我目前正在编写一个应用程序(使用boost),该应用程序将有一个生产者抓取框架和一个消费者阅读框架。我在生产者中添加了一个sleep语句来模拟抓取框架的时间。我希望消费者在条件变量上等待,并在生产者的第一个通知中被唤醒以读取框架。但是,我在日志文件中看到的是消费者(主线程)在等待条件变量,但是生产者在消费者退出等待读取帧之前经历了几次通知。

这是我的工人。

class Worker {
static log4cxx::LoggerPtr m_log;

public:
    Worker();
    virtual ~Worker();

    void start();
    void stop();
    void getCurrentFrame(/*cv::Mat& frame*/);

private:
    void processFrames();

    volatile bool m_stopRequested;

    bool m_bFrameReady;
    boost::mutex m_mutex;
    boost::condition_variable condF;

    boost::shared_ptr<boost::thread> m_thread;
};


工作人员

LoggerPtr Worker::m_log(Logger::getLogger("fdx.Worker"));

Worker::Worker() {
    m_bFrameReady = false;

    LOG4CXX_INFO(m_log, "Worker() c-tor");

    m_stopRequested = false;

}

Worker::~Worker() {
    LOG4CXX_INFO(m_log, "Worker() d-tor");
}

void Worker::start()
{
    LOG4CXX_INFO(m_log, "Worker()::start()");
    assert(!m_thread);

    m_thread = boost::shared_ptr<boost::thread>(new boost::thread(&Worker::processFrames, this));

    LOG4CXX_WARN(m_log, "Worker()::start() thread[" << m_thread->get_id() << "] started!");
}

void Worker::stop()
{
    LOG4CXX_INFO(m_log, "Worker()::stop()");

    if(m_thread != NULL)
    {
        LOG4CXX_INFO(m_log, "Worker()::stop() ThrId [" << m_thread->get_id() << "]");
        m_stopRequested = true;
        m_thread->join();
    }
    else
    {
        LOG4CXX_WARN(m_log, "Worker()::stop() The thread for this camera was never started.");
    }

LOG4CXX_INFO(m_log, "Worker()::stop() thread stopped!");
}

void Worker::processFrames()
{
    LOG4CXX_WARN(m_log, "Worker()::processFrames() Thread[" << boost::this_thread::get_id() << "] starting...");

    int rc = 0;
    std::stringstream ss;

    while(!this->m_stopRequested)
    {
        boost::mutex::scoped_lock lock(m_mutex);
        LOG4CXX_WARN(m_log, "Worker()::processFrames() Got a Write lock");

        m_bFrameReady = true;
        LOG4CXX_WARN(m_log, "Worker()::processFrames() Frame ready set to true");

        boost::this_thread::sleep(boost::posix_time::milliseconds(200));

        LOG4CXX_WARN(m_log, "Worker()::processFrames() Write Un-lock");

        lock.unlock();

        LOG4CXX_WARN(m_log, "Worker()::processFrames() Notify");

        condF.notify_one();
    }
}

void Worker::getCurrentFrame()
{
    boost::mutex::scoped_lock lock(m_mutex);

    while(!this->m_bFrameReady)
    {
        LOG4CXX_WARN(m_log, "Worker::getCurrentFrame() wait for Read lock");
        condF.wait(lock);
    }

    LOG4CXX_WARN(m_log, "Worker::getCurrentFrame() Frame ready; Got a Read lock");

    m_bFrameReady = false;

    LOG4CXX_WARN(m_log, "Worker::getCurrentFrame() Frame ready set to false");

    LOG4CXX_WARN(m_log, "Worker::getCurrentFrame() Read Un-lock");
    lock.unlock();

}


main.cpp

LoggerPtr logger(Logger::getLogger("TCamApp"));

int main(int argc, char** argv)
{
int rc = 0;

char cwDir[FILENAME_MAX];

Worker* pWorker = NULL;

memset(cwDir, 0, sizeof(cwDir));
getcwd(cwDir, FILENAME_MAX);

std::cout << "Current Working Dir[" << cwDir << "]" << endl;

std::stringstream ss;
ss << "" << cwDir << "/logs.properties";
std::cout << "logs.properties file[" << ss.str() << "]" << endl;

struct stat st;
if(!stat(ss.str().c_str(), &st))
{
    PropertyConfigurator::configure(ss.str());
}
else
{
    BasicConfigurator::configure();
}

LOG4CXX_INFO(logger, "Application [" << argv[0] << "] starting...");

pWorker = new Worker();
assert(pWorker);

pWorker->start();

for(int i = 0; i < 100; i++)
{
    pWorker->getCurrentFrame();

    LOG4CXX_INFO(logger, "Iteration [" << i << "]");


    //boost::this_thread::sleep(boost::posix_time::milliseconds(20));
}

pWorker->stop();

LOG4CXX_INFO(logger, "Application [" << argv[0] << "] stopping...");

return rc;
}


以下是我的日志文件的摘录:

2012-07-11 15:33:53,943 [0x7f5707bcf780] INFO  TCamApp - Application [/home/op/workspace/TestThreads/Debug/TestThreads] starting...
2012-07-11 15:33:53,944 [0x7f5707bcf780] WARN  fdx.Worker - Worker()::start() thread[0x15e4c50] started!
2012-07-11 15:33:53,944 [0x7f5707bcf780] WARN  fdx.Worker - Worker::getCurrentFrame() wait for Read lock
2012-07-11 15:33:53,944 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Thread[0x15e4c50] starting...
2012-07-11 15:33:53,944 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Got a Write lock
2012-07-11 15:33:53,944 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Frame ready set to true
2012-07-11 15:33:54,145 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Write Un-lock
2012-07-11 15:33:54,145 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Notify
2012-07-11 15:33:54,145 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Got a Write lock
2012-07-11 15:33:54,145 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Frame ready set to true
2012-07-11 15:33:54,345 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Write Un-lock
2012-07-11 15:33:54,345 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Notify
2012-07-11 15:33:54,345 [0x7f5707bcf780] WARN  fdx.Worker - Worker::getCurrentFrame() Frame ready; Got a Read lock
2012-07-11 15:33:54,345 [0x7f5707bcf780] WARN  fdx.Worker - Worker::getCurrentFrame() Frame ready set to false
2012-07-11 15:33:54,345 [0x7f5707bcf780] WARN  fdx.Worker - Worker::getCurrentFrame() Read Un-lock
2012-07-11 15:33:54,346 [0x7f5707bcf780] INFO  TCamApp - Iteration [0]
2012-07-11 15:33:54,346 [0x7f5707bcf780] WARN  fdx.Worker - Worker::getCurrentFrame() wait for Read lock
2012-07-11 15:33:54,346 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Got a Write lock
2012-07-11 15:33:54,346 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Frame ready set to true
2012-07-11 15:33:54,546 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Write Un-lock
2012-07-11 15:33:54,547 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Notify
2012-07-11 15:33:54,547 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Got a Write lock
2012-07-11 15:33:54,547 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Frame ready set to true
2012-07-11 15:33:54,747 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Write Un-lock
2012-07-11 15:33:54,747 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Notify
2012-07-11 15:33:54,747 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Got a Write lock
2012-07-11 15:33:54,747 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Frame ready set to true
2012-07-11 15:33:54,948 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Write Un-lock
2012-07-11 15:33:54,948 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Notify
2012-07-11 15:33:54,948 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Got a Write lock
2012-07-11 15:33:54,948 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Frame ready set to true
2012-07-11 15:33:55,148 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Write Un-lock
2012-07-11 15:33:55,149 [0x7f57059c1700] WARN  fdx.Worker - Worker()::processFrames() Notify
2012-07-11 15:33:55,149 [0x7f5707bcf780] WARN  fdx.Worker - Worker::getCurrentFrame() Frame ready; Got a Read lock
2012-07-11 15:33:55,149 [0x7f5707bcf780] WARN  fdx.Worker - Worker::getCurrentFrame() Frame ready set to false
2012-07-11 15:33:55,149 [0x7f5707bcf780] WARN  fdx.Worker - Worker::getCurrentFrame() Read Un-lock
2012-07-11 15:33:55,149 [0x7f5707bcf780] INFO  TCamApp - Iteration [1]


从日志中可以看到,主线程等待读取,但另一个线程将在主线程退出其wait()之前产生多个通知。

我研究了一些内容,并认为我已经正确编码了,但是它的表现不符合我的预期。对于解决方案的任何建议,我将不胜感激。谢谢。

最佳答案

这是预料之中的,因为生产者线程正在休眠且互斥锁处于锁定状态。一旦唤醒,它将通知使用者并再次锁定它。对于谁将锁定互斥锁,不能保证“公平”。

您似乎要实现的是异步队列。它通常包含2个条件变量:一个在队列已满时抑制生产者,另一个在队列为空时抑制使用者。无论生产或消费队列中的项目花费多长时间,互斥锁仅在推/弹出操作期间会被锁定-这应该是非常快的。

您的sleep语句可能只是使操作系统的调度程序偏向于将优先级赋予生产者线程。将sleep移出关键部分,以模拟推送操作之外的处理,您应该看到使用者线程的响应速度更快。

与此相关的是,您可以轮询一个前哨对象(即特殊值,例如指针队列中的空指针),而不是轮询原子变量以终止,以使使用者线程知道它们必须停止。

关于c++ - Boost Threads生产者/消费者意外行为,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/11441965/

10-11 23:00
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