[LightDM] normal to have 2 persistant lightdm processes?

[Plmalternate Plmalternate]

Under Ubuntu 14.04 with plain Openbox, lightdm, and
lightdm-gtk-greeter, lxtask shows me 2 lightdm processes all of the
time, whereas I would have expected 1. The output of

ps aux | grep lightdm | grep -v grep

is

root       894  0.0  0.1  35192  3492 ?        SLsl 22:19   0:00 lightdm
root      2766  1.9  1.3  98744 26980 tty7     Ssl+ 22:49   0:45
/usr/bin/X -core :0 -seat seat0 -auth /var/run/lightdm/root/:0
-nolisten tcp vt7 -novtswitch
root      2852  0.0  0.1  19876  3796 ?        Sl   22:49   0:00
lightdm --session-child 12 19

So is that as it should be or have I broken something? If it is as it
should be, maybe you could point me toward something to read on the
topic. Thanks.