ThreadPoolExecutor(二)——execute_threadpoolutil.execute

 /*
     * Methods for creating, running and cleaning up after workers
     */
 
    /**
     * Checks if a new worker can be added with respect to current
     * pool state and the given bound (either core or maximum). If so,
     * the worker count is adjusted accordingly, and, if possible, a
     * new worker is created and started running firstTask as its
     * first task. This method returns false if the pool is stopped or
     * eligible to shut down. It also returns false if the thread
     * factory fails to create a thread when asked, which requires a
     * backout of workerCount, and a recheck for termination, in case
     * the existence of this worker was holding up termination.
     *
     * @param firstTask the task the new thread should run first (or
     * null if none). Workers are created with an initial first task
     * (in method execute()) to bypass queuing when there are fewer
     * than corePoolSize threads (in which case we always start one),
     * or when the queue is full (in which case we must bypass queue).
     * Initially idle threads are usually created via
     * prestartCoreThread or to replace other dying workers.
     *
     * @param core if true use corePoolSize as bound, else
     * maximumPoolSize. (A boolean indicator is used here rather than a
     * value to ensure reads of fresh values after checking other pool
     * state).
     * @return true if successful
     */
    private boolean addWorker(Runnable firstTask, boolean core) {
        retry:
        for (;;) {
            int c = ctl.get();
            int rs = runStateOf(c);
 
            // Check if queue empty only if necessary.
            if (rs >= SHUTDOWN &&
                ! (rs == SHUTDOWN &&
                   firstTask == null &&
                   ! workQueue.isEmpty()))
                return false;
 
            for (;;) {
                int wc = workerCountOf(c);
                if (wc >= CAPACITY ||
                    wc >= (core ? corePoolSize : maximumPoolSize))
                    return false;
                if (compareAndIncrementWorkerCount(c))
                    break retry;
                c = ctl.get();  // Re-read ctl
                if (runStateOf(c) != rs)
                    continue retry;
                // else CAS failed due to workerCount change; retry inner loop
            }
        }
 
        Worker w = new Worker(firstTask);
        Thread t = w.thread;
 
        final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            // Recheck while holding lock.
            // Back out on ThreadFactory failure or if
            // shut down before lock acquired.
            int c = ctl.get();
            int rs = runStateOf(c);
 
            if (t == null ||
                (rs >= SHUTDOWN &&
                 ! (rs == SHUTDOWN &&
                    firstTask == null))) {
                decrementWorkerCount();
                tryTerminate();
                return false;
            }
 
            workers.add(w);
 
            int s = workers.size();
            if (s > largestPoolSize)
                largestPoolSize = s;
        } finally {
            mainLock.unlock();
        }
 
        t.start();
        // It is possible (but unlikely) for a thread to have been
        // added to workers, but not yet started, during transition to
        // STOP, which could result in a rare missed interrupt,
        // because Thread.interrupt is not guaranteed to have any effect
        // on a non-yet-started Thread (see Thread#interrupt).
        if (runStateOf(ctl.get()) == STOP && ! t.isInterrupted())
            t.interrupt();
 
        return true;
    }

if (compareAndIncrementWorkerCount(c))
                    break retry;

// Recheck while holding lock.
            // Back out on ThreadFactory failure or if
            // shut down before lock acquired.
            int c = ctl.get();
            int rs = runStateOf(c);
 
            if (t == null ||
                (rs >= SHUTDOWN &&
                 ! (rs == SHUTDOWN &&
                    firstTask == null))) {
                decrementWorkerCount();
                tryTerminate();
                return false;
            }

3.1.addWorker局部分析（一）

// Check if queue empty only if necessary.
            if (rs >= SHUTDOWN &&
                ! (rs == SHUTDOWN &&
                   firstTask == null &&
                   ! workQueue.isEmpty()))
                return false;

3.2.addWorker局部分析（二）

for (;;) {
                int wc = workerCountOf(c);
                if (wc >= CAPACITY ||
                    wc >= (core ? corePoolSize : maximumPoolSize))
                    return false;
                if (compareAndIncrementWorkerCount(c))
                    break retry;
                c = ctl.get();  // Re-read ctl
                if (runStateOf(c) != rs)
                    continue retry;
                // else CAS failed due to workerCount change; retry inner loop
            }

2.入参core为true，表示 addWorker的时候，wc还没到达corePoolSize，和corePoolSize比较

final ReentrantLock mainLock = this.mainLock;
        mainLock.lock();
        try {
            // Recheck while holding lock.
            // Back out on ThreadFactory failure or if
            // shut down before lock acquired.
            int c = ctl.get();
            int rs = runStateOf(c);
 
            if (t == null ||
                (rs >= SHUTDOWN &&
                 ! (rs == SHUTDOWN &&
                    firstTask == null))) {
                decrementWorkerCount();
                tryTerminate();
                return false;
            }
 
            workers.add(w);
 
            int s = workers.size();
            if (s > largestPoolSize)
                largestPoolSize = s;
        } finally {
            mainLock.unlock();
        }

4.ctl

private static int CAPACITY = (1 << COUNT_BITS) - 1;

private static int COUNT_BITS = Integer.SIZE - 3;

private static final int RUNNING    = -1 << COUNT_BITS;

private static final int STOP       =  1 << COUNT_BITS;

private static final int TIDYING    =  2 << COUNT_BITS;

private static final int TERMINATED =  3 << COUNT_BITS;

5.和ctl相关的几组方法

private static int runStateOf(int c)     { return c & ~CAPACITY; }

private static int workerCountOf(int c)  { return c & CAPACITY; }