Noisy warning messages without CONFIG_CGROUPS enabled in kernel

[tofurky]

Per 7e5b324 if /sys/fs/cgroup/cgroup.subtree_control doesn't exist (as it won't for kernels built without CONFIG_CGROUPS - the default for SMALL_FLASH) instance_add_cgroup() will now return -ENOENT and then trigger a bunch of the new ULOG_WARN("failed adding instance cgroup for %s: %s\n", ...) messages.

Perhaps this should be if (ret && ret != -ENOENT) { or something instead of if (ret), or it should return a "non error" 0 if CGROUPS aren't enabled?

Example from a boot of 25.12.0:

# logread |grep cgroup
Wed Mar  4 02:03:09 2026 user.warn kernel: [    9.254527] procd: failed adding instance cgroup for ubus: No error information
Wed Mar  4 02:03:09 2026 daemon.warn procd: failed adding instance cgroup for rpcd: No error information
Wed Mar  4 02:03:09 2026 daemon.warn procd: failed adding instance cgroup for chronyd: No error information
Wed Mar  4 02:03:09 2026 daemon.warn procd: failed adding instance cgroup for chronyd: No error information
Wed Mar  4 02:03:09 2026 daemon.warn procd: failed adding instance cgroup for dnsmasq: No error information
Wed Mar  4 02:03:09 2026 daemon.warn procd: failed adding instance cgroup for dnsmasq: No error information
Wed Mar  4 02:03:11 2026 daemon.warn procd: failed adding instance cgroup for wpad: No error information
Wed Mar  4 02:03:11 2026 daemon.warn procd: failed adding instance cgroup for wpad: No error information
Wed Mar  4 02:03:11 2026 daemon.warn procd: failed adding instance cgroup for network: No error information
Wed Mar  4 02:03:11 2026 daemon.warn procd: failed adding instance cgroup for adblock: No error information
Wed Mar  4 02:03:11 2026 daemon.warn procd: failed adding instance cgroup for cron: No error information
Wed Mar  4 02:03:12 2026 daemon.warn procd: failed adding instance cgroup for sshd: No error information
Wed Mar  4 02:03:12 2026 daemon.warn procd: failed adding instance cgroup for ustpd: No error information
Wed Mar  4 02:03:13 2026 daemon.warn procd: failed adding instance cgroup for nut-server: No error information
Wed Mar  4 02:03:13 2026 daemon.warn procd: failed adding instance cgroup for nut-server: No error information
Wed Mar  4 02:03:13 2026 daemon.warn procd: failed adding instance cgroup for https-dns-proxy: No error information
Wed Mar  4 02:03:13 2026 daemon.warn procd: failed adding instance cgroup for nut-monitor: No error information
Wed Mar  4 02:03:13 2026 daemon.warn procd: failed adding instance cgroup for dropbear: No error information
Wed Mar  4 02:03:13 2026 daemon.warn procd: failed adding instance cgroup for irqbalance: No error information
Wed Mar  4 02:03:13 2026 daemon.warn procd: failed adding instance cgroup for openvpn: No error information
Wed Mar  4 02:03:13 2026 daemon.warn procd: failed adding instance cgroup for openvpn: No error information
Wed Mar  4 02:03:13 2026 daemon.warn procd: failed adding instance cgroup for openvpn: No error information
Wed Mar  4 02:03:15 2026 daemon.warn procd: failed adding instance cgroup for lcd4linux: No error information
Wed Mar  4 02:03:16 2026 daemon.warn procd: failed adding instance cgroup for dnsmasq: No error information
Wed Mar  4 02:03:19 2026 daemon.warn procd: failed adding instance cgroup for dnsmasq: No error information
Wed Mar  4 02:03:19 2026 daemon.warn procd: failed adding instance cgroup for dnsmasq: No error information
Wed Mar  4 02:03:19 2026 daemon.warn procd: failed adding instance cgroup for fwknopd: No error information
Wed Mar  4 02:03:19 2026 daemon.warn procd: failed adding instance cgroup for https-dns-proxy: No error information
Wed Mar  4 02:03:19 2026 daemon.warn procd: failed adding instance cgroup for nut-monitor: No error information
Wed Mar  4 02:03:22 2026 daemon.warn procd: failed adding instance cgroup for dnsmasq: No error information
Wed Mar  4 02:03:28 2026 daemon.warn procd: failed adding instance cgroup for nut-monitor: No error information

Anyways, I'll just go ahead and enable CGROUPS, but the messages might still be a problem for SMALL_FLASH (unconfirmed).

[DragonBluep]

Perhaps this should be if (ret && ret != -ENOENT) { or something instead of if (ret), or it should return a "non error" 0 if CGROUPS aren't enabled?

Make sense. Ping @dangowrt

[dangowrt]

Hm, true, we still got targets on which CGROUPS isn't enabled. Should check that and silently return 0 in this case...

[tofurky]

Thanks for pushing that fix (and the strerror thing).

I saw procd get updated here to 2026-03-11: openwrt/openwrt@ab0872a

But, in checking procd.git, it seems main and master are now out of sync; not sure how that is supposed to work. Maybe a force push is required to true them up?

They were identical at 2881a59

Edit: was fixed; branches are now identical.