Tvheadend

Set the priority of the streaming profile you are using. For example, if you want to make sure that live TV in Kodi is only interrupted by a recording with a higher priority, set the htsp streaming profile to 'DVR Override:<Your Preferred Priority>' then ensure any recordings you want to override this have a higher priority.

For example, by default, recordings have no (or default) priority so they are all treated equally. If you set the htsp profile to 'DVR Override: High' then only recordings with a priority higher than 'High' will be allowed to interrupt live TV.

I have not tested this (as I doubt with 8 tuners I'll ever have a clash) but it would be good if you could let me know if this works for you.

EDIT: Obviously if you're not using htsp as your default streaming profile (if you're using Kodi you should be :) ) then substitute htsp with your profile.