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/* |
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* Written by Doug Lea with assistance from members of JCP JSR-166 |
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* Expert Group and released to the public domain, as explained at |
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* http://creativecommons.org/licenses/publicdomain |
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*/ |
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package jsr166y; |
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import java.util.*; |
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import java.util.concurrent.*; |
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import java.util.concurrent.locks.*; |
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import java.util.concurrent.atomic.*; |
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import sun.misc.Unsafe; |
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import java.lang.reflect.*; |
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/** |
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* Host for a group of ForkJoinWorkerThreads. A ForkJoinPool provides |
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* the entry point for tasks submitted from non-ForkJoinTasks, as well |
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* as management and monitoring operations. Normally a single |
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* ForkJoinPool is used for a large number of submitted |
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* tasks. Otherwise, use would not usually outweigh the construction |
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* and bookkeeping overhead of creating a large set of threads. |
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* |
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* <p>ForkJoinPools differ from other kinds of Executor mainly in that |
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* they provide <em>work-stealing</em>: all threads in the pool |
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* attempt to find and execute subtasks created by other active tasks |
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* (eventually blocking if none exist). This makes them efficient when |
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* most tasks spawn other subtasks (as do most ForkJoinTasks) but |
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* possibly less so otherwise. It is however fine to combine execution |
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* of some plain Runnable- or Callable- based activities with that of |
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* ForkJoinTasks. |
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* |
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* <p>A ForkJoinPool may be constructed with a given parallelism level |
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* (target pool size), which it attempts to maintain by dynamically |
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* adding, suspending, or resuming threads, even if some tasks have |
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* blocked waiting to join others. However, no such adjustments are |
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* performed in the face of blocked IO or other unmanaged |
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* synchronization. The nested ManagedBlocker interface enables |
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* extension of the kinds of synchronization accommodated. |
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* |
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* <p>The target parallelism level may also be set dynamically. You |
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* can limit the number of threads dynamically constructed using |
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* method <tt>setMaximumPoolSize</tt> and/or |
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* <tt>setMaintainParallelism</tt>. |
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* |
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* <p>In addition to execution and lifecycle control methods, this |
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* class provides status check methods (for example |
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* <tt>getStealCount</tt>) that are intended to aid in developing, |
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* tuning, and monitoring fork/join applications. Also, method |
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* <tt>toString</tt> returns indications of pool state in a convenient |
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* form for informal monitoring. |
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* |
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* <p><b>Implementation notes</b>: This implementation restricts the |
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* maximum parallelism to 32767. Attempts to create pools with greater |
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* than the maximum result in IllegalArgumentExceptions. |
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*/ |
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public class ForkJoinPool extends AbstractExecutorService |
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implements ExecutorService { |
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/* |
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* See the extended comments interspersed below for design, |
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* rationale, and walkthroughs. |
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*/ |
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/** Mask for packing and unpacking shorts */ |
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private static final int shortMask = 0xffff; |
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/** Max pool size -- must be a power of two minus 1 */ |
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private static final int MAX_THREADS = 0x7FFF; |
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/** |
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* Factory for creating new ForkJoinWorkerThreads. A |
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* ForkJoinWorkerThreadFactory must be defined and used for |
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* ForkJoinWorkerThread subclasses that extend base functionality |
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* or initialize threads with different contexts. |
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*/ |
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public static interface ForkJoinWorkerThreadFactory { |
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/** |
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* Returns a new worker thread operating in the given pool. |
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* |
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* @param pool the pool this thread works in |
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* @throws NullPointerException if pool is null; |
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*/ |
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public ForkJoinWorkerThread newThread(ForkJoinPool pool); |
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} |
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/** |
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* Default ForkJoinWorkerThreadFactory implementation, creates a |
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* new ForkJoinWorkerThread. |
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*/ |
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public static class DefaultForkJoinWorkerThreadFactory |
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implements ForkJoinWorkerThreadFactory { |
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public ForkJoinWorkerThread newThread(ForkJoinPool pool) { |
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try { |
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return new ForkJoinWorkerThread(pool); |
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} catch (OutOfMemoryError oom) { |
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return null; |
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} |
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} |
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} |
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/** |
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* The default ForkJoinWorkerThreadFactory, used unless overridden |
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* in ForkJoinPool constructors. |
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*/ |
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private static final DefaultForkJoinWorkerThreadFactory |
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defaultForkJoinWorkerThreadFactory = |
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new DefaultForkJoinWorkerThreadFactory(); |
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/** |
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* Permission required for callers of methods that may start or |
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* kill threads. |
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*/ |
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private static final RuntimePermission modifyThreadPermission = |
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new RuntimePermission("modifyThread"); |
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/** |
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* If there is a security manager, makes sure caller has |
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* permission to modify threads. |
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*/ |
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private static void checkPermission() { |
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SecurityManager security = System.getSecurityManager(); |
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if (security != null) |
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security.checkPermission(modifyThreadPermission); |
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} |
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/** |
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* Generator for assigning sequence numbers as pool names. |
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*/ |
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private static final AtomicInteger poolNumberGenerator = |
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new AtomicInteger(); |
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/** |
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* Array holding all worker threads in the pool. Array size must |
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* be a power of two. Updates and replacements are protected by |
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* workerLock, but it is always kept in a consistent enough state |
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* to be randomly accessed without locking by workers performing |
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* work-stealing. |
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*/ |
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volatile ForkJoinWorkerThread[] workers; |
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/** |
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* Lock protecting access to workers. |
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*/ |
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private final ReentrantLock workerLock; |
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/** |
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* Condition for awaitTermination. |
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*/ |
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private final Condition termination; |
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/** |
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* The uncaught exception handler used when any worker |
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* abrupty terminates |
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*/ |
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private Thread.UncaughtExceptionHandler ueh; |
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/** |
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* Creation factory for worker threads. |
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*/ |
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private final ForkJoinWorkerThreadFactory factory; |
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/** |
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* Head of stack of threads that were created to maintain |
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* parallelism when other threads blocked, but have since |
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* suspended when the parallelism level rose. |
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*/ |
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private volatile WaitQueueNode spareStack; |
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/** |
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* Sum of per-thread steal counts, updated only when threads are |
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* idle or terminating. |
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*/ |
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private final AtomicLong stealCount; |
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/** |
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* Queue for external submissions. |
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*/ |
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private final LinkedTransferQueue<ForkJoinTask<?>> submissionQueue; |
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/** |
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* Head of Treiber stack for barrier sync. See below for explanation |
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*/ |
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private volatile WaitQueueNode barrierStack; |
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/** |
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* The count for event barrier |
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*/ |
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private volatile long eventCount; |
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/** |
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* Pool number, just for assigning useful names to worker threads |
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*/ |
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private final int poolNumber; |
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/** |
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* The maximum allowed pool size |
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*/ |
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private volatile int maxPoolSize; |
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/** |
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* The desired parallelism level, updated only under workerLock. |
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*/ |
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private volatile int parallelism; |
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/** |
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* Holds number of total (i.e., created and not yet terminated) |
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* and running (i.e., not blocked on joins or other managed sync) |
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* threads, packed into one int to ensure consistent snapshot when |
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* making decisions about creating and suspending spare |
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* threads. Updated only by CAS. Note: CASes in |
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* updateRunningCount and preJoin running active count is in low |
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* word, so need to be modified if this changes |
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*/ |
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private volatile int workerCounts; |
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private static int totalCountOf(int s) { return s >>> 16; } |
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private static int runningCountOf(int s) { return s & shortMask; } |
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private static int workerCountsFor(int t, int r) { return (t << 16) + r; } |
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/** |
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* Add delta (which may be negative) to running count. This must |
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* be called before (with negative arg) and after (with positive) |
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* any managed synchronization (i.e., mainly, joins) |
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* @param delta the number to add |
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*/ |
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final void updateRunningCount(int delta) { |
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int s; |
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do;while (!casWorkerCounts(s = workerCounts, s + delta)); |
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} |
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/** |
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* Add delta (which may be negative) to both total and running |
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* count. This must be called upon creation and termination of |
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* worker threads. |
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* @param delta the number to add |
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*/ |
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private void updateWorkerCount(int delta) { |
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int d = delta + (delta << 16); // add to both lo and hi parts |
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int s; |
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do;while (!casWorkerCounts(s = workerCounts, s + d)); |
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} |
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/** |
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* Lifecycle control. High word contains runState, low word |
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* contains the number of workers that are (probably) executing |
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* tasks. This value is atomically incremented before a worker |
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* gets a task to run, and decremented when worker has no tasks |
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* and cannot find any. These two fields are bundled together to |
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* support correct termination triggering. Note: activeCount |
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* CAS'es cheat by assuming active count is in low word, so need |
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* to be modified if this changes |
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*/ |
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private volatile int runControl; |
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// RunState values. Order among values matters |
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private static final int RUNNING = 0; |
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private static final int SHUTDOWN = 1; |
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private static final int TERMINATING = 2; |
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private static final int TERMINATED = 3; |
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private static int runStateOf(int c) { return c >>> 16; } |
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private static int activeCountOf(int c) { return c & shortMask; } |
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private static int runControlFor(int r, int a) { return (r << 16) + a; } |
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/** |
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* Increment active count. Called by workers before/during |
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* executing tasks. |
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*/ |
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final void incrementActiveCount() { |
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int c; |
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do;while (!casRunControl(c = runControl, c+1)); |
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} |
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/** |
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* Decrement active count; possibly trigger termination. |
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* Called by workers when they can't find tasks. |
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*/ |
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final void decrementActiveCount() { |
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int c, nextc; |
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do;while (!casRunControl(c = runControl, nextc = c-1)); |
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if (canTerminateOnShutdown(nextc)) |
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terminateOnShutdown(); |
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} |
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/** |
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* Return true if argument represents zero active count and |
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* nonzero runstate, which is the triggering condition for |
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* terminating on shutdown. |
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*/ |
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private static boolean canTerminateOnShutdown(int c) { |
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return ((c & -c) >>> 16) != 0; // i.e. least bit is nonzero runState bit |
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} |
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/** |
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* Transition run state to at least the given state. Return true |
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* if not already at least given state. |
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*/ |
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private boolean transitionRunStateTo(int state) { |
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for (;;) { |
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int c = runControl; |
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if (runStateOf(c) >= state) |
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return false; |
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if (casRunControl(c, runControlFor(state, activeCountOf(c)))) |
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return true; |
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} |
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} |
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/** |
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* Controls whether to add spares to maintain parallelism |
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*/ |
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private volatile boolean maintainsParallelism; |
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// Constructors |
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/** |
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* Creates a ForkJoinPool with a pool size equal to the number of |
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* processors available on the system and using the default |
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* ForkJoinWorkerThreadFactory, |
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* @throws SecurityException if a security manager exists and |
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* the caller is not permitted to modify threads |
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* because it does not hold {@link |
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* java.lang.RuntimePermission}<tt>("modifyThread")</tt>, |
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*/ |
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public ForkJoinPool() { |
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this(Runtime.getRuntime().availableProcessors(), |
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defaultForkJoinWorkerThreadFactory); |
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} |
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/** |
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* Creates a ForkJoinPool with the indicated parellelism level |
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* threads, and using the default ForkJoinWorkerThreadFactory, |
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* @param parallelism the number of worker threads |
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* @throws IllegalArgumentException if parallelism less than or |
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* equal to zero |
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* @throws SecurityException if a security manager exists and |
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* the caller is not permitted to modify threads |
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* because it does not hold {@link |
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* java.lang.RuntimePermission}<tt>("modifyThread")</tt>, |
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*/ |
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public ForkJoinPool(int parallelism) { |
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this(parallelism, defaultForkJoinWorkerThreadFactory); |
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} |
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/** |
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* Creates a ForkJoinPool with a pool size equal to the number of |
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* processors available on the system and using the given |
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* ForkJoinWorkerThreadFactory, |
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* @param factory the factory for creating new threads |
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* @throws NullPointerException if factory is null |
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* @throws SecurityException if a security manager exists and |
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* the caller is not permitted to modify threads |
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* because it does not hold {@link |
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* java.lang.RuntimePermission}<tt>("modifyThread")</tt>, |
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*/ |
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public ForkJoinPool(ForkJoinWorkerThreadFactory factory) { |
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this(Runtime.getRuntime().availableProcessors(), factory); |
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} |
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/** |
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* Creates a ForkJoinPool with the indicated target number of |
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* worker threads and the given factory. |
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* |
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* @param parallelism the targeted number of worker threads |
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* @param factory the factory for creating new threads |
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* @throws IllegalArgumentException if parallelism less than or |
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* equal to zero, or greater than implementation limit. |
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* @throws NullPointerException if factory is null |
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* @throws SecurityException if a security manager exists and |
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* the caller is not permitted to modify threads |
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* because it does not hold {@link |
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* java.lang.RuntimePermission}<tt>("modifyThread")</tt>, |
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*/ |
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public ForkJoinPool(int parallelism, ForkJoinWorkerThreadFactory factory) { |
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if (parallelism <= 0 || parallelism > MAX_THREADS) |
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throw new IllegalArgumentException(); |
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if (factory == null) |
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throw new NullPointerException(); |
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checkPermission(); |
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this.factory = factory; |
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this.parallelism = parallelism; |
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this.maxPoolSize = MAX_THREADS; |
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this.maintainsParallelism = true; |
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this.poolNumber = poolNumberGenerator.incrementAndGet(); |
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this.workerLock = new ReentrantLock(); |
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this.termination = workerLock.newCondition(); |
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this.stealCount = new AtomicLong(); |
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this.submissionQueue = new LinkedTransferQueue<ForkJoinTask<?>>(); |
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createAndStartInitialWorkers(parallelism); |
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} |
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/** |
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* Create new worker using factory. |
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* @param index the index to assign worker |
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* @return new worker, or null of factory failed |
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*/ |
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private ForkJoinWorkerThread createWorker(int index) { |
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Thread.UncaughtExceptionHandler h = ueh; |
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ForkJoinWorkerThread w = factory.newThread(this); |
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if (w != null) { |
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w.poolIndex = index; |
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w.setDaemon(true); |
403 |
|
|
w.setName("ForkJoinPool-" + poolNumber + "-worker-" + index); |
404 |
|
|
if (h != null) |
405 |
|
|
w.setUncaughtExceptionHandler(h); |
406 |
|
|
} |
407 |
|
|
return w; |
408 |
|
|
} |
409 |
|
|
|
410 |
|
|
/** |
411 |
|
|
* Return a good size for worker array given pool size. |
412 |
|
|
* Currently requires size to be a power of two. |
413 |
|
|
*/ |
414 |
|
|
private static int arraySizeFor(int ps) { |
415 |
|
|
return ps <= 1? 1 : (1 << (32 - Integer.numberOfLeadingZeros(ps-1))); |
416 |
|
|
} |
417 |
|
|
|
418 |
|
|
/** |
419 |
|
|
* Create or resize array if necessary to hold newLength |
420 |
|
|
* @return the array |
421 |
|
|
*/ |
422 |
|
|
private ForkJoinWorkerThread[] ensureWorkerArrayCapacity(int newLength) { |
423 |
|
|
ForkJoinWorkerThread[] ws = workers; |
424 |
|
|
if (ws == null) |
425 |
|
|
return workers = new ForkJoinWorkerThread[arraySizeFor(newLength)]; |
426 |
|
|
else if (newLength > ws.length) |
427 |
|
|
return workers = Arrays.copyOf(ws, arraySizeFor(newLength)); |
428 |
|
|
else |
429 |
|
|
return ws; |
430 |
|
|
} |
431 |
|
|
|
432 |
|
|
/** |
433 |
|
|
* Try to shrink workers into smaller array after one or more terminate |
434 |
|
|
*/ |
435 |
|
|
private void tryShrinkWorkerArray() { |
436 |
|
|
ForkJoinWorkerThread[] ws = workers; |
437 |
|
|
int len = ws.length; |
438 |
|
|
int last = len - 1; |
439 |
|
|
while (last >= 0 && ws[last] == null) |
440 |
|
|
--last; |
441 |
|
|
int newLength = arraySizeFor(last+1); |
442 |
|
|
if (newLength < len) |
443 |
|
|
workers = Arrays.copyOf(ws, newLength); |
444 |
|
|
} |
445 |
|
|
|
446 |
|
|
/** |
447 |
|
|
* Initial worker array and worker creation and startup. (This |
448 |
|
|
* must be done under lock to avoid interference by some of the |
449 |
|
|
* newly started threads while creating others.) |
450 |
|
|
*/ |
451 |
|
|
private void createAndStartInitialWorkers(int ps) { |
452 |
|
|
final ReentrantLock lock = this.workerLock; |
453 |
|
|
lock.lock(); |
454 |
|
|
try { |
455 |
|
|
ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps); |
456 |
|
|
for (int i = 0; i < ps; ++i) { |
457 |
|
|
ForkJoinWorkerThread w = createWorker(i); |
458 |
|
|
if (w != null) { |
459 |
|
|
ws[i] = w; |
460 |
|
|
w.start(); |
461 |
|
|
updateWorkerCount(1); |
462 |
|
|
} |
463 |
|
|
} |
464 |
|
|
} finally { |
465 |
|
|
lock.unlock(); |
466 |
|
|
} |
467 |
|
|
} |
468 |
|
|
|
469 |
|
|
/** |
470 |
|
|
* Worker creation and startup for threads added via setParallelism. |
471 |
|
|
*/ |
472 |
|
|
private void createAndStartAddedWorkers() { |
473 |
|
|
resumeAllSpares(); // Allow spares to convert to nonspare |
474 |
|
|
int ps = parallelism; |
475 |
|
|
ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(ps); |
476 |
|
|
int len = ws.length; |
477 |
|
|
// Sweep through slots, to keep lowest indices most populated |
478 |
|
|
int k = 0; |
479 |
|
|
while (k < len) { |
480 |
|
|
if (ws[k] != null) { |
481 |
|
|
++k; |
482 |
|
|
continue; |
483 |
|
|
} |
484 |
|
|
int s = workerCounts; |
485 |
|
|
int tc = totalCountOf(s); |
486 |
|
|
int rc = runningCountOf(s); |
487 |
|
|
if (rc >= ps || tc >= ps) |
488 |
|
|
break; |
489 |
|
|
if (casWorkerCounts (s, workerCountsFor(tc+1, rc+1))) { |
490 |
|
|
ForkJoinWorkerThread w = createWorker(k); |
491 |
|
|
if (w != null) { |
492 |
|
|
ws[k++] = w; |
493 |
|
|
w.start(); |
494 |
|
|
} |
495 |
|
|
else { |
496 |
|
|
updateWorkerCount(-1); // back out on failed creation |
497 |
|
|
break; |
498 |
|
|
} |
499 |
|
|
} |
500 |
|
|
} |
501 |
|
|
} |
502 |
|
|
|
503 |
|
|
/** |
504 |
|
|
* Sets the handler for internal worker threads that terminate due |
505 |
|
|
* to unrecoverable errors encountered while executing tasks. |
506 |
|
|
* Unless set, the current default or ThreadGroup handler is used |
507 |
|
|
* as handler. |
508 |
|
|
* |
509 |
|
|
* @param h the new handler |
510 |
|
|
* @return the old handler, or null if none |
511 |
|
|
* @throws SecurityException if a security manager exists and |
512 |
|
|
* the caller is not permitted to modify threads |
513 |
|
|
* because it does not hold {@link |
514 |
|
|
* java.lang.RuntimePermission}<tt>("modifyThread")</tt>, |
515 |
|
|
*/ |
516 |
|
|
public Thread.UncaughtExceptionHandler |
517 |
|
|
setUncaughtExceptionHandler(Thread.UncaughtExceptionHandler h) { |
518 |
|
|
checkPermission(); |
519 |
|
|
Thread.UncaughtExceptionHandler old = null; |
520 |
|
|
final ReentrantLock lock = this.workerLock; |
521 |
|
|
lock.lock(); |
522 |
|
|
try { |
523 |
|
|
old = ueh; |
524 |
|
|
ueh = h; |
525 |
|
|
ForkJoinWorkerThread[] ws = workers; |
526 |
|
|
for (int i = 0; i < ws.length; ++i) { |
527 |
|
|
ForkJoinWorkerThread w = ws[i]; |
528 |
|
|
if (w != null) |
529 |
|
|
w.setUncaughtExceptionHandler(h); |
530 |
|
|
} |
531 |
|
|
} finally { |
532 |
|
|
lock.unlock(); |
533 |
|
|
} |
534 |
|
|
return old; |
535 |
|
|
} |
536 |
|
|
|
537 |
|
|
/** |
538 |
|
|
* Returns the handler for internal worker threads that terminate |
539 |
|
|
* due to unrecoverable errors encountered while executing tasks. |
540 |
|
|
* @return the handler, or null if none |
541 |
|
|
*/ |
542 |
|
|
public Thread.UncaughtExceptionHandler getUncaughtExceptionHandler() { |
543 |
|
|
Thread.UncaughtExceptionHandler h; |
544 |
|
|
final ReentrantLock lock = this.workerLock; |
545 |
|
|
lock.lock(); |
546 |
|
|
try { |
547 |
|
|
h = ueh; |
548 |
|
|
} finally { |
549 |
|
|
lock.unlock(); |
550 |
|
|
} |
551 |
|
|
return h; |
552 |
|
|
} |
553 |
|
|
|
554 |
|
|
// Execution methods |
555 |
|
|
|
556 |
|
|
/** |
557 |
|
|
* Common code for execute, invoke and submit |
558 |
|
|
*/ |
559 |
|
|
private <T> void doSubmit(ForkJoinTask<T> task) { |
560 |
|
|
if (isShutdown()) |
561 |
|
|
throw new RejectedExecutionException(); |
562 |
|
|
submissionQueue.offer(task); |
563 |
|
|
signalIdleWorkers(true); |
564 |
|
|
} |
565 |
|
|
|
566 |
|
|
/** |
567 |
|
|
* Performs the given task; returning its result upon completion |
568 |
|
|
* @param task the task |
569 |
|
|
* @return the task's result |
570 |
|
|
* @throws NullPointerException if task is null |
571 |
|
|
* @throws RejectedExecutionException if pool is shut down |
572 |
|
|
*/ |
573 |
|
|
public <T> T invoke(ForkJoinTask<T> task) { |
574 |
|
|
doSubmit(task); |
575 |
|
|
return task.join(); |
576 |
|
|
} |
577 |
|
|
|
578 |
|
|
/** |
579 |
|
|
* Arranges for (asynchronous) execution of the given task. |
580 |
|
|
* @param task the task |
581 |
|
|
* @throws NullPointerException if task is null |
582 |
|
|
* @throws RejectedExecutionException if pool is shut down |
583 |
|
|
*/ |
584 |
|
|
public <T> void execute(ForkJoinTask<T> task) { |
585 |
|
|
doSubmit(task); |
586 |
|
|
} |
587 |
|
|
|
588 |
|
|
// AbstractExecutorService methods |
589 |
|
|
|
590 |
|
|
public void execute(Runnable task) { |
591 |
|
|
doSubmit(new AdaptedRunnable<Void>(task, null)); |
592 |
|
|
} |
593 |
|
|
|
594 |
|
|
public <T> ForkJoinTask<T> submit(Callable<T> task) { |
595 |
|
|
ForkJoinTask<T> job = new AdaptedCallable<T>(task); |
596 |
|
|
doSubmit(job); |
597 |
|
|
return job; |
598 |
|
|
} |
599 |
|
|
|
600 |
|
|
public <T> ForkJoinTask<T> submit(Runnable task, T result) { |
601 |
|
|
ForkJoinTask<T> job = new AdaptedRunnable<T>(task, result); |
602 |
|
|
doSubmit(job); |
603 |
|
|
return job; |
604 |
|
|
} |
605 |
|
|
|
606 |
|
|
public ForkJoinTask<?> submit(Runnable task) { |
607 |
|
|
ForkJoinTask<Void> job = new AdaptedRunnable<Void>(task, null); |
608 |
|
|
doSubmit(job); |
609 |
|
|
return job; |
610 |
|
|
} |
611 |
|
|
|
612 |
|
|
protected <T> RunnableFuture<T> newTaskFor(Runnable runnable, T value) { |
613 |
|
|
return new AdaptedRunnable(runnable, value); |
614 |
|
|
} |
615 |
|
|
|
616 |
|
|
protected <T> RunnableFuture<T> newTaskFor(Callable<T> callable) { |
617 |
|
|
return new AdaptedCallable(callable); |
618 |
|
|
} |
619 |
|
|
|
620 |
|
|
/** |
621 |
|
|
* Adaptor for Runnables. This implements RunnableFuture |
622 |
|
|
* to be compliant with AbstractExecutorService constraints |
623 |
|
|
*/ |
624 |
|
|
static final class AdaptedRunnable<T> extends ForkJoinTask<T> |
625 |
|
|
implements RunnableFuture<T> { |
626 |
|
|
final Runnable runnable; |
627 |
|
|
final T resultOnCompletion; |
628 |
|
|
T result; |
629 |
|
|
AdaptedRunnable(Runnable runnable, T result) { |
630 |
|
|
if (runnable == null) throw new NullPointerException(); |
631 |
|
|
this.runnable = runnable; |
632 |
|
|
this.resultOnCompletion = result; |
633 |
|
|
} |
634 |
|
|
public T getRawResult() { return result; } |
635 |
|
|
public void setRawResult(T v) { result = v; } |
636 |
|
|
public boolean exec() { |
637 |
|
|
runnable.run(); |
638 |
|
|
result = resultOnCompletion; |
639 |
|
|
return true; |
640 |
|
|
} |
641 |
|
|
public void run() { invoke(); } |
642 |
|
|
} |
643 |
|
|
|
644 |
|
|
/** |
645 |
|
|
* Adaptor for Callables |
646 |
|
|
*/ |
647 |
|
|
static final class AdaptedCallable<T> extends ForkJoinTask<T> |
648 |
|
|
implements RunnableFuture<T> { |
649 |
|
|
final Callable<T> callable; |
650 |
|
|
T result; |
651 |
|
|
AdaptedCallable(Callable<T> callable) { |
652 |
|
|
if (callable == null) throw new NullPointerException(); |
653 |
|
|
this.callable = callable; |
654 |
|
|
} |
655 |
|
|
public T getRawResult() { return result; } |
656 |
|
|
public void setRawResult(T v) { result = v; } |
657 |
|
|
public boolean exec() { |
658 |
|
|
try { |
659 |
|
|
result = callable.call(); |
660 |
|
|
return true; |
661 |
|
|
} catch (Error err) { |
662 |
|
|
throw err; |
663 |
|
|
} catch (RuntimeException rex) { |
664 |
|
|
throw rex; |
665 |
|
|
} catch (Exception ex) { |
666 |
|
|
throw new RuntimeException(ex); |
667 |
|
|
} |
668 |
|
|
} |
669 |
|
|
public void run() { invoke(); } |
670 |
|
|
} |
671 |
|
|
|
672 |
|
|
public <T> List<Future<T>> invokeAll(Collection<? extends Callable<T>> tasks) { |
673 |
|
|
ArrayList<ForkJoinTask<T>> ts = |
674 |
|
|
new ArrayList<ForkJoinTask<T>>(tasks.size()); |
675 |
|
|
for (Callable<T> c : tasks) |
676 |
|
|
ts.add(new AdaptedCallable<T>(c)); |
677 |
|
|
invoke(new InvokeAll<T>(ts)); |
678 |
|
|
return (List<Future<T>>)(List)ts; |
679 |
|
|
} |
680 |
|
|
|
681 |
|
|
static final class InvokeAll<T> extends RecursiveAction { |
682 |
|
|
final ArrayList<ForkJoinTask<T>> tasks; |
683 |
|
|
InvokeAll(ArrayList<ForkJoinTask<T>> tasks) { this.tasks = tasks; } |
684 |
|
|
public void compute() { |
685 |
|
|
try { invokeAll(tasks); } catch(Exception ignore) {} |
686 |
|
|
} |
687 |
|
|
} |
688 |
|
|
|
689 |
|
|
// Configuration and status settings and queries |
690 |
|
|
|
691 |
|
|
/** |
692 |
|
|
* Returns the factory used for constructing new workers |
693 |
|
|
* |
694 |
|
|
* @return the factory used for constructing new workers |
695 |
|
|
*/ |
696 |
|
|
public ForkJoinWorkerThreadFactory getFactory() { |
697 |
|
|
return factory; |
698 |
|
|
} |
699 |
|
|
|
700 |
|
|
/** |
701 |
|
|
* Sets the target paralleism level of this pool. |
702 |
|
|
* @param parallelism the target parallelism |
703 |
|
|
* @throws IllegalArgumentException if parallelism less than or |
704 |
|
|
* equal to zero or greater than maximum size bounds. |
705 |
|
|
* @throws SecurityException if a security manager exists and |
706 |
|
|
* the caller is not permitted to modify threads |
707 |
|
|
* because it does not hold {@link |
708 |
|
|
* java.lang.RuntimePermission}<tt>("modifyThread")</tt>, |
709 |
|
|
*/ |
710 |
|
|
public void setParallelism(int parallelism) { |
711 |
|
|
checkPermission(); |
712 |
|
|
if (parallelism <= 0 || parallelism > maxPoolSize) |
713 |
|
|
throw new IllegalArgumentException(); |
714 |
|
|
final ReentrantLock lock = this.workerLock; |
715 |
|
|
lock.lock(); |
716 |
|
|
try { |
717 |
|
|
if (!isTerminating()) { |
718 |
|
|
int p = this.parallelism; |
719 |
|
|
this.parallelism = parallelism; |
720 |
|
|
if (parallelism > p) |
721 |
|
|
createAndStartAddedWorkers(); |
722 |
|
|
else |
723 |
|
|
trimSpares(); |
724 |
|
|
} |
725 |
|
|
} finally { |
726 |
|
|
lock.unlock(); |
727 |
|
|
} |
728 |
|
|
signalIdleWorkers(false); |
729 |
|
|
} |
730 |
|
|
|
731 |
|
|
/** |
732 |
|
|
* Returns the targeted number of worker threads in this pool. |
733 |
|
|
* This value does not necessarily reflect transient changes as |
734 |
|
|
* threads are added, removed, or abruptly terminate. |
735 |
|
|
* |
736 |
|
|
* @return the targeted number of worker threads in this pool |
737 |
|
|
*/ |
738 |
|
|
public int getParallelism() { |
739 |
|
|
return parallelism; |
740 |
|
|
} |
741 |
|
|
|
742 |
|
|
/** |
743 |
|
|
* Returns the number of worker threads that have started but not |
744 |
|
|
* yet terminated. This result returned by this method may differ |
745 |
|
|
* from <tt>getParallelism</tt> when threads are created to |
746 |
|
|
* maintain parallelism when others are cooperatively blocked. |
747 |
|
|
* |
748 |
|
|
* @return the number of worker threads |
749 |
|
|
*/ |
750 |
|
|
public int getPoolSize() { |
751 |
|
|
return totalCountOf(workerCounts); |
752 |
|
|
} |
753 |
|
|
|
754 |
|
|
/** |
755 |
|
|
* Returns the maximum number of threads allowed to exist in the |
756 |
|
|
* pool, even if there are insufficient unblocked running threads. |
757 |
|
|
* @return the maximum |
758 |
|
|
*/ |
759 |
|
|
public int getMaximumPoolSize() { |
760 |
|
|
return maxPoolSize; |
761 |
|
|
} |
762 |
|
|
|
763 |
|
|
/** |
764 |
|
|
* Sets the maximum number of threads allowed to exist in the |
765 |
|
|
* pool, even if there are insufficient unblocked running threads. |
766 |
|
|
* Setting this value has no effect on current pool size. It |
767 |
|
|
* controls construction of new threads. |
768 |
|
|
* @throws IllegalArgumentException if negative or greater then |
769 |
|
|
* internal implementation limit. |
770 |
|
|
*/ |
771 |
|
|
public void setMaximumPoolSize(int newMax) { |
772 |
|
|
if (newMax < 0 || newMax > MAX_THREADS) |
773 |
|
|
throw new IllegalArgumentException(); |
774 |
|
|
maxPoolSize = newMax; |
775 |
|
|
} |
776 |
|
|
|
777 |
|
|
|
778 |
|
|
/** |
779 |
|
|
* Returns true if this pool dynamically maintains its target |
780 |
|
|
* parallelism level. If false, new threads are added only to |
781 |
|
|
* avoid possible starvation. |
782 |
|
|
* This setting is by default true; |
783 |
|
|
* @return true if maintains parallelism |
784 |
|
|
*/ |
785 |
|
|
public boolean getMaintainsParallelism() { |
786 |
|
|
return maintainsParallelism; |
787 |
|
|
} |
788 |
|
|
|
789 |
|
|
/** |
790 |
|
|
* Sets whether this pool dynamically maintains its target |
791 |
|
|
* parallelism level. If false, new threads are added only to |
792 |
|
|
* avoid possible starvation. |
793 |
|
|
* @param enable true to maintains parallelism |
794 |
|
|
*/ |
795 |
|
|
public void setMaintainsParallelism(boolean enable) { |
796 |
|
|
maintainsParallelism = enable; |
797 |
|
|
} |
798 |
|
|
|
799 |
|
|
/** |
800 |
|
|
* Returns the approximate number of worker threads that are not |
801 |
|
|
* blocked waiting to join tasks or for other managed |
802 |
|
|
* synchronization. |
803 |
|
|
* |
804 |
|
|
* @return the number of worker threads |
805 |
|
|
*/ |
806 |
|
|
public int getRunningThreadCount() { |
807 |
|
|
return runningCountOf(workerCounts); |
808 |
|
|
} |
809 |
|
|
|
810 |
|
|
/** |
811 |
|
|
* Returns the approximate number of threads that are currently |
812 |
|
|
* stealing or executing tasks. This method may overestimate the |
813 |
|
|
* number of active threads. |
814 |
|
|
* @return the number of active threads. |
815 |
|
|
*/ |
816 |
|
|
public int getActiveThreadCount() { |
817 |
|
|
return activeCountOf(runControl); |
818 |
|
|
} |
819 |
|
|
|
820 |
|
|
/** |
821 |
|
|
* Returns the approximate number of threads that are currently |
822 |
|
|
* idle waiting for tasks. This method may underestimate the |
823 |
|
|
* number of idle threads. |
824 |
|
|
* @return the number of idle threads. |
825 |
|
|
*/ |
826 |
|
|
final int getIdleThreadCount() { |
827 |
|
|
int c = runningCountOf(workerCounts) - activeCountOf(runControl); |
828 |
|
|
return (c <= 0)? 0 : c; |
829 |
|
|
} |
830 |
|
|
|
831 |
|
|
/** |
832 |
|
|
* Returns true if all worker threads are currently idle. An idle |
833 |
|
|
* worker is one that cannot obtain a task to execute because none |
834 |
|
|
* are available to steal from other threads, and there are no |
835 |
|
|
* pending submissions to the pool. This method is conservative: |
836 |
|
|
* It might not return true immediately upon idleness of all |
837 |
|
|
* threads, but will eventually become true if threads remain |
838 |
|
|
* inactive. |
839 |
|
|
* @return true if all threads are currently idle |
840 |
|
|
*/ |
841 |
|
|
public boolean isQuiescent() { |
842 |
|
|
return activeCountOf(runControl) == 0; |
843 |
|
|
} |
844 |
|
|
|
845 |
|
|
/** |
846 |
|
|
* Returns an estimate of the total number of tasks stolen from |
847 |
|
|
* one thread's work queue by another. The reported value |
848 |
|
|
* underestimates the actual total number of steals when the pool |
849 |
|
|
* is not quiescent. This value may be useful for monitoring and |
850 |
|
|
* tuning fork/join programs: In general, steal counts should be |
851 |
|
|
* high enough to keep threads busy, but low enough to avoid |
852 |
|
|
* overhead and contention across threads. |
853 |
|
|
* @return the number of steals. |
854 |
|
|
*/ |
855 |
|
|
public long getStealCount() { |
856 |
|
|
return stealCount.get(); |
857 |
|
|
} |
858 |
|
|
|
859 |
|
|
/** |
860 |
|
|
* Accumulate steal count from a worker. Call only |
861 |
|
|
* when worker known to be idle. |
862 |
|
|
*/ |
863 |
|
|
private void updateStealCount(ForkJoinWorkerThread w) { |
864 |
|
|
int sc = w.getAndClearStealCount(); |
865 |
|
|
if (sc != 0) |
866 |
|
|
stealCount.addAndGet(sc); |
867 |
|
|
} |
868 |
|
|
|
869 |
|
|
/** |
870 |
|
|
* Returns the total number of tasks currently held in queues by |
871 |
|
|
* worker threads (but not including tasks submitted to the pool |
872 |
|
|
* that have not begun executing). This value is only an |
873 |
|
|
* approximation, obtained by iterating across all threads in the |
874 |
|
|
* pool. This method may be useful for tuning task granularities. |
875 |
|
|
* @return the number of queued tasks. |
876 |
|
|
*/ |
877 |
|
|
public long getQueuedTaskCount() { |
878 |
|
|
long count = 0; |
879 |
|
|
ForkJoinWorkerThread[] ws = workers; |
880 |
|
|
for (int i = 0; i < ws.length; ++i) { |
881 |
|
|
ForkJoinWorkerThread t = ws[i]; |
882 |
|
|
if (t != null) |
883 |
|
|
count += t.getQueueSize(); |
884 |
|
|
} |
885 |
|
|
return count; |
886 |
|
|
} |
887 |
|
|
|
888 |
|
|
/** |
889 |
|
|
* Returns the approximate number tasks submitted to this pool |
890 |
|
|
* that have not yet begun executing. This method takes time |
891 |
|
|
* proportional to the number of submissions. |
892 |
|
|
* @return the number of queued submissions. |
893 |
|
|
*/ |
894 |
|
|
public int getQueuedSubmissionCount() { |
895 |
|
|
return submissionQueue.size(); |
896 |
|
|
} |
897 |
|
|
|
898 |
|
|
/** |
899 |
|
|
* Returns true if there are any tasks submitted to this pool |
900 |
|
|
* that have not yet begun executing. |
901 |
|
|
* @return <tt>true</tt> if there are any queued submissions. |
902 |
|
|
*/ |
903 |
|
|
public boolean hasQueuedSubmissions() { |
904 |
|
|
return !submissionQueue.isEmpty(); |
905 |
|
|
} |
906 |
|
|
|
907 |
|
|
/** |
908 |
|
|
* Removes and returns the next unexecuted submission if one is |
909 |
|
|
* available. This method may be useful in extensions to this |
910 |
|
|
* class that re-assign work in systems with multiple pools. |
911 |
|
|
* @return the next submission, or null if none |
912 |
|
|
*/ |
913 |
|
|
protected ForkJoinTask<?> pollSubmission() { |
914 |
|
|
return submissionQueue.poll(); |
915 |
|
|
} |
916 |
|
|
|
917 |
|
|
/** |
918 |
|
|
* Returns a string identifying this pool, as well as its state, |
919 |
|
|
* including indications of run state, parallelism level, and |
920 |
|
|
* worker and task counts. |
921 |
|
|
* |
922 |
|
|
* @return a string identifying this pool, as well as its state |
923 |
|
|
*/ |
924 |
|
|
public String toString() { |
925 |
|
|
int ps = parallelism; |
926 |
|
|
int wc = workerCounts; |
927 |
|
|
int rc = runControl; |
928 |
|
|
long st = getStealCount(); |
929 |
|
|
long qt = getQueuedTaskCount(); |
930 |
|
|
long qs = getQueuedSubmissionCount(); |
931 |
|
|
return super.toString() + |
932 |
|
|
"[" + runStateToString(runStateOf(rc)) + |
933 |
|
|
", parallelism = " + ps + |
934 |
|
|
", size = " + totalCountOf(wc) + |
935 |
|
|
", active = " + activeCountOf(rc) + |
936 |
|
|
", running = " + runningCountOf(wc) + |
937 |
|
|
", steals = " + st + |
938 |
|
|
", tasks = " + qt + |
939 |
|
|
", submissions = " + qs + |
940 |
|
|
"]"; |
941 |
|
|
} |
942 |
|
|
|
943 |
|
|
private static String runStateToString(int rs) { |
944 |
|
|
switch(rs) { |
945 |
|
|
case RUNNING: return "Running"; |
946 |
|
|
case SHUTDOWN: return "Shutting down"; |
947 |
|
|
case TERMINATING: return "Terminating"; |
948 |
|
|
case TERMINATED: return "Terminated"; |
949 |
|
|
default: throw new Error("Unknown run state"); |
950 |
|
|
} |
951 |
|
|
} |
952 |
|
|
|
953 |
|
|
// lifecycle control |
954 |
|
|
|
955 |
|
|
/** |
956 |
|
|
* Initiates an orderly shutdown in which previously submitted |
957 |
|
|
* tasks are executed, but no new tasks will be accepted. |
958 |
|
|
* Invocation has no additional effect if already shut down. |
959 |
|
|
* Tasks that are in the process of being submitted concurrently |
960 |
|
|
* during the course of this method may or may not be rejected. |
961 |
|
|
* @throws SecurityException if a security manager exists and |
962 |
|
|
* the caller is not permitted to modify threads |
963 |
|
|
* because it does not hold {@link |
964 |
|
|
* java.lang.RuntimePermission}<tt>("modifyThread")</tt>, |
965 |
|
|
*/ |
966 |
|
|
public void shutdown() { |
967 |
|
|
checkPermission(); |
968 |
|
|
transitionRunStateTo(SHUTDOWN); |
969 |
|
|
if (canTerminateOnShutdown(runControl)) |
970 |
|
|
terminateOnShutdown(); |
971 |
|
|
} |
972 |
|
|
|
973 |
|
|
/** |
974 |
|
|
* Attempts to stop all actively executing tasks, and cancels all |
975 |
|
|
* waiting tasks. Tasks that are in the process of being |
976 |
|
|
* submitted or executed concurrently during the course of this |
977 |
|
|
* method may or may not be rejected. Unlike some other executors, |
978 |
|
|
* this method cancels rather than collects non-executed tasks, |
979 |
|
|
* so always returns an empty list. |
980 |
|
|
* @return an empty list |
981 |
|
|
* @throws SecurityException if a security manager exists and |
982 |
|
|
* the caller is not permitted to modify threads |
983 |
|
|
* because it does not hold {@link |
984 |
|
|
* java.lang.RuntimePermission}<tt>("modifyThread")</tt>, |
985 |
|
|
*/ |
986 |
|
|
public List<Runnable> shutdownNow() { |
987 |
|
|
checkPermission(); |
988 |
|
|
terminate(); |
989 |
|
|
return Collections.emptyList(); |
990 |
|
|
} |
991 |
|
|
|
992 |
|
|
/** |
993 |
|
|
* Returns <tt>true</tt> if all tasks have completed following shut down. |
994 |
|
|
* |
995 |
|
|
* @return <tt>true</tt> if all tasks have completed following shut down |
996 |
|
|
*/ |
997 |
|
|
public boolean isTerminated() { |
998 |
|
|
return runStateOf(runControl) == TERMINATED; |
999 |
|
|
} |
1000 |
|
|
|
1001 |
|
|
/** |
1002 |
|
|
* Returns <tt>true</tt> if the process of termination has |
1003 |
|
|
* commenced but possibly not yet completed. |
1004 |
|
|
* |
1005 |
|
|
* @return <tt>true</tt> if terminating |
1006 |
|
|
*/ |
1007 |
|
|
public boolean isTerminating() { |
1008 |
|
|
return runStateOf(runControl) >= TERMINATING; |
1009 |
|
|
} |
1010 |
|
|
|
1011 |
|
|
/** |
1012 |
|
|
* Returns <tt>true</tt> if this pool has been shut down. |
1013 |
|
|
* |
1014 |
|
|
* @return <tt>true</tt> if this pool has been shut down |
1015 |
|
|
*/ |
1016 |
|
|
public boolean isShutdown() { |
1017 |
|
|
return runStateOf(runControl) >= SHUTDOWN; |
1018 |
|
|
} |
1019 |
|
|
|
1020 |
|
|
/** |
1021 |
|
|
* Blocks until all tasks have completed execution after a shutdown |
1022 |
|
|
* request, or the timeout occurs, or the current thread is |
1023 |
|
|
* interrupted, whichever happens first. |
1024 |
|
|
* |
1025 |
|
|
* @param timeout the maximum time to wait |
1026 |
|
|
* @param unit the time unit of the timeout argument |
1027 |
|
|
* @return <tt>true</tt> if this executor terminated and |
1028 |
|
|
* <tt>false</tt> if the timeout elapsed before termination |
1029 |
|
|
* @throws InterruptedException if interrupted while waiting |
1030 |
|
|
*/ |
1031 |
|
|
public boolean awaitTermination(long timeout, TimeUnit unit) |
1032 |
|
|
throws InterruptedException { |
1033 |
|
|
long nanos = unit.toNanos(timeout); |
1034 |
|
|
final ReentrantLock lock = this.workerLock; |
1035 |
|
|
lock.lock(); |
1036 |
|
|
try { |
1037 |
|
|
for (;;) { |
1038 |
|
|
if (isTerminated()) |
1039 |
|
|
return true; |
1040 |
|
|
if (nanos <= 0) |
1041 |
|
|
return false; |
1042 |
|
|
nanos = termination.awaitNanos(nanos); |
1043 |
|
|
} |
1044 |
|
|
} finally { |
1045 |
|
|
lock.unlock(); |
1046 |
|
|
} |
1047 |
|
|
} |
1048 |
|
|
|
1049 |
|
|
// Shutdown and termination support |
1050 |
|
|
|
1051 |
|
|
/** |
1052 |
|
|
* Callback from terminating worker. Null out the corresponding |
1053 |
|
|
* workers slot, and if terminating, try to terminate, else try to |
1054 |
|
|
* shrink workers array. |
1055 |
|
|
* @param w the worker |
1056 |
|
|
*/ |
1057 |
|
|
final void workerTerminated(ForkJoinWorkerThread w) { |
1058 |
|
|
updateStealCount(w); |
1059 |
|
|
updateWorkerCount(-1); |
1060 |
|
|
final ReentrantLock lock = this.workerLock; |
1061 |
|
|
lock.lock(); |
1062 |
|
|
try { |
1063 |
|
|
ForkJoinWorkerThread[] ws = workers; |
1064 |
|
|
int idx = w.poolIndex; |
1065 |
|
|
if (idx >= 0 && idx < ws.length && ws[idx] == w) |
1066 |
|
|
ws[idx] = null; |
1067 |
|
|
if (totalCountOf(workerCounts) == 0) { |
1068 |
|
|
terminate(); // no-op if already terminating |
1069 |
|
|
transitionRunStateTo(TERMINATED); |
1070 |
|
|
termination.signalAll(); |
1071 |
|
|
} |
1072 |
|
|
else if (!isTerminating()) { |
1073 |
|
|
tryShrinkWorkerArray(); |
1074 |
|
|
tryResumeSpare(true); // allow replacement |
1075 |
|
|
} |
1076 |
|
|
} finally { |
1077 |
|
|
lock.unlock(); |
1078 |
|
|
} |
1079 |
|
|
signalIdleWorkers(false); |
1080 |
|
|
} |
1081 |
|
|
|
1082 |
|
|
/** |
1083 |
|
|
* Initiate termination. |
1084 |
|
|
*/ |
1085 |
|
|
private void terminate() { |
1086 |
|
|
if (transitionRunStateTo(TERMINATING)) { |
1087 |
|
|
stopAllWorkers(); |
1088 |
|
|
resumeAllSpares(); |
1089 |
|
|
signalIdleWorkers(true); |
1090 |
|
|
cancelQueuedSubmissions(); |
1091 |
|
|
cancelQueuedWorkerTasks(); |
1092 |
|
|
interruptUnterminatedWorkers(); |
1093 |
|
|
signalIdleWorkers(true); // resignal after interrupt |
1094 |
|
|
} |
1095 |
|
|
} |
1096 |
|
|
|
1097 |
|
|
/** |
1098 |
|
|
* Possibly terminate when on shutdown state |
1099 |
|
|
*/ |
1100 |
|
|
private void terminateOnShutdown() { |
1101 |
|
|
if (!hasQueuedSubmissions() && canTerminateOnShutdown(runControl)) |
1102 |
|
|
terminate(); |
1103 |
|
|
} |
1104 |
|
|
|
1105 |
|
|
/** |
1106 |
|
|
* Clear out and cancel submissions |
1107 |
|
|
*/ |
1108 |
|
|
private void cancelQueuedSubmissions() { |
1109 |
|
|
ForkJoinTask<?> task; |
1110 |
|
|
while ((task = pollSubmission()) != null) |
1111 |
|
|
task.cancel(false); |
1112 |
|
|
} |
1113 |
|
|
|
1114 |
|
|
/** |
1115 |
|
|
* Clean out worker queues. |
1116 |
|
|
*/ |
1117 |
|
|
private void cancelQueuedWorkerTasks() { |
1118 |
|
|
final ReentrantLock lock = this.workerLock; |
1119 |
|
|
lock.lock(); |
1120 |
|
|
try { |
1121 |
|
|
ForkJoinWorkerThread[] ws = workers; |
1122 |
|
|
for (int i = 0; i < ws.length; ++i) { |
1123 |
|
|
ForkJoinWorkerThread t = ws[i]; |
1124 |
|
|
if (t != null) |
1125 |
|
|
t.cancelTasks(); |
1126 |
|
|
} |
1127 |
|
|
} finally { |
1128 |
|
|
lock.unlock(); |
1129 |
|
|
} |
1130 |
|
|
} |
1131 |
|
|
|
1132 |
|
|
/** |
1133 |
|
|
* Set each worker's status to terminating. Requires lock to avoid |
1134 |
|
|
* conflicts with add/remove |
1135 |
|
|
*/ |
1136 |
|
|
private void stopAllWorkers() { |
1137 |
|
|
final ReentrantLock lock = this.workerLock; |
1138 |
|
|
lock.lock(); |
1139 |
|
|
try { |
1140 |
|
|
ForkJoinWorkerThread[] ws = workers; |
1141 |
|
|
for (int i = 0; i < ws.length; ++i) { |
1142 |
|
|
ForkJoinWorkerThread t = ws[i]; |
1143 |
|
|
if (t != null) |
1144 |
|
|
t.shutdownNow(); |
1145 |
|
|
} |
1146 |
|
|
} finally { |
1147 |
|
|
lock.unlock(); |
1148 |
|
|
} |
1149 |
|
|
} |
1150 |
|
|
|
1151 |
|
|
/** |
1152 |
|
|
* Interrupt all unterminated workers. This is not required for |
1153 |
|
|
* sake of internal control, but may help unstick user code during |
1154 |
|
|
* shutdown. |
1155 |
|
|
*/ |
1156 |
|
|
private void interruptUnterminatedWorkers() { |
1157 |
|
|
final ReentrantLock lock = this.workerLock; |
1158 |
|
|
lock.lock(); |
1159 |
|
|
try { |
1160 |
|
|
ForkJoinWorkerThread[] ws = workers; |
1161 |
|
|
for (int i = 0; i < ws.length; ++i) { |
1162 |
|
|
ForkJoinWorkerThread t = ws[i]; |
1163 |
|
|
if (t != null && !t.isTerminated()) { |
1164 |
|
|
try { |
1165 |
|
|
t.interrupt(); |
1166 |
|
|
} catch (SecurityException ignore) { |
1167 |
|
|
} |
1168 |
|
|
} |
1169 |
|
|
} |
1170 |
|
|
} finally { |
1171 |
|
|
lock.unlock(); |
1172 |
|
|
} |
1173 |
|
|
} |
1174 |
|
|
|
1175 |
|
|
|
1176 |
|
|
/* |
1177 |
|
|
* Nodes for event barrier to manage idle threads. |
1178 |
|
|
* |
1179 |
|
|
* The event barrier has an event count and a wait queue (actually |
1180 |
|
|
* a Treiber stack). Workers are enabled to look for work when |
1181 |
|
|
* the eventCount is incremented. If they fail to find some, |
1182 |
|
|
* they may wait for next count. Synchronization events occur only |
1183 |
|
|
* in enough contexts to maintain overall liveness: |
1184 |
|
|
* |
1185 |
|
|
* - Submission of a new task to the pool |
1186 |
|
|
* - Creation or termination of a worker |
1187 |
|
|
* - pool termination |
1188 |
|
|
* - A worker pushing a task on an empty queue |
1189 |
|
|
* |
1190 |
|
|
* The last case (pushing a task) occurs often enough, and is |
1191 |
|
|
* heavy enough compared to simple stack pushes to require some |
1192 |
|
|
* special handling: Method signalNonEmptyWorkerQueue returns |
1193 |
|
|
* without advancing count if the queue appears to be empty. This |
1194 |
|
|
* would ordinarily result in races causing some queued waiters |
1195 |
|
|
* not to be woken up. To avoid this, a worker in sync |
1196 |
|
|
* rescans for tasks after being enqueued if it was the first to |
1197 |
|
|
* enqueue, and aborts the wait if finding one, also helping to |
1198 |
|
|
* signal others. This works well because the worker has nothing |
1199 |
|
|
* better to do anyway, and so might as well help alleviate the |
1200 |
|
|
* overhead and contention on the threads actually doing work. |
1201 |
|
|
* |
1202 |
|
|
* Queue nodes are basic Treiber stack nodes, also used for spare |
1203 |
|
|
* stack. |
1204 |
|
|
*/ |
1205 |
|
|
static final class WaitQueueNode { |
1206 |
|
|
WaitQueueNode next; // only written before enqueued |
1207 |
|
|
volatile ForkJoinWorkerThread thread; // nulled to cancel wait |
1208 |
|
|
final long count; // unused for spare stack |
1209 |
|
|
WaitQueueNode(ForkJoinWorkerThread w, long c) { |
1210 |
|
|
count = c; |
1211 |
|
|
thread = w; |
1212 |
|
|
} |
1213 |
|
|
final boolean signal() { |
1214 |
|
|
ForkJoinWorkerThread t = thread; |
1215 |
|
|
thread = null; |
1216 |
|
|
if (t != null) { |
1217 |
|
|
LockSupport.unpark(t); |
1218 |
|
|
return true; |
1219 |
|
|
} |
1220 |
|
|
return false; |
1221 |
|
|
} |
1222 |
|
|
} |
1223 |
|
|
|
1224 |
|
|
/** |
1225 |
|
|
* Release at least one thread waiting for event count to advance, |
1226 |
|
|
* if one exists. If initial attempt fails, release all threads. |
1227 |
|
|
* @param all if false, at first try to only release one thread |
1228 |
|
|
* @return current event |
1229 |
|
|
*/ |
1230 |
|
|
private long releaseIdleWorkers(boolean all) { |
1231 |
|
|
long c; |
1232 |
|
|
for (;;) { |
1233 |
|
|
WaitQueueNode q = barrierStack; |
1234 |
|
|
c = eventCount; |
1235 |
|
|
long qc; |
1236 |
|
|
if (q == null || (qc = q.count) >= c) |
1237 |
|
|
break; |
1238 |
|
|
if (!all) { |
1239 |
|
|
if (casBarrierStack(q, q.next) && q.signal()) |
1240 |
|
|
break; |
1241 |
|
|
all = true; |
1242 |
|
|
} |
1243 |
|
|
else if (casBarrierStack(q, null)) { |
1244 |
|
|
do { |
1245 |
|
|
q.signal(); |
1246 |
|
|
} while ((q = q.next) != null); |
1247 |
|
|
break; |
1248 |
|
|
} |
1249 |
|
|
} |
1250 |
|
|
return c; |
1251 |
|
|
} |
1252 |
|
|
|
1253 |
|
|
/** |
1254 |
|
|
* Returns current barrier event count |
1255 |
|
|
* @return current barrier event count |
1256 |
|
|
*/ |
1257 |
|
|
final long getEventCount() { |
1258 |
|
|
long ec = eventCount; |
1259 |
|
|
releaseIdleWorkers(true); // release to ensure accurate result |
1260 |
|
|
return ec; |
1261 |
|
|
} |
1262 |
|
|
|
1263 |
|
|
/** |
1264 |
|
|
* Increment event count and release at least one waiting thread, |
1265 |
|
|
* if one exists (released threads will in turn wake up others). |
1266 |
|
|
* @param all if true, try to wake up all |
1267 |
|
|
*/ |
1268 |
|
|
final void signalIdleWorkers(boolean all) { |
1269 |
|
|
long c; |
1270 |
|
|
do;while (!casEventCount(c = eventCount, c+1)); |
1271 |
|
|
releaseIdleWorkers(all); |
1272 |
|
|
} |
1273 |
|
|
|
1274 |
|
|
/** |
1275 |
|
|
* Wake up threads waiting to steal a task. Because method |
1276 |
|
|
* sync rechecks availability, it is OK to only proceed if |
1277 |
|
|
* queue appears to be non-empty. |
1278 |
|
|
*/ |
1279 |
|
|
final void signalNonEmptyWorkerQueue() { |
1280 |
|
|
// If CAS fails another signaller must have succeeded |
1281 |
|
|
long c; |
1282 |
|
|
if (barrierStack != null && casEventCount(c = eventCount, c+1)) |
1283 |
|
|
releaseIdleWorkers(false); |
1284 |
|
|
} |
1285 |
|
|
|
1286 |
|
|
/** |
1287 |
|
|
* Waits until event count advances from count, or some thread is |
1288 |
|
|
* waiting on a previous count, or there is stealable work |
1289 |
|
|
* available. Help wake up others on release. |
1290 |
|
|
* @param w the calling worker thread |
1291 |
|
|
* @param prev previous value returned by sync (or 0) |
1292 |
|
|
* @return current event count |
1293 |
|
|
*/ |
1294 |
|
|
final long sync(ForkJoinWorkerThread w, long prev) { |
1295 |
|
|
updateStealCount(w); |
1296 |
|
|
|
1297 |
|
|
while (!w.isShutdown() && !isTerminating() && |
1298 |
|
|
(parallelism >= runningCountOf(workerCounts) || |
1299 |
|
|
!suspendIfSpare(w))) { // prefer suspend to waiting here |
1300 |
|
|
WaitQueueNode node = null; |
1301 |
|
|
boolean queued = false; |
1302 |
|
|
for (;;) { |
1303 |
|
|
if (!queued) { |
1304 |
|
|
if (eventCount != prev) |
1305 |
|
|
break; |
1306 |
|
|
WaitQueueNode h = barrierStack; |
1307 |
|
|
if (h != null && h.count != prev) |
1308 |
|
|
break; // release below and maybe retry |
1309 |
|
|
if (node == null) |
1310 |
|
|
node = new WaitQueueNode(w, prev); |
1311 |
|
|
queued = casBarrierStack(node.next = h, node); |
1312 |
|
|
} |
1313 |
|
|
else if (Thread.interrupted() || |
1314 |
|
|
node.thread == null || |
1315 |
|
|
(node.next == null && w.prescan()) || |
1316 |
|
|
eventCount != prev) { |
1317 |
|
|
node.thread = null; |
1318 |
|
|
if (eventCount == prev) // help trigger |
1319 |
|
|
casEventCount(prev, prev+1); |
1320 |
|
|
break; |
1321 |
|
|
} |
1322 |
|
|
else |
1323 |
|
|
LockSupport.park(this); |
1324 |
|
|
} |
1325 |
|
|
long ec = eventCount; |
1326 |
|
|
if (releaseIdleWorkers(false) != prev) |
1327 |
|
|
return ec; |
1328 |
|
|
} |
1329 |
|
|
return prev; // return old count if aborted |
1330 |
|
|
} |
1331 |
|
|
|
1332 |
|
|
// Parallelism maintenance |
1333 |
|
|
|
1334 |
|
|
/** |
1335 |
|
|
* Decrement running count; if too low, add spare. |
1336 |
|
|
* |
1337 |
|
|
* Conceptually, all we need to do here is add or resume a |
1338 |
|
|
* spare thread when one is about to block (and remove or |
1339 |
|
|
* suspend it later when unblocked -- see suspendIfSpare). |
1340 |
|
|
* However, implementing this idea requires coping with |
1341 |
|
|
* several problems: We have imperfect information about the |
1342 |
|
|
* states of threads. Some count updates can and usually do |
1343 |
|
|
* lag run state changes, despite arrangements to keep them |
1344 |
|
|
* accurate (for example, when possible, updating counts |
1345 |
|
|
* before signalling or resuming), especially when running on |
1346 |
|
|
* dynamic JVMs that don't optimize the infrequent paths that |
1347 |
|
|
* update counts. Generating too many threads can make these |
1348 |
|
|
* problems become worse, because excess threads are more |
1349 |
|
|
* likely to be context-switched with others, slowing them all |
1350 |
|
|
* down, especially if there is no work available, so all are |
1351 |
|
|
* busy scanning or idling. Also, excess spare threads can |
1352 |
|
|
* only be suspended or removed when they are idle, not |
1353 |
|
|
* immediately when they aren't needed. So adding threads will |
1354 |
|
|
* raise parallelism level for longer than necessary. Also, |
1355 |
|
|
* FJ applications often enounter highly transient peaks when |
1356 |
|
|
* many threads are blocked joining, but for less time than it |
1357 |
|
|
* takes to create or resume spares. |
1358 |
|
|
* |
1359 |
|
|
* @param joinMe if non-null, return early if done |
1360 |
|
|
* @param maintainParallelism if true, try to stay within |
1361 |
|
|
* target counts, else create only to avoid starvation |
1362 |
|
|
* @return true if joinMe known to be done |
1363 |
|
|
*/ |
1364 |
|
|
final boolean preJoin(ForkJoinTask<?> joinMe, boolean maintainParallelism) { |
1365 |
|
|
maintainParallelism &= maintainsParallelism; // overrride |
1366 |
|
|
boolean dec = false; // true when running count decremented |
1367 |
|
|
while (spareStack == null || !tryResumeSpare(dec)) { |
1368 |
|
|
int counts = workerCounts; |
1369 |
|
|
if (dec || (dec = casWorkerCounts(counts, --counts))) { // CAS cheat |
1370 |
|
|
if (!needSpare(counts, maintainParallelism)) |
1371 |
|
|
break; |
1372 |
|
|
if (joinMe.status < 0) |
1373 |
|
|
return true; |
1374 |
|
|
if (tryAddSpare(counts)) |
1375 |
|
|
break; |
1376 |
|
|
} |
1377 |
|
|
} |
1378 |
|
|
return false; |
1379 |
|
|
} |
1380 |
|
|
|
1381 |
|
|
/** |
1382 |
|
|
* Same idea as preJoin |
1383 |
|
|
*/ |
1384 |
|
|
final boolean preBlock(ManagedBlocker blocker, boolean maintainParallelism){ |
1385 |
|
|
maintainParallelism &= maintainsParallelism; |
1386 |
|
|
boolean dec = false; |
1387 |
|
|
while (spareStack == null || !tryResumeSpare(dec)) { |
1388 |
|
|
int counts = workerCounts; |
1389 |
|
|
if (dec || (dec = casWorkerCounts(counts, --counts))) { |
1390 |
|
|
if (!needSpare(counts, maintainParallelism)) |
1391 |
|
|
break; |
1392 |
|
|
if (blocker.isReleasable()) |
1393 |
|
|
return true; |
1394 |
|
|
if (tryAddSpare(counts)) |
1395 |
|
|
break; |
1396 |
|
|
} |
1397 |
|
|
} |
1398 |
|
|
return false; |
1399 |
|
|
} |
1400 |
|
|
|
1401 |
|
|
/** |
1402 |
|
|
* Returns true if a spare thread appears to be needed. If |
1403 |
|
|
* maintaining parallelism, returns true when the deficit in |
1404 |
|
|
* running threads is more than the surplus of total threads, and |
1405 |
|
|
* there is apparently some work to do. This self-limiting rule |
1406 |
|
|
* means that the more threads that have already been added, the |
1407 |
|
|
* less parallelism we will tolerate before adding another. |
1408 |
|
|
* @param counts current worker counts |
1409 |
|
|
* @param maintainParallelism try to maintain parallelism |
1410 |
|
|
*/ |
1411 |
|
|
private boolean needSpare(int counts, boolean maintainParallelism) { |
1412 |
|
|
int ps = parallelism; |
1413 |
|
|
int rc = runningCountOf(counts); |
1414 |
|
|
int tc = totalCountOf(counts); |
1415 |
|
|
int runningDeficit = ps - rc; |
1416 |
|
|
int totalSurplus = tc - ps; |
1417 |
|
|
return (tc < maxPoolSize && |
1418 |
|
|
(rc == 0 || totalSurplus < 0 || |
1419 |
|
|
(maintainParallelism && |
1420 |
|
|
runningDeficit > totalSurplus && mayHaveQueuedWork()))); |
1421 |
|
|
} |
1422 |
|
|
|
1423 |
|
|
/** |
1424 |
|
|
* Returns true if at least one worker queue appears to be |
1425 |
|
|
* nonempty. This is expensive but not often called. It is not |
1426 |
|
|
* critical that this be accurate, but if not, more or fewer |
1427 |
|
|
* running threads than desired might be maintained. |
1428 |
|
|
*/ |
1429 |
|
|
private boolean mayHaveQueuedWork() { |
1430 |
|
|
ForkJoinWorkerThread[] ws = workers; |
1431 |
|
|
int len = ws.length; |
1432 |
|
|
ForkJoinWorkerThread v; |
1433 |
|
|
for (int i = 0; i < len; ++i) { |
1434 |
|
|
if ((v = ws[i]) != null && v.getRawQueueSize() > 0) { |
1435 |
|
|
releaseIdleWorkers(false); // help wake up stragglers |
1436 |
|
|
return true; |
1437 |
|
|
} |
1438 |
|
|
} |
1439 |
|
|
return false; |
1440 |
|
|
} |
1441 |
|
|
|
1442 |
|
|
/** |
1443 |
|
|
* Add a spare worker if lock available and no more than the |
1444 |
|
|
* expected numbers of threads exist |
1445 |
|
|
* @return true if successful |
1446 |
|
|
*/ |
1447 |
|
|
private boolean tryAddSpare(int expectedCounts) { |
1448 |
|
|
final ReentrantLock lock = this.workerLock; |
1449 |
|
|
int expectedRunning = runningCountOf(expectedCounts); |
1450 |
|
|
int expectedTotal = totalCountOf(expectedCounts); |
1451 |
|
|
boolean success = false; |
1452 |
|
|
boolean locked = false; |
1453 |
|
|
// confirm counts while locking; CAS after obtaining lock |
1454 |
|
|
try { |
1455 |
|
|
for (;;) { |
1456 |
|
|
int s = workerCounts; |
1457 |
|
|
int tc = totalCountOf(s); |
1458 |
|
|
int rc = runningCountOf(s); |
1459 |
|
|
if (rc > expectedRunning || tc > expectedTotal) |
1460 |
|
|
break; |
1461 |
|
|
if (!locked && !(locked = lock.tryLock())) |
1462 |
|
|
break; |
1463 |
|
|
if (casWorkerCounts(s, workerCountsFor(tc+1, rc+1))) { |
1464 |
|
|
createAndStartSpare(tc); |
1465 |
|
|
success = true; |
1466 |
|
|
break; |
1467 |
|
|
} |
1468 |
|
|
} |
1469 |
|
|
} finally { |
1470 |
|
|
if (locked) |
1471 |
|
|
lock.unlock(); |
1472 |
|
|
} |
1473 |
|
|
return success; |
1474 |
|
|
} |
1475 |
|
|
|
1476 |
|
|
/** |
1477 |
|
|
* Add the kth spare worker. On entry, pool coounts are already |
1478 |
|
|
* adjusted to reflect addition. |
1479 |
|
|
*/ |
1480 |
|
|
private void createAndStartSpare(int k) { |
1481 |
|
|
ForkJoinWorkerThread w = null; |
1482 |
|
|
ForkJoinWorkerThread[] ws = ensureWorkerArrayCapacity(k + 1); |
1483 |
|
|
int len = ws.length; |
1484 |
|
|
// Probably, we can place at slot k. If not, find empty slot |
1485 |
|
|
if (k < len && ws[k] != null) { |
1486 |
|
|
for (k = 0; k < len && ws[k] != null; ++k) |
1487 |
|
|
; |
1488 |
|
|
} |
1489 |
|
|
if (k < len && (w = createWorker(k)) != null) { |
1490 |
|
|
ws[k] = w; |
1491 |
|
|
w.start(); |
1492 |
|
|
} |
1493 |
|
|
else |
1494 |
|
|
updateWorkerCount(-1); // adjust on failure |
1495 |
|
|
signalIdleWorkers(false); |
1496 |
|
|
} |
1497 |
|
|
|
1498 |
|
|
/** |
1499 |
|
|
* Suspend calling thread w if there are excess threads. Called |
1500 |
|
|
* only from sync. Spares are enqueued in a Treiber stack |
1501 |
|
|
* using the same WaitQueueNodes as barriers. They are resumed |
1502 |
|
|
* mainly in preJoin, but are also woken on pool events that |
1503 |
|
|
* require all threads to check run state. |
1504 |
|
|
* @param w the caller |
1505 |
|
|
*/ |
1506 |
|
|
private boolean suspendIfSpare(ForkJoinWorkerThread w) { |
1507 |
|
|
WaitQueueNode node = null; |
1508 |
|
|
int s; |
1509 |
|
|
while (parallelism < runningCountOf(s = workerCounts)) { |
1510 |
|
|
if (node == null) |
1511 |
|
|
node = new WaitQueueNode(w, 0); |
1512 |
|
|
if (casWorkerCounts(s, s-1)) { // representation-dependent |
1513 |
|
|
// push onto stack |
1514 |
|
|
do;while (!casSpareStack(node.next = spareStack, node)); |
1515 |
|
|
|
1516 |
|
|
// block until released by resumeSpare |
1517 |
|
|
while (node.thread != null) { |
1518 |
|
|
if (!Thread.interrupted()) |
1519 |
|
|
LockSupport.park(this); |
1520 |
|
|
} |
1521 |
|
|
w.activate(); // help warm up |
1522 |
|
|
return true; |
1523 |
|
|
} |
1524 |
|
|
} |
1525 |
|
|
return false; |
1526 |
|
|
} |
1527 |
|
|
|
1528 |
|
|
/** |
1529 |
|
|
* Try to pop and resume a spare thread. |
1530 |
|
|
* @param updateCount if true, increment running count on success |
1531 |
|
|
* @return true if successful |
1532 |
|
|
*/ |
1533 |
|
|
private boolean tryResumeSpare(boolean updateCount) { |
1534 |
|
|
WaitQueueNode q; |
1535 |
|
|
while ((q = spareStack) != null) { |
1536 |
|
|
if (casSpareStack(q, q.next)) { |
1537 |
|
|
if (updateCount) |
1538 |
|
|
updateRunningCount(1); |
1539 |
|
|
q.signal(); |
1540 |
|
|
return true; |
1541 |
|
|
} |
1542 |
|
|
} |
1543 |
|
|
return false; |
1544 |
|
|
} |
1545 |
|
|
|
1546 |
|
|
/** |
1547 |
|
|
* Pop and resume all spare threads. Same idea as |
1548 |
|
|
* releaseIdleWorkers. |
1549 |
|
|
* @return true if any spares released |
1550 |
|
|
*/ |
1551 |
|
|
private boolean resumeAllSpares() { |
1552 |
|
|
WaitQueueNode q; |
1553 |
|
|
while ( (q = spareStack) != null) { |
1554 |
|
|
if (casSpareStack(q, null)) { |
1555 |
|
|
do { |
1556 |
|
|
updateRunningCount(1); |
1557 |
|
|
q.signal(); |
1558 |
|
|
} while ((q = q.next) != null); |
1559 |
|
|
return true; |
1560 |
|
|
} |
1561 |
|
|
} |
1562 |
|
|
return false; |
1563 |
|
|
} |
1564 |
|
|
|
1565 |
|
|
/** |
1566 |
|
|
* Pop and shutdown excessive spare threads. Call only while |
1567 |
|
|
* holding lock. This is not guaranteed to eliminate all excess |
1568 |
|
|
* threads, only those suspended as spares, which are the ones |
1569 |
|
|
* unlikely to be needed in the future. |
1570 |
|
|
*/ |
1571 |
|
|
private void trimSpares() { |
1572 |
|
|
int surplus = totalCountOf(workerCounts) - parallelism; |
1573 |
|
|
WaitQueueNode q; |
1574 |
|
|
while (surplus > 0 && (q = spareStack) != null) { |
1575 |
|
|
if (casSpareStack(q, null)) { |
1576 |
|
|
do { |
1577 |
|
|
updateRunningCount(1); |
1578 |
|
|
ForkJoinWorkerThread w = q.thread; |
1579 |
|
|
if (w != null && surplus > 0 && |
1580 |
|
|
runningCountOf(workerCounts) > 0 && w.shutdown()) |
1581 |
|
|
--surplus; |
1582 |
|
|
q.signal(); |
1583 |
|
|
} while ((q = q.next) != null); |
1584 |
|
|
} |
1585 |
|
|
} |
1586 |
|
|
} |
1587 |
|
|
|
1588 |
|
|
/** |
1589 |
|
|
* Returns approximate number of spares, just for diagnostics. |
1590 |
|
|
*/ |
1591 |
|
|
private int countSpares() { |
1592 |
|
|
int sum = 0; |
1593 |
|
|
for (WaitQueueNode q = spareStack; q != null; q = q.next) |
1594 |
|
|
++sum; |
1595 |
|
|
return sum; |
1596 |
|
|
} |
1597 |
|
|
|
1598 |
|
|
/** |
1599 |
|
|
* Interface for extending managed parallelism for tasks running |
1600 |
|
|
* in ForkJoinPools. A ManagedBlocker provides two methods. |
1601 |
|
|
* Method <tt>isReleasable</tt> must return true if blocking is not |
1602 |
|
|
* necessary. Method <tt>block</tt> blocks the current thread |
1603 |
|
|
* if necessary (perhaps internally invoking isReleasable before |
1604 |
|
|
* actually blocking.). |
1605 |
|
|
* <p>For example, here is a ManagedBlocker based on a |
1606 |
|
|
* ReentrantLock: |
1607 |
|
|
* <pre> |
1608 |
|
|
* class ManagedLocker implements ManagedBlocker { |
1609 |
|
|
* final ReentrantLock lock; |
1610 |
|
|
* boolean hasLock = false; |
1611 |
|
|
* ManagedLocker(ReentrantLock lock) { this.lock = lock; } |
1612 |
|
|
* public boolean block() { |
1613 |
|
|
* if (!hasLock) |
1614 |
|
|
* lock.lock(); |
1615 |
|
|
* return true; |
1616 |
|
|
* } |
1617 |
|
|
* public boolean isReleasable() { |
1618 |
|
|
* return hasLock || (hasLock = lock.tryLock()); |
1619 |
|
|
* } |
1620 |
|
|
* } |
1621 |
|
|
* </pre> |
1622 |
|
|
*/ |
1623 |
|
|
public static interface ManagedBlocker { |
1624 |
|
|
/** |
1625 |
|
|
* Possibly blocks the current thread, for example waiting for |
1626 |
|
|
* a lock or condition. |
1627 |
|
|
* @return true if no additional blocking is necessary (i.e., |
1628 |
|
|
* if isReleasable would return true). |
1629 |
|
|
* @throws InterruptedException if interrupted while waiting |
1630 |
|
|
* (the method is not required to do so, but is allowe to). |
1631 |
|
|
*/ |
1632 |
|
|
boolean block() throws InterruptedException; |
1633 |
|
|
|
1634 |
|
|
/** |
1635 |
|
|
* Returns true if blocking is unnecessary. |
1636 |
|
|
*/ |
1637 |
|
|
boolean isReleasable(); |
1638 |
|
|
} |
1639 |
|
|
|
1640 |
|
|
/** |
1641 |
|
|
* Blocks in accord with the given blocker. If the current thread |
1642 |
|
|
* is a ForkJoinWorkerThread, this method possibly arranges for a |
1643 |
|
|
* spare thread to be activated if necessary to ensure parallelism |
1644 |
|
|
* while the current thread is blocked. If |
1645 |
|
|
* <tt>maintainParallelism</tt> is true and the pool supports it |
1646 |
|
|
* (see <tt>getMaintainsParallelism</tt>), this method attempts to |
1647 |
|
|
* maintain the pool's nominal parallelism. Otherwise if activates |
1648 |
|
|
* a thread only if necessary to avoid complete starvation. This |
1649 |
|
|
* option may be preferable when blockages use timeouts, or are |
1650 |
|
|
* almost always brief. |
1651 |
|
|
* |
1652 |
|
|
* <p> If the caller is not a ForkJoinTask, this method is behaviorally |
1653 |
|
|
* equivalent to |
1654 |
|
|
* <pre> |
1655 |
|
|
* while (!blocker.isReleasable()) |
1656 |
|
|
* if (blocker.block()) |
1657 |
|
|
* return; |
1658 |
|
|
* </pre> |
1659 |
|
|
* If the caller is a ForkJoinTask, then the pool may first |
1660 |
|
|
* be expanded to ensure parallelism, and later adjusted. |
1661 |
|
|
* |
1662 |
|
|
* @param blocker the blocker |
1663 |
|
|
* @param maintainParallelism if true and supported by this pool, |
1664 |
|
|
* attempt to maintain the pool's nominal parallelism; otherwise |
1665 |
|
|
* activate a thread only if necessary to avoid complete |
1666 |
|
|
* starvation. |
1667 |
|
|
* @throws InterruptedException if blocker.block did so. |
1668 |
|
|
*/ |
1669 |
|
|
public static void managedBlock(ManagedBlocker blocker, |
1670 |
|
|
boolean maintainParallelism) |
1671 |
|
|
throws InterruptedException { |
1672 |
|
|
Thread t = Thread.currentThread(); |
1673 |
|
|
ForkJoinPool pool = (t instanceof ForkJoinWorkerThread? |
1674 |
|
|
((ForkJoinWorkerThread)t).pool : null); |
1675 |
|
|
if (!blocker.isReleasable()) { |
1676 |
|
|
try { |
1677 |
|
|
if (pool == null || |
1678 |
|
|
!pool.preBlock(blocker, maintainParallelism)) |
1679 |
|
|
awaitBlocker(blocker); |
1680 |
|
|
} finally { |
1681 |
|
|
if (pool != null) |
1682 |
|
|
pool.updateRunningCount(1); |
1683 |
|
|
} |
1684 |
|
|
} |
1685 |
|
|
} |
1686 |
|
|
|
1687 |
|
|
private static void awaitBlocker(ManagedBlocker blocker) |
1688 |
|
|
throws InterruptedException { |
1689 |
|
|
do;while (!blocker.isReleasable() && !blocker.block()); |
1690 |
|
|
} |
1691 |
|
|
|
1692 |
|
|
|
1693 |
|
|
// Temporary Unsafe mechanics for preliminary release |
1694 |
|
|
|
1695 |
|
|
static final Unsafe _unsafe; |
1696 |
|
|
static final long eventCountOffset; |
1697 |
|
|
static final long workerCountsOffset; |
1698 |
|
|
static final long runControlOffset; |
1699 |
|
|
static final long barrierStackOffset; |
1700 |
|
|
static final long spareStackOffset; |
1701 |
|
|
|
1702 |
|
|
static { |
1703 |
|
|
try { |
1704 |
|
|
if (ForkJoinPool.class.getClassLoader() != null) { |
1705 |
|
|
Field f = Unsafe.class.getDeclaredField("theUnsafe"); |
1706 |
|
|
f.setAccessible(true); |
1707 |
|
|
_unsafe = (Unsafe)f.get(null); |
1708 |
|
|
} |
1709 |
|
|
else |
1710 |
|
|
_unsafe = Unsafe.getUnsafe(); |
1711 |
|
|
eventCountOffset = _unsafe.objectFieldOffset |
1712 |
|
|
(ForkJoinPool.class.getDeclaredField("eventCount")); |
1713 |
|
|
workerCountsOffset = _unsafe.objectFieldOffset |
1714 |
|
|
(ForkJoinPool.class.getDeclaredField("workerCounts")); |
1715 |
|
|
runControlOffset = _unsafe.objectFieldOffset |
1716 |
|
|
(ForkJoinPool.class.getDeclaredField("runControl")); |
1717 |
|
|
barrierStackOffset = _unsafe.objectFieldOffset |
1718 |
|
|
(ForkJoinPool.class.getDeclaredField("barrierStack")); |
1719 |
|
|
spareStackOffset = _unsafe.objectFieldOffset |
1720 |
|
|
(ForkJoinPool.class.getDeclaredField("spareStack")); |
1721 |
|
|
} catch (Exception e) { |
1722 |
|
|
throw new RuntimeException("Could not initialize intrinsics", e); |
1723 |
|
|
} |
1724 |
|
|
} |
1725 |
|
|
|
1726 |
|
|
private boolean casEventCount(long cmp, long val) { |
1727 |
|
|
return _unsafe.compareAndSwapLong(this, eventCountOffset, cmp, val); |
1728 |
|
|
} |
1729 |
|
|
private boolean casWorkerCounts(int cmp, int val) { |
1730 |
|
|
return _unsafe.compareAndSwapInt(this, workerCountsOffset, cmp, val); |
1731 |
|
|
} |
1732 |
|
|
private boolean casRunControl(int cmp, int val) { |
1733 |
|
|
return _unsafe.compareAndSwapInt(this, runControlOffset, cmp, val); |
1734 |
|
|
} |
1735 |
|
|
private boolean casSpareStack(WaitQueueNode cmp, WaitQueueNode val) { |
1736 |
|
|
return _unsafe.compareAndSwapObject(this, spareStackOffset, cmp, val); |
1737 |
|
|
} |
1738 |
|
|
private boolean casBarrierStack(WaitQueueNode cmp, WaitQueueNode val) { |
1739 |
|
|
return _unsafe.compareAndSwapObject(this, barrierStackOffset, cmp, val); |
1740 |
|
|
} |
1741 |
|
|
} |