/* 232 problems with threads example.  Compile with: 
 *
 *      g++ -O2 -o 232_demo 232_demo.c -lpthread  
 *
 * Run on a dual core machine.  Adjust the number of threads NTHREADS.
 * Adjust the atomicity of the increment in "do_stuff" (i.e., uncomment different versions).
 */

/* Linux with glibc:
 *   _REENTRANT to grab thread-safe libraries
 *   _POSIX_SOURCE to get POSIX semantics
 */
#ifdef __linux__
#  define _REENTRANT
#  define _POSIX_SOURCE
#endif

/* Hack for LinuxThreads */
#ifdef __linux__
#  define _P __P
#endif

#include <pthread.h>
#include <string.h>	/* for strerror() */

#include <stdio.h>
#include <unistd.h>
#include <stdlib.h>

#define NTHREADS 1

#define errexit(code,str)                          \
  fprintf(stderr,"%s: %s\n",(str),strerror(code)); \
  exit(1);

volatile unsigned counter = 0;

/******** this is the thread code */
void *do_stuff(void * arg) {
  for (int i = 0 ; i < 200000000/NTHREADS ; ++ i) {
	 ++ counter;
	 // asm ("incl counter"); 
	 // asm ("lock incl counter" : : "g" (&counter)); 
  }
  return arg;
}

/******** this is the main thread's code */
int main(int argc,char *argv[]) {
  int worker;
  pthread_t threads[NTHREADS];                /* holds thread info */
  int ids[NTHREADS];                          /* holds thread args */
  int errcode;                                /* holds pthread error code */
  int *status;                                /* holds return code */

  /* create the threads */
  for (worker=0; worker<NTHREADS; worker++) {
    ids[worker]=worker;
    if (errcode=pthread_create(&threads[worker],/* thread struct             */
		       NULL,                              /* default thread attributes */
		       do_stuff,                          /* start routine             */
		       &ids[worker])) {                   /* arg to routine            */
      errexit(errcode,"pthread_create");
    }
  }
  /* reap the threads as they exit */
  for (worker=0; worker<NTHREADS; worker++) {
    /* wait for thread to terminate */
    if (errcode=pthread_join(threads[worker],(void **) &status)) { 
      errexit(errcode,"pthread_join");
    }
    /* check thread's exit status and release its resources */
    if (*status != worker) {
      fprintf(stderr,"thread %d terminated abnormally\n",worker);
      exit(1);
    }
  }
  printf("counter = %d\n", counter);
  return(0);
}

/* EOF simple.c */