Function vm_object_busy

freebsd/vm/vm_object.c:2456–2465

* Busy the vm object. This prevents new pages belonging to the object from * becoming busy. Existing pages persist as busy. Callers are responsible * for checking page state before proceeding. */

 * for checking page state before proceeding.
 */
void
vm_object_busy(vm_object_t obj)
{

	VM_OBJECT_ASSERT_LOCKED(obj);

	blockcount_acquire(&obj->busy, 1);
	/* The fence is required to order loads of page busy. */
	atomic_thread_fence_acq_rel();
}

void
vm_object_unbusy(vm_object_t obj)