POSIX多线程之创建线程pthread_create && 线程清理pthread_cleanup
pthreads定义了一套C程序语言类型、函数、与常量。以pthread.h和一个线程库实现。
数据类型：
pthread_t:线程句柄
pthread_attr_t:线程属性
线程操作函数：
pthread_create():创建一个线程
pthread_exit():终止当前线程
pthread_cancel():中断另外一个线程的运行
pthread_join():阻塞当前的线程，直到另外一个线程运行结束
pthread_attr_init():初始化线程的属性
pthread_attr_setdetachstate():设置脱离状态的属性
pthread_attr_getdetachstate():获取脱离状态的属性
pthread_attr_destroy():删除线程的属性
pthread_kill():向线程发送一个信号
.....
创建线程：
int pthread_create(pthread_t *thread, const pthread_attr_t *attr, void *(*start_rtn) (void*),void *arg);
*thread:线程id (指向线程标识符的指针)
*attr:线程属性（通常为空）
*start_rtn:线程要执行的函数（线程运行函数的起始地址）
*arg:start_rtn的参数
返回值为零才算成功，其它表示错误
编译时需要加上 -lpthread库
示例一：
#include <stdio.h>
#include <pthread.h>
void *pthread_1(void) //线程1执行的函数
{
inti;
for(i=1; i < 5; i++){
printf("pthread1.\n");
sleep(1);
}
return (void *)0;
}
void *pthread_2(void) //线程2执行的函数
{
inti;
for(i=1;i < 5; i++){
printf("pthread2.\n");
sleep(1);
}
return (void *)0;
}
int main(int argc, char argv[])
{
intret = 0;
pthread_tpthid1, pthid2; //线程的id
ret= pthread_create(&pthid1,NULL, (void *)pthread_1, NULL);
if(ret) // 非0则创建失败
{
perror("createthread 1 failed.\n");
return1;
}
ret= pthread_create(&pthid2, NULL, (void *)pthread_2, NULL);
if(ret)
{
perror("createthread 2 failed.\n");
return1;
}
pthread_join(pthid1,NULL); //等待pthid1，否则不会等待，继续往下执行
pthread_join(pthid2,NULL); //如无，遇到下面的return会结束进程
return0;
}
示例二：传递参数，初始化
/*
*pthread_init.c
*
* Created on: Jan 20, 2013
* Author: [email protected]
*/
#include <stdio.h>
#include <pthread.h>
void *create(void *arg)
{
int *num;
num = (int*)arg;
printf("theinput number is: %d.\n", *num);
return(void *)0;
}
int main(int argc, char argv[])
{
intret;
intt;
printf("Inputone number:");
scanf("%d",&t);
int*attr = &t;
pthread_tpthid;
ret= pthread_create(&pthid, NULL, (void *)create, (void *)attr);
if(ret)
{
perror("createthread failed.\n");
return1;
}
pthread_join(pthid,NULL);
return0;
}
示例三：共享数据
/*
*pthread_share.c
*
* Created on: Jan 20, 2013
* Author: [email protected]
*/
#include <stdio.h>
#include <pthread.h>
static int i = 3;
void *pthread_1(void)
{
printf("thread1, i is: %d.\n", i);
return(void *)0;
}
void *pthread_2(void)
{
printf("thread2, i is: %d.\n", i);
return(void *)0;
}
int main(int argc, char argv[])
{
intret = 0;
inti = 5;
pthread_tpthid1, pthid2;
printf("mainthread, i is: %d.\n", i);
ret= pthread_create(&pthid1, NULL, (void *)pthread_1, NULL);
if(ret)
{
printf("createthread 1 failed.\n");
return1;
}
ret= pthread_create(&pthid2, NULL, (void *)pthread_2, NULL);
if(ret)
{
printf("createthread 2 failed.\n");
return1;
}
pthread_join(pthid1,NULL);
pthread_join(pthid2,NULL);
return0;
}
此段程序之中两个线程是对等的，不存在先后顺序；
i 为全局变量，main函数内部为局部的变量。
http://www.kernel.org/doc/man-pages/online/pages/man3/pthread_create.3.html
http://baike.baidu.com/view/974776.htm
线程清理：pthread_cleanup_push() & pthread_cleanup_pop()
A cancellation clean-up handler is poppedfrom the stack and executed in
The following circumstances:(三种情况会执行线程清理)
1. When a thread is canceled, allof the stacked clean-up handlers are popped and executed in the reverse of theorder in which they were pushed onto the stack. (线程取消)
2. When a thread terminates bycallingpthread_exit(3),all clean-up handlers are executed as described in the preceding point. (Clean-up handlers are not called if thethread terminates by performing a return from the thread start function.) (push与pop之间执行了pthread_exit)
3. When a thread calls pthread_cleanup_pop()with a nonzero execute argument, the top-most clean-up handler is popped andexecuted.(pop内为非零参数)
示例代码：
/*
*pthread_push_pop.c
*
* Created on: Jan 21, 2013
* Author: [email protected]
*/
#include <stdio.h>
#include <pthread.h>
void *clean1(void *arg)
{
printf("clean1func: %s\n", arg);
return(void *)0;
}
void *clean2(void *arg)
{
printf("clean2func: %s\n", arg);
return(void *)0;
}
void *thread(void )
{
pthread_tthid;
thid= pthread_self(); //获取线程ID
printf("thethread is: %d.\n",thid);
printf("theprocess id is: %d.\n", getpid()); //进程ID
pthread_cleanup_push((void*)clean1,"first push");
pthread_cleanup_push((void*)clean2, "second push");
printf("Inthread.\n");
pthread_exit("threadexit.\n"); //退出线程，会执行push指定函数
/*return NULL; */ //不会执行push指定函数
pthread_cleanup_pop(0);//为0,只有在异常退出时才会执行push指定的函数,pop第一个
pthread_cleanup_pop(1);//为非0,即便是正常,也会执行push指定的函数,pop第二个
returnNULL;
}
int main(int argc, char argv[])
{
intret = 0;
pthread_tpthid;
ret= pthread_create(&pthid, NULL,(void *)thread,NULL);
if(ret)
{
printf("createthread failed.\n");
return-1;
}
printf("theprocess is: %d.\n", getpid()); //获取进程ID
pthread_join(pthid,NULL);
}
运行结果：
the process is: 3893.
the thread is:1738999552.
the process id is: 3893.
In thread.
clean2 func: second push
clean1 func: first push
push与pop采用栈方式，先进后出，后进先出，所以clean2会在前面。
需要注意的几点：
1) 线程属于进程的，只有一个进程ID，一样的；
2) push和pop是采用栈方式；
3) pthread_cleanup_pop后面为0则执行push指定函数，非0则即便正常也执行
4) push与pop之间代码若异常退出，包括pthread_exit，会进行相应的函数处理，但是若其间执行了return，则直接结束线程，不执行push指定函数。
参考文档：
http://man7.org/linux/man-pages/man3/pthread_cleanup_push.3.html