/**
 * A simple pthread program illustrating RT pthread scheduling.
 *
 * Figure 6.20
 *
 * To compile:
 *
 *	gcc posix-rt.c -o posix-rt -lpthread
 *
 * @author Gagne, Galvin, Silberschatz
 * Operating System Concepts  - Ninth Edition
 * Copyright John Wiley & Sons - 2013.
 *
 * Revised by X. Meng for classroom demo
 * CSCI 315, fall 2013
 */

#include <pthread.h>
#include <stdio.h>
#define NUM_THREADS 50

/* the thread runs in this function */
void *runner(void *param); 

/* get the current scheduling policy */
void show_policy(pthread_attr_t * attr, int * policy) {

  int policy_cp;
  if (pthread_attr_getschedpolicy(attr,&policy_cp) != 0)
    fprintf(stderr, "Unable to get policy.\n");
  else {
    if (policy_cp == SCHED_OTHER)
      printf("SCHED_OTHER\n");
    else if (policy_cp == SCHED_RR)
      printf("SCHED_OTHER\n");
    else if (policy_cp == SCHED_FIFO)
      printf("SCHED_FIFO\n");
  }

  (*policy) = policy_cp;
}

void print_sched_policy() {

  printf("Possible scheduling policies \n");
  printf("SCHED_OTHER %d\n", SCHED_OTHER);
  printf("SCHED_RR %d\n", SCHED_RR);
  printf("SCHED_FIFO %d\n", SCHED_FIFO);
}


int main(int argc, char *argv[])
{
	int i, policy;
	pthread_t tid[NUM_THREADS]; 	/* the thread identifier */
	pthread_attr_t attr; 		/* set of attributes for the thread */

	print_sched_policy();

	/* get the default attributes */
	pthread_attr_init(&attr);

	/* get the current scheduling policy */
	show_policy(&attr, &policy);
	
	/* set the scheduling policy - FIFO, RT, or OTHER */
	//	if (pthread_attr_setschedpolicy(&attr, SCHED_OTHER) != 0)
	//		printf("unable to set scheduling policy to SCHED_OTHER \n");

	if (pthread_attr_setschedpolicy(&attr, SCHED_FIFO) != 0)
	  printf("unable to set scheduling policy to SCHED_FIFO \n");
	//	if (pthread_attr_setschedpolicy(&attr, SCHED_RR) != 0)
	//		printf("unable to set scheduling policy to SCHED_RR \n");

	/* get the current scheduling policy */
	show_policy(&attr, &policy);

	/* create the threads */
	for (i = 0; i < NUM_THREADS; i++) 
		pthread_create(&tid[i],&attr,runner,NULL); 

	/**
	 * Now join on each thread
	 */
	for (i = 0; i < NUM_THREADS; i++) 
		pthread_join(tid[i], NULL);
}

/**
 * The thread will begin control in this function.
 */
void *runner(void *param) 
{
  int i;
  double j = 0;
  /* do some work ... */
  while(j < 10000) {
    for (i = 0; i < 100000; i ++);
    usleep(10);
    j = j + 1;
  }
  pthread_exit(0);
}