man/io_uring_register.2: add another ENXIO case
@@ -210,5 +210,9 @@ or
.BR IORING_UNREGISTER_FILES
was specified, but there were no buffers or files registered.
.TP
+.B ENXIO
+Attempt to register files or buffers on an io_uring instance that is already
+undergoing file or buffer registration, or is being torn down.
+.TP
.B EOPNOTSUPP
User buffers point to file-backed memory.
