pthread_create中参数传递不正确

发表于 2010-7-30 21:49

typedef struct {
      int    param1;
      int    param2;
      int    param3;
      int    param4;
}agent_threadParma;

int canReceive(void *pParams)
{
      agent_threadParma  *param;
      param = (agent_threadParma*)pParams;
      fd = param ->param1;  //此数传递有时正确有时不正确
      while(1)
               {
                        ......
               }
}

int cansio_open()
{
      agent_threadParma threadParams;  //自定义结构
pthread_t          canthread;
      int fd;

......
      fd = open( candev, O_RDWR|O_NONBLOCK );
   if (-1 == fd)
   {
      perror("Can't can Port");
      return -1;
   }
   threadParams.param1 = fd;
   pthread_create(&canthread,NULL,(void *)canReceive,(void*)&threadParams);
.......
}

我使用 pthread_create来产生线程,但是 threadParams.param1 参数传递传递有时正确有时不正确,我不知到为什么会
这样,谁能给我分析一下?

发表于 2010-7-30 22:04

你这段代码肯定有问题，你要传递的参数结构体存在于函数栈上，当函数执行完成后，就被释放了，
所以等到线程开始执行时得到的参数就是个不确定值。其实这个问题的主要原因在于被创建的线程何时执行，
如果
1）立刻执行，那么传递的参数正确
2） cansio_open()结束后某个时刻执行，那如前所述肯定错误

所以你应该采用静态静态结构体或者动态分配，比如采用动态分配

int canReceive(void *pParams)
{
      agent_threadParma  *param;
      param = (agent_threadParma*)pParams;
      fd = param ->param1;  //此数传递有时正确有时不正确

/* 如果你只是用来传递fd, 那么此时你应该释放内存 */
      free(param);

      while(1)
               {
                        ......
               }
}

int cansio_open()
{
agent_threadParma *threadParams = (agent_threadParma *)malloc(sizeof(*threadParams));

...

threadParams->param1 = fd;
pthread_create(&canthread,NULL,(void *)canReceive,&threadParams);

...
}

发表于 2010-7-31 09:11

楼上的回答得可真够详细的

pthread_create中参数传递不正确

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