如何使用共享内存在进程之间共享信号量

问题描述

我必须将 N 个客户端进程与一台服务器同步.这些进程由我声明了 3 个信号量的主函数分叉.我决定使用 POSIX 信号量，但我不知道如何在这些进程之间共享它们.我认为共享内存应该可以正常工作，但我有一些问题:

I have to synchronize N client processes with one server. These processes are forked by a main function in which I declared 3 semaphores. I decided to use POSIX semaphores but I don't know how to share them between these processes. I thought that shared memory should work correctly, but I have some questions:

• 如何在我的段中分配正确的内存空间?
• 我可以在 shmget 的 size_t 字段中使用 sizeof(sem_t) 来准确分配我需要的空间吗?
• 有人有类似这种情况的例子吗?

• How can I allocate the right space of memory in my segment?
• Can I use sizeof(sem_t) in size_t field of shmget in order to allocate exactly the space I need?
• Does anyone have some examples similar to this situation?

推荐答案

轻松分享命名POSIX信号量

It's easy to share named POSIX semaphores

• 为您的信号量选择一个名称

• Choose a name for your semaphore

#define SNAME "/mysem"

在创建它们的过程中使用 sem_open 和 O_CREAT

sem_t *sem = sem_open(SNAME, O_CREAT, 0644, 3); /* Initial value is 3. */

在其他进程中打开信号量

Open semaphores in the other processes

sem_t *sem = sem_open(SEM_NAME, 0); /* Open a preexisting semaphore. */

如果你坚持使用共享内存，那当然是可能的.

int fd = shm_open("shmname", O_CREAT, O_RDWR);
ftruncate(fd, sizeof(sem_t));
sem_t *sem = mmap(NULL, sizeof(sem_t), PROT_READ | PROT_WRITE,
    MAP_SHARED, fd, 0);

sem_init(sem, 1, 1);

我还没有测试过上述内容，所以它可能完全是疯狂的.

I haven't tested the above so it could be completely bonkers.

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