Something

// Prototypes
void* customer(void* num);
void* barber(void* num);

// Global Data
sem_t BtoC;
sem_t CtoB;
sem_t haircutDone;
pthread_mutex_t mutex = PTHREAD_MUTEX_INITIALIZER;
int waitingCustomersNo = 0;

int numChairs = 0;
int numCustomers = 0;
int numBarbers = 0;

int main(int argc, char** argv)
{
	pthread_t barbers_tid[100];
	pthread_t customers_tid[100];


	if(argc != 4)
	{
		printf("Usage: %s #customers #chairs #barbers\n", argv[0]);
		return -1;
	}

	numCustomers = atoi(argv[1]);
	numChairs = atoi(argv[2]);
	numBarbers = atoi(argv[3]);

	//Initialize semaphores:
	sem_init(&BtoC, 0, 0);
	sem_init(&CtoB, 0, 0);
	sem_init(&haircutDone, 0, 0);

	for(int i = 1; i <= numBarbers; i++)
	{		
		if(pthread_create(&barbers_tid[i-1], NULL, barber, (void*) i) == 0)
		{
			//printf("Created barber #%d.\n",i);
		}
		else
		{
			printf("Failed to create barber #%d! So only %d barbers will be used.\n",i, i-1);
			numBarbers = i-1;
			break;
		}
	}

	for(int i = 1; i <= numCustomers; i++)
	{
		if(pthread_create(&customers_tid[i-1], NULL, customer, (void*) i) == 0)
		{
			sleep(1);
			//printf("Created customer #%d.\n",i);
		}
		else
		{
			printf("Failed to create customer #%d! So only %d customers will be used.\n",i, i-1);
			numCustomers = i-1;
			break;
		}
	}

	for(int i = 0; i < numBarbers; i++)
	{
		pthread_join(barbers_tid[i], NULL);
	}

	for(int i = 0; i < numCustomers; i++)
	{
		pthread_join(customers_tid[i], NULL);
	}


	return 0;

}


void* customer(void* number)
{
	int myNum = (int) number;
	
	pthread_mutex_lock(&mutex);
	

	printf("Customer #%d has arrived.  \t\t#customers=%d seats_left=%d\n", myNum, waitingCustomersNo, numChairs-waitingCustomersNo);
	fflush(stdin);
	if(numChairs > waitingCustomersNo)
	{
		waitingCustomersNo++;
		printf("Customer #%d took a seat.\t\t#customers=%d seats_left=%d\n", myNum, waitingCustomersNo, numChairs-waitingCustomersNo);

		//pthread_mutex_unlock(&mutex);
		sem_post(&CtoB);
		pthread_mutex_unlock(&mutex);

		printf("CUSTOMER #%d is calling wait(BtoC)\n", myNum);
		sem_wait(&BtoC);
		printf("Customer #%d is now receiving a haircut.\t#customers=%d seats_left=%d\n", myNum, waitingCustomersNo, numChairs-waitingCustomersNo);
		sem_wait(&haircutDone);
		//printf("Customer #%d's haircut is done.\t\t#customers=%d seats_left=%d\n", myNum, waitingCustomersNo, numChairs-waitingCustomersNo);
		
	}
	else
	{
		printf("Customer #%d notices there are no open seats.\t#customers=%d seats_left=%d\n", myNum, waitingCustomersNo, numChairs-waitingCustomersNo);
		pthread_mutex_unlock(&mutex);
	}
	
	printf("Customer #%d left the barber shop.\t#customers=%d seats_left=%d\n", myNum, waitingCustomersNo, numChairs-waitingCustomersNo);
	pthread_exit(NULL);
}


void* barber(void* number)
{
	int myNum = (int) number;
	
	printf("Barber #%d has arrived.\t\t\t#customers=%d seats_left=%d\n", myNum, waitingCustomersNo, numChairs-waitingCustomersNo);
	
	while(1)
	{
		sem_wait(&CtoB);
		pthread_mutex_lock(&mutex);
		//sleep(10);
		waitingCustomersNo--;
		if(waitingCustomersNo < 0)
		{
			printf("WTF?!?!?!?!\n"); //should never reach this point!
			//pthread_mutex_unlock(&mutex);
		}
		printf("Barber #%d took the next waiting customer.\t\t#customers=%d seats_left=%d\n", myNum, waitingCustomersNo, numChairs-waitingCustomersNo);
		sem_post(&BtoC);
		pthread_mutex_unlock(&mutex);
		
		sleep(2);
		sem_post(&haircutDone);
		printf("Barber #%d is done with the haircut.\t#customers=%d seats_left=%d\n", myNum, waitingCustomersNo, numChairs-waitingCustomersNo);
	}

	pthread_exit(NULL);
}