| /* |
| * 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 java.util.concurrent; |
| |
| /** |
| * 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); |
| } |
| } |
| } |
| } |