/**
 * A pthread program illustrating how to
 * create a simple thread and some of the pthread API
 * This program implements the summation function where
 * the summation operation is run as a separate thread.
 *
 * Most Unix/Linux/OS X users
 * gcc thrd.c -lpthread
 *
 * Solaris users must enter
 * gcc thrd.c -lpthreads
 *
 * Figure 4.9
 *
 * @author Gagne, Galvin, Silberschatz
 * Operating System Concepts  - Ninth Edition
 * Copyright John Wiley & Sons - 2013
 *
 * Revised X. Meng
 * 09-11-2013
 * to display the values of attributes
 */

#include <pthread.h>
#include <stdio.h>

int sum; /* this data is shared by the thread(s) */

void *runner(void *param); /* the thread */
void display_attr(pthread_attr_t attr); /* display attribute values */

int main(int argc, char *argv[])   {

  pthread_t tid; /* the thread identifier */
  pthread_attr_t attr; /* set of attributes for the thread */

  if (argc != 2) {
    fprintf(stderr,"usage: %s <integer value>\n", argv[0]);
    /*exit(1);*/
    return -1;
  }

  if (atoi(argv[1]) < 0) {
    fprintf(stderr,"Argument %d must be non-negative\n",atoi(argv[1]));
    /*exit(1);*/
    return -1;
  }

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

  /* create the thread */
  pthread_create(&tid,&attr,runner,argv[1]);

  /* 
   * pthread_getattr_np() is a GNU extension to pthread, non-standard.
   * This function retrieves attributes that include stack information
   */

  pthread_getattr_np(pthread_self(), &attr);

  /* display various attribute default values */
  display_attr(attr);

  /* now wait for the thread to exit */
  pthread_join(tid,NULL);

  printf("sum = %d\n",sum);

  return 0;
}

/**
 * The thread will begin control in this function
 */
void *runner(void *param)  {

  int i, upper = atoi(param);
  sum = 0;

  if (upper > 0) {
    for (i = 1; i <= upper; i++)
      sum += i;
  }
  
  pthread_exit(0);
}

void display_attr(pthread_attr_t attr) {

  int s, i;
  struct sched_param sp;
  size_t v;
  void *stkaddr;
  pthread_t tid = pthread_self();
  
  printf("Attributes for thread %lu\n", tid);

  s = pthread_attr_getschedpolicy(&attr, &i);
  printf("Scheduling policy   = %s\n",
	 (i == SCHED_OTHER) ? "SCHED_OTHER" :
	 (i == SCHED_FIFO)  ? "SCHED_FIFO" :
	 (i == SCHED_RR)    ? "SCHED_RR" :
	 "???");

  s = pthread_attr_getschedparam(&attr, &sp);
  printf("Scheduling priority = %d\n", sp.sched_priority);

  s = pthread_attr_getstack(&attr, &stkaddr, &v);
  printf("Stack address       = %p\n", stkaddr);
  printf("Stack size          = 0x%x bytes\n", v);
}