C/C++中多进程之间的线程如何利用XSI IPC共享内存分配互斥量进行同步

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#include <stdio.h>

#include <stdlib.h>

#include <pthread.h>

#include <unistd.h>

#include <sys/wait.h>

#include <errno.h>

#include <sys/types.h>

#include <sys/ipc.h>

#include <sys/shm.h>

#define handle_error_en(en, msg) \

do { errno = en; perror(msg); exit(EXIT_FAILURE); } while (0)

static pthread_mutex_t *mtx;

static void *original_owner_thread(void *ptr){

printf("[original owner] Setting lock...\n");

pthread_mutex_lock(mtx);

printf("[original owner] Locked. Now exiting without unlocking.\n");

pthread_exit(NULL);//加锁后退出不释放锁

}

int main(){

pid_t pid_robust;

int shmid;

        //利用XSI IPC，分配互斥量的内存

shmid = shmget(IPC_PRIVATE,sizeof(pthread_mutex_t),IPC_CREAT|IPC_EXCL);

//获取内存区指针

         mtx=shmat(shmid,0,0);

pid_robust = fork();

int proc_status;

int ret;

if(pid_robust <0 ){

                printf("[main process] fork error!\n");

return -1;

        } 

if (pid_robust > 0){

pthread_t thr_p;

pthread_mutexattr_t attr;

pthread_mutexattr_init(&attr);

pthread_mutexattr_setpshared(&attr,PTHREAD_PROCESS_SHARED);

pthread_mutexattr_setrobust(&attr, PTHREAD_MUTEX_ROBUST);

pthread_mutex_init(mtx, &attr);

pthread_create(&thr_p, NULL, original_owner_thread, NULL);

}else if(0==pid_robust){

int err_code;

sleep(2);

printf("[fork main thread] Attempting to lock the robust mutex.\n");

err_code = pthread_mutex_lock(mtx);

if (err_code == EOWNERDEAD) {

printf("[fork main thread] pthread_mutex_lock() returned EOWNERDEAD\n");

printf("[fork main thread] Now make the mutex consistent\n");

err_code = pthread_mutex_consistent(mtx);//调用函数进行更换锁的属主，也就是锁从以前拥有者更换为当起线程

if (err_code != 0){

handle_error_en(err_code, "pthread_mutex_consistent");

}

printf("[fork main thread] Mutex is now consistent; unlocking\n");

err_code = pthread_mutex_unlock(mtx);

if (err_code == 0 ){

printf("[fork main thread] pthread_mutex_lock() unexpectedly succeeded\n");

}else{

handle_error_en(err_code, "pthread_mutex_unlock");

}

}else{

printf("[fork main thread] lock success! %d\n",err_code);

}

exit(0);

}

printf("parent main thread waiting fork process \n");

sleep(2);

if(waitpid(pid_robust,&proc_status,0) < 0){

printf("[parent main thread] waiting for fork process error.\n");

        return 127;

} 

if(WIFEXITED(proc_status)){

return 0;

}

return 127;

}

···

编译：

gcc -lpthread -o  muti_proc_thread_lock muti_proc_thread_lock.c

结果：

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