atomic_race.c

#include <stdio.h>
#include <stdlib.h>
#include <stdint.h>
#include <stdatomic.h>
#include <threads.h>
#include <time.h>

_Atomic(uint64_t) v = 0;

int f1(void* x) {

  (void)x;
  atomic_store_explicit(&v, 10L, memory_order_release);
  thrd_sleep(&(struct timespec){.tv_sec=1}, NULL); // sleep 1 sec

  return 0;
}

int f2(void* x) {

  (void)x;
  (void)atomic_load_explicit(&v, memory_order_acquire);
  thrd_sleep(&(struct timespec){.tv_sec=1}, NULL); // sleep 1 sec

  return 0;
}

int main() {

  thrd_t t1, t2;

  if(thrd_create(&t1, (thrd_start_t)f1, NULL) != thrd_success)
    return EXIT_FAILURE;
  if(thrd_create(&t2, (thrd_start_t)f2, NULL) != thrd_success)
    return EXIT_FAILURE;

  thrd_join(t1, NULL);
  thrd_join(t2, NULL);

  printf("v = %ld\n", v);

  return EXIT_SUCCESS;
}