Function _mi_page_try_use_delayed_free

3rd/mimalloc-2.0.9/src/page.c:135–160

}

bool _mi_page_try_use_delayed_free(mi_page_t* page, mi_delayed_t delay, bool override_never) {
  mi_thread_free_t tfreex;
  mi_delayed_t     old_delay;
  mi_thread_free_t tfree;
  size_t yield_count = 0;
  do {
    tfree = mi_atomic_load_acquire(&page->xthread_free); // note: must acquire as we can break/repeat this loop and not do a CAS;
    tfreex = mi_tf_set_delayed(tfree, delay);
    old_delay = mi_tf_delayed(tfree);
    if mi_unlikely(old_delay == MI_DELAYED_FREEING) {
      if (yield_count >= 4) return false;  // give up after 4 tries
      yield_count++;
      mi_atomic_yield(); // delay until outstanding MI_DELAYED_FREEING are done.
      // tfree = mi_tf_set_delayed(tfree, MI_NO_DELAYED_FREE); // will cause CAS to busy fail
    }
    else if (delay == old_delay) {
      break; // avoid atomic operation if already equal
    }
    else if (!override_never && old_delay == MI_NEVER_DELAYED_FREE) {
      break; // leave never-delayed flag set
    }
  } while ((old_delay == MI_DELAYED_FREEING) ||
           !mi_atomic_cas_weak_release(&page->xthread_free, &tfree, tfreex));

  return true; // success
}

/* -----------------------------------------------------------
  Page collect the `local_free` and `thread_free` lists