Comment # 8 on bug 931964 from Thomas Blume

(In reply to Roland Bernet from comment #7)
> I can confirm, the network does not get switched off. 
> 
> If I catch the soft lockup within a few minutes, I can still login over ssh
> and reboot the machine. After 5 minutes or so, login does not work anymore -
> password is accepted, but no login prompt - over ssh or console. However I
> still get system messages per email or remote logging for some time before
> it does not even respond to ping.

Please boot one of your machines that show the problem with:

systemd.log_level=debug systemd.log_target=kmsg log_buf_len=1M debug

and remove the 'quiet' boot option.
When you see the soft lockup and still can login, please save the output of:

dmesg
journalctl -axb
systemctl list-jobs
systemctl status

and attach it.