diff --git a/sys/dev/usb/usb_subr.c b/sys/dev/usb/usb_subr.c
index 7401b9dbfd37..a9fcdd8418ab 100644
--- a/sys/dev/usb/usb_subr.c
+++ b/sys/dev/usb/usb_subr.c
@@ -708,12 +708,19 @@ usbd_set_config_index(struct usbd_device *dev, int index, int msg)
 	usb_bos_descriptor_t *bdp = NULL;
 	usbd_status err;
 	int i, ifcidx, nifc, len, selfpowered, power;
+	struct lwp *l;
 
+	if ((l = atomic_cas_ptr(&dev->ud_configlock, NULL, curlwp)) != NULL) {
+		panic("bus %u device %u: concurrent %s by lwp %u [%s]",
+		    dev->ud_bus->ub_busnum, dev->ud_addr, __func__,
+		    l->l_lid, l->l_name ? l->l_name : l->l_proc->p_comm);
+	}
 
 	if (index >= dev->ud_ddesc.bNumConfigurations &&
 	    index != USB_UNCONFIG_INDEX) {
 		/* panic? */
 		printf("usbd_set_config_index: illegal index\n");
+		atomic_store_relaxed(&dev->ud_configlock, NULL);
 		return USBD_INVAL;
 	}
 
@@ -739,6 +746,9 @@ usbd_set_config_index(struct usbd_device *dev, int index, int msg)
 		dev->ud_config = USB_UNCONFIG_NO;
 	}
 
+	KASSERT(dev->ud_config == USB_UNCONFIG_NO);
+	KASSERT(dev->ud_ifaces == NULL);
+
 	if (index == USB_UNCONFIG_INDEX) {
 		/* We are unconfiguring the device, so leave unallocated. */
 		DPRINTF("set config 0", 0, 0, 0, 0);
@@ -747,6 +757,7 @@ usbd_set_config_index(struct usbd_device *dev, int index, int msg)
 			DPRINTF("setting config=0 failed, err = %jd", err,
 			    0, 0, 0);
 		}
+		atomic_store_relaxed(&dev->ud_configlock, NULL);
 		return err;
 	}
 
@@ -754,11 +765,13 @@ usbd_set_config_index(struct usbd_device *dev, int index, int msg)
 	err = usbd_get_config_desc(dev, index, &cd);
 	if (err) {
 		DPRINTF("get_config_desc=%jd", err, 0, 0, 0);
+		atomic_store_relaxed(&dev->ud_configlock, NULL);
 		return err;
 	}
 	len = UGETW(cd.wTotalLength);
 	if (len < USB_CONFIG_DESCRIPTOR_SIZE) {
 		DPRINTF("empty short descriptor", 0, 0, 0, 0);
+		atomic_store_relaxed(&dev->ud_configlock, NULL);
 		return USBD_INVAL;
 	}
 	cdp = kmem_alloc(len, KM_SLEEP);
@@ -929,6 +942,7 @@ usbd_set_config_index(struct usbd_device *dev, int index, int msg)
 		}
 	}
 
+	atomic_store_relaxed(&dev->ud_configlock, NULL);
 	return USBD_NORMAL_COMPLETION;
 
 bad:
@@ -942,6 +956,7 @@ bad:
 		kmem_free(bdp, UGETW(bdp->wTotalLength));
 		dev->ud_bdesc = NULL;
 	}
+	atomic_store_relaxed(&dev->ud_configlock, NULL);
 	return err;
 }
 
@@ -1455,6 +1470,7 @@ usbd_new_device(device_t parent, struct usbd_bus *bus, int depth, int speed,
 
 	dev->ud_quirks = &usbd_no_quirk;
 	dev->ud_addr = USB_START_ADDR;
+	dev->ud_config = USB_UNCONFIG_NO;
 	dev->ud_ddesc.bMaxPacketSize = 0;
 	dev->ud_depth = depth;
 	dev->ud_powersrc = up;
diff --git a/sys/dev/usb/usbdivar.h b/sys/dev/usb/usbdivar.h
index 2ff3cbe6cfbd..c0a427eeea13 100644
--- a/sys/dev/usb/usbdivar.h
+++ b/sys/dev/usb/usbdivar.h
@@ -228,6 +228,8 @@ struct usbd_device {
 	char		       *ud_serial;	/* serial number, can be NULL */
 	char		       *ud_vendor;	/* vendor string, can be NULL */
 	char		       *ud_product;	/* product string can be NULL */
+
+	struct lwp	       *ud_configlock;
 };
 
 struct usbd_interface {