QWaitCondition issue

  • Hi Folks,

    I have an unit test code, which should test the thread safety behavioral of a test class. The testcode is the following:
    public: threadWorker() {

    public: virtual void run();

    public: static const int logCountPerThread;
    public: static const int threadCount;
    public: static QWaitCondition waitCondition;
    public: static cacheType logs;

    private: QMutex _sync;
    private: QMutex _end;

    private: cacheType _cache;

    The definition of the static variables:
    cacheType threadWorker::logs;
    const int threadWorker::threadCount = 100;
    QWaitCondition threadWorker::waitCondition;
    const int threadWorker::logCountPerThread = 10000;

    and the worker method itself:
    void threadWorker::run() {
    qDebug() << "thread started, and _sync locked";

    qDebug() << "woke up";
    for(int count = 0; count < logCountPerThread; count++) {
        _cache.insert(core::logging::log(core::logging::logSeverity::info, QString()).id, 0);
    QMutexLocker lock(&_end);
    qDebug() << "_end locked";
    for(cacheType::iterator it = _cache.begin(); it != _cache.end(); ++it) {
        logs.insert(it.key(), 0);

    I deploy the threads from the following method:
    void logTest::concurentInsatnce() {
    QVector<threadWorker*> pool;
    for(int count = 0; count < threadWorker::threadCount; count++) {
    pool.push_back(new threadWorker());

    qDebug() << "wake all sent";
    for(threadWorker* thread: pool) {
        qDebug() << "start for waiting thread";
        qDebug() << "thread exited";
    QVERIFY2(threadWorker::logs.size() == threadWorker::logCountPerThread * threadWorker::threadCount,   "unequal object count");

    (OFF: I'm sorry for the lot's of debug outputs)

    I observed two main error cases:

    • I start only one thread by adjusting the value of threadWorker::threadCount. In this case, it seems, that the execution is terminated at the "waitCondition.wait(&_sync);", however the debugger output tell, that the wakeAll() signal sent.
    • another error case is the current state, what you can see: I start 100 threads. In this case, I see, that few threads are finising its work, and exit normaly, but another threads "don't see" the wakeAll.

    Can anybody help me?


Log in to reply

Looks like your connection to Qt Forum was lost, please wait while we try to reconnect.