src/jsr166e/ForkJoinWorkerThread.java

/*
 * 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 jsr166e;


/**
 * A thread managed by a {@link ForkJoinPool}, which executes
 * {@link ForkJoinTask}s.
 * This class is subclassable solely for the sake of adding
 * functionality -- there are no overridable methods dealing with
 * scheduling or execution.  However, you can override initialization
 * and termination methods surrounding the main task processing loop.
 * If you do create such a subclass, you will also need to supply a
 * custom {@link ForkJoinPool.ForkJoinWorkerThreadFactory} to
 * {@linkplain ForkJoinPool#ForkJoinPool use it} in a {@code ForkJoinPool}.
 *
 * @since 1.7
 * @author Doug Lea
 */
public class ForkJoinWorkerThread extends Thread {
    /*
     * ForkJoinWorkerThreads are managed by ForkJoinPools and perform
     * ForkJoinTasks. For explanation, see the internal documentation
     * of class ForkJoinPool.
     *
     * This class just maintains links to its pool and WorkQueue.  The
     * pool field is set immediately upon construction, but the
     * workQueue field is not set until a call to registerWorker
     * completes. This leads to a visibility race, that is tolerated
     * by requiring that the workQueue field is only accessed by the
     * owning thread.
     */

    final ForkJoinPool pool;                // the pool this thread works in
    final ForkJoinPool.WorkQueue workQueue; // work-stealing mechanics

    /**
     * Creates a ForkJoinWorkerThread operating in the given pool.
     *
     * @param pool the pool this thread works in
     * @throws NullPointerException if pool is null
     */
    protected ForkJoinWorkerThread(ForkJoinPool pool) {
        // Use a placeholder until a useful name can be set in registerWorker
        super("aForkJoinWorkerThread");
        this.pool = pool;
        this.workQueue = pool.registerWorker(this);
    }

    /**
     * Returns the pool hosting this thread.
     *
     * @return the pool
     */
    public ForkJoinPool getPool() {
        return pool;
    }

    /**
     * Returns the unique index number of this thread in its pool.
     * The returned value ranges from zero to the maximum number of
     * threads (minus one) that may exist in the pool, and does not
     * change during the lifetime of the thread.  This method may be
     * useful for applications that track status or collect results
     * per-worker-thread rather than per-task.
     *
     * @return the index number
     */
    public int getPoolIndex() {
        return workQueue.poolIndex >>> 1; // ignore odd/even tag bit
    }

    /**
     * Initializes internal state after construction but before
     * processing any tasks. If you override this method, you must
     * invoke {@code super.onStart()} at the beginning of the method.
     * Initialization requires care: Most fields must have legal
     * default values, to ensure that attempted accesses from other
     * threads work correctly even before this thread starts
     * processing tasks.
     */
    protected void onStart() {
    }

    /**
     * Performs cleanup associated with termination of this worker
     * thread.  If you override this method, you must invoke
     * {@code super.onTermination} at the end of the overridden method.
     *
     * @param exception the exception causing this thread to abort due
     * to an unrecoverable error, or {@code null} if completed normally
     */
    protected void onTermination(Throwable exception) {
    }

    /**
     * This method is required to be public, but should never be
     * called explicitly. It performs the main run loop to execute
     * {@link ForkJoinTask}s.
     */
    public void run() {
        Throwable exception = null;
        try {
            onStart();
            pool.runWorker(workQueue);
        } catch (Throwable ex) {
            exception = ex;
        } finally {
            try {
                onTermination(exception);
            } catch (Throwable ex) {
                if (exception == null)
                    exception = ex;
            } finally {
                pool.deregisterWorker(this, exception);
            }
        }
    }
}
Revision:	1.5
Committed:	Wed Jun 19 14:55:40 2013 UTC (10 years, 10 months ago) by dl
Branch:	MAIN
Changes since 1.4:	+10 -8 lines
Log Message:	Sync with jdk8 versions
#	User	Rev	Content
1	dl	1.1	/*
2			* Written by Doug Lea with assistance from members of JCP JSR-166
3			* Expert Group and released to the public domain, as explained at
4			* http://creativecommons.org/publicdomain/zero/1.0/
5			*/
6
7			package jsr166e;
8
9	dl	1.5
10	dl	1.1	/**
11			* A thread managed by a {@link ForkJoinPool}, which executes
12			* {@link ForkJoinTask}s.
13			* This class is subclassable solely for the sake of adding
14			* functionality -- there are no overridable methods dealing with
15			* scheduling or execution. However, you can override initialization
16			* and termination methods surrounding the main task processing loop.
17			* If you do create such a subclass, you will also need to supply a
18	dl	1.5	* custom {@link ForkJoinPool.ForkJoinWorkerThreadFactory} to
19			* {@linkplain ForkJoinPool#ForkJoinPool use it} in a {@code ForkJoinPool}.
20	dl	1.1	*
21			* @since 1.7
22			* @author Doug Lea
23			*/
24			public class ForkJoinWorkerThread extends Thread {
25			/*
26			* ForkJoinWorkerThreads are managed by ForkJoinPools and perform
27			* ForkJoinTasks. For explanation, see the internal documentation
28			* of class ForkJoinPool.
29	dl	1.3	*
30			* This class just maintains links to its pool and WorkQueue. The
31	dl	1.4	* pool field is set immediately upon construction, but the
32			* workQueue field is not set until a call to registerWorker
33			* completes. This leads to a visibility race, that is tolerated
34			* by requiring that the workQueue field is only accessed by the
35			* owning thread.
36	dl	1.1	*/
37
38			final ForkJoinPool pool; // the pool this thread works in
39	dl	1.4	final ForkJoinPool.WorkQueue workQueue; // work-stealing mechanics
40	dl	1.2
41			/**
42	dl	1.1	* Creates a ForkJoinWorkerThread operating in the given pool.
43			*
44			* @param pool the pool this thread works in
45			* @throws NullPointerException if pool is null
46			*/
47			protected ForkJoinWorkerThread(ForkJoinPool pool) {
48	dl	1.4	// Use a placeholder until a useful name can be set in registerWorker
49			super("aForkJoinWorkerThread");
50	dl	1.3	this.pool = pool;
51	dl	1.4	this.workQueue = pool.registerWorker(this);
52	dl	1.1	}
53
54			/**
55			* Returns the pool hosting this thread.
56			*
57			* @return the pool
58			*/
59			public ForkJoinPool getPool() {
60			return pool;
61			}
62
63			/**
64	dl	1.5	* Returns the unique index number of this thread in its pool.
65			* The returned value ranges from zero to the maximum number of
66			* threads (minus one) that may exist in the pool, and does not
67			* change during the lifetime of the thread. This method may be
68			* useful for applications that track status or collect results
69			* per-worker-thread rather than per-task.
70	dl	1.1	*
71			* @return the index number
72			*/
73			public int getPoolIndex() {
74	dl	1.5	return workQueue.poolIndex >>> 1; // ignore odd/even tag bit
75	dl	1.1	}
76
77			/**
78			* Initializes internal state after construction but before
79			* processing any tasks. If you override this method, you must
80			* invoke {@code super.onStart()} at the beginning of the method.
81			* Initialization requires care: Most fields must have legal
82			* default values, to ensure that attempted accesses from other
83			* threads work correctly even before this thread starts
84			* processing tasks.
85			*/
86			protected void onStart() {
87			}
88
89			/**
90			* Performs cleanup associated with termination of this worker
91			* thread. If you override this method, you must invoke
92			* {@code super.onTermination} at the end of the overridden method.
93			*
94			* @param exception the exception causing this thread to abort due
95			* to an unrecoverable error, or {@code null} if completed normally
96			*/
97			protected void onTermination(Throwable exception) {
98			}
99
100			/**
101			* This method is required to be public, but should never be
102			* called explicitly. It performs the main run loop to execute
103			* {@link ForkJoinTask}s.
104			*/
105			public void run() {
106			Throwable exception = null;
107			try {
108			onStart();
109			pool.runWorker(workQueue);
110			} catch (Throwable ex) {
111			exception = ex;
112			} finally {
113			try {
114			onTermination(exception);
115			} catch (Throwable ex) {
116			if (exception == null)
117			exception = ex;
118			} finally {
119			pool.deregisterWorker(this, exception);
120			}
121			}
122			}
123			}