Question

我不得不用我没有经验的Posix Pthreads解决读者-作家问题中的同步问题。

该任务包括产生3个阅读器和1个编写器，编写器将队列填充以供阅读器打印。我在同步访问队列时遇到麻烦。队列包含我已测试并显示为有效的方法。

如果队列已满，则应向读取器发出信号以读取/清空队列。然后，一旦其为空，编写器应再次开始使用随机值填充队列。仅适用于total_tasks。

我大多不确定锁定/解锁和信号的正确位置。

当前执行时，得到以下输出。似乎在完成任何操作之前已经完成了线程处理？

先谢谢了。

Reader Thread 0 Created
Reader Thread 1 Created
Reader Thread 2 Created
Writer Thread Created
Reader Thread 0 Finished
Reader Thread 1 Finished
Reader Thread 2 Finished
Writer Thread Finished
<<STUCK FOREVER>>

#include <stdio.h>
#include <string.h>
#include <pthread.h>

#define TRUE 1
#define FALSE 0

int total_tasks = 0; 
int fin = FALSE; 

pthread_cond_t qEmpty = PTHREAD_COND_INITIALIZER;
pthread_cond_t qFull = PTHREAD_COND_INITIALIZER;
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;

void* writer();
void* reader();

#include "rw.h"
#include "queue.h"

queue* q; 

int main()
{
    int i, j; 
    total_tasks = 15; 
    q = newQueue(5);

    pthread_t readerTID[3];
    pthread_t writerID; 

    //Create 1 Writer Thread
    printf("Writer Thread Created\n");
    pthread_create(&writerID, NULL, writer, NULL);

    printf("Writer Thread Finished\n");
    pthread_join(writerID, NULL);


    return 0; 
}

void* writer()
{
    int num1 = 0;
    int num2;
    int fin = FALSE; 

    time_t t;
    srand((unsigned) time(&t));

    while(!fin)
    {
        printf("w1");
        pthread_mutex_lock(&mutex);

        while(isFull(q))//While the queue is full 
        {
            pthread_cond_wait(&qEmpty, &mutex); //Wait for the readers to empty the queue
        }     

        if(num1 < total_tasks)//if we havent done all the tasks
        {
            while(!(isFull)) //If the queue isnt full - Fill with values 
            {
                printf("w2");
                num2 = (rand() % 20);
                enqueue(q, num1, num2);

                num1++;
            }

            pthread_cond_signal(&qFull); //Signal queue is full 
        }
        else
        {
            fin = TRUE; 
        }

        pthread_mutex_unlock(&mutex);
    }
}

Posix Pthreads的同步在读写器问题中不起作用

0 个答案: