/*
 *  This example base on code from: 
 *  B. Nichols, D. Buttlar, and J. Proulx Farrell,  "Pthreads Programming,"
 *  O'reilly, 1996.
 *  
 */

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

void do_another_thing(int *);
void do_one_thing(int *);
void do_wrap_up(int, int);


int r1 = 0, r2 = 0, r3 = 0;
pthread_mutex_t r3_mutex=PTHREAD_MUTEX_INITIALIZER;

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

  pthread_t thread1, thread2;
  pthread_attr_t custom_sched_attr;

  /* set scheduling policy to system so braindead solaris doesn't
     run threads sequentially */
  pthread_attr_init(&custom_sched_attr);
  pthread_attr_setscope(&custom_sched_attr,PTHREAD_SCOPE_SYSTEM);

  r3 = 34;

  /* start two threads */
  pthread_create(&thread1, &custom_sched_attr, (void *) do_one_thing, (void *) &r1);
  pthread_create(&thread2, &custom_sched_attr, (void *) do_another_thing, (void *) &r2);

  /* wait till threads complete */
  pthread_join(thread1,NULL);
  pthread_join(thread2,NULL);

  /* print results */
  do_wrap_up(r1,r2);
  return 0;

}


void do_one_thing(int *pnum_times) 
{
  int i,j,x;

  /* protect access to r3 */
  pthread_mutex_lock(&r3_mutex);
  if (r3 >0) {
    x = r3;
    r3 --;
  } else {
    x = 1;
  }
  pthread_mutex_unlock(&r3_mutex);

  for (i = 0; i < 4;i++) {
    printf("doing one thing\n");
    for (j = 0; j < 10000000; j++) 
      x = x + i;
    (*pnum_times)++;
  }
}


void do_another_thing(int *pnum_times) 
{
  int i,j,x;

  /* protect access to r3 */
  pthread_mutex_lock(&r3_mutex);
  if (r3 >0) {
    x = r3;
    r3 --;
  } else {
    x = 1;
  }
  pthread_mutex_unlock(&r3_mutex);

  for (i = 0; i < 4;i++) {
    printf("doing another thing\n");
    for (j = 0; j < 10000000; j++) 
      x = x + i;
    (*pnum_times)++;
  }
}


void do_wrap_up(int first, int second) {

  int total;

  total = first+second;
  printf("Wrap up: one thing %d, another %d, total %d, r3 %d\n",
	 first,second, total, r3);
}