Subj : I write a multithread program with pthread, and meet a program
To   : comp.programming.threads
From : zhengda1936
Date : Sun Apr 10 2005 10:53 am

I want to use pthread_cancel() to stop a thread, but it can not do
correctly.
Here is a sample:
void *thread_run(void *)
{
    int state;
    pthread_mutex_lock(&mutex);
    pthread_cond_signal(&cond); <------------------(1)
    cout<<"------------send a signal"<<endl;
    pthread_mutex_unlock(&mutex);
    cout<<"------------thread start"<<endl;
    while(true){
        pthread_setcancelstate(PTHREAD_CANCEL_DISABLE , &state);
        cout<<"-----------thread loop"<<endl;
        for(int i=0 ; i < 10000 ; i++);
        cout<<"----------start to sleep"<<endl;
        pthread_setcancelstate(state , &state);
        sleep(1);
    }
}

int main()
{
    for(int i=0 ; i < 1000 ; i++){
	pthread_t id;
	cout<<"create a thread:"<<i<<endl;
	pthread_mutex_lock(&mutex);
	pthread_create(&id , NULL , thread_run , NULL);
	cout<<"start to wait"<<endl;
	pthread_cond_wait(&cond , &mutex);
	pthread_mutex_unlock(&mutex);
	//cout<<"wait for the new thread to run"<<end;
	//pthread_cond_wait(&cond , &mutex);
	cout<<"cancel a thread"<<endl;
	pthread_cancel(id);
	void *reval;
	cout<<"wait for a thread to die"<<endl;
	pthread_join(id , &reval);
	cout<<endl<<endl;
    }
}

When the new thread is running to the point 1 and the main thread call
pthread_cancel() to stop it, the new pthread can not be stopped
correctly.
Can anyone explain why?
Thanks.

.