POSIX多线程之创建线程pthread_create && 线程清理pthread_cleanup

多线程之pthread_create创建线程

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: linuxdba@qq.com

*/

#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: linuxdba@qq.com

*/

#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
多线程设计之线程清理pthread_cleanup

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: linuxdba@qq.com

*/

#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