$ stress -c 1 -t 60 &
[1] 2578
$ sudo chrt -r -p 95 2578
chrt: failed to set pid 2578's policy: Operation not permitted

Why this doesn't work? My actual problem is that Jack Audio can't use real-time scheduling, but this example should demonstrate that there is a general problem probably. (getting  ERROR: Cannot use real-time scheduling (RR/10) (1: Operation not permitted), ERROR: AcquireSelfRealTime error)

 

$ uname -a
Linux odroidc2 6.6.16-current-meson64 #1 SMP PREEMPT Mon Feb  5 20:14:39 UTC 2024 aarch64 GNU/Linux

$ lsb_release -a
No LSB modules are available.
Distributor ID: Debian
Description:    Armbian 24.2.1 bookworm
Release:        12
Codename:       bookworm

 

Edited February 26, 20242 yr by Rado Buransky

After hours of trying I found this solution: 

 

I wasn't able to set the kernel variable using armbian-config but I created new file "/etc/sysctl.d/50-my-app.conf" and added "kernel.sched_rt_runtime_us=-1" to it. Rebooted and it works.