Linux内核提供的常见的进程通信机制有哪些

# Linux内核提供的常见的进程通信机制有哪些

## 引言

在现代操作系统中，进程通信（Inter-Process Communication, IPC）是实现多任务协作的核心机制。Linux作为类Unix操作系统的代表，提供了丰富多样的IPC机制以满足不同场景下的进程间数据交换需求。本文将深入剖析Linux内核中常见的进程通信机制，包括其工作原理、实现细节、适用场景及实际应用案例。

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## 一、管道（Pipe）与命名管道（FIFO）

### 1.1 匿名管道（Pipe）
```c
#include <unistd.h>
int pipe(int pipefd[2]);

#include <sys/stat.h>
int mkfifo(const char *pathname, mode_t mode);

#include <sys/msg.h>
int msgget(key_t key, int msgflg);
int msgsnd(int msqid, const void *msgp, size_t msgsz, int msgflg);
ssize_t msgrcv(int msqid, void *msgp, size_t msgsz, long msgtyp, int msgflg);

#include <sys/sem.h>
int semget(key_t key, int nsems, int semflg);
int semop(int semid, struct sembuf *sops, unsigned nsops);

#include <sys/shm.h>
int shmget(key_t key, size_t size, int shmflg);
void *shmat(int shmid, const void *shmaddr, int shmflg);

------ Messages Limits --------
max queues system wide = 32000
max size of message (bytes) = 8192
default max size of queue (bytes) = 16384

------ Shared Memory Limits --------
max number of segments = 4096
max seg size (kbytes) = 18014398509465599
max total shared memory (kbytes) = 18014398509481980

------ Semaphore Limits --------
max number of arrays = 32000
max semaphores per array = 32000
max semaphores system wide = 1024000000
max ops per semop call = 500

#include <mqueue.h>
mqd_t mq_open(const char *name, int oflag, mode_t mode, struct mq_attr *attr);

#include <semaphore.h>
int sem_init(sem_t *sem, int pshared, unsigned int value);

#include <sys/mman.h>
void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset);

#include <signal.h>
void (*signal(int sig, void (*handler)(int)))(int);

union sigval {
    int sival_int;
    void *sival_ptr;
};
int sigqueue(pid_t pid, int sig, const union sigval value);

#include <sys/socket.h>
int socket(int domain, int type, int protocol);

本地通信延迟（同一主机）：
  - UNIX域套接字：~0.5μs
  - TCP本地回环：~1.2μs
  - 管道：~0.8μs

#include <fcntl.h>
int fcntl(int fd, int cmd, struct flock *lock);

void *mmap(void *addr, size_t length, int prot, int flags, int fd, off_t offset);

graph TD
    A[task_struct] --> B[files_struct]
    B --> C[pipe_inode_info]
    A --> D[signal_struct]
    A --> E[mm_struct]
    E --> F[vm_area_struct]
    F --> G[shmid_kernel]