When issuing vmstat -i, some interrupt entries have no label, instead there is just a plus symbol. interrupt number also does not appear in the output of devinfo -u
Behaviour observed on 1st gen Raspberry PI model B & BeagleBone Black.
Thank you for the report, I'm sorry this didn't receive attention earlier. I've just tested a recent revision on my BBB and RPI2, and all interrupt entries have appropriate labels. I do remember this wasn't the case some ~2 years ago, so it would seem to have been fixed at some point in that time. Closing this now, but please reopen the issue if you are able to reproduce on a supported release.