[CentOS] CentOS 7, X issue

One of my users is reporting that he's working (heavy graphics, I
believe), and X freezes. So, to save him from rebooting, I did init 3. And
waited. Almost a minute and a half later, it had not completed. I quit,
killed X, and then could init 3, then init 5.

I'm not finding clues as to what hung. In messages, I see
ay 31 12:07:14 <workstation name> gnome-session: (tracker-miner-fs:1931):
GLib-GObject-WARNING **: g_object_notify: object class 'UpDevice' has no
property named 'g-name-owner'
May 31 12:08:28 <workstation name> abrt-hook-ccpp: Process 31430 (Xorg) of
user 0 killed by SIGABRT - dumping core
May 31 12:08:29 <workstation name> gnome-session:
(gnome-settings-daemon:1677): Gdk-WARNING **: gnome-settings-daemon: Fatal
IO error 11 (Resource temporarily unavailable) on X server :0.

The abrt is, I believe, when I killed X. I can't find anything googling,
anyone got any thoughts on this? 7.3.1611. Looking at yum.log, I see the
cron job updated glibc, dracut, and systemd a few days after I fully
updated and rebooted it.

      mark