问pthread不能使用pthread_cond_signal()和pthread_cond_wait()

EN

#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>

pthread_mutex_t mutex;
pthread_cond_t cond;

//Read input value
void* readinput(void *arg)
{
    pthread_mutex_lock(&mutex);
        int a;
        printf("Input:");
        scanf("%d",&a);
        printf("Value: %d\n",a);
        /*
        if condition correct then "printinput" function
        else ignore that function
        */
        if (a>=2 && a<=8)
        {
            pthread_cond_signal(&cond);
        }
    pthread_mutex_unlock(&mutex);
    pthread_exit((void *)a);
}

//print input value if condition correctly
void* printinput(void *arg)
{
    pthread_mutex_lock(&mutex);
    //Block and wait for cond Singal
        pthread_cond_wait(&cond,&mutex);
        printf("Your value between 2 and 8 \n\n");
    pthread_mutex_unlock(&mutex);
    pthread_exit(NULL);
}
int main()
{
    pthread_mutex_init(&mutex, NULL);
    pthread_cond_init(&cond, NULL);
    pthread_t th1;
    pthread_t th2;
    while (1)
    {

        //Create pthread
        pthread_create(&th1,NULL,&printinput,NULL);
        pthread_create(&th2,NULL,&readinput,NULL);

        //Wait pthread done
        pthread_join(th1,NULL);
        pthread_join(th2,NULL);
        Sleep(1000);
    }
}

Input:5 
Value: 5 
Your value between 2 and 8 
Input:10 Value: 10