Question

I used Eclispse Indigo + CDT 8.0.2 + cygwin to develope a multi-thread systerm, the code is below:

pthread_mutex_t mutexCmd = PTHREAD_MUTEX_INITIALIZER;
pthread_cond_t signalCmd = PTHREAD_COND_INITIALIZER;

void * Func(void * arg)
{
    int iStatus;
    while (1)
    {
        int a = 1;
        pthread_cleanup_push(pthread_mutex_unlock, &mutexCmd);
        pthread_mutex_lock(&mutexCmd);
        iStatus = pthread_cond_wait(&signalCmd, &mutexCmd);
        if (iStatus) {
                err_abort(iStatus, "signalCmd status error");
        }
        if(arg->Cmd != navi_Go) //Just a command tag;
        {
            pthread_mutex_unlock(&(pNaviCtrl->mutexCmd));
            continue;
        }
        //do some work
        //.....
        pthread_mutex_unlock(&mutexCmd);
        pthread_cleanup_pop(1);
    }
//pthread_detach(pthread_self());
return  NULL;
}

int main()
{
    int iStatus = 0;
    pthread = tid;
     iStatus = pthread_create(&tid;NULL, Func, NULL);
     if(iStatus)
    {
    err_abort(iStatus, "Start pthread error");
    }
    // do some work
    ...
    //Cancel thread
   void * retval;
   iStatus = pthread_cancel(tid) 
   iStatus = pthread_join(tid; &retval);
   if(iStatus){
        err_abort(iStatus,"Stop thread error");
    }
    return iStatus;
}

where program run, it stop at “iStatus = pthread_join(tid1; &retval);” couldn’t go forward anymore, I think the thread could be happed to deadlock, but can’t find the reason. I supposed after call pthread_cancel(), the thread will exit and return to the pthread_join(),
who can tell me what’s wrong with my code?

Answer 1

Don’t put cleanup_push and _pop inside the while loop. Don’t call them more than once. If you look at them, they are macros that wrap the code between them in { }. They setup a longjump that is used when you call pthread_cancel.