Linux
linux下多进程共享资源互斥访问实例
linux下多进程共享资源互斥访问实例
#include #include #include #include #include #include pthread_mutex_t* g_mutex; //创建共享的mutex void init_mutex(void) { int ret; //g_mutex
- #include <stdio.h>
- #include <stdlib.h>
- #include <unistd.h>
- #include <fcntl.h>
- #include <sys/mman.h>
- #include <pthread.h>
- pthread_mutex_t* g_mutex;
- //创建共享的mutex
- void init_mutex(void)
- {
- int ret;
- //g_mutex一定要是进程间可以共享的,否则无法达到进程间互斥
- g_mutex=(pthread_mutex_t*)mmap(NULL, sizeof(pthread_mutex_t), PROT_READ|PROT_WRITE, MAP_SHARED|MAP_ANONYMOUS, -1, 0);
- if( MAP_FAILED==g_mutex ) //使用匿名存储映射,只能在具有亲缘关系的进程间使用,
- { //若要在非亲缘关系进程间使用需要mmap文件映射结合SHARED //标志或者共享内存IPC
- perror("mmap");
- exit(1);
- }
- //设置attr的属性
- pthread_mutexattr_t attr;
- pthread_mutexattr_init(&attr);
- //一定要设置为PTHREAD_PROCESS_SHARED
- //具体可以参考http://blog.chinaunix.net/u/22935/showart_340408.html
- ret=pthread_mutexattr_setpshared(&attr,PTHREAD_PROCESS_SHARED);
- if( ret!=0 )
- {
- perror("init_mutex pthread_mutexattr_setpshared");
- exit(1);
- }
- pthread_mutex_init(g_mutex, &attr);
- }
- int main(int argc, char *argv[])
- {
- init_mutex();
- int ret;
- char str1[]="this is child process/r/n";
- char str2[]="this is father process/r/n";
- int fd=open("tmp", O_RDWR|O_CREAT|O_TRUNC, 0666);
- if( -1==fd )
- {
- perror("open");
- exit(1);
- }
- pid_t pid;
- pid=fork();
- if( pid<0 )
- {
- perror("fork");
- exit(1);
- }
- else if( 0==pid )
- {
- ret=pthread_mutex_lock(g_mutex);
- if( ret!=0 )
- {
- perror("child pthread_mutex_lock");
- }
- sleep(10);//测试是否能够阻止父进程的写入
- write(fd, str1, sizeof(str1));
- ret=pthread_mutex_unlock(g_mutex);
- if( ret!=0 )
- {
- perror("child pthread_mutex_unlock");
- }
- }
- else
- {
- sleep(2);//保证子进程先执行
- ret=pthread_mutex_lock(g_mutex);
- if( ret!=0 )
- {
- perror("father pthread_mutex_lock");
- }
- write(fd, str2, sizeof(str2));
- ret=pthread_mutex_unlock(g_mutex);
- if( ret!=0 )
- {
- perror("father pthread_mutex_unlock");
- }
- }
- wait(NULL);
- munmap(g_mutex, sizeof(pthread_mutex_t));
- }
运行后tmp文件内容为:
this is child process
this is father process
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