多线程设计之线程清算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