关于linux中的清除问题

chuwangmvp

#include <stdio.h>
#include <pthread.h>
#include <unistd.h>
void *clean(void *arg)
{
    printf("cleanup :%s  \n",(char *)arg);
    return (void *)0;
}
void *thr_fn1(void *arg)
{
    printf("thread 1 start  \n");
    pthread_cleanup_push( (void*)clean,"thread 1 first handler");
    pthread_cleanup_push( (void*)clean,"thread 1 second hadler");
    printf("thread 1 push complete  \n");
    if(arg)
    {
        return((void *)4);
    }
    pthread_cleanup_pop(0);
    pthread_cleanup_pop(0);
    return (void *)4;
}


void *thr_fn2(void *arg)
{
    printf("thread 2 start  \n");
    pthread_cleanup_push( (void*)clean,"thread 2 first handler");
    pthread_cleanup_push( (void*)clean,"thread 2 second handler");
    printf("thread 2 push complete  \n");
    if(arg)
    {
        pthread_exit((void *)2);
    }
    pthread_cleanup_pop(0);
    pthread_cleanup_pop(0);
    pthread_exit((void *)2);
}



int main(void)
{
    int err;
    pthread_t tid1,tid2;
    void *tret;

    err=pthread_create(&tid1,NULL,thr_fn1,(void *)1);
    if(err!=0)
    {
        printf("error .... \n");
        return -1;
    }
    err=pthread_create(&tid2,NULL,thr_fn2,(void *)1);

    if(err!=0)
    {
        printf("error .... \n");
        return -1;
    }
    err=pthread_join(tid1,&tret);
    if(err!=0)
    {
        printf("error .... \n");
        return -1;
    }
    printf("thread 1 exit code %d  \n",(int)tret);

    err=pthread_join(tid2,&tret);
    if(err!=0)
    {
        printf("error .... ");
        return -1;
    }

    printf("thread 2 exit code %d  \n",(int)tret);
   
    return 1;
}
运行结果：
thread 2 start
thread 2 push complete
clean up: thread 2 second handler
clean up: thread 2 first handler
thread 1 start
thread 1 push complete
thread 1 exit code 4
thread 2 exit code 2
我当时猜想的是：
thread 1 start
thread 1 push complete
thread 2 start
thread 2 push complete
clean up: thread 2 second handler
clean up: thread 2 first handler
thread 1 exit code 4
thread 2 exit code 2
问题：
为什么是thread 2 先执行了的。。。。

theophilus

1. 线程的执行顺序是靠调度器决定的
2. pthread_cleanup_pop完全用错了，好好看man

chuwangmvp

theophilus 发表于 2012-4-11 16:37
1. 线程的执行顺序是靠调度器决定的
2. pthread_cleanup_pop完全用错了，好好看man ...

1.能不能提供下资料，具体的看下咯；
2，pthread_cleanup_pop  我是看国嵌的用法用的，里面的参数决定是否执行接下来的程序（非0:执行; 0:不执行）；

theophilus

1. 我是记得APUE的Thread那章就有讲（有点久了，记不太清）。要保证执行顺序，需要同步机制。等会我找找
2. 我说错了，那段代码是对的，我太二逼了。


打字的时候翻了翻APUE2，有这么一句

When a thread is created, there is no guarantee which runs first: the newly created thread or the calling thread.

再往后翻一点，那段代码就是APUE的嘛，我二到极点了，看来看书不认真啊。