diff --git a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk7backported/ThreadLocalRandom.java b/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk7backported/ThreadLocalRandom.java
deleted file mode 100644
index f08a773b013d..000000000000
--- a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk7backported/ThreadLocalRandom.java
+++ /dev/null
@@ -1,197 +0,0 @@
-package org.infinispan.commons.util.concurrent.jdk7backported;
-
-/*
- * 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/
- */
-
-import java.util.Random;
-
-/**
- * A random number generator isolated to the current thread. Like the
- * global {@link java.util.Random} generator used by the {@link
- * java.lang.Math} class, a {@code ThreadLocalRandom} is initialized
- * with an internally generated seed that may not otherwise be
- * modified. When applicable, use of {@code ThreadLocalRandom} rather
- * than shared {@code Random} objects in concurrent programs will
- * typically encounter much less overhead and contention. Use of
- * {@code ThreadLocalRandom} is particularly appropriate when multiple
- * tasks (for example, each a {@link ForkJoinTask}) use random numbers
- * in parallel in thread pools.
- *
- *
Usages of this class should typically be of the form:
- * {@code ThreadLocalRandom.current().nextX(...)} (where
- * {@code X} is {@code Int}, {@code Long}, etc).
- * When all usages are of this form, it is never possible to
- * accidently share a {@code ThreadLocalRandom} across multiple threads.
- *
- *
This class also provides additional commonly used bounded random
- * generation methods.
- *
- * @since 1.7
- * @author Doug Lea
- */
-public class ThreadLocalRandom extends Random {
- // same constants as Random, but must be redeclared because private
- private static final long multiplier = 0x5DEECE66DL;
- private static final long addend = 0xBL;
- private static final long mask = (1L << 48) - 1;
-
- /**
- * The random seed. We can't use super.seed.
- */
- private long rnd;
-
- /**
- * Initialization flag to permit calls to setSeed to succeed only
- * while executing the Random constructor. We can't allow others
- * since it would cause setting seed in one part of a program to
- * unintentionally impact other usages by the thread.
- */
- boolean initialized;
-
- // Padding to help avoid memory contention among seed updates in
- // different TLRs in the common case that they are located near
- // each other.
- private long pad0, pad1, pad2, pad3, pad4, pad5, pad6, pad7;
-
- /**
- * The actual ThreadLocal
- */
- private static final ThreadLocal localRandom =
- new ThreadLocal() {
- protected ThreadLocalRandom initialValue() {
- return new ThreadLocalRandom();
- }
- };
-
-
- /**
- * Constructor called only by localRandom.initialValue.
- */
- ThreadLocalRandom() {
- super();
- initialized = true;
- }
-
- /**
- * Returns the current thread's {@code ThreadLocalRandom}.
- *
- * @return the current thread's {@code ThreadLocalRandom}
- */
- public static ThreadLocalRandom current() {
- return localRandom.get();
- }
-
- /**
- * Throws {@code UnsupportedOperationException}. Setting seeds in
- * this generator is not supported.
- *
- * @throws UnsupportedOperationException always
- */
- public void setSeed(long seed) {
- if (initialized)
- throw new UnsupportedOperationException();
- rnd = (seed ^ multiplier) & mask;
- }
-
- protected int next(int bits) {
- rnd = (rnd * multiplier + addend) & mask;
- return (int) (rnd >>> (48-bits));
- }
-
- /**
- * Returns a pseudorandom, uniformly distributed value between the
- * given least value (inclusive) and bound (exclusive).
- *
- * @param least the least value returned
- * @param bound the upper bound (exclusive)
- * @throws IllegalArgumentException if least greater than or equal
- * to bound
- * @return the next value
- */
- public int nextInt(int least, int bound) {
- if (least >= bound)
- throw new IllegalArgumentException();
- return nextInt(bound - least) + least;
- }
-
- /**
- * Returns a pseudorandom, uniformly distributed value
- * between 0 (inclusive) and the specified value (exclusive).
- *
- * @param n the bound on the random number to be returned. Must be
- * positive.
- * @return the next value
- * @throws IllegalArgumentException if n is not positive
- */
- public long nextLong(long n) {
- if (n <= 0)
- throw new IllegalArgumentException("n must be positive");
- // Divide n by two until small enough for nextInt. On each
- // iteration (at most 31 of them but usually much less),
- // randomly choose both whether to include high bit in result
- // (offset) and whether to continue with the lower vs upper
- // half (which makes a difference only if odd).
- long offset = 0;
- while (n >= Integer.MAX_VALUE) {
- int bits = next(2);
- long half = n >>> 1;
- long nextn = ((bits & 2) == 0) ? half : n - half;
- if ((bits & 1) == 0)
- offset += n - nextn;
- n = nextn;
- }
- return offset + nextInt((int) n);
- }
-
- /**
- * Returns a pseudorandom, uniformly distributed value between the
- * given least value (inclusive) and bound (exclusive).
- *
- * @param least the least value returned
- * @param bound the upper bound (exclusive)
- * @return the next value
- * @throws IllegalArgumentException if least greater than or equal
- * to bound
- */
- public long nextLong(long least, long bound) {
- if (least >= bound)
- throw new IllegalArgumentException();
- return nextLong(bound - least) + least;
- }
-
- /**
- * Returns a pseudorandom, uniformly distributed {@code double} value
- * between 0 (inclusive) and the specified value (exclusive).
- *
- * @param n the bound on the random number to be returned. Must be
- * positive.
- * @return the next value
- * @throws IllegalArgumentException if n is not positive
- */
- public double nextDouble(double n) {
- if (n <= 0)
- throw new IllegalArgumentException("n must be positive");
- return nextDouble() * n;
- }
-
- /**
- * Returns a pseudorandom, uniformly distributed value between the
- * given least value (inclusive) and bound (exclusive).
- *
- * @param least the least value returned
- * @param bound the upper bound (exclusive)
- * @return the next value
- * @throws IllegalArgumentException if least greater than or equal
- * to bound
- */
- public double nextDouble(double least, double bound) {
- if (least >= bound)
- throw new IllegalArgumentException();
- return nextDouble() * (bound - least) + least;
- }
-
- private static final long serialVersionUID = -5851777807851030925L;
-}
diff --git a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/BoundedEquivalentConcurrentHashMapV8.java b/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/BoundedEquivalentConcurrentHashMapV8.java
index edd94301bf76..a33299d90263 100644
--- a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/BoundedEquivalentConcurrentHashMapV8.java
+++ b/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/BoundedEquivalentConcurrentHashMapV8.java
@@ -31,6 +31,8 @@
import java.lang.reflect.Type;
import java.util.*;
import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.CountedCompleter;
+import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.TimeUnit;
import java.util.concurrent.atomic.AtomicLong;
import java.util.concurrent.atomic.AtomicReference;
diff --git a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/CountedCompleter.java b/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/CountedCompleter.java
deleted file mode 100644
index fbd530ea35f0..000000000000
--- a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/CountedCompleter.java
+++ /dev/null
@@ -1,747 +0,0 @@
-// Revision 1.29
-
-/*
- * 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 org.infinispan.commons.util.concurrent.jdk8backported;
-
-/**
- * A {@link ForkJoinTask} with a completion action performed when
- * triggered and there are no remaining pending
- * actions. CountedCompleters are in general more robust in the
- * presence of subtask stalls and blockage than are other forms of
- * ForkJoinTasks, but are less intuitive to program. Uses of
- * CountedCompleter are similar to those of other completion based
- * components (such as {@link java.nio.channels.CompletionHandler})
- * except that multiple pending completions may be necessary
- * to trigger the {@link #onCompletion} action, not just one. Unless
- * initialized otherwise, the {@link #getPendingCount pending count}
- * starts at zero, but may be (atomically) changed using methods
- * {@link #setPendingCount}, {@link #addToPendingCount}, and {@link
- * #compareAndSetPendingCount}. Upon invocation of {@link
- * #tryComplete}, if the pending action count is nonzero, it is
- * decremented; otherwise, the completion action is performed, and if
- * this completer itself has a completer, the process is continued
- * with its completer. As is the case with related synchronization
- * components such as {@link java.util.concurrent.Phaser Phaser} and
- * {@link java.util.concurrent.Semaphore Semaphore}, these methods
- * affect only internal counts; they do not establish any further
- * internal bookkeeping. In particular, the identities of pending
- * tasks are not maintained. As illustrated below, you can create
- * subclasses that do record some or all pending tasks or their
- * results when needed. As illustrated below, utility methods
- * supporting customization of completion traversals are also
- * provided. However, because CountedCompleters provide only basic
- * synchronization mechanisms, it may be useful to create further
- * abstract subclasses that maintain linkages, fields, and additional
- * support methods appropriate for a set of related usages.
- *
- *
A concrete CountedCompleter class must define method {@link
- * #compute}, that should in most cases (as illustrated below), invoke
- * {@code tryComplete()} once before returning. The class may also
- * optionally override method {@link #onCompletion} to perform an
- * action upon normal completion, and method {@link
- * #onExceptionalCompletion} to perform an action upon any exception.
- *
- *
CountedCompleters most often do not bear results, in which case
- * they are normally declared as {@code CountedCompleter}, and
- * will always return {@code null} as a result value. In other cases,
- * you should override method {@link #getRawResult} to provide a
- * result from {@code join(), invoke()}, and related methods. In
- * general, this method should return the value of a field (or a
- * function of one or more fields) of the CountedCompleter object that
- * holds the result upon completion. Method {@link #setRawResult} by
- * default plays no role in CountedCompleters. It is possible, but
- * rarely applicable, to override this method to maintain other
- * objects or fields holding result data.
- *
- *
A CountedCompleter that does not itself have a completer (i.e.,
- * one for which {@link #getCompleter} returns {@code null}) can be
- * used as a regular ForkJoinTask with this added functionality.
- * However, any completer that in turn has another completer serves
- * only as an internal helper for other computations, so its own task
- * status (as reported in methods such as {@link ForkJoinTask#isDone})
- * is arbitrary; this status changes only upon explicit invocations of
- * {@link #complete}, {@link ForkJoinTask#cancel}, {@link
- * ForkJoinTask#completeExceptionally} or upon exceptional completion
- * of method {@code compute}. Upon any exceptional completion, the
- * exception may be relayed to a task's completer (and its completer,
- * and so on), if one exists and it has not otherwise already
- * completed. Similarly, cancelling an internal CountedCompleter has
- * only a local effect on that completer, so is not often useful.
- *
- *
Sample Usages.
- *
- *
Parallel recursive decomposition. CountedCompleters may
- * be arranged in trees similar to those often used with {@link
- * RecursiveAction}s, although the constructions involved in setting
- * them up typically vary. Here, the completer of each task is its
- * parent in the computation tree. Even though they entail a bit more
- * bookkeeping, CountedCompleters may be better choices when applying
- * a possibly time-consuming operation (that cannot be further
- * subdivided) to each element of an array or collection; especially
- * when the operation takes a significantly different amount of time
- * to complete for some elements than others, either because of
- * intrinsic variation (for example I/O) or auxiliary effects such as
- * garbage collection. Because CountedCompleters provide their own
- * continuations, other threads need not block waiting to perform
- * them.
- *
- *
For example, here is an initial version of a class that uses
- * divide-by-two recursive decomposition to divide work into single
- * pieces (leaf tasks). Even when work is split into individual calls,
- * tree-based techniques are usually preferable to directly forking
- * leaf tasks, because they reduce inter-thread communication and
- * improve load balancing. In the recursive case, the second of each
- * pair of subtasks to finish triggers completion of its parent
- * (because no result combination is performed, the default no-op
- * implementation of method {@code onCompletion} is not overridden). A
- * static utility method sets up the base task and invokes it
- * (here, implicitly using the {@link ForkJoinPool#commonPool()}).
- *
- *
{@code
- * class MyOperation { void apply(E e) { ... } }
- *
- * class ForEach extends CountedCompleter {
- *
- * public static void forEach(E[] array, MyOperation op) {
- * new ForEach(null, array, op, 0, array.length).invoke();
- * }
- *
- * final E[] array; final MyOperation op; final int lo, hi;
- * ForEach(CountedCompleter p, E[] array, MyOperation op, int lo, int hi) {
- * super(p);
- * this.array = array; this.op = op; this.lo = lo; this.hi = hi;
- * }
- *
- * public void compute() { // version 1
- * if (hi - lo >= 2) {
- * int mid = (lo + hi) >>> 1;
- * setPendingCount(2); // must set pending count before fork
- * new ForEach(this, array, op, mid, hi).fork(); // right child
- * new ForEach(this, array, op, lo, mid).fork(); // left child
- * }
- * else if (hi > lo)
- * op.apply(array[lo]);
- * tryComplete();
- * }
- * }}
- *
- * This design can be improved by noticing that in the recursive case,
- * the task has nothing to do after forking its right task, so can
- * directly invoke its left task before returning. (This is an analog
- * of tail recursion removal.) Also, because the task returns upon
- * executing its left task (rather than falling through to invoke
- * {@code tryComplete}) the pending count is set to one:
- *
- *
{@code
- * class ForEach ...
- * public void compute() { // version 2
- * if (hi - lo >= 2) {
- * int mid = (lo + hi) >>> 1;
- * setPendingCount(1); // only one pending
- * new ForEach(this, array, op, mid, hi).fork(); // right child
- * new ForEach(this, array, op, lo, mid).compute(); // direct invoke
- * }
- * else {
- * if (hi > lo)
- * op.apply(array[lo]);
- * tryComplete();
- * }
- * }
- * }
- *
- * As a further improvement, notice that the left task need not even
- * exist. Instead of creating a new one, we can iterate using the
- * original task, and add a pending count for each fork. Additionally,
- * because no task in this tree implements an {@link #onCompletion}
- * method, {@code tryComplete()} can be replaced with {@link
- * #propagateCompletion}.
- *
- *
{@code
- * class ForEach ...
- * public void compute() { // version 3
- * int l = lo, h = hi;
- * while (h - l >= 2) {
- * int mid = (l + h) >>> 1;
- * addToPendingCount(1);
- * new ForEach(this, array, op, mid, h).fork(); // right child
- * h = mid;
- * }
- * if (h > l)
- * op.apply(array[l]);
- * propagateCompletion();
- * }
- * }
- *
- * Additional improvements of such classes might entail precomputing
- * pending counts so that they can be established in constructors,
- * specializing classes for leaf steps, subdividing by say, four,
- * instead of two per iteration, and using an adaptive threshold
- * instead of always subdividing down to single elements.
- *
- *
Searching. A tree of CountedCompleters can search for a
- * value or property in different parts of a data structure, and
- * report a result in an {@link
- * java.util.concurrent.atomic.AtomicReference AtomicReference} as
- * soon as one is found. The others can poll the result to avoid
- * unnecessary work. (You could additionally {@linkplain #cancel
- * cancel} other tasks, but it is usually simpler and more efficient
- * to just let them notice that the result is set and if so skip
- * further processing.) Illustrating again with an array using full
- * partitioning (again, in practice, leaf tasks will almost always
- * process more than one element):
- *
- *
{@code
- * class Searcher extends CountedCompleter {
- * final E[] array; final AtomicReference result; final int lo, hi;
- * Searcher(CountedCompleter p, E[] array, AtomicReference result, int lo, int hi) {
- * super(p);
- * this.array = array; this.result = result; this.lo = lo; this.hi = hi;
- * }
- * public E getRawResult() { return result.get(); }
- * public void compute() { // similar to ForEach version 3
- * int l = lo, h = hi;
- * while (result.get() == null && h >= l) {
- * if (h - l >= 2) {
- * int mid = (l + h) >>> 1;
- * addToPendingCount(1);
- * new Searcher(this, array, result, mid, h).fork();
- * h = mid;
- * }
- * else {
- * E x = array[l];
- * if (matches(x) && result.compareAndSet(null, x))
- * quietlyCompleteRoot(); // root task is now joinable
- * break;
- * }
- * }
- * tryComplete(); // normally complete whether or not found
- * }
- * boolean matches(E e) { ... } // return true if found
- *
- * public static E search(E[] array) {
- * return new Searcher(null, array, new AtomicReference(), 0, array.length).invoke();
- * }
- * }}
- *
- * In this example, as well as others in which tasks have no other
- * effects except to compareAndSet a common result, the trailing
- * unconditional invocation of {@code tryComplete} could be made
- * conditional ({@code if (result.get() == null) tryComplete();})
- * because no further bookkeeping is required to manage completions
- * once the root task completes.
- *
- *
Recording subtasks. CountedCompleter tasks that combine
- * results of multiple subtasks usually need to access these results
- * in method {@link #onCompletion}. As illustrated in the following
- * class (that performs a simplified form of map-reduce where mappings
- * and reductions are all of type {@code E}), one way to do this in
- * divide and conquer designs is to have each subtask record its
- * sibling, so that it can be accessed in method {@code onCompletion}.
- * This technique applies to reductions in which the order of
- * combining left and right results does not matter; ordered
- * reductions require explicit left/right designations. Variants of
- * other streamlinings seen in the above examples may also apply.
- *
- *
{@code
- * class MyMapper { E apply(E v) { ... } }
- * class MyReducer { E apply(E x, E y) { ... } }
- * class MapReducer extends CountedCompleter {
- * final E[] array; final MyMapper mapper;
- * final MyReducer reducer; final int lo, hi;
- * MapReducer sibling;
- * E result;
- * MapReducer(CountedCompleter p, E[] array, MyMapper mapper,
- * MyReducer reducer, int lo, int hi) {
- * super(p);
- * this.array = array; this.mapper = mapper;
- * this.reducer = reducer; this.lo = lo; this.hi = hi;
- * }
- * public void compute() {
- * if (hi - lo >= 2) {
- * int mid = (lo + hi) >>> 1;
- * MapReducer left = new MapReducer(this, array, mapper, reducer, lo, mid);
- * MapReducer right = new MapReducer(this, array, mapper, reducer, mid, hi);
- * left.sibling = right;
- * right.sibling = left;
- * setPendingCount(1); // only right is pending
- * right.fork();
- * left.compute(); // directly execute left
- * }
- * else {
- * if (hi > lo)
- * result = mapper.apply(array[lo]);
- * tryComplete();
- * }
- * }
- * public void onCompletion(CountedCompleter caller) {
- * if (caller != this) {
- * MapReducer child = (MapReducer)caller;
- * MapReducer sib = child.sibling;
- * if (sib == null || sib.result == null)
- * result = child.result;
- * else
- * result = reducer.apply(child.result, sib.result);
- * }
- * }
- * public E getRawResult() { return result; }
- *
- * public static E mapReduce(E[] array, MyMapper mapper, MyReducer reducer) {
- * return new MapReducer(null, array, mapper, reducer,
- * 0, array.length).invoke();
- * }
- * }}
- *
- * Here, method {@code onCompletion} takes a form common to many
- * completion designs that combine results. This callback-style method
- * is triggered once per task, in either of the two different contexts
- * in which the pending count is, or becomes, zero: (1) by a task
- * itself, if its pending count is zero upon invocation of {@code
- * tryComplete}, or (2) by any of its subtasks when they complete and
- * decrement the pending count to zero. The {@code caller} argument
- * distinguishes cases. Most often, when the caller is {@code this},
- * no action is necessary. Otherwise the caller argument can be used
- * (usually via a cast) to supply a value (and/or links to other
- * values) to be combined. Assuming proper use of pending counts, the
- * actions inside {@code onCompletion} occur (once) upon completion of
- * a task and its subtasks. No additional synchronization is required
- * within this method to ensure thread safety of accesses to fields of
- * this task or other completed tasks.
- *
- *
Completion Traversals. If using {@code onCompletion} to
- * process completions is inapplicable or inconvenient, you can use
- * methods {@link #firstComplete} and {@link #nextComplete} to create
- * custom traversals. For example, to define a MapReducer that only
- * splits out right-hand tasks in the form of the third ForEach
- * example, the completions must cooperatively reduce along
- * unexhausted subtask links, which can be done as follows:
- *
- *
{@code
- * class MapReducer extends CountedCompleter { // version 2
- * final E[] array; final MyMapper mapper;
- * final MyReducer reducer; final int lo, hi;
- * MapReducer forks, next; // record subtask forks in list
- * E result;
- * MapReducer(CountedCompleter p, E[] array, MyMapper mapper,
- * MyReducer reducer, int lo, int hi, MapReducer next) {
- * super(p);
- * this.array = array; this.mapper = mapper;
- * this.reducer = reducer; this.lo = lo; this.hi = hi;
- * this.next = next;
- * }
- * public void compute() {
- * int l = lo, h = hi;
- * while (h - l >= 2) {
- * int mid = (l + h) >>> 1;
- * addToPendingCount(1);
- * (forks = new MapReducer(this, array, mapper, reducer, mid, h, forks)).fork;
- * h = mid;
- * }
- * if (h > l)
- * result = mapper.apply(array[l]);
- * // process completions by reducing along and advancing subtask links
- * for (CountedCompleter c = firstComplete(); c != null; c = c.nextComplete()) {
- * for (MapReducer t = (MapReducer)c, s = t.forks; s != null; s = t.forks = s.next)
- * t.result = reducer.apply(t.result, s.result);
- * }
- * }
- * public E getRawResult() { return result; }
- *
- * public static E mapReduce(E[] array, MyMapper mapper, MyReducer reducer) {
- * return new MapReducer(null, array, mapper, reducer,
- * 0, array.length, null).invoke();
- * }
- * }}
- *
- *
Triggers. Some CountedCompleters are themselves never
- * forked, but instead serve as bits of plumbing in other designs;
- * including those in which the completion of one of more async tasks
- * triggers another async task. For example:
- *
- *
{@code
- * class HeaderBuilder extends CountedCompleter<...> { ... }
- * class BodyBuilder extends CountedCompleter<...> { ... }
- * class PacketSender extends CountedCompleter<...> {
- * PacketSender(...) { super(null, 1); ... } // trigger on second completion
- * public void compute() { } // never called
- * public void onCompletion(CountedCompleter caller) { sendPacket(); }
- * }
- * // sample use:
- * PacketSender p = new PacketSender();
- * new HeaderBuilder(p, ...).fork();
- * new BodyBuilder(p, ...).fork();
- * }
- *
- * @since 1.8
- * @author Doug Lea
- */
-@SuppressWarnings("restriction")
-public abstract class CountedCompleter extends ForkJoinTask {
- private static final long serialVersionUID = 5232453752276485070L;
-
- /** This task's completer, or null if none */
- final CountedCompleter completer;
- /** The number of pending tasks until completion */
- volatile int pending;
-
- /**
- * Creates a new CountedCompleter with the given completer
- * and initial pending count.
- *
- * @param completer this task's completer, or {@code null} if none
- * @param initialPendingCount the initial pending count
- */
- protected CountedCompleter(CountedCompleter completer,
- int initialPendingCount) {
- this.completer = completer;
- this.pending = initialPendingCount;
- }
-
- /**
- * Creates a new CountedCompleter with the given completer
- * and an initial pending count of zero.
- *
- * @param completer this task's completer, or {@code null} if none
- */
- protected CountedCompleter(CountedCompleter completer) {
- this.completer = completer;
- }
-
- /**
- * Creates a new CountedCompleter with no completer
- * and an initial pending count of zero.
- */
- protected CountedCompleter() {
- this.completer = null;
- }
-
- /**
- * The main computation performed by this task.
- */
- public abstract void compute();
-
- /**
- * Performs an action when method {@link #tryComplete} is invoked
- * and the pending count is zero, or when the unconditional
- * method {@link #complete} is invoked. By default, this method
- * does nothing. You can distinguish cases by checking the
- * identity of the given caller argument. If not equal to {@code
- * this}, then it is typically a subtask that may contain results
- * (and/or links to other results) to combine.
- *
- * @param caller the task invoking this method (which may
- * be this task itself)
- */
- public void onCompletion(CountedCompleter caller) {
- }
-
- /**
- * Performs an action when method {@link #completeExceptionally}
- * is invoked or method {@link #compute} throws an exception, and
- * this task has not otherwise already completed normally. On
- * entry to this method, this task {@link
- * ForkJoinTask#isCompletedAbnormally}. The return value of this
- * method controls further propagation: If {@code true} and this
- * task has a completer, then this completer is also completed
- * exceptionally. The default implementation of this method does
- * nothing except return {@code true}.
- *
- * @param ex the exception
- * @param caller the task invoking this method (which may
- * be this task itself)
- * @return true if this exception should be propagated to this
- * task's completer, if one exists
- */
- public boolean onExceptionalCompletion(Throwable ex, CountedCompleter caller) {
- return true;
- }
-
- /**
- * Returns the completer established in this task's constructor,
- * or {@code null} if none.
- *
- * @return the completer
- */
- public final CountedCompleter getCompleter() {
- return completer;
- }
-
- /**
- * Returns the current pending count.
- *
- * @return the current pending count
- */
- public final int getPendingCount() {
- return pending;
- }
-
- /**
- * Sets the pending count to the given value.
- *
- * @param count the count
- */
- public final void setPendingCount(int count) {
- pending = count;
- }
-
- /**
- * Adds (atomically) the given value to the pending count.
- *
- * @param delta the value to add
- */
- public final void addToPendingCount(int delta) {
- int c; // note: can replace with intrinsic in jdk8
- do {} while (!U.compareAndSwapInt(this, PENDING, c = pending, c+delta));
- }
-
- /**
- * Sets (atomically) the pending count to the given count only if
- * it currently holds the given expected value.
- *
- * @param expected the expected value
- * @param count the new value
- * @return true if successful
- */
- public final boolean compareAndSetPendingCount(int expected, int count) {
- return U.compareAndSwapInt(this, PENDING, expected, count);
- }
-
- /**
- * If the pending count is nonzero, (atomically) decrements it.
- *
- * @return the initial (undecremented) pending count holding on entry
- * to this method
- */
- public final int decrementPendingCountUnlessZero() {
- int c;
- do {} while ((c = pending) != 0 &&
- !U.compareAndSwapInt(this, PENDING, c, c - 1));
- return c;
- }
-
- /**
- * Returns the root of the current computation; i.e., this
- * task if it has no completer, else its completer's root.
- *
- * @return the root of the current computation
- */
- public final CountedCompleter getRoot() {
- CountedCompleter a = this, p;
- while ((p = a.completer) != null)
- a = p;
- return a;
- }
-
- /**
- * If the pending count is nonzero, decrements the count;
- * otherwise invokes {@link #onCompletion} and then similarly
- * tries to complete this task's completer, if one exists,
- * else marks this task as complete.
- */
- public final void tryComplete() {
- CountedCompleter a = this, s = a;
- for (int c;;) {
- if ((c = a.pending) == 0) {
- a.onCompletion(s);
- if ((a = (s = a).completer) == null) {
- s.quietlyComplete();
- return;
- }
- }
- else if (U.compareAndSwapInt(a, PENDING, c, c - 1))
- return;
- }
- }
-
- /**
- * Equivalent to {@link #tryComplete} but does not invoke {@link
- * #onCompletion} along the completion path: If the pending count
- * is nonzero, decrements the count; otherwise, similarly tries to
- * complete this task's completer, if one exists, else marks this
- * task as complete. This method may be useful in cases where
- * {@code onCompletion} should not, or need not, be invoked for
- * each completer in a computation.
- */
- public final void propagateCompletion() {
- CountedCompleter a = this, s = a;
- for (int c;;) {
- if ((c = a.pending) == 0) {
- if ((a = (s = a).completer) == null) {
- s.quietlyComplete();
- return;
- }
- }
- else if (U.compareAndSwapInt(a, PENDING, c, c - 1))
- return;
- }
- }
-
- /**
- * Regardless of pending count, invokes {@link #onCompletion},
- * marks this task as complete and further triggers {@link
- * #tryComplete} on this task's completer, if one exists. The
- * given rawResult is used as an argument to {@link #setRawResult}
- * before invoking {@link #onCompletion} or marking this task as
- * complete; its value is meaningful only for classes overriding
- * {@code setRawResult}.
- *
- *
This method may be useful when forcing completion as soon as
- * any one (versus all) of several subtask results are obtained.
- * However, in the common (and recommended) case in which {@code
- * setRawResult} is not overridden, this effect can be obtained
- * more simply using {@code quietlyCompleteRoot();}.
- *
- * @param rawResult the raw result
- */
- public void complete(T rawResult) {
- CountedCompleter p;
- setRawResult(rawResult);
- onCompletion(this);
- quietlyComplete();
- if ((p = completer) != null)
- p.tryComplete();
- }
-
-
- /**
- * If this task's pending count is zero, returns this task;
- * otherwise decrements its pending count and returns {@code
- * null}. This method is designed to be used with {@link
- * #nextComplete} in completion traversal loops.
- *
- * @return this task, if pending count was zero, else {@code null}
- */
- public final CountedCompleter firstComplete() {
- for (int c;;) {
- if ((c = pending) == 0)
- return this;
- else if (U.compareAndSwapInt(this, PENDING, c, c - 1))
- return null;
- }
- }
-
- /**
- * If this task does not have a completer, invokes {@link
- * ForkJoinTask#quietlyComplete} and returns {@code null}. Or, if
- * this task's pending count is non-zero, decrements its pending
- * count and returns {@code null}. Otherwise, returns the
- * completer. This method can be used as part of a completion
- * traversal loop for homogeneous task hierarchies:
- *
- *
{@code
- * for (CountedCompleter c = firstComplete();
- * c != null;
- * c = c.nextComplete()) {
- * // ... process c ...
- * }}
- *
- * @return the completer, or {@code null} if none
- */
- public final CountedCompleter nextComplete() {
- CountedCompleter p;
- if ((p = completer) != null)
- return p.firstComplete();
- else {
- quietlyComplete();
- return null;
- }
- }
-
- /**
- * Equivalent to {@code getRoot().quietlyComplete()}.
- */
- public final void quietlyCompleteRoot() {
- for (CountedCompleter a = this, p;;) {
- if ((p = a.completer) == null) {
- a.quietlyComplete();
- return;
- }
- a = p;
- }
- }
-
- /**
- * Supports ForkJoinTask exception propagation.
- */
- void internalPropagateException(Throwable ex) {
- CountedCompleter a = this, s = a;
- while (a.onExceptionalCompletion(ex, s) &&
- (a = (s = a).completer) != null && a.status >= 0)
- a.recordExceptionalCompletion(ex);
- }
-
- /**
- * Implements execution conventions for CountedCompleters.
- */
- protected final boolean exec() {
- compute();
- return false;
- }
-
- /**
- * Returns the result of the computation. By default
- * returns {@code null}, which is appropriate for {@code Void}
- * actions, but in other cases should be overridden, almost
- * always to return a field or function of a field that
- * holds the result upon completion.
- *
- * @return the result of the computation
- */
- public T getRawResult() { return null; }
-
- /**
- * A method that result-bearing CountedCompleters may optionally
- * use to help maintain result data. By default, does nothing.
- * Overrides are not recommended. However, if this method is
- * overridden to update existing objects or fields, then it must
- * in general be defined to be thread-safe.
- */
- protected void setRawResult(T t) { }
-
- // Unsafe mechanics
- private static final sun.misc.Unsafe U;
- private static final long PENDING;
- static {
- try {
- U = getUnsafe();
- PENDING = U.objectFieldOffset
- (CountedCompleter.class.getDeclaredField("pending"));
- } catch (Exception e) {
- throw new Error(e);
- }
- }
-
- /**
- * 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() {
- try {
- return sun.misc.Unsafe.getUnsafe();
- } catch (SecurityException tryReflectionInstead) {}
- try {
- return java.security.AccessController.doPrivileged
- (new java.security.PrivilegedExceptionAction() {
- public sun.misc.Unsafe run() throws Exception {
- Class k = sun.misc.Unsafe.class;
- for (java.lang.reflect.Field f : k.getDeclaredFields()) {
- f.setAccessible(true);
- Object x = f.get(null);
- if (k.isInstance(x))
- return k.cast(x);
- }
- throw new NoSuchFieldError("the Unsafe");
- }});
- } catch (java.security.PrivilegedActionException e) {
- throw new RuntimeException("Could not initialize intrinsics",
- e.getCause());
- }
- }
-}
diff --git a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/EquivalentConcurrentHashMapV8.java b/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/EquivalentConcurrentHashMapV8.java
index 2dea186006ff..bc21eb08e525 100644
--- a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/EquivalentConcurrentHashMapV8.java
+++ b/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/EquivalentConcurrentHashMapV8.java
@@ -17,6 +17,8 @@
import java.lang.reflect.Type;
import java.util.*;
import java.util.concurrent.ConcurrentMap;
+import java.util.concurrent.CountedCompleter;
+import java.util.concurrent.ForkJoinPool;
import java.util.concurrent.atomic.AtomicReference;
import java.util.concurrent.atomic.AtomicInteger;
import java.util.concurrent.locks.LockSupport;
diff --git a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/ForkJoinPool.java b/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/ForkJoinPool.java
deleted file mode 100644
index a31505a8c362..000000000000
--- a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/ForkJoinPool.java
+++ /dev/null
@@ -1,3429 +0,0 @@
-// Revision 1.57
-
-/*
- * 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 org.infinispan.commons.util.concurrent.jdk8backported;
-
-import java.util.ArrayList;
-import java.util.Arrays;
-import java.util.Collection;
-import java.util.Collections;
-import java.util.List;
-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;
-
-/**
- * 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 static {@link #commonPool()} is available and appropriate for
- * most applications. The common pool is used by any ForkJoinTask that
- * is not explicitly submitted to a specified pool. Using the common
- * pool normally reduces resource usage (its threads are slowly
- * reclaimed during periods of non-use, and reinstated upon subsequent
- * use).
- *
- *
For applications that require separate or custom pools, a {@code
- * ForkJoinPool} may be 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 I/O 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)
- *
- *
- *
- *
The common pool is by default constructed with default
- * parameters, but these may be controlled by setting three {@link
- * System#getProperty system properties} with prefix {@code
- * java.util.concurrent.ForkJoinPool.common}: {@code parallelism} --
- * an integer greater than zero, {@code threadFactory} -- the class
- * name of a {@link ForkJoinWorkerThreadFactory}, and {@code
- * exceptionHandler} -- the class name of a {@link
- * java.lang.Thread.UncaughtExceptionHandler
- * Thread.UncaughtExceptionHandler}. Upon any error in establishing
- * these settings, default parameters are used.
- *
- *
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 randomly 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 are
- * restricted to executing local tasks that they submitted (or in
- * the case of CountedCompleters, others with the same root task).
- * However, because most shared/external queue operations are more
- * expensive than internal, and because, at steady state, external
- * submitters will compete for CPU with workers, ForkJoinTask.join
- * and related methods disable them from repeatedly helping to
- * process tasks if all workers are active. 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 qlock), 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 "plock" is a form of sequence lock with a saturating
- * shutdown bit (similarly for per-queue "qlocks"), mainly
- * protecting updates to the workQueues array, as well as to
- * enable shutdown. When used as a lock, it is normally only very
- * briefly held, so is nearly always available after at most a
- * brief spin, but we use a monitor-based backup strategy to
- * block when needed.
- *
- * Recording WorkQueues. WorkQueues are recorded in the
- * "workQueues" array that is created upon first use 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. Worker queues are at odd indices. Shared
- * (submission) queues are at even indices, up to a maximum of 64
- * slots, to limit growth even if array needs to expand to add
- * more workers. 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. However, many other threads may notice the same task
- * and each signal to wake up a thread that might take it. So in
- * general, pools will be over-signalled. When a submission is
- * added or another worker adds a task to a queue that has fewer
- * than two tasks, they signal waiting workers (or trigger
- * creation of new ones if fewer than the given parallelism level
- * -- signalWork), and may leave a hint to the unparked worker to
- * help signal others upon wakeup). These primary signals are
- * buttressed by others (see method helpSignal) whenever other
- * threads scan for work or do not have a task to process. On
- * most platforms, signalling (unpark) overhead time is noticeably
- * long, and the time between signalling a thread and it actually
- * making progress can be very noticeably long, so it is worth
- * offloading these delays from critical paths as much as
- * possible.
- *
- * 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 a
- * given period -- a short period if there are more threads than
- * parallelism, longer as the number of threads decreases. This
- * will slowly propagate, eventually terminating all workers after
- * periods of non-use.
- *
- * Shutdown and Termination. A call to shutdownNow atomically sets
- * a plock bit and then (non-atomically) sets each worker's
- * qlock 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) 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. It 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.
- *
- * Helping actions for CountedCompleters are much simpler: Method
- * helpComplete can take and execute any task with the same root
- * as the task being waited on. However, this still entails some
- * traversal of completer chains, so is less efficient than using
- * CountedCompleters without explicit joins.
- *
- * 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.
- *
- * Common Pool
- * ===========
- *
- * The static common Pool always exists after static
- * initialization. Since it (or any other created pool) need
- * never be used, we minimize initial construction overhead and
- * footprint to the setup of about a dozen fields, with no nested
- * allocation. Most bootstrapping occurs within method
- * fullExternalPush during the first submission to the pool.
- *
- * When external threads submit to the common pool, they can
- * perform some subtask processing (see externalHelpJoin and
- * related methods). We do not need to record whether these
- * submissions are to the common pool -- if not, externalHelpJoin
- * returns quickly (at the most helping to signal some common pool
- * workers). These submitters would otherwise be blocked waiting
- * for completion, so the extra effort (with liberally sprinkled
- * task status checks) in inapplicable cases amounts to an odd
- * form of limited spin-wait before blocking in ForkJoinTask.join.
- *
- * 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 (including
- * several unnecessary-looking hoisted null checks) 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 final class DefaultForkJoinWorkerThreadFactory
- implements ForkJoinWorkerThreadFactory {
- public final ForkJoinWorkerThread newThread(ForkJoinPool pool) {
- return new ForkJoinWorkerThread(pool);
- }
- }
-
- /**
- * 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 externalPush. 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. Seeds are then
- * randomly modified upon collisions using xorshifts, which
- * requires a non-zero seed.
- */
- static final class Submitter {
- int seed;
- Submitter(int s) { seed = s; }
- }
-
- /**
- * 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 {
- private static final long serialVersionUID = -7721805057305804111L;
- 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 external/shared push, 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 lock ("qlock") is
- * forced to -1 on termination, causing all further lock attempts
- * to fail. (Note: we don't need CAS for termination state because
- * upon pool shutdown, all shared-queues will stop being used
- * anyway.) Nearly all lock bodies are set up so that exceptions
- * within lock bodies are "impossible" (modulo JVM errors that
- * would cause failure anyway.)
- *
- * 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. 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 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
-
- // Heuristic padding to ameliorate unfortunate memory placements
- volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
-
- 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 hint; // steal or signal hint (index)
- int poolIndex; // index of this queue in pool (or 0)
- final int mode; // 0: lifo, > 0: fifo, < 0: shared
- int nsteals; // number of steals
- volatile int qlock; // 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
- volatile ForkJoinTask currentJoin; // task being joined in awaitJoin
- ForkJoinTask currentSteal; // current non-local task being executed
-
- volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
- volatile Object pad18, pad19, pad1a, pad1b, pad1c, pad1d;
-
- WorkQueue(ForkJoinPool pool, ForkJoinWorkerThread owner, int mode,
- int seed) {
- this.pool = pool;
- this.owner = owner;
- this.mode = mode;
- this.seed = seed;
- // 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.getObject
- (a, (long)((m & (s - 1)) << ASHIFT) + ABASE) == null)));
- }
-
- /**
- * Pushes a task. Call only by owner in unshared queues. (The
- * shared-queue version is embedded in method externalPush.)
- *
- * @param task the task. Caller must ensure non-null.
- * @throws 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
- int j = (((m = a.length - 1) & s) << ASHIFT) + ABASE;
- U.putOrderedObject(a, j, task);
- if ((n = (top = s + 1) - base) <= 2) {
- if ((p = pool) != null)
- p.signalWork(this);
- }
- else if (n >= m)
- growArray();
- }
- }
-
- /**
- * 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.
- */
- final ForkJoinTask[] growArray() {
- ForkJoinTask[] oldA = array;
- int size = oldA != null ? oldA.length << 1 : INITIAL_QUEUE_CAPACITY;
- if (size > MAXIMUM_QUEUE_CAPACITY)
- throw new RejectedExecutionException("Queue capacity exceeded");
- 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;
- }
-
- /**
- * Takes next task, if one exists, in LIFO order. Call only
- * by owner in unshared queues.
- */
- 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 (very rare)
- }
- }
- 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.
- * (A shared version is available only via FJP.tryExternalUnpush)
- */
- 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;
- }
-
- /**
- * 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;
- }
-
- // Specialized 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) on any CAS
- * or consistency check failure so caller can retry.
- *
- * @return false if no progress can be made, else true
- */
- final boolean tryRemoveAndExec(ForkJoinTask task) {
- boolean stat = true, removed = false, empty = 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)
- stat = false;
- break;
- }
- }
- }
- if (removed)
- task.doExec();
- return stat;
- }
-
- /**
- * Polls for and executes the given task or any other task in
- * its CountedCompleter computation.
- */
- final boolean pollAndExecCC(ForkJoinTask root) {
- ForkJoinTask[] a; int b; Object o;
- outer: while ((b = base) - top < 0 && (a = array) != null) {
- long j = (((a.length - 1) & b) << ASHIFT) + ABASE;
- if ((o = U.getObject(a, j)) == null ||
- !(o instanceof CountedCompleter))
- break;
- for (CountedCompleter t = (CountedCompleter)o, r = t;;) {
- if (r == root) {
- if (base == b &&
- U.compareAndSwapObject(a, j, t, null)) {
- base = b + 1;
- t.doExec();
- return true;
- }
- else
- break; // restart
- }
- if ((r = r.completer) == null)
- break outer; // not part of root computation
- }
- }
- return false;
- }
-
- /**
- * Executes a top-level task and any local tasks remaining
- * after execution.
- */
- final void runTask(ForkJoinTask t) {
- if (t != null) {
- (currentSteal = t).doExec();
- currentSteal = null;
- ++nsteals;
- if (base - top < 0) { // process remaining local tasks
- if (mode == 0)
- popAndExecAll();
- else
- pollAndExecAll();
- }
- }
- }
-
- /**
- * Executes a non-top-level (stolen) task.
- */
- final void runSubtask(ForkJoinTask t) {
- if (t != null) {
- ForkJoinTask ps = currentSteal;
- (currentSteal = 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);
- }
-
- // Unsafe mechanics
- private static final sun.misc.Unsafe U;
- private static final long QLOCK;
- private static final int ABASE;
- private static final int ASHIFT;
- static {
- try {
- U = getUnsafe();
- Class k = WorkQueue.class;
- Class ak = ForkJoinTask[].class;
- QLOCK = U.objectFieldOffset
- (k.getDeclaredField("qlock"));
- ABASE = U.arrayBaseOffset(ak);
- int scale = U.arrayIndexScale(ak);
- if ((scale & (scale - 1)) != 0)
- throw new Error("data type scale not a power of two");
- ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
- } catch (Exception e) {
- throw new Error(e);
- }
- }
- }
-
- // 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;
-
- /**
- * Per-thread submission bookkeeping. Shared across all pools
- * to reduce ThreadLocal pollution and because random motion
- * to avoid contention in one pool is likely to hold for others.
- * Lazily initialized on first submission (but null-checked
- * in other contexts to avoid unnecessary initialization).
- */
- static final ThreadLocal submitters;
-
- /**
- * Permission required for callers of methods that may start or
- * kill threads.
- */
- private static final RuntimePermission modifyThreadPermission;
-
- /**
- * Common (static) pool. Non-null for public use unless a static
- * construction exception, but internal usages null-check on use
- * to paranoically avoid potential initialization circularities
- * as well as to simplify generated code.
- */
- static final ForkJoinPool common;
-
- /**
- * Common pool parallelism. Must equal common.parallelism.
- */
- static final int commonParallelism;
-
- /**
- * Sequence number for creating workerNamePrefix.
- */
- private static int poolNumberSequence;
-
- /**
- * Returns the next sequence number. We don't expect this to
- * ever contend, so use simple builtin sync.
- */
- private static final synchronized int nextPoolId() {
- return ++poolNumberSequence;
- }
-
- // static constants
-
- /**
- * Initial timeout value (in nanoseconds) for the thread
- * triggering quiescence to park waiting for new work. On timeout,
- * the thread will instead try to shrink the number of
- * workers. The value should be large enough to avoid overly
- * aggressive shrinkage during most transient stalls (long GCs
- * etc).
- */
- private static final long IDLE_TIMEOUT = 2000L * 1000L * 1000L; // 2sec
-
- /**
- * Timeout value when there are more threads than parallelism level
- */
- private static final long FAST_IDLE_TIMEOUT = 200L * 1000L * 1000L;
-
- /**
- * Tolerance for idle timeouts, to cope with timer undershoots
- */
- private static final long TIMEOUT_SLOP = 2000000L;
-
- /**
- * The maximum stolen->joining link depth allowed in method
- * tryHelpStealer. Must be a power of two. 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 = 64;
-
- /**
- * 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 plock is an int packed with:
- * SHUTDOWN: true if shutdown is enabled (1 bit)
- * SEQ: a sequence lock, with PL_LOCK bit set if locked (30 bits)
- * SIGNAL: set when threads may be waiting on the lock (1 bit)
- *
- * The sequence number enables simple consistency checks:
- * Staleness of read-only operations on the workQueues array can
- * be checked by comparing plock 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 EVENMASK = 0xfffe; // even short bits
- private static final int SQMASK = 0x007e; // max 64 (even) slots
- 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;
-
- // plock bits
- private static final int SHUTDOWN = 1 << 31;
- private static final int PL_LOCK = 2;
- private static final int PL_SIGNAL = 1;
- private static final int PL_SPINS = 1 << 8;
-
- // access mode for WorkQueue
- static final int LIFO_QUEUE = 0;
- static final int FIFO_QUEUE = 1;
- static final int SHARED_QUEUE = -1;
-
- // bounds for #steps in scan loop -- must be power 2 minus 1
- private static final int MIN_SCAN = 0x1ff; // cover estimation slop
- private static final int MAX_SCAN = 0x1ffff; // 4 * max workers
-
- // Instance fields
-
- /*
- * Field layout of 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.
- */
-
- // Heuristic padding to ameliorate unfortunate memory placements
- volatile long pad00, pad01, pad02, pad03, pad04, pad05, pad06;
-
- volatile long stealCount; // collects worker counts
- volatile long ctl; // main pool control
- volatile int plock; // shutdown status and seqLock
- volatile int indexSeed; // worker/submitter index seed
- final int config; // mode and parallelism level
- WorkQueue[] workQueues; // main registry
- final ForkJoinWorkerThreadFactory factory;
- final Thread.UncaughtExceptionHandler ueh; // per-worker UEH
- final String workerNamePrefix; // to create worker name string
-
- volatile Object pad10, pad11, pad12, pad13, pad14, pad15, pad16, pad17;
- volatile Object pad18, pad19, pad1a, pad1b;
-
- /**
- * Acquires the plock lock to protect worker array and related
- * updates. This method is called only if an initial CAS on plock
- * fails. This acts as a spinlock for normal cases, but falls back
- * to builtin monitor to block when (rarely) needed. This would be
- * a terrible idea for a highly contended lock, but works fine as
- * a more conservative alternative to a pure spinlock.
- */
- private int acquirePlock() {
- int spins = PL_SPINS, r = 0, ps, nps;
- for (;;) {
- if (((ps = plock) & PL_LOCK) == 0 &&
- U.compareAndSwapInt(this, PLOCK, ps, nps = ps + PL_LOCK))
- return nps;
- else if (r == 0) { // randomize spins if possible
- Thread t = Thread.currentThread(); WorkQueue w; Submitter z;
- if ((t instanceof ForkJoinWorkerThread) &&
- (w = ((ForkJoinWorkerThread)t).workQueue) != null)
- r = w.seed;
- else if ((z = submitters.get()) != null)
- r = z.seed;
- else
- r = 1;
- }
- else if (spins >= 0) {
- r ^= r << 1; r ^= r >>> 3; r ^= r << 10; // xorshift
- if (r >= 0)
- --spins;
- }
- else if (U.compareAndSwapInt(this, PLOCK, ps, ps | PL_SIGNAL)) {
- synchronized (this) {
- if ((plock & PL_SIGNAL) != 0) {
- try {
- wait();
- } catch (InterruptedException ie) {
- try {
- Thread.currentThread().interrupt();
- } catch (SecurityException ignore) {
- }
- }
- }
- else
- notifyAll();
- }
- }
- }
- }
-
- /**
- * Unlocks and signals any thread waiting for plock. Called only
- * when CAS of seq value for unlock fails.
- */
- private void releasePlock(int ps) {
- plock = ps;
- synchronized (this) { notifyAll(); }
- }
-
- /**
- * Tries to create and start one worker if fewer than target
- * parallelism level exist. Adjusts counts etc on failure.
- */
- private void tryAddWorker() {
- long c; int u;
- while ((u = (int)((c = ctl) >>> 32)) < 0 &&
- (u & SHORT_SIGN) != 0 && (int)c == 0) {
- long nc = (long)(((u + UTC_UNIT) & UTC_MASK) |
- ((u + UAC_UNIT) & UAC_MASK)) << 32;
- if (U.compareAndSwapLong(this, CTL, c, nc)) {
- ForkJoinWorkerThreadFactory fac;
- Throwable ex = null;
- ForkJoinWorkerThread wt = null;
- try {
- if ((fac = factory) != null &&
- (wt = fac.newThread(this)) != null) {
- wt.start();
- break;
- }
- } catch (Throwable e) {
- ex = e;
- }
- deregisterWorker(wt, ex);
- break;
- }
- }
- }
-
- // Registering and deregistering workers
-
- /**
- * Callback from ForkJoinWorkerThread to establish 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 wt the worker thread
- * @return the worker's queue
- */
- final WorkQueue registerWorker(ForkJoinWorkerThread wt) {
- Thread.UncaughtExceptionHandler handler; WorkQueue[] ws; int s, ps;
- wt.setDaemon(true);
- if ((handler = ueh) != null)
- wt.setUncaughtExceptionHandler(handler);
- do {} while (!U.compareAndSwapInt(this, INDEXSEED, s = indexSeed,
- s += SEED_INCREMENT) ||
- s == 0); // skip 0
- WorkQueue w = new WorkQueue(this, wt, config >>> 16, s);
- if (((ps = plock) & PL_LOCK) != 0 ||
- !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
- ps = acquirePlock();
- int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
- try {
- if ((ws = workQueues) != null) { // skip if shutting down
- int n = ws.length, m = n - 1;
- 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) & EVENMASK) + 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; // volatile write orders
- ws[r] = w;
- }
- } finally {
- if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
- releasePlock(nps);
- }
- wt.setName(workerNamePrefix.concat(Integer.toString(w.poolIndex)));
- return w;
- }
-
- /**
- * Final callback from terminating worker, as well as upon failure
- * to construct or start a worker. 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 construction failed
- * @param ex the exception causing failure, or null if none
- */
- final void deregisterWorker(ForkJoinWorkerThread wt, Throwable ex) {
- WorkQueue w = null;
- if (wt != null && (w = wt.workQueue) != null) {
- int ps;
- w.qlock = -1; // ensure set
- long ns = w.nsteals, sc; // collect steal count
- do {} while (!U.compareAndSwapLong(this, STEALCOUNT,
- sc = stealCount, sc + ns));
- if (((ps = plock) & PL_LOCK) != 0 ||
- !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
- ps = acquirePlock();
- int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
- try {
- int idx = w.poolIndex;
- WorkQueue[] ws = workQueues;
- if (ws != null && idx >= 0 && idx < ws.length && ws[idx] == w)
- ws[idx] = null;
- } finally {
- if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
- releasePlock(nps);
- }
- }
-
- 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.array != null) {
- w.cancelAll(); // cancel remaining tasks
- WorkQueue[] ws; WorkQueue v; Thread p; int u, i, e;
- while ((u = (int)((c = ctl) >>> 32)) < 0 && (e = (int)c) >= 0) {
- if (e > 0) { // activate or create replacement
- if ((ws = workQueues) == null ||
- (i = e & SMASK) >= ws.length ||
- (v = ws[i]) == null)
- break;
- long nc = (((long)(v.nextWait & E_MASK)) |
- ((long)(u + UAC_UNIT) << 32));
- if (v.eventCount != (e | INT_SIGN))
- break;
- if (U.compareAndSwapLong(this, CTL, c, nc)) {
- v.eventCount = (e + E_SEQ) & E_MASK;
- if ((p = v.parker) != null)
- U.unpark(p);
- break;
- }
- }
- else {
- if ((short)u < 0)
- tryAddWorker();
- break;
- }
- }
- }
- if (ex == null) // help clean refs on way out
- ForkJoinTask.helpExpungeStaleExceptions();
- else // rethrow
- ForkJoinTask.rethrow(ex);
- }
-
- // Submissions
-
- /**
- * Unless shutting down, adds the given task to a submission queue
- * at submitter's current queue index (modulo submission
- * range). Only the most common path is directly handled in this
- * method. All others are relayed to fullExternalPush.
- *
- * @param task the task. Caller must ensure non-null.
- */
- final void externalPush(ForkJoinTask task) {
- WorkQueue[] ws; WorkQueue q; Submitter z; int m; ForkJoinTask[] a;
- if ((z = submitters.get()) != null && plock > 0 &&
- (ws = workQueues) != null && (m = (ws.length - 1)) >= 0 &&
- (q = ws[m & z.seed & SQMASK]) != null &&
- U.compareAndSwapInt(q, QLOCK, 0, 1)) { // lock
- int b = q.base, s = q.top, n, an;
- if ((a = q.array) != null && (an = a.length) > (n = s + 1 - b)) {
- int j = (((an - 1) & s) << ASHIFT) + ABASE;
- U.putOrderedObject(a, j, task);
- q.top = s + 1; // push on to deque
- q.qlock = 0;
- if (n <= 2)
- signalWork(q);
- return;
- }
- q.qlock = 0;
- }
- fullExternalPush(task);
- }
-
- /**
- * Full version of externalPush. This method is called, among
- * other times, upon the first submission of the first task to the
- * pool, so must perform secondary initialization. It also
- * detects first submission by an external thread by looking up
- * its ThreadLocal, and creates a new shared queue if the one at
- * index if empty or contended. The plock lock body must be
- * exception-free (so no try/finally) so we optimistically
- * allocate new queues outside the lock and throw them away if
- * (very rarely) not needed.
- *
- * Secondary initialization occurs when plock is zero, to create
- * workQueue array and set plock to a valid value. This lock body
- * must also be exception-free. Because the plock seq value can
- * eventually wrap around zero, this method harmlessly fails to
- * reinitialize if workQueues exists, while still advancing plock.
- */
- private void fullExternalPush(ForkJoinTask task) {
- int r = 0; // random index seed
- for (Submitter z = submitters.get();;) {
- WorkQueue[] ws; WorkQueue q; int ps, m, k;
- if (z == null) {
- if (U.compareAndSwapInt(this, INDEXSEED, r = indexSeed,
- r += SEED_INCREMENT) && r != 0)
- submitters.set(z = new Submitter(r));
- }
- else if (r == 0) { // move to a different index
- r = z.seed;
- r ^= r << 13; // same xorshift as WorkQueues
- r ^= r >>> 17;
- z.seed = r ^ (r << 5);
- }
- else if ((ps = plock) < 0)
- throw new RejectedExecutionException();
- else if (ps == 0 || (ws = workQueues) == null ||
- (m = ws.length - 1) < 0) { // initialize workQueues
- int p = config & SMASK; // find power of two table size
- int n = (p > 1) ? p - 1 : 1; // ensure at least 2 slots
- n |= n >>> 1; n |= n >>> 2; n |= n >>> 4;
- n |= n >>> 8; n |= n >>> 16; n = (n + 1) << 1;
- WorkQueue[] nws = ((ws = workQueues) == null || ws.length == 0 ?
- new WorkQueue[n] : null);
- if (((ps = plock) & PL_LOCK) != 0 ||
- !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
- ps = acquirePlock();
- if (((ws = workQueues) == null || ws.length == 0) && nws != null)
- workQueues = nws;
- int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
- if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
- releasePlock(nps);
- }
- else if ((q = ws[k = r & m & SQMASK]) != null) {
- if (q.qlock == 0 && U.compareAndSwapInt(q, QLOCK, 0, 1)) {
- ForkJoinTask[] a = q.array;
- int s = q.top;
- boolean submitted = false;
- try { // locked version of push
- if ((a != null && a.length > s + 1 - q.base) ||
- (a = q.growArray()) != null) { // must presize
- int j = (((a.length - 1) & s) << ASHIFT) + ABASE;
- U.putOrderedObject(a, j, task);
- q.top = s + 1;
- submitted = true;
- }
- } finally {
- q.qlock = 0; // unlock
- }
- if (submitted) {
- signalWork(q);
- return;
- }
- }
- r = 0; // move on failure
- }
- else if (((ps = plock) & PL_LOCK) == 0) { // create new queue
- q = new WorkQueue(this, null, SHARED_QUEUE, r);
- if (((ps = plock) & PL_LOCK) != 0 ||
- !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
- ps = acquirePlock();
- if ((ws = workQueues) != null && k < ws.length && ws[k] == null)
- ws[k] = q;
- int nps = (ps & SHUTDOWN) | ((ps + PL_LOCK) & ~SHUTDOWN);
- if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
- releasePlock(nps);
- }
- else
- r = 0; // try elsewhere while lock held
- }
- }
-
- // 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 create or activate a worker if too few are active.
- *
- * @param q the (non-null) queue holding tasks to be signalled
- */
- final void signalWork(WorkQueue q) {
- int hint = q.poolIndex;
- long c; int e, u, i, n; WorkQueue[] ws; WorkQueue w; Thread p;
- while ((u = (int)((c = ctl) >>> 32)) < 0) {
- if ((e = (int)c) > 0) {
- if ((ws = workQueues) != null && ws.length > (i = e & SMASK) &&
- (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.hint = hint;
- w.eventCount = (e + E_SEQ) & E_MASK;
- if ((p = w.parker) != null)
- U.unpark(p);
- break;
- }
- if (q.top - q.base <= 0)
- break;
- }
- else
- break;
- }
- else {
- if ((short)u < 0)
- tryAddWorker();
- break;
- }
- }
- }
-
- // Scanning for tasks
-
- /**
- * Top-level runloop for workers, called by ForkJoinWorkerThread.run.
- */
- final void runWorker(WorkQueue w) {
- w.growArray(); // allocate queue
- do { w.runTask(scan(w)); } while (w.qlock >= 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 queues (starting at a random
- * index, and relying on registerWorker to irregularly scatter
- * them within array to avoid bias), checking each at least twice.
- * 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. Otherwise, if not
- * activated, it signals workers (that may include itself) and
- * returns so caller can retry. Also returns for true if the
- * worker array may have changed during an empty scan. 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 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 possibly shrink
- * pool.
- *
- * * If already enqueued and none of the above apply, possibly
- * park awaiting signal, else lingering to help scan and signal.
- *
- * * If a non-empty queue discovered or left as a hint,
- * help wake up other workers before return.
- *
- * @param w the worker (via its WorkQueue)
- * @return a task or null if none found
- */
- private final ForkJoinTask scan(WorkQueue w) {
- WorkQueue[] ws; int m;
- int ps = plock; // read plock before ws
- if (w != null && (ws = workQueues) != null && (m = ws.length - 1) >= 0) {
- int ec = w.eventCount; // ec is negative if inactive
- int r = w.seed; r ^= r << 13; r ^= r >>> 17; w.seed = r ^= r << 5;
- w.hint = -1; // update seed and clear hint
- int j = ((m + m + 1) | MIN_SCAN) & MAX_SCAN;
- do {
- WorkQueue q; ForkJoinTask[] a; int b;
- if ((q = ws[(r + j) & m]) != null && (b = q.base) - q.top < 0 &&
- (a = q.array) != null) { // probably nonempty
- int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
- ForkJoinTask t = (ForkJoinTask)
- U.getObjectVolatile(a, i);
- if (q.base == b && ec >= 0 && t != null &&
- U.compareAndSwapObject(a, i, t, null)) {
- if ((q.base = b + 1) - q.top < 0)
- signalWork(q);
- return t; // taken
- }
- else if ((ec < 0 || j < m) && (int)(ctl >> AC_SHIFT) <= 0) {
- w.hint = (r + j) & m; // help signal below
- break; // cannot take
- }
- }
- } while (--j >= 0);
-
- int h, e, ns; long c, sc; WorkQueue q;
- if ((ns = w.nsteals) != 0) {
- if (U.compareAndSwapLong(this, STEALCOUNT,
- sc = stealCount, sc + ns))
- w.nsteals = 0; // collect steals and rescan
- }
- else if (plock != ps) // consistency check
- ; // skip
- else if ((e = (int)(c = ctl)) < 0)
- w.qlock = -1; // pool is terminating
- else {
- if ((h = w.hint) < 0) {
- if (ec >= 0) { // try to enqueue/inactivate
- long nc = (((long)ec |
- ((c - AC_UNIT) & (AC_MASK|TC_MASK))));
- w.nextWait = e; // link and mark inactive
- w.eventCount = ec | INT_SIGN;
- if (ctl != c || !U.compareAndSwapLong(this, CTL, c, nc))
- w.eventCount = ec; // unmark on CAS failure
- else if ((int)(c >> AC_SHIFT) == 1 - (config & SMASK))
- idleAwaitWork(w, nc, c);
- }
- else if (w.eventCount < 0 && ctl == c) {
- Thread wt = Thread.currentThread();
- Thread.interrupted(); // clear status
- U.putObject(wt, PARKBLOCKER, this);
- w.parker = wt; // emulate LockSupport.park
- if (w.eventCount < 0) // recheck
- U.park(false, 0L); // block
- w.parker = null;
- U.putObject(wt, PARKBLOCKER, null);
- }
- }
- if ((h >= 0 || (h = w.hint) >= 0) &&
- (ws = workQueues) != null && h < ws.length &&
- (q = ws[h]) != null) { // signal others before retry
- WorkQueue v; Thread p; int u, i, s;
- for (int n = (config & SMASK) - 1;;) {
- int idleCount = (w.eventCount < 0) ? 0 : -1;
- if (((s = idleCount - q.base + q.top) <= n &&
- (n = s) <= 0) ||
- (u = (int)((c = ctl) >>> 32)) >= 0 ||
- (e = (int)c) <= 0 || m < (i = e & SMASK) ||
- (v = ws[i]) == null)
- break;
- long nc = (((long)(v.nextWait & E_MASK)) |
- ((long)(u + UAC_UNIT) << 32));
- if (v.eventCount != (e | INT_SIGN) ||
- !U.compareAndSwapLong(this, CTL, c, nc))
- break;
- v.hint = h;
- v.eventCount = (e + E_SEQ) & E_MASK;
- if ((p = v.parker) != null)
- U.unpark(p);
- if (--n <= 0)
- break;
- }
- }
- }
- }
- 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 a given
- * duration. 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 != null && w.eventCount < 0 &&
- !tryTerminate(false, false) && (int)prevCtl != 0 &&
- ctl == currentCtl) {
- int dc = -(short)(currentCtl >>> TC_SHIFT);
- long parkTime = dc < 0 ? FAST_IDLE_TIMEOUT: (dc + 1) * IDLE_TIMEOUT;
- long deadline = System.nanoTime() + parkTime - TIMEOUT_SLOP;
- Thread wt = Thread.currentThread();
- while (ctl == currentCtl) {
- Thread.interrupted(); // timed variant of version in scan()
- U.putObject(wt, PARKBLOCKER, this);
- w.parker = wt;
- if (ctl == currentCtl)
- U.park(false, parkTime);
- w.parker = null;
- U.putObject(wt, PARKBLOCKER, null);
- if (ctl != currentCtl)
- break;
- if (deadline - System.nanoTime() <= 0L &&
- U.compareAndSwapLong(this, CTL, currentCtl, prevCtl)) {
- w.eventCount = (w.eventCount + E_SEQ) | E_MASK;
- w.hint = -1;
- w.qlock = -1; // shrink
- break;
- }
- }
- }
- }
-
- /**
- * Scans through queues looking for work while joining a task; if
- * any present, signals. May return early if more signalling is
- * detectably unneeded.
- *
- * @param task return early if done
- * @param origin an index to start scan
- */
- private void helpSignal(ForkJoinTask task, int origin) {
- WorkQueue[] ws; WorkQueue w; Thread p; long c; int m, u, e, i, s;
- if (task != null && task.status >= 0 &&
- (u = (int)(ctl >>> 32)) < 0 && (u >> UAC_SHIFT) < 0 &&
- (ws = workQueues) != null && (m = ws.length - 1) >= 0) {
- outer: for (int k = origin, j = m; j >= 0; --j) {
- WorkQueue q = ws[k++ & m];
- for (int n = m;;) { // limit to at most m signals
- if (task.status < 0)
- break outer;
- if (q == null ||
- ((s = -q.base + q.top) <= n && (n = s) <= 0))
- break;
- if ((u = (int)((c = ctl) >>> 32)) >= 0 ||
- (e = (int)c) <= 0 || m < (i = e & SMASK) ||
- (w = ws[i]) == null)
- break outer;
- long nc = (((long)(w.nextWait & E_MASK)) |
- ((long)(u + UAC_UNIT) << 32));
- if (w.eventCount != (e | INT_SIGN))
- break outer;
- if (U.compareAndSwapLong(this, CTL, c, nc)) {
- w.eventCount = (e + E_SEQ) & E_MASK;
- if ((p = w.parker) != null)
- U.unpark(p);
- if (--n <= 0)
- 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.
- *
- * @param joiner the joining worker
- * @param task the task to join
- * @return 0 if no progress can be made, negative if task
- * known complete, else positive
- */
- private int tryHelpStealer(WorkQueue joiner, ForkJoinTask task) {
- int stat = 0, steps = 0; // bound to avoid cycles
- if (joiner != null && task != null) { // hoist null checks
- restart: for (;;) {
- ForkJoinTask subtask = task; // current target
- for (WorkQueue j = joiner, v;;) { // v is stealer of subtask
- WorkQueue[] ws; int m, s, h;
- if ((s = task.status) < 0) {
- stat = s;
- break restart;
- }
- if ((ws = workQueues) == null || (m = ws.length - 1) <= 0)
- break restart; // shutting down
- if ((v = ws[h = (j.hint | 1) & m]) == null ||
- v.currentSteal != subtask) {
- for (int origin = h;;) { // find stealer
- if (((h = (h + 2) & m) & 15) == 1 &&
- (subtask.status < 0 || j.currentJoin != subtask))
- continue restart; // occasional staleness check
- if ((v = ws[h]) != null &&
- v.currentSteal == subtask) {
- j.hint = h; // save hint
- break;
- }
- if (h == origin)
- break restart; // cannot find stealer
- }
- }
- for (;;) { // help stealer or descend to its stealer
- ForkJoinTask[] a; int b;
- if (subtask.status < 0) // surround probes with
- continue restart; // consistency checks
- if ((b = v.base) - v.top < 0 && (a = v.array) != null) {
- int i = (((a.length - 1) & b) << ASHIFT) + ABASE;
- ForkJoinTask t =
- (ForkJoinTask)U.getObjectVolatile(a, i);
- if (subtask.status < 0 || j.currentJoin != subtask ||
- v.currentSteal != subtask)
- continue restart; // stale
- stat = 1; // apparent progress
- if (t != null && v.base == b &&
- U.compareAndSwapObject(a, i, t, null)) {
- v.base = b + 1; // help stealer
- joiner.runSubtask(t);
- }
- else if (v.base == b && ++steps == MAX_HELP)
- break restart; // v apparently stalled
- }
- else { // empty -- try to descend
- ForkJoinTask next = v.currentJoin;
- if (subtask.status < 0 || j.currentJoin != subtask ||
- v.currentSteal != subtask)
- continue restart; // stale
- else if (next == null || ++steps == MAX_HELP)
- break restart; // dead-end or maybe cyclic
- else {
- subtask = next;
- j = v;
- break;
- }
- }
- }
- }
- }
- }
- return stat;
- }
-
- /**
- * Analog of tryHelpStealer for CountedCompleters. Tries to steal
- * and run tasks within the target's computation.
- *
- * @param task the task to join
- * @param mode if shared, exit upon completing any task
- * if all workers are active
- */
- private int helpComplete(ForkJoinTask task, int mode) {
- WorkQueue[] ws; WorkQueue q; int m, n, s, u;
- if (task != null && (ws = workQueues) != null &&
- (m = ws.length - 1) >= 0) {
- for (int j = 1, origin = j;;) {
- if ((s = task.status) < 0)
- return s;
- if ((q = ws[j & m]) != null && q.pollAndExecCC(task)) {
- origin = j;
- if (mode == SHARED_QUEUE &&
- ((u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0))
- break;
- }
- else if ((j = (j + 2) & m) == origin)
- break;
- }
- }
- return 0;
- }
-
- /**
- * 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 pool
- * may become starved.
- */
- final boolean tryCompensate() {
- int pc = config & SMASK, e, i, tc; long c;
- WorkQueue[] ws; WorkQueue w; Thread p;
- if ((ws = workQueues) != null && (e = (int)(c = ctl)) >= 0) {
- if (e != 0 && (i = e & SMASK) < ws.length &&
- (w = ws[i]) != null && w.eventCount == (e | INT_SIGN)) {
- long nc = ((long)(w.nextWait & E_MASK) |
- (c & (AC_MASK|TC_MASK)));
- if (U.compareAndSwapLong(this, CTL, c, nc)) {
- w.eventCount = (e + E_SEQ) & E_MASK;
- if ((p = w.parker) != null)
- U.unpark(p);
- return true; // replace with idle worker
- }
- }
- else if ((tc = (short)(c >>> TC_SHIFT)) >= 0 &&
- (int)(c >> AC_SHIFT) + pc > 1) {
- long nc = ((c - AC_UNIT) & AC_MASK) | (c & ~AC_MASK);
- if (U.compareAndSwapLong(this, CTL, c, nc))
- return true; // no compensation
- }
- else if (tc + pc < MAX_CAP) {
- long nc = ((c + TC_UNIT) & TC_MASK) | (c & ~TC_MASK);
- if (U.compareAndSwapLong(this, CTL, c, nc)) {
- ForkJoinWorkerThreadFactory fac;
- Throwable ex = null;
- ForkJoinWorkerThread wt = null;
- try {
- if ((fac = factory) != null &&
- (wt = fac.newThread(this)) != null) {
- wt.start();
- return true;
- }
- } catch (Throwable rex) {
- ex = rex;
- }
- deregisterWorker(wt, ex); // clean up and return false
- }
- }
- }
- 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 = 0;
- if (joiner != null && task != null && (s = task.status) >= 0) {
- ForkJoinTask prevJoin = joiner.currentJoin;
- joiner.currentJoin = task;
- do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
- joiner.tryRemoveAndExec(task)); // process local tasks
- if (s >= 0 && (s = task.status) >= 0) {
- helpSignal(task, joiner.poolIndex);
- if ((s = task.status) >= 0 &&
- (task instanceof CountedCompleter))
- s = helpComplete(task, LIFO_QUEUE);
- }
- while (s >= 0 && (s = task.status) >= 0) {
- if ((!joiner.isEmpty() || // try helping
- (s = tryHelpStealer(joiner, task)) == 0) &&
- (s = task.status) >= 0) {
- helpSignal(task, joiner.poolIndex);
- if ((s = task.status) >= 0 && tryCompensate()) {
- if (task.trySetSignal() && (s = 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));
- }
- }
- }
- joiner.currentJoin = prevJoin;
- }
- 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
- */
- final void helpJoinOnce(WorkQueue joiner, ForkJoinTask task) {
- int s;
- if (joiner != null && task != null && (s = task.status) >= 0) {
- ForkJoinTask prevJoin = joiner.currentJoin;
- joiner.currentJoin = task;
- do {} while ((s = task.status) >= 0 && !joiner.isEmpty() &&
- joiner.tryRemoveAndExec(task));
- if (s >= 0 && (s = task.status) >= 0) {
- helpSignal(task, joiner.poolIndex);
- if ((s = task.status) >= 0 &&
- (task instanceof CountedCompleter))
- s = helpComplete(task, LIFO_QUEUE);
- }
- if (s >= 0 && joiner.isEmpty()) {
- do {} while (task.status >= 0 &&
- tryHelpStealer(joiner, task) > 0);
- }
- joiner.currentJoin = prevJoin;
- }
- }
-
- /**
- * Returns a (probably) non-empty steal queue, if one is found
- * during a scan, else null. This method must be retried by
- * caller if, by the time it tries to use the queue, it is empty.
- * @param r a (random) seed for scanning
- */
- private WorkQueue findNonEmptyStealQueue(int r) {
- for (;;) {
- int ps = plock, m; WorkQueue[] ws; WorkQueue q;
- if ((ws = workQueues) != null && (m = ws.length - 1) >= 0) {
- for (int j = (m + 1) << 2; j >= 0; --j) {
- if ((q = ws[(((r + j) << 1) | 1) & m]) != null &&
- q.base - q.top < 0)
- return q;
- }
- }
- if (plock == ps)
- return null;
- }
- }
-
- /**
- * 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;;) {
- long c; WorkQueue q; ForkJoinTask t; int b;
- while ((t = w.nextLocalTask()) != null) {
- if (w.base - w.top < 0)
- signalWork(w);
- t.doExec();
- }
- if ((q = findNonEmptyStealQueue(w.nextSeed())) != null) {
- if (!active) { // re-establish active count
- 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) {
- if (q.base - q.top < 0)
- signalWork(q);
- w.runSubtask(t);
- }
- }
- else if (active) { // decrement active count without queuing
- long nc = (c = ctl) - AC_UNIT;
- if ((int)(nc >> AC_SHIFT) + (config & SMASK) == 0)
- return; // bypass decrement-then-increment
- if (U.compareAndSwapLong(this, CTL, c, nc))
- active = false;
- }
- else if ((int)((c = ctl) >> AC_SHIFT) + (config & SMASK) == 0 &&
- U.compareAndSwapLong(this, CTL, c, c + AC_UNIT))
- return;
- }
- }
-
- /**
- * 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.nextSeed())) == null)
- return null;
- if ((b = q.base) - q.top < 0 && (t = q.pollAt(b)) != null) {
- if (q.base - q.top < 0)
- signalWork(q);
- return t;
- }
- }
- }
-
- /**
- * Returns a cheap heuristic guide for task partitioning when
- * programmers, frameworks, tools, or languages have little or no
- * idea about task granularity. In essence by offering this
- * method, we ask users only about tradeoffs in overhead vs
- * expected throughput and its variance, rather than how finely to
- * partition tasks.
- *
- * In a steady state strict (tree-structured) computation, each
- * thread makes available for stealing enough tasks for other
- * threads to remain active. Inductively, if all threads play by
- * the same rules, each thread should make available only a
- * constant number of tasks.
- *
- * The minimum useful constant is just 1. But using a value of 1
- * would require immediate replenishment upon each steal to
- * maintain enough tasks, which is infeasible. Further,
- * partitionings/granularities of offered tasks should minimize
- * steal rates, which in general means that threads nearer the top
- * of computation tree should generate more than those nearer the
- * bottom. In perfect steady state, each thread is at
- * approximately the same level of computation tree. However,
- * producing extra tasks amortizes the uncertainty of progress and
- * diffusion assumptions.
- *
- * So, users will want to use values larger (but not much larger)
- * than 1 to both smooth over transient shortages and hedge
- * against uneven progress; as traded off against the cost of
- * extra task overhead. We leave the user to pick a threshold
- * value to compare with the results of this call to guide
- * decisions, but recommend values such as 3.
- *
- * When all threads are active, it is on average OK to estimate
- * surplus strictly locally. In steady-state, if one thread is
- * maintaining say 2 surplus tasks, then so are others. So we can
- * just use estimated queue length. However, this strategy alone
- * leads to serious mis-estimates in some non-steady-state
- * conditions (ramp-up, ramp-down, other stalls). We can detect
- * many of these by further considering the number of "idle"
- * threads, that are known to have zero queued tasks, so
- * compensate by a factor of (#idle/#active) threads.
- *
- * Note: The approximation of #busy workers as #active workers is
- * not very good under current signalling scheme, and should be
- * improved.
- */
- static int getSurplusQueuedTaskCount() {
- Thread t; ForkJoinWorkerThread wt; ForkJoinPool pool; WorkQueue q;
- if (((t = Thread.currentThread()) instanceof ForkJoinWorkerThread)) {
- int p = (pool = (wt = (ForkJoinWorkerThread)t).pool).config & SMASK;
- int n = (q = wt.workQueue).top - q.base;
- int a = (int)(pool.ctl >> AC_SHIFT) + p;
- return n - (a > (p >>>= 1) ? 0 :
- a > (p >>>= 1) ? 1 :
- a > (p >>>= 1) ? 2 :
- a > (p >>>= 1) ? 4 :
- 8);
- }
- return 0;
- }
-
- // 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) {
- int ps;
- if (this == common) // cannot shut down
- return false;
- if ((ps = plock) >= 0) { // enable by setting plock
- if (!enable)
- return false;
- if ((ps & PL_LOCK) != 0 ||
- !U.compareAndSwapInt(this, PLOCK, ps, ps += PL_LOCK))
- ps = acquirePlock();
- int nps = ((ps + PL_LOCK) & ~SHUTDOWN) | SHUTDOWN;
- if (!U.compareAndSwapInt(this, PLOCK, ps, nps))
- releasePlock(nps);
- }
- for (long c;;) {
- if (((c = ctl) & STOP_BIT) != 0) { // already terminating
- if ((short)(c >>> TC_SHIFT) == -(config & SMASK)) {
- synchronized (this) {
- notifyAll(); // signal when 0 workers
- }
- }
- return true;
- }
- if (!now) { // check if idle & no tasks
- WorkQueue[] ws; WorkQueue w;
- if ((int)(c >> AC_SHIFT) != -(config & SMASK))
- return false;
- if ((ws = workQueues) != null) {
- for (int i = 0; i < ws.length; ++i) {
- if ((w = ws[i]) != null) {
- if (!w.isEmpty()) { // signal unprocessed tasks
- signalWork(w);
- return false;
- }
- if ((i & 1) != 0 && w.eventCount >= 0)
- return false; // unqueued inactive worker
- }
- }
- }
- }
- if (U.compareAndSwapLong(this, CTL, c, c | STOP_BIT)) {
- for (int pass = 0; pass < 3; ++pass) {
- WorkQueue[] ws; WorkQueue w; Thread wt;
- if ((ws = workQueues) != null) {
- int n = ws.length;
- for (int i = 0; i < n; ++i) {
- if ((w = ws[i]) != null) {
- w.qlock = -1;
- if (pass > 0) {
- w.cancelAll();
- if (pass > 1 && (wt = w.owner) != null) {
- if (!wt.isInterrupted()) {
- try {
- wt.interrupt();
- } catch (Throwable ignore) {
- }
- }
- U.unpark(wt);
- }
- }
- }
- }
- // 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 && i >= 0 &&
- (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.qlock = -1;
- if ((p = w.parker) != null)
- U.unpark(p);
- }
- }
- }
- }
- }
- }
- }
-
- // external operations on common pool
-
- /**
- * Returns common pool queue for a thread that has submitted at
- * least one task.
- */
- static WorkQueue commonSubmitterQueue() {
- ForkJoinPool p; WorkQueue[] ws; int m; Submitter z;
- return ((z = submitters.get()) != null &&
- (p = common) != null &&
- (ws = p.workQueues) != null &&
- (m = ws.length - 1) >= 0) ?
- ws[m & z.seed & SQMASK] : null;
- }
-
- /**
- * Tries to pop the given task from submitter's queue in common pool.
- */
- static boolean tryExternalUnpush(ForkJoinTask t) {
- ForkJoinPool p; WorkQueue[] ws; WorkQueue q; Submitter z;
- ForkJoinTask[] a; int m, s;
- if (t != null &&
- (z = submitters.get()) != null &&
- (p = common) != null &&
- (ws = p.workQueues) != null &&
- (m = ws.length - 1) >= 0 &&
- (q = ws[m & z.seed & SQMASK]) != null &&
- (s = q.top) != q.base &&
- (a = q.array) != null) {
- long j = (((a.length - 1) & (s - 1)) << ASHIFT) + ABASE;
- if (U.getObject(a, j) == t &&
- U.compareAndSwapInt(q, QLOCK, 0, 1)) {
- if (q.array == a && q.top == s && // recheck
- U.compareAndSwapObject(a, j, t, null)) {
- q.top = s - 1;
- q.qlock = 0;
- return true;
- }
- q.qlock = 0;
- }
- }
- return false;
- }
-
- /**
- * Tries to pop and run local tasks within the same computation
- * as the given root. On failure, tries to help complete from
- * other queues via helpComplete.
- */
- private void externalHelpComplete(WorkQueue q, ForkJoinTask root) {
- ForkJoinTask[] a; int m;
- if (q != null && (a = q.array) != null && (m = (a.length - 1)) >= 0 &&
- root != null && root.status >= 0) {
- for (;;) {
- int s, u; Object o; CountedCompleter task = null;
- if ((s = q.top) - q.base > 0) {
- long j = ((m & (s - 1)) << ASHIFT) + ABASE;
- if ((o = U.getObject(a, j)) != null &&
- (o instanceof CountedCompleter)) {
- CountedCompleter t = (CountedCompleter)o, r = t;
- do {
- if (r == root) {
- if (U.compareAndSwapInt(q, QLOCK, 0, 1)) {
- if (q.array == a && q.top == s &&
- U.compareAndSwapObject(a, j, t, null)) {
- q.top = s - 1;
- task = t;
- }
- q.qlock = 0;
- }
- break;
- }
- } while ((r = r.completer) != null);
- }
- }
- if (task != null)
- task.doExec();
- if (root.status < 0 ||
- (u = (int)(ctl >>> 32)) >= 0 || (u >> UAC_SHIFT) >= 0)
- break;
- if (task == null) {
- helpSignal(root, q.poolIndex);
- if (root.status >= 0)
- helpComplete(root, SHARED_QUEUE);
- break;
- }
- }
- }
- }
-
- /**
- * Tries to help execute or signal availability of the given task
- * from submitter's queue in common pool.
- */
- static void externalHelpJoin(ForkJoinTask t) {
- // Some hard-to-avoid overlap with tryExternalUnpush
- ForkJoinPool p; WorkQueue[] ws; WorkQueue q, w; Submitter z;
- ForkJoinTask[] a; int m, s, n;
- if (t != null &&
- (z = submitters.get()) != null &&
- (p = common) != null &&
- (ws = p.workQueues) != null &&
- (m = ws.length - 1) >= 0 &&
- (q = ws[m & z.seed & SQMASK]) != null &&
- (a = q.array) != null) {
- int am = a.length - 1;
- if ((s = q.top) != q.base) {
- long j = ((am & (s - 1)) << ASHIFT) + ABASE;
- if (U.getObject(a, j) == t &&
- U.compareAndSwapInt(q, QLOCK, 0, 1)) {
- if (q.array == a && q.top == s &&
- U.compareAndSwapObject(a, j, t, null)) {
- q.top = s - 1;
- q.qlock = 0;
- t.doExec();
- }
- else
- q.qlock = 0;
- }
- }
- if (t.status >= 0) {
- if (t instanceof CountedCompleter)
- p.externalHelpComplete(q, t);
- else
- p.helpSignal(t, q.poolIndex);
- }
- }
- }
-
- // 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(Math.min(MAX_CAP, 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.factory = factory;
- this.ueh = handler;
- this.config = parallelism | (asyncMode ? (FIFO_QUEUE << 16) : 0);
- long np = (long)(-parallelism); // offset ctl counts
- this.ctl = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
- int pn = nextPoolId();
- StringBuilder sb = new StringBuilder("ForkJoinPool-");
- sb.append(Integer.toString(pn));
- sb.append("-worker-");
- this.workerNamePrefix = sb.toString();
- }
-
- /**
- * Constructor for common pool, suitable only for static initialization.
- * Basically the same as above, but uses smallest possible initial footprint.
- */
- ForkJoinPool(int parallelism, long ctl,
- ForkJoinWorkerThreadFactory factory,
- Thread.UncaughtExceptionHandler handler) {
- this.config = parallelism;
- this.ctl = ctl;
- this.factory = factory;
- this.ueh = handler;
- this.workerNamePrefix = "ForkJoinPool.commonPool-worker-";
- }
-
- /**
- * Returns the common pool instance. This pool is statically
- * constructed; its run state is unaffected by attempts to {@link
- * #shutdown} or {@link #shutdownNow}. However this pool and any
- * ongoing processing are automatically terminated upon program
- * {@link System#exit}. Any program that relies on asynchronous
- * task processing to complete before program termination should
- * invoke {@code commonPool().}{@link #awaitQuiescence}, before
- * exit.
- *
- * @return the common pool instance
- * @since 1.8
- */
- public static ForkJoinPool commonPool() {
- // assert common != null : "static init error";
- return common;
- }
-
- // 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();
- externalPush(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();
- externalPush(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);
- externalPush(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();
- externalPush(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);
- externalPush(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);
- externalPush(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);
- externalPush(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.
- ArrayList> futures = new ArrayList>(tasks.size());
-
- boolean done = false;
- try {
- for (Callable t : tasks) {
- ForkJoinTask f = new ForkJoinTask.AdaptedCallable(t);
- futures.add(f);
- externalPush(f);
- }
- for (int i = 0, size = futures.size(); i < size; i++)
- ((ForkJoinTask)futures.get(i)).quietlyJoin();
- done = true;
- return futures;
- } finally {
- if (!done)
- for (int i = 0, size = futures.size(); i < size; i++)
- futures.get(i).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 config & SMASK;
- }
-
- /**
- * Returns the targeted parallelism level of the common pool.
- *
- * @return the targeted parallelism level of the common pool
- * @since 1.8
- */
- public static int getCommonPoolParallelism() {
- return commonParallelism;
- }
-
- /**
- * 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 (config & SMASK) + (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 (config >>> 16) == FIFO_QUEUE;
- }
-
- /**
- * 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 = (config & SMASK) + (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) + (config & SMASK) == 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;
- WorkQueue[] ws; WorkQueue w;
- if ((ws = workQueues) != null) {
- for (int i = 1; i < ws.length; i += 2) {
- if ((w = ws[i]) != null)
- count += w.nsteals;
- }
- }
- 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;
- 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.nsteals;
- if (w.isApparentlyUnblocked())
- ++rc;
- }
- }
- }
- }
- int pc = (config & SMASK);
- 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 = plock < 0 ? "Shutting down" : "Running";
- return super.toString() +
- "[" + level +
- ", parallelism = " + pc +
- ", size = " + tc +
- ", active = " + ac +
- ", running = " + rc +
- ", steals = " + st +
- ", tasks = " + qt +
- ", submissions = " + qs +
- "]";
- }
-
- /**
- * Possibly initiates an orderly shutdown in which previously
- * submitted tasks are executed, but no new tasks will be
- * accepted. Invocation has no effect on execution state if this
- * is the {@link #commonPool()}, and 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);
- }
-
- /**
- * Possibly attempts to cancel and/or stop all tasks, and reject
- * all subsequently submitted tasks. Invocation has no effect on
- * execution state if this is the {@link #commonPool()}, and no
- * additional effect if already shut down. Otherwise, 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) == -(config & SMASK));
- }
-
- /**
- * 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 I/O,
- * 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) != -(config & SMASK));
- }
-
- /**
- * Returns {@code true} if this pool has been shut down.
- *
- * @return {@code true} if this pool has been shut down
- */
- public boolean isShutdown() {
- return plock < 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. Because the {@link
- * #commonPool()} never terminates until program shutdown, when
- * applied to the common pool, this method is equivalent to {@link
- * #awaitQuiescence} but always returns {@code false}.
- *
- * @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 {
- if (Thread.interrupted())
- throw new InterruptedException();
- if (this == common) {
- awaitQuiescence(timeout, unit);
- return false;
- }
- long nanos = unit.toNanos(timeout);
- if (isTerminated())
- return true;
- long startTime = System.nanoTime();
- boolean terminated = false;
- synchronized (this) {
- for (long waitTime = nanos, millis = 0L;;) {
- if (terminated = isTerminated() ||
- waitTime <= 0L ||
- (millis = unit.toMillis(waitTime)) <= 0L)
- break;
- wait(millis);
- waitTime = nanos - (System.nanoTime() - startTime);
- }
- }
- return terminated;
- }
-
- /**
- * If called by a ForkJoinTask operating in this pool, equivalent
- * in effect to {@link ForkJoinTask#helpQuiesce}. Otherwise,
- * waits and/or attempts to assist performing tasks until this
- * pool {@link #isQuiescent} or the indicated timeout elapses.
- *
- * @param timeout the maximum time to wait
- * @param unit the time unit of the timeout argument
- * @return {@code true} if quiescent; {@code false} if the
- * timeout elapsed.
- */
- public boolean awaitQuiescence(long timeout, TimeUnit unit) {
- long nanos = unit.toNanos(timeout);
- ForkJoinWorkerThread wt;
- Thread thread = Thread.currentThread();
- if ((thread instanceof ForkJoinWorkerThread) &&
- (wt = (ForkJoinWorkerThread)thread).pool == this) {
- helpQuiescePool(wt.workQueue);
- return true;
- }
- long startTime = System.nanoTime();
- WorkQueue[] ws;
- int r = 0, m;
- boolean found = true;
- while (!isQuiescent() && (ws = workQueues) != null &&
- (m = ws.length - 1) >= 0) {
- if (!found) {
- if ((System.nanoTime() - startTime) > nanos)
- return false;
- Thread.yield(); // cannot block
- }
- found = false;
- for (int j = (m + 1) << 2; j >= 0; --j) {
- ForkJoinTask t; WorkQueue q; int b;
- if ((q = ws[r++ & m]) != null && (b = q.base) - q.top < 0) {
- found = true;
- if ((t = q.pollAt(b)) != null) {
- if (q.base - q.top < 0)
- signalWork(q);
- t.doExec();
- }
- break;
- }
- }
- }
- return true;
- }
-
- /**
- * Waits and/or attempts to assist performing tasks indefinitely
- * until the {@link #commonPool()} {@link #isQuiescent}.
- */
- static void quiesceCommonPool() {
- common.awaitQuiescence(Long.MAX_VALUE, TimeUnit.NANOSECONDS);
- }
-
- /**
- * 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();
- if (t instanceof ForkJoinWorkerThread) {
- ForkJoinPool p = ((ForkJoinWorkerThread)t).pool;
- while (!blocker.isReleasable()) { // variant of helpSignal
- WorkQueue[] ws; WorkQueue q; int m, u;
- if ((ws = p.workQueues) != null && (m = ws.length - 1) >= 0) {
- for (int i = 0; i <= m; ++i) {
- if (blocker.isReleasable())
- return;
- if ((q = ws[i]) != null && q.base - q.top < 0) {
- p.signalWork(q);
- if ((u = (int)(p.ctl >>> 32)) >= 0 ||
- (u >> UAC_SHIFT) >= 0)
- break;
- }
- }
- }
- if (p.tryCompensate()) {
- try {
- do {} while (!blocker.isReleasable() &&
- !blocker.block());
- } finally {
- p.incrementActiveCount();
- }
- break;
- }
- }
- }
- else {
- do {} while (!blocker.isReleasable() &&
- !blocker.block());
- }
- }
-
- // 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;
- private static final long STEALCOUNT;
- private static final long PLOCK;
- private static final long INDEXSEED;
- private static final long QLOCK;
-
- static {
- // initialize field offsets for CAS etc
- try {
- U = getUnsafe();
- Class k = ForkJoinPool.class;
- CTL = U.objectFieldOffset
- (k.getDeclaredField("ctl"));
- STEALCOUNT = U.objectFieldOffset
- (k.getDeclaredField("stealCount"));
- PLOCK = U.objectFieldOffset
- (k.getDeclaredField("plock"));
- INDEXSEED = U.objectFieldOffset
- (k.getDeclaredField("indexSeed"));
- Class tk = Thread.class;
- PARKBLOCKER = U.objectFieldOffset
- (tk.getDeclaredField("parkBlocker"));
- Class wk = WorkQueue.class;
- QLOCK = U.objectFieldOffset
- (wk.getDeclaredField("qlock"));
- Class ak = ForkJoinTask[].class;
- ABASE = U.arrayBaseOffset(ak);
- int scale = U.arrayIndexScale(ak);
- if ((scale & (scale - 1)) != 0)
- throw new Error("data type scale not a power of two");
- ASHIFT = 31 - Integer.numberOfLeadingZeros(scale);
- } catch (Exception e) {
- throw new Error(e);
- }
-
- submitters = new ThreadLocal();
- ForkJoinWorkerThreadFactory fac = defaultForkJoinWorkerThreadFactory =
- new DefaultForkJoinWorkerThreadFactory();
- modifyThreadPermission = new RuntimePermission("modifyThread");
-
- /*
- * Establish common pool parameters. For extra caution,
- * computations to set up common pool state are here; the
- * constructor just assigns these values to fields.
- */
-
- int par = 0;
- Thread.UncaughtExceptionHandler handler = null;
- try { // TBD: limit or report ignored exceptions?
- String pp = System.getProperty
- ("java.util.concurrent.ForkJoinPool.common.parallelism");
- String hp = System.getProperty
- ("java.util.concurrent.ForkJoinPool.common.exceptionHandler");
- String fp = System.getProperty
- ("java.util.concurrent.ForkJoinPool.common.threadFactory");
- if (fp != null)
- fac = ((ForkJoinWorkerThreadFactory)ClassLoader.
- getSystemClassLoader().loadClass(fp).newInstance());
- if (hp != null)
- handler = ((Thread.UncaughtExceptionHandler)ClassLoader.
- getSystemClassLoader().loadClass(hp).newInstance());
- if (pp != null)
- par = Integer.parseInt(pp);
- } catch (Exception ignore) {
- }
-
- if (par <= 0)
- par = Runtime.getRuntime().availableProcessors();
- if (par > MAX_CAP)
- par = MAX_CAP;
- commonParallelism = par;
- long np = (long)(-par); // precompute initial ctl value
- long ct = ((np << AC_SHIFT) & AC_MASK) | ((np << TC_SHIFT) & TC_MASK);
-
- common = new ForkJoinPool(par, ct, fac, handler);
- }
-
- /**
- * 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() {
- try {
- return sun.misc.Unsafe.getUnsafe();
- } catch (SecurityException tryReflectionInstead) {}
- try {
- return java.security.AccessController.doPrivileged
- (new java.security.PrivilegedExceptionAction() {
- public sun.misc.Unsafe run() throws Exception {
- Class k = sun.misc.Unsafe.class;
- for (java.lang.reflect.Field f : k.getDeclaredFields()) {
- f.setAccessible(true);
- Object x = f.get(null);
- if (k.isInstance(x))
- return k.cast(x);
- }
- throw new NoSuchFieldError("the Unsafe");
- }});
- } catch (java.security.PrivilegedActionException e) {
- throw new RuntimeException("Could not initialize intrinsics",
- e.getCause());
- }
- }
-}
diff --git a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/ForkJoinTask.java b/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/ForkJoinTask.java
deleted file mode 100644
index 956d112bd119..000000000000
--- a/commons/src/main/java/org/infinispan/commons/util/concurrent/jdk8backported/ForkJoinTask.java
+++ /dev/null
@@ -1,1512 +0,0 @@
-// Revision 1.12
-
-/*
- * 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 org.infinispan.commons.util.concurrent.jdk8backported;
-
-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;
-
-/**
- * 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 it is
- * explicitly submitted to a {@link ForkJoinPool}, or, if not already
- * engaged in a ForkJoin computation, commenced in the {@link
- * ForkJoinPool#commonPool()} via {@link #fork}, {@link #invoke}, or
- * related methods. 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 I/O, 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 I/O. Event-style async
- * tasks that are never joined (for example, those subclassing {@link
- * CountedCompleter}) 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 most computations that do not return results,
- * {@link RecursiveTask} for those that do, and {@link
- * CountedCompleter} for those in which completed actions trigger
- * other actions. 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.
- *
- *
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 java.util.concurrent.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 tagged with a {@code short}
- * value using {@link #setForkJoinTaskTag} or {@link
- * #compareAndSetForkJoinTaskTag} and checked using {@link
- * #getForkJoinTaskTag}. The ForkJoinTask implementation does not use
- * these {@code protected} methods or tags 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.
- * (Method names for tagging 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
- */
-@SuppressWarnings("restriction")
-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.
- *
- * These control bits occupy only (some of) the upper half (16
- * bits) of status field. The lower bits are used for user-defined
- * tags.
- */
-
- /** 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 = 0x00010000; // must be >= 1 << 16
- static final int SMASK = 0x0000ffff; // short bits for tags
-
- /**
- * Marks completion and wakes up threads waiting to join this
- * task.
- *
- * @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 >>> 16) != 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);
- }
- if (completed)
- s = setCompletion(NORMAL);
- }
- return s;
- }
-
- /**
- * Tries to set SIGNAL status unless already completed. Used by
- * ForkJoinPool. Other variants are directly incorporated into
- * externalAwaitDone etc.
- *
- * @return true if successful
- */
- final boolean trySetSignal() {
- int s = status;
- return s >= 0 && U.compareAndSwapInt(this, STATUS, s, s | SIGNAL);
- }
-
- /**
- * Blocks a non-worker-thread until completion.
- * @return status upon completion
- */
- private int externalAwaitDone() {
- int s;
- ForkJoinPool.externalHelpJoin(this);
- boolean interrupted = false;
- 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();
- ForkJoinPool.externalHelpJoin(this);
- 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;
- return (s = status) < 0 ? s :
- ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
- (w = (wt = (ForkJoinWorkerThread)t).workQueue).
- tryUnpush(this) && (s = doExec()) < 0 ? s :
- wt.pool.awaitJoin(w, this) :
- externalAwaitDone();
- }
-
- /**
- * Implementation for invoke, quietlyInvoke.
- *
- * @return status upon completion
- */
- private int doInvoke() {
- int s; Thread t; ForkJoinWorkerThread wt;
- return (s = doExec()) < 0 ? s :
- ((t = Thread.currentThread()) instanceof ForkJoinWorkerThread) ?
- (wt = (ForkJoinWorkerThread)t).pool.awaitJoin(wt.workQueue, this) :
- externalAwaitDone();
- }
-
- // 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