pthread_cond_wait und pthread_cond_signal

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

void *functionRead(void *argv);
void *functionWrite(void *argv);
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER; 
pthread_cond_t condRead = PTHREAD_COND_INITIALIZER;
pthread_cond_t condWrite = PTHREAD_COND_INITIALIZER;

FILE* Datei1;
FILE* Datei2;

int n, x = 1, i = 0, j, c = 0, d = 0, rc;

pthread_t pRead;
pthread_t pWrite;

char ringpuffer[10000];


int main(int argc, char **argv)
{
	if (argc == 4){
		n = atoi(argv[3]);
	} else {
		printf("Need 3 Parameter: File1, File2, Charblock Size n!\n");
		exit(EXIT_FAILURE);
	}
	printf("File to Copy: %s\nTarget: %s\nHow many chars: %s\n", argv[1], argv[2], argv[3]);
	
	pthread_create(&pWrite, NULL, &functionWrite, ((void *)argv));
	pthread_create(&pRead, NULL, &functionRead, ((void *)argv));
	
	printf("Created, Sending Signal\n");
	pthread_cond_signal(&condRead);
	
	pthread_join(pWrite, NULL);
	printf("Everything's done!\n");
	return 0;
}

void *functionRead(void *argv){
	char **args = (char **) argv;
	if ((Datei1=fopen(args[1], "r")) == NULL){perror("fopen\n"); exit(EXIT_FAILURE);}
	n = atoi(args[3]);
	printf("Entered functionRead\n");
	do{
		pthread_mutex_lock(&mutex);
		pthread_cond_wait(&condRead, &mutex);
		i = 0;
		for(i = 0; i<=n; i++){
			c = fgetc(Datei1);
			ringpuffer[i] = c;
			i++;
		}
		x++;
		pthread_mutex_unlock(&mutex);
		pthread_cond_signal(&condWrite);
	}while ((c=fgetc(Datei1)) != EOF);
	
	if ((fclose(Datei1)) == EOF){perror("fclose\n"); exit(EXIT_FAILURE);}
	return 0;
}

void *functionWrite(void *argv){
	char **args = (char **) argv;
	if ((Datei2=fopen(args[2], "w")) == NULL){perror("fopen\n"); exit(EXIT_FAILURE);}
	n = atoi(args[3]);
	printf("Entered functionWrite\n");
	sleep(5);
	for (j = 0; j < x; j++){
		pthread_mutex_lock(&mutex);
		pthread_cond_wait(&condWrite, &mutex);
		fwrite(ringpuffer, 1, sizeof(ringpuffer), Datei2);
		pthread_mutex_unlock(&mutex);
		pthread_cond_signal(&condRead);
	}
	
	if ((fclose(Datei2)) == EOF){perror("fclose\n"); exit(EXIT_FAILURE);}
	return 0;
}