Question

我正在为我的操作系统课程做一个CPU调度模拟器项目。该程序应包含两个线程：生产者和消费者线程。生产者线程包括在系统中生成进程的生成器和选择多个进程的长期调度程序，并将它们放在名为Buffer的ReadyQueue类型的对象中（由消费者和生产者共享对象）。消费者线程包括短期调度程序，其从队列中获取进程并启动调度算法。我编写了整个程序而没有使用线程，它工作正常，但现在我需要添加线程，我从来没有使用线程所以我很感激，如果有人可以告诉我如何修改我在下面显示的代码来实现所需的线程。 / p>

这是Producer类的实现：

public class Producer extends Thread{

    ReadyQueue Buffer = new ReadyQueue(20); // Shared Buffer of size 20 between consumer and producer  
    JobScheduler js = new JobScheduler(Buffer);

    private boolean systemTerminate = false; // Flag to tell Thread that there are no more processes in the system 

    public Producer(ReadyQueue buffer) throws FileNotFoundException{
        Buffer = buffer;
        Generator gen = new Generator();   // Generator generates processes and put them in a vector called memory     
        gen.writeOnFile();
    }

    @Override
    public  void run() {

        synchronized(this){
            js.select();  // Job Scheduler will select processes to be put in the Buffer

            Buffer = (ReadyQueue) js.getSelectedProcesses();

            while(!Buffer.isEmpty()){      
                try {
                    wait();     // When Buffer is empty wait until getting notification
                } catch (InterruptedException e) {
                    e.printStackTrace();
                }
                systemTerminate = js.select();
                Buffer = (ReadyQueue) js.getSelectedProcesses();
                if(systemTerminate)     // If the flag's value is true the thread yields
                    yield();
            }
        }
    }   

    public ReadyQueue getReadyQueue(){
        return Buffer;
    }
}

这是Consumer类实现：

public class Consumer extends Thread{

    ReadyQueue Buffer = new ReadyQueue(20);
    Vector<Process> FinishQueue = new Vector<Process>();
    MLQF Scheduler ;
    public Consumer(ReadyQueue buffer){
        Buffer = buffer;
        Scheduler = new MLQF(Buffer,FinishQueue);   // An instance of the multi-level Queue Scheduler
    }

    @Override
    public  void run() {
        int count = 0;         // A counter to track the number of processes

        while(true){
            synchronized(this){
                Scheduler.fillQueue(Buffer);    // Take contents in Buffer and put them in  a separate queue in the scheduler
                        Scheduler.start();              // Start Scheduling algorithm
                count++;
            }
            if(count >= 200)   // If counter exceeds the maximum number of processes thread must yeild
                yield();
            notify();               // Notify Producer thread when buffer is empty
        }
    }

    public void setReadyQueue(ReadyQueue q){
        Buffer = q;
    }
}

这是主线程：

public class test {

    public static void main(String[] args) throws FileNotFoundException,InterruptedException {       
        ReadyQueue BoundedBuffer = new ReadyQueue(20);
        Producer p = new Producer(BoundedBuffer);
        Consumer c = new Consumer(p.getReadyQueue());
        p.start();
        System.out.println("Ready Queue: "+p.getReadyQueue());
        p.join();
        c.start();
        c.join();
        }
}

提前谢谢。

Answer 1

您的代码存在的一个问题是，它遇到了多线程生产者/消费者模型中的常见错误。您必须使用while查看wait()次来电。例如：

try {
    // we must do this test in a while loop because of consumer race conditions
    while(!Buffer.isEmpty()) {
        wait();     // When Buffer is empty wait until getting notification
        ...
    }
} catch (InterruptedException e) {
    e.printStackTrace();
}

问题在于，如果你有多个正在消费的线程，你可以notify一个线程，然后另一个线程通过并将刚刚添加的项目出列。当一个线程在被通知后从WAIT队列移动到RUN队列时，它通常会被放在队列的末尾，可能在等待this同步的其他线程之后。

有关详细信息，请参阅我的documentation about this。

生产者/消费者线程不给出结果

1 个答案: