############## ORIGINAL CODE ##################################
-       map_guard = atomic_add_return(1, &mux->map_guard);
-       if (map_guard == 1) {
-               if (!request_mem_region(uport->mapbase, dec_kn_slot_size,
-                                       "dz")) {
-                       atomic_add(-1, &mux->map_guard);
-                       printk(KERN_ERR
-                              "dz: Unable to reserve MMIO resource\n");
                        return -EBUSY;
                }
        }

############## INITIAL APPROACH ##################################
+       refcount_inc(&mux->map_guard);
+       if (refcount_read(&mux->map_guard) == 1) {
+               if (!request_mem_region(uport->mapbase, dec_kn_slot_size, "dz")) {
+                       refcount_dec(&mux->map_guard);
+                       printk(KERN_ERR "dz: Unable to reserve MMIO resource\n");
                        return -EBUSY;
                }
        }

############## ALTERNATE APPROACH ##################################

+       if (!refcount_inc_not_zero(&mux->map_guard)) {
+               refcount_inc(&mux->map_guard);
+               if (!request_mem_region(uport->mapbase, dec_kn_slot_size, "dz")) {
+                       refcount_dec(&mux->map_guard);
+                       printk(KERN_ERR "dz: Unable to reserve MMIO resource\n");
                        return -EBUSY;
                }
        }