AFAIK you can’t do this with BPF as it doesn’t have any kind of sleep functionality. I’m also not sure how would you achive this using cgroup, which are about quotas AFAIK.

There is?

I can actually define this in TCL:

% proc ifn't {cond cmds} {if {!$cond} {uplevel $cmds}}
% ifn't false {puts 12}
12
% ifn't true {puts 12}
%