linux - Unix:共享内存。 shm_open() 返回 -1

Question

注意:实际问题在于使用 fork() 函数。所以找到了解决方案。

---

 //create shared memoery
        int shmfd;
        void *shared_memory = (void *)0;
        shmfd = shm_open("/shm2_rev_to_upp", O_RDWR | O_CREAT | O_EXCL, 0666); //reverse to upper
        if (shmfd == -1) {
           perror("shm_open");
           exit(1);
        }

        if(ftruncate(shmfd, sizeof(struct shared_use_st)) == -1){
          perror("ftruncate");
          exit(1);
        }

        shared_memory = mmap(NULL, sizeof(struct shared_use_st), PROT_READ | PROT_WRITE, MAP_SHARED, shmfd, 0);

        if(shared_memory == MAP_FAILED){
          perror("mmap");
          exit(1);
        }

    //some code here

    munmap(shared_memory, sizeof(struct shared_use_st));
    shm_unlink("/shm2_rev_to_upp");
    close(shmfd);

我在运行时遇到了这个错误

shm_open: File exists

然后 shm_open() 返回 -1 为什么会这样？!! 请注意，我运行程序的头几次，错误没有出现!!

我该如何解决这个问题？!

Answer 1

手册页解释了各种错误代码:

EEXIST: Both O_CREAT and O_EXCL were specified to shm_open() and the shared memory object specified by name already exists.