#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <sched.h>
#include <sys/types.h>

#define NUM_TASKS   5
#define PARENT_PRIO 10   /* Parent's rt priority */

static void child_yielder(int rt_prio);

int main (int argc, char **argv)
{
        struct sched_param sp;
	pid_t child;
	int i = 0;

        memset (&sp, 0, sizeof sp);
        sp.sched_priority = PARENT_PRIO;
        if (sched_setscheduler (0, SCHED_FIFO, &sp) != 0)
        {
		perror("sched_setscheduler()");
		exit (1);
        }

	for (i = 1; i <= NUM_TASKS; i++) {
		child = fork();
		switch (child) {
		case 0: /* Child */
			/* Child has lower rt priority than parent */
			child_yielder(PARENT_PRIO + i);
			break;
		case -1: /* Error */
			perror("fork()");
			kill(0, SIGTERM);
			break;
		default: /* Parent */
			printf ("Parent: craete child pid %d\n", child);
			break;
		}
	}

	printf("-- Parent END --\n");
	
	/* Exit and leave child processes running */
	/* kill(0, SIGTERM); */
	return 0;
}

static void child_yielder(int rt_prio)
{
        struct sched_param sp;

	printf ("Child running: pid = %d\n", getpid());

        memset (&sp, 0, sizeof sp);
        sp.sched_priority = rt_prio;

        if (sched_setscheduler (0, SCHED_FIFO, &sp) != 0)
        {
		perror("sched_setscheduler()");
		exit (1);
        }

	while (1) {
		sched_yield();
	}
}