如何不用sleep实现线程同步？
不使用sleep的话，pthreadcondwait(&transformed, &lock)还未执行，transform信号就先发出了，就没有用了
如何不用sleep，尽量不用pause，使pthreadcondwait(&transformed, &lock)执行？

#include <stdio.h> 
#include <stdlib.h> 
#include <string.h> 
#include <sys/types.h> 
#include <signal.h> 
#include <pthread.h>   
void *sender(void *); 
void *receiver(void *);  
char msg[60]; 
int tfed; 
pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER; 
pthread_cond_t inputed = PTHREAD_COND_INITIALIZER;
pthread_cond_t transformed = PTHREAD_COND_INITIALIZER;  
int main(int argc, char **argv) { 
    int err; void *sent; 
    pthread_t sthd, rthd;  
    err = pthread_create(&rthd, NULL, receiver, NULL); 
    err = pthread_create(&sthd, NULL, sender, NULL); 
    if (err != 0) {        
        fprintf(stderr, "can't create sender thread: %s\n", strerror(err));        
        exit(1); 
    } 
    pthread_join(sthd, &sent); 
    pthread_join(rthd, &sent); 
    pthread_mutex_destroy(&lock); 
    pthread_cond_destroy(&inputed); 
    pthread_cond_destroy(&transformed); 
    printf("Sent Messsages %d\n", (int)sent); 
}   

void *sender(void *arg){     
    FILE *fp;   
    char line[132], output[132];   
    int sent_msg=0, sender_pid;            
    while (1) {     
        pthread_mutex_lock(&lock);     
        fgets(msg, sizeof(msg), stdin);     
        pthread_mutex_unlock(&lock);     
        pthread_cond_signal(&inputed);          
        sent_msg++;            
        if (strcmp(line, "end\n") == 0) break;            
        pthread_mutex_lock(&lock);     
        pthread_cond_wait(&transformed, &lock);     
        printf("Output msg:%s\n", msg);     
        pthread_mutex_unlock(&lock);   
    }     
    pthread_exit((void *)sent_msg);  
}  

void *receiver(void *arg){     
    FILE *fp;   
    char line[132], output[132];   
    int sent_msg=0, i;      
    while(1){     
        pthread_mutex_lock(&lock);     
        pthread_cond_wait(&inputed, &lock);     
        strcpy(line, msg);          
        if (strcmp(msg, "end\n") == 0) break;                      
        for(i=0;i<strlen(line);i++) msg[i]= toupper(line[i]);       
        msg[i]='\0';       
        strcpy(output, msg);     
        pthread_mutex_unlock(&lock);     
        //printf("Transformed msg:%s\n", output);     
        sent_msg++;          
        sleep(1);     
        pthread_cond_signal(&transformed);   
    }     
    pthread_exit((void *)sent_msg);  
}