mutex

mutex.c

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

int x;
pthread_mutex_t mut = PTHREAD_MUTEX_INITIALIZER;

void add_x(int a) {
  pthread_mutex_lock(&mut);
  x += a;
  pthread_mutex_unlock(&mut);
}

void* doit(void *arg) {
  for (int i = 0 ; i < 100 ; i++) {
    add_x(1);
  }
  printf("hello from another thread: %d\n", x);
  return NULL;
}

int main(int argc, char* argv[]) {
  for (int cur = 0 ; cur < 100 ; cur++) {
    pthread_t thread;
    pthread_create(&thread, NULL, *doit, NULL);
  }
  sleep(3);
  printf("total: %d\n", x);
  return 0;
}