If you create a GInputStream out of a GTcpConnection and try to read
asynchronously some data out of it and no data comes out immediatly
and you decide to close that GTcpConnection.

You can decide to gracefully end the connection by setting the
"graceful-disconnect" property to TRUE. In that case the socket is
shutdown() which stops the asynchronous read operation emitting the
G_IO_HUP event on the file descriptor.

If you device to not gracefully end the connection, the socket is just
close(), which now makes the filedescriptor of that socket invalid. In
that case the asynchronous read operation will never terminate because
the GSource doesn't consider the G_IO_NVAL signal on the file
descriptor a valid event to dispatch the callback and let the read
operation terminate with an error. It also constantly wakes up the
GMainLoop which leads to a 100% cpu consumption
(https://bugs.freedesktop.org/show_bug.cgi?id=64923).