source: trunk/src/corelib/concurrent/qthreadpool.cpp@ 643

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**
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#include "qthreadpool.h"
#include "qthreadpool_p.h"

#ifndef QT_NO_THREAD

QT_BEGIN_NAMESPACE

inline bool operator<(int priority, const QPair<QRunnable *, int> &p)
{
    return p.second < priority;
}
inline bool operator<(const QPair<QRunnable *, int> &p, int priority)
{
    return priority < p.second;
}

Q_GLOBAL_STATIC(QThreadPool, theInstance)

/*
    QThread wrapper, provides synchronizitaion against a ThreadPool
*/
class QThreadPoolThread : public QThread
{
public:
    QThreadPoolThread(QThreadPoolPrivate *manager);
    void run();
    void registerTheadInactive();

    QThreadPoolPrivate *manager;
    QRunnable *runnable;
};

/*
    QThreadPool private class.
*/


/*!\internal

*/
QThreadPoolThread::QThreadPoolThread(QThreadPoolPrivate *manager)
    :manager(manager), runnable(0)
{ }

/* \internal

*/
void QThreadPoolThread::run()
{
    QMutexLocker locker(&manager->mutex);
    for(;;) {
        QRunnable *r = runnable;
        runnable = 0;

        do {
            if (r) {
                const bool autoDelete = r->autoDelete();


                // run the task
                locker.unlock();
#ifndef QT_NO_EXCEPTIONS
                try {
#endif
                    r->run();
#ifndef QT_NO_EXCEPTIONS
                } catch (...) {
                    qWarning("Qt Concurrent has caught an exception thrown from a worker thread.\n"
                             "This is not supported, exceptions thrown in worker threads must be\n"
                             "caught before control returns to Qt Concurrent.");
                    registerTheadInactive();
                    throw;
                }
#endif
                locker.relock();

                if (autoDelete && !--r->ref)
                    delete r;
            }

            // if too many threads are active, expire this thread
            if (manager->tooManyThreadsActive())
                break;

            r = !manager->queue.isEmpty() ? manager->queue.takeFirst().first : 0;
        } while (r != 0);

        if (manager->isExiting) {
            registerTheadInactive();
            break;
        }

        // if too many threads are active, expire this thread
        bool expired = manager->tooManyThreadsActive();
        if (!expired) {
            ++manager->waitingThreads;
            registerTheadInactive();
            // wait for work, exiting after the expiry timeout is reached
            expired = !manager->runnableReady.wait(locker.mutex(), manager->expiryTimeout);
            ++manager->activeThreads;
    
            if (expired)
                --manager->waitingThreads;
        }
        if (expired) {
            manager->expiredThreads.enqueue(this);
            registerTheadInactive();
            break;
        }
    }
}

void QThreadPoolThread::registerTheadInactive()
{
    if (--manager->activeThreads == 0)
        manager->noActiveThreads.wakeAll();
}


/* \internal

*/
QThreadPoolPrivate:: QThreadPoolPrivate()
    : isExiting(false),
      expiryTimeout(30000),
      maxThreadCount(qAbs(QThread::idealThreadCount())),
      reservedThreads(0),
      waitingThreads(0),
      activeThreads(0)
{ }

bool QThreadPoolPrivate::tryStart(QRunnable *task)
{
    if (allThreads.isEmpty()) {
        // always create at least one thread
        startThread(task);
        return true;
    }

    // can't do anything if we're over the limit
    if (activeThreadCount() >= maxThreadCount)
        return false;

    if (waitingThreads > 0) {
        // recycle an available thread
        --waitingThreads;
        enqueueTask(task);
        return true;
    }

    if (!expiredThreads.isEmpty()) {
        // restart an expired thread
        QThreadPoolThread *thread = expiredThreads.dequeue();
        Q_ASSERT(thread->runnable == 0);

        ++activeThreads;

        if (task->autoDelete())
            ++task->ref;
        thread->runnable = task;
        thread->start();
        return true;
    }

    // start a new thread
    startThread(task);
    return true;
}

void QThreadPoolPrivate::enqueueTask(QRunnable *runnable, int priority)
{
    if (runnable->autoDelete())
        ++runnable->ref;