--- x/net/bluetooth/hci_request.c
+++ y/net/bluetooth/hci_request.c
@@ -102,6 +102,7 @@ void hci_req_sync_complete(struct hci_de
 {
 	bt_dev_dbg(hdev, "result 0x%2.2x", result);
 
+	hci_req_sync_lock(hdev);
 	if (hdev->req_status == HCI_REQ_PEND) {
 		hdev->req_result = result;
 		hdev->req_status = HCI_REQ_DONE;
@@ -111,6 +112,7 @@ void hci_req_sync_complete(struct hci_de
 		}
 		wake_up_interruptible(&hdev->req_wait_q);
 	}
+	hci_req_sync_unlock(hdev);
 }
 
 /* Execute request and wait for completion. */