I know that non-root users can renice a process up, but not renice a process priority down.
$ nice yes >/dev/null & p=$!
$ renice 15 -p $p
8414: old priority 10, new priority 15
$ renice 12 -p $p
renice: 8414: setpriority: Permission denied
$ kill $p
I understand that as a non-root user I should not have the ability to (re)nice a process into negative nice territory, or that root may have started a process on my behalf at a higher nice level.
The question is for what logical reason can a non-root user not renice their own processed downward, even if just no further down to the original priority in which it was instatiated?