在 c 中使用 posix 信号量的读取器-写入器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，读取器打印此数据变量。任何时候只有一个写入器可以写入，但当写入器不写入数据时，所有读取器都可以打印数据。
附加的代码有时会成功运行，但有时会出现分段错误。

读写器代码

#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: %dn", 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

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