在两个生产者和一个消费者的线程安全队列中提升条件不起作用

Question

I have two threads that add to a "thread safe" queue. However when the second thread attempts to "push" contents. The consumer is not notified that contents are available. The queue continues to grow but the notify_one() never notifies the conditional in the consuming method. Why is this?

#ifndef CONCURRENT_QUEUE_H
#define CONCURRENT_QUEUE_H

#include <queue>
#include <boost/thread.hpp>

template<typename Data>
class concurrent_queue {
private:
    std::queue<Data> the_queue;
    mutable boost::mutex the_mutex;
    boost::condition_variable the_condition_variable;
public:
    void push(Data const& data) {
        boost::mutex::scoped_lock lock(the_mutex);
        the_queue.push(data);
        lock.unlock();
        the_condition_variable.notify_one();
    }

    void wait_and_pop(Data& popped_value) {
        boost::mutex::scoped_lock lock(the_mutex);
        while(the_queue.empty()) {
            the_condition_variable.wait(lock);
        }

        popped_value=the_queue.front();
        the_queue.pop();
    }
};
#endif

---

This code does work in Fedora 14 using boost 1.51.0, however it does not work in boost 1.50.0 in windows 7.

INCLUDEPATH += \
    . \
    /home/mehoggan/Devel/x86-fps/boost_1_50_0/include

LDFLAGS += -Wl,-rpath=/home/mehoggan/Devel/x86-fps/boost_1_50_0/lib

LIBS += \
    -L/home/mehoggan/Devel/x86-fps/boost_1_50_0/lib \
    -lboost_system \
    -lboost_thread \
    -lz

#ifndef CONCURRENT_QUEUE_H
#define CONCURRENT_QUEUE_H

#include <queue>
#include <boost/thread.hpp> // Using boost 1.50.0

template<typename Data>
class concurrent_queue {
private:
    std::queue<Data> the_queue;
    mutable boost::mutex the_mutex;
    boost::condition_variable the_condition_variable;
public:
    void push(Data const& data) {
        boost::mutex::scoped_lock lock(the_mutex);
        the_queue.push(data);
        lock.unlock();
        the_condition_variable.notify_all();
    }

    void wait_and_pop(Data& popped_value) {
        boost::mutex::scoped_lock lock(the_mutex);
        while(the_queue.empty()) {
            the_condition_variable.wait(lock);
        }

        popped_value=the_queue.front();
        the_queue.pop();
    }
};
#endif

concurrent_queue<int> the_queue;

void thread1func() {
    do {
        the_queue.push(1);
    } while (true);
}

void thread2func() {
    do {
        the_queue.push(2);
    } while (true);
}

void thread3func() {
    do {
        int read;
        the_queue.wait_and_pop(read);

        std::cout << "I read from thread " << read << std::endl;
    } while (true);
}

int main(int argc, char *argv[]) {
    boost::thread thread1 = boost::thread(thread1func);
    boost::thread thread2 = boost::thread(thread2func);
    boost::thread thread3 = boost::thread(thread3func);

    thread1.join();
    thread2.join();
    thread3.join();
}

Answer 1

Your Makefile doesn't seem to use -pthread/-mthreads. In general don't expect your code to work at all if you are not asking for the compiler to generate multi-threaded code.