cgroup_add_cftypes(9)

📦 version 7.3.1, in nixpkgs unstable

💅 cgroup_add_cftypes(9) — like, the Kernel API Manual page you actually wanna read 🎀

okay bestie, so this is the cgroup_add_cftypes page from section 9 of the Kernel API Manual, and it's lowkey a glow-up moment for your cgroup subsystem. let's get into it ✨

🌸 NAME 🌸

cgroup_add_cftypes — add an array of cftypes to a subsystem. that's it, that's the whole vibe. it's giving "here, take these files, they're yours now" 🫶

✨ SYNOPSIS ✨

int cgroup_add_cftypes (struct cgroup_subsys *ss , struct cftype *cfts );

like, you hand it a subsystem and an array of cftypes, and it gives you back an int. simple. iconic. no notes 💅

🦋 ARGUMENTS 🦋

  • ss — the target cgroup subsystem 👑 you know, the one getting all the new files.
  • cfts — a cftype array that's terminated by a zero-length name. yes, zero-length name terminated — that's the little sentinel at the end telling everyone "we're done here, nothing more to see" 🙈

🔥 DESCRIPTION 🔥

So what actually happens? You register cfts to ss. Periodt. 💖

The files described by cfts get created for all existing cgroups that ss is attached to — and ngl, every single future cgroup is gonna have them too. no cap. ✨

And the best part? You can call this function anytime — whether ss is attached or not. it does not care. it's unbothered. main character energy 🌈

⚠️ okay but read this part carefully bestie:

It returns 0 on successful registration, and -errno on failure. 💀 That's the normal contract, love that for us.

But — and this is the part that's lowkey messy — this function currently returns 0 as long as the cfts registration was successful, even if some file creation attempts on existing cgroups fail. like, those failures just... happen and don't show up in the return value 😭 so don't assume 0 means every single file popped into existence perfectly. it means the registration itself slayed. that's the distinction, iykyk 🍓

🧚 SEE ALSO 🧚

like yes, that's a lot of cross-references and no, i did not skip any of them, we don't do that here 💅🌺

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🫶 okay that's the page!! this one lives in ./kernel/cgroup, dated October 2026, and it's the cgroup_add_cftypes(9) entry from the Kernel API Manual. go forth and register your cftypes, bestie — you're gonna absolutely ate it 💖✨🎀

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