thread_with_mutex.c

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

int x = 0;
int n = 100;
pthread_t tid[100];
pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER;

void* calc()
{
  int j = 0;
  for (j = 0; j < 10000000; j++) {
    pthread_mutex_lock(&mut);
    x = x + 1;
    x = x - 1;
    pthread_mutex_unlock(&mut);
  }
  return ((void *)0);
}

int main()
{
  int i = 0;
  int err;

  for (i = 0; i < n; i++) {
    err = pthread_create(&(tid[i]), NULL, &calc, NULL);
    if (err != 0)
        printf("\ncan't create thread :[%s]", strerror(err));
  }

  for (i = 0; i < n; i++) {
    err = pthread_join(tid[i], NULL);
    if (err != 0)
        printf("\ncan't join with thread :[%s]", strerror(err));
  }

  printf("x is %d\n", x);
  exit(0);
}