使用fork或者pthread库来处理多线程问题。。。1、共享内存使用方法 1>定义一个共享内存的KEY: shm_key 2>创建获取共享内存区域: key_t shmid = shmget(shm_key, 共享区域大小, IPC_CREAT | 0660) 3>取得区享区域指针: char * addr = shmat(shmid, 0, 0); 4>每个进程使用完毕后，需要关闭共享区域: shmdt(addr); 5>主进程删除共享区域: shmctl(shmid, IPC_RMID, 0)2、在使用共享内存的时候，需要注意数据的同步互斥，可使用pthread_mutex_t来处理互斥 1>定义全局的互斥对象：pthread_mutex_t * g_mutex = NULL; 2>初始化互斥对象： // 映射到进程共享 g_mutex = mmap(NULL, sizeof(pthread_mutex_t), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); // 设置属性 pthread_mutexattr_t attr; pthread_mutexattr_init(&attr); pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED); pthread_mutex_init(g_mutex, &attr); 3>互斥的使用： pthread_mutex_lock() pthread_mutex_unlock() 将要保护的内容放置于两个中间，达到互斥访问的要求 4>删除互斥对象 pthread_mutex_destroy(g_mutex); munmap(g_mutex, sizeof(pthread_mutex_t));// process_mutex.cpthread_mutex_t * g_mutex = NULL;struct shared_context{ int ref_cnt; // 计数器 int last_process;};#define key_shared_context 1234int main(int argc, char * argv[]){ // 映射到进程共享 g_mutex = mmap(NULL, sizeof(pthread_mutex_t), PROT_READ | PROT_WRITE, MAP_SHARED | MAP_ANONYMOUS, -1, 0); // 设置属性 pthread_mutexattr_t attr; pthread_mutexattr_init(&attr); pthread_mutexattr_setpshared(&attr, PTHREAD_PROCESS_SHARED); pthread_mutex_init(g_mutex, &attr); key_t shmid = shmget(key_shared_context, sizeof(struct shared_context), IPC_CREAT | 0660); struct shared_context * sctx = (struct shared_context*)shmat(shmid, 0, 0); if (fork() == 0) { // 子进程 pthread_mutex_lock(g_mutex); struct shared_context * sctx = (struct shared_context*)shmat(shmid, 0, 0); sctx->ref_cnt++; sctx->process = getpid(); shmdt((char*)sctx); pthread_mutex_unlock(g_mutex); } else { // 父进程 pthread_mutex_lock(g_mutex); sctx->ref_cnt++; sctx->process = getpid(); shmdt((char*)sctx); pthread_mutex_unlock(g_mutex); } shmctl(shmid, IPC_RMID); return 0;}使用pthread库来实现多线程// thread.cpthread_mutex_t g_mutex;// 消耗过程void * consume_proc(void * arg){ printf("ready consume proc/n"); pthread_mutex_lock(&mutex); printf("wait 5 sec for consume/n"); sleep(5); printf("consume unlock/n"); pthread_mutex_unlock(&mutex); printf("exit consume proc/n"); return 0;}// 产生过程void * build_proc(void * arg){ printf("ready build proc/n"); pthread_mutex_lock(&mutex); printf("wait 5 sec for build/n"); sleep(5); printf("build unlock/n"); pthread_mutex_unlock(&mutex); printf("exit build proc/n"); return 0;}
int main(int argc, char * argv[]){ // 使用线程时，处理互斥更为简单，不需要创建共享对象来供其他进程来使用 pthread_mutex_init(&g_mutex); pthread_t thd_build, thd_consume; // 创建两个新线程 pthread_create(&thread_build, NULL, &build_proc, NULL); pthread_create(&thread_consume, NULL, &consume_proc, NULL); // 等待线程的结束 pthread_join(&thread_build); pthread_join(&thread_consume); pthread_mutex_destroy(&g_mutex); return 0;}
