MASK) |
- ((c - TC_UNIT) & TC_MASK) |
- (c & ~(AC_MASK|TC_MASK)))));
-
- if (!tryTerminate(false, false) && w != null) {
- w.cancelAll(); // cancel remaining tasks
- if (w.array != null) // suppress signal if never ran
- signalWork(); // wake up or create replacement
- if (ex == null) // help clean refs on way out
- ForkJoinTask.helpExpungeStaleExceptions();
- }
-
- if (ex != null) // rethrow
- U.throwException(ex);
- }
-
-
- // Submissions
-
- /**
- * Unless shutting down, adds the given task to a submission queue
- * at submitter's current queue index (modulo submission
- * range). If no queue exists at the index, one is created. If
- * the queue is busy, another index is randomly chosen. The
- * submitMask bounds the effective number of queues to the
- * (nearest power of two for) parallelism level.
- *
- * @param task the task. Caller must ensure non-null.
- */
- private void doSubmit(ForkJoinTask task) {
- Submitter s = submitters.get();
- for (int r = s.seed, m = submitMask;;) {
- WorkQueue[] ws; WorkQueue q;
- int k = r & m & SQMASK; // use only even indices
- if (runState < 0 || (ws = workQueues) == null || ws.length <= k)
- throw new RejectedExecutionException(); // shutting down
- else if ((q = ws[k]) == null) { // create new queue
- WorkQueue nq = new WorkQueue(this, null, SHARED_QUEUE);
- Mutex lock = this.lock; // construct outside lock
- lock.lock();
- try { // recheck under lock
- int rs = runState; // to update seq
- if (ws == workQueues && ws[k] == null) {
- ws[k] = nq;
- runState = ((rs & SHUTDOWN) | ((rs + 2) & ~SHUTDOWN));
- }
- } finally {
- lock.unlock();
- }
- }
- else if (q.trySharedPush(task)) {
- signalWork();
- return;
- }
- else if (m > 1) { // move to a different index
- r ^= r << 13; // same xorshift as WorkQueues
- r ^= r >>> 17;
- s.seed = r ^= r << 5;
- }
- else
- Thread.yield(); // yield if no alternatives
- }
- }
-
- // Maintaining ctl counts
-
- /**
- * Increments active count; mainly called upon return from blocking.
- */
- final void incrementActiveCount() {
- long c;
- do {} while (!U.compareAndSwapLong(this, CTL, c = ctl, c + AC_UNIT));
- }
-
- /**
- * Tries to activate or create a worker if too few are active.
- */
- final void signalWork() {
- long c; int u;
- while ((u = (int)((c = ctl) >>> 32)) < 0) { // too few active
- WorkQueue[] ws = workQueues; int e, i; WorkQueue w; Thread p;
- if ((e = (int)c) > 0) { // at least one waiting
- if (ws != null && (i = e & SMASK) < ws.length &&
- (w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
- long nc = (((long)(w.nextWait & E_MASK)) |
- ((long)(u + UAC_UNIT) << 32));
- if (U.compareAndSwapLong(this, CTL, c, nc)) {
- w.eventCount = (e + E_SEQ) & E_MASK;
- if ((p = w.parker) != null)
- U.unpark(p); // activate and release
- break;
- }
- }
- else
- break;
- }
- else if (e == 0 && (u & SHORT_SIGN) != 0) { // too few total
- long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
- ((u + UAC_UNIT) & UAC_MASK)) << 32;
- if (U.compareAndSwapLong(this, CTL, c, nc)) {
- addWorker();
- break;
- }
- }
- else
- break;
- }
- }
-
-
- // Scanning for tasks
-
- /**
- * Top-level runloop for workers, called by ForkJoinWorkerThread.run.
- */
- final void runWorker(WorkQueue w) {
- w.growArray(false); // initialize queue array in this thread
- do { w.runTask(scan(w)); } while (w.runState >= 0);
- }
-
- /**
- * Scans for and, if found, returns one task, else possibly
- * inactivates the worker. This method operates on single reads of
- * volatile state and is designed to be re-invoked continuously,
- * in part because it returns upon detecting inconsistencies,
- * contention, or state changes that indicate possible success on
- * re-invocation.
- *
- * The scan searches for tasks across a random permutation of
- * queues (starting at a random index and stepping by a random
- * relative prime, checking each at least once). The scan
- * terminates upon either finding a non-empty queue, or completing
- * the sweep. If the worker is not inactivated, it takes and
- * returns a task from this queue. On failure to find a task, we
- * take one of the following actions, after which the caller will
- * retry calling this method unless terminated.
- *
- * * If pool is terminating, terminate the worker.
- *
- * * If not a complete sweep, try to release a waiting worker. If
- * the scan terminated because the worker is inactivated, then the
- * released worker will often be the calling worker, and it can
- * succeed obtaining a task on the next call. Or maybe it is
- * another worker, but with same net effect. Releasing in other
- * cases as well ensures that we have enough workers running.
- *
- * * If not already enqueued, try to inactivate and enqueue the
- * worker on wait queue. Or, if inactivating has caused the pool
- * to be quiescent, relay to idleAwaitWork to check for
- * termination and possibly shrink pool.
- *
- * * If already inactive, and the caller has run a task since the
- * last empty scan, return (to allow rescan) unless others are
- * also inactivated. Field WorkQueue.rescans counts down on each
- * scan to ensure eventual inactivation and blocking.
- *
- * * If already enqueued and none of the above apply, park
- * awaiting signal,
- *
- * @param w the worker (via its WorkQueue)
- * @return a task or null of none found
- */
- private final ForkJoinTask scan(WorkQueue w) {
- WorkQueue[] ws; // first update random seed
- int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
- int rs = runState, m; // volatile read order matters
- if ((ws = workQueues) != null && (m = ws.length - 1) > 0) {
- int ec = w.eventCount; // ec is negative if inactive
- int step = (r >>> 16) | 1; // relative prime
- for (int j = (m + 1) << 2; ; r += step) {
- WorkQueue q; ForkJoinTask t; ForkJoinTask[] a; int b;
- if ((q = ws[r & m]) != null && (b = q.base) - q.top < 0 &&
- (a = q.array) != null) { // probably nonempty
- int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
- t = (ForkJoinTask)U.getObjectVolatile(a, i);
- if (q.base == b && ec >= 0 && t != null &&
- U.compareAndSwapObject(a, i, t, null)) {
- q.base = b + 1; // specialization of pollAt
- return t;
- }
- else if (ec < 0 || j <= m) {
- rs = 0; // mark scan as imcomplete
- break; // caller can retry after release
- }
- }
- if (--j < 0)
- break;
- }
- long c = ctl; int e = (int)c, a = (int)(c >> AC_SHIFT), nr, ns;
- if (e < 0) // decode ctl on empty scan
- w.runState = -1; // pool is terminating
- else if (rs == 0 || rs != runState) { // incomplete scan
- WorkQueue v; Thread p; // try to release a waiter
- if (e > 0 && a < 0 && w.eventCount == ec &&
- (v = ws[e & m]) != null && v.eventCount == (e | INT_SIGN)) {
- long nc = ((long)(v.nextWait & E_MASK) |
- ((c + AC_UNIT) & (AC_MASK|TC_MASK)));
- if (ctl == c && U.compareAndSwapLong(this, CTL, c, nc)) {
- v.eventCount = (e + E_SEQ) & E_MASK;
- if ((p = v.parker) != null)
- U.unpark(p);
- }
- }
- }
- else if (ec >= 0) { // try to enqueue/inactivate
- long nc = (long)ec | ((c - AC_UNIT) & (AC_MASK|TC_MASK));
- w.nextWait = e;
- w.eventCount = ec | INT_SIGN; // mark as inactive
- if (ctl != c || !U.compareAndSwapLong(this, CTL, c, nc))
- w.eventCount = ec; // unmark on CAS failure
- else {
- if ((ns = w.nsteals) != 0) {
- w.nsteals = 0; // set rescans if ran task
- w.rescans = (a > 0) ? 0 : a + parallelism;
- w.totalSteals += ns;
- }
- if (a == 1 - parallelism) // quiescent
- idleAwaitWork(w, nc, c);
- }
- }
- else if (w.eventCount < 0) { // already queued
- if ((nr = w.rescans) > 0) { // continue rescanning
- int ac = a + parallelism;
- if (((w.rescans = (ac < nr) ? ac : nr - 1) & 3) == 0)
- Thread.yield(); // yield before block
- }
- else {
- Thread.interrupted(); // clear status
- Thread wt = Thread.currentThread();
- U.putObject(wt, PARKBLOCKER, this);
- w.parker = wt; // emulate LockSupport.park
- if (w.eventCount < 0) // recheck
- U.park(false, 0L);
- w.parker = null;
- U.putObject(wt, PARKBLOCKER, null);
- }
- }
- }
- return null;
- }
-
- /**
- * If inactivating worker w has caused the pool to become
- * quiescent, checks for pool termination, and, so long as this is
- * not the only worker, waits for event for up to SHRINK_RATE
- * nanosecs. On timeout, if ctl has not changed, terminates the
- * worker, which will in turn wake up another worker to possibly
- * repeat this process.
- *
- * @param w the calling worker
- * @param currentCtl the ctl value triggering possible quiescence
- * @param prevCtl the ctl value to restore if thread is terminated
- */
- private void idleAwaitWork(WorkQueue w, long currentCtl, long prevCtl) {
- if (w.eventCount < 0 && !tryTerminate(false, false) &&
- (int)prevCtl != 0 && !hasQueuedSubmissions() && ctl == currentCtl) {
- Thread wt = Thread.currentThread();
- Thread.yield(); // yield before block
- while (ctl == currentCtl) {
- long startTime = System.nanoTime();
- Thread.interrupted(); // timed variant of version in scan()
- U.putObject(wt, PARKBLOCKER, this);
- w.parker = wt;
- if (ctl == currentCtl)
- U.park(false, SHRINK_RATE);
- w.parker = null;
- U.putObject(wt, PARKBLOCKER, null);
- if (ctl != currentCtl)
- break;
- if (System.nanoTime() - startTime >= SHRINK_TIMEOUT &&
- U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
- w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
- w.runState = -1; // shrink
- break;
- }
- }
- }
- }
-
- /**
- * Tries to locate and execute tasks for a stealer of the given
- * task, or in turn one of its stealers, Traces currentSteal ->
- * currentJoin links looking for a thread working on a descendant
- * of the given task and with a non-empty queue to steal back and
- * execute tasks from. The first call to this method upon a
- * waiting join will often entail scanning/search, (which is OK
- * because the joiner has nothing better to do), but this method
- * leaves hints in workers to speed up subsequent calls. The
- * implementation is very branchy to cope with potential
- * inconsistencies or loops encountering chains that are stale,
- * unknown, or so long that they are likely cyclic. All of these
- * cases are dealt with by just retrying by caller.
- *
- * @param joiner the joining worker
- * @param task the task to join
- * @return true if found or ran a task (and so is immediately retryable)
- */
- private boolean tryHelpStealer(WorkQueue joiner, ForkJoinTask task) {
- WorkQueue[] ws;
- int m, depth = MAX_HELP; // remaining chain depth
- boolean progress = false;
- if ((ws = workQueues) != null && (m = ws.length - 1) > 0 &&
- task.status >= 0) {
- ForkJoinTask subtask = task; // current target
- outer: for (WorkQueue j = joiner;;) {
- WorkQueue stealer = null; // find stealer of subtask
- WorkQueue v = ws[j.stealHint & m]; // try hint
- if (v != null && v.currentSteal == subtask)
- stealer = v;
- else { // scan
- for (int i = 1; i <= m; i += 2) {
- if ((v = ws[i]) != null && v.currentSteal == subtask &&
- v != joiner) {
- stealer = v;
- j.stealHint = i; // save hint
- break;
- }
- }
- if (stealer == null)
- break;
- }
-
- for (WorkQueue q = stealer;;) { // try to help stealer
- ForkJoinTask[] a; ForkJoinTask t; int b;
- if (task.status < 0)
- break outer;
- if ((b = q.base) - q.top < 0 && (a = q.array) != null) {
- progress = true;
- int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
- t = (ForkJoinTask)U.getObjectVolatile(a, i);
- if (subtask.status < 0) // must recheck before taking
- break outer;
- if (t != null &&
- q.base == b &&
- U.compareAndSwapObject(a, i, t, null)) {
- q.base = b + 1;
- joiner.runSubtask(t);
- }
- else if (q.base == b)
- break outer; // possibly stalled
- }
- else { // descend
- ForkJoinTask next = stealer.currentJoin;
- if (--depth <= 0 || subtask.status < 0 ||
- next == null || next == subtask)
- break outer; // stale, dead-end, or cyclic
- subtask = next;
- j = stealer;
- break;
- }
- }
- }
- }
- return progress;
- }
-
- /**
- * If task is at base of some steal queue, steals and executes it.
- *
- * @param joiner the joining worker
- * @param task the task
- */
- private void tryPollForAndExec(WorkQueue joiner, ForkJoinTask task) {
- WorkQueue[] ws;
- if ((ws = workQueues) != null) {
- for (int j = 1; j < ws.length && task.status >= 0; j += 2) {
- WorkQueue q = ws[j];
- if (q != null && q.pollFor(task)) {
- joiner.runSubtask(task);
- break;
- }
- }
- }
- }
-
- /**
- * Tries to decrement active count (sometimes implicitly) and
- * possibly release or create a compensating worker in preparation
- * for blocking. Fails on contention or termination. Otherwise,
- * adds a new thread if no idle workers are available and either
- * pool would become completely starved or: (at least half
- * starved, and fewer than 50% spares exist, and there is at least
- * one task apparently available). Even though the availability
- * check requires a full scan, it is worthwhile in reducing false
- * alarms.
- *
- * @param task if non-null, a task being waited for
- * @param blocker if non-null, a blocker being waited for
- * @return true if the caller can block, else should recheck and retry
- */
- final boolean tryCompensate(ForkJoinTask task, ManagedBlocker blocker) {
- int pc = parallelism, e;
- long c = ctl;
- WorkQueue[] ws = workQueues;
- if ((e = (int)c) >= 0 && ws != null) {
- int u, a, ac, hc;
- int tc = (short)((u = (int)(c >>> 32)) >>> UTC_SHIFT) + pc;
- boolean replace = false;
- if ((a = u >> UAC_SHIFT) <= 0) {
- if ((ac = a + pc) <= 1)
- replace = true;
- else if ((e > 0 || (task != null &&
- ac <= (hc = pc >>> 1) && tc < pc + hc))) {
- WorkQueue w;
- for (int j = 0; j < ws.length; ++j) {
- if ((w = ws[j]) != null && !w.isEmpty()) {
- replace = true;
- break; // in compensation range and tasks available
- }
- }
- }
- }
- if ((task == null || task.status >= 0) && // recheck need to block
- (blocker == null || !blocker.isReleasable()) && ctl == c) {
- if (!replace) { // no compensation
- long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
- if (U.compareAndSwapLong(this, CTL, c, nc))
- return true;
- }
- else if (e != 0) { // release an idle worker
- WorkQueue w; Thread p; int i;
- if ((i = e & SMASK) < ws.length && (w = ws[i]) != null) {
- long nc = ((long)(w.nextWait & E_MASK) |
- (c & (AC_MASK|TC_MASK)));
- if (w.eventCount == (e | INT_SIGN) &&
- U.compareAndSwapLong(this, CTL, c, nc)) {
- w.eventCount = (e + E_SEQ) & E_MASK;
- if ((p = w.parker) != null)
- U.unpark(p);
- return true;
- }
- }
- }
- else if (tc < MAX_CAP) { // create replacement
- long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
- if (U.compareAndSwapLong(this, CTL, c, nc)) {
- addWorker();
- return true;
- }
- }
- }
- }
- return false;
- }
-
- /**
- * Helps and/or blocks until the given task is done.
- *
- * @param joiner the joining worker
- * @param task the task
- * @return task status on exit
- */
- final int awaitJoin(WorkQueue joiner, ForkJoinTask task) {
- int s;
- ForkJoinTask prevJoin = joiner.currentJoin;
- if ((s = task.status) >= 0) {
- joiner.currentJoin = task;
- long startTime = 0L;
- for (int k = 0;;) {
- if ((joiner.isEmpty() ? // try to help
- !tryHelpStealer(joiner, task) :
- !joiner.tryRemoveAndExec(task))) {
- if (k == 0) {
- startTime = System.nanoTime();
- tryPollForAndExec(joiner, task); // check uncommon case
- }
- else if ((k & (MAX_HELP - 1)) == 0 &&
- System.nanoTime() - startTime >=
- COMPENSATION_DELAY &&
- tryCompensate(task, null)) {
- if (task.trySetSignal() && task.status >= 0) {
- synchronized (task) {
- if (task.status >= 0) {
- try { // see ForkJoinTask
- task.wait(); // for explanation
- } catch (InterruptedException ie) {
- }
- }
- else
- task.notifyAll();
- }
- }
- long c; // re-activate
- do {} while (!U.compareAndSwapLong
- (this, CTL, c = ctl, c + AC_UNIT));
- }
- }
- if ((s = task.status) < 0) {
- joiner.currentJoin = prevJoin;
- break;
- }
- else if ((k++ & (MAX_HELP - 1)) == MAX_HELP >>> 1)
- Thread.yield(); // for politeness
- }
- }
- return s;
- }
-
- /**
- * Stripped-down variant of awaitJoin used by timed joins. Tries
- * to help join only while there is continuous progress. (Caller
- * will then enter a timed wait.)
- *
- * @param joiner the joining worker
- * @param task the task
- * @return task status on exit
- */
- final int helpJoinOnce(WorkQueue joiner, ForkJoinTask task) {
- int s;
- while ((s = task.status) >= 0 &&
- (joiner.isEmpty() ?
- tryHelpStealer(joiner, task) :
- joiner.tryRemoveAndExec(task)))
- ;
- return s;
- }
-
- /**
- * Returns a (probably) non-empty steal queue, if one is found
- * during a random, then cyclic scan, else null. This method must
- * be retried by caller if, by the time it tries to use the queue,
- * it is empty.
- */
- private WorkQueue findNonEmptyStealQueue(WorkQueue w) {
- // Similar to loop in scan(), but ignoring submissions
- int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
- int step = (r >>> 16) | 1;
- for (WorkQueue[] ws;;) {
- int rs = runState, m;
- if ((ws = workQueues) == null || (m = ws.length - 1) < 1)
- return null;
- for (int j = (m + 1) << 2; ; r += step) {
- WorkQueue q = ws[((r << 1) | 1) & m];
- if (q != null && !q.isEmpty())
- return q;
- else if (--j < 0) {
- if (runState == rs)
- return null;
- break;
- }
- }
- }
- }
-
- /**
- * Runs tasks until {@code isQuiescent()}. We piggyback on
- * active count ctl maintenance, but rather than blocking
- * when tasks cannot be found, we rescan until all others cannot
- * find tasks either.
- */
- final void helpQuiescePool(WorkQueue w) {
- for (boolean active = true;;) {
- ForkJoinTask localTask; // exhaust local queue
- while ((localTask = w.nextLocalTask()) != null)
- localTask.doExec();
- WorkQueue q = findNonEmptyStealQueue(w);
- if (q != null) {
- ForkJoinTask t; int b;
- if (!active) { // re-establish active count
- long c;
- active = true;
- do {} while (!U.compareAndSwapLong
- (this, CTL, c = ctl, c + AC_UNIT));
- }
- if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
- w.runSubtask(t);
- }
- else {
- long c;
- if (active) { // decrement active count without queuing
- active = false;
- do {} while (!U.compareAndSwapLong
- (this, CTL, c = ctl, c -= AC_UNIT));
- }
- else
- c = ctl; // re-increment on exit
- if ((int)(c >> AC_SHIFT) + parallelism == 0) {
- do {} while (!U.compareAndSwapLong
- (this, CTL, c = ctl, c + AC_UNIT));
- break;
- }
- }
- }
- }
-
- /**
- * Gets and removes a local or stolen task for the given worker.
- *
- * @return a task, if available
- */
- final ForkJoinTask nextTaskFor(WorkQueue w) {
- for (ForkJoinTask t;;) {
- WorkQueue q; int b;
- if ((t = w.nextLocalTask()) != null)
- return t;
- if ((q = findNonEmptyStealQueue(w)) == null)
- return null;
- if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null)
- return t;
- }
- }
-
- /**
- * Returns the approximate (non-atomic) number of idle threads per
- * active thread to offset steal queue size for method
- * ForkJoinTask.getSurplusQueuedTaskCount().
- */
- final int idlePerActive() {
- // Approximate at powers of two for small values, saturate past 4
- int p = parallelism;
- int a = p + (int)(ctl >> AC_SHIFT);
- return (a > (p >>>= 1) ? 0 :
- a > (p >>>= 1) ? 1 :
- a > (p >>>= 1) ? 2 :
- a > (p >>>= 1) ? 4 :
- 8);
- }
-
- // Termination
-
- /**
- * Possibly initiates and/or completes termination. The caller
- * triggering termination runs three passes through workQueues:
- * (0) Setting termination status, followed by wakeups of queued
- * workers; (1) cancelling all tasks; (2) interrupting lagging
- * threads (likely in external tasks, but possibly also blocked in
- * joins). Each pass repeats previous steps because of potential
- * lagging thread creation.
- *
- * @param now if true, unconditionally terminate, else only
- * if no work and no active workers
- * @param enable if true, enable shutdown when next possible
- * @return true if now terminating or terminated
- */
- private boolean tryTerminate(boolean now, boolean enable) {
- Mutex lock = this.lock;
- for (long c;;) {
- if (((c = ctl) & STOP_BIT) != 0) { // already terminating
- if ((short)(c >>> TC_SHIFT) == -parallelism) {
- lock.lock(); // don't need try/finally
- termination.signalAll(); // signal when 0 workers
- lock.unlock();
- }
- return true;
- }
- if (runState >= 0) { // not yet enabled
- if (!enable)
- return false;
- lock.lock();
- runState |= SHUTDOWN;
- lock.unlock();
- }
- if (!now) { // check if idle & no tasks
- if ((int)(c >> AC_SHIFT) != -parallelism ||
- hasQueuedSubmissions())
- return false;
- // Check for unqueued inactive workers. One pass suffices.
- WorkQueue[] ws = workQueues; WorkQueue w;
- if (ws != null) {
- for (int i = 1; i < ws.length; i += 2) {
- if ((w = ws[i]) != null && w.eventCount >= 0)
- return false;
- }
- }
- }
- if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) {
- for (int pass = 0; pass < 3; ++pass) {
- WorkQueue[] ws = workQueues;
- if (ws != null) {
- WorkQueue w;
- int n = ws.length;
- for (int i = 0; i < n; ++i) {
- if ((w = ws[i]) != null) {
- w.runState = -1;
- if (pass > 0) {
- w.cancelAll();
- if (pass > 1)
- w.interruptOwner();
- }
- }
- }
- // Wake up workers parked on event queue
- int i, e; long cc; Thread p;
- while ((e = (int)(cc = ctl) & E_MASK) != 0 &&
- (i = e & SMASK) < n &&
- (w = ws[i]) != null) {
- long nc = ((long)(w.nextWait & E_MASK) |
- ((cc + AC_UNIT) & AC_MASK) |
- (cc & (TC_MASK|STOP_BIT)));
- if (w.eventCount == (e | INT_SIGN) &&
- U.compareAndSwapLong(this, CTL, cc, nc)) {
- w.eventCount = (e + E_SEQ) & E_MASK;
- w.runState = -1;
- if ((p = w.parker) != null)
- U.unpark(p);
- }
- }
- }
- }
- }
- }
- }
-
- // Exported methods
-
- // Constructors
-
- /**
- * Creates a {@code ForkJoinPool} with parallelism equal to {@link
- * java.lang.Runtime#availableProcessors}, using the {@linkplain
- * #defaultForkJoinWorkerThreadFactory default thread factory},
- * no UncaughtExceptionHandler, and non-async LIFO processing mode.
- *
- * @throws SecurityException if a security manager exists and
- * the caller is not permitted to modify threads
- * because it does not hold {@link
- * java.lang.RuntimePermission}{@code ("modifyThread")}
- */
- public ForkJoinPool() {
- this(Runtime.getRuntime().availableProcessors(),
- defaultForkJoinWorkerThreadFactory, null, false);
- }
-
- /**
- * Creates a {@code ForkJoinPool} with the indicated parallelism
- * level, the {@linkplain
- * #defaultForkJoinWorkerThreadFactory default thread factory},
- * no UncaughtExceptionHandler, and non-async LIFO processing mode.
- *
- * @param parallelism the parallelism level
- * @throws IllegalArgumentException if parallelism less than or
- * equal to zero, or greater than implementation limit
- * @throws SecurityException if a security manager exists and
- * the caller is not permitted to modify threads
- * because it does not hold {@link
- * java.lang.RuntimePermission}{@code ("modifyThread")}
- */
- public ForkJoinPool(int parallelism) {
- this(parallelism, defaultForkJoinWorkerThreadFactory, null, false);
- }
-
- /**
- * Creates a {@code ForkJoinPool} with the given parameters.
- *
- * @param parallelism the parallelism level. For default value,
- * use {@link java.lang.Runtime#availableProcessors}.
- * @param factory the factory for creating new threads. For default value,
- * use {@link #defaultForkJoinWorkerThreadFactory}.
- * @param handler the handler for internal worker threads that
- * terminate due to unrecoverable errors encountered while executing
- * tasks. For default value, use {@code null}.
- * @param asyncMode if true,
- * establishes local first-in-first-out scheduling mode for forked
- * tasks that are never joined. This mode may be more appropriate
- * than default locally stack-based mode in applications in which
- * worker threads only process event-style asynchronous tasks.
- * For default value, use {@code false}.
- * @throws IllegalArgumentException if parallelism less than or
- * equal to zero, or greater than implementation limit
- * @throws NullPointerException if the factory is null
- * @throws SecurityException if a security manager exists and
- * the caller is not permitted to modify threads
- * because it does not hold {@link
- * java.lang.RuntimePermission}{@code ("modifyThread")}
- */
- public ForkJoinPool(int parallelism,
- ForkJoinWorkerThreadFactory factory,
- Thread.UncaughtExceptionHandler handler,
- boolean asyncMode) {
- checkPermission();
- if (factory == null)
- throw new NullPointerException();
- if (parallelism <= 0 || parallelism > MAX_CAP)
- throw new IllegalArgumentException();
- this.parallelism = parallelism;
- this.factory = factory;
- this.ueh = handler;
- this.localMode = asyncMode ? FIFO_QUEUE : LIFO_QUEUE;
- long np = (long)(-parallelism); // offset ctl counts
- this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
- // Use nearest power 2 for workQueues size. See Hackers Delight sec 3.2.
- int n = parallelism - 1;
- n |= n >>> 1; n |= n >>> 2; n |= n >>> 4; n |= n >>> 8; n |= n >>> 16;
- int size = (n + 1) << 1; // #slots = 2*#workers
- this.submitMask = size - 1; // room for max # of submit queues
- this.workQueues = new WorkQueue[size];
- this.termination = (this.lock = new Mutex()).newCondition();
- this.stealCount = new AtomicLong();
- this.nextWorkerNumber = new AtomicInteger();
- int pn = poolNumberGenerator.incrementAndGet();
- StringBuilder sb = new StringBuilder("ForkJoinPool-");
- sb.append(Integer.toString(pn));
- sb.append("-worker-");
- this.workerNamePrefix = sb.toString();
- lock.lock();
- this.runState = 1; // set init flag
- lock.unlock();
- }
-
- // Execution methods
-
- /**
- * Performs the given task, returning its result upon completion.
- * If the computation encounters an unchecked Exception or Error,
- * it is rethrown as the outcome of this invocation. 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 current thread
- * as well as the thread actually encountering the exception;
- * minimally only the latter.
- *
- * @param task the task
- * @return the task's result
- * @throws NullPointerException if the task is null
- * @throws RejectedExecutionException if the task cannot be
- * scheduled for execution
- */
- public T invoke(ForkJoinTask task) {
- if (task == null)
- throw new NullPointerException();
- doSubmit(task);
- return task.join();
- }
-
- /**
- * Arranges for (asynchronous) execution of the given task.
- *
- * @param task the task
- * @throws NullPointerException if the task is null
- * @throws RejectedExecutionException if the task cannot be
- * scheduled for execution
- */
- public void execute(ForkJoinTask task) {
- if (task == null)
- throw new NullPointerException();
- doSubmit(task);
- }
-
- // AbstractExecutorService methods
-
- /**
- * @throws NullPointerException if the task is null
- * @throws RejectedExecutionException if the task cannot be
- * scheduled for execution
- */
- public void execute(Runnable task) {
- if (task == null)
- throw new NullPointerException();
- ForkJoinTask job;
- if (task instanceof ForkJoinTask) // avoid re-wrap
- job = (ForkJoinTask) task;
- else
- job = new ForkJoinTask.AdaptedRunnableAction(task);
- doSubmit(job);
- }
-
- /**
- * Submits a ForkJoinTask for execution.
- *
- * @param task the task to submit
- * @return the task
- * @throws NullPointerException if the task is null
- * @throws RejectedExecutionException if the task cannot be
- * scheduled for execution
- */
- public ForkJoinTask submit(ForkJoinTask task) {
- if (task == null)
- throw new NullPointerException();
- doSubmit(task);
- return task;
- }
-
- /**
- * @throws NullPointerException if the task is null
- * @throws RejectedExecutionException if the task cannot be
- * scheduled for execution
- */
- public ForkJoinTask submit(Callable task) {
- ForkJoinTask job = new ForkJoinTask.AdaptedCallable(task);
- doSubmit(job);
- return job;
- }
-
- /**
- * @throws NullPointerException if the task is null
- * @throws RejectedExecutionException if the task cannot be
- * scheduled for execution
- */
- public ForkJoinTask submit(Runnable task, T result) {
- ForkJoinTask job = new ForkJoinTask.AdaptedRunnable(task, result);
- doSubmit(job);
- return job;
- }
-
- /**
- * @throws NullPointerException if the task is null
- * @throws RejectedExecutionException if the task cannot be
- * scheduled for execution
- */
- public ForkJoinTask submit(Runnable task) {
- if (task == null)
- throw new NullPointerException();
- ForkJoinTask job;
- if (task instanceof ForkJoinTask) // avoid re-wrap
- job = (ForkJoinTask) task;
- else
- job = new ForkJoinTask.AdaptedRunnableAction(task);
- doSubmit(job);
- return job;
- }
-
- /**
- * @throws NullPointerException {@inheritDoc}
- * @throws RejectedExecutionException {@inheritDoc}
- */
- public List> invokeAll(Collection> tasks) {
- // In previous versions of this class, this method constructed
- // a task to run ForkJoinTask.invokeAll, but now external
- // invocation of multiple tasks is at least as efficient.
- List> fs = new ArrayList>(tasks.size());
- // Workaround needed because method wasn't declared with
- // wildcards in return type but should have been.
- @SuppressWarnings({"unchecked", "rawtypes"})
- List> futures = (List>) (List) fs;
-
- boolean done = false;
- try {
- for (Callable t : tasks) {
- ForkJoinTask f = new ForkJoinTask.AdaptedCallable(t);
- doSubmit(f);
- fs.add(f);
- }
- for (ForkJoinTask f : fs)
- f.quietlyJoin();
- done = true;
- return futures;
- } finally {
- if (!done)
- for (ForkJoinTask f : fs)
- f.cancel(false);
- }
- }
-
- /**
- * Returns the factory used for constructing new workers.
- *
- * @return the factory used for constructing new workers
- */
- public ForkJoinWorkerThreadFactory getFactory() {
- return factory;
- }
-
- /**
- * Returns the handler for internal worker threads that terminate
- * due to unrecoverable errors encountered while executing tasks.
- *
- * @return the handler, or {@code null} if none
- */
- public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() {
- return ueh;
- }
-
- /**
- * Returns the targeted parallelism level of this pool.
- *
- * @return the targeted parallelism level of this pool
- */
- public int getParallelism() {
- return parallelism;
- }
-
- /**
- * Returns the number of worker threads that have started but not
- * yet terminated. The result returned by this method may differ
- * from {@link #getParallelism} when threads are created to
- * maintain parallelism when others are cooperatively blocked.
- *
- * @return the number of worker threads
- */
- public int getPoolSize() {
- return parallelism + (short)(ctl >>> TC_SHIFT);
- }
-
- /**
- * Returns {@code true} if this pool uses local first-in-first-out
- * scheduling mode for forked tasks that are never joined.
- *
- * @return {@code true} if this pool uses async mode
- */
- public boolean getAsyncMode() {
- return localMode != 0;
- }
-
- /**
- * Returns an estimate of the number of worker threads that are
- * not blocked waiting to join tasks or for other managed
- * synchronization. This method may overestimate the
- * number of running threads.
- *
- * @return the number of worker threads
- */
- public int getRunningThreadCount() {
- int rc = 0;
- WorkQueue[] ws; WorkQueue w;
- if ((ws = workQueues) != null) {
- for (int i = 1; i < ws.length; i += 2) {
- if ((w = ws[i]) != null && w.isApparentlyUnblocked())
- ++rc;
- }
- }
- return rc;
- }
-
- /**
- * Returns an estimate of the number of threads that are currently
- * stealing or executing tasks. This method may overestimate the
- * number of active threads.
- *
- * @return the number of active threads
- */
- public int getActiveThreadCount() {
- int r = parallelism + (int)(ctl >> AC_SHIFT);
- return (r <= 0) ? 0 : r; // suppress momentarily negative values
- }
-
- /**
- * Returns {@code true} if all worker threads are currently idle.
- * An idle worker is one that cannot obtain a task to execute
- * because none are available to steal from other threads, and
- * there are no pending submissions to the pool. This method is
- * conservative; it might not return {@code true} immediately upon
- * idleness of all threads, but will eventually become true if
- * threads remain inactive.
- *
- * @return {@code true} if all threads are currently idle
- */
- public boolean isQuiescent() {
- return (int)(ctl >> AC_SHIFT) + parallelism == 0;
- }
-
- /**
- * Returns an estimate of the total number of tasks stolen from
- * one thread's work queue by another. The reported value
- * underestimates the actual total number of steals when the pool
- * is not quiescent. This value may be useful for monitoring and
- * tuning fork/join programs: in general, steal counts should be
- * high enough to keep threads busy, but low enough to avoid
- * overhead and contention across threads.
- *
- * @return the number of steals
- */
- public long getStealCount() {
- long count = stealCount.get();
- WorkQueue[] ws; WorkQueue w;
- if ((ws = workQueues) != null) {
- for (int i = 1; i < ws.length; i += 2) {
- if ((w = ws[i]) != null)
- count += w.totalSteals;
- }
- }
- return count;
- }
-
- /**
- * Returns an estimate of the total number of tasks currently held
- * in queues by worker threads (but not including tasks submitted
- * to the pool that have not begun executing). This value is only
- * an approximation, obtained by iterating across all threads in
- * the pool. This method may be useful for tuning task
- * granularities.
- *
- * @return the number of queued tasks
- */
- public long getQueuedTaskCount() {
- long count = 0;
- WorkQueue[] ws; WorkQueue w;
- if ((ws = workQueues) != null) {
- for (int i = 1; i < ws.length; i += 2) {
- if ((w = ws[i]) != null)
- count += w.queueSize();
- }
- }
- return count;
- }
-
- /**
- * Returns an estimate of the number of tasks submitted to this
- * pool that have not yet begun executing. This method may take
- * time proportional to the number of submissions.
- *
- * @return the number of queued submissions
- */
- public int getQueuedSubmissionCount() {
- int count = 0;
- WorkQueue[] ws; WorkQueue w;
- if ((ws = workQueues) != null) {
- for (int i = 0; i < ws.length; i += 2) {
- if ((w = ws[i]) != null)
- count += w.queueSize();
- }
- }
- return count;
- }
-
- /**
- * Returns {@code true} if there are any tasks submitted to this
- * pool that have not yet begun executing.
- *
- * @return {@code true} if there are any queued submissions
- */
- public boolean hasQueuedSubmissions() {
- WorkQueue[] ws; WorkQueue w;
- if ((ws = workQueues) != null) {
- for (int i = 0; i < ws.length; i += 2) {
- if ((w = ws[i]) != null && !w.isEmpty())
- return true;
- }
- }
- return false;
- }
-
- /**
- * Removes and returns the next unexecuted submission if one is
- * available. This method may be useful in extensions to this
- * class that re-assign work in systems with multiple pools.
- *
- * @return the next submission, or {@code null} if none
- */
- protected ForkJoinTask pollSubmission() {
- WorkQueue[] ws; WorkQueue w; ForkJoinTask t;
- if ((ws = workQueues) != null) {
- for (int i = 0; i < ws.length; i += 2) {
- if ((w = ws[i]) != null && (t = w.poll()) != null)
- return t;
- }
- }
- return null;
- }
-
- /**
- * Removes all available unexecuted submitted and forked tasks
- * from scheduling queues and adds them to the given collection,
- * without altering their execution status. These may include
- * artificially generated or wrapped tasks. This method is
- * designed to be invoked only when the pool is known to be
- * quiescent. Invocations at other times may not remove all
- * tasks. A failure encountered while attempting to add elements
- * to collection {@code c} may result in elements being in
- * neither, either or both collections when the associated
- * exception is thrown. The behavior of this operation is
- * undefined if the specified collection is modified while the
- * operation is in progress.
- *
- * @param c the collection to transfer elements into
- * @return the number of elements transferred
- */
- protected int drainTasksTo(Collection> c) {
- int count = 0;
- WorkQueue[] ws; WorkQueue w; ForkJoinTask t;
- if ((ws = workQueues) != null) {
- for (int i = 0; i < ws.length; ++i) {
- if ((w = ws[i]) != null) {
- while ((t = w.poll()) != null) {
- c.add(t);
- ++count;
- }
- }
- }
- }
- return count;
- }
-
- /**
- * Returns a string identifying this pool, as well as its state,
- * including indications of run state, parallelism level, and
- * worker and task counts.
- *
- * @return a string identifying this pool, as well as its state
- */
- public String toString() {
- // Use a single pass through workQueues to collect counts
- long qt = 0L, qs = 0L; int rc = 0;
- long st = stealCount.get();
- long c = ctl;
- WorkQueue[] ws; WorkQueue w;
- if ((ws = workQueues) != null) {
- for (int i = 0; i < ws.length; ++i) {
- if ((w = ws[i]) != null) {
- int size = w.queueSize();
- if ((i & 1) == 0)
- qs += size;
- else {
- qt += size;
- st += w.totalSteals;
- if (w.isApparentlyUnblocked())
- ++rc;
- }
- }
- }
- }
- int pc = parallelism;
- int tc = pc + (short)(c >>> TC_SHIFT);
- int ac = pc + (int)(c >> AC_SHIFT);
- if (ac < 0) // ignore transient negative
- ac = 0;
- String level;
- if ((c & STOP_BIT) != 0)
- level = (tc == 0) ? "Terminated" : "Terminating";
- else
- level = runState < 0 ? "Shutting down" : "Running";
- return super.toString() +
- "[" + level +
- ", parallelism = " + pc +
- ", size = " + tc +
- ", active = " + ac +
- ", running = " + rc +
- ", steals = " + st +
- ", tasks = " + qt +
- ", submissions = " + qs +
- "]";
- }
-
- /**
- * Initiates an orderly shutdown in which previously submitted
- * tasks are executed, but no new tasks will be accepted.
- * Invocation has no additional effect if already shut down.
- * Tasks that are in the process of being submitted concurrently
- * during the course of this method may or may not be rejected.
- *
- * @throws SecurityException if a security manager exists and
- * the caller is not permitted to modify threads
- * because it does not hold {@link
- * java.lang.RuntimePermission}{@code ("modifyThread")}
- */
- public void shutdown() {
- checkPermission();
- tryTerminate(false, true);
- }
-
- /**
- * Attempts to cancel and/or stop all tasks, and reject all
- * subsequently submitted tasks. Tasks that are in the process of
- * being submitted or executed concurrently during the course of
- * this method may or may not be rejected. This method cancels
- * both existing and unexecuted tasks, in order to permit
- * termination in the presence of task dependencies. So the method
- * always returns an empty list (unlike the case for some other
- * Executors).
- *
- * @return an empty list
- * @throws SecurityException if a security manager exists and
- * the caller is not permitted to modify threads
- * because it does not hold {@link
- * java.lang.RuntimePermission}{@code ("modifyThread")}
- */
- public List shutdownNow() {
- checkPermission();
- tryTerminate(true, true);
- return Collections.emptyList();
- }
-
- /**
- * Returns {@code true} if all tasks have completed following shut down.
- *
- * @return {@code true} if all tasks have completed following shut down
- */
- public boolean isTerminated() {
- long c = ctl;
- return ((c & STOP_BIT) != 0L &&
- (short)(c >>> TC_SHIFT) == -parallelism);
- }
-
- /**
- * Returns {@code true} if the process of termination has
- * commenced but not yet completed. This method may be useful for
- * debugging. A return of {@code true} reported a sufficient
- * period after shutdown may indicate that submitted tasks have
- * ignored or suppressed interruption, or are waiting for IO,
- * causing this executor not to properly terminate. (See the
- * advisory notes for class {@link ForkJoinTask} stating that
- * tasks should not normally entail blocking operations. But if
- * they do, they must abort them on interrupt.)
- *
- * @return {@code true} if terminating but not yet terminated
- */
- public boolean isTerminating() {
- long c = ctl;
- return ((c & STOP_BIT) != 0L &&
- (short)(c >>> TC_SHIFT) != -parallelism);
- }
-
- /**
- * Returns {@code true} if this pool has been shut down.
- *
- * @return {@code true} if this pool has been shut down
- */
- public boolean isShutdown() {
- return runState < 0;
- }
-
- /**
- * Blocks until all tasks have completed execution after a shutdown
- * request, or the timeout occurs, or the current thread is
- * interrupted, whichever happens first.
- *
- * @param timeout the maximum time to wait
- * @param unit the time unit of the timeout argument
- * @return {@code true} if this executor terminated and
- * {@code false} if the timeout elapsed before termination
- * @throws InterruptedException if interrupted while waiting
- */
- public boolean awaitTermination(long timeout, TimeUnit unit)
- throws InterruptedException {
- long nanos = unit.toNanos(timeout);
- final Mutex lock = this.lock;
- lock.lock();
- try {
- for (;;) {
- if (isTerminated())
- return true;
- if (nanos <= 0)
- return false;
- nanos = termination.awaitNanos(nanos);
- }
- } finally {
- lock.unlock();
- }
- }
-
- /**
- * Interface for extending managed parallelism for tasks running
- * in {@link ForkJoinPool}s.
- *
- *
A {@code ManagedBlocker} provides two methods. Method
- * {@code isReleasable} must return {@code true} if blocking is
- * not necessary. Method {@code block} blocks the current thread
- * if necessary (perhaps internally invoking {@code isReleasable}
- * before actually blocking). These actions are performed by any
- * thread invoking {@link ForkJoinPool#managedBlock}. The
- * unusual methods in this API accommodate synchronizers that may,
- * but don't usually, block for long periods. Similarly, they
- * allow more efficient internal handling of cases in which
- * additional workers may be, but usually are not, needed to
- * ensure sufficient parallelism. Toward this end,
- * implementations of method {@code isReleasable} must be amenable
- * to repeated invocation.
- *
- *
For example, here is a ManagedBlocker based on a
- * ReentrantLock:
- *
- */
- public static interface ManagedBlocker {
- /**
- * Possibly blocks the current thread, for example waiting for
- * a lock or condition.
- *
- * @return {@code true} if no additional blocking is necessary
- * (i.e., if isReleasable would return true)
- * @throws InterruptedException if interrupted while waiting
- * (the method is not required to do so, but is allowed to)
- */
- boolean block() throws InterruptedException;
-
- /**
- * Returns {@code true} if blocking is unnecessary.
- */
- boolean isReleasable();
- }
-
- /**
- * Blocks in accord with the given blocker. If the current thread
- * is a {@link ForkJoinWorkerThread}, this method possibly
- * arranges for a spare thread to be activated if necessary to
- * ensure sufficient parallelism while the current thread is blocked.
- *
- *
If the caller is not a {@link ForkJoinTask}, this method is
- * behaviorally equivalent to
- *
{@code
- * while (!blocker.isReleasable())
- * if (blocker.block())
- * return;
- * }
- *
- * If the caller is a {@code ForkJoinTask}, then the pool may
- * first be expanded to ensure parallelism, and later adjusted.
- *
- * @param blocker the blocker
- * @throws InterruptedException if blocker.block did so
- */
- public static void managedBlock(ManagedBlocker blocker)
- throws InterruptedException {
- Thread t = Thread.currentThread();
- ForkJoinPool p = ((t instanceof ForkJoinWorkerThread) ?
- ((ForkJoinWorkerThread)t).pool : null);
- while (!blocker.isReleasable()) {
- if (p == null || p.tryCompensate(null, blocker)) {
- try {
- do {} while (!blocker.isReleasable() && !blocker.block());
- } finally {
- if (p != null)
- p.incrementActiveCount();
- }
- break;
- }
- }
- }
-
- // AbstractExecutorService overrides. These rely on undocumented
- // fact that ForkJoinTask.adapt returns ForkJoinTasks that also
- // implement RunnableFuture.
-
- protected RunnableFuture newTaskFor(Runnable runnable, T value) {
- return new ForkJoinTask.AdaptedRunnable(runnable, value);
- }
-
- protected RunnableFuture newTaskFor(Callable callable) {
- return new ForkJoinTask.AdaptedCallable(callable);
- }
-
- // Unsafe mechanics
- private static final sun.misc.Unsafe U;
- private static final long CTL;
- private static final long PARKBLOCKER;
- private static final int ABASE;
- private static final int ASHIFT;
-
- static {
- poolNumberGenerator = new AtomicInteger();
- nextSubmitterSeed = new AtomicInteger(0x55555555);
- modifyThreadPermission = new RuntimePermission("modifyThread");
- defaultForkJoinWorkerThreadFactory =
- new DefaultForkJoinWorkerThreadFactory();
- submitters = new ThreadSubmitter();
- int s;
- try {
- U = getUnsafe();
- Class k = ForkJoinPool.class;
- Class ak = ForkJoinTask[].class;
- CTL = U.objectFieldOffset
- (k.getDeclaredField("ctl"));
- Class tk = Thread.class;
- PARKBLOCKER = U.objectFieldOffset
- (tk.getDeclaredField("parkBlocker"));
- ABASE = U.arrayBaseOffset(ak);
- s = U.arrayIndexScale(ak);
- } catch (Exception e) {
- throw new Error(e);
- }
- if ((s & (s-1)) != 0)
- throw new Error("data type scale not a power of two");
- ASHIFT = 31 - Integer.numberOfLeadingZeros(s);
- }
-
- /**
- * Returns a sun.misc.Unsafe. Suitable for use in a 3rd party package.
- * Replace with a simple call to Unsafe.getUnsafe when integrating
- * into a jdk.
- *
- * @return a sun.misc.Unsafe
- */
- private static sun.misc.Unsafe getUnsafe() {
- return Unsafe.instance;
- }
-
-}
diff --git a/akka-actor/src/main/java/akka/jsr166y/ForkJoinTask.java b/akka-actor/src/main/java/akka/jsr166y/ForkJoinTask.java
deleted file mode 100644
index fe12152c3a..0000000000
--- a/akka-actor/src/main/java/akka/jsr166y/ForkJoinTask.java
+++ /dev/null
@@ -1,1506 +0,0 @@
-/*
- * 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/publicdomain/zero/1.0/
- */
-
-package akka.jsr166y;
-import java.io.Serializable;
-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;
-import akka.util.Unsafe;
-
-/**
- * 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" {@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 {@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 #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.
- *
- *
In the most typical usages, a fork-join pair act like 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, 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 other's
- * methods), some of them may only be called from within other
- * 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}.
- *
- *
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
- * 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
- * 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 {
-
- /*
- * 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.
- */
-
- /*
- * 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 (anded with
- * DONE_MASK) 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, mainly by arranging that every synchronized
- * block performs a wait, notifyAll or both.
- */
-
- /** The run status of this task */
- volatile int status; // accessed directly by pool and workers
- static final int DONE_MASK = 0xf0000000; // mask out non-completion bits
- static final int NORMAL = 0xf0000000; // must be negative
- static final int CANCELLED = 0xc0000000; // must be < NORMAL
- static final int EXCEPTIONAL = 0x80000000; // must be < CANCELLED
- static final int SIGNAL = 0x00000001;
- static final int MARKED = 0x00000002;
-
- /**
- * Marks completion and wakes up threads waiting to join this
- * task. A specialization for NORMAL completion is in method
- * doExec.
- *
- * @param completion one of NORMAL, CANCELLED, EXCEPTIONAL
- * @return completion status on exit
- */
- private int setCompletion(int completion) {
- for (int s;;) {
- if ((s = status) < 0)
- return s;
- if (U.compareAndSwapInt(this, STATUS, s, s | completion)) {
- if ((s & SIGNAL) != 0)
- synchronized (this) { notifyAll(); }
- return completion;
- }
- }
- }
-
- /**
- * 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 | NORMAL)) {
- if ((s & SIGNAL) != 0)
- synchronized (this) { notifyAll(); }
- return NORMAL;
- }
- }
- }
- return s;
- }
-
- /**
- * Tries to set SIGNAL status. Used by ForkJoinPool. Other
- * variants are directly incorporated into externalAwaitDone etc.
- *
- * @return true if successful
- */
- final boolean trySetSignal() {
- int s;
- return U.compareAndSwapInt(this, STATUS, s = status, s | SIGNAL);
- }
-
- /**
- * Blocks a non-worker-thread until completion.
- * @return status upon completion
- */
- private int externalAwaitDone() {
- boolean interrupted = false;
- int s;
- while ((s = status) >= 0) {
- if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
- synchronized (this) {
- if (status >= 0) {
- try {
- wait();
- } catch (InterruptedException ie) {
- interrupted = true;
- }
- }
- else
- notifyAll();
- }
- }
- }
- if (interrupted)
- Thread.currentThread().interrupt();
- return s;
- }
-
- /**
- * Blocks a non-worker-thread until completion or interruption.
- */
- private int externalInterruptibleAwaitDone() throws InterruptedException {
- int s;
- if (Thread.interrupted())
- throw new InterruptedException();
- while ((s = status) >= 0) {
- if (U.compareAndSwapInt(this, STATUS, s, s | SIGNAL)) {
- synchronized (this) {
- if (status >= 0)
- wait();
- else
- notifyAll();
- }
- }
- }
- return s;
- }
-
-
- /**
- * Implementation for join, get, quietlyJoin. Directly handles
- * only cases of already-completed, external wait, and
- * unfork+exec. Others are relayed to ForkJoinPool.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)) {
- if (!(w = (wt = (ForkJoinWorkerThread)t).workQueue).
- tryUnpush(this) || (s = doExec()) >= 0)
- s = wt.pool.awaitJoin(w, this);
- }
- else
- s = externalAwaitDone();
- }
- return s;
- }
-
- /**
- * Implementation for invoke, quietlyInvoke.
- *
- * @return status upon completion
- */
- private int doInvoke() {
- int s; Thread t; ForkJoinWorkerThread wt;
- if ((s = doExec()) >= 0) {
- if ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)
- s = (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue,
- this);
- else
- s = externalAwaitDone();
- }
- return s;
- }
-
- // Exception table support
-
- /**
- * 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 static final ExceptionNode[] exceptionTable;
- private static final ReentrantLock exceptionTableLock;
- private static final ReferenceQueue