eventfd 進程間同步

先打印“parent”，後打印“child”

#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <sys/eventfd.h>
#include <unistd.h>
#include <sys/wait.h>
#include <sched.h>
#define STACK_SIZE (1024 * 1024)

int child(void *arg) {
        int efd = *((int*)arg);

        // 等待父進程的通知
        uint64_t u;
        ssize_t ret;
        ret = read(efd, &u, sizeof(uint64_t));
        if (ret != sizeof(uint64_t)) {
                printf("child error\n");
        }

        printf("child\n");

        return 0;
}

int main() {
		int efd = eventfd(0, 0);
		if (efd < 0) {
        	printf("create eventfd error\n");
        	return -1;
    	}
    
        char *stack = malloc(STACK_SIZE);
        char *stackTop = stack + STACK_SIZE;
        
        clone(child, stackTop, SIGCHLD, (void*)(&efd));

        printf("parent\n");

        // 通知子進程
        ssize_t ret = write(efd, &(uint64_t){1}, sizeof(uint64_t));
        if (ret != sizeof(uint64_t))    {
                printf("parent error\n");
                return -1;
        }
}

結果：
parent
child

參考
https://zhuanlan.zhihu.com/p/40572954