#include <sys/types.h>#include <sys/ipc.h>#include <sys/sem.h>#include <pthread.h>#include <errno.h>#include <vector>#include <iostream>using namespace std; union semun { int val; /* Value for SETVAL */ struct semid_ds *buf; /* Buffer for IPC_STAT, IPC_SET */ unsigned short *array; /* Array for GETALL, SETALL */ struct seminfo *__buf; /* Buffer for IPC_INFO (Linux specific) */}; //工作线程函数void * workproc(void * param){ int sid = *(int *)param; //信号量ID pthread_t tid = pthread_self(); //线程ID cout <<"thread " <<tid <<"/t opt 1 is ok!" <<endl; //第一步操作执行完成 //信号量减1 sembuf b; b.sem_num = 0; b.sem_op = -1; b.sem_flg = 0; int ret = semop(sid, &b, 1); if (ret != 0) return (void *)-1; //等待信号量变成0 cout <<"thread " <<tid <<"/t begin wait for all thread ok!" <<endl; b.sem_op = 0; ret = semop(sid, &b, 1); if (ret != 0) return (void *)-1; cout <<"thread " <<tid <<"/t end wait for all thread ok!" <<endl; //执行第二步操作 cout <<"thread " <<tid <<"/t opt 2 is ok!" <<endl; return 0;} int main(){ //创建信号量 int sid = semget(IPC_PRIVATE, 1, IPC_CREAT|0660); if (sid == -1) { cout <<"create sem error!" <<endl; return -1; } //设置信号量的初始值为5 semun un; un.val = 5; int ret = semctl(sid, 0, SETVAL, un); if (ret == -1) return -1; //启动一组工作线程 vector<pthread_t> ids; //保存启动的线程ID数组 pthread_t id; for (int i = 0; i < 5; ++i) { pthread_create(&id, NULL, workproc, &sid); ids.push_back(id); } //等待所有的工作线程结束 int num = ids.size(); for (int i = 0; i < num ; ++i) { pthread_join(ids[i], NULL); } //删除信号量 semctl(sid, 1, IPC_RMID); return 1;}
