如何正确退出可能正在等待std::condition_variable的std::线程

我有一个类，它实现了一个线程生产者/消费者系统，使用一个互斥锁和两个条件变量进行同步。当有物品需要使用时，生产者向消费者线程发出信号，而消费者在消费了物品后向生产者线程发出信号。线程继续生产和消费，直到析构函数通过设置一个布尔变量请求它们退出。因为任何一个线程都可能在等待一个条件变量，所以我必须实现对quit变量的第二次检查，这感觉是错误的和混乱的…

我将问题简化为以下示例(在GNU/Linux上使用g++4.7):

// C++11and Boost required.
#include <cstdlib> // std::rand()
#include <cassert>
#include <boost/circular_buffer.hpp>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <iostream>
#include <mutex>
#include <thread>
#include <vector>
// Creates a single producer and single consumer thread.
class prosumer
{
    public:
        // Create the circular buffer and start the producer and consumer thread.
        prosumer()
            : quit_{ false }
            , buffer_{ circular_buffer_capacity }
            , producer_{ &prosumer::producer_func, this }
            , consumer_{ &prosumer::consumer_func, this }
        {}
        // Set the quit flag and wait for the threads to exit.
        ~prosumer()
        {
            quit_ = true;
            producer_.join();
            consumer_.join();
        }
    private:
        // Thread entry point for the producer.
        void producer_func()
        {
            // Value to add to the ringbuffer to simulate data.
            int counter = 0;
            while ( quit_ == false )
            {
                // Simulate the production of some data.
                std::vector< int > produced_items;
                const auto items_to_produce = std::rand() % circular_buffer_capacity;
                for ( int i = 0; i < items_to_produce; ++i )
                {
                    produced_items.push_back( ++counter );
                }
                // Get a lock on the circular buffer.
                std::unique_lock< std::mutex > lock( buffer_lock_ );
                // Wait for the buffer to be emptied or the quit flag to be set.
                buffer_is_empty_.wait( lock, [this]()
                        {
                            return buffer_.empty() == true || quit_ != false;
                        } );
                // Check if the thread was requested to quit.
                if ( quit_ != false )
                {
                    // Don't let the consumer deadlock.
                    buffer_has_data_.notify_one();
                    break;
                }
                // The buffer is locked by this thread. Put the data into it.
                buffer_.insert( std::end( buffer_ ), std::begin( produced_items ), std::end( produced_items ) );
                // Notify the consumer that the buffer has some data in it.
                buffer_has_data_.notify_one();
            }
            std::cout << "producer thread quitn";
        }

        // Thread entry for the consumer.
        void consumer_func()
        {
            int counter_check = 0;
            while ( quit_ == false )
            {
                std::unique_lock< std::mutex > lock( buffer_lock_ );
                // Wait for the buffer to have some data before trying to read from it.
                buffer_has_data_.wait( lock, [this]()
                        {
                            return buffer_.empty() == false || quit_ != false;
                        } );
                // Check if the thread was requested to quit.
                if ( quit_ != false )
                {
                    // Don't let the producer deadlock.
                    buffer_is_empty_.notify_one();
                    break;
                }
                // The buffer is locked by this thread. Simulate consuming the data.
                for ( auto i : buffer_ ) assert( i == ++counter_check );
                buffer_.clear();
                // Notify the producer thread that the buffer is empty.
                buffer_is_empty_.notify_one();
            }
            std::cout << "consumer thread quitn";
        }
        // How many items the circular buffer can hold. 
        static const int circular_buffer_capacity = 64;
        // Flag set in the destructor to signal the threads to stop.
        std::atomic_bool quit_;
        // Circular buffer to hold items and a mutex for synchronization.
        std::mutex buffer_lock_;
        boost::circular_buffer< int > buffer_;
        // Condition variables for the threads to signal each other.
        std::condition_variable buffer_has_data_;
        std::condition_variable buffer_is_empty_;
        std::thread producer_;
        std::thread consumer_;
};

int main( int argc, char **argv )
{
    (void)argc; (void) argv;
    prosumer test;
    // Let the prosumer work for a little while.
    std::this_thread::sleep_for( std::chrono::seconds( 3 ) );
    return EXIT_SUCCESS;
}

如果你看一下producer_func和consumer_func线程函数，你可以看到它们循环，直到退出变量被prosumer析构函数设置，但它们也会在锁定循环缓冲区后再次检查退出变量。如果设置了quit变量，它们会互相发送信号以防止死锁。

我的另一个想法是在析构函数的条件变量上调用notify_one()，这是一个更好的解决方案吗?

有更好的方法吗?

更新1:我忘了提一下，在这种情况下，当线程被请求退出时，消费者不需要消耗循环缓冲区中的任何剩余数据，如果生产者产生更多一点也没关系。只要它们都退出并且不死锁，就可以了。