在 c 中使用 posix 信号量的 reader-writer 应用程序中的分段错误

Question

在此代码中，编写器递增数据变量并reader打印此数据变量。任何时候只有一个写入器可以写入，但是当写入器不写入数据时，所有 reader 都可以打印数据。
附带的代码运行有时会成功，但有时会出现分段错误。

Reader-作者代码

#include<stdio.h>
#include<pthread.h>
#include<semaphore.h>
#include<stdlib.h>
#include<unistd.h>

int reader_count;
int data = 10; /* data on which writer write update & reader read */

/* sem_write: to isolate reader & writer thread */
sem_t sem_write;
/* sem_read: to increment reader counter & sem_write */
sem_t sem_read;


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

int main(void)
{
    pthread_t t[10];
    int i = 10;

    if (sem_init(&sem_read, 0, 1)) 
        exit(1);
    if (sem_init(&sem_write, 0, 1)) 
        exit(1);

    /* 5 writer create */
    while (i != 5)
        pthread_create(&t[i--], NULL, writer, NULL);
    /* 5 reader create */
    while (i)
        pthread_create(&t[i--], NULL, reader, NULL);

    /* wait for all threads to completed */
    while (i != 10)
        pthread_join(t[i++], NULL);

    sem_destroy(&sem_read);
    sem_destroy(&sem_write);
    return 0;
}

void *writer(void *arg)
{
    sem_wait(&sem_write);
    sleep(1);   /* writing work */
    data++;
    sem_post(&sem_write);
    pthread_exit(NULL);
}

void *reader(void *arg)
{
    sem_wait(&sem_read);
    reader_count++;
    if (reader_count == 1)
        sem_wait(&sem_write);
    sem_post(&sem_read);

    sleep(1);   /* reading work */
    printf("Data: %d\n", data);

    sem_wait(&sem_read);
    reader_count--;
    if (!reader_count)
        sem_post(&sem_write);
    sem_post(&sem_read);
    pthread_exit(NULL);
}

Answer 1

您在访问 t[10]

时越界了

int i = 10;
....
 while (i != 5)
    pthread_create(&t[i--], NULL, writer, NULL);

在 c 中使用 posix 信号量的 reader-writer 应用程序中的分段错误

Segmentation fault in reader-writer appilication using posix semaphore in c

c

semaphore

pthreads

readerwriterlock

Reader-作者代码