pthread-16.c

/* 
 *user login queue demo
 */

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

#define THREAD_NUM 16

sem_t semaphore;

void* routine(void* args){
	printf("(%d) waiting in the login queue\n",*(int*)args);
	sem_wait(&semaphore);
        printf("(%d) logged in\n",*(int*)args);	
	sleep(rand() % 5 + 1);
        printf("(%d) logged out\n",*(int*)args);	
	sem_post(&semaphore);
	free(args);
}

int main(int argc, char * argv[]){
	pthread_t th[THREAD_NUM];
	sem_init(&semaphore,0,12);
	int i;
	for(i=0;i<THREAD_NUM;i++){
		int* a = malloc(sizeof(int));
		*a = i;
		if(pthread_create(&th[i], NULL, &routine, a)!=0){
			perror("failed to create thread");
		}
	}
	for(i=0;i<THREAD_NUM;i++){
		if(pthread_join(th[i], NULL)!=0){
			perror("failed to join thread");
		}
	}
	sem_destroy(&semaphore);
	return 0;
}