CS471/571 - Operating Systems

Displaying ./code/Pthreads/p2.c

#define _GNU_SOURCE
#include <stdio.h>
#include <unistd.h>
#include <pthread.h>

#define NT	4

// gcc -o p2 p2.c -lpthread

pthread_mutex_t lock = PTHREAD_MUTEX_INITIALIZER;
int sum = 0;

void *thread_main(int *tid)
{
  for(int i=0; i < 1000000; i++) {
    pthread_mutex_lock(&lock);
    sum = sum + 1;
    pthread_mutex_unlock(&lock);
  }
  return NULL;
}

int main(void)
{
  pthread_t thread_handle[NT];
  int thread_id[NT];

  printf("parent thread id = %d, process id = %d\n", gettid(), getpid());

  // Launch the NT number of threads:
  for(int i=0; i < NT; i++) {
    thread_id[i] = i;
    pthread_create(&thread_handle[i], NULL, (void *)thread_main, &thread_id[i]);
  }

  // Wait for the threads to complete:
  for(int i=0; i < NT; i++) {
    pthread_join(thread_handle[i], NULL);
  }

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

  return 0;
}