pthread_once_* 简单使用-优快云博客

本文通过一个C语言示例程序详细介绍了如何使用pthread_once进行初始化操作，并结合pthread_mutex来实现线程间的同步。主要探讨了在多线程环境下如何确保代码块仅被执行一次以及如何正确地加锁解锁。

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

pthread_once_t once_block = PTHREAD_ONCE_INIT;
pthread_mutex_t mutex;

void once_init_routine(void)
{
    int status;
    status = pthread_mutex_init(&mutex, NULL);
    if (status != 0) {
        perror("Init Mutex error!");
    }
    printf("once_init_routine success!\n");
}

void *thread_routine(void *arg)
{
    int status;
    status = pthread_once(&once_block, once_init_routine);
    if (status != 0) {
        perror("pthread_once error!\n");
    }

    status = pthread_mutex_lock(&mutex);
    if (status != 0) {
        perror("Lock mutex error!");
    }
    printf("thread routine has locked the mutex.\n");
    status = pthread_mutex_unlock(&mutex);
    if (status != 0) {
        perror("pthread_mutex_unlock() error!");
    }

    return 0;
}

int main(int argc, char *argv[])
{
    pthread_t thread_id;
    
    int status;
    
    status = pthread_create(&thread_id, NULL, thread_routine, NULL);
    if (status != 0)  {
        perror("pthread_create() error!");
    }

    status = pthread_once(&once_block, once_init_routine);
    if (status != 0) {
        perror("pthread_once() error!");
    }
    
    status = pthread_mutex_lock(&mutex);
    if (status != 0) {
        perror("pthread_mutex_lock error!");
    }
    printf("Main has locked the mutex.\n");
    status = pthread_mutex_unlock(&mutex);
    if (status != 0) {
        perror("pthread_mutex_unlock()!");
    }

    status = pthread_join(thread_id, NULL);
    if (status != 0) {
        exit(-1);
    }

    return 0;
}

转载于:https://my.oschina.net/tsh/blog/1498774