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
#	Content
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
10	/**
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	* custom {@link ForkJoinPool.ForkJoinWorkerThreadFactory} to
19	* {@linkplain ForkJoinPool#ForkJoinPool use it} in a {@code ForkJoinPool}.
20	*
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	*
30	* This class just maintains links to its pool and WorkQueue. The
31	* 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	*/
37
38	final ForkJoinPool pool; // the pool this thread works in
39	final ForkJoinPool.WorkQueue workQueue; // work-stealing mechanics
40
41	/**
42	* 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	// Use a placeholder until a useful name can be set in registerWorker
49	super("aForkJoinWorkerThread");
50	this.pool = pool;
51	this.workQueue = pool.registerWorker(this);
52	}
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	* 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	*
71	* @return the index number
72	*/
73	public int getPoolIndex() {
74	return workQueue.poolIndex >>> 1; // ignore odd/even tag bit
75	}
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	}