标签：logs each 线程同步 合作 pid size 代码 span 写入
0x00.什么是线程同步
同步，又称直接制约关系，是指多个线程（或进程）为了合作完成任务，必须严格按照规定的 某种先后次序来运行
0x01.案例代码
1 void* PthreadFunc(void* argc); 2 int flag_num = 1; 3 4 int main(int argc, char* argv[]) 5 { 6 pthread_t pid; 7 void* ret_val; 8 9 int create_status = pthread_create(&pid, NULL, &PthreadFunc, NULL); 10 if(0 != create_status) 11 { perror("main()->pthread_create error"); 12 exit(1); 13 } 14 15 //input data to public source area 16 for(int i = 0; i < 10; ++i) 17 { 18 if(flag_num == 1) 19 { 20 printf("1"); 21 flag_num = 2; 22 }else{ 23 sleep(1); 24 } 25 } 26 27 int join_status = pthread_join(pid, &ret_val); 28 if(0 != join_status) 29 { 30 perror("main()->pthread_join error"); 31 exit(1); 32 } 33 34 //print array‘s data 35 for(int i = 0; i < 10; ++i) 36 { 37 printf("%d ", arr[i]); 38 } 39 40 return 0; 41 } 42 43 void* PthreadFunc(void* argc) 44 { 45 if(flag_num == 2) 46 { 47 printf("2"); 48 flag_num = 1; 49 }else{ 50 sleep(1); 51 } 52 }
执行结果:
reacher@ubuntu:~/projects/proj$ ./syn
1212121212
结论:利用条件避免无休止抢占公共资源
0x02.修改代码获取新知识点 …(⊙_⊙;)
1 void* PthreadFunc(void* argc); 2 int arr[10]; 3 4 int main(int argc, char* argv[]) 5 { 6 pthread_t pid; 7 void* ret_val; 8 9 int create_status = pthread_create(&pid, NULL, &PthreadFunc, NULL); 10 if(0 != create_status) 11 { perror("main()->pthread_create error"); 12 exit(1); 13 } 14 15 //input data to public source area 16 for(int i = 0; i < 10; ++i) 17 { 18 arr[i] = i; 19 } 20 21 int join_status = pthread_join(pid, &ret_val); 22 if(0 != join_status) 23 { 24 perror("main()->pthread_join error"); 25 exit(1); 26 } 27 28 //print array‘s data 29 for(int i = 0; i < 10; ++i) 30 { 31 printf("%d ", arr[i]); 32 } 33 34 return 0; 35 } 36 37 void* PthreadFunc(void* argc) 38 { 39 for(int i = 0; i < 10; ++i) 40 { 41 arr[i] = i + 10; 42 } 43 }
执行代码结果:
reacher@ubuntu:~/projects/proj$ ./syn
10 11 12 13 14 15 16 17 18 19
当时出现结果一脸懵,后来查资料发现了线程是有优先级的：main(for()) 属于主线程,PthreadFunc(for())属于子线程、
主线程的优先级大于子线程,所以main.for()先对arr进行了数据写入，pthread.for()后写入数据，输出结果为线程输入数据
标签：logs each 线程同步 合作 pid size 代码 span 写入
原文地址：http://www.cnblogs.com/ReacherGua/p/7352967.html
