寻找对我的读者/作家实施的批评

我在C 11中实现了读者/作家问题…我想知道它是什么问题，因为这些事情很难自行预测。

• 共享数据库：
  • 读者可以访问数据库时
  • 当没有读者或作家时，作家可以访问数据库
  • 一个线程一次操纵状态变量

该示例有3位读者和1位作家，但也使用2个或更多作家....

代码：

class ReadersWriters {
private:
    int AR; // number of active readers
    int WR; // number of waiting readers
    int AW; // number of active writers
    int WW; // number of waiting writers
    mutex lock;
    mutex m;
    condition_variable okToRead;
    condition_variable okToWrite;
    int data_base_variable;
public:
    ReadersWriters() : AR(0), WR(0), AW(0), WW(0), data_base_variable(0) {}
    void read_lock() {
        unique_lock<mutex> l(lock);
        WR++; // no writers exist
        // is it safe to read?
        okToRead.wait(l, [this](){ return WW == 0; });
        okToRead.wait(l, [this](){ return AW == 0; });
        WR--; // no longer waiting
        AR++;  // now we are active
    }
    void read_unlock() {
        unique_lock<mutex> l(lock);
        AR--; // no longer active
        if (AR == 0 && WW > 0) { // no other active readers
            okToWrite.notify_one(); // wake up one writer
        }
    }
    void write_lock() {
        unique_lock<mutex> l(lock);
        WW++; // no active user exist
        // is it safe to write?
        okToWrite.wait(l, [this](){ return AR == 0; });
        okToWrite.wait(l, [this](){ return AW == 0; });
        WW--; // no longer waiting
        AW++; // no we are active
    }
    void write_unlock() {
        unique_lock<mutex> l(lock);
        AW--; // no longer active
        if (WW > 0) { // give priority to writers
            okToWrite.notify_one(); // wake up one writer
        }
        else if (WR > 0) { // otherwize, wake reader
            okToRead.notify_all(); // wake all readers
        }
    }
    void data_base_thread_write(unsigned int thread_id) {
        for (int i = 0; i < 10; i++) {
            write_lock();
            data_base_variable++;
            m.lock();
            cout << "data_base_thread: " << thread_id << "...write: " << data_base_variable << endl;
            m.unlock();
            write_unlock();
            std::this_thread::sleep_for(std::chrono::milliseconds(10));
        }
    }
    void data_base_thread_read(unsigned int thread_id) {
        for (int i = 0; i < 10; i++) {
            read_lock();
            m.lock();
            cout << "data_base_thread: " << thread_id << "...read: " << data_base_variable << endl;
            m.unlock();
            read_unlock();
            std::this_thread::sleep_for(std::chrono::milliseconds(10));
        }
    }
};
int main() {
    // your code goes here
    ReadersWriters rw;
    thread w1(&ReadersWriters::data_base_thread_write, &rw, 0);
    thread r1(&ReadersWriters::data_base_thread_read, &rw, 1);
    thread r2(&ReadersWriters::data_base_thread_read, &rw, 2);
    thread r3(&ReadersWriters::data_base_thread_read, &rw, 3);
    w1.join();
    r1.join();
    r2.join();
    r3.join();
    cout << "nThreads successfully completed..." << endl;
    return 0;
}