/**
 * A simple pthread program illustrating POSIX scheduling.
 *
 * Figure 6.8
 *
 * To compile:
 *
 *	gcc posix-sched.c -o posix-sched -lpthread
 *
 * @author Gagne, Galvin, Silberschatz
 * Operating System Concepts  - Ninth Edition
 * Copyright John Wiley & Sons - 2013.
 *
 * Revised by X. Meng for class demo
 * CSCI 315, fall 2013
 */

#include <pthread.h>
#include <stdio.h>
#define NUM_THREADS 5

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

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

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

	/* first inquire on the current scope */
	if (pthread_attr_getscope(&attr,&scope) != 0)
		fprintf(stderr, "Unable to get scheduling scope.\n");
	else {
		if (scope == PTHREAD_SCOPE_PROCESS)
			printf("PTHREAD_SCOPE_PROCESS\n");
		else if (scope == PTHREAD_SCOPE_SYSTEM)
			printf("PTHREAD_SCOPE_SYSTEM\n");
		else 
			fprintf(stderr,"Illegal scope value.\n");
	}
	
	/* set the scheduling algorithm to PCS or SCS */
	if (pthread_attr_setscope(&attr, PTHREAD_SCOPE_SYSTEM) != 0)
	  printf("unable to set scheduling policy.\n");

	// we can't set PTHREAD_SCOPE_PROCESS 

	/*
	if (pthread_attr_setscope(&attr, PTHREAD_SCOPE_PROCESS) != 0)
		printf("unable to set scheduling policy.\n");
	*/
	/* 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) 
{
	/* do some work ... */
  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);
}